JPH09197298A - Endoscope eyepiece system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the loss of a light receiving quantity and to lower the sensitivity with the deterioration in imaging performance by a dimensional error by consisting an eyepiece system, successively from an eye side, of a first lens group including a positive lens, a second lens group including a negative lens and positive lens and a third lens group including a positive meniscus lens concave to an image guide side and providing the extreme eye side face of the second lens group with negative refracting power. SOLUTION: This eyepiece system consists, successively from the eye side, the first lens group 10 including one element of the positive lens, the second lens group 20 including one element of the negative lens 21 and one element of the positive lens 22 and the third lens group 30 including the positive meniscus lens concave to the image guide side facing the luminous flux exit end face of the image guide. The extreme eye side face of the second lens group 20 has the negative refracting power. The eyepiece system satisfies the following equations I to III: 0.4<f/f1 <0.8...(I), -0.4<f/f2 <0.9...(II), 0.2<f/f3 <1.1...(III). In the equations, fi is the combined focal length of the i-th lens group and (f) is the combined focal length of the entire system.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a lens of an endoscope eyepiece optical system.

[0002]

2. Description of the Related Art In clinical examinations using a medical endoscope, it is indispensable to attach an adapter lens for photography and photograph and record. Therefore, some eyepiece optical systems of endoscopes have a built-in light receiving element for measuring the amount of exposure light. As a method of photometry by the light receiving element, there is use of light blocked by a fixed diaphragm. In this method, the light receiving element also serves as a fixed diaphragm, and the light blocked by the fixed diaphragm (light for photometry) is used for photometry. In order to obtain a sufficient amount of light for photometry, it is desired to reduce the blocking of the light by a fixing member or the like.

Generally, in lens design, spherical aberration and coma are corrected by focusing on light that has reached the eye without being blocked by the fixed diaphragm (light for viewing), so that it reaches outside the fixed diaphragm diameter. Correction of these aberrations with respect to light (light for photometry) is not sufficiently performed. The light for photometry in which the aberration is insufficiently corrected should pass through each surface of the eyepiece lens and reach the fixed diaphragm, but a large aberration is generated in a surface where the light enters (or exits) at a high angle. Occurrence occurs, and the light for photometry may be an abnormal path light due to its influence. Such light not only reaches the field of view by being reflected directly or by a member etc. and reduces the resolving power, but also all of the photometric light does not reach the fixed diaphragm that also functions as a light receiving element, resulting in insufficient light quantity. It may also cause poor photometry.

An endoscope eyepiece optical system in which aberrations have been corrected to some extent by the positive, negative, and positive three-group construction has already been reported.
However, in this conventional example, the positive refractive power of the first lens on the image guide side is strong, and the amount of spherical aberration generated by that lens is very large. In order to correct this spherical aberration, the refractive power of the negative lens immediately after the positive lens becomes strong, and the radius of curvature of the ray incident surface of the negative lens becomes small. Such a lens has a high sensitivity (the degree of deterioration of the imaging performance due to a dimensional error within the tolerance of the lens shape) and is not very desirable as an eyepiece optical system having a high magnification.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to prevent the loss of the amount of light received by a light receiving element for measuring the amount of exposure light, to reduce abnormal path light, and to reduce the degree of deterioration of the imaging performance due to dimensional errors within the tolerance of the lens shape. An object is to provide an endoscope eyepiece system having low sensitivity and low sensitivity.

[0006]

SUMMARY OF THE INVENTION The present invention relates to an endoscope eyepiece system for observing an image of a light exiting end face of an image guide, a first lens group including at least one positive lens and at least one lens in order from the eye side. A second lens group including a negative lens and a positive lens, and a third lens group facing the light exit end face of the image guide, the third lens group including a concave positive meniscus lens on the image guide side, and The surface of the two lens groups closest to the eye has a negative refractive power.

The endoscope eyepiece system of the present invention preferably satisfies the following conditional expressions (1) to (3). (1) 0.4 <f / f ₁ <0.8 (2) -0.4 <f / f ₂ <0.9 (3) 0.2 <f / f ₃ <1.1 where f _i : Synthetic focal length of the i-th lens group, f: synthetic focal length of the entire system, Further, it is preferable that the following conditional expression (4) is satisfied. (4) −1.1 <f / r ₂₁ <−0.6, where r ₂₁ is the radius of curvature of the most eye-side surface of the second lens group.

The endoscope eyepiece system of the present invention preferably further satisfies the following conditional expressions (5) and (6). (5) 0.8 <f / r ₃₁ <1.9 (6) 1.6 <N _1p where r ₃₁ : radius of curvature of the surface of the positive meniscus lens of the third lens group on the eye side, N _1p : It is the average value of the refractive index of the glass material of the positive lens constituting one lens group.

The second lens group preferably includes at least one set of cemented lenses. It is desirable that this one set of cemented lenses is composed of a cemented lens of a positive lens and a negative lens, and satisfies the following conditional expressions (7) and (8). (7) ν _p −ν _n > 25.0 (8) N _n −N _p > 0.2 where ν _p : Abbe number for the d line of the positive lens, ν _n : Abbe for the d line of the negative lens N _n : Refractive index of the negative lens with respect to d-line, N _p : Refractive index of the positive lens with respect to d-line, If the third lens group is composed of a single meniscus lens, the lens structure becomes simpler.

[0010]

FIG. 31 shows an embodiment of the endoscope eyepiece lens system of the present invention. The left side of the figure is the eye side, the right side is the image guide IG side, and the cover glass C in order from the eye side.
G, a diaphragm (light receiving element) S, a first lens group 10, a second lens group 20, a third lens group 30, and a cover glass CG. The first lens group 10 includes at least one positive lens, and is composed of a single meniscus lens convex on the eye side in the illustrated example. The second lens group 20 includes at least one negative lens and one positive lens. In the illustrated example, the second lens group 20 includes a cemented lens of a negative lens 21 and a positive lens 22 and a positive lens 23 in order from the eye side. ing. The third lens group 30 includes a positive meniscus lens concave on the image guide side, which faces the light exit surface of the image guide IG, and is a positive meniscus single lens in the illustrated example. The surface of the second lens group closest to the eye has a negative refractive power.

The third lens group of the endoscope eyepiece lens system of the present invention includes a positive meniscus positive lens having a concave surface (convex surface on the eye side) facing the image guide side. With this shape, the following effects can be obtained. Since the incident angle of the divergent light from the end face of the image guide to the lens and the exit angle from the lens are small, it is possible to suppress the occurrence of spherical aberration in this lens. A divergent light beam is emitted from the image guide. Therefore, in order to avoid increasing the lens size without increasing the diameter of the lens that follows,
The lens closest to the image guide needs to be a positive lens and satisfies this condition.

Further, by arranging the negative lens closest to the eye in the second lens group and giving the first surface (the surface on the eye side) a negative refracting power, it is possible to prevent the generation of abnormal path light. it can. In the conventional example of FIG. 32, two positive lenses 2 and 3 are arranged immediately in front of the biconcave lens 1 having a strong negative refractive power (on the image guide side). In such a case, the exit angle of the convex surface of the lens having a positive refractive power and the incident angle of the concave surface, which is the negative refractive surface, are high. A large amount of spherical aberration or coma is generated on such a surface, and abnormal path light is generated. In order to eliminate the extraordinary path light generated by such factors, it is necessary to dispose the surface and the power so that the incident or exit angle of the off-axis ray becomes a low angle. The present invention
By giving a negative refractive power to the first surface of the second lens group,
The power arrangement of the lens is obtained such that the incident angle or the exit angle of the light ray on each surface is low, and as a result, spherical aberration and coma are not significantly generated, so that the generation of abnormal path light can be prevented. Therefore, sufficient light for photometry reaches the fixed diaphragm S that also serves as a light receiving element, and accurate photometry is possible.

For comparison, FIG. 33 is a skeleton drawing of the endoscope eyepiece lens system according to the present invention and the conventional lens system of FIG. The F number and back focus of both lens systems are the same. Both lens systems are
It is composed of a first lens group 10 having a single-lens structure, a second lens group 20 having a single-lens structure, and a third lens group 30 having a single-lens structure, and has a total of four positive lenses and one negative lens. . The difference is that in the present invention, the negative lens in the second lens group 20 is located closest to the eye side, whereas in the conventional example, the negative lens is sandwiched between two positive lenses in the second group. That is the point.

In both of these lens systems, the spherical aberration generated by the four positive lenses is corrected by returning to the over with one negative lens. In the conventional example, two positive lenses exist before the negative lens. On the other hand, in the present invention, only one positive lens exists before the negative lens. Since the positive lens has a function of converging the light flux, the incident height h _A of the axial marginal ray of the negative lens in the conventional example is lower than the incident height h _B of the negative lens in the present invention. If the refracting powers of both negative lenses are the same, it is possible to generate a large spherical aberration on the over side when the incident height of the axial marginal ray is high. If the amount of generation is the same, the refractive power of the negative lens of the present invention can be made smaller than that of the negative lens of the conventional example. That is, in the conventional example, the spherical aberration is balanced by the negative lens and the positive lens having a large refractive power, whereas the spherical aberration can be balanced by the negative lens and the positive lens having a small refractive power in the present invention. Since the sensitivity of the lens is lower as the refractive power is smaller, according to the present invention, the endoscope eyepiece system can be configured with the lens having lower sensitivity.

When a positive meniscus lens having a concave surface facing the image guide is arranged immediately after the image guide, divergent light from the image guide is incident on the concave surface at a low angle, so that a spherical surface generated on that surface is generated. Aberration can be reduced.

Conditional expression (1) is a condition relating to the combined focal length of the first lens group. The positive refracting power of the first lens group can correct astigmatism of the entire system in a well-balanced manner. In addition, the positive contribution to the Petzval sum is reduced to suppress field curvature. When the positive refractive power of the first lens group becomes weaker than the lower limit, the astigmatism generated in the negative lens in the second lens group is canceled out and a well-balanced astigmatism correction cannot be performed. When the upper limit is exceeded and the positive refractive power becomes strong, the positive contribution to the Petzval sum increases,
The field curvature becomes large.

Conditional expression (2) is a condition relating to the combined focal length of the second lens group. The negative lens included in the second lens group is important in correcting the spherical aberration generated in the positive lenses of the other groups. When the negative refractive power of the second lens group becomes stronger below the lower limit, the spherical aberration correction effect is improved, but the effective diameter of the light beam incident on the subsequent lens seen from the fiber side becomes large, and therefore the lens outer diameter becomes large. turn into.
When the refractive power of the second lens group exceeds the upper limit and takes a positive value,
Spherical aberration caused by the positive refracting power of the first and third lens groups cannot be sufficiently corrected by the negative lens included in the second lens group.

Conditional expression (3) is a condition relating to the combined focal length of the third lens group. When the lower limit of conditional expression (3) is exceeded and the positive refractive power of the third lens group becomes weak, the height of incidence of off-axis rays on the subsequent lens (as seen from the fiber side) increases, and the outer diameter of the subsequent lens increases. Will become bigger. When the value exceeds the upper limit and the positive refractive power of the third lens group becomes strong, the contribution of the positive refractive power to the Petzval sum becomes large, and the curvature of field increases. In addition, spherical aberration is also under.

Conditional expression (4) is a condition related to the radius of curvature of the eye-side surface of the negative lens arranged in the second lens group.
The spherical aberration that is under due to the positive refracting power of the first and third lens groups is returned to the over side due to the negative refracting power of this surface, and the overall balance is maintained. Further, by giving the first surface (the surface on the eye side) of this second lens group a negative refractive power, it is possible to prevent the generation of abnormal path light as described above.

If the radius of curvature becomes smaller than the lower limit of the conditional expression (4), the negative refracting power becomes strong, the spherical aberration becomes excessive, and the correction becomes excessive. If the radius of curvature increases beyond the upper limit, the negative refracting power is weakened, and the spherical aberration becomes too undercorrected, resulting in insufficient correction.

Conditional expression (5) is a condition relating to the radius of curvature of the meniscus lens forming the third lens group. By satisfying this conditional expression, the positive refractive power of the third lens group is suppressed, the outer diameter of the subsequent lens viewed from the fiber side can be reduced, and the lens shape can be easily processed. Beyond the lower limit, if the radius of curvature increases, the positive refractive power weakens, and the subsequent lens (viewed from the fiber side)
The height of the off-axis marginal ray is increased and the effective diameter of the ray is increased. When the radius of curvature becomes smaller than the upper limit, the edge surface of the meniscus lens moves away from the center of the lens thickness, and the lens shape becomes difficult to process and hold.

Conditional expression (6) is a condition relating to the refractive index of the glass material of the positive lens in the first lens group. Since the overall magnification of the eyepiece optical system has a positive value, the Petzval sum should be as close to 0 as possible in order to reduce the field curvature. When the refractive index of the glass material of the positive lens becomes smaller than the lower limit, the Petzval sum of the lens becomes large on the positive side, and the field curvature cannot be sufficiently corrected. In addition, the radius of curvature of the lens becomes small in order to obtain a constant refracting power, and the spherical aberration becomes too low.

Conditional expression (7) is a condition regarding the dispersion value of the glass material of the cemented lens of the positive lens and the negative lens in the second lens group. In order to correct chromatic aberration, it is preferable to use a cemented lens in which a positive lens having a small dispersion and a negative lens having a large dispersion are combined. In order to enhance the effect of chromatic aberration correction, it is necessary to increase the difference between both dispersion values. If the difference between the dispersion values becomes smaller than the lower limit, chromatic aberration cannot be sufficiently corrected.

Conditional expression (8) is a condition concerning the refractive index of the glass material of the positive lens and the negative lens of the cemented lens in the second lens group. By increasing the refractive index difference between the two lenses, the negative refractive power of this surface is increased. The negative refracting power of this surface has the effect of correcting spherical aberration to the over side, and at the same time, the astigmatism generated by the positive refracting power of the first lens group is corrected by the negative refracting power of this surface. . If the difference in refractive index becomes smaller than the lower limit, the effect of correcting spherical aberration and astigmatism due to the refractive power of the bonding surface becomes small.

The present invention will be described with reference to specific numerical examples. In all the lens configuration diagrams of Examples 1 to 15 below, as in FIG. 31, the left side of the figure is drawn as the eye side and the right side is drawn as the image guide side, and the surface numbers are counted from the eye side surface. ing. All the basic lens configurations are the same as those in FIG. 31, and cover glass CG, diaphragm (light receiving element) S, first lens group 10, second lens group 2 from the eye side.
0, the third lens group 30, and the cover glass CG. Table 1 is a list of the number of constituent lenses of each lens group of each embodiment. The third lens group 30 includes, in all the examples,
It consists of a positive meniscus single lens with the convex surface facing the eye.

Table 1 Example No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Number of 1st group 1 1 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 1 Number of 2nd group 3 2 3 3 3 3 2 3 3 3 3 3 3 3 2 3 Number of third group 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

[Embodiment 1] FIGS. 1 and 2 are a lens configuration diagram and various aberration diagrams of Embodiment 1 of an endoscope eyepiece lens system of the present invention. The first lens group 10 is composed of a positive meniscus single lens having a convex surface facing the eye side, and the second lens group 20 is composed of, in order from the eye side, a cemented lens of a negative lens 21 and a positive lens 22, and a positive lens 23. ing.

Table 2 shows specific numerical data of this lens system. In the various aberration diagrams, chromatic aberration and chromatic aberration of magnification indicated by spherical aberration at d-line, g-line, and C-line, at respective wavelengths, S is sagittal, and M is meridional astigmatism. In addition, ray tracing is also performed from the eye side, and super-optical performance such as aberration is evaluated on the exit end face of the image guide.

In the tables and drawings, F _NO is the F number, f is the focal length of the entire system of the eyepiece system of the endoscope, W is the included angle, and f _B is the back surface from the final surface of the lens (cover glass CG) to the imaging surface. Represents focus. R is the radius of curvature, D is the lens thickness or lens interval, N _d is the refractive index of the d-line, and ν _d is the Abbe number of the d-line.

[0029]

[Table 2] F _NO = 1: 1.3 f = 7.81 W = 5.7 f _B = 0.70 No. RDN _d ν _d 1 ∞ 2.40 1.51633 64.1 2 ∞ 3.85--3 8.600 1.90 1.83400 37.2 4 23.588 3.28--5 -8.600 0.80 1.84666 23.9 6 8.600 3.30 1.48749 70.2 7 -8.600 0.20--8 12.107 2.26 1.77250 49.6 9 -19.975 0.20--10 5.700 3.07 1.88300 40.8 11 5.175 1.79--12 ∞ 0.40 1.51633 64.1 13 ∞---

[Embodiment 2] FIGS. 3 and 4 are lens configuration diagrams and various aberration diagrams of Embodiment 2 of the endoscope eyepiece lens system of the present invention, and Table 3 shows specific numerical data thereof. The first lens group 10 is composed of a positive meniscus single lens whose convex surface faces the eye side, and the second lens group 20 is composed of a cemented lens of a negative lens 21 and a positive lens 22 in order from the eye side.

[0031]

[Table 3] F _NO = 1: 1.3 f = 7.82 W = 5.7 f _B = 0.70 No. RDN _d ν _d 1 ∞ 2.40 1.51633 64.1 2 ∞ 3.57--3 8.269 2.17 1.83400 37.2 4 271.114 2.25--5 -11.976 1.50 1.84666 23.8 6 5.000 4.88 1.48749 70.2 7 -7.101 0.62--8 5.308 3.00 1.88300 40.8 9 21.402 1.68--10 ∞ 0.40 1.51633 64.1 11 ∞---

[Embodiment 3] FIGS. 5 and 6 are lens configuration diagrams and various aberration diagrams of Embodiment 3 of the endoscope eyepiece lens system of the present invention, and Table 4 shows specific numerical data thereof. The first lens group 10 is composed of a positive meniscus single lens having a convex surface facing the eye side, and the second lens group 20 is a cemented lens of a negative lens 21 and a positive lens 22 and a positive lens 2 in order from the eye side.
It consists of three.

[0033]

[Table 4] F _NO = 1: 1.3 f = 7.82 W = 5.7 f _B = 0.70 No. RDN _d ν _d 1 ∞ 2.40 1.51633 64.1 2 ∞ 3.59--3 8.325 1.95 1.78300 36.1 4 23.734 2.74--5 -8.751 0.88 1.84666 23.8 6 8.369 3.60 1.53172 48.9 7 -8.854 0.21--8 14.023 2.18 1.71300 53.8 9 -18.188 0.38--10 5.545 3.33 1.77250 49.6 11 5.135 1.80--12 ∞ 0.40 1.51633 64.1 13 ∞---

[Embodiment 4] FIGS. 7 and 8 are lens configuration diagrams and various aberration diagrams of Embodiment 4 of the endoscope eyepiece lens system of the present invention, and Table 5 shows specific numerical data thereof. The first lens group 10 is composed of a positive meniscus single lens having a convex surface facing the eye side, and the second lens group 20 is a cemented lens of a negative lens 21 and a positive lens 22 and a positive lens 2 in order from the eye side.
It consists of three.

[0035]

[Table 5] F _NO = 1: 1.3 f = 7.81 W = 5.7 f _B = 0.70 No. RDN _d ν _d 1 ∞ 2.40 1.51633 64.1 2 ∞ 3.54--3 7.993 2.00 1.72342 37.9 4 23.647 3.46--5 -8.391 0.80 1.84666 23.8 6 8.363 3.28 1.48749 70.2 7 -8.931 0.20--8 12.479 2.25 1.77250 49.6 9 -18.759 0.20--10 5.464 3.12 1.88300 40.8 11 5.061 1.80--12 ∞ 0.40 1.51633 64.1 13 ∞---

[Embodiment 5] FIGS. 9 and 10 are lens configuration diagrams and various aberration diagrams of Embodiment 5 of the endoscope eyepiece lens system of the present invention, and Table 6 shows specific numerical data thereof. First
The lens group 10 is composed of a positive meniscus single lens having a convex surface facing the eye side, and the second lens group 20 is composed of, in order from the eye side, a cemented lens of a negative lens 21 and a positive lens 22, and a positive lens 23. .

[0037]

[Table 6] F _NO = 1: 1.3 f = 7.81 W = 5.7 f _B = 0.70 No. RDN _d ν _d 1 ∞ 2.40 1.51633 64.1 2 ∞ 3.74--3 9.425 2.24 1.83400 37.2 4 61.269 2.33--5 -12.125 1.61 1.80518 25.4 6 5.296 3.91 1.58913 61.2 7 -12.756 0.44--8 8.160 2.50 1.88300 40.8 9 -69.857 0.20--10 9.215 2.00 1.88300 40.8 11 9.117 1.68--12 ∞ 0.40 1.51633 64.1 13 ∞---

[Embodiment 6] FIGS. 11 and 12 are lens configuration diagrams and various aberration diagrams of Embodiment 6 of the endoscope eyepiece lens system of the present invention, and Table 7 shows specific numerical data thereof. The first lens group 10 is composed of a positive meniscus single lens having a convex surface facing the eye side, and the second lens group 20 is sequentially arranged from the eye side.
It comprises a cemented lens of a negative lens 21 and a positive lens 22, and a positive lens 23.

[0039]

[Table 7] F _NO = 1: 1.5 f = 9.23 W = 5.9 f _B = 0.61 No. RDN _d ν _d 1 ∞ 2.40 1.51633 64.1 2 ∞ 3.72--3 8.327 1.88 1.81600 46.6 4 29.750 4.03--5 -8.930 0.80 1.84666 23.8 6 8.930 3.20 1.48749 70.2 7 -8.930 0.20--8 22.490 1.83 1.88300 40.8 9 -22.490 0.20--10 5.310 2.59 1.88300 40.8 11 5.285 2.10--12 ∞ 0.40 1.51633 64.1 13 ∞---

[Embodiment 7] FIGS. 13 and 14 are lens configuration diagrams and aberration diagrams of Embodiment 7 of the endoscope eyepiece lens system of the present invention, and Table 8 shows specific numerical data thereof. The first lens group 10 is composed of a positive meniscus single lens having a convex surface facing the eye side, and the second lens group 20 is sequentially arranged from the eye side.
It consists of a cemented lens of a negative lens 21 and a positive lens 22.

[0041]

[Table 8] F _NO = 1: 1.5 f = 9.25 W = 5.9 f _B = 0.70 No. RDN _d ν _d 1 ∞ 2.40 1.51633 64.1 2 ∞ 3.75--3 8.081 2.09 1.88300 40.8 4 26.766 3.03--5 -14.501 1.00 1.84666 23.8 6 5.094 4.60 1.53172 48.9 7 -8.000 0.20--8 5.948 4.28 1.88300 40.8 9 10.539 1.69--10 ∞ 0.40 1.51633 64.1 12 ∞---

[Embodiment 8] FIGS. 15 and 16 are lens configuration diagrams and various aberration diagrams of Embodiment 8 of the endoscope eyepiece lens system of the present invention, and Table 9 shows specific numerical data thereof. The first lens group 10 is composed of a positive meniscus single lens having a convex surface facing the eye side, and the second lens group 20 is sequentially arranged from the eye side.
It comprises a cemented lens of a negative lens 21 and a positive lens 22, and a positive lens 23.

[0043]

[Table 9] F _NO = 1: 1.5 f = 9.22 W = 5.9 f _B = 0.70 No. RDN _d ν _d 1 ∞ 2.40 1.51633 64.1 2 ∞ 3.85--3 8.710 1.86 1.81600 46.6 4 33.696 3.83--5 -9.680 1.00 1.84666 23.8 6 9.680 3.01 1.48749 70.2 7 -9.680 0.21--8 21.400 1.87 1.81600 46.6 9 -21.400 0.20--10 5.637 2.74 1.88300 40.8 11 5.700 2.08--12 ∞ 0.40 1.51633 64.1 13 ∞---

[Embodiment 9] FIGS. 17 and 18 are lens configuration diagrams and various aberration diagrams of Embodiment 9 of the endoscope eyepiece lens system of the present invention, and Table 10 shows specific numerical data thereof.
The first lens group 10 is composed of a positive meniscus single lens having a convex surface facing the eye side, and the second lens group 20 is composed of, in order from the eye side, a cemented lens of a negative lens 21 and a positive lens 22, and a positive lens 23. ing.

[0045]

[Table 10] F _NO = 1: 1.5 f = 9.25 W = 5.9 f _B = 0.70 No. RDN _d ν _d 1 ∞ 2.40 1.51633 64.1 2 ∞ 3.70--3 7.966 2.01 1.83400 37.2 4 23.700 3.19--5 -11.017 1.00 1.84666 23.8 6 7.448 3.57 1.48749 70.2 7 -9.088 0.20--8 19.153 1.80 1.77250 49.6 9 -27.241 0.20--10 5.510 2.98 1.88300 40.8 11 5.068 2.00--12 ∞ 0.40 1.51633 64.1 13 ∞---

[Embodiment 10] FIGS. 19 and 20 are lens configuration diagrams and aberration diagrams of Embodiment 10 of the endoscope eyepiece lens system of the present invention, and Table 11 shows specific numerical data thereof. The first lens group 10 is composed of a positive meniscus single lens having a convex surface facing the eye side, and the second lens group 20 is composed of, in order from the eye side, a cemented lens of a negative lens 21 and a positive lens 22, and a positive lens 23. ing.

[0047]

[Table 11] F _NO = 1: 1.5 f = 9.25 W = 5.9 f _B = 0.70 No. RDN _d ν _d 1 ∞ 2.40 1.51633 64.1 2 ∞ 3.70--3 7.733 2.05 1.70000 48.1 4 37.282 3.73--5 -8.971 1.00 1.80518 25.4 6 8.042 3.34 1.48749 70.2 7 -8.951 0.20--8 19.247 1.85 1.72916 54.7 9 -22.670 0.33--10 4.943 2.39 1.88300 40.8 11 5.068 2.04--12 ∞ 0.40 1.51633 64.1 13 ∞---

[Embodiment 11] FIGS. 21 and 22 are lens configuration diagrams and various aberration diagrams of Embodiment 11 of the endoscope eyepiece lens system of the present invention, and Table 12 shows specific numerical data thereof. The first lens group 10 is composed of a cemented lens of two meniscus lenses 11 and 12 with a convex surface facing the eye,
The lens group 20 is composed of, in order from the eye side, a cemented lens of a negative lens 21 and a positive lens 22, and a positive lens 23.

[0049]

[Table 12] F _NO = 1: 1.3 f = 7.81 W = 5.7 f _B = 0.70 No. RDN _d ν _d 1 ∞ 2.40 1.51633 64.1 2 ∞ 3.64--3 8.643 1.02 1.81600 46.6 4 8.799 1.70 1.83400 37.2 5 22.232 2.79 --6 -8.724 0.87 1.84666 23.8 7 8.724 3.26 1.48749 70.2 8 -8.724 0.20--9 11.990 2.25 1.77250 49.6 10 -20.450 0.20--11 5.417 2.90 1.88300 40.8 12 5.000 1.81--13 ∞ 0.40 1.51633 64.1 14 ∞---

[Embodiment 12] FIGS. 23 and 24 are lens configuration diagrams and various aberration diagrams of Embodiment 12 of the endoscope eyepiece lens system of the present invention, and Table 13 shows specific numerical data thereof. The first lens group 10 is composed of two cemented lenses of meniscus lenses 11 and 12 having a convex surface facing the eye side, and the second lens group 20 is a cemented lens of a negative lens 21 and a positive lens 22 in order from the eye side. , And a positive lens 23.

[0051]

[Table 13] F _NO = 1: 1.3 f = 7.80 W = 5.7 f _B = 0.70 No. RDN _d ν _d 1 ∞ 2.40 1.51633 64.1 2 ∞ 3.76--3 9.889 1.56 1.81600 46.6 4 24.886 0.80--5 12.013 1.56 1.77250 49.6 6 30.131 1.68--7 -10.776 0.80 1.84666 23.8 8 10.776 2.75 1.48749 70.2 9 -10.776 0.20--10 ∞ 1.70 1.77250 49.6 11 -12.485 0.20--12 5.000 2.07 1.88300 40.8 13 7.020 1.68--14 ∞ 0.40 1.51633 64.1 15 ∞---

[Embodiment 13] FIGS. 25 and 26 are lens configuration diagrams and various aberration diagrams of Embodiment 13 of the endoscope eyepiece lens system of the present invention, and Table 14 shows specific numerical data thereof. The first lens group 10 is composed of two cemented lenses of meniscus lenses 11 and 12 having a convex surface facing the eye side, and the second lens group 20 is a cemented lens of a negative lens 21 and a positive lens 22 in order from the eye side. , And a positive lens 23.

[0053]

[Table 14] F _NO = 1: 1.5 f = 9.25 W = 5.9 f _B = 0.70 No. RDN _d ν _d 1 ∞ 2.40 1.51633 64.1 2 ∞ 3.68--3 8.533 1.91 1.81600 46.6 4 80.298 1.00--5 80.463 1.00 1.48749 70.2 6 16.788 2.08--7 -8.615 1.00 1.84666 23.8 8 8.615 2.99 1.48749 70.2 9 -8.615 0.20--10 16.530 1.89 1.81600 46.6 11 -19.337 0.20--12 5.058 2.00 1.88300 40.8 13 5.068 2.50--14 ∞ 0.40 1.51633 64.1 15 ∞---

[Embodiment 14] FIGS. 27 and 28 are lens configuration diagrams and aberration diagrams of Embodiment 14 of the endoscope eyepiece lens system of the present invention, and Table 15 shows specific numerical data thereof. The first lens group 10 is composed of a cemented lens of a positive lens 11 and a negative lens 12 having a convex surface facing the eye side, and the second lens group 20 is a cemented lens of a negative lens 21 and a positive lens 22 in order from the eye side, and It consists of a positive lens 23.

[0055]

[Table 15] F _NO = 1: 1.5 f = 9.25 W = 5.9 f _B = 0.70 No. RDN _d ν _d 1 ∞ 2.40 1.51633 64.1 2 ∞ 3.68--3 9.054 2.10 1.81600 46.6 4 ∞ 1.00 1.48749 70.2 5 24.096 2.55 --6 -9.776 1.00 1.84666 23.8 7 9.776 2.98 1.48749 70.2 8 -9.776 0.20--9 23.005 1.88 1.81600 46.6 10 -19.394 0.20--11 5.926 2.13 1.88300 40.8 12 6.703 2.73--13 ∞ 0.40 1.51633 64.1 14 ∞---

[Embodiment 15] FIGS. 29 and 30 are lens configuration diagrams and aberration diagrams of Embodiment 15 of the endoscope eyepiece lens system of the present invention, and Table 16 shows specific numerical data thereof. The first lens group 10 is composed of a positive meniscus single lens having a convex surface facing the eye side, and the second lens group 20 is composed of, in order from the eye side, a cemented lens of a negative lens 21 and a positive lens 22, and a positive lens 23. ing. In this example, there is no cover glass on the eye side. If there is no cover glass on the eye side, the eye can be brought closer to the lens.

[0057]

[Table 16] F _NO = 1: 1.4 f = 8.44 W = 5.2 f _B = 0.70 No. RDN _d ν _d 1 8.873 1.75 1.88300 40.8 2 25.990 2.84--3 -9.800 1.02 1.84666 23.8 4 9.800 2.99 1.58913 61.2 5- 9.800 0.20--6 27.915 1.66 1.80610 40.9 7 -27.915 0.20--8 6.189 2.43 1.80610 40.9 9 8.923 2.81--10 ∞ 0.40 1.51633 64.1 11 ∞---

Table 17 shows values for the conditional expressions of Examples 1 and 15.

[Table 17] Conditional expression (1) Conditional expression (2) Conditional expression (3) Conditional expression (4) Example 1 0.509 0.580 0.214 -0.908 Example 2 0.767 -0.321 1.063 -0.653 Example 3 0.504 0.541 0.221 -0.894 Implementation Example 4 0.493 0.549 0.264 -0.931 Example 5 0.597 0.885 0.069 -0.644 Example 6 0.677 0.392 0.345 -1.034 Example 7 0.743 -0.270 0.860 -0.638 Example 8 0.662 0.369 0.342 -0.952 Example 9 0.680 0.355 0.279 -0.840 Example 10 0.683 0.344 0.406 -1.031 Example 11 0.501 0.578 0.240 -0.896 Example 12 0.693 0.188 0.587 -0.724 Example 13 0.644 0.531 0.302 -1.074 Example 14 0.677 0.386 0.356 -0.946 Example 15 0.580 0.298 0.470 -0.861 Conditional expression (5 ) Conditional expression (6) Conditional expression (7) Conditional expression (8) Example 1 1.370 1.83400 46.4 0.35917 Example 2 1.473 1.83400 46.4 0.35917 Example 3 1.410 1.78300 25.1 0.31494 Example 4 1.430 1.72342 46.4 0.35917 Example 5 0.848 1.83400 35.8 0.21605 Example 6 1.739 1.81600 46.4 0.35917 Example 7 1.556 1.88300 25.1 0.31494 Example 1.636 1.81600 46.4 0.35917 Example 9 1.679 1.83400 46.4 0.35917 Example 10 1.871 1.70000 44.8 0.31769 Example 11 1.443 1.82500 46.4 0.35917 Example 12 1.560 1.79425 46.4 0.35917 Example 13 1.829 1.81600 46.4 0.35917 Example 14 1.561 1.81600 46.4 1.35917 Example 1.88300 37.4 0.25753

As is apparent from Table 17, the numerical values of Examples 1 to 15 satisfy the conditional expressions (1) to (8), and each aberration is relatively well corrected.

[0060]

According to the present invention, the light receiving amount loss of the light receiving element for measuring the exposure light amount is prevented, the abnormal path light is reduced, and the degree of deterioration of the image forming performance due to the dimensional error within the tolerance of the lens shape is reduced. An endoscope eyepiece system having low sensitivity and low sensitivity can be obtained.

[Brief description of drawings]

FIG. 1 is a lens configuration diagram of a first embodiment of an endoscope eyepiece lens according to the present invention.

FIG. 2 is a diagram illustrating various aberrations of the lens system in FIG. 1;

FIG. 3 is a lens configuration diagram of a second embodiment of the endoscope eyepiece lens according to the present invention.

FIG. 4 is a diagram illustrating various aberrations of the lens system in FIG. 3;

FIG. 5 is a lens configuration diagram of a third embodiment of the endoscope eyepiece lens according to the present invention.

FIG. 6 is a diagram illustrating various aberrations of the lens system in FIG. 5;

FIG. 7 is a lens configuration diagram of a fourth example of the endoscope eyepiece lens according to the present invention.

8 is a diagram illustrating various aberrations of the lens system in FIG. 7;

FIG. 9 is a lens configuration diagram of a fifth embodiment of the endoscope eyepiece lens according to the present invention.

FIG. 10 is a diagram of various types of aberration of the lens system in FIG.

FIG. 11 is a lens configuration diagram of a sixth example of the endoscope eyepiece lens according to the present invention.

12 is a diagram illustrating various aberrations of the lens system in FIG. 11;

FIG. 13 is a lens configuration diagram of a seventh example of the endoscope eyepiece lens according to the present invention.

FIG. 14 is a diagram illustrating various aberrations of the lens system in FIG. 13;

FIG. 15 is a lens configuration diagram of an eighth example of the endoscope eyepiece lens according to the present invention.

FIG. 16 is a diagram illustrating various aberrations of the lens system in FIG. 15;

FIG. 17 is a lens configuration diagram of a ninth embodiment of the endoscope eyepiece lens according to the present invention.

18 is a diagram illustrating various aberrations of the lens system in FIG. 17;

FIG. 19 is a lens configuration diagram of a tenth example of the endoscope eyepiece lens according to the present invention.

20 is a diagram of various types of aberration in the lens system of FIG.

FIG. 21 is a lens configuration diagram of an eleventh embodiment of the endoscope eyepiece lens according to the present invention.

22 is a diagram of various types of aberration in the lens system of FIG. 21.

FIG. 23 is a lens configuration diagram of a twelfth embodiment of the endoscope eyepiece lens according to the present invention.

FIG. 24 is a diagram of various types of aberration of the lens system in FIG. 23.

FIG. 25 is a lens configuration diagram of a thirteenth embodiment of the endoscope eyepiece lens according to the present invention.

FIG. 26 is a diagram of various types of aberration of the lens system in FIG. 25.

FIG. 27 is a lens configuration diagram of a fourteenth embodiment of the endoscope eyepiece lens according to the present invention.

28 is a diagram of various types of aberration of the lens system in FIG. 27.

FIG. 29 is a lens configuration diagram of a fifteenth embodiment of the endoscope eyepiece lens according to the present invention.

FIG. 30 is a diagram of various types of aberration of the lens system in FIG. 29.

FIG. 31 is a diagram showing an example of an endoscope eyepiece lens system according to the present invention.

FIG. 32 is a diagram showing an example of a conventional endoscope eyepiece lens system.

FIG. 33 is a skeleton diagram for comparison between the present invention and a conventional endoscope eyepiece lens system.

[Explanation of symbols]

 10: First lens group 20: Second lens group 30: Third lens group S: Aperture

Claims (6)

[Claims] 1. In an endoscope eyepiece lens system for observing an image of a light exit end face of an image guide, a first lens group including at least one positive lens, at least one negative lens, and It is composed of a second lens group including one positive lens and a third lens group facing the light beam exit end surface of the image guide and including a concave positive meniscus lens on the image guide side. An eyepiece system for an endoscope, wherein the surface on the eye side has a negative refractive power. 2. The endoscope eyepiece system according to claim 1, wherein the following conditional expressions (1) to (3) are satisfied. (1) 0.4 <f / f ₁ <0.8 (2) -0.4 <f / f ₂ <0.9 (3) 0.2 <f / f ₃ <1.1 where f _i : Synthetic focal length of the i-th lens group, f: synthetic focal length of the entire system. 3. The endoscope eyepiece system according to claim 2, which satisfies the following conditional expression (4). (4) −1.1 <f / r ₂₁ <−0.6, where r ₂₁ : the radius of curvature of the surface of the second lens group closest to the eye. 4. An endoscope eyepiece system according to claim 3, wherein the following conditional expressions (5) and (6) are satisfied. (5) 0.8 <f / r ₃₁ <1.9 (6) 1.6 <N _1p where r ₃₁ : radius of curvature of the surface of the positive meniscus lens of the third lens group on the eye side, N _1p : The average value of the refractive index of the glass material of the positive lens that constitutes one lens group. 5. The endoscope eyepiece system according to claim 4, wherein the second lens group includes at least one cemented lens. 6. The endoscope eyepiece lens according to claim 5, wherein the pair of cemented lenses is a cemented lens of a positive lens and a negative lens, and which satisfies the following conditional expressions (7) and (8). system. (7) ν _p −ν _n > 25.0 (8) N _n −N _p > 0.2 where ν _p : Abbe number for the d line of the positive lens, ν _n : Abbe for the d line of the negative lens Number, N _n : Refractive index of the negative lens for d line, N _p : Refractive index of the positive lens for d line.