Development of 3D Measurement System Using Phase Shift Digital Holography

Abstract

SUMMARYThe demand for three‐dimensional (3D) measurement technology has been increasing, but in many of the traditional 3D measurement methods, such as the method using phase shift pattern projection, it is difficult to measure the shape of specular‐reflective and transparent objects, because the power of the light reflected from specular reflective objects is too high and that from transparent objects is too low. Consequently, digital cameras cannot acquire accurate information from reflected light. Digital holography has been used as a means of resolving this problem. In traditional digital holography, the interference fringes of the light from the object being measured and the reference light can be captured by a digital camera. Using the Fresnel diffraction principle, the phase information in the light from the object being measured can be acquired and the shape of the object can be calculated by interferometry. Digital holography can be used to measure reflective and transparent objects. However, by the principle of Fresnel diffraction, dc and conjugate components exist in the calculated phase information a noises, so that the accuracy of measurements is reduced. Phase shift digital holography can remove noise by using special devices to change the phase of the reference light, but the devices are costly and the systems are complex, so that practical application of phase shift digital holography has been difficult. In this paper, we propose a new method of phase shift digital holography using the light detection principle. We also propose a digital holography reconstruction method using the convolution approach rather than the traditional Fresnel approach. The proposed method results in a compact phase shift holography system with lower cost and greater accuracy than the 3D measurement method. Therefore, the practical applications of digital holography can be realized less expensively and more accurately.