Abstract: A rotor 10 rotatable around a predetermined centerline direction includes: a columnar magnet 12; and a first rotating shaft 70 with a first columnar part 71 and a cylinder-shaped first cylindrical part 72 covering a part of a first outer circumferential surface 913 of the magnet 12, wherein the first outer circumferential surface 913 of the magnet 12 and a first inner circumferential surface 721 of the first cylindrical part 72 of the first rotating shaft 70 are joined, and a first end surface 912 of the magnet 12 and a first end surface 731 of the first rotating shaft 70 are not joined.

Abstract: The range of operating angles of a position transducer is widened, and its signal-to-noise ratio is improved. The position transducer includes a light source and a detector including at least one pair of photodiodes (PDs) disposed on a predetermined circle. The detector receives light emitted from the light source to output a signal varying depending on the areas of regions where the light is received on two PDs forming a pair. The PDs are formed on separate chips, respectively, and the chips are disposed on a substrate so that one or more pairs of PDs surround the entirety of a predetermined region and have an annular shape as a whole.

Abstract: Provided is a position transducer which can be manufactured at low cost, improve the signal-to-noise ratio of an output obtained from a detector, and obtain a stable output even if the temperature changes. A position transducer 100 includes a butterfly-shaped reflector 7 attached to a rotating shaft 2 of a rotation restriction motor 1, an LED die 4 disposed to face a central portion of the reflection surface of the reflector 7, a diffused-light absorbing member disposed on the surfaces of a diffused light absorber 3 and a case 5, installed on the fixed side of the motor 1 so as to surround the reflector 7 with a distance from the reflector 7 at the rear of the reflector 7 as viewed from the LED die 4 and absorbing illumination light from the LED die 4 which has not illuminated the reflection surface, and detectors 11 mounted on the same printed circuit board 6 as the LED die 4 to detect an image reflected by the reflector 7.