Xerox Corporation

James P Martin

Fred F Hubble, Iii

Michael D Borton

Ralph A Shoemaker

Kenneth Russell Ossman

Edward A Powers

Jeffrey J Folkins

Thomas J Hammond

Theresa K Mattioli

Steven C Hart

David G Anderson

Alan J Werner, Jr

Jerry Floyd Adams

Mehrdad Zomorrodi

Li-Fung Cheung

Alfred J Claflin, Jr

Robert E Crumrine

John M Mitchell, Jr

Peter P White

Randolph H Bullock

Virginia R Nichols

Virginia N MacDonald

A maintenance system for an ink jet printer of the type having a full width array printhead has a movable carriage with a droplet sensor and a nozzle recovery device. As the carriage moves along the length of the printhead, each nozzle checked, one at a time, by the droplet sensor for the presence or absence of an ejected droplet and if the droplet has the correct directionality. Any problem nozzle is identified during a single traversal of the carriage across the printhead, and during a second traversal, the identified problem nozzles have a recovery operation performed on them such as being cleaned to remove any dried ink or other contaminating particles or being primed in the case of a clogged nozzle. The problem nozzles which have had a recovery operation performed on them and checked again by the droplet sensor is required for the entire array of nozzles, and ink is conserved since only predetermined nozzles are printed.

Drop sensing and recovery system for an ink jet printer

An optical element uniformly distributes radiant energy on a target surface, such as for discharging an area of a photoreceptor in a xerographic printer, or for applying infrared energy to dry an ink-jet image. A cylinder lens collimates light beams from a light source and directs the collimated light beams to a preselected area on the target surface. First and second refractive portions, each attached to and extending parallel to the cylinder lens, totally internally reflect light beams from the light source and direct the light beams reflected therein to the target surface.

Optical element and device for providing uniform irradiance of a surface

An infrared densitometer which measures the diffuse component of reflectivity as marking particles are progressively deposited on a moving photoconductive belt. Collimated light rays are projected onto a test patch including the marking particles. The light rays reflected from the test patch are collected and directed onto a photodiode array. The photodiode array generates electrical signals proportional to the total flux and a diffuse component of the total flux of the reflected light rays. Circuitry compares the electrical signals and determines the difference to generate an electrical signal proportional to the specular component of the total flux of the reflected light rays. Additional circuitry adds the electrical signals proportional to the total flux and the diffuse component of the total flux of the reflected light rays and compares the result of the summed signal to the specular component to provide a total diffuse signal for controlling developed mass.

Control develop mass in a color system

An apparatus and method for reliably monitoring the position of a radiant energy beam, for example, a scanning laser beam such as that produced by a raster output scanning system to expose a photoresponsive member, where the beam traverses the surface of a photoreceptive member at a high rate of speed. The apparatus, which includes a lateral-effect photodiode, is also capable of signaling when the radiant energy beam traverses a specific location. The apparatus may also be used to determine the relative intensity of the radiant energy beam, thereby significantly reducing the space and expense necessary to monitor the radiant energy beam by combining multiple sensing operation in a single apparatus.

Apparatus and method for beam steering in a raster output scanner

An apparatus for positional tracking a moving photoconductive belt and adjusting an imager in an electrophotographic printing machine to correct for alignment errors when forming a composite image. Registration errors are sensed by developing an appropriate set of target marks, detecting the target marks, and controlling the position of the imager.

Apparatus for image registration

Beam steering sensor for a raster scanner using a lateral effect

An apparatus and method of adjusting an imager in an electrophotographic printing machine to correct for registration errors when forming a composite image. Registration errors are sensed by forming one or more target lines on the photoreceptor surface, detecting the center of the lines and controlling the operation of the imager in response thereto. In one embodiment, four LED print bars form a composite color image in a single pass. A photosensor is placed beneath the print bars; a narrow target line is formed on the belt surface a few scan lines before the start of an exposure frame. The center of the line is detected by circuitry connected to the sensor output which produces a signal corresponding to detection of the center of the target line. This output signal is generated for each of the three downstream print bars and a signal is applied to each print bar to start the image exposure sequence in registration with first image exposure. In a second embodiment, skew registration adjustments are enabled by forming two line marks at opposite ends of the photoreceptor, detecting the center of each mark and making the adjustments of the position of the downstream print bars based on time differences between detection of the generation of the two signals.

Mark detection circuit for an electrographic printing machine

A Raster Output Scanner (ROS) color printer is formed by providing several ROS imagers adjacent image exposure locations of a photoreceptor belt. Each ROS imager forms a separate color image in response to video input signals with each color image superimposed in registration over the previously formed images. Registration in the process direction is enabled by a quad cell photosensor whose output is continually compared to determine whether process registration deviations from a previously established position are necessary. Correction signals are generated in an iterative fashion until a preselected process registration position is re-established. The quad cell detector is also used for a second function; to produce the start and end of scan signals which enable image registration in the cross-process direction.

Raser output scanner color printer with improved start of scan detection

A precision belt hole sensor and associated conditioning circuitry provides precise trigger signals that enable synchronous printing in a color printer. An image bar recording system, which, in a preferred embodiment, utilizes a plurality of LED image bars, forms a plurality of latent images on a moving photoreceptor which may subsequently be developed in different colors. A pair of sensors associated with each printbar views illuminated pixels at the end of a printbar, through a pair of oppositely aligned photoreceptor holes. The signals detected by the sensor are amplified and processed to provide inputs to a comparitor circuit which generates an output signal at a time which precisely defines the passage of the trailing edge of the hole, past the sensors. The signal from the comparitor is used to accomplish skew registration of the printbar and to provide sync signals to enable precise formation of the leading edge of the associated image frame.

Method and apparatus for registration of sequential images in a single

The invention comprises a sensor system in a printhead scanner which is capable of achieving accurate pixel to pixel registration. A plastic film strip with alternating fiducial bars and spaces is scanned. A voltage pattern is triggered by the zero slope points of the voltage induced by a sensing mechanism being moved along the plastic film strip.

Linear encoder for digital printing applications

An infrared densitometer which measures the reflectivity of a selected region on a moving photoconductive belt covered at least partially with marking particles. Collimated light rays are projected onto the selected region of the moving photoconductive member with or without marking particles thereon. The light rays reflected from the selected region of the moving photoconductive member are collected and directed onto a photodiode array. A photodiode array generates electrical signals proportional to the diffuse component of the total reflectivity of the selected region of the photoconductive member with and without marking particles thereon. Circuitry determines a control signal as a function of the difference in electrical signals.

Densitometer for measuring developability

A densitometer which measures the reduction in the specular component of the reflectivity of a portion of a surface having a liquid deposited thereon. Collimated light rays, in the visible spectrum, are projected onto the portion of the surface having the liquid thereon. The light rays reflected from the portion of the surface having the liquid deposited thereon are collected and directed onto a photodiode array. The photodiode array generates electrical signals proportional to the total flux and the diffuse component of the total flux of the reflected light rays. Circuitry compares the electrical signals and determines the difference therebetween to generate an electrical signal proportional to the specular component of the total flux of the reflected light rays.

Densitometer for a liquid developer material

A flash exposure photocopier provides a mechanism for automatically controlling photoreceptor exposure levels to compensate for the effects of documents having backgrounds of different densities. A photosensor and lens assembly is located within a flash housing in a position whereby a large portion of the document is imaged by the lens onto the surface of a chip having a plurality of individual photosensors contained thereon. The outputs of each photosensor are integrated and applied to a comparator set at a particular reference level. The comparator output controls the duration of the flash source so as to quench lamp operation when an input level is reached corresponding to the particular reference level set. The integrated photosensor outputs are also summed and a signal representing their average value is compared to the signal which triggers the comparator. The ratio of these signals is used to identify documents with high area coverage and hence high toner usage. The toner dispensing rate is then regulated accordingly.

Automatic exposure control system for flash exposure photocopiers

A light collector for an LED array for efficiently collecting and collimating light emitting from the LEDs and projecting the light into an optical wave guide which directs that light onto a photoreceptor surface. Each LED is centered in a hemispherical cavity in the collector array in order that radiation from the LED enters the collector essentially unrefracted. The collector array provides a convex lens portion and a parabolic reflecting surface portion. Light that exits from the LED that is substantially perpendicular to the substrate supporting the LED is applied to the convex lens and is collimated. Light exiting substantially parallel to the substrate strikes a parabolic reflecting surface at greater than the critical angle and is also collimated. The two concentric collimated beams are combined and applied to the photoreceptor surface via a light pipe or optical wave guide secured to the collector.

Collector for an LED array

The present invention is concerned with a self-adjusting document sensor compensating for degradation of the sensor system. A suitable light source and a detector are provided, the output of the detector being fed into an amplifier whose gain depends upon a feedback signal. Periodically, the output of the amplifier is compared to a reference. If the output of the amplifier falls below the reference, a pulse is sent to a ripple counter whose digital output is fed back to the amplifier to change the gain of the amplifier. If the detector is an unbiased photodiode operating in the transconductance mode, the leakage currents and their subsequent effect on output with amplifier gain changes will be minimized.

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Rochester, NY, United States of America

James P Martin