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by defterGoose
3062 days ago
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Laser light is "coherent" both spatially and temporally. Spatial coherence allows the beam to be "collimated", which basically just means that it looks like a cylinder and not a cone. That's why you can shine a laser at the moon and see the spot; most of the energy from the laser makes it to the same place, bounces back to your eyes, and you get a bright spot. Shining a flashlight doesn't work because the light spreads out too much. Technically some of the light still gets to the moon and back to your eyes, it's just below the threshold of your eye's ability to distinguish differences in brightness. For the glasses, the laser is probably being scanned using a mems mirror (like how a DLP tv works, sorta), and modulated in brightness periodically to create the pixels. Since there's only one "point" of contact between your lens and the beam, the lens doesn't distort the beam like it would an image. That's where the idea of focus comes in. If you were looking at a photograph with your eye, there would be many sources and colors of light. Since the lens refracts incoming light based on direction, position, and color, your lens' job is to make sure the "pixels" of the photograph stay spatially organized with respect to each other. That's what being in focus means. And since the laser has only one color and one direction, all that light stays together and makes a nice dot on your retina. The only thing left to do is make a correction to the overall distortion pattern your lens introduces ,which is similar for pretty much everyone. Same reason you need to add barrel distortion before sending video to an HMD. I think that's what they were showing with that "warping" red image of the glasses' display. |
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