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Comment: Re:Journal Article (Score 1) 120

by CrazyColin (#32040684) Attached to: OLED Film Could Provide Cheap Night Vision For Cars
Oh, yeah, with the scanning beam it'd work fine. The image would still have to be captured from the perspective of the driver somehow and it wouldn't be relevant to anyone but the driver, but it would work. Since it didn't mention that I assumed the film itself was supposed to be a standalone night vision apparatus.

As far as the second paragraph, what you're talking about definitely works, but only when the lights are up close. In this case, the light right on top of an element will illuminate that element a whole lot more than the other lights because it's many times closer and the incident light is less tangential. When the lights are far away, say a couple hundred yards, the difference in angle of incident light from each light on an OLED element will be a tiny, tiny fraction of a degree; essentially zero. The difference in distance is also essentially zero. So all four lights are illuminating the element approximately equally. (I get what you mean with weaker flux density, but just saying less flux would be more accurate :) Light intensity can be described as a 2D density (e.g. W/m^2), and flux is multiplying that by an area to get a power.)

This goes back again to the frosted glass analogue. With a scanning visible light beam (akin to the scanning IR beam you suggested), you can project an image on it. Normally though, you can't see through it because of scattering. When lights are up close, you can differentiate them, but as they get farther away, they're harder to make out.

Comment: Re:Journal Article (Score 1) 120

by CrazyColin (#32039382) Attached to: OLED Film Could Provide Cheap Night Vision For Cars
As I said, this stuff is hard to explain (and I seem to have failed).

I overemphasized the importance of the OLED's ability to emit light in a specific direction. As you know, OLEDs emitting light in all directions are perfectly fine for TVs and such, so they are absolutely capable of creating an image. And yes, there exists technology to make that image only viewable under a small range of viewing angles. This technology is probably not advanced enough to restrict the viewing to only the driver of the car, but even if it was, the layer of IR sensors is the real issue.

Solid-state IR sensors such as these do not know where the incident light is coming from. They only measure the amount of incident light. If, say, a light is moved around the sensor but kept at the same distance, the amount of incident light will remain the same and the sensor will not know the light is moving. It's this loss of information that makes the whole IR-film-overlaying-an-OLED-film-for-night-vision impossible. If you're sitting in the car, whether or not the OLEDs can emit light directionally, and There Are 4 Lights on the other side of the window, you will not be able to tell whether there are 4 lights or there is one light that's simply 4x brighter. This is because the IR sensors do not even know that, so they cannot convey that information to the OLEDs, which convey the information to you.

The bottom line is that when you want to capture an image (say, of the area in front of your car), you do not use a big array of IR sensors with no lenses. You put an array of sensors behind the focal point of a lens, where the light is focused. i.e. you use a camera.

I hope that helps. In order to display an image, you have to fist capture an image to display. And you can't capture an image with an unadorned array of sensors unless the thing you're imaging is sidled right up next to the array.

Comment: Re:Journal Article (Score 2, Insightful) 120

by CrazyColin (#32035806) Attached to: OLED Film Could Provide Cheap Night Vision For Cars
See the reply "No, this won't work." It's akin to a frosted piece of glass or translucent plastic. Light enters the film but directionality is not preserved because OLEDs cannot choose where the light goes, they just emit in all directions at once. Optics is not an easy thing to explain or understand fully, which is why so few people picked up on why this doesn't work. I'll try though. Transparency in optics means that light can get through something without being scattered. That is, emitted photons have non-random directionality based on the incident photons. It's frosting of glass that introduces this random directionality, since all incoming photons are sent out of the glass in random directions. That's the problem with this film. Incoming photons are turned into electrical signals by the IR sensors, then those electrical signals tell the OLEDs to emit photons. The emitted photons are emitted randomly, so the effect is scattering. And scattering in a windshield is a very bad thing if you want to be able to make out objects on the other side.

Comment: Re:Journal Article (Score 1) 120

by CrazyColin (#32035250) Attached to: OLED Film Could Provide Cheap Night Vision For Cars
Yeah, the fact that they didn't address the directionality of light makes me assume they didn't solve that problem. So you can't just slap the film on a windshield and have night vision, you need to project an IR image on the windshield (in which case the image would only be relevant for the driver.) A lot less exciting than they make it sound.

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