Abstract: A photoconductor wear reduction system includes a photoconductor drum clutch and a control circuit for controlling the clutch. Wear on the photoconductor drum is reduced by mechanically decoupling the photoconductor drum from the drive train in the electrophotographic printer at the end of a print job while the drive train is still rotating. In a first embodiment of the photoconductor drum clutch, the application of electrical power is required to mechanically couple the photoconductor drum to the drive. In the second and third embodiments of the photoconductor drum clutch, the photoconductor drum clutch mechanically couples the photoconductor drum to the drive train without electrical power applied. The application of power to the photoconductor drum clutch is required to mechanically decouple the photoconductor drum from the drive train.

Abstract: A fixing device includes a fusing roller, a backing roller and an adjustable heater for selectively heating the fusing roller and the backing roller. The adjustable heater includes a heating element and a reflector. The reflector can be positioned to direct heat from the heating element upon the fusing roller or the backing roller. The reflector is coupled to the shaft of a solenoid. Positioning of the reflector is controlled by alternately energizing or de-energizing the solenoid. During the time period between the passing of successive units of the media through the fixing device, the reflector is positioned to heat the backing roller. Heating the backing roller melts toner accumulated on its surface. When the next unit of the media passes between the fusing roller and the backing roller, toner accumulated on the surface of the backing roller is moved onto to the media.

Abstract: New interpolation techniques allow improved efficiency and speed in performing color space conversions. A radial interpolation technique accomplishes an interpolation by generating successive sub-cubes. A value of a vertex of the final sub-cube generated is used as the result of the interpolation. Sub-cubes are generated by averaging a selected vertex value with the vertex values of each of the remaining vertices. A pruned radial interpolation technique employs a subset of the vertex values of the initially selected cube to generate the result of the interpolation, thereby improving upon the efficiency of the radial interpolation. A tetrahedral interpolation technique accomplishes an interpolation by generating successive sub-cubes. A value of a vertex of the final sub-cube generated is used as the result of the interpolation. Sub-cubes are generated by applying a mathematical relationship which allows computation of sub-cube vertex values through a series of logical AND, logical OR and averaging operations.

Abstract: A fixing device control system controls multiple heating elements included in the fuser so that the duty cycle of the power applied to the multiple heating elements results in an optimal temperature profile over the length of the fuser. Multiple thermistors are used in a feedback control circuit to regulate the temperature profile of the fuser. A formatter uses print data from a host to generate data defining the size and location of a printing area on the print media. Using the data defining the size and location of the printing area, the formatter generates a command to send to a controller. The controller applies power to the multiple heating elements in order to generate the fuser temperature profile corresponding to the command. In a first embodiment of the fixing device control system, the formatter generates the command by using the data defining the size and location of the printing area to access information stored in a table.

Abstract: A print data processing pipeline for use in a color electrophotographic printer optimizes print quality and minimizes memory usage by separately processing lossy and lossless print data. Lossy print data may include print data for images and lossless print data may include print data for text, line art, and graphics. Partitioning print data into lossy and lossless elements allows application of the print data compression operations optimized for each type of print data. High compression ratios can be achieved on lossy print data by applying visually lossless compression operations designed for the lossy print data. In addition, high compression ratios can be achieved on the lossless print data by applying lossless compression operations designed for the lossless print data. A merge unit combines the lossy and lossless print data streams after decompression to reconstruct the original image using merge data.

Abstract: In a color electrophotographic printing system using a transfer belt, residual toner remains on the surface of the transfer belt after the printing of a page. To prevent print defects from occurring, the residual toner on the surface of the transfer belt must be removed. A transfer belt charge roller driven by a high voltage power supply is used to positively charge the residual toner to permit electrostatic transfer of the residual toner from the surface of the transfer belt to the surface of a photoconductor drum for removal by a cleaning blade. By applying an AC waveform and a positive DC offset, the residual toner is effectively positively charged for electrostatic removal from the transfer belt.

Abstract: A first embodiment of the system to detect the amount of toner includes a first and a second light pipe attached in a substantially parallel orientation from the top to the bottom of a sidewall in the toner reservoir. An infra-red light emitting diode illuminates the first light pipe. A rotatable auger has an attached first arm. A light bridge attached to the first arm is positioned so that during rotation of the auger, the light bridge moves adjacent to the first and the second light pipe as the light bridge moves from the top to the bottom of the toner reservoir. When the light bridge is outside of the toner and adjacent to the first and the second light pipe, light is transmitted between the first and the second light pipe. When the light bridge is inside of the toner, light transmission between the first and the second light pipe is interrupted. A circuit detects light transmitted from the second light pipe using a photodiode.

Abstract: New interpolation techniques allow improved efficiency and speed in performing color space conversions. A radial interpolation technique accomplishes an interpolation by generating successive subcubes. A value of a vertex of the final subcube generated is used as the result of the interpolation. Subcubes are generated by averaging a selected vertex value with the vertex values of each of the remaining vertices. A pruned radial interpolation technique employs a subset of the vertex values of the initially selected cube to generate the result of the interpolation, thereby improving upon the efficiency of the radial interpolation. A tetrahedral interpolation technique accomplishes an interpolation by generating successive subcubes. A value of a vertex of the final subcube generated is used as the result of the interpolation. Subcubes are generated by applying a mathmatical relationship which allows computation of subcube vertex values through a series of logical AND, logical OR and averaging operations.

Abstract: A print data processing pipeline for use in a color electrophotographic printer optimizes print quality and minimizes memory usage by separately processing lossy and lossless print data. Lossy print data may include print data for images and lossless print data may include print data for text, line art, and graphics. Partitioning print data into lossy and lossless components allows application of the print data compression operations optimized for each type of print data. High compression ratios can be achieved on lossy print data by applying visually lossless compression operations designed for the lossy print data. In addition, high compression ratios can be achieved on the lossless print data by applying lossless compression operations designed for the lossless print data. A merge unit combines the lossy and lossless print data streams after decompression to reconstruct the original image.

Abstract: A print data processing pipeline for use in a color electrophotographic printer optimizes print quality and minimizes memory usage by separately processing lossy and lossless print data. Lossy print data may include print data or images and lossless print data may include print data for text, line art, and graphics. Partitioning print data into lossy and lossless components allows application of the print data compression operations optimized for each type of print data. High compression ratios can be achieved on lossy print data by applying visually lossless compression operations designed for the lossy print data. In addition, high compression ratios can be achieved on the lossless print data by applying lossless compression operations designed for the lossless print data. A merge unit combines the lossy and lossless print data streams after decompression to reconstruct the original image.

Abstract: The development of the edges of discharged areas on a photoconductor drum in an electrophotographic printing system is controlled by the ratio of the DC component of the developer bias to the magnitude of the difference between the DC component of the developer bias and the DC component of the bias supplied to the photoconductor charge roller. A development system using a developer, a photoconductor charge roller, a high voltage power supply, an optical density sensor, and a controller for controlling the high voltage power supply optimizes the electrophotographic edge development. The optical density sensor is used in a calibration process to determine the value of the DC component of the developer bias necessary to ensure the optical density of developed areas will meet the minimum specified optical density.

Abstract: An apparatus for dispensing toner in an electrophotographic printing system includes a housing for containing a supply of toner and toner filled containers for replenishing the supply of toner. Toner is allowed to flow to a developer assembly in the electrophotographic printing system by removal of a housing toner seal. The bottom of the container is dimensioned so that it can be inserted through the opening in the top of the housing and the opening in the top of another substantially identical container. A toner dam seal is attached to the container to close the bottom opening. In the preferred embodiment, the toner dam seal includes a length of flexible material for use in removal of the toner dam seal. In an alternative embodiment, cutting blades are attached to the interior of the sidewalls of both the housing and the container for cutting the toner dam seal upon installation of the container into the housing or into a previously installed container.

Abstract: An apparatus for generating parity blocks in a RAID system includes a PRAM control unit, two parity memories each coupled to the PRAM control unit, and in several alternative embodiments, a valid contents memory for tracking the contents of the parity memories. Parity blocks are generated by performing an exclusive OR operation between all of the corresponding data words in the data blocks of the stripe. Results of the exclusive OR operations are alternately stored in the two parity memories. Alternately dedicating one parity memory for storing the results of the exclusive OR operation which will be performed and one parity memory from which the results of the previous exclusive OR operation are loaded allows computation of the parity block to be performed at a higher rate than configurations which use a single parity memory. In a first embodiment of the PRAM control unit, a flip/flop tracks which of the two parity memories contains the valid contents.

Abstract: The first embodiment of an electrophotographic component cleaning apparatus includes a sheet of cleaning media, formed from a material such as felt, cloth or abrasive impregnated plastic fibers. Attached to the cleaning media is a retaining device. Preferably, the retaining device includes a plastic tab bonded to the sheet of cleaning media. Attached to the plastic tab is a plastic strap with an adhesive located on the free end. For use, the cleaning media is inserted into the print media path of the printer with the plastic strap looped around any conveniently protruding feature inside the printer. The rotation of the drum against the cleaning media results in the removal of contaminants. A second embodiment of an electrophotographic component cleaning apparatus includes an oversized cleaning roller which is installed into the printer in place of the transfer roller. A reservoir pivotally attached to the shaft of the cleaning roller contains cleaning fluid which is absorbed into the cleaning roller.

Abstract: A charge roller displacement mechanism prevents the build up of a sharply defined circumferential ring of contaminants on the surface of a charge roller in an electrophotographic printing system, thereby reducing the severity of the print defect caused by the contaminants. By cyclically laterally displacing the charge roller parallel to the longitudinal axis of a photoconductor drum as the photoconductor drum rotates, contaminants which reach the surface of the charge roller will not form a sharply defined circumferential ring that interferes with the uniform charging of a photoconductor drum charged by the charge roller. The charge roller displacement mechanism includes a first gear that engages the gear used to rotate paddles in a waste hopper of an electrophotographic printer cartridge. A second gear engages the first gear to provide a reduction of approximately 400 to 1.

Abstract: A print data processing pipeline for use in a color electrophotographic printer optimizes print quality and minimizes memory usage by separately processing lossy and lossless print data. Lossy print data may include print data for images and lossless print data may include print data for text, line art, and graphics. Partitioning print data into lossy and lossless components allows application of the print data compression operations optimized for each type of print data. High compression ratios can be achieved on lossy print data by applying visually lossless compression operations designed for the lossy print data. In addition, high compression ratios can be achieved on the lossless print data by applying lossless compression operations designed for the lossless print data. A merge unit combines the lossy and lossless print data streams after decompression to reconstruct the original image.

Abstract: A toner depletion detection system in an electrophotographic printer uses an optical density sensor to detect the depletion of toner. The optical density sensor is used by the electrophotographic printer to maintain the developed optical density at an optimum value by adjusting a DC offset voltage supplied to a developer to compensate for changes in the developed optical density. Additionally, the optical density sensor is used in a calibration which linearizes the relationship between the optical density of a developed halftone pattern and increments of the laser pulse width. In a first embodiment of the toner depletion detection system, the magnitude of the DC offset voltage supplied to the developer to compensate for changes in the developed optical density is monitored. When the magnitude of this DC offset voltage exceeds an empirically determined threshold value, the toner depletion condition is indicated.

Abstract: A current steering circuit accomplishes high speed switching of drive current through a vertical cavity surface emitting laser (VCSEL) diode. The preferred embodiment of the current steering circuit includes a first and second schottky diode, connected anode to anode, as the circuit elements used to steer the current that flows into the common connection point of the schottky diodes. The cathode of the first schottky diode is connected to the anode of the VCSEL diode. The cathode of the second schottky diode is connected to one side of a network formed from three resistors. The other side of the network is connected to the output of a CMOS invertor used to buffer the video signal which controls the steering of the current. With the output of the CMOS invertor at a high level, the second schottky diode is in the off state and the first schottky diode is in the on state, forcing drive current to flow through the VCSEL diode.

Abstract: An apparatus for generating interpolator input data for a color space conversion from a RGB color space to a CMYK color space includes an address generator having eight outputs and a memory having eight inputs each connected to one of the address generator outputs. The inputs to the address generator are the three sets of four higher order bits, RH, GH, and BH, of the twenty four bit RGB color space value and two bits for selecting one of the dimensions in the CMYK space to which the conversion will be directed. From these inputs, the address generator can generate 19,652 addresses for accessing interpolator input data stored in the memory. The address generator simultaneously generates eight addresses for accessing interpolator input data stored in the memory.

Abstract: A method and apparatus for implementing a zero order hold function in the digital to analog conversion process in a digital control system reduces the phase lag contributed by the digital to analog conversion process relative to a conventional implementation of the zero order hold function. The apparatus for implementing the reduced phase lag zero order hold function employs a digital signal processor, a plurality of digital buffers, a digital multiplexing element, and a digital to analog converter. Phase lag is reduced by generating, from the digital to analog converter, for a fraction of the sample period, a waveform having a constant analog voltage with an amplitude which is scaled by the reciprocal of said fraction relative to a conventional zero order hold function. During the remainder of the sample period a substantially constant offset analog voltage is generated by the digital to analog converter.