laser video projector Q&A

This is not related to scanning as far as vector drawing, but is a question about creating a raster (for TV) and modulating the RGB lasers to make a TV picture. The idea of it does not seen difficult except that the scanning requirement to create a raster like a TV picture would be a linear horizontal sweep of 15.75KHz and a linear vertical sweep of 60Hz. Certain problems could be gotten rid of by going to VGA scanning, a non interlaced raster of 60Hz vertical and 31.5KHz horizontal. Once a scan is complete the beam must be returned to the starting point for the next scan line within 10us for the H scan. V is much slower.

Is it even possible for a hobbyist?

The PicoP engine made by Microvision uses a MEMS scanner among other optics, but building that at home is beyond my skills and I'd need to work with parts that are not so miniature. It's a great product and is the most powerful 'consumer' unit, however the power is lower than I would like. Still I could see this made into a notebook PC or a thicker than usual iPad.
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The only thing that really holds them back is the commercialization of the true green laser diode.

Meanwhile I have various 650nm, green DPSS, and a nice 300mw Aixiz blue lasers lying around that could be modulated. Since first reading in the tech journals and then pop sci about laser TV sets in the 1970's (haha yes I am 'mature'), I've always wanted one. Back then it was vary large gas lasers and hundreds of $K... but today it almost seems possible for an experimenter.

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Originally Posted by opcom

..but today it almost seems possible for an experimenter.

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Opcom, I have great news for you.. Now, thanks to 'Klitmün's incredible homebrew-design, it's not only *possible*, it's no further away than your pantry-cubboard... and perhaps a quick rummage thru the utility-drawer:

http://www.photonlexicon.com/forums/...7&d=1326705717 :)

Happy Lazing! :p
j

ps - if you're wondering, '.. wt:confused:?!' that little 'gem of a sketch', came from this fine-thread / discussion.. http://www.photonlexicon.com/forums/...aser-Projector ...both informative / interesting, and entertaining.. :p
cheers..

The "trick" is to use a resonant scanner. The miracle is taking the "linear" video data from a random source, and A. Getting it to match the sinusoid deflection and position feedback of the resonant scanner. B. Having enough buffer memory to wait for A to happen.

The dude with the homemade scanner usually shows a still frame of "Lena" for a reason. I wonder if he precorrected it for pincushion.

The best selling rear projection laser video system uses stacks of boxes of UV diodes, each projecting on its own 8" by 8" phosphor screen. The phosphor has enough persistance to allow for some errors.

The resonant scanner in commercial systems is always a submultiple of 15,570 Hz. Usually around 8Khz or 4Khz. Then there are optical tricks used to "multiplex" the beams.

Steve

Why not drop back to the old standby? A polygonal spinning mirror with accurate position detection? (Think hard disc drive spindle, only faster.)

48 sides on the mirror at 19,625 RPM will give you 15.7 KHz on the horizontal with a 15 degree scan angle. Not too bad...

Vertical frequency is low enough for standard galvos to handle.

I thought this was a solved problem. Weren't they doing this back in 2002?

Adam

PS: Still pissing myself laughing at Jon's drawing. :D

Quote:

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Originally Posted by buffo

Why not drop back to the old standby? A polygonal spinning mirror with accurate position detection? (Think hard disc drive spindle, only faster.)

48 sides on the mirror at 19,625 RPM will give you 15.7 KHz on the horizontal with a 15 degree scan angle. Not too bad...

Vertical frequency is low enough for standard galvos to handle.

I thought this was a solved problem. Weren't they doing this back in 2002?

Adam

PS: Still pissing myself laughing at Jon's drawing. :D

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Its been solved, many, many times, but NEVER seems to catch on. At least outside the military and the UV phosphor wall folks, who are rolling in DOSH from strong sales. They have it working far cheaper then a LED wall for the resolution and available spectrum. That bird in John's drawing is going to be my new company logo frame....

Steve

I STILL have that sketch hanging on my refrigerator. But if this really does work then why hasn't it caught on, laser safety? Furthermore, rather than combining diodes for brightness, use vertical strips of 10-20 diodes to increase vert. scan rates and/or resolution and brightness.