This invention is directed to an apparatus and method for photography and more particularly to an apparatus and method for providing stereographic photographs.
Stereoscopy has been found useful and successfully applied in a wide variety of scientific and technical areas as well as in commercial, professional and amateur photography. While ordinary photographs may be pleasing the stereophotograph makes the scene come to "life."
Stereoscopy is the visual perception of the three-dimensional space surrounding us by the reproduction of images giving the impression of spatial extent and solidity of the objects portrayed. In the human physiological and psychological sense the mind combines the images viewed from both eyes forming the perception of a three-dimensional scene. Artificially the means of reproducing stereoscopic images should desirably be accomplished without the use of particular or individual optical devices, e.g., an anaglyphic viewer. Furthermore the viewing of artificially produced stereoscopic images should produce integral spatial images, i.e., not only should the images be viewed stereoscopically, but they should be seen from all possible viewpoints so as to present different spatial aspects. The optical spatial image may be artificially created in the mind of the observer without any objectively real construction of a three-dimensional image. For example, if each eye views a flat picture photographed from the right and left eye viewpoints then in the observer's mind the two images will combine to create the spatial image. The stereoscopic image created from the flat photograph can be enhanced considerably as well as directly influenced by such factors as color; contrast; apparent sense of depth perception; the type, source and direction of illumination; shading; brightness of the object; definition within the photograph, e.g., sharp or ill-defined edges or borders; object shape; viewing angle; variations in human vision and the observer's familiarity with the objects being viewed.
One technique for reproducing spatial images is the use of lenticular or fine raster screens. The images are integrated by the screen by optically combining the elementary image planes received by the raster system. Each lens component of the screen is the objective lens for a small element of the image, the integration or composite of all such lenses when viewed with both eyes produces a spatial image effect. The small element of the image is provided by a corresponding screen which permits only the printing of that element on the sensitive film. The sensitive film itself may have individual lens components.
A photographic stereogram may be prepared by several methods: (1) a photograph taken with a conventional camera having a single objective and moving it or the object to successive viewpoints; or (2) a photograph taken with a camera having a single objective and an optical stereo attachment which enables two photographs of an object to be taken simultaneously from two viewpoints or (3) a photograph of an object with a camera having two objectives whose separation is equal to the normal stereoscopic base of approximately 65 mm. A combination of any of the foregoing methods may also be used. Each of the photographs is photographically broken up into a series of narrow strips representing alternatively the picture of the left and right stereogram.
In each of the above techniques the stereoscopic effect is directly related to the accuracy of superimposition of a plurality of images or the optical integration of a plurality of portions of an image. It is therefore seen that the registration of the images for purposes of viewing or printing is of considerably importance.
Furthermore in each of the above methods the single or multiple camera objectives are directed to an aim point. The aim point is the point of convergence of the lenses in a multi-objective lens camera or the center of arc of a single lens camera which rotates around the subject or the center of rotation of the subject which rotates during the camera exposure. The aim point is a vertical line within the image that will be at the rear surface of the lenticular screen when the finished picture is viewed. The aim point is therefore established and fixed before or when the photosensitive material is exposed. After exposure the aim point cannot be changed or adjusted.