An apparatus for wavefront detection includes a wavefront source for the production of a wavefront, an optical system transforming the wavefront, a diffraction grating through which the transformed wavefront passes, and a spatially resolving detector following the diffraction grating. The illumination-invariant object tracking method involves: designating an initial position of an object of interest to be tracked in an image; constructing a probability map for object tracking in consideration of a color ratio of adjacent pixels in the image; and performing Kalman filtering based on the initial position of the object and the probability map. Accordingly, the heat generated by the semiconductor chip can be efficiently dissipated via the heat radiation electrode, the metal plate and the second supporting member.