Opto-mechanical apparatus adapted for mounting optical elements with small cross sections

An opto-mechanical assembly including a housing and an internally supported optical element, such as a lens, mounted along an axis. At least one of the housing and optical element includes a radially extending chamber. Adhesive disposed in the chamber interacts with the housing and the optical element to prevent axial motion between the optical element and housing.

BACKGROUND OF THE INVENTION

Field of the Invention

This invention generally relates to optical-mechanical apparatus and more specifically to opto-mechanical apparatus having a small cross section that includes a housing and an optical element.

Description of Related Art

A significant effort has been made and continues to be made toward the development of opto-mechanical apparatus with increasingly smaller transverse cross sections. This is particularly true in the medical field where diagnosis and related treatment regimens for endoscopic devices is expanding with the introduction of smaller, reliable and reasonably priced opto-mechanical apparatus. Presently there are efforts underway to produce cylindrical lenses that have diameters less than 2 mm and even in the range of 1 mm or less.

Such small opto-mechanical apparatus generally has several major components. For purposes of describing this invention there are two such components, namely: (1) an optical element that may comprise a lens, an optical window or combination of one or more of each and (2) a housing that supports each optical element on an optical axis. As the demand for smaller and smaller diameter lenses continues to increase, new problems have emerged that can detract from the efficacy of such new apparatus. First, the housing can overlie the imaging surface of an optical element and thereby reduce the optical field of view for that apparatus. Second, the method by which the optical device is retained in the housing can fail during use. Third, such apparatus must be constructed so that its exterior surface is smooth for easy cleaning.

FIG. 1depicts a prior art opto-mechanical assembly10that maximizes the field of view, but includes a retaining structure that is subject to failure. The assembly10includes a conventional biconvex lens11as an optical element. A housing12has a distal end13and aligns the lens11along an optical axis14. The right side of the assembly10inFIG. 1extends to a proximal end (not shown, but known in the art). The housing12also contains an integral, radially inwardly extending band15that forms a shoulder or seat16against which the proximal side of the lens11seats. Adhesive material17fills gaps18and19between the outer periphery of the lens11and the coextensive spaced inner surfaces of the housing12. When completed, the distal ends of the lens11and the housing12are flush and create a smooth surface to facilitate cleaning and reduce contamination during use by eliminating any crevices or the like in the apparatus. The retention of the lens11within the housing12of this apparatus10, however, depends solely upon the adhesion that exists between the adhesive material17and the adjacent surfaces of the lens11and housing12. Such adhesion, in turn, depends upon the contact area for the adhesive material that, in the configuration ofFIG. 1, is proportional to lens diameter and length. Adhesion is also dependent upon the surface roughness and the materials that contact the adhesive material.

Such opto-mechanical assemblies can be subjected to environmental conditions that create forces on the bonds produced by the adhesive material. Such forces can be generated by accident, as by exposing the bond to a mechanical shock, by dropping the assembly, or by wide temperature or other environmental factors that produce differential expansions of the lens11and the housing15. If such a force is large enough to exceed the adhesion characteristics of the adhesive material17, the adhesive material could decouple from the lens11and/or housing12whereupon the bi-convex lens11could shift distally and become unstable axially or even completely separate from the housing12. In either event, the opto-mechanical assembly10would require factory repair or even replacement. Also, if the lens11were to separate from the housing12, negative consequences for the procedure being performed with the assembly could result. Thus, as will be apparent to those skilled in the art, the specific opto-mechanical assembly inFIG. 1provides a maximum field of view and smooth distal surface, but a less than optimal resistance to shock and other environmental factors.

FIGS. 2A and 2Bdepict variations of opto-mechanical assemblies that utilize mechanical retention structures that, as will become apparent, strengthen the retention characteristics, but also decrease field of view and result in non-smooth surfaces.FIG. 2Adiscloses an opto-mechanical assembly20with a housing21and a plano-convex lens22. The opto-mechanical assembly20has an optical axis23. In this variation, an angular radially inwardly extending lip24forms a positioning stop25that blocks any distal shift of the lens22. During manufacture, the lens22is inserted from the proximal end of housing21until it reaches the shoulder25. Thereafter, a mechanical element such as a lens spacer26is inserted into the housing21from the proximal end. Other means lock the lens spacer26into its axial position so the lens spacer26blocks any proximal shift of the lens22.

In the other variation ofFIG. 2Ban opto-mechanical assembly30includes a housing31with a bi-convex lens32extending along an optical axis33. The lens32is loaded into the housing from the distal end34until it contacts a shoulder on a positioning band35that is integral with the housing31thereby to block any further proximal lens shift. At a distal end34, the housing31receives a retainer element36that includes an internally threaded extension37that mates with an axially distally extending extension38from the housing31. A radially inwardly extending lip39engages the lens32and prevents any distal lens shift of the lens32.

Each of these embodiments provides a structure that blocks any proximal or distal shift and that can withstand mechanical shock, and other environmental conditions that generate forces between the optical and mechanical elements. However, the lip24inFIG. 2Aand the lip39inFIG. 2Blimit the field of view because they overlap the distal ends of the lenses22and32respectively, thereby reducing their clear apertures and because they extend axially beyond the distal lens surface. In addition, as these retaining structures extend beyond the distal surface of their respective lenses, the distal surface of the lens22inFIG. 2Aand the distal surface of the lens32inFIG. 2Bare not flush with the distal most surfaces of the housings21and32, respectively. Cleaning of the exterior surface, which is not smooth, is therefore more difficult due to the interior angles. These non-smooth surfaces also act as locations for buildup of contamination during use. For an opto-mechanical assembly of a given size, the cost of adding in separate locking elements and fastening them in a secure manner increases the expense of manufacture. Moreover, as the apparatus size decreases, manufacturing complexity and concomitant costs increase. In fact for lens assemblies that are very small, for example less than 2 mm, the cost of adopting such a construction technique can become commercially and technically prohibitive.

What is needed is an opto-mechanical assembly that is adapted for including small optical elements in a small housing that optimizes field of view, that optimizes the mechanical structure for reliable mechanical containment and that facilitates cleaning. What also is needed is such an apparatus that is commercially and technically feasible.

SUMMARY OF THE INVENTION

Therefore it is an object of this invention to provide an opto-mechanical assembly that provides a reliable mechanical connection between an optical element and a housing for carrying that optical element.

Another object of this invention is to provide an opto-mechanical assembly in which one surface of an optical element is flush with one end of a housing and in which any axial shift of the optical element is blocked.

Still another object of this invention is to provide an opto-mechanical assembly that provides a reliable mechanical connection for an optical supporting housing and that maximizes field of view.

Yet another object of this invention is to provide an opto-mechanical assembly that provides a reliable mechanical connection for an optical element in a supporting housing and that is commercially and technologically feasible.

In accordance with one aspect of this invention, an opto-mechanical assembly as at last one end and comprises an optical element, a mechanical housing, a cavity in at least one of said optical element and mechanical housing, and adhesive in each cavity. The optical element has first and second polished end surfaces and an intermediate body portion through which light passes and has a given outer periphery and a given cross section transverse to an optical axis for the opto-mechanical assembly. The mechanical housing positions the optical element along the optical axis at the one end so that the first polished end surface of the optical element is substantially flush with the one end of the mechanical housing. A cavity is formed in one of the optical element and mechanical housing. The mechanical properties of the adhesive in the cavity enable the adhesive to lock the optical element axially within the mechanical housing independently of any adhesive bond.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

InFIG. 3an opto-mechanical assembly40includes a mechanical housing41and an optical element in the form of a bi-convex lens42. As known, such lenses have first and second end surfaces and an intermediate body portion through which light passes. A specific optical element may have a circular or polygonal cross section and other peripheral features. InFIG. 3the bi-convex lens is cylindrical.

The mechanical housing41includes an integral positioning band43that forms an annular stop for blocking any proximal shift of the lens42(i.e., to the right inFIG. 3). The housing41also supports the lens42along an optical axis44. The positioning band43locates the lens42so its distal surface45is flush with a distal end surface46of the housing41.

In accordance with this invention, adhesive50is disposed about the periphery of the lens42and the corresponding surfaces of the housing41. More specifically and referring toFIGS. 3 and 4, the housing41includes a lens body engaging portion51with a diameter that is slightly larger than the lens diameter such that a gap exists between the surfaces52of the housing41and53of the lens42. A peripherally extending annular channel54forms an inwardly facing cavity55that is intermediate the housing distal end surface46and is distal to the positioning band43. The housing also defines a reduced diameter opening56that extends from the channel54to the distal end surface46.

Still referring toFIG. 3, the distal surface45of the lens42is beveled at57to form a relief that defines a second cavity58between the inner surface of the housing41and channel54. The cavities55and58have openings facing each other. Thus when adhesive material50fills the cavities55and58and a peripheral gap59, the adhesive material50in the first and second cavities55and58maximizes the retentive function of the adhesive material and minimizes its failure due to shock. This occurs because failure of the adhesive material structure requires a greater force than is necessary to overcome the bonding forces in the apparatus ofFIG. 1for smaller lenses. As will also be apparent, the addition of the elements in the apparatus ofFIG. 3reduces the field of view of the optical element, such as the lens42, less than would a mechanical retainer extending distally to the surface of the lens42.

FIGS. 1, 2A, 2B and 3disclose cross sections of circular housings and cylindrical lenses.FIGS. 5 and 6depict a view of the distal end of a completed opto-mechanical assembly60with a cylindrical housing61that supports a rectangular optical window62in a matching rectangular passage such that the distal surface63of the optical window62is flush with the distal end surface64of the housing61. Adhesive material65appears as a wide band66across one side of the optical window62and as narrow bands67along the other sides of the optical window62. Other patterns of adhesive placement could be substituted for the specifically disclosed pattern.

As shown in more detail inFIG. 6, the housing includes a relief in the form of a channel70formed in one side of the housing passage surface that defines a housing cavity71that opens toward a coextensive portion of the optical window62. The optical window62has a relief in the form of a bevel72that defines a second cavity73that opens toward the first cavity71. The openings of the cavities71and73inFIG. 6also enable the adhesive material65to fill each of the cavities71and73. The adhesive material65between the edge of the optical window62and the coextensive surfaces of the housing passage forms a continuous adhesive body with portions in each of the cavities71and73. The housing is also formed with an internal positioning band74for seating the optical window62and blocking any proximal shift of the optical window62after assembly. Similarly toFIG. 3, the opto-mechanical assembly60ofFIG. 6includes adhesive material65in the cavities71and73to form a mechanical structure that blocks any distal shift of the optical window62, even in the event of failure of the adhesive properties of the adhesive material. As will also be apparent, the addition of the cavities71and73and contained adhesive material65does not reduce the field of view for the opto-mechanical apparatus60as much as would a mechanical retainer extending distally to the surface of the window62.

FIG. 7depicts another version of opto-mechanical assembly60ofFIG. 6. This embodiment is useful when there is only a minimal risk of failure of one of the adhesive bonds, particularly the bond between the adhesive material65and the housing61during specified use of the opto-mechanical assembly60. Using the reference numbers ofFIG. 6, this variation of the opto-mechanical assembly60inFIG. 7has the cylindrical housing61that supports the rectangular optical window62such that the distal surface63of the optical window62is flush with the distal end surface64of the housing61. Adhesive material65appears as a wide band66across one side of the optical window62and as narrow bands67along the other sides of the optical window62. If the bond between the adhesive65and the lens63were to fail without breakage of the adhesive, the adhesive in the wide band66mechanically locks the lens63axially in place independently of any bond failure. That is, inFIG. 7, the cavity70shown inFIG. 6is eliminated.

As will now be apparent, the embodiments of this invention shown inFIG. 3connection between an optical element and a supporting housing. Each provides an apparatus in which an exterior surface of an optical element is flush with a corresponding housing surface for easy cleaning. Each provides an optical apparatus in which the disclosed retention structure minimizes the reduction of the field of view for the apparatus and that is commercially and technologically feasible to manufacture.

This invention has been disclosed in terms of certain embodiments. It will be apparent that many modifications can be made to the disclosed apparatus without departing from the invention. For example, the disclosed optical apparatus includes lenses of different shapes. For different implementations apparatus incorporating this invention could include lenses of other shapes or types.FIGS. 3 and 4disclose cavities that extend about the cylindrical inner surface of a housing.FIGS. 5 through 7disclose rectangular optical elements with cavities positioned only along one complete side. In other embodiments a cavity may extend only over a portion of a specific surface. Specifically disclosed cavity cross-sections may be replaced by cavities of different cross-sections. Each of the embodiments inFIGS. 3, 5 and 7depict apparatus wherein the adhesive is applied axially from the distal end of the apparatus. As an alternative more radial fill holes could be incorporated in a housing for directing adhesive from a supply through the wall of the housing to a channel or other gap between the housing and the lens. Therefore, it is the intent of the appended claims to cover all such variations and modifications as come within the true spirit and scope of this invention.