JPH07134246A - Hard mirror optical system - Google Patents

Abstract

PURPOSE:To well correct the axial chromatic aberration and to reduce the cost to a throw-away level by correcting the axial chromatic aberration of the observation optical system in an insertion part by an optical system in an eyepiece part. CONSTITUTION:The negative single lens of objective lens O in the observation optical system of the insertion part does not contribute much to the correction of the axial chromatic aberrations. On the other hand, the eyepiece optical system E is formed by using the many combined lenses which generate the positive axial chromatic aberration and the large positive axial chromatic aberration remains in this eyepiece optical system E alone. The axial chromatic aberration by tracing the rays in the reverse direction by the eyepiece optical system E alone is of a code reverse from the code of the axial chromatic aberration of the observation optical system of the insertion part and the absolute values thereof are nearly equal. The image positions of the respective wavelengths by both modules, therefore, match in the images in the juncture if the insertion observation part and the eyepiece optical system E are connected. The axial chromatic aberration of the overall observation optical system combining the insertion part observation optical system and the eyepiece optical system E is corrected down to a practicable level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rigid endoscope (hard endoscope) widely used in the medical field, and more particularly to a disposable rigid endoscope.

[0002]

2. Description of the Related Art In recent years, minimally invasive surgery using an endoscope and a dedicated treatment tool has become widespread in the field of medical surgery. Conventionally, it becomes possible to treat a disease requiring an open surgery under the endoscope with minimal invasiveness, and the social burden on the patient is reduced by shortening the hospitalization period. In this way, endoscopic surgery
Further development is expected in the future.

An endoscope is divided into a flexible endoscope and a rigid endoscope depending on the structure of the insertion portion. Among them, a rigid endoscope with excellent image quality is used for endoscopic surgery. Further, the rigid endoscope has an advantage that it can be steam-sterilized (autoclave). Nosocomial infections have become a big problem in recent years, and awareness of sterilization of medical devices has become extremely high. This steam sterilization device is more widely used than other sterilization devices, and an endoscope is required to be one that can withstand this steam sterilization. Since the rigid endoscope does not have a soft portion, it is easy to select a material and a structure that can withstand steam sterilization.

On the other hand, as a method for preventing nosocomial infection of a rigid endoscope, an attempt has been made to dispose the rigid endoscope itself. In order to realize such a disposable rigid endoscope,
An important issue is how to reduce costs while ensuring practical performance.

FIG. 7 is a view showing an observation optical system of a conventional rigid endoscope. As shown in this figure, in the conventional rigid endoscope, an objective optical system O, a relay optical system R, and an eyepiece optical system E are integrated in the main body. Such a conventional rigid endoscope is provided with a plurality of cemented lenses that play a major role in aberration correction. Therefore, even if a plastic lens is used, for example, the number of parts is large and the number of assembling steps for joining is large, so that the cost cannot be low enough to make it disposable.

Further, Japanese Patent Laid-Open No. 2-503361 discloses that
A disposable rigid endoscope is disclosed. The rigid endoscope disclosed in this publication uses plastic lenses for an objective lens system, a relay lens system, and an inspection (eyepiece) lens system in consideration of cost reduction and mass productivity. Further, in consideration of the assemblability and the number of parts, a cemented lens for correcting the axial chromatic aberration is not used. Therefore, it is difficult to secure a practical image quality.

Next, the reason will be described based on a simple calculation example. First, chromatic aberration due to the relay optical system will be described.
FIG. 8 is a power arrangement diagram of the relay optical system, where R is the relay optical system, O _d and O _F are object positions of d line and F line, and I.
_d and I _F are image positions of d line and F line. Actually O _d ,
Positive power for pupil transmission is arranged in the vicinity of I _d , but it is ignored since it has almost no effect on the axial chromatic aberration. Further, in the center of this figure, a positive power for image transmission at the same size is arranged. In the optical system shown in this figure, the difference due to the difference in the wavelength of the positive power in the center appears as axial chromatic aberration as it is. First, d line (wavelength 58
7.56 nm) and the F-line (wavelength 486.13 nm), the axial chromatic aberration ΔF per relay is
It is expressed as follows.

ΔF = 4 (f _F −f _d ) (a) Here, f _F is the focal length on the F line, and f _d is the focal length on the d line.

Further, the following relationship is established between f _F and f _d .

F _d (n _d −1) = f _F (n _F −1) (b) Here, n _d and n _F are the refractive indices at the d line and the F line, respectively.

When f _F is deleted from the equations (a) and (b) and the equations are arranged, the following equation (c) can be obtained.

ΔF = 4f _d [(n _d −n _F ) / (n _F −1)] (c) Here, when one relay length is 100 mm, f _d = 25 m
m, or n _{d if an} acrylic plastic lens is used
= 1.492, n _F = 1.498, and ΔF = −1.20 mm from the formula (c). Usually, the length of the insertion portion of the rigid endoscope is 300 mm or more, and the axial chromatic aberration of the F line when relayed three times is 3ΔF = −3.60 mm.

Considering the case where the eyepiece lens having an observation magnification of 10 times (focal length 25 mm) is combined with the above-mentioned three times relay system, the axial chromatic aberration is converted into diopter by -3.6.
Axial chromatic aberration of 0mm is -3.60 / (- 25 ^2/100
0) = 5.76 [m ^-1 ], which corresponds to the diopter deviation.

[0014] above, for example, observation diopter in d line is to -1 m ^-1, observation diopter F line 4.76M ^-1 becomes, the image of the F-line on the retina of the human eye It gets very blurry. Normally, the human observation diopter adjustment range is -4 m ^{-1 to 0} m
It is about ^-1 and has an adjustment range of ± 2 m ^-1 . The diopter deviation of 5.76 m ⁻¹ due to the axial chromatic aberration is within the adjustment range of ± 2
It is much larger than m ^-1 . At least 400 visible light
Since the wavelength range from nm to 700 nm is taken into consideration, taking into consideration the axial chromatic aberration due to light other than the F-line, an optical system having axial chromatic aberration such as the above example should be able to properly reproduce an image of an object having a wide range of colors. Is impossible.

[0015]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a rigid mirror optical system in which axial chromatic aberration is well corrected and the cost can be reduced to a disposable level.

[0016]

According to the present invention, in a rigid endoscope in which an insertion part and an eyepiece part are separable from each other, axial chromatic aberration generated in an observation optical system in the insertion part is corrected by an optical system in the eyepiece part. It is characterized by having done.

FIGS. 5 and 6 are views for explaining the outline of a rigid endoscope to which the present invention can be applied. In FIG. 5, the rigid endoscope is divided into an insertion portion 1 and an eyepiece portion 2. The insertion portion 1 includes an objective lens O therein and a relay lens R for sequentially forming an object image (indicated by an arrow) formed by the objective lens and guiding it to the eyepiece. Further, the eyepiece section 2 includes an eyepiece lens E. In this example, the lens on the object side of the eyepiece lens E bears a part of the function of the relay lens, and the object image is formed inside the eyepiece lens E. The flat plates provided before and after the eyepiece lens are cover glasses.

In this rigid endoscope, the insertion section 1 and the eyepiece section 2 can be freely attached and detached by an appropriate mechanism, and when used, the insertion section 1 and the eyepiece section 2 are combined to form an eyepiece lens. The object image is observed through the two, and after use, the two are separated and the insertion section 1 is thrown away.

On the other hand, in FIG. 6, the rigid endoscope is the insertion portion 1.
And a television camera adapter 3 and a camera head 4. The TV camera adapter 3 includes an imaging lens T inside, and the camera head includes a CCD image sensor inside. Here, the insertion portion 1, the adapter 3, and the camera head 4 are detachable from each other by appropriate mechanisms. When these are combined during use, the object image transmitted by the relay lens of the insertion section 1 is re-imaged on the CCD image sensor in the camera head 4 by the imaging lens T in the adapter 3. .
Then, the image signal obtained from this CCD image sensor is displayed on a monitor TV (not shown) for observation, and after use, these are separated and the insertion section 1 is disposable.

In such a structure, the present invention reduces the cost by making the insertion part as simple as possible, while at the same time, the parts and structures that must be expensive are connected to the eyepiece part and the adapter. The optical system was constructed based on the design concept of focusing on etc. That is, the optical system arranged in the insertion section has a configuration as simple as possible, and as a result, in order to cover the fact that sufficient aberration correction cannot be performed in these optical systems, the aberration correction is performed inside the eyepiece section or the adapter. An optical system is provided for the purpose of ensuring a good level of aberration correction for the rigid endoscope optical system as a whole. As a result, even if the configuration of the optical system in the eyepiece section or the adapter becomes complicated and expensive, these sections are not disposable and there is no problem at all.

In order to prevent the portion other than the insertion portion from being soiled, for example, the configuration shown in FIG. 9 may be used. In this example, the rigid endoscope system includes an insertion portion 1, an eyepiece portion 2 and a television camera 4 attached to the eyepiece portion 2, but a sterilization cover 10 having a tip integrated with the insertion portion 1 is used. If provided, a member behind the eyepiece is housed in the sterilization cover 10. In this configuration, after the use, the insertion part 1 and the sterilization cover 10 are integrally removed from the eyepiece part and discarded, and the remaining part is kept clean.

[0022]

EXAMPLES In all of the examples shown below, it is particularly important to correct the axial chromatic aberration generated by the objective lens and the relay lens arranged in the insertion portion by the optical system of the eyepiece.

FIG. 1 is a sectional view of an optical system according to a first embodiment of the present invention, where O is an objective optical system, R is a relay optical system, and E is an eyepiece optical system. This Example 1 is used for a rigid endoscope as shown in FIG. 5, and the data of this Example are as follows. Example 1 Object distance = -35, Observed diopter = ^-1 m ^-1 , Incident NA = 0.0076, Angle of view = 70 ° Image height = 1.48 r ₁ = ∞ d ₁ = 0.7000 n ₁ = 1.52566 ν ₁ = 56.28 r _{2 = 1.5912 d 2 = 3.1900 r 3} = -11.7850 d 3 = 4.9000 n 2 = 1.52566 ν 2 = 56.28 r 4 = -11.0852 d 4 = 34.8500 r 5 = 24.6414 d 5 = 8.8741 n 3 = 1.52566 ν 3 = 56.28 r 6 = ∞ (virtual _{stop) d 6 = 10.6659 n 4 =} 1.52566 ν 4 = 56.28 r 7 = -24.6414 d 7 = 38.7900 r 8 = 24.6414 d 8 = 19.5400 n 5 = 1.52566 ν 5 = 56.28 r 9 = -24.6414 d 9 ＝ 39.4600 r ₁₀ ＝ 24.6414 d ₁₀ ＝ 19.5400 n ₆ ＝ 1.52566 ν ₆ ＝ 56.28 r ₁₁ ＝ -24.6414 d ₁₁ ＝ 39.4600 r ₁₂ ＝ 24.6414 d ₁₂ ＝ 19.5400 n ₇ ＝ 1.52566 ν ₇ ＝ 56.28 r ₁₃ = -24.6414 d ₁₃ = 39.4600 r ₁₄ = 24.6414 d ₁₄ = 19.5400 n ₈ = 1.52566 ν ₈ = 56.28 r ₁₅ = -24.6414 d ₁₅ = 39.4600 r ₁₆ = 24.6414 d ₁₆ = 19.5400 n ₉ = 1.52566 ν ₉ = 56.28 r ₁₇ = -24.6414 d ₁₇ = 15.0000 r ₁₈ = ∞ d ₁₈ = 1.0000 n ₁₀ = 1.51633 ν ₁₀ = 64.15 r ₁₉ = ∞ d ₁₉ = 3.5400 r ₂₀ = 26.3700 d ₂₀ = 2.5000 n ₁₁ = 1.77250 ν ₁₁ = 49.60 r ₂₁ = -8.6370 d ₂₁ = 1.0000 n ₁₂ = 1.84666 ν ₁₂ ＝ 23.78 r ₂₂ ＝ -90.9350 d ₂₂ ＝ 0.5000 r ₂₃ ＝ 26.3700 d ₂₃ ＝ 2.5000 n ₁₃ ＝ 1.77250 ν ₁₃ ＝ 49.60 r ₂₄ ＝ -8.6370 d ₂₄ = 1.0000 n ₁₄ ＝ 1.84666 ν ₁₄ ＝ 23.78 r ₂₅ = -90.9350 d ₂₅ = 7.9500 r ₂₆ = ∞ d ₂₆ = 2.0000 n ₁₅ = 1.77250 v ₁₅ = 49.60 r ₂₇ = -5.3520 d ₂₇ = 1.0000 n ₁₆ = 1.78472 v ₁₆ = 25.71 r ₂₈ = ∞ d ₂₈ = 0.0300 r ₂₉ = ∞ d ₂₉ = 2.0000 n ₁₇ = 1.77250 ν ₁₇ = 49.60 r ₃₀ = -5.3520 d ₃₀ = 1.0000 n ₁₈ = 1.78472 ν ₁₈ = 25.71 r ₃₁ = ∞ d ₃₁ = 14.6100 r ₃₂ = 9.0340 d ₃₂ = 3.8000 n ₁₉ = 1.77250 ν ₁₉ ＝ 49.60 r ₃₃ ＝ -6.4830 d ₃₃ = 1.0000 n ₂₀ ＝ 1.84666 ν ₂₀ ＝ 23.78 r ₃₄ ＝ 24.0550 d ₃₄ ＝ 6.9800 r ₃₅ ＝ ∞ d ₃₅ = 13.3700 r ₃₆ = 19.7060 d ₃₆ ＝ 3.50 00 n ₂₁ = 1.69680 ν ₂₁ ＝ 55.53 r ₃₇ ＝ -7.8250 d ₃₇ = 1.0000 n ₂₂ = 1.80610 ν ₂₂ ＝ 40.95 r ₃₈ ＝ -17.4010 d ₃₈ ＝ 4.0400 r ₃₉ ＝ ∞ d ₃₉ = 1.0000 n ₂₃ ＝ 1.51633 ν ₂₃ ＝ 64.15 r ₄₀ = ∞ Aspherical surface coefficient (2nd surface) K = -0.8146, (4th surface) K = 5.9508, (5th surface) K = -2.3156 (7th surface) K = -2.3156, (8th surface) ) K = -2.3156,
(9th surface) K = -2.3156 (10th surface) K = -2.3156, (11th surface) K = -2.3156 (12th surface) K = -2.3156, (13th surface) K = -2.3156 (14th surface) Surface) K = -2.3156, (15th surface) K = -2.3156 (16th surface) K = -2.3156, (17th surface) K = -2.3156 In the above data, r ₁ , r ₂ , ... Are lenses The radius of curvature of each surface, d ₁ , d ₂ , ... Are the thicknesses and lens intervals of each lens, n ₁ , n ₂ , ... Are the refractive indices of each lens, and ν
₁ , ν ₂ , ... are the Abbe numbers of each lens.

The aspherical surface used in the above embodiment is represented by the following equation.

Z = (y ² / r) / [1+ {1- (k +
1) (y / r) ² } ^1/2 ] where z is the distance in the optical axis direction with respect to the intersection of the surface and the optical axis, y is the distance from the optical axis, r is the radius of curvature, and k is 2 This is a parameter indicating the shape of the quadric surface.

In the first embodiment, r _{1 to} r ₁₇ are insertion portion observation optical systems. For this observation optical system only,
Ray tracing is performed from the object side to the eyepiece side, and the axial chromatic aberration at the final image position of the observation optical system is as follows.

C line: 1.395, F line: -3.519,
g line: -6.650 The above values are based on the image position of the d line, and the eyepiece side is positive.

Further, r _{18 to} r ₄₀ are eyepiece optical systems. The axial chromatic aberration at the final image position when ray tracing is performed from the eyepoint side of only the eyepiece optical system toward the insertion portion side is as follows.

C line: -1.032, F line: 3.299,
g line: 7.205 Similarly, the above value is positive on the insertion portion side with reference to the image position of the d line.

The observation optical system (objective optical system O and relay optical system R) of the insertion portion 1 of Example 1 is composed of only a single lens and does not include a cemented lens. Such a positive single lens normally causes negative axial chromatic aberration (the image forming position of the short wavelength light is displaced toward the object side from the image forming position of the long wavelength light).
In the case of a negative single lens, positive axial chromatic aberration occurs.

In the first embodiment, in the insertion portion observation optical system,
Although the objective lens O includes one negative single lens, this negative single lens is provided for widening the angle of view and correcting the field curvature, and contributes much to the correction of axial chromatic aberration. do not do. Since all the other lenses are positive single lenses, even if low-dispersion optical materials are used, the rate of negative residual chromatic aberration is overwhelmingly high only with the insertion section observation optical system. Therefore, negative axial chromatic aberration remains only with the insertion portion observation optical system.

On the other hand, the eyepiece optical system E frequently uses a cemented lens which produces positive axial chromatic aberration, and the eyepiece optical system E alone has a large positive axial chromatic aberration remaining. The axial chromatic aberration due to the backward ray tracing of only the eyepiece optical system E is
It has the opposite sign to the axial chromatic aberration of the insertion section observation optical system, and the absolute values are almost the same. Therefore, when the insertion observation section and the eyepiece optical system are connected, the image positions of the respective wavelengths of both modules match in the image at the connection section, so that the total observation optical system combining the insertion section observation optical system and the eyepiece optical system E. The axial chromatic aberration of the system is corrected to a practical level.

FIG. 3 is an aberration diagram of the entire system including the insertion observation optical system and the eyepiece optical system of the first embodiment. As shown in this figure, the diopter shift due to the axial chromatic aberration in the entire system is within ± 2 m ^{−1 at} the C line, the F line, and the g line, which is an acceptable level for visual observation. Further, other aberrations are well corrected.

The above-described Example 1 can be applied to a rigid endoscope dedicated to television observation in addition to the rigid endoscope that can be visually observed.
2 relates to an optical system used for a television observation rigid endoscope as shown in FIG. 6 and has a configuration as shown in FIG. In addition, Example 2 has the following data. Example 2 Object distance = -35, incident NA = 0.0076, angle of view = 70 °, image height = 2.14 r ₁ = ∞ d ₁ = 0.7000 n ₁ = 1.52566 ν ₁ = 56.28 r ₂ = 1.5912 d ₂ = 3.1900 r _{3 = -11.7850 d 3 = 4.9000 n 2} = 1.52566 ν 2 = 56.28 r 4 = -11.0852 d 4 = 34.8500 r 5 = 24.6414 d 5 = 8.8741 n 3 = 1.52566 ν 3 = 56.28 r 6 = ∞ ( virtual stop) d ₆ = 10.6659 n ₄ = 1.52566 ν ₄ = 56.28 r ₇ = -24.6414 d ₇ = 38.7900 r ₈ = 24.6414 d ₈ = 19.5400 n ₅ = 1.56566 ν ₅ = 56.28 r ₉ = -24.6414 d ₉ = 39.4600 r ₁₀ = 24.6414 d _{10 = 19.5400 n 6 = 1.52566 ν 6} = 56.28 r 11 = -24.6414 d 11 = 39.4600 r 12 = 24.6414 d 12 = 19.5400 n 7 = 1.52566 ν 7 = 56.28 r 13 = -24.6414 d 13 = 39.4600 r 14 = 24.6414 d 14 _{= 19.5400 n 8 = 1.52566 ν 8} = 56.28 r 15 = -24.6414 d 15 = 39.4600 r 16 = 24.6414 d 16 = 19.5400 n 9 = 1.52566 ν 9 = 56.28 r 17 = -24.6414 d 17 = 15.0000 r 18 = ∞ d 18 = 1 .0000 n ₁₀ = 1.51633 ν ₁₀ = 64.15 r ₁₉ = ∞ d ₁₉ = 3.5400 r ₂₀ = 26.3700 d ₂₀ = 2.5000 n ₁₁ = 1.77250 ν ₁₁ = 49.60 r ₂₁ = -8.6370 d ₂₁ = 1.0000 n ₁₂ = 1.84666 ν ₁₂ = _{23.78 r 22 = -90.9350 d 22 =} 0.5000 r 23 = 26.3700 d 23 = 2.5000 n 13 = 1.77250 ν 13 = 49.60 r 24 = -8.6370 d 24 = 1.0000 n 14 = 1.84666 ν 14 = 23.78 r 25 = -90.9350 d 25 = 7.9500 r ₂₆ = ∞ d ₂₆ = 2.0000 n ₁₅ = 1.77250 ν ₁₅ = 49.60 r ₂₇ = -5.3520 d ₂₇ = 1.0000 n ₁₆ = 1.78472 ν ₁₆ = 25.71 r ₂₈ = ∞ d ₂₈ = 0.0300 r ₂₉ = ∞ d ₂₉ = 2.0000 n ₁₇ = 1.77250 ν ₁₇ = 49.60 r ₃₀ = -5.3520 d ₃₀ = 1.0000 n ₁₈ = 1.78472 ν ₁₈ = 25.71 r ₃₁ = ∞ d ₃₁ = 9.9713 r ₃₂ = 6.5209 d ₃₂ = 3.8000 n ₁₉ = 1.77250 ν ₁₉ = 49.60 r ₃₃ = -4.3080 d ₃₃ = 1.0000 n ₂₀ = 1.84666 ν ₂₀ = 23.78 r ₃₄ = 8.0115 Aspheric surface coefficient (2nd surface) K = -0.8146, (4th surface) K = 5.9508, (5th surface) K = -2.3156 The seventh surface) K = -2.3156, (eighth surface) K = -2.3156,
(9th surface) K = -2.3156 (10th surface) K = -2.3156, (11th surface) K = -2.3156 (12th surface) K = -2.3156, (13th surface) K = -2.3156 (14th surface) surface) K = -2.3156, (fifteenth surface) K = -2.3156 (16 surface) K = -2.3156, (seventeenth surface) K = -2.3156 this second embodiment, the observation optical to r ₁ ~r ₁₇ The system is the same as in Example 1. Therefore, the axial chromatic aberration is also as described above. Further, r _{18 to} r ₃₄ are image forming optical systems for television cameras, and the axial chromatic aberration when the ray is traced backward from the solid-state image pickup element to the insertion portion is as follows.

C line: -1.165, F line: 3.682,
g line: 8.027 The image position of the d line is used as a reference, and the insertion portion side is positive.

The second embodiment also includes a disposable insertion section,
TV camera adapter 3 as a reusable part
It is composed of In the second embodiment, as in the first embodiment, the insertion portion has a simple structure to reduce the cost, and high-cost parts and the like are concentrated in the TV camera adapter which is the reuse portion. In this case, the TV camera adapter and the TV camera may be integrated to form an imaging optical system.

The second embodiment is an image forming optical system T for a television camera.
In addition, a lot of cemented lenses are used, and a large positive axial chromatic aberration remains in this optical system alone. This positive axial chromatic aberration can correct the negative axial chromatic aberration of the insertion portion observing optical system as in the cemented optical system of the first embodiment. FIG. 4 is a total aberration diagram in which the insertion portion observing optical system of Example 2 and the television camera imaging optical system are combined. In Example 2, since the paraxial magnification of the image forming optical system for the television camera is approximately equal, it is possible to compare the axial chromatic aberration of the final image of the insertion section observing optical system with the axial chromatic aberration of the entire system. I can. Figure 4
As is apparent from the above, the axial chromatic aberration of the entire system of Example 2 is excellent because the axial chromatic aberration in the final image of the insertion portion observation optical system is significantly improved. Further, other aberrations of the entire system are well corrected.

The above-mentioned both embodiments will be described in detail below.

In Example 1 and Example 2, the same insertion portion observation optical system is used. This insertion portion observation optical system uses low-dispersion optical plastic as an optical material of each lens. Since the present invention considers that the insertion part is disposable, it is desirable to use a plastic lens so that mass production is possible and cost can be reduced by mass production. Moreover, since aspherical surfaces are often used for the lenses forming the insertion portion observing optical system, mass production is not possible and the cost is increased by the method of polishing the lenses made of glass to form the aspherical surfaces. However, if lenses are processed by pressing glass, mass production becomes possible. Therefore, a glass press lens may be used.

In the above embodiment, the insertion part observation optical system has eight lenses, but all the lenses except the two lenses closest to the object side have the same shape and the same material, as is clear from the above data. Is. Therefore, only three types of molding dies are required, and it is possible to obtain advantages by reducing the die cost and increasing the number of the same lenses. In addition, the objective lens usually has a lens configuration different from that of the relay optical system and has a short overall length, so that in the embodiment, the lens used in the relay optical system is diverted to make the parts common and close to one relay. The number of relays is reduced by ensuring the full length. The aspherical surface used in the relay optical system is for correcting aberrations other than chromatic aberration as described above, and mainly controls spherical aberration and astigmatism. In a relay optical system consisting of a single lens having only a spherical surface, normally, negative spherical aberration occurs. Therefore, in the relay optical system of the above-mentioned embodiment, spherical aberration is corrected by using an aspherical surface having a shape with a weak curvature at the periphery. ing.

Since the observation optical system in the rigid endoscope has a very large cost ratio of the parts, the insertion portion as described above can be made very inexpensive.

Next, in Example 1, an eyepiece optical system is used. This eyepiece optical system is not a loupe but an intermediate image of a real image is formed in the optical system. The intermediate image is formed in this way because it is necessary to form a pupil inside the eyepiece optical system.

In an eyepiece optical system such as a magnifying glass that does not form an intermediate image, the pupil cannot be arranged there because the pupil is almost at the same position as the eye point.

Since the eyepiece optical system of Example 1 (the eyepiece optical system used in the present invention) needs to generate a large positive axial chromatic aberration, if an attempt is made to generate a large axial chromatic aberration only with the lens away from the pupil. At the same time, a large amount of chromatic aberration of magnification occurs. Therefore, a lens that produces a large positive axial chromatic aberration must be collected near the pupil position in the eyepiece optical system. Therefore, in the first embodiment, the intermediate image formation of the real image is performed inside the eyepiece optical system, and many cemented lenses are arranged near the pupil position generated on the object side of this image formation position. Further, in this embodiment, since the intermediate image is formed, it becomes an erect image.

It is desirable that the number N _{OC of} cemented lenses included in this eyepiece optical system satisfies the following condition (4).

(4) N _OC ≧ N _R +1 where N _R is the number of relays of the relay optical system in the insertion section.

In a conventional relay optical system in which axial chromatic aberration is well corrected, usually one cemented lens is used for one relay. Therefore, unlike the present invention, since no cemented lens is used in the relay optical system, the eyepiece optical system must bear the load for correcting the axial chromatic aberration. Further, since one relay of the intermediate image forming part of the eyepiece optical system is added, the number of cemented lenses of the eyepiece optical system needs to be at least equal to the number of relay times of the relay system plus one. If it is less than that, axial chromatic aberration correction is required. Can not.

It is desirable that the eyepiece optical system has a focusing mechanism in order to adjust the variation of the focus generated on the insertion section observation optical system side. When a plastic lens is used in the insertion section observation optical system, the optical constant changes greatly depending on temperature and humidity, and a large focus fluctuation occurs. In order to reduce the cost of the insertion part, it is not possible to adjust the focus by the insertion part alone, so the insertion part was kept inexpensive unless a focusing mechanism was provided in the eyepiece to compensate for variations in the focus of the insertion part. It is impossible to prevent blurring of the image due to out of focus. As a focusing mechanism for that,
The attachment part of the insertion part may be moved in the optical axis direction, or the entire eyepiece optical system may be moved in the optical axis direction within the eyepiece part.
Alternatively, an inner focus may be used which moves some lenses of the eyepiece optical system along the optical axis.

Next, the image forming optical system in the case of using the image forming optical system for the television camera as in the second embodiment will be described.
The number N _{TV of} cemented lenses used in this image forming optical system for a television camera must satisfy the following condition (5).

(5) N _TV ≧ N _R +1 Unless this condition (5) is satisfied, axial chromatic aberration cannot be corrected.

Further, it is preferable that the image forming optical system for the television camera is provided with a focusing mechanism. As this focusing mechanism, there is a method of moving the attachment portion of the insertion portion in the optical axis direction. Further, the entire imaging optical system for a TV camera may be moved in the optical axis direction inside the TV camera adapter or a TV camera having an imaging optical system. Moreover, you may use the inner focus which moves a part of lens in the imaging optical system for television cameras. Further, in the case of a television camera having an image pickup optical system, the solid-state image pickup device may be moved in the optical axis direction.

Although the medical-use disposable rigid endoscope has been described above, the cost of the reusable rigid endoscope for medical and industrial purposes can be reduced.

In the conventional rigid endoscope shown in FIG. 7, a large number of cemented lenses are arranged in the insertion portion. In particular, the relay optical system has to increase the number of cemented lenses by the number of relays and include many cemented lenses. In particular, a cemented lens having a surface with a strong curvature inevitably requires a higher processing cost than a lens having a large diameter. Further, since the lens has a small diameter, it is difficult to automate the joining, so that the cost associated with the joining operation becomes very large. Therefore, if the cemented lens in the insertion part, especially the cemented lens in the relay optical system, can be moved to a part other than the insertion part with a small outer diameter restriction, the cost can be reduced even if the number of parts does not change. Therefore, the configuration of the optical system shown in FIG. 7 may be stored in a single rigid endoscope as it is, and an objective optical system, a relay optical system, and an eyepiece optical system other than the insertion portion may be provided in the insertion portion. In this case, the axial chromatic aberration generated in the objective optical system and the relay optical system may be corrected by the eyepiece optical system.

[0054]

The rigid endoscope of the present invention has a construction in which the insertion section and the eyepiece section are separated, and the axial chromatic aberration of the observation optical system in the insertion section is corrected by the optical system in the eyepiece section. By doing so, the structure of the insertion portion is simple and inexpensive, and it is extremely effective in making the insertion portion disposable.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment of the present invention.

FIG. 2 is a sectional view of a second embodiment of the present invention.

FIG. 3 is an aberration curve diagram of Example 1 of the present invention.

FIG. 4 is an aberration curve diagram of Example 2 of the present invention.

FIG. 5 is a diagram showing a configuration of a disposable type rigid endoscope in which the optical system of the present invention is used.

FIG. 6 is a diagram showing a configuration of a disposable type television-observing rigid endoscope in which the optical system of the present invention is used.

FIG. 7 is a diagram showing a configuration of a conventional rigid endoscope.

FIG. 8 is a diagram showing a relationship of image formation by a relay optical system.

FIG. 9 is a diagram showing a configuration of an insertion portion with a sterilization cover of a rigid endoscope.

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Claims (3)

[Claims] 1. A rigid endoscope in which an insertion part and an eyepiece part are separable, each of which comprises an observation optical system arranged in the insertion part and an optical system arranged in the eyepiece part. A rigid-mirror optical system, wherein axial chromatic aberration generated in the system is corrected by an optical system in the eyepiece. 2. An optical system for television observation, wherein the insertion portion and a television camera adapter or a television camera having an imaging optical system can be separated from each other, and the observation optical system arranged in the insertion portion and the television camera adapter or connection. The optical system comprises another optical system arranged in a television camera having an image optical system, and axial chromatic aberration generated in the observation optical system is corrected by the other optical system. TV observation rigid endoscope system optical system. 3. A rigid endoscope including an objective optical system, a relay optical system, and an eyepiece optical system, wherein the objective optical system and the relay optical system are provided inside the insertion portion, and the eyepiece optical system is provided at a portion other than the insertion portion. A rigid mirror optical system, wherein axial chromatic aberration generated in the objective optical system and the relay optical system is corrected by the eyepiece optical system.