Abstract: A highly accurate and stable, but continuous fixed-phase fixed-frequency, quartz crystal oscillator frequency source, typically of 80 Mhz frequency, is used as the primary frequency standard for (i) synchronized, and (ii) variable, pixel placement timing in a bee-scanning image generator. A fixed-frequency timing chain appropriately synchronized to the scanning energy beam is generated by selecting, in accordance with a sensed start-of-scan condition, from among a number, typically 23, of variably-phase-delayed, typically by less than 1 nanosecond and normally by 0.8 nanosecond, replications of a fixed-phase timing chain that is produced from the crystal oscillator. The synchronized fixed-frequency timing chain so derived is then converted to the required variable-frequency pixel placement timing chain by timing-data-driven recombination of variably-phase-delayed replications, typically 13 such replications at a delay of 1.

Abstract: A photosensitive medium, normally a diazo printing plate or photopolymer-based proof, is exposed in a series of exposures each of a small rectangular area. Typically several linearly-arrayed Deformable Mirror Devices (DMD's) each spatially encode a light beam in order to expose corresponding pixels within corresponding regions of the medium. Between successive exposures, the several DMD's are moved to a new position relative to the medium along a first, x, axis so that new exposures of new regions can be made. Normally the arrayed DMD's are moved relative to the imager's frame by a screw drive. There is an additional, separate relative movement between the DMD's and the medium along another, perpendicular, y, axis. Normally the medium is moved relative to the imager's frame by nip rollers. In order to provide a required precision in registering successively imaged regions of the medium along either or both axis, reference marks are exposed directly on the medium.

Abstract: A web of material, typically paper, metal or film and most commonly roll photographic plate material, passes between a first, driven, roller made from material with a high coefficient of friction, typically neoprene rubber, and a second, driven, roller made from material with a low coefficient of friction, typically metal or nylon. The high-friction drive roller (only) is positionally adjustable. The web is driven straight ahead, without appreciable undesirable steering or skew, over a broad range of adjustments of the separation, and the parallelism, between the two rollers. The web motion is responsive substantially to only the high-friction drive roller, and the web speed may accordingly be regulated, including so as to be maintained highly uniform, in response to the drive roller (only).

Abstract: The separation between two plates or electrodes--between which plates a developer solution is applied to develop a latent electrostatic charge image on a photoconductive medium within an electrophotographic imager--is varied in proportion to a detected concentration of toner within the developer solution. Resultantly to this control of the separation of the two plates, the proximity of the medium's photoconductive surface to a one plate, and the strength of the electric field between that plate and the photoconductive surface, is also controlled. By the control the thickness and density of the applied toner film is maintained constant, and a high quality image is maintained, despite depletion of toner from the developer solution. The toner concentration is preferably sensed as electrical resistance. A control circuit responsive to this sensed resistance preferably includes an analog-digital converter, a microprocessor, a stepper motor driver/controller, and a stepper motor rotating a cam.

Abstract: A very stable deflection system usable with a beam of radiant energy incorporates a self-resonant scanning galvanometer located within an evacuated chamber. The chamber has a hermetic radiant energy transmissive window. An exterior laser source provides a beam of monochromatic light which is directed onto the mirror of the galvanometer. Repetitive deflection of the galvanometer mirror at a predetermined frequency results in the beam being projected onto a target so as to form a very stable and repeatable scanning line. Movement of the target provides a multi-line raster on which an image can be formed.

Abstract: A light beam, typically 780 nanometer coherent light generated by a laser diode, is focused, preferably by a wide angle graded index optics lens having a numerical aperture of 0.46 and a diameter of 1.8 mm, into a diffraction limited spot, of approximate diameter 0.039 to 0.3 mils, upon an encoder wheel. The encoder wheel is typically a photoetched radial reticular grating on Mylar.RTM. plastic having lines at 0.00025" width at a radius of 1". The focused light beam intercepts the encoder wheel at this 1" radius and is alternately transmitted and obstructed by the reticular grating of the rotating encoder wheel. The selectivity transmitted light beam is received at a detector, typically a phototransistor. Greater than 10,000 transitions per encoder wheel revolution are detectable.

Abstract: Transition-encoded information for a single scan line of a font image consists of flags at the addresses of all points of transition upon the scan line from black to white, and from white to black, in order to generate one scan line of the font image. This information is produced, scan line by scan line, in a system receiving the vertical position, the horizontal position, and a starting address within a font memory whereat a run-length-encoded description of a particular character font is stored. This information is developed by adding, in an adder, the initial horizontal displacement plus, in a cumulative fashion, the run-length-encoded font information for each character which appears, in some portion, upon an individual scan line. The transition-encoded information is used to control pixel by pixel image generation in an image generator equivalently to full bit-mapped control but with lower cost, higher speed of conversion, and greater flexibility in the images generated.

Abstract: Transition-encoded font image information is a form of information flagging all pixel displacement locations upon a scan line of a raster scan image generator, nominally a laser printer, whereat black to white, and white to black, transitions occur during generation of the one scan line of a font image. Transition-encoded information for plural, superimposed, font images may be combined prior to generation of a synthesis image. In this combination of transition-encoded information for generating superimposed font images the flags representing transitions must not be overwritten, there being a limit that a single scan line pixel position must either transit black to white, transit white to black, or maintain the state of the previous pixel. The combining of transition encoded information encodes transitions for these one or ones of addresses (pixels) wherein two flags would otherwise overlap so that the total transitions within the combined font information are preserved.

Abstract: Transition-encoded font image information--being a form of information flagging all pixel displacement locations upon a scan line of a raster scanning image generator, nominally a laser printer, whereat a marker, nominally a laser beam, transits from marking white to marking black, and from marking black to marking white, during the generation of the one scan line of a font image--is stored in two random access memories (RAMs) each having a nominal 10,320+ address corresponding to the 1200 pixel positions per inch across an 8.6" scan line. The two RAMs are sequentially read in parallel from the start-of-scan of the scanning marker, or laser beam. The successively read transition-encoded information is used to decrement a counter upon each black-to-white transition and to increment the same counter upon each white-to-black transition.

Abstract: A photosensitive, photoconductive media moving in a first direction relative to a laser light beam scanning in a second direction, transverse to the first direction, incurs velocity variations. These velocity variations result in variations in the absolute and relative heights of white and black image features. This printed image nonuniformity is especially visually detectable for closely spaced parallel lines in the second direction, and/or gray scale. An optical velocity sensor senses instantaneous media velocity. An analog or digital velocity error processor maintains a running average velocity and determines, by subtraction, an instantaneous velocity error as the difference between currently sensed and running average velocities. The instantaneous velocity error so determined is used to adjust the intensity of the laser light beam to be proportionally brighter (dimmer), exposing a wider (narrower) scan line, on a faster-moving (slower-moving) media region.

Abstract: Integrations of the historical numbers of times that a light beam scanned in an oscillatory course by a self-resonant galvanometer scanner does traverse so far in a first direction so as to impinge upon a Beginning-of-Trace (BOT) sensor, and does traverse so far in the opposite direction so as to impinge upon an End-of-Trace (EOT) sensor, are each used to separately control the voltage level developed in a first, BOT, electrical tank circuit and in a second, EOT, electrical tank circuit. Voltage from each tank circuit is amplified and applied to drive the self-resonant scanner, at a polarity to induce continued oscillation, during one-half of each oscillatory cycle. Amplitude and centering control thereby obtained of the sinusoidal oscillation of the self-resonant scanner is repeatable to better than one part in ten thousand between cycles.