ワンショット位相シフトデジタルホログラフィによる三次元計測装置の開発

Abstract

In these years, demand for 3D measurement technology is increasing. However, in many of the conventional 3D measurement methods, such as phase-shift patterns projection method, it is difficult to measure shape of specular reflective and transparent objects. This is because power of reflected light is too high from specular reflective objects or too low from transparent objects, so that reflected light cannot be captured accurately by digital camera. Digital Holography has been used for resolving this problem. In digital holography, interference fringe of object wave and reference wave is recorded by digital camera. Phase of object wave can be calculated using Fresnel diffraction, and shape of object can be calculated using interferometry. Although shape of specular reflective and transparent objects can be measured using digital holography, DC and virtual term exist in single interference fringe as noises, decreases measurement accuracy. For higher accuracy measurement, phase-shift digital holography has been developed. However, for generating four phase-shift interference fringes, measurement system is expensive and complex. Moreover, phase-shift interference fringes are instable due to vibration of measurement environment. For these reasons, conventional phase-shift digital holography is difficult to apply. We propose a new method of generating phase-shift interference fringes using wave detection principle, and developed a low price measurement system using the proposal method to solve the problem. This paper uses a measuring method of phase-shift digital holography using single interference fringe. The experimental result shows how the stable 3D measurement system using single-shot phase-shift digital holography can achieve with low-cost and high accuracy.