| 摘要 |
[Object] A measurement method and an evaluating apparatus are provided which are capable of easily and accurately evaluating the light amount of a spot beam, the diffraction efficiency, and the intensity distribution in the optical axis direction by detecting even a weak diffracted beam in an arbitrary wavelength range converged by a diffraction optical element as an imaging lens. [Means for Attaining the Object] Light emitted from a white light source 11 passes through a wavelength band-pass filter 12 and is diaphragmed by a pinhole slit 13. The resultant light is paralleled by a collimator lens 14 and enters a diffraction optical element 16 as an imaging lens. The light getting out from the diffraction optical element 16 is converged to be a spot beam 17, is magnified by a microscope 18, and is then projected on a CCD 19. A distance changing member 56 changes the distance between the CCD 19 and the diffraction optical element 16, and then, the intensity distribution in the optical axis direction is measured. In-plane intensity distribution perpendicular to the optical axis is also measured.
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