Patent ID: 8228389
Filing Date: 2012-07-24
Classification: G02B,G03B,H04N

Abstract:
1. An image pickup apparatus comprising: a lens; an ultrasonic motor that moves the lens; a motor driving part that applies a periodically changing voltage to the ultrasonic motor, the voltage being applied for driving the ultrasonic motor; a storage part that stores as a reference frequency characteristic a relationship between a frequency of voltage applied by the motor driving part and a driving speed of the ultrasonic motor at the time of the voltage application; and a correction control part capable of executing a correction process, the correction process including steps of: measuring the relationship between the frequency of the voltage applied by the motor driving part to the ultrasonic motor and the driving speed of the ultrasonic motor, correcting the reference frequency characteristic on the basis of the correlation between the measured relationship and the reference frequency characteristic, and calculating a correction frequency characteristic that exhibits an updated relationship between the frequency of the voltage applied by the motor driving part and the driving speed of the ultrasonic motor, wherein the correction control part controls the motor driving part so that during measuring the relationship between the frequency of the applied voltage and the driving speed of the ultrasonic motor, the lens moves round-trip within a predetermined range in an optical axis direction, wherein the driving speed of the ultrasonic motor varies periodically, and the correction control part controls the motor driving part so that the predetermined range corresponds to a distance for moving the lens for a time period corresponding to multiples of a period of the variation in the driving speed.