Abstract: In forming an optical thin film on a curved surface of a material to be deposited, a specific space, which is part of a space in a processing chamber and is a space between an arrangement part and a target, is surrounded by a shielding part. In this state, when deposition is performed by a sputtering step in which a voltage is applied to the target in the processing chamber which is in a vacuum state and supplied with an active gas and an inert gas, an optical thin film of a substantially equal optical thickness is formed on the curved surface.

Abstract: An antireflection film, including an optical element, formed on an optical surface of an optical member and preventing reflection of a light beam incident on the optical surface. It has a maximum reflectance P1 in a first wavelength region and a maximum reflectance P2 in a second wavelength region at a wavelength side longer than the first wavelength region, and satisfies a relation of P1>P2, as a spectral reflectance property when a light beam is incident on the optical surface at a 0 degree incident angle. It also shifts a wavelength range where the reflectance is a specific value or less, to a wavelength longer than the second wavelength region, the reflectance in the second wavelength region decreases, and the reflectance in the first wavelength region increases so that a luminance difference is small between a ghost in the first wavelength region and the second wavelength region.