Patent Number: 7,710,670

Title: ND filter

Abstract: An ND filter including an alternating layer which is composed of two films being alternately stacked and formed on a transparent substrate, the two films having different refractive indexes, wherein the alternating layer has a substrate-side reflected light attenuating multi-layered film and a transmittance adjusting multi-layered film formed on the transparent substrate in the stated order from the transparent substrate side, and the light absorption amount of the substrate-side reflected light attenuating multi-layered film is set to be 20% or more and 30% or less. Thus, an ND filter having satisfactory front surface reflection characteristics and rear surface reflection characteristics can be stably obtained while the transmittance of 4% or more and 11% or less is maintained with respect to the entire visible region (400 nm or more and 700 nm or less).

Inventors: Abe; Susumu (Utsunomiya, JP), Amano; Sayoko (Utsunomiya, JP)

Assignee: Canon Kabushiki Kaisha

International Classification: G02B 5/22 (20060101); G02B 1/10 (20060101)

Expiration Date: 5/04/12018