Abstract: An anti-reflection film includes first through ninth layers. Regarding light having a wavelength of 550 nm, where the refractive indexes of the first through ninth layers are n1 through n9 respectively, the optical film thicknesses d1 through d9 (nm) respectively, and the maximum value of the difference in the refractive index between adjoining layers for layers 1 through 8 is ?n, the following conditions are satisfied. 1.60?n1?1.70, 15 nm?d1?140 nm, 2.00?n2?2.40, 20 nm?d2?120 nm, 1.60?n3?1.70, 11 nm?d3?70 nm, 2.00?n4?2.40, 20 nm?d4?165 nm, 1.60?n5?1.70, 15 nm?d5?45 nm, 2.00?n6?2.40, 90 nm?d6?175 nm, 1.60?n7?1.70, 50 nm?d7?110 nm, 2.00?n8?2.40, 20 nm?d8?50 nm, 1.20?n9?1.28, 140 nm?d9?160 nm, and 0.40??n?0.67.

Abstract: The optical element of the present invention has an anti-reflection film formed on a substrate. The anti-reflection film comprises a low refractive index layer that is formed by mutually binding hollow fine particles, each of which has a vacancy therein, using a binder, and the low refractive index layer consists of a first layer serving as an outermost layer and a second layer which is adjacent to the first layer and is located on the substrate side. Here, the filling ratio of the binder to the first layer is lower than the filling ratio of the binder to the second layer, the refractive index of the first layer is 1.1 or more but not more than 1.25 and the refractive index of the second layer is 1.26 or more but not more than 1.35.

Abstract: An anti-reflection film includes first through ninth layers. Regarding light having a wavelength of 550 nm, where the refractive indexes of the first through ninth layers are n1 through n9 respectively, the optical film thicknesses d1 through d9 (nm) respectively, and the maximum value of the difference in the refractive index between adjoining layers for layers 1 through 8 is ?n, the following conditions are satisfied. 1.60?n1?1.70, 15 nm?d1?140 nm, 2.00?n2?2.40, 20 nm?d2?120 nm, 1.60?n3?1.70, 11 nm?d3?70 nm, 2.00?n4?2.40, 20 nm?d4?165 nm, 1.60?n5?1.70, 15 nm?d5?45 nm, 2.00?n6?2.40, 90 nm?d6?175 nm, 1.60?n7?1.70, 50 nm?d7?110 nm, 2.00?n8?2.40, 20 nm?d8?50 nm, 1.20?n9?1.28, 140 nm?d9?160 nm, and 0.40??n?0.67.

Abstract: An optical element includes a substrate that is transparent, and an antireflective film laminated on the substrate. The antireflective film includes, in order from the substrate, a first layer, a second layer, and a third layer. The substrate has a refractive index of 1.80 to 2.05 for the d-line. The first layer is an inorganic oxide film having a refractive index of 1.43 to 1.47 for the d-line and a physical film thickness of 29.0 to 40.0 nm and containing silica as a main component. The second layer is an inorganic oxide film having a refractive index of 2.00 to 2.20 for the d-line and a physical film thickness of 12.0 to 41.0 nm. The third layer is a film having a refractive index of 1.23 to 1.26 for the d-line and a physical film thickness of 110.0 to 130.0 nm and containing silica nanoparticles.

Abstract: The optical element of the present invention has an anti-reflection film formed on a substrate. The anti-reflection film comprises a low refractive index layer that is formed by mutually binding hollow fine particles, each of which has a vacancy therein, using a binder, and the low refractive index layer consists of a first layer serving as an outermost layer and a second layer which is adjacent to the first layer and is located on the substrate side. Here, the filling ratio of the binder to the first layer is lower than the filling ratio of the binder to the second layer, the refractive index of the first layer is 1.1 or more but not more than 1.25 and the refractive index of the second layer is 1.26 or more but not more than 1.

Abstract: An optical system includes an optical element formed of resin. On at least one of optical surfaces on the light incidence side of the optical element formed of resin, a plurality of depressions or protrusions of a size not larger than the wavelengths of visible light is formed without a periodic structure or in a random arrangement.

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).

Abstract: An optical system includes an optical element formed of resin. On at least one of optical surfaces on the light incidence side of the optical element formed of resin, a plurality of depressions or protrusions of a size not larger than the wavelengths of visible light is formed without a periodic structure or in a random arrangement.

Abstract: Provided is 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).

Abstract: A thin-film-type ND filter which attenuates the amount of light transmission is formed on a transparent substrate by using two or more types of metallic oxide having a refractive index n and an attenuation coefficient k which are in the range of 1.0 to 3.0 in the wavelength region of the visible region, making it possible to obtain flat transmittance characteristics.

Abstract: In the single lens reflex camera whose movable mirror for reflecting light from the photographic lens to the finder is made partly half-mirrored to give a portion of the light to the photosensitive element, the finder is provided with a focusing screen of high diffusing property, the movable mirror having a half-mirrored portion at the center of the entire area with the surrounding area being made perfectly reflective is provided with a pattern of finely divided areas some of which are half-mirrored and the others of which are perfectly reflective in gradually varying area ratios in a boundary area between the central and surrounding areas, and a mask is provided on the back surface of the movable mirror for shutting off the passed light through the finely divided area pattern.

Abstract: This invention provides a method for preventing reflection. For this purpose and for decreasing the reflecting power of the surface of a light absorbing body of a metal or semi-metal material, the light absorbing body is covered by a light absorbing material of the simple substance of a metal or semi-metal.