Abdul Awwal - Academia.edu (original) (raw)
Papers by Abdul Awwal
Proceedings of SPIE, Mar 27, 1997
ABSTRACT
Optical Society of America Annual Meeting, 1992
Restoration of velocity-degraded images owing to phosphor persistence may be achieved by using a ... more Restoration of velocity-degraded images owing to phosphor persistence may be achieved by using a Fourier transform filter setup. However, such a system suffers from very stringent alignment and filter fabrication requirements and is therefore less amenable to a real-time restoration scheme. In this work a joint Fourier transform setup is used to perform real-time adaptive restoration on images degraded owing to relative motion and phosphor persistence.
Optics and Laser Technology, Feb 1, 1998
Ecient parallel schemes for carry-propagation-free addition of modi®ed signed-digit trinary numbe... more Ecient parallel schemes for carry-propagation-free addition of modi®ed signed-digit trinary numbers are presented. The necessary minterms for implementation using an optical programmable logic array area are derived. The proposed schemes require only a truth table of 25 entries compared with an earlier scheme of 625 entries. The proposed schemes are amenable to optical implementation. Experimental results using an optical programmable logic array are demonstrated. The experiments show the problems of noise and crosstalk. This suggests some dc bias is necessary to increase the signal-to-noise ratio of the optical circuit.
Optical Society of America Annual Meeting, 1992
Among many Gaussian laser beam diameter measurement techniques, a relatively fast and inexpensive... more Among many Gaussian laser beam diameter measurement techniques, a relatively fast and inexpensive technique is provided by the use of ruling1, 2 where a Gaussian beams scans the ruling and a detector placed directly on the other side is used to detect the maximum and the minimum transmitted power through the ruling. The ratio P min /P max is found to be a function of the ratio r O /L (beam radius to ruling period).
Proceedings of SPIE, Dec 6, 2001
ABSTRACT In this paper, a new algorithm to determine the adaptive threshold formula for the trina... more ABSTRACT In this paper, a new algorithm to determine the adaptive threshold formula for the trinary associative memory model is presented. The optimal threshold is chosen to yield the best performance. Different threshold parameters have been investigated to obtain the optimal range of threshold parameters. In order to validate our performance model, character recognition problems are investigated.
Proceedings of SPIE, Feb 10, 2011
The heart of the National Ignition Facility is a megajoule-class laser system consisting of 192 b... more The heart of the National Ignition Facility is a megajoule-class laser system consisting of 192 beams used to drive inertial confinement fusion reactions. A recently installed system of programmable, liquid-crystal-based spatial light modulators adds the capability of arbitrarily shaping the spatial beam profiles in order to enhance operational flexibility. Its primary intended use is for introducing "blocker" obscurations to shadow isolated flaws on downstream optical elements. To optimize the system, both the position and shape of the obscurations must be carefully verified prior to high-fluence operations. An automatic alignment algorithm is used to perform detection and estimation of the imposed blocker centroid positions compared to their intended locations. Furthermore, in order to minimize the spatially-varying nonlinear response of the device, a calibration of the local magnification is performed at multiple sub-image locations. In this paper, we describe the control and associated image processing of this device that helps to enhance the performance of the overall system.
Proceedings of SPIE, Nov 1, 2002
A novel uni-complex valued trinary associative model, which is implementable in the optical domai... more A novel uni-complex valued trinary associative model, which is implementable in the optical domain, is proposed. Retrieval of the stored pattern is accomplished using an threshold formula in the inner product domain. An algorithm to determine adaptive threshold formula ...
Proceedings of SPIE, Jul 13, 2000
Journal of Modern Optics, 1999
The model of a coupled double-cavity optical interference ®lter consisting of three mirror layers... more The model of a coupled double-cavity optical interference ®lter consisting of three mirror layers and two one-wavelength cavities is developed. The transmission response of the coupled double-cavity ®lter containing absorbing thermo-optical media is predicted, when a laser pulse is incident on the ®lter. Pulse narrowing and pulse regeneration are observed for a restricted range of frequencies and intensities.
Optical Society of America Annual Meeting
Among the various nonbinary number systems introduced for solving the bottleneck of carry propaga... more Among the various nonbinary number systems introduced for solving the bottleneck of carry propagation, modified signed-digit (MSD) arithmetic1 appears to be the most promising because it provides parallel, carry-free addition and borrow-free subtraction with storage complexity proportional to the length of the bit string. In MSD carry-free addition schemes, the pair of numbers to be added is first converted into an intermediate pair such that the addition of the latter pair will not generate any carry. In this paper, we extend the higher-order symbolic substitution (SS) technique to incorporate the MSD numbers. The propos d method ensures that both addition and sub traction operations can be implemened in only two steps, irrespective of the number of bits to be processed, thus saving a tremendous amount of computation time. Further, a new set of carry-free SS rules that are based upon checking a pair of reference bits from the next-lower-order bit position is derived. Finally, a con...
Optical Society of America Annual Meeting
The lossless transmission of power using a diffraction-free Bessel laser1 could have unlimited po... more The lossless transmission of power using a diffraction-free Bessel laser1 could have unlimited possibilities in electrooptics. A holographically generated2 Bessel beam is handicapped because of its limited efficiency. Refractive systems have recently been designed for transforming a circularly Gaussian beam into a Bessel beam with almost unity efficiency.3 However, the feasibility of its fabrication is somewhat limited since the surfaces are nonlinear in nature. In this paper, we develop a different approach for achieving a refracting system which lends to spherical shape for both input and output surfaces. This is accomplished by iteratively varying the radius of curvature while maintaining an input-output energy distribution relationship and optical path length constant. The resulting refractive system is comparatively easier to machine and hence can be implemented directly.
Optical Society of America Annual Meeting
The joint-Fourier-transform-based correlator is capable of real-time matching and tracking operat... more The joint-Fourier-transform-based correlator is capable of real-time matching and tracking operations without the fabrication of a complex filter. However, its autocorrelation peaks are relatively weak when compared to that of the de peak. Such problems are now being handled by suppressing the de peaks by means of optical disks.1,2 In this work, we propose to solve this same problem and at the same time further increase the autocorrelation peaks by carefully preprocessing the reference objects. We show that when the reference amplitude is suitably thresholded, the resulting autocorrelation peak heights significantly increase while the de peaks can be significantly suppressed. We further show that the ratio of the autocorrelation peak value to the de peak value can be increased by suitably optimizing the threshold used in the preprocessing of the reference.
Optics and Photonics for Information Processing XIII, Nov 1, 2019
OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Aug 10, 2016
Trinary associative memory combines merits and overcomes major deficiencies of unipolar and bipol... more Trinary associative memory combines merits and overcomes major deficiencies of unipolar and bipolar logics by combining them in three-valued logic that reverts to unipolar or bipolar binary selectively, as needed to perform specific tasks. Advantage of associative memory: one ...
Proceedings of SPIE, Aug 25, 1998
Proceedings of SPIE, Mar 27, 1997
ABSTRACT
Optical Society of America Annual Meeting, 1992
Restoration of velocity-degraded images owing to phosphor persistence may be achieved by using a ... more Restoration of velocity-degraded images owing to phosphor persistence may be achieved by using a Fourier transform filter setup. However, such a system suffers from very stringent alignment and filter fabrication requirements and is therefore less amenable to a real-time restoration scheme. In this work a joint Fourier transform setup is used to perform real-time adaptive restoration on images degraded owing to relative motion and phosphor persistence.
Optics and Laser Technology, Feb 1, 1998
Ecient parallel schemes for carry-propagation-free addition of modi®ed signed-digit trinary numbe... more Ecient parallel schemes for carry-propagation-free addition of modi®ed signed-digit trinary numbers are presented. The necessary minterms for implementation using an optical programmable logic array area are derived. The proposed schemes require only a truth table of 25 entries compared with an earlier scheme of 625 entries. The proposed schemes are amenable to optical implementation. Experimental results using an optical programmable logic array are demonstrated. The experiments show the problems of noise and crosstalk. This suggests some dc bias is necessary to increase the signal-to-noise ratio of the optical circuit.
Optical Society of America Annual Meeting, 1992
Among many Gaussian laser beam diameter measurement techniques, a relatively fast and inexpensive... more Among many Gaussian laser beam diameter measurement techniques, a relatively fast and inexpensive technique is provided by the use of ruling1, 2 where a Gaussian beams scans the ruling and a detector placed directly on the other side is used to detect the maximum and the minimum transmitted power through the ruling. The ratio P min /P max is found to be a function of the ratio r O /L (beam radius to ruling period).
Proceedings of SPIE, Dec 6, 2001
ABSTRACT In this paper, a new algorithm to determine the adaptive threshold formula for the trina... more ABSTRACT In this paper, a new algorithm to determine the adaptive threshold formula for the trinary associative memory model is presented. The optimal threshold is chosen to yield the best performance. Different threshold parameters have been investigated to obtain the optimal range of threshold parameters. In order to validate our performance model, character recognition problems are investigated.
Proceedings of SPIE, Feb 10, 2011
The heart of the National Ignition Facility is a megajoule-class laser system consisting of 192 b... more The heart of the National Ignition Facility is a megajoule-class laser system consisting of 192 beams used to drive inertial confinement fusion reactions. A recently installed system of programmable, liquid-crystal-based spatial light modulators adds the capability of arbitrarily shaping the spatial beam profiles in order to enhance operational flexibility. Its primary intended use is for introducing "blocker" obscurations to shadow isolated flaws on downstream optical elements. To optimize the system, both the position and shape of the obscurations must be carefully verified prior to high-fluence operations. An automatic alignment algorithm is used to perform detection and estimation of the imposed blocker centroid positions compared to their intended locations. Furthermore, in order to minimize the spatially-varying nonlinear response of the device, a calibration of the local magnification is performed at multiple sub-image locations. In this paper, we describe the control and associated image processing of this device that helps to enhance the performance of the overall system.
Proceedings of SPIE, Nov 1, 2002
A novel uni-complex valued trinary associative model, which is implementable in the optical domai... more A novel uni-complex valued trinary associative model, which is implementable in the optical domain, is proposed. Retrieval of the stored pattern is accomplished using an threshold formula in the inner product domain. An algorithm to determine adaptive threshold formula ...
Proceedings of SPIE, Jul 13, 2000
Journal of Modern Optics, 1999
The model of a coupled double-cavity optical interference ®lter consisting of three mirror layers... more The model of a coupled double-cavity optical interference ®lter consisting of three mirror layers and two one-wavelength cavities is developed. The transmission response of the coupled double-cavity ®lter containing absorbing thermo-optical media is predicted, when a laser pulse is incident on the ®lter. Pulse narrowing and pulse regeneration are observed for a restricted range of frequencies and intensities.
Optical Society of America Annual Meeting
Among the various nonbinary number systems introduced for solving the bottleneck of carry propaga... more Among the various nonbinary number systems introduced for solving the bottleneck of carry propagation, modified signed-digit (MSD) arithmetic1 appears to be the most promising because it provides parallel, carry-free addition and borrow-free subtraction with storage complexity proportional to the length of the bit string. In MSD carry-free addition schemes, the pair of numbers to be added is first converted into an intermediate pair such that the addition of the latter pair will not generate any carry. In this paper, we extend the higher-order symbolic substitution (SS) technique to incorporate the MSD numbers. The propos d method ensures that both addition and sub traction operations can be implemened in only two steps, irrespective of the number of bits to be processed, thus saving a tremendous amount of computation time. Further, a new set of carry-free SS rules that are based upon checking a pair of reference bits from the next-lower-order bit position is derived. Finally, a con...
Optical Society of America Annual Meeting
The lossless transmission of power using a diffraction-free Bessel laser1 could have unlimited po... more The lossless transmission of power using a diffraction-free Bessel laser1 could have unlimited possibilities in electrooptics. A holographically generated2 Bessel beam is handicapped because of its limited efficiency. Refractive systems have recently been designed for transforming a circularly Gaussian beam into a Bessel beam with almost unity efficiency.3 However, the feasibility of its fabrication is somewhat limited since the surfaces are nonlinear in nature. In this paper, we develop a different approach for achieving a refracting system which lends to spherical shape for both input and output surfaces. This is accomplished by iteratively varying the radius of curvature while maintaining an input-output energy distribution relationship and optical path length constant. The resulting refractive system is comparatively easier to machine and hence can be implemented directly.
Optical Society of America Annual Meeting
The joint-Fourier-transform-based correlator is capable of real-time matching and tracking operat... more The joint-Fourier-transform-based correlator is capable of real-time matching and tracking operations without the fabrication of a complex filter. However, its autocorrelation peaks are relatively weak when compared to that of the de peak. Such problems are now being handled by suppressing the de peaks by means of optical disks.1,2 In this work, we propose to solve this same problem and at the same time further increase the autocorrelation peaks by carefully preprocessing the reference objects. We show that when the reference amplitude is suitably thresholded, the resulting autocorrelation peak heights significantly increase while the de peaks can be significantly suppressed. We further show that the ratio of the autocorrelation peak value to the de peak value can be increased by suitably optimizing the threshold used in the preprocessing of the reference.
Optics and Photonics for Information Processing XIII, Nov 1, 2019
OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Aug 10, 2016
Trinary associative memory combines merits and overcomes major deficiencies of unipolar and bipol... more Trinary associative memory combines merits and overcomes major deficiencies of unipolar and bipolar logics by combining them in three-valued logic that reverts to unipolar or bipolar binary selectively, as needed to perform specific tasks. Advantage of associative memory: one ...
Proceedings of SPIE, Aug 25, 1998