Optical filter
View Patent ↗Provided is an optical filter integrally provided with a light blocking film capable of suppressing stray light. An optical filter may be used for an imaging apparatus having a built-in image sensing device on which light from a subject or a light source is incident. The optical filter includes: an optical filter main body arranged between the subject or the light source and the image sensing device and having a transmission property for the incident light; and a frame-shaped light blocking film integrally formed on at least one surface of the optical filter main body. The light blocking film satisfies the following condition (1) and/or condition (2). (1) A concavity/convexity is formed on at least a part of an inner peripheral surface of the light blocking film. (2) A thin part is formed on at least a part of an inner edge of the light blocking film.
1. An optical filter comprising:
an optical filter main body having a planar form and being transmissive to an incident light; and
a light blocking film having a frame shape, and being integrally formed on at least one surface of the optical filter main body along an outer periphery of the optical filter main body,
wherein the optical filter satisfies at least one of condition (1) and condition (2), (1) at least a part of an inner periphery of the frame shape of the light blocking film is constituted by a reference line and irregular concavities and convexities formed on the reference line in a plane of the planar form of the optical filter main body, and (2) the light blocking film has a thin portion which is thinner than a portion other than the thin portion, along at least a part of the inner periphery of the frame shape of the light blocking film.
2. The optical filter according to claim 1 ,
wherein distances between the reference line and peaks of the convexities and distances between the reference line and bottoms of the concavities are in a range of from 0.4 to 50 μm in the plane of the planar form of the optical filter main body.
3. The optical filter according to claim 1 ,
wherein a light transmittance of the thin portion is 0.5% or more.
4. The optical filter according to claim 2 ,
wherein a light transmittance of the thin portion is 0.5% or more.
5. The optical filter according to claim 1 ,
wherein the thin portion has a belt shape and a width of the belt shape of the thin portion is from 0.4 to 50 μm.
6. The optical filter according to claim 2 ,
wherein the thin portion has a belt shape and a width of the belt shape of the thin portion is from is 0.4 to 50 μm.
7. The optical filter according to claim 3 ,
wherein the thin portion has a belt shape and a width of the belt shape of the thin portion is from 0.4 to 50 μm.
8. The optical filter according to claim 4 ,
wherein the thin portion has a belt shape and a width of the belt shape of the thin portion is from is 0.4 to 50 μm.
9. The optical filter according to claim 1 ,
wherein the thin portion has an inclined surface such that the thin portion gradually decreases in thickness toward the inner periphery of the frame shape of the light blocking film.
10. The optical filter according to claim 1 , wherein the optical filter cuts a near-infrared light.
11. The optical filter according to claim 1 ,
wherein the optical filter main body comprises infrared absorbing glass that absorbs light in an infrared wavelength region.
12. The optical filter according to claim 1 ,
wherein the optical filter main body comprises an infrared absorbent that absorbs light in an infrared wavelength region.
13. The optical filter according to claim 1 , wherein a light transmittance of the portion other than the thin portion is less than 0.5%.
14. The optical filter according to claim 1 , wherein both condition (1) and condition (2) are satisfied.
15. The optical filter according to claim 14 , wherein distances between the reference line and peaks of the convexities and distances between the reference line and bottoms of the concavities are in a range of from 0.4 to 50 μm in the plane of the planar form of the optical filter main body.
16. The optical filter according to claim 15 , wherein a light transmittance of the thin portion is 0.5% or more and a light transmittance of the portion other than the thin portion is less than 0.5%.
17. The optical filter according to claim 1 , wherein a value of |Δd 1 −Δd 2 |/d is 0.05 or more, where provided that a height of a convexity is a distance between the reference line and a peak of the convexity and a depth of a concavity is a distance between the reference line and a bottom of the concavity, Δd 1 is a peak difference which is a difference between heights of two convexities which are adjacent to each other, Δd 2 is a peak difference adjacent to Δd 1 , and d is a sum of a maximum height of convexities and a maximum depth of concavities.
18. The optical filter according to claim 1 , wherein the light blocking film has a matte surface.
19. The optical filter according to claim 18 , wherein an arithmetic average roughness (Ra) of the matte surface of the light blocking film is 0.1 μm or more.
20. The optical filter according to claim 1 , wherein the light blocking film comprises carbon black, titanium black or both.