| 摘要 |
A diffractive optical element includes a first layer having a relief type grating, a second layer having a relief type grating, and a third layer having a relief type grating. The first, second and third layers are formed of different materials. The diffractive optical element has at least three diffraction optical parts in the boundary areas of the respective layers. The diffractive optical element is set so that at least wavelengths, the diffraction efficiency thereof for diffracted light of a predetermined order may be maximum. The three wavelengths are substantially coincident with the main wavelengths of the three primary colors.
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