METHOD FOR CONTROLLING ULTRASONIC MOTOR AND SURVEYING INSTRUMENT FOR THE SAME

Provided is a method for controlling an ultrasonic motor to reduce deterioration of automatic tracking performance, and a surveying instrument for the same. The present invention provides a method for controlling an ultrasonic motor in a surveying instrument including a rotary shaft, an ultrasonic motor that drives a rotary shaft, a tracking unit that includes a light emitting unit and a light receiving unit and tracks a target, and a clock signal oscillation unit that outputs a clock signal, wherein at the time of low-speed rotation of the ultrasonic motor, based on the clock signal, a ratio of an acceleration period in which a drive signal is applied and a deceleration period in which the drive signal is stopped in a drive cycle of the drive signal of the ultrasonic motor is set, and the light emitting unit is made to emit light in the deceleration period.