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cmjohnson
Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s
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| Posted: Mon Jan 04, 2010 3:51 am Post subject: |
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Gary's right on that. Brightness is a function of how much time the individual DMD mirror spends reflecting light to the screen. It does not take more pixels for brighter light.
Every DMD mirror oscillates between the on and off position at a high rate, several megahertz, if I remember correctly, when it's active
and outputting any greyscale tone other than pure black. It's a single bit DAC using light.
CJ
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon Jan 04, 2010 3:53 am Post subject: |
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| garyfritz wrote: | | Um, minor quibble. The brightness isn't determined by the NUMBER of mirrors, but by HOW MUCH TIME each pixel's mirror is flipped to the "full on brightness" position. Those little suckers flap like a mofo to regulate the level of brightness -- more "on" time (during a single frame) translates to a brighter pixel during that frame. See e.g. bullet 2 on this page. |
Very good student. 
edited for correction.
Last edited by macgyver655 on Thu Jan 07, 2010 4:31 pm; edited 1 time in total
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon Jan 04, 2010 4:02 am Post subject: |
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| cmjohnson wrote: | It's not NECESSARY, though. Each DMD in a 3 chip system gets fed separate red, green, and blue light anyway. Why mix and unmix from RGB to white then back to RGB? You lose lumens by doing that as no optical system is 100 percent efficient.
A 3 chip does not use a color wheel. It uses prisims to separate the white light and then allow each color to hit its own DMD. So it starts as white, separates to RGB and is then recombined as an image.
I don't quite understand youir comment "and although 3 chip is possible I haven't heard of any yet". Certainly you know that 3 chip DLP engines were the first type of DLP engines to be developed and all the highest output projectors use 3 chip engines.
My comment was that I haven't heard of any 3 chip LEDs as of yet.
The Phlatlight is also available in a single RGB module (driven sequentially, R, then G, then B, typically) for use with one chip engines, and they're available in individual color modules as well.
The one DMD DLP's currently available use separate LEDs. There may be a single rgb led but I havn't seen it in application. And there aren't many LED DLPs out there yet.
The single RGB module, driven sequentially, allows you to create a single chip DLP projector that has NO color wheel, too.
This by itself is a nice development because we know that the color wheel motor is a weak point in the design. Particularly
in unsealed optical engines.
No LED DLPs have a color wheel.
I think that the ideal configuration would be to dedicate one Phlatlight color module to its own DMD optical system, lighting it up right at the DMD with appropriate light guides to ensure even DMD illumination and minimal losses. The system output would be combined conventionally into a single lens.
CJ |
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon Jan 04, 2010 4:03 am Post subject: |
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edited for correction.
Last edited by macgyver655 on Thu Jan 07, 2010 4:32 pm; edited 1 time in total
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon Jan 04, 2010 4:07 am Post subject: |
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edited for correction.
Last edited by macgyver655 on Thu Jan 07, 2010 4:33 pm; edited 1 time in total
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon Jan 04, 2010 4:10 am Post subject: |
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| garyfritz wrote: |
Ahh. I got it, Mac. The light from the 3 lasers (LEDs) follows the path in your diagram, but NOT AT THE SAME TIME. It never mixes into white light (except in your visual perception system) because only one of the 3 LEDs is on at once. Duh.  |
See, I new you would get it....
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ecrabb
Forum Moderator
Joined: 13 Mar 2006
Posts: 15909
Location: Utah
TV/Projector: JVC RS40, Epson 5010
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| Posted: Mon Jan 04, 2010 4:14 am Post subject: |
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| macgyver655 wrote: | | OH, I remember now. This is the difference between brightness and contrast. How long its on is brightness and a group is for contrast. |
This makes no sense to me.
| macgyver655 wrote: | | There is more then 1 mirror per pixel. |
Nor does this.
SC
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bbfarmht
Joined: 27 May 2006
Posts: 1273
Location: Where the Mississippi runs east to west!!
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| Posted: Mon Jan 04, 2010 4:27 am Post subject: |
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| ecrabb wrote: | | macgyver655 wrote: | | OH, I remember now. This is the difference between brightness and contrast. How long its on is brightness and a group is for contrast. |
This makes no sense to me.
| macgyver655 wrote: | | There is more then 1 mirror per pixel. |
Nor does this.
SC |
Think stacking. How do we get more lumens and better contrast with crt. I think I'm on the right track, I'll get corrected if I am.
_________________
Adam
"Any society that would give up a little liberty to gain a little security will deserve neither and lose both"
Benjamin Franklin
Last edited by bbfarmht on Mon Jan 04, 2010 4:43 am; edited 1 time in total
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon Jan 04, 2010 4:33 am Post subject: |
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| ecrabb wrote: | | macgyver655 wrote: | | OH, I remember now. This is the difference between brightness and contrast. How long its on is brightness and a group is for contrast. |
This makes no sense to me.
| macgyver655 wrote: | | There is more then 1 mirror per pixel. |
Nor does this.
SC |
Let me rephrase these things. I'm not sittings here looking up information, I'm going off memory of theory of operation that I went through years ago. I was going to point out in the beginning of the description that my explanations may not have accurate numbers, such as specific color wheel speeds and reflections per second. I'm just giving a basics of operation. The DMD reflects light and thats about as far as I want to go into it.
I do not wish to get into every specific operation of every minuet operation of the projector. Everyone can search for specific info. I really dont have time to get to involved with this. Sorry.
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AnalogRocks
Forum Moderator
Joined: 08 Mar 2006
Posts: 26706
Location: Toronto, Ontario, Canada
TV/Projector: Sony 1252Q, AMPRO 4000G
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| Posted: Mon Jan 04, 2010 4:44 am Post subject: |
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| macgyver655 wrote: | | I really dont have time to get to involved with this. Sorry. |
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AnalogRocks
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Joined: 08 Mar 2006
Posts: 26706
Location: Toronto, Ontario, Canada
TV/Projector: Sony 1252Q, AMPRO 4000G
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| Posted: Mon Jan 04, 2010 4:44 am Post subject: |
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What exactly do you want to cover Mac?
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Spanky Ham
Joined: 22 Mar 2006
Posts: 5643
Location: Comedy Central
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| Posted: Mon Jan 04, 2010 4:44 am Post subject: |
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That's cool, Mac.
As for 3 chip LED, it could happen, but I doubt it. The only advantage that I could think of is adding multiple LEDs to increase brightness, if this is possible. For HT, it would negate the advantages unless you need the lumens. With no color wheel and 1 chip you get no rainbows and no convergence errors. It is the best of both worlds for dlp.
Looking at your diagram Mac, I just can't get it out of my head that one could take the cheap LG LED pj and put a 1080p chip in there.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon Jan 04, 2010 4:47 am Post subject: |
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I'm going to finish up with this post and everyone can do their own investigating.
In the LED DLP what was done is remove the lamp and the color wheel (other stuff too but I'm not going into that, remember).
So now there are 3 LEDs (RGB), that pulse at a very high rate (no specifics given). Slowing this down, as the red led comes on, the light is reflected to the DMD and certain mirrors are turned on to reflect certain parts of the image into the lens. Then the green led comes on and its light reflected to the DMD and so on.
In the bulb type DLP, the lamp, ballast and color wheel were the most problematic parts so removing these is a good thing.
But, in the LED DLP, the leds run very hot and require some cooling so the reliability of the leds are not yet known. I am aware of some that have been in for repairs which seems to be a low number but there also is not a large number of them out there yet.
I will put up some pictures of the LED DLP in my next post.
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AnalogRocks
Forum Moderator
Joined: 08 Mar 2006
Posts: 26706
Location: Toronto, Ontario, Canada
TV/Projector: Sony 1252Q, AMPRO 4000G
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| Posted: Mon Jan 04, 2010 4:49 am Post subject: |
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Ahh just the basic's eh? I thought this was going to be more in-depth like your capacitor thread.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon Jan 04, 2010 4:52 am Post subject: |
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| AnalogRocks wrote: | | What exactly do you want to cover Mac? |
Pretty much just the basic operation of the LED DLP. I started with the bulb type to give a basic understanding of DLP so as to make the LED change more understandable.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon Jan 04, 2010 4:54 am Post subject: |
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| AnalogRocks wrote: | | Ahh just the basic's eh? I thought this was going to be more in-depth like your capacitor thread. |
Nah, that thread wore me out, and I still have to finish that one with the ESR part like I promised. I just have some new projects going on here taking up a lot of time.
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ecrabb
Forum Moderator
Joined: 13 Mar 2006
Posts: 15909
Location: Utah
TV/Projector: JVC RS40, Epson 5010
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| Posted: Mon Jan 04, 2010 4:55 am Post subject: |
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| macgyver655 wrote: | | I do not wish to get into every specific operation of every minuet operation of the projector. Everyone can search for specific info. I really dont have time to get to involved with this. Sorry. |
No problem, Mac. I'm just saying... As far as I know, for anything recent/current, there's a mirror on the DMD array for each pixel on screen. So, for a 1080p projector, the DMD has an array of 1920x1080 mirrors on the DMD, or exactly 2,073,600 mirrors. Or, in a 3-chip machine, 3 separate DMD's, with 2,073,600 mirrors each.
Pixel brightness is modulated by binary pulse width on the DMD mirrors. Real contrast (both on/off and ansi) is a fixed parameter, a combination of bulb brightness and light engine and lens design/performance. We'll leave things like image processing and variable iris out of the discussion for sake of simplicity.
Oh, and one more thing... There's really no need for a 3-chip LED-based DMD device... The 3-chip design was born out of necessity to eliminate the color wheel. With LED light source, they can modulate each primary color, and no color wheel is necessary. The only reason I can think of that a 3-chip design could be advantageous would possibly for increased color gamut... I don't know enough about LED color emission to speak intelligently, but if the current LED primaries aren't ideal, you could use additional DMD devices and alternate colors of LEDs to make more full-spectrum wider-gamut images. Of course, tjeu could probably do that without additional DMD's, too...
SC
Last edited by ecrabb on Mon Jan 04, 2010 4:56 am; edited 2 times in total
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AnalogRocks
Forum Moderator
Joined: 08 Mar 2006
Posts: 26706
Location: Toronto, Ontario, Canada
TV/Projector: Sony 1252Q, AMPRO 4000G
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| Posted: Mon Jan 04, 2010 4:55 am Post subject: |
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I understand now 'O wise one. 
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon Jan 04, 2010 5:07 am Post subject: |
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This is a LED DLP is current production.
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garyfritz
Joined: 08 Apr 2006
Posts: 12088
Location: Fort Collins, CO
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| Posted: Mon Jan 04, 2010 5:12 am Post subject: |
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| macgyver655 wrote: | | There is more then 1 mirror per pixel. |
Nuh-uh. I can't find an authoritative source that explicitly says 1 mirror per pixel, but that dlp.com site I cited earlier says DLP chips contain "up to 2 million hinge-mounted microscopic mirrors." 1920*1080 = 2,073,600. Google "dlp mirror per pixel" and you'll find plenty of non-authoritative sites that say it's one mirror per pixel.
| Quote: | | OH, I remember now. This is the difference between brightness and contrast. How long its on is brightness and a group is for contrast. |
No, one mirror = one pixel. How long determines brightness, but there's nothing about contrast. The pixel is just on from 0% to 100% brightness.
As far as I know there's nothing in the DLP implementation that groups pixels. You may be thinking about the dithering effects that are visible with DLPs in low-light areas? That comes from adjacent mirrors flipping on at different times, if I understand right.
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