Patent ID: 8878125

Claim:
An encoder comprising: a position detecting device including a gear mechanism, a main shaft, n stub shafts coupled to the main shaft via the gear mechanism to rotate in synchronization with the main shaft wherein n is an integer of 1 or more, and (1+n) position detecting sections operable to detect the respective angular positions of the main shaft and the n sub shafts an optical encoder device configured to detect the angular position of the main shaft by utilizing light; a housing that houses the position detecting device and the optical encoder device, and, a circuit substrate including a detecting circuit operable to detect the absolute position of the main shaft based on a signal output from the position detecting device and a signal output from the optical encoder device, wherein: the optical encoder device includes a rotary disc fixed to the main shaft, and a light emitting element and a light receiving element which are fixed to the circuit substrate; the housing includes a partition wall portion provided with a plurality of bearings capable of rotatably supporting the main shaft and the n sub shafts, a first housing portion configured to house the (1+n) position detecting sections and the optical encoder device, and a second housing portion configured to house the gear mechanism; and the partition wall portion separates the gear mechanism from the (1+n) position detecting sections, the optical encoder device, and the circuit substrate.