Hi guys.
I have a few Casio projectors I will experiment on. There are several things you need to by-pass in order to be able to use the dlp. You can get the projectors rather cheaply from laser people who harvest the blue diodes from them. Apart from the laser diodes, you have a bright red led, a spinning color wheel for turning blue light into green, and fans to by-pass. I do not know if it is possible to get the projectors to work for holography, but I hope so.
The problem is that there are a lot of controllers that shut down the projector if something is missing. I will try to by-pass the diodes with resistors. Not sure if this approach is viable for the other devices. A second approach is to be able to mimic the devices with other electronics. There is some work on this at Photonlexicon.
The second issue is what you talk about above. Even if diodes, LED, wheel and fans are by-passed, is it possible to control the dlp so it doesn´t switch between RGB? You need to send just one color image from the computer, say red, and then use this color channel also for green and blue images (or of course switch channels as long as it is a single one with only one color info at a time). You need to convert a black and white image (or one for each color channel if color holography) into a black and red image.
On the other hand, when thinking about it. Shouldn´t it be possible to use a black and white (grayscale) image directly? The question is how much effect the switching between the different color channels in the dlp has on the fringes. Since the dlp produces black by tilting the micromirror away and white (or rather bright) by tilting it towards the light, and creating grayscales by switching back and forth rapidly, one could assume that the micromirrors flipping to another color channel state wouldn´t be any different than when the micromirrors flip during a one color image. If this is the case, then you just need a grayscale image for single beam work, or three color separated channel images displayed one at a time for RGB work.
I´m still amazed that dlp:s are supposed to work for holographic registrations since the mirrors switch up to several thousand times per second.
See also:
Running the XJ-A140 With Missing Diodes
Getting a projector to work without LD's
DLP projector for stereograms
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favalora
DLP projector for stereograms
Hi -
I've worked quite a bit with DLP-based projectors in autostereoscopic displays whose operation demands that the PWM be stifled. Rest assured, you will be able to find several vendors of electronic controllers for DLP systems that allow you to load, store, and play back many "frames" or "slices," with control over the tiniest of time-slice. What I mean is, yes, you can tell the mirrors exactly when to flip. See, for example, the ALP electronics from ViALUX (Germany).
Also, the TI booth at Photonics West hosted several companies with a variety of TI DMD controller boards. You can find these through a link on the DLP website which I've forgotten.
A bigger concern, perhaps, is diffraction. I'm sure this is something you've thought about already, but just be careful that you aperture the thing the right way.
Best,
Gregg
I've worked quite a bit with DLP-based projectors in autostereoscopic displays whose operation demands that the PWM be stifled. Rest assured, you will be able to find several vendors of electronic controllers for DLP systems that allow you to load, store, and play back many "frames" or "slices," with control over the tiniest of time-slice. What I mean is, yes, you can tell the mirrors exactly when to flip. See, for example, the ALP electronics from ViALUX (Germany).
Also, the TI booth at Photonics West hosted several companies with a variety of TI DMD controller boards. You can find these through a link on the DLP website which I've forgotten.
A bigger concern, perhaps, is diffraction. I'm sure this is something you've thought about already, but just be careful that you aperture the thing the right way.
Best,
Gregg
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holorefugee
DLP projector for stereograms
Thank you Gregg!A bigger concern, perhaps, is diffraction. I'm sure this is something you've thought about already, but just be careful that you aperture the thing the right way.
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Justin W
DLP projector for stereograms
Hi DJ! Three separated color channels displayed in grayscale: My plan exactly! I've just finished programming the first module in my soon-to-be-executable that will manage the finding, retrieving and displaying of the whole heap of images that will go into my eventual RGB work. Between Flowstone and Irfanview, I can really put my 'puter to work handling a lot of the grunt labor involved!DJM wrote: If this is the case, then you just need a grayscale image for single beam work, or three color separated channel images displayed one at a time for RGB work.
I´m still amazed that dlp:s are supposed to work for holographic registrations since the mirrors switch up to several thousand times per second.
But jeeeeeez... So we're still not even certain that a DMD displaying grayscale images is stable (at least without a lot of modifications)? I don't plan on tearing the little Pico projector apart too much. In fact, my plan is to not disconnect anything. I'll just leave the RGB LEDs dangling from their wires and make sure they aren't shining anywhere.
But it still would be good to know whether grayscale imagery projected from the lil bugger will be still enough for holography!
Hullo Gregg!favalora wrote: several companies with a variety of TI DMD controller boards. You can find these through a link on the DLP website which I've forgotten.
A bigger concern, perhaps, is diffraction. I'm sure this is something you've thought about already, but just be careful that you aperture the thing the right way.
Is this darn projector just not gonna work for holography in its out-of-the-box configuration? For simple grayscale display, will I need to hot-rod this unit? I understand the Optoma PK series to utilize a Texas Instruments DMD, which I guess bodes well for finding the additional gizmos I would need, but I gotta admit - I really don't relish the thought of having to re-wire the thing! Please advise on the degree of modification you suspect an Optoma PK101 projector would require for use in a multiplex hologram set-up.
On the matter of the diffraction - I must admit (to my considerable embarrassment), that I'm not sure exactly what you mean. Diffraction at the output? Somewhere inside the projector guts? Where do you imagine I will want to place an aperture? I appreciate the insights and your patience, bro.
Big thanks and much respect to everyone who's been posting here in an attempt to learn me up about using these DLPs for my intended purpose! Please keep the advice coming
DLP projector for stereograms
An animation showing how Casio DLP projector works:
http://www.greenslimprojector.com/features
Look at the rotating color wheel for green and blue and at the dichroic filter for red/blue.
Also, there is no green LED or green LD in this projector.
It will not be a simple task to use this projector for color holography, unless essential modifications are undertaken, including reprogramming the DPL controller .
But it will work fine for single color holography, by simply removing the red/blue dichro and replacing the red LD with your laser.
http://www.greenslimprojector.com/features
Look at the rotating color wheel for green and blue and at the dichroic filter for red/blue.
Also, there is no green LED or green LD in this projector.
It will not be a simple task to use this projector for color holography, unless essential modifications are undertaken, including reprogramming the DPL controller .
But it will work fine for single color holography, by simply removing the red/blue dichro and replacing the red LD with your laser.
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Jeffrey Weil
DLP projector for stereograms
Hello Everyone,
Justin I have a question for you? Why do it digitally? There's only 2 reasons to make stereograms digitally. 1 your making so many you just don't have the time for film, 2 you really just like doing it digitally as its fun from your standpoint.
If your answer is 2, super cool. Have a great time. I can't wait to see the results. I don't think 1 applies to you. I could be wrong but I doubt your planing on doing a few hundred stereograms per year.
If your just about the final image and not the tech I suggest you stick with film. It might take a little longer to make the image but when you look at the time you'll be putting into making the projector work it really is less work. Film will give you a much better image than almost anything digitally that you could do.
The contrast will be better with film, the resolution will be better with film and the time for you to get your system up and running will be much shorter.
I've been through this with another holographer. We were doing an embossed project together. He had a full film system all ready to go. Instead of just doing the security holo's for this Euro government with film he wanted to spend months rebuilding the system as digital. He was dead set on this. We debated it for days. During that entire time he couldn't really say why he wanted to go digital. We did the job on film and it looked great. He never mentioned going digital again and we did a number of jobs together.
The diffraction Gregg mentions is from all the mirrors. Every edge of every mirror in the dlp will diffract light. Take a full size mirror and fill it with an expanded beam. Make sure the light is bigger than the mirror, it has to go over the edges. Now look at the mirrors reflection on the wall. Do you see the edges diffraction?
Jeff Weil
Justin I have a question for you? Why do it digitally? There's only 2 reasons to make stereograms digitally. 1 your making so many you just don't have the time for film, 2 you really just like doing it digitally as its fun from your standpoint.
If your answer is 2, super cool. Have a great time. I can't wait to see the results. I don't think 1 applies to you. I could be wrong but I doubt your planing on doing a few hundred stereograms per year.
If your just about the final image and not the tech I suggest you stick with film. It might take a little longer to make the image but when you look at the time you'll be putting into making the projector work it really is less work. Film will give you a much better image than almost anything digitally that you could do.
The contrast will be better with film, the resolution will be better with film and the time for you to get your system up and running will be much shorter.
I've been through this with another holographer. We were doing an embossed project together. He had a full film system all ready to go. Instead of just doing the security holo's for this Euro government with film he wanted to spend months rebuilding the system as digital. He was dead set on this. We debated it for days. During that entire time he couldn't really say why he wanted to go digital. We did the job on film and it looked great. He never mentioned going digital again and we did a number of jobs together.
The diffraction Gregg mentions is from all the mirrors. Every edge of every mirror in the dlp will diffract light. Take a full size mirror and fill it with an expanded beam. Make sure the light is bigger than the mirror, it has to go over the edges. Now look at the mirrors reflection on the wall. Do you see the edges diffraction?
Jeff Weil
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favalora
DLP projector for stereograms
Justin -
No problem. The reason that you might want to consider using a fancy DLP controller-board (e.g. ALP, Discovery, etc.) is that if you don't then the mirrors never achieve 0% or 100% duty cycle. That is, they're occasionally flipping on and off regardless of what you tell them. Mind you, things may have changed since I last investigated! Your first step ought to be to buy a PIN photodiode, the proper resistor and biasing voltage-supply, and watch the actual performance of the DMD on an oscilloscope.
Regarding diffraction, I agree with Jeffrey. (Jeffrey, right?) Any time light goes through an aperture or, equivalently, is modulated by a reflector with edges (i.e. anything of not infinite extent), you'll get diffraction. The DMD pixels are - what are they these days - 13-14 microns on a side, with a small spacing between them, and with various tiny features. If you shine a laser (or probably, I bet, a decently narrowband LED) light source off a DMD, you'll get an unfortunately impressive pattern on the wall.
I'm sorry, though, I don't recall where the right place would be to put an aperture to block the diffracted light. I guess you'd play with your projector by moving around a little business card (a target) inside, seeing where the light goes. After the DMD you'll see the +/- 1, 2, ... orders splay off in various directions around the central (0 order) modulated shaft of light. Block everything but the 0 order. Be careful of your eyes, and be careful you don't burn the business card.
Google DLP diffraction and you get stuff like this: http://e2e.ti.com/support/dlp__mems_mic ... 20881.aspx.
g
No problem. The reason that you might want to consider using a fancy DLP controller-board (e.g. ALP, Discovery, etc.) is that if you don't then the mirrors never achieve 0% or 100% duty cycle. That is, they're occasionally flipping on and off regardless of what you tell them. Mind you, things may have changed since I last investigated! Your first step ought to be to buy a PIN photodiode, the proper resistor and biasing voltage-supply, and watch the actual performance of the DMD on an oscilloscope.
Regarding diffraction, I agree with Jeffrey. (Jeffrey, right?) Any time light goes through an aperture or, equivalently, is modulated by a reflector with edges (i.e. anything of not infinite extent), you'll get diffraction. The DMD pixels are - what are they these days - 13-14 microns on a side, with a small spacing between them, and with various tiny features. If you shine a laser (or probably, I bet, a decently narrowband LED) light source off a DMD, you'll get an unfortunately impressive pattern on the wall.
I'm sorry, though, I don't recall where the right place would be to put an aperture to block the diffracted light. I guess you'd play with your projector by moving around a little business card (a target) inside, seeing where the light goes. After the DMD you'll see the +/- 1, 2, ... orders splay off in various directions around the central (0 order) modulated shaft of light. Block everything but the 0 order. Be careful of your eyes, and be careful you don't burn the business card.
Google DLP diffraction and you get stuff like this: http://e2e.ti.com/support/dlp__mems_mic ... 20881.aspx.
g
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Justin W
DLP projector for stereograms
Hi again, my friends.
So I've retitled the rest of this thread because I fear that we have become tangled in the details of using a DLP for RGB work, when in fact my primary concern is centered around single-wavelength exposures of grayscale images. The RGB of it all will be sorted later but will still be based on displaying grayscales.
So the question remains: Will an essentially unmodified Pico projector display a GRAYSCALE laser image stable enough for holography? Or are those micromirrors still flippin and floppin and twitching and angling and generally spaz-ing out too much for stable fringes to form on film?
And on the matter of the diffraction from the edges of these countless tiny mirrors - where and how does an aperture help manage this?
Would an LCoS projector get around this diffraction issue?
Thanks again, fellas.
EDIT - while I was posting this, Gregg returned with some of the answers I just requested. It's beginning to look as though I'm simply going to have to buy one and see if it makes a hologram, then modify it appropriately if it doesn't...
So I've retitled the rest of this thread because I fear that we have become tangled in the details of using a DLP for RGB work, when in fact my primary concern is centered around single-wavelength exposures of grayscale images. The RGB of it all will be sorted later but will still be based on displaying grayscales.
So the question remains: Will an essentially unmodified Pico projector display a GRAYSCALE laser image stable enough for holography? Or are those micromirrors still flippin and floppin and twitching and angling and generally spaz-ing out too much for stable fringes to form on film?
And on the matter of the diffraction from the edges of these countless tiny mirrors - where and how does an aperture help manage this?
Would an LCoS projector get around this diffraction issue?
Thanks again, fellas.
EDIT - while I was posting this, Gregg returned with some of the answers I just requested. It's beginning to look as though I'm simply going to have to buy one and see if it makes a hologram, then modify it appropriately if it doesn't...
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favalora
DLP projector for stereograms
Hi Justin - Did our messages cross?
Also - yes, I bet a picoprojector's default DLP controller would "twitch" the mirrors.
You have enough questions that, at this point, you might want to call TI's DLP group, or any of the places that make DLP projector boards:
DLP projector kits
DLP design houses - ask these engineers your questions
g
Also - yes, I bet a picoprojector's default DLP controller would "twitch" the mirrors.
You have enough questions that, at this point, you might want to call TI's DLP group, or any of the places that make DLP projector boards:
DLP projector kits
DLP design houses - ask these engineers your questions
g
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Justin W
DLP projector for stereograms
Oh and an additional concern I've just realized that Gregg could possibly help me out with:
My intended final machine will be one big USB device. The stepper motor that drives the slit will be off a USB hub, as will the control board that works my shutter(s).
Everything sounded hunky-dory when I thought I was going to be able to plug my projector into the same USB hub and feed it images that way. Now that I'm considering the possibility of having to replace some of the projectors' guts with other guts, I'm concerned that I may lose the units' inherent USB connectivity.
Do these DMD hop-up boards still allow me to maintain the original input configuration?
My intended final machine will be one big USB device. The stepper motor that drives the slit will be off a USB hub, as will the control board that works my shutter(s).
Everything sounded hunky-dory when I thought I was going to be able to plug my projector into the same USB hub and feed it images that way. Now that I'm considering the possibility of having to replace some of the projectors' guts with other guts, I'm concerned that I may lose the units' inherent USB connectivity.
Do these DMD hop-up boards still allow me to maintain the original input configuration?