An illumination apparatus emits illumination light S1 with an intensity distribution that changes with time. A photodetector measures reflected light from an object. A reconstruction processing unit reconstructs an intermediate image Hi(x, y) of the object for every predetermined number of changes of the intensity distribution using a correlation calculation between detection intensities based on the output of the photodetector and the intensity distributions of the illumination light. A combining processing unit calculates shift amounts Δx and Δy for matching between the current reconstructed image Gi(x, y) obtained by combining the previous intermediate images H(x, y) and the current intermediate image Hi(x, y). Subsequently, the current reconstructed image Gi(x, y) is shifted based on the shift amounts Δx and Δy. The shifted reconstructed image Gi(x−Δx, y−Δy) is combined with the latest intermediate image Hi(x, y) to create a new reconstructed image Gi+1(x, y).