Image pickup apparatus
In an image pickup apparatus including an optical system and an image pickup element, the optical system includes, in order from an object side to an image side, lens(es), an aperture stop, and lens(es). The lens arranged at the most image side in the optical system is a negative lens, and an infrared cut film is formed on at least one lens surface in the optical system. An optical axial distance from the exit pupil of the optical system to the image plane when focusing on an infinite object, an optical axial distance from the lens surface provided with the infrared cut film to the image plane when focusing on the infinite distance object, the curvature radius of the lens surface provided with the infrared cut film, and a radius of a circle circumscribed about an effective imaging area of the image pickup element are appropriately set.
1. An image pickup apparatus comprising:
an optical system; and
an image pickup element configured to pick up an image formed by the optical system,
wherein the optical system includes, in order from an object side to an image side, one or more lenses, an aperture stop, and one or more lenses,
the lens arranged at the most image side in the optical system is a negative lens,
an infrared cut film is formed on at least one lens surface in the optical system, and
the following conditional expressions are satisfied:
0.1<( Lepw−Lc )/ Rc< 1.5; and
1.0<| Lepw|Y max<2.5,
where Lepw denotes an optical axial distance from an exit pupil of the optical system to an image plane when the optical system focuses on an infinite distance object, Lc denotes an optical axial distance from the lens surface provided with the infrared cut film to the image plane when the optical system focuses on the infinite distance object, Rc denotes a curvature radius of the lens surface provided with the infrared cut film, and Ymax denotes a radius of a circle circumscribed about an effective imaging area of the image pickup element.
2. The image pickup apparatus according to claim 1 , wherein the infrared cut film is formed on a lens surface arranged on the image side of the aperture stop.
3. The image pickup apparatus according to claim 1 , wherein
the following conditional expression is satisfied,
0.5<| fn|/fw< 15.0
where fn denotes a focal length of the negative lens arranged at the most image side in the optical system, and fw denotes a focal length of the optical system.
4. The image pickup apparatus according to claim 1 , wherein the following conditional expression is satisfied,
0.5<( Rnb+Rna )/( Rnb−Rna )<5.0,
where Rna denotes a curvature radius of an object-side lens surface of the negative lens arranged at the most image side in the optical system, and Rnb denotes a curvature radius of the image-side lens surface of the negative lens.
5. The image pickup apparatus according to claim 1 , wherein the infrared cut film is formed on an object-side lens surface of the negative lens arranged at the most image side in the optical system.
6. The image pickup apparatus according to claim 1 , wherein the infrared cut films are formed on a plurality of lens surfaces.
7. The image pickup apparatus according to claim 1 , wherein an infrared absorption filter is provided between the optical system and the image pickup element.
8. The image pickup apparatus according to claim 1 , wherein the optical system is a zoom lens.
9. The image pickup apparatus according to claim 8 , wherein the negative lens arranged at the most image side in the optical system moves to the object side during zooming from a wide angle end to a telephoto end.
10. The image pickup apparatus according to claim 8 , wherein the following conditional expression is satisfied,
1.1<β nt/βnw< 3.0,
where βnw denotes a lateral magnification of the negative lens arranged at the most image side in the optical system when the optical system focuses on the infinite distance object at the wide angle end, and βnt denotes the lateral magnification of the negative lens arranged at the most image side in the optical system when the optical system focuses on the infinite distance object at the telephoto end.