Robert A Fredrickson

US Patent:

43674658, Jan 4, 1983

Filed:

Apr 4, 1980

Appl. No.:

6/137103

Inventors:

Nicholas P. Mati - Loveland CO
Frederick J. Porter - Loveland CO
Robert W. Fredrickson - Fort Collins CO

Assignee:

Hewlett-Packard Company - Palo Alto CA

International Classification:

G09G 116

US Classification:

340707

Abstract:

A graphics system for a raster scan CRT implements a light pen tracked by a cursor. Hits corresponding to the cursor are distinguished from those corresponding to background data by a selective interlacing technique. A threshold level shifting technique providing accurate measurement of a horizontal component of the cursor allows accurate prediction of the location of the center of the field of view during the next frame.