Some of the main concerns related to using projectors as illumination sources include irradiation alignment and incident angle calculation; the latter was essential for targeted and homogeneous irradiances in the lesion. A simplified illumination model is demonstrated in Fig. 3. and represent the coordinates of the camera and projector, respectively, is the image plane, and is the projector plane. Given the known 3-D coordinates of the skin diseases, the mapping relation from the image plane coordinate to the projector coordinates can be described as follows: Display Formula
(2)where is the map function of the pixels from the camera plane to the projector plane. The maximum irradiance received by the disease voxel from a projector pixel can be estimated as follows: Display Formula
(3)where is the luminous power of the lamp, is the utilization rate of light energy, is the projector resolution, is the angle between the incident ray and the surface normal of the disease, is the angle between and the optical axis of the projector, and is the zoom factor of the projector, which is approximated by Eq. (4) Display Formula
(4)where is the distance from the target voxel in the projector coordinates and is the projector focal length that can be achieved during calibration.