Girmay Keleta Girmay

US Patent:

61219924, Sep 19, 2000

Filed:

Oct 19, 1998

Appl. No.:

9/175209

Inventors:

Girmay K. Girmay - La Mirada CA

Assignee:

Xerox Corporation - Stamford CT

International Classification:

B41J 247

US Classification:

347234

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. A proportional integral derivative controller, the motor polygon assembly and a speed detector form the synchronization system for each ROS unit.

US Patent:

59206837, Jul 6, 1999

Filed:

Jun 27, 1997

Appl. No.:

8/883946

Inventors:

Girmay K. Girmay - La Mirada CA

Assignee:

Xerox Corporation - Stamford CT

International Classification:

H03K 908

US Classification:

395109

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.

US Patent:

51305658, Jul 14, 1992

Filed:

Sep 6, 1991

Appl. No.:

7/756241

Inventors:

Girmay K. Girmay - Inglewood CA

Assignee:

Xerox Corporation - Stamford CT

International Classification:

H03K 504

US Classification:

307265

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.

US Patent:

53772334, Dec 27, 1994

Filed:

Aug 19, 1993

Appl. No.:

8/108275

Inventors:

Girmay K. Girmay - Inglewood CA
Peter K. Wu - La Palma CA
Harmik Sarian - Tarzana CA

Assignee:

Xerox Corporation - Stamford CT

International Classification:

H03D 302

US Classification:

375119

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.

US Patent:

53793218, Jan 3, 1995

Filed:

Feb 1, 1993

Appl. No.:

7/966912

Inventors:

Girmay K. Girmay - Mirada CA

Assignee:

Xerox Corporation - Stamford CT

International Classification:

H03K 908

US Classification:

375 22

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.

US Patent:

54733600, Dec 5, 1995

Filed:

Dec 27, 1993

Appl. No.:

8/173014

Inventors:

Girmay K. Girmay - La Mirada CA

Assignee:

Xerox Corporation - Stamford CT

International Classification:

B41J 247

US Classification:

347247

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.

US Patent:

56195990, Apr 8, 1997

Filed:

May 12, 1995

Appl. No.:

8/439841

Inventors:

James M. Wilson - Glendora CA
Girmay K. Girmay - La Mirada CA

Assignee:

Xerox Corporation - Stamford CT

International Classification:

G02B 600

US Classification:

385 12

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.