Imaging optical system, stereo camera device and car-mounted camera device

Patent metadata

Field	Value
Publication number	US-10281690-B2
Application number	US-201514638923-A
Country	US
Kind code	B2
Filing date	Mar 4, 2015
Priority date	Mar 5, 2014
Publication date	May 7, 2019
Grant date	May 7, 2019

Abstract

An imaging optical system including, in order from an object side to an image side, a first lens group having a negative refractive power, an aperture stop, a second lens group having a positive refractive power, is provided. The first lens group includes in order from the object side a first lens having a positive refractive power and a meniscus shape turning a convex surface to the object side, a second lens having a negative refractive power, and a third lens having a positive refractive power. A lens surface positioned closest to the image side in the first lens group is a concave surface to the image side, and a lens surface positioned closest to the object side in the second lens group is a concave surface to the object side.

First claim

What is claimed is:

1. An imaging optical system, consisting of, in order from an object side to an image side:
a first lens group having a negative refractive power;
an aperture stop; and
a second lens group having a positive refractive power,
wherein the first lens group consists of, in order from the object side, a first lens having a positive refractive power and a meniscus shape turning a convex surface to the object side, a second lens having a negative refractive power, and a third lens having a positive refractive power,
wherein a lens surface positioned closest to the image side in the first lens group is a concave surface to the image side, and a lens surface positioned closest to the object side in the second lens group is a concave surface to the object side,
wherein a focal distance f of a whole system of the imaging optical system and a focal distance fa of an air lens which is formed between a lens surface positioned closest to the image side in the first lens group and a lens surface positioned closest to the object side in the second lens group satisfy the following condition (1)
0.15 <|f/fa |<1.00,  (1)

wherein the focal distance f of a whole system of the imaging optical system and a focal distance f 1 of the first lens group satisfy the following condition (2)
2.00 <|f 1 /f |<20.00,  (2)

wherein the third lens having a positive refractive power is a single lens, and
wherein the second lens group includes three lens including, in order from the object side, a first biconcave lens which is cemented to a second biconvex lens.

2. The imaging optical system according to claim 1 , wherein the focal distance f of a whole system of the imaging optical system and a focal distance f 1 of the first lens group satisfy the following condition (2A)
2.50 <|f 1 /f |<15.00  (2A).

3. The imaging optical system according to claim 1 , wherein the focal distance f of a whole system of the imaging optical system and a distance AL on an optical axis between a lens surface positioned closest to the object side in the first lens group and an imaging plane satisfy the following condition (3)
0.15 <f/AL <0.50  (3).

4. The imaging optical system according to claim 1 , wherein the focal distance f of a whole system of the imaging optical system and a distance AL on an optical axis between a lens surface positioned closest to the object side in the first lens group and an imaging plane satisfy the following condition (3A)
0.20 <f/AL <0.40  (3A).

5. The imaging optical system according to claim 1 , wherein the focal distance f of a whole system of the imaging optical system and a distance AL on an optical axis between a lens surface positioned closest to the object side in the first lens group and an imaging plane satisfy the following condition (3)
0.15 <f/AL <0.50  (3).

6. The imaging optical system according to claim 1 , wherein the focal distance f of a whole system of the imaging optical system and a distance AL on an optical axis between a lens surface positioned closest to the object side in the first lens group and an imaging plane satisfy the following condition (3)
0.15 <f/AL <0.50  (3).

7. The imaging optical system according to claim 1 , wherein the second lens group having a positive refractive power positioned in the image side of the aperture stop includes a second F lens group having a positive refractive power and a second R lens group having a positive refractive power, the second F lens group includes at least one lens having a negative refractive power and at least one lens having a positive refractive power, the second R lens group includes a lens having a positive refractive power.

8. The imaging optical system according to claim 7 , wherein the focal distance f of a whole system of the imaging optical system and a focal distance f 2 F of the second F lens group satisfy the following condition (4)
0.50 <f 2 F/f <2.50  (4).

9. The imaging optical system according to claim 1 , wherein all lenses of the first lens group and the second lens group are glass spherical lenses.

10. A stereo camera device comprising the imaging optical system according to claim 1 .

11. A car-mounted camera device comprising the imaging optical system according to claim 1 .

12. A car-mounted camera device comprising the stereo camera device according to claim 10 .

13. The stereo camera device according to claim 10 , further comprising a processor configured to digitize a photographed image with the imaging optical system.

14. The car-mounted camera device according to claim 11 , further comprising a processor configured to digitize a photographed image with the imaging optical system.

15. The imaging optical system according to claim 1 , wherein an air gap between the second lens in the first lens group and the third lens in the first lens group is widest in the imaging optical system.

Assignees

• Nakayama Takahiro
• Nakanuma Hiroshi
• Ricoh Co Ltd

Inventors

• Nakayama Takahiro
• Nakanuma Hiroshi

Classifications

• G02B13/005 Primary

  having spherical lenses only · CPC title

• G02B13/0045

  having five or more lenses · CPC title

• G02B9/64

  having more than six components · CPC title

• G02B13/04

  Reversed telephoto objectives · CPC title

• G03B35/00

  Stereoscopic photography · CPC title