Multi-wavelength imaging with extended depth of field using coded apertures and radial quartic phase functions

Abstract

This study demonstrates a new multi-wavelength imaging technique with an extended depth of field. The spatial and spectral information of the objects is encoded into a single bipolar function of sparse dots using coded phase masks (CPMs) and a radial quartic phase function (RQPF). Each wavelength produces an intensity response of sparse dots with a unique set of distances between the dots, enabling the decoding of multispectral information. The RQPF is introduced to extend the depth of focus for different wavelengths. A library of point spread holograms (PSHs) is prerecorded with uniquely designed CPMs by placing the point objects of multiple wavelengths at the system input. For reconstruction, the object hologram is cross-correlated with a PSH corresponding to the wavelength of the object. The results are compared with direct imaging and with the conventional technique of interferenceless coded aperture correlation holography. The method is unique because the number of camera shots required for multi-wavelength imaging is the same as for monochromatic imaging.