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Thread: LCD projector

  1. #1

    LCD projector

    I'm not sure where to post this, but I guess I need help with optics, so this is probably the closest category. Tom feel free to move the message to the appropriate category if ever there's a more suitable one.

    OK, I'm thinking of starting to do performances with a group of dancers. I'm thinking of setting up a duo with a dancer. On virtual projected onto gauze or smoke, one in flesh and bones.
    I thought I could try with only a slide projector, but I think I'm not really pleased with the rigidity of the sequence. I'd like to have an option for improvising. so this calls for a specially designed interface. I might use Jitter for Max or the equivalent for Puredata. But this is not exactly the question I had for you. But if you're familiar with such softwares i'd like to hear from you too.

    Either I buy a video projector, some are really cheap now or I build one.
    I was given a cheap 17" LCD monitor and I've disassembled it. I took the fluorescent back-lighting off the LCD screen. So now it's see-though. I checked and it's still working.
    I was thinking I could use an overhead projector, an old one with the light coming from the bottom, but most of them are very bad when it comes to picture quality. So I figured I would build one from a powerful lamp with a parabolic projector and condenser lens plus a large lens. Have you any suggestion regarding this (lamp, reflector, condenser and lens) ?
    Otherwise the cheapest would be to buy one of the Fresnel lenses sold on eBay. Have you tried this yourself? Or at least seen one of the DIY projectors?
    I'm a bit concerned too by the temperature of the screen and how the LCD might behave if it gets too hot. I need to vent the projector, but will it be enough if I put a 500W or 1kW bulb in it?

    OK, this is all very far from pinhole except the pictures will be made using a pinhole camera.
    Anyway I'll keep you informed of how all of this goes...

    thanks!

  2. #2

    LCD projector

    Hello POB -

    I don't know if higher performance LCD's have exactly the same restrictions as simple glass ones on oldercalculators, etc, but they do not like heat very much...I seem to recall a logging thermometer I had blackening at 120 F (I liked to leave it in the car in the summer at a place I worked that had a freshly-tarred lot with no shade..the 'min-max' feature captured 121 F once and it was totally black - I put it in the air vent to cool it off & it did return to normal.

    For example, a Philips Wide Screen consumer grade LCD monitor I just looked up had some info about operating environment up to 40C (probably assumes an internal temperature rise above this ambient limit), and storage to 60C.

    The following site has specs for LCD glass - 105C for very special stuff, 80C operate/store for TN wide temp range and lower for STN (see site for abbreviations).

    http://www.altadox.com/lcd/knowledge/lcd_temperature_ranges.htm

    On APUG there is a guy named Richard Ide - he built some enlargers up to something huge like 20" x 24" with a vacuum wall I think 8 x 16 feet - with condenser lenses and replaced incandescents with fluorescents - I have run some ideas by him & he is helpful. NO email there, but if you register (free) you can PM him

  3. #3

    LCD projector

    Hi POB,

    Murry is right in that the liquid crystal will change state if it gets too hot. The recommended temperature for the monitor is probably a pretty good indication of the temperature you need to stay within. You may also notice some degradation of the image contrast as the temperature changes.

    Greg

  4. #4

    LCD projector

    Thanks boys!

    Yes, I didn't think of fluorescent light. It's much cooler. And I've already seen LCD turning all black and weird because of heat.

    Do you have any idea how much heat the polarising filter generates by removing half the light? I have to get back to lux and my old optic lessons... I'm afraid that even a really strong fluorescent light might cause too much heat because of the filter.

    What I really need help with is whether I need a condenser lens or not?

    thanks again!

  5. #5

    LCD projector

    I would suggest renting a video projector for a day or three, and use it to make tests with the fog machine setup, and verify/determine the optimal projection parameters prior to investing the time and money into building a homebrew projector. You may find that to achieve the optimal visual projection effect onto the fog may require a brightness level or angle of view that the homebrew projector may not furnish.

    ~Joe

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