| 摘要 |
PURPOSE:To measure the absolute power of light to be subjected to photometry by allowing a photodetor to receive the light which is obtained by passing the light for photometry through polarization converting element and diffracting it by a diffraction grating. CONSTITUTION:The light to be subjected to photometry which is incident from an incidence part 1 is transmitted through the polarization converting element 2. The element 2 is a parallel flat plate formed by sticking the wedge of uniaxial birefringent crystal whose optical axis (45 deg. arrow) is parallel to the surface and at 45 deg. to the groove (Z axis) of the diffraction grating or the wedge of biaxial birefringent crystal whose two main axes are parallel to the plane and at 45 deg. to the groove direction of the diffraction grating on the wedge of glass which is nearly equal in refractive index. The element 2 projects light which is not polarized on the whole and the light is diffracted spectrally through a concave mirror 3, a diffraction grating 4 rotated by a driving part 28, and a concave mirror 5. Then an arithmetic part 23 calculates the absolute power from the output signal of the light receiving part according to information on the detection efficiency of a measuring instrument from a memory part 22 and the absolute power is displayed on the display part 27.
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