Abstract: A camera 14 has a shutter 42 that is reciprocally movable by a motor 54 that is in positive engagement with the shutter 42. The motor 54 provides harmonic motion to the shutter 42 between its open and closed positions. A second motor 78 advances the film within the camera body. Both motors are connected to electronic brakes 104,118 to stop the motors when they are deactuated. The shutter has a mirror 50 mounted therein to provide a viewing of the image beam by the lens 36 through an eyepiece 122 when the shutter 42 is closed.

Abstract: A method and apparatus for measuring strains in a test object in any of a plurality of directions. The object is illuminated with coherent light so that light is reflected to a focussing lens and a shearing diffraction grating having lines extending in a plurality of directions. The various diffracted orders interfere at the focal plane of the lens and are recorded on a photographic media. The object is then stressed and a second exposure is made on the same media, resulting in interference between the fringes produced on the two exposures. The media is developed as a transparency and subjected to optical processing to detect strain in any direction.