Computervision Corporation

David Friedman

Gilbert G Fryklund

Kenneth Levy

Barry N Mansell

Gerd Schliemann

Alan J Fleming

Philip Mandel

Vance Parker

David Corbin

A method and apparatus for improving the display of objects on an interlaced raster-scan television are disclosed. The invention takes each data point that will appear as a pixel on the screen and makes it appear also at pixel locations displaced by one unit in each of two axes, individually or collectively if desired. The direction of displacement is uniform for any given picture. The additional appearance is not stored as part of the picture data, but instead is generated 'on the fly' as part of reading the data and preparing it for presentation on the television screen.

Method and apparatus for displaying objects on an interlaced raster scan

A method and apparatus for controlling a stepper motor involves the generation of command currents which drive the stepper motor and provided critical damping of the natural resonance of the stepper motor. Digital error signals are developed by selectively combining a position signal and a digital velocity signal which is derived from a feedback signal proportional to velocity. In one embodiment, the digital error signals are converted into command currents for driving the stepper motor in such a manner as to achieve damping of the motor's natural resonance. In an anternative embodiment, the digital error signals and feed forward acceleration signals and/or feed forward velocity signals are converted into command currents for driving the stepper motor so as to achieve damping of the motor's natural resonance, as well as correction for positional errors induced by either velocity or acceleration.

Method and apparatus for controlling stepper motors

A method and apparatus for damping stepper motors are disclosed. A tachometer feedback is used to modulate the phase angle of the stepper motor command currents to achieve damping.

Method and apparatus for damping stepper motors

An automatic wafer loading and pre-alignment system for integrated circuit wafer-mask Aligners. A belt feed track system is employed to transport wafers from a 'send' wafer storage carrier to a wafer pre-alignment station. The wafer is machanically pre-aligned with respect to the wafer chuck of the Aligner by means of a roller arm and flat-finder system. After completion of the pre-alignment process, the Aligner turntable is rotated to carry the pre-aligned wafer and chuck to the home position of the turntable and at the same time position another chuck at the pre-alignment station. If the new chuck at the pre-alignment station contains a wafer, the wafer is transported from the chuck to a 'receive' wafer storage carrier by means of a belt return track system. The feed and return wafer belt track systems have a common portion between the pre-alignment station and the respective 'send' and 'receive' wafer storage carriers. Photosensors are used to detect the presence or absence of wafers at critical locations in the loading system and at the pre-alignment station.

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Bedford, MA, United States of America

David Friedman