Optical system, image pickup device and digital apparatus

• US 20060087747A1
• Filed: 10/20/2005
• Published: 04/27/2006
• Est. Priority Date: 10/21/2004
• Status: Active Grant

• Current Assignee: Konica Minolta OPTO Incorporated (Konica Minolta Inc.)
• Original Assignee: Konica Minolta OPTO Incorporated (Konica Minolta Inc.)
• Inventors: Matsusaka, Keiji, Ohzawa, Soh
• Granted Patent: US 7,286,302 B2
• Time in Patent Office: Days
• US Class Current: 359/749
• CPC Class Codes: G02B 13/04 Reversed telephoto objectives
• CPC Class Codes: G02B 13/18 with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration G02B13/002 takes precedence

Abstract

An optical system having a wide angle of view for forming an optical image of a photographic subject on light-receiving surfaces of an imaging element that converts the optical image into an electrical signal comprises a first lens having a negative optical power and a group of lenses each having a positive optical power, which are serially disposed from an object side. The first lens comprises at least one aspherical surface, and has a concave surface centered around an optical axis in vicinity of the optical axis on an image-side surface thereof. Further, an optical entire length T (mm) of the entire system, half angle of view θ, and focal distance f_tot (mm) of the entire system satisfy the following conditional expressions.
10 mm<T×sin θ<30 mm
7<T/f_tot<20 Thereby, the wide-angle optical system achieving a wide angle of view, reducing the optical entire length and capable of favorably correcting an aberration can be obtained. An image pickup device comprising the wide-angle optical system can be provided in a compact size, however, is still capable of photographing a wide region. Therefore, the image pickup device is suitable for monitor cameras such as an in-vehicle camera and a security camera.

Claims

1. An optical system comprising from an object side:

a first lens having a negative optical power, including at least an aspherical surface and having a concave surface centered around an optical axis in vicinity of the optical axis on an image-side surface; and

a lens group having a positive optical power, wherein the following conditions are satisfied,

10 mm<

T×

sin θ

<

30 mm,
7<

T/f_tot<

20,

where

T;

optical entire length of entire system (mm)

θ

;

half angle of view

f_tot;

focal distance of entire system (mm).

2. An optical system according to claim 1, wherein the following condition is satisfied,

350<

Hk₁

where

Hk₁;

Knoop hardness of first lens.

3. An optical system according to claim 1, wherein the following condition is satisfied,

−

0.6<

f₁/f_tot<

−

0.2

where

f₁;

focal distance of first lens (mm).

4. An optical system according to claim 1, wherein the first lens includes an aspherical surface as the object-side surface and a periphery of the aspherical surface has the positive optical power larger than that of a central part thereof.

5. An optical system according to claim 1, wherein the following condition is satisfied,

30<

v₁
1.6<

N₁

where

v₁;

dispersion of first lens

N₁;

refractive index of first lens.

6. An imaging apparatus comprising:

imaging elements for converting an optical image to an electrical signal; and

an optical system that forms an optical image of the object on a receiving surface of said imaging elements,

wherein said optical system includes from an object side;

a first lens having a negative optical power, including at least an aspherical surface and having a concave surface centered around an optical axis in vicinity of the optical axis on an image-side surface; and

a lens group having a positive optical power, wherein the following conditions are satisfied,

10 mm<

T×

sin θ

<

30 mm,
7<

T/f_tot<

20,

where

T;

optical entire length of entire system (mm)

θ

;

half angle of view

f_tot;

focal distance of entire system (mm).

7. An imaging apparatus according to claim 6, wherein the following condition is satisfied,

350<

Hk₁

where

Hk₁;

Knoop hardness of first lens.

8. An imaging apparatus according to claim 6, wherein the following condition is satisfied,

−

0.6<

f₁/f_tot<

−

0.2

where

f₁;

focal distance of first lens (mm).

9. An imaging apparatus according to claim 6, wherein the first lens includes an aspherical surface as the object-side surface and a periphery of the aspherical surface has the positive optical power larger than that of a central part thereof.

10. An imaging apparatus according to claim 6, wherein the following condition is satisfied,

30<

v₁
1.6<

N₁

where

v₁;

dispersion of first lens

N₁;

refractive index of first lens.

11. An imaging apparatus according to claim 6, wherein the following condition is satisfied,

3.0×

10<sup>−

2</sup><

D/f_tot<

3.0×

10<sup>−

1</sup>

provided that,

D;

shift amount (direction where the positive power is intensified is positive, unit;

mm) of the aspherical surface from a reference curved surface (spherical surface) at a position through which a principal ray having an image height of 80% of a maximum image height (H) is transmitted in the light-receiving surfaces of the imaging element.

12. An imaging apparatus according to claim 6, wherein the imaging apparatus is mounted at a predetermined position, and picks up an image of a peripheral region of the predetermined position.

13. A digital apparatus comprising an imaging unit which includes imaging elements for converting an optical image to an electrical signal, and an image pickup optical system that forms an optical image of the object on a receiving surface of said imaging elements,

wherein said optical system includes from an object side:

a first lens having a negative optical power, including at least an aspherical surface and having a concave surface centered around an optical axis in vicinity of the optical axis on an image-side surface; and

a lens group having a positive optical power, wherein the following conditions are satisfied,

10 mm<

T×

sin θ

<

30 mm,
7<

T/f_tot<

20,

where

T;

optical entire length of entire system (mm)

θ

;

half angle of view

f_tot;

focal distance of entire system (mm).