Effects of noises in images used for height map reconstruction of cartridge cases using photometric stereo

Photometric stereo (PS) is commonly used in examination of ballistic marks and this study investigated the effects of noises present in images on the reconstructed depth map based on PS and the sensitivity of different error measures to different kinds of noises. The images of 3D synthetic objects with known light conditions and Lambert reflection model were calculated first. Thermal noise, Schottky noise and speckle noise with different amplitudes were added to these images. A common effect seen in images, the vignetting effect, was also modelled. Surface normals were calculated using these noisy images and the height maps were reconstructed. Normalized absolute error and normalized gradient error were calculated for all cases and the results were compared.