| Iceshack |
| :mad: That is really not nice at all.What is this world comming to when this happens.It is out and out stealing.I hope you have a way of going after this person/s that did this to you. |
|
|
| PEBurton |
I have read for what seems like days, weeks and months, trying to get caught up to where everyone is at the present time. I would like to make an observation and ask a question at the same time.
It seems in the quest to get better picture quality for the OHP at first, and then in the Custom built projectors to follow, everyone is going to a larger screen. Larger screens provide better res and are cheaper I am assuming.
But with the larger screen you require much more light and with the light comes the heat problems and heat displacement measures i.e. glass, low e glass and the likes, which are not 100% effecient so you need even more light, which washes out the screen, and the resulting image is not bright enough so you go to a bigger lcd.
With the bigger screens you require more optics to make the larger LCD image evenly lit and small enough to fit on the projection lens.
and the cycle starts all over.
I have looked at the lcd projectors and they are not getting bigger as they are getting brighter and better.
Would it not be easier to start with a very high quality small LCD which would be able to handle a smaller more focuses back light sorce having less heat problems and less optics to blow the immage down then blow it back up again to view.
I am no scientist but I am learning, but it makes sence to me. In this case I am not sure bigger is better. We seam to be making bigger and bigger which needs brighter and brighter which creates hotter and hotter, which requires more low eglass and cold lenses which cuts down on the bigger light source you just put in.
Am I totaly off here or does it make sence?
Thank you for taking the time to read and respond.
PEBurton |
|
|
| zardoz |
I believe you are right...this LCD will be "unworthy". You have the right idea but there is a problem....as far as I know NO ONE has managed to find a "small" LCD that was worth buying for the money asked or the performance offered. What I mean to say is...."tiny perfect LCD's" are worth their weight in gold to the seller and "affordable small LCD's" are crappy low res toys.
Keep hunting and maybe you will save the day for us all.
zardoz
|
|
|
| slize |
sorry to say that, but leds won't work. do you see the brightness of these things: white leds 5000-7500 mcd.
:nod: 5000-7500 milli candela!!! ; candela = lumens
we are talking about 5 to 7,5 lumens !!!!!!!
in this forum we have problems with lamps which have 10000 to 35000 lumens because they are not bright enough to make a good picture.
And u are really think about 5 to 7,5 lumens. I would say forget about the led thing... there might be refelctors which make the leds 5 times brighter but even then, we are just talking about 35 lumens...
so may be they are good for a backlight of a tft but they will be never good enough for a projection, or if so they won't be payable... |
|
|
| XanderSnyder |
I would tend to disagree with you about the led's. I am a member of diyprojection.com and we have been bouncing arround the idea of leds for a while (by the way if you havent seen that forum you need to it rocks and every is really helpful) but i was thinking about using an array of 120 to 140 10000mcd super bright white leds (these average about 12.3 to 20 lumens depending on quality) thanks that that fourm we have found a place that sells then in packs of 20 for $20.14 US, ill post the link later. so that meens that the output would range between 1,722 lumens and 2,800 lumens, if you were to use that in conjunction with BRF film from 3m that should be birght enough to watch in a dimly lit room
Xander |
|
|
| Redevil |
The future is L.E.D lighting.
I have already seen trucks in my area using the LEDS for there
brake lights. They are also thinking of using them in our street lights. Ten year life span, no color shifting, very very low power
consumption. They will also be making car headlight with these things.
Then I grabed my $30.00 LED flashlight and put it behind my LCD
and behold, I laughed. Not much of a picture for a two LED
light, but sure enought it was there.
It may be worth it for someone to atleast try it.
L8r |
|
|
| noodles |
| A Luxeon Star LED has about 660 candela. And if candela = lumens... then well, you know the rest. |
|
|
| verbose mustafa |
| daaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! cd does not = lumens!!! I am going to make a section of my web site on how to convert the numbers. One 10,000 mcd led with a viewing angle of 15 degres is 2.1509 lumens. I lexeon emitter (if i remember from their website) can go as high as high as 150 lumens. |
|
|
| slize |
| no its not its 6,66 lumens :scratch: |
|
|
| slize |
ooopsss :eek:
yes u are right: here is the formula
so 10000mcd * 15angle --->>> 150000 m lumens
so 150 lumens is right...
but even then we are just talking about 150!!! lumens and is still a long way too 35000 lumens...
and the leds posted here had max 7500 mcd that would be 112,5... |
|
|
| slize |
| quote: | Originally posted by noodles
A Luxeon Star LED has about 660 candela. And if candela = lumens... then well, you know the rest. |
so the luxeon star led would have about 10000 lumens, but i think the viewing angle is the problem. u won't be able the light up the whole lcd.
there would start again with a small lcd with good resolution... :( |
|
|
| slize |
What I ordered is a Luxeon Star/O LED, part number LXHL-ND94. I grabbed the datasheet from Luxeon's website, as well as a few other interesting documents. Let me give you the quick technical specs on this LED: Typical Candela on axis 660 Cd
Dominant wavelength 627 nm
Typical luminous flux 44 lumens <----- :cool:
Junction material Aluminum Indium Gallium Phosphide
Typical forward voltage (Vf) 2.95 V
Forward test current (If) 350 mA
Max. forward current 385 mA
Cost US $15
the link: http://www.bit-tech.net/review/82/ |
|
|
| noodles |
^ Yeah that's where I saw it.
I went to the Luxeon website and it says their most powerful light output of the Luxeon family is the flood. It consists of 12 or 18 emitters. With an 18-emitter white Luxeon Flood... the typical luminous flux is 325lm. I bet the price of these things is pretty high too...
But the best part is that it's low-heat which means you don't need noisy overheadprojector fans. And they last around 10 years, so you don't need to buy replacement bulbs. I'm sure when 10 years comes around though, commercial LCD projectors will be extraordinarily cheap... but whatever. It's not an easy or cheap task... but it's nice overall. |
|
|
| verbose mustafa |
| Actualy, luxeons are not low heat. You really need to have a heatsink when you run those things. |
|
|
| noodles |
Ok... then I guess we can rule that one out then...
Is Metal Halide still the reigning king of projector lighting? What do they use in those commercial LCD projectors? |
|
|
| verbose mustafa |
| Well, that can be delt with, but at $40 for a 150 lumen 5 watt emmiter... thats a little pricey. |
|
|
| slize |
no leds are not bad after all, may be in 2 years they have one that we can use...
but for now i would say MH bulbs are best for diy projectors... the hours about 2000h - 8000h depends on the model is ok. only problem is you need at least 400W and better 1000W what i heard... i am still waiting for my 400W MH bulb, then i can say more... MH lamps are ok in price (about 50-100$)
in projectors they use NSI bulb for example. don't ask me whats that exactly. all i know it is very expensive (about 400$ one bulb). they last 2000h and have a lumen output of 100.000+ with 250W. some are in a vacuum. i guess these lamps are so expensive because of their special producing |
|
|
| prjctr_builder |
hi guys, i have a few questions and requests for you all. i want to install 50W Metal Halide bulbs into my cars headlights, so what i am looking for are two 50W MH bulbs and 2 ballasts that would power them. if anyone has any information on where i can get these items at a reasonable/cheap price, please let me know asap. my email: ikutuyev@sbcglobal.net thanks in advance
P.S. keep up the good work...
aleksey:bigeyes: |
|
|
| eebasist |
| definitely easier to buy a retrofit kit for like 300-400$. This is for multiple reasons...the MH lights in cars are the quick start ones....you cant afford for them not to light up instantly like we can with projectors. Second, the DS2 (one of the types) bulbs are vibration resistant most others are not. Also these ballasts need to be the high voltage kind of ignitors, plus weather protected.....this is one of the few areas a DIY should not try and source ontheir own (unless you can get the same parts cheaper). Another issue is that the lights wont be as good as factory HID lighting because the reflectors are designed differently. |
|
|
| tikaro |
Hello forum!
This spring and summer, I'd like to start a "guerilla drive-in" in my hometown. I want to attach an LCD projector and an FM transmitter to my car, and hold last-minute drive-in movies at secret locations, advertised via flyer and email:
http://www.guerilladrivein.com
Now, here's my challenge: I don't have $2,000.00 to spend on a super-bright LCD projector. I don't even have $400, or $300. I want to build my own punk-rock commando projector.
So far, I've been impressed by Zark's twin-fluorex projector, and I've already got the worklights purchased and in the closet. I plan on building a prototype as quickly as possible, then testing it outoors in a snowy field (maybe John Carpenter's The Thing?)
I have some questions, and I'd appreciate any advice or encouragement you can give me. Mainly, I'm wondering about the distance a CRT rear-projection video lens will throw an image. Is the angle so wide that I'll have to keep my commando projector super-close to the screen? That might not be the best thing for a drive-in. Any thoughts on selecting a good lens?
I'd also be interested to hear your thoughts about the feasability of the project in general. Image quality isn't paramount, as slightly blurry DIVX rips of "Repo Man" at 640x480 will be fine. Also, ambient light won't be so much of a problem, as we'll be picking moonless nights and dark locations. However, the distance from the screen will be much longer than is usual in a home-theater setup.
Do y'all have any thoughts? I'll be sure to post results.
Best regards,
John Young |
|
|
| zardoz |
I've had the same thoughts :) ...bear in mind you will be thumping the "copyright" laws maybe...along with possible tresspass/illeagal gathering laws that may apply. But it would be fun :devily: At 10 feet from my screen my 3M 9550 puts up a 10 foot by 8 foot image, I have no idea how far I can push this image. At this moment I can't get the PJ in a location with a longer throw.
I'm experimenting with a 12 volt DC "mini PC" to see if it will accept my LCD controller, so far however no luck (my controller doesn't like AMIBIOS, it prefers AWARD)
zardoz |
|
|
| tikaro |
| Zardoz, believe it or not, I'm going to try to stay legal by getting a project licence from Criterion USA, and asking private property owners' permission first. I'm doing this with my wife's younger brother, who's a punk rocker: I'm going to be in charge of not getting TOO illegal, and he's going to be in charge of not getting TOO dorky! |
|
|
| rmccoll |
I have two lcds for sale for $125
Sony Playstion 5 inch lcd, it does not have a backlitand and it is not in its plastic case I can send it with the lcd if you want, it works great power supply included.
Parts Express 4 inch lcd still works, but only half the screen works I tried to extend the ribbon cable, backlit works power supply also included.
2 13 watt flouresent bulbs (eqiv. to 75watt) ballast and switch included, a 12 volt cooling fan.
And a assortment of lenses 3in Delta lense, 3 and 4 inch glass magnifying lens |
|
|
| zardoz |
That's cool...it would be a blast to organise. I'd recomend that you use something more conventional in the lighting department if you are looking for "the side of a barn" sized images...LOA's just AINT gonna do that. Do this project right and your onto something...do it with junk and you'll waste your money and you'll never live it down with your friends ;)
zardoz |
|
|
| Johnny |
HI ALL!!!
I am a hungarian boy.
I can't buy small LCD panel in my country, but I want to build a projector.
I thought that I will buy a TFT monitor with 1024x768 resolution.
With that panel+a fresnel lens+metal halide bulb+lens I build my projector. What do you think? Sorry, but I don't speak (and write) english very well.
thanks: Johnny |
|
|
| mgerny |
I just received my 5" Lcd from a private seller on ebay.
I had the Lcd working, and looking good. All I had to do was set the distances for the fresnel, and the lcd. The lcd stopped working after about 15 minutes of play. The power is good to the unit, but the unit is no longer working. Help. Does any one have an idea. |
|
|
| ap0the0sis |
heat kills, ehh.... were you keeping an eye on the temperature of the lcd? sounds to me like it burnt or the controller burnt. Maybe it was "defective" and you should consider returning it for a new one.
ap0 |
|
|
| mgerny |
I guess that is possible, except the lcd was only in front of the light source for 2 minutes of the bench test.
I think the unit has a defect.
Unfortunately this was purchased from a private seller.
It is a parts express 5" lcd module.
I think I will try another one, but i have recently stumbled across a 2" lcd that has the same resolution. 896 x 230
http://www.vfmstore.com/tv212.htm
what does everybody think?
I am currently trying to get the specs on this lcd to see if it there is a way to get the light through it. |
|
|
| davesos |
Fellow DIYers:
I have been following various threads on this website with the efforts of so many to construct a straightforward projector of reasonable size and cost.
I believe the ideal first projector is embodied in the CTX 550 design which has a single LCD panel of 6.4", compact size, 800 by 600 svga, and simple construction. For more details, consult (http://www.gotocol.com/ctx550.html ).
I would, of course, jack up the light source for more lumens, use a larger lens and put it into a different package. However, the design is straight forward.
The chief question is where can we obtain a panel that small with that resolution?
David |
|
|
| zardoz |
a laptop
zardoz
| quote: | Originally posted by davesos
The chief question is where can we obtain a panel that small with that resolution?
David |
|
|
|
| slize |
hi dave,
the answer is: no where. Not for a good price... firms buy 10000 of this lcd s that's why they are able to build a projector for 1800$ or 1200$.
To buy such a thing is not a bad idea. But for me the main question is, what costs a replacement bulb... normally 250$ up to 600$. That's why i don't buy such a thing, because i can't afford the bulbs. And if you buy such a lcd panel it will cost you 1000$ plus the controller to connect it to the TV...
but may be i can help you. i found a page with a 10" panel (800x600) plus controller for about 500$ here in Germany. If I find the link i will post it.
best regards andy |
|
|
| zardoz |
You would waste your money. For less money you can buy an LCD controller and a laptop screen with better resollution, contrast, etc.... Buy the LCD from Ebay and you have a very wide sellection of screens to choose from, and cheap.
zardoz
|
|
|
| slize |
so YOU would get a better resolution than 1024x768 with a laptop panel at 12"??? i don't think so... and if it is like that, please show me the links. And if i got you right you will need a laptop too? Because if you need one it will be hard to find one for about 399$ plus panel plus controller plus remote controler. But please show me the links i am very interested in that... And if you don't need one... please show me the links...
By the way everybody knows laptop panels have a bad response time and a bad contrast ratio too, worser than that panel; at least those we can afford... |
|
|
| zardoz |
Check out the LG 121X04 panel. 1024x768 on a 12.1 inch LCD, I bought one on Ebay for $25.16 USD. Yes a seperate controller card is required. I bought mine for approximately $150.00 USD and it will support several LCD types. Who exactly is EVERYONE? Currently I am running an OLD LCD very slow compared to what is on the way to my house, the old panel I am using does not have responce time issues (I'm replacing it for the higher resollution). I think you need to look some more....150:1 is NOT a good contrast ratio, my crappy old Sharp LCD has 300:1 contrast.
Also look at the very tightly integrated setup of the unit you linked. It does not look to be easily dissasembled ie: remove controller board out of the way and remove backlight. If you destroy the LCD trying to make this work you are left with basically junk (unless you can find another of the same panel it uses) If I break an LCD panel...I throw it away and look for another (I have a big list of approved panels for my controller)
zardoz
| quote: | Originally posted by slize
so YOU would get a better resolution than 1024x768 with a laptop panel at 12"??? i don't think so... and if it is like that, please show me the links. And if i got you right you will need a laptop too? Because if you need one it will be hard to find one for about 399$ plus panel plus controller plus remote controler. But please show me the links i am very interested in that... And if you don't need one... please show me the links...
By the way everybody knows laptop panels have a bad response time and a bad contrast ratio too, worser than that panel; at least those we can afford... |
|
|
|
| slize |
you are right.
do u have pictures of your projector? i am very interested in it.
where did u get your controller card from? does it work single? or is a pc required? does it support pal or just ntsc? what bulb do you use? etc. etc. I guess you have a homepage about that. Can u give me the link?
P.S.: EVERYONE is basicly me :rolleyes: ok that's not everyone but it is MY opinion...
best regards
Andy |
|
|
| zardoz |
I don't have a web site up yet.. but think I might soon. My controller is a PCI LCD controller, so a computer is needed. There are a lot of suppliers for these but they aren't easy to buy as "one off's" they can be expensive when bought individually. My controller is a Spectrah LD S270M, it has limited use for gamers as it has only 8 megs of Ram.
It plays DVD's and games like AOE just fine though, I have other "non related" uses for this card though so it was a good choice for me. If you want a "stand alone" controller it will cost more.
My system is currently using a "low grade" LCD and gives me a wonderfull image (my much anticipated new LCD's arrived smashed :( ) I run a 3M 9550 OHP to provide the light, it is un modified so far....
I have a VERY large lens on the way that I might play with before I decide on the PJ's final form of construction and eventual use.
For TV I use a TV tuner card.
zardoz |
|
|
| chbright |
I am looking at some lcd screens and was would like to know what is more important: response time or contrast ratio.
I've found some NEC panels but the contrast is 150:1 with a response time os 12ms from full white to black. this is a 14.1 in panel. If i move up to a 15.4 with a 7ms resonse amd a 200:1 contrast ratio, but this would be difficult to put on a ohp. Any recomendations.
Also found this6.3 sxga |
|
|
| ace3000_1 |
Here is a simple idea to make your fans quieter for your ohp projector or the fans in your diy projector casing.
Well its quite simple realy just use rubber gromets that you find in the electrical store for next to nothing and put them in the mounting holes, simple..............
Also the fans you buy that they say are quieter have ball bearings rather than a bushing so if you go to buy a fan from some surplus store get the biggest you can get depending on the size you can fit, the slowest rpm say about 2500rpm is the best and make sure it is a bearing type, use the rubber gromets in the mounting holes and magic, the only noise you should hear is the air moving not the fans.
Regaurds Trev..........;) |
|
|
| slize |
What do you all think about that?
This is just to give this forum new inspirations. I had this idea yesterday so i didn't have the time to try it perfectly. I tried it with simple conditions. With a picture on an ohp foil a simple lamp...
To all those using a tft from laptops or pcs or whatever. didn't you always think how to extend the ribbon cables on the back of the tft? Well i'm sure you did in order to use the whole tft just like i did think about it. it is a hard thing, nearly impossible, to extend those and dangerous too because you could destroy the whole tft. with my idea you wont need to extend it and will still have the whole tft for the projection.
here is the idea:
why not taking all out of the tft as usual; backlights etc... but instead of puuting the whole tft apart, after that you put it togehter again and then the projection will work. How is that possible you ask...
Take a look.
You put a mirror right behind the tft, where there was the backlicght etc. i used a mirror burned on polysterol. it is a special mirror (it has no glas before the reflecting area, so the glas won't reflect too) and it is cheap... it just costs about 5$...
the new thing is you won't let shine th elight through the tft but right onto it; advantage you can use the wohle tft without taking it apart. after you placed the mirror behind the matrix you put it back together... i made sketches of that: it works but i hadn't have th etime to test it with a fresnel lense yet...
the biggest advantage is you wont have to take your tft apart at all after placing the mirror...
and may be ther ewill be more light because of th emirro; but i will hav to test that...
and may be you wont have temperature problems if you coll th emirror etc... but i will have to test that either...
here are the sketches:
i am sure everyone of you who has taken a TFT PC Monitor or whatever knwos what i am talking about; so let me know what you think about that... |
|
|
| verbose mustafa |
| I think the image will be washed out and blurry, and light would not reflect at that angle the right way... Nice idea though, worth a test. |
|
|
| ace3000_1 |
I think that idea would work because some projectors do work like that, but i tend to agree with verbose because an LCD can only be veiwed at certain angles before it gets washed out, but if u can get the light to as close as possible so it is more or less right in front of the Lcd then it could be a goer, Great idea though.
Ive included a pic in what ive done with my Lcd to give you guys some ideas, also if you bend the small Lcd Ribbon cable so its strait you risk it very badly to breakage, that is why ive done this with mine.
Trev
P.S my cable looks like it has been pulled strait but it hasnt its at a right angle, sorry for the bad pic too lol |
|
|
| 18wheeler |
| quote: | Originally posted by slize
What do you all think about that?
the new thing is you won't let shine th elight through the tft but right onto it; advantage you can use the wohle tft without taking it apart. after you placed the mirror behind the matrix you put it back together... i made sketches of that: it works but i hadn't have th etime to test it with a fresnel lense yet...
|
you can use a reflective projector to try it first. |
|
|
| ace3000_1 |
| That is what i meant i just coudnt think in the name of it as ive seen too manny with fancy names lol but yess i would give it ago if i wasnt so busy building one already that ive planed;) |
|
|
| biteon |
ohp people
if u raise the lcd panel, dont you get way way more more light going through the lcd panel. the way i see it is the light all around the panel thats on the fresnel/glass is just waste and more light to light up the room. i got to go to work later.
:) :) :) :) |
|
|
| ace3000_1 |
Ok i dont have a ohp but i know how frensels work as im building my own custom projector from scratch with a frensel involved.
Ok now those of u who use smaller lcd's like say a 6inch or a lcd that is smaller than the top of the ohp u will have much light loss around the lcd because that light isnt going through the lcd and just lighting up the room, now the thing is the frensel on a ohp is not fully focused to the frensel on a ohp because it is manufactured so the light source covers the whole of the top of the ohp.
Now because u can not move the frensel up and down to find a focal point , try to move the light up and down inside to make the bulb show on the wall (u can do this and u should see the actual light bulb on ther wall) and therfore being a brightness increase to max output.
I know for a 6inch lcd that would be fine but for other sizes it would be a trial and error to get the desired size for your screen and ofcourse u will get some light still in the room but mask it off around the lcd, and by doing this u are getting the most light out of the ohp for your size lcd u can get, i hope i didnt make it too hard to explain but im alittle tyred right now.
Regaurds Trev
Good Luck!!!! |
|
|
| ace3000_1 |
sorry guys i meant the ohp's frensel is not focused to the light inside of the ohp for smaller sizes, also put the lcd ontop of the projector and see if the lcd is bigger than the bulb on the wall and just focus so the light is just alittle bigger than the lcd on the wall so u dont get any bright spots
Trev;) |
|
|
| davesos |
Dear slize:
I think you have a great idea! I encourage you to pursue it so that we can all benefit from your experience. Essentially what you are talking about in terms of the light placement and the use of a mirror as a reflective device behind the lcd panel, is a reflective system. The concept is sound.
There are two types of projection systems used commercially that embody the reflective concept. First and most common is the dlp system by Texas Instruments that is a micro reflective mirror, albeit using a micro mirrors and a color wheel, but it is reflective and offering some of the best images out there.
If you want to see a knockout system look at Samsung's brand new rear view dlp projection unit. I saw one in Circuit City that just arrived this week, and it is phenominal! It blows the doors off the lcd and plasma panels and the super sized cathode ray tubes. The image is brilliant, intense colors and highly contrasted. You can adjust the picture values on this system, and I did so, that they are surrealistically intensely without color bleeding. Look for more models to follow. It is pricey in a 50" unit for about $3500.
The second system is a reflective LCD unit that does largely what you are proposing namely using an exterior light directed at the panel rather than through it.
The advantages of you succeeding is our having to avoid disassembling the panels as extensively, potentially using more of the light by having the combination of the reflected light from the surface of the panel combined with the light that passes through and is reflected from the mirror foil and back through the lcd panel.
The trick will be testing the angle of light incidence with respect to the lcd panel surface in terms of the polarization effect, the absortion of light in the panel and panel surface, and how much light passes into the panel is reflected and passes out panel.
Assuming you can master the angles of light, you then have the task of gathering the two sources of light, surface and back reflected, with a lens to project to a screen surface. You may be well served to use a thin fresnel behind the lcd panel if you can master that to focus the light rays into the projection lens.
I urge you to experiment and advise us of your effort.
David |
|
|
| Mavmesa |
Finally read this entire thread... exercise in preseverance.
I am building a PJ with 400 watt MH and Desktop LCD panel as I want the higher quality specs. and possibly the salad bowl reflector.
I picked up the NEC 1550V Panel today as I read in the DIYPROJECTION forum that someone in New York used the NEC 1545V with good results. The actual LCD module is a LG Phillips LM150X05. I have it disassembled to that point, but cannot find a way to remove the final partial medal shield. Anyone have any ideas? Its almost as if they "glued" 2 or 3 overlapping metal plates together during assembly. I could bend the medal away, but am afraid I will damage the thin circuits underneath.
I love the idea of using the LCD PCI card, but I need more than 8 Meg of Ram!
I love the salad bowl idea.
I did find a small lighting shop that carries Maglatek (?) ballasts, but they carry only magnetic ballasts. Guys, do I want a magnetic ballast (multi-tap)? Are there electronic ones? Do you notice any noise from your ballasts? This lighting guy is intrigued by the PJ idea, and is going to let me go through his old stock to see what kind of reflectors I can find.
Thanks for stepping into holes before I get to them. |
|
|
| slize |
hi davesos,
thats where i got the idea origianlly from: from the dlp concept. but i figuered out one problem: the anles. the problem is th emirror is behind the lcd and then you project it with an angle of 45 degrees. then the point which was orriginally lets say green goes through a red point and the light will not come on the wall in the right way.
my newer idea is to solve this problem with a mirror which lets pass light through one side and on the other reflect. made a sketch of that again...
problem is to find thos mirrors. i remember someone came up with thos mirrors with another idea, so someone found it. i think they weren't that expensive... i'll keep on looking for that
what is this type of mirror called again? may be we get a little closer to th eproblem with the heat through this kind of mirror...
best regards andy |
|
|
| verbose mustafa |
| I have seen designs like that on the forum before, but i do not belive any one has tried it. It's worth a shot. |
|
|
| verbose mustafa |
| According to that site, the side that the light is on would reflect the light all over, and very little would pass through, and little bit of the light reflecting off the lcd would go right through the mirror back into the light chamber. |
|
|
| HanClinto |
Hey! Great thinking on putting the mirror in place of the backlight!
The only thing I see with that is that you're going to be passing your light through the LCD twice, and that could definately kill alot of your sharpness (shadowed images), and much darker (because it's going to pass through the LCD twice). The tighter the angle that you make, the less ghosting that you will have. Also, because it polarises the light going through the LCD, and that's where the majority of your light loss occurs, you might not have too much of a problem with the double-pass light-loss.
In conclusion, there seem to be drawbacks to this idea, but I would like to see if the penalties from such a method outweigh the advantages. :)
--Clint |
|
|
| slize |
| new idea that will work i think: |
|
|
| slize |
old design:
you see the difference? the new design would be very compact: |
|
|
| zardoz |
Where does the fresnel go?....among other obstacles..
zardoz |
|
|
| verbose mustafa |
Zordos,
This seems to be more like the zark design where you just brute force light all over the place and some eventually hits the lcd. |
|
|
| ace3000_1 |
Heya guys i personal think the frensel would go between the lcd and mirror but the light would go through it 2 times, the only mirror u could use for this aplication would be a surface mirror not a standard one because with a standard one u would get too much interference with and loose too much light in the process and also i personally think the image woulkd be blury because the light source would interact with the projected image light coming out, therfore the image blury and washed out.
Trev |
|
|
| slize |
sorry to say that, but you're not right verbose,
the fresnel is beetween the tft and the mirror. just like the ohp on light type in contrast to the ohp through light style... |
|
|
| ace3000_1 |
| too much interference with differences |
|
|
| slize |
hi ace
i think the light washing out the colors of the lcd will be a problem...
i will see that, when testing it
i am thinking an projector working like an epsidiakop, there the thing works too, without washing out the colors from the pictures... |
|
|
| zardoz |
epsidiakop?
zardoz |
|
|
| slize |
ace,
i am using a mirror from a homework department,
the mirror surface is burned on polysterol -->> no interferences whatsoever |
|
|
| ace3000_1 |
Heya slize, i think your design is very doable but do some research and thinking before u experiment so u dont waste too much materials lol im making a projector at the moment and touch woood mines going smooth mainly because i did some research and alot of thinking, give me a couple of days and ill think of an idea for yours but bear in mind the optics might cost abit like the surface mirror and another thing im thinking in for ya that ill draw up soon.
Trev |
|
|
| slize |
| in german it is called episdiakop i'll post a link as soon as i find one |
|
|
| ace3000_1 |
ahhhhh i dont know that place or shop or that mirror lol just get a surface mirror with no glass on the front of it, the type that has the mirror before the glass and thats the first step to getting it going and make sure it can handle heat, another thing with heat use not only a uv filter glass but also a clear ir filter glass cos ir carries the radiant heat not so much the uv and if u use the ir glass filter u will not need a cold mirror as the ir filter glass does the same as the cold mirror but just a diff aplication.
Trev |
|
|
| slize |
that's what i meant trev :)
me has bad english :( |
|
|
| verbose mustafa |
| quote: | Originally posted by slize
sorry to say that, but you're not right verbose,
the fresnel is beetween the tft and the mirror. just like the ohp on light type in contrast to the ohp through light style... |
I tend to differ! :) If the light is first going through the lcd then a fresnel, hitting a mirror, then going back through the lcd, the colors would become distorted and the image would be nothing but a blur. Please correct me if im wrong on that. Many people in the forum seem to be a little fresnel crazy, but it is fully possible to make a projector without one. |
|
|
| zardoz |
Glare from the light first touching the LCD will be more than enough to overpower and wash out any image is my bet. The "epsidiakop" looks like an "artograph" we've had members try those I think....as I recall they were less than suitable.
Good luck if your idea is significantly different from an artograph and you make it work.
zardoz |
|
|
| ace3000_1 |
Slize this would work forsure but u need to get the 2way mirror glass, they use it in the 3 lcd projectors.
Trev:idea: |
|
|
| ace3000_1 |
Better to put a convex lens over the light to intensify it rather than a frensel, im sure the frensel will wash it out as we say
Trev |
|
|
| verbose mustafa |
| Im telling you, that fresnel with blur out the image. You are basicaly sending a projected image through it twice. Fresnels are not made for projection! |
|
|
| ace3000_1 |
| Funny that projectors have them!! |
|
|
| ace3000_1 |
I know what u are saying verbose but let the guy experiment abit eh? with a surface mirror and a page magnifier it could work as the tollerences with the image are so small compared with a normal mirror and with the light going it through it the first time how can the image be focused on the mirror to wash it out? it will be out of focus the first time cos its so close to the mirror and therfore the light will be magnified and the main lens focuses to the front of the lcd very well lit up, the only prob ocurs is if u focus to the mirror not the front of the lcd, anyway lets see what happends, as i say i ionow what u are says verbose but i think with the surface mirror it could work.
Trev |
|
|
| verbose mustafa |
| Your right. I dont mean to put everyones ideas down and it is a only a fresnel. I cant wait to see the results of this project if anyone tries it. |
|
|
| ace3000_1 |
| Yeah i would try it but at the moment im in the middle of building this one...... |
|
|
| slize |
i would try it too, but i finished with my projector now, and it's awesome, as soon as i get a digi cam i will post pictures...
100" image
400W MH bulb
PC TFT Monitor
self build casing, and it works great!!! |
|
|
| Mavmesa |
well, with help from my friends, I got my projector going tonight. What did they want to watch? Matrix, of course. This was a preliminary run to test the design. It works. Just need to seal light leaks, work on lense positioning, work on brightness, install fans, etc. Good image, but it can be so much better.
I am getting some haloing ( light bleeding in one direction) around words and such. Any suggestions?
Ken |
|
|
| verbose mustafa |
| You know... I really dont think much. I just started a class in video editing. Guess what??? I have acess to a top of the line digi-cams... The problem? No more diy projector... :mad: |
|
|
| neededandwanted |
On a reflective LCD system you absolutely don't want anything between the LCD screen and the mirror (except the built-in polarizing filter or a replacement one).
You want the light to go into each pixel as nearly perpendicular as possible, undergo it polarization and color filtration hit the mirror and come right back out.
The mirror should be a surface mirror, but not because of multiple reflections, but for reasons of shortening the distance the light travels between its two trips through the pixel.
A reflection perpendicular to a mirror will not have any multiple reflections to speak of. That problem only occurs when the light hits the mirror at an angle and you get two reflections--one from the glass and one from the metallic reflector on the back of the glass (the silver part).
As far as such a thing as a "one-way mirror" or "two-way mirror"--pretend that such a thing does not exist. They don't work the way you think they do if you are planning on using one like this. They block half of the light and pass the other half. They are 50% silvered on one side.
In use, they rely on a dark room / light room combination for their effect. Not much different than looking out you living room windo at night when the living room lights are on.
One problem with using a transmissive LCD panel as a reflective panel (for those of you trying this design with a panel designed to be backlit) is that the black lines between the pixels will look very different. On a transmissive panel, the black lines are opaque and get their "blackness" from blocking light from coming through. When you instead shine a light on the front of this panel, these lines will be illuminated, and tend to be a BRIGHT gray. (picture opening a window at night and shining a flashlight through the screen. You will lose a ton of contrast in the resulting image because the reflective light from the screen door will be scattered.
Slize, your design from 04/03/03 labelled "new style" will work using a reflective style LCD panel, but you need to modify it one of two directions:
[1] get the light landing on the panel more parallel and use a second lens between the panel and the final lens. It is possible to do this while sending the light throught the same lens toward the LCD (in the other direction). I'll send along a picture.
[2] go for the super diffuse lighting bombardment of the LCD panel and use a really big lens to capture all of the light coming back from the LCD to get it to the screen.
On other point about using a reflective screen-- If the arrangement is all in one box like this there will be a loss of color contrast as well. Here's an example: Imagine that you are showing an image on your screen like a Canadian flag. Lots of red and white. Inside the box, you will have lots of extra red and white bouncing around and this stray light, if it was only white could further illuminate your panel. But with a lot of red in it, it's gong to shine a bunch of extra red light on your panel, which will tend to cast a red glow on the image a bit. (As if the color temp on your source light was just lowered.) |
|
|
| neededandwanted |
Since the intention is to get a brighter (and larger) screen image, while maintaining picture quality, I thought I would toss in some data (and design viewpoints) regarding the treatment of light efficiency.
It would seem that, electricity being so cheap and all, that the efficiency of the system can be regarded lightly, but I would assert that this is not the case.
Any light emitted by the lamp that does not show up on the screen is wasted as heat somewhere. Some of it can leak out as well and go wrong places, lowering the contrast of the viewed image.
For each loss, if we can't recover the energy as useful light, we should at least control where it goes. IR light (for instance) getting absorbed by a filter is better than IR light being absorbed by semiconductors and LCD's.
So, let's follow the light path:
You have a lamp that is rated at (for example) 10,000 lumens. How much of that is visible light and how much is outside the one-octave range of human eyeballs? For our purposes, any component of the light in the IR and UV range is at best useless and at worst harmful to the components. There are passive substances that can recycle UV and IR light into visible light. They tend to be either expensive or useless. (In the useless category, think of a glow-in-the-dark frisbee, you can shine invisible light on it in a dark room and it will glow. That's the same principle that the expensive devices use: throw photons at something to raise its energy level. As the individual atoms drop back to their non-excited states the emit different-colored photons, in the visible spectrum.)
So, let's assume that we lose about one third of our energy to UV and IR light that wouldn't entertain us if it made it to the screen anyway. The thing to do here is first, find out about the emission spectra of the available lamps (some will have a lot more visible light than others), and second, proactively waste this light by shunting or filtering it out before it gets too far from the lamp.
Our 10,000 lumens is now down to about 6667 lumens.
The efficiency of our reflectors can be made really high, but since they tend to be made from rather shallow parabolas, lots of light is going to miss the target. We'll assume that some light is bouncing around non-parallel (for you LOA guys, this will be a TON of light) and will miss the panel, or strike it so obliquely that it can't go through. All of the designs I have seen using the point-source/parabolic method are casting a circle of parallel light at a rectangular target and the area outside the rectangle just gets masked off. That 'circle-outside-of-the-rectangle' we'll call one third of the light. This depends on the aspect ratio and how much bigger the circle is than the square, but one-third will be a good working estimate. (If your mask is a mirror with a panel-sized hole in the middle, score extra points here, since the returning light has some chance of eventually returning and becoming useful).
Our 6667 lumens just went down to 4444.
Next, we start to go through the LCD. First, the polarizer.
A perfect polarizer would cut the volume of light by about half. The cheap films used on LCD's will cut off about 2/3. Can we recycle the light? Yep. It's expensive or complex. You could work out a reflection-off-of-glass scheme that would convert all of the light to the correct polarity and even remove the first polarizer from the panel. It's doable, but not easy. (Do a search on "polarized" and "Brewster's Angle" if interested in persuing this.)
Our polarizing film just took our 4444 lumens and knocked it down to 1481.
Now the light is going through the liquid crystal itself. We have already accounted for the waste of the non-perpendicular light (for the point-source/parabola guys, not the LOA'ers), but we haven't accounted for reflection off of the panel. Shine perfectly polarized light on a panel and some light will bounce back at you. We'll be optimistic and call this reflective loss only 10%.
Our 1481 lumens just became 1333.
Here comes a whammy. (stick with me here...)
Now out white light goes through the panels Red, Green and Blue filters. All of the white light going through a red filter, gets stripped of its blue and green. The same goes for the other two colors. With a perfect set of filters this loss would be 2/3 of our light. We'll say our RGB filters are only 10% less than perfect. We'll also say that the "screen door" lines between the filters are only 10% of the total area of the panel.
Our perfect filters would have taken 2/3 of our light (and converted it to heat), so our 1333 lumens became 444 lumens. Our 10% less-than-perfect filters cost us another 10%, so we are at 400 lumens. The 10% for the "screen door" brings us down to 360 lumens.
One more polarizing film on the way out of the panel... But this one doesn't hurt so much, because our light has become 'twisted' in polarity to match up to it. We take 10% off for less-than-perfect alignment and filtering.
We have 324 lumens remaining that still have a chance at being a viewable image.
To get out of the box, our light will need to go through at least one lens (or curved mirror, but I haven't seen that tried yet). The most efficient designs are using a combination of a near fresnel and a far conventional lens, to avoid having to use a BIG lens. Each of these surfaces has some unwanted reflection. Each of these materials have some transmissive losses (and get slightly warm) and each have some surface imperfections which cause a small amount of stray light. For all of these, we'll say we get 90% of the light to go through (not get reflected or absorbed) and land on the screen exactly where we want it.
Our 10,000 lumens have been reduced to 292 lumens and we haven't hit the screen yet.
For everyone that ever asked "where in the hell did all of my light go?"
There are lots of points above where these losses could be cut drastically. The current fix is to simply dump in a LOT more light. You just need to make sure that the wasted light above (97.1% of the light we started with) doesn't leak out and cause a bigger contrast problem, and doesn't damage your internal components. |
|
|
| neededandwanted |
There are a few mis-conceptions about light that should be cleared up. After reading 1300 posts here and on the "part one" version of this thread, I thought a few people might be interested in some of this data.
"Lighting a small LCD is more efficient than lighting a large one."
Nope. Not true. The only real efficiency gained by using a small LCD panel is that the exit lens system can use smaller lenses, and the light source can be aimed at a smaller "target."
A small LCD panel, however, has to be enlarged MUCH more by the lens system than a large panel. You can get by with smaller diameter lenses, but they better be higher quality. This includes not only surface imperfections, but chromatic abberation correction. A single lens (made of a single type of glass) is really just a rounded prism of sorts. It bends some colors of light more than others. When you magnify more, this separation of color is proportionally more pronounced. For a given screen size, a 2 inch LCD would need to be magnified 6 times as much as a 12 inch panel.
Afraid of damaging an LCD with too much light? You should know that you will need to put 36 times as much light (per square inch) through a 2 inch panel as through a 12 inch panel.
The guys doing the OHP/big panel with a near-fresnel and a distant small lens system are getting the benefits of both large and small LCD systems (assuming a high-quality fresnel is employed).
Small LCD panels will typically also have a much more pronounced screen-door effect, since the ratio of pixel space to divider space is much worse (in available, inexpensive panels).
Also, (and this is a biggie for the "can't live with the screen door" crowd) a large panel can easily have enough extra resolution to "oversample" the pixels using line-doubling, or even line-tripling or quadrupling. When this is employed, each screen "hole" is divided up into smaller "holes," so the effect is much less pronounced.
So, even when you find that 2 inch "dream panel" with full HDTV resolution, think twice. There are drawbacks.
"Light spreads out and gets weaker with distance"
Waste that datum right now. Replace it with this one:
"Light travels in straight lines" and another "Parallel lines don't spread out" and "Light doesn't get weaker unless something converts it into something else (like heat)"
So, if you are worried about having you light source too far from your LCD, but it (and its reflector) are putting out parallel lines, stop worrying. If you have a really good parabolic reflector and a point source lamp, you could put it a on the moon (properly aimed at your LCD on earth, and it would work just the same, as long as nothing was between them to absorb or scatter you light.
You can make a projector that keeps all of the light in parallel rays all of the way from the lamp reflector to the final lens, and the spacing between all of the elements in between would be a non-issue. (Your final lens(es) would need to be as big as your panel, but all of the placements get much simpler.)
By the way, clean air doesn't interfere with light too much at all, (except when it is unevenly hot and cold.) The size of your projector might get out of hand, but don't worry about going through "extra air" between elements.
"Lenses bend light"
This one is a bit of a subtle distinction. Light will bend when going from one medium to another if the two materials have a different index of refraction. The difference between the index of refraction of the two materials will also delineate how much the light will get bent. So, light going from air to glass gets bent a lot. If you took that lens under water if would bend light less. Out in space, it would bend light more.
And, all of the bending happens at the surface where the two materials meet each other. The light bends when it leaves the air and enters the glass, not inside of the glass, and bends again when it leaves the glass and enters the air.
How much the light gets bent is also determined by the angle that the ray of light crosses from one material into another. If light hits the glass perpendicular to the surface where it enters, it will not get bent at all.
That also explains how a Fresnel lens works-- it's nearly all surface and no middle, but on a lens, the surfaces do all of the work. (By the way, if you start designing a projection system that uses lasers, stay away from fresnels; they won't work well with monochromatic light.)
And a flat pane of glass is really only a special type of lens. It does bend the light entering it, but the light gets bent the other direction when it goes out the other side. The ray of light does get shifted over a little bit, but will always come out of the other side in parallel with the ray that went in. With really thick glass, it gets shifted over a bunch. Try looking though the thick bullet-proof stuff at the bank and you'll see what I mean.
"You could use a one-way mirror here..."
A one-way mirror (as popularly imagined) does not exist. Light doesn't care which direction it goes through a piece of glass. Imagine taking this magic one-way mirror glass and making a hollow ball out of it, with the shiny side on the inside. You could just shine light at it all day long and all of the light would go inside and bounce around forever and never come out.
That would be fun. You wouldn't be able to see it (since the light would bounce back at you) and it would just be a really black ball. Then one day you poke a hole in it, and BLAMMO! all of the stored-up light finally escapes.
Find me some of this sort of glass, and I'll get you on TV and make you rich. I promise.
One-way mirrors in police interrogations rooms, stores and even in dressing rooms are much less magic. They are half-silvered so that half of the light goes through (in both directions). They rely on the viewer being in a darker room and the person being viewed being in a brighter room.
There are, however types of glass with a thin film applied to them that will pass certain colors (frequencies) of light and not others. This is where we get the semi-magical "cold mirrors" and "hot mirrors." Be careful in ordering and using these because their effects only work when the light hits them at a specific angle (nearly always 45 degrees or 90 degrees). If you don't put parallel light rays through a cold mirror, it ain't gonna work right.
"Some types of glass does not have chromatic aberration."
Nope. Still no magic glass out there. Anything that refracts light will bend some colors more than others. All prisms, all lenses, all drops of water, a bubble of air underwater, etc.
A color-correcting lens is actually made up of two lenses made of two types of glass operating together. The two materials have two different indexes of refraction, so they mess up the color by different amounts. Typically, one lens is concave and one is convex, so the color problems from the two lenses cancel each other out.
By the way, you can do almost anything with a curved mirror that you can do with a lens and mirrors don't have color problems; they "bend" all frequencies of light by the exact same amount.
"An LCD panel will still work if I take off the polarizing file from the font or the back."
Not unless you replace it somewhere. You could wear polarized sunglasses while watching it. If fact, no one else would even see the image on the screen, until they put on their polaroids.
You could put a piece of polarized material elsewhere in the light path (as long as it is on the same side of the LCD as the one you removed). It could go at the light source, or at the lens.
You could also use something else to polarize the light. At the correct angle you could bounce the light off of a piece of glass or a bucket of water, or make it go through certain crystals. Lots of things can polarize light. Light why polarized sunglasses were invented, they cut down on the "glare" of reflected light bouncing off of glass and water, because they block light polarized in a certain direction.
When light comes out of a LCD screen, it is polarized. If you put on your polarized sunglasses and tilt your head at a 45 degree angle, the picture on the screen goes nearly black.
That also why nearly all LCD panels have their polarization diagonally, rather than vertically or horizontally; so people can still use them with their sunglasses on.
All that an LCD screen really does is twist the polarization of the light. A white pixel is a twisted pixel. Light that came in that little hole in the back way polarized one way, then twisted 90 degrees so that it could get out through the front.
This also give of the contrast ratio problem with LCD's. The darkest a pixel can ever be is the amount that polarized light from the back gets blocked by the film on the front. If you were to hold up two sheets of polaroid flim and look through them while turning one of them, you would see it get darker and lighter. At it darkest, you can still se throught it somewhat, and at the lightest, it still blocks a bunch of light. The difference between the darkest and the lightest is what defines the LCD's rather wimpy contrast ratio. And that why the blackest of the black part of your movies look pretty darn gray.
If you take off the front and back polarizing films from your LCD panel and look through it, all of the light will come through. All you will see is the "screen door." |
|
|
| ace3000_1 |
| The 2 way mirror is a dichloric mirror if that spelling is right |
|
|
| zardoz |
May I ask your proffession? You've served the members some prety "hard won" information :nod: Salute!
Good information!
zardoz..."goes to bed a little less stupid tonight" I try to every day... |
|
|
| ace3000_1 |
| I think this guy is a physics teacher or holds a master degree in it lol |
|
|
| jjasniew |
Here's an opportunity to buy a lens that's perfect for LCD projection. 18" focal length, very efficient / fast.
This lens was removed from a device meant to project illuminated opaque pages, so it really makes a bright image. I believe it's in great optical condition.
I'm offering it here, so someone who really wants it wont have to compete on ebay - they can just buy it from me.
I want $75 for it. Probably the best single investment you can make for your DIY projector project using a backlit 14-15" LCD panel!
First to respond to joejas@ihpc.net get it. |
|
|
| chbright |
anyone seen this on ebay.
I know some of you want this real bad. |
|
|
| proto5 |
I used to think putting the upper fresnel on top of the LCD would surely blur the image.....not so.
Much better edge to edge brightness and use of 15" LCD.
This is 85" diagonal. |
|
|
| verbose mustafa |
| Wow... You just proved half of us wrong... Im impressed. What kind of fresnel are you using? |
|
|
| proto5 |
Verbose:
It's the original Elmo- I separated the 2 halves. It's a pain in the a**., but well worth the effort. |
|
|
| Video Freak |
| well slap me around and call me susie,........... when you seperated the fresnels how did you orient(SP) them, smooth side toward the lcd panel top and bottom etc? |
|
|
| neededandwanted |
| quote: | Originally posted by proto5
I used to think putting the upper fresnel on top of the LCD would surely blur the image.....not so.
Much better edge to edge brightness and use of 15" LCD.
This is 85" diagonal. |
Proto: You have just GOTTA post this pic over on the "Double Fresnel vs. Two single ones" thread on this board. They need to see this.
Hopefully, someone can do some before and after pics...?
| quote: | Originally posted by Video Freak
well slap me around and call me susie,........... when you seperated the fresnels how did you orient(SP) them, smooth side toward the lcd panel top and bottom etc? |
VFreak: take a look at that thread as well. MUCH discussion on this. Basically, the orientation of the fresnels should remain unchanged after separation. In about 100.5% of the cases, it will be the opposite of how you asked--that is the smooth sides get the non-parallel light, and the side with the ridges will face that LCD panel (both of them). |
|
|
| proto5 |
Needed is right.
grooved sides of fresnels face LCD on both sides. |
|
|
|
