Absolute rotational position detection device.

摘要

On a circumferential side surface of a single cylindrical member constituting a main body of a rotor section (3) are disposed, in parallel, a first pattern (3a) which repeats change in the circumferential direction with a predetermined pitch and a second pattern (3b) which has a change of one cycle with respect to one circumference. A detection head section (1, 2) which is provided in proximity to the rotor section changes its relation of correspondence to the respective patterns in accordance with rotational position of the rotor section and produces output signals corresponding to the relation of correspondence. A relatively rough absolute value of a rotational position within one rotation is established by an output signal produced in response to the second pattern (3b) and its accuracy is established with a high resolution by an output signal produced in response to the first pattern (3a). By disposing the first and second patterns in parallel on the single cylindrical member of the rotor section, the construction of the device can be simplified.