Application Cases

Experiment Name: Scheme of a Sinusoidal Phase Modulation Laser Interferometry Nanoscale Displacement Measurement System

Test Equipment: High-voltage amplifier, Electro-optic phase modulator, Photodetector, He-Ne single-frequency laser, etc.

Experimental Process:

Figure 1: Schematic diagram of the optical path structure of the sinusoidal phase modulation laser interferometry nanoscale displacement measurement system

The optical path structure of the sinusoidal phase modulation laser interferometry nanoscale displacement measurement system is shown in Figure 1. The system utilizes a He-Ne single-frequency laser and a transverse electro-optic phase modulator (EOM) to construct the sinusoidal phase modulation laser interferometric displacement measurement system. For clarity, the optical path from the beam splitter BS to the reference corner cube mirror M1 is denoted as lr, the path from BS to the corner cube mirror M2 is denoted as lo, and the displacement of the corner cube mirror M2 is denoted as Δl. The interference signal detected by the photodetector PD is acquired through an ADC chip and input into the FPGA signal processing module. The FPGA multiplies the acquired interference signal with the fundamental and second harmonic of the carrier frequency, applies low-pass filtering, processes the filtered results with a Kalman filter to correct the AC amplitude and DC bias of the quadrature components, and then performs an arctangent operation to obtain the demodulated phase. The FPGA module uses a Direct Digital Synthesizer (DDS) to generate the carrier phase modulation signal sinωct for the EOM, which is amplified by a high-voltage amplifier (HVA) before modulating the EOM. Simultaneously, the FPGA module connects to a host computer via a serial interface to visualize the phase demodulation results and monitor various parameters during the displacement measurement process.

Experimental Results:

The experiment introduced the principles related to transverse electro-optic phase modulation, described the optical path of the sinusoidal phase modulation laser interferometry nanoscale displacement measurement system, and set up an experimental system for testing.

High-Voltage Amplifier Recommendation: ATA-2088

Figure: ATA-2088 High-Voltage Amplifier Specifications

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