Abstract: A laser beam projected through a prism in a direction normal to the surface of a circular wafer is focused into a spot area and scanned along a spiral path on this surface. The focusing means comprises a relatively large aperture lens and the prism is on the lens axis. The retroreflected specular light passes through the lens and is prevented from reaching a light detector in the image plane of the lens by the prism. When the beam illuminates a microscopic surface defect on the wafer, the light is diffracted and reflected therefrom, and the lens captures that portion of the reflected light within the solid angle subtended by the lens, and passes that portion thereof not blocked by the prism, to the light detector. The output of the detector may be employed to intensity modulate the beam of a cathode-ray tube display, the beam of which is spirally scanned in synchronism with the scanning of the light beam.

Abstract: The ratio of the intensity of two light beams is determined by an apparatus which includes a chopper wheel for chopping one of the light beams, a photodetector for detecting the intensity of both light beams applied simultaneously thereto, and a logarithmic amplifier for amplifying the current produced by the photodetector. The AC component of the logarithmically amplified current represents the ratio of the intensity of the two light beams.

Abstract: A diffractive subtractive filter is made tunable by controllably varying the index of refraction of a fluid medium in contact with a surface relief pattern of a solid diffractive phase medium. A liquid crystal is the preferred fluid.

Abstract: A group of separate large-size color or black-and-white pictures to be recorded on a master as very finely-screened (e.g. 10 micrometer period) micropictures in a given format, such as microfiche, are first reduced to a continuous-tone first recording at an intermediate size on a medium, such as 70 millimeter film. Then a relatively fine-screened (e.g. 40 micrometer period), high-contrast second recording, made from the first recording by contact printing, is reduced to micropicture size in the given format.

Abstract: Rectangular groove profile grating, having an effective line spacing no greater than 2.mu.m, has grating parameters specified to provide at least acceptable or, preferably, good zero diffraction order color characteristics for subtractive primary colors and green when grating is illuminated with unpolarized white light.

Abstract: A projector for projecting pictures from zero-order diffractive subtractive filters, which may make use of an extraordinarily large amount of light flux, is achieved by a mask which transmits zero order light through an array of transparent regions separated by opaque regions which block higher diffraction order light.

Abstract: By providing a given thickness for a positive photoresist layer on a substrate which, if unexposed, after development has a maximum depth just equal to the sum of the individual depths of two, at least partly superimposed, rectangular relief-profile diffraction gratings in the developed photoresist layer, it is possible to make a single master recording, which can be used to provide a stamper for embossing two of the three primary colors in a single surface of a transparent plastic sheet in the fabrication of diffractive subtractive filters.

Abstract: A phase grating structure is defined in which a series of predetermined sawtooth phase delay steps has the property of focusing respective wavelength components of a spectrum of incident wave energy in accordance with their wavelength at different spots in the near field. Although not limited thereto, the invention has particular utility for spatially separating the color components of polychromatic light. Useful applications for this phase filter include (1) recording color pictures on black-and-white film for display in full color, and (2) a single-gun color television camera.

Abstract: The present invention takes advantage of the fact that the first and second optical depths of a diffractive subtractive color filter respectively manifesting cyan and yellow zero-order diffraction light may be so selected that an optical depth equal to the sum of the first and second optical depths manifests green zero-order diffraction light. This permits a variable optical amplitude first grating, manifesting cyan, yellow and green, to be combined with a fixed optical amplitude second grating, manifesting magenta, to provide a full gamut of colors.

Abstract: A focused-image hologram recorded in a thin phase medium having a high-frequency line spacing, such that the ratio of this line spacing to the wavelength of the readout light beam is greater than one but less than two, when read out with a light beam inclined at an angle greater than 30.degree. with respect to the normal to the plane of the focused image hologram, results in an optical readout efficiency approaching 50%, compared to the theoretical maximum optical readout efficiency of about 34% of a coarse sinusoidal phase grating having a line spacing much larger tha twice the wavelength of the readout light beam.

Abstract: A subtractive color filtering technique, suitable for the projection of color pictures, employs diffraction, rather than color dyes, for discriminatingly subtracting unwanted spectral wavelength portions of polychromatic illuminating light. The useful output light may consist of solely the zero-order diffraction output light or, alternatively, one or a certain combination of diffraction orders other than the zero diffraction order (such as the aggregate of all diffraction orders other than the zero diffraction order which corresponds to the complement of the zero-order diffraction output light).