True three-dimensional imaging in photography, cinematography and videography is achieved by recording separate left and right eye images of a scene with the viewpoints of the said left and right images separated along the horizontal plane in the manner of human eyes. There are a number of methods and apparatus for acquisition and projection of a stereoscopic pair of images including my own U.S. Pat. No. 6,721,500 B2 (Perisic) and U.S. Pat. No. 4,678,298 (Perisic)
The stereoscopic pair of images can be viewed by projecting them through a pair of polarizing filters onto a front projection screen, such screen being coated with a metallic surface capable of maintaining polarization. The two polarizing filters are set with their polarizing axis at 90 degrees to each other so that when the projected images are viewed through glasses with corresponding polarization, the left eye sees only the image acquired from the left viewpoint and the right eye sees only the images acquired from the right viewpoint. The resultant effect has genuine depth within the scene which extends forward from the screen towards the viewer as well as beyond the projection screen, which is perceived as a window. Objects within the scene can appear to float in space between the viewer and the screen. The extent of the three dimensional depth can be controlled by varying the convergence angle between the axis of the two images and is best done during acquisition although it can also be done in projection to a limited degree.
When a pair of identical two-dimensional images are projected in place of a true stereo pair, in the same manner as described above, the resultant effect is an increased perception of depth within the scene, commonly referred to as pseudo 3D. The depth in pseudo 3D extends only beyond the screen; objects within the image cannot be made to appear forward of the projection screen.
The extent of the apparent depth in pseudo 3D can be controlled by varying the amount of overlap of the left and right images in the horizontal plane. This is accomplished by altering the angle of convergence between the projection axis of the two images. The angle of view and subject matter of the original two dimensional image are some of the factors contributing to the effectiveness of a pseudo three-dimensional scene. Consequently different scenes may require different convergence settings in order to achieve the optimum result.
The simplest way to achieve a pseudo 3D effect is to use two projectors and two identical copies of the image. A more sophisticated approach is to make a duplicate copy, with appropriate sideways shift built in, so that the two images can be projected as a pseudo three-dimensional pair by means of existing digital stereoscopic projection systems such as Real D.
It would therefore be advantageous to provide an apparatus for creating a pair of pseudo three-dimensional images from a single two-dimensional image or series of images during projection with a single projector.