Vacuum film holder for holograms

Claim 1

In a film holder for making holograms, a pair of open-ended concentric cylinders having a vacuum chamber formed between the walls thereof, means providing a plurality of passages through the walls of the inner one of said concentric cylinders, said passages being of a size commensurate with the thickness and stiffness of the film used aNd being arranged in a regular pattern, whereby a sheet of film inside said inner cylinder in a covering relationship to said passages is held immovably when a vacuum is formed in said chamber, said pair of concentric cylinders comprising an outer cylinder and an inner cylinder, said outer cylinder having an exterior fitting forming a vacuum passage from said vacuum chamber to the exterior of said outer cylinder and adapted to be connected to a vacuum source for developing a vacuum in said chamber, sealing means at each end of said cylinders for forming said vacuum chamber, an outer flange formed on one end of said outer cylinder, an inner flange formed on the opposite end of said outer cylinder, an outer flange on one end of said inner cylinder, a plurality of bolts for bolting said outer flanges together with sealing means compressed therebetween and with sealing means compressed between said inner flange and the unflanged end of said inner cylinder to seal said vacuum chamber and to accurately align said inner cylinder within said outer cylinder so that said vacuum chamber is of uniform dimensions to apply a uniform vacuum to each of said plurality of passages to thereby enable the ready removal of said inner cylinder from said outer cylinder to facilitate inspection and cleaning and to insure the application of a uniform vacuum to all areas of said film, said cylinders being of a non-reflective black finish to minimize reflections during the making of holograms, and including a transparent cylinder having interior dimensions similar to said inner cylinder for holding holograms for readout.