GB2195469A

GB2195469A - Holder for optical elements in a mount

Info

Publication number: GB2195469A
Application number: GB08722211A
Authority: GB
Inventors: Wilhelm Schmidt
Original assignee: Carl Zeiss AG
Current assignee: Carl Zeiss AG
Priority date: 1986-09-27
Filing date: 1987-09-21
Publication date: 1988-04-07
Anticipated expiration: 2007-09-21
Also published as: GB8722211D0; JPS6358204U; GB2195469B; DE8625896U1

Abstract

The holder 4 is a closed ring, the cross-section of which has the form of an angle with sides 5,6 exerting spring tension against each other. When the holder 4 is in the holding position in its mount, one of the sides 5 rests on the surface of optical element 1, while the second side 6 engages an annular groove 7 of the mount 2 due to spring action. The optical element 1, e.g. a lens, rests on a support 3. <IMAGE>

Description

SPECIFICATION Holder for optical elements in a mount The present invention relates to a holder for optical elements in a mount in which part of the optical element rests on one side on a support of the mount and is held in this position by an elastic holder resting on part of its other side.

Well-known holders for optical elements have been listed in the book "Bauelemente der Optik" by Naumann/Schraeder (Karl Hanser Verlag München/Wien 1983), pp.

267/273. For all these holders, the mount features a support which determines the position of the optical element and on which parts of one side of the optical component rest.

Furthermore, a mechanical component which rests on the other surface of the optical element is also provided, thus holding the optical element stably in the position given. This mechanical component is mostly in the form of a threaded ring. In order to prevent the axial pressure from exceeding a defined value, the mount is provided with a mechanical stop which is matched to the thickness of the element; this stop limits the rotation of the threaded ring and hence the pressure exerted by it.

Such a holder is relatively expensive, as the mount must feature a thread with a defined stop and as the threaded ring itself is expensive to make.

It is known from DE-GM 7101047 that a holder of a hard elastic plastic material can be used for fastening lens elements in centred optical systems. This holder is in the form of a cylindrical ring with a conically bevelled surface which snaps into position on the inside of the mount behind a protruding annular flange. These holders and the recesses in the mount must be made to a very high accuracy, as there may only be a slight difference between the outer diameter of the holder and the inner diameter of the annular flange of the mount. Such a mount is hence still very expensive.

EP-OS 0 16 29 61 describes a holder for an optical element which features a clamping device consisting of a spring with a U-shaped cross-section. In the holding position, when the optical element rests on a support of the mount, the spring ends of this device engage in undercuts of the mount, with the stressed underside located between the ends resting on the optical element, thus securing it in its axial position. This holder has the disavantage that the optical element is only held by the spring tongues located in the bottom of the clamping device so that the force exerted on the element is not uniformly distributed over the support of the mount. This can lead to undesirable stress and possibly to deformation of the optical component.

The object of the present invention is to provide a holder for optical elements in a mount in accordance with the umbrella term of claim 1 which shall enable the optical element to be held stably in a given position using simple, easy-to-mount parts which can be manufactured at a low price and permit the optical element to be subjected to a force uniformly distributed over the support and limited to safe values.

The invention achieves this object by providing a holder designed in accordance with the characteristics of claim 1.

This holder has the advantage that the mount need only be provided with an easy-tomake annular groove, and that the mechanical holder itself is a simple component made, for example, by injection moulding. For mounting the optical eiement, this mechanical holder is pressed down into the mount, e.g. by using a stamp, until one side engages with the groove of the mount. Here, the mechanical holder is held stably in its given position and the axial pressure does not exceed a given value and acts uniformly on the entire support.

Suitable embodiments of the mechanical holder are described in claims 2-4. By a suitable choice of the length of the connecting side in the embodiment in accordance with claim 3 it is possible to adjust the elasticity of the holder and thus the holding force acting on the optical element.

Claim 5 describes a suitable embodiment of the annular groove which ensures a smooth transition between the mount and the holder when the optical element has been inserted.

The invention is shown by way of example in the accompanying drawings and will be described in detail below, in which: Figure 1 is a partial section of a holder designed according to a first embodiment; Figure 2 is an illustration in perspective of a magnifier in which the lens element is fastened using a holder designed according to Fig. 1; Figure 3 is a partial section of a holder designed according to another embodiment.

In Fig. 1. (1) designates a lens element held in mount (2). Mount (2) is provided with support (3) on which element (1) rests on a small part of circumference. (4) designates a mechanical holder which, in the example shown, is in the form of a closed ring, the crosssection of which is an angle with two sides.

Sides (5) and (6) of the cross-section enclose an obtuse angle. When installed, side (5) rests on element (1) along a narrow annular area.

The second side (6) engages in annular groove (7) of mount (1) due to spring action.

The selection of the appropriate material for the holder causes the spring action of sides (5) and (6) of holder (4) to act against each other.

This material, for example, can be POM (polyoxymethylene) which is available under the tradename Delrin. This material permits holder (4) to be manufactured by projection mould ing.

For mounting, lens element (1) is first inserted into mount (2) such that it rests on support (3). Holder (4) is then pressed down using a stamp whose action is indicated by arrow (8). Due to the action of this stamp, side (6) finally springs into annular groove (7).

This completes the mounting of lens element (1) which is now secured in its axial position by holder (4); the holding force acting on the lens element is uniformly distributed over the entire contact area of side (5).

The holding force exerted by holder (4) is determined by the material used and the design of holder (4) and the design of annular groove (7). The holder force is chosen such that lens element (1) is stably mounted without damaging forces acting on the lens element.

In the illustration of Fig. 1, holder (4) is asymmetric. Other embodiments are also possible; the sides of the cross-section can be symmetrical, for example.

As an example of a possible application, Fig. 2 shows a magnifier with its lens element (1) fastened in mount (2) by means of holder (4). In the illustration, boundary line (9) is recognizable between sides (5) and (6) of holder (4). The use of the holder as- invented is of particular advantage, as this holder permits substantial savings compared with conventional holders.

In the embodiment shown in Fig. 3, lens element (1) to be held rests on support (3) of mount (2). For fastening of lens element (1), holder (10) is now provided, the cross-section of which has the form of an angle with three sides. The external sides (11) and (12) have roughly the same direction as the axis of mount (2), while side (13) serves to connect the two external sides. In the example shown, third side (13) forms an obtuse angle with the two other sides (11) and (12).

For insertion of holder (10) a stamp is used to exert a force on holder (10) which is indicated by arrow (14). Due to the action of this force, side (10) rests on lens element (11) and side (12) springs into annular groove (7) due to the spring action.

By a suitable choice of length for connecting side (13), it is possible to adjust the elasticity of holder (10) and thus the holding force acting on lens element (1).

In both embodiments illustrated in Fig. 1 and Fig. 3, the depth of annular groove (7) has been chosen such that it corresponds to the thickness of the engaging side (6) or (12) of holder (4) or (10). This ensures a smooth transition between mount (2) and the holder, as is also apparent from the embodiment in Fig. 2.

Claims

1. Holder for optical elements in a mount in which areas of the optical element rest on one side on a support of the mount and in which the optical element is fixed in this position by an elastic holder pressing down against areas of the element's other side, characterized by the fact that mount (2) is provided with an annular groove (7) opposite support (3), and that holder (4) is in the form of a closed ring, the cross-section of which is in the form of an angle with sides (5,6) exerting spring tension against each other; that, when holder (4) is in the holding position, one of the sides (5) rests on the other surface of optical element (1), while the second side (6) engages annular groove (7) of mount (2) due to spring action.

2. Holder according to claim 1, characterized by the fact that the cross-section of holder (4) is in the form of an angle with two sides, with the two sides (5,6) enclosing an obtuse angle.

3. Holder according to claim 1, characterized by the fact that the cross-section of holder (10) has three sides, with the first and second side having roughly the same direction as the axis of mount (2), with third side (13) elastically connecting the two other sides.

4. Holder according to claim 3, characterized by the fact that the third side (13) forms an obtuse angle with at least one of the other sides (11, 12).

5. Holder according to claim 1, characterized by the fact that the depth of annular groove (7) is matched to the thickness of the engaging side (6, 12) of holder (4, 10).