Camera shading calibration using a spatially modulated field

Camera shading calibration is investigated using an illumination field with sinusoidal spatial intensity modulation, instead of using an idealized flat field. The modulated field can be set up simply with a relatively imperfect display device such as an LCD computer monitor, or as a printed card under constant illumination. Several images are taken with different horizontal and vertical translations of the camera position with respect to the field. The calibration algorithm simultaneously estimates the field and the camera shading by estimating the camera translations and performing equation iteration. Simulation and experiment show that shading correction images can be obtained to an accuracy dominated only by temporal pixel noise.