| 摘要 |
PROBLEM TO BE SOLVED: To decrease wavelength dependence of the diffraction efficiency and to prevent production of flare due to irregularity or light in the unnecessary orders of diffraction by forming a relief pattern on the interface between a first layer and a second layer and controlling the refractive indices of the first layer and the second layer to satisfy specified conditions. SOLUTION: The first layer 2 consists of an optical material which is substantially transparent in the wavelength range to be used, while the second layer 1 consists of an energy-hardening resin which is substantially transparent in the wavelength range to be used. A sawtooth relief pattern 3 is formed on the interface between the first layer 2 and the second layer 1. The refractive index n1 (λ) of the first layer 2 and the refractive index n2 (λ) of the second layer 1 satisfy the relations of n1 (λ)>n2 (λ) and (n1 (λ2 )-n2 (λ2 ))/(n1 (λ1 )-n2 (λ1 ))> (n1 (λ2 )-1)/(n1 (λ1 )-1), whereinλ1 <λ<λ2 andλ,λ1 ,λ2 are the wavelengths of arbitrary light.
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