Laser projectors general? [zero lag & zero blur!!!]

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Light23
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Re: Laser projectors general?

Post by Light23 » 20 Dec 2014, 22:54

flood wrote:why 6 lasers?

Well for one I can get the display a lot brighter by using 6 lasers.
Second thing is it improves the color gamut a bit since as you mentioned they are monochromatic and a very narrow bandwidth.
Image
The color range, or "gamut," of a laser projector depends on the spacing of the laser wavelengths. The gamut is represented by the area enclosed by lines drawn between the three laser wavelengths on the chromaticity diagram. As can be seen, the color gamut depends strongly on the choice of green, but the red and blue wavelengths have little impact. Green sources emitting at 520–535 nm usually are considered to give the best gamut.
I know 3 RGB lasers covers almost all colors, but adding 3 more at different wavelengths allows linear combination to cover more of the possible stimulation.
(My 442nm blue is more ultraviolet purple in nature than blue and struggles to do royal "true blue" while my 450nm blue laser does "true blue" with no problem at all.. So it helps the overall color in my opinion to use both.)

The only way more primaries could expand the presentation of an image is if it expands the color gamut.

And although the red and blue wavelength variations have little impact on gamut color when it come to perceived RGB mixed white color temperature, they do with overall brightness.

In the wavelength region of red for instance, luminous efficacy rapidly increases as wavelength shortens.

Current red laser diodes used in the current display engine lase at 642nm. By moving toward a shorter wavelength ,even by a mere 4 nm – the human eye perceives this red light as being much brighter. In this case, at a fixed brightness, red light at 638nm appears about 33% brighter than the same light output at 642nm! :shock: Similarly, the blue laser diode being used in the 1st version emitted light at 442nm. By increasing that wavelength to 450nm, perceived brightness would also increase. That is why I have included six of those specific wavelength lasers in the monitor.

Then you have the overall increase of adding another set of RGB lasers to the mix. :)

flood
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Re: Laser projectors general?

Post by flood » 21 Dec 2014, 09:01

wait wtf are you making your own display from scratch?

with what content will you be able to take advantage of the additional gamut space?

you should use uv plots for comparing gamuts as xy is perceptually nonuniform. here's an article that you may want to look at:http://www.tftcentral.co.uk/articles/co ... _gamut.htm

Amalion
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Re: Laser projectors general?

Post by Amalion » 21 Dec 2014, 09:55

Wow! This is impressive. I was not expecting anything so complex, let alone so gorgeously retro - In the photo, it even looks IBM beige! Guess it's going to be more expensive than I thought but I'd still like to hear!

What's the resolution and aspect ratio of your prototype? What's the physical size and weight? I noted in the youtube post from upthread that a commenter is now claiming that there will be a HDMI version of the airpico; if it's true, I was toying with the idea of tiling four of those for 2560*1440.

I don't fully have my head around colour gamuts, but how would one calibrate it so that sRGB content looked as-intended?

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Light23
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Re: Laser projectors general?

Post by Light23 » 21 Dec 2014, 21:06

flood wrote:wait wtf are you making your own display from scratch?
Yup! :D
flood wrote: with what content will you be able to take advantage of the additional gamut space?
ProPhoto RGB, Sony DSC-F828 with 4-Color RGBE RAW output, Adobe RGB & Rec. 2020 (UHDTV) color space to name a few.
(Most normal cameras only use R/G/B subpixels to make up an image, the F828's sensor uses four colors, Red, Green, Blue and Bluish-Cyan. By using cyan or near 490 nm (blue green) creates a better overall white image also.)
Image

The issue with this kind of laser display tech is the difference between primary colors and secondaries that fill in the color space. The primary colors are VERY vibrant, however the spaces between them have a lot less energy. (It is like having a very loud sound system that only have 32 narrow bands of power. Yes it is loud, and can extend from 20-20k possibly, but that doesn't make a nice flat response.) The level difference between the RGB spikes and the spaces is around 90-95%. Yes that may make the image look punched, but it has to be. The color spaces that are not covered end up over saturated because there is nothing else the projector profile can be programmed to do. To combat this my multi color laser display will need to have filters on the peaks of the RGB lasers and to include the other 3 secondary emitters without filters to ensure a flat base light before the imaging section of the projector. So that means the inclusion of not only 532nm green, but a Green 510nm- 516nm laser as well to cover the cyan part of the gamut better.
(Which I have just obtained 3 days ago.) 8-)

The 6 color laser display I'm building would still look better at color reproduction than most conventional viewing options when you take all these other things into account.
flood wrote: you should use uv plots for comparing gamuts as xy is perceptually nonuniform. here's an article that you may want to look at:http://www.tftcentral.co.uk/articles/co ... _gamut.htm
Thanks for that link Flood! VERY interesting article :)
Amalion wrote: What's the resolution and aspect ratio of your prototype?
848x480 (50 Lumen) 2 VGA imputs
The next prototype will be 2560x1440 HD 16:9 100 lumen 1 HDMI imput (Requires Warpalizer software) 4 way HDMI input/output converter will be built into the monitor.
I hope to build several different models at different AFFORDABLE price points and resolutions.
But the cost of these materials is high. Maybe I should Kickstarter this. lol
Amalion wrote:I don't fully have my head around colour gamuts, but how would one calibrate it so that sRGB content looked as-intended?

This wide gamut display can be set for an sRGB emulation mode quite easily so when you do wish to play a game, or work outside color managed app's that assume sRGB, you're all set. Press a button in the software, you're back to wide gamut behavior and one that you've calibrated for a screen to print match.


The monitor will be precalibrated by myself with color checker software. (I worked 10 years as a photo tech and manager on a Noritsu printer.)
Any more color tweaks you can do to taste in the video settings of you own graphics card or color settings on your OS.


There are monitors that can show more than the typical rRGB colour gamut, but they do come at an extra cost, and typically they're not optimized at all for games (their response times are slower, which is very annoying for games, but rather irrelevant for say like editing photos). Some of them can reach the Adobe RGB colour space.

aeliusg
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Re: Laser projectors general?

Post by aeliusg » 22 Dec 2014, 08:44

You make this sound almost straightforward. :lol: I think there'd definitely be some Kickstarter interest beyond the enthusiasts here on this forum. My question is, will this be multi-sync capable a la CRT?

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Post by Chief Blur Buster » 22 Dec 2014, 09:51

On one hand: Making a laser display from scratch is a lot more doable than it sounds. It's basically some high-speed microcontroller, fast piezo mirror, and a bunch of off-the-shelf lasers, and running a fast "laser show" (raster-scanning the lasers CRT-style) that ends up making a display.

However, it is still very impressive -- very far beyond the technical abilities of most people; it requires a very good understanding of how displays are refreshed, the signal pipeline (e.g. already know how to fiddle custom resolutions, and understand CRT scanning behavior) while also being knowledgeable in advanced hobby electronics. A hobby CRT TV builder (of which many existed back in the olden days), with some digital-era skills additions, would be able to construct a laser projector from scratch. The Microvision doing 480p would be doing a horizontal scanrate of about ~31.5KHz (~31,500 rows of pixels per second). You only need approximately four times the horizontal scanrate (135KHz) in order to achieve 1080p 120Hz. I imagine that a multi-faceted (e.g. polygonal) mirrored spinning cylinder would easily be able to scan a laser beam back and fourth 135,000 times a second while spinning far more slowly. A different slower mirror would do the vertical. The bigger challenge, probably, is beam focus needs to be really tight, and laser modulation would need to be far higher speed to get crystal clear pixels at high dotclocks.

The laser de-speckling film is pure genius. We wouldn't need to wait for OLED to get our zero-blur zero-lag CRT-replacement display. It could even be built into a box. Much more bulky than a flat panel, but thinner than a CRT, and relatively lightweight.

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flood
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Re: Laser projectors general?

Post by flood » 22 Dec 2014, 13:49

Light23 wrote: The monitor will be precalibrated by myself with color checker software. (I worked 10 years as a photo tech and manager on a Noritsu printer.)
>software
uwotm8
you need to have a good colorimeter and possibly a spectro

even then calibration for laser displays is going to be very tricky.
see https://www.youtube.com/watch?v=C5iAYzai3ZI
the issue gets worse for displays with more saturated primaries. you can find a long thread on avsforum about people's troubles calibrated quantom dot lcd displays... but beware that thread has both very knowledgable and very clueless posts

anyway have you actually began work on this or are you still researching stuff?

flood
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Re: <

Post by flood » 22 Dec 2014, 13:56

Chief Blur Buster wrote:I imagine that a multi-faceted (e.g. polygonal) mirrored spinning cylinder would easily be able to scan a laser beam back and fourth 135,000 times a second while spinning far more slowly.
i'm not so sure about the "far more slowly" part. even with a six sided prism/mirror you'd need 135000/6 = 22500 revolutions per SECOND

the other issue is that the prism needs to be very well aligned. if one face is off by 0.1 degree, the resulting image will have every 6th line be displaced by 2 pixels or so

and the final issue is that the rotation needs to be perfectly synchronized to the hsync signal

more links:
http://en.wikipedia.org/wiki/Laser_scan ... al_effects
Some special laser scanners use, instead of moving mirrors, acousto-optic deflectors or electrooptic deflectors. These mechanisms allow the highest scanning frequencies possible so far. They are used, for example, in laser TV systems. On the other hand, these systems are also much more expensive than mirror scanning systems.
http://hackaday.com/2011/12/31/full-color-laser-tv/

blargg
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Re: <

Post by blargg » 22 Dec 2014, 14:30

flood wrote:
Chief Blur Buster wrote:I imagine that a multi-faceted (e.g. polygonal) mirrored spinning cylinder would easily be able to scan a laser beam back and fourth 135,000 times a second while spinning far more slowly.
i'm not so sure about the "far more slowly" part. even with a six sided prism/mirror you'd need 135000/6 = 22500 revolutions per SECOND
That's far more slowly than 135000 revs per sec :)
the other issue is that the prism needs to be very well aligned. if one face is off by 0.1 degree, the resulting image will have every 6th line be displaced by 2 pixels or so
Allow calibration of each of the six "phases".
and the final issue is that the rotation needs to be perfectly synchronized to the hsync signal
You'd be using an optical mechanism to detect each revolution, or even each sixth of a revolution. Have a scanline buffer to allow for local variation in hsync-mirror variation, and adjust motor speed to keep overall sync.

alex47
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Re: Laser projectors general?

Post by alex47 » 22 Dec 2014, 16:15

What about input lag? Is there any noticable? Do you feel any delay in mouse movement and displaying mouse movement? How slow is it compared to a CRT?
Also I read that using HDMI (digital signal) in monitors causes delay compared to VGA (analog [in CRT])
What I'm trying to ask is that wether using VGA over HDMI might be faster

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