Restoration of broadband imagery steered with a liquid-crystal optical phased array

Abstract

In many imaging applications, it is highly desirable to replace mechanical beam-steering components (i.e., mirrors and gimbals) with a nonmechanical device. One such device is a nematic liquid crystal optical phased array (LCOPA). An LCOPA can implement a blazed phase grating to steer the incident light. However, when a phase grating is used in a broadband imaging system, two adverse effects can occur. First, dispersion will cause different incident wavelengths arriving at the same angle to be steered to different output angles, causing chromatic aberrations in the image plane. Second, the device will steer energy not only to the first diffraction order, but to others as well. This multiple-order effect results in multiple copies of the scene appearing in the image plane. We describe a digital image restoration technique designed to overcome these degradations. The proposed postprocessing technique is based on a Wiener deconvolution filter. The technique, however, is applicable only to scenes containing objects with approximately constant reflectivities over the spectral region of interest. Experimental results are presented to demonstrate the effectiveness of this technique.