| rmccoll |
Here is a update on my projector, like I said before I have recieved my lcd screen. I have started to build the case for my projector its pretty small 12X9X4.
Im using a 50 watt halogen bulb for my light source, but its only for test purposes and after using that bulb I know a 75 or 100 watt bulb may not be enough to light my projector, so I might use one of those halogen worklight bulbs at least 150 watts with a aluminium reflector made from a soup ladel. A condenser lense system from surplus shed will be used to focus the light, this system consist of two lense that are 70mm in dia. it also has a heat filter between the lense to reduce heat. Or I may just might make a system using two PCX lense which will be cheaper.
My projector lense system is still in the works, I have to order a lens that have a focul length of 75mm, since my lcd screen is so small.
I will post some pictures Monday or Tuesday. |
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| dbc105 |
I am curious to see the results from the tiny LCD. If the resolution is good it will make RPTV a lot easier.
David |
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| Mesuge |
Hi let me ressurect this awsome thread if you don't mind :D
Just a couple of observations and maybe suggestions:
We have to crack down this design - just imagine a 40-50"
front projection lcd/mh lamp kit by diydisplyes or others under 1k$ that would be a paradise..
In terms of the design - a shinny funnel between the lamp and lcd is a must - I think Hezz utilizes this concept a lot.. and I think it appeared somehow on that old crt-projection tv diagram before in this thread..
Where I'm still at sea is the optics - specifically the small space between the projection screen and inner optics - would small 8-10" lcd help make the trick?
Also, an embeded PC is a must in this application - I'd say that a passively cooled ITX board (small) via epia 1ghz featuring digital TV PCI card and ATI remote are up to the 'average' TV task. For ultimate DVD viewing a dedicated HTPC is necessary though (in my current setup already placed in another room for noise reasons)..
Has anyone come up with a more defined optical setting that we can start with experimenting with these different projection screen materials and move the project further??
thanks |
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| Mesuge |
I'm sorry - forgot to include a small but important note on the OHP-RPTV version - accidentally I came across the following OHP design thread which might be usefull to JR and others as well:
- If I got it right he's using his LCD up side down because of antireflexive coating and is projecting backwards through a big mirror and it all looks quite similar to the guts of RPTV!
Diagram:
http://diyaudio.com/forums/attachment.php?s=&postid=312509
The entire thread:
http://diyaudio.com/forums/showthre...6820&highlight=
- Pls. can anybody comment on the feasibility of this OHP setting for 40-50" RPTV set up mainly in terms of the short distance between the main mirror and screen ..
Btw. another page has nice intro to the RPTV basics and suggests using "sandwich" technology for the screen -> plexi and thin plastic fresnel lens sheeet attached to each other .. that big&thin foldable fresnel has also appeared at some eshop link earlier in this thread and was for cca70usd
RPTV overview&screen detail:
<b>dbc105 &</b> Please post some pictures :bigeyes:
<b>rmccoll</b> |
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| rmccoll |
Here is a picture of the lcd and the controller board, but the picture did not come out clear, I will have to buy another camera that takes better pictures. I'm not sure if this lcd will work, the resolution is great but, it is hard to find lenses that will magnify the lcd enough to fill my screen. The lenses I have found so far will only magnify the lcd to fill a 20" screen which is only half of what I'm looking for. If anyone is looking for 1.8" LCD, I'll sell this one $50.00. I paid $72.00 for it, I still have it's casing, backlit and speaker if you want it, they still work. The lcd will be great for front projection or car tv.
Another idea that has been on my mine is to use Red, Blue and Green LED the superbright ones and hook it up to a RGB source. Then take two mirrors, one vertical and one horizontal that vibrate at the frequency(refresh rate) coming from the RGB source. The LED will be projected on to a screen as one pixel, the mirrors will make the projected pixel fill the screen creating a picture. |
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| Mesuge |
rmccoll> there has been a suggestion in one old rptv thread to use some of those lenses from photography magnifiers -> they might posses the power to make the transition from small lcd to big rptv..
btw. would you pls. post more images of your set up the picture quality doesn't matter I'm more curious about the actual setting of your project. Thanks
On the OHP/RPTV thingy I got a preliminary response from its author (the german guy) and he will test it over the next week and post some results.. |
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| joe2000chevy |
| I have lens asembly out of lcd projectorsa which use three small lcd's these will work for your 1.8" lcd also. |
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| rmccoll |
Well I'm back from spring break and I got bad news the 1.8 lcd broke the lcd broke from the ribbon cable. I was trying the stand it up and it fell, but I caught the ac adatper cord( the white cord in the picture), when I caught it the lcd fell off.:bawling: :mad: 70 bucks down the drain.
I sold my Psone lcd to buy this one and know I'm going to buy the Psone lcd again because its my best choice. |
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| dbc105 |
Man that is sad. Money has been me hold up. Had to by my daughter another car, then all the car tags came due, suit for a funeral. Seems every week it's been something. I am still wanting to try an OHP displaying on the rear of the screen. You know, initial testing could be done with just the OHP and anything transparent. Get all that done then work on the LCD.
David |
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| ebswift |
| Money's been my holdup too, not to mention time. I'd love to start a project soon. I wish they'd make this thread permanent, and I also wish they'd stop moderating me soon, it's ANNOYING having moderation without any of the promised thread upgrades. |
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| dbc105 |
I think the moderation is dependent on the number of post you have made. It took a while before I made enough post for the moderation to stop. I guess its good though, helps keep down the riff-raff, anyone that is not really interested in the forum will not hang around that long. I was reading about a new chip that Intel is working on that is supposed to cut the cost of big screen in half. Also read about an up-coming screen type that is going to replace plasma at less than half the cost.
David |
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| rmccoll |
| Glad to see you guys are trying to keep the thread up. Since I broke my 1.8 LCD, I bought a Sony Psone Lcd of Ebay for $60.00. It should be here sometime this week. I will show how to dismantle it for projection. I'm trying to build this projector cheap, at most $100.00. Early today I went to Lowes and bought 150w halogen flood light for $10.00. Its perfect for the LCD because the glass in front of the lamp is just under 5 inches so it will fit perfectly with the LCD. This will be that last part I will buy because money is getting tight with me to, I have to pay $100.00 room deposit for next year and pay for summer school. So when I get the LCD I will post pictures. |
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| rmccoll |
| Well I've gotten along with the projector. Here it is with the fan, the light and the Fiji lense. I have not recieved the LCD I ordered off Ebay. I may change the position of the fan to blow air onto the LCD. Once I get the LCD I'll post the results. |
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| dbc105 |
rmccoll, where did you get that lense? It looks a lot like one of the lenses in the pioneer RPTV I have in the basement for parts. Well you got a start. I have so many things going on that I can't find the time to do anything.
David |
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| rmccoll |
dbc105, I got that lense from www.surplusshed.com. It is the same fijinon lense people are talking about.
Monday or Tuesday I should be getting 5 Psone lcd screen, I bought them on ebay for $33.00. I sold the 1.8in. lcd for $36.00 even though is was broken and near impossiable to fix someone still bought it.
I want be able to finish this project until I get out of school. Thankfully thats only two more weeks.:happy1: |
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| Mesuge |
Guys thanks for this update of your respective projects but would you be please so kind and post more pictures on the actual setting - such as frame, alignment of the light engine etc..
Just to get a broader picture from that all..
:@ ) |
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| Dnt32 |
I found this tv on the side of the road its 42".
It has three lens inside the screen is in good condition.
The reflector to my surprise is just some reflective plastic sheeting
looks more Christmas wrapping paper than a reflector
it powers up no picture any suggestions or is the lens any use. |
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| rmccoll |
| How big are the lenses? If they are 4 or 5 inches keep them, they can be used to make another projector using a LCD. Also the keep the screen. |
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| Dnt32 |
the lens are 4-5 inches cant get a accurate measurement, but they are more than 4"
looks like they are some kind of lens assembly.
I havent broken it down yet just looking from outside the box.
Doug |
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| Dnt32 |
I have opened it up and they are delta 21's these were made for 5"crt's.
there is 3 lens at least, in this configuration that I can tell.
Any know anything about these lens. |
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| rmccoll |
Well I got my LCDs today. They came Tuesday but I was not here to get them. I didnt know they came Tuesday, I was still waiting on them. So today I called Fedex and they told me my they had been delivered. Come to find out my dorm director signed for them and they were in his office for two days.
All of the lcds are in great condition but one it as a broken hinge. They all look like they work. I have no way of testing them because I do not have a power supply. |
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| rmccoll |
Well I'm home and I tested all the lcds. All of them works, the backlit on two them do not work. A great deal 33.49.
I build the projector that goes inside case, but I don't think its bright enough. I can barely watch it on the wall. Looks like I might have to find a new light source. If anyone has any ideas post them.
In the picture its basically the design as my first one. I used the Figinon lens form surplus shed, Sony Psone LCD, a fan and a light source. The light source is a 150 watt halogen bulb, which is not bright enough. I might try one of those MH bulbs other people are using and see what happens. |
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| rmccoll |
Here is the start of my new rear projection tv. Its basically the same as the first one, but I figured out how to make the screen more viewable. The first one I build the screen was lower which caused me to look down on the screen to see it. The new screen will be 6 to 12 inches higher which should make it eye level. I also solved the brightness problem by making something that keeps alot of the light in. All it is three pieces of wood, two of them has a circle cut out the center the diameter of my Figinon lense. The other has a rectangle cut out of it to hold the screen. Now no light is leaked out when it is turned.
The picture I post does not have the right sized mirror thats why the projected picture is so small. A mirror the size of screen is better because increased brightness and makes the tv thinner in it's depth. A glass mirror the size of my screen will be heavy and expensive thats why I'm going for a acrylic mirror from www.usplastics.com 48X24 only $26.00.
Later this week I will post some pictures to show my progress. |
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| rmccoll |
| Here is another picture |
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| joe2000chevy |
| Most og the specs for rear projection tv's call for screen to be 30-36" above ground for better viewing. |
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| I_eat_flowers |
| quote: | Originally posted by rmccoll
......
I build the projector that goes inside case, but I don't think its bright enough. I can barely watch it on the wall. Looks like I might have to find a new light source. If anyone has any ideas post them.
In the picture its basically the design as my first one. I used the Figinon lens form surplus shed, Sony Psone LCD, a fan and a light source. The light source is a 150 watt halogen bulb, which is not bright enough. I might try one of those MH bulbs other people are using and see what happens. |
heya rmccoll,
nice job.
there's a mod for that psone-lcd makes the picter brighter. see here .. http://diyaudio.com/forums/showthre...0154#post400154
i'm usin a 70 W hqi from osram in my pj. that's bright enough to see already in the dawn. for a rear-pro it'll be enough.
hope that helps abit. |
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| rmccoll |
| Here are_my latest result from my project. I figured out that I don’t need to use a mirror the size of my screen to get a brighter picture. The mirror I’m using now is only 20X16, the gold trim around the mirror is causing a reflection on the screen. As you can see in the picture my projected image is smaller, but only by 4 inches. Once I get the whole thing build and paint the inside black the image will be much brighter. |
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| jrhilton |
Hot spotting should not be a problem, if it is here are two of the reasons:
1) Too much direct light is getting through the screen,e.g. the screen is not diffracting the light. Sorry a shower curtain will never work! As it is not diffracting enough light. Hot spotting is ocouring because too many of the rays of light are able to pass straight through the screen in comparison to the number that are being diffracted. Hopefully the following diagram will help you
***Hopefully the diagram I am now going to refer to will upload ok with this post!***
In diagram 1 the black lines are the light that passes straight through the screen, the grey lines are the lines that are are being diffracted by the pitts in the glass. By the way the only way to go is a screen made out of glass!! Basically what is hanening is you are seeing too many rays of light coming straight from the blub e.g. the black lines!!!
In diagram 2 the screen is far more pitted on the back so all of the light is diffracted. Imagine millions more light lines of course, the result is a dimmer screen but with no noticeable hot spotting. Very little light just goes straight through the screen, un-diffracted, now that is the secret to success.
By the way, anyone wondering why the glass is thicker on picture 2, it’s not intended to be, when I was drawing it in Paint I forgot to move the straight line, and started to put in the light lines, then I realized and couldn’t be bothered to start agin!
To anyone wondering if this works, back in the 1980’s I did presentations using 16mm film projectors with screens sometimes greater than 6 feet in diameter, with no hot spotting problems. Some “serious film amateurs” (very serious in my mind!!!) had small cimemas in their houses and used rear projection because you can hide some of the sound of the projectors, and again no hot spot problems. The surface of the glass is not smooth, it is very very very pitted, so the light is diffracted in all directions.
2) Reason two, is down to incorrect optics, e.g. focal length of light condenser lenses, sorry I cant give any more info here but it is really a case by case scenario.
As for making a screen, they are called ground glass, but having talked to some of my ex-colleagues recently, it would appear that the name is a little deceptive; a better description is ‘severely sand blasted glass’, where the glass is really white and ruff on the projection surface (any one who has done any sand blasting of glass will recognise what I mean by that), not just a little white, but really white. Easy to make if you have a compressor and sand blasting gun. The firm I used to work for made our own screens in our workshop, so it can be done, we didn’t have any special tools ect. Now a very interesting idea I have been told about is that once the screen was sand blasted severely, it was often given a coat of black paint, then using sand paper or steel wool it was scraped back to reveal the top “humps” as it were of glass, leaving a slight back coating, it would improve viewing a wide angles as only diffracted light went through and bright ambient room light was reflected. Diagram 3 shows this idea. It would be interesting for someone to try this again! This was done before the days of easily available anti-reflective coatings. This is also basically the same idea as glass impregnated black plastic screens!
Just one more thing, please stop using / recommending shower curtains, I hope from what I have written above you will all see why they will never work, though I guess they are good just to test your ideas!
I’m working on my own design at the moment, to see if it will work with some old kit that I have accumulated over the years, I will post some results when I get started properly. |
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| rmccoll |
I already knew about defraction and how it make your viewing area better. I can tell from your diagram that you paid a visit to www.uspto.gov because I know how they diagrams look like. It is a great place to visit when you need diagram of something.
I can see what you are saying, but everyone does not have the resources or the money to buy sand blasted glass. Sure it will make a better screen than a shower curtain but right now I using that. Another choice is a large fresnel from www.elec-goldmine.com it a little expensive $70.00 but it will work great. |
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| jrhilton |
| quote: | | I can tell from your diagram that you paid a visit to www.uspto.gov |
Just to be fussy, actually I have never even seen that site, I just drew them on Paint myself. As for cost, I'll give you that one, it would be expensive to buy, but there is always a chance that people know friends who have sand blasting equiptment, it's not all that expensive and people who are into cars would prob have an air compressor, or you could hire it really cheap for the day.
But jibes aside, i'm very interested to know about resolution issues, you say you are using a 'Sony Psone LCD', must confess I had to ask my son if he knew what it was, it looks like it is low resolution compared with tv, e.g. tv here in the uk we have 625 lines, or 720x576 pxs (not that you can even get that through a SCART cable anyway as it doens't have the bandwidth I would say it's more like 400x576 pxs), how does your panel compare to that, as in reality of course you are only getting 288 lines every 1/50 of a second as both fields of the interlaced frame are never shown at the same time. And even with say a progressive dvd player the output frame, although progressive on a dvd which is encoded using progressive frames, will prob still be split into odd and even scan lines as SCART cabels just don't have the bandwidth. So my question is really, what resolution do you actually get from small panels, what is your panel and how big is your screen, do you see and pixls ect?
Second, say you have a panel that is 288 x 352 pxs. Are these panels clever enough to display the 288 odd lines then 288 even scan lines one after another or not?
I already have a Panasonic RPTV that I bought several years back for our living room, and am thinking about building one from my bedroom, you never know, I might get lucky, the wife may like the idea, but i'm not holding my breath. So a small pannel would be easy to get, as oposed to ripping apart a computer LCD screen.
Ages ago I posted an idea I had for using an OHP, but looking around on the Internet I see that there is just not the range of OHPs on the market today, many of what I would have considdered the better makes to buy seem to not even exist anymore, the same applies for projection lens. Since leaving the A/V industry in the mid 80's i'm amazed how far it's progressed in such a short time. The same aplies for prices of items, e.g. mirrors and as you say glass!! |
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| rmccoll |
My screen is 960X234 and it shows really good up to 70'' on the wall. I'm using this screen because I trying to build it on a budget $200 or less and it keeps my overall design small. Try building a rear projection tv using a computer LCD monitor and OHP projector. Sure it will bright and the resolution will be good, but it will huge as a whole. My entire tv is 36''X30''X40'' its small, light and easy to move.
It seems you know alot about television can you help me with this idea I have. Ok you know RGB signals that some televisions use. What if I take Red, Green and Blue LEDs the bright kind and feed a RGB signal into them. It will result in them flashing from the incoming signal. Then I use a lens to focus the light into a single dot and use two mirrors one horizontal and on vertical to create a picture. I'm sure it will work, what about you? |
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| jrhilton |
| quote: | | My screen is 960X234 and it shows really good up to 70'' on the wall |
I’m surprised, so in fact quite a low resolution screen, I’m guessing the 960 is not it’s native horizontal but it’s total RGB horizontal resolution. 70” is certainly very impressive for $200, you have my respect!
I did wonder about resolutions of lcd panels, as back when I was in the business it was CRT all the way, LCD was brand spanking new technology out of reach of all but the largest companies, (to be honest I have yet to see a LCD projector or LCD RPTV that makes me think LCD is better, they certainly don’t have the contrast that CRT has, but I don’t think this is the place for a LCD vs CRT argument as from what I have read on these pages both have their die hard fans!) and with CRTs, horizontal resolution was not really an issue being analogue. I think you are right about small panels as a small footprint for the tv is certainly beneficial for most people’s homes these days.
| quote: | | It seems you know alot about television |
Well, don’t credit me with too much, I don’t think I really deserve it, I left the A/V industry, (back then some of us still called it the A/F industry (audio/film)) in the mid 1980’s, it was then that all the new technology came along, e.g. digital picture processing, LCDs and flat screen crt tvs started to take off after spending years in the shadows. I never really ventured into the inner workings of tvs, film was my department, but we all help each other out so over time learnt about the theories behind tvs ect, the closest I ever came was helping set up CRT projectors/RPTVs (not for the faint hearted I would add!) and building some elementary video processing circuits, e.g. RGB to Video and vice versa ect.
As for you idea, do you mean use 3 leds to project an image using mirrors, just like an Optical printer in fact, but use leds instead of Lasers?
If this is the case, there would be several issues to overcome, 1st would be an issue of a screen, you would need one like a tv, e.g. it would need to hold a latent image for a while, as obviously the leds cant scan every pxl all the time. Second would be the ability to acrutly plot out the lines on the screen, very difficult I suspect.
If I have misunderstood you, and in fact you mean to have 3 leds for every pxl and have rows of these, both vertical and horizontally, then project this whole image which is made up using all the leds, well in theory it would be possible, as this is how in part some very big ‘video walls’ work, using leds. But I would not have a clue how to build a processing circuit to assign each bit of colour information to each group of 3 leds. It would have to be a very heavy duty circuit as video has a very high band width, I would say the biggest problem would be to create a good usable time base, as when a video signal is sent along a wire, due to bandwidth issues the individual pixels as it were can get merged or become mixed or combined, this is not really an issue with a CRT but could be for a video wall, hope that is clear. This is a big issue with NTSC, the bandwidth is just not available to have it’s maximum theoretical resolution and full colour too, hence why (no offence to anyone who’s country’s standard is NTSC!!) it looks pretty shoddy, as it’s based on a black and white picture with very minimal additional colour information)
So if the 2nd idea is in fact what you mean, it is possible but I would say it is very hard to do, and the electronics necessary would be very expensive to build/design. I mean that is after all basically what LCD panels are doing.
If I have completely misunderstood you, do say and I’ll have another crack at trying to answer your question for you. |
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| rmccoll |
| No its one group of RGB leds that forms one pixel on the screen. Its like a regular tv tube, were electron gun in the back scan the picture on screen. Like a big electron gun using LEDs. Using this modified cable I think I may be able to get the LEDs work, but I'm no electronics expert. |
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| justme |
Hey, I read somewhere that you could sand blast plexiglass to get a similar effect to sandblasted glass. Having read the earlier post suggesting "ground glass" and then visiting a couple of links describing how to do it yourself, I wonder if a similar effect could be done on plexi in a similar way. I was thinking that automotive rubbing compound and a piece of regular glass as the surface you rub with might work. I assume that the reason that the instructions for glass required using a second piece of glass was so the abrasion would be more uniform.
Any Ideas? |
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| justme |
" I’m guessing the 960 is not it’s native horizontal but it’s total RGB horizontal resolution. "
A lot of lcd monitors are being advertised on ebay as being "High Resolution" and giving numbers like that. They're giving numbers like 224,460---116,160- and using pixels and dots interchangably. I try to tell myself that it's just a translation error or someone is misinformed but find it very hard to do so. You likely already did this but if you assume that they mean dots multiplied by rows then the above is almost 4:3 resolution.
Very confusing and irritating. |
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| telemonster |
Okay, this one is odd.
I want to use a OHP + LCD to project against two mirrors, and rear project on plexiglass. I'm looking to mount a 7' wide x 5.25' high plexiglass window in side of a step van. I figured I would use real rear projection material stretched on a frame up against the back of the plexiglass. I plan to mount the projector + mirror on a frame that is sitting on air suspension. My focal distance might be an issue, the cargo area of the truck I want to use is 10' long total.
My big worry is the plexiglass. I'm afraid the outside will reflect too much light (it will be shiny). Any thoughts? Should I bead blast the outside of the plexi? Will the image focus nicely?
I plan to use a 400 watt MH lamp on an overhead. Think it will be bright? |
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| justme |
Project against two mirrors is to reach the size you're looking for, right?
The air suspension is because the vehicle will be moving and you want to have a steady picture, is that correct? If so have you made sure you will not find yourself in trouble with the fuzz? They can get real snotty.
I think you could use some kind of sheer fabric over the plexi (on the outside) if it doesn't restrict the field of view too much. |
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| telemonster |
Yea, I'm not sure what the laws will have to say about it. My goal when moving is to show a static logo for a website and have the background move at the exact same speed the vehicle is moving.
I was thinking, perhaps if the out side of the plexiglass was glass bead blasted or something, that would eliminate the glossy factor and allow the projection to hit that part. No idea if that would really work, and with the projector side being glossy how much light scatter would be created. |
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| rmccoll |
Hi, I read your post and I think I can help you. Instead of plexi-glass alone put thin sheets of HPDE over it. HPDE looks like sanded thin sheets of plexi-glass, it will form around your van very easily. You can find some good sized sheets on ebay.
As for mounting the project, try attaching it to your screen with some pieces of wood so it can move with your screen. |
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| Tek1 |
| Real fine sandpaper works well. Under 800 grit seems to leave some abrasions. you can also buy plexiglass that is frosted from window shops. |
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| skullkeeper |
here is a good helpfull site on building a rptv http://www.toppan.co.jp/english/pro...nics/fcscreens/
i also have an idea if you can find a big enuff peace of grey tracing paper and put it on the back of a peace of plexi glass i bet it would work great, and maybe a real light window tint on the front of the plexi glass to block some light from going in. |
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| nothingtolose31 |
| I dont know if this was said because there are like 15 pages, but to make the light more even, could you try putting a fresnel lense in between the back light and the lcd, kind of like on an overhead projector? |
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| dbc105 |
SkullKeeper, do you know where those screens can be bought in the USA? It looks like the type on the newer HD Tv's rather than the older type that had the ridges on the outside.
dbc105 |
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| skullkeeper |
| no i dont iv been looking myself. im in az iv tryd seaching the web for them but no luck yet. |
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| dbc105 |
I have been looking at this for about a year. Have not done anything yet though. I have a bad Pioneer 42" big screen in the basement that looks like it would be perfect for a Lilliput retrofit. It is already setup with the lenses, front side mirror, screen, it's just not wide screen. I keep putting it off though because big screens keep getting cheaper. I would like to see one of the DIY projectors first so I would kow the resolution would be good enough after you enlager a 7" screen to a 42". Though about calling the rental place to see if they had an overhead and a panel to do some testing first. Just don't want to spend time and money on something I'm not going to be happy with.
David |
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| Nads |
| Have not had time to read ALL of the posts, but as for diffussion, how about the glass spray etch? or a VERY large sheet of greaseproof paper. I have tried greaseproof paper at A3 size, the biggest I could find, and got very good results with an epson emp s1 projector with minor hotspot. the glass etch could be used on two pieces of glass, placed back to back if hotspot is not eliminated by just one. I bet that someone produces greaseproof paper bigger. Another suggestion, which is totally untested by me, is if you used bare fibreoptic cable or plexi rod to make a `sandwich` of rods running vertically. This may be totaly impractical or cost prohibitive, but if the rods were stuck to a plexi panel......l |
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| mbates14 |
I have a spare 53" projo screen i pulled from defective TV with bad tubes.
Find a way to come get it, or figure out how to ship it, you can have it. |
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| Nads |
| Some years ago, Tomorrows World, a BBC technology program demostrated a product that one of the universitys here in the UK was creating. I think it was Cambridge university, anyway the plastic film was placed half over a casio 2.5inch tv and the difference in quality was amazing. The plastic film was created by etching micro lens into the plastic using a laser. The process to give an image is very similar to collomation lenses, but on a microscopic scale. Now I have searched the net and not found anything to do with this, but someone must know what happened, anyway IF we could use a large scale injet printer to print some sort of polymer on to a clear acrylic sheet, the result of which would be a dot of liquid, which would dry and if I am correct it would pool in a lens shape. This may or may not be possible but if it could be done it would create some stunning rear projection screens for DIY RP tv`s. The beauty about this was the fact that it gave NO hotspot and when off, the plastic was opaque, which if you placed it on a window, the window would work as normal, but when an image was shone onto it via a projector, it would be displayed on the `screen`, and it worked as a FS screen too which would allow normal projection, but with higher brightness and contrast AND you could look directly at the projector light beam, as long as the screen was between you and the projector, which resulted in a bright vibrant image. The program aired circa 1986. The attached image is of what I can remember of the layout of the lenses |
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| Nads |
rmccoll. I am fortunate that among the things that company I work for sells, we have a fabric shop. Find below the products I have `borrowed` to test for screen use (RP rear pro, FP front pro) compared to my commercialy available vynyl screen and my Epson EMP S1H and a small bit of 25% grey tint plexi/perspex:
6` width Commercial vynyl screen: very minor relection from screen. Annoying but livable. Cost £79.00. Ease of use: Good
6` width white cotton fabric roll down blind: FP. 5/10% less brightness, image quality similar. RP similar brightness, negligable hotspot, image quality very minor smudging, contrast bright without plexi, good with. Ease of use
60" width white blackout lining FP: good brightness/contrast with similar to commercial, but no reflection, good colour rendition. RP no good cos it blocks ALL light. Cost £5.00 mt ease of use, well i had to build a frame to hang it.
72" shower curtain: RP as its partially opaque, hotspotting was a big issue, with the sides being washed out and the center bright, FP was not any better, but now with reflection. In my case could not recommend. I also tried a white shower curtain, but due to the fact it had an embossed pattern, it coulnd`t be used seriously, but turned in similar FP results as the commercial, but RP was good, and better with the 25% plexi over the front |
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| Mesuge |
| Nads> As goes the saying, picture speaks a thousand words, could you pls. shot some comparison pictures of these materials, thanks.. |
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| Nads |
| <chuckles> asking the near impossible, but can do. |
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| lesko |
Hello,
I have been using drafting velum for my LL front projection screen for a while now and love it...it comes at 56" high and lets alot of light through...but it pretty defused so there is really no hot shot at all...I painted the back side of mine with alum. paint and get deep rich bright colors...better than blackout cloth...BC sometimes gets to washed out...you can pick this stuf up at any large print house (here in phoenix It's called Thomas Repro graphics) so I guess any Repro Graphics print house will have it...just ask for Drafting Velum...You can get any size but wide but only 56" high...
Staple gun it to some wood and so on...
you can also find the defuser film in large sizes that is inside a lcd. that would work great also
http://www.gestructuredproducts.com..._amer/index.jsp
anyway I just thought i would pass it on.
Lesko |
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| corryn00 |
screen be here
I saw this and said "gotta show the guys on diy in case they need it"
Gordon |
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| slize |
| i am palnning one of those to built... |
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| KANA007 |
Hi Guys,
I have a dead 53 inch Sony crt rptv. Not widescreen. Can I
put an overhead projector in the bottom, on its side, and
shoot the image throuh the center crt lens? Leaving the center
lens where it is now mounted. It has a Delta78 with 4 inch lens.
I would like to use 15 inch lcd but a 7 inch lcd might fit better.
Here is a sketch.
Thanks |
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| ibleed |
| Hello. New to this tread. Trying to understand things. Some people are talking about using lcd panels (ranging from 1.8" upwards) with 200W lamps or whatever and im wondering how they do this. Are these people taking the panels apart, removing the backlight and using one of their own? |
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| ancorp |
| quote: | Originally posted by KANA007
Hi Guys,
I have a dead 53 inch Sony crt rptv. Not widescreen. Can I
put an overhead projector in the bottom, on its side, and
shoot the image throuh the center crt lens? Leaving the center
lens where it is now mounted. It has a Delta78 with 4 inch lens.
I would like to use 15 inch lcd but a 7 inch lcd might fit better.
Here is a sketch.
Thanks |
Nope, that unfourtinately wont work. The CRT lenses are meant to be very close or completely up against the source, and only capture an image as big as its rear end. A 2-4" LCD might work (as far as I remember, a 4" lcd wont fit under a Delta 78)
Cheers,
Alex |
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| ancorp |
| quote: | Originally posted by ibleed
Hello. New to this tread. Trying to understand things. Some people are talking about using lcd panels (ranging from 1.8" upwards) with 200W lamps or whatever and im wondering how they do this. Are these people taking the panels apart, removing the backlight and using one of their own? |
Yup, than slap on some proper optics, cooling, and wiring, and off they go :)
Cheersm
Alex |
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| tomsenior9999 |
I have just bought one of these yesterday and hope to use it as a standard front DLP projector. Is there a way of switching the horizontal picture or will I have to use another mirror?
http://www.surplusshed.com/pages/item/i1478.html
Cheers for any advice on this. Also would a home brew halogen lamp be easy to install on this as it seems to be a specially designed lamp that may be difficult to locate
Cheers Tom |
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| tjh |
I really wish I had a spare $175 right now :D That thing looks awesome.
The latest trend in DIY seems to be retrofitting so if everything on the DLP works it should actually be easier than with an actual projector b/c it is all open and not as small. Not the greatest wealth of details on surplus shed though. Looks like it has a nice VGA connector though. The one question I have is whether or not there is a projection lens included or was it used for some other purpose? I couldn't tell from the pics, or maybe I missed something..
edit: never-mind I see they stated that "projection optics" are there.
Definitely keep us updated on what you do with it. Looks like a great project. |
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| tomsenior9999 |
I ordered it yesterday should be here within the week cost me $365 delivered to the UK. Read this and you may be able to compare this to other spec DLP Projectors out there. I`m hoping to be able to adjust the image size and focus easily. The main problem would be flipping the picture horizontally. I would rather do this digitally as the mirrors would cost more and affect picture quality. The light seems to be my biggest stumbling block the site quotes a specialist light source and holder yet company documents seem to indicate a simple halogen bulb. I take great comfort in this news. I hope this unit would be able to project an image well in excess of 100" with near perfect quaility. The projected price total of the project is around $600 or £300. Home systems with anything like this performance start from £1100.
http://www.dvc400.com/papers/dlp_image98.pdf#search='DIAMOND%20VISIONICS%20DLP%20PROJECTION%20SYSTEM'
I will keep all informed about the project and total expenditure. Surplus Shed is an excellent place. For once I`m envious of our American cousins. LOL
Cheers Tom |
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| tjh |
After taking a quick look over the document it indeed does look like it is a halogen, a 12V to be exact. Although it was unclear whether they meant for the prototype or the production version, thought they could be the same. (Not sure which the surplus shed one is either, if it is proto it is only 800x600, but if it is a production version it is 1024x768). I'm not too clear on the basics of DLP but it looks like this system was designed for a 26" screen, so you might end up having to change out some optics or something in order to get a focused image of a bigger size.
I did some other searching for background into Diamond Visionics but it just looks like they are a contractor for a lot of big corporations, and the U.S. Government. And I couldn't find any further info on the DLP system other than that PDF you linked too.
Looks like a great project. Maybe you will discover some special properties of this thing since it was designed for the military ;) |
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| tomsenior9999 |
Spoke to a helpful woman at Visonoics. She has sent me a copy of the user manual. If you let me have your e-mail address i`ll send you a copy and maybe you could give me a hand to figure out a work around for the bulb. The correct buld is a L6072 from Hamamatsu. They retail at $700 but they don`t make them anymore. Stephanie says she can get me one but it bumps the project price too high.
Cheers Tom |
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| MadSkillzMan |
hi guys, ive skimmed through this reading in hope to find a cheap soloution for a screen.
i just garbage picked a 53" Toshiba RPTV, holy **** is it deluxe. Only 1 problem, its missing the front screen, and as we watch it, all we see are the RGB tubes in the back of the image...the front fresnel is there, i cant find anything else wrong with it.
is there either A a cheaper soloution? or B somewhere i can order the screen...my dad loves it, hes even willing to help chip in a 100$ for the new screen..
or would i be better off asking a repair shop?
thanks in advance. |
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| mbates14 |
| I got one that might fit, i live towards cincinatti. its a 53" |
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| MadSkillzMan |
| hmm, im in cleveland...gotta think if i have any reason to come near cin |
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| mbates14 |
| well, i got one here if you want it. |
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| MadSkillzMan |
how towards cin are you?
if i can get out there ill definently take you up on your offer |
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| MadSkillzMan |
hi guys. think ive got something here:
http://cgi.ebay.com/REAR-PROJECTION...1QQcmdZViewItem
Im thinkin about emailing them with some questions. Looks to me in the picture they just have a front projection screen
Im looking do to a screen thats 40" tall, and 34" high, so i get:
46" x 40"=1840
1840/144=12.7777778 rounded =13
13x 7.85= 102.50$
Not TOO bad, considaring this is one deluxe tv i found lol. it already has the fresnel lense.
ive been talking to Mbates for quite some time, he has a screen exactly for my use, however transportation isnt exactly on either of our sides to get it to cleveland |
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| spytek1974 |
| Is there a way to mod the psone lcd to accept Y PR PB connections so that I can use the progressive scan options on my diy projector??? |
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| ironslave |
| i noticed some pople here were complaining about the light bleeding on the outer edges of the image... i was wondering if the old Tv projecter( upside down Tv with a frenzel lens) trick of painting the inside of the unit black helps with the lightting issues... noting on how it is better on the unit... also other than getting a shower curtin from walmart should'nt there be an affordable way to build a screen than that.... i am figuring that the easiest way to make your own would be to buy some old broken projection Tv and just slap your own home made unit in there... |
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| ironslave |
ive read every post on here... has anyone found a good solution to the screen material yet? i am curious about it... i dont like the idea of using the shower curtin because it is to transparent... i was thinking about using sheets of the flouresent light fixtures (transparent design) to place behind the curtin and work as a double, diffuser/light blocker...
also i noticed some cheap low res projectors on ebay for 189$ would that be a simple way to make a projector as in all i need to do is put the image against something, no worries on how to even out hotspotting.
i am going to build my box out of those black hefty trashbags as a an idea of how the unit would work with the interior compleatly blacked out... it would keep the ambient light out... than later i would like to build the wood and paint it black if it works out... this will require much work...
i am also thinking of skipping the plexiglass all togeather...
any suggestions? |
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| rcavictim |
I've been offering a 41" NEC RPTV with no takers. If any of you sleepyheads want a big leg up on a DIY RPTV project this would be a terrific way to start. It is about 1-1/4 hr's NW of Toronto. If not picked up within a week it is going outside and that will be the practical end of it. It will immediately become frozen cracked optics junk.
My patience grows thin as I really need the room. I don't care now that I have $250 tied up in it. My PM is enabled. Hint hint. |
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| fillajarapoo |
| Im working on building a DIY projector, but if i can get a rear screen projector working, i would favor that most. i just bought a sand blaster for numerous jobs around the garage. i was just wondering how effective is this concept. does any one have any complaints on this? |
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| jrhilton |
Don't know about Plexiglass but sandblasted glass works a treat, I used to use it for 16mm RP. And used to make it myself.
Give it a try, sounds like you have all the kit, a good tip is to blast it more than you think would be neccessory, so the glass looks almost white. The results are very good, with no hot spots if sand blased sufficiently. Oh and another advantage is glass/ plexiglass is cheap.
And to add a coment regarding rear projection screens for projectors that you can buy, good quality ones tend to be very expensive, dont go for the cheaper ones, they are not really worth the money, and will eat light form the projector.
Hope this helps,
James |
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| fillajarapoo |
| i might have to try that, do u have any other suggestions on a DIY rear screen? |
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| MadSkillzMan |
| im just gonna ask the garbage pickers in my area if they got any...these guys score EVERYTHING! |
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| jrhilton |
| quote: | | do u have any other suggestions on a DIY rear screen? |
well not really to be honest with you, well not any suggestions that will result in a quality screen that can be made at home anyway. There have been suggestions of using shower curtains or lots of sheets of tracing paper, but few have had good results with these.
As far as I see it, the problem of building a DIY PRTV / Projector is one of cost now, the alternatives are now very cheap. Here in the UK you can buy a very good LCD or DLP projector designed for home cinema use for under £500 GBP often including a deal to get a free spare bulb (thats about 700USD aprox)
a quick look on google brought up this:
E.g. BenQ W100
DLP: WVGA 954x480 (so fine for watching TV)
1300 lumens
for £498 GBP including VAT and delivery, and a bulb is only £82 with the included vouchers. And I have seen new WXGA or XGA ones going for about £500 as well, just have to shop around, and haggle sometimes.
And LCD and Plasma tvs are dropping in price very quickly now HDTV is avalable here, granted that very few of them can actully display the format Sky is broadcasting but still.
But dont let that put you off, after all buying something doesnt have the fun of making something for yourself! |
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| GreenApple123 |
I know that this is a random post but it seems like everyone in here is really knowledgable about technology and theater compnents so I thought I post anyway.
I love my RPTV and recently the lamp blew out on it. I bought a new one from an online site I found called http://www.laptopsforless.com/rptvlamp and it works great. Has anyone else purchased replacement lamps for their RPTV before? Is it OK to do through an online company? |
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| cromaclear-crt |
Jrhiltion
James
Throughout this lonnnnnggggggggggg thread Ive noticed that you believe 'sandblasted glass until white' is the best method to make an RPTV screen but no one actually tried it.
Could you tell us what thickness or and type of glass is best...also the sand what guage should it be to achieve best results.
Thanks |
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| rcavictim |
| quote: | Originally posted by cromaclear-crt
Jrhiltion
James
Throughout this lonnnnnggggggggggg thread Ive noticed that you believe 'sandblasted glass until white' is the best method to make an RPTV screen but no one actually tried it.
Could you tell us what thickness or and type of glass is best...also the sand what guage should it be to achieve best results.
Thanks |
Sandblasted glass will work but it has a pretty wide light scattering pattern (wide angles of view) which will mean that it won`t be as bright to the viewer for any given brightness available from the projector as compared to engineered fresnel lens screen systems that increase brightness cleverly with directional gain.
The glass should be as thin as practical to close up the spacing of the double image you will get from the reflection of the unblasted surface. Project onto the blasted side. Ordinary beach sand works as well as commercial sandblasting sand. I cannot say which gives a superior result as i didn`t explore this very far while experimenting with it almost 20 years ago now. |
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| Isaack |
Hello,
I'm planning to create a screen made of 4-6 smaller panels and software to combine it into one big image. However, to get rid of the borders from each panel. I'm planning to use Rear Projection in a short distance, hence the post in this topic.
I've already acquired some plexi glass samples, off one is a small piece of RP dark plexi glass. I tried testing with a simple transparent sheet with a color image. However due to the lack of knowledge within this technique, I don't really know how to project a sharp image onto it. If I backlit it and keep it just up against the panel, the image becomes sharp and looks fine.
However if I keep sheet at a distance, the image becomes more blurry the farther away I pull the image. I suspect that I need a lense in between to like "focus", is this correct?
Would it be a fresnel ?
As I don't want to project each panel much bigger than they already are, I hope that it can be achieved with a very short focal length. I basically just need a few percentage more to project the images up against each other on the big RP panel seamlessly. |
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| chemlins |
| Hi, ive tried the diffuser sheet from the backlight of an lcd and it works fine.There seems to be no hot spot , the image is very sharp and clear and the light is evenly distributed at a good brightness.Does anyone know where i could get large quantities of the sheet so that i could use it as my screen.THanks |
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| Tobias Claren |
Hello.
The foils often are from 3M.
What is the best well-known DIY rearpro solution?
Is there still nothing? |
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| Skital |
That 3M film is most likely the one used in Vikuiti's black rear projection screen. I have a rigid rear screen sample with the film on it. It is AWESOME. Too bad that a 95" version costs about $5,000 and even a 60" version costs more than a 65" HDTV.
The screen is basically a black absorbing layer on the back of a matte acrylic sheet with a thin diffusion layer on the back with millions of microspheres (glass beads) that redirect the light creating a bright, high contrast image with a wide viewing angle. The screen trumps every material I've tried; it's incredible.
I think I may have possibly found away to make a DIY versioin of the Vikuiti black rear projection screen, but it will cost at least $115 just to try out with experimenting. There is a clear paint with microsphere beads in it. I want to combine it with a matte/frosted clear paint and possibly transparent black dye and would like to try in layers too. A single layer would probably create the brightest picture though. My goal is to make a 10.5' x 5.9' rear projection tv with my commercial home theater projector
If anyone else is interested in this project and wants to contribute to help get this project off the ground asap sign up here and the cost of the materials can be split between everyone interested and the results (with pictures/screenshots) will be posted here. I don't think anyone wants to shell out $100 to try something that might work, so if anyone thinks this is a good idea and is interested in contributing let me know. I am willing to pay at least 20-25% of the cost myself if I have to.
Maybe there is someone here willing to shell out $100+ though himself to get the project running. If so, that is great too. The more contributors the less cost between everyone. Hopefully this has enough interest, because if it turns out to be as good or close to the vikuiti one could potentiall build upto a 10+ wide rear projection tv. |
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| Tobias Claren |
Someone guessed me from Röhm at the telephone that Degussa (competitor!) has a cheaper solution. Not the High end stage of this Röhm screen, but very well for private. Not much “more badly”.
The Degussa back projection screen contains “embedded micro lenses”. |
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| TvWatcher |
I'm a new member. It's so really fun and rewarding to find such dedicated people. The site is fast and easy to post to and the intelligence level is on par with the best of the best. : )
I belong to probably 30 forums. This one will be fun to visit and contribute to. My background is onlocation sound recording for symphonic orchestra. I stopped when digital came along due to the cost and I had to go to college.
Now I'm making portable battery packs for fun and friends and enjoying retirement at 54 next year.
As always if anyone is wanting any kind of help with electronics, batteries, sciences of any kind, chemisty,
or research help I'm glad to assist. Just PM me and ask away!
Andre |
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| jvisaria |
Hey folks i used to be all over this DIY projector business... anyhow I just dug up a brand new Delta IV lens in my old boxes... are you guys still using these?
If anyone wants it just PM me, I'll let it go for cheap I just don't want to throw it out. |
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| penguinpaul |
Just a quick question(s),
Im thinking of building a rptv but first I wanted to know some things:
Could I use the insides of a slide projector for the projection part?
I have an old OHP, should I use the fresnal lens from this?
And one more question, do you guys reccomend any LCDs? Should it be big or small, an in car one? 5-7 inch?
Many thanks,
Paul |
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| jmoorez2001 |
| hey all i have a older type rear projector that may be of some use for one of u its a 45 inch diagnal size it is messed up and i dont have the money to fix it but the cabnet is in good condtion and the front screen measures 34"x24" any one need it shoot me a price for it im located in gray kentucky for the whole thing or parts that u might need |
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| penguinpaul |
| grrr. why do you have to be in the us........... does anyone know, inside a rptv, is the projector unit seperate/enclosed, or is each part (lcd etc) all seperate. |
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| jmoorez2001 |
| quote: | Originally posted by penguinpaul
grrr. why do you have to be in the us........... does anyone know, inside a rptv, is the projector unit seperate/enclosed, or is each part (lcd etc) all seperate. |
hmmm not sure but i could post some pics of it but i dont know how yet tho yea its a ****** to live so m many miles form something that ur looking for that u realy need i know i have done it so many times when looking for something that i realy needed at the time but then went a differnt rought with something tottle differtn but even then some times if doesnt work out |
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| penguinpaul |
| yeh, i had the same problem when trying to get a projection panel - they were all in the US - And when I finally managed to get one in the UK (costed me 3 times the price of one in the us on ebay - £80) 3 weeks after having it, my little sister went and tripped over the cable, knocked the thing of my OHP, and smashed the glass! |
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