Optical: systems and elements – Stereoscopic
Patent
1996-01-11
1997-09-23
Henry, Jon W.
Optical: systems and elements
Stereoscopic
359463, 348 49, 348 59, 354115, 352 61, G02B 2722, H04N 1304, H04N 1500, G03B 3508
Patent
active
056710895
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a device for forming autostereoscopic images by using an array of cylindrical lenses.
A device for forming autostereoscopic and orthostereoscopic images is known from European patent application EP-84598, which device comprises both a first lens array having convex lenses that form an image which is autostereoscopic and pseudostereoscopic (i.e. in "inverted relief"), and a second lens array having convex lenses which form an orthostereoscopic image.
That device suffers from the drawbacks of requiring two lens arrays, thereby giving rise to very severe constraints concerning tolerances and alignment.
European patent EP 305 274 in the name of the Applicant describes a method whereby elementary images are individually reversed about their own axes or centers of symmetry by means of an electronic process, and are recombined so as to supply an orthostereoscopic image.
The methods of the prior art for obtaining an orthostereoscopic image thus require the implementation of a system that has two stages.
The problem posed by the invention is to obtain directly an image which is autostereoscopic and orthostereoscopic.
To this end, the invention provides a device for forming autostereoscopic images by implementing a cylindrical lens array, the device being characterized in that it comprises in succession: substantially in the image focal plane of the entrance objective, said array having a focal length such that for an image area equal to the pitch (p) of the lenses making it up, the image of the entrance pupil of the entrance objective has a nominal width equal to said pitch; and image.
Downstream from the pupil P.sub.1 of the entrance objective, and in particular between the objective and the lens array, the device may include a cylindrical element that is crossed relative to the lens array and that compensates astigmatism, at least in part. The cylindrical element may be a converging cylindrical lens having a focal length suitable for compensating said astigmatism, at least in part. In a variant, the cylindrical element may be a second diverging lens array whose focal plane coincides substantially with that of the first diverging array.
The invention also provides an image-forming device characterized in that it comprises an image sensor and in that the transfer optical system projects the rays emerging from the 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 is situated substantially at the pupil of the transfer optical system.
The image sensor may be constituted by a charge coupled sensor, in particular constituted by a set of three individual sensors associated with a prismatic three-color beam-splitter forming images on the three sensors that are nominally aligned with one another image point by image point.
The lens array may be oriented in the direction of the lines of the image sensor. The entrance objective, which is advantageously telecentric, may include an entrance lens whose pupil is substantially equal to 100 mm. The lens array may have a pitch of 0.4 mm. The transfer optical system may have a magnification substantially equal to 0.1. It may have a circular diaphragm, in particular of the iris type.
The invention also provides an autostereoscopic video system including an image forming device as defined above.
Other characteristics and advantages appear more clearly on reading the following description, given by way of non-limiting example and with reference to the accompanying drawing, in which:
FIG. 1 and FIG. 1a shows an image forming device and system of the invention; and
FIGS. 2a and 2b show a preferred embodiment of a device of the invention.
FIG. 2c shows an enlarged portion of the device of the preferred embodiment of FIGS. 2a and 2b.
FIG. 1 shows a camera device of the invention. It comprises the following elements:
1) A
REFERENCES:
patent: 1960011 (1934-05-01), Ives
patent: 4487490 (1984-12-01), McKee
patent: 4621897 (1986-11-01), Bonnet
patent: 5099320 (1992-03-01), Allio
R.L. de Montebello, "Wide-Angle Integral Photography--The Integram System", Proceedings of the Society of Photo-Optical Instrumentation Engineers, Three-Dimensional Imaging, vol. 120, Aug. 25-26, 1977, San Diego, California, pp. 73-91.
Patent Abstracts of Japan, JP A 60 244 943, Apr. 12, 1985, Seizaburou Kimura --vol. 10, No. 116 (P-452) Apr. 30, 1986.
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