Reading lens for scanner

• US 5,311,364 A
• Filed: 06/22/1992
• Issued: 05/10/1994
• Est. Priority Date: 08/30/1989
• Status: Expired due to Fees

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Kouchiwa, Taira, Kohno, Yoshitsugu, Ichimiya, Kohji, Harada, Naomi, Kanoshima, Yuichiro, Nishina, Kiichiro
• Primary Examiner(s): Arnold, Bruce Y.
• Assistant Examiner(s): Phan, James
• Application Number:
  US07/903,484
• Time in Patent Office: 687 Days
• Field of Search: 350/432, 350/464, 350/450, 359/708, 359/740, 359/756, 359/776, 359/771-772
• US Class Current: 359/756
• CPC Class Codes: G02B 9/62 having six components only

Abstract

A reading lens for a scanner to read an original in a reduced magnification, the lens comprising six lenses, i.e., from a first lens to a sixth lens in order on an optical axis. The first lens is a positive lens having a first lens-surface and a second lens-surface. The second lens is a negative lens disposed in contact with the first lens and has the second lens-surface in common with the first lens and a third lens-surface. The third lens is a meniscus lens and has a fourth lens-surface and a fifth lens-surface. The fourth lens is a meniscus lens and has a sixth lens-surface and a seventh lens-surface. The fifth lens is a negative lens and has a eighth lens-surface and a ninth lens-surface. The sixth lens is a positive lens disposed in contact with the fifth lens and has the ninth lens-surface in common with the fifth lens and a tenth lens-surface. At least one of the ten lens-surfaces is formed as an aspherical surface.

Claims

1. A reading lens for a scanner to read an original in a reduced magnification, said lens comprising:

a first lens disposed on an optical axis and composed of a positive lens having a first lens-surface on an object side thereof and a second lens-surface on an image side thereof;

a second lens disposed on said optical axis in contact with said second lens-surface of said first lens and composed of a negative lens having said second lens-surface in common with said first lens on an object side thereof and a third lens-surface on an image side thereof;

a third lens disposed on said optical axis in an image side of said second lens and composed of a meniscus lens having a fourth lens-surface on an object side thereof and a fifth lens-surface on an image side thereof;

a fourth lens disposed on said optical axis in an image side of said third lens and composed of a meniscus lens having a sixth lens-surface on an object side thereof and a seventh lens-surface on an image side thereof;

a fifth lens disposed on said optical axis in an image side of said fourth lens and composed of a negative lens having an eighth lens-surface on an object side thereof and a ninth lens-surface on an image side thereof; and

a sixth lens disposed on said optical axis in contact with said ninth lens-surface of said fifth lens and composed of a positive lens having said ninth lens-surface in common with said fifth lens on an object side thereof and a tenth lens-surface on an image side thereof,

said first lens-surface being an aspherical surface which has a conic constant K₁ satisfying a condition of

3. A reading lens for a scanner according to claim 1, wherein said reading lens further comprises an aperture stop disposed between said third lens and said fourth lens on said optical axis and a seventh lens disposed on said optical axis in an image side of said sixth lens and composed of a plane glass plate having parallel side surfaces.

2. -0. 035<

K₁ <

0.

4. A reading lens for a scanner to read an original in a reduced magnification, said lens comprising:

a first lens disposed on an optical axis and composed of a positive lens having a first lens-surface on an object side thereof and a second lens-surface on an image side thereof;

a second lens disposed on said optical axis in contact with said second lens-surface of said first lens and composed of a negative lens having said second lens-surface in common with said first lens on an object side thereof and a third lens-surface on an image side thereof;

a third lens disposed on said optical axis in an image side of said second lens and composed of a meniscus lens having a fourth lens-surface on an object side thereof and a fifth lens-surface on an image side thereof;

a fourth lens disposed on said optical axis in an image side of said third lens and composed of a meniscus lens having a sixth lens-surface on an object side thereof and a seventh lens-surface on an image side thereof;

a fifth lens disposed on said optical axis in an image side of said fourth lens and composed of a negative lens having an eighth lens-surface on an object side thereof and a ninth lens-surface on an image side thereof; and

a sixth lens disposed on said optical axis in contact with said ninth lens-surface of said fifth lens and composed of a positive lens having said ninth lens-surface in common with said fifth lens on an object side thereof and a tenth lens-surface on an image side thereof,

said third lens-surface being an aspherical surface which has a conic constant K₃ satisfying a condition of

space="preserve" listing-type="equation">0.097<

K.sub.3 <

1.009.

5. A reading lens for a scanner to read an original in a reduced magnification, said lens comprising:

a first lens disposed on an optical axis and composed of a positive lens having a first lens-surface on an object side thereof and a second lens-surface on an image side thereof;

a second lens disposed on said optical axis in contact with said second lens-surface of said first lens and composed of a negative lens having said second lens-surface in common with said first lens on an object side thereof and a third lens-surface on an image side thereof;

a third lens disposed on said optical axis in an image side of said second lens and composed of a meniscus lens having a fourth lens-surface on an object side thereof and a fifth lens-surface on an image side thereof;

a fourth lens disposed on said optical axis in an image side of said third lens and composed of a meniscus lens having a sixth lens-surface on an object side thereof and a seventh lens-surface on an image side thereof;

a fifth lens disposed on said optical axis in an image side of said fourth lens and composed of a negative lens having an eighth lens-surface on an object side thereof and a ninth lens-surface on an image side thereof; and

a sixth lens disposed on said optical axis in contact with said ninth lens-surface of said fifth lens and composed of a positive lens having said ninth lens-surface in common with said fifth lens on an object side thereof and a tenth lens-surface on an image side thereof,

said fourth lens-surface being an aspherical surface which has a conic constant K₄ satisfying a condition of

space="preserve" listing-type="equation">-0.09<

K.sub.4 <

-0.04.

6. A reading lens for a scanner to read an original in a reduced magnification, said lens comprising:

a first lens disposed on an optical axis and composed of a positive lens having a first lens-surface on an object side thereof and a second lens-surface on an image side thereof;

a second lens disposed on said optical axis in contact with said second lens-surface of said first lens and composed of a negative lens having said second lens-surface in common with said first lens on an object side thereof and a third lens-surface on an image side thereof;

a third lens disposed on said optical axis in an image side of said second lens and composed of a meniscus lens having a fourth lens-surface on an object side thereof and a fifth lens-surface on an image side thereof;

a fourth lens disposed on said optical axis in an image side of said third lens and composed of a meniscus lens having a sixth lens-surface on an object side thereof and a seventh lens-surface on an image side thereof;

a fifth lens disposed on said optical axis in an image side of said fourth lens and composed of a negative lens having an eighth lens-surface on an object side thereof and a ninth lens-surface on an image side thereof; and

a sixth lens disposed on said optical axis in contact with said ninth lens-surface of said fifth lens and composed of a positive lens having said ninth lens-surface in common with said fifth lens on an object side thereof and a tenth lens-surface on an image side thereof,

said fifth lens-surface being an aspherical surface which has a conic constant K₅ satisfying a condition of

space="preserve" listing-type="equation">0<

K.sub.5 <

0.055.

7. A reading lens for a scanner to read an original in a reduced magnification, said lens comprising:

a first lens disposed on an optical axis and composed of a positive lens having a first lens-surface on an object side thereof and a second lens-surface on an image side thereof;

a second lens disposed on said optical axis in contact with said second lens-surface of said first lens and composed of a negative lens having said second lens-surface in common with said first lens on an object side thereof and a third lens-surface on an image side thereof;

a third lens disposed on said optical axis in an image side of said second lens and composed of a meniscus lens having a fourth lens-surface on an object side thereof and a fifth lens-surface on an image side thereof;

a fourth lens disposed on said optical axis in an image side of said third lens and composed of a meniscus lens having a sixth lens-surface on an object side thereof and a seventh lens-surface on an image side thereof;

a fifth lens disposed on said optical axis in an image side of said fourth lens and composed of a negative lens having an eighth lens-surface on an object side thereof and a ninth lens-surface on an image side thereof; and

a sixth lens disposed on said optical axis in contact with said ninth lens-surface of said fifth lens and composed of a positive lens having said ninth lens-surface in common with said fifth lens on an object side thereof and a tenth lens-surface on an image side thereof,

said sixth lens-surface being an aspherical surface which has a conic constant K₆ satisfying a condition of

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

K.sub.6 <

0.007.

8. A reading lens for a scanner to read an original in a reduced magnification, said lens comprising:

a first lens disposed on an optical axis and composed of a positive lens having a first lens-surface on an object side thereof and a second lens-surface on an image side thereof;

a second lens disposed on said optical axis in contact with said second lens-surface of said first lens and composed of a negative lens having said second lens-surface in common with said first lens on an object side thereof and a third lens-surface on an image side thereof;

a third lens disposed on said optical axis in an image side of said second lens and composed of a meniscus lens having a fourth lens-surface on an object side thereof and a fifth lens-surface on an image side thereof;

a fourth lens disposed on said optical axis in an image side of said third lens and composed of a meniscus lens having a sixth lens-surface on an object side thereof and a seventh lens-surface on an image side thereof;

a fifth lens disposed on said optical axis in an image side of said fourth lens and composed of a negative lens having an eighth lens-surface on an object side thereof and a ninth lens-surface on an image side thereof; and

a sixth lens disposed on said optical axis in contact with said ninth lens-surface of said fifth lens and composed of a positive lens having said ninth lens-surface in common with said fifth lens on an object side thereof and a tenth lens-surface on an image side thereof,

said seventh lens-surface being an aspherical surface which has a conic constant K₇ satisfying a condition of

9. -0. 014<

K₇ <

0.

10. A reading lens for a scanner to read an original in a reduced magnification, said lens comprising:

a first lens disposed on an optical axis and composed of a positive lens having a first lens-surface on an object side thereof and a second lens-surface on an image side thereof;

a second lens disposed on said optical axis in contact with said second lens-surface of said first lens and composed of a negative lens having said second lens-surface in common with said first lens on an object side thereof and a third lens-surface on an image side thereof;

a third lens disposed on said optical axis in an image side of said second lens and composed of a meniscus lens having a fourth lens-surface on an object side thereof and a fifth lens-surface on an image side thereof;

a fourth lens disposed on said optical axis in an image side of said third lens and composed of a meniscus lens having a sixth lens-surface on an object side thereof and a seventh lens-surface on an image side thereof;

a fifth lens disposed on said optical axis in an image side of said fourth lens and composed of a negative lens having an eighth lens-surface on an object side thereof and a ninth lens-surface on an image side thereof; and

a sixth lens disposed on said optical axis in contact with said ninth lens-surface of said fifth lens and composed of a positive lens having said ninth lens-surface in common with said fifth lens on an object side thereof and a tenth lens-surface on an image side thereof,

said eighth lens-surface being an aspherical surface which has a conic constant K₈ satisfying a condition of

11. 74<

K₈ <

9.51.

12. A reading lens for a scanner to read an original in a reduced magnification, said lens comprising:

a first lens disposed on an optical axis and composed of a positive lens having a first lens-surface on an object side thereof and a second lens-surface on an image side thereof;

a second lens disposed on said optical axis in contact with said second lens-surface of said first lens and composed of a negative lens having said second lens-surface in common with said first lens on an object side thereof and a third lens-surface on an image side thereof;

a third lens disposed on said optical axis in an image side of said second lens and composed of a meniscus lens having a fourth lens-surface on an object side thereof and a fifth lens-surface on an image side thereof;

a fourth lens disposed on said optical axis in an image side of said third lens and composed of a meniscus lens having a sixth lens-surface on an object side thereof and a seventh lens-surface on an image side thereof;

a fifth lens disposed on said optical axis in an image side of said fourth lens and composed of a negative lens having an eighth lens-surface on an object side thereof and a ninth lens-surface on an image side thereof; and

a sixth lens disposed on said optical axis in contact with said ninth lens-surface of said fifth lens and composed of a positive lens having said ninth lens-surface in common with said fifth lens on an object side thereof and a tenth lens-surface on an image side thereof,

said tenth lens-surface being an aspherical surface which has a conic constant K₁₀ satisfying a condition of

13. -0. 06<

K₁₀ <

0.