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99th meeting of the Acoustical Society of America
Pennsylvania papers on pseudo-optic holography and inverse scattering were presented. A comparison between Bojarski exact inverse scattering theory and holography as applied to the holographic reconstruction of holographic radio camera recordings was made, and it was emphasized that holographic reconstruction is usually a poor solution to inverse scattering problems.
of whether coherent or incoherent future still remains open.
processing has a brighter
It was a good idea indeed of the IOCC Steering Committee to invite W. Anacker from the IBM Thomas J. Watson Research Laboratory to give a special presentation on Josephson computer technology for ultrahigh systems performance. Although strictly speaking the topic was not really related to optical computing it was, nevertheless very instructive and inspiring even to those mainly involved in optics.
Papers on image acquistition and processing were so numerous that they had to be discussed in two sessions. Session 6 chaired by E.N. Leith of the University of Michigan, mainly discussed recording procedures, while Session 9, chaired by H.J. Caulfield of Aerodyne Research, placed the emphasis on problems in processing recorded optical data in conjunction with implementation. One of the most interesting approaches to recording optical data was that presented by J.M. Jonathan and M. May of the Institut d’optique in France who used a polarization sensitive photographic emulsion derived from bleached, high-resolution photographic plates using the ‘Weigert effect’ first described more than 50 years ago in 1919.
In Session 4, chaired by H.H. Barrett of the University of Arizona, papers dealing with image reconstruction from projection were discussed. It is worth mentioning that this method, originally developed for medical purposes (computer tomography) seems to have gained importance not only in nuclear fuel motion detection but also in fields such as Tokamak diagnostics.
Each of the four papers presented in Session 7 chaired by P. Kellman of ESL Inc showed that time-integration optical processing may solve some radar and communication band signal processing problems. In particular, the new ideas of A. Korpel from the University of Iowa on acousto-optic signal processing using cavity resonances and Bragg imaging were very stimulating.
The evening session of the conference was partially devoted to postdeadline papers and to papers that seemed to be more or less theoretical. The paper of Yu Ping Ho, currently visiting scientist at the Institute of Advanced Study, Princeton University caused great interest since it gave quite a good review on optical computing activities in China.
In Session 8 ‘numerical optical processing’ operations of different numerical optical data processors were discussed under the chairmanship of W.W. Stoner of Science Application Inc. An indication of seceral of the presentations was that optical numerical computers based on residue number systems seem to have to come into fashion.
In Session 5, chairman D. Psaltis of Carnegie-Mellon University elucidated the problems of polychromatic optical processing placing amphasis on the application of spatially and temporally incoherent light. The paper of S.C. Wang from Xerox Electra-Optical Systems on a new panchromatic hollow-cathode laser clearly demonstrated that the question
Summing up the impressions gained at this conference, I think the Technical Program Committee did an excellent job, and that the conference showed a realistic and good cross-section of the present state of the art of optical computing. l? Greguss
99th meeting of the Acoustical Society of America Atlanta,
Georgia, USA April 21-25
1980
This last meeting before the centenary meeting of the Acoustical Society of America was, as usual, a survey of the present acoustical activities in the States, although its attendance was in my opinion, not as large as it used to be. Nevertheless, it is hopeless to try to give a fair account of all the papers presented, even if one restricts oneself to more or less outlined subjects such as speech, underwater acoustics and ultrasonics. If one wishes to choose a ‘living’ topic which exemplifies most of the basic problems of acoustics, then the topic of ‘Ears adapted to detect motion, how echo-locating bats exploit the capcities of the mammalian auditory system’ is the right one, as G. Neuweiler of the Johann Wolfgang Goethe Universitat, Frankfurt-am-Main, FRG demonstrated in his plenary session: the bat’s auditory system analyzes spectral and temporal parameters of sound patterns for detecting, precisely locating and identifying a target. The increasingly noticeable tendency to bring acoustics and
OPTICS AND LASER TECHNOLOGY.
DECEMBER
1980
optics closer was apparent in this very instructive talk, especially when a patch on the basilar membrane specialized as filter was described in analogy to the visual fovea as ‘acoustical’ fovea. That such an acoustical fovea is not only a privilege of some echo-locating animals, at least so far as aural discrimination of target echoes goes, was well demonstrated by the poster talk of D.W. Martin, W. Witlow and L. Au of the Naval Ocean Systems Centre, Kailua, Hawaii. They have conducted echo discrimination experiments with human observers, using targets employed in a dolphin echo recognition study, the results of which showed that humans can do practically as well as these remarkable animals, with the target echo played back at l/50 of the original sample rate. Based on the same idea, J.W. Hicks, Jr and B. Klepper of the Institute of Advanced Study of Communication Processes at the University of Florida presented their first data on an auditory homing method for divers. These data proved the
323
validity of this approach as well as demonstrating learning effect.
a powerful
The effect of recent optical developments on acoustics was felt listening to the technical papers presented in one of the sessions on engineering acoustics. Optical devices for detecting acoustic signals are currently under investigation in a number of laboratories. Although the technical specifications of these acoustic sensors may be quite different they all operate by modulating the optical intensity or phase. According to a model developed by J. Jarzynski, R. Hughes, T.R, Hickman and J.A. Bucaro of the Naval Research Laboratory, Washington, DC only the lowestorder mode of vibration leads to a net optical phase shift in the fibre coil, and the pressure sensitivity is near the resonant frequency for the lowest order radial mode. N. Lagakos of the Catholic University of America, Washington DC proposed the introduction of microbending to the fibre with a set of two corrugated plates, called deformers, which if properly attached, cause light coupling between core modes and clad modes if pressure is applied. The proposed sensor could also be used to detect displacement, stress, temperature etc. It was claimed that displacements less than 1 A or pressure SO-60 dB ( -1pPa) can be detected by this method. Another marriage of optics and acoustics was apparent from opto-acoustic devices based on the measurement of chopped optical energy producing sound at the chopping frequency. The device described by W.M. Wright of the Department of Physics, Kalamazoo College, Kalamazoo, D.H. Stedman of the Department of Chemistry, University of Michigan and A. Arbor was intended for the measurement of concentration of nitrogen oxide as low as 1 ppm of atmospheric pollutants.
That the laser has its acoustic analogue was shown in the presentation of R.M. Detsch and H.E. Bass of the Department of Physics and Astronomy, University of Mississippi. They reported on the experimental observation of sound amplification of controlled gas-phase excitation reactions. and the results obtained show agreement with pulsed chemical laser experiments.
The application of acoustic holographic techniques to solve acoustic imaging problems is still controversial. None of the papers presented could demonstrate the practical and economical effectiveness of this holographic technique’s acoustic analogue. Far more promising seems to be the new nematic liquid acousto-optic conversion cell described by S. Candau and G. Waton of the Laboratoire d’Acoustique Moleculaire, Universite Louis Pasteur, Strasbourg and W. Hamidzada and S. Letcher of the Department of Physics, University of Rhode Island. By using a simple but ingenious mosaic technique they could improve the resolution of this type of acousto-optical converter since they could suppress degradation effects arising from acoustic streaming. Last but not least, some of the papers showed that old, wellknown optical techniques can also be successfully used to solve today’s problems. For example H.D. Dardy et al of the Naval Research Laboratory used stress induced birefringence imaging to study resonance properties of cylinders. This and similar techniques such as Schlieren and shadowgraphic methods, combined with dignal processing techniques. have been successfully used to analyze the scattering of sound and shock waves at boundaries reported by J.A. Clark and T. Kia of the Acousto-optics Laboratory at the Catholic University of America. P. Greguss
Association for high speed photography spring conference 1980 Leeds, UK, 15-l 6 Apri I 1980 The invitation to hold the Association conference at Leeds University came from J.S. Mulligan of their photographic department and the delegates were welcomed by B. Cole (mechanical engineering) who commented that despite the long history of photography, the last 30 years have probably seen the greatest advances. He was particularly pleased that the initial event of our 21st year should be at Leeds. The programme was quite a mixed bag with a number of application papers on a variety of topics. The two papers of particular note had been selected to open each day’s proceedings, the Tuesday one by N. Dombrowski (Leeds University) on spray studies and the Wednesday one by K. Frank (Proxitronic, Darmstadt) on gated proximity diodes. Dombrowski reviewed the many photographic techniques used to study liquid sprays or atomizers and as he had been a leader in this topic since 19.54, his review was, as one later speaker said, ‘a tour de force’. He defined the objects of study as the orifice action, the liquid sheet and the drop size
measurement, and showed examples of these by specular and diffuse illumination, front and back lit, shadowgraph and Schlieren, single and muliple flush and monochrome and colour differentiation. He ended with a tine film solving an unexpected problem in nozzle behaviour with particular reference to the relationship of drop size with viscosity. Frank is with Funk at Darmstadt manufacturing a new image intensifier called a ‘Proxifier’. Initial work was done at Bosch by Funk who permitted him to start a new company Proxitronic for this device. Essentially the tube is the simplest possible, a plane photocathode and a plane phosphor screen placed in close proximity so that with a suitable electric field, electrons travel the shortest possible paths so an image on the cathode will also appear on the screen. The difficulty is in technology when the potential gradient is as llighas 6 kV mm-’ with possible total voltages of 20 kV. A typical case has a gap of 1.5 mm and the intensity gain of light output from the screen to cathode input increases from xl .5 at
324
OPTICS
AND
LASER
TECHNOLOGY.
DECEMBER
1980
of whether coherent or incoherent future still remains open.
processing has a brighter
It was a good idea indeed of the IOCC Steering Committee to invite W. Anacker from the IBM Thomas J. Watson Research Laboratory to give a special presentation on Josephson computer technology for ultrahigh systems performance. Although strictly speaking the topic was not really related to optical computing it was, nevertheless very instructive and inspiring even to those mainly involved in optics.
Papers on image acquistition and processing were so numerous that they had to be discussed in two sessions. Session 6 chaired by E.N. Leith of the University of Michigan, mainly discussed recording procedures, while Session 9, chaired by H.J. Caulfield of Aerodyne Research, placed the emphasis on problems in processing recorded optical data in conjunction with implementation. One of the most interesting approaches to recording optical data was that presented by J.M. Jonathan and M. May of the Institut d’optique in France who used a polarization sensitive photographic emulsion derived from bleached, high-resolution photographic plates using the ‘Weigert effect’ first described more than 50 years ago in 1919.
In Session 4, chaired by H.H. Barrett of the University of Arizona, papers dealing with image reconstruction from projection were discussed. It is worth mentioning that this method, originally developed for medical purposes (computer tomography) seems to have gained importance not only in nuclear fuel motion detection but also in fields such as Tokamak diagnostics.
Each of the four papers presented in Session 7 chaired by P. Kellman of ESL Inc showed that time-integration optical processing may solve some radar and communication band signal processing problems. In particular, the new ideas of A. Korpel from the University of Iowa on acousto-optic signal processing using cavity resonances and Bragg imaging were very stimulating.
The evening session of the conference was partially devoted to postdeadline papers and to papers that seemed to be more or less theoretical. The paper of Yu Ping Ho, currently visiting scientist at the Institute of Advanced Study, Princeton University caused great interest since it gave quite a good review on optical computing activities in China.
In Session 8 ‘numerical optical processing’ operations of different numerical optical data processors were discussed under the chairmanship of W.W. Stoner of Science Application Inc. An indication of seceral of the presentations was that optical numerical computers based on residue number systems seem to have to come into fashion.
In Session 5, chairman D. Psaltis of Carnegie-Mellon University elucidated the problems of polychromatic optical processing placing amphasis on the application of spatially and temporally incoherent light. The paper of S.C. Wang from Xerox Electra-Optical Systems on a new panchromatic hollow-cathode laser clearly demonstrated that the question
Summing up the impressions gained at this conference, I think the Technical Program Committee did an excellent job, and that the conference showed a realistic and good cross-section of the present state of the art of optical computing. l? Greguss
99th meeting of the Acoustical Society of America Atlanta,
Georgia, USA April 21-25
1980
This last meeting before the centenary meeting of the Acoustical Society of America was, as usual, a survey of the present acoustical activities in the States, although its attendance was in my opinion, not as large as it used to be. Nevertheless, it is hopeless to try to give a fair account of all the papers presented, even if one restricts oneself to more or less outlined subjects such as speech, underwater acoustics and ultrasonics. If one wishes to choose a ‘living’ topic which exemplifies most of the basic problems of acoustics, then the topic of ‘Ears adapted to detect motion, how echo-locating bats exploit the capcities of the mammalian auditory system’ is the right one, as G. Neuweiler of the Johann Wolfgang Goethe Universitat, Frankfurt-am-Main, FRG demonstrated in his plenary session: the bat’s auditory system analyzes spectral and temporal parameters of sound patterns for detecting, precisely locating and identifying a target. The increasingly noticeable tendency to bring acoustics and
OPTICS AND LASER TECHNOLOGY.
DECEMBER
1980
optics closer was apparent in this very instructive talk, especially when a patch on the basilar membrane specialized as filter was described in analogy to the visual fovea as ‘acoustical’ fovea. That such an acoustical fovea is not only a privilege of some echo-locating animals, at least so far as aural discrimination of target echoes goes, was well demonstrated by the poster talk of D.W. Martin, W. Witlow and L. Au of the Naval Ocean Systems Centre, Kailua, Hawaii. They have conducted echo discrimination experiments with human observers, using targets employed in a dolphin echo recognition study, the results of which showed that humans can do practically as well as these remarkable animals, with the target echo played back at l/50 of the original sample rate. Based on the same idea, J.W. Hicks, Jr and B. Klepper of the Institute of Advanced Study of Communication Processes at the University of Florida presented their first data on an auditory homing method for divers. These data proved the
323
validity of this approach as well as demonstrating learning effect.
a powerful
The effect of recent optical developments on acoustics was felt listening to the technical papers presented in one of the sessions on engineering acoustics. Optical devices for detecting acoustic signals are currently under investigation in a number of laboratories. Although the technical specifications of these acoustic sensors may be quite different they all operate by modulating the optical intensity or phase. According to a model developed by J. Jarzynski, R. Hughes, T.R, Hickman and J.A. Bucaro of the Naval Research Laboratory, Washington, DC only the lowestorder mode of vibration leads to a net optical phase shift in the fibre coil, and the pressure sensitivity is near the resonant frequency for the lowest order radial mode. N. Lagakos of the Catholic University of America, Washington DC proposed the introduction of microbending to the fibre with a set of two corrugated plates, called deformers, which if properly attached, cause light coupling between core modes and clad modes if pressure is applied. The proposed sensor could also be used to detect displacement, stress, temperature etc. It was claimed that displacements less than 1 A or pressure SO-60 dB ( -1pPa) can be detected by this method. Another marriage of optics and acoustics was apparent from opto-acoustic devices based on the measurement of chopped optical energy producing sound at the chopping frequency. The device described by W.M. Wright of the Department of Physics, Kalamazoo College, Kalamazoo, D.H. Stedman of the Department of Chemistry, University of Michigan and A. Arbor was intended for the measurement of concentration of nitrogen oxide as low as 1 ppm of atmospheric pollutants.
That the laser has its acoustic analogue was shown in the presentation of R.M. Detsch and H.E. Bass of the Department of Physics and Astronomy, University of Mississippi. They reported on the experimental observation of sound amplification of controlled gas-phase excitation reactions. and the results obtained show agreement with pulsed chemical laser experiments.
The application of acoustic holographic techniques to solve acoustic imaging problems is still controversial. None of the papers presented could demonstrate the practical and economical effectiveness of this holographic technique’s acoustic analogue. Far more promising seems to be the new nematic liquid acousto-optic conversion cell described by S. Candau and G. Waton of the Laboratoire d’Acoustique Moleculaire, Universite Louis Pasteur, Strasbourg and W. Hamidzada and S. Letcher of the Department of Physics, University of Rhode Island. By using a simple but ingenious mosaic technique they could improve the resolution of this type of acousto-optical converter since they could suppress degradation effects arising from acoustic streaming. Last but not least, some of the papers showed that old, wellknown optical techniques can also be successfully used to solve today’s problems. For example H.D. Dardy et al of the Naval Research Laboratory used stress induced birefringence imaging to study resonance properties of cylinders. This and similar techniques such as Schlieren and shadowgraphic methods, combined with dignal processing techniques. have been successfully used to analyze the scattering of sound and shock waves at boundaries reported by J.A. Clark and T. Kia of the Acousto-optics Laboratory at the Catholic University of America. P. Greguss
Association for high speed photography spring conference 1980 Leeds, UK, 15-l 6 Apri I 1980 The invitation to hold the Association conference at Leeds University came from J.S. Mulligan of their photographic department and the delegates were welcomed by B. Cole (mechanical engineering) who commented that despite the long history of photography, the last 30 years have probably seen the greatest advances. He was particularly pleased that the initial event of our 21st year should be at Leeds. The programme was quite a mixed bag with a number of application papers on a variety of topics. The two papers of particular note had been selected to open each day’s proceedings, the Tuesday one by N. Dombrowski (Leeds University) on spray studies and the Wednesday one by K. Frank (Proxitronic, Darmstadt) on gated proximity diodes. Dombrowski reviewed the many photographic techniques used to study liquid sprays or atomizers and as he had been a leader in this topic since 19.54, his review was, as one later speaker said, ‘a tour de force’. He defined the objects of study as the orifice action, the liquid sheet and the drop size
measurement, and showed examples of these by specular and diffuse illumination, front and back lit, shadowgraph and Schlieren, single and muliple flush and monochrome and colour differentiation. He ended with a tine film solving an unexpected problem in nozzle behaviour with particular reference to the relationship of drop size with viscosity. Frank is with Funk at Darmstadt manufacturing a new image intensifier called a ‘Proxifier’. Initial work was done at Bosch by Funk who permitted him to start a new company Proxitronic for this device. Essentially the tube is the simplest possible, a plane photocathode and a plane phosphor screen placed in close proximity so that with a suitable electric field, electrons travel the shortest possible paths so an image on the cathode will also appear on the screen. The difficulty is in technology when the potential gradient is as llighas 6 kV mm-’ with possible total voltages of 20 kV. A typical case has a gap of 1.5 mm and the intensity gain of light output from the screen to cathode input increases from xl .5 at
324
OPTICS
AND
LASER
TECHNOLOGY.
DECEMBER
1980