We present an improved detection scheme for a two-wave mixing interferometer with a Bi12SiO20 crystal. The proposed detection scheme allows quasi-balanced detection of ultrasonic signals whereby electrical disturbances are suppressed. Quasi-balancing is achieved by changing the polarity of the high voltage at the photorefractive crystal, leading to an inversion of the optical interference signal, in combination with inversion of the detector signal using a signal inverter before the data acquisition device. The polarity of the high voltage is changed by utilizing an H-bridge consisting of five high-voltage relays. Microcontrollers are used to synchronize the reversion of the high voltage at the photorefractive crystal and the inversion of the measured signals. We demonstrate remote measurement of ultrasonic waves and shown that electrical disturbances are suppressed using the quasi-balanced mode.

中文翻译：

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用于远程超声检测的准平衡两波混合干涉仪

我们提出了一种改进的检测方案，用于具有 Bi12SiO20 晶体的两波混合干涉仪。所提出的检测方案允许对超声波信号进行准平衡检测，从而抑制电干扰。准平衡是通过改变光折变晶体处高压的极性来实现的，导致光干涉信号的反相，结合使用数据采集设备之前的信号反相器对检测器信号的反相。通过使用由五个高压继电器组成的 H 桥来改变高压的极性。微控制器用于同步光折变晶体处高压的反转和测量信号的反转。