Reading lens

• US 6,028,711 A
• Filed: 07/30/1998
• Issued: 02/22/2000
• Est. Priority Date: 07/31/1997
• Status: Expired due to Fees

• Current Assignee: Asahi Kogaku Kogyo Kabushiki Kaisha
• Original Assignee: Asahi Kogaku Kogyo Kabushiki Kaisha
• Inventors: Adachi, Yuka
• Primary Examiner(s): Epps, Georgia
• Assistant Examiner(s): LUCAS, MICHAEL A
• Application Number:
  US09/124,968
• Time in Patent Office: 572 Days
• Field of Search: 359/784-792, 359/642
• US Class Current: 359/642
• CPC Class Codes: G02B 13/24 for reproducing or copying at short object distances
• CPC Class Codes: G02B 27/0037 with diffracting elements G02B27/0056 takes precedence; holographic optical elements G02B5/32; zone systems G02B5/1876
• CPC Class Codes: G02B 27/4211 correcting chromatic aberrations G02B27/0056, G02B27/4222, G02B27/4227 take precedence

Abstract

Disclosed is a reading lens consisting of one glass lens and first and second plastic lenses. A positive diffraction lens structure being is formed on one surface of the surfaces of the first and second plastic lenses. The positive diffraction lens structure functions at least to compensate a longitudinal chromatic aberration which is caused by refractive power of the glass lens and the first and second plastic lenses.

Claims

1. A reading lens consisting of one glass lens and first and second plastic lenses, a positive diffraction lens structure being formed on one of surfaces of said first and second plastic lenses, said positive diffraction lens structure functions at least to compensate chromatic aberration caused by refractive powers of said glass lens and said first and second plastic lenses.

2. The reading lens according to claim 1, wherein said diffraction lens compensates a longitudinal chromatic aberration caused by refractive powers of said glass lens and said first and second plastic lenses.

3. The reading lens according to claim 2, wherein a lateral chromatic aberration is compensated by configuration of said glass lens and said first and second plastic lenses.

4. The reading lens according to claim 2, wherein each of said glass lens and said first and second plastic lenses are positive lenses.

5. The reading lens according to claim 4, which satisfies conditions:

space="preserve" listing-type="equation">0.10<

φ

d/φ

t<

0.25;

space="preserve" listing-type="equation">φ

p1/φ

t<

0.50;

and

space="preserve" listing-type="equation">φ

p2/φ

t<

0.50,

wherein,

φ

d represents power of said diffraction lens structure;

φ

t represents power of said reading lens as a whole;

φ

p1 represents power of said first plastic lens; and

φ

p2 represents power of said second plastic lens.

6. The reading lens according to claim 2, said glass lens having a positive power, one of said first and second plastic lenses having a negative power, the other of said first and second plastic lenses having a positive power.

7. The reading lens according to claim 6, which satisfies conditions:

space="preserve" listing-type="equation">0.02<

φ

d/φ

t<

0.20;

space="preserve" listing-type="equation">|φ

p1/φ

g|<

0.85;

and

space="preserve" listing-type="equation">|φ

p2/φ

g|<

0.85,

wherein,

φ

d represents power of said diffraction lens structure;

φ

t represents power of said reading lens as a whole;

φ

p1 represents power of said first plastic lens;

φ

p2 represents power of said second plastic lens; and

φ

g represents power of said glass lens.

8. The reading lens according to claim 2, which includes an aperture stop, and wherein one of said surfaces of said first and second plastic lenses, on which said diffraction lens structure is formed faces said aperture stop.

9. A reading lens consisting of one glass lens and first and second plastic lenses, a positive diffraction lens structure being formed on one of surfaces of said first and second plastic lenses, said positive diffraction lens structure functions at least to compensate chromatic aberration caused by refractive powers of said glass lens and said first and second plastic lenses, and

an aperture stop, wherein one of the surfaces of said first and second plastic lenses, on which said diffraction lens structure is formed, faces said aperture stop.