George W. Stroke

Fourier-transform spectroscopy using holographic imaging without computing and with stationary interferometers

Fourier-transform spectroscopy using holographic imaging without computing and with stationary interferometers

White-light reconstruction of holographic images using the Lippmann-Bragg diffraction effect☆

Abstract An extension of the 1962 Denisyuk method to record reflection holograms in Lippmann emulsions has permitted us to reconstruct monochromatic images with white light (e.g. sun) and demonstrate possibilities of simulating three-dimensional gratings for crystallographic studies.

White-light reconstruction of holographic images using transmission holograms recorded with conventionally-focused images and `in-line' background

Abstract A new extension of Gabors wavefront-reconstruction principle permits to reconstruct three-dimensional images by transmission of white light through a hologram recorded in a new arrangement using an ‘in-line’ coherent background superposed onto a conventionally focused.

TWO‐BEAM INTERFEROMETRY BY SUCCESSIVE RECORDING OF INTENSITIES IN A SINGLE HOLOGRAM

The amount of gain, its onset at a drift field high enough for the electron drift velocity to equal the elastic wave velocity, and the observed decrease in gain upon changing the resistivity from the optimum value, are all similar to the case of bulk wave amplification. It should be noted that in these experiments the drift field existed only between the transducers, whereas the illumination was uniform both between and beneath the transducers, producing some constant attenuation at the transducers. A higher gain per unit length would be observed if the illumination or crystal conductivity were altered so as to eliminate this loss beneath the transducers. Surface-wave propagation has been observed in CdS crystals having their c axes either normal or parallel to the surface plane. For both orientations, a surface-wave velocity of (1.73 ± 0.05) X lOS em/sec was inferred from the period of the transducer electrodes (2.20 X 10-2 em) and the measured frequency which maximized the received pulse amplitude. This velocity agrees well with the value 1.70 X lOS em/sec calculated for CdS from an expression derived by Stoneler which is applicable to the firstmentioned orientation. The velocity of surface waves in CdS is only slightly smaller than the velocity of transverse bulk waves. That we have indeed dealt here with surface waves rather than bulk transverse waves is shown by the following: (a) velocity measurements in experiments with crystalline quartz (in which the velocities of bulk and surface waves are weJI separated) showed that the electrodes function as surface wave transducers; (b) on quartz, excellent transmission was observed from one electrode transducer to a metallic comb surface-wave transducer as described by Viktorov,4 and Arzt and Dransfeld;5 (c) a drop of acetone or alcohol on the CdS surface produced apparently complete absorption of the elastic pulse; (d) probing the CdS crystal with a narrow beam of light directed parallel to the plane surface produced a variable attenuation of the received pulse which showed that the wave amplitude was high near the surface and that it was negligible at large depths. This work was supported in part by the U. S. Army Research Office Durham, under Grant

Some New Advances in Grating Ruling, Replication, and Testing

A report on some significant recent advances in the art of grating ruling, blazing, replication, and testing-with a more detailed description of the construction and performance of a newly completed interfero, metrically controlled ruling engine recently put into operation at Jarrell-Ash Company.

Spectroscopic implications of new holographic imaging methods

Abstract Significant increases in luminosity, detection and resolution capabilities may result from extending to spectroscopic and astronomical instruments some of the new advances, recently made in the field of wavefront-reconstruction imaging (holography), first described by D. Gabor in 1948 1 ) 2 ) 3 ) 4 ). The recent advances 4−11 ) of which we have briefly described some early aspects elsewhere have already permitted us to obtain spectra in a holographic Fourier- transforming 7 ) 8 ) arrangement, using no scanning in the interferometer, and displaying the spectra by optical Fourier-transform reconstruction from the interferometric hologram 9 ), rather than by digital computation. In another work, we have now been able to holographically compensate a posteriori for the “slit spreading-effect”, in a coherent-light imaging system, and to retrieve the resolution by a corrtion-reconstruction method 10 ) 11 ). “Erasing” of selected image portions, by actually adding the complex amplitudes in two images, 180° out of phase, in a holographic arrangement has also been achieved 12 ) and may be used for increasing detection of selected image portions in astronomical and spectroscopic plates. Previously unpublished advances and some details of the new holographic imaging methods are given.

Interferometric reconstruction of phase objects using diffuse ‘coding’ and two holograms

Abstract In contrast with previously described multiply-exposed single holograms, used for interferometry according to a principle first described by Gabor, Stroke, Restrick, Funkhouser and Brumm, interferometric image ‘coding’ and ‘decoding’ may be accomplished in diffuse light with two separately recorded holograms.