DIY Video Projector Part II

[NautTBoy]

Hi I have a portable dvd player that still work but with a bad screen(TFT). Backlight(square tube) went out. I was wonder if it's possible to turn that in to LCD projector. I'm trying to get away from the big box projector (15" screen) I want to try to get it as small as possible as the same size as the real one for $1,000+. I dont really need 150", as long as I have a big enough screen 50"+. Anyone have suggestion?

I haven't had time to upload my plan diagram.

[elstcb]

The chances are that the screen will have an appalling resolution, slow response time and poor contrast ratio, however if you think you can live with these then there's no reason not to use it. I'd imagine it would be ok on a small projection screen if you're planning to use it to watch TV, don't expect cinema / theatre quality from it though.

One thing you will need to do is to ensure that any circuitry behind the LCD can be folded out of the way, preferably before destroying your player altogether. You might need to extend an FCC cable (flat small ribbon cable) or two which whilst a bit fiddly isn't too expensive.

If you find that you can't fold the circuitry out of the way then maybe take a look at the Lilliput screens or the PS2 screen, people on here have managed to get some very good results with them. Again they're fairly cheap and I believe are easy to work with.

Have you looked for other parts yet? You may need to be careful with the bulb dimensions as some can be quite long and therefore would needlessly increase the size of your box. At least if you are only after a small projection screen then you can go with a 250W MH bulb or equivalent.

HTH, hopefully others have some points to add.

Steve

[Guy Grotke]

If the LCD is really only 4" diagonal, then you can make a very tiny simple projector using a CRT projection lens. These go for under $15 on eBay and surplusshed.com all the time, and can project up to a 5" LCD. This kind of lens goes right up against the LCD, which makes for a small box.

I would put a 150 Watt double-ended MH lamp behind it with the shortest focal length fresnel you can find (maybe 200 mm?) as a condensor about 25 mm before the LCD. The lamp to fresnel spacing would be the same as the focal length of the fresnel.

Add a spherical reflector for the lamp, some fans, UV and IR filters, and you will have a very small projector that can make a small screen image that will be limited only by your LCD's resolution. But you could start with the $15 lens and a bright incandescent floodlight to see what the image quality will look like before buying any of the rest.

[NautTBoy]

Thanks for the advice and suggestion guys. I will try it and learn as i go. These are what i'm working with just to get the idea of projection.

Mintek 5" 4:3 Portable DVD TFT with the player outside the box.
Kodak Lens F:2.8 102mm (heard that it's wrong choice)
Plastic Fresh Snail Len
Home Torcheire Halogen Lamps

I like that plan from ....i forgot the ID......5" PS1 LCD screen. I think that's small enough for me.

OH, I put 4" screen instead of 5"

[Guy Grotke]

The one advantage of a CRT projection lens is that you can be pretty sloppy about the lighting, and still get a reasonable image. If you really want to try one of those long skinny halogen tubes, then I would make a beer-can reflector: Cut open an aluminum can by cutting off the ends and then making one neat cut up the side. (Wear gloves! Very easy to cut yourself doing this.) Then open it up and form a two dimensional parabola. You may have to add some wood or metal pieces for the sides to keep the can metal in the right shape. If you put your halogen tube an inch or so from the center of the parabola, you should get a pretty even parallel beam from the whole reflector surface. Play around with the shape until you do.

Put that right behind the LCD and it should work okay without any fresnels at all, as long as you are using a CRT projection lens that is as large as the LCD.

If you want to use a smaller lens, then you will have to use fresnels to condense a point-source lamp's light into the lens.

Either way, a halogen lamp will give you a yellow-tinted image. Not as bad a those parking lot sodium lights, but metal halide lamps look much whiter.

[NautTBoy]

Hey thanks again for the help Guy. I look under "CRT PROJECTOR LENS" on ebay I don't see any under $50. With "BUY IT NOW" filter, I saw $70 plus $30S&H the cheapest price. I went to surplusshed.com and I didn't know what to put in the search because there wasn't "CRT" for me to select. You're probably saying "dang, this boy!" Well, I'm a newbie

[Guy Grotke]

Here is an expensive example from eBay. I have seen a lot of these go for more like $15 US:

http://cgi.ebay.com/ws/eBayISAPI.dll...765839493&rd=1

The lens specs would be at least 5" (125 mm) diameter, focal length in the 6" to 8" range (150 to 200 mm). If they only tell you focal length and f-ratio, then diameter = fl / f-ratio. So a 200 mm fl f1.6 would have a diameter of 125 mm.

It doesn't look like surplusshed has any right now, but you could try doing a google (or froogle) search for "CRT projection lens". There was also mention on some thread in this forum about somebody having around 50 of them in his basement.

[Mikey p]

Originally posted by Guy Grotke
There was also mention on some thread in this forum about somebody having around 50 of them in his basement.

That would be Curt Palme. If you're interested in that type of lens you can contact him here http://www.curtpalme.com/

[redd38]

I'm about to start buying parts.... let me know if I'm missing something, or if there's a better part I could be using.

LCD: ProView PL576Ws 15.4" Widescreen LCD Display
Lamp: UHI-S400DD USHIO
Ballast: High Pressure Sodium Sola/Howard (maybe something else???)
Lense: 135mm Long-Throw Projection Lens Triplet
Fresnel: 320mm x 400mm 550mm FL (I'm doing a split design and I don't know what the first fresnel should be)
Reflector: i don't know

I'm using a 15" LCD so I don't need a condensor lense right?

[wussboy]

Originally posted by elstcb
By now I'd imagine there's enough information in these forums for anybody to be able to create their own DIY projector and I'm guessing a lot of people are following pre-made build instructions (e.g. the ones available on http://www.lumenlab.com/ ) rather than experimenting.

Are there more websites like this one? I'd like to try this, but am nervous to go it alone. Thanks!