Optical element, optical system, image pickup apparatus, and lens apparatus

An optical system, comprising:

• an optical element that includes
• a substrate,
• a surface layer including a plurality of thin films, and
• an absorption layer provided between the surface layer and the substrate, the absorption layer having transmittance that varies depending on a position on the substrate,
• wherein the surface layer includes:
• a first film disposed at a position farthest from the substrate and having a refractive index of no less than 1.05 nor more than 1.4 at a wavelength of 550 nm,
• a second film disposed at a position closer to the substrate than the first film and having a higher refractive index than the substrate at a wavelength of 550 nm, and
• a third film disposed at a position adjacent to the second film and having a lower refractive index than the second film at a wavelength of 550 nm, and
• wherein the absorption layer has an extinction coefficient of no more than 0.5 at wavelengths of from 400 nm to 700 nm.

An image pickup apparatus, comprising:

• an image sensor;
• and
• an optical system,
• wherein the optical system includes an optical element,
• wherein the optical element includes
• a substrate,
• a surface layer including a plurality of thin films, and
• an absorption layer provided between the surface layer and the substrate, the absorption layer having transmittance that varies depending on a position on the substrate,
• wherein the surface layer includes:
• a first film disposed at a position farthest from the substrate and having a refractive index of no less than 1.05 nor more than 1.4 at a wavelength of 550 nm,
• a second film disposed at a position closer to the substrate than the first film and having a higher refractive index than the substrate at a wavelength of 550 nm, and
• a third film disposed at a position adjacent to the second film and having a lower refractive index than the second film at a wavelength of 550 nm, and
• wherein the absorption layer has an extinction coefficient of no more than 0.5 at wavelengths of from 400 nm to 700 nm.