| 摘要 |
<p>PURPOSE:To switch the distribution of photometric sensitivity by forming a relief type diffraction structure having a semitransmissive part A on one junction face of a transparent plate and forming a semitransmissive part B having an area different from that of the part A on the other non-junction face. CONSTITUTION:Luminous flax E2 obtained by transmitting luminous flux E1 through the semitransmissive area A is partially reflected by the semitransmissive area B formed on the exit side of the transparent plate 2, reversely advanced on the plate 2 and then reflectively diffracted by a reflective diffraction grating 1a. Since the inclination of a relief grating is reversed against the advancing direction of the light beams E1 at that time, the light beams E2 are guided to a 2nd photoelectric detector DB1 arranged on the reverse side against a 1st photoelectric detector DA1. Since the area B is smaller than the area A and the reflection factor of the area B is higher than that of the area B, the photometric sensitivity distribution received by a 2nd photoelectric detector DB2 approaches partial photometry. The sensitivity distribution such as average photometry, partial photometry and centroid average photometry can be switched by selecting the detectors DA1, DA2 or executing weighting arithmetic operation.</p> |
