Taking photos through opaque objects

10 May 2010
Posted by Chris Smith.

Something which has always tantalised many people ranging from surveillance agencies to the more dubious parts of society is being able to see through opaque objects. If the object absorbs all the light hitting it then this is impossible but if an object is translucent, and scatters light in lots of random directions mixing up the image so much it is impossible for our eyes to decode it, but in theory none of the information about what is behind it is lost.

Nikon D700 cameraSebastian Popoff and collegues at the Langevin Institute in Paris have worked out a way of getting this information back. They have managed to see through a slide covered with zinc oxide particles which to your eyes look white. They have done it by first shining a series of carefully calibrated laser pulses through the slide, and working out what patterns these produce on a camera sensor. From this they can work out what effect the slide is happening on the light, so when they put an object behind the slide, the pattern will change and they can work out from this change in pattern what the object looked like.

This is certainly not going to let us see through a wall, and seeing through frosted glass is still very difficult without a lot of careful setup and illumination, but it may be useful in the short term for seeing through an opaque sample in a microscope, and it has been suggested that the same technique could make a white wall behave like a mirror.

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