Improved superresolution in coherent optical systems

Objects that temporally vary slowly can be superresolved by the use of two synchronized moving masks such as pinholes or gratings. This approach to su perresolution allows one to exceed Abbe's limit of resolution. Moreover, un der coherent illumination, superresolution requires a certain approximation based on the time averaging of intensity rather than of field distribution . When extensive digital postprocessing can be incorporated into the optica l system, a detector array and some postprocessing algorithms can replace t he grating that is responsible for information decoding. In this way, no ap proximation is needed and the synchronization that is necessary when two gr atings are used is simplified. Furthermore, we present two novel approaches for overcoming distortions when extensive digital postprocessing cannot be incorporated into the optical system. In the first approach, one of the gr atings, in the input or at the output plane, is shifted at half the velocit y of the other. In the second approach, various spectral regions are transm itted through the system's aperture to facilitate postprocessing. Experimen tal results are provided to demonstrate the properties of the proposed meth ods. (C) 2001 Optical Society of America.