JPH09304693A - Hard mirror objective optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of image quality by assembling condition and to improve the assembling easiness in a hard mirror whose insertion part has a comparatively small outside diameter, <= about 3mm, especially. SOLUTION: The objective lens is composed of a cover glass 31, a plane- concave lens 32, a 30 deg. prism 33, a plane-convex positive lens 34 and a bonded lens 35; and the cover glass 31 has a concave surface on an image side and is fixed on a leading end frame 30 integrally formed with an outer tube 21 by means of adhesion. In such a case, the outside diameter of the lens 35: ϕ=2.000; the thickness of the lens 35: d=6.499; d/ϕ=3.250; the glass path length of the positive lens of the lens 35: d1=1.633; and the glass path length backward from the positive lens of the lens 35: d2=4.866.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a rigid endoscope objective optical system,
More specifically, the present invention relates to a rigid-mirror objective optical system characterized by the shape of the cemented lens.

[0002]

2. Description of the Related Art Hard medical endoscopes for medical use which are inserted into a body cavity for observation and treatment are widely used. For example, various types of objective optical systems for rigid endoscopes have been disclosed.

That is, for example, in a rigid-mirror objective optical system disclosed in Japanese Examined Patent Publication No. 4-14324, as shown in FIG. 19, a negative lens group 101, a positive lens group 102, and a concave surface are oriented toward the object side from the object. It is composed of a meniscus lens 103.

In this structure, although not shown, the aerial image 104 formed by the objective optical system is transmitted by the relay lens at the subsequent stage and is imaged in front of the eyepiece lens, and the image is magnified and observed by the eyepiece lens. It has become.

In this rigid endoscope, the negative field curvature generated by the relay lens is made positive by the objective lens by the concave action of the meniscus lens 103, and the field curvature of the entire rigid mirror observation optical system is corrected. ing.

Further, as shown in FIG. 20, the hard-mirror objective optical system disclosed in Japanese Patent Laid-Open No. 5-288986 is a front lens group divergent system cemented lens 11 consisting of a negative meniscus lens including an aspherical surface.
The rear group convergence system 111 is composed of at least two lens components including 0, and the cemented lens 112 in the latter stage is constructed by cementing three lenses.

Further, as shown in FIG. 21, the rigid-mirror objective optical system disclosed in Japanese Patent Laid-Open No. 60-140312 has a retrofocus type objective lens 121 and a refractive index distribution type relaying an image by the objective lens 121. Lens 122
It is composed of

[0008]

At present, in orthopedics, obstetrics and gynecology, and urology, which are the fields of application of medical rigid endoscopes, rigid endoscopes having an insertion portion with an outer diameter of 4 mm are the mainstream. A lens having an outer diameter of less than 3 mm is used as the lens. Further, in the rigid endoscope, a small CCD camera is attached to the eyepiece to make a diagnosis on a TV monitor.

Since such a rigid endoscope is used by inserting it into the patient's body, the rigid endoscope having a smaller diameter, for example, the outer diameter of the insertion portion, is made to be minimally invasive so as to reduce the burden on the patient. Development of a rigid mirror or the like having a lens outer diameter of about 3 mm and a lens outer diameter of less than 2 mm is desired.

Although the outer diameter of the lens is reduced by making the insertion portion of the rigid endoscope thin, generally, the reduction of the lens outer diameter leads to deterioration of various optical performances.

That is, first, there is a decrease in the brightness of the image due to the reduction in the outer diameter of the lens. In order to maintain the brightness of the image, if the lens data of the optical system of the rigid endoscope having a large outer diameter is multiplied by a coefficient, the optical system of the rigid rigid endoscope can be realized, but the total length becomes short. On the contrary, in order to secure the full length, the number of relays is increased, but since the number of lenses is increased, the cost is limited, and the brightness is darker than that of a rigid endoscope having a large diameter.

Secondly, the image quality of the image is deteriorated. The inner diameter tolerance of the cylindrical mechanical frame that supports the lens of the rigid endoscope and the outer diameter tolerance of the lens are determined by the processing capacity and are almost constant. As the outer diameter of the objective optical system becomes smaller, the gap between the lens and the cylindrical mechanical frame becomes relatively larger, and the inclination of the lens becomes larger. The tilt of the lens leads to one-sided blurring of the image and deteriorates the image quality. Even if the design performance is sufficient, there is a problem that due to the tilt of the lens, one-sided blurring of the image is likely to occur and the final image quality deteriorates during assembly.

As the performance of CCDs has improved in recent years, their sensitivity has improved, and there has been room for reducing the diameter of the insertion portion with respect to the above-mentioned problem of brightness. However, the conventional rigid-mirror objective optical system cannot solve the above-mentioned problem of image quality deterioration.

That is, when the objective optical system of Japanese Patent Publication No. 4-14324 is applied to the case where the lens outer diameter is 2 mm or less, the thickness of the positive lens group and the meniscus lens is small and easily tilted, and the image quality is deteriorated. I have a problem. Further, there is a problem that the lens becomes small, the handling at the time of assembling is difficult, and the assembling property is poor.

Further, in Japanese Unexamined Patent Publication No. 5-288986, the length of the cemented lens is short and the lens easily tilts, so that there is a problem of image deterioration as in Japanese Patent Publication No. 4-14324.

Further, in Japanese Patent Laid-Open No. 60-140312, there is an assembling problem that an image is just on the final surface of the objective lens and dust on the adhesive surface attached to the final surface is easily seen. Further, the length of the cemented lens cannot be said to be sufficiently long, and again there is a problem of image quality deterioration due to the inclination of the lens.

The present invention has been made in view of the above circumstances, and prevents deterioration of the image quality due to the assembling conditions and the assembling property of a rigid endoscope having an insertion portion having a relatively small outer diameter, particularly about 3 mm or less. It is an object of the present invention to provide a rigid-mirror objective optical system that can improve

[0018]

A rigid-mirror objective optical system of the present invention is a rigid-mirror observing optical system including an objective optical system and a relay lens for transmitting an object image in order from the object side. From the side, in order from the side, it has a divergence lens system of negative power as a whole consisting of at least one negative lens, a positive lens having a convex surface on the image side, and a cemented surface with a concave surface facing the object side having negative refractive power. And a cemented lens having a positive refractive index as a whole, and the following conditional expression (1):
It is configured to satisfy (2).

Conditional expression: (1) 2.5 <d / φ <7 (2) 2d1 <d2 where d and φ are the cemented lens thickness and outer diameter, d1
Is the glass path length before the cemented surface of the cemented lens, and d2 is the glass path length behind the cemented surface of the cemented lens.

In the objective optical system for the rigid scope of the present invention, by satisfying the above conditional expressions (1) and (2), deterioration of the image quality due to the inclination of the lens at the time of assembly is prevented and the assembling property is improved. It is longer than the conventional cemented lens, solves the above-mentioned problems, and prevents deterioration of image quality due to assembly conditions and improves assemblability, especially in the case of a rigid endoscope with a relatively small outer diameter of the insertion part, especially about 3 mm or less. It is possible to That is, by making the cemented lens long, the tilt angle in the cylindrical mechanical frame in which the lens of the objective optical system is arranged becomes small, the deterioration of the image quality due to the tilt of the lens is prevented, and the cemented lens becomes long. As a result, handling at the time of assembling becomes easy, and the assembling property can be improved.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

1 to 12 relate to a first embodiment of the present invention, and FIG. 1 is a sectional view showing the structure of a rigid endoscope, and FIG.
2 is a sectional view showing the configuration of the tip of the rigid endoscope shown in FIG. 1, and FIG.
4 is a configuration diagram showing the configuration of the objective lens of FIG. 4, FIG. 4 is an aberration diagram showing the aberration state of the rigid endoscope of FIG. 1, FIG. 5 is a configuration diagram showing the configuration of the first modification of the objective lens of FIG. 3, and FIG. FIG. 7 is an aberration diagram showing an aberration state of a rigid endoscope including the objective lens of FIG.
8 is a configuration diagram showing a configuration of a second modification of the objective lens of FIG.
9 is an aberration diagram showing an aberration state of a rigid endoscope including the objective lens of FIG. 7, FIG. 9 is a configuration diagram showing a configuration of a third modification of the objective lens of FIG. 3, and FIG. 10 is provided with the objective lens of FIG. FIG. 11 is an aberration diagram showing an aberration state of the rigid endoscope, FIG. 11 is a configuration diagram showing a configuration of a fourth modification of the objective lens of FIG. 3, and FIG. 12 is an aberration state of the rigid endoscope having the objective lens of FIG. It is an aberration diagram.

As shown in FIG. 1, the rigid endoscope 1 of the present embodiment is roughly divided into an object lens (front end side) and an objective lens 2, for example, seven relay lenses 3 (1) to 3 (7).
Is installed, and the light guide fiber 4
A rod-shaped portion 11 called an outer tube made of metal, which is a portion to be actually inserted into the human body, and a rod-shaped portion 11
An LG joint portion 12 extending from the base end side portion of the light guide fiber 4 for connecting the light guide fiber 4 to the illumination light emitted from a light source device (not shown) to the light guide fiber 4, and the relay lens 3 ( 7) Optically connected to the base end surface of 7), and is composed of an eyepiece lens 5 and a base portion 13 having an eyepiece portion 7 containing a cover glass 6.

In the rod-shaped portion 11 of the rigid endoscope 1, as shown in FIG. 2, the structural members are composed of an outer tube 21, a fiber tube 22 and a system tube 23 in order from the outside, and have a triple structure. There is.

The fiber tube 22 is a cylindrical structural member which is inserted and fixed in the outer tube 21 and which fixes the light guide fiber 4 in a manner sandwiching the outer tube 21.
The system tube 23 is inserted into the inside.

The system tube 23 includes the objective lens 2,
The objective lens 2 and the relay lenses 3 (1) to 3 (7) are inserted into the system tube 23, which is a cylindrical structural member in which an optical lens including the relay lenses 3 (1) to 3 (7) is inserted. The objective lens 2 may be inserted into the system tube 23 after being fixed in a cylindrical frame called an objective frame containing an objective optical system excluding the cover glass, but in the present embodiment, the objective frame is used. Without objective lens 2,
Connect the relay lenses 3 (1) to 3 (7) to the system tube 2
Inserted directly in 3.

The objective lens 2 which is a rigid mirror objective optical system,
Cover glass 31, plano-concave lens 32, 30 ° prism 3
3, a plano-convex positive lens 34 and a cemented lens 35,
The cover glass 31 has a concave surface on the image side, and is fixed to the tip frame 30 formed integrally with the outer tube 21 by adhesion or the like. The cover glass 31 is, for example, A
The main component is l ₂ O ₃ .

As shown in FIG. 3, the plano-concave lens 32 has three
It is adhered on the 0 ° prism 33 and forms a divergent lens system together with the cover glass 31.

Here, the cover glass 31 of the diverging lens system
By using an aspherical surface on the object side surface of the divergence lens 32 next to the optical axis, the radius of curvature of which gradually decreases from the optical axis toward the periphery, distortion is reduced, and image distortion in the peripheral portion is reduced. An optical system with little or no distortion can be realized.

The 30 ° prism 33 has a cover glass 31.
And a first prism 36 located at a position where a light ray from a diverging lens system including the plano-concave lens 32 is incident,
The second prism 37 has two reflecting surfaces. The reflecting surface of the 30 ° prism 33 is made of Al
It is made of a reflective coat. It is better to increase the reflectance with a multilayer reflection increasing film instead of the Al reflection coat. The 30 ° prism 33 is bonded to the plano-convex positive lens 34.

The cemented lens 35 is a biconvex positive lens 38.
And a concave flat bar-shaped lens 39 and a plano-convex lens 40. It should be noted that a concave flat lens 39 and a plano-convex lens 40
If it is formed integrally, it will be easier to assemble and better.

In the present embodiment, between the positive lens 34 integrated with the 30 ° prism 33 and the cemented lens 35, a spacer (a spacer of a tubular mechanical member adhered to an objective frame for providing a space therebetween) ( It does not have a space tube) and is bonded to the system tube 23.

That is, returning to FIG. 2, the system tube 23 is provided with a small hole 41. By filling the hole 41 with an adhesive, the positive lens 34 and the cemented lens 35 are directly attached to the system tube 23. It is glued.

Further, after the cemented lens 35, a spacer 42 for defining a distance from the relay lens 3 (1) is inserted, and hereinafter, the relay lenses 3 (2) to 3 (7) are alternately inserted with the spacer 42. Has been done.

Here, Table 1 shows lens data of the rigid endoscope 1 of the present embodiment, and FIG. 4 shows an aberration diagram. Each optical parameter of the objective lens 2 has a focal length of f = 1.
000; Numerical aperture: NA = 0.087; Image height: Imh =
0.716; Object distance = 7.383; Viewing angle: 2ω
= 88 °; Outer diameter of the cemented lens 35: φ = 2.000;
Thickness of cemented lens 35: d = 6.499; d / φ =
3.250; Glass path length of positive lens 38 of cemented lens 35: d1 = 1.633; Positive lens 3 of cemented lens 35
Glass path length after 8: d2 = 4.866; | f concave / f
| = 0.524 (focal length of diverging lens 35: f concave);
R1 / R2 = 3.443 (curvature radius of concave surface of cover glass 31: R1, radius of curvature of most image side of diverging lens 35: R2); Di / φ = 1.132 (most image side surface of cemented lens 35) Distance between the image formed immediately after and the objective optical system:
Di).

[0036]

[Table 1] S R D n ν 1 ∞ 0.2237 1.76820 71.79 2 1.8178 0.1678 1.3 ∞ 0.2237 1.69680 55.53 4 0.5280 0.1678 1.5 ∞ 1.4423 1.78590 44.19 6 (pupil) ∞ 3.2224 1.78590 44.19 7 -2.1030 1.3535 1. 8 3.1926 1.6332 1.56873 63.16 9 -1.5538 4.3067 1.84666 23.78 10 ∞ 0.5593 1.84666 23.78 11 -8.0251 6.1171 1. 12 13.9840 1.1186 1.88300 40.78 13 ∞ 15.2022 1.51633 64.15 14 -3.3984 0.4475 1.59551 39.21 15 -7.0161 7.6402 1.16 7.0161 0.4475 1.59551 39.202 172 1.51633 64.15 18 ∞ 1.1186 1.88300 40.78 19 -13.9840 1. In addition, S is the lens surface number, R is the radius of curvature of the lens surface, D
Is the distance between lens surfaces, n is the refractive index, and ν is the Abbe number. Further, S = 12 to 19 is the relay lens 3
The lens data of (1) is shown, and the same lens data as the relay lens 3 (1) is added to the lens surface number after S = 19 as the lens data of the relay lenses 3 (2) to 3 (7). Repeated times.

As described above, in the objective lens 2 which is the rigid mirror objective optical system of the rigid endoscope 1 of the present embodiment, d /
φ = 3.250, d1 = 1.633, d2 = 4.866
The conditional expression: (1) 2.5 <d / φ <7 (2) 2d1 <d2 is satisfied.

Conditional expression (1) showing a condition for making the cemented lens long enough to be hard to tilt with respect to the lens outer diameter.
When d / φ is smaller than the lower limit of the conditional expression (1), the inclination of the lens in the cylindrical frame is large, and it is difficult to prevent the deterioration of the image quality due to the lens decentering.

Further, if d / φ exceeds the upper limit of the conditional expression (1), there are problems in reduction of peripheral light quantity and aberration correction. If only the cemented lens is shortened without changing the positions of the diverging lens system and the positive lens based on the image position immediately after the objective optical system, the most image side surface of the cemented lens acts as a field lens surface and has a large power. If you trace the ray from the direction of the image to the direction of the object, the luminous flux is in the direction of spreading,
Since there is a cemented surface with negative power in the middle, the surface further spreads, or the surface closest to the image side of the positive lens,
Alternatively, the light beam is eclipsed on the surface of the cemented lens closest to the object image, and the amount of peripheral light is reduced.

When the length of the objective optical system is shortened, that is, when the cemented lens is shortened while reducing the distance between the image-side surface of the cemented lens and the image immediately after the objective, the cemented surface having negative power is obtained. As the image approaches the image, the light beam enters the cemented surface at a position where it does not spread sufficiently. Therefore, spherical aberration and coma cannot be sufficiently corrected.

In the present embodiment, by satisfying the conditional expression (1), the cemented lens is made longer than the conventional cemented lens in order to prevent the deterioration of the image quality due to the inclination of the lens at the time of assembling and to improve the assembling property. , Which solves the above-mentioned problems and has a relatively small outer diameter of the insertion portion, particularly in a rigid endoscope having a diameter of about 3 mm or less
It is possible to prevent deterioration of the image quality due to the assembling conditions and improve the assembling property.

That is, by making the cemented lens long, the tilt angle in the cylindrical mechanical frame in which the lens of the objective optical system is arranged becomes small, the deterioration of the image quality due to the tilt of the lens is prevented, and the cemented lens is By making the length longer, it becomes easier to handle at the time of assembling, and the assembling property can be improved.

If the lower limit of conditional expression (2) is exceeded, the cemented surface comes to a position close to the image, and the light flux of the peripheral image is incident on the cemented surface at a thin position, so that coma aberration can be sufficiently corrected. Disappear.

In the present embodiment, the divergence lens system has a strong negative value by satisfying the conditional expression (2) indicating the range in which the cemented surface is close to the object side of the cemented lens and the aberration can be sufficiently corrected. Since it has power and the radius of curvature is small, the off-axis upper ray is largely bent, and coma aberration occurs, but this aberration is generated at a position close to the cemented surface having negative power near the pupil. Since the lower ray is made incident on the peripheral portion of the surface to correct coma, it is possible to prevent deterioration of image quality.

Further, in this embodiment, | f concave / f | =
0.524, which satisfies the conditional expression: (3) 0.4 <| f concave / f | <0.7.

Conditional expression (3) defines the ratio of the focal lengths of the diverging lens system of the objective optical system and the whole objective optical system.

When the upper limit of this conditional expression (3) is exceeded, the focal length of the diverging lens system becomes long, and when an attempt is made to widen the angle, an off-axis chief ray should be incident at an angle set with respect to the optical axis. Therefore, the light beam is largely vignetted on the most image-side surface of the positive lens. On the other hand, when the value goes below the lower limit, the focal length of the diverging lens system becomes too short, which makes it difficult to correct aberrations, resulting in an optical system that is easily affected by decentering during assembly.

In the present embodiment, the above problem is solved by satisfying conditional expression (3).

Further, in the present embodiment, R1 / R2 =
3.443, which satisfies the conditional expression: (4) 3 <R1 / R2 <30.

Conditional expression (4) defines the ratio of R1 and R2 for preventing light rays from being blocked on the most object side surface of the cover glass. If the lower limit of conditional expression (4) is exceeded, the radius of curvature of the concave surface of the cover glass becomes small, which may make it difficult to adjust one-sided blur due to eccentricity and cause an assembly problem. The problem is solved by satisfying the expression (4).

Further, in the present embodiment, Di / φ = 1.
132, and the conditional expression: (5) 0.4 <Di / φ <1.5 is satisfied.

If the lower limit of conditional expression (5) is exceeded, there is a problem that the image and the lens surface come close to each other, and dust on the lens surface of the assembling work becomes conspicuous. There is.

On the other hand, if the upper limit is exceeded, the rigid mirror objective optical system is generally telecentric, so the chief ray of all image heights is almost parallel to the optical axis, and the dependent rays are NA determined by the relay. Since the light flux of the peripheral image spreads from the image position toward the object side, the light flux of the peripheral image is eclipsed by the edge of the lens of the cemented lens closest to the image side. This causes a decrease in the amount of light in the periphery.

In the present embodiment, the above problem is solved by satisfying conditional expression (5).

Further, in the objective lens 2 which is the rigid mirror objective optical system of the rigid endoscope 1 of the present embodiment, the diverging lens system is composed of the plano-concave cover glass 31 and the plano-concave lens 32 as described above. Therefore, the height of the light beam on the first surface of the cover glass 31 can be lowered, and there is an effect of preventing the vignetting around the image due to an error in assembly.

Furthermore, since there is no spacer between the positive lens 34 and the cemented lens 35 and the spacer is bonded to the system tube 23, it is possible to reduce the vignetting of the off-axis light beam and prevent a reduction in the peripheral light amount. effective.

Further, the rigid endoscope 1 includes the outer tube 2
Since it has a triple structure of 1, the fiber tube 22 and the system tube 23, the system tube 23
It is possible to assemble the optical system with the lens out, and it is easy to adjust the one-sided blur and the like, and there is the effect that the repair can be done easily.

The relay lens 3 (n) (n = 1 to 1)
7) is not limited to the relay lens of the above lens data,
For example, a relay lens having the lens data shown in Table 3 below may be used, and the configuration of the objective lens 2 of the rigid endoscope which is the first modified example using this relay lens is shown in FIG.
FIG. 4 is an aberration diagram of the rigid endoscope of the first modified example, and Table 2 shows the objective lens 2.
The lens data of is shown.

The optical parameters of the objective lens 2 of the first modification are f = 1.000; NA = 0.
087; Imh = 0.707; Object distance = 7.30
1; 2ω = 88 °; φ = 2.000; d = 5.92
5; d / φ = 2.962; d1 = 1.652; d2
= 4.273; | f concave / f | = 0.554; R1 /
R2 = 27.540; Di / φ = 1.493.

[0060]

[Table 2] S R D n ν 1 ∞ 0.2212 1.76820 71.79 2 11.2724 0.1659 1.3 ∞ 0.2212 1.69680 55.53 4 0.4093 0.1659 1.5 ∞ 1.4279 1.78590 44.19 6 (pupil) ∞ 3.1815 1.78590 44.19 7 -2.2376 0.4730 1. 8 2.9948 1.6522 1.56873 63.16 9 -1.6021 4.2729 1.84666 23.78 10 -6.8705 As a second modified example of the rigid endoscope, a rigid mirror having the lens data shown in Table 3 may be used. FIG. 7 shows the configuration of FIG. 7, and FIG. 8 shows an aberration diagram of the rigid endoscope of the second modified example.

The optical parameters of the objective lens 2 are f = 1.000; NA = 0.087; Imh
= 0.561; Object distance = 8.852; 2ω = 6
0.2 °; φ = 1.7; d = 4.9783; d /
φ = 2.928; d1 = 0.9729; d2 = 4.
005; | f concave / f | = 0.536; Di / φ =
It is 1.146.

[0062]

[Table 3] S R D n ν 1 ∞ 0.2629 1.76820 71.79 2 ∞ 0.1315 1.3 ∞ 0.1735 1.77250 49.60 4 0.4137 0.2279 1.5 ∞ 1.2533 1.78590 44.19 6 (pupil) ∞ 2.3314 1.78590 44.19 7 -1.7161 1.2095 1. 8 2.4366 0.9729 1.56873 63.16 9 -1.3129 4.0054 1.84666 23.78 10 -8.0897 4.7093 1. 11 7.9855 0.8765 1.88300 40.78 12 ∞ 11.9111 1.51633 64.15 13 -2.6627 0.3506 1.59551 39.21 14 -5.4972 5.9862 1.15 5.4972 0.3506 1.59551 39.21 16 2.6627 11.9111 1.51633 64765.15 1.88300 40.78 18 -10.9567 1. In addition, S = 11-18 shows the lens data of the relay lens of the 2nd modification, and S = 12-19 of Table 1 is shown in the lens surface number after S = 18. Relay lens 3 shown in
Lens data obtained by multiplying the lens data of (1) by a coefficient so that the combined focal length of the objective lens and the relay lens becomes 1 is repeated 6 times as the lens data of the relay lenses 3 (2) to 3 (7).

In the second modified example as described above, the radius of curvature of the surface of the relay lens closest to the object side is made small so as not to be common to other relay lenses. As a result, the principal ray of the off-axis light converges toward the object side, and the dependent rays of the off-axis ray also change the angle toward the optical axis side, reducing the vignetting on the most image-side surface of the cemented ball. It is possible to prevent the decrease of the light amount around the image.

Similar to the second modified example, the third modified example in which the radius of curvature of the surface of the relay lens closest to the object side is made small to make it non-common to other relay lenses, or the fourth non-common type. Modifications may be used. Tables 4 and 5 show lens data of a rigid endoscope as the third and fourth modified examples, and the configuration of the objective lens 2 of the rigid endoscope as the third and fourth modified examples at this time. 9 and 11 are shown, and FIGS. 10 and 12 are aberration diagrams of the rigid endoscopes of the third and fourth modifications.

The optical parameters of the objective lens 2 of the third modification are f = 1.000; NA = 0.
075; Imh = 0.696; Object distance = 7.17
8; 2ω = 78 °; φ = 1.795; d = 7.15
5; d / φ = 4.046; d1 = 1.024; d2
= 6.238; | f concave / f | = 0.48; Di / φ
= 1.437.

[0066]

[Table 4] S R D n ν 1 ∞ 0.2175 1.76820 71.79 2 ∞ 0.1631 1. 3 ∞ 0.2175 1.88300 40.78 4 0.4241 0.1631 1.5 ∞ 1.1598 1.78590 44.19 6 (pupil) ∞ 3.2628 1.78590 44.19 7 -2.0393 0.2575 1. 8 2.9292 1.0239 1.56873 63.16 9 -1.8015 6.2379 1.84666 23.78 10 -13.2527 6.1309 1. 11 6.2315 16.1728 1.58913 61.18 12 ∞ 1.6670 1.13 5.8339 0.9462 1.61272 58.75 14 -3.6576 2.3928 1.78800 47.39 15 3.6576 0.9462 1.61272 58.75 16 -5.8339 1.6770 1. 17 ∞ 16.1728 1.58913 61.18 18 -7.8330 7.5436 1. 19 7.8330 16.1728 1.58913 61.18 20 ∞ 1.6770 1.21 5.8339 0.9462 1.61272 58.75 22 -3.6576 2.3928 1.78800 47.38 23 3.6576 0.9462 1.61272 58.75 24 -5.8339 1.6770 1. 25 ∞ 16.1728 1.58913 61.18 26 -7.8330 3.7718 1 In the third modified example, S = 11 to 18 represents lens data of the first relay lens, and S = 19 to.
Reference numeral 26 indicates lens data of the second relay lens. Then, S = 19 is added to the lens surface number after S = 26.
The same lens data as the second relay lens of No. 26 to No. 26 is 5 as the lens data of the relay lenses 3 (3) to 3 (7).
Repeated times.

Further, each optical parameter in the objective lens 2 of the fourth modified example is f = 1.000; NA = 0.
075; Imh = 0.515; Object distance = 8.12
1; 2ω = 60 °; φ = 1.5; d = 4.977;
d / φ = 3.318; d1 = 0.836; d2 =
4.1411; | f concave / f | = 0.646; Di /
φ = 1.028.

[0068]

[Table 5] S R D n ν 1 ∞ 0.2412 1.76820 71.79 2 ∞ 0.1206 1.3 ∞ 0.1608 1.69680 55.53 4 0.4503 0.1287 1.5 ∞ 1.1177 1.78800 47.38 6 (pupil) ∞ 2.5007 1.78800 47.38 7 -1.6074 0.4825 1. 8 2.4686 0.8363 1.56873 63.16 9 -1.2930 4.1411 1.84666 23.78 10 -6.4078 4.3317 1. 11 5.7911 11.9569 1.58913 61.18 12 ∞ 1.2399 1. 13 4.3132 0.6996 1.61272 58.75 14 -2.7042 1.769 1.78800 47.38 15 2.7042 0.6996 1.61272 58.75 16 -4.3132 1.2399 1. 17 ∞ 11.9569 1.58913 61.18 18 -5.7911 1. In addition, S = 11-18 shows the lens data of the relay lens of the 4th modification, and S = 11-19 of Table 1 is shown in the lens surface number after S = 18. Relay lens 3 shown in
The same lens data as in (1) applies to relay lens 3 (2)-
It is repeated 6 times as the lens data of 3 (7).

13 to 18 relate to the second embodiment of the present invention. FIG. 13 is a sectional view showing the structure of the tip of a rigid endoscope, and FIG. 14 is a perspective view showing the appearance of the objective frame of FIG. FIG. 15 is a configuration diagram showing a configuration of a modified example of the objective lens of FIG. 13 provided with a 70 ° prism, and FIG. 16 is a configuration diagram showing a configuration of a first modified example of the objective lens of FIG. 13 provided with a 12 ° prism. FIG. 17 is a configuration diagram showing a configuration of a second modification of the objective lens of FIG. 13 provided with a 12 ° prism, and FIG.
FIG. 14 is a configuration diagram showing a configuration of a third modification of the objective lens of FIG. 13 provided with a prism.

Since the second embodiment is almost the same as the first embodiment, only different points will be described, the same components will be denoted by the same reference numerals, and description thereof will be omitted.

Optical system lens data is the same as that in the first embodiment.

At the tip of the rod-shaped portion 11 of the rigid endoscope of this embodiment, as shown in FIG. 13, an outer tube 21, a fiber tube 22, and an objective frame 51 are arranged in this order from the outside. In the present embodiment, the system tube is omitted, and the rod-shaped portion 11 has a double structure in the relay lens portion.

The cover glass 31 of the objective lens 2 is fixed to an annular mechanical member called a frame, and then bonded to the tip frame 30 integrally formed with the outer tube 21 by adhesion or the like as in the first embodiment. It is fixed.

The prism 33, the positive lens 34, and the cemented lens 35, which constitute the objective optical system, are put in the objective frame 51, and are bonded and fixed by filling a hole 52 provided in the objective frame 51 with an adhesive. There is.

The image-side tip of the objective frame 51 is abutted against the relay lens 3 (1) and plays a role of a spacer for defining the position of the relay lens 3 (1).

As shown in FIG. 14, a slanting cut portion 53 is provided at the front end of the objective frame 51 on the object side. The optical system of the prism 33 in the objective frame 51 is installed so that its visual field direction is oriented in a predetermined direction with respect to the oblique cut direction.

Specifically, the first prism 3 on the upper side
A cut portion 53 having a cross-section whose direction coincides with the surface of the upper surface of 6 or the surface to be joined with the second prism 37 on the lower side is formed, and the prism 33 is rotated and bonded so as to match the oblique cut portion 53. On the other hand, on the side of the tip frame 30, there is also an objective frame receiving portion 54 having a similar oblique cut portion, and by inserting the objective frame 51, the optical axis direction of the cover glass 31 attached to the tip frame 30 and the prism 33. The optical axis directions defined by are aligned.

Here, in the prism 33, the incident surface other than the plano-concave lens 32 that is adhesively fixed is painted black, for example, to prevent light from entering the prism 33 from other than the plano-concave lens 32. Not limited to black coating, a light shielding plate or the like may be adhered, and it is possible to prevent light from entering the prism 33 from other than the plano-concave lens 32.

Other configurations and operations are the same as those in the first embodiment, and the lens data and aberration chart of the rigid endoscope 1 are as follows.
This is the same as Table 1 and FIG. 4 shown in the first embodiment.

As described above, in this embodiment, in addition to the effects of the first embodiment, only by inserting the objective lens 1,
The visual field can be directed to a predetermined direction, which has the effect of improving the assembling property.

Similar effects are obtained in the case of the objective lens 2 using the 70 ° prism 61 as shown in FIG. 15 and the objective lens 2 using the 12 ° prism 62 as shown in FIGS. 16 to 18. Can be obtained.

[Additional Notes] 1. In a rigid-scope observation optical system including an objective optical system and a relay lens for transmitting an object image in order from the object side, the objective optical system is a divergent lens having a negative power as a whole and is composed of at least one negative lens in order from the object side. System, a positive lens with a convex surface on the image side, and a cemented lens with a positive refractive index as a whole having a cemented surface with a concave surface facing the object side and having a negative refractive power. Formula (1), (2)
An objective optical system for a rigid endoscope, which satisfies:

Conditional expression: (1) 2.5 <d / φ <7 (2) 2d1 <d2 where d and φ are the cemented lens thickness and outer diameter, and d1
Is the glass path length before the cemented surface of the cemented lens, and d2 is the glass path length behind the cemented surface of the cemented lens.

2. The objective optical system for a rigid endoscope according to item 1, wherein the objective optical system has a lens outer diameter of 2 mm or less.

3. 3. The rigid-mirror objective optical system according to item 1 or 2, further comprising a prism optical system for changing a visual field direction between the diverging lens system and the positive lens.

4. 4. The rigid-mirror objective optical system according to any one of appendices 1, 2 or 3, wherein the diverging lens system includes a cover glass having a flat surface at least on the object side.

In the structure of appendix 4, by providing a cover glass made of a material that can withstand high temperature and high pressure steam sterilization at the tip of the rigid mirror, it becomes possible to sterilize the rigid mirror with high temperature and high pressure steam.

5. The rigid-mirror objective optical system described in appendix 4, wherein the following condition (3) is satisfied.

Conditional expression: (3) 0.4 <| f concave / f | <0.7 where f concave is the focal length of the diverging lens system, and f is the focal length of the objective optical system.

6. 6. The rigid-mirror objective optical system according to appendix 5, wherein the diverging lens system includes a cover glass of a negative lens having a concave surface facing the image side, and satisfies the following conditional expression (4).

Conditional expression: (4) 3 <R1 / R2 <30 where R1 is the radius of curvature of the concave surface of the cover glass, and R2 is the radius of curvature of the most image-side surface of the diverging lens system.

7. 7. The rigid mirror objective optical system according to item 4 or 6, wherein the cover glass in the divergent lens system contains Al ₂ O ₃ as a main component.

8. The rigid-mirror objective optical system according to appendix 4, wherein the distance between the cemented lens and the image formed immediately after the objective optical system satisfies the following conditional expression (5).

Conditional expression: (5) 0.4 <Di / φ <1.5 where Di is the distance between the most image side surface of the cemented lens and the image formed immediately after the objective optical system, and φ is the cemented lens. It is the outer diameter.

9. The objective optical system for a rigid endoscope according to appendix 4 or 5, wherein the objective optical system is arranged in a tubular frame, and the positive lens and the cemented lens are bonded to the tubular frame. .

10. 5. An oblique cut portion is provided at a front end portion of the objective frame on the object side.
The rigid endoscope objective optical system according to any one of 5 and 9.

[0097]

As described above, according to the objective optical system for a rigid endoscope of the present invention, the conditional expressions (1) and (2) are satisfied.
It is possible to prevent deterioration of image quality due to assembling conditions and improve assemblability in a rigid endoscope having an insertion portion with a relatively small outer diameter, particularly about 3 mm or less.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of a rigid endoscope according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the configuration of the tip of the rigid endoscope shown in FIG.

FIG. 3 is a configuration diagram showing a configuration of the objective lens in FIG.

FIG. 4 is an aberration diagram showing an aberration state of the rigid endoscope shown in FIG.

5 is a configuration diagram showing a configuration of a first modification of the objective lens in FIG.

6 is an aberration diagram showing an aberration state of a rigid endoscope including the objective lens of FIG.

7 is a configuration diagram showing a configuration of a second modification of the objective lens in FIG.

FIG. 8 is an aberration diagram showing an aberration state of a rigid endoscope including the objective lens of FIG.

9 is a configuration diagram showing a configuration of a third modification of the objective lens in FIG.

10 is an aberration diagram showing an aberration state of a rigid endoscope including the objective lens of FIG.

11 is a configuration diagram showing a configuration of a fourth modification of the objective lens in FIG.

12 is an aberration diagram showing an aberration state of a rigid endoscope including the objective lens of FIG.

FIG. 13 is a cross-sectional view showing the configuration of the tip of a rigid endoscope according to a second embodiment of the present invention.

FIG. 14 is a perspective view showing the appearance of the objective frame in FIG.

15 is a configuration diagram showing a configuration of a modified example of the objective lens of FIG. 13 provided with a 70 ° prism.

16 is a configuration diagram showing a configuration of a first modification of the objective lens of FIG. 13 including a 12 ° prism.

17 is a configuration diagram showing a configuration of a second modification of the objective lens of FIG. 13 including a 12 ° prism.

18 is a configuration diagram showing a configuration of a third modification of the objective lens of FIG. 13 including a 12 ° prism.

FIG. 19 is a configuration diagram showing a configuration of a rigid endoscope objective optical system of a first conventional example.

FIG. 20 is a configuration diagram showing the configuration of a second objective of a rigid endoscope objective optical system.

FIG. 21 is a configuration diagram showing a configuration of a rigid endoscope objective optical system of a third conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Rigid mirror 2 ... Objective lens 3 (1) -3 (7) ... Relay lens 4 ... Light guide fiber 5 ... Eyepiece lens 6, 31 ... Cover glass 7 ... Eyepiece part 11 ... Rod part 12 ... LG joint part 13 ... Base 21 ... Outer tube 22 ... Fiber tube 23 ... System tube 30 ... Tip frame 32 ... Plano-concave lens 33 ... 30 ° prism 34, 38 ... Positive lens 35 ... Bonded lens 36 ... First prism 37 ... Second prism 39 ... Rod lens 40 ... Plano-convex lens 41 ... Hole

[Procedure amendment]

[Submission date] January 23, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

As shown in FIG. 20, the objective optical system for a rigid mirror disclosed in Japanese Patent Laid-Open No. 5-288986 is cemented with a front lens group diverging system 110 composed of a negative meniscus lens including an aspherical surface.
The rear-group convergent system 111 is composed of at least two lens components including a lens, and the cemented lens 112 in the rear stage is composed of
It is composed by cementing two lenses.

[Procedure amendment 2]

[Document name to be amended] Drawing

[Correction target item name] FIG.

[Correction method] Change

[Correction contents]

FIG.

Claims (1)

[Claims] 1. A rigid endoscope observation optical system comprising an objective optical system and a relay lens for transmitting an object image in order from the object side, wherein the objective optical system is composed of at least one negative lens in order from the object side. Negative power diverging lens system,
It is composed of a positive lens having a convex surface on the image side and a positive cemented lens having a cemented surface with a concave surface facing the object side, which has a negative refractive power, and has the following conditional expressions (1) and (2): An objective optical system for a rigid endoscope, which satisfies: Conditional expression: (1) 2.5 <d / φ <7 (2) 2d1 <d2 where d and φ are the thickness and outer diameter of the cemented lens, and d1
Is the glass path length before the cemented surface of the cemented lens, and d2 is the glass path length behind the cemented surface of the cemented lens.