Two-partite Optical Components With Air Space

Abstract

A multiple lens combination with an air space in which at least three similar spacer bodies of the type which are commercially available in large quantities with relatively small tolerances, such as steel balls, are held in abutment against an internal bore of the lens mounting by a cage ring whereby the quotient of the permissive tolerance of the air space between the mutually facing lens surfaces and the diameter tolerance of the internal bore is at least approximately equal to the tangent of the wedge angle of the air space at its edge.

Description

The present invention relates to multiple lens combinations, and more particularly to multiple lens combinations having an air space between components thereof.

The present invention is concerned with the task to be able to maintain in objectives composed of several lenses, the air space between two lenses or components within smallest possible tolerances also in case of manufacture of large series. It is known in connection therewith to insert intermediate rings between the lenses placed loosely into the mounting or barrel; if the air space has to be kept within narrow tolerances, then the rings have to be machined correspondingly accurately whence they are then very costly. The same is true in case that the lenses are mounted in rings which abut against one another with one surface each and thus have to be matched very accurately at these surfaces.

In contradistinction thereto, the present invention proposes to determine the air space between two lenses or components by spacer bodies which are available in very large numbers and generally with very high dimensional accuracies. Thus, it is known for many decades in connection with telescope achromats of the two-component lens type, to determine the very narrow air space between the two lenses by a tin-foil ring or also by only three small tin-foil pieces which are mounted equidistant along the edge. The objective designer calculates from the predetermined axial length of the air space and from the curvatures of the abutting surfaces, the air space thickness at the lens edge, tin-foil of this thickness can be selected by relatively simple thickness measurements that can be carried out accurately. More appropriate is the reverse method followed for quite some time which consists of selecting a commercial value or size for the edge thickness of the air space and the thickness of the tin-foil or of another intermediate layer corresponding thereof, of calculating from the abutting radii of the surfaces the axial length of the air space and of matching thereto the correction of the system. This method is also applicable to the subject matter of the present invention.

The present invention modifies the described method especially in the direction of larger air space lengths, in that it utilizes as spacer bodies for the determination of the air space lengths, mechanical measuring or standardized parts, for example, steel balls inserted between the surfaces. Such balls are, as is known, commercial items available everywhere and at all times with very small tolerances in the diameter thereof. In the same manner as described above, the diameter of the steel balls is, for the most part, predetermined, and the calculation is matched thereto; more rarely is it appropriate to determine the required diameter from the given air space thickness.

In order to secure three balls which--as is known--define an unequivocal position of the mutually facing lens surfaces, equidistantly at the edge, it is necessary to keep the recess or bore of the mounting in those places, where the balls abut thereat according to the present invention, within tolerances in accordance with the differences in radii of curvature of the two abutting glass surfaces. The quotient of the possible tolerance of the air space, on the one hand, and of the tolerance of the diameter of the bore, on the other, is thereby equal or larger than the tangent of the wedge-angle of the air space at its edge. If, for example, the air space is formed by concentric surfaces, i.e., has the same thickness along the axis as at the edge, as measured perpendicularly to the surfaces, then the bore of the mounting may be kept within very large tolerances at this place because a displacement of the balls in the radial direction does not influence at all the air space.

However, the more the shape of the air space approaches a converging or dispersing lens, the more the bore for the abutment of the balls has to be kept within small tolerances, i.e., the smaller the tolerance for the bore. If the air space has the shape of a dispersing lens, then a force exists seeking to press the balls toward the outside, and the balls abut without further measures at the bore of the mounting; by the use of a conventional cage ring which may be force-locking, though not decisive from any point of view, it is easy to assure the same spacing and a spatially unchanged position of the balls.

If, however, the air space has the shape of a converging or focusing lens, then there results a force seeking to press the balls toward the inside which has to be absorbed by the cage ring.

The cage ring presses the balls outwardly, even when self-locking exists due to friction. For this purpose, the cage ring is made according to the present invention from elastic material, for example, of synthetic resinous material of any known type, and is so dimensioned that a pre-stress exists at all times which presses the balls outwardly with sufficient force.

If, however, the air space should be wedge-shaped so strongly at the place of the balls that no self-locking occurs any longer as a result of friction, i.e., if the axial pressure holding together the lenses in the mounting endeavors by means of a component to displace the balls inwardly, then the force supplied by the cage ring has to be chosen carefully and must be clearly larger in order to prevent the same with certainty. It is then appropriate to construct the cage ring rigidly.

The axial lens pressure in the mounting and the radial pressure exerted by the cage ring on the balls thus must be able to be appropriately matched to each other. Consequently, it is part of the present invention that the lenses are held axially in the mounting or barrel by the interposition of an elastic member, for example, of a rubber ring. This ring is appropriately an intermediate layer or spacer between a lens and a securing member, for example, a threaded or bayonet ring, mounted in the normal manner.

During the tightening of such a ring there exists the danger that a tangentially effective force is exerted on the elastic intermediate layer and therewith on the lens adjacent thereto, which has as a consequence a rotation of the entire arrangement, or at least of one lens thereof. This, however, leads to mutual proportioning of the radial and axial forces that is not completely satisfactory. It is therefore additionally proposed according to the present invention to insert a rigid intermediate or spacer ring between the securing member and the elastic intermediate layer which rigid intermediate ring is secured against rotation by conventional means. The axially effective pressure is then produced by a means determining the same, for example, by means of three screws extending in the axial direction through the securing element which are tightened with a measurable force and abut against the intermediate ring.

It can be readily seen that the axial pressure which is transmitted from the lens surfaces to the three balls, for the most part comparatively small in diameter, involves only very small surfaces of the lenses so that elastic indentations in the glass and therewith reductions of the air space lengths exceeding the permitted tolerances occur already at very slight axial pressures which do not assure a position of the lenses secure against rotation.

Consequently, it is part of the present invention to utilize more than three balls for the definition of the air space which is appropriate when the permissive tolerance of the air space is clearly larger than the diameter tolerance of the balls. With a very small axial pressure, the two mutually facing lens surfaces initially abut or rest on three balls. If the pressure is increased, then flat impressions or indentations in the lens surfaces result from these three balls, however, further balls assume little by little portions of the increasing pressure force until finally all of the balls more or less carry out a support function whereby the deepest elastic indentation in one of the lens surfaces is approximately equal to the tolerance range of the ball diameter. It has been found that this amount in practice does not lead by a long shot to the destruction of the lens surface.

Instead of securing the rigid intermediate ring located between the elastic intermediate layer and the securing member against axial rotation, this locking action can be realized also directly at the lenses. It is part of the present invention to insert into the mounting, appropriately at the outer surfaces of the lenses, an elastic member with strong surface friction, for example, a soft rubber ring which is only slightly deformed by the lens; the correct position of the lens continues to be determined, as before, by its abutment at a rigid mounting part.

Instead of such a ring, there may also be provided in a mounting portion a bore disposed parallel to the axis, which meets in one place at least the mounting support of the cylindrical lens edge, if possible, however, also the axial support of a lens surface. After the assembly of all lenses and mounting parts, this opening, appropriately a dead-end bore, is filled with an adhesive and curable material so that the lens is connected into one piece with the mounting, at least to the extent that the rotation is prevented. In order to avoid a corrosion of the spacer bodies, the optical components may be closed off in a tight manner on both sides by elastic rings.

These and further objects, features, and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawing which shows, for purposes of illustration only, several embodiments in accordance with the present invention, and wherein:

FIG. 1 is a partial axial cross-sectional view through a first embodiment of a multi-lens combination with an air space in accordance with the present invention;

FIG. 2 is a partial transverse cross-sectional view, at right angle to the axis of the multiple lens combination, through a cage ring in accordance with the present invention;

FIG. 3 is a partial axial cross-sectional view through a second embodiment of a multiple lens combination with an air space in accordance with the present invention; and

FIGS. 4, 5, and 6 are partial cross-sectional views through still further modified embodiments of multiple lens combinations with an air space in accordance with the present invention.

Referring now to the drawing wherein like reference numerals are used throughout the various views to designate like parts, and more particular to FIG. 1, reference numeral 1 designates in this figure a converging or focusing lens and reference numeral 2 a dispersing lens which are held inside a conventional mounting 3; both lenses 1 and 2 are secured by the elastic intermediate layer 4, for example, in the form of a rubber ring, and by a locking ring 5. Appropriately, a stepped cut 6 is provided for that purpose at the lens 2. Reference numeral 7 designates a conventional lacquer protection which forms no part of the present invention and which, adhesively applied, secures the various parts against mutual rotation after drying or curing of the lacquer.

Three steel balls 12 of identical diameter and placed along the edge between the lenses 1 and 2 serve for the definition of the air space between the two lenses; the steel balls 12 are held equidistant, on the one hand, by the cage ring 13 made of conventional synthetic resinous material and are pressed, on the other, by the cage ring 13 against the internal bore 14 of the mounting 3, whose diameter tolerance may be the larger the more parallel the mutually facing surfaces of the lenses 1 and 2.

A part of the cage ring 13 is shown in FIG. 2 in a transverse cross section as viewed in the axial direction; each of the three steel balls 12 is pressed outwardly by a web 15 of the ring 13.

FIG. 3 illustrates a mounting 3 with more than three balls 12 and a rigid cage ring 13; the lens 1 is secured against axial rotation by the soft rubber ring 16.

In FIG. 4, a subsequently injected and cured synthetic resinous material plug 17 in a bore of the mounting 3 secures the lens 1 against rotation.

In both FIGS. 3 and 4, reference numeral 18 designates a rigid intermediate ring secured against rotation.

In FIG. 5, the rigid ring 4 is pressed against the lens 2 with predetermined measurable force by the use of several screws 19 distributed over the circumference; the screws 19 are supported in the securing element 5 which is in the form of a threaded ring.

FIG. 6 finally illustrates a sealing ring 20, for example, made from silicon rubber which in conjunction with the soft rubber ring 16 seals off the air space between the lenses 1 and 2 and therewith the space between the same against the outside.

While we have shown and described several embodiments in accordance with the present invention, it is understood that the same is not limited thereto but is susceptible of numerous changes and modifications as known to those skilled in the art, and we therefore do not wish to be limited to the details shown and described herein but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims.

Claims

We claim:

1. The combination of a lens mounting and of a two-partite optical component with an air space therebetween mounted within the lens mounting, characterized in that at least three similar spacer members in the form of balls which are adapted to be made in large quantities with relatively narrow tolerances serve for defining the air space and are held abuttingly against a bore of the lens mounting by a cage ring means and in abutment with the mutually facing lens surfaces of the two-partite optical component, and in that the quotient of the permissive tolerance of the air space between the mutually facing lens surfaces and the diameter tolerance of the bore are at least approximately equal to the tangent of the wedge angle of the air space at its edge formed by the curvature of the spaced mutually facing lens surfaces.

2. The combination according to claim 1, characterized in that said spacer members are steel balls.

3. The combination according to claim 1, characterized in that the abutment force, by means of which the spacer members are pressed radially against the internal bore, is larger than the force component effective in the radial direction which results from the force exerted in the axial direction on the lenses by elastic intermediate means and from the angular position of the surface areas of the lenses in contact with the spacer members.

4. The combination according to claim 1, characterized in that steel balls having substantially the same diameter within small tolerances, which are used as spacer members, form an essentially gapless ring.

5. The combination according to claim 3, characterized in that an intermediate rigid ring secured against rotation is disposed between the elastic intermediate means and the securing means.

6. The combination according to claim 5, characterized in that the axial pressure is produced by at least three axial, threaded elements which press the intermediate ring with predetermined force against the elastic intermediate means.

7. The combination according to claim 3, characterized in that an elastic element of large surface friction is provided between an outer lens surface and the mounting.

8. The combination according to claim 7, characterized in that a plug is provided near the edge of a lens.

9. The combination according to claim 8, characterized in that said plug has a high inherent friction.

10. The combination according to claim 8, characterized in that said plug has a high adhesive force.

11. The combination according to claim 7, characterized by seal means for sealing the air space between the lenses against the outside.

12. The combination according to claim 7, characterized in that said seal means include elastic rings.

13. The combination according to claim 1, characterized in that said quotient is larger than said tangent.

14. The combination according to claim 1, characterized by securing means retaining the lenses in the mounting, and intermediate means between the lenses and said securing means.

15. The combination according to claim 14, characterized in that an intermediate rigid ring secured against rotation is disposed between the elastic intermediate means and the securing means.

16. The combination according to claim 14, characterized in that the axial pressure is produced by at least three axial, threaded elements which press an intermediate ring with predetermined force against the elastic intermediate means.

17. The combination according to claim 1, characterized in that an elastic element of large surface friction is provided between an outer lens surface and the mounting.

18. The combination according to claim 1, characterized in that a plug is provided near the edge of a lens.

19. The combination according to claim 18, characterized in that said plug has a high inherent friction.

20. The combination according to claim 18, characterized in that said plug has a high adhesive force.

21. The combination according to claim 1, characterized by seal means for sealing the air space between the lenses against the outside.

22. The combination according to claim 21, characterized in that said seal means include elastic rings.

23. The combination of a lens mounting and a multiple lens optical system of spaced lenses arranged in said lens mounting, characterized in that at least three similar spacer members adapted to be made in large quantities with relatively narrow tolerances are held in contact with mutually facing refractive surfaces of the lenses and abuttingly against a bore of the lens mounting by a cage ring means such that the lenses are maintained a fixed axial distance apart.

24. The combination according to claim 23, wherein the spacer members are balls.