Position detector for a scanning device
A position detector for a scanning device includes a movable light blocker, at least two light detectors which are located behind the light blocker and which can be covered by the light blocker at different extents of coverage as the light blocker is being moved, so that the position of the light blocker can be determined, and at least one light source for emitting light onto the light detectors. A reflector is provided which is located in front of the light blocker. The light source is arranged such that the light emitted therefrom is emitted onto the reflector. Furthermore, the reflector is arranged such that the light impinging thereon is reflected onto the light detectors.
1. Position detector for a scanning device comprising: a single movable light blocker; at least two light detectors located behind the light blocker, wherein the light detectors can be covered by the light blocker at different extents of coverage as the light blocker is being moved, from which different extents of coverage a position of the light blocker can be determined; and at least one light source for emitting light onto the light detectors, wherein a reflector is provided in front of the light blocker, and the light source is arranged such that the light emitted therefrom is emitted onto the reflector, and wherein the reflector is arranged such that the light impinging thereon is reflected onto the light detectors.
2. Position detector according to claim 1 , wherein the light source is arranged sidewards of and adjacent to the light detectors.
3. Position detector according to claim 1 , wherein the reflector is a diffuse reflector.
4. Position detector according to claim 1 , wherein the reflector comprises a reflecting varnish.
5. Position detector according to claim 1 , wherein the reflector is provided in the form of a coating applied to a substrate.
6. Position detector according to claim 5 , wherein the substrate is a cover by which the position detector is closed and sealed toward the front.
7. Position detector according to claim 1 , wherein at least two light sources are provided.
8. Position detector according to claim 1 , wherein the light blocker is arranged rotatably, and wherein each of the light detectors has a shape of a section of an annulus.
9. Position detector according to claim 8 , wherein at least four light detectors are provided, wherein the light detectors are arranged around a rotational axis of the light blocker in such a fashion that respectively two light detectors arranged diametrically with respect to each other are covered essentially to the same extent by the light blocker.
10. Position detector according to claim 8 , wherein each light detector comprises a light sensitive element which is provided with a mask comprising a recess having a shape of a section of an annulus, by which the corresponding light detector's shape of the section of the annulus is formed.
11. Position detector according to claim 8 , wherein each light detector comprises a light sensitive element, and wherein a common mask is provided for at least a plurality of the light detectors, the mask being provided with a corresponding number of recesses having a shape of a section of an annulus, by which the corresponding light detector's shape of the section of the annulus is formed.
12. Position detector according to claim 9 , wherein the light detectors are connected to a control device which has a structure such that output signals of the two light detectors, respectively having the same extent of coverage, are added, thereby calculating two addition signals, and such that a difference of the two addition signals is formed, thereby generating a linear output signal proportional to a position of the light blocker.
13. Position detector according to claim 1 , wherein two adjacent light detectors are formed as a slit diode.
14. Position detector according to claim 1 , wherein a control unit is provided which has a structure such that output signals of the light detectors are added, thereby generating an overall addition signal, and such that an intensity of radiation of the light source(s) is controlled in accordance with the overall addition signal.
15. Position detector according to claim 1 , wherein the light detectors and the light source(s) are essentially arranged in one plane.
16. Position detector according to claim 1 , wherein the light detectors and the light source(s) are arranged on a common printed circuit board.
17. Scanning device comprising a position detector according to claim 1 .