| remp |
Fender4
The shape formula for an orthogonal is very complex. Do it by DIY means. The general shape is very similar to a parabolic but images to a point. Say you have a long arc bulb stuck into the reflector. The long arc will radiate at all sorts of angles which is basically uncontrollable but you can collect all the 90 degree rays coming from the bulb. OK there is this long bulb and the rays you want are coming out from the bulb at 90 degrees. Starting at the scew in end of the bulb draw a light ray 90 degrees to the long bulb. Without a reflector that ray would keep going and end up somewhere but you put a refective surface say an inch away and angle that reflective surface so the light ray goes to a focus point on the optical axis say 12 inches in front of the bulb. Thats the first ray. move along the bulb a millimeter and do the same. After an hour or so you will have moved right along the bulb and reflected all the 90 degree light beams to your focus point. You can put an aperture (1/2 inch hole in a peice of metal) just in front of the focus point to allow only the best rays to go through. Your reflector will have got wider as you go You should look at the patent and look at my reflector shaper. Make life much easier. |
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| Myren |
1 inch+ isnt so bad. look at an OHP bulb. a lot of them have rather large projection areas. mines about 1 inches long. still get nice sharp focus
the thing is, your not trying to focus light from your point source to the screen. your focusing light from the LCD to the screen. thats why were not seeing each individual curl of wire on the bulb, each small imperfection in the light.
1 inch+ arc length really isnt a problem.
the thing with the aforementioned parabollic solution is that only the light coming off perpendicular to the bulb will get to the focus. i suspect were talking gigantic light inefficiency here.
i could be wrong though.
myren |
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| SuperDave |
I am still convinced that a Fresnel is needed for our work with any type of reflector unless we have absolute accuracy with the reflector, LCD, lightsource and lens. I want to build my elliptical reflector as accurate as possible, but I can deal with any minor flaws....My main goal is to get as much light to the reflector with as few bounces off my reflector as possible...If I am slightly off with my reflector and/or lightsource I really dont care because most ligh will still hit the fresnel either directrly or with only one bounce off my reflector. Even if I screw up kinda bad and 30% of my light takes a few bounces off my reflector the fresnel is still going to pick up a HUGE percentage of light as long as my reflector has above 90% reflectivity.
This all depends on my questions earlier as to a suggested difference between reflected and non-reflected light hitting the fresnel...sorry, but I still dont see it being an issue...If I'm wrong someone please correct me now before I move too far along.
locust....you say you are working on an ellipsoidal reflector...Can you give me details? Are you taking a different approach than the crazy method I'm trying? If you have any suggestions for me or others on making a decent ellipsoidal reflector I and others would be interested.
tech_head....dont apologize for buying a projector. I will probably eventually buy one myself someday (maybe soon). I am not out to build the worlds best and smalles projector...I want something to make myself. If I buy one it will be for home theater and be mounted on my ceiling out of the way...I will then use my DIY projector to play games on...Imagine counter-strike on a 100" screen....OHH YA!!
tech_head....are you saying that the first fresnal lens will only catch light that is converging on it? If so that is interesting...never realized that...anyone know where I can get some detailed info on fresnels?
Later,
Dave |
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| remp |
Myren
Not as inefficient as one might think. Consider an ordinary electric long bar heater with a reflector behind. Stand right in front and you get very warm. Stand to one side, not so warm. If you say 1 inch+ lamps are ok thats fine. I was just offering an alternative to consider. |
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| SushiMasterX |
Is there a known way to repair ribbon cables that have been torn off of the glass substrate of a panel?
This is a higher res screen (520x240) that I would like to use again. You can see the leads on the glass after the ribbon's area are still intact. Is there some way the ribbon can be reconnected?
If it were a larger cable I could do some micro-soldering. But, with
this one it would have to be nano-soldering!
Some sort of glue & heat process in the factory, originally, I guess.
I hate to toss it. And the picture was enjoyable to watch.
Anyone with the in's and out's of it?
Any advice welcomed!
Thanks |
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| xblocker |
Hi Richard,
good to see you have dropped in here. wanna ask you, which program do you use to make these drawings?
xblocker |
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| SushiMasterX |
Oh yeah! I started a DIY small panel thread, for us types.
Volksprojektor uber alles!
Thought it would be better to discuss this angle somewhere else. Where us slightly pixel-disadvantaged folk can chat. |
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| remp |
Hi Xblocker
Hows everything. I dropped in here because I got a projection panel from Joe and I want to try and make it work. Picked up a lot of very useful information so far. Might be able to contribute something. I use Windoze paint and save as .jpg file. You have to actually select the "save as type" to be jpg. If you just name it xx.jpg windows will save it as a bitmap file which is too big to be loaded here. Windows 98 that is. |
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| lokost |
SuperDave
My approach is even wilder. I figured out the shape I needed and made a cardboard cut-out. (Actually two pieces of intercepting half ellipses). The next step was to walk through Garden Ridge sticking this cardboard model in the large pots; the idea was to use a pot as a starting point for making a cast with Bondo.
I lucked out and found a 18" dia x 17" deep aluminum reflector (similar to this one: http://cgi.ebay.com/ws/eBayISAPI.dl...indexURL=0&rd=1 )
My plan now is to cut this up in sections to fit my model. |
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| Marklar |
| Just for your information bondo hardens enough to where you cant form it in about 10 minutes. There is a UV activated bondo but I had bad luck with that stuff before whenI was doing body work to my old car. I would suggest plaster of paris mabey, it can be found at most craft stores. |
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| Gunawan W |
thank's xblocker,
my setup using PCX lens with fl=12", close to image source diagonal size=11", is it not enough?
Do you know the perfect lens fl for 11" diagonal size, or in common, the formula for given image source diagonal size will need lens with what focal length?
I have some thinking about reflector and fresnel panel, please correct me if I'm wrong.
Most of us using rather big LCD panel as an image source (6" to 15") and 3" to 4" lens dia to projecting image. To convergent the light, we use fresnel panel behind LCD panel.
To get best convergent light, we need point light source, why? because if we use non point light (such as LOA), the light rays come out from fresnel panel will focus at different point as big as lamp+reflector size. (ie: lamp+reflector act as biiiig point source light!)
If we use pointlight source, placed at 2f of fresnel panel, we get the same size point light spot at 2f in front of the panel, don't put the lens right at 2f, because it get so hot, place the lens slightly out of focus close to panel so the whole lens will covered by light beam.
Of course with this setup, the light beam come out from fresnel not in parallel rays when they hit LCD panel.
If we want parallel rays, place the lamp at 1f of the fresnel, but when light beam come out from LCD panel it is not convergent (it's parallel rays) and we will lost some (about 50% roughly) light beam which not hit the lens.
This is my drawing showing the setup. |
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| jvisaria |
Gunawan W
I am a little confused about your drawings.... you fresnel panel is that of an OHP fresnel, as opposed to the page magnifier type fresnel, right?
Also... I i think everyone seems to be frightened of putting a fresnel on the other side of the LCD because of quality purposes... I think it might be worth a shot -- since the LCDs we are using are so large, i think loss of quality may be less than we think.
Jay |
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| Gunawan W |
Jay Visaria
Yes, I'm using OHP fresnel panel.
In my drawing, I draw fresnel panel only.
From my drawing, LCD panel should be placed close to fresnel panel, at the right side.
see you. |
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| SushiMasterX |
Sweet drawings! Are you an optics engineer?!
Are you making large panel projector? Are there any suppliers/manufacturers in Jakarta for small panel?
I miss Indonesia sooo much right now too! I'm looking for a teaching job in Jogja. Waiting for info.
I have picture of Jelan Surabaya Antique on my simple web page. I look like Dalek's people! ha-ha!
Here is simple web page link
Also, a picture near Parantritis beach, Jogja.
Anyhow, please tell me if you know some suppliers/manufacturers. I am doing 'small panel' style. Like "drunken master" style! ha-ha! Just kidding!
Please check out 'DIY small panel projector' thread here.
Terama Kasih! |
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| xblocker |
Gunawan,
here's a picture from an optics book. It's a slide projector, but it's in principal the same. These 2 condensors can be replaced with a single one, which is a fresnel in OHPs. An important issue is: the filament is imaged first by the spherical refector so that the filaments image lays directly beside the original at the otherside of the optical axis.This means the original filament has to be placed slightly off center, so that one side touches the optical axis.
Further, through the condensor(s) these 2 filaments are magnified and projected into the plane of the projection lens so, that they fill the pupil of that. You can hold a sheet of paper into the plane and look if there's an image of 2 filaments.
If there's only 1 filament then something is wrong with adjustment. If the reflector reflects back right into the primary filament there's a huge increase of heat there, and the lamp burn out.
There exist different types of filaments. The ones with gaps between have to be adjusted so that the reflected image comes between the gaps. I'v learnt this by adjustung filmprojectors.
And don't mistake the lighting path for the image path. Projecting this way is an interplay between both. Only when the lighting path has it's optimum, the image has max. brightness.
With a given size of panel the focus length of projection lens has to be at minimum the diagonal size of that, but this can only reached by very precise and expensive optics. That would mean the F-ratio (F/d=1,0). In practice it's mostly another value (1 upward).
Hope this helps little bit.
Richard, thanks for info, i alredy used paint, but it's not so good to draw optical lightpaths with all these reflections(angles)
cheers
xblocker |
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| xblocker |
Sorry, forgot the pic!
xblocker |
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| oftheend |
Update: I did a night time test of my projector the night before last, finished 5 mins before i had to leave for work(3rd shift). Slept from when i got home till 2 hours after i was supposed to be at work last night, so i did not have time to post results.
With the 250 MH and still lots of light leakage (old reflector), the image was super bright in the dark. Unfortunatly, there were white streaks of light all over it, and the four corners were dim compared to the center. I switched lens, to test, and the same. So I reached into the case, pulled the fresnal out from behind the lcd, and boom, clear, huge, bright image. Right now the image is slightly dimmer at the bottom, which simply means I have to unscrew the bulb support and move it up a bit. I will play around a bit more to perfect it, but right now the only thing keeping me from feeling like i am at a theater is some big tall guy with a fat head sitting in front of me.
A note: after removing the fresnal, the lcd got a lovely black spot, where it was overheating. I think i will put a plain glass panel there instead as an insulater.
SuperDave:
To answer your questions: The bulb is 1/2 inch longer than the MV, same shape, and yes, it does have that little "eye" at the top.
I think the light does reflect better if you have it lengthwise parallel to the lcd, as opposed to perpindicular as it is in your setup. Plus with MH, you can only put it one way or the other, depending on the bulb. The setup i am using is this 250 watt fixture , I have removed the socket from the reflector setup, and installed it in place of the MV. The ballast is entirely seperable from the rest of the fixture, and has its own case with switch. The socket is wired with a plug on the end that plugs into the ballast assembley, so it is real easy to seperate from the fixture, no rewiring. The fixture does come with a nice reflector, but the thing is huge, 14 1/2 inch diameter. It cost me 64, with shipping, and there is no bulb included. But the convience of no rewiring was nice, plus i have a little enclosure for the ballast.
There is no hotspotting and the light is dispersed evenly, with the fresnal removed from the setup.
Edit: Like i said before, the colors on the MV suck. You might be able to correct it if you were running your video through DSCALER first, though i did not try. (just picked up TV card the other day). MH rules as far as the colors go.
For anyone who wants to know, My TV card is the ATI tv-wonder VE (no stereo). I picked it up at walmart for 44, and it is compatible with DSCALER. Dscalers web site only list the stereo version for compatability. I prob. could have gotten it cheaper on ebay, but i was right there with money in my pocket. |
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| prjctr_builder |
I have been following your forum from the beginning, but today is the first day that i can acually post something, yessssss!!!
I am about to buy an LCD TFT panel, but i need a way to make it display the image from my computer. I am sorry for my ignorance, but PLESSSSSS help me and tell me what kind of cpnnectors i need to buy and the kind of a power supply i will need, please answer this asap!!! i will be very thankfull because i have an idea that may put an end to this forum-we will successfully build a projector, but this is just a guess. A very strong, supported guess. The only thing that stops me now is a way to make the LCD's from ebay, like this one: http://cgi.ebay.com/ws/eBayISAPI.dl...item=2024275785 or this one http://cgi.ebay.com/ws/eBayISAPI.dl...item=2024765214
display the stuff that is coming from my computer. just a little hint, i have solved the cooling and light loss problems, hehe!!! i had an LCD monitor, but my friend fried it in his own project, i have no meny to buy a new one!!! so i will have to settle for a n TFT LCD Screeen, help me plzzzzz!!!!
Thank you. Aleksey |
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| sharkwong |
Hi everybody,
I just discovered this forum in the last few days, and have been reading as much as I could to see the ideas being bounced around for making a video projector. Disclaimer: I haven't actually built anything yet, I'm still getting parts and I was hoping to get a bit of advice as well.
First of all, I'm not particularly technically inclined, so my own DIY video projector is going to be the one that was discussed by eac74 earlier on in this thread, essentially just an LCD display from a handheld TV put into a slide projector. It's not going to give the best quality results, but I'll try this first and if I get it working I might get more ambitious and experiment with some of the setups that a lot of you guys have tried out.
I managed to get a Kodak Carousel 4700 slide projector relatively cheap, with shipping $44 Cdn. The problem now is the LCD display/TV. I've pretty well resigned myself to spending some real money here. I've looked around quite a bit for one that would fit my needs, there's plenty of stuff on ebay, it seems like everybody is selling the Casio ones. Problem is, they're not the greatest, either 39,000 or 60,000 pixels, and just the fact that everybody wants to get rid of them is not encouraging. I think I finally found the handheld TV that would be best, the Sony FDL-252T, active matrix LCD 112,000 pixels. Very rough calculation, if the image is blown up to a 4m x 2.5m area, each pixel is about 1 cm squared. I guess that's pretty pixellated, but it'll do for me. I've found the TV for about $120 US on the net.
Some expected problems: slide projectors take standard 2" x 2" slides, the above LCD is approx. 1.4" x 2.2" (2.5" diagonal), so I'll probably have to play around with my setup, or just deal with having my picture cut off. From what I hear, heat's going to be a problem as well, with the bulb being very close to the LCD, I believe eac74 used a couple of PC processor fans to cool his setup, I hope it's enough. Of course the image is going to be pretty dim, being from a slide projector bulb. Does anyone know if brighter bulbs are sold for slide projectors? Taking apart the TV and removing the backlight safely is probably going to be tricky, any tips in this regard would be appreciated.
Expected total cost of project (Cdn pesos):
$44 slide projector
$225 handheld LCD TV (with shipping)
$60 power supply and processor fans
$40 all white blackout shade or Plas-tex for screen
$100 other stuff I don't know I need yet?
If I can get this working for under $500 Cdn I'll still be happy. I guess I'm doing this for the satisfaction of saying "Gee whiz ma look what I made" :)
Anybody else have success with this setup? Looking forward to any comments or tips, even if you just want to say that I'm totally wasting my money. Thanks. |
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| fender4 |
Aleksey,
Do not buy those types of LCD's! :eek: They come from laptops, and each has a proprietary pinout scheme that will be very difficult/expensive to make usable. There are NO driver boards included with a panel like that, and I don't think a standalone driverboard would be feasable.
While the price is appealing, it also should give an idea of its utility. Why would people be buying $100 OHP panels with 640x480 resolution if they could get an XGA panel for $9? They just aren't practical, if not impossible, to use in this project. Sorry to give bad news, but this has been covered numerous times in this thread.
Hint: When you need to search for info in this seemingly endless thread, click on the "Show printable version" link at the bottom of the page. This will show the entire thread on one page and will allow you to use Ctrl-F to search for a keyword.
Just curious...what are your "ideas"?
sharkwong,
I wouldn't spend $225 for the handheld TV, IMO. You should be able to find a 2.5" LCD with similar resolution for much cheaper. Allied has a 2.5" for $132 that looks nice, but I'm not sure if the driver boards can be moved. If you haven't already, check out the "DIY Small Panel Projector" thread on this board. Good luck!
later,
f4 |
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| prjctr_builder |
can you give me the idea of an LCD that would work with my PC right away, give me some links plz!!!!
I cannot tell you the way that i am cooling the lamp and conserving the light YET, but i swear that i will tell you very soon. Please tell me the link where i can get an LCD for under 110-130$.
Also the other question i have is why are you using the LCD's with so low resolution, the image produced will suck!!!
wouldn't it be better to use a larger LCD (like 14-15") and have and excellent resolution. Remmember that light loss issue that happens when the LCD is too bog for the lenses is not an issue any more!!!
help me plz, i may be your only way to successs, hehe!!!
ALEKSEY |
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| lokost |
| Aleksey try searching for projection panel or lcd monitor or projector panel on ebay. |
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| ZeCo |
Fender
Hint: When you need to search for info in this seemingly endless thread, click on the "Show printable version" link at the bottom of the page.
You are my hero!!!!!! Thanks for the great hint. I was getting frustrated by not being able to search properly.
lokost
Ouch!! 2,000??? I'd try with the camera for $80 ;)
Thanks for the info.
BTW, got my LCP panel and I can say that Im pretty impressed with the "quality" of a 100:1 640x480 panel/OHP. Im displaying 75" 4x3 (my room is only 11ft and the focus of the OHP is a 14")
I don't even need the room dark to watch. No motion problems. Perfect. I think I have the right panel (large one) to start working for a while on a true DIY project.
I can watch during the night and day as well (with curtains closed) |
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| xblocker |
Aleksey, are you the messias? Tell us the truth !
xblocker |
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| gav |
ya know ya gotta give a little to get a little aleksey ;)
(added bit)
bTW, ebay aust has this : http://cgi.ebay.com.au/ws/eBayISAPI...indexURL=0&rd=1
at the mo, not entirely sure what reserve is tho...as it say sit comes without globe, does anyone see a concern with modifying it to house a different (ie cheaper) bulb?? just a thought... |
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| prjctr_builder |
I WILL GIVE YOU MY COOLING METHOD TOMMOROW BECAUSE I NEED TO MAKE THE PLANS, IT IS A BIT COMPLICATED
ALEKSEY |
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| SushiMasterX |
Sharkwong,
Dont get the 2.5" you will find it difficult to mount in a slide projector.
You are correct about it being 2x2 in a slide projector well. And, the .2" left over is covering for the frame of a slide itself.
Stick to 1.8" or less. It fits just perfectly for every projector I've mounted one in (No, lost picture). Must have been why the designers made this size common, originally.
That size is used on the back of digital camera's too. Maybe, easy to find since so many of them. But, I'm still hunting for a reputable dealer for the high-res (520x240) ones. Or, you can purchase the 320x240 currently from Unipac ~100$.
Lots to search! Come over to the DIY small panel thread for more! |
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| prjctr_builder |
let me tell you a little story.....
i was building a projector with one of my friends, but right before we got the whole thing going, he had to move, to another city. he took the whole assmbly with himself, and told me that he will contact me. But i haven't heard from him since, i think he got it going... that is what usually happens when people succeed... Good thing is that i kept the lenses, we had 2 sets, and i have the whole plan in my head...hehe.
first we tried to use hlagen, then flourescent bulbs, and so on. but they were just too hot and he fried his LCD right away. Then we got a new LCD and designed a cooling system (water cooled).
right now you probably think that i am a noob, but no, the results were beyond all our expectations. we used a fan to draw the air out of the chamber where the bulb was, and on the other side of the chamber we made a hole and connected a 4" hose to it. then put a nomber of tubes through the hose, and connected the tubes together by rubber hoses. we used a small pump to circulate the coolant from the car (absorbs heat real good) through the tubes. what we got from that is the air that entered the lamp chamber was very cool, and most of the hear was drawn away...hehe. after a few modifications , the system worked flawlessly, and the pump was completely silent too.
later of course, i discovered the lamps from the new cars. they emit a lot more light, and a triple computer fans themselves can deal with the heat alright.
i hope that you understood what i mean.
i would like to know if any of you know where i can get Semi-Permiable mirrors, like the ones that are used in the rooms with witnesses and stuff ( it is like a normal mirror on one side and the other is a see-through side). i have an idea on how it may be handy.
also i think that we need to work together and develop a plan of our projects so that we can get this thing done a lot faster.
hope this is some help........ possbly not
aleksey |
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| Scot_lad |
Do you plan on letting the light pass through the two-way mirror towards the LCD then any light that doesn't go through the LCD will be reflected again by the mirror, this time on the reflective side, to go through the LCD?
Good idea, but how is the light that doesn't go through the LCD properly going to get bounced back? It just gets lost. You can get polarisers that reflect light back if it's not at the right angle or polarization.
| quote: | | i think that we need to work together and develop a plan of our projects so that we can get this thing done a lot faster |
Good idea - because all we've been doing so far is posting our own information and ignoring everything that everyone else posts :p |
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| phazei |
Wow, this is getting really really long.
I'm currently still reading through all the pages till I hit the end. I wasn't going to post till I finished but I drew the attached picture while I was sitting here bored at work tonight and figured I might as well post it. I'm still at page 84 so it is going to be 35 some pages untill I actually get to any comments on it. O well.
O yeah, an idea for everyone doing the LCD with all the optics and not taking the OHP route.
Paint the inside of the box flat/dull black. Any light that reflects off the walls and goes through is just going to wash the image out since the light won't be parallel.
O yeah, just though of something on the picture. That picture with the reflector, if the light is at the focus point, most of what is getting bounced off of the reflector is parallel. I didn't draw the beams of light that would be coming out of the front of the bulb. Those would still be radiating from it at different angles. If a small fresnel was cut and put in front of it that would make most of the beam parallel. I'll draw another picture of it when I can.
I'm only at page 84 though |
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| thelaw |
Xblocker, i can completely confirm that picture you posted as i today picked up a Prinzmatic 500 slide projector from a car boot sale for £10 (about $15 or something) which actually works, although i dont think im gonna be keeping the bulb thats in it, cos it would be impossible to get a replacement.
Main thing is, it has a nice lens, and just about every pcx dcv etc lens needed, in the exact config as your pic. I will try and dig out my digital camera and take a few pics.
Cya, |
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| xblocker |
Phazei,
your last pic seems to be a good idea. The little lens just in front of the lightsource hasn't to be a fresnel, it also could be a normal glass lens. Nevertheless considering the lightrays which come parallel from the reflector are now refracted from the smaller lens out of the main lightpath and are lost. What you win with reflector is lost again, exept the little filament area. To eliminate unwanted light radiation maybe a blind or even a second reflector instead of a lens would be a better choice. A second reflector which reflects light back to the main reflector could be a huge gain, but is very tricky to calculate.
We should have a raytracing program for optical design to do that!
xblocker |
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| Gunawan W |
Hallo SushiMasterX, saya disini baik-baik saja, terima kasih.
Wish I'm an optics engineer, but actually my job nothing to do with all of this, I'm an architect.
Nice pictures in your website.
I'm too, still searching for the best LCD panel (size & price).
Your LCD panel seems perfect in size, but I need higher resolution (SVGA=600x800).
Sampai bertemu anda di Jakarta, e-mail me.
xblocker, thank's for your explanation, but you didn't mention what is the purpose having double filament image? Is it for reducing color aberration or something else? Tell me more, please.
Now about spherical aberration.
I think this solution will reduce spherical aberration problem, ---> "For lenses made with spherical surfaces, rays which are parallel to the optic axis but at different distances from the optic axis fail to converge to the same point."
Thanks Jamie for the links.
Just change the word "mirror" with "lens" in that links and now, it is relevant with my problem.
So IMO, we should use lens with diameter as large as we can find and blocking 1/3 to 1/2 of lens diameter.
I use PCX lens 41/2" dia., blocking it so the dia. become 2/12", the result is:
at 4 outer sides of projected image, now become sharper and better contrast, with a little bit reduce in overall brightness.
But....
that's not solving my problem with Chromatic Aberration --> "A lens will not focus different colors in exactly the same place because the focal length depends on refraction and the index of refraction for blue light (short wavelengths) is larger than that of red light (long wavelengths)."
Poor me. |
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| xblocker |
Gunawan,
Doubling filament image has the simple intention to get more luminance. Note: This only matches for halogen lamps, not arc lamps!
Spherical and chromatic abberations can not be corrected with single lenses. Mostly correction is done with either 2 meniscus lenses or three and more lenses, OHPs have often double lenses or triplets. The more the F-ratio value tends to 1, the more correction lens elements have to be used.
xblocker |
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| Undream |
Gunawan,
So, you're saying that if I block about 1/3 or so of my 5 7/8" diameter PCX lens (say, to 4" or so?), my quality will be increased, at cost of some brightness? I've got an entirely working system right now, and, all I need is a brighter light source. After I get the newer light source, I'm going to be building a painted-black wood box to hold everything. The 10,500 lumen quartz halogen I'm using right now gets too hot and isn't bright enough. Its good enough for midnight viewing, but, thats about it. |
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| prjctr_builder |
Just as i said before- everyone is talking about their own thing....
If we need a better resolution, why no use a larger LCD?!?!?
We can get those LCDs from monitors and just separate the LCD side from the rest of the assembly.
And stop giving yourselves headaches trying to find a light source, just buy a good set of car lights, the white ones, and if you want them any brighter (which i doubt) just increase the voltage!!!! it may give you a brightest bulb, with 15000 hours, i think i can live with that, ain't i right?
I am drawing a diagram right now, will be done soon!!!
Aleksey |
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| prjctr_builder |
| here is what i am going to start assembling on JUNE 8th. |
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| prjctr_builder |
| the first pic was too big, this one is hella small, if you want the begger picture, just email me at: predator3do@yahoo.com |
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| Scot_lad |
| You know why BMP files aren't used on the internet much? It's 'cos they're not compressed. Try changing it to JPG and you'll find it fits the 100k limit fine. |
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| fender4 |
Here is a link to an excellent article about light efficiency . It also has a good review of a chip that converts RGB to NTSC for $8 (sounds like the "Cheese Box" that sells for much more than that!).
http://www.tinaja.com/glib/muse95.pdf
I have included an adaptation of a graph from the article. Please note that halogen lamps (like a car headlamp) are the second-most inefficient bulbs out there. Sodium bulbs are the most efficient, but they put out an AWEFUL red-orange color (some streetlamps use this). Metal Halide is the most efficient light on this graph that is useful for us. Of course, most of us already know that. Metal Vapor is relatively inefficient....I think that pretty much seals the fate of the MV possibility.
prjctr_builder:
The bottom line is: Even if you could get enough brightness out of a car headlamp, you would DEFINITELY need some sort of water cooling to remove the ridiculous amount of heat generated. Instead, use a metal halide at the same brightness and use a small fan, or possibly just good ventilation.
Car headlamps have been addressed before...if the entire thread is too long to read, at least click on "Show Printable Version" at the bottom of the page and use Ctrl-F to search for a keyword.
As far as resolution goes, I don't want a higher resolution than 640x480. Others do. And several ARE taking the computer LCD monitor approach (example=SuperDave). Please read the posts from the last few weeks for details, or do a search.
Sorry to sound like a disciplinarian, but I just don't want the thread to get flooded with "less than helpful" suggestions that could be avoided by doing your homework. :cool:
Best of luck to everyone!
-f4 |
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| fender4 |
| Here is the chart of light efficiency: |
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| ChuckReese |
Undream,
10K lumens is not enough? I do not see how this is possible since most OHPs do not exceed 4K and many are having good success with those.
CR |
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| prjctr_builder |
i had a car headlight lamp, and it barely produced any heat yet was very bright. And if i am going to use the design that i have illustrated above, i won't need as much light. The only thing that stops me now is the fact that i need a semi-permiable mirror. if you can get me one or at least tell me where to get it without an absurd price, i can see myself getting somewhere.
i want to use the mirror with an LCD because that way i will barely loose any light, and i won't need those 10000 lumens, omg that is way too much!!! my colors might be a little dull, just a little, but i am planning to use the projector in my pitch black garage. If i take my time making the projector, i will be able to conserve the light.
looking back at Vince, you may still remmember him, i understand one thing, i need to take my time making the projector. Most of the people's problem is that they rush, fail, and give up.
Also i am planning to make a website, with a membership. Break the members down into groups of about 5 and let them concentrate on one design, so that they can perfect it!!! how does that sound?
anyway, i am sure that we will not need 10000 lumens, and i will still try to go with the headlights from a car (because they already come with a condensing lense). If they are too hot i think i will have to find a way to cool them. i am not saying that finding the solution is impossible, it just doesn't happen overnight. i bet that the guys who designed the high tech projectors, did not build theirs overnight. I will keep pursuing my goal no matter what and if someone failed with the car lamps, that doesn't mean that i will fail as well. I JUST HOPE THAT I WON'T BE THE ONLY ONE WORKING ON THE PROBLEM. because if i'll get it all right (without your help), don't even think that i am going to tell you!!!
Aleksey :mad: :mad: :( :( |
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| Scot_lad |
Aleksey - your suggestion that you're the only one doing any work on this project was quite funny. Everyone here was just sitting on their **** waiting for you to come along to show us what to do, and we're so glad you could stop by.
I'm glad you have decided to start a little group where you can "split people up" and make them figure out various problems - it's not like that's what the entire forum has been doing since it began.
You sound really convincing with your "tell me how to do this then I will offer you information but I can't tell you until you tell me..." Why don't you try sharing info freely just like everyone else does - nobody else thinks they're the messiah just for figuring something out. And your car headlight plan has already been looked into and failed, so if you can prove us wrong then go ahead with some pics, but don't just go in a huff because we don't believe you.
As for people rushing the project, failing and giving up, that's just rubbish. If you'd bothered to read the forum for what everyone else has already said, you'd see how long some of us have been on it for.
Don't mean to get at you but we've had so many people pop up saying "show me what to do NOW" that it's just annoying. |
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| xblocker |
ChuckReese,
my halogen lamp in my OHP is specified to have 16000 lumens, but the OHP specifcaction say 5200 lumens. Thats's what in reality come out ! That isn't so much for LCD panels.
xblocker |
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| xblocker |
And here are resumed some proposals for projector setups, which are discussed recently. Most of setups can be made by using or ripping parts of an OHP, exept large sized elliptical or parabolic reflectors.
The only thing that has to be considered, the light path of illumination has to go along the image path at the right side of the drawing. This requires a carefull adjustment of the components on the left side. Light cone on the right side MUST match the image path.
This setup should work with LCDs up to 12". If LCDs size is smaller the components must be customized to that. For very small LCDs the slide projector design could be a good choice, but there should be done much additive cooling. HEAT is the greatest enemy of LCDs.
Remember: The focus lenght of the projection lens can never be smaller than diagonal size of the panel !! For sharper image it's better to have factor 1,2 upwards!
cheers
xblocker |
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| Myren |
the idea of trying to use a good parabolic or elliptical with a fresnel in front sounds good. catch more light. the problem is, it doesnt work.
the light coming from the bulb will get bent by the fresnel one direction. the the light off the reflector is incoming to the fresnel from a different direction, and will hence be bent in a different direction. lights going everywhere. failure.
OHP's just use a spherical mirror, which bounces a light at the focus right back to the focus. thats what you want, if your using a fresnel. all the light, coming from one place.
xblocker: good graph. the OHP is, however, inacurate. the reflectors on OHP are classically spherical. they bounce light directly back to the light source. thus twice the light coming from a single point.
fender4: ah... i'm suspicious of that graph. metal halides can easily give off 40k lumens for 400 watts. thats over a 5x increase in efficiency over what that efficiency graph marked.
metal halides are the most efficient light bulbs.
prjctr_builder: my stable system, the one i have up and running for daily constant usage, is 15,000 lumens. probably only 5000 lumens, at best, make it to the screen, before the panel is even in place. with my panel, i get a pretty damned good image.
but i want more. i demand more. and i suspect a lot of others would too. its the difference between something that works, and something that really shines, something which is exceptional. hence why people are using 250 watt and 400 watt metal halides, capable of outputting upwards of 40,000 lumens. i'm aiming for 93% light efficiency (a mere 7% light loss) with my next ellipsoidal, custom built for a specific 42,000 lumen 400w metal halide. between these two i expect a HUGE improvement. you need a fracking lot of light.
myren |
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| Myren |
just wanted to note, light efficency, using more of the light made available, is a good alternative to using brighter lights. just something to keep in mind.
oh yeah, and ellipsoidals dont suffer from spherical abberation. go ellipsoidals.
(sodium bulbs were also more efficient than the graph indicated, to be fair. however, they are steeped in sepia toned badness, and unusuable, not to mention physically dangerous (high pressure)).
heres the thing about lenses, fresnels included. lenses do not make light go a certain direction. they make light go off in a direction that is a function of their incoming direction. if you have light coming in from different angles, its going to redirect them in different directions.
sushimasterx: that happened to me on my LCD monitor. i put all the parts back into the monitor, made it look fairly untouched and sent it back to viewsonic. "its broken. fix it". replacement came in a little over a month.
i had tried soldering the connector back on, and it nearly worked. any pressure at all though and it kept snapping right back off. annoying. as it turns out, usually the solder tabs on the ribbon cable stay soldered to whatever it was they were soldered to, and the ribbon cable rips off its tabs, so theres nothing left to try and solder. very sad. still barely workable, but very very hard.
end rant.
myren |
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| xblocker |
Myren.
you're right, my classical OHP drawing isn't quite correct. I know OHPs have spherical reflectors, but they are bouncing the lightsource back not right INTO the filament, but directly BESIDE it.
BTW, to overcome the problem with a parabolic reflector+fresnel, how about a blind directly in front of the lightsource, so that only reflected light hits the fresnel?
xblocker |
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| prjctr_builder |
if i you do use a metal halide lamp in your projector, how do you condense the light???????
i know that if i get a headlight projector lights, the condensors are already factory installed.
hehe |
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| fender4 |
Myren,
The number under the MH in the graph is "115" lumens per watt. Sorry if it didn't show up properly. Using a 400 watt MH, following this data, would produce 46000 lumens. That is pretty close to the 40000 lumens you are getting with your 400watt MH. Just wanted to straighten that out. :cool:
Also, make sure to look into the orthogonal parabolic or elliptical reflectors (remp's post a couple of days ago). These make much more sense for long filament bulbs, like MH's, since the true focal point of the reflector actually only covers a small part of the filament. Without an orthogonal reflector, light produced outside of the true focal point will travel in a slightly aberrant path....leading to inefficiency (and that is the enemy! :eek: )
For those who have experience with OHPs:
Don't some of the OHP's use a bulb, a small reflector (parabolic perhaps), and a short focal length PCX lens to disperse the light? If so, what are the advantages/disadvantages of this as opposed to a strict reflector style light setup? Just curious.
-f4 |
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| remp |
Fender4
I have looked harder at that orthogonal reflector and found a better description at US patent # 5037191. The inventor claims it is the best thing since sliced bread and as well as collecting light to a point he says the point is infinitely small. They dont get much smaller than that. I have also checked out radiation from a hot body such as a light source and all the light leaves at 90 degrees only excepting if the source has a non smooth surface in which case thee is radiation from the lumps in non 90 degrees but the majority is at 90 degrees. Could be a useful reflector. |
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| xblocker |
fender4,
as i said 2 posts before, OHPs have spherical reflectors. Some have an additional PCX-lens directly ober the bulb, some not. PCX lens is a simple condensor, which shares his job with the fresnel. More of lightrays can be refracted and a smaller overall size of projector case can be reached.
Richard,
could you point out a little more this 90 degree thing ?
xblocker |
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| MuzzMan |
I found some details about the Delta 67 and Delta 77 lenses I have been trying to use with my 5" LCD for rear projection:
The focal lengths are 67mm and 77mm respectively (could have guessed!)
They are designed to be used with a 5" raster diagonal CRT, which is absolutely perfect, but......
They are intended for use with a CURVED crt faceplate (radius 350mm), so they are no good for our purposes at all!
:( :mad: :(
So I now have to go back to trying to design a multi element lens setup using PCX or DCX simple lenses, or see if another complex lens like the delta is available surplus.
I know some people have bought other lenses surplus intended for rear projection (I remember Delta 20, fujinon or something?).
Has anyone managed to get a completely in focus image out of one of these that would indicate it is designed for a flat CRT? Most of these lenses would have been intended for 5" to 7" image size on the CRT. |
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| piGuy |
I had a few questions regarding some comments on optics. Myren, you said that a spherical mirror will reflect light at the focus back to the focus? How is this? IIRC, a light at the focus will result in parallel light reflecting outwards. And prjctr_builder, I'm not so sure a semi-permeable mirror will work. A two way mirror works by contrast. You have a light on one side and darkness on the other side. If you're on the light side, you see the light reflect back. If you're on the dark side, you see the light come in. If you put in a two way mirror, the light will reflect back towards the light source. If I'm not making sense, think of it this way: A two way mirror could be reversed and it will still work the same way. It all has to do with the lighting on each side. That's why an interrigation room is well lit, and the observation room is much dimmer. For an example, take a pop-tart wrapper. It looks reflective normally, but if you put it up to the sun, you can see through it, because there's greater contrast. I didn't take a close look at your setup, but I'm not sure if there would be a way to incorporate a two way mirror that would keep the light from the bulb from reflecting back. I don't really have much experience with two way mirrors (other than learning about them briefly in physics), but I'm personally not aware of a mirror that actually only lets light in one way. Sorry if someone else has already addressed this. This thread is so long its impossible to remember everything that's been said. :-)
BTW, I know I had talked about my distaste for an LCD based projector, but just how good of results are you guys getting? Has anyone tried a side by side comparison between a homemade and commercial LCD projector? (I think Myren mentioned this once) I haven't tried building one, but I suppose that the length of this thread would indicate that the results are better than ****-poor. |
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| remp |
Xblocker,
The 90 degree thing is to do with this orthogonal reflector I found at the US patent database #5037191. I mentioned this reflector several pages ago and Myren thought there might be large inefficiency. I thought he could be right in which case the reflector would be useless but looked at radiation leaving a hot body. If you look at an ordinary light bulb it seems to emit the same amount of light all the way round. Except the fillament end of course. So I looked at theoretical radiation from hot bodies and it is at 90 degrees to the surface. If the surface is not dead smooth which is the case in practical devices there is always some radiation at odd angles but the majority is at 90 degrees to the surface. This orthogonal reflector allows you to use a long light source takes all the 90 degree radiation and focus that to a very small point. Dimensionless point the inventor says. I have never seen one of these reflectors but looks fairly easy to make. |
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| Marklar |
| Well I gave up finding the bridge rectifier so i just took the light and ballast out of my OHP. My OHP was rated at 7000 lumens but I looked at the sylvania site and looked up the bulb it is 49,000 lumens. Today i tried a 250W MH i wraped it in foil and cut a hole about 1.5 inches across placed a 5" magnifing glass in front of it and it made a very bright spot about 6" across when i stuck my hand in front of it i put it in my OHP and got it to project the lcd on the wall but it wasnt bright enough. This bulb has about 30,000 lumens less than the origional so I found a compact 400W MH that GE makes that puts out 50,000 lumens and its half the size of the 250W so its going to be easier to cram it in there. |
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| remp |
Marklar
You can make a bridge rectifier from 4 diodes for about a dollar. If you cannot locate the diodes I can post you 4 diodes made into a bridge. Be prepared though that even if you bridge has failed it could have been taken out by parts after the bridge. Your system uses DC on the light I would guess hence the bridge to change your household AC voltage into DC voltage. Invariably after the bridge is a capacitor to store/smooth the Dc. They fail as well. But failure in bridge rectifiers is fairly common so you could be lucky. Let me know if you want a drawing or some parts |
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| fender4 |
xblocker,
I wasn't doubting what you said earlier--you are correct about some OHP's using spherical reflectors. But what would be the advantage of using a PCX after a bulb/reflector that is already producing diverging light rays? I thought the point of the PCX lens was to take parallel rays produced by a parabolic reflector and then spread them the cover the fresnel. I know that some OHP's use them...I just don't understand why if they are really using spherical reflectors. Can you help me out? And now, onto:
Raiders of the Lost Arc!
Below is an ugly sketch of what I think I understand about the orthogonal reflectors. Please tell me if this is wrong so noboby gets contaminated with my flawed logic ;) . If the arc is placed in the axis perpendicular to the LCD, the area of the reflector that is actually BEHIND the arc acts as a normal parabolic reflector, with the back edge of the arc as the focal point. At points along the arc, however, the parabolic curvature changes to reflect radial light from the arc in parallel. This curvature continues until the end of the arc, where it resumes a parabolic shape. Is this right??? Maybe?
This would take advantage of the radial light from a long arc, which should be brighter and at least easier to control. In a conventional parabolic or elliptical reflector, much of the light is "wasted" if it is not being produced precisely at the focal point. Since we can't get our hands on a small arc bulb for a reasonable price, maybe this is our best bet?
-f4 |
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| prjctr_builder |
DID ANYONE IN THIS FORUM ACTUALLY BUILT A WORKING PROJECTOR??????? IF SO< WHAT WAS THE DESIG AND WHO IS THE GUY WHO BUILT IT?????
tell me plz.... aleksey:confused: :confused: :confused: :confused: |
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| remp |
Fender4
Not quite right. In your #3 sketch all your parallel rays dont go parallel, they converge to a point to the right of the bulb. See my drawing few days ago. |
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| ChuckReese |
I found a site that sells metal halide bulbs integrated with an elliptical reflector. They guarantee 1000 lumens focused to a 4mm spot. It comes complete with ballast and cooling solution.
See the LM60 from Welch Allyn:
http://www.walamp.com/FiberOpticIll...Search.asp?id=4
CR |
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| remp |
Got my very first large screen projection today. It is absolutly terrible but I am wrapped. Using elderly low cost slide projector Cabin 1000A with projection lens on. 2 feet away is the lcd panel. Adjust the panel closer/further away until round light from projector just covers LCD panel. Connect panel to video. OK so far. Panel correctly determines I am on PAL TV system. I can see pictures on LCD panel. Slide projector screen placed 5 feet from LCD panel. Picture on screen all blurry. Place page magnifier fresnel at 12 inches in front of LCD. Picture focused now on screen. Picture is terrible but its 6 feet wide and can watch with lights on. Page magnifier is one the cat dragged in. Its wrinkled and wont sit straight and too small to show whole picture.
Took it out.
Experimented with some 50mm dia glass lens in small portion of picture. Best result from magnifying glass shaped lens. Excellent quality can focus pixels quite clearly but they are not obtrusive. Defocus slightly and they disappear. Colour is not special. Seems flat not vibrant colours. Could be the bulb in the slide projector on its last legs. I am scared to pull it out in case it breaks.
Conclusion.
Its great to have a large screen projector.
Panel Infocus Powerview 820. 800x600 and video
Very surprised at what excellent quality light coming out of slide projector. Inside is just like your diagram Xblocker
Light is even right across
Virtually no heat in light at all
Fan is quiet
No discernable blurring on full motion video.
Picture size not very big but still much bigger than my TV.
Page magnifier does a job. Will buy a better one. Has to be size of LCD plus an inch or two. Glass lens do a far better job but chances of getting a 12 inch glass lens could be remote. Only trouble is picture upside down and writting back to front. Fixed the upside down picture by turning the panel down instead of up but writting still reversed. Could need a mirror somewhere unless the panel has reverse switch which I have not seen. |
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| Gunawan W |
Yes, blocking 1/3 of the lens, will increase sharpness & contras, especially at 4 far-side of the image, try yourself or learn more from the link I gave in previous post and don't forget telling me the result, please.(you use exactly the same lens as mine).
see you. |
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| Undream |
| well, I figured all this testing on a plain old wall isn't cool enough, so I went and bought a sheet of plas-tex, and $24 worth of lumber. time to build myself a screen. I'll post pictures when I'm done. I got up early this morning to head out to meijer and pick up some liquid nails and black spraypaint for the framing ;) |
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| xblocker |
Richard,
as you described your setup, it cannot work! Did you remove the original condensor lenses? They are useless for this panel. Remember: Condensors must not only have at least the size of panels diagonal, they also must have the right focus lenght to match with the image path. You also can completely forget the slide projectors projection lens. Usable should be the lamp and reflector. Concerning panels image orientation, isn't there a setup where you can choose the kind of projection, rear ,front, reverse..?
fender4,
the use of parabolic reflector only makes sense, if it has the at least the size of the panel. A spherical reflector primairly doubles the filament of the bulb for better brightness, that means it makes a real image on filaments plane. A PCX lens in every case converges lightrays, if parallel or not. In OHP the PCX lens pre- converge them before they go to the fresnel, which converges them finally to the projection lens.
Gunawan,
are you working with a single PCX lens as projection lens? If yes, this always will lead to spherical aberations. It's the same in photography. Either small blind and better sharpness, less brightness, or full aperture, less sharpness, more brightness.
Proposal: Go to the next eye glass optical store and ask for 2 used ore slightly damaged eye glasses with focal lenght of about 620 mm. Maybe you get them for nothing. Eye glasses are meniscus lenses. Then fit them together with the convex side outside. Now you have a projection lens which a focal lenght of about 310 mm, which should have better properties than your single lens.
xblocker |
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| Undream |
heh, funny story, when I went to get that parkland plastics stuff, I asked someone about it, he said aisle 20, so, I went and searched. After 5 mins, I nearly gave up to go ask him again, and, I finally saw the UPC code on a rack. underneath something else, I found one sheet of the stuff I needed. It was BEAT TO HELL. it had rust marks ALL over it, and scratches up the wazoo. I went back to the guy, and said "Yeah, I found what I'm looking for, but the one you have is all beat up and looks horrible." He said, "Why does it matter? its going underneath something else, right?"
I said "uhh.. Actually I'm going to make a movie screen out of it." He said "ohhkay.. let me see if we have any more". Now, I knew they had more, because when I was at the Lowes in my home town, and I checked for it and they didnt have it, they told me that this other location had 57 sheets of it. So, he started walking down aisles looking up towards the ceiling. Finally, we saw the stuff -- It was BURIED underneath a huge pile of other 4x8sheet flats 15 feet off the ground. The guy muttered something like "The gods are not smiling at me today" and went and got their huge forklift thing. Anyways, 10 minutes later, I had a shiny new sheet of it. Not the top sheet on the flat though, it was way too scratched up.
Laugh, I think he hated me. |
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| tech head |
xblocker
I think that the way the Richard has his setup will work. From how he described it he is using the slide projector as a divergent back light and then using the ferensl to focus. that is why the sides of the picture is being cut off. |
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| xblocker |
Techhead,
Eh mmmh, now does it work or not?
xblocker |
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| tech head |
think about it. it is like an ohp with no ferensl and a really big focusing lens.
Draw it out on paper. It looks like it should work. |
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| ChuckReese |
remp,
Do not use the fresnel lens in front of the LCD. I asked a friend of mine from JPL who builds space-based telescopes about this, and she said the fresnel lens will not produce a high quality image. Keep the fresnel behind the LCD to use as a condenser lens (but remember that you need two of them unless you are using the double sided OHP type).
CR |
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| ChuckReese |
I was wondering if the following will work. I am using the OHP-style large LCD plan:
source -> condenser lens -> LCD -> projection lens -> screen
Right now I have two $5 page enlargers for the condenser lens (each has a focal length of about 12 inches). I am trying to find out what to use for the projection lens. I want to get 4x magnification on the screen at a distance of 96 inches. I think this means I need to put the LCD 24 inches in front of the projection lens and the focal length should be 19.2 inches (488 mm). The condenser lens has no effect on the magnification; I just need to be sure the LCD is illuminated.
I'm pretty lost here. Please advise.
CR |
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| xblocker |
ChuckReese,
1.try focal lenght 12,2" upwards for projection lens, but never use fresnels as projection lens! Look at my advice to Gunawan some posts before.
In case you use 2 fresnels (f=12") together for condensor they add up to focal lenght of 6"(1/fn=1/f1+1/f2).
2. Get them at the LCD at the lamp side. Be shure the distance between lamp and fresnels is little more than 6".
3. Take a sheet of paper and hold it at the other side of panel in a distance about 12". There should now be a spot. In that plane the projection lens has to be adjusted later. You also can try this without the panel.
4. If you're a smoker blow smoke into the lightpath to see it's shape.
5. If the spot on the paper is too large, slightly move the lightsource or the fresnel back and forewards, until smallest otimum is reached. Done!
At the first state don't worry about magnification, be glad if it works!
xblocker |
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| ChuckReese |
| quote: | Originally posted by xblocker
In case you use 2 fresnels (f=12") together for condensor they add up to focal lenght of 6"(1/fn=1/f1+1/f2).
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I don't think so. My fresnel lenses are not double-sided.
CR |
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| xblocker |
ChuckReeves,
if you put them together they are like doublesided!
In General: If you have two lenses with a given focal length, you can calculate the common(?) focal lenght with this formula!
xblocker |
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| tech head |
Superdave
I was thinking, instead of making your own reflector, why not check the mirror section on www.surplusshed.com
they have a lot of spherical mirrors and the like. |
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| jjasniew |
Richard,
That panel has an option to reverse the video, to correct your backward spelling - |
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| ChuckReese |
xblocker:
My fresnel lenses are page magnifiers so the grating is only on one side. The first lens produces a collimated beam from a point source 12 inches behind it. The second lens takes the collimated beam from the first lens and focuses it to a point 12 inches in front.
I do not see why putting them back to back will result in an effective focal length of 6 inches.
CR |
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| tech head |
ChuckReese
Focal length is the distance it takes for parallel light to be converged to a point(or image). If you put the two ferensl lenses together it will have a 6" focal length. But you are right that it will take 24" to go from a point light to a point convergence. but in order to make the light parallel through the two lenses the light source would have to be at 6".
hope that helps |
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| xblocker |
ChuckReese,
to determine the focal length let the sun shine through and measure the distance to the focal point.
In the meantime i doubt, that the fresnels really have 12".
and, it doesn't matter, if the gratings are only on one side, impotant is only focal lenght. One sided means a quasi planconvex lens.
xblocker |
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| SuperDave |
tech_head...the mirrors at surplusshed are all relatively flat...Now I know they are selling spherical mirrors, but these are geared towards telescopes and are thus somewhat flat...They are part of a VERY large shpere (imaging having a 5 ft. sphere and just cutting out a small sectiion on the outer shell...thats what these do).
I would not be able to gather enough light...but thanks.
On a side note...I am frustrated...I did nothing on my projector this weekend and its been 2-3 weeks since I touched it. HOPEFULLY I have most of this week to work on it.
Good luck everyone...
Dave |
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| ChuckReese |
| quote: | Originally posted by xblocker
to determine the focal length let the sun shine through and measure the distance to the focal point.
In the meantime i doubt, that the fresnels really have 12". |
Yeah, it did that already... which is why I think the focal length is 12".
CR |
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| Myren |
remp: i think your suggested reflector might actually work pretty well, upon further thought. i was thinking only the light coming off directly perpendicular to the light would go where we wanted, but there should be a decent arc of acceptability. having an adjustable stop would be nice, you could trade off between crispness and brightness. no clue how it'd be made though.
congradulations on your sucess.
piguy: the reflector your thinking of is parabolic. sphericals reflect light back to the center. think about it. if a light were in the middle of a sphere, all the light would be reflected right back to where it came. spherical mirrors just use a part of the sphere.
marklar: can you link or name this GE light? the size of these 400 w mh's is getting cumbersome.
prjctr_builder: i'm one of the numerous people who built a successful one, and as far as i know i've been one of the few people successful in tearing myself away from projector long enough to keep posting. to everyone else who fought the battle and is still here, go you.
please dont ever use all caps again. i hate it when people scream.
chuckreese: the problem with the light you listed (with reflector) is that the reflector is too small. the reflectors were dealing with are huge by comparison, they have to be, were using them as the sole element to put the light through the LCD, and thus they need to be as big as the LCD, or bigger. there are some decent resolution LCD's under 4mm in size, but they're very very expensive.
undream: go plas-tex. soon as i get some cash, i'm buying a whole boatload of it. might have to make a road trip to get it though, dont know if its stocked in metro area. i figure a road trip'll probably be cheaper than ordering it, given how many sheets i want (4).
myren |
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| SuperDave |
Myren...like I mentioned before the Plat-tex stuff is pretty sweet. You should be able to get it at almost any lowes or HomeDepot. I live in Pasadena (basically L.A.) and it is availble a a number of places within 15 miles from me.
What I did was I just got the UPC code and called to ask how many they had in stock. If you try to explain the name or what it is you will NEVER (not yelling...I emphasizing hehhehe) find anyone that has a clue. Just get the part number from the AVS link I posted a while back (probably 10 pages). The part number is on the second page of the discussion I think.
I heard you (maybe someone else) talk about getting a bunch of these and glueing them together. I really dont think this is going to be your best bet. No matter what you do I can not imagine that you are going to be able to mask the seam. If you caulk them together with white glue/caulk and move them tightly together I still have to believe you will notice it. Maybe not when the projector is off, but when you are projecting the caulk will have a different gain and reflective capabilities.
If you are planning on painting these with paint or the goosystem stuff then you dont need to wast your time with the plas-tex because you will be painting right over what makes this stuff soooo good.
So...if you do go that route pleeeeez let me know how it works out, because if it works nicely for you I am going a very similar route. If you are planning on something else I would like to hear details if you care to share. |
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| SuperDave |
Myren, and anyone else....the sku for the parkland plas-tex screen is:
637553000012
Later,
Dave |
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| xblocker |
ChuckReese,
i have to correct one point. The distance between the lightsource and fresnels should not be 6", but around 12" to get the lightsource imaged on the other side at the same distance. Then you should get 2 symmetrical light cones the first diverging to fresnels, and the second converging to projection lens plane.
Good luck!
xblocker |
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| remp |
Xblocker
My projector setup does work. I don't say things work if they don't. But note the words in my first sentance "it is terrible".
Basically I just used a slide projector as a backlight and a fresnel as a projecting lens. As you can imagine the fresnel does not make a very good projection lens but never mind. At least I now have a terrible projector which I will improve.
I did notice something if anyone is interested. As mentioned the writing was reversed. I turned the LCD panel around so the front of the panel faced the slide projector. The writing was now the correct way but for some reason the picture quality improved quite noticably. Dont know why. There was no risk of burning the panel because as mentioned the light from the slide projector contained no disernable heat. Just shows you eh the things you find out. |
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| ChuckReese |
| quote: | Originally posted by Myren
<b>the problem with the light you listed (with reflector) is that the reflector is too small. the reflectors we're dealing with are huge by comparison, they have to be, were using them as the sole element to put the light through the LCD, and thus they need to be as big as the LCD, or bigger. </b>
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I suggested these reflectors because they allow you get the most of the light concentrated to a small (2-4 mm) spot. I am fully aware you would still need a condenser lens, but at least you get a decent metal halide that is a point source.
Something else I forgot to mention... the Solarc bulbs (marketspeak for their metal halide technology) have a very short arc gap so they can focused to a small spot. Combine a short arc gap with an elliptical reflector and you get a point source. The LM60 can put 1000 lumens through a 4mm spot.
These source are are really tiny. The bulb module measures 80mm x 70mm x 70mm. The ballast measures 60mm x 60mm x 30mm.
CR |
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| Marklar |
I said earlier that I got the 250W MH thats only rated at like 10,000 lumens here are some pics of some ideas and my progress.
Here you can see I just wraped foil around the bulb this is only temp unless it really works on the big bulb I then used a normal maginifing glass to spread the beam onto the mirror.
There is just a small hole in the foil for the light to come out and the bulb is in a sealed area it does have a large fan to keep from burning up I had it on for about 2 hours to see what would happen the only part that got real hot was the top door cause its touching it. The new bulb Im getting is going to be smaller so I won't have to worry about that.
looks like a normal OHP setup Im going to stick with this until I get it working properly then I will build a nice case for it all to fit in to keep all the light from shining out.
I put a paper plate under the projection lens and you can see the shape of the arc tube its not a point of light its a rectangle about 1 inch X 3inches
This is my plan on how to make the focus point an even square so it will light up the LCD panel evenly.
This is about 6 foot from the projector.
This is about 17 foot from the projector the room had to be very dark to see the image there is no way this bulb could make a visiable image in low lighting conditions. |
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| prjctr_builder |
I finally got all my funds in place and now i am very much ready to START where i left off. I have a whole notebook of drawings and calculations, hehe....
Anyway, MYREN, you said that you have built a projector successfully, what kind of design did you use? The overhead type or stratight in line?
The reason that i want to make a projector is that i want to run FLIGHT SIMULATOR 2002 on it. i think that it will look very good in the wall.
I think that i am going to use a 17" ViewSonic LCD monitor as my LCD screen, and try to build it in a straight line design....hehe
But before i insert an LCD in there,i just want ro make a really bright projector, and then try to focus it.
ok, just updating you...hehe
aleksey |
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| xblocker |
Richard,
ok, working is a relative term. All is working anyhow, for me working means to do the job. But if the panel works this is most important.
Did you find a setup menu where you can adjust projection parameters? How is the image improved projecting the 'wrong' side? I would say there's a lot to improve in your actual assembly, but you know it yourself.
Welcome in the Pixelfriends club!!
Good luck !
xblocker |
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| xblocker |
Aleksey,
could it be that we all experience a big surprise, if you have finished your flight simulator training....Hehe ?
Seriously, 17" has of course great resolution, but is way to big to get affordable parts for it, especialy condensors, and you would need projection lens with focal lenght more then 17". This projector will be a huge chickenhouse,,,hehe!!
xblocker |
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| remp |
Xblocker
Not a lot to improve. Just picture quality, colour, more light, I spent all night looking for 12 inch lens no luck but did find surplus site with lots of lenses
www.goldmine-elec.com
No can find the text reverse. Must be computer controlled. There is a menu. Its no problem at the moment.
Picture improved when panel reversed by more light through. Better colour and page magnifier not nearly so critical in position.
Could be the panel is made to accomodate angle in light it would get when sitting on an OHP. |
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| xblocker |
Richard,
why not improvise with 2 eyeglasses, each with about 600 mm. So you get a projection lens with f=300mm. Eye glasses are better than planconvex lenses because of less spherical aberation. The formula of dioptrics: dpt=1/f. I got a lot of glasses for 0-Bucks !
xblocker |
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| prjctr_builder |
i dunno, but i think that i will use a projector headlgihts ( from a car) as a light source. It has a condenser lence installed, and spreads light evenly.
as to the size, i have a 3 car garage, lmao..... all i want is to make the image appear on the wall, and then try to modify it and make it smaller.
i am pobably going to buy a PROXIMA 842 projecton panel from ebay.com, just in case it will take time to get the monitor and take it apart. i am anxious to start.
Tell me what you think.
P.S. don't tell me car headlights produce a lot of heat, because i WILL remove it, after all i have a head on my shoulders for some reason, it may be useful now. |
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| SushiMasterX |
Maybe worth a call, I might get lucky.
I may delve into some of the ebay virtual glasses soon:
Sony's 700 Glasstron has 800xRGBX600 0.7" x2 color panels (~$700)! The 50-55's have 800xRGBx234 (still great for wide screen- DVD! 100-300$). Can't get any spec's on these like contrast. But, could be a way to pick up some small hi-res lcd's for a projector.
.....THAT'S IT! To tread further, is to contemplate the sound of one hand clapping:
GunawanD: Saya e-mel anda pada masa sekarang. Beberapa maklumat sangat rahsia! Tidak seorang pun dapat memahami, ha-ha-ha! I am always joking! Jantung sedih, saya mempunyai. he-he....1,000,000 lumens?! Wow!....Mereka tidak memahami....Cuaca bagaimana? Is it really THAT secretive!?!...Saya menganggap mereka sebagai semua percubaan gila sekarang!...Okay, be careful with the plutonium!...Kami ketawa sedemikian keras sekarang. Ha-ha-ha!
Don't get the I-visor or Cy-visor unless you want to go the reflective way. Which seems troublesome for me at this point since it requires three (RGB) light sources and their timing and modulating mechanism's.
But, this may well be the best technology has to offer currently, as one of the JVC model's with reflective panels has impressed some journalists' into saying it appears as good as "35 mm print"!
They are really great with color saturation and contrast. Problem is, they require twice as much wattage to get the same lumens out, as transmissive do.
Still, cheaper (per lumen) than the BEST the other technology's have to offer, though! Lokost is working with one now in addition to his large panel. If he can DIY the lighting req's that could be a smaller portable hi-res (svga,xga,sxga) alternative. |
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| prjctr_builder |
Today i went to the auto parts store....
-Hi, do you have projector headlights?
-No
-do you know where i can get them?
-Probably Home Depot
-do you have anything else that may be as bright?
-Check on the shelf, there's everyhting we've got...
-i need projector lights because they have condenser lenses on them installed.
-what are the con-cond-condenser lenses...hehe
-ok never mind!!!
guess i have to go to Home Depot to try my luck out.
Aleksey |
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| remp |
| Bought a larger page viewer today for my setup. Nealy gives the whole screen. Much better than the old one I was using. With the front of the panel facing backwards and the new page viewer the picture is just about showing pixelation so resolution is definitely improving. Also took my panel down to friendly lighting shop | | | |
