Patent ID: 8345091

Claim:
An endoscope system including an image pickup device picking up an image of an object and an objective optical system, the endoscope system comprising: an actuator having a shape memory element and driving a moving member for moving the objective optical system; an actuator drive unit driving the actuator; a resistance value detection section detecting a resistance value of the shape memory element for detecting a position of the moving member; an instruction input unit to which an instruction to move the objective optical system is inputted; and a control section outputting a driving signal to the actuator drive unit on a basis of the instruction inputted to the instruction input unit and the position of the moving member corresponding to the resistance value detected by the resistance value detection section, wherein in response to a moving instruction inputted to the instruction input unit to move the objective optical system from a first position to a second position, the control section outputs the driving signal so that a current for moving the moving member from the first position to a third position beyond the second position is passed through the shape memory element, when the moving member reaches the third position, the control section outputs the driving signal so that a first constant current is passed through the shape memory element until the resistance value of the shape memory element becomes a first resistance value smaller than a resistance value of the shape memory element corresponding to the third position and larger than a minimum resistance value within a moving range of the moving member, when the resistance value of the shape memory element becomes the first resistance value, the control section outputs the driving signal so that a first holding constant current smaller than the first constant current is passed through the shape memory element, and when the resistance value of the shape memory element becomes a second resistance value larger than the first resistance value during passage of the first holding constant current through the shape memory element, the control section outputs the driving signal so that a current is passed through the shape memory element, the current being for holding the moving member at a position farther than the second position from the first position within a range in which the resistance value of the shape memory element does not reach the minimum resistance value.