| 摘要 |
PURPOSE:To easily detect an abnormal state of a BPF in addition to an irradiated illumination monitor by a method wherein two or more photodetector systems whose spectral sensitivity characteristic differs from each other are installed in positions to detect the passing light from the BPF and a change in the spectral sensitivity characteristic of the BPF is detected in accordance with individual signals from the photodetector systems. CONSTITUTION:When the light transmitted through a BPF 3 is received by photodetectors 13a, 13b, electric signals whose magnitude differs from each other are obtained from the photodetectors 13a, 13b. Accordingly, it these electric signals with different magnitude are compared and operated by an operational amplifier 15 and this result is output as an output signal of the operational amplifier 15, it is possible to recognize that a central wavelength of a spectral sensitivity characteristic of the BPF 3 has changed. Positive values or negative values of a difference between the mutual output signals of the photodetector 13a and the photodetector 13b or ratios of the output signals are compared, and it is judged whether the central wavelength of the spectral sensitivity characteristic of the BPF 3 is shifted to a long wavelength side or a short wavelength side.
|
