Abstract: Safety mechanisms for use in recording holographic images of human subjects are disclosed for preventing a human subject from exposure to the reference beam and the object beam. The safety mechanisms comprise an array of light generating elements, and associated light sensing elements such as photocells arranged along the periphery of the reference beam path. When a subject blocks the reference beam path, the subject will also block sensing light from reaching a photocell, which will prevent the reference beam from traversing its normal path, preferably by disabling the energization circuit of the laser. Another embodiment of a safety mechanism comprises a protective housing which encloses the reference beam path. A safety mechanism is also disclosed for disabling the laser in response to the absence of ground glass screen diffuser in the path of the object beam.

Abstract: A method for recording and reconstructing a hologram recorded with two pulse laser beams having different wavelengths in order to increase the illuminance of the reconstructed image recorded in one of said channels is disclosed. The method comprises the steps of generating a first reconstruction beam at a wavelength shifted from the wavelength of the recording beam having the lesser illuminance if the two recording beams had equal irradiance toward a direction of the other recording beam. The wavelength of the second reconstruction beam has a value shifted from its associated recording beam by an amount equal the value that said first reconstruction beam is shifted from its associated recording beam. The resultant reconstructed images from the two reconstruction beams are generally equal in size and are in co-registration. The amount of shift is chosen so that the reconstruction wavelengths have substantially equal illuminance for an equal amount of irradiation.

Abstract: An apparatus and method for making holographic copies of film holograms via a contact copying process is disclosed. The apparatus comprises a tray having a clear flat bottom which receives the hologram master film, the blank film and a cover sheet. A pressure roller is provided to move across the cover sheet, to establish good optical contact between the films, in unison with and in alignment with a slit defining curtain being moved across the underside of the tray. A hologram reconstruction beam is beneath and aimed at the curtain so that light passes through the slit and duplicates onto the blank film only that part of the master hologram and film hologram subject to pressure from the pressure roller.

Abstract: A metal gasket for making a fluid tight sealed joint between opposed parallel surfaces has a radially inward part and a radially outward part each formed with a peripheral groove; also at least one of the end faces of the gasket is formed with annular grooves of substantially rectangular profile in radial planes. Thereby there is provided a compressible yet resilient gasket which can satsifactorily be used to form a fluid tight joint.