LPD: Laser Phosphor Display - Successor to CRT?

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ChaosCloud
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LPD: Laser Phosphor Display - Successor to CRT?

Post by ChaosCloud » 10 Oct 2020, 15:01

Did some searching and was surprised to find that this technology was not discussed here.

Essentially, it is a rear projection display using a scanning laser (ultraviolet) which excites coloured phosphors on the screen - Very similar principle to CRT (which steers an electron beam instead.).

There is even a company, Prysm, selling these displays right now, albeit as large format video walls for the commercial market.
They are able to achieve 6864 x 1872 @ 360 Hz
(using modules of 624 x 468 pixels, 22" diagonal size)
https://www.youtube.com/watch?v=YYFgf6ax8Vg
https://www.youtube.com/watch?v=fjwJunJ2oZY

I don't see why this tech could not be scaled down to make enthusiast gaming displays. The Sony MP-CL1 projector fits in a pocket and projects 1920x720 @ 60Hz using RGB laser scanning.

The main disadvantage of CRT was size and weight. LPD has no reason to be heavier than a typical LCD, and the size could be reduced compared to CRT by using mirrors to reflect the beam (picture the proportions of the late 2000s RPTVs)

LPD has much lower power consumption than CRT, possibly even lower than modern LCD.

LPD also has much better contrast than LCD.

It seems like the holy grail of display tech, at least until 1000Hz/1000fps becomes feasible. Thoughts?

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Re: LPD: Laser Phosphor Display - Successor to CRT?

Post by Chief Blur Buster » 11 Oct 2020, 22:00

phpBB [video]


Product line link: https://www.prysmsystems.com/displays/l ... duct-line/

Very interesting tech! However, it appears that the 360 Hz is a field rate, which suggests either interlaced or color-sequential, or other field sequencing method. Various field sequencing methods can have artifacts (interlacing, dither noise, rainbow artifacts) so I wonder how it field-sequences -- it would be interesting to see.

Single-pass scanning will be extremely good (zero motion blur); there are some small laser projectors that does it from what I hear -- as long as you skip the bounce-scan projectors (the sweep has to be top to bottom instead).

There are some old threads:
Laser projectors general? [zero lag & zero blur!!!]
No motion blur on my laser projector?!
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ChaosCloud
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Re: LPD: Laser Phosphor Display - Successor to CRT?

Post by ChaosCloud » 12 Oct 2020, 15:37

Good point, yes, it could be interlaced which theoretically might deliver a progressive refresh of 180Hz - still quite good if it's single pass scanning.

If RGB sequential I guess it could be considered equivalent to 120Hz. Personally, I do see "rainbow effects" with DLP and similar tech, and find it distracting, though I have not seen any evidence of such artifacts with Prysm, at least not from watching videos.

phpBB [video]


On another note, seems like Prysm has had some financial issues and have split the company? Maybe they should look into the enthusiast gaming market! It seems like people are starting to appreciate what was lost in the move from CRT to LCD.

thatoneguy
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Re: LPD: Laser Phosphor Display - Successor to CRT?

Post by thatoneguy » 15 Oct 2020, 18:56

Heh, I've known about this tech for years now. Nobody wants to use Phosphor in their displays anymore because they don't want phosphor trails.
ChaosCloud wrote:
10 Oct 2020, 15:01
I don't see why this tech could not be scaled down to make enthusiast gaming displays. The Sony MP-CL1 projector fits in a pocket and projects 1920x720 @ 60Hz using RGB laser scanning.
This has been debunked by Karl Guttag years ago. It doesn't really resolve that resolution. In reality it resolves about 640x360.
https://kguttag.com/2016/09/22/laser-be ... omparison/

The tech never went anywhere and Microvision has been basically selling snake oil for almost 3 decades.

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Re: LPD: Laser Phosphor Display - Successor to CRT?

Post by Chief Blur Buster » 16 Oct 2020, 14:41

thatoneguy wrote:
15 Oct 2020, 18:56
Heh, I've known about this tech for years now. Nobody wants to use Phosphor in their displays anymore because they don't want phosphor trails.
Everyone has preferences on their preferred artifacts -- witness CRT and plasma users holding onto displays. Displays are inherently pick-your-poison. Dislike ghosting/coronas? Dislike flicker? Dislike display motion blur? Dislike phosphor trails? Etc.

Some laser phosphor projectors have its place, though it is a niche purpose.

A CRT rolling-scan emulator (electron gun simulator) on a 1000Hz+ OLED/MicroLED could still be able to successfully emulate the look of CRT refreshing, so theoretically a sufficiently "retina resolution + retina refresh + retina HDR" display of the future could emulate almost any historic refreshing pattern, once it maxes out human vision integration behaviors for typical display sizes and eye tracking speeds.
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Re: LPD: Laser Phosphor Display - Successor to CRT?

Post by ChaosCloud » 16 Oct 2020, 20:43

thatoneguy wrote:
15 Oct 2020, 18:56
Nobody wants to use Phosphor in their displays anymore because they don't want phosphor trails.
Was phosphor trail significant on CRT? I seem to recall it being more of a thing on Plasma.

IMO the worst thing about phosphor is that contrast suffers in a lit room, since the phosphor coating is not truly black.

thatoneguy wrote:
15 Oct 2020, 18:56
It doesn't really resolve that resolution. In reality it resolves about 640x360.
https://kguttag.com/2016/09/22/laser-be ... omparison/

The tech never went anywhere and Microvision has been basically selling snake oil for almost 3 decades.
I don't know about the Celluon, but I actually have tested the MP-CL1. Resolution is approaching 720p, but it's hard to say without sharply defined pixels or scanlines.
Pics here compared with a 1080p LCD.
https://www.avsforum.com/threads/sony-m ... t-44716993

blurfreeCRTGimp
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Re: LPD: Laser Phosphor Display - Successor to CRT?

Post by blurfreeCRTGimp » 17 Oct 2020, 19:43

I honestly think the Highsense dual cell LCD's are going to get us damn close to a display with BFI for smooth motion, good brightness, color and contrast at an eventually affordable price.

I love the idea of the MEMS and LPD concepts. Sometimes I wonder if we could just put 3 laser diodes in the back light of an LCD for a very very bright burst of white light to offset brightness loss from ULMB modes?

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Re: LPD: Laser Phosphor Display - Successor to CRT?

Post by Chief Blur Buster » 17 Oct 2020, 19:54

blurfreeCRTGimp wrote:
17 Oct 2020, 19:43
I honestly think the Highsense dual cell LCD's are going to get us damn close to a display with BFI for smooth motion, good brightness, color and contrast at an eventually affordable price.
It will be interesting to see how fast the GtG pixel response on Hisense LCDs are on both layers of the LCD (the local dimming layer, and the color layer). Both GtG's need to be really fast to allow GtG to finish in the dark period of a BFI cycle (whether be driven by the local dimming layer or via the backlight, or both).

If the GtG of the local dimming LCD layer is fast enough, and can be dual-scanned (ON scan, OFF scan, both at the same time) then the local dimming LCD layer of the HiSense LCD could double as a scanning backlight. Theoretically, both layers can be BFI'd at the same time for maximum BFI contrast...
blurfreeCRTGimp wrote:
17 Oct 2020, 19:43
I love the idea of the MEMS and LPD concepts. Sometimes I wonder if we could just put 3 laser diodes in the back light of an LCD for a very very bright burst of white light to offset brightness loss from ULMB modes?
Theoreteically that would work. Better yet, the laser backlight should be scannable so that it can illuminate a "bar" of screen somewhere behind the phase of the LCD scanout (illuminate only GtG-completed portions of LCD as seen in Electronics Hacking: Creating a Strobe Backlight), and to keep average number of photons hitting eyeballs constant (since sequential-scan strobing techniques are less eyestrain than global-flash strobing).

Scanning backlight can have worse strobe crosstalk than global-flash backlights UNLESS engineered well, then it can have less strobe crosstalk. It was long covered at the 2012 website www.scanningbacklight.com before it renamed to Blur Busters (now www.blurbusters.com/faq/scanningbacklight archive)
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ChaosCloud
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Re: LPD: Laser Phosphor Display - Successor to CRT?

Post by ChaosCloud » 18 Oct 2020, 20:13

Chief Blur Buster wrote:
16 Oct 2020, 14:41
A CRT rolling-scan emulator (electron gun simulator) on a 1000Hz+ OLED/MicroLED could still be able to successfully emulate the look of CRT refreshing,
A display with these capabilities would be amazing, but I think it will be at least a decade before we get there. MicroLED does not seem to have a cost-effective method of production (at least for consumer format displays), and OLED, while now being produced, is still quite vulnerable to burn-in. The brighter the pixels are run, the faster they burn-in, and to have a line-by-line scan similar to CRT would require extreme brightness for that line of pixels. MicroLED may have the same vulnerability as well.

I see LPD as a potential stopgap solution. >120Hz with single pass scanning would be a marked improvement over what current LCDs are capable of.

blurfreeCRTGimp
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Re: LPD: Laser Phosphor Display - Successor to CRT?

Post by blurfreeCRTGimp » 20 Oct 2020, 13:33

If you had a MEMS laser doing raster style scan out, and you used quantum dot pixels on the face of the glass as opposed to a traditional phosphor wouldn't you get the best of all possible worlds?

Motion resolution

Variable resolution inputs as opposed to fixed pixel

infinite contrast

great color without burn in?

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