Albert Macovski

Time-lapse interferometry and contouring using television systems.

A novel approach to time-lapse interferometry and contouring is introduced that uses television rather than photographic techniques. A first interferogram is stored on a video storage device such as a magnetic disk. After a change in the stress of the object, a second interferogram is electronically compared to the stored pattern to form a signal representative of the fringe pattern caused by the deformation. This signal may be directly displayed on a cathode-ray tube or employed by some automatic inspection device.

Spatial and Temporal Analysis of Scanned Systems

An analysis of input-output characteristics of scanned systems is presented from the input camera to the output reproducer. The system characteristics are developed in terms of both spatial coordinates and spatial frequency responses in both dimensions. These include the effects of the scanning apertures of both the camera and the reproducer, in addition to the electrical filter on the resultant signal. The effects of time varying input patterns are also considered in terms of the temporal responses of the camera and the phosphor characteristic of the reproducer.

Hologram Information Capacity

This paper presents an analysis of the number of diffraction-limited resolvable elements and the spatial extent of object space when a hologram of a specific number of independent elements is used. The analysis includes a study of both plane and spherical reference waves, and both plane and solid objects. A generalized spatial offset of the reference wave is used to separate the desired hologram terms. The spatial extent and number of elements that can be defined in the object are reduced by spatial offset. A system is mentioned in which separation is accomplished without spatial offset, by temporal offset of the frequency of the reference beam. Without spatial offset, in the optimum configuration, the number of resolvable elements of a plane object, using the Rayleigh criterion, is equal to the number of independent elements in the hologram. For solid objects, a hologram with n × n independent samples can resolve n3/3 elements in object space, if the optimum configuration is used.

Considerations for Diagnostic Ultrasonic Imaging

It is becoming increasingly apparent that ultrasonic imaging (focused and holographic) will develop into a useful tool for diagnostic medicine. In this paper we examine the benefits to be derived with this application, particularly as they compare to the results obtainable with currently-used techniques of diagnostic ultrasonics.

Encoding and decoding of color information.

Color information is recorded on a colorless substrate by having each color separation amplitude modulate a different spatial frequency carrier. This is accomplished in a single exposure using an appropriate color-encoding filter. The reconstruction of the color scene involves a point source projector with a color decoding mask. The light output of the projector, for sources of a given brightness, is shown to be proportional to the total number of lines in the encoding filter. The relatively, high efficiency of an encoded phase transparency is evaluated, and a decoding method is shown.

EFFICIENT HOLOGRAPHY USING TEMPORAL MODULATION

A method is shown of recording a hologram without spatially offsetting the reference beam. The temporal frequency of the reference beam is offset and the the resultant intensity pattern is scanned using a television camera. The desired conjugate image signals are separated from the undesired terms using a bandpass filter on the electrical signal. This method significantly reduces the resolution requirements of the hologram recorder.

Considerations of Television Holography

Television holography systems are considered with particular emphasis on the resolution requirements of the camera and reproducer. Methods are shown whereby conventional cameras and reproducers can be efficiently used at real-time scan rates. The spatial frequency requirements for the camera are minimized by using an on-axis reference wave. This wave is shifted in frequency or phase so as to create a signal that allows for the separation of the desired image terms.

Spatial-Frequency Encoding Techniques Applied to a One-Tube Color Television Camera

An analysis and experimental results are presented of a new color camera technique using a single camera tube. To avoid the difficult registration problem of conventional color cameras, the color information is encoded as the amplitude of two diffraction grating patterns. This is accomplished by imaging the colored scene onto a pair of colored diffraction gratings. The recovery of the color information is done by bandpass filtering of each channel followed by envelope detection. The three color signals are derived using linear combinations of the two decoded carriers along with the average signal, which represents a weighted sum of all three colors.

COHERENT OPTICAL DETECTION OF ULTRASONIC IMAGES USING ELECTRONIC SCANNING

Visualization of ultrasonic wavefields incident on an optically reflecting surface is effected by coherent optical detection of the deformations of this surface. A Twyman‐Green interferometer is used in which the orthogonal reference beam is frequency‐offset with an ultrasonic light modulator. The recombined light field is scanned with an image dissector, and the resulting image displayed on a kinescope.

Encoding and Decoding of Color Information Using Two-Dimensional Spatial Filtering

Spatial frequency encoding is described as it applies to both photographic and television systems. In each case, color separations amplitude modulate spatial frequency carriers. The photographic system separates the carriers in the two-dimensional Fourier transform plane using coherent optics; the television system employs a two-dimensional electrical filter to perform the same separation. These filters are synthesized so that the two-dimensional bandwidths of the television camera are used efficiently. Nonlinear processing techniques are also described to minimize crosstalk between channels.