Super-resolution imaging technique based on a LCoS display: Increase of CCD resolution limit

摘要

The resolution of any imaging system is limited by many factors, as by the diffraction resolution limit of the system or by resolution limitations related to the geometry of the optical elements. One of the main geometrical limitations in optical systems is due to CCD cameras used for the image acquisition. In particular, pixel size, shape and pixel pitch of the used CCD camera always impose a limit in resolution. This paper faces the problem of the geometric super-resolution limitation, providing an approach free of mechanical movements, which helps to overcome the problems related to CCD pixels pitch. To this aim, a parallel aligned (PA) liquid crystal on silicon (LCoS) display is placed at the Fourier plane of a transparent object, and different linear phases are addressed to it. Afterwards, an image-forming optical system provides the final image of the object at the CCD camera plane. By addressing different linear phases to the LCoS display, object images with different sub-pixel displacements in 1-D are acquired by the CCD camera. Afterwards, all the shifted images are combined, leading to a final super-resolved image with larger dimension than the original object image. In addition, an inverse filtering process is also included into the proposed method, leading to certain extent, to a decrease of the blurring effect. The experimental comparison of the object images obtained with and without using the proposed technique provides the improvement, in terms of resolution, achieved by applying our technique.