Stereoscopic Motion-Picture Projection Equipment

equipment designed to project on a screen the combined right and left images of frames constituting a stereopair and to enable the viewer to see these images separately with the right and left eye.

Two synchronously operated projectors are required if the stereoscopic images are projected from two separate films. Projectors for single films containing both images of a stereopair have two lenses and an optical attachment that projects on the screen the combined images of stereopairs. In anaglyphic and polarized methods of stereoscopic projection, viewers use special eyeglasses to separate the images, and the projection lenses are equipped with correspondingly colored or polarized filters. Methods of stereoscopic projection that do not require the use of eyeglasses use a slit- or lens-type raster screen as an optical device to create zones in the auditorium where the right and left images can be viewed exclusively by the right and left eyes. Such methods require that the projectors be carefully positioned with respect to the screen.

Figure 1 shows the arrangement of equipment for a stereoscopic projection method that does not require the use of eyeglasses proposed by the Soviet inventor S. P. Ivanov in 1935. The center of the exit pupil of the lens projecting the right image of a stereopair is located at the point D₀, and the exit pupil of the lens projecting the left image is centered at the point G₀. The raster has radial slits that converge toward the point O. The raster divides the right image on the screen located behind it into the radial

Figure 1. Diagram of the arrangement of equipment for stereoscopic motion-picture projection using the method of S. P. Ivanov: (1) reflecting screen, (2) perspective raster, (a, b, . . .) radial slits converging toward the point 0, (D₀) and (G₀) centers of the lenses producing the right and left images, respectively, (OD₁) and (OG₁) axes of the zones of selective vision of combined images of a stereopair (I = 1, 2,...)

strips k, I, . . ., which also converge toward O. The left image, in turn, is also separated into radial strips, which are located in the spaces between the strips k, l, . . . . The right image is thus visible from all points on the lines OD₀, OD₁ OD₂ and the left image can be seen from all points of the lines OG₀, OG₁ OG₂ . . . . These lines, called lines of selective vision, form a plane of selective vision. The zones of vision for the right and left images extend adjacent to each of the lines OD_i and OG_i. In these zones, illumination decreases linearly from a maximum to zero as the distance from the axis of the zone increases.