| 摘要 |
PROBLEM TO BE SOLVED: To improve a utilizing efficiency of light related with image formation. SOLUTION: As for the illuminating device, in order to refract the light with a limit wavelength on a short wavelength side and the light with the limit wavelength on a long wavelength side transmitted through a condenser lens 3 and the Fresnel lens of a condensing part 4 by a prescribed refractive index and output them to the incident pupil of a projecting lens 6, the center wavelength of the light for a condensing lens 3 and the Fresnel lens is set. Besides, the center wavelength is set so as to obtain the refractive index for making the separation axis quantity from an optical axis Oa of the light with the limit wavelength on the short wavelength side nearly equivalent to that of the light with the limit wavelength on the long wavelength side at the incident pupil 6a.
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