Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1980-11-13
1982-10-12
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
340710, G01J 120
Patent
active
043541020
ABSTRACT:
Graphic data entry in an interactive graphic display system is achieved by means of an apparatus that provides automatic centering of a pointing laser beam on a hand held cursor. The graphic display system provides a means for displaying and comparing through superposition full size overlaid graphical data and projected graphical data on a common display screen. It includes a steerable pointing laser the beam of which scans the display screen in response to a laser beam deflection circuit. The system also includes laser beam position sensing and indicating circuits which accurately measure the laser beam position. Centering of the laser beam on the cursor at the display screen is accomplished by dithering the beam uniformly about its average position in a discrete dither pattern and utilizing the dither pattern to determine misalignment of the beam's average position with respect to the center of the cursor. The cursor includes photo detector elements that are geometrically configured to conform to the dither pattern so that signals derived from an eccentric relationship of the beam dither pattern and the photo detector element configuration can be processed to provide beam misalignment direction and magnitude error signals. These error signals drive a servo system that centers the average beam position on the cursor. The function of the cursor is to manually or automatically measure the coordinator of graphical features on the display screen.
REFERENCES:
patent: 3997891 (1976-12-01), Iwamura et al.
patent: 4152586 (1979-05-01), Elliott et al.
patent: 4318096 (1982-03-01), Thornburg et al.
Bell Irving J.
Burns Richard H.
Crabtree Kenneth
Smith Michael R.
Matthews, Jr. Willard R.
Nelms David C.
Singer Donald J.
The United States of America as represented by the Secretary of
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