Patent ID: 6188193
Filing Date: 2001-02-13
Classification: G03B

Abstract:
A light valve for varying the size of an opening through which a light beam passes comprising:a pair of spaced apart rotatable shafts,a corresponding vane mounted on each shaft so the vanes extend side by side into the space between the shafts,in which light is directed toward the vanes so that rotation of the shafts causes the vanes to move through an angle toward or away from each other for varying the size of the light beam passing between the vanes,a separate servo motor coupled to each shaft for rotating the shafts in unison to adjust the amount of light passing between the vanes, and for each servo motor a closed loop servo system responsive to a vane position input signal representing a desired position of each vane for varying the size of the light beam passing between the vanes, in which a separate position feedback signal is generated as a function of the actual position of the vane on each rotatable shaft throughout operation of the light valve, and a controller responsive to the vane position input signal and to each position feedback signal for producing separate motor control signals for independently controlling operation of each servo motor to rotate each shaft and vane to constantly pass a selected amount of light between the vanes, in which: (1) the vanes are aligned on a common plane, (2) the vanes both rotate about parallel axes in the same rotational direction away from opposite sides of the plane to enlarge the light opening between the vanes, (3) the vanes both rotate in the same rotational direction toward the plane to reduce the light opening between the vanes, and (4) the relative lengths of the vanes are such that they produce a slight overlap along their confronting outer edges when rotating to the closed position on the common plane, to prevent jamming of the vanes as they move to the closed position.