Xerox Corporation

Olive Tree Technology, Inc.

S&r Tech Development, Inc.

Melvin E Swanberg

Robert P Loce

Martin Edward Banton

William L Lama

Michael S Cianciosi

Girmay K Girmay

Kevin J Garcia

Susan E Feth

Peter K Wu

Jean-Michel Guerin

Harry P Brueggemann

Yee-Ming Chung

Robert T Cunningham

Raymond Eskenazi

A pulsed imaging, facet tracked, Raster Output Scanner utilizes pulse width modulation in conjunction with spatial filtering to form three exposure levels at the surface of a charged photoreceptor medium, one of the levels associated with a specific color. This type of scanner with a nominal video rendering experiences a color line growth in the process direction. The line growth problem is caused by a coherent optical effect. The resultant output print has bolded color lines in the process direction. Several techniques are set forth to compensate for this line growth. In a preferred technique, the video data stream is modified by locating or positioning video pulses representing white information at the start of an associated pixel time period. When the color pixel is imaged, it will therefore, always abut an adjoining white pulse and will be inhibited from spreading into the adjacent pixel period. Other techniques rely upon inversion of white pulses, or separation of white pulses into two signals, each segment moved to the beginning and the end of the associated pixel period. According to another technique, the input data stream is buffered and pixel groups examined to identify neighboring white and color signals. These signals are then either narrowed or in the case of a sequence of color signals, the lead and trail edge of the color signals are trimmed.

Pulsed imaging, pulse width modulation scanner for a tri-level highlight

In a raster output scanner, a system for using one original beam and one facet of a rotating polygon to generate two consecutive scan lines. The original beam is first separated into two beams in a beam splitter. The resultant beams are polarized ninety degrees apart, and directed to the modulator. The beams are a sufficient distance apart so that the A/O modulator can modulate each beam with a minimum of crosstalk. The output beams are then brought together to within one scan line separation by a beam recombiner, which is a reversed beam splitter. The beams can be brought together to this close proximity without optical interference because the beams are plarized ninety degrees apart.

Multiple beam optical modulation system

A pulsed imaging Raster Output Scanner utilizes pulse width modulation in conjunction with spatial filtering to form three exposure levels at the surface of a recording medium, one of the levels associated with a specific color.

Pulsed imaging, pulse width modulation raster output scanner for

A swept frequency modulator for use in a 'Scophony' raster output scanner is disclosed. Input video [136] is mixed with a fixed RF frequency [137] provided by a fixed frequency oscillator [138], in a first mixer [139]. The resulting amplitude modulated RF [140] is fed into a vestigial sideband filter [142], producing a vestigial sideband signal [144], which is in turn fed into a second mixer [148], where it is mixed with a swept RF frequency [147]. The output of the second mixer [148] is swept frequency vestigial sideband RF [150], which is input to a driver [152]. The driver [152] drives an acoustooptic modulator [154], which modulates optical beam [156] to produce a modulated, facet-tracking beam [158]. The modulated optical beam [158] tracks a facet of a rotating mirror array which scans it across the photoreceptor. The invention enables achievement of all the potential advantages of a Scophony raster output flying spot scanner: (a) high image resolution, (b) improved depth of focus, and (c) linear system response.

Vestigial sideband scophony imaging modulator

A scanner system includes a light source for producing a light beam and a scanner for directing the light beam to a spot on a surface to a be scanned and for moving the spot across the surface along a scan line of predetermined length in a series of scan cycles. A reference clock produces a train of M reference pulses during each of the scan cycles such that each of the reference pulses represents the occurrence of a respective one of M segments of the scan cycle. An oscillator produces a train of clock pulses for use in controlling the light beam at a predetermined number of desired pixel positions along the scan line while a frequency control circuit responsive to the reference pulses varies the frequency of the oscillator during the occurrence of each of the M segments of the scan cycle in order to approximate an ideal frequency variation curve the entire scan cycle.

Scanner with non-linearity compensating pixel clock

A scanner system includes a light source for producing a light beam and a director that directs the light beam to a spot on a surface to be scanned moving the spot across the surface along a scan line of predetermined length in a series of scan cycles. The scanner system has a pixel clock for producing a train of clock pulses during each of the scan cycles configured so that some of the clock pulses are spaced apart by a first time interval and others are spaced apart by a longer second time interval in order to maintain timing of the clock pulses according to spot position along the scan line in a manner that compensates for scanner non-linearity in order to reduce pixel position distortion. The pixel clock includes a reference clock for producing a train of reference pulses having a period such that at least M reference pulses occur during the time the spot moves from a first end of the scan line to a point along the scan line that is a distance from the first end of the scan line equal to L/N, where L is the length of the scan line, M is a predetermined integer, and N is a predetermined integral number of pixel positions along the scan line. The first time interval represents the occurrence of M reference pulses and the second time interval represents the occurrence of M+I reference pulses, where I is an integer.

Scanner with a linearized pixel clock

A scanner system includes a light source for producing a light beam and scanning components for directing the light beam to a spot on a surface to be scanned that is located at a predetermined location relative to the scanning means, moving the spot across the surface along a scan line of predetermined length in a series of scan cycles. The system includes a pixel clock that produces a train of clock pulses during each of the scan cycles using a VCO circuit for producing the train of clock pulses and a control circuit for varying the timing of the clock pulses. The control circuit includes an waveshaping circuit for causing the control signal to have a waveform such that the timing of the clock pulses varies according to the position of the spot along the scan line in order to compensate for scanner non-linearity in a manner reducing pixel position distortion. One embodiment includes a digital to analog converter circuit, an absolute value circuit, and a multiple-slope amplifier circuit that shape the control signal waveform to a straight line fit of a desired curve, and the pixel clock circuitry is configured to produce exposure control pulses that reduce pixel exposure distortion.

Scanner with a linearized VCO pixel clock

A scanner system includes a light source and scanning components for moving a spot of light across a surface along a scan line of predetermined length. An electronic control system is included for controlling the light beam in order to produce a plurality of pixels on the surface along the scan line. It is configured to control the position and exposure of each of the pixels in order to compensate for pixel position distortion and pixel exposure distortion caused by variations in spot velocity. Preferably, the control system produces a digital scan clock signal or other control signal that defines a pixel interval and an exposure interval for each of a plurality of desired pixel positions along the scan line according to stored pixel interval and exposure interval data.

Scanner with electronic non-linearity compensation and method of

An improved flying spot scanner (48, 68) is disclosed, which is particularly applicable to use with a raster output scanner (ROS). The primary scan provided by an ROS is a continuous scan of the optical beam (26) along the scan line (40). The present invention provides a discontinuous pixel-by-pixel scan in the opposite direction to the continuous primary scan. Thus each pixel is positioned statically at its correct location on the photoreceptor (54) during the pixel's duration. At the end of each pixel's duration, the beam snaps rapidly to the position of the next pixel. Use of this invention will form a non-blurred image of each pixel on the photoreceptor (54). The invention uses an optical deflector (50, 70) to drive the beam opposite to the direction of the primary beam scan during each pixel's duration. The optical deflector (50, 70) may be an angle deflector (50) when used in a collimated optical beam (60), or it may be a translation deflector (70) when used in a non-collimated optical beam (72). This invention provides a flying spot scanner (48, 68) in which all the gray scale detail and resolution available in a pixel is preserved, with no smearing or blurring of pixels, independent of the content of adjacent pixels.

Resolution improvement in flying spot scanner

In a phase reversed bit stream, to increase the power in the fundamental frequency and reduce harmonics, each group of positive and negative ON bits is stretched by one pulse width. A stretch of slightly less than one pulse width may also be used to prevent glitches. This invention is useful in an optical raster output scanner where a greater amount of power in the fundamental frequency will result in a grater image intensity for the same data rate.

Full pixel pulse stretching for phase reversal scophony transmission

This invention relates to a pyramid polygon scanner wherein the differential scan length between multiple beams can be eliminated by tilting the beams with respect to the photoreceptor surface. Then the beam with the shorter scan lengths when the beams are normal to the photoreceptor, travel a greater distance before they impinge on the photoreceptor. At the start or end of scan the scan angle is not zero, so the scan lengths for the beams with the larger travel distances are increased by the extra distance multiplied by the tangent of the scan angle. At the proper tilt angle, all scan lengths at the photoreceptor are the same. Since the angular scan rate of all the beams are always the same, over the entire scan, the scan lengths of the individual beams will always be the same, at any fraction of the total scan. Thus the information written onto the photoreceptor by the multiple beams will be in alignment for all simultaneous beams.

Polycone.TM. scanning system with multiple beams

This invention relates to a multi-phase printed circuit board (PCB) tachometer for accurate measurement of the rotational speed and direction of an electric motor. The multi-phase output not only provides rotation velocity in the form of the conventional a-c output signal, but also provides rotation direction information, in addition to providing a higher rotational resolution than conventional PCB tachometers. According to a first embodiment of the present invention, a multi 'winding', multi-phase PCB tachometer that uses a single multi-pole magnet is constructed by using double sided boards with plated through holes. In a second embodiment, a multi-phase tachometer configuration is disclosed in which the number of radial printed circuit traces and the number of pole magnets are not equal, whereby the individual voltages generated across each radial segment will not be in phase, and thus can provide rotational direction information as well as velocity information.

Multi-phase printed circuit board tachometer

A pixel placement sensing arrangement, useable in a spatial synchronization system, having a split photodetector, RC integrating circuits having time constants long relative to the exposure time of the photodetector connected to the respective halves of the split photodetector such that the current accumulated in the capacitors of the integrating circuits results in voltages proportional to the respective exposures of the halves of the photodetector, and a different amplifier which provides an output reflective of any difference in said voltages.

Pixel placement sensing arrangement using split detecting elements

A spatial pixel clock synchronization system with jitter correction for an optical scanning system having a continuously running pixel clock source, start of scan and end of scan split photodetectors, circuitry for producing signals proportional to the respective light exposures of the halves of said photodetectors, and circuitry, including a switched filter circuit with two storage elements for each facet of the polygon of the system, for generating from said exposure signals a frequency correction signal for the pixel clock source.

Spatial pixel clock synchronization system

A temporal pixel clock synchronization system with jitter correction for an optical scanning system having a continuously running pixel clock source, circuitry for generating timing error signals having an amplitude representing any phase error between start of scan and start of pixel count pulses and any phase error between end of scan and end of pixel count pulses and circuitry, including a switched filter circuit with two storage elements for each facet of the polygon of the system, for generating a frequency correction signal for the pixel clock source.

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Claremont, CA, United States of America

Melvin E Swanberg