| In the optical shadow casting (OSC) system digital computing is done by decoding projected shadows of coded inputs. In this system, the inputs were encoded using opaque and transparent cells. Accordingly, the original OSC system was limited to simple logical operations and half addition only. The scope of the OSC scheme has been greatly increased by the introduction of polarized codes for encoding inputs, source and decoding masks. It was realized that the polarization-encoded optical shadow-casting (POSC) will overcome the limitations of the OSC system in terms of lack of hardware flexibility. Further no systematic design rules were present to justify the superiority of the POSC scheme over the OSC scheme and its versatility in terms of designing any arbitrary arithmetic/logic unit.;A formal POSC design algorithm is developed which is very systematic and general as it may be easily utilized to determine the pixel encoding, source configuration and output decoding mask for any binary combinational unit. The POSC system is based on the laws of overlap, analogous to what is known as Boolean algebra in digital system design.;The algorithm has been deterministically employed to design a binary adder, a binary subtracter, a trinary half adder, a trinary full adder, a highly efficient adder based on truth table partitioning, programmable logic array, multiplier, carry free adder, and J-K flip-flop.;The image processing capability of the POSC system was explored next by designing a serial and parallel gray level image adder, an edge detector, and a median filter. In each of the designs, encodings for the inputs as well as the characteristics of the source and decoding mask are identified.;Before processing the data in the POSC system, they must be encoded. Some real time and nonreal time encoding schemes are identified. One dimensional coherent encoding, two dimensional incoherent, birefringent encoding, liquid crystal, polarization-encoded spatial light modulators are discussed as possible candidates for this purpose. A novel shadow displacement technique is proposed. |
