Patent ID: 7554245

Claim:
An ultrasonic probe comprising: a group of piezoelectric elements including a plurality of piezoelectric elements of a narrow card shape arrayed in a long-axis direction thereof and also connecting wires connected electrically to said piezoelectric elements and extending outward from at least one end side in a short-axis direction; a rotational mechanism portion that rotates and oscillates said group of piezoelectric elements in the short-axis direction about the center of said long-axis direction; a reference position detection sensor that detects a reference position of said group of piezoelectric elements in said short-axis direction; and a drive shaft and a stepping motor that are linked to said reference position detection sensor and drive said rotational mechanism portion; wherein an optical rotary plate for said reference position sensor, which has a boundary region between a light-blocking portion and a light-transmitting portion, is linked to said control shaft; said light-blocking portion and said light-transmitting portion are formed sequentially at a predetermined angle in mutually opposite directions from the center of said optical rotary plate, with reference to said boundary region, and also said optical rotary plate rotates no further than said predetermined angle with reference to said boundary region; said boundary region is detected by the transmission or blocking of light by said light-blocking portion and said light-transmitting portion; and thus the reference position of said group of piezoelectric elements is detected and set on the basis of said boundary region.