Device for interlocking a laser emission optical channel and a reception optical channel

Abstract

The invention relates to an optronic device (1) with two optical paths (2’, 2’’) according to a sighting direction (D1), the two optical paths (2’, 2’’) comprising an optical emission path (2’) and an optical reception path (2’’), the optronic device (1) comprising:a first reflective face (10’) configured to reflect a light beam of the first optical emission path (2’),a second reflective face (10’’) configured to reflect a light beam of the second optical reception path (2’’),the first reflective face (10’) and the second reflective face (10’’) being orthogonal with respect to one another.

Description

 Title of the invention: Device for interlocking a laser emission optical channel and a reception optical channel The invention relates to the field of optronic systems. In particular, it relates to systems with two optical paths constituted by an optical emission path and a reception path sensitive to this same optical radiation, both orientable in a direction called “line of sight”, and in which the relative orientation of one path with respect to the other must be controlled with great precision. The field of the invention relates more particularly to systems using a laser but can be adapted to any optical flux.There exist in the prior art several solutions aiming to control the orientation of one optical path with respect to another optical path.For example, the use of an orientable plane mirror common to the two optical paths is known. This type of solution presents a high risk of light pollution of the reception path by the laser emission path, which can render the reception path inoperative.In order to prevent the crossing of the optical paths and therefore the risk of light pollution, the plane mirror of each path is dissociated. Nevertheless, the two plane mirrors being dissociated, the orientation of one plane mirror is not retranscribed on the second plane mirror and an orientation difference can be observed, also called bias. It has also been envisaged to measure the relative position of one optical path with respect to the other optical path in order to be able to have knowledge and a precise measurement of the bias, or orientation difference, between the two optical paths. It is thus possible to adapt the positioning of one path with respect to the other thanks to this measurement of the optical bias. However, this bias measurement is valid only at a given instant, and is potentially no longer representative of the real bias in the event of evolution of the operating conditions notably mechanical or thermal (evolution of the temperature, thermal gradients) and in the event of change of the orientation of the two paths. It is then necessary to carry out the bias measurement for the different possible orientations of the line of sight, and to redo this set of measurements as soon as the temperature evolves significantly. This solution consisting in measuring the bias then imposes multiplying the number of measurements as a function of the different observed operating cases, which is not desirable.In order to reduce the number of measurements of the bias at each change of operating conditions, it can be envisaged to make the movement of a mirror of an optical path depend on the mirror of the other optical path, so that the movement of the first optical path induces to the movement of the second optical path and therefore that the possible positioning errors of the orientable mirrors are common to the two optical paths, their movement being identical, no relative movement of one with respect to the other is observable.To do this, a servo-control device such as an arm, a connecting rod or else a belt is added to the two plane mirrors. Nevertheless, this type of device is not optimal with respect to vibrations and thermal environments, because the quality of the mechanical connection between the two plane mirrors is then insufficient, which can generate a bias between the two mirrors.In order to control the relative orientation between a laser emission path and a reception path, an orientable platform making it possible to orient the two paths as a whole can also be used. Nevertheless, the main limitation of this solution is based on the need to orient the whole system, which leads to significant inertias, high bulk and therefore a significant power requirement on the part of the actuator.The invention aims to overcome all or part of the problems cited above by proposing a simple optical device making it possible to reduce or even eliminate any risk of pollution of the reception path by the optical emission path.For this purpose, the subject matter of the invention is an optronic device with two optical paths according to a sighting direction, the two optical paths comprising an optical emission path and an optical reception path, the optronic device comprising:a first reflective face configured to reflect a light beam of the first optical emission path,a second reflective face configured to reflect a light beam of the second optical reception path,the first reflective face and the second reflective face being orthogonal with respect to one another.According to one aspect of the invention, the optronic device comprises a two-faced mirror, the first reflective face being a first face of the mirror, the second reflective face being a second face of the mirror, the first reflective face being mechanically integral with the second reflective face.According to one aspect of the invention, the first reflective face is in contact with the second reflective face.According to one aspect of the invention, the mirror is mobile in rotation about a first axis of rotation perpendicular to the sighting direction, the first axis of rotation being secant to the first reflective face and to the second reflective face.According to one aspect of the invention, the optical emission path comprises an optical emission path entrance and wherein the optical reception path comprises an optical reception path exit, the optical emission path entrance and the optical reception path exit being coincident with the first axis of rotation.According to one aspect of the invention, the first axis of rotation forms an angle of 45° with the normal to the first reflective face and the first axis of rotation forms an angle of 45° with the normal to the second reflective face.According to one aspect of the invention, the mirror is mobile in rotation according to a second axis of rotation perpendicular to the first axis of rotation and perpendicular to the sighting direction.According to one aspect of the invention, the first reflective face or the second reflective face is offset according to the first axis respectively with respect to the second reflective face or with respect to the first reflective face so as to bring the first reflective face closer to the second reflective face.According to one aspect of the invention, the first reflective face comprises a first end and the second reflective face comprises a second end, the projection of the first end and the projection of the second end being coincident according to the first axis of rotation.According to one aspect of the invention, the mirror is produced from a single material.According to one aspect of the invention, the mirror is monolithic.The invention will be better understood and other advantages will appear upon reading the detailed description of an embodiment given by way of example, the description being illustrated by the attached drawings in which:figure 1 represents an optronic device according to the invention;figure 2 represents the optronic device of figure 1 with an additional axis of mobility;figure 3 represents the optronic device in an optimized architecture.For the sake of clarity, the same elements will bear the same references in the different figures.Figure 1 represents an optronic device 1 with two optical paths 2. The two optical paths 2 comprise an optical emission path 2’ of an optical flux and an optical reception path 2’’ of the optical flux. The emission path 2’ of the optical flux comprises an optical emission path entrance 20’ and an optical emission path exit 22’. The optical reception path of the optical flux 2’’ of the optical flux comprises, for its part, an optical reception path entrance 20’’ and an optical reception path exit 22’’. The optronic device 1 is configured so as to allow the generation and emission of an optical flux, such as for example laser radiation, which passes through the emission path 2’ of optical flux by means of the entrance of the optical emission path 20’ then by means of the exit of the optical emission path 20’’. The optical flux is then reflected in a medium external 3 to the optronic device 1 and is superposed with the flux directly emitted by the external medium 3, in order to pass through the optical reception path 2’’. More precisely, this same optical flux emitted through the optical emission path 2’ is received at the level of the entrance of the reception optical path 20’’ before being transmitted toward the exit of the optical reception path 22’’.The optronic device 1 is also configured to emit the optical flux according to a sighting direction D1. Thus, the exit of the optical emission path 22’ is oriented so as to be parallel to the sighting direction D1. The sighting direction D1 determines the emission direction of the optical flux so that the optronic device 1 is oriented in the direction of the sighting direction D1 and emits the optical flux parallel to this sighting direction D1. Likewise, the entrance of the reception path 20’’ is also oriented so as to be parallel to the sighting direction D1. In other words, the exit of the emission path 22’ and the entrance of the reception path 20’’ are both directed parallel with respect to the sighting direction D1, as represented in figure 1.The exit of the optical emission path 22’ and the entrance of the optical reception path 20’’are oriented according to directions parallel to one another.The entrance of the optical emission path 20’ is oriented according to a first axis A1 coincident with the direction of the exit of the optical reception path 22’’. In other words, the direction of the optical flux passing through the entrance of the optical emission path 20’ and passing through the exit of the optical reception path 22’’ are coincident with the first axis A1 perpendicular to the first direction D1.Thus, the entrance of the optical emission path 20’ and the exit of the optical reception path 22’’ are oriented according to a same direction D2, coincident with the first axis A1, and the exit of the optical emission path 20’’ and the entrance of the optical reception path are parallel to the first direction D1.To do this, the optronic device 1 comprises a first reflective face 10’ configured to reflect the light beam, namely the optical flux such as the laser radiation, in the first optical emission path 2’. The first reflective face 10’ makes it possible to orient the optical flux between the entrance of the optical emission path 20’ and the exit of the optical emission path 22’.It should be noted that the sighting direction D1 is orthogonal to the second direction D2. The first reflective face 10’ then makes it possible to reflect the optical flux with an angle of 90° between the entrance of the optical emission path 20’ and the exit of the optical emission path 22’.By way of indication, the first reflective face 10’ is positioned at 45° from the second direction D2 in the clockwise direction and at 135° from the sighting direction D1 in the clockwise direction.In other words, the normal to the first reflective face 10’ forms an angle of 45° with the direction of the entrance of the optical emission path 20’ and with respect to the second direction D2 at the first reflective face 10’ in a clockwise direction. And, the normal to the first reflective face 10’ forms an angle of 45° with the exit direction of the optical emission path 22’ and with respect to the first direction D1 at the first reflective face 10’ in a counterclockwise direction.The optronic device 1 also comprises a second reflective face 10’’ configured to reflect the light beam, namely the optical flux such as the laser radiation or the flux directly emitted by the external medium 3, in the second optical reception path 2’’.The second reflective face 10’’ makes it possible to orient the optical flux between the entrance of the optical reception path 20’’ and the exit of the optical reception path 22’’.The second reflective face 10’’ then makes it possible to reflect the optical flux with an angle of 90° between the entrance of the optical reception path 20’’ and the exit of the optical reception path 22’’.By way of indication, the second reflective face 10’’ is positioned at 135° from the second direction D2 in the clockwise direction and at 45° from the sighting direction D1 in the clockwise direction.In other words, the normal to the second reflective face 10’’ forms an angle of 45° with the exit direction of the optical reception path 22’’ and with respect to the second direction D2 at the second reflective face 10’’ in a counterclockwise direction. And, the normal to the second reflective face 10’’ forms an angle of 45° with the direction of the entrance of the optical reception path 20’’ and with respect to the first direction D1 at the first reflective face 10’ in a clockwise direction.The first reflective face 10’ and the second reflective face 10’’ are orthogonal with respect to one another.The optronic device 1 has the advantage of preventing any crossing between the emission optical flux comprised in the optical emission path 2’ and the reception optical flux comprised in the optical reception path 2’’. Indeed, these two optical fluxes, namely the emission optical flux and the reception optical flux, are systematically parallel to one another and distant from one another. Thus, the risk of crossing of optical flux is eliminated.Advantageously, the first reflective face 10’ can be mechanically integral with the second reflective face 10’’. From then on, the orientation of the second reflective face 10’’ depends on the orientation of the first reflective face 10’ so that no bias is detectable between the first reflective face 10’ and the second reflective face 10’’.Advantageously, the first reflective face 10’ can be connected, according to a first end 102’ of the first reflective face 10’, to the second reflective face 10’’ according to a second end 104’’ of the second reflective face 10’’. The first reflective face 10’ is mechanically connected to the second reflective face 10’’. From then on, the first reflective face 10’ and the second reflective face 10’’ are mechanically linked to one another. The movement of the first reflective face 10’ induces the movement of the second reflective face 10’’ and conversely. The first reflective face 10’ and the second reflective face 10’’ thus form a reflective component.In other words, the optronic device 1 can comprise a two-faced mirror 10 of which the first reflective face 10’ is a first face of the mirror 10 and of which the second reflective face 10’’ is a second face of the mirror 10.The mirror 10 can be constituted by a supporting structure 100 on which the first reflective face 10’ and the second reflective face 10’’ are fixed. In this configuration, it can be envisaged to use the same material for the different parts, namely the supporting structure 100, the first reflective face 10’ and the second reflective face 10’’, in order to render thermal deformations negligible.In other words, the two-faced mirror 10 can be produced from a single material. The mirror 10 is then an assembly of several components, namely the supporting structure 100, the first reflective face 10’ and the second reflective face 10’’ all produced in a single material. By way of indicative example, the supporting structure 100, the first reflective face 10’ and the second reflective face 10’’ can be produced from metal, in a metal alloy, from ceramic or else from glass.As a variant, it can advantageously be envisaged to machine directly the the first reflective face 10’ and the second reflective face 10’’ on the supporting structure 100, in order to better make integral the first reflective face 10’ and the second reflective face. The mirror 10 is then a monolithic structure directly comprising the supporting structure 100, the first reflective face 10’ and the second reflective face 10’’. The monolithic mirror 10 makes it possible to reduce thermal deformations at the level of the first reflective face 10’ and of the second reflective face 10’’, but also to increase the stiffness between the first reflective face 10’ and the second reflective face 10’’, and therefore to reduce the amplitude of the vibrations of one reflective face with respect to the other reflective face.It can also be envisaged to add a coating on the first reflective face 10’ and on the second reflective surface 10’’ to modify the reflection of the first reflective face 10’ and the reflection of the second reflective face 10’’.In order to vary the sighting direction D1 of the optronic device 1, the optronic device 1 can be mobile about the first axis A1. More precisely, the mirror 10 is mobile in rotation according to the first axis A1 parallel to the second direction D2 of the entrance of the optical emission path 20’ and to the second direction D2 of exit of the optical reception path 22’’.The first axis A1 can form an angle of 45° with the normal to the first reflective face 10’ and an angle of 45° with the normal to the second reflective face 10’’.The mirror 10 can also be mobile in rotation according to a second axis A2 perpendicular to the first direction D1, and perpendicular to the first axis A1, as represented in figure 2. The first direction D1, the first axis A1 and the second axis A2 are thus perpendicular two by two. The sighting direction D1 can then vary in a plane perpendicular to the second axis A2 and passing through the first axis A1. Nevertheless, the angular variation according to this second axis A2 is limited due to the need to have a contact between the optical flux of the optical emission path 2’ and the first reflective face 10’ and between the optical flux of the optical reception path 2’’ and the second reflective face 10’’.In other words, the mirror 10 is mobile in rotation according to two axes of rotation, a first axis of rotation which is the first axis A1 and a second axis of rotation which is the second axis A2.The mobility of the second reflective face 10’’ is thus dependent on the mobility of the first reflective face 10’ so that the relative orientation of the optical emission path 2’ with respect to the optical reception path 2’’ is controlled with great precision according to two axes, namely the first axis A1 and the second axis A2, including in the event of thermal variations and / or vibrations. In other words, no bias can appear between the first reflective face 10’ and the second reflective face 10’’.It can also be envisaged to optimize the shape of the mirror 10 with respect to the bulk of the optronic device 1 or with respect to the optical flux emitted or received. More precisely, the two-faced mirror 10 can be hollowed out, as represented in figure 3 according to any one of its reflective faces from among the first reflective face 10’ or the second reflective face 10’’.The hollowed-out reflective face 11’’ is a planar reflective surface, like the second reflective face 10’’ of which the position along the first axis A1 is offset, and brought closer to the first reflective face 10’. The hollowed-out reflective face 11’’ presents structural dimensions, in the plane formed by the first direction D1 and the first axis A1, and notably a length L smaller than the structural dimensions, and notably the length L’, of the second reflective face 10’’.The hollowed-out reflective face 11’’ is connected to the first reflective face 10’ by means of the supporting structure 100 of the mirror 10. The hollowed-out reflective face 11’’ is thus brought closer to the first reflective face 10’ with respect to the second reflective face 10’’.In a configuration of optimized mirror 10, as represented in figure 3, the second reflective face 10’’ can then be replaced by the hollowed-out reflective face 11’’. In other words, the second face of the mirror 10 is offset according to the first axis A1 with respect to the first reflective face 10’ so as to bring the face of the mirror 10, namely the hollowed-out reflective face 11’’, closer to the first reflective face 10’. Consequently, the reflective face of the reception path, that is to say the second face of the mirror 10, is reduced in size.As a variant, this optimization can concern the first reflective face rather than the second reflective face. In this case, the first face of the mirror 10 is offset according to the first axis A1 with respect to the second reflective face 10’’ so as to bring the first face of the mirror 10 closer to the second reflective face 10’’. And, the reflective face of the emission path, that is to say the first face of the mirror 10, is reduced in size.Advantageously, it can also be envisaged that the first axis A1 is secant at the level of the median of the first reflective face 10’ in the plane formed by the first axis A1 and by the normal to the first reflective face 10’. In other words, the first axis A1 of the mirror 10 is secant of the first reflective face 10’ so as to divide the length L’ by two in the plane formed by the first axis A1 and the normal to the first reflective face 10’. The first axis A1 is centered on the first reflective face 10’ so that the entirety of the optical flux emitted in the optical emission path 2’ is reflected by the first reflective face 10’.And, similarly, it can be envisaged that the first axis A1 is secant at the level of the median of the second reflective face 10’’ in the plane formed by the first axis A1 and by the normal to the second reflective face 10’’. In other words, the first axis A1 of the mirror 10 is secant with the second reflective face 10’’ so as to divide the length L’’ of the second reflective face 10’’ by two in the plane formed by the first axis A1 and by the normal to the second reflective face 10’’. The first axis A1 is centered on the second reflective face 10’’ so that the entirety of the re-emitted optical flux or the flux directly emitted by the external medium 3 in the optical reception path 2’’ is reflected by the second reflective face 10’’.And, if it is an optimized mirror 10 as represented in figure 3, then it can also be envisaged that the first axis A1 is secant with the median of the hollowed-out reflective face 11’’ in the plane formed by the first axis A1 and by the normal to the hollowed-out reflective face 11’’. In other words, the first axis A1 of the mirror 10 is secant with the hollowed-out reflective face 11’’ so as to divide the length L of the hollowed-out reflective face 11’ by two in the plane formed by the first axis A1 and by the normal to the hollowed-out reflective face 11’’. The first axis A1 is centered on the hollowed-out reflective face 11’’ so that the entirety of the re-emitted optical flux or the flux directly emitted by the external medium 3 in the optical reception path 2’’ is reflected by the hollowed-out reflective face 11’’.As indicated above, it can be envisaged that the two faces of the mirror 10, namely the first reflective face 10’ and the second reflective face 10’’ or a reflective face, from among the first reflective face 10’ and the second reflective face 10’’, and the hollowed-out reflective face 11’, are substantially orthogonal.Indeed, a right angle between the two reflective faces makes it possible to have an optical flux at the exit 22’ of the optical emission path 2’and an optical flux at the entrance 20’’ of the optical reception path 2’’ oriented in a substantially parallel manner and to avoid any crossing.Substantially orthogonal is understood to mean an angular difference less than or equal to 1 mrad with respect to a right angle between the two reflective faces of the mirror 10. Ideally, the two reflective faces of the mirror 10 are orthogonal.Nevertheless, an angular variation greater than 3° can be accepted provided that substantial optical measurements and a specific dimensioning of the optronic device 1 are carried out.    

Claims

1. Optronic device (1) with two optical paths (2’, 2’’) according to a sighting direction (D1), the two optical paths (2’, 2’’) comprising an optical emission path (2’) and an optical reception path (2’’), the optronic device (1) comprising:a first reflective face (10’) configured to reflect a light beam of the first optical emission path (2’),a second reflective face (10’’) configured to reflect a light beam of the second optical reception path (2’’),the first reflective face (10’) and the second reflective face (10’’) being orthogonal with respect to one another.

2. Optronic device (1) according to claim 1, comprising a two-faced mirror (10), the first reflective face (10’) being a first face of the mirror (10), the second reflective face (10’’) being a second face of the mirror (10), the first reflective face (10’) being mechanically integral with the second reflective face (10’’).

3. Optronic device (1) according to claim 2, the first reflective face (10’) being in contact with the second reflective face (10’’).

4. Optronic device (1) according to claim 2 or 3, wherein the mirror (10) is mobile in rotation about a first axis of rotation (A1) perpendicular to the sighting direction (D1), the first axis of rotation (A1) being secant to the first reflective face (10’) and to the second reflective face (10’’).

5. Optronic device (1) according to claim 4, wherein the optical emission path (2’) comprises an optical emission path entrance (20’) and wherein the optical reception path (2’’) comprises an optical reception path exit (22’’), the optical emission path entrance (20’) and the optical reception path exit (22’’) being coincident with the first axis of rotation (A1).

6. Optronic device (1) according to claim 4 or claim 5, wherein the first axis of rotation (A1) forms an angle of 45° with the normal to the first reflective face (10’) and wherein the first axis of rotation (A1) forms an angle of 45° with the normal to the second reflective face (10’’).

7. Optronic device (1) according to claim 1 to 6, wherein the mirror (10) is mobile in rotation according to a second axis of rotation (A2) perpendicular to the first axis of rotation (A1) and perpendicular to the sighting direction (D1).

8. Optronic device (1) according to claim 1 to 7, wherein the first reflective face (10’) or the second reflective face (10’’) is offset according to the first axis(A1) respectively with respect to the second reflective face (10’’) or with respect to the first reflective face (10’) so as to bring the first reflective face (10’) closer to the second reflective face (10’’).

9. Optronic device according to one of claims 1 to 8, wherein the first reflective face (10’) comprises a first end (102’) and wherein the second reflective face (10’’) comprises a second end (104’’), the projection of the first end (102’) and the projection of the second end (104’’) being coincident according to the first axis of rotation (A1).

10. Optronic device (1) according to one of claims 2 to 9, wherein the mirror (10) is produced from a single material.

11. Optronic device (1) according to one of claims 2 to 10, wherein the mirror (10) is monolithic.     

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