Lensless camera adjusts focus after image capture
To prove their concept, he researchers have built a lensless prototype camera comprising a patterned film with concentric circles about one millimeter away from the image sensor.
As light passes through the concentric interference film, a shadow image forms onto the image sensor. Computational image reconstruction is performed by superimposing a similar concentric-circle pattern onto the shadow, which creates Moiré fringes whose spacing is dependent on the incidence angle of the light beam. Using a Fourier transform, the full image of the object in front of the sensor can be reconstructed, while focus depth can be freely adjusted by changing the superimposed concentric-circle patterns applied to the shadow image.
The lensless camera was proven with a 1cm2 image sensor at 30fps, and the researchers claim the computational load for such image processing was about 300 times lower than that of alternative lensless cameras found in literature, running from a standard notebook PC.
As well as being lighter and thinner than traditional cameras, such a lensless camera relaxes design rules, the researchers say, making it suitable for many applications from smartphones to car, drones or wearables. One image capture allows for multiple focus imaging, opening many new applications, potentially including depth sensing.
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