Mohammad A. Karim

A new impulse detector for switching median filters

A new impulse noise detection technique for switching median filters is presented, which is based on the minimum absolute value of four convolutions obtained using one-dimensional Laplacian operators. Extensive simulations show that the proposed filter provides better performance than many of the existing switching median filters with comparable computational complexity. In particular, the proposed filter is directed toward improved line preservation.

Fringe-adjusted joint transform correlation

Improved correlation discrimination is achieved by using a fringe-adjusted joint transform correlator (JTC). This technique is found to yield significantly better correlation output than the classical and binary JTCs for input scenes involving single as well as multiple objects. It also avoids the computation-intensive Fourier-plane joint power spectrum binarization processing of a binary JTC. Two optical implementations for the proposed technique are also suggested.

Modified-signed digit arithmetic using an efficient symbolic substitution

An efficient symbolic substitution scheme for modified-signed digit arithmetic operations is introduced. In this technique, an additional bit is used along with each pair of the input bits so that the nth additional bit is a characteristic of the (n - 1)th pair of input bits. The truth table minimization thereby shows that relatively fewer minterms are to be included in the corresponding optical content-addressable memory.

Optical interconnection networks

Publisher Summary This chapter discusses the optical interconnection networks. Ongoing advances in high-speed integrated circuit device technology along with increasing demand in data communication, digital signal and image processing, neural network, and machine vision systems necessitate the design of efficient interconnections topology. In electrical interconnections, the scope of the systems is limited by interference and the planar nature of very large-scale integrated (VLSI) circuits. The chip speed—in particular, is limited by interconnect delays. Intrachip connections pose further difficulty. Optical interconnects, because of their inherent parallelism, high speed, and negligible mutual interference, offer a reasonable solution to this intricate problem. Optical techniques may provide an alternative means for fast, secure interconnections of the devices directly to the interior of a chip. Optical computing research involving optical bistable devices, nonlinear Fabry–Perots, hybrid electrooptic devices, and optical interconnects has contributed to two distinct, parallel interconnect architectures. One approach uses integrated optics to interconnect optical logic devices, while the other involves 2D arrays of devices interconnected in free-space. Free-space interconnection, in turn, is classified as either focused (obtained by lens, beamsplitter, etc.) or unfocused (obtained by imaging light through holographic elements). The index-guided waveguide interconnects may be either space variant or space invariant.

Multiple target detection using a modified fringe-adjusted joint transform correlator

We investigate the performance of a modified fringe-adjusted joint transform correlator for detecting multiple targets present in an input scene. This technique, involving adjustment of the joint power spectrum (JPS) on the basis of the input-scene-only power spectrum, and apodization of the modified JPS on the basis of the reference signal power spectrum, is found to yield good correlation output. Simulation results are presented to verify the performance of the proposed technique.

Improved correlation discrimination using an amplitude-modulated phase-only filter

A novel amplitude-modulated phase-only filter (AMPOF) is proposed for achieving improved correlation discrimination. The proposed AMPOF has an amplitude spectrum which is the inverse of a biased amplitude spectrum of the object function and a phase spectrum which is a complex conjugate of the phase spectrum of the object function. When compared with the phase-only filters, the AMPOF is found to have significantly superior correlation discrimination capability.

Polarization-encoded optical shadow-casting logic units: design

A general design algorithm is presented for the multioutput polarization-encoded optical shadow-casting scheme. A set of POSC equations is obtained from the truth table of the desired logic unit and is solved in terms of four possible pixel characteristics (transparent, opaque, vertically polarized, and horizontally polarized) and four possible source characteristics (off, unpolarized, vertically polarized, and horizontally polarized). To demonstrate its feasibility, the algorithm is used to determine the input pixel characteristics of a full adder and a full subtracter.

Multiprocessor design using polarization-encoded optical shadow-casting

An efficient algorithm for designing a multiprocessor logic unit using a polarization-encoded optical shadow casting system is presented. Both efficient minterm pairing and associative memory mapping with dual addresses are exploited for the design. For illustration, the algorithm is used to design a parallel adder-subtracter unit.

Modulation transfer function of charge-coupled devices

A method for calculating the modulation transfer function (MTF) of charge-coupled devices (CCD) is presented. The analysis accommodates both the time- and space-variant properties of CCDs as well as input images moving with constant velocity within a scan interval. The model developed accounts for both the static and the dynamic MTF of CCD imaging systems.

Polarization-encoded optical shadow-casting scheme: design of multioutput trinary combinational logic units.

The input encoding algorithm of the polarization-encoded optical shadow-casting (POSC) scheme is modified to include the design of trinary combinational logic units. For illustration, the modified algorithm is deterministically employed in the design of trinary adders. Two design approaches are examined for identifying the constraints and flexibilities that are encountered depending on whether the zero-output conditions are considered. The more complicated POSC overlap equations are handled by incorporating LED source encoding to the input encoding process.