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Building Cheap 100 Inch TVs
Nastar writes "If you visit eBay and such places there are guys selling 'kits' so that you can easily build your own 100 inch projection screen. There are websites such as 100InchTV selling the instructions for around $10 a pop. They say "this is the only product of this kind on the web" and "it is now possible to convert any type of television or computer monitor into a 100 inch video system that's truly amazing!". I don't like the idea of these people selling this information, especially when you can get it free from the good people at BSTV BSTV. Ihaven't built mine yet, but the reports of quality differ from so-so to fantastic! I suppose it depends on perfecting the technique involved. "
I can't believe this is on Slashdot... so disappointing.
This is as stupid as blowing up a 150x150 pixel image to 1600x1200 in photoshop and expecting a good result.
You'll end up with a dark, low contrast, blurry mess, but go for it.
Imagine the consumer response. .
But it's. .
I would imagine that the resulting quality would depend partly on the quality of parts you use. A 3.5" portable tv certainly won't project a 100" image of the quality a 32" tv would. You still get what you pay for. But I wouldn't be too concerned with the average joe tearing apart tvs (or putting them back together) just yet. Speaking of which, don't tvs contain very large capacitors that hold deadly amounts of power for a long time? Whatch those fingers.
How is this any different than (say) O'Reilly selling books on Perl/Oracle/Linux, when people can get all that information for free on the web as well ? Someone has gone to the trouble of packaging the information, and sending it to people who may not even have web access, or may want printed instructions, so I say all the more power to them.
Why do TVs work then, you ask? Well, the phosphors on your TV are individually much much brighter than an LED shined on a surface from some distance away. Also, the phosphors continue to glow for some time after the electron beam has already passed.
main(c,r){for(r=32;r;) printf(++c>31?c=!r--,"\n":c<r?" ":~c&r?" `":" #");}
A TV scans across (the horizontal refresh rate) the picture tube at 15.7 KHz. The mirror would have to match this rate to reproduce a picture from a convention broadcast facility, so it would have to vibrate across the chosen field of view 15,700 times per second. I don't know the physics involved behind making a mirror move that fast, but it sure would sound awful, since its vibration would cause compression waves in the air at a very high pitch.
The TV scans from the top of the screen to the bottom (the vertical trace and retrace) 60 times per second. The mirror would therefore also have to deflect up and down 60 times a second. In my opinion, that makes the mirror movement pretty complicated.
Don't despair, all is not lost! I remember seeing an early head mounted display that used a column of pixels and a mirror that vibrated left and right 60 times per second. I think that a pretty good image could be created by making a row of 640 clusters of LEDs (each cluster being 3 LEDs - a red, green and blue) and scanning the mirror up and down 30 times per second (Only 30 instead of 60 because you can paint both the odd and even frames at the same time). There would be some electronics involved, since the horizontal picture image must be captured and store in the LEDs. This also has the advantage of providing way more light than 3 LEDs, so you'd have a brighter image.
Good luck
I did this about a year ago.
I bought a Sharp LCD projector for $150 from ebay plus a virtually brand new OHP for £50 from loot.
Total cost including shipping ~£200.
The sharp LCD is pretty cool, it's got VGA, SVideo and Composite video inputs, and a remote control, 800x600 resolution, takes PAL + NTSC signals (and sound too, but I use my stereo instead).
I've got my PC, DVD, VHS and OnDigital (digital set top box) connected to it, and I have a 6ft diag. screen. Because of the size of the LCD panel, the quality is excellent, it's easy to clean, and stray hairs/fluff doesn't get magnified like it does with a dedicated projector and its crappy little LCD. Because the OHP has separate optics you can choose one that fits your needs, mine has fixed zoom but was v. cheap. It's pretty bright too, you can see the picture without curtains unless it's sunny. You can also anti-alias the picture by de-focusing slightly.
There are lots of interesting things you can do with this, G-force with line in from a mic gives very hypnotic (real!) wallpaper. FPS and driving games are great, you get some peripheral vision if you sit close, which makes for a much more immersive game.
In fact, a I've just bought another LCD panel for a friend who say mine and asked me to help him set one up, it cost about £90 + £15 shipping, this one is "only" 640x480, but still higher than TV resolution, and it has a back light, so you can use it as a monitor if you so desire (it also came with a PCMCIA drive so he's apparently going to fill it with JPEGs, hang it on the wall and use it as a picture frame also!).
The downside? The OHP gets through lamps quite quickly (I think that's my mains voltage) - I get about a month from a bulb using it three or four hours each day, they cost £6 each. Also it's not as neat as a dedicated projector unit. And you have to find somewhere to hang the screen.
Anyway hope this was of interest, I'll post pics if anyone is interested....