# Patent

## Title
Endoscope objective lens unit and endoscope

## Abstract

An endoscope objective lens unit includes a front lens group and a rear lens group with a diaphragm interposed therebetween. The front lens group includes a first lens and a second lens, and the rear lens group includes a third lens, a fourth lens and a fifth lens. The endoscope objective lens unit satisfies following expressions (1A) to (4): (1A) −3 <SF −1; (2) −3 <Fr/Ff <−1.1; (3) −1.6 <Ff/f <−0.6; and (4) Ff/f1 <1.6, where SF is a shape factor, Ff is a focal length of the front lens group, Fr is a focal length of the rear lens group, f is a focal length of the entire unit, and f1 is a focal length of the first lens.

## Background
CROSS REFERENCE TO RELATED APPLICATION
This application is a continuation application of PCT/JP2011/060911 filed on May 12, 2011 and claims benefit of Japanese Application No. 2010-116526 filed in Japan on May 20, 2010, the entire contents of which are incorporated herein by this reference.


BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an endoscope objective lens unit arranged at a distal end portion of an endoscope and an endoscope including the endoscope objective lens unit.
2. Description of the Related Art
In a medical field, endoscopes are used for, e.g., treatment/diagnosis of sites that are difficult to observe from outside of bodies of patients. There is a large demand for a further diameter reduction in endoscopes with small diameters, represented by nasal endoscopes. Reduction in diameter of endoscopes largely depends on development of small-sized image pickup devices such as CCDs, and pixel pitches of image pickup devices are reduced year by year. Accompanied by such reduction, there is a need for endoscope objective lens units (hereinafter also referred to as “lens units”) to provide satisfactory performance while achieving size reduction, and various types of configurations have been developed.
For example, in Japanese Patent Application Laid-Open Publication No. 6-308381, the present applicant discloses an endoscope objective lens including a front lens group and a rear lens group with a diaphragm interposed therebetween, in which the front lens group includes a first group of negative lenses and a second group having a positive refractive power in this order from an object side, the second group has a shape including a surface having a small curvature radius provided on an image side, the rear lens group includes a positive single lens and a cemented lens of a positive lens and a negative lens, and the endoscope objective lens satisfies a predetermined condition.
Meanwhile, in Japanese Patent Application Laid-Open Publication No. 2006-51132, the present applicant also discloses a lens unit including a lens that includes a high refractive index material that exhibits excellent sterilization durability.
SUMMARY OF THE INVENTION
An endoscope objective lens unit according to an embodiment of the present invention includes a front lens group and a rear lens group with a diaphragm interposed therebetween. The front lens group includes a first lens having a negative refractive power and a second lens having a positive refractive power in this order from an object side. The rear lens group includes a third lens having a positive refractive power, and a fourth lens having a positive refractive power and a fifth lens having a negative refractive power, the fourth lens and the fifth lens being cemented to each other. The endoscope objective lens unit satisfies expressions (1A), (2), (3) and (4) below:

−3<SF≦−1;  (1A)

−3.0<Fr/Ff<−1.1;  (2)

−1.6<Ff/f<−0.6; and  (3)

Ff/f1<1.6,  (4)

where SF is a shape factor of (R2+R1)/(R2−R1), in which R1 is an object-side curvature radius of the second lens and R2 is an image-side curvature radius of the second lens, Ff is a focal length of the front lens group, Fr is a focal length of the rear lens group, f is a focal length of the entire unit, and f1 is a focal length of the first lens.

Also, an endoscope according to another embodiment of the present invention includes the endoscope objective lens unit, and an image pickup device that picks up an image provided by the endoscope objective lens unit.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a cross-sectional diagram taken along an optical axis for illustrating a lens unit according to example 1;
FIG. 1B is a spherical aberration diagram for illustrating the lens unit according to example 1;
FIG. 1C is a coma aberration diagram (M) for illustrating the lens unit according to example 1;
FIG. 1D is a coma aberration diagram (S) for illustrating the lens unit according to example 1;
FIG. 1E is a field curvature diagram for illustrating the lens unit according to example 1;
FIG. 2A is a cross-sectional diagram taken along an optical axis for illustrating a lens unit according to example 2;
FIG. 2B is a spherical aberration diagram for illustrating the lens unit according to example 2;
FIG. 2C is a coma aberration diagram (M) for illustrating the lens unit according to example 2;
FIG. 2D is a coma aberration diagram (S) for illustrating the lens unit according to example 2;
FIG. 2E is a field curvature diagram for illustrating the lens unit according to example 2;
FIG. 3A is a cross-sectional diagram taken along an optical axis for illustrating a lens unit according to example 3;
FIG. 3B is a spherical aberration diagram for illustrating the lens unit according to example 3;
FIG. 3C is a coma aberration diagram (M) for illustrating the lens unit according to example 3;
FIG. 3D is a coma aberration diagram (S) for illustrating the lens unit according to example 3;
FIG. 3E is a field curvature diagram for illustrating the lens unit according to example 3;
FIG. 4A is a cross-sectional diagram taken along an optical axis for illustrating a lens unit according to example 4;
FIG. 4B is a spherical aberration diagram for illustrating the lens unit according to example 4;
FIG. 4C is a coma aberration diagram (M) for illustrating the lens unit according to example 4;
FIG. 4D is a coma aberration diagram (S) for illustrating the lens unit according to example 4;
FIG. 4E is a field curvature diagram for illustrating the lens unit according to example 4;
FIG. 5A is a cross-sectional diagram taken along an optical axis for illustrating a lens unit according to example 5;
FIG. 5B is a spherical aberration diagram for illustrating the lens unit according to example 5;
FIG. 5C is a coma aberration diagram (M) for illustrating the lens unit according to example 5;
FIG. 5D is a coma aberration diagram (S) for illustrating the lens unit according to example 5;
FIG. 5E is a field curvature diagram for illustrating the lens unit according to example 5;
FIG. 6A is a cross-sectional diagram taken along an optical axis for illustrating a lens unit according to example 6;
FIG. 6B is a spherical aberration diagram for illustrating the lens unit according to example 6;
FIG. 6C is a coma aberration diagram (M) for illustrating the lens unit according to example 6;
FIG. 6D is a coma aberration diagram (S) for illustrating the lens unit according to example 6;
FIG. 6E is a field curvature diagram for illustrating the lens unit according to example 6;
FIG. 7A is a cross-sectional diagram taken along an optical axis for illustrating a lens unit according to example 7;
FIG. 7B is a spherical aberration diagram for illustrating the lens unit according to example 7;
FIG. 7C is a coma aberration diagram (M) for illustrating the lens unit according to example 7;
FIG. 7D is a coma aberration diagram (S) for illustrating the lens unit according to example 7;
FIG. 7E is a field curvature diagram for illustrating the lens unit according to example 7;
FIG. 8A is a cross-sectional diagram taken along an optical axis for illustrating a lens unit according to example 8;
FIG. 8B is a spherical aberration diagram for illustrating the lens unit according to example 8;
FIG. 8C is a coma aberration diagram (M) for illustrating the lens unit according to example 8;
FIG. 8D is a coma aberration diagram (S) for illustrating the lens unit according to example 8;
FIG. 8E is a field curvature diagram for illustrating the lens unit according to example 8;
FIG. 9A is a cross-sectional diagram taken along an optical axis for illustrating a lens unit according to example 9;
FIG. 9B is a spherical aberration diagram for illustrating the lens unit according to example 9;
FIG. 9C is a coma aberration diagram (M) for illustrating the lens unit according to example 9;
FIG. 9D is a coma aberration diagram (S) for illustrating the lens unit according to example 9;
FIG. 9E is a field curvature diagram for illustrating the lens unit according to example 9;
FIG. 10A is a cross-sectional diagram taken along an optical axis for illustrating a lens unit according to example 10;
FIG. 10B is a spherical aberration diagram for illustrating the lens unit according to example 10;
FIG. 10C is a coma aberration diagram (M) for illustrating the lens unit according to example 10;
FIG. 10D is a coma aberration diagram (S) for illustrating the lens unit according to example 10;
FIG. 10E is a field curvature diagram for illustrating the lens unit according to example 10;
FIG. 11A is a cross-sectional diagram taken along an optical axis for illustrating a lens unit according to example 11;
FIG. 11B is a spherical aberration diagram for illustrating the lens unit according to example 11;
FIG. 11C is a coma aberration diagram (M) for illustrating the lens unit according to example 11;
FIG. 11D is a coma aberration diagram (S) for illustrating the lens unit according to example 11;
FIG. 11E is a field curvature diagram for illustrating the lens unit according to example 11;
FIG. 12A is a cross-sectional diagram taken along an optical axis for illustrating a lens unit according to example 12;
FIG. 12B is a spherical aberration diagram for illustrating the lens unit according to example 12;
FIG. 12C is a coma aberration diagram (M) for illustrating the lens unit according to example 12;
FIG. 12D is a coma aberration diagram (S) for illustrating the lens unit according to example 12;
FIG. 12E is a field curvature diagram for illustrating the lens unit according to example 12;
FIG. 13A is a cross-sectional diagram taken along an optical axis for illustrating a lens unit according to example 13;
FIG. 13B is a spherical aberration diagram for illustrating the lens unit according to example 13;
FIG. 13C is a coma aberration diagram (M) for illustrating the lens unit according to example 13;
FIG. 13D is a coma aberration diagram (S) for illustrating the lens unit according to example 13;
FIG. 13E is a field curvature diagram for illustrating the lens unit according to example 13;
FIG. 14A is a cross-sectional diagram taken along an optical axis for illustrating a lens unit according to example 14;
FIG. 14B is a spherical aberration diagram for illustrating the lens unit according to example 14;
FIG. 14C is a coma aberration diagram (M) for illustrating the lens unit according to example 14;
FIG. 14D is a coma aberration diagram (S) for illustrating the lens unit according to example 14;
FIG. 14E is a field curvature diagram for illustrating the lens unit according to example 14;
FIG. 15A is a cross-sectional diagram taken along an optical axis for illustrating a lens unit according to example 15;
FIG. 15B is a spherical aberration diagram for illustrating the lens unit according to example 15;
FIG. 15C is a coma aberration diagram (M) for illustrating the lens unit according to example 15;
FIG. 15D is a coma aberration diagram (S) for illustrating the lens unit according to example 15;
FIG. 15E is a field curvature diagram for illustrating the lens unit according to example 15;
FIG. 16A is a cross-sectional diagram taken along an optical axis for illustrating a lens unit according to example 16;
FIG. 16B is a spherical aberration diagram for illustrating the lens unit according to example 16;
FIG. 16C is a coma aberration diagram (M) for illustrating the lens unit according to example 16;
FIG. 16D is a coma aberration diagram (S) for illustrating the lens unit according to example 16;
FIG. 16E is a field curvature diagram for illustrating the lens unit according to example 16;
FIG. 17A is a cross-sectional diagram taken along an optical axis for illustrating a lens unit according to example 17;
FIG. 17B is a spherical aberration diagram for illustrating the lens unit according to example 17;
FIG. 17C is a coma aberration diagram (M) for illustrating the lens unit according to example 17;
FIG. 17D is a coma aberration diagram (S) for illustrating the lens unit according to example 17;
FIG. 17E is a field curvature diagram for illustrating the lens unit according to example 17;
FIG. 18A is a cross-sectional diagram taken along an optical axis for illustrating a lens unit according to example 18;
FIG. 18B is a spherical aberration diagram for illustrating the lens unit according to example 18;
FIG. 18C is a coma aberration diagram (M) for illustrating the lens unit according to example 18;
FIG. 18D is a coma aberration diagram (S) for illustrating the lens unit according to example 18;
FIG. 18E is a field curvature diagram for illustrating the lens unit according to example 18;
FIG. 19A is a cross-sectional diagram taken along an optical axis for illustrating a lens unit according to example 19;
FIG. 19B is a spherical aberration diagram for illustrating the lens unit according to example 19;
FIG. 19C is a coma aberration diagram (M) for illustrating the lens unit according to example 19;
FIG. 19D is a coma aberration diagram (S) for illustrating the lens unit according to example 19;
FIG. 19E is a field curvature diagram for illustrating the lens unit according to example 19;
FIG. 20A is a cross-sectional diagram taken along an optical axis for illustrating a lens unit according to example 20;
FIG. 20B is a spherical aberration diagram for illustrating the lens unit according to example 20;
FIG. 20C is a coma aberration diagram (M) for illustrating the lens unit according to example 20;
FIG. 20D is a coma aberration diagram (S) for illustrating the lens unit according to example 20;
FIG. 20E is a field curvature diagram for illustrating the lens unit according to example 20;
FIG. 21A is a cross-sectional diagram taken along an optical axis for illustrating a lens unit according to example 21;
FIG. 21B is a spherical aberration diagram for illustrating the lens unit according to example 21;
FIG. 21C is a coma aberration diagram (M) for illustrating the lens unit according to example 21;
FIG. 21D is a coma aberration diagram (S) for illustrating the lens unit according to example 21;
FIG. 21E is a field curvature diagram for illustrating the lens unit according to example 21;
FIG. 22A is a cross-sectional diagram taken along an optical axis for illustrating a lens unit according to example 22;
FIG. 22B is a spherical aberration diagram for illustrating the lens unit according to example 22;
FIG. 22C is a coma aberration diagram (M) for illustrating the lens unit according to example 22;
FIG. 22D is a coma aberration diagram (S) for illustrating the lens unit according to example 22;
FIG. 22E is a field curvature diagram for illustrating the lens unit according to example 22;
FIG. 23A is a cross-sectional diagram taken along an optical axis for illustrating a lens unit according to example 23;
FIG. 23B is a spherical aberration diagram for illustrating the lens unit according to example 23;
FIG. 23C is a coma aberration diagram (M) for illustrating the lens unit according to example 23;
FIG. 23D is a coma aberration diagram (S) for illustrating the lens unit according to example 23;
FIG. 23E is a field curvature diagram for illustrating the lens unit according to example 23;
FIG. 24A is a cross-sectional diagram taken along an optical axis for illustrating a lens unit according to example 24;
FIG. 24B is a spherical aberration diagram for illustrating the lens unit according to example 24;
FIG. 24C is a coma aberration diagram (M) for illustrating the lens unit according to example 24;
FIG. 24D is a coma aberration diagram (S) for illustrating the lens unit according to example 24;
FIG. 24E is a field curvature diagram of the lens unit according to example 24;
FIG. 25A is a cross-sectional diagram taken along an optical axis for illustrating a lens unit according to example 25;
FIG. 25B is a spherical aberration diagram for illustrating the lens unit according to example 25;
FIG. 25C is a coma aberration diagram (M) for illustrating the lens unit according to example 25;
FIG. 25D is a coma aberration diagram (S) for illustrating the lens unit according to example 25;
FIG. 25E is a field curvature diagram for illustrating the lens unit according to example 25;
FIG. 26A is a cross-sectional diagram taken along an optical axis for illustrating a lens unit according to example 26;
FIG. 26B is a spherical aberration diagram for illustrating the lens unit according to example 26;
FIG. 26C is a coma aberration diagram (M) for illustrating the lens unit according to example 26;
FIG. 26D is a coma aberration diagram (S) for illustrating the lens unit according to example 26;
FIG. 26E is a field curvature diagram for illustrating the lens unit according to example 26; and
FIG. 27 is a configuration diagram of an endoscope according to example 27.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An endoscope objective lens unit according to an embodiment of the present invention is described below.
1. The endoscope objective lens unit includes a front lens group and a rear lens group with a diaphragm interposed therebetween. The front lens group includes a first lens having a negative refractive power and a second lens having a positive refractive power in this order from an object side. The rear lens group includes a third lens having a positive refractive power, and a fourth lens having a positive refractive power and a fifth lens having a negative refractive power, the fourth lens and the fifth lens being cemented to each other. The endoscope objective lens unit satisfies expressions (1), (2), (3) and (4) below:

−6<SF<0;  (1)

−3.0<Fr/Ff<−1.1;  (2)

−1.6<Ff/f<−0.6; and  (3)

Ff/f1<1.6,  (4)

where SF is a shape factor of (R2+R1)/(R2−R1), in which R1 is an object-side curvature radius of the second lens and R2 is an image-side curvature radius of the second lens, Ff is a focal length of the front lens group, Fr is a focal length of the rear lens group, f is a focal length of the entire unit, and f1 is a focal length of the first lens.

Condition (1) is a condition for designating a direction of a surface for favorable correction of a chromatic aberration of magnification. Satisfaction of condition (1) enables favorable correction of a chromatic aberration of magnification. With a value less than the lower limit of condition (1), although a chromatic aberration of magnification can favorably be corrected with the total length kept small, i.e., the reduced size maintained, it is difficult to correct other aberrations. With a value exceeding the upper limit of condition (1), it is difficult to correct a chromatic aberration of magnification.
Furthermore, satisfaction of condition (1A) below instead of condition (1) enables more favorable correction of a chromatic aberration of magnification:

−3<SF≦−1.  (1A)

Furthermore, satisfaction of condition (1B) below instead of condition (1A) enables more favorable correction of a chromatic aberration of magnification:

−3<SF<−1.2.  (1B)

Conditions (2) and (3) are conditions for achieving size reduction. With a value less than the lower limit of condition (2), a lens unit meeting the recent size reduction cannot be provided, and with a value exceeding the upper limit of condition (2), although a small-sized lens unit can be supplied, it is difficult to correct other aberrations.
With a value less than the lower limit of condition (3), the total length of the lens unit is long, disabling supply of a small-sized lens unit, and with a value exceeding the upper limit of condition (3), although a small-sized lens unit can be supplied, it is difficult to correct coma aberrations occurred in the front lens group.
Furthermore, satisfaction of condition (2A) below instead of condition (2) enables further size reduction:

−1.8<Fr/Ff<−1.2.  (2A)

Furthermore, satisfaction of condition (2B) below instead of condition (2A) enables further size reduction:

−1.75<Fr/Ff<−1.3.  (2B)

Furthermore, satisfaction of condition (3A) below instead of condition (3) enables further size reduction:

−1.5<Fr/f<−0.9.  (3A)

Furthermore, satisfaction of condition (3B) below instead of condition (3A) enables further size reduction:

−1.4<Fr/f<−0.95.  (3B)

Condition (4) is a condition for favorably correcting a field curvature with reduction in size of the lens unit taken into account. With a value exceeding the upper limit of condition (4), excessive field curvature correction is provided, resulting in difficulty in correction of a field curvature.
Furthermore, satisfaction of condition (4A) below instead of condition (4) enables more favorable field curvature correction:

Ff/f1<1.51.  (4A)

Furthermore, satisfaction of condition (4B) below instead of condition (4A) enables more favorable field curvature correction:

Ff/f1<1.39.  (4B)

Furthermore, the lens unit according to the embodiment of the present invention enables easy provision of a long back focal length. The lens unit according to the embodiment, which has a long back focal length, enables a prism to be disposed immediately in front of a CCD of an image pickup device to place the CCD horizontally. In other words, as in examples 6, 7, 10 or 18, which are described later, a lens unit including an optical member L7 having a long optical path, the optical member being joined to a glass lid of the CCD, can use a right angle prism as the optical member L7, enabling provision of what is called a horizontally-arranged CCD. In other words, the lens unit according to the embodiment of the present invention enables easy provision of a horizontally-arranged CCD.
2. The lens unit according to section 1 above, in which a refractive index n1 (for an e-line) of a material of the first lens satisfies expression (5) below:

n1>2.  (5)

It is preferable to satisfy condition (5) because the power of the front lens group can easily be increased.
3. The lens unit according to section 1 or 2 above, in which the material of the first lens satisfies expression (6) below:

n1×Hk>2000,  (6)

where n1 is a refractive index (for an e-line) and Hk is a Knoop hardness (N/mm2).
Use of the material satisfying condition (6) enables provision of a lens unit including an outer surface lens (first lens) having resistance to cracking and lens scratching.
4. The material of the first lens includes yttria-stabilized zirconia.
Yttria-stabilized zirconia (YSZ) is a specific example of the material satisfying section 3 above. In other words, in YSZ, n1=2.1825, Hk=1200 N/mm2 and n1×Hk=2617>2000.
An endoscope according to the present invention includes the endoscope objective lens unit according to sections 1 to 4 above.
Next, examples of the lens unit according to the present invention will be indicated.
EXAMPLE 1
Numerical data, etc. of optical members included in a lens unit 1 according to example 1 are indicated below. In the numerical data, r is a curvature radius of each surface, d is a thickness of each optical member or an air space between the respective optical members, n is an refractive index of each optical member for an e-line, ν is an Abbe number of each optical member for the e-line, and FNO represent an F-number. The unit of r and d is mm.
These signs are used in common to numerical data, etc. of later-described other examples.
Numerical data in example 1 is indicated below.










TABLE 1







r1 = ∞
d1 = 0.4000
n1 = 1.88815
ν1 = 40.76


r2 = 0.8439
d2 = 0.3813
n2 = 1.85504
ν2 = 23.78


r3 = ∞
d3 = 0.7337
n3 = 1.51564
ν3 = 75.00


r4 = −9.6109
d4 = 0.1912
n4 = 1.83932
ν4 = 37.16


r5 = ∞
d5 = 0.5652
n5 = 1.69979
ν5 = 55.53


r6 = ∞(STO)
d6 = 0.1599
n6 = 1.93429
ν6 = 18.90


r7 = 9.4824
d7 = 1.2442
n7 = 1.51825
ν7 = 64.14


r8 = −1.9686
d8 = 0.0529
n8 = 1.61379
ν8 = 50.20


r9 = 3.9815
d9 = 1.2483


r10 = −1.2679
d10 = 0.4334


r11 = −5.8682
d11 = 1.0546


r12 = ∞
d12 = 0.7000


r13 = ∞
d13 = 0.7500


r14 = ∞





FNO = 4.68


Focal length of entire unit: f = 1 mm, image height = 0.946 mm, object distance = 20 mm, angle of view = 128.05°


Fr = 1.617 mm,


Ff = −1.123 mm,


f1 = −0.950 mm






FIG. 1A is a configuration diagram of the lens unit 1 according to the present example, and FIGS. 1B to 1E are aberration diagrams of the lens unit 1. As illustrated in FIG. 1A, a lens unit 1 includes a front lens group FL and a rear lens group RL with a diaphragm STO interposed therebetween. The front lens group FL includes a first lens L1 having a negative refractive power and a second lens L2 having a positive refractive power in this order from an object side. The rear lens group RL includes a third lens L4 having a positive refractive power, and a fourth lens L5 having a positive refractive power and a fifth lens L6 having a negative refractive power, the fourth lens L5 and the fifth lens L6 being cemented to each other. In FIG. 1A, r14 is an image pickup surface of an image pickup device such as a CCD.
In FIG. 1A, an optical member L3 is a filter, particularly preferably, an infrared cut filter. In the later-described other examples, an optical member L3 is a functional filter: however, use of a color filter instead of an infrared cut filter enables variation in color-reproducibility of an endoscopic image.
Furthermore, a plurality of filters, for example, three infrared cut filters may be disposed at a position of the optical member L3 if it is possible. Furthermore, filters having different functions, for example, an infrared cut filter and a notch filter, may be disposed, or an infrared cut filter, a color filter and a notch filter may be disposed.
A position where the filter is arranged is not limited the position of the optical member L3. For example, it is possible to use normal transparent glass as the optical member L3 and dispose an infrared cut filter at a position that is different from the position of the optical member L3. In other words, for a lens unit with no filter disposed in later-described examples, it is possible to arbitrarily dispose a necessary filter in an air space.
Furthermore, it is preferable that the filter include a functional film, such as a YAG laser cut film, formed at least one surface thereof, and it is particularly preferable that the filter include a functional film, such as a YAG laser cut film or an LD laser cut film, formed at another surface thereof. In other words, it is preferable that the filter include a functional film including an antireflective film formed at one surface or each of opposite surfaces thereof. Alternatively, plural functional films having different functions may be stacked on one of surfaces of the filter.
FIG. 1B indicates spherical aberration, FIGS. 1C and 1D each indicate coma aberration, and FIG. 1E indicates a field curvature (field aberration). In FIG. 1B, symbols indicate measured wavelength lines: (CL) indicates 656.27 nm, i.e., a C-line; (dL) indicates 587.56 nm, i.e., a d-line; (eL) indicates 546.07 nm, i.e., an e-line; (F) indicates 486.13 nm, i.e., an F-line; and (g) indicates 435.83 nm, i.e., a g-line. FIG. 1C indicates coma aberration ΔM (meridional) for the e-line, and FIG. 1D indicates a coma aberration ΔS (sagittal). In FIG. 1E, ΔS is indicated by a solid line and ΔM is indicated by a dashed line. The same applies to the following aberration diagrams.
EXAMPLE 2
Numerical data, etc. of optical members included in a lens unit 2 according to example 2 are indicated below.










TABLE 2







r1 = ∞
d1 = 0.4030
n1 = 1.88815
ν1 = 40.76


r2 = 0.8788
d2 = 0.4814
n2 = 1.85504
ν2 = 23.78


r3 = −10.0294
d3 = 0.7668
n3 = 1.51564
ν3 = 75.00


r4 = −4.696
d4 = 0.2364
n4 = 1.83932
ν4 = 37.16


r5 = ∞
d5 = 0.5676
n5 = 1.69979
ν5 = 55.53


r6 = ∞(STO)
d6 = 0.1612
n6 = 1.93429
ν6 = 18.90


r7 = 9.5228
d7 = 1.2725
n7 = 1.51825
ν7 = 64.14


r8 = −2.0903
d8 = 0.0531
n8 = 1.61379
ν8 = 50.20


r9 = 4.3821
d9 = 1.2536


r10 = −1.2663
d10 = 0.4353


r11 = −6.0967
d11 = 0.8910


r12 = ∞
d12 = 1.4000


r13 = ∞
d13 = 0.3000


r14 = ∞





FNO = 4.868


Focal length of entire unit: f = 1 mm, image height = 1 mm, object distance = 17 mm, angle of view = 140.05°


Fr = 1.729 mm,


Ff = −1.280 mm,


f1 = −0.989 mm






FIG. 2A is a configuration diagram of the lens unit 2 according to the present example, and FIGS. 2B to 2E are aberration diagrams of the lens unit 2.
EXAMPLE 3
Numerical data, etc. of optical members included in a lens unit 3 according to example 3 are indicated below.










TABLE 3







r1 = ∞
d1 = 0.4072
n1 = 1.88815
ν1 = 40.76


r2 = 0.8765
d2 = 0.5877
n2 = 1.85504
ν2 = 23.78


r3 = −10.1323
d3 = 0.7329
n3 = 1.51564
ν3 = 75.00


r4 = −4.2879
d4 = 0.1773
n4 = 1.83932
ν4 = 37.16


r5 = ∞
d5 = 0.5734
n5 = 1.69979
ν5 = 55.53


r6 = ∞(STO)
d6 = 0.1629
n6 = 1.93429
ν6 = 18.90


r7 = 9.6206
d7 = 1.2981
n7 = 1.51825
ν7 = 64.14


r8 = −2.0932
d8 = 0.0537
n8 = 1.61379
ν8 = 50.20


r9 = 4.598
d9 = 1.2665


r10 = −1.2298
d10 = 0.4398


r11 = −6.2165
d11 = 0.9322


r12 = ∞
d12 = 1.2969


r13 = ∞
d13 = 0.3546


r14 = ∞





FNO = 6.18


Focal length of entire unit: f = 1 mm, image height = 1.33 mm, object distance = 10 mm, angle of view = 147.36°


Fr = 1.766 mm,


Ff = −1.353 mm,


f1 = −0.987 mm






FIG. 3A is a configuration diagram of the lens unit 3 according to the present example, and FIGS. 3B to 3E are aberration diagrams of the lens unit 3.
EXAMPLE 4
Numerical data, etc. of optical members included in a lens unit 4 according to example 4 are indicated below.










TABLE 4







r1 = ∞
d1 = 0.4054
n1 = 1.88815
ν1 = 40.76


r2 = 0.8755
d2 = 0.5851
n2 = 1.85504
ν2 = 23.78


r3 = −11.9923
d3 = 0.6742
n3 = 1.51564
ν3 = 75.00


r4 = −4.9781
d4 = 0.1924
n4 = 1.83932
ν4 = 37.16


r5 = ∞
d5 = 0.5708
n5 = 1.69979
ν5 = 55.53


r6 = ∞(STO)
d6 = 0.1614
n6 = 1.93429
ν6 = 18.90


r7 = 9.5779
d7 = 1.3297
n7 = 1.51825
ν7 = 64.14


r8 = −2.1418
d8 = 0.0605
n8 = 1.61379
ν8 = 50.20


r9 = 4.7428
d9 = 1.2609


r10 = −1.2532
d10 = 0.4378


r11 = −5.2230
d11 = 0.8500


r12 = ∞
d12 = 1.4485


r13 = ∞
d13 = 0.5015


r14 = ∞





FNO = 5.601


Focal length of entire unit: f = 1 mm, image height = 1.04 mm, object distance = 10 mm, angle of view = 151.25°


Fr = 1.771 mm,


Ff = −1.276 mm,


f1 = −0.986 mm






FIG. 4A is a configuration diagram of the lens unit 4 according to the present example, and FIGS. 4B to 4E are aberration diagrams of the lens unit 4.
EXAMPLE 5
Numerical data, etc. of optical members included in a lens unit 5 according to example 5 are indicated below.










TABLE 5







r1 = ∞
d1 = 0.4055
n1 = 1.88815
ν1 = 40.76


r2 = 0.8722
d2 = 0.5855
n2 = 1.85504
ν2 = 23.78


r3 = −12.8483
d3 = 0.6720
n3 = 1.51564
ν3 = 75.00


r4 = −3.9869
d4 = 0.1622
n4 = 1.83932
ν4 = 37.16


r5 = ∞
d5 = 0.5710
n5 = 1.69979
ν5 = 55.53


r6 = ∞(STO)
d6 = 0.1614
n6 = 1.93429
ν6 = 18.90


r7 = ∞
d7 = 1.2857
n7 = 1.51825
ν7 = 64.14


r8 = −2.014
d8 = 0.0605
n8 = 1.61379
ν8 = 50.20


r9 = 4.3322
d9 = 1.2613


r10 = −1.354
d10 = 0.4379


r11 = −5.327
d11 = 1.0850


r12 = ∞
d12 = 0.8700


r13 = ∞
d13 = 0.7368


r14 = ∞





FNO = 4.407


Focal length of entire unit: f = 1 mm, image height = 0.956 mm, object distance = 11 mm, angle of view = 128.38°


Fr = 1.797 mm,


Ff = −1.439 mm,


f1 = −0.982 mm






FIG. 5A is a configuration diagram of the lens unit 5 according to the present example, and FIGS. 5B to 5E are aberration diagrams of the lens unit 5.
EXAMPLE 6
Numerical data, etc. of optical members included in a lens unit 6 according to example 6 are indicated below.










TABLE 6







r1 = ∞
d1 = 0.4049
n1 = 1.88815
ν1 = 40.76


r2 = 0.9156
d2 = 0.5512
n2 = 1.85504
ν2 = 23.78


r3 = −18.7064
d3 = 0.6718
n3 = 1.51564
ν3 = 75.00


r4 = −7.2381
d4 = 0.1367
n4 = 1.83932
ν4 = 37.16


r5 = ∞
d5 = 0.5701
n5 = 1.73234
ν5 = 54.68


r6 = ∞(STO)
d6 = 0.0302
n6 = 1.93429
ν6 = 18.90


r7 = ∞
d7 = 1.5316
n7 = 1.51825
ν7 = 64.14


r8 = −2.061
d8 = 0.0604
n8 = 1.61379
ν8 = 50.20


r9 = 17.9166
d9 = 1.2833


r10 = −1.177
d10 = 0.4372


r11 = −2.6698
d11 = 1.0074


r12 = ∞
d12 = 1.8234


r13 = ∞
d13 = 0.7356


r14 = ∞





FNO = 5.807


Focal length of entire unit: f = 1 mm, image height = 0.954 mm, object distance = 10.5 mm, angle of view = 128.1°


Fr = 1.868 mm,


Ff = −1.228 mm,


f1 = −1.031 mm






FIG. 6A is a configuration diagram of the lens unit 6 according to the present example, and FIGS. 6B to 6E are aberration diagrams of the lens unit 6.
EXAMPLE 7
Numerical data, etc. of optical members included in a lens unit 7 according to example 7 are indicated below.










TABLE 7







r1 = ∞
d1 = 0.4060
n1 = 1.88815
ν1 = 40.76


r2 = 0.8641
d2 = 0.4849
n2 = 1.85504
ν2 = 23.78


r3 = −10.1016
d3 = 0.7113
n3 = 1.51564
ν3 = 75.00


r4 = −4.3464
d4 = 0.0974
n4 = 1.08642
ν4 = 34.97


r5 = ∞
d5 = 0.5716
n5 = 1.73234
ν5 = 54.68


r6 = ∞(STO)
d6 = 0.1619
n6 = 1.93429
ν6 = 18.90


r7 = 33.7158
d7 = 1.3665
n7 = 1.51825
ν7 = 64.14


r8 = −2.0717
d8 = 0.0535
n8 = 1.61379
ν8 = 50.20


r9 = 9.2024
d9 = 1.2868


r10 = −1.1832
d10 = 0.4384


r11 = −3.0147
d11 = 1.0102


r12 = ∞
d12 = 1.5354


r13 = ∞
d13 = 0.7376


r14 = ∞





FNO = 5.743


Focal length of entire unit: f = 1 mm, image height = 0.957 mm, object distance = 10 mm, angle of view: 127.8°


Fr: 1.853 mm,


Ff = −1.294 mm,


f1 = −0.973 mm






FIG. 7A is a configuration diagram of the lens unit 7 according to the present example, and FIGS. 7B to 7E are aberration diagrams of the lens unit 7.
EXAMPLE 8
Numerical data, etc. of optical members included in a lens unit 8 according to example 8 are indicated below.










TABLE 8







r1 = ∞
d1 = 0.4056
n1 = 1.88815
ν1 = 40.76


r2 = 0.8771
d2 = 0.4340
n2 = 1.85504
ν2 = 23.78


r3 = −10.0931
d3 = 0.7204
n3 = 1.51564
ν3 = 75.00


r4 = −4.1906
d4 = 0.1258
n4 = 1.80642
ν4 = 34.97


r5 = ∞
d5 = 0.5712
n5 = 1.73234
ν5 = 54.68


r6 = ∞(STO)
d6 = 0.1623
n6 = 1.93429
ν6 = 18.90


r7 = −50.9076
d7 = 1.4039
n7 = 1.51825
ν7 = 64.14


r8 = −2.0934
d8 = 0.0707
n8 = 1.61379
ν8 = 50.20


r9 = 9.3818
d9 = 1.2857


r10 = −1.1935
d10 = 0.4381


r11 = −2.7935
d11 = 1.6149


r12 = ∞
d12 = 0.7570


r13 = ∞
d13 = 0.7370


r14 = ∞





FNO = 5.673


Focal length of entire unit: f = 1 mm, image height = 0.956 mm, object distance = 10.4 mm, angle of view = 127.98°


Fr = 1.877 mm,


Ff = −1.332 mm,


f1 = −0.988 mm






FIG. 8A is a configuration diagram of the lens unit 8 according to the present example, and FIGS. 8B to 8E are aberration diagrams of the lens unit 8.
EXAMPLE 9
Numerical data, etc. of optical members included in a lens unit 9 according to example 9 are indicated below.










TABLE 9







r1 = ∞
d1 = 0.4503
n1 = 1.88815
ν1 = 40.76


r2 = 0.7879
d2 = 0.4033
n2 = 1.85504
ν2 = 23.78


r3 = ∞
d3 = 0.8870
n3 = 1.51564
ν3 = 75.00


r4 = −18.3149
d4 = 0.2253
n4 = 1.88815
ν4 = 40.76


r5 = ∞
d5 = 0.5990
n5 = 1.59143
ν5 = 61.14


r6 = ∞(STO)
d6 = 0.0544
n6 = 1.93429
ν6 = 18.90


r7 = ∞
d7 = 1.2211
n7 = 1.51825
ν7 = 64.14


r8 = −1.8991
d8 = 0.0901
n8 = 1.61379
ν8 = 50.20


r9 = 3.3716
d9 = 1.0692


r10 = −1.6233
d10 = 0.2600


r11 = −5.4907
d11 = 1.5993


r12 = ∞
d12 = 0.7255


r13 = ∞
d13 = 0.7255


r14 = ∞





FNO = 4.095


Focal length of entire unit: f = 1 mm, image height = 0.941 mm, object distance = 18.013 mm, angle of view = 128°


Fr = 1.661 mm,


Ff = −0.967 mm,


f1 = −0.887 mm






FIG. 9A is a configuration diagram of the lens unit 9 according to the present example, and FIGS. 9B to 9E are aberration diagrams of the lens unit 9.
EXAMPLE 10
Numerical data, etc. of optical members included in a lens unit 10 according to example 10 are indicated below.










TABLE 10







r1 = ∞
d1 = 0.3428
n1 = 1.88815
ν1 = 40.76


r2 = 0.8151
d2 = 0.3428
n2 = 1.93429
ν2 = 18.90


r3 = ∞
d3 = 0.5877
n3 = 1.88815
ν3 = 40.76


r4 = −4.3418
d4 = 0.5526
n4 = 1.73234
ν4 = 54.68


r5 = ∞(STO)
d5 = 0.3145
n5 = 1.93429
ν5 = 18.90


r6 = −9.0742
d6 = 0.5507
n6 = 1.51825
ν6 = 64.10


r7 = −1.6398
d7 = 0.0490


r8 = 9.8128
d8 = 0.8160


r9 = −1.1151
d9 = 0.3732


r10 = −2.7514
d10 = 1.6657


r11 = ∞
d11 = 0.9189


r12 = ∞





FNO = 5.152


Focal length of entire unit: f = 1 mm, image height = 0.945 mm, object distance = 19.591 mm, angle of view = 128.18°


Fr = 1.593 mm,


Ff = −1.383 mm,


f1 = −0.918 mm






FIG. 10A is a configuration diagram of the lens unit 10 according to the present example, and FIGS. 10B to 10E are aberration diagrams of the lens unit 10.
EXAMPLE 11
Numerical data, etc. of optical members included in a lens unit 11 according to example 11 are indicated below.










TABLE 11







r1 = ∞
d1 = 0.3415
n1 = 1.88815
ν1 = 40.76


r2 = 0.8021
d2 = 0.3415
n2 = 1.93429
ν2 = 18.90


r3 = 19.5162
d3 = 0.5855
n3 = 1.88815
ν3 = 40.76


r4 = −5.5767
d4 = 0.5374
n4 = 1.73234
ν4 = 54.68


r5 = ∞(STO)
d5 = 0.3008
n5 = 1.93429
ν5 = 18.90


r6 = −10.1204
d6 = 0.5486
n6 = 1.51825
ν6 = 64.10


r7 = −1.6388
d7 = 0.0488


r8 = 9.33
d8 = 0.8161


r9 = −1.1122
d9 = 0.3718


r10 = −2.746
d10 = 1.6684


r11 = ∞
d11 = 0.9154


r12 = ∞





FNO = 5.27


Focal length of entire unit: f = 1 mm, image height = 0.942 mm, object distance = 19.516 mm, angle of view = 128.19°


Fr = 1.567 mm,


Ff = −1.320 mm,


f1 = −0.903 mm






FIG. 11A is a configuration diagram of the lens unit 11 according to the present example, and FIGS. 11B to 11E are aberration diagrams of the lens unit 11.
EXAMPLE 12
Numerical data, etc. of optical members included in a lens unit 12 according to example 12 are indicated below.










TABLE 12







r1 = ∞
d1 = 0.4500
n1 = 1.88815
ν1 = 40.76


r2 = 0.8070
d2 = 0.4179
n2 = 1.93429
ν2 = 18.90


r3 = ∞
d3 = 0.7529
n3 = 1.51564
ν3 = 75.00


r4 = −18.8614
d4 = 0.1692
n4 = 1.88815
ν4 = 40.76


r5 = ∞
d5 = 0.5632
n5 = 1.73234
ν5 = 54.68


r6 = ∞(STO)
d6 = 0.0545
n6 = 1.93429
ν6 = 18.90


r7 = ∞
d7 = 1.1960
n7 = 1.51825
ν7 = 64.14


r8 = −1.8960
d8 = 0.1058
n8 = 1.61379
ν8 = 50.20


r9 = 6.3884
d9 = 1.1373


r10 = −1.3424
d10 = 0.4320


r11 = −3.9951
d11 = 1.5444


r12 = ∞
d12 = 0.7300


r13 = ∞
d13 = 0.7500


r14 = ∞





FNO = 3.777


Focal length of entire unit: f = 1 mm, image height = 0.943 mm, object distance = 16 mm, angle of view = 127.83°


Fr = 1.668 mm,


Ff = −0.993 mm,


f7 = −0.909 mm






FIG. 12A is a configuration diagram of the lens unit 12 according to the present example, and FIGS. 12B to 12E are aberration diagrams of the lens unit 12.
EXAMPLE 13
Numerical data, etc. of optical members included in a lens unit 13 according to example 13 are indicated below.










TABLE 13







r1 = ∞
d1 = 0.4000
n1 = 1.88815
ν1 = 40.76


r2 = 0.8406
d2 = 0.6160
n2 = 1.85504
ν2 = 23.78


r3 = −5.8882
d3 = 0.7945
n3 = 1.51564
ν3 = 75.00


r4 = −3.9255
d4 = 0.2866
n4 = 1.83932
ν4 = 37.16


r5 = ∞
d5 = 0.5627
n5 = 1.59143
ν5 = 61.14


r6 = ∞(STO)
d6 = 0.1599
n6 = 1.93429
ν6 = 18.90


r7 = 11.8394
d7 = 1.3354
n7 = 1.51825
ν7 = 64.14


r8 = −2.1677
d8 = 0.0527


r9 = 3.4717
d9 = 1.1636


r10 = −1.4365
d10 = 0.4316


r11 = −6.1946
d11 = 1.0000


r12 = ∞
d12 = 2.0100


r13 = ∞





FNO = 6.888


Focal length of entire unit: f = 1 mm, image height = 0.96 mm, object distance = 9.8 mm, angle of view = 129.73°


Fr = 1.863 mm,


Ff = −1.226 mm,


f1 = −0.946 mm






FIG. 13A is a configuration diagram of the lens unit 13 according to the present example, and FIGS. 13B to 13E are aberration diagrams of the lens unit 13.
EXAMPLE 14
Numerical data, etc. of optical members included in a lens unit 14 according to example 14 are indicated below. A material of a first lens L1 of each of lens units 14 to 25 is yttria-stabilized zirconia (YSZ).










TABLE 14







r1 = ∞
d1 = 0.5433
n1 = 2.18246
ν1 = 33.01


r2 = 0.9685
d2 = 0.4165
n2 = 1.93429
ν2 = 18.90


r3 = ∞
d3 = 0.7243
n3 = 1.51564
ν3 = 75.00


r4 = −5.4012
d4 = 0.1449
n4 = 1.88815
ν4 = 40.76


r5 = ∞
d5 = 0.5614
n5 = 1.73234
ν5 = 54.68


r6 = ∞(STO)
d6 = 0.0543
n6 = 1.93429
ν6 = 18.90


r7 = ∞
d7 = 1.5375
n7 = 1.51825
ν7 = 64.14


r8 = −2.181
d8 = 0.1992
n8 = 1.61379
ν8 = 50.20


r9 = 5.1839
d9 = 1.1770


r10 = −1.3201
d10 = 0.4305


r11 = −4.2501
d11 = 1.5232


r12 = ∞
d12 = 0.7600


r13 = ∞
d13 = 0.7243


r14 = ∞





FNO = 4.88


Focal length of entire unit: f = 1 mm, image height = 0.94 mm, object distance = 18.108 mm, angle of view = 127.62°


Fr = 1.812 mm,


Ff = −1.135 mm,


f1 = −0.819 mm






FIG. 14A is a configuration diagram of the lens unit 14 according to the present example, and FIGS. 14B to 14E are aberration diagrams of the lens unit 14.
EXAMPLE 15
Numerical data, etc. of optical members included in a lens unit 15 according to example 15 are indicated below.










TABLE 15







r1 = ∞
d1 = 0.5440
n1 = 2.18246
ν1 = 33.01


r2 = 0.9605
d2 = 0.4171
n2 = 1.93429
ν2 = 18.90


r3 = ∞
d3 = 0.7253
n3 = 1.51564
ν3 = 75.00


r4 = −4.8664
d4 = 0.1451
n4 = 1.88815
ν4 = 40.76


r5 = ∞
d5 = 0.5621
n5 = 1.73234
ν5 = 54.68


r6 = ∞(STO)
d6 = 0.0544
n6 = 1.93429
ν6 = 18.90


r7 = ∞
d7 = 1.5159
n7 = 1.51825
ν7 = 64.14


r8 = −2.1868
d8 = 0.1993
n8 = 1.61379
ν8 = 50.20


r9 = 5.9359
d9 = 1.1787


r10 = −1.3219
d10 = 0.4311


r11 = −3.8915
d11 = 1.5247


r12 = ∞
d12 = 0.7510


r13 = ∞
d13 = 0.7253


r14 = ∞





FNO = 3.752


Focal length of entire unit: f = 1 mm, image height = 0.941 mm, object distance = 18.134 mm, angle of view = 127.85°


Fr = 1.832 mm,


Ff = −1.174 mm,


f1 = −0.812 mm






FIG. 15A is a configuration diagram of the lens unit 15 according to the present example, and FIGS. 15B to 15E are aberration diagrams of the lens unit 15.
EXAMPLE 16
Numerical data, etc. of optical members included in a lens unit 16 according to example 16 are indicated below.










TABLE 16







r1 = ∞
d1 = 0.5435
n1 = 2.18246
ν1 = 33.01


r2 = 0.9913
d2 = 0.6042
n2 = 1.93429
ν2 = 18.90


r3 = ∞
d3 = 0.7247
n3 = 1.51564
ν3 = 75.00


r4 = −4.7185
d4 = 0.1449
n4 = 1.88815
ν4 = 40.76


r5 = ∞
d5 = 0.5617
n5 = 1.73234
ν5 = 54.68


r6 = ∞(STO)
d6 = 0.0544
n6 = 1.93429
ν6 = 18.90


r7 = ∞
d7 = 1.4653
n7 = 1.51825
ν7 = 64.14


r8 = −2.3106
d8 = 0.1992
n8 = 1.61379
ν8 = 50.20


r9 = 6.1978
d9 = 1.1777


r10 = −1.3208
d10 = 0.4308


r11 = −4.093
d11 = 1.5433


r12 = ∞
d12 = 0.7498


r13 = ∞
d13 = 0.7247


r14 = ∞





FNO = 3.979


Focal length of entire unit: f = 1 mm, image height = 0.94 mm, object distance = 18.118 mm, angle of view = 127.81°


Fr = 1.933 mm,


Ff = −1.310 mm,


f1 = −0.838 mm






FIG. 16A is a configuration diagram of the lens unit 16 according to the present example, and FIGS. 16B to 16E are aberration diagrams of the lens unit 16.
EXAMPLE 17
Numerical data, etc. of optical members included in a lens unit 17 according to example 17 are indicated below.










TABLE 17







r1 = ∞
d1 = 0.4500
n1 = 2.18246
ν1 = 33.01


r2 = 1.0405
d2 = 0.4448
n2 = 1.93429
ν2 = 18.90


r3 = ∞
d3 = 0.8448
n3 = 1.51564
ν3 = 75.00


r4 = −7.461
d4 = 0.1978
n4 = 1.80642
ν4 = 34.97


r5 = ∞
d5 = 0.5584
n5 = 1.73234
ν5 = 54.68


r6 = ∞(STO)
d6 = 0.0540
n6 = 1.93429
ν6 = 18.90


r7 = ∞
d7 = 1.7385
n7 = 1.51825
ν7 = 64.14


r8 = −2.3919
d8 = 0.1101
n8 = 1.61379
ν8 = 50.20


r9 = 6.4097
d9 = 1.1708


r10 = −1.3886
d10 = 0.4282


r11 = −3.4605
d11 = 1.2423


r12 = ∞
d12 = 1.8883


r13 = ∞
d13 = 0.7300


r14 = ∞





FNO = 6.285


Focal length of entire unit: f = 1 mm, image height = 0.935 mm, object distance = 17.89 mm, angle of view = 127.85°


Fr = 1.967 mm,


Ff = −1.290 mm,


f1 = −0.880 mm






FIG. 17A is a configuration diagram of the lens unit 17 according to the present example, and FIGS. 17B to 17E are aberration diagrams of the lens unit 17.
EXAMPLE 18
Numerical data, etc. of optical members included in a lens unit 18 according to example 18 are indicated below.










TABLE 18







r1 = ∞
d1 = 0.4483
n1 = 2.18246
ν1 = 33.01


r2 = 1.0038
d2 = 0.3786
n2 = 1.93429
ν2 = 18.90


r3 = ∞
d3 = 0.9165
n3 = 1.51564
ν3 = 75.00


r4 = −6.1690
d4 = 0.3261
n4 = 1.83932
ν4 = 37.16


r5 = ∞
d5 = 0.5597
n5 = 1.73234
ν5 = 54.68


r6 = ∞(STO)
d6 = 0.0542
n6 = 1.93429
ν6 = 18.90


r7 = ∞
d7 = 1.2616
n7 = 1.51825
ν7 = 64.14


r8 = −2.2838
d8 = 0.2388
n8 = 1.61379
ν8 = 50.20


r9 = 6.9881
d9 = 1.1735


r10 = −1.3162
d10 = 0.4293


r11 = −3.2867
d11 = 1.7932


r12 = ∞
d12 = 0.7422


r13 = ∞
d13 = 0.7222


r14 = ∞





FNO = 4.067


Focal length of entire unit: f = 1 mm, image height = 0.937 mm, object distance = 17.932 mm, angle of view = 127.96°


Fr = 1.931 mm,


Ff = −1.144 mm,


f1 = −0.849 mm






FIG. 18A is a configuration diagram of the lens unit 18 according to the present example, and FIGS. 18B to 18E are aberration diagrams of the lens unit 18.
EXAMPLE 19
Numerical data, etc. of optical members included in a lens unit 19 according to example 19 are indicated below.










TABLE 19







r1 = ∞
d1 = 0.5000
n1 = 2.18246
ν1 = 33.01


r2 = 0.9456
d2 = 0.4142
n2 = 1.93429
ν2 = 18.90


r3 = ∞
d3 = 0.7204
n3 = 1.51564
ν3 = 75.00


r4 = −7.4010
d4 = 0.3945
n4 = 2.18246
ν4 = 33.01


r5 = ∞
d5 = 0.5583
n5 = 1.73234
ν5 = 54.68


r6 = ∞(STO)
d6 = 0.2341
n6 = 1.93429
ν6 = 18.90


r7 = 15.5855
d7 = 1.2410
n7 = 1.51825
ν7 = 64.14


r8 = −2.6460
d8 = 0.1987
n8 = 1.61379
ν8 = 50.20


r9 = 6.2845
d9 = 1.1706


r10 = −1.3129
d10 = 0.4282


r11 = −8.7654
d11 = 1.4404


r12 = ∞
d12 = 0.7600


r13 = ∞
d13 = 0.7000


r14 = ∞





FNO = 4.29


Focal length of entire unit: f = 1 mm, image height = 0.935 mm, object distance = 18 mm, angle of view = 127.93°


Fr = 1.756 mm,


Ff = −1.000 mm,


f1 = −0.800 mm






FIG. 19A is a configuration diagram of the lens unit 19 according to the present example, and FIGS. 19B to 19E are aberration diagrams of the lens unit 19.
EXAMPLE 20
Numerical data, etc. of optical members included in a lens unit 20 according to example 20 are indicated below.










TABLE 20







r1 = ∞
d1 = 0.5000
n1 = 2.18246
ν1 = 33.01


r2 = 0.9247
d2 = 0.5971
n2 = 1.93429
ν2 = 18.90


r3 = ∞
d3 = 0.7238
n3 = 1.51564
ν3 = 75.00


r4 = −4.4671
d4 = 0.1448
n4 = 1.88815
ν4 = 40.76


r5 = ∞
d5 = 0.5609
n5 = 1.73234
ν5 = 54.68


r6 = ∞(STO)
d6 = 0.0543
n6 = 1.93429
ν6 = 18.90


r7 = ∞
d7 = 1.2470
n7 = 1.51825
ν7 = 64.14


r8 = −2.0417
d8 = 0.1990
n8 = 1.61379
ν8 = 50.20


r9 = 4.9784
d9 = 1.1761


r10 = −1.3191
d10 = 0.4302


r11 = −6.7685
d11 = 1.3457


r12 = ∞
d12 = 0.7500


r13 = ∞
d13 = 0.7238


r14 = ∞





FNO = 4.141


Focal length of entire unit: f = 1 mm, image height = 0.939 mm, object distance = 18.1 mm, angle of view = 127.41°


Fr = 1.830 mm,


Ff = −1.235 mm,


f1 = −0.782 mm






FIG. 20A is a configuration diagram of the lens unit 20 according to the present example, and FIGS. 20B to 20E are aberration diagrams of the lens unit 20.
EXAMPLE 21
Numerical data, etc. of optical members included in a lens unit 21 according to example 21 are indicated below.










TABLE 21







r1 = ∞
d1 = 0.5164
n1 = 2.18246
ν1 = 33.01


r2 = 0.8569
d2 = 0.5680
n2 = 1.93429
ν2 = 18.90


r3 = ∞
d3 = 0.6885
n3 = 1.51564
ν3 = 75.00


r4 = −4.4337
d4 = 0.1377
n4 = 1.88815
ν4 = 40.76


r5 = ∞
d5 = 0.5336
n5 = 1.73234
ν5 = 54.68


r6 = ∞(STO)
d6 = 0.0516
n6 = 1.93429
ν6 = 18.90


r7 = ∞
d7 = 1.1807
n7 = 1.51825
ν7 = 64.14


r8 = −1.9271
d8 = 0.1893
n8 = 1.61379
ν8 = 50.20


r9 = 4.6518
d9 = 1.1188


r10 = −1.2548
d10 = 0.4092


r11 = −8.2907
d11 = 1.4631


r12 = ∞
d12 = 0.7000


r13 = ∞
d13 = 0.6885


r14 = ∞





FNO = 4.448


Focal length of entire unit: f = 1 mm, image height = 0.893 mm, object distance = 17.2 mm, angle of view = 117.85°


Fr = 1.764 mm,


Ff = −1.110 mm,


f1 = −0.725 mm






FIG. 21A is a configuration diagram of the lens unit 21 according to the present example, and FIGS. 21B to 21E are aberration diagrams of the lens unit 21.
EXAMPLE 22
Numerical data, etc. of optical members included in a lens unit 22 according to example 22 are indicated below.










TABLE 22







r1 = ∞
d1 = 0.4583
n1 = 2.18246
ν1 = 33.01


r2 = 0.7351
d2 = 0.3564
n2 = 1.85504
ν2 = 23.78


r3 = ∞
d3 = 0.5199
n3 = 1.51564
ν3 = 75.00


r4 = −4.1679
d4 = 1.3580
n4 = 1.83932
ν4 = 37.16


r5 = ∞
d5 = 0.4857
n5 = 1.59143
ν5 = 61.14


r6 = ∞(STO)
d6 = 0.0509
n6 = 1.93429
ν6 = 18.90


r7 = ∞
d7 = 1.1253
n7 = 1.51825
ν7 = 64.14


r8 = −1.6538
d8 = 0.1867
n8 = 1.61379
ν8 = 50.20


r9 = 3.6894
d9 = 1.0133


r10 = −1.2375
d10 = 0.4035


r11 = −3.4546
d11 = 1.6970


r12 = ∞
d12 = 0.7127


r13 = ∞
d13 = 0.6788


r14 = ∞





FNO = 5.548


Focal length of entire unit: f = 1 mm, image height = 0.881 mm, object distance = 17.01 mm, angle of view = 115.4°


Fr = 1.612 mm,


Ff = −0.838 mm,


f1 = −0.622 mm






FIG. 22A is a configuration diagram of the lens unit 22 according to the present example, and FIGS. 22B to 22E are aberration diagrams of the lens unit 22.
EXAMPLE 23
Numerical data, etc. of optical members included in a lens unit 23 according to example 23 are indicated below.










TABLE 23







r1 = ∞
d1 = 0.5000
n1 = 2.18246
ν1 = 33.01


r2 = 1.0234
d2 = 0.4160
n2 = 1.93429
ν2 = 18.90


r3 = ∞
d3 = 0.7234
n3 = 1.51564
ν3 = 75.00


r4 = −5.2110
d4 = 0.0543
n4 = 1.88815
ν4 = 40.76


r5 = ∞
d5 = 0.5606
n5 = 1.73234
ν5 = 54.68


r6 = ∞(STO)
d6 = 0.1447
n6 = 1.93429
ν6 = 18.90


r7 = −7.9337
d7 = 1.3989
n7 = 1.51825
ν7 = 64.14


r8 = −1.9816
d8 = 0.1989
n8 = 1.61379
ν8 = 50.20


r9 = 11.4247
d9 = 1.1756


r10 = −1.3087
d10 = 0.4300


r11 = −2.8801
d11 = 1.8085


r12 = ∞
d12 = 0.7505


r13 = ∞
d13 = 0.7234


r14 = ∞





FNO = 5.672


Focal length of entire unit: f = 1 mm, image height = 0.939 mm, object distance = 18 mm, angle of view = 127.86°


Fr = 1.868 mm,


Ff = −1.231 mm,


f1 = −0.865 mm






FIG. 23A is a configuration diagram of the lens unit 23 according to the present example, and FIGS. 23B to 23E are aberration diagrams of the lens unit 23.
EXAMPLE 24
Numerical data, etc. of optical members included in a lens unit 24 according to example 24 are indicated below.










TABLE 24







r1 = ∞
d1 = 0.5429
n1 = 2.18246
ν1 = 33.01


r2 = 1.0687
d2 = 0.4162
n2 = 1.93429
ν2 = 18.90


r3 = −36.1952
d3 = 0.7239
n3 = 1.51564
ν3 = 75.00


r4 = −4.6981
d4 = 0.0543
n4 = 1.88815
ν4 = 40.76


r5 = ∞
d5 = 0.5610
n5 = 1.73234
ν5 = 54.68


r6 = ∞(STO)
d6 = 0.1448
n6 = 1.93429
ν6 = 18.90


r7 = −5.7493
d7 = 1.4630
n7 = 1.51825
ν7 = 64.14


r8 = −1.9553
d8 = 0.1991
n8 = 1.61379
ν8 = 50.20


r9 = 15.0851
d9 = 1.1763


r10 = −1.2907
d10 = 0.4303


r11 = −2.7220
d11 = 1.9002


r12 = ∞
d12 = 0.7400


r13 = ∞
d13 = 0.7239


r14 = ∞





FNO = 6.176


Focal length of entire unit: f = 1 mm, image height = 0.939 mm, object distance = 18.098 mm, angle of view = 128.03°


Fr = 1.894 mm,


Ff = −1.301 mm,


f1 = −0.904 mm






FIG. 24A is a configuration diagram of the lens unit 24 according to the present example, and FIGS. 24B to 24E are aberration diagrams of the lens unit 24.
EXAMPLE 25
Numerical data, etc. of optical members included in a lens unit 25 according to example 25 are indicated below.










TABLE 25







r1 = ∞
d1 = 0.3920
n1 = 2.18246
ν1 = 33.01


r2 = 1.0035
d2 = 0.3395
n2 = 1.93429
ν2 = 18.90


r3 = 19.3992
d3 = 0.5820
n3 = 1.88815
ν3 = 40.76


r4 = −4.4012
d4 = 0.5308
n4 = 1.73234
ν4 = 54.68


r5 = ∞(STO)
d5 = 0.4829
n5 = 1.93429
ν5 = 18.90


r6 = −11.6039
d6 = 0.5453
n6 = 1.51825
ν6 = 64.10


r7 = −1.7296
d7 = 0.0485


r8 = 15.3992
d8 = 0.9673


r9 = −1.1572
d9 = 0.3696


r10 = −2.7323
d10 = 1.7957


r11 = ∞
d11 = 0.9099


r12 = ∞





FNO = 6.122


Focal length of entire unit: f = 1 mm, image height = 0.913 mm, object distance = 18.93 mm, angle of view = 123.19°


Fr = 1.687 mm,


Ff = −1.346 mm,


f1 = −0.849 mm






FIG. 25A is a configuration diagram of the lens unit 25 according to the present example, and FIGS. 25B to 25E are aberration diagrams of the lens unit 25.
EXAMPLE 26
Numerical data, etc. of optical members included in a lens unit 26 according to example 26 are indicated below.










TABLE 26







r1 = ∞
d1 = 0.5010
n1 = 2.01169
ν1 = 28.27


r2 = 0.8712
d2 = 0.4166
n2 = 1.93429
ν2 = 18.90


r3 = ∞
d3 = 0.5993
n3 = 1.51564
ν3 = 75.00


r4 = −8.5465
d4 = 0.1449
n4 = 1.88815
ν4 = 40.76


r5 = ∞
d5 = 0.4554
n5 = 1.73234
ν5 = 54.68


r6 = ∞(STO)
d6 = 0.0543
n6 = 1.93429
ν6 = 18.90


r7 = ∞
d7 = 1.8080
n7 = 1.51825
ν7 = 64.14


r8 = −2.0398
d8 = 0.1993
n8 = 1.61379
ν8 = 50.20


r9 = 4.5503
d9 = 1.1775


r10 = −1.4905
d10 = 0.4307


r11 = −5.8142
d11 = 1.4790


r12 = ∞
d12 = 0.7246


r13 = ∞
d13 = 0.7246





FNO = 6.346


Focal length of entire unit: f = 1 mm, image height = 0.94 mm, object distance = 18.116 mm, angle of view = 128.00°


Fr = 1.733 mm,


Ff = −1.042 mm,


f1 = −0.861 mm






FIG. 26A is a configuration diagram of the lens unit 26 according to the present example, and FIGS. 26B to 26E are aberration diagrams of the lens unit 26.
Summary of Examples 1 to 26
Tables 27 and 28 list respective configurations of the lens units according to examples 1 to 26. In Tables 27 and 28, configurations of lens units disclosed in Japanese Patent Application Laid-Open Publication No. 6-308381 are listed as comparative examples 1 to 3. In Table 2, a circle indicates that the relevant condition is satisfied, and x indicates that the relevant condition is not satisfied.
The lens units according to comparative example 1 to 3 have the following configurations, respectively:
Comparative example 1: f=1 mm, Fr=1.838 mm, Ff=−1.752 mm, f1=−1.020 mm
Comparative example 2: f=1 mm, Fr=1.877 mm, Ff=−1.812 mm, f1=−1.041 mm
Comparative example 3: f=1 mm, Fr=1.889 mm, Ff=−2.062 mm, f1=−0.808 mm















TABLE 27







SF
Fr/Ff
Ff/f
Ff/f1
n1
Hk
n1 × Hk























Example 1
−1.000
−1.440
−1.123
1.182
1.8882
710
1340.6


Example 2
−2.761
−1.351
−1.280
1.294
1.8882
710
1340.6


Example 3
−2.467
−1.306
−1.353
1.371
1.8882
710
1340.6


Example 4
−2.419
−1.388
−1.276
1.294
1.8882
710
1340.6


Example 5
−1.900
−1.249
−1.439
1.465
1.8882
710
1340.6


Example 6
−2.262
−1.521
−1.228
1.191
1.8882
710
1340.6


Example 7
−2.510
−1.432
−1.294
1.330
1.8882
710
1340.6


Example 8
−2.420
−1.409
−1.332
1.348
1.8882
710
1340.6


Example 9
−1.000
−1.718
−0.967
1.090
1.8882
710
1340.6


Example
−1.000
−1.151
−1.383
1.507
1.8882
710
1340.6


10


Example
−0.556
−1.187
−1.320
1.462
1.8882
710
1340.6


11


Example
−1.000
−1.680
−0.993
1.093
1.8882
710
1340.6


12


Example
−5.000
−1.520
−1.226
1.295
1.8882
710
1340.6


13


Example
−1.000
−1.596
−1.135
1.386
2.1825
1200
2617.0


14


Example
−1.000
−1.561
−1.174
1.445
2.1825
1200
2617.0


15


Example
−1.000
−1.476
−1.310
1.562
2.1825
1200
2617.0


16


Example
−1.000
−1.742
−1.129
1.283
2.1825
1200
2617.0


17


Example
−1.000
−1.688
−1.144
1.347
2.1825
1200
2617.0


18


Example
−1.000
−1.756
−1.000
1.250
2.1825
1200
2617.0


19


Example
−1.000
−1.482
−1.235
1.579
2.1825
1200
2617.0


20


Example
−1.000
−1.588
−1.110
1.532
2.1825
1200
2617.0


21


Example
−1.000
−1.924
−0.838
1.348
2.1825
1200
2617.0


22


Example
−1.000
−1.518
−1.231
1.422
2.1825
1200
2617.0


23


Example
−1.298
−1.456
−1.301
1.440
2.1825
1200
2617.0


24


Example
−0.630
−1.253
−1.346
1.586
2.1825
1200
2617.0


25


Example
−1.000
−1.663
−1.042
1.210
2.0117
700
1408.2


26


Compar-
−1.000
−1.049
−1.751
1.718
1.8882
710
1340.6


ative


example 1


Compar-
−1.000
−1.036
−1.812
1.740
1.8882
710
1340.6


ative


example 2


Compar-
−1.085
0.916
2.063
2.553
1.8882
710
1340.6


ative


example 3























TABLE 28







Condition (1)
Condition (2)
Condition (3)
Condition (4)
Condition (5)
Condition (6)



−6 < SF < 0
−3 < (Fr/Ff) < −1.1
−1.6 < (Ff/f) < −0.6
(Ff/f1) < 1.6
n1 > 2
N1 × Hk > 2000






















Example 1
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Example 2
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Example 3
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Example 4
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Example 5
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Example 6
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Example 8
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Example 9
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Example 10
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Example 11
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Example 12
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Example 13
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Example 14
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Example 15
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Example 16
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Example 17
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Example 18
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Example 19
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Example 20
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Example 21
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Example 22
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Example 23
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Example 24
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Example 25
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Example 26
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example 1


Comparative
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example 2


Comparative
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example 3









From the above results, it is clear that the lens units according to the examples are effective. In other words, in comparative examples 1 to 3, a cementing surface of a cemented lens disposed in a rear lens group for correction of a chromatic aberration of magnification exhibits poor workability, and it is not easy to achieve the recent size reduction while correcting other aberrations such as a field curvature. Meanwhile, the aforementioned problems have been solved in the lens unit according to the examples. In other words, the lens units according to examples 1 to 25 provide only small chromatic aberration of magnification.
Furthermore, the lens units according to examples 13 to 25 satisfy condition (6), i.e., n1×Hk>2000, and thus, an outer surface lens (first lens L1) exhibits a high resistance to cracking and lens scratching compared to the lens units according to example 1 to 12.
EXAMPLE 27
Next, an endoscope 30 including a lens unit 27 according to example 15 of the present invention will be described. An endoscope system 40, which is illustrated in FIG. 27, includes an endoscope 30 including an insertion portion 31 that is inserted into an inner portion of a body of a subject, a light source device 41 that illuminates the inner portion of the body, and a processor 42 that performs signal processing. In other words, a light guide fiber 45 that guides illuminating light from the light source device 41 to a distal end portion 32 is inserted in the insertion portion 31 and illuminates the inner portion of the body via an illumination optical system 32. The processor 42 can be used as an endoscope system adapted to various purposes by combining various endoscopes and/or various light source devices. Furthermore, the endoscope system 40 includes a monitor 43 that displays, e.g., an endoscopic image, and an input unit 44 such as a keyboard for a surgeon to perform, e.g., settings.
The endoscope 30 is an electronic endoscope including a CCD 33, which is an image pickup section that picks up a color endoscopic image, an pre-process (P/P) section 34, and an A/D conversion section 35 and a parallel/serial conversion (P/S) section 36, at the distal end portion 32 of the insertion portion 31 connected to an operation section 37. The lens unit 27 for forming an optical image and a CCD 33 for taking an image of the inner portion of the subject are disposed at the distal end portion 32. An endoscopic image taken by the CCD 33 is converted into digital signals and transmitted to the processor 42. For the image pickup section, e.g., a CMD (charged modulation device) image pickup device, a C-MOS image pickup device, an AMI (amplified MOS imager) or a BCCD (back illuminated CCD) may be employed instead of the CCD 33. Also, it is possible to use a black-and-white CCD instead of a color CCD and chronologically change illumination into RBG signals.
The lens unit 27 of the endoscope 30 has a configuration similar to that of, e.g., the lens unit 13 according to example 1, which has already been described. As already described, e.g., the lens unit 13 has a small diameter and exhibits excellent optical characteristics. Thus, the endoscope 30 has a small diameter and exhibits good characteristics in picked-up images. In other words, an image picked up by the image endoscope 30 has only small chromatic aberration of magnification.
Furthermore, as a material of a first lens L1 of the lens unit 27, a material including at least any component from among Zr, Y, Gd, Ta, Nb, La and Hf as a main component thereof and having a refractive index exceeding 2, for example, yttria-stabilized zirconia, is used. Thus, the first lens L1) has resistance to cracking and lens scratching. Furthermore, the lens unit 27 also has durability for a severe condition in a saturated water vapor-used sterilization system with a high temperature of around 140° C. and a high pressure, such as that in what is called autoclave sterilization.
The present invention is not limited to the above-described embodiments, and various alterations, modifications and the like are possible as long as such alterations and modifications do not change the spirit of the present invention.

## Claims

1. An endoscope objective lens unit comprising a front lens group and a rear lens group with an aperture stop interposed therebetween,
wherein the front lens group includes a first lens having a negative refractive power and a second lens having a positive refractive power in this order from an object side,
wherein the rear lens group includes a third lens having a positive refractive power, and a fourth lens having a positive refractive power and a fifth lens having a negative refractive power, the fourth lens and the fifth lens being cemented to each other, and
wherein the endoscope objective lens unit satisfies expressions (1A), (2), (3) and (4) below:


−3<SF≦−1;  (1A)



−3.0<Fr/Ff<−1.1;  (2)



−1.6<Ff/f<−0.6; and  (3)



Ff/f1<1.6,  (4)



where SF is a shape factor of (R2+R1)/(R2−R1), in which R1 is an object-side radius of curvature of the second lens and R2 is an image-side radius of curvature of the second lens, Ff is a focal length of the front lens group, Fr is a focal length of the rear lens group, f is a focal length of the entire unit, and f1 is a focal length of the first lens.

2. The endoscope objective lens unit according to claim 1, wherein a refractive index n1 (for an e-line) of a material of the first lens satisfies expression (5) below:


n1>2.  (5)

3. The endoscope objective lens unit according to claim 2, wherein the material of the first lens satisfies expression (6) below:


n1×Hk>2000,  (6)

where n1 is a refractive index (for an e-line) and Hk is a Knoop hardness (N/mm2).

4. The endoscope objective lens unit according to claim 3, wherein the material of the first lens includes yttria-stabilized zirconia.

5. An endoscope comprising an endoscope objective lens unit, and an image pickup device that picks up an image formed by the endoscope objective lens unit,
wherein the endoscope objective lens unit includes a front lens group and a rear lens group with an aperture stop interposed therebetween,
wherein the front lens group includes a first lens having a negative refractive power and a second lens having a positive refractive power in this order from an object side,
wherein the rear lens group includes a third lens having a positive refractive power, and a fourth lens having a positive refractive power and a fifth lens having a negative refractive power, the fourth lens and the fifth lens being cemented to each other, and
wherein the endoscope objective lens unit satisfies expressions (1A), (2), (3) and (4) below:


−3<SF≦−1;  (1A)



−3.0<Fr/Ff<−1.1;  (2)



−1.6<Ff/f<0.6; and  (3)



Ff/f1<1.6,  (4)



where SF is a shape factor of (R2+R1)/(R2−R1), in which R1 is an object-side radius of curvature of the second lens and R2 is an image-side radius of curvature of the second lens, Ff is a focal length of the front lens group, Fr is a focal length of the rear lens group, f is a focal length of the entire unit, and f1 is a focal length of the first lens.

6. The endoscope according to claim 5, wherein a refractive index n1 (for an e-line) of a material of the first lens satisfies expression (5) below:


n1>2.  (5)

7. The endoscope according to claim 6, wherein the material of the first lens satisfies expression (6) below:


n1×Hk>2000,  (6)

where n1 is a refractive index (for an e-line) and Hk is a Knoop hardness (N/mm2).

8. The endoscope according to claim 7, wherein the material of the first lens includes yttria-stabilized zirconia.