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Thread: Paradigm Shift, My A$$!

  1. #11
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    Quote Originally Posted by mixedgas View Post
    The second law of thermodynamics has a optical corollary, Etendue.

    Etendue says, you cant win, you cant loose, you cant even play the game.
    Hey Steve,

    sure you're right about this, but only if you're not willing to trade power. It is always possible to cut out a fraction from your transversal phase space with the corresponding loss in power. One Example: In my work I did spectroscopy and needed a spatially coherent beam of light from 600nm to 1000nm wavelength. I ended up coupling an arc lamp into a single mode fiber. Perfect beam quality but I lost 99.999999 percent of the light.
    I haven't done the math here yet but assuming the emitter size is double of the 500mW Nichias which are known to collimate quite well, I would say with loosing 50% of the power one can get a good beam (define good ).
    And I think thats the point here: Now this diodes are so cheap that it simply does not hurt to throw away half of the light and 300mW of blue is still a lot for the average hobbyist projector.
    Anyway this will be just a transition phase, I think. All this modern mobile projectors like the piccoprojector use single mode blues and it is just a matter of time till these are cheaply available as well. I think all the enthusiasm comes from the fact that now for the first time a really high power blue laser was used in a consumer product. I await more to come!

    Greetings
    Andreas

  2. #12
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    while I agree I also disagree... it might not be a paradigm shift for the entire laser show industry, but it sure will be for chinese projectors... which means more watts in the hands of people that shouldn't be entrusted with a 5mW pointer

  3. #13
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    Quote Originally Posted by heroic View Post
    I met the guy who invented DLP while I was at TI. He told me what they're used for; I looked into it, and then quit a month later... part of it was that I had a better offer, and part was that I don't like working for that kind of customer.
    Intriguing .
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  4. #14
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    Indeed.

    Totally wild guess, take a DLP chip, add a lens as if you were building a video projector (but made to pass far IR), now replace the lamp with a thermopile (or other non imaging IR sensor), apply suitable video signals while monitoring the thermopile output and you have effectively built a flying spot scanner in the deep IR (The spot size is variable so you can do a fast course scan then narrow down once you have some targets). In practise you would play clever binary search games to optimise acquisition time.

    You would want to cool the mirror array and the sensor for best sensitivity, peltier effect in a toy, or expand a small tank of liquefied gas across the sensor in a real one (and an N2 fill would be good to prevent condensation).

    An IR Missile guidance camera that John Logie Baird would have recognised!

    Just a wild guess, but it seems like something that would work.

    In fact a fun lab experiment given that we have all these dead single chip video projectors kicking around these days might be to place a photodiode in place of the light source and make a flying spot video camera....

    Regards, Dan.

  5. #15
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    Actually, with the addition of a moderate rep rate q-switched laser (dpss yag would work reasonably well) it would be very possible to make a time of flight camera out of it. If it runs at 85Hz you would get an effective 250Hz update rate by (since you don't care about r/g/b), if you want say a .1Hz update rate (not stellar, but I would say its usable) you can get 2500 pixles- a 50x50 grid. I then propose that with some careful optics you could use several detectors (perhaps divide the chip into quadrants? a 3x3 grid should also be possible) and you are getting into 100x100 pixel range, which is better than most of the demo units I have seen.

    I propose the down conversion circuitry shouldn't be that hard to make, 1" works out to about 100 picoseconds in the time domain, so with a 10GHz clock source (downright easy with mini-circuits type stuff) and a good quality PIN diode you should be able to get going for less than the blue you just didn't buy would cost.

  6. #16
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    So, your saying take the vag burner and an old projector out sailing and make some pictures of the wrecks on the bottom of Liverpool bay?
    532 will penetrate sea water quite well, and the time of flight will take most of the turbidity out of the picture.

    Actually if the illumination and the camera are pointing the same way, you only need 5Ghz as it is round trip time you are gating, but that charge amp will need to be fast..

    Interesting notion, and you might be able to do quite a bit better then that resolution by playing tomographic games with the fact that you can switch multiple points on the mirror array to the sensor for each shot (Then do a sort of computed tomography type thing to produce the final image).

    This needs thought (And I need to pick up one of those projectors).

    Regards, Dan.

  7. #17
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    Quote Originally Posted by DMills View Post
    Indeed.

    Totally wild guess, take a DLP chip, add a lens as if you were building a video projector (but made to pass far IR), now replace the lamp with a thermopile (or other non imaging IR sensor), apply suitable video signals while monitoring the thermopile output and you have effectively built a flying spot scanner in the deep IR (The spot size is variable so you can do a fast course scan then narrow down once you have some targets). In practise you would play clever binary search games to optimise acquisition time.

    You would want to cool the mirror array and the sensor for best sensitivity, peltier effect in a toy, or expand a small tank of liquefied gas across the sensor in a real one (and an N2 fill would be good to prevent condensation).

    An IR Missile guidance camera that John Logie Baird would have recognised!

    Just a wild guess, but it seems like something that would work.

    In fact a fun lab experiment given that we have all these dead single chip video projectors kicking around these days might be to place a photodiode in place of the light source and make a flying spot video camera....

    Regards, Dan.
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