Far-infrared camera lens, lens unit, and imaging apparatus

• US 7,835,072 B2
• Filed: 03/17/2008
• Issued: 11/16/2010
• Est. Priority Date: 09/10/2007
• Status: Expired due to Fees

• Current Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Original Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Inventors: Izumi, Tatsuya
• Primary Examiner(s): Font; Frank G
• Application Number:
  US12/076,343
• Publication Number:
  US 20090067041A1
• Time in Patent Office: 974 Days
• Field of Search: 359/356, 359/357, 359/784, 359/785
• US Class Current: 359/356
• CPC Class Codes: G02B 13/14 for use with infrared or ultraviolet radiation G02B13/008, G02B13/16 take precedence

Abstract

Three lenses formed of ZnS are used in combination. A first lens is a meniscus lens having a middle portion which is convex on an object side. A second lens has a middle portion that is a meniscus, which is concave on an object side and has positive refractive power, and a peripheral portion, which is convex on the object side. The first and second lenses have positive refractive power in combination. A third lens is provided adjacent to the second lens with a distance therebetween 1 mm or less and has a middle portion, which is a convex meniscus on an object side, and a peripheral portion which is concave on the object side. A diffraction surface is formed in either surface of the lens.

Claims

1. A far-infrared camera lens comprising:

a first lens that is formed of ZnS and has a middle portion that is a meniscus, which is convex on an object side and concave on an image surface side, and a peripheral portion, which is concave on the object side and convex on the image surface side;

a second lens that is formed of ZnS and has a middle portion that is a meniscus, which is concave on an object side and has positive refractive power, and a peripheral portion, which is convex on the object side; and

a third lens that is formed of ZnS, is provided adjacent to the second lens, and has a middle portion which has a convex meniscus shape on an object side and a peripheral portion which is concave on the object side, wherein

a diffraction surface is formed in either lens surface of at least one of the first lens, the second lens, or the third lens, and

a viewing angle is 50°

to 70°

.

2. The far-infrared camera lens according to claim 1, wherein

the third lens is provided adjacent to the second lens with a distance therebetween 1 mm or less.

3. The far-infrared camera lens according to claim 1, wherein

a total focal distance f is 6 mm to 11 mm, and

a focal distance f₁₂ of only the first and second lenses is 5 mm to 18 mm.

4. The far-infrared camera lens according to claim 1, wherein

when the total focal distance of the three lenses is f, the focal distance of only the first and second lenses is f₁₂, 0.9≦

f₁₂/f≦

1.6.

5. The far-infrared camera lens according to claim 1, wherein

the first, second, and third lenses formed of ZnS are manufactured by molding ZnS raw powder by heat compression using a lens-shaped mold.

6. The far-infrared camera lens according to claim 1, wherein

in all of the first, second, and third lenses,

sag amount<

5 mm,

1.5 mm<

central thickness<

8 mm, and

1 mm<

edge thickness<

8 mm.

7. A lens unit using the lens according to claim 1.

8. An imaging apparatus comprising:

the lens unit according to claim 7; and

an imaging unit that images an image formed on the lens unit.

9. The far-infrared camera lens according to claim 1, wherein

the first lens is located at a first distance from an image plane,

the second lens is located at a second distance from the image plane, the second distance being smaller than the first distance, and

the third lens is located at a third distance from the image plane, the third distance being smaller than the second distance.