60Hz DLP with 180Hz shutterglasses

[iondrive]

OK, the topic title is technically inaccurate but it got your attention for possibly a great idea. Let me explain.

This idea is for using a DLP projector at 60Hz while your shutterglasses shutter at 180Hz but actually I should say 90Hz per eye.

EDIT: this idea turned out to be not really usable. See the Oct 21st post for details why.

First let's see if I understand DLP projectors in general. Please correct what I have wrong.

A DLP takes in one complete frame at a time and then shows it so it's not like a CRT that traces a beam across it's face that takes more time to paint the image. A DLP has a color wheel and one chip with mirrors on it. The color wheel has three colors and some black inbetween the colors. Normally for my projector, the wheel spins at 60Hz and the mirrors change during the black phase for each new color. That means that at 60Hz it's actually projecting 180 images per second: 1 red + 1 green + 1 blue = 1/60th sec. So when you project a frame-sequential movie, it shows 3 left-eye colors and then 3 right-eye colors: L-red, L-green, L-blue, R-red, R-green, R-blue. Now switch the greens and shutter your glasses at 90Hz. You get L-red, R-green, L-blue, R-red, L-green, R-blue, and so on. So you see now alternating frames are still left/right and the RGB sequence is still in tact. Crazy eh?

Let's talk about the video output for a sec. Since you switched the green channels of corresponding 3d image pairs, odd frames would look like green/magenta anaglyphs and even frames would look like magenta/green anaglyphs or visa versa. This is something like a process called Stereobright but it would interleave alternating left/right views instead of outputting to a dual LCD projector system. Holy crap, I can do this! I was hoping to give this to someone else who would try it for me. The reason I say I can do it is because I've been working on my "Dual out to single shutterglass signal conversion" project and have made some progress but am not ready to post info yet. I need to buy stereoplayer and use its StereoBright output and my interleaver and then I can play a 3d movie and I'll have the image stream I need. Otherwise anyone could just process some 3d video to get that interleaved-StereoBright video stream. Actually, it's better that way. Next issue.

Next I need to generate the shutterglass signals. I think I can just use RAGEDemon's 555 timer circuit in oscillator mode set to the right freq and that should do it.
http://www.mtbs3d.com/phpBB/viewtopic.php?f=26&t=25" onclick="window.open(this.href);return false;

Then start the shuttering with E-D Activator.

Why do all this? Well just to see if it works. It would be good for others to be able to buy a cheap 60Hz DLP projector and have it function as if it was a 180Hz 3d projector. Personally, I've said elsewhere that I'm happy at 60Hz.

I'm going to have to try this eventually. I hate to say it but check back in 2-4 months. Time goes fast for me. Next on my todo list is some more posting and hard drive data recovery.

Please post comments in the meantime.

--- iondrive ---

PS: next I'll have to ask iZ3D to create a StereoBright output mode and maybe an alternating version too. Those guys are great but I don't really know if I want to bother them with that. It's hard to know if anyone will actually use it. Also the alternating version would have the same sync problems as their shutterglass mode.

[mickeyjaw]

I had this idea privately some time ago, and there are 2 potential pitfalls with this solution:

1) Most DLP projectors have at least 4 colour wheel segments, some (I believe the ones advertised with BrilliantColor) have up to 7. In the 4 segment wheel, the 4th segment is WHITE and displays the luma value for the overall image. You would either have to black out the white segment with a massive loss of light or hack the firmware of the projector to composite the luma values from only the green or only the red and blue. The wheels with more segments also have white segments. They may even have complimentary colour components leading to the projector's firmware compositing images with Red+Green / Green+Blue mixed together.

2) Seeing just the green on one frame and the red and blue on another may well lead to colour strobing/flickering and increased rainbow effect, although you won't know for sure until you try

Your best bet for trying this would be to use one of the new LED micro projectors. They use seperate R, G and B LEDs so maybe you (or someone else on this forum) could open one up and stick some oscilloscope probes across the LEDs. If you are lucky you might find they will only fire one at a time, in which case this technique would work. I strongly suspect that they will interleave the colours at many many times the frame rate, however, so you will probably need some damn fast shutter glasses, or yet another firmware hack.

[mickeyjaw]

Forgot to say that if you use an LED projector you can probably tap the drive signal to the LED's to drive the shutterglasses too.

Anyone willing to test their micro/pico projector to see if the LEDs fire one at a time then?

[iondrive]

Hi Mickeyjaw, thanks for posting.

First a question to anyone who knows. How does the projector do shades of a single color? Does it make a 50% red pixel by moving the pixel's mirror to show black halfway through the red display phase? That's the only way I can think of but shouldn't that make a red streak as the mirror moves away? I guess it does but it's so fast that it's very dim and you can't see it. Oh, I guess you answered that already. There's a Luma segment on the color wheel but still there must be a way to get different gray values so the above idea still holds. Is that right? Next question.

How can you tell how many segments your projector's colorwheel has if it doesn't say in the manual? That's w/o opening the case. If I move my eyes fast away from the screen, I can see different colors. Maybe you can use a mirror or something and turn it fast so it shows separate colored streaks on the wall and then count the different phases visible? I guess I'll have to crack my projector open after all but I'm sort of afraid of getting dust in there. Oh, I guess there's already a fan blowing dust in there.

Of course the main idea from post 1 depends on the colorwheel segments being the same width and that seems reasonable but I do have a colorwheel from an unknown device with 3 colors in four segments. One color is half the width of the other colors but is in 2 places on the wheel. A projector like that would need a special customized shutterglass signal that would be more easily done with wired glasses than with IR ones.

I don't think point 2 from your post above would be a problem but timing is critical of course. Like you said, I'll just have to try it and see.

Point 1, the white segment would be a problem though. I'll have to switch out the color wheel with a different one. No, that's not a good idea because of the electronics and degrading the functioning of the projector.

I still think this is a good idea for some company to make a 3d projector out of one with a 3-phase color wheel. Final question for now: what's the max freq for shutterglasses to work good at? I think I'll start a new thread about shutterglass signals since I have some info to share and Q's to ask.

Too bad I don't have an LED projector. Maybe someday I'll get one but I'm pretty happy with my viewsonic PJ503D.

bye for now.

--- iondrive ---

Forgot to mention. I'm not surprised that someone else thought of this before me. That's par for the course with all my ideas.

[cybereality]

I know next to nothing about DLP projectors, so I will let the projector pros handle this one.

Final question for now: what's the max freq for shutterglasses to work good at?

Not sure what the max is, but I got the Another Eyes 2000 to run at 170Hz no problem and it looked pretty good (little to no flicker).

[iondrive]

Thanks Cyber, that's good news. Soon you will no longer know next to nothing.

I wanted to mention something about how the projector works in relation to parallax inversion. So you see, from the first post, the PJ shows complete frames of red, green and blue. This is why DLPs often are out of sync with the shutterglasses. They have buffered a complete frame and then they show the RGB channels one at a time. As stated before, a CRT just paints the image on the screen as the data come in... no image buffering there. Got it?

OK, just did a test and I'm sure my projector has a 3-segment color wheel. Here's how I did it: (funny way first)

I have some Christmas tree ornaments that are like little mirrored disco-balls. If I hold one from the string, I can spin it in front of the projector beam reflecting lots of little dots all over the walls. When the projector has no signal, it shows a blue screen and there are only blue dots on the walls for all spin speeds. This gives me a clue that there is no white segment on the color wheel. Then I did the same with a TV video signal going into the PJ and at some point the ball spins at just the right speed so that I can clearly see on the wall trails of dots that consist of only a 3-color cycle. Viola, no white dots. Only RGB.

For those or you with no disco-balls, this is what I did next. Just take a hand mirror and deflect the beam and give the mirror a good fast turn/flick/twist. You shoud see a multicolored smear. Now go crazy. Shake the mirror turning it left and right as fast as you can and look at the output. I saw reflections of only 3 primary colors and no white. That clinches it for me. No white segment. Hurray. And to think I was just on the verge of cracking it open.

The other way to do it would be to use your 555 timer circuit in non-oscillating mode and make the output pulse very narrow, then use only one shutter-glass lens (the dimmer one) while adjusting the delay time through one complete cycle and you should see each colorwheel segment one at a time. Got it? I didn't do this but maybe someday I will. Maybe not. Anyway, that's all for now.

Later.

PS: you gottta love instructions that include the phrase "now go crazy".

PPS: just figured something out. So Cyber, you started out at 85Hz and used sync-doubling mode to get to 170Hz, right? Oh, well I guess if your monitor can handle it, you could just do it the normal way as long as windows allowed that freq.

[jem454]

Probably a little easier for you, if you remove the lamp, the colorwheel will be staring right at you.

[iondrive]

Hi Jem,

This didn't occur to me because I've taken the bulb out before and didn't remember seeing any color wheel. So I tried it and you're right. It is right there but it's encased in a metal housing so I can only see like 1/10th of it and I couldn't see any easy way to turn it manually so I wouldn't be able to get a good idea of the whole wheel without turning it. I didn't really want to try and take it apart any more than that. Anyways, the mirror method is quick and easy for verifying that there is no white segment but it doesn't help with proportions of colors and dark spaces. The disco balls however, do give an idea of the proportions since it spins at a near constant rate over the time of one frame. Using that method, I can see that there is equal spacing between two pairs of colors, then a wider space between the last pair. That's probably the time inbetween full frames and might be a problem for this idea since all colors are not evenly spaced in time between frames. In other words, the time between colors in a single frame is different than the time between frames. The difference is pretty small though so it might be OK. Otherwise I need a custom timing that is not completely regular. I can do that if I put enough work into it.

mickeyjaw, I understand your point 2 better now. For a single eye, the time between a blue frame and the next blue frame is still 1/30th sec so flicker may still be visible. Actually your point is more about the color cycling more slowly than before. One frame's colors are spread out across 1/30th sec instead of 1/60th sec. As you said, I'll just have to try it and see. This is getting me curious so I'll have to bump it up on my list of things to do.

bye now.

[relaxman]

hi
can you explain somebody why i cannot use my edimensional shutterglasses
with infocus x9 dlp projector? i connect it with vga cable.
with crt it works perfect. but when i connect the projector, dual ddc option isnt anymore
in the selection list at nvidia s3d drivers (162.50)
i know my x9 dont have 100/120Hz, but at night maybe 70-80 is enough for me.

is there a workaround for this? maybe a registry hack?

thank you

[mickeyjaw]

relaxman: Disconnect the DDC channel of the VGA cable between the dongle and the projector (but leave them connected from the VGA port to the dongle). The easiest way to do this is probably to just pull the appropriate pin out at the projector end of the cable with a pair of needle nose pliers. I think the DDC is on pin 15, but it may be pin 12. I am sure if you search the forums this has been discussed many times. This prevents the GFX card from detecting what type of display device you have connected, causing the driver to fall back and assume the display is a CRT supporting all modes and refreshes.

[cybereality]

relaxman: Disconnect the DDC channel of the VGA cable between the dongle and the projector (but leave them connected from the VGA port to the dongle). The easiest way to do this is probably to just pull the appropriate pin out at the projector end of the cable with a pair of needle nose pliers. I think the DDC is on pin 15, but it may be pin 12. I am sure if you search the forums this has been discussed many times. This prevents the GFX card from detecting what type of display device you have connected, causing the driver to fall back and assume the display is a CRT supporting all modes and refreshes.

You can do that with a pass-through extension cable too, I believe. Might be better than damaging the hardwired cables.

[iondrive]

To those interested in this project, I ordered some parts (3-pin DIN male and female connectors) and am waiting for them before I go further. The rest of this post is for relaxman.

Hi relaxman,

Previous posts are correct but let's get back to your first Q, why can you not just use it. Well, I think the answer is because sometimes windows likes to give us problems and I think that's like the best answer you will find. I thought I had a good handle on using registry settings to tweak and enable things and then I plug in an LCD monitor and all I get is anaglyph mode and all reg edits have no effect. What a pain. Anyway as far as solutions go, I would go with cyber's suggestion to hack an extension cable. You can hack the pin or cut into the middle of the cable and find the DDC wire with a multimeter although that is awkward because of the shielding and poking random wires with a needle to check continuity with pin 12.

Normally I would say edit ShowAllViewerTypes to equal 1 but I'm pretty sure you know that one already.
When DDC stereo mode is selected then "StereoViewerType"=dword:00000001 so you could try setting that directly and then don't run the medical test because it will reset things. I still don't think it will work because of my experience with my LCD display and I think the same thing is happening to you. Else you could try downgrading to stereo driver 91.31 if you're playing older games. You only have anaglyph mode, is that correct? I'm assuming you know where in the registry this goes, else use the search function.

DDC:
I've learned over the past month that there are at least 3 different kinds of DDC but the pin 12 hack should do it. Pin 15 is used for a sync signal in another mode. I'll let you research that on your own if you want.

Caveat:
I remember one of RAGEDemon's posts that said he wanted pin 12 to be connected during boot so the system would ID his display and then after that he would want pin 12 disconnected to enable more freqs for his display. I don't know if you'll need a setup like that but if so, then you need to put in a little switch. It's really too bad it's such a hassle.

One more idea. You could try using a KVM if you have one lying around. I actually don't think that will work since the KVM should let the DDC signals through but there's a chance it might work as if windows sees the KVM as a CRT and enables all freqs and doesn't stop you from selecting ddc. (you said dual ddc but I think you meant ddc, yes?)

bye now.

[relaxman]

thanks all of you, i will test is soon

iondrive: now i connect back the dongle to my 17" Acer TFT monitor, and the shutterglass option stay in the list, i can select it, and it even work with the tft. Test application flickers at 60Hz. But of course there isnt any 3d effect with the glasses, because the tft light is polarized.

"you said dual ddc but I think you meant ddc, yes"

yes, sorry for mistake.

edit: i tested it! removed pin 15, and my X9 worked like a CRT, i can select shutterglass! Thank you! It can do only 60Hz, so picture flickers a lot! But the 3D on my wall in 2m size is fantastic!!
I need a 100Hz one

[iondrive]

relaxman, congrats on fixing your problem, nice going. Play in the dark and I think the flicker won't bother you. Regarding that LCD monitor problem I described, that was with driver 17?.?? so I guess 162.50 doesn't do that.

Colorwheel detection update:
I found a better way to check your colorwheel and all you have to do is wave a white stick back and forth in the beam. A pen works great and better yet, you can attatch it to a string or rubberband (longer is better) and just spin it around in the beam. I guess you could use a slow variable-speed drill gun to spin it but don't blame me for accidents. Anyway, using this method I found out that mickeyjaw was right... my PJ does have a white frame. The reason I missed it before is because the white frame is often little-used. It's mostly for on-screen text and very white things like bright clouds and stuff but it also depends on your settings. So if you want to check your PJ, just turn on an OSD like the time-remaining on a video or the PJ's on-screen menu and then spin your pen and read the text in the air. I could see that my frame sequence was not RGB but blue, red, green, and white. I still don't know which is first but I'm guessing white is either first or last. I'll find out after I do some other tests after I put together a certain shutterglass control circuit.

Problem or no problem:
At first I thought I could just do L-blue, R-red, L-green, R-white, etc at 120Hz per eye but I soon realized that's no good because the white gets generated inside the PJ which only gets RBG color data input through an analog line. If I switch in a L-green into a right-eye view, then the white frame will be a combo of both eyes and there will be white ghosting due to that. I thought I was at a dead end until I decided to check something. The PJ has different modes: standard, brightest, presentation, photo, and cinematic. I tried all of these and cinematic mode never uses any white frames. hurray. That's not HURRAY because I find cinematic mode to often be too dark or red. You can of course change the color temp and tint so it might still end up ok and I can still go forward with this project. I now believe the colorwheel has 4 equal quadrants and so I think I need a custom shutterglass control circuit.

The other reason that idea is no good is because after right-white would be another left-blue and you would never have a right-blue. You would have to have some kind of irregular pattern but that actually might not be a dead end after all. Maybe right-white, right-blue could be OK but let's not go there.

So thanks, mickeyjaw. If not for you, I would not have even known to look for a white frame. I might have found it by accident but it's nice to have a heads up.

Hopefully I'll have more info on this within two weeks. I'm still busy with other things too. Darn.

PS: incidentally, the concept under "problem or no problem" might be a reason why anaglyph movies like shrek-3d didn't look as good on my PJ as it did on my LCD. With anaglyph, the PJ makes a white frame and it is a combo of the RGB color data which means it's a combo of both L and R eye-views = white ghosting. I'll have to try "Journey to the Center of the Earth" in cinematic mode and compare it to standard mode. I still think it's my glasses' color not matching the PJ's colors but still, to be safe, watch anaglyph movies in cinematic mode.

EDIT: Woops, got carried away. Now I think the previous PS is wrong. With anaglyph, if a pixel is white, it's white because the left eye is supposed to see red there and the right eye is supposed to see cyan there. The filters do the rest so the red eye doesn't see the cyan eye's data. It functions with color-separation using filters, not time-separation using shutters. I just got confused there for a second.

Question: If I had anaglyph glasses made out of the same material as my PJ's colorwheel, would that give me the best anaglyph experience with my PJ? Or would it maybe be better with more special filters that pass a more narrow band of wavelengths?

[relaxman]

my x9 projector is about 3m from the pc.
When i do this vga cable hack and test i bring the x9 near the pc.
but know i want see the 2m picture from my bed, so i need a vga cable extender.
Or is there another solution? This hack doesnt work with DVI?
because i have a 15m hdmi cable between pc and x9.
maybe with e-d activator i can manually switch on the glasses?
it seems not work when the dongle is not used.

So i need to buy a vga extender? i will buy for sure, when i know
it will also work with my future projector, eg. it can transmit 720p signal at 120Hz.

thx

[relaxman]

and sorry for a little offtopic..

iondrive: will the new optoma hd65 firmware work at real 120Hz?
maybe this will be the total solution

[relaxman]

i was fast, i have my 3m shielded vga extender cable
i want my edimensional dongle near me, because its wired.
so i connect the extender to the vga card,
the dongle to the extender end, and the
projector to the dongle with the 15pin hacked cable.
But this setup DOESNT work! Anybody knows why?

If i connect the dongle to the vga card directly, and then
the extender, and the hacked cable, it works!
the picture is sharp, the cables are OK.
whats the explanation?

now i also need a 3,5jack extender to the syncro cable.

thx

[mickeyjaw]

relaxman:

I don't know for sure, but I have my suspicions. The dongle is powered from the VGA port on the computer, so maybe the cable is too long therefore the voltage has dropped or maybe the cable simply does not connect all of the pins. Power on a VGA port is an optional part of the specification and is carried on pin 9. I cannot think of any other device than a shutter glasses dongle which uses it, many cables do not have this pin at all - look at your cable to see if it has a single pin missing, and if so if the missing pin is pin 9.

Probably your best bet is to get a normal 3.5mm stereo jack extension from a hi-fi/music store though as it will probably be cheaper and easier than finding another VGA extension which has pin 9 connected. Sounds like you're not having too much luck with wiring all this S3D gubbins up!

PS VGA pinouts here:
http://en.wikipedia.org/wiki/VGA_connector

More on DDC etc here:
http://pinouts.ru/Video/VGA15_pinout.shtml

[relaxman]

Bingo! You have absolutely right!
Pin 9 SENSE +5 V DC from gfx adapter
this is the only one thats missing from the extender cable!

I just started to view 3D on my wall with jack extension cable.
I think i need a wireless glass in the future
Interesting, in a dark room at 60Hz, only bright area is flickering.
I think 100/120Hz would be very good to my eyes.

thank you!

[iondrive]

hi mickeyjaw and relaxman,

Nice posting mickey, that was pretty much exactly what I would have said but I would still recommend metering the pin 9 on the extension cable even if it was there but I know not everyone has a multimeter.

relaxman,
I'm afraid I don't know anything about the optoma hd65 firmware. Tell us what you know about it if you think it's relevant. Normally I don't mind some off-topic posts but all I would ask is that you give more details next time like if you said that you get a blank screen like there's no signal to the monitor, that would help us know that there's no 9V to the dongle. Watch out for VGA Y-cables too. They can be missing the 9 pin also. Since the analog VGA is going out of style so you might be able to find a KVM switch on sale cheap and it might have some VGA extension cables included. You just need a little luck or check ebay for them. Have the seller check the cables for you. I also have a little power plug that adds power to pin 9 if needed by connecting to the ps2 keyboard jack or a/c adaptor but I guess those are hard to find and not helpful in your case since you need a longer cable. Anyway, here's an off-topic post: it turns out that you can connect the dongle to the output of a 4-port KVM and use one dongle with 4 computers on one monitor but you need to use one of the power inserters I just mentioned.

Regarding 60Hz, I did a side-by-side comparison with my CRT and DLP projector in sync and there is a significant difference in how noticable the flicker is on them. It turns out that the DLP shows much less flicker than the CRT. It's just a matter of different tech. Of course the walls in the room have the same flicker but in the dark, I don't see that. So anyways, all 60Hz are not the same. So how do you feel about 85Hz? I think you should like that. How high can your projector go?

Update: I haven't made any progress on this project because someone got me posting mplayer posts instead but I think I should be done with those soon.

[relaxman]

"I'm afraid I don't know anything about the optoma hd65 firmware. Tell us what you know about it"
i also dont know more than the announcement few months ago, that it will support in the future.
Some new model, and the hd65 with new firmware. But if its also will be checkerboard like the viewsonic, then
i dont care it.


"all I would ask is that you give more details next time like if you said that you get a blank screen like there's no signal to the monitor"
yeah, sorry for not mention this, just "dont work"

"You just need a little luck or check ebay for them."
Now i use the syncro extension cable for glass, if i have more time i wiil buy a wireless glass.

"It turns out that the DLP shows much less flicker than the CRT."
Please give more details CRT at what refresh?
Because the higher refresh the more ghost you get.
With my Flatron F900P i get many ghost at 120Hz, but almost zero at 60/72Hz.
Picture is more sharp, but true, its flicker.

"So how do you feel about 85Hz? I think you should like that. How high can your projector go?"
I will test 85Hz at lower resolution, but im afraid X9 only accept 85Hz, but downconvert to 60.

bye

[iondrive]

hi again,

"im afraid X9 only accept 85Hz, but downconvert to 60"

I hate when they do that. Oh well.

The side-by-side synced CRT/DLP test I did was at 800x600 at 60 Hz. I get color mismatch with the DLP if I'm at any other freq but I've read this can be fixed with a shutterglass signal tweak. Yet another thing to try someday.

I think the CRT looks good at 85 Hz even though there is some darkness near the top. 120Hz really has undetectable flicker though.

[relaxman]

"I think the CRT looks good at 85 Hz even though there is some darkness near the top"
i dont see darkness at the top. this is a crt or glass issue?

"120Hz really has undetectable flicker though"
but on my crt it has almost unacceptable ghosting. while 72/85 doesnt have crosstalk

[iondrive]

Hi all, long time, no post, anywayz...

relaxman,

Darkness at top of CRT screen:
the darkness near the top of my CRT is, I believe, just from timing issues and the time it takes for the glasses to turn clear. I have an oscilloscope now and I can look at the shutterglass signal on the scope while wearing the glasses and, with one eye shut, I can see the scope trace dissappear and reappear as the glasses shutter. It's pretty cool but anyway, looking at that broken-line trace, I can tell that my glasses take about 1 millisecond to turn clear and that's right at the top of my CRT display so that's why it's a little dark there. If you don't have this, I'm kind of surprised but I guess it's just a case of different hardware. Also, the darkness grows a little at higher refresh rates which makes sense with this theory. To try and fix this, I guess I could increase the back porch for the vertical sweep but it doesn't bother me that much so I usually just ignore it. Maybe I will try that now that you've got me thinking about it. It would help confirm my understanding of the meaning of the back porch. By the way, the shutterglass gets dark faster than it clears... 1/2 ms instead of 1 ms.

So what refresh rate are you happy at with your DLP in the dark?

C ya.

[iondrive]

OK...

More colorwheel detection methods:

Well, it looks like mickeyjaw was right again, darn. He said earlier that my projector might use more than 4 colors and now I see that he was right all along, well sort of anyway. Let me explain. For anyone interested in this idea, here's what you do to figure out details about how your projector uses it's colorwheel. Connect your computer and DLP, put on your shutterglasses and activate them while looking at a white display like an empty Notepad document or a fully white Paint bitmap. Shut one eye and twirl a white pen on the end of a string in the projector's beam and memorize the color pattern you see. That's the color sequence that your DLP uses to put one frame on the screen. The reason you use the shutterglasses with one eye is so that you can ID one frame's color sequence. Without the glasses, you see a continuous banding pattern of colors and you can't tell which color is first in the sequence of each frame. At this point, you should be using "Brightest" or "Presentation" mode so that you can check for the color white in your color wheel. "Cinema" mode doesn't use white in my case and "Photo" mode uses only a little. In my case, at 60 Hz, I see the pattern: "red", green, white, blue, red, green, white, blue, and "red" when using either eye. "red" means red, but narrower and fainter than the other colors and, by using other experiments, I've come to know that the first "red" really is the first color in the sequence and the last "red" is accidently visible, but really is the first color of the next frame so that the sequence of one frame is:

*** color sequence for one frame at 60Hz:
red, green, white, blue,
red, green, white, blue.

So the colorwheel might really only have 4 colors on it but what's important is how it's used. My point is that even if you could see the entire physical wheel, that's not enough info to tell you how it's used so you still have to use the shutterglasses. Aynway, since it shows 8 colors across a 16.7 ms time period, that means about 2ms per color so it's just not a good idea to try to shutter the glasses one per color since it takes 1 ms for the glasses to go clear and 1/2 ms to go dark. Also, it's more complicated than that since the green band is like twice as wide as the other colors so it's not going to be easy to get the timings right for each color or pairs of colors if one wanted to do that.


non-60 Hz Color Mismatch understanding:

At other freqs, the color pattern is different. At 70/72/75/85 Hz, I get this on my viewsonic-PJ503D:

*** color sequence for one frame at non-60Hz:
eye 1: red, green, white, blue, red, green
eye 2: white, blue, red, green, white, blue

That's 12 colors across 2 frames as opposed to 16 colors across 2 frames for the case of a 60Hz refresh rate. It's odd but it explains the color mismatch between your eye-views when using shutterglasses at these freqs. One view is more blue and the other is more green since the first red in eye 1 is faint due to shutterglass clear-time. The good thing to come from all this is that now that I understand this, I can make a circuit that fixes the color mismatch problem by changing the timings of the shutterglass lenses. The one problem is that my solution will only be good for wired glasses since wireless glasses work differently. The thing is that there will be some time during the shutterglass cycle when both lenses will be dark and I can't really do that with a wireless IR setup because of the way it works... one lens is always the opposite of the other for an IR setup. I'll start another topic about this if I ever actually make a circuit like that to fix DLP color mismatch for non-60 Hz freqs.


Advice for viewing green/magenta anaglyph on a DLP:

One reason for going down this path was for a potential solution to my anaglyph viewing problem. Well, it turns out that it's not necessary since I've figured some things out:

1) Don't use "Presentation" mode, and
2) Use your computer to play the anaglyph DVD instead of a DVD player.

For some reason, the computer gives much less color-ghosting than my DVD player. It might just be color leakage in the composite cable. As for Presentation mode, if you fill your screen with pure magenta using Paint or another program, you can spin a white pen in your DLP projector's beam and see that there is some green in the sequence that the projector just decided to stick in there to make the image brighter. This means that for a green/magenta anaglyph, the magneta view will have some green in it that your "green" eye will see. Your green eye will see some of the image meant for only the magenta eye. In practice, it depends on the scene and so sometimes Presentation mode will be OK but from my test-run last night of green/magenta "Journey to the Center of the Earth", I recommend starting with Photo mode with brightness/contrast settings of 40/60 and adjusting from there. Other than green/magenta, I believe Presentation mode should be OK for red/cyan and yellow/blue or colortone. Hmmm, I guess I'll post this advice in the 3d movie forum.


Bye now:
I think that's it for this project. Too bad it didn't give more results but I think it was worthwhile and I'm glad to have learned the things I did because of it. I'll post more if I think of anything else that I might have left out.

it's been fun, or at least interesting,
--- iondrive ---

PS: to all who have been following this thread, sorry I didn't catch this colorwheel sequencing earlier. The reason is because I normally don't have my computer connected to the projector so when I twirled my pen, I didn't get the idea to wear the shutterglasses. Normally I just have the DVD player and DTV converter box connected.

PPS: At 60 Hz, you get 8 separate single-color images in 1/60th sec. That's like 480 frames per second!!! Man those mirrors are fast! If only there was a way to make shutterglasses using DLP chips... hmmm)