Richard L Hunter

US Patent:

40036600, Jan 18, 1977

Filed:

Dec 3, 1975

Appl. No.:

5/637391

Inventors:

John S. Christie - McLean VA
Richard S. Hunter - McLean VA
S. Upton Jenkins - Fairfax VA

Assignee:

Hunter Associates Laboratory, Inc. - Fairfax VA

International Classification:

G01J 350

US Classification:

356178

Abstract:

A sensing head assembly for a multi-color printing press on-line densitometer movably mounted on support members that extend across the width of a printed web of paper that has printed thereon, in addition to the printed matter being monitored, a plurality of spaced-apart color bars that extend across the width of the paper at predetermined intervals along its length. During operation, the sensing head assembly is traversed back and forth across the width of the material in a manner such that a sensing head assembly views a selected color bar at different points along the width and length of the printed web of material. At least two high luminance lamps are mounted within the sensing head housing for projecting light through a window onto a specimen plane of the material being printed to thereby define an inspection zone for illuminating a single selected color bar at any point along the width and length of the printed material. A receptor objective lens having a maximum numerical aperture views the area of the printed material passing through the inspection zone and illuminated by the high luminance lamps and projecting an image plane through an aperture plate that is located in a position just below the best focused color bar image. The aperture plate has a respective aperture opening for each discrete elemental color area comprising the color bar and high impedance semiconductor light sensitive photodetector cells are positioned to allow a respective elemental color light passing through the respective aperture openings to impinge on their light sensitive surface.