Development of low-cost heterodyne interferometer with virtual electronic phasemeter

Abstract

Commercial laser interferometers are conventionally used to measure the positioning error of a long linear stage in multiaxis computer numerical control machine tools. However, commercial laser interferometers are costly and difficult to use. Therefore, a low-cost photodetector-based heterodyne interferometer combined with an electronic phasemeter module was proposed for precise measurement of the positioning error of a long linear stage. The proposed heterodyne interferometer was combined with a virtual electronic phasemeter that employs a self-developed signal-processing technique. Our core algorithm and proposed photoelectric-signal-processing technique were developed using the LabVIEW human–machine interface. Moreover, to verify the performance of the proposed heterodyne interferometer, a laboratory-built prototype was constructed and used to measure the positioning error of a long linear stage. The experimental results indicated that the positioning accuracy of the proposed interferometer was ±4.5 μm for a linear stage with a displacement of 250 mm; the results obtained were comparable to those obtained with a commercially available laser interferometer. The proposed heterodyne interferometer can thus be used in other applications related to precision engineering.

Dynamic range extension for heterodyne fibre‐optic hydrophone by using instantaneous frequency‐tracking method

“…For the commonly used IQ quadrature demodulation algorithm [9], when the phase of successive sampling points exceeds ± π , the demodulator undergoes a significant phase wrapping [17]. To overcome the phase wrapping, the adopted IF-tracking method is added after the algorithm to correct the phase distortion, as shown in Figure 3.…”