Error analysis and compensation method of displacement measurements based on reflection projection imaging

Abstract

Displacement measurement technology based on an image recognition method can realize high-performance more easily than traditional technology. Compared with a transmission-type displacement measurement method illuminated by parallel light, a method based on reflection projection recognition can achieve smaller volume and have great advantages in an application environment with limited volume. However, due to the spherical light-field effects of point light used in reflection-type displacement measurement, the illumination intensity in different areas of an image sensor is different, resulting in some displacement measurement errors. Therefore, this study analyzed displacement measurement error based on reflective projection imaging and presented a corresponding error compensation method. First, taking the point light as the emission source, a miniaturized displacement measurement mechanism was proposed based on reflection projection imaging. Then, according to the wavefront recording model of the point light, a model of measurement error caused by differing illumination intensity was established. Finally, the corresponding compensation method was proposed and verified by simulations and experiments. After simulation analysis, the influencing factors of reflection-type displacement measurement error were established. When a circular grating with 86 mm diameter was used in experiments, the error compensation function proposed improved the measurement accuracy from 7.03 arcsec to 5.4 arcsec. Research done in this study demonstrated the error influencing factors of the reflective-type displacement measurement method and proposed an effective error compensation method, which thus laid a foundation for miniaturization and high-precision reflective-type displacement measurement technology.