Centrosymmetric changer for optical elements

Abstract

This invention minimizes the needed space for a changer device for optical elements which can be mounted in front or in the back or on either fork side of telescopes. It implements a design whose profile is circular and centrosymmetric and gravitanionally neutral in respect to the path of light of the surrounding optical devices as well as an optimized mechanical depth. This is achieved by moving the centrosymmetrically arranged optical elements individually into the optical path i.e. the central opening of the changing device in contrary to prior art designs wherein the optical elements are mounted on a revolving disk whose axis of rotation is not congruent with the optical axis. The invention minimizes the obstructing area and shape of the changing device as well as the gravitational stress on surrounding structures by incorporating a design with minimal space requirements.

Claims

1: A changing device for optical elements comprising: an outer body which is circular and centrosymmetric with respect to a central opening (z-axis) that permits the passing through of light. one or more optical elements that are movably arranged (mounted) within said outer body. The optical elements call be moved manually or driven by one or more actuators into the center opening.

2: A changing device for optical elements according to claim 1 wherein the movable optical elements are arranged in one or more layers, placed behind each other in respect to the path of light (z-axis).

3: A changing device for optical elements according to claim 1 or 2 comprising either linear movement of the optical elements or rotary movement of levers on which the optical elements are mounted.

4: A changing device for optical elements according to claims 1-3 wherein the optical element's movement is made by one or more actuators.

5: A changing device for optical elements according to claim 1-3 comprising a cam-groove-disk for controlling the movement of the optical elements into the center opening.

6: A changing device for optical elements according to any preceding claim comprising two planes of optical elements, controlled by one cam-groove-disk with a timing-groove on each side.

7: A changing device for optical elements according to any preceding claim comprising three, four or five optical elements in one plane.

8: A changing device for optical elements according to any preceding claim comprising either a rotational offset of the timing-grooves on each side of the disk of Nπ/F[rad] (F, N ∈ N) where F is the number of holders for optical elements and N an integer multiple. or a complementary design wherein the two layers are rotated in respect to each other (rotational axis being the z-axis) by Nπ/F[rad] instead of an offset of the two timing-grooves.

9: A changing device for optical elements according to any preceding claim comprising three, four, five, six, eight, or ten holders for optical elements.

10: A changing device for optical elements according to any preceding claim wherein the outer diameter (the diameter responsible for the amount of light obstruction in the x-y-plane according to the conventions defined in this document) is less or equal 3.5 times the diameter of an individual optical element.

11: A changing device for optical elements according to any preceding claim comprising the use of individual actuators for each optical element.

12: A changing device for optical elements according to any preceding claim comprising the use of individual actuators for each axis of rotation of the holder-levers, thus two levers of different layers that share all axis of rotation are moved by one actuator.

13: A changing device for optical elements according to any preceding claim, wherein the optical elements are selected from optical filters, polarizers, lenses, field flat-teners, wedges or prisms.

14: A changing device for optical elements according to any preceding claim, which can be adjusted in a way that incoming light can pass through without interaction with one or more of the mounted optical elements in the same plane and without the need of an empty position of one or more holders for optical elements contrary to prior art filter wheels which need an opening in the rotating disk for the unaltered passing through of light which cannot be used for optical elements.

15: The usage of a changing device for optical elements according to any preceding claim on telescopes for earthbound as well as observation with telescopes mounted on air- and spacecrafts.

Description

DETAILED DRAWINGS DESCRIPTION

[0046] FIG. 1: A common prior art filter wheel design. The filter wheel 1 houses a various number of optical filters 5. It is mounted in a way that its rotational axis 4 is parallel to the optical axis 3 of the image-capture-device 6. The individual filters are moved into the optical axis, respectively in front of the detection chip, 2 by rotation of the filter disk. It is clearly seen that the minimal possible obstruction caused by the filter wheel's outer diameter is not centro-symmetric in respect to the optical axis 3.

[0047] FIG. 2: A prior art ‘centered-filter wheel’ design. Two overlapping filter disks 2 and 3 move the optical filters 1 into the optical axis 4 by revolving around their axis of rotation 5 and 6. One filter holder on each disk is needed to be empty in order not to shadow the other disks filter. This design provides symmetrical but not circular obstruction. Furthermore the obstructing area is unsatisfactorily large and two filter holders are left to be empty. Thus the relation between obstructing area and number of usable filters (i.e. the usable area of housed optical elements) is rather low.

[0048] FIG. 3: a) Illustration of the resulting central obstruction (also referred to as central-vignetting) of a prime-focus telescope. When mounted on the camera 2 in the telescopes prime-focus (in front of the primary mirror 1, the prior art filter wheel 3 causes non-symmetric obstruction 6 of the incoming light 5 in respect to the optical axis 4. The diameters 8a and 8b illustrate the need for minimization of the filter-changer's mechanical length, because of the divergent beam of rays. [0049] b) In contrast to prior art filter wheels the invention provides minimized and circular centrosymmetric obstruction while housing the same number of usable filters without the need for empty holders.

[0050] FIG. 4: a) Circular centrosymmetric changer for optical elements with levers 2 for the movement of the holders for the optical elements 1. The individual holders are moved into the optical axis 4 by rotation of the holder-levers 2 around the axis of rotation 5. This movement can either be driven manually or by actuators directly mounted on, or respectively driving the axis of rotation 5. FIG. 3a shows a filter in working position. [0051] b) The holder moved away from the optical axis 4 (respectively the opening in the center of the filter-changer for the passing through of light) into parking position.

[0052] FIG. 5: a) Example of a cam-groove-disk drive for the holder movement. The disk 1 has a cam-groove 2 whose outer maximum diameter resembles the parking position of the holder-levers. The inner minimal diameter resembles the working position for the holder-levers. [0053] b) The negative-cam-grove-disk's timing function is transmitted to the holder-levers by the means of a pin 2 engaged with the groove 6. One full rotation (2π[rad]) of the disk in respect to the optical axis 4 (z-axis) will move all holders consecutively into the optical axis and back into parking position. The example demonstrates a design with F=4 holders. Therefore the maximum rotation angle for the in-and-out movement of a single holder-lever must be smaller than π/4[rad]. When F=5 holders per plane are used, the rotation angle for a single holder's movement (in and out) would be 2π/5[rad].

[0054] FIG. 6: Exploded view of a two layer cam-groove-disk design. This figure depicts a plane-symmetrical cam-groove-disk with an offset of the holder-levers rotational axis 5a and 5b by π/4[rad].

[0055] FIG. 7: Embodiment with two individual layers of holders for optical elements using individual actuators for each holder-lever.

[0056] FIG. 8: Design example using one actuator for each of the four rotational axis. Counterclockwise rotation moves the holders in the upper layer into the optical axis. Clockwise rotation moves the lower holders (or vice versa). All filters are moved back into parking position the means of springs (or any other suitable mean of restoring force) when the actuator changes the direction of rotation.

[0057] FIG. 9: Design example incorporating linear movement of the filters actuated by a cam-groove-disk and two symmetrical filter arrays on each side of the disk. [0058] a) The rectangular holder frames 1 are mounted in linear guides 5. The guiding pin 2 is engaged in the cam-groove 6a and moves the holders into the optical axis 4 and back into parking position when the cam-groove-disk 3a rotates. The figure also shows the second layer of holders and the second cam-groove 6b which is rotated by π/2[rad] in respect to the optical axis (z-axis). Further rotation of the disk by π/2[rad] will result in the current working holder being moved into parking position while the next holder (of the second layer) is being moved simultaneously into the optical axis. [0059] b) Isometric view of a two-layer cam-groove-disk design with rectangular holders for optical elements.