Optical filter having differing reflectance depending on light incident side
AssigneeCanon Kabushiki Kaisha
InventorsKazue Uchida, Tomohiko Ishibashi
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Abstract
The disclosed optical filter is provided on a substrate. The optical filter includes a first layer, an absorption layer, and a second layer in order from a substrate side. The condition of |R1−R2|≥10 is satisfied where R1 [%] represents a reflectance of the optical filter for light whose wavelength is 550 nm and that makes incident on the optical filter from a side opposite to the substrate, and R2 [%] represents a reflectance of the optical filter for light whose wavelength is 550 nm and that makes incident on the optical filter from the substrate side.
Claims13
An optical filter provided on a substrate, the optical filter comprising in order from a substrate side:
- a first layer made of a material whose extinction coefficient at the wavelength of 550 nm is 0.02 or less;
- an absorption layer having light absorbency;
- and
- a second layer made of a material whose extinction coefficient at the wavelength of 550 nm is 0.02 or less, the substrate, the first layer, the absorption layer, and the second layer being mutually adjacent,
- wherein the following conditions are satisfied:
- R2−R1≥10[%], and
- 8
- [
- nm
- ]
- ≤
- ∑
- j
- =
- 1
- m
-
- kj
- ×
- dj
- ≤
- 13
-
- 2
- [
- nm
- ]
- where R1 [%] represents a reflectance of the optical filter for light whose wavelength is 550 nm and that makes incident on the optical filter from a side opposite to the substrate, and R2 [%] represents a reflectance of the optical filter for light whose wavelength is 550 nm and that makes incident on the optical filter from the substrate side, and
- where m represents a number of films constituting the absorption layer, kj represents an extinction coefficient of a j-th film counted from the substrate side among the m films at the wavelength of 550 nm, and dj [nm] represents a physical film thickness of the j-th film.
An optical filter provided on a substrate, the optical filter comprising in order from a substrate side:
- a first layer made of a material whose extinction coefficient at the wavelength of 550 nm is 0.02 or less;
- an absorption layer having light absorbency;
- and
- a second layer made of a material whose extinction coefficient at the wavelength of 550 nm is 0.02 or less, the substrate, the first layer, the absorption layer, and the second layer being mutually adjacent,
- wherein a number of films constituting the first layer is larger than a number of films constituting the second layer, and
- wherein the following condition is satisfied:
- R2−R1≥10[%]
- where R1 [%] represents a reflectance of the optical filter for light whose wavelength is 550 nm and that makes incident on the optical filter from a side opposite to the substrate, and R2 [%] represents a reflectance of the optical filter for light whose wavelength is 550 nm and that makes incident on the optical filter from the substrate side.
An optical element comprising:
- a substrate made of glass or plastic;
- and
- an optical filter provided on the substrate,
- wherein the optical filter comprises in order from a substrate side:
- a first layer made of a material whose extinction coefficient at a wavelength of 550 nm is 0.02 or less;
- an absorption layer having light absorbency;
- and
- a second layer made of a material whose extinction coefficient at the wavelength of 550 nm is 0.02 or less, the substrate, the first layer, the absorption layer, and the second layer being mutually adjacent,
- wherein a thickness of the substrate is 0.2 mm or more and 8.0 mm or less, and
- wherein the following condition is satisfied:
- R2−R1≥10[%]
- where R1 [%] represents a reflectance of the optical filter for light whose wavelength is 550 nm and that makes incident on the optical filter from a side opposite to the substrate, and R2 [%] represents a reflectance of the optical filter for light whose wavelength is 550 nm and that makes incident on the optical filter from the substrate side.
Dependencies are inferred from the claim text.