Researchers create focus-free camera with new flat lens
Depth of field for a normal camera is a function of the relative aperture size (f-number), focal length and distance to the subject. This camera is able to create a huge depth of field with a far smaller aperture than would be expected with a conventional camera.So how does it break the laws of physics? Well it doesn't; it cheats by not preserving the phase of the light. In a normal lens, the phase of the light is preserved. Light that must travel further to reach the point of focus travels faster as it passes through less lens material (where it travels slower than the speed of light).The lens is also made on a flat disc a little bit like a Fresnel lens. The difference with this lens is that it doesn't have a single point of focus, instead light is focused onto many planes, simultaneously with equal power of light focused onto each plane. In this paper the planes were chosen to be between 5 and 1200mm. A clever computer algorithm calculates the exact shape of the lens to get this distribution given a specific wavelength of light.The end result is a lens which has amazing depth of field but the trade off of only operating well at a single frequency and poor efficiency. Most of the incoming light is being focused on a plane that the sensor isn't on. Indeed at 1200mm it has an equivalent f-number of 555 requiring some insanely bright lighting and long exposure time to get a good image.I can't see many real world applications of this camera given the downsides but in a world of more computational photography this could be one part of a better imaging system.