Abstract: Novel methods are disclosed for designing and constructing miniature optical systems and devices employing light diffractive optical elements (DOES) for modifying the size and shape of laser beams produced from a commercial-grade laser diodes, over an extended range hitherto unachievable using conventional techniques. The systems and devices of the present invention have uses in a wide range of applications, including laser scanning, optical-based information storage, medical and analytical instrumentation, and the like. In the illustrative embodiments, various techniques are disclosed for implementing the DOEs as holographic optical elements (HOEs), computer-generated holograms (CGHs), as well as other diffractive optical elements.

Abstract: A hologram system is comprised of two identical volume holograms. Both holograms have Bragg planes oriented perpendicular to the surface of the hologram. The first volume hologram separates a single beam into two orthogonal polarization component beams. The second volume hologram diffracts one of the polarization component beams such that a desired separation angle is achieved between the two beams. This separation angle may be precisely adjusted during manufacture by orienting the Bragg planes of the second volume hologram at a rotational angle with respect to the Bragg planes of the first volume hologram.

Abstract: An optical data storage system includes a pivotally mounted hologram. Rotation of the hologram results in beam displacement at the optical medium for purposes of fine tracking. The hologram is designed and positioned relative to the focusing lens, such that the beam always passes through the center aperture of the lens even when the beam is displaced at the optical medium. Thus, the beam is not truncated at the focusing lens and loss of light and aberration problems are prevented.

Abstract: A hologram system comprises two volume holograms on two separate substrates which are cemented together with an optical cement. The two volume holograms are manufactured with identical Bragg planes. The two volume holograms are oriented with respect to one another such that the Bragg planes are optically aligned. The result is that the two volume holograms operate as a single thicker volume hologram wherein the Bragg angle sensitivity is greatly increased.

Abstract: A first volume hologram diffracts a portion of the beam of light as a first beam and transmits the remaining portion of the beam of light as a second beam. A second volume hologram diffracts either the first or the second beam to a desired angle and transmits the remaining beam undiffracted. Desired beam separations at desired angles may thereby be achieved for use in optical data storage systems.

Abstract: A hologram element receives a first and second laser beams at a first angle relative to one another. The hologram element emits the laser beams at a second angle relative to one another. The second angle is less than the first angle. The result is that laser beams from widely divergent laser sources may be directed into the same optical channel. Closely spaced beams are thereby provided for multiple beam optical data storage systems.

Abstract: A multiple beam optical system includes a housing which contains a pair of laser diodes and a pair of optical detectors. The lasers produce overlapping beams of light. The housing includes a beam directing and reflecting member which selectively focuses light from one of the lasers to a corresponding optical detector located in the housing and selectively focuses light from the other laser to its corresponding optical detector located within the housing. The individual power of each of the overlapping laser beams is thereby monitored by the separate detectors.

Abstract: A laser array provides multiple closely spaced light beams. These light beams are reflected off of an optical recording medium. A faceted prism is used to separate the closely spaced beams sets for detection by an optical detector array and detector circuit. The detector circuit provides data, power, tracking and focus signals.

Abstract: An optical data storage system having a highly integrated optical storage head that (1) integrates the read, write and servo paths, (2) comprises a monolithic laser-detector storage array that is integrated on a single chip an, wherein laser-detector alignment desirably is fixed at the time of fabrication, and (3) comprises a four-hologram optical element that directs light to an optical disk and divides the returning light into one track error and two focus error servo beams and two polarization component beams for data detection, and also provides a satellite beam of the incident laser beam for monitoring power of the laser beam.

Abstract: A dual beam laser array provides two overlapping beams for use in a direct read after write (DRAW) optical data storage system. A first portion of the overlapping beams is directed to a first optical detector and a second portion of the overlapping beams is directed to a second optical detector. A logic circuit connected to the optical detectors generates power signals representative of the power levels of each of the overlapping beams without the need to completely separate the beams.

Abstract: A multi-faceted holographic disk can be copied in a one-step process by using a source disk, actually a sandwich of two thin film layers of photosensitive material. The first thin film layer is capable of producing multiple reference beams simultaneously. The second thin film layers is a "master" copy of the disk to be copied. Both layers are produced using known off-axis holographic techniques. A target disk, having an unexposed film of photosensitive material is located ajacent the second thin film layer. The source disk is illuminated with coherent light, preferably in the form of a conical beam with an apparent point of origin on an axis through the common centers of the source and target disks. Several optical elements capable of producing the conical beam are illustrated.

Abstract: A holographic scanner includes a rotating glass disk carrying a plurality of scan line generating holograms, a laser light source and means for detecting reflected optical energy. The scanner is improved by adding a plurality of relatively small position-indicating holograms in alternation with the scan line generating holograms. The position-indicating holograms redirect the laser beam along desired paths on the same side of the disk as the laser. The redirected laser beam may be detected by the system photodetector or an auxiliary photodetector to provide signals indicating the current disk position. The position information can be used by a system processor to optimize scanner parameters as a function of the characteristics of the next active scan line generating hologram.

Abstract: This disclosure describes a technique for reading bar codes scanned by focussed scan lines having different focal lengths where at least one of the scan lines has a beam that is small relative to irregularities of the surface on which the label appears. The scan lines are generated using a holographic disk so as to have a predetermined focal length and focal zone. The focal zone of each generated scan line overlaps the focal point of at least one adjacent scan line. Any bar code label which might be scanned by a beam so small that it would be degraded by surface scatter noise is also scanned by a slightly larger beam. The slightly larger beam "averages out" the surface scattering noise to produce a smoother or cleaner return signal.

Abstract: A system is disclosed for preventing processing of duplicative coded label signals generated by a scanner lacking item detectors. The system establishes a variable lockout time as a function of operator performance. Any detected label candidate which duplicates a candidate received within the lockout time is assumed to be duplicative. Any transfer to the terminal is inhibited. Operator performance is tracked by measuring the inter-item arrival times for candidates actually transferred to the terminal. The inter-item arrival times are averaged over a given number of items. The average value is used to select a lockout time which is generally proportional to the average inter-item arrival time.

Abstract: An optical scanner uses frequency modulation and detection techniques to produce and utilize multiple, simultaneous scan patterns in which corresponding scan lines have different focal lengths. Two or more solid state lasers are modulated at unique frequencies. The frequency modulated output beams pass through different combinations of focusing lenses and are deflected by a single beam deflecting apparatus. Light reflected from any scanned object is detected. The resulting multi-frequency signal is applied to a plurality of bandpass filters to separate the returned signal into a plurality of separately decodable signals.

Abstract: Operating parameters for a multiple facet holographic disc scanner are adjusted on real time basis as a function of the actual diffraction efficiency of the facet region aligned with the impinging laser beam. The operating parameters are adjusted to achieve optimum signal levels independent of facet characteristics. Diffraction efficiency is inversely related to zero order beam power for a given level of input beam power. A photodetector measures the zero order beam power. The output of this photodetector is used to control video amplifier gain and/or semiconductor laser current.

Abstract: An optical scanner in a retail store checkout stand includes a single item detector upstream of the scanner window. Output signals from the item detector and from symbol recognition logic are used to open and close a shutter in the beam path of the scanner laser. The shutter is opened and a first time out sequence is started when the beam path is interrupted. A second, short time out sequence is restarted each time a valid symbol is recognized. A third time out sequence of intermediate length supersedes the first time out sequence when the beam path is cleared. The laser shutter is closed and the symbol is transferred to a terminal or controller upon the completion of any active time out sequence or upon recognition of a predetermined number of identical symbols, whichever comes first.

Abstract: Production quantities of a multi-element holographic scanner disc are made by optically replicating a silver halide master disc one element at a time in a dichromated gelatin film. The dichromated gelatin film swells during processing. The swell is monitored during production by determining the shift in the angle of the Bragg surfaces within the gel. The angle of the replicating beam for each element is changed from that of the original reference beam to establish a Bragg angle at exposure which will be tilted to the proper angle after swelling in order to maximize the diffraction efficiency of the element at the original reference beam angle.

Abstract: A scan pattern for a bar code scanner is produced by the combination of a coherent light source, a rotating disc with holographic facets and an array of fixed, beam folding mirrors. Light reflected from a bar code label follows a retroreflective path to a photodetector within the scanner. To reduce variations in the amount of light collected through different facets, the areas of the facets are varied as a function of beam elevation and beam path length.