The present invention relates to color-separating prism systems for video cameras, and is, in part, an improvement of the prism system set forth in the copending application of Arthur Cox and Rudolf Hartmann, Ser. No. 06/005,187 filed on even date herewith and assigned to the assignee of the present invention, now abandoned.
The Cox and Hartmann application discloses a very small color-separating prism system uniquely adapted for use with very small solid-state detector devices, such as charge injection devices (CID's), in portable video color cameras suitable for private home use, preferably in conjunction with a video tape recording system.
Conventional color-separating prism systems for video cameras consist of prism components which have dichroic coatings applied directly to the prism faces. This requires careful handling of the components during the coating process to prevent damage from chipping, and also requires custom-made, expensive tooling for the handling of the prism during the coating thereof. Also, since the surfaces to be coated must be laid into holders, some margins of the surfaces will not receive coating. If coatings turn out to be unacceptable, the prisms must be stripped and recoated, a procedure which is quite expensive and subjects the prisms to additional danger of damage.
Additionally, it is imperative in video color cameras that the individual color detectors be very accurately positioned with respect to the associated prism output faces. More particularly, each detector must be carefully positioned without tilt with respect to a certain optical axis of the optical system, must be carefully positioned in directions parallel to and perpendicular to that axis, and the three detectors must be positioned without rotation relative to each other. This positioning is particularly critical and delicate in connection with very small solid-state detectors such as charge-injection devices. In conventional video cameras expensive and complicated detector mountings have been necessary to insure maintenance of each detector in its predetermined position.