Abstract: A novel laser raster scanner that scans, in response to control signals from a controller, an exposure beam across a substrate by means of a rotating polygonal mirror having a plurality of reflective facets provides passive facet tracking by means of a plurality of glass windows configured with the polygonal mirror to cooperate with corresponding ones of the reflective facets. A first beam steering mechanism provides the laser beam to a window at a first surface thereof. A second beam steering mechanism receives the laser beam from an opposed second window surface and provides an illumination beam to the corresponding reflective facet. Each window is positioned to displace the laser beam from the incident axis so as to produce a corresponding displacement of the illumination beam on the facet in the direction of mirror rotation.

Abstract: A method and apparatus that provides skip line asynchronous imaging is characterized by a controller that computes pixel signals in a sequence of arrays and stores those arrays in a buffer. A controller will adjust the rate advancement of the write platen and synchronize therewith the presentation of a signal array to a mirror facet should the controller determine that the next line of data is not ready for imaging.

Abstract: A highly accurate positioning system used in connection with a photoplotter assembly employing a dual axis drive system having low mass and low inertia components. The drive elements of the system are low cost, high tensile strength drive bands that orient the driven members with high accuracy, low noise and require no lubrication. A photoplotter head and a moveable work table are similarly mounted to a base structure in a slideable manner utilizing a recirculating ball guide assembly and a flat rail roller assembly. The drive bands are moved by friction drive motors and a closed loop feedback control system orienting the photoplotter head and the work table relative to each other and utilize input only from the actual placement of the photoplotter head and the work table in calculating further movements. The work table is a lightweight element formed from a honeycomb infrastructure that provides individual vacuum chambers to hold a workpiece down on the work surface without external holding means.

Abstract: An indexing system for selectively orienting one of a series of arcuately oriented different sized and/or shaped apertures formed around an aperture disc used in a photohead for exposing upon a photosensitive surface detailed graphic information using a light beam. The aperture disc has formed thereon, equidistantly spaced indicators in the form of slots allowing radiant energy generated by a light emitter to impede upon and energize a split cell photosensitive detector. A control system rotates an aperture wheel to a next selected position at a first velocity until a selected aperture is within the vicinity of the next selected position and subsequently rotates the aperture disc at a second slower velocity to precisely position the next selected position in registry with the light beam.

Abstract: A novel method and apparatus for determining the accuracy of artwork produced from a laser direct imaging system employs a calibration substrate which has images of opposed, perpendicular scales and registration marks thereon. The overall system dimensional error is determined directly from substrate measurements, as is the magnitude of the mechanical and processing errors.

Abstract: A novel apparatus for use in generating a scan timing signal in a laser raster scanner includes an optical diffuser positioned to receive a scanned reference beam through a reference mask. The diffused, modulated reference beam is presented to an array of photodetectors. The number of photodetectors in the array is selected to be sufficient so that at least two photodetectors receive the diffused modulated reference beam simultaneously as the reference beam is scanned along the reference mask.

Abstract: A system for rapidly generating an image of a pattern in successive lines each being formed of a plurality of pixels, the system storing the previously generated line, producing one or more replacement pixels, and providing successively generated lines of the image by selectively delivering stored pixels or replacement pixels in accordance with commands defining the boundaries of the pattern. The pixels of the previously generated line are updated with the replacement pixels.

Abstract: A novel method and apparatus for improving the overall accuracy and repeatability of an optical photoplotter which is characterized by a controller which determines an image position error from interferometric feedback signals and position command signals and subsequently provides displacement of the image in dependence thereon.

Abstract: A system for projecting a spot of radiant energy includes a lamp for projecting a light spot onto a surface and includes means for providing a selection of differently sized spots. Drive means moves the light spot relative to the surface and is capable of moving the light spot at a maximum given velocity which is the same for all of the differently sized spots. Velocity output means produces a velocity signal representing the velocity of the spot and a normalized velocity signal is produced by dividing the volocity signal by the maximum given velocity. Each differently sized spot is assigned a different lamp command voltage signal and a selected one of the lamp command voltage signals is multiplied by the normalized velocity signal to produce a resultant lamp command voltage signal which energizes the lamp.

Abstract: An indexing system for selectively orienting one of a series of arcuately oriented different sized and/or shaped apertures formed around an aperture disc used in a photohead for exposing upon a photosensitive surface detailed graphic information using a light beam. The aperture disc has formed thereon, equidistantly spaced indicators in the form of slots allowing radiant energy generated by a light emitter to impede upon and energize a split cell photosensitive detector. A control system rotates an aperture wheel to a next selected position at a first volocity until a selected aperture is within the vicinity of the next selected position and subsequently rotates the aperture disc at a second slower velocity to precisely position the next selected position in registry with the light beam.

Abstract: A highly accurate positioning system used in connection with the photoplotter assembly employing a dual axis drive system having low mass and low inertia components. The drive elements of the system are low cost, high tensile strength drive bands that orient the driven members with high accuracy, low noise and require no lubrication. A photoplotter head and a moveable work table are similarly mounted to a base structure in a slideable manner utilizing a recirculating ball guide assembly and a flat rail roller assembly. The drive bands are moved by friction drive motors and a closed loop feedback control system orienting the photoplotter head and the work table relative to each other and utilize input only from the actual placement of the photoplotter head and the work table in calculating further movements. The work table is a lightweight element formed from a honeycomb infrastructure that provides individual vacuum chambers to hold a workpiece down on the work surface without external holding means.

Abstract: In a photoplotting apparatus and method using a flash lamp to expose a line on a photosensitive surface, and wherein the photohead has a number of apertures of different size to vary the width of the generated line, the quality of line drawn with each aperture is controlled by controlling or setting for each aperture the factor by which the flash rate of the lamp is related to the speed of the photohead. A signal representing the speed of the photohead over the photosensitive surface is divided by a division factor uniquely associated with the selected aperture to produce a flash rate command signal controlling the flash rate of the flash lamp. Taking into account the dividing factor associated with each aperture, the speed of the photohead is limited to one at which the flash lamp flashes at or slightly below its maximum flash rate, thereby producing maximum throughput for the apparatus.

Abstract: A line following system comprising a matrix generating optical scanning device which produces a matrix representing a portion of a line being followed and a computer which locates points on said line from said matrixes and directs the optical scanning device to proceed along the line based on a course indicated by vectors between previously located points.

Abstract: Laser imaging system and method for imaging a plurality of printed pages on an output medium in positions and orientations corresponding to an imposition format. Different areas of the medium are scanned to form the images for different pages with the beam traveling and being modulated to provide the proper orientation and position for each page.

Abstract: A photoplotter having a photohead that moves in one coordinate direction and a film table movable in another coordinate direction employs a dual-axis, single mirror and reflector interferometer system for measuring movement of the film and photohead relative to one another. The photohead is mounted on a bridge over the movable film table and a first interferometer mounted on the head cooperates with an elongated mirror at the edge of the table for measuring the relative position of the film and head in the first coordinate direction. Another interferometer mounted on the bridge cooperates with a retroreflector on the head to measure movement of the head relative to the film in the second coordinate direction. The two measurements from the interferometers are employed as feedback signals in a closed loop positioning system for the photohead and table.

Abstract: In a belt and pulley system wherein motion is transferred between the two members, the belt is a metal belt having a pulley engaging face made of a relatively soft material and the pulley is one having a regular pattern of small hard protuberances, such as formed by knurling, on its belt engaging face which press into the soft metal of the belt to form permanent depressions arranged in a matching pattern which mesh with the protuberances to provide a positive slip-free motion transfer. The belt and pulley drive may be used advantageously in a device such as an X-Y plotter for accurately positioning, with good repeatibility and fine resolution, an associated member driven in one coordinate direction by the metal belt driven in turn by the knurled pulley.

Abstract: A manual control valve for installation in a vacuum system including a contiguously-zone vacuum table permits an operator to progressively increase or decrease the number of energized vacuum zones of the table. The valve includes a housing having an outlet securable to a vacuum source and a plurality of inlet passageways connectable with the table so as to communicate with the respective vacuum zones. A plug is rotatably received in the housing, and a network of passageways within the plug and housing interact upon rotation of the plug with respect to the housing to provide communication between the housing outlets and various ones of the housing inlets. The valve also includes indexing means by which the plug is releasably held in place at each of several rotational positions with respect to the housing.

Abstract: A low inertia plotter having a carrier consisting solely of a relatively thin sheet of support material defining a surface for carrying a sheet of plotting media and supported by an air bearing for movement in one coordinate direction relative to a frame and a plotting instrument supported on the frame for movement in another coordinate direction and in plotting relation to the plotting media. The carrier and the plotting instrument are driven in response to command signals received from a controller.

Abstract: An automatically controlled plotter that generates graphic information on recording material in response to a plot program includes an optical sensor for detecting the traces or lines that are generated in the plot on the recording medium. The detected lines are compared with the programmed lines to establish if an omission or gap exists, and where there is a gap, the plotting process is interrupted or the program is repeated to retrace the defective portion of the plot, or the defect can be recorded for subsequent correction.

Abstract: An interferometer for analyzing electromagnetic frequency spectra including a movable mirror supported on two air bearings such that the center of support of the bearings continuously coincides with the center of gravity of the movable mirror during the motion of the mirror. The air bearings engage two parallel, spaced apart lateral rods that maintain the optical alignment of the mirror. To facilitate making spectral measurements, the interferometer also incorporates a laser for producing monochromatic light that is directed through a primary beam splitter to provide a periodic fringe pattern as the mirror moves and a white light directed through a secondary beam splitter to provide a reproducible reference point.