Experimental investigation of an interferometric technique for background radiation compensation

Abstract

The ability of optical systems to obtain images of desired objects is sometimes limited by the presence of background radiation. The background radiation can arise from scattering, self-radiation, or out-of-focus images, all originating from regions axially displaced from the object plane of interest. Techniques such as confocal microscopy, computer image reconstruction, various holographic techniques, and timegating tomography are all being developed in order to address the problem. Some of the prior techniques have been successfully applied in various fields where the imaging problem is encountered. All of the prior techniques have some advantages and some disadvantages. Recently, a new technique of background compensation has been proposed that utilizes controlled phase shifts in the pupil plane of the imaging instrument to distinguish in-focus radiation from background radiation. The new technique can potentially offer several advantages over the prior techniques, and may be applicable in situations for which no other technique is suitable. The present work describes the technique and reviews some relevant theoretical aspects and theoretical predictions for the technique. In addition, an experiment to test the basic concepts of the technique is described. The experiment consists of several discrete phases, and the results of the experiment are compared to the theoretical predictions. The results of each phase of the present experiment support the theoretical expectations for the technique, and it is concluded that the technique should be further investigated. The technique appears to represent a novel and potentially far-reaching alternative method by which the problem of imaging in the presence of undesired background radiation can be successfully addressed.