Time-Folded Optics: shrinking and enhancing camera lenses


Barmak: If you have a sensor that has a time
resolution comparable to the speed of light, then you can actually do some
crazy things to camera optics. Nobody has looked at the the optics itself. So in
this project we wanted to really think about what will happen to the design of
optics and optics of a camera when your sensor has time resolution that is
comparable to the speed of light. We have used a cavity that is too
semi-transparent mirrors to trap the light inside this space. You can use a
cavity to to fold an optical path in time. Now a cavity is basically a trap for
light so when you have a trap that light gets trapped in and wants to
escape you can call it a cavity. Matthew: Imagine you have a room and you place a mirror at one end and a mirror at the other end. And now if I were to stand in that
cavity, and turn on a flashlight, think about where this photons go. They’ll go
to the front of the room, bounce off the wall, and then come right back. Now if I
exited that room those photons would just bounce back and forth forever. Now
what we’re working with is very similar to that. The only difference is when it
hits one wall a little bit of the light passes through, and that’s what we end up measuring with our sensor. Barmak: But now that your sensor becomes very high time resolution or ultra fast, you can actually use each of these round trips
to create the image that you desire. Guy: One of the interesting applications of time folded imaging is the ability to measure multi-spectral signatures of our scene.
Measuring multi-spectral information is very important for industrial
applications. We want to classify objects based on their spectral signature. Matthew: We turned this huge 30 centimeter lens into a tiny 3.1 centimeter lens. Reducing the
size of the camera lens is an important problem. If you look at I phones nowadays
there’s a little bump at the bottom and that’s because we can’t make the lenses
any smaller, so you can imagine using techniques like this to reduce the sizes
further. Barmak: Now that the cameras are everywhere and the sensors are becoming
faster and faster time-folded optics can enable these cameras to not only capture
the scene but capture more and more information about what’s in front of
them.

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