Multidimensional imaging using a lensless randomly coded aperture camera

Some of the recent advances in the image engineering technology are three-dimensional and multi-spectral image acquisition. In order to obtain depth information of objects, many technologies are possible such as stereography, ToF, coded aperture and so on. Optical filters, diffraction gratings and variation of light source are available for multi-/hyperspectral imaging. A simple scheme for realizing those advanced technologies are discussed in this study. The proposed system includes only a monochromatic image sensor and a randomly coded aperture without lenses. The lensless imaging technologies are available not only for conventional image acquisition but also for refocusing method. As a statistical optics approach associating with the random coded aperture, simple imaging optics with diffusers are introduced. Those have been applied to acquire depth information and color images. However, none of the proposal to acquire depth and color information simultaneously has been discussed. The size of the point spread function (PSF) of a randomly coded aperture depends on the depth position of a point source. The inverse function of the PSF can retrieve the image on the corresponding depth position, because PSFs of different depths do not correlate to each other. The different wavelengths lead the different PSFs even for the same depth position. It is caused by the nature of diffraction of the aperture. Because of the nature, the selectivities of depth and wavelength are independent, then the proposed system realizes fourdimensional image acquisition with a deterministic approach by using a designed randomly coded aperture.