Endoscope for automatically adjusting an angle with a shape memory alloy

摘要

An endoscope includes a bending member having a shape memory alloy. A pair of heating current supplying wires and a pair of resistance detecting wires are connected at one end to the ends of the shape memory alloy. The other end of the heating current supplying wire is connected to a current supply circuit, and the other end of the resistance detecting wire is connected to a resistance detector. The resistance detector is constituted by a bridge circuit having a branch opened and the shape memory alloy is connected in the opened branch via the resistance detecting wires. A controller controls the current supply circuit according to the detected resistance. The current supply is effected by supplying a current pulse, and the amount of heating current and the bending degree can be controlled by controlling the pulse width of the current pulse. Since no heating current is supplied to the resistance detecting wires, the resistance thereof is not changed even when the shape memory alloy is heated by passing a heating current therethrough. Therefore, it is possible to precisely detect variation in the resistance of only the shape memory alloy member and measure the bending degree of the bending member.