Abstract: This invention provides a lens which operates in a waveband in the infra-red region of the electromagnetic spectrum and which has a variable focus or magnification. The invention relates particularly to an infra-red zoom lens. The lens has a front part and a rear part which are adjustable axially towards and away from one another and a middle part whose function is to provide different focal length or magnification settings. The adjustability of the front and rear parts of the lens assists in overcoming the defocussing effect of temperature variations, the front and rear parts being held stationary when a focussed image of an object is formed in a desired image plane. In a zoom lens the middle part is a zoom part with elements movable axially to vary the image size in the image plane, the front and rear parts being adjustable axially relative to each other and to the range of movement of the elements of the zoom part.

Abstract: A method, and apparatus for performing the method, of manufacturing a blazed diffraction grating by making a photographic record of the interference fringes produced at the intersection of two coherent secondary light beams derived from a common coherent primary light beam, in which one of the two secondary light beams is compressed or expanded in at least one dimension before it is incident on the region where intersection with the other beam takes place, the angle of intersection between the two secondary beams being such that they are perfectly in register across a certain plane in the region of intersection, the interference fringes formed at the plane being recorded photographically by exposing a photo-sensitive material, preferably an etchable photo-resist, at this plane. Expansion can be achieved by passing one of the recording beams through a prism or by effecting the separation of the primary beam into two secondary beams by means of a blazed diffraction grating.

Abstract: The invention provides a holographic device for X-ray or .gamma. ray imaging, especially for tomography in the medical field, in which low frequencies of radiation can be included in the image construction by virtue of having a mask with a particular transmittance law.For example the transmittance law of the mask may be such that transmittance is a function of x.sup.2 +y.sup.2 or of .sqroot.x.sup.2 +y.sup.2 where x and y are spatial co-ordinates of the mask.

Abstract: An interference filter having a plurality of alternating layers of high and low index of refraction and layer thickness increasing toward the center can compensate for errors in spectral energy distribution produced by an optical system.

Abstract: A phase shifter for adding a deterministic phase to an original information to be recorded in hologram. The phase shifter consists of a number of unit cells arranged in a matrix. A set of the unit cells are provided which will cause a certain phase shift to a light passing through each kind of the unit cells so as to distribute the light irradiance of the original information more evenly over the Fourier transformed plane. The invention suggests a solution to make the phase shifter with the unit cells arranged by the deterministic phase distribution.

Abstract: A redundant Fraunhofer or Fresnel hologram is recorded by interfering a temporal-information beam with a reference beam of mutually coherent light. The temporal-information beam is intensity-modulated with each of a series of samples of the temporal information signal. The relative phase difference between the two interfering beams is selectively determined for each sample of the series and the effective value of the angular displacement between the two interfering beams is changed for each successive sample of the series. The hologram can be recorded directly from an electronic signal, such as television, without the need for a coherently illuminated object, or an intermediate imaging step, such as transcribing from television to film.

Abstract: An apparatus is disclosed for making unchirped holographic diffraction gratings that are formed from curved lines in a thin film. The gratings so made focus as well as reflect light that is confined to the film incorporating the grating. SUBACKGROUND OF THE INVENTIONGratings have been incorporated in integrated optics devices for several purposes, including the fabrication of distributed feedback lasers, light-wave couplers, and band-rejection filters. Integrated-optics gratings known to the prior art were composed at straight lines, and therefore could not focus the light being processed. Gratings that combine focusing and diffraction were known to be desirable, but the prior art was unable to produce them.The closest prior art that has come to our attention is a method and apparatus for producing curved-line holographic gratings that have unequally spaced, or chirped, lines (U.S. Pat. No. 3,578,845, issued on May 18, 1971 to K. E. Brooks et al).

Abstract: A holographic storage cell for storing volume holograms wherein a plate of either Bi.sub.12 SiO.sub.20 or Bi.sub.12 GeO.sub.20 is provided with electrodes producing an electric field transversed to the plate. These electrodes may be on opposite ends of the plate, or in the form of interdigitated combs. In one embodiment, such a cell is utilized as a holographic memory wherein the modulation of the object beam and the deflection of the reference and object beams are controlled electronically. The cell may also be utilized to perform calculations by superpositioning data to perform addition and substraction.

Abstract: Geometrical image modifications such as coordinate transformations and local translation, inversion, reflection, stretching which require space-variant optical coherent systems are provided by introducing phase filters having a predetermined phase function into optical coherent systems in such a manner that the local phase variations influence light from local object areas. In one embodiment, the object distribution is multiplied by the phase function so that its spectrum at the frequency plane constitutes the desired transformation. In a second embodiment, the aforementioned concept is applied to produce a transformation in an image plane. The phase filters, in a preferred embodiment, comprise computer generated holograms.

Abstract: Disclosed are a method and apparatus for verifying an identification card or the like having visible indicia thereon and also having on a portion thereof a hologram of said visible indicia as originally placed on the identification card. The method comprises the steps of: producing an optical image of the visible indicia on the identification card; producing a reconstructed image of the hologram on the identification card; projecting the optical image and the reconstructed holographic image, in superimposed register, and either continuously or intermittently, e.g., alternately, upon a common optical image plane; and comparing the images on the image plane. The apparatus comprises suitable optical elements for carrying out these steps using either a single laser light source or such a light source together with a conventional light source.

Abstract: An optical system for a object illuminating light source includes a phase plate for giving "0"-relative phases or ".pi."-relative phases to the incident light fluxes to cancel with respect to one another all the interference fringes except for those two light fluxes incident to define a maximum angle.

Abstract: In the system disclosed, a hologram diffracts a portion of a reconstruction beam into an image-carrying beam which is projected onto a screen. The hologram is substantially flat and one dimension along the flat of the hologram is smaller than the flat dimension orthogonal thereto. Along the direction parallel to the larger dimension the screen is shaped to convert the image of the image-carrying beam orthoscopically along that direction. The screen includes means for diffusing the light of the beam in a direction parallel to the smaller dimension.

Abstract: The use of a lenticular array in the formation of the object-illuminating beam used in the recording of either a Fresnel, a Fraunhofer or an image plane hologram, permits the reconstructed image of the object, on playback of the hologram, to be directly viewed over an expanded image viewing area.

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 reflection free optical glass coated, in succession, with a medium refractive index layer, such as CeF.sub.3 or Al.sub.2 O.sub.3, a high refractive index layer such as TiO.sub.2, CeO.sub.2 or ZrO.sub.2 which layer contains a plurality of thin layers of MgF.sub.2 of about 10-100A in thickness uniformly interposed in the high refractive index material at intervals of about one eighth of the design wavelength. The outermost coating of the multi-layer optical glass is a low refractive index layer of MgF.sub.2.

Abstract: To form a hologram of a section of an object surface one end of each of a pair of elongated, flexible, optical fibers is illuminated with a laser beam through an optical mechanism which allows adjustment of the amount of light that falls on each of the fiber ends. The opposite end of one of the fibers is disposed adjacent to the object of which the hologram is to be formed so that the light output of that fiber diffuses and illuminates the relevant surface. A photographic plate is disposed to receive light reflected from the object surface as well as a reference beam radiating from the output end of the other fiber. A photodetector device receives a portion of the reference beam at one input and a portion of the object beam at another input and provides a visual indication of the relative intensity of the beams. The input to the fiber elements is adjusted to achieve the desired beam ratio for forming a hologram.

Abstract: A system for optically correlating two signals, e.g., radar, sonar, etc., incorporating both time shifts and doppler shifts is described. The correlation of the signals is produced as a two-dimensional distribution of light on a light detector/display plane wherein the amplitude of the light distribution is proportional to the correlation of the two signals as a function of relative time shifts, .DELTA.t (X direction), and relative doppler shifts, .alpha..omega. (Y direction), between the signals. Doppler shifts are introduced into the processor by the incorporation of a channelized cylindrical lens in one signal channel while using a cylindrical lens in the other signal channel.

Abstract: A holographic laser beam deflector has an approximately flat field scan. The scan is produced by illuminating a rotating hologram on a circular surface by a laser beam. The virtual source of the illuminating beam is offset from the center of rotation of the hologram. The hologram is produced by interference of a pair of coherent laser beams, each beam having a source or virtual source on a line containing the rotational center of the surface of the hologram, one source or virtual source outside the surface, the other inside. The virtual source for the inside beam is also displaced from the center of rotation.

Abstract: A process and apparatus is disclosed for imposing selectable, sequential, spatial modulations upon a reference beam for the storage in a suitable medium of a hologram. Changing the spatial modulations enables the storage of several, different holograms in the same medium. Each hologram can be individually reconstructed by imposing upon the reconstructing illumination beam the same spatial modulations.

Abstract: An incoming longwave infrared beam sharing the same aperture with an outgoing high power laser beam is separated from the laser beam path by a combination of a dichroic mirror and a diffraction grating.