An injection device for use with tissue of a mammalian body comprising a first tubular member and a second tubular member slidably disposed in the first tubular member. The speed control module controls a speed of a motor based on an error signal generated based on a desired speed and back electromotive force. At this time, a maximum magnification ratio setting circuit sets the maximum variable magnification ratio of electrical zoom processing in the camera signal processing circuit. The chargedischarge circuit is coupled to the current mirror circuit.