PURPOSE: To correct the dispersion of the output characteristic of at least two light receiving parts by easy calculation.

CONSTITUTION: A sensor 1 is provided with a light projecting part L projecting light toward a photographer and the light receiving parts CL1 and CL2 receiving reflected light from at least two points of the photographer and outputting photoelectric current, and an inclination detection part 2 calculates each inverse number of the square root of the photoelectric current outputted from the light receiving parts CL1 and CL2. Based on a specified correction value stored in a correction value(correction factor) storage part 4, a correction part 3 corrects the photoelectric current or the inverse number of the square root of the photoelectric current, and further a difference between values corresponding to the light receiving parts CL1 and CL2 is calculated and outputted as an inclination signal.