STEREOSCOPIC PROJECTION

Abstract: The invention provides a pair of photographic trans­ parencies for stereoscopic projection. Each of the transparencies comprises a photographic film 14 on which is formed a non-polarising image 16 representing the same object viewed at slightly different angles and an overlay of polarising film 18. The directions of polarisation 20, 22 of the overlays are substantially angled, preferably at right angles, with respect to each other when the transparencies are arranged for projection. The images are formed on normal photographic film and the transparencies do not require a special projector, but may be projected by a pair of simple projectors. Furth­ ermore, the transparencies of each pair may be projected by either projector and a slide show may include pairs of the stereoscopic transparencies interspersed with single 2-D transparencies which are projected through only one of the projectors.

Description: STEREOSCOPIC PROJECTION This invention relates to photographic transparencies for the projection of stereoscopic images. It is known to provide photographic transparency which comprises a piece of polarising film bearing one image and bonded thereto a further piece of oppositely polarised film bearing a slightly different image. When projected onto a screen and viewed through spectacles or the like having oppositely polarised eye pieces a stereoscopic image can be obtained. A disadvantage of such transparencies is that a special processing step is required in making the transparencies to transfer the images from normal photographic film onto polarising film. It is known to transfer the images using a dye-transfer technique. It is also known to provide stereoscopic images using a pair of non-polarising transparencies and projecting them through separate projectors, each fitted with a polarizing filter. A disadvantage of such a system is that the projectors must be adapted to receive the polarising filters. Furthermore, when giving a slide show, if 2-D transparencies are includedatraigst the pairs of stereoscopic transparencies and projected through one or other of the two projectors, the viewer can see the 2-D image through only one eye unless the spectacles are removed. In accordance with the present invention, there is provided a pair of photographic transparencies for stereoscopic projection, each transparency comprising a photographic film on which is formed a non-polarising image representing the same object viewed at slightly different angles and an overlay of polarising film the polarising prqsty of which is uniform across the film, the directions of polarisation of the overlays being substantially angled, preferably at right angles, with respect to each other when the transparencies are arranged for projection. The projected image is viewed through a pair of spectacles or the like having a pair of polarising eye pieces with the directions of polarisation at right angles to each other and corresponding to the directions of polarisation of the polarising film of the transparencies. The transparencies according to the invention have the following advantages: the images are formed in a standard manner on normal photographic film rather than by using special processing techniques to form the images on a special film; the transparencies do not require a special projector, but may be projected by a pair of simple projectors; the transparencies of each pair may be projected by either projector; and a slide show may include pairs of transparencies according to the invention interspersed with single 2-D transparencies which are projected through one of the projectors without the need for viewer to remove his or her stereoscopic spectacles. A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing which is an exploded view of one of a pair of transparencies according to the invention. Referring to the drawing one transparency 10 of a pair comprises a mount 12 on which are mounted a piece of non-polarising photographic film 14 on which is formed an image 16 of an object and a piece of uniform light polarising film 18. The polarising film may be bonded to the photographic film, for example by an adhesive. The direction of polarisation of the film is diagonally across the film as indicated by the line and arrows 20. The other transparency of the pair is similar to the transparency 10 with two exceptions. Firstly the image is produced by photographing the object at a slightly different angle to that used for the first transparency. Secondly, the direction of polarisation of the polarising film of the other transparency is at right angles to polarisation direction of the first transparency, as indicated by the dotted line and arrows 22 in the drawing. Mounts may be used which have projections to engage in sprocket holes along the edge of the photographic film to ensure that the photographic film is correctly located in the mount.

Claims: CLAIMS 1. A pair of photographic transparencies for stereoscopic projection, characterised in that each transparency (10) comprises a photographic film (14) on which is formed a non-polarising image (16) representing the same object viewed at slightly different angles and an overlay of polarising film (18) the polarising property of which is uniform across the film, the directions of polarisation (20, 22) of the overlays being substantially angled with respect to each other when the transparencies are arranged for projection. 2. A pair of transparencies as claimed in Claim 1, wherein the directions of polarisation are generally at right angles to each other when the transparencies are arranged for projection. 3. A pair of transparencies as claimed in Claim 1 or 2, wherein.each overlay is bonded to the respective transparency. 4. A pair of transparencies as claimed in Claim 1 or 2, wherein each transparency includes a mount for the photographic and polarising films each of which is mounted in the mount.

Inventors: WOODROOFE, DAVID KENNETH
Applicants: KARRAN PRODUCTS LIMITED
Application year: 1984
Main classification: G03B21
IPC codes: G03B21