WO2013110785A1

WO2013110785A1 - Device for attaching an optical member, attachment system and cryogenic device comprising such a device, method of manufacturing such a device and corresponding attachment method

Info

Publication number: WO2013110785A1
Application number: PCT/EP2013/051497
Authority: WO
Inventors: Marc JAQUET; Laurent Martin; Marc LLORED
Original assignee: Centre National De La Recherche Scientifique (Cnrs)
Priority date: 2012-01-27
Filing date: 2013-01-25
Publication date: 2013-08-01
Also published as: FR2986336B1; FR2986336A1

Abstract

The invention relates to an attachment device (16) for attaching at least one optical member (12) and to the corresponding method. The attachment device is designed to be mounted in a support (14) to accept the at least one optical member. The support has a cavity (18) and at least three attachment lugs (20) around the periphery of the cavity which are intended to accept an attachment member of the attachment device. The attachment device comprises a clamp (24) with an internal face (26) intended to be positioned facing the at least one optical member (12), and at least three attachment members to engage with the attachment lugs (20). The clamp (24) is made of an elastically deformable material and comprises at least three open loops (28) of said material constituting attachment members, connected, through continuity of material, by segments (30) of said material. The attachment device further comprises at least three leaves (32), each made of an elastically deformable material and comprising a first end (34) and a second end (36), these leaves each being connected by their first end (34) to the internal face (26) of the clamp (24), their second ends (36) being intended to hold the at least one optical member (12) by contact.

Description

DEVICE FOR FIXING AN OPTICAL MEMBER, FIXING SYSTEM AND CRYOGENIC DEVICE COMPRISING SUCH A DEVICE, METHOD FOR MANUFACTURING SUCH A DEVICE AND METHOD FOR

FIXING CORRESPONDING

The present invention relates to a device for fixing an optical member, a fixing system comprising such a fixing device, a cryogenic device comprising such a fixing device, a method of manufacturing such a device and a method for fixing the device. an optical organ.

It is known to use supports adapted to receive optical organs in order to fix them in a stable and precise position.

In a cryogenic environment or in high temperatures, the differences of thermal expansion (CTE for "coefficient ofi thermal expansion" in English) between the materials of the optical organs and the materials constituting the supports can cause enormous stresses on the optical organs. These constraints can damage or misalign the optical organs.

US-4,733,945 discloses a device for fixing an optical member on a support. The fixing device comprises flexible means bonded to both the optical member and the support in order to fix the optical member to the support. The flexible blades also make it possible to partially reduce the stresses on the optical member generated by the difference in thermal expansion between the optical member and the support during use of the fixing device in a variable temperature environment.

Nevertheless, the use of glue for fixing the flexible blades to both the optical member and the support causes several drawbacks, for example glue aging problems, impossible dismantling of the optical member of the support and problems. degassing intensified in a cryogenic environment or in high temperatures.

The object of the present invention is to provide a device for fixing at least one optical member overcoming the aforementioned drawbacks.

More particularly, the invention aims to provide a device for fixing at least one optical member adapted to be used in extreme temperature conditions both in the very high temperatures and in the very low temperatures, that is to say say between 4 K and 600 K while ensuring a precise maintenance of the optical organ. For this purpose and according to a first aspect, the invention proposes a device for fixing at least one optical member, said fixing device being adapted to be mounted in a support for receiving the at least one optical member, said support comprising a cavity and at least three fixing studs at the periphery of the cavity intended to receive a fixing member of the fixing device, wherein said fixing device comprises a flange with an internal face intended to be positioned facing the at least one optical member, and at least three fasteners for allowing engagement with the mounting studs, where:

the flange is of elastically deformable material and comprises at least three open loops of said material constituting fasteners, connected in continuity of material by segments of said material; and

the fixing device comprises at least three lamellae, each consisting of an elastically deformable material and comprising a first and a second end and are each connected by their first end to the inner face of the flange and their second end are intended to maintain contact the at least one optical member.

Such a fixing device makes it possible to ensure isostatic maintenance of the optical element without harmful deformation during large temperature variations, in a cryogenic environment or in high temperatures. In addition, the fixing device can easily be mounted / removed from the support.

According to preferred embodiments, the invention comprises one or more of the following characteristics taken separately or in combination:

the open loops constituting the fasteners are distributed at equal angular intervals;

the open loops constituting the fasteners are each formed of an arc subtending an angle between 180 ° and 320 °;

each open loop constituting the fasteners is adapted to open or close by elastic deformation to open or close the corners between the second ends of the flexible strips and the inner face of the flange;

the flange is made of material having a coefficient of thermal expansion greater than or equal to S. 10 K ^-1 ;

the flange is made of material having a Young's modulus greater than 70 MPa;

the flange is made of material mainly comprising titanium;

the flange is substantially circular, elliptical or triangular; the optical member to be fixed comprises a circumferential groove and in that each lamella is adapted so that their second end is inserted into the circumferential groove of the optical member to be fixed;

each lamella has at its second end in contact with the optical member to fix a lateral holding means of the optical member to fix U-shaped; and the optical member to be fixed is selected from the list consisting of a filter, a lens, a prism, a grating and a lens.

According to a second aspect, the invention also relates to a system for fixing at least one optical member comprising a support comprising at least one cavity and at least three fixing studs for receiving the at least one optical element and at least one optical device. fixation as described above.

According to a third aspect, the invention also relates to a cryogenic device comprising at least one system for fixing at least one optical element as described above.

In addition, according to a fourth aspect, the invention relates to a method for manufacturing a fastening device as described above, characterized in that it comprises at least one step of cutting by electro-erosion to the wires of the device flange. of fixation.

The invention also relates to a method of fixing at least one optical element to a support using a fixing device as described above, comprising the following steps:

opening the flange (24) of the fixing device by simultaneous elastic deformation of the at least three open loops (28) by a radial spacing means;

installation of the optical member inside the open flange;

- Lateral maintenance of the optical member inside the flange by closing the flange by inverse elastic deformation of the at least three open loops (28) simultaneously; and

fixing the device for fixing the optical member on the support by using the at least three open loops (28) of the fixing device.

Other characteristics and advantages of the invention will appear on reading the description which follows, given by way of example and with reference to the appended drawings:

FIGS. 1 and 2 are diagrammatic diagrams respectively in perspective and in section of a system for fixing at least one optical element according to the invention, FIG. 3 is a block diagram in perspective of a first embodiment of a device for fixing an optical device according to the invention,

FIG. 4 is a front schematic diagram of the fixing device of FIG. 3,

FIG. 5 is a block diagram in perspective of a second embodiment of a device for fixing an optical device according to the invention,

FIG. 6 is a front schematic diagram of the fixing device of FIG. 5,

FIGS. 7 and 8 are diagrammatic diagrams in section of a device for fixing two optical members according to the invention, and

FIG. 9 is a block diagram in perspective of a system for fixing a plurality of optical members according to the invention.

In the various figures, the analogous elements are designated by identical references.

With reference to FIGS. 1 and 2, a system 10 for fixing an optical member is described.

12.

The optical member 12 is for example a filter, a gray, a prism, a network or a lens. In the remainder of the description and unless otherwise stated, the optical member is cylindrical in shape with a circular base, such as a filter or a lens.

The optical member 12 comprises two main faces, each adapted to transmit light radiation and an edge peripheral portion 13 of the optical member.

The fastening system 10 comprises a support 14 and at least one fixing device 16 of this optical element 12 to the support 14.

A single optical element is shown in Figure 1 to simplify the description of the system. Of course, several optical members can be attached simultaneously by the fastening system by means of one or more fastening device 16, as will be described in more detail later.

The support 14 is intended for example to be placed in a cryogenic device.

It comprises a cavity 18 and at least three fixing studs 20, each located at the periphery of the cavity.

For example, the support 14 is made of material comprising aluminum, in particular aluminum.

The fixing device 16 is adapted to be mounted on the support 14 to receive the optical members 12. For this purpose, the support 14 comprises at least three fixing studs 20 and the fixing device 16 comprises at least three fastening members to allow engagement with the fixing studs 20 of the support 14 which are each intended to receive a fastening members of the fastening device 16.

Each fixing stud 20 is for example a cylinder in relief relative to the surface of the support. In this case, the cylinder is in the light of the support. Of course, the fixing studs can have other forms.

Preferably, the support 14 comprises only three fixing studs 20 and the fixing device 16 comprises three fasteners to allow engagement with the three fixing studs 20.

The fixing device will now be described in more detail with reference to FIGS. 3 and 4 illustrating a first embodiment respectively in perspective and from the front.

The fixing device comprises a flange 24 having an inner face 26 intended to be positioned facing each optical member 12 to be fixed.

The flange 24 is of elastically deformable material. Preferably, the flange 24 is of material having a coefficient of thermal expansion greater than or equal to 5.10 ^"6 K ^{" 1} and having a Young's modulus of at least greater than or equal to 70 MPa. In addition, the flange 24 is made of material having a yield strength greater than or equal to 400 MPa. These values make it possible to ensure a good retention of the fastening device 16 on the support 14 while having both good thermal accommodation in view of the differential expansions of the materials and good mechanical strength.

For example, and advantageously, the flange 24 is made of metallic material mainly comprising titanium, in particular titanium.

In addition, the flange 24 is substantially circular, elliptical or triangular. Preferably, the flange 24 is of substantially circular shape.

It comprises at least three open loops 28 of said material each constituting a fastener. Each open loop 28 is connected in continuity of material by segments 30 of the material so that the flange is formed of a single piece.

The open loops 28 constituting the fasteners are distributed at equal angular intervals. Thus, for example if the flange 24 has only three open loops, they will be spaced angularly 120 °.

In addition, they are each formed an arc subtending an angle of between 180 ° and

320 °. The flange 24 is for example manufactured by a method comprising at least one electro-erosion cutting step son according to the invention thus allowing the flange is formed in one piece. Such a manufacturing process makes it possible to obtain an extremely precise and inexpensive piece.

The fastening device 16 comprises at least three strips 32, each made of an elastically deformable material and comprising a first and a second end.

Each strip 32 is connected in continuity of material with the flange 24 by its first end 34 to the inner face 26 of the flange. Of course, according to other embodiments, each strip 32 may be fixed for example by welding by its first end 34 to the inner face 26 of the flange 24.

The second ends 36 of each lamella 32 are intended to maintain by contact each optical member 12 to be fixed. For this purpose, the second ends 36 are supported on a portion of the peripheral portion 13 of the optical member 12.

The lamellae 32 are distributed at equal angular intervals. They are oriented towards the geometric center of the flange 24. The large face of the flanges 32 forms an angle noted β with the plane tangent to the flange 24 at the point of connection between the first end 34 and the inner face 26 of the flange.

Preferably, there are as many slats 32 as open loops 28, allowing respectively to associate each slat 32 to an open loop 28.

The angular difference, noted a in Figure 4, between the first end 34 of a strip 32 and the center of an open loop 28 is substantially between 10 ° and 60 °.

Each open loop 28 constituting the fasteners is adapted to open or close by elastic deformation to open or close the angles β in Figure 4, between the second ends 36 of the flexible strips 32 and the inner face 26 of the flange 24.

Such an embodiment allows each lamella to ensure isostatic maintenance of the optical member without damaging deformation during large temperature variations, for example during a cooling phase. Advantageously, it ensures the maintenance of the optical member without the use of glue and a minimum vignetting on the optical member.

In particular, in the case where the optical member 12 comprises a groove 38 partially or completely circumferential part of the peripheral portion 13 of the optical member, each blade 32 may be adapted so that its second end 36 fits into the throat 38 circumferential of the optical member 12, as shown in Figures 2 and 4. The groove 38 is shown in dashed lines in Figure 4.

Such an embodiment, in which each lamella is inserted into the circumferential groove of the optical member to be fixed, is particularly advantageous because it makes it possible to guarantee very good lateral retention of the optical member without the use of glue and minimum vignetting. on the optical organ 12.

A second embodiment of the fixing device 56 is illustrated in FIGS. 5 and 6. The fixing device 56 is identical to that described in the first embodiment except for the second end 66 of the lamellae 52.

Indeed, according to this second embodiment, each blade 52 comprises at its second end 66 in contact with the optical member 12 a lateral holding means 68 of the optical member 12. This lateral holding means 68 is in the form of U.

The fixing device according to this second embodiment is particularly suitable for optical members without a circumferential groove.

Such an embodiment, in which each lamella terminates U-shaped is particularly advantageous because it ensures a lateral retention of the optical member from the outside thereof also without the use of glue.

Whatever the embodiment, such a fixing device according to the invention inserted at the interface between the support and the optical member makes it possible to maintain the optical member by elastic deformation.

Indeed, the fixing device behaves like a clamp around the optical member 12. During large temperature variations, for example of the order of 200 K, the expansions are absorbed by the elastic deformation of the slats that play. the role of springs. The optical member sees about ten times less effort at the supports of the second ends of the lamellae than the force applied on each of the open loops constituting the fasteners (radial forces). The thermal flexibility and the mechanical strength are obtained in particular by the use of a material comprising titanium.

Such systems for fixing at least one optical member find, for example, applications in devices subject to high temperature variations, and in particular in cryogenic devices comprising at least one fastening system according to the invention. According to the invention, the optical system may comprise a plurality of fixing devices in order to fix several optical members.

For example, Figure 7 illustrates a fastening system 70 for simultaneously fixing two lenses 72A, 72B having a support 74 and two fasteners as described above.

The two fixing devices 16A, 16B illustrated are fixing devices according to the first embodiment and the optical members 72A, 72B are each provided with a circumferential groove 38. Of course, the fastening system 70 may comprise fastening devices according to the first or second embodiment and the optical members to be fixed by the device are provided or not with a circumferential groove and this whatever the embodiment of the chosen fastening device.

In the example illustrated in FIG. 7, the two fixing devices 16A, 16B are fixed on either side of the support 74. Of course, the two fastening devices 16A, 16B can be fixed on the same side of the support 74 according to other embodiments.

The mounting pads 20 of the support 74 are intended to receive both the fastening members of the first and second optical devices 16A, 16B. Of course, according to other embodiments, the support 74 may comprise a first group of at least three fixing studs 20 intended to receive the fixing members of one of the fixing devices 16A and a second group of at least three fixing studs 20 for receiving the fasteners of the other fixing devices 16B. The two groups of fixing studs 20 can then be angularly or non-angularly shifted. FIG. 8 illustrates another example of a fastening system 80 making it possible to simultaneously fix two prisms 82A, 82B comprising a support 84 and two fastening devices as described herein. -above.

The support 84 comprises at least one group of at least three fixing studs (not visible in the present figure) intended to receive the fasteners of the fastening device or devices 16A, 16B.

The two fixing devices 16A, 16B illustrated are fixing devices according to the first embodiment and the optical members 82A, 82B are each provided with a circumferential groove 38. Of course, the fastening system 80 may comprise fixing devices according to the first or second embodiment and the optical members to be fixed by the device are provided or not with a circumferential groove and whatever the embodiment of the chosen fastening device. Such an embodiment of a fixing device makes it possible for the skilled person to call up stacks of optical members by guaranteeing a very precise isostatic centering of the optical members.

FIG. 9 illustrates another exemplary embodiment of a fastening system 90, adapted for simultaneously fixing a plurality of optical members 92, comprising a support 94 and a plurality of fixing devices 56.

The support 94 comprises a plurality of cavities and at least as many groups of at least three fixing studs 20.

The cavities are preferably arranged by minimizing the space between two cavities. For example, the cavities are distributed at equal angular intervals and equidistant from the geometric center of the support 94.

Each group of at least three fixing studs 20 is disposed at the periphery of a cavity and each fixing stud of the same group is intended to receive a fixing member of a fixing device placed opposite said cavity.

The fixing devices 56 illustrated are fastening devices according to the second embodiment. Of course, the fastening system 90 may comprise fixing devices according to the first or second embodiment and the optical members to be fixed by the device may or may not be provided with a circumferential groove, whatever the mode of operation. realization of the selected fastening device.

Fixing devices 56 are arranged in the same plane, each facing a cavity.

Such an embodiment is useful for producing, for example, optical filter wheels. This is possible thanks to the compactness of the fastening devices according to the invention. A fixing method according to the invention of at least one optical element 12 on a support 14 using a fixing device as described above will now be detailed.

This fixing method comprises a step of opening the flange 24 of the fixing device by simultaneous elastic deformation of the at least three open loops 28 by a radial spacing means. This radial spacing means is for example an interior micrometer making it possible to obtain a measured separation of the open loops. Then, the optical member 12 is installed inside the open flange 24. The optical member 12 is then held laterally inside the flange 24 by closing the flange 24 by inverse elastic deformation of the open loops 28 simultaneously.

According to one embodiment, once the flange mounted around the optical member, the flexible strips being trapped in the circumferential groove of the optical member if it is provided with, all form a unitary assembly, as shown in FIG. Figure 4.

According to another embodiment, in the case of a non-machined optical element, that is to say devoid of circumferential groove, the flexible strips hold prisoner the optical organ from the outside this time and the whole. also forms a unitary assembly, as illustrated in FIG.

In addition, it is possible to adjust in rotation the optical member along its axis of revolution, for example for a network, the optical member not being bonded to the fixing device.

The fixing device of the optical member 12 is then fixed on the support 14 by using the open loops 28 of the fixing device. For this, the open loops 28 are again opened by a radial spacing means to engage each of them around one of the fixing studs of the support. This angular aperture is made with a smaller amplitude than in the step of opening the flange 24 in order to guarantee a minimum retention of the optical member 12 in the fixing device.

The open loops 28, each constituting a fastener member thus engaged around the fixing studs of the support, make it possible to ensure that the fastening device of the optical member is held in position on the support.

The clamping force on the flexible lamellae is decoupled by a factor of about 10 with respect to the mounting force of the fasteners on the fixing studs of the support. With such a ratio of effort, the invention guarantees a clamping dispersion of about ± 10% for temperatures of 80 K and pairs of materials such as glass, silica for the optical member, aluminum for the support and titanium for the clamp of the fastening device.

For optical organs of a few grams and holding forces of several hundred grams, it has been shown by the inventors that the invention provides a maintenance in position by friction that largely withstands 10 G quasi-static.

Such a fixing device can be implemented in any optical instrument subjected to large temperature variations, in particular any optical instrument used in the infrared at 80 K such as cameras, telescopes, etc. A fastening device according to the invention makes it possible to hold the optical member firmly and precisely without sticking and without deformation, in particular in a cryogenic environment. The invention also has the advantage of providing a very precise isostatic centering and allows a stack of optical members on the mounting pads of the support.

In addition, the absence of bonding allows adjustment in rotation of the optical member along its axis of revolution, which is very useful for adjusting for example optical networks or prisms.

In addition, its high compactness makes it possible to insert it in a small space and to associate several of them in a system for fixing a plurality of optical members.

Of course, the present invention is not limited to the examples and embodiments described and shown, but it is capable of many variants accessible to those skilled in the art. For example, a person skilled in the art will adapt the number and the position of the open loops and slats in order to be able to use a fixing device according to the invention for fixing optical members of substantially rectangular or square shape in order to preserve the advantages described herein. -before.

Claims

1. Fixing device (16; 56) for at least one optical element (12; 72; 82; 92), said fixing device being adapted to be mounted in a support (14; 74; 84; the at least one optical member, said support comprising a cavity (18) and at least three fixing studs (20) at the periphery of the cavity intended to receive a fixing member of the fixing device, wherein said fixing device comprises a flange (24) with an inner face (26) to be positioned facing the at least one optical member (12; 72; 82; 92), and at least three fasteners to allow engagement with the mounting studs (20). ), characterized in that

the flange (24) is of elastically deformable material and comprises at least three open loops (28) of said material constituting fasteners, connected in continuity of material by segments (30) of said material; and

the fixing device comprises at least three lamellae (32; 52), each made of an elastically deformable material and comprising a first (34) and a second end (36; 66) and are each connected by their first end (34) to the inner face (26) of the flange (24; 76,77; 96) and their second end (36; 66) are for holding the at least one optical member (12; 72; 82; 92) in contact.

2. Fastening device according to claim 1, characterized in that the open loops (28) constituting the fasteners are distributed at equal angular intervals.

3. Fastening device according to claim 1 or 2, characterized in that the open loops (28) constituting the fasteners are each formed of an arc subtending an angle between 180 ° and 320 °.

4. Fastening device according to any one of claims 1 to 3, characterized in that each open loop (28) constituting the fasteners is adapted to open or close by elastic deformation to open or close the angles between the second ends (36; 66) of the flexible strips (32; 52) and the inner face (26) of the flange (24).

5. Fastening device according to any one of claims 1 to 4, characterized in that the flange (24) is of material having a coefficient of thermal expansion greater than or equal to S. 10 K ^-1 .

6. Fastening device according to any one of claims 1 to 5, characterized in that the flange (24) is made of material having a Young's modulus greater than 70 MPa.

7. Fastening device according to any one of claims 1 to 6, characterized in that the flange (24) is made of material comprising mainly titanium.

8. Fastening device according to any one of claims 1 to 7, characterized in that the flange (24) is substantially circular, elliptical or triangular.

9. Fastening device according to any one of claims 1 to 8, characterized in that the optical member to be fixed (12; 72; 82; 92) comprises a circumferential groove (38) and in that each strip (32) ) is adapted so that their second end (36) is inserted into the circumferential groove (38) of the optical member to be fixed (12; 72; 82; 92).

10. Fastening device according to any one of claims 1 to 8, characterized in that each strip (52) comprises at its second end (66) in contact with the optical member to be fixed a lateral holding means (68). of the U-shaped optical member to be fixed (12; 72; 82; 92).

11. Fastening device according to any one of claims 1 to 10, characterized in that the optical member to be fixed (12; 72; 82; 92) is selected from the list consisting of a filter, a gray, a prism , a network and a lens.

12. Fastening system (10; 70; 80; 90) of at least one optical element (12; 72; 82; 92) comprising a support (14; 74; 84; 94) comprising at least one cavity (18) and at least three attachment studs (20) for receiving the at least one optical member (12; 72; 82; 92) and at least one attachment device (16; 56) according to any one of claims 1 to 11.

13. Cryogenic device comprising at least one fastening system (10; 70; 80; 90) of at least one optical member (12; 72; 82; 92) according to claim 12.

14. A method of manufacturing a fastening device (16; 56) according to any one of claims 1 to 11 characterized in that it comprises at least one step of cutting by electro-erosion to the son of the flange (24). ) of the fixing device.

15. A method of fixing at least one optical member (12; 72; 82; 92) on a support (14; 74; 84; 94) by means of a fastening device (16; 56) according to the invention. any one of claims 1 to 11, comprising the steps of:

installation of the optical member inside the open flange;