Self-Calibrating Sparse Far-Field Photometric Stereo With Collocated Light

Photometric stereo is one common surface normal estimation technique, which can be utilized for various industrial tasks such as 3-D surface detail reconstruction and defect inspection. To further satisfy the requirement of the industrial inspection, the uncalibrated photometric stereo is needed. This article proposes a collocated light method for uncalibrated far-field photometric stereo to achieve accurate surface normal estimation under a small number of lights. Collocated light is the light close to the camera, with the angle between the lighting direction of the collocated light and the viewing direction of the camera being less than 10°. The image under the collocated light could be utilized to extract features related to the shadings and the shadows that are the key to the light self-calibration. Thus, the collocated light is introduced to realize the light self-calibration, with the accuracy being less influenced by the number of lights. Then, the normal estimation network with collocated light is integrated to give precise surface normal estimations under a small number of lights. Both synthetic and real experiments validate that the proposed method can achieve the state-of-the-art performance.