An Improved N-step Phase Shift Method for High-temperature Objects

N-step phase shift method is widely used because of its high accuracy and efficiency. However, when the detected object is at high temperature, the infrared radiation generated by the detected object would cause great interference to the projected image, which seriously affect the accuracy of unwrapped phase. To solve this problem, we establish a physical model of high temperature thermal radiation. By analyzing the model, an improved N-step phase shift method for high-temperature objects is obtained. We first mix the phase shift fringe images into color images with weak infrared radiation, and then obtain a high precision phase information by analyzing and calculating color phase shift fringe images modulated by the object surface. To verify the method in this paper, we compare this method with N-step phase shift method in different phase shift steps. The experimental results show that this method in this paper could get high-precision of the unwrapped phase. The detection accuracy is improved by about 20.83%.