Position detector and light deflection apparatus

A position detector (1, 2, 61, 77, 93, 123) for determining the rotation angle position (α) of an object (3) which is rotatably supported, in combination with the rotatably supported object (3), comprising:

• a light source (5) for producing a light beam (17),
• a diffraction grating (9),
• a mirror (7) which is connected to the object (3) in such a way that it co-rotates with the object (3) during a rotation of the object and which is disposed in such way that the light beam (17) is reflected therefrom onto the diffraction grating (9) and that, during a rotation of the mirror (7), the reflected light beam (18) passes over the diffraction grating (9) according to the rotation, wherein the light of the reflected light beam is diffracted by the diffraction grating (9), thereby producing diffraction light (29),
• an optical interference device (11, 12, 79, 95) which is disposed in the optical path of the diffraction light (29) and is configured such as to be able to bring different diffraction orders (m=−1, m=+1) of the diffraction light (29) to interference, thereby producing an interference pattern (41, 73, 88, 113),
• a light detector (13, 63, 81, 97) which is disposed and configured such as to be able to detect a change in brightness of the interference pattern (41, 73, 88, 113), which is caused by said passing over of the diffraction grating (9) with the reflected light beam (18), as well as a brightness course (57, 89) comprising the change in brightness, and
• an evaluation unit (15) which is connected with the light detector (13, 63, 81, 97) and is configured such as to be able to determine the rotation angle position (α) of the object (3) based on the brightness course (57, 89).