[REQ] DIY DepthQ?

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Voidling
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[REQ] DIY DepthQ?

Post by Voidling »

I have been researching 3D projection for the the past few months seeing if there was a way to use passive polarized glasses with one projector. After much research I found out that liquid crystals have the unique property of rotating a polarization field, when a charge is applied, and can be produced very cheap. After more research I came across DepthQ which does exactly what I trying unfortunately they want to bankrupt you for there technology.

So here is where my question comes up. It doesn't seem all that hard to make a passive projection system the same way DepthQ did but for much cheaper. The way I imagine it would work would be to set up a projector with 120hz and connect it to a computer with a HDMI out port. Connect the liquid crystal to the PC possibly through USB and give a charge to it every time the PC flips between the two images. If you are using DLP projection then you would need a polarization filter before the liquid crystal.

I am a Computer Science major and not an Electrical Engineer so dealing with electronic parts is no my strong suit. So does anyone know if this sounds plausible?
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Re: [REQ] DIY DepthQ?

Post by Likay »

The depthq is a dlp projector what i know about. However it can be used for passive viewing using polarized glasses and silverscreen. For this you also need the polarizationmodulator (and yes, it's an lcd-panel which rotates the polarization syncronous with the eyeshifting of the projector). The image still shifts fast between the eyes as with shutters but polarized glasses are required instead of shutters.
The diy route would be modifying a dlp. Changing the colorwheel to one with 6 or 8 colorfields (depending on 3 or 4 basecolors) which are clockwise resp counterclockwise circulary polarized. The electronics needs to be modified as well.
Or: using a dlp with bluelinecoding (iz3d for example supports it) and use the blueline to sync the modulator. I don't think you can build your own good working modulator though. If you success it would probably be very slow if working at all.
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Re: [REQ] DIY DepthQ?

Post by tritosine5G »

-theres a thread somewhere on avsforum(?) where some ex-US military engineering guy claims that during iraq desert storm they made such ad-hoc "polarwheel". Upon seeing the depthQ he said it 'd worth around 40 usd in parts.

He found it funny DLP's are used with shutters nowdays, instead of this. Actually you should try 120hz shutter I think it works extremely well, plus , screen properties wont really matter.
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Re: [REQ] DIY DepthQ?

Post by Voidling »

Thanks Likay and tritosine for the fast response! Now the only problem I have with shutter glasses is that I'm a college student with a limited budget and the point of having a 3D projector (for me) is to watch 3D movies at home with friends. I cant afford 15 glasses for when my friends come over for a movie night. As for the polarwheel I will look into that, I saw a few mentions of that on this form today but haven't had a chance to do any research yet and I think its a bit out of my technical range.

I'm not following why you would need a special projector that has a polarwheel or that uses bluelinecoding. The method I'm proposing is once the light leaves the projector to polarize it with a filter at 45 degrees (for linear polarization) and use a modulator after that to switch the polarization for each eye. To my knowledge it shouldn't matter what the projector does as long as its not polarizing the light which I don't believe DLP projectors do.
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Re: [REQ] DIY DepthQ?

Post by tritosine5G »

http://www.avsforum.com/avs-vb/showthre ... 73&page=18" onclick="window.open(this.href);return false;
I don know how bright this would be or how it'd look with linear polarizer, but count me interested.
Last edited by tritosine5G on Wed Jun 23, 2010 4:33 am, edited 1 time in total.
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Re: [REQ] DIY DepthQ?

Post by Likay »

Voidling wrote:I'm not following why you would need a special projector that has a polarwheel or that uses bluelinecoding. The method I'm proposing is once the light leaves the projector to polarize it with a filter at 45 degrees (for linear polarization) and use a modulator after that to switch the polarization for each eye. To my knowledge it shouldn't matter what the projector does as long as its not polarizing the light which I don't believe DLP projectors do.
It's correct but you still need to syncronize the modulator with the shutterfrequency of the projector. The bluelinecoding (comes from the stereodriver if the bluelinemode is choosen) is a standard for identifying and syncing left and right eyeviews. Otherwise you'll risque and experience eyeswapping.
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Re: [REQ] DIY DepthQ?

Post by Voidling »

A simple fix might be to use a LCD projector. LCD's come already polarized (although I'm not sure if the 3LCD technology polarize the same direction which could cause problems), they don't use a shutter (at-least I don't think) and they are brighter which is crucial to passive polarization. (please correct me if any of this is wrong I'm just going off what I have researched these past few months).

Also I'm not familiar with the shutter on DLP projectors. I tried looking it up but cant seem to find anything on it. Does it just do what the name implies (shuts light off between frames)? If so would it be possible to put a light sensing diode on the modulator to sense when the shutter is active? (this is assuming that my idea of shutter is correct and that light sensing diodes can react that fast)
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Re: [REQ] DIY DepthQ?

Post by tritosine5G »

theres no shutter inside a DLP pj. Light is just reflected towards the colorwheel (colors), or away from it (blacks).

Only DLP do 120hz right now so thats the deal I guess. Oh and it has 750 lumen in 120hz mode, thats pretty low, but you compensate with 3x gain paint that preserves polarization as well, you should end up

750*0.38*3 , just over 800, not much, but in the dark, thats just optimal. The problem is the gain multiplier of the screen, it only gives that much gain in , say, 0-10° degree, plus, to avoid hotspotting you need slight curvature.
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Re: [REQ] DIY DepthQ?

Post by OzOnE2k10 »

Hi,

@Voidling, I hope you don't mind me posting a reply here, but it very much continues along a similar subject... :)

As long as it is darkchip3 , I dont care how hard is it

I told this to Petrus too, but Im telling you now. I can get you PCB's made, I think I can get reflow stuff, and I know 3 ppl skilled with professional layout SW
I think I can get DLP chips from a repairman.

LED luma: http://readalert.atw.hu/THE_ULTRA_HIGH_GAIN_SCREEN.pdf" onclick="window.open(this.href);return false;
PowerLEDs could be used to simulate an "iris" as well . Contrast would be killer, and the hardware brightness slider ... hmmmmmmmmmmm!!!!!! (im in love)

After using this 120hz DLP for a while. I can safely say , we want no more than 120hz. Thats as purrfect as it gets, still pictures, screenshots , purrfect. Rainbow is gone for me, others say its there, but its a very distant memory to me. Actually, we'd want less refresh rate , because sustaining 120fps in games is quite hard , and 50hz vsync would be way easier , hence 100hz shuttering. 150 Usd gfx hardware does that easily!!

ps.: Im prepared to sell ALL my vintage audio stuff to fund this project .

EDIT: forgot I can get you switch mode power supplies in all shapes & sizes
@tritosine - I'm still interested in getting a PCB made for controlling a DMD chip. I've fixed a fair few projectors before, but it's rare to find one with a Darkchip 3 for the sort of money I pay for faulty projectors (around £60 - £70 maximum from "your friendly neighbourhood auction site").

We basically need a board similar to George's design. A personal preference would be to have an Altera FPGA instead of the Xilinx though (I don't like the Xilinx software, and I'm much more familiar with Altera Quartus). Here's the link to George's DLP project files...

http://www.mediafire.com/?gkdozrrybqk2sv6" onclick="window.open(this.href);return false;

btw, I included a PDF file from TI (in the zip) because it contains some basic background info on how a DMD is controlled (page 20).

There are a few options here...

We don't even necessarily need the USB connection, just some spare pins for inputting digital video (or a DVI / HDMI receiver chip). I don't know how much memory bandwidth would be needed for say 100Hz, but I would think we'd want a fast chunk of DDR memory eventually. I'll have to work out some of the bandwidth stuff in advance.

It looks like many of the recent pocket LED projectors simply change the colour every time a horizontal "strip" of the image is updated (usually 16 "reset blocks" on a DMD), so it should be possible to get rid of the rainbow effect completely if we used LEDs. This can get expensive though, as you will eventually want to buy Phlatlight LEDs for decent brightness (believe me, these are still the best LEDs for the money but it soon adds up).

I currently have three brand new PCBs sitting here which I don't have parts for yet. Although this is for another project, the FPGA is of course completely generic - I did intend to try interfacing one to a DMD at some point.

The board has a fast enough FPGA, but I only used SDRAM for now (might still work for XGA @ 100Hz??). I'll have enough money to buy the parts soon, but I don't have a toaster oven for soldering the chips yet (the FPGA has VERY fine pin spacings). If anyone can help with assembling the board fairly cheaply then we might be able to work something out?

Having said all that, we would still need a separate PCB containing the DMD itself and a DAD1000 type reset chip, so we might as well start from scratch with a smaller FPGA (easier to solder, but still powerful enough). Or, just get a generic DMD / reset PCB made, then experiment with it using a separate connection from a cheap dev kit...

http://www.terasic.com.tw/cgi-bin/page/ ... ish&No=364" onclick="window.open(this.href);return false;

Remember, with any modern FPGA, decoding shutterglasses sync would be a piece of cake (he says :lol:). Also, with a DVI / HDMI receiver chip, it wouldn't be too difficult to support the modern 3D Blu-Ray modes directly (I've done a fair bit of research on this already, it requires some custom EDID data too).

So, some things to think about. I know it is doable with the right PCB and it won't be hugely expensive unless you start playing with Phlatlight LEDs and 3-chip DMD stuff. :twisted:

George has laid out most of the groundwork already, we just a PCB first.

OzOnE.
EDIT: I've probably mentioned this before, but here's what my LED projector and DIY RGB combiner look like (minus the FPGA board)...
http://img31.imageshack.us/img31/9523/file0085.jpg" onclick="window.open(this.href);return false;
(Notice the nice Xbox 360 GPU heatsink there - obviously wasn't working too well in the Xbox anyway. :lol: )
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Re: [REQ] DIY DepthQ?

Post by tritosine5G »

I know LED's are pricey, we investigated it half year ago. OFC I'm willing to help , and want to take part at all costs , lol . Also tryin to invite a few ppl here MTBS3d seems a good gather place afterall (maybe a new topic, cuz I don't like non depolarizing screen criteria :mrgreen: ).
________________
One of my friends played with hdmi receivers already for audio, talking to him on MSN right now, tryin to grab his attention. He would be the best bet, the best at PCB design I know. Also had a LED lamp project at work awhile ago . Also he likes Altera stuff. Too bad he just buried himself into room acoustics (the pricey way) , lol.

Reflow - 2 ppl. I can safely say, thats no problem. PCB design is time consuming though, hope to grab attention yet . :)

Good news about Geohot's work, very good . ;)
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MSN update: lot of hdmi 1.3 receiver chips are available 10+ :mrgreen:
Darkchip3... hmmm.... :) There must be a way.
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Re: [REQ] DIY DepthQ?

Post by OzOnE2k10 »

Hi,

Sounds like people are still trying to figure out how to buy an HDMI receiver chip on it's own (so they can stream 8-channel PCM). The manufacturers don't make it easy, do they?

Don't mention "room acoustics", another one of my obsessions from diyaudio as you might have seen. :lol: Been a while since I looked at my surround amp / DSP project - it's still collecting dust unfortunately.

Thanks for the help with the PCB stuff. It took me weeks to finally get the Eagle layout done for my "cart emu" FPGA project...

http://forums.benheck.com/viewtopic.php ... 28#p422428" onclick="window.open(this.href);return false;

I paid around £60 to get only three PCBs made! They look rather nice, but there's a possibility that I've made the FPGA pads a tiny bit too short. I had to do that so it would pass the "Design Rule Check" - (The Electra auto-router just wouldn't play ball with the default layout).

Seeing that we need a PCB for the DMD, I might as well just modify George's design to change the FPGA for an Altera, there should be enough pins left over for a digital video input.

I might need one of your PCB gurus to check it over before manufacture. If they can assemble and reflow the board, then even better. ;)

EDIT: Forgot that we would want at least a 720p DMD. I think this would be more hassle than even an XGA chip because most modern DMDs use a DDR type interface. Without some more specific info about the protocol, it could cause problems compared to just using an older XGA chip and George's base design. :?

OzOnE.
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Re: [REQ] DIY DepthQ?

Post by tritosine5G »

Got an OK on reflow and PCB manufacturing ;)

I like 1024*768 , thats fine for me!!! I'd even prefer 16:10 over 16:9. 16:9 seems slim vertically, 4:3 might be more "VR", and 4:3 lends itself for 3d vision surround . ;)

16:9 seems to be better for movies and ps3. Little concern for me.
__________

http://avnetexpress.avnet.com/store/em/ ... eId=500201" onclick="window.open(this.href);return false;
also found this link in my email archives, someone (invited :mrgreen: ) said these would act cool as a pulsed light source:
Using three of those LEDs we reach something like 4900 lm of green, at a price of about 80 euros (plus shipping and taxes).
It's a bit expensive, but the total output (4900+700+2450) is more than 8000 lm.
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Re: [REQ] DIY DepthQ?

Post by OzOnE2k10 »

Cool. 8-)
If I can get blue-line decoding working on this controller (Petrus'), I'll start working on modifying Geohot's DLP project.

I learnt more about the basic Altera FPGA layout from my other project. It took quite a bit of head-scratching to figure out how the pins should be tied and how to connect the config IC. I can just copy the FPGA diagram over to the DMD / Reset chip / DDR Ram diagram.

I'll have to find the pinout for an XGA DMD chip too. I have quite a lot of service diagrams for projectors and DLP RPTV's, so I should be able to find the pinout for my old IBM iL2215 (InFocus LP335, I think). We then might need the connector / holder for the DMD.

I'm wondering if the DMD board should be made more generic with just the DMD and reset chip on it? That way, it might be possible to use one FPGA to control more than one DMD at once (would need some serious speed though).

I remember that the DMD in the InFocus X1 is on a separate daughterboard, unfortunately I don't think it has the reset IC on the same board? It might make it easier to connect to the DMD though. I'll check the service diagram later on to see what the daughterboard contains.

We also need to get hold of the DAD1000 reset chips - Geohot said that he had to buy his direct from Hong Kong? Shouldn't be too much of a problem, but failing that I'll just steal the DMD and DAD1000 off an old projector.

OzOnE.
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Re: [REQ] DIY DepthQ?

Post by tritosine5G »

dad1000 is a walk in the park i can get those in 1 week. Only the dmd is unobtanium.
Also I'd order those LED's once we settle on a type. I'm expert at avoiding customs fees.

Want to add me at M-S-N, brighter1@vipmail.hu (not an email, some 8yr old thing).

Hopefully a buddy can review your pcb too.
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Re: [REQ] DIY DepthQ?

Post by Petrus »

This topic should be renamed to "DIY Polarization Modulator" or "DIY Z-screen", DepthQ make projectors too and it's a bit confusing, at first I thought this topic was about a DIY DepthQ-like projector.

In theory Polarization Modulator it is quite simple to build. It's basically just one side of a sutterglasses with the output polarizer removed. But it may be more complicated, I don't know, I never build one.
And LCD projectors are too slow to alternate the L&R picture, you will need a 120Hz or 85Hz DLP projector.

A made a specific topic about DIY/modified DLP projectors : http://www.mtbs3d.com/phpBB/viewtopic.php?f=26&t=11344" onclick="window.open(this.href);return false;
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Re: [REQ] DIY DepthQ?

Post by mickeyjaw »

Can you not use one of these?

http://www.nuvision3d.com/download/17-21SX.pdf" onclick="window.open(this.href);return false;

I know it's meant to go on top of a crt, but it's a polarisation modulator, so maybe you can project through it. I may be able to get hold of the 17" ones for cheapish (<£100 or so).
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Re: [REQ] DIY DepthQ?

Post by knowhere »

Petrus wrote:This topic should be renamed to "DIY Polarization Modulator" or "DIY Z-screen", DepthQ make projectors too and it's a bit confusing, at first I thought this topic was about a DIY DepthQ-like projector.

In theory Polarization Modulator it is quite simple to build. It's basically just one side of a sutterglasses with the output polarizer removed. But it may be more complicated, I don't know, I never build one.
And LCD projectors are too slow to alternate the L&R picture, you will need a 120Hz or 85Hz DLP projector.

A made a specific topic about DIY/modified DLP projectors : http://www.mtbs3d.com/phpBB/viewtopic.php?f=26&t=11344" onclick="window.open(this.href);return false;
I've been pondering this for a while now, and had the same conclusion.
Doesn't this mean you can take the polarizing film out of a pair of shutterglasses and place it in front of one of these cheap 120hz projectors?
I was looking over the LC TEC "polarization modulator", and it looks like it's just few standard sheets of liquid crystal in a stack for better polarization.
Has anyone tried this?
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Re: [REQ] DIY DepthQ?

Post by tritosine5G »

http://tyrell-innovations-usa.com/shop/ ... 1&Itemid=4

the guy talked about "pi cell" -s at avsforum, so indeed , thats giving it away imho (glasses).
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Re: [REQ] DIY DepthQ?

Post by faaborg »

Hi everybody. Anybody knows, where I can buy that "lcd-panel which rotates the polarization syncronous with the eyeshifting of the projector"?
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Re: [REQ] DIY DepthQ?

Post by xhonzi »

faaborg wrote:Hi everybody. Anybody knows, where I can buy that "lcd-panel which rotates the polarization syncronous with the eyeshifting of the projector"?
http://www.depthq.com/modulator.html
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