Objective lens for endoscopes
First Claim
1. A zoom objective lens for endoscopes, characterized by having an angle of view (2ω
- ) of 100°
or greater at a wide-angle end, and comprising, in order from an object side thereof, a positive first group, a negative second group and a positive third lens group, wherein;
said third group comprises a positive first (3-1) subgroup and a positive second (3-2) subgroup,the second group comprises subgroups, wherein a lens subgroup in at least said second group moves to (1) bring about a change in a focal length of a whole system and (2) correct an image position for movement in association with a focal length change, andone subgroup in said second group and said third group moves to an image side from a longer working distance (WD) side being a far end toward a shorter working distance side being a near end to correct a focal position for movement in association with a working distance change, and wherein said zoom objective lens for endoscopes satisfies the following conditions;
0.4<
(D12t−
D12w)/fw≦
1.077
(1)′
0.02<
Δ
Dwd/fw<
0.4
(2)
0<
(rb+ra)/(rb−
ra)<
2
(3)
−
0.7<
1/β
wd<
0.2
(4)where fw is a focal length of a whole system at the wide-angle end, a figure being obtained in a far end-defining working distance;
D12w is a spacing between the first group and the second group at the wide-angle end;
D12t is a spacing between the first group and the second group at a telephoto end;
Δ
Dwd is an amount of movement of a moving group upon changing of the working distance from a far end to a near end, provided that a plus sign is indicative of a direction of movement of the moving group to an image side;
ra is a radius of curvature of an image-side surface of a first lens in the first group;
rb is s radius of curvature of an object-side surface of a second lens in the first group; and
β
wd is an imaging magnification of the moving group upon a working distance change, a figure being obtained at the wide-angle end in a far end-defining working distance.
3 Assignments
0 Petitions
Accused Products
Abstract
The inventive objective lens for endoscopes has independently a zooming function and a focusing function, and is capable of magnified viewing. The objective lens has an angle of view (2ω) of 100° or greater, and comprises a positive first group G1, a negative second group G2 and a positive third group G3. The third group G3 comprises a positive first (3-1) subgroup G31 and a positive second (3-2) subgroup G32. A subgroup in at least the second group G2 moves to (1) bring about a change in the focal length of the whole system and (2) correct an image position for movement in association with a focal length change, and one subgroup in the second group G2 and the third group G3 moves to the image side from a longer side toward a shorter side of the working distance (WD) to (3) correct the focal position for movement in association with a working distance change.
57 Citations
9 Claims
-
1. A zoom objective lens for endoscopes, characterized by having an angle of view (2ω
- ) of 100°
or greater at a wide-angle end, and comprising, in order from an object side thereof, a positive first group, a negative second group and a positive third lens group, wherein;said third group comprises a positive first (3-1) subgroup and a positive second (3-2) subgroup, the second group comprises subgroups, wherein a lens subgroup in at least said second group moves to (1) bring about a change in a focal length of a whole system and (2) correct an image position for movement in association with a focal length change, and one subgroup in said second group and said third group moves to an image side from a longer working distance (WD) side being a far end toward a shorter working distance side being a near end to correct a focal position for movement in association with a working distance change, and wherein said zoom objective lens for endoscopes satisfies the following conditions;
0.4<
(D12t−
D12w)/fw≦
1.077
(1)′
0.02<
Δ
Dwd/fw<
0.4
(2)
0<
(rb+ra)/(rb−
ra)<
2
(3)
−
0.7<
1/β
wd<
0.2
(4)where fw is a focal length of a whole system at the wide-angle end, a figure being obtained in a far end-defining working distance; D12w is a spacing between the first group and the second group at the wide-angle end; D12t is a spacing between the first group and the second group at a telephoto end; Δ
Dwd is an amount of movement of a moving group upon changing of the working distance from a far end to a near end, provided that a plus sign is indicative of a direction of movement of the moving group to an image side;ra is a radius of curvature of an image-side surface of a first lens in the first group; rb is s radius of curvature of an object-side surface of a second lens in the first group; and β
wd is an imaging magnification of the moving group upon a working distance change, a figure being obtained at the wide-angle end in a far end-defining working distance.- View Dependent Claims (3, 4, 5, 6, 7, 8, 9)
- ) of 100°
-
2. A zoom objective lens for endoscopes, characterized by having an angle of view (2ω
- ) of 100°
or greater at a wide-angle end, and comprising, in order from an object side thereof, a positive first group, a negative second group and a positive third lens group, wherein;the second group has an aperture stop, the third group comprises a positive first (3-1) subgroup and a positive second (3-2) subgroup, the second group comprises subgroups, wherein a lens subgroup in at least said second group moves to (1) bring about a change in a focal length of a whole system and (2) correct an image position for movement in association with a focal length change, and one subgroup in the second group and the third group moves to an image side from a longer working distance (WD) side being a far end toward a shorter working distance side being a near end to correct a focal position for movement in association with a working distance change, and wherein said zoom objective lens for endoscopes satisfies the following conditions;
0.4<
(D12t−
D12w)/fw≦
1.077
(1)′
0.02<
Δ
Dwd/fw<
0.4
(2)
0<
(rb+ra)/(rb−
ra)<
2
(3)
−
0.7<
1/β
wd<
0.2
(4)where fw is a focal length of a whole system at the wide-angle end, a figure being obtained in a far end-defining working distance; D12w is a spacing between the first group and the second group at the wide-angle end; D12t is a spacing between the first group and the second group at a telephoto end; Δ
Dwd is an amount of movement of a moving group upon changing of the working distance from a far end to a near end, provided that a plus sign is indicative of a direction of movement of the moving group to an image side;ra is a radius of curvature of an image-side surface of a first lens in the first group; rb is s radius of curvature of an object-side surface of a second lens in the first group; and β
wd is an imaging magnification of the moving group upon a working distance change, a figure being obtained at the wide-angle end in a far end-defining working distance.
- ) of 100°
Specification