Abstract: In a feedback color control system for controlling the flows of two colorants used to color an article, a first error signal is generated as a function of deviations in the color saturation of the article from a desired saturation, and a second error signal is generated as a function of deviations in the hue of the article from a desired hue. The flows of the dyes are varied in the same sense in response to the first error signal and are varied in opposite senses in response to the second error signal.

Abstract: An optical shoe assembly for use with an optical head in an on-line system for continuously monitoring the color, opacity and brightness of a moving web of paper, or the like, in which the shoe frame supports a length of the web over a housing opening, the edge of which is normally in a sealing relationship with the edge of a first side of a block rotatably supported in the housing.This first block side is formed with an optically black recess covered by a quartz shoe carrying a transversely extending white background over a portion thereof to provide spaced white and black backgrounds in the normal operating condition of the shoe assembly. Respective second and third sides of the block carry a white standard, such, for example, as a mirror, and a black standard which standards may selectively be positioned in the housing opening by a motor which drives the block mounting shaft.

Abstract: An on-line system for continuously monitoring the color, opacity and brightness of a moving web of paper or the like in which an optical shoe providing black and white backgrounds spaced in the direction of movement of the web supports a portion of the web below and generally in registry with an optical head made up of a light integrating sphere for directing light from a source onto the web over the shoe and a plurality of elongated sensing units mounted in the upper portion of the sphere and including a centrally located brightness measuring unit oriented generally perpendicularly to the web toward a point over the black background, four circumferentially spaced color tristimulus sensing units, each of which is oriented at an angle to the axis of the central unit so as to be directed at the same point as is that unit and a sixth opacity sensing unit angularly oriented with respect to the axis of the central unit so as to be directed toward a point over the white background spaced downstream of the first poi