| 摘要 |
PURPOSE: A present invention relates to an optical device and a Fresnel lens sheet comprising it. The object of the present invention is to provide an optical device through which the angle of light passing and going out has little wavelength dependency and which is well applicable to Fresnel lenses with little coloration of light passing through it. CONSTITUTION: Provided is an optical device through which the angle of light passing and going out has little wavelength dependency and which is well applicable to Fresnel lenses with little coloration of light passing through it. The optical device has a diffraction grating formed on one surface and capable of diffracting rays of light incident thereon. The optical device also has a refracting member(e.g., a Fresnel lens) formed on the other surface opposite to the diffraction grating and capable of refracting the diffracted rays of light from the diffraction grating to make the refracted rays of light go out of it, in which the wavelength dependency of the diffractive angle of the main rays diffracted by the diffraction grating compensates for the wavelength dependency of the refractive angle thereof refracted by the refracting member, or that is, the former wavelength dependency is opposite to and cancels out the latter one.
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