ROTATIONAL POSITION SENSOR

1 . A rotational position sensor assembly for detecting the selected rotational position of a rotatable selector comprising:

a reference member positioned about an axis;

a proximity sensor disposed on the reference member;

a rotatable selector defining an inner surface, the rotatable selector mounted about the fixed reference member and rotatable about the axis, the inner surface and the proximity sensor defining a gap there between, wherein the gap varies with respect to the rotational position of the rotatable selector, the proximity sensor generating a signal proportional to the size of the gap; and

a processor and a non-transitory computer readable storage medium, the computer readable storage medium including instructions executable by the processor to:

receive the signal proportional to the size of the gap from the proximity sensor; and

correlate the signal with a rotational position of the rotatable selector.

2 . The rotational position sensor assembly of claim 1 , wherein the processor is further configured to correlate the rotational position of the rotatable selector with a user selected setting.

3 . The rotational position sensor assembly of claim 1 , wherein the processor is further configured to generate an output signal corresponding to the user selected setting.

4 . The rotational position sensor assembly of claim 2 , wherein the user selected setting is a magnification setting.

5 . The rotational position sensor assembly of claim 1 , wherein the reference member is a ring defining a central opening.

6 . The rotational position sensor assembly of claim 1 , wherein the proximity sensor is an optical proximity sensor.

7 . The rotational position sensor assembly of claim 1 , wherein gap includes a range of 1-5 mm.

8 . The rotational position sensor assembly of claim 1 , wherein the selector is a ring.

9 . A rotational position sensor assembly for detecting the selected rotational position of a rotatable selector comprising:

a fixed reference member positioned about an axis and defining a first surface;

a rotatable selector mounted about the fixed reference member and rotatable about the axis, the rotatable selector defining a second surface opposing the first surface;

a proximity sensor disposed on one of the fixed reference member and the rotatable selector, wherein the proximity sensor and the second surface define a gap therebetween when the proximity sensor is disposed on the fixed reference member and the proximity sensor and the first surface define the gap therebetween when the proximity sensor is disposed on the rotatable selector, wherein the gap varies with the rotational position about the axis of the rotatable selector with respect to the fixed reference member, the proximity sensor generating a signal proportional to the size of the gap; and

a processor and a non-transitory computer readable storage medium, the computer readable storage medium including instructions executable by the processor to:

receive the signal proportional to the size of the gap from the proximity sensor; and

correlate the signal with a rotational position of the rotatable selector.

10 . The rotational position sensor assembly of claim 9 , wherein the processor is further configured to correlate the rotational position of the rotatable selector with a user selected setting.

11 . The rotational position sensor assembly of claim 10 , wherein the user selected setting is a magnification setting.

12 . The rotational position sensor assembly of claim 9 , wherein the fixed reference member is a ring defining a central opening.

13 . The rotational position sensor assembly of claim 9 , wherein the proximity sensor is an optical proximity sensor.

14 . The rotational position sensor assembly of claim 9 , wherein gap includes a range of 1-5 mm.

15 . The rotational position sensor assembly of claim 9 , wherein the processor is further configured to generate an output signal corresponding to the user selected setting.

16 . The rotational position sensor assembly of claim 9 , wherein the selector is a ring.

17 . An aiming device for displaying a down-range image and a reticle display field comprising:

a housing defining an axis;

an objective disposed in the housing for producing the image of the down-range image;

an eyepiece disposed in the housing for displaying a down-range image and a reticle display field;

a lens element disposed in the housing and having adjustable optical magnification;

a rotational position sensor assembly comprising:

a fixed reference ring positioned about the axis;

a proximity sensor disposed on the fixed reference ring;

a rotatable selector to adjust an optical magnification of the image of the down-range image, the selector defining an inner surface, the rotatable selector mounted about the fixed reference member and rotatable about the axis, the inner surface and the proximity sensor defining a gap there between, wherein the gap varies with respect to the rotational position about the axis of the rotatable selector, the proximity sensor generating a signal proportional to the size of the gap; and

a processor and a non-transitory computer readable storage medium, the computer readable storage medium including instructions executable by the processor to:

receive the signal proportional to the size of the gap from the proximity sensor; and

correlate the signal with a rotational position of the rotatable selector.

18 . The aiming device of claim 17 , wherein the processor is further configured to correlate the rotational position of the rotatable selector with a user selected setting.

19 . The rotational position sensor assembly of claim 18 , wherein the user selected setting is a magnification setting.

20 . The rotational position sensor assembly of claim 17 , wherein the proximity sensor is an optical proximity sensor.

21 . The rotational position sensor assembly of claim 17 , wherein gap includes a range of 1-5 mm.