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Seeing Around Corners With Dual Photography
An anonymous reader writes "This project (which is part of this year's SIGGRAPH) has absolutely blown my mind. Basically they photograph an object with the photosensor at one point, and the light projector at another, and use the Helmholtz reciprocity algorithm to virtually switch the locations of the camera and projector, showing exactly what the light source "sees"! If that doesn't make sense to you, check out the research page and make sure to watch the 60MB video at the bottom. The playing card trick will leave you speechless!"
With a video projector providing structured illumination, reciprocity permits us to generate pictures from the viewpoint of the projector, even though no camera was present at that location.
Other than using electrons instead of light, that's how a scanning electron microscope works. An object is scanned (raster scan) and one or more sensors near the target pick up the reflections to generate an image. In the SEM the image appears as viewed from the scanning electron beam source.
In the optical one mentioned in the article, the light source is a raster scanning projector which lights a target. The image is produced from photodiodes picking up reflected light.
These two systems are very much alike. One uses photons and the other electrons. The end image is generated the same way.
The truth shall set you free!
Note: I haven't read the paper yet, but it is downloading.
It seems like this might have some military applications as a result. Imagine sticking a photo-resistor array under a door or through a window and then getting "viewpoints" from any of the lights in the room. Could aid in target aquisition and elimination.
Not sure how well it works for something like that, but this is a rather impressive (at least to me) research project.
There are only 10 kinds of people in this world... those who understand binary and those who don't
Which gets me wondering: say you can see in someone's window, but the view is not very interesting: you only see a section of wall; everything else in the room is out of view. But: there is a CRT TV on in that room, and you can see its reflected light on the wall.
How much information can you gather from that reflected light?
You could of course recinstruct the image on the CRT, but that's not very interesting.
The TV does not scan a focused image on its surroundings like the projector does, so you couldn't get a TVs-eye view of the room witht eh same technique.
OTOH, it is clear that from sampling even just a single point on the wall, you could get a silhouette of anything occlusion over the screen seen from that point. At least provided you had a pure white image on the CRT, OR knew what image was on and could calibrate for it.
How far could you get with all the information escaping the window in your direction?
sudo ergo sum