Wide-angle lens system and image-taking device

• US 7,375,906 B2
• Filed: 04/06/2006
• Issued: 05/20/2008
• Est. Priority Date: 04/11/2005
• Status: Active Grant

• Current Assignee: Konica Minolta OPTO Incorporated (Konica Minolta Inc.)
• Original Assignee: Konica Minolta OPTO Incorporated (Konica Minolta Inc.)
• Inventors: Isono, Masashi, Hirose, Masatoshi
• Primary Examiner(s): THOMPSON, TIMOTHY J
• Application Number:
  US11/398,947
• Publication Number:
  US 20060227434A1
• Time in Patent Office: 775 Days
• Field of Search: 359/749, 359/750, 359/751, 359/752, 359/753, 359/754, 359/755, 359/756, 359/680, 359/681, 359/682, 359/683
• US Class Current: 359/749
• CPC Class Codes: G02B 13/001 Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras G02B23/243 takes precedence
• CPC Class Codes: G02B 13/004 having four lenses
• CPC Class Codes: G02B 13/06 Panoramic objectives; So-called "sky lenses" including panoramic objectives having reflecting surfaces
• CPC Class Codes: G02B 9/34 having four components only

Abstract

A wide-angle lens system has, from the object side thereof: a first lens element having a negative optical power and having a meniscus shape convex to the object side; a second lens element having a biconcave shape; a third lens element having a biconvex shape; and a fourth lens element having a negative optical power and having a meniscus shape convex to the image side. Alternatively, a wide-angle lens system has, from the object side thereof: a first lens element having a negative optical power; a second lens element having a negative optical power; a third lens element having a positive optical power; and a fourth lens element having a positive optical power.

Claims

1. A wide-angle lens system consisting essentially of, from an object side thereof:

a first lens element having a negative optical power and having a meniscus shape convex to the object side;

a second lens element having a biconcave shape;

a third lens element having a biconvex shape; and

a fourth lens element having a positive optical power and having a meniscus shape convex to an image side.

2. The wide-angle lens system of claim 1,

wherein the second lens element fulfills the following conditional formula:

0.2<

(r3+r4)/(r3−

r4)<

0.9

where

r3 represents an object-side paraxial radius of curvature of the second lens element; and

r4 represents an image-surface-side paraxial radius of curvature of the second lens element.

3. The wide-angle lens system of claim 1,

wherein the following conditional formula is fulfilled

2W>

140 degrees

where

2W represents a total angle of view of the wide-angle lens system.

4. The wide-angle lens system of claim 1,

wherein the first lens element fulfills the following conditional formula:

0.01<

f/r1<

0.12

where

f represents a focal length of the entire wide-angle lens system; and

r1 represents an object-side radius of curvature of the first lens element.

5. The wide-angle lens system of claim 1,

wherein the second lens element fulfills the following conditional formula:

−

0.8<

f/f2<

−

0.2

where

f represents a focal length of the entire wide-angle lens system; and

f2 represents a focal length of the second lens element.

6. The wide-angle lens system of claim 1, further comprising

an aperture stop disposed between the third and fourth lens elements.

7. The wide-angle lens system of claim 1,

wherein the first lens element is a glass lens element, and the second to fourth lens elements each have an aspherical surface on at least one side thereof.

8. An image-taking device comprising:

the wide-angle lens system of claim 1,

wherein the image-taking device forms an image on a solid-state image sensor by using the wide-angle lens system.

9. The wide-angle lens system of claim 1, wherein the second lens element and third lens element are not either cemented or joined together.