WO1991009334A1

WO1991009334A1 - Optical system for multidirectional observation authorizing the selection of a direction

Info

Publication number: WO1991009334A1
Application number: PCT/FR1990/000896
Authority: WO
Inventors: Léon ANLEN; Robert Dufes; Hubert Leauthaud; Daniel Legrand
Original assignee: S.O.T.R.A.F.A.
Priority date: 1989-12-12
Filing date: 1990-12-10
Publication date: 1991-06-27
Also published as: FR2655741B1; AU6913791A; FR2655741A1

Abstract

The present invention relates to the optical field and more particularly an optical system for periscopic observation, wherein a separator prism (5, 5') is arranged between groups of fields (8, 8'...) and a collector (1), the structure and arrangement being such that the light beam (17, 17') issued from the group of fields associated with the prism and penetrating through a so-called input face (15) of the latter is totally reflected on the base of the prism forming a reflecting face (7) and comes out through the other so-called output face (16) to arrive to the collector. Furthermore, at least the group of fields has its optical centre (O) offset with respect to the axis of the beams (17), at the opposite of said reflecting base; a selector member (6) allows to let the beams issued from the groups of fields pass only one after the other.

Description

"OPTICAL MULTIDIRECTIONAL OBSERVATION SYSTEM AUTHORIZING THE SELECTION OF A DIRECTION"

The present invention is in the field of optics and more particularly relates to a device essentially consisting of lenses and prisms intended to allow endoscopic, periscopic and / or panoramic observations.

We know the panoramic observation devices, called periscopic, comprising a group of fields, one or two prisms with roreal reflection, and an ocular assembly or means of electronic transmission of the image. A first type of periscope is made up of a single eyepiece and a single objective, its field of vision is 60 °; it can however turn around its axis to ensure observation in all directions. A - _Λ second type periscope has two goals and two eyepieces and wider field of ESR observations. A third type of periscope includes several lenses and several eyepieces so that one can observe in all directions. Finally a periscope, called panoramic, is equipped with a large mirror on which all the images transmitted by the jecrifs converge.

The aim of the present invention is to propose a particular arrangement of diprres (lenses and prisms) allowing multidirectional, or even panoramic, observation at long or short distance (endoscopic observation), er which can also lend itself to very great miniaturization. authorize its embarkation aboard heavy equipment requiring low weight. Another object of the invention is to propose an operative system with several opric axes allowing the sequential scanning of the observations following these various axes and the electronic processing of the images in order to restore a panorama. According to the present invention an optical observation system, of the kind which may comprise at least one optical group called fields, at least one prism with total reflection intended to return at right angles the optical axis and the light beam coming from said group of fields at least, and at least one optical group called collector intended to process the light beam to provide either a virtual image usable by the eye for example, or a real image usable by a photosensitive caprex, said sensor, to indirectly provide an electronic image, is generally characterized in that between each of the field groups and at least the collector beam is arranged a prism whose angle and refractive index (n) are such that the light beam coming from the field group associated with the prism and penetrating through a face called d entry of the latter, is reflected entirely on the base of the prism forming a reflecting face, this face being roughly parallel to the axis, or median radius, of the beam arriving on the face of entry of the prism, and re-emerges through the other face known as of exit, with a direcrion of exit substantially parallel to its direction of entry, to arrive on the collector, and in that at least the group of fields presents an offset from its optical center relative to the optical axis, the offset having an opposite direction relative to said reflective base. It follows from these two joint arrangements, that for each assembly forming the optical system, the beam from each group of fields is conveyed separately through the associated prism said, for this reason, separator, and that a certain correction of the chromatic aberation provided by each constituent element of the optical system.

According to another general characteristic, advantageous but incidental, of the invention, a member, called a selector, is interposed on the path of the beams coming from the separating prisms, in order to be able to select and only pass, alternatively, the beam from only one of the separating prisms.

According to a form of embodiment, the optical axis of the group of fields of at least one of said sets, is made perpendicular to the axis of its separating prism by the interposition of a return prism

(radial observation), while for at least one other of the said sets the optical axis of its group of fields is located in the extension of the axis of its separating prism (axial observation). It follows from this arrangement that it is possible to select alternately the radial observation and the axial observation.

According to an embodiment, called "intra-axial", all the bases of the sonr separating prisms, relative to the axes of the separating prisms, arranged, facing one another, that is to say located inside of all the "optical axes" of separating prisms.

According to another mode, an alternative to the previous one, called "extra-axial", all the bases of the separator prisms are located outside the set of axes of the separator prisms.

In a third embodiment, called "mixed", certain reflecting bases are inside the device, that is to say still close to a central axis, while others are at

Outside.

According to another embodiment, mainly applicable according to the intra-axial mode, the separating prisms are cut, on their lateral faces other than their reflecting face, to be contiguous and form a solid block.

According to another embodiment, the separating prisms are equally distributed in the volume of a cylindrical crown, a central space forming the center of the volume allowing the passage of a axial beam. This embodiment can be treated as well in intra-axial mode as in extra-axial mode.

According to another characteristic 5 of the invention, at least one group of fields (but preferably all) is formed of lenses cut asymmetrically with respect to their optical axis.

According to another subsidiary feature the optical axes of each of the sets _j _o converge towards one same first sensitive surface, for, thanks to the selector, it sequentially succeed.

The present invention will be better understood, and details will become apparent from the description which will be made of preferred forms of

15 embodiment, in relation to the figures and diagrams of the appended plates, in which:

- fig.l is a schematic representation of a conventional periscopic observation device,

20 - fig.2 is an illustration similar to that of fig.l of a device comparable to that of this figure, but incorporating the characteristics of the present invention,

FIG. 3 is a simplified diagram making it possible to understand the invention in its generality, in the case of axial observation, and to give definitions thereof,

- fig.4 completes the previous figure by extending it to radial observation,

3 _Q - fig.5 is a schematic illustrarion of an embodiment, according to an intra-axial mode, of a device of the invention allowing axial and radial observations,

- fig.6 is a perspective illustration 35 of the same,

- fig.7 is a representation of the same seen along the axis of the device,

- fig.8 is a sectional illustration of another embodiment according to an extra-axial mode of a device of the invention, - fig.9 is a representation in axial view of the same,

- Fig.10 is an illustration in axial view similar to that of Fig.7 and 9 of another embodiment of a device of the invention, - Fig.ll is an axial representation of a another embodiment of a device of the invention, and

- fig.12 is the corresponding cross-sectional representation of the same. Fig.l recalls that a conventional periscopic observation device comprises a group of fields 1 consisting of a certain number of lenses forming them a converging or alternatively afocal opric system, two prisms 2, 2 'with total reflection and an ocular optical group 3 said collector; the prisms 2, 2 'with total reflection are used to return the optical axis 4,4', 4 "at a right angle. In such a simplified device the field group whose angular aperture is generally not greater than 90 °, rotates around a vertical part of the optical axis, with the disadvantage of mechanical means and a significant correlative size.

In fig.2 a panoramic observation system of the invention comprises as essential differences the presence of separating prisms 5 and a selector member 6; we also note that groups of fields 8 are lenses cut asymmetrically.

This comparison with the prior art having been made, we will now, with the following figure, give a more precise definition of the invention. In ^" fig.3 a light beam 10, coming from an object located at infinity, meets a group of fields 11 which focuses it, for example, at a point 12; on the path of the beam, and in downstream of the group of fields 11, a prism 5, called a separator, is arranged, the fictitious edge of which is shown in 13, is octagonal to the axis of the beam; the prism 5 comprises (see also fig. 4) a base face 7 shaped, by silvering or other spreading, on the completely reflecting face; another face 7a) is cut parallel to the base; the distance separating these faces is defined as the thickness of the prism; the prism 5 has substantially the shape of a rod whose end faces, respectively entry face 15 and exit face 16, converge symmetrically towards the edge 13; in other words the section of the prism by a plane perpendicular to its edge 13 has substantially the shape of an isosceles trapezoid. We define as the axis of the prism the line 18 t the midpoints of these inlet and outlet faces; the reflecting face 7 is parallel to the prism axis thus defined.

The index of the glass constituting the prism and the prism angle thereof, that is to say the dihedral angle formed by the planes of the inlet and outlet faces, are such that a radius light propagating along the axis of the prism is reflected towards about the middle of the reflecting face and emerges from the prism in the extension of itself.

The luminous brush which represents the whole of the entry face has been represented by 17 and we can see how this brush reverses by crossing the prism; the axis 14 of the brush or median radius, which is also the axis of the beam, coincides with the axis 18 of the prism.

A group of fields, represented in dashes by 11 as, and assimilated to, a thin lens, would, according to the prior art, be centered on the axis14. However, in accordance with a feature of the invention tion, this lens is offset parallel to itself and perpendicular to the axis of the brush to come occu¬ per the position shown in 11 'in thick line, the distance d_ offset is such that the edge of the brush 17 meet again the edge of the lens.

The useful part of the lens is shown by cross-hatching which after deca¬ lage is crossed by the brush 17.

It is clear that the shift of the lens with respect to the axis of the prism was carried out opposite, with respect to this axis, of the reflective face, or that the displacement corresponds to a distance from the optical center 0 ′, 0 of the lens with respect to the reflecting face 7. This will always be the case, in accordance with the invention, whatever the arrangement of the prism and of its reflecting face in the entire optical system.

In another way it can be said that the lens and the separating prism are offset transversely with respect to each other and perpendicularly with respect to the path of the rays so that a ray having a long optical path in the prism , has a short optical path in the lens (or in the group of fields) and vice versa. We sketched in dashes in fig.4 the presence of a reflective surface 2 inclined at 45 ° on the axis of the prism to return on the latter a brush 17 'perpendicular to the brush 17. Fig.4, which illustrates this last case, shows that by applying the rule of symmetry with respect to a plane, the offset of the optical center of the lens always proceeds from its distance from the reflecting face of the prism. Obviously, it must be understood that it is the offset of the optic center 0_ of the lens which is sufficient to characterize the invention, the asymmetrical cutting bringing the additional advantage of saving weight and / or bulk. In the following figures, the same references will always be given to similar elements; thus we will designate by 2.2 ', 2 "... a return prism, by 3.3' a collector, by 5.5 'a separating prism, by 6.6' a selector, by 7.7 'the reflective face of a separating prism, by 8.8 'a group of fields, by 14.14' an axis, or central radius of a light brush, by 18.18 'the "axis" of a separating prism rel such axis has been defined above, with an axis 19 ^'of a central device, the reflecting faces paralelle st through roughly the center of gravity of disposirif, 20 by a sensitive surface such as phorocathode for example.

In Figs. 5,6 and 7, an intraxial device is comparable to that of Fig.2, except that it has an axis 14 'of axial vision, that the collector 6 is perpendicular to the 'central axis 19, and that it has, instead of an eyepiece, a sensitive plate 20. Fig.6 makes it easy to understand, by offering them a three-dimensional correspondence, the meaning of fig.5 and 7. In the in the case of the device of these figures, two separating prisms 5,5 ′ are joined by their reflecting ases 7,7 ′.

On fig.8 and 9 a device of the extra-axial type is quite comparable to that of fig.2, except that the separating prisms 5,5 'are joined by their faces opposite to the reflecting bases 7,7'; it will be observed that the groups of fields 8,8 'are inverted with respect to those of fig. 2. In the case of the figure, the collector 3 has been represented as a 'zoom' with a widely variable focal length.

In fig.10, the device is also of the extra-axial type but it comprises four separating prisms, each being cut like a triangular prism, with a section of isosceles right triangle and with end faces converging towards the rectangular edge; the prisms are joined by their faces adjacent to the retangular edge; these edges merge with the central axis 19; the transverse secretion of the assembly perpendicular to the axis 19 is a square; a section through a plane passing through the axis 19 and through the middle of one of the reflecting faces would be comparable to FIG. 8; the reflecting face of each of the prisms is the face opposite the rectangular edge; the four field claws, open at 90 °, cover, if the axis 19 is vertical, the toralire of the horizon.

In fig. 11 and 12, a device, of the extra-axial type, comprises eight prisms cut in the shape of curled pyramids with recrangular bases, and joined by their lateral faces to fit into a cylindrical crown and to form around the central axis 19 a hollow space 25 which can be used to allow the passage of an axial beam of light which can be received on a large aperture system of the grandangular type. The hollow central space could also be used to house a device with four separating prisms such as that of FIG. 10 but shown for the axial position (absence of deflection prisms and central axis merged with the optical axis of a single group of fields). The nonlimiting examples which have just been given illustrate the extreme diversity of the possibilities offered for the application of the rule provided by the invention, and it should be understood that the scope of the latter is not limited to the examples given, but extends to the general definition above.

Claims

R E V E N D I C A T I O N S

1.- An optical periscopic observation system of the kind which may include at least one optical group called fields, at least one prism with total reflection intended to return at right angles the optical axis and the light beam coming from said group of fields at less, and at least one optical group known as a collector intended to process the light beam to provide an evening viral image usable by the eye for example, or a real image usable by a photosensi¬ ble sensor, called a sensor, to indiscriminately provide an image electronic, characterized: in that ¹ between each of. field groups (8,8 '...) er said collector (3) at least esr arranged a prism said separator (5,5' ...) whose angle (13,13 '...) and l 'refractive index (n) sonr such that the light beam (17,17' ...) coming from the field group associated with the prism and penetrating through a so-called entry face (15) of the latter, is reflected in all on the base of the prism, form reflective face (7) and comes out through the other face (16) called output to reach the collector, and in that at least the group of fields has its optical center (0) offset relative to the axis of the beam (17), opposite the said reflective base, whence it results at the same time that a certain correcrion of aberation is achieved for each set chromatic provided by each constituent element of the set, and that the beam from each group of fields is conveyed separately through the associated prism dir, for some reason, separator (fig .3, 4); 2.- Device according to claim 1, characterized: in that a member, said selector

(6), is interposed on the path of the beams coming from the separating prisms, in order to be able to select and let pass, alternatively, only the beam coming from only one of these prisms (fig. 2,5,8);

3.- Device according to claim 2, characterized: in that for at least one of the dirs together the optical axis of its group of fields

(8J is made perpendicular to the axis (18) of its associated separating prism (5), thanks to the interposition of a return prism (2) (radial observation), while for at least one of the directions together l 'optical axis (18') of its group of fields (8 ') is located in the extension of the axis of its separating prism (5') (axial observation), from which it follows that it is possible alternately select radial observation and axial observation (fig. 5 to 7);

4.- Device according to claim 2, characterized: in that all the reflecting bases (7,7 '...) of separating prisms are, with respect to the axes (18,18' ...) of the prisms, arranged opposite one another, that is to say located inside all of the axes of the separating prisms (fig.5);

5.- Device according to claim 2, characterized: in that all the reflecting bases (7,7 '...) of the separating prisms are, with respect to the axes of the prisms, arranged opposite to each other , i.e. located outside the set of axes of the separating prisms (fig. 8,10,12); 6.- Device according to claim 5, characterized: in that the separating prisms are cut, on their lateral faces other than their reflective face (7,7 '...), to be contiguous and form a solid block (fig. 5 to 10);

1. - Device according to claim 4, characterized: in that the separating prisms are equally distributed in the volume of a cylindrical crown, a central space (25) forming the center of a volume allowing the passage of a beam axial

(fig.11,12);

8.- Device according to claim 2, characterized: in that at least one said group of fields is formed of lenses cut asymmetrically with respect to their axis (fig.5 to 12);

9.- Device according to claim 2, characterized: in that the axes of the beams passing through each of the assemblies, converge towards a single sensitive surface (20) (fig.8).