Patent ID: 7104133

Claim:
A torsional vibration measuring instrument comprising: a plurality of reflecting means arranged with stipulated intervals therebetween along surface of a rotator of which torsional vibration is to be measured; a pulse light irradiating means for irradiating a repetitive pulse light beam to the plurality of reflecting means; an outgoing-transmitting means for transmitting the irradiated pulse light beam; a plurality of transmitting-receiving means for irradiating the transmitted pulse light beam to the plurality of reflecting means, and for receiving plurality of reflected pulse light beams which have been reflected by the plurality of reflecting means; an incoming-transmitting means for transmitting the plurality of reflected pulse light beams which have been received; a plurality of detecting means for detecting the plurality of reflected pulse light beams which have been transmitted by the incoming-transmitting means; and a signal processing means for processing a plurality of pulse output signals which have been outputted from the plurality of detecting means and for calculating torsional vibration frequency of the rotator by averaging rotational periods through a number of pulse light beams which are irradiated to one of the reflecting means and are reflected at the one of the reflecting means during a time period when the one of the reflecting means passes in front of one of the transmitting-receiving means.