Abstract: Method and apparatus for increasing the visibility of low contrast images. In accordance with the invention, the visibility of a selected area of an image is increased relative to another area of said image which differs only slightly in brightness from said selected area by causing said selected area to periodically vary in brightness while maintaining the brightness of said other area constant.The apparatus for carrying out the invention comprises an optical circuit including an electro-optic photosensitive storage device having a photosensitive characteristic in which the conductance of the device varies as a function of the intensity of the radiation incident upon it, and an electro-optic birefringent characteristic in which the birefringence varies as a function of an electric field applied across it. An image of an object is read into the device which is then read-out onto a screen by placing the device between two polarizers in a readout light beam.

Abstract: A method and apparatus for inspecting the contour of an article is disclosed. Nondestructive viewing techniques including the projection of a light pattern onto the article to be inspected and the imaging of said light pattern to a display screen are discussed. The concepts taught enable the viewing of article regions which were formerly obstructed in conventional viewing systems.

Abstract: To obtain a photographic record of an object surface having superimposed interference fringes arrayed as a function of the deformation which results in the object from an applied stress, which may be mechanical, thermal, or the like, the object is first illuminated with coherent light. The illuminated surface is then photographed with a camera having an optical wedge disposed over half of its lens to record two slightly displaced overlapping images of the object on the camera film. The object is then stressed by changing the ambient temperature or pressure or other mechanical loading, and the undeveloped film is exposed to a second set of overlapping images. The developed photograph contains a set of equal amplitude fringes representing the interference pattern between the two fringe sets generated by the two exposures and arrayed as a function of the strain in the object as a result of the stress.

Abstract: The spatial locations of points defining a specular surface are determined by disposing the specular surface in the field of view of a lens and by using the specular surface to view by reflection an irradiated reference surface disposed successively in different positions. Reference surface indicia viewed in common line of sight relation to each specular surface point in such different positions of the reference surface are identified. Radiant energy reflected by a specular surface point through the lens node and the location of the lens node defines a further line in space. The intersection of this further line and such line of sight defines the spatial location of such specular surface point. Photographic records made with the reference surface in such different positions contain representations of reflected radiant energy for all specular surface points in the field of view of the lens and in line of sight relation to the reference surface.

Abstract: An optical system having a single spherical mirror for collecting light from two directions combined by a beam splitter after the light has been scattered from the surface of a turbine blade or the like. The spherical mirror is located at an equal optical distance from both the surface of the test specimen and a linear detector array so that it operates at a one-to-one magnification ratio. The linear detector array receives light focused by the mirror along a path folded by the beam splitter. This arrangement is helpful in contouring the surface of a turbine blade near a vertical obstruction such as a shroud of a turbine blade since the collection axes of the pickup legs view the incident spot from different directions. None of the optical elements of the inspection system are located in the plane of movement of the test specimen so that even particularly long items such as a helicopter rotor blade can be contoured.