ROTATIONAL SPEED DETECTION DEVICE, VISCOSITY MEASUREMENT DEVICE USING SAID DEVICE, ROTATIONAL SPEED DETECTION METHOD, AND ROTATING BODY USED IN SAID METHOD

摘要

Provided is a rotational speed detection device which can detect the rotational speed of a rotating body with high accuracy by means of a simple control using a small optical apparatus that is relatively cheap, and of which the cost and size can be reduced while maintaining and improving the detection accuracy of the rotational speed of the rotating body. A rotational speed detection device having an irradiation unit (5), a light reception unit (6), a light reception data acquisition unit (13), and a rotational speed computation unit (15) for computing the rotational speed of a rotating body (3), wherein the rotating body (3) has an irregular uneven part (3A) on the rotating surface thereof, the light reception data acquisition unit (13) acquires chronological data of the light reception data of light that reflected off the uneven part (3A), and the rotational speed computation unit (15) computes the rotational speed of the rotating body (3) from the periodicity of the chronological data.