Claims
- 1. A conversion lens comprising, from front to rear:
- a first lens unit or group made of glass material;
- a second lens unit or group made of plastic material; and
- a third lens unit or group made of glass material said lens units or groups being separated from each other with at least a partial air space therebetween.
- 2. A conversion lens according to claim 1, wherein said first lens unit or group has a positive refractive power, and said third lens unit or group has a negative refractive power said lens units or groups being separated from each other with at least a partial air space therebetween.
- 3. A conversion lens according to claim 1, wherein said first lens unit has a negative refractive power, and said third lens unit has a positive refractive power.
- 4. A conversion lens according to claim 1, satisfying the following condition:
- 0.5<D/L<0.85
- where D is the distance from the frontmost lens surface of said second lens unit to the rearmost lens surface thereof, and L is the distance from the frontmost lens surface of said first lens unit to the rearmost lens surface of said third lens unit.
- 5. A conversion lens according to claim 2, wherein said first lens unit has a lens of meniscus form convex toward the front, said second lens unit has a bi-convex lens, and said third lens unit has a bi-concave lens.
- 6. A conversion lens according to claim 2, wherein said first lens unit has a lens of meniscus form convex toward the front, said second lens unit has a lens of meniscus form convex toward the front, and said third lens unit has a bi-concave lens.
- 7. A conversion lens according to claim 2, wherein said first lens unit has a bi-convex lens, said second lens unit has a lens of meniscus form convex toward the rear, and said third lens unit has a bi-concave lens.
- 8. A conversion lens according to claim 3, wherein said first lens unit has a lens of meniscus form convex toward the front, said second lens unit has a lens of meniscus form convex toward the rear, and said third lens unit has a lens whose front surface is convex toward the front.
- 9. A conversion lens according to claim 3, wherein said first lens unit has a bi-concave lens, said second lens unit has a lens of meniscus form convex toward the front, and said third lens unit has a bi-convex lens.
- 10. A conversion lens according to claim 3, wherein said first lens unit has a lens whose front surface is convex toward the front, said second lens unit has a bi-concave lens, and said third lens unit has a bi-convex lens.
- 11. A conversion lens according to claim 1, satisfying the following condition:
- .upsilon..sub.1 >.upsilon..sub.2, .upsilon..sub.3 >.upsilon..sub.2
- where .upsilon..sub.1 and .upsilon..sub.3 are respectively the equivalent values of Abbe number of said first and said third lens units, and .upsilon..sub.2 is the value of Abbe number of said second lens unit, and .upsilon.k can be expressed by the following formula:
- .PHI./.upsilon.k=.SIGMA..phi.i/.upsilon.i
- where .PHI. is the refractive power of the entire lens system, and .phi.i and .upsilon.i are respectively the refractive power and Abbe number of the material of the i-th constituent lens element in the k-th lens unit.
- 12. A front conversion lens comprising a front lens unit made of glass material, an intermediate lens unit made of plastic material and having the largest thickness of said front conversion lens and a rear lens unit made of glass material.
- 13. A front conversion lens according to claim 12, wherein said front lens unit has a positive refractive power, and said rear lens unit has a negative refractive power.
- 14. A front conversion lens according to claim 12, wherein said front lens unit has a negative refractive power, and said rear lens unit has a positive refractive power.
- 15. A front conversion lens according to claim 12, satisfying the following condition:
- 0.5<D/L<0.85
- where D is the distance from the frontmost lens surface of said intermediate lens unit to the rearmost lens surface thereof, and L is the distance from the frontmost lens surface of said front lens unit to the rearmost lens surface of said rear lens unit.
- 16. A conversion lens comprising, from front to rear:
- a first lens unit or group made of glass material;
- a second lens unit or group made of plastic material;
- a third lens unit or group made of glass material said lens units or groups being separated from each other with at least a partial air space therebetween, and satisfying the following condition:
- 0.5<D/L<0.85
- where D is the distance from the frontmost lens surface of said second lens unit or group to the rearmost lens surface thereof, and L is the distance from the frontmost lens surface of said first lens unit or group to the rearmost lens surface of said third lens unit or group.
- 17. A conversion lens according to claim 16, satisfying the following condition:
- .upsilon..sub.1 >.upsilon..sub.2, .upsilon..sub.3 >.upsilon..sub.2
- where .upsilon..sub.1 and .upsilon..sub.3 are respectively the equivalent values of Abbe number of said first and said third lens units, and .upsilon..sub.2 is the value of Abbe number of said second lens unit, and .upsilon.k can be expressed by the following formula:
- .PHI./.upsilon.k=.SIGMA..phi.i/.upsilon.i
- wherein .PHI. is the refractive power of the entire lens system, and .phi.i are respectively the refractive power and Abbe number of the material of the i-th constituent lens element in the k-th lens unit.
Priority Claims (6)
Number |
Date |
Country |
Kind |
61-205644 |
Sep 1986 |
JPX |
|
61-205645 |
Sep 1986 |
JPX |
|
61-205646 |
Sep 1986 |
JPX |
|
61-205647 |
Sep 1986 |
JPX |
|
61-205648 |
Sep 1986 |
JPX |
|
61-205649 |
Sep 1986 |
JPX |
|
Parent Case Info
This application is a continuation of application Ser. No. 089,750 filed Aug. 27, 1987, now abandoned.
US Referenced Citations (4)
Continuations (1)
|
Number |
Date |
Country |
Parent |
89750 |
Aug 1987 |
|