| 摘要 |
PURPOSE:To obtain high-accuracy position detection signals as many as bits except the LSP from the bits even when the same A/D converter is used by performing the full-wave rectification of outputs of a sensor at a position which corresponds to a position in the scanning direction of an acoustic lens and across which polarities are different. CONSTITUTION:The scan of the acoustic lens is detected by a position sensor 2. The sensor 2 uses a PSD outputting an AC signal which is 0 almost in the center of the scan width of the lens 1 and different in polarity on both sides, and its output signal is rectified by a full-wave rectifying circuit 3 on a full- wave basis. The output of this circuit 3 is converted by the A/D converter 4 into a digital signal and output variation of a bit which is one higher than the LSB of the output is used as a trigger for transmission timing pulse generation. Consequently, transmit pulses of the lens 1 are controlled. Thus, even when the same A/D converter is used, high-accuracy position detection signals as many as bits except the LSB are obtained from the bits.
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