Photography – Plural image recording – Stereoscopic
Reexamination Certificate
2002-02-01
2004-04-13
Mahoney, Christopher (Department: 2851)
Photography
Plural image recording
Stereoscopic
C352S065000, C359S462000
Reexamination Certificate
active
06721500
ABSTRACT:
The present invention relates to apparatus for generating left and right eye images for three-dimensional photography, cinematography and videography and the means of viewing those images to produce a full stereoscopic effect.
Three-dimensional photography is achieved by recording separate left and right eye images. One technique for recording the separate left and right eye images is to use separate lenses and/or optical arrangements for the separate left and right eye images and to alter the optical properties of each image, for example by using different colour filters for the left and right eye images such as blue for one eye and red for the other, and to record the optically different images together on a recording medium so as to provide a single composite image. When viewed with suitable viewing devices, for example blue/red glasses, the composite image provides a three dimensional effect. However, because opposite colour filters are used to cancel out each other so that each eye would see only the appropriate image the resultant stereoscopic image is essentially monochromatic. This is known as the anaglyph method.
A more effective method was developed whereby the two stereoscopic views are recorded as separate images in full colour. The left and right images are projected simultaneously onto a front projection screen coated with a metallic surface. The separation between the two images is accomplished by means on polarizing filters placed in the projection beam of the left and right image with polarizing axis set at 90° to each other and therefore cancelling each other. To ensure that each eye sees only the corresponding image the stereoscopic scene is viewed through glasses with polarizing filters whose polarizing axis are set at 90° to other. The resultant stereoscopic image is in full colour. The stereoscopic images can be recorded by various means from two cameras set side by side to a split lens system designed to record a stereoscopic pair of images side by side or one image above the other. The latter scheme is known as the ‘over-under’ approach.
An alternative technique has also been developed for cinematography whereby the discrete left and right eye images are recorded separately and sequentially on the image recording medium. One way of achieving this is to record the left and right images on alternate sections of the image recording medium, i.e. on alternate frames of photographic film. The images can be viewed either by simultaneously projecting both the left and right eye images through an optical arrangement that superimposes both images onto the screen or by projecting the images sequentially at double the normal frame rate. Crossed polarising filters are placed in the projected beam of the appropriate image. The images are viewed through glasses with polarising filters whose polarisation axes are at 90° to one another corresponding to the polarisation axes of the projected images. However in the case of the “over-under” method, where a single projection lens and additional optical arrangements are used to project both images the projection arrangement has a detrimental effect that the optical distortions introduced by the optical elements required to image the separate left and right images, mainly spherical aberrations, tend to be exaggerated when the two images are superimposed onto each other for viewing. A perfect match between the two images is not possible because both images are part of the same image circle, i.e. the top corners of the upper image really match the bottom corners of the lower image instead of the corresponding corners.
It would therefore be advantageous to provide apparatus for recording and viewing three-dimensional images that has the advantages of the present known systems, but that mitigates the known disadvantages of these systems.
According to a first aspect of the present invention there is provided an apparatus for providing left and right eye images along the axis of a camera lens, the apparatus comprising optical means arranged to provide said left and right eye images, whereby the left and right eye images may be simultaneously recorded as a pair of head-to-head images.
It is therefore possible to provide optical apparatus that records separate left and right eye images onto a single frame of a photographic film, or other recording medium, with the left and right eye images being recorded in a head-to-head format, i.e. when the frame is viewed directly, one image appears to be upside down above the other.
Preferably, the optical means comprises first and second optical elements arranged to receive the left and right eye images respectively and a further optical element arranged to receive said left and right eye images from said first and second optical elements and to provide said left and right eye images along the axis of the camera lens. The camera lens may be of a standard focal length i.e. 50 mm for a 35 mm format.
Preferably, the apparatus includes interocular adjustment means arranged to adjust the distance between the image axes of the first and second optical elements such that they are separated by a distance substantially consistent with the interocular distance of natural eyes. The interocular adjustment may be effected by synchronously moving the first and second optical elements along their respective image axes, thus resulting in a variation in the separation between the image axes.
Preferably, the apparatus includes convergence adjustment means, wherein the convergence of the axes of the left and right eye images as received by the apparatus can be adjusted. Preferably, the convergence adjustment means comprises an adjustment mechanism for adjusting the angle at which the first and second optical elements are set in relation to each other and to said further optical element. The convergence adjustment means may comprise a rotary adjustment mechanism. Preferably, the first and second optical elements are interconnected by a mechanical linkage, wherein the first and second optical elements are constrained to being arranged at the same angle of convergence with respect to the further optical element.
Preferably, the apparatus further includes an afocal optical element arranged to provide a relatively wide angle of view of the apparatus of approximately 60°. Preferably, the afocal optical element comprises a pair of optically identical first afocal lenses or lens groups of negative optical power, each first afocal lens or lens group being located along the respective axis of the left and right eye images and in front of said first and second optical elements. The afocal optical element further comprises a second afocal lens group, of positive optical power, located along the axis of the camera lens between the camera lens and the further optical element such that both left and right eye images are incident on the second afocal lens group. Preferably, the optical members comprising the first afocal group are each placed in front of said first and second optical elements in correct optical alignment with the optical axis of the camera lens. The two members of the first afocal group join together optically to form a circle—an optically cohesive unit preserving the spherical properties of the system.
Preferably the front lens group comprises a pair of individual half optical elements, each half optical element being placed in front of said first and second optical elements in correct optical alignment with the optical axis of the camera lens. These two halves join together optically to form a circle—an optically cohesive unit preserving the spherical properties of the system.
Preferably, both members of the first afocal group are coupled to the convergence adjustment means, wherein operation of the convergence adjustment means causes adjustment of the pair of first optical elements.
Preferably, the first and second optical elements comprise plane mirrors and the further optical element comprises a triangular prism, the plane mirrors each being arranged to reflect the light rays of the left and right eye imag
Mahoney Christopher
Marrs Roger A.
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