Television – Stereoscopic – Picture signal generator
Patent
1996-01-11
1998-02-17
Au, Amelia
Television
Stereoscopic
Picture signal generator
352 60, 396330, H04N 1302
Patent
active
057196206
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a single-camera autostereoscopic video device implementing an array of cylindrical lenses.
United States patent U.S. Pat. No. 3,932,699 discloses an autostereoscopic picture-taking device having an array of lenses on which light rays from an object are focused, the lens array being placed against a window that is sensitive to light and constitutes part of a Vidicon tube, for example.
Such a picture-taking device suffers from numerous drawbacks, and in particular from considerable geometrical distortion and small depth of field.
A much more elaborate stereoscopic picture-taking device was proposed by McCormick et al. at the stereoscopic television colloquium that was held in London on Oct. 15, 1992. He proposed taking stereoscopic video pictures by recording an image that is projected onto a diffusing screen by two autocollimated lens arrays. That device suffers from the drawback of considerable complexity and in particular the use of three lens arrays that must be in perfect alignment otherwise the image is affected by extremely troublesome moire phenomena.
In a first aspect, the present invention provides an autostereoscopic picture-taking device that does not suffer from the above-specified drawbacks, and more particularly a stereoscopic picture-taking device that is simple to implement and that provides high optical quality.
French patent FR 1 362 617 (Yarmonkine) relates to a picture-taking device having a plurality of entrance objectives, specifically two lenses, each having its own optical axis, thus providing two entrance objectives with two optical axes corresponding to respective viewpoints. To obtain a composite image with interlacing, a frosted screen is placed on the plane face of the plate 7 and the screen is scanned horizontally by a normal camera. The screen gives rise to losses of light intensity and of contrast. In addition, given that the microlenses of the array 7 must have a field angle enabling them to see both objective lenses, certain light rays are very highly inclined relative to the optical axis, thus giving rise to problems of vignetting.
The idea on which the invention is based is to implement a single entrance objective, on a single optical axis, while still making it possible without a frosted screen to obtain an autostereoscopic image having two or more viewpoints. To this end, the invention provides a single-camera autostereoscopic picture-taking device implementing an array of cylindrical lenses, characterized in that it comprises in succession: the entrance objective, said array having a focal length such that for an image area equal to the pitch of the lenses making it up, the image of the entrance pupil of the entrance objective has a nominal width equal to said pitch; lens array onto the image sensor, the image of the lens array in the transfer optical system being such that the pitch of the lenses of the lens array corresponds therein to an integer number of image points (pixels) of the image sensor, and the image of the pupil of the entrance objective, in the absence of the lens array, being situated substantially at the pupil of the transfer optical system.
Because of its orthoscopic transfer optical system, this device makes it possible, in particular, to conserve a stereoscopic baseline corresponding to the inlet pupil diameter of the entrance objective, in spite of the reduction in the format of the image on the sensor. In addition, the picture-taking device of the invention uses only one lens array, which is particularly favorable for optical quality.
The image sensor may be a charge-coupled type of sensor, and it is preferably constituted by a set of three individual sensors associated with a prismatic three-color beam-splitter forming images on the three sensors, which images that are nominally in mutual alignment, image point by image point. This makes it possible to obtain a high degree of separation between viewpoints without having to subdivide the inlet pupil into as many sub-pupils.
Optimum separation between viewpoints is
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patent: 3674921 (1972-07-01), Goldsmith
patent: 3932699 (1976-01-01), Tripp
patent: 4945407 (1990-07-01), Winnek
patent: 5099320 (1992-03-01), Allio
patent: 5448322 (1995-09-01), Bacs, Jr.
patent: 5546120 (1996-08-01), Miller et al.
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