Ecrm Incorporated

Massachusetts Institute of Technology

Am International Incorporated

Donald E Troxel

William F Schreiber

John L Connolly, Iii

M Joseph Niland

David J Connor

James J Guerrera

Embodiments of the invention provide systems and methods for correcting scan position errors in an imaging system. In one embodiment of the present invention, the method includes determining an image beam velocity error as a function of a position within a scan line of an image, and using the image beam velocity error to determine a plurality of pixel clock frequencies to be respectively applied to a plurality of positions within the scan line.

System and method for correcting scan position errors in an imaging system

A method for transferring data (for example, image data) from disk storage directly to a peripheral device (for example, a pelbox) in which address information identifying disk storage locations where the data is stored is sent to the peripheral device, and a command is sent to the peripheral device to initiate data transfer from disk storage directly to the peripheral device using the address information received by the peripheral device.

Transferring data from disk storage directly to a peripheral device

In digital halftone color printing, low spatial frequency patterning can occur due to the interaction of the overlapping angled halftone screens. The moire patterning can be minimized by automatically constructing digital haltone angled screens from screen tiles which are designed to minimize the low spatial frequency patterning. The screen tile boundaries are generated in response to selected integers which, together with the number of screen dots along a side of the tile in the direction of screen pitch measurement, determine the a limit on the magnitude of screen angle error. Based upon these values, each pixel within the tile boundary is associated with one of the screen dots of the image. Typically, the pixels are added to potential candidate lists from which they can be selected for inclusion within a particular screen dot.

Method and apparatus for generating digital, angled halftone screens

An apparatus and method for synchronizing to a scanning galvanometer system provide for magnification changes on the order of one part in a thousand. The apparatus employs two phase locked loops connected in series with a digital counter divider. The combination of phase locked loop, digital divider, and phase locked loop provide a multiplication factor equal to a*c/b which enables the required precision in magnification step change to be achieved. Critical to operation of the circuitry is the provision for resetting the divider counter when the first phase locked loop is sufficiently synchronized to a ruled grating which is part of the scanning system.

Method and apparatus for synchronizing to a pulse train packet signal

An apparatus is provided for generating a random (mezzotint) screen for producing halftone copies of continuous tone documents. The random screen comprises a matrix of random numbers representing a sequence of digital reference values with respect to which video (scan) signals are compared for producing halftone picture elements (pels). The apparatus comprises a first and a second random number generator, the first being disposed for providing an initial or starting state for the second, in response to applied clock pulses. Using the supplied starting state, the second random number generator produces the random screen reference values in response to applied clock signals. The random screen reference values produced by the apparatus permits minimum halftone dot size (i.e., the size of the dot used in producing halftone images) to be varied, and halftone patterns to be selectively repeated or not repeated.

Random screen generator apparatus for producing halftone images

Processing of digitally-coded pictures to improve perceived quality without increasing transmission channel capacity, featuring dividing the video signal into a low, middle and high frequency signals (16, 26), finely quantizing the low frequency signal (18), adding pseudo-random noise (33) to the middle frequency signal prior to quantizing (28), enhancing (36) and adding pseudo-random noise (48) prior to coarsely quantizing (50) the high frequency signal. The pseudo-random signals are subtracted (37, 52) from the respective signals at the receiver.

Growing community of inventors

Belmont, MA, United States of America

Donald E Troxel