Abstract: A single pass ROS system provides a plurality of latent images which may subsequently be developed in different colors. A method and apparatus is provided for aligning ROS units in a single pass printing system, so that each ROS unit is aligned along the process or X-axis. After this alignment, the images formed by each ROS unit will be in proper registration within the prescribed tolerances. A signal in a closed feedback loop regulates the angular velocity and phase of the rotating polygon mirror of the first ROS unit. The same signal is also the reference signal to the feedback loops of the other rotating polygon mirrors of the other ROS units to synchronize all of the rotating polygon mirrors. The position of the scan lines formed by their respective ROS units are fixed relative to one another and thus, lacking any other error sources, are registered in the process direction.

Abstract: An apparatus enhances the image in a high addressability printer by generating phase signals from a pulse width modulator and a programmable delay or buffer which are XORed with adjacent phase signals and combined with a corresponding data signal to form SET and RESET signals. The SET and RESET signals are used to form a phase and width modulated serial data signal.

Abstract: The present invention is a method and apparatus for logic based resolution conversion and enhancement of digital images. The invention employs a selectively controllable architecture wherein a plurality of input resolutions can be converted to a common output resolution. The system has particular use in highlight color systems, wherein the highlight color data may be processed separately for each color plane, using the present invention, and then recombined to produce enhanced highlight color output. Moreover, the hardware preferably employs an interlocked area mapping technique to produce the resolution converted bit planes of digital image data.

Abstract: The present invention is a method and apparatus for logic based resolution conversion of digital images. The invention employs an interlocked area mapping technique to provide one or more resolution converted bit planes of digital image data. The system has particular use in highlight color systems, wherein the highlight color data may be processed separately for each color plane, using the present invention, and then recombined to produce enhanced highlight color output.

Abstract: A remote split scan detector is disclosed which utilizes two rectangular cross section light pipes to transfer the light beam from a raster output scanner (ROS) housing onto two light sensors outside of the housing. Each one of the light pipes is designed to receive a light beam at its input end and transfer the light beam to an output end where the light beam exits the light pipe through a diffused portion of a side wall. Two sensors are placed in such a manner that each faces one diffused surface to receive the light beam exiting the diffused surface.

Abstract: A look ahead circuit for enabling the calibration of a ROS laser to be calibrated during the active part of the scan. A register takes a number of pixels from the stream of video and compares them to a plurality of possible matching pixel patterns. If a match is found, the pixel pattern is applied to a table look up to produce a digital representation of the laser power that should be produced as a result of these pixels, and this representation is converted in a digital to analog converter to an analog voltage which corresponds to the laser power that the laser should be putting out when generating this set of pixels. During the time when these pixels are being printed, a detector measures the laser power and that is compared to the analog voltage to produce a difference. At the same time, a capture circuit, as the result of finding the match, turns on a sample and hold circuit which couples out the difference as the error output, which is used to correct the laser output.

Abstract: A circuit for reducing the amount of instability in a pulse width modualtion circuit by providing a minimum amount of overdrive after the crossover point between a ramp and a voltage threshold level, and a constant amount of discharge time between the end on one ramp and the beginning of the next. Also, a feedback loop is privided to increase or decrease the slope to compensate for a decreasing or increasing amount of time between clock pulses, to maintain the duty cycle of the output when the clock frequency varies.

Abstract: A circuit for seamlessly printing data from a remote source that is arriving at a clock rate that is equal to the clock rate of the local data, but that has a different clock phase, due to the longer path used by the remote data. The circuit generates a number of local clock phases, compares these phases to the phase of the remote clock, and uses for both local and remote data the clock whose phase is nearest that of the remote clock.

Abstract: 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.

Abstract: 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.

Abstract: A circuit for producing an exact duty cycle for a system having a variable system clock frequency. In the calibrate phase, a waveshape with an exact duty cycle is made by ANDing two or more clock pulse trains, each of which is a multiple of the system clock frequency. This is compared against the output of a current-controlled pulse width modulator which is programmed to produce the same duty cycle. The polarity of the comparator output as a result of the error between the exact duty cycle and the one produced by the modulator increments or decrements a counter, the output of which controls a DAC, which in turn corrects the output of the modulator. After a suitable number of interations, the modulator, which is now calibrated, will reproduce the exact duty cycle. The circuit is then put into the operate mode by disabling the counter, and programming the pulse width modulator to output the desired system duty cycle.