Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A printing machine in which magnetically permeable marking particles develop a latent image recorded on a photoconductive member. A read head is positioned on the opposite of the photoconductive member to detect magnetic field intensity effects produced by the leading edge and the trailing edge of the marking particles on the characters recorded. The detected signals are used to control the magnetic quality of the developed image.

Abstract: 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.

Abstract: A magnetic ink monitoring system is provided including a reader which outputs an electrical signal representative of a magnetic flux, a storage mechanism which stores an integral representation of a signal from a standard magnetic ink display, and a comparator operatively connected to the read means and the storage means to compare an integral signal of the electrical signal of the magnetic ink display to the integral representation of a signal from a standard magnetic ink character.

Abstract: A method and apparatus is provided for lateral registration of image exposures on photoreceptive belts subject to lateral deviation from linear travel. In one embodiment, a plurality of Raster Output Scanner (ROS) imagers in a digital color printer are positioned so as to form successive images on the surface of the belt. A plurality of split cell photodetectors are positioned beneath the belt, one each associated with each of the ROS imagers. An aperture is formed in the belt in a non-image area, but in alignment with the detectors. Scan lines from each ROS unit are periodically visible through the aperture and illuminate the photodetector. The outputs from each of the photodetector photosites are compared and lateral belt movement errors thereby identified. Appropriate correction signals are generated to maintain the correct lateral registration.

Abstract: 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.

Abstract: The present invention is directed to a precise method of registering plurality of imaging stations, so as to form sequential images on a photoreceptor belt in a single pass. A belt hole is formed in the photoreceptor belt, outside the image area, but within the scan of the imager scan line. The scan line is sequentially swept in a transverse direction across the width of the belt. As the leading edge of the belt hole advances into the sweeping beam, a plurality of beam sweeps will occur while the leading edge is moving through the sweep area. Due to the gaussian illumination of the scanning beam, the exposure at the belt edge gradually increases to a maximum point coinciding with the maximum illumination of the scanning beam. A detector is placed beneath the belt to provide a signal representing the exposure level of each scanning beam which crosses the leading edge of the advancing belt hole. The detectors produce a current output representative of the exposure level.

Abstract: 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.

Abstract: 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.

Abstract: A media discriminating and presence sensor that can detect and discriminate between paper and transparency uses a light emitting diode and two defectors configured so as to measure both diffuse and specular reflectivity of the media, and a media support surface that suppresses unwanted reflections.

Abstract: 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.

Abstract: 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.

Abstract: An infrared densitometer which measures the reduction in the specular component of reflectivity as marking particles are progressively deposited on a moving photoconductive belt. Collimated light rays are projected onto the marking particles. The light rays reflected from at least the marking particles are collected and directed onto a photodiode array. The photodiode array generates electricl 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: An integral, compact infrared reflectance densitometer including a substrate supporting an LED, a control photodiode to compensate for component degradation, a background photodiode to compensate for background radiation, and a large area photodiode to provide an electrical signal representative of the amount of toner particles on the photosensitive surface. Also carried on the substrate is a field lens to focus light rays reflected from the photosensitive surface onto the signal photodiode. The substrate is precisely secured to a molded housing having integral collector and collimating lenses. Four extending pins on the housing engage four apertures on the substrate to locate the substrate with respect to the housing and align the LED and field lens carried on the substrate with the collector and collimating lenses of the housing.

Abstract: A corona generating device having a corona electrode supported between a pair of endblock assemblies, each endblock assembly defining a space for the passage of the electrode, and non-conductive inserts seated in the spaces in the endblock assemblies and surrounding the electrode. The non-conductive inserts are made of a material with high dielectric strength and resistent to corrosive atmosphere. The inserts can be easily and inexpensively replaced and they protect the endblock assemblies from effects of applying high voltages to the corona electrode.