High dynamic range 3D shape determination based on automatic exposure selection

Traditional multi-exposure based high dynamic range fringe projection profilometry (FPP) technique is an effective method to obtain the 3D profiles of objects with drastic surface reflectivity variations. However, in this technique different exposure times often need to be selected empirically, making this method rather complicated. In this paper a completely automatic multi-exposure based FPP technique is proposed. No human intervention is required while applying the proposed method, which greatly simplify the whole reconstruction process. It is mathematically proved that once a pixel's modulation is larger than a threshold, the phase quality of this pixel can be considered satisfactory. This threshold can be used to guide the calculation of the needed exposure times. The software then automatically adjusts the camera's exposure time and captures the needed fringe images. Experiments show that with these captured images, the final reconstruction with a high dynamic range can be readily obtained.