FR2679051A1 - STEREOSCOPIC CAMERA. - Google Patents

Abstract

A stereoscopic camera has a single lens (14) which forms a parallel beam of light from any point on an object (13), a single imaging lens (20), and a dual lens (16) placed between the two lenses. The lens (20) is preferably of the compound type such that its exit pupil, for an entrance pupil close to the biprism (16), is close to the rear surface of the imaging lens (20). A deflector (24) removes the overlap of the two images.

Description

The present invention relates to a stereo camera.

  scopic, and in particular, but not exclusively, a camera intended to give stereoscopic television images. More specifically, the invention relates to a stereoscopic camera which comprises a single objective, a photosensitive image-forming device, a single lens for focusing images on the photosensitive device and a

  biprism placed between the objective and the focusing lens

  tion of images so that two images are formed.

  Thanks to the use of a single lens instead of two lenses placed side by side, the stereoscopic camera can be produced with a very small footprint, so that it allows for example inspection in confined spaces. that the objective and the image focusing lens can both be composite lenses, that is to say that each of them can

  have several lenses having a common optical axis.

  Preferably, a deflector is placed between the photosensitive device and the image focusing lens in a plane parallel to the optical axis of the image focusing lens and in which the apex of the biprism is located. This prevents any overlapping of the two images The deflector advantageously has a T shape, the transverse bar of the T being adjacent to the image focusing lens and perpendicular to its optical axis. Preferably, the objective is of a collimator type so that the light coming from a point of an object arrives in the form of a parallel beam on the biprism Consequently, the distance included between the objective and the biprism is not essential The camera is focused by moving the lens towards or away from the object, and no movement of the other elements is necessary In a variant, the lens can have telescopic properties, comprising two distant converging lenses intended to form an intermediate image between them, and such that the light from a point on the object reaches the biprism in the form

of a parallel beam.

  The image focusing lens is preferably

  rence such that an entrance pupil is at the location of the biprism, the corresponding exit pupil, which is virtual, being as close as possible to the crossbar of the deflector so that the light losses due to the deflector are reduced to a minimum In the embodiment of the invention described below, the exit pupil is only about 120 mm from the crossbar (on the side of the crossbar which is distant from the sensor); on the contrary, with a conventional lens, the exit pupil is approximately 200 mm from the

cross-bar.

  The photosensitive image-forming device can be a photographic film or an electronic image sensor. The two images can be produced side by side.

  or can be trained on a common training device

  tion of images or, using mirrors, the two images can be formed on two separate devices of

image formation.

  The optical elements of the camera can also be used in reverse order so that they recombine

  a pair of stereoscopic images.

  Other features and advantages of the invention

  tion will emerge better from the description which follows

  of an exemplary embodiment, made with reference to the appended drawings in which: FIG. 1 is a schematic section of a stereoscopic camera; and Figure 2 shows in more detail a section of

the camera of figure 1.

  Reference is made to FIG. 1 which represents a section along the optical axis of a stereoscopic camera 10 Light rays 12 coming from an object 13 are collimated by a collimating lens 14 so that they reach in the form of parallel rays on a biprism 16 The biprism 16 divides the light into two parallel beams 17, 18 which diverge The beams 17 and 18 are focused by an image forming lens 20 intended to form two images side by side 21, 22 above and at below the optical axis of the camera 10 respectively A deflector plate 24 is disposed along the optical axis from the proximity of the rear surface of the lens 20 to the proximity of the plane in which the images 21 are located,

  22; it is a flat plate in the plane perpendicular to

  figure (that is to say the plane in which the top of the biprism 16 is located, more precisely the plane dividing the two parts of the biprism 16) and it has a T shape having a transverse bar 25 close to the rear surface of the lens 20 and perpendicular to the optical axis of the camera 10 The deflector plate 24,

  with its crossbar 25, minimizes the overlap

  really possible of the two images 21 and 22.

  In a variant of the above provision,

  indicated in dashed lines, mirrors 30 are used

  so that the two images 21 and 22 are formed at

  good distance from each other This variant is advantageous

  geuse when images 21 and 22 must be performed on two separate electronic image sensors, because a larger space is thus available for each sensor. Referring now to Figure 2 which shows in more detail the stereoscopic camera 10 The collimating lens 14 is a compound lens comprising four distant elementary lenses 31, 32, 33, 34 held in a tubular metal support 35 The biprism 16 and the lens 20 for image formation are also supported in a respective tubular metal support 36 The biprism 16 has the construction of a doublet minimizing the chromatic aberration, and it comprises a first biprism 37, plane on one side and delimiting, on the other side, two surfaces inclined at 7.90 relative to the planar surface, and two thin biprisms 38 having an apex angle, 6, fixed to the inclined surfaces of the first biprism 37 with the vertices in cooperation (and intersecting the optical axis 39) The first biprism 37 is formed of type F 2 glass and the prisms 38 are formed of type BK glass 7, these

  references being references of "Schott" glass types.

  The image forming lens 20 is also composed and comprises a thick doublet meniscus (lenses 40 and 41), and four other distant elementary lenses 42, 43, 44 and 45 The transverse bar 25 has a height of 8.5 mm in this case and it abuts against the back surface of

lens 45.

  The characteristics of the lenses are indicated in the tables which give the radii of the successive surfaces, the distance of separation along the axis 39 between a first surface and the following, the observation diameters and the types of glass The lenses of the collimating lens 14 are indicated in table 1 and those of the imaging lens 20 in table 2 It should be noted that the total diameter of the collimating lens 14, including the support 35, does not necessarily exceed approximately 45 mm then than that of the

  image forming lens 20 does not exceed necessary

approximately 55 mm.

  As indicated above, the optical elements of the camera, that is to say the collimating lens 14, the biprism and the imaging lens 20, can be used in reverse for the recombination of two

  stereoscopic images In this case, stereosco-

  spikes occupy the position of images 21 and 22 of the

figure 1.

  Radius mm -92 -206 -55 -112 -43 Radius mm -24 -33 -205

-71

-213 -72

61

  -138 Separation mm, 5 4.1 6.0 7.4 2.0 19.6, 5 Separation mm, 6 1.5, 0 0, 3, 0 0.3 7.0 2.6 1.5 0 , 35 8.3

TABLE 1

Diameter mm

TABLE 2

  Diameter numm Material LAK 9 air BK 7 air SF 8 air SK 4 Material air LAK 9 SSK 5 air LAK 9 air LAK 9 air SF 6 air LAK 9 Lens Lens

Claims (8)

  1 stereoscopic camera (10), characterized in that it comprises a single objective (14), a photosensitive image-forming device, a single lens (20) for focusing images (21, 22) on the photosensitive device , and a biprism (16) placed between the objective (14) and the lens (20) for focusing images so that   two images (21, 22) are formed.   2 stereoscopic camera according to claim 1, characterized in that it further comprises a deflector (24) disposed between the photosensitive device and the focusing lens (20) so that it prevents light   to intersect the plane parallel to the optical axis of the   image focusing lens (20) in which is located the summit of biprism (16).   3 stereoscopic camera according to claim 2, characterized in that the deflector comprises an element (25) adjacent to the lens (20) for focusing images   which stops the light coming from the focusing lens -   tion of images in a region placed on either side of the plane. 4 Stereoscopic camera according to claim 3, characterized in that the deflector (24) has a T shape, the transverse bar of the T being adjacent to the lens (20) for focusing images and perpendicular to its optical axis. Stereoscopic camera according to any one of   previous claims, characterized in that the object   tif (14) is a collimation lens.   6 Stereoscopic camera according to any one of   previous claims, characterized in that the object   tif (14) and the lens (20) for focusing images are compound lenses.   7 Optical instrument intended to combine two stereoscopic images, characterized in that it comprises a single converging objective (20) intended to receive the light from the two stereoscopic images (21, 22), the two images   (21, 22) being at equal optical distances from the object   tif and the light of the two images (21, 22) being received by respective non-overlapping objective segments (20), a single focusing lens (14), and a biprism (16) placed between the objective (20) and the focusing lens (14) so that the light received by said segments passes through the prisms   respective of the biprism (16) and that the focusing lens tion (14) creates a single image.   8 Optical instrument according to claim 7, characterized in that it further comprises a deflector (24) intended to prevent the reception of light from a first image (24) by the objective segment (20) which corresponds to the other image (22).   9 optical instrument according to one of claims   7 and 8, characterized in that it further comprises a device (25) intended to prevent the reception of light from one or the other image (21, 22) by a region   of the objective (20) placed between said segments.