| 摘要 |
1,084,701. Angular position determination. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. Jan. 8, 1965 [Jan. 11, 1964], No. 938/65. Heading G1A. [Also in Division G4] In order to determine the angular position of a moving member a polygonal reflector having a number of peripheral outwardly-facing reflective faces disposed round its axis of rotation in a regular manner is coupled to the moving member so as to rotate about the same axis with it. A ruled grating 3 having a line separation d is illuminated by lamp 1 through lens 2. Light from the slots of the grating is made parallel by lens 8 and directed on to the polygonal reflector from whence it is returned through the lens to form an image in the plane of grating sections 4. There are four of these short grating sections each placed over a pair of photo-cells 16, 17 and located with a phase shift of 90‹ relative to their neighbours. The outputs of the photo-cell pairs are fed to a position indicating device 20. The number of faces on the polygonal reflector is made large (in a practical embodiment 360) and the grating line separation d corresponds to where f is the focal length of lens 8 and n the number of reflector faces. |
