Forget LCDs and LEDs, Here Come LPDs

waderoush writes "It's not every day you hear about a brand new display technology, but San Jose, CA-based Prysm came out of stealth mode yesterday to talk about its plans for manufacturing laser phosphor displays, or LPDs. The new devices, which the company will show off at the Integrated Systems Europe trade show in Amsterdam next month, reportedly use 25 percent as much electricity as equivalently-sized LCD screens. And they should be easier to manufacture too, since they don't have a backplane of transistors like LCD screens: the image is generated by a laser beam that sweeps across phosphor stripes under the control of a scanning mirror. The venture-funded startup, which plans to build and sell LPD screens under its own brand, is promoting them as a low-cost, low-maintenance way to display information in lobbies, airports, broadcast studios, command centers, and the like."

Comments

do not want

[drinkypoo]

guaranteed to be thicker than LED or LCD, and with phosphor delay; I want LED so that I can have [effectively] instant transitions. we can get back the delay effect with processing, but you can't eliminate phosphor delays when you've got phosphors.

Re:do not want

[pz]

guaranteed to be thicker than LED or LCD, and with phosphor delay; I want LED so that I can have [effectively] instant transitions. we can get back the delay effect with processing, but you can't eliminate phosphor delays when you've got phosphors.

There is essentially zero phosphor delay (I defy you to measure it ... I am a visual neuroscientist and have, so yes, it is possible, and no, it is not easy) on the scale of perceptual latencies. I believe the latency from excitation to phosphor emission is on the nanosecond scale. The typical perceptual delays in the early visual system (retina and the first few stages of processing in the brain) are on order of 30 milliseconds, going from the time photons enter the eye to the first wave of activity in primary visual cortex. Different orders of magnitude. Like 6. Phosphor delay is irrelevant.

What you are perhaps thinking of is the phosphor DECAY which is another thing entirely. When phosphors are excited (such as by an impinging electron or photon beam) the emitted brightness steps up almost instantaneously and then decays down through an exponential relaxation curve. That decay time can tend to blur images when too long, or induce eye bleed (to use the vernacular) when the update rate is too low. The thing is that phosphor decays can be adjusted by reformulating the compounds, and are determined ultimately at time of manufacturing. Very fast phosphors are available to support KHz updates, but also very slow ones (some older oscilloscopes have phosphor decay constants measured in seconds).

Contemporary LCD monitors have typically 2 or 3 frames of latency because of the push to get faster transition times. Those 5 ms response time LCDs get fast specs by overdriving the pixels in a highly controlled fashion, but one that requires knowing what is on the next handful of frames. Since we live in a causal world, that means introducing a 2-3 frame latency for processing within the display. Since the update rates on LCDs are typically 60 Hz, that's on order of 45 ms latency, a non-trivial fraction of the loop from visual perception to motor action (known in the gaming vernacular as twitch response). If you're watching a movie, that latency is irrelevant and wholly, entirely unperceived. If you're playing a game, then it is very important.

Mitsubishi LaserVue

[ArhcAngel]

How is this better than Mitsubishi's LaserVue technology? It's basically a laser DLP to phosphor opposed to whatever material is used by Mitsubishi for a standard DLP screen. It even looks like the LaserVue uses less power than this.

Re:How Thick is the Display?

[natehoy]

Yeah, but cost is also a factor in a lot of cases, and this could well be an acceptable compromise for a lot of people.

These are supposedly a lot cheaper to manufacture and draw a lot less power, so if you are willing to put up with something that has some depth, you may be able to skip the 55 inch screen and go straight to 70 inches for the same money, and lower long-term costs of operation. Or get that 55-inch screen and have $800 left to buy a whole lot of movies to play on it.

A lot of people still have CRT or back-projection televisions. Something like this could appeal to those people, because they are already used to their TV having some depth anyway, and you can get them to high def in an affordable way. I have to imagine a laser projection could at least be slimmer than a CRT.

Plus, CRTs are HEAVY in addition to being bulky. It sounds like something like this would be a box filled with mostly air, so it's at least easier to move around.

Actually, if you made 4 lasers (or 1 laser with a very clever series of 4 mirrors), each one could be responsible for 1/4 of the screen and you'd end up with something shallower than a 1-laser rig. 16 lasers or mirrors would make it shallower still. But then you're starting to draw as much power as an LCD and manufacturing costs are probably as high or higher. So there are adaptations to this technology that could make them slimmer, if you're willing to pay for them, and if you don't apply them to the point you are exceeding the cost of LCD.

Ouch

[idiotnot]

Lasers+moving mirror == great reliability! Have a feeling these are going to make DLP or LCD lamp replacement look downright economical. Still prefer Plasma, personally, but the LED/LCD my SO's dad bought isn't horrible. Even at 240Hz, I did still notice some streaking, though (watching a football game).

Similar to LaserVue?

[RingDev]

If it is similar to Mitshibishi's LaserVue http://www.mitsubishi-tv.com/product/L65A90 a 65" display would be around 10" deep.

-Rick

Re:How Thick is the Display?

[stevew]

Well - I designed what would be portion 320 in the diagram, the image modulation system for a scanning LED TV. The first problem was that LEDs were too dim at the time. The lasers in this system against a phosphor take care of that issue. The second issue you have is what is called the pin-cushion effect. As you scan the laser over the surface of the rotating polygon, it will tend to modulate the length of the scanline making the picture look like a pin cushion. I had a way to fix this in the modulation controller - can't talk about HOW to fix it ;-) Just know that is a pretty big problem to overcome.

Once you have a method to overcome the pin-cushion effect, then you need to have to have a way to align the TVs in production (another REAL headache I didn't come up with a solution for..but then we only got to the prototype stage so didn't have to face that issue.)

Finally - there is the issue of NOISE. Rotating mirrors can be REALLY loud. Our prototype sounded like a jet engine when we spooled up the motors. The precision optics are also expensive. The mechanical engineers believed they could build a much quieter mirror assembly - maybe with air bearings.

So there are a lot of real - practical - tough design problems with this approach.

Finally - I expect it to be a relatively BIG TV.

It's a neat technology - but I don't believe there is any market for it.

Vaguely familiar

[C9OE-6015-B8]

This is not far removed from the Scophony projection system of the 1930's.

Re:How Thick is the Display?

[jcr]

It has to be far enough back to reach all edges.

No, it just has to have some mirror arrangement that allows it to reach the whole screen. I don't see any reason why the laser has to strike the phosphor at anything close to a perpendicular alignment.

-jcr

Forget LAPD, I'm waiting for FEDs

[Max(10)]

FEDs (Field emission displays) are superior to CRTs, LCDs and these new LPDs in every way. FEDs have the same thin 2-4 mm profile as LCDs, but unlike LCDs produce very bright and clear images even in direct sunlight (which is why they were used as HUDs in airplanes) while consuming up to 10 times less power. Sony had a 36" FED prototype that consumed only 14 W, which is 1/8 of what a typical LCD and 1/2 of what an LPD of that size would consume.

Re:How Thick is the Display?

[cool_story_bro]

I don't see any reason why the laser has to strike the phosphor at anything close to a perpendicular alignment.

The angle at which the beam strikes the phosphor would determine the shape of the intersecting region, which may be difficult to correct for. However, a small mirror near each "pixel" that redirected the beam straight at the phosphor would likely correct the situation without taking up too much extra space.

Re:How Thick is the Display?

[Pinky's Brain]

Precision optics seem like overkill to me ... all that shit with f-theta lenses and optical correction of pin-cushions seems so ... archaic.

As long as the distortion is static and a sufficient maximum distance between lines is maintained you can just correct it digitally can't you? Transistors are cheap nowadays, really really cheap, hardware to perform an image warp on a HD signal is pennies worth of die space on an ASIC (in volume, the million dollar mask costs have to be earned back first of course).

Re:How Thick is the Display?

[wiredlogic]

The back surface of the image plane doesn't have to be flat. There could be ridges molded in place to reflect/refract the laser into the phosphors.