WO1993010581A1

WO1993010581A1 - Mounting for a laser mirror

Info

Publication number: WO1993010581A1
Application number: PCT/US1992/009888
Authority: WO
Inventors: James Harmon Fisher; Michael Gerard Ressl
Original assignee: Amoco Corporation
Priority date: 1991-11-15
Filing date: 1992-11-16
Publication date: 1993-05-27
Also published as: EP0571603A1; JPH06504883A

Abstract

An optical mounting (10) is disclosed having a base (12) and receiving means (14) for receiving an optical component (40). The receiving means (14) has a wall (24) of generally elastic material which has a circumferential exterior groove (28) such that when opposite ends of the wall (24) are compressed together a portion of the interior surface of the wall (24) is moved inwardly to fix the position of the optical component (40) relative to the wall (24). The base (12) and the receiving means (14) are connected together by a thin bendable tube (20).

Description

MOUNTING FOR A LASER MIRROR Technical Field

This invention relates to the general subject of optics, and in particular to devices used to adjustably mount an optical component of a laser.

Background of the Invention

Lasers utilize, for their operation, an active material located within a laser cavity which is made optically resonant by placing reflectors at either end thereof to form the optical resonator of the laser. One of the reflectors functions as an output coupler or means for transmitting laser light out of the laser cavity. Resonator reflector design is often specified to be within 1/10 or 1/20 of a wavelength of light and frequency to be within 1/100 of a wavelength of light. In other words, deviations in excess of 1/1,000,000 of an inch may not be acceptable.

It has long been recognized that the alignment of all of the laser components is of critical importance in order to maintain maximum output. Especially important is the alignment of the output coupler. US Patent 4,730,335, which is assigned to the assignee of the present invention, describes one means by which laser components are aligned. US Patent 4,890,296, which is also assigned to the assignee of the present invention, describes another means for mounting the output coupler of a laser.

Laser systems also may make use of one or more optical mirrors for bending, splitting, focusing or redirecting beams of light. These mirrors are usually attached to some form of mounting device which is anchored to a supporting surface. It is essential that the mirrors, or other optical components in the path of the laser beam, are in precise and accurate optical alignment with respect to the impinging beam of light. Quite often, after the mounting device is affixed to the supporting surface, some adjustment is necessary. In the past, adjustments have been achieved by inserting one or more shims between the mount and the supporting surface or base. Some of the disadvantages of this technique are that: it very often involves removing the fasteners which are used to affix the mount to the supporting surface; it is time consuming; that it is not always very accurate; and it is sometimes very difficult to carry out successfully. Small adjustments may be very difficult to make.

Another approach has been to use ball and socket joint mounting devices or double gimbel type mounting devices to hold a mirror on the supporting surface. Although these types of mounting devices enable controlled adjustments to be made, they are relatively expensive and hence not very practical for many applications.

Another difficulty has been the means by which an optical component is secured to the mounting. Humidity changes and shock can cause undesired movements. Press fitting and gluing, while good, are not easily applied. Glues and bonding agents are also difficult to remove. Adhesives can also outgas and coat the surfaces of optical components and mirrors.

Clearly, there is a need for a simple and relatively inexpensive mounting for an optical component which has an easy to use adjustment capability and a sturdy, clean and rigid means for holding an optical component in such a mounting. Summary of the Invention

A general object of the invention is to provide an adjustable mounting for an optical component of a laser.

Yet another object of the invention is to provide a mounting for an optical component having deformable means for mechanically holding the optical component in place.

Still another object of the invention is to provide an apparatus for adjustably mounting an output coupler of a laser.

One specific object of the invention is to provide a means for mechanically holding an optical component in a cup-like mounting having mechanically compressible walls.

Another object of the invention is to provide an optical component which is aligned by bending a metal support beyond its elastic limit.

In accordance with the present invention, an optical mounting is provided comprising: a base which is adapted to be fixedly held in place and which defines a reference axis; and receiving means, carried by said base, for receiving an optical component, said receiving means having a receiving optical axis which is generally parallel to said reference axis, and having a wall of generally elastic material which has two opposite axial ends, which defines an optic receiving interior and an exterior, and which has a groove located intermediate said ends of said wall and along said exterior of said wall, said groove having a depth and width such that when said ends of said wall are compressed together a portion of said interior surface of said wall which is adjacent to said groove is moved inwardly and towards said reference axis to fix the position of said optical component relative to said wall.

The apparatus allows one to securely hold an optical component in place. By using a thin walled tube to join the base to the receiving means and inelastically bending the tube, the axis of the secured optical component can be easily tilted. Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention, the embodiments described therein, from the claims, and from the accompanying drawings.

Brief Description of the Drawings FIG's. 1, 2 and 3 are bottom, cross-sectional side and top views of one embodiment of the optical mounting that is the subject of the present invention; FIG's. 4 and 5 are partial, enlarged cross-sectional views of the top or upper end of the optical receiving means which is the subject of the present invention;

FIG. 6 is a perspective view of the optical mounting of FIG's 1, 2 and 3; FIG's. 7, 8 and 9 are bottom, cross-sectional side and partial top views of another embodiment of the present invention;

FIG. 10 is a perspective view of the moving means shown in FIG's.

8 and 9;

FIG. 11 is a partial perspective view of the mounting shown in FIG's. 1. 8 and 9.

FIG. 12 is an exploded assembly drawing of the mounting of FIG's. 7, 8 and 9; and

FIG. 13 is a side elevational view of the mounting of FIG. 8 when the moving means of FIG. 10 is used to change the position of the optical receiving means.

Detailed Description While this invention is susceptible of embodiment in many different forms, there is shown in the drawings, and will herein be described in detail, two specific embodiments of the invention. It should be understood, however, that the present disclosure is to be considered an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated. Turning to FIG. 6, one embodiment of the optical mounting 10 which is the subject of the present invention is illustrated. In particular, the mounting 10 comprises a generally circular flat base 12, a cup-like optical component receiving means 14 for receiving an optical component 40 therein (See FIG. 12) and a thin walled tube 20 which joins the base to the receiving means. In the embodiment illustrated, the base 12 has three mounting holes 16a, 16b and 16c, three clearance holes 18a, 18b and 18c, and a central aperture 22.

The receiving means 14 comprises generally cylindrical wall 24 and a flat bottom 26. The wall 24 has a circumferential groove 28 along its exterior and a generally smooth interior. The bottom 26 has a central opening 30 and the tube 20 has one end which is open to the central opening in the receiving means 14 and has an opposite end which is open to the central aperture 22 in the base 12. These openings allow light to pass axially therethrough (see arrow 32 in FIG. 4). The exterior groove 28 in the wall 24 has sufficient depth and width (see FIG. 4), relative to the thickness of the wall and the yield strength of the material forming the wall, such that, when the top and bottom ends of the wall are compressed together (see FIG. 5), a portion 28a of the interior of the wall is forced towards the interior of the receiving means 14. Thus, if an optical component 40 is located in the receiving means, one can secure it in place by axially compressing the walls of the receiving means 14. The exact depth and width of the groove are determined, in part, by considering the material properties of the receiving means 14, the thickness of the wall 24 and the differences between the outer diameter of the optical component 40 and the inner diameter of the wall.

In one specific embodiment, the mounting 10 was machined out of one piece of INVAR, the wall 24 had an inner diameter of about 0.31 inches and an outer diameter of about 0.39 inches, the optical component 40 (e.g., a laser output coupler) had an outer diameter of 0.30 inches and the groove 28 was rounded to have a width and depth of 0.03 inches. The tube 20 had a length of about 0.13 inches, an inner diameter of 0.10 inches and an outer diameter of 0.12 inches. Preferably, the ridge 28a (See Fig. 5), which formed when the groove 28' is compressed, should not apply enough force to the optical component 40 to excessively stress it or change its optical properties (e.g., a stress induced birefringence, as in quartz). Turning to FIG. 11 another embodiment 10' of the invention is illustrated. Those parts which are the same as the previous embodiment are identified with similar reference numbers. The major difference is the addition of a circumferential shoulder 50 around the lower end of the receiving means 14' and the addition of a washer-like member or collar 52 (see FIG. 10) which snugly fit around the outside of cylindrical wall 24 of the receiving means 14. The primary purpose of the collar 52 is to provide a means by which the tube portion 20 of the mounting 10' can be bend (See FIG. 13).

The tube portion 20 of either mounting 10 and 10' is made sufficiently thin to allow for easy bending beyond the elastic limit of the material forming the tube portion. In the first embodiment 10 any suitable tool (e.g., pry bar, jack-screws, etc.) can be used for this purpose.

In the second embodiment, the collar 52 is itself a tool which can be easily manipulated by one's fingers or with the assistance of other tools which would increase the mechanical advantage. Bending the tube 20 has the effect of tilting or moving the optical axis 54 of the optical component 40 through an angle θ to a new position 54'. From the foregoing description, it will be observed that numerous variations, alternatives and modifications will be apparent to those skilled in the art. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the manner of carrying out the invention. Various changes may be made, materials substituted and features of the invention may be utilized. For example, although the invention has been described in the context of a mounting for an output coupler of a laser the invention can be used to adjustably support other optical elements, such as an aperture disk. As another example, referring to FIG's. 4 and 5, the wall 24 of the optical receiving means 14 need not be cylindrical (e.g., square, rectangular, etc.) or even continuous (e.g, castellated). Finally, in some situations it may be desirable to make the optical mounting (or at least the tube portion 20) from a shape-memory alloy such as a nickel-titanium alloy (e.g., Nitinol from Shape Memory Applications, Inc., of Sunnyvale, California). Examples of shape-memory alloys are disclosed in U.S. Patent No. 3,174,851; 3,351,463; and 3,403,238 (all patents being assigned to the United States of America as represented by the Secretary of the Navy). Such alloys have a "memory." If it is given a first shape or configuration and subjected to appropriate treatment, and thereafter if its shape or configuration is changed, it will retain that changed shape or configuration until such time as it is subjected to a predetermined elevated temperature. When it is subjected to that temperature, it tends quite strongly to return to its original shape or configuration. Thus, small temperature changes, unevenly applied to the tube portion 20, could be used to gradually tilt the axis 54 of the optical element 40.

Thus, it will be appreciated that various modifications, alternatives, variations, etc., may be made without departing from the spirit and scope of the invention as defined in the appended claims. It is of course, intended to cover by the appended claims all such modifications involved within the scope of the claims.

Claims

CLAIMSClaims is made for:

1. Apparatus, comprising: a) a base which is adapted to be fixedly held in place and which defines a reference axis; and b) receiving means, carried by said base, for receiving an optical component, said receiving means having a receiving optical axis which is generally parallel to said reference axis, and having a wall of generally elastic material which has two opposite axial ends, which defines an optic receiving interior and an exterior, and which has a groove located intermediate said ends of said wall and along said exterior of said wall, said groove having a depth and width such that when said ends of said wall are compressed together a portion of said interior surface of said wall which is adjacent to said groove is moved inwardly and towards said reference axis to fix the position of said optical component relative to said wall.

2. The apparatus of Claim 1, wherein said wall is generally cylindrical in shape; and wherein said groove extends around at least part of the circumference of said wall.

3. The apparatus of Claim 1, further including bendable means for inelasticly and moveably connecting said receiving means to said base and for restricting axial movement of said optical component along said reference axis.

4. The apparatus of Claim 3, further including moving means, carried by said receiving means, for bending said bendable means relative to said base along axes which are generally peφendicular to said reference axis.

5. The apparatus of Claim 4, wherein said wall of said receiving means has a shoulder located along at least a portion of its exterior; and wherein said moving means comprises a collar which is adapted to fit around said exterior of said wall and to be carried by said shoulder.

6. The apparatus of Claim 3, wherein said bendable means comprises a generally thin walled tube having two opposite ends and having an axis which is generally parallel to said reference axis.

7. The apparatus of Claim 4, wherein said moving means includes a portion which is located at a predetermined radial distance from said axis of said tube.

8. The apparatus of Claim 3, wherein said wall is generally cylindrical and has a center axis which is parallel to said reference axis; wherein said bendable means is a cylindrical tube which has a center axis which is generally parallel to said reference axis and which has one end connected to said base and an opposite end connected to said receiving means.

9. The apparatus of Claim 1, wherein said base includes at least one mounting aperature.

10. An optical mounting, comprising: a) a base which has an aperture at its center which defines a reference axis; b) a generally cylindrical wall having two opposite ends, having a circular floor which is connected to one end of said wall and which has a central aperture therein, and having an optical axis generally parallel to said reference axis, said wall having a circumferential exterior groove which is located between its ends and which is of sufficient depth and width such that when said ends of said wall are compressed together at least a portion of the interior of said wall forms a ridge which faces said reference axis, which is located adjacent to said groove and which fixes the position of an optical component relative to said wall; and c) a generally thin walled tube, having two opposite ends and having an axis which is generally parallel to said reference axis, for connecting said receiving means to said base, said tube having a center axis which is generally parallel to said reference axis, having one end connected to said base and an opposite end connected to said receiving means, and having a hollow interior which is in open communication with said aperture in said floor and in said base.

11. The optical mounting of Claim 10, wherein said wall has a shoulder located along at least a portion of its exterior; and further including moving means, carried by said shoulder for bending said thin walled tube relative to said base along axes which are generally peφendicular to said reference axis.

12. The apparatus of Claim 11, wherein said moving means comprises a circular collar which is adopted to fit around said exterior of said wall and adjacent to said shoulder.

13. The optical mounting of Claim 10, wherein said thin walled tube is formed from a shape memory alloy.

14. Apparatus, comprising: a) a base which is adapted to be fixedly held in place and which defines a reference axis; b) receiving means, carried by said base, for receiving an optical component, said receiving means having a receiving optical axis which is generally parallel to said reference axis and having a wall which is made from a generally deformable material, which has two opposite axial ends, which defines an optic receiving interior and an exterior, and which has an exterior groove located intermediate said ends of said wall and in a plane which is generally peφendicular to said reference axis, said groove having sufficient depth and width such that when said ends of said wall are compressed together a portion of said interior surface of said wall moves inwardly and towards said reference axis to fix the position of said optical component relative to said wall; and c) thin wall means, located between said base and said receiving means, connecting said receiving means to said base.

15. The apparatus of Claim 14, further including moving means, carried by said receiving means, for bending said thin wall means relative to said base along axes which are generally peφendicular to said reference axis.

16. The apparatus of Claim 15, wherein said thin wall means comprises a generally thin walled tube having two opposite ends, having an axis which is generally parallel to said reference axis, and having a diameter which much less than the lateral dimension of said receiving means.

17. A mounting for a laser output coupler, comprising: a) a base which is adapted to be fixedly held in place and which defines an opening which defines a vertical reference axis; b) receiving means, joined to said base by a tube, for receiving an output coupler and passing light therethrough, said receiving means having a receiving optical axis which is generally parallel to said reference axis, and having a wall which is made from a generally compressible material, which has two opposite axial ends, which defines an output coupler receiving interior and an exterior, and which has an exterior groove located intermediate said ends of said wall and in a generally horizontal plane, said groove having sufficient size such that when said ends of said wall are compressed together a portion of said interior surface of said wall moves inwardly and towards said reference axis to fix the position of said output coupler relative to said wall; and c) moving means, adapted to be carried by said receiving means, for bending said tube relative to said base along axes which are generally peφendicular to said vertical reference axis.

18. The apparatus of Claim 17 wherein said tube is made of metal; and wherein said moving means is used to bend said tube beyond its elastic limit.

19. The appartus of Claim 17, wherein said tube is made from a shape memory alloy; and wherein said moving means comprises means for heating said tube.

20. A mounting for a laser output coupler, comprising: a) a circular generally flat base which is adapted to be fixedly held in place, which has a central aperture and which defines a reference axis; and b) a generally cylindrical metal cup joined to said base by a thin cylinder, for receiving a laser output coupler, said cup having a receiving optical axis which is generally parallel to said reference axis, having an open top and a generally flat bottom which has an aperture therein and having an exterior circumferential groove which is located intermediate said top and bottom, said groove having a depth and a width such that when said top and bottom of said cup are compressed together a portion of said cup which is adjacent to said groove is moved inwardly and towards said reference axis to fasten said output coupler to said cup, said cylinder having an interior which is open to said central aperture in said base and to said aperture in said bottom of said cup.