JP3353910B2 - Objective optical system for rigid endoscope - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective optical system used for a rigid endoscope using a relay lens for an image transmission system, and particularly to a rigid internal endoscope having resistance to high-temperature and high-pressure steam sterilization and having a wider field of view. The present invention relates to an objective optical system for an endoscope.

[0002]

2. Description of the Related Art Conventionally, a rigid endoscope as shown in FIG. 28 has been known. That is, the objective optical system O and the relay lens R
₁ , R ₂ , and R ₃ are used to form an object image by the objective optical system O in the field lens F, and the aberration is satisfactorily corrected. The feature of such a type of rigid endoscope is that the exit pupil of the objective optical system O is transmitted to the relay lens systems R ₁ , R ₂ , and R ₃ using the field lens F. The point that the generated positive field curvature is canceled out by generating a negative field curvature with a retrofocus type objective optical system so that the entire endoscope optical system eliminates the field curvature. Another advantage is that a cemented lens having a cemented surface R having a concave action is arranged in a positive lens group of a retrofocus type objective optical system, so that coma aberration is well corrected.

Disadvantages of such a type of rigid endoscope optical system are that the angle of view varies due to manufacturing problems, and that the field curvature becomes insufficiently corrected with an increase in the number of relays. The above-mentioned variation in the angle of view means that the field lens F
The pupil of the field lens F is transmitted due to the distance between the objective optical system O and the field lens F, the distance between the field lens F and the relay lens system, the thickness of the field lens F, etc. The effect is to vary, which causes the angle of view to vary. The insufficient correction of the field curvature is because the positive field curvature of the relay lens system is proportional to the number of relays. Therefore, for example, when the number of relays is three, even if the correction is satisfactorily performed due to the negative curvature of field of the objective optical system, when the number of relays is five, the correction is insufficient and the correction is insufficient.

On the other hand, an objective optical system described in Japanese Patent Application Laid-Open No. Sho 59-226315 is known to compensate for the above-mentioned disadvantages of the optical system. The endoscope optical system arranged meniscus lens L ₁ with a concave surface facing the image side in the objective optical system O as shown in FIG. 29, Lord diverge or converge in front of the meniscus lens L ₁ The light beam is made substantially parallel to the optical axis, the exit pupil of the objective optical system O is set to infinity, and the pupil is transmitted to the relay lens system. As described above, the so-called telecentric system in which the pupil is transmitted at infinity between the objective optical system O and the relay lens system is used. It is possible to obtain a rigid endoscope optical system with little variation in the angle of view without affecting the angle. Further, if a meniscus lens having a negative Petzval sum is disposed, the Petzval sum of the objective optical system becomes a large negative value compared with the optical system as shown in FIG. 28, so that a large negative field curvature occurs. I do. As a result, the field curvature of the entire optical system of the rigid endoscope can be favorably corrected.

[0005] Since the rigid endoscope is used by being inserted into a body cavity or the like, it needs to be sterilized before use. Since steam sterilization using high-temperature and high-pressure steam is effective in this sterilization process, a material resistant to such high-temperature and high-pressure, for example, Al ₂ O ₃ is used as a cover glass for the distal end portion of the rigid endoscope. Some are mainly composed of artificial sapphire.

[0006]

In order to obtain a wide-angle optical system, for example, an optical system having a viewing angle of 120 ° or more, a conventional rigid endoscope objective optical system has a curvature radius of a negative lens closest to the object. It becomes too small to make. FIG.
As shown in FIG. 30, an optical system in which one more negative lens is added to the front group is also conceivable, but as the angle of view increases, the ray height on the first surface (the first surface of the cover glass C) increases. This is not preferable because the light beam shown in FIG. If the water vapor-resistant cover glass C is removed to prevent such light beam eclipse, the optical system will be eroded during sterilization.

An object of the present invention is to provide an objective optical system used in a rigid endoscope having a wide field of view and resistant to high-temperature, high-pressure water vapor.

[0008]

The objective optical system according to the present invention comprises:
It is used for a rigid endoscope in which a relay lens for relaying an object image is arranged on the image side as shown in FIG. 2, and for example, as shown in FIG. a negative lens L ₁ with its, and having at least constitutes a negative lens L _2, is the addition RLG converging system which was constituted by at least two positive lens components.

[0009] The objective optical system of the present invention, a wide angle without burdening as described above, the negative lens L ₂ by placing a negative lens L ₁ further before negative lens L ₂ to the front group divergent system This is to obtain a viewing angle. The material, for example, Al ₂ O ₃ is resistant lens L ₁ to the high-temperature high-pressure steam sterilization
(Artificial sapphire).

It is desirable that the optical system satisfies the following condition (1). (1) −0.5 ≦ r ₂ / r ₁ ≦ 0.5 where r ₁ and r ₂ are the radii of curvature of the object-side and image-side surfaces of the lens L ₁ , respectively.

The condition (1) is that the most object side negative lens L ₁
Of which was to define a curvature radius ratio of double-sided, if deviated from this condition (1), in order to obtain the power required divergence angle of the curvature of the second surface r ₂ radius becomes small This is not preferable because the workability of the lens is deteriorated. Preferably, the surface h is a flat surface or a surface relatively close to a flat surface. When the negative lens closest to the object (first negative lens) is formed of artificial sapphire or the like, the artificial sapphire has high hardness and requires a special process for polishing to a curved surface.
Therefore, when polishing both surfaces, the cost increases. Furthermore when used in water, the surface r ₁ is a curved recess along its curved surface can, bubbles lens center or Matowari with the periphery, vignetting, etc. of flare or the observation field is generated.
Surface r ₁ For these reasons it is desirable that the near surface plane or in.

Further, it is desirable that the objective optical system of the present invention satisfies the following condition (2). (2) 1 ≦ f ₁ / f ₂ ≦ 25 where f ₁ and f ₂ are the focal lengths of the negative lens L ₁ on the object side and the next negative lens L ₂ .

Condition (2) is that the negative lens L ₁ of the front group divergence system
In which a defines the ratio of the focal length of L _2. Conditions f ₁ exceeds the upper limit is too short or f ₂ too long (2), that when you try to wide field for burden concave surface facing the image side of the negative lens L ₂ is offset, a negative lens ray at the first surface of the L ₁ is hinder observation field vignetting. In order to prevent the eclipse of the ray must be the diameter of the lens L ₁ on a large, not preferred as an objective optical system of the endoscope that is compact is required. Also the lower limit of the condition (2), it is difficult to obtain a wide field for either f ₂ f ₁ becomes too short too long. That becomes almost the same type as the conventional endoscope objective optical system to approach the plane becomes curvature loosely concave facing the image side of the negative lens L _2, to a wide field of view in the negative lens L ₁ A large burden is applied, and lens processing becomes difficult. Especially in the case of the material lens L ₁ is an artificial sapphire, processing becomes extremely difficult.

In the endoscope objective optical system according to the present invention, it is more desirable that the following conditions (3) and (4) are satisfied. (3) 0.5 ≦ | f _F /f|≦0.8 (4) 2 ≦ f _R /f≦4.5 where f, f _F and f _R are the whole system, the front group divergence system, and the rear group, respectively. This is the focal length of the convergent system.

The condition (3) defines the ratio of the focal length of the front group divergence system to the entire objective optical system, that is, the negative refractive power of the front group divergence system. When the value exceeds the upper limit of the condition (3), the focal length of the front group diverging system becomes too long, and the focal length of the rear group converging system must be shortened for widening the angle. Is not preferable because it becomes difficult. If the lower limit of the condition (3) is exceeded, the focal length of the front divergence system becomes too short, which makes it difficult to correct aberrations and eccentricity during assembly, which is not preferable. At this time, the image height is considered to be constant.

Condition (4) defines the ratio of the focal lengths of the rear group converging system and the entire system, that is, the positive refractive power of the rear group converging system. When the value exceeds the upper limit of the condition (4), the focal length of the rear group converging system becomes too long, and the angle of a light ray incident on the rear group converging system becomes small. In this case, in order to widen the angle, the focal length of the front divergence system must be shortened, and it becomes difficult to correct aberration and eccentricity during assembly, which is not preferable. If the lower limit of the condition (4) is exceeded, the focal length of the rear group converging system becomes too short, and the angle of incidence of the off-axis principal ray entering the rear group converging system becomes large. In off-axis principal ray angles converging subpopulation before becomes large with respect to the optical axis in distance to place the prism when providing the visual field changing prism P ₁ between Accordingly example the rear group and the front group, as shown in FIG. 7 The ray height increases. As a result, the outer diameter of the lens becomes undesirably large. Also in this case, the image height is considered to be constant.

Further, the objective optical system of the present invention has the following condition (5):
Is preferably satisfied. (5) h ₁ / I _max ≦ 1.2 where h ₁ is the maximum ray height of the first surface of the negative lens L ₁ disposed closest to the object side of the front divergence system, and I _max is rigid endoscope This is the maximum image height of the objective optical system of the mirror.

[0018] Condition (5) is a condition for defining a ray height of the negative lens first surface of the L ₁ arranged closest to the object side when aimed at a wide angle of the objective optical system of a rigid endoscope. Ray height h ₁ exceeds the range of the condition (5) becomes too large, there is a fear that the observation field is kicked in the negative lens L _1.
To prevent Re this vignetting has to the outer diameter of the lens L ₁ on a large, unfavorably tip of the rigid endoscope for large. Also, when I _max is reduced, the obtained image becomes small, and it becomes difficult to observe a bright and good image.

[0019]

Next, an embodiment of an objective optical system for a rigid endoscope according to the present invention will be described. Example 1 Where r ₁ , r ₂ ,... Are the radii of curvature of the respective surfaces of the lens, d
_.. , D ₂ ,...
, n ₁ , n ₂ ,... are the refractive indices of the respective lenses, ν ₁ , ν ₂ ,
... is the Abbe number of each lens.

Embodiment 1 is an objective optical system shown in FIG.
The rigid endoscope is configured by using the relay lens having the configuration shown in FIG.

The second embodiment has a similar configuration, and is an optical system of five relays as shown in FIG.

The third embodiment has the configuration shown in FIG. 3 and shows the entire rigid endoscope optical system including the relay lens of the three-time relay. The objective optical system has a configuration similar to that of the first embodiment.

Embodiment 4 uses the objective optical system shown in FIG.
Is used as a rigid endoscope by using the relay lens shown in FIG.

Embodiment 5 is a rigid endoscope optical system having a relay lens system of three relays as shown in FIG. 5, and the objective optical system has a configuration similar to that shown in FIG.

In the sixth embodiment, the objective optical system shown in FIG. 6 is a relay having five relay lenses. Embodiments 7 and 8 are examples of an objective optical system in which a viewing direction changing prism is arranged.
The seventh embodiment has a configuration as shown in FIG. 7 and the eighth embodiment has a configuration as shown in FIG. That is, in each case, the viewing direction conversion prism is disposed between the front group diverging system and the rear group converging system, and the viewing direction is 70 ° with respect to the optical axis in the seventh embodiment, and 30 ° with respect to the optical axis in the eighth embodiment.
It is. The eighth embodiment is a surface is aspherical second object side of the negative lens L _2, the positive lens component of the rear group converging system L ₄ is 3
This is a cemented lens. In the eighth embodiment, the distortion that increases with the wide angle is corrected by the aspherical surface, and the distortion when used underwater is 5% despite the wide angle of view of 120 °. Corrected well. As described above, observation with an image having a wide angle and almost no distortion is possible, so that the subject can be observed accurately, which is extremely effective in preventing misdiagnosis in the medical field, for example.

In the ninth and tenth embodiments, the objective optical systems are shown in FIGS.
As shown in FIG. The ninth embodiment is an example of an objective optical system used for a rigid endoscope optical system when a relay lens is used three times, and has a wide viewing angle of 140 ° when used in the air. The example 10 is an example of the objective optical system in the five rigid endoscope relay lens component L ₄ of the rear group converging system is different from the objective optical system of Example 9.

[0027] Examples 11 and 12 are each in the configuration shown in FIGS. 11 and 12, first the most negative lens disposed on the object side L ₁
The surfaces are convex and concave, respectively.

The objective optical system of the present invention, by adding a negative lens L _1, the lens element to the negative Petzval sum is increased. This in keeping a wide field of view, it is possible to reduce the burden on the negative lens L ₂ and the lens L ₅ in the rear group converging engagement when more satisfactorily correct field curvature in the entire endoscope optical system configuration I can do it.

The above described hard endoscope objective optical system of the present invention, the negative lens L ₁ which is the most object side lens in the crystals as a main component material, i.e. Al ₂ O ₃ that are resistant to steam sterilization One of the objectives is to configure it.

FIGS. 25 and 26 are views showing the tip of a rigid endoscope incorporating the objective optical system of the present invention. FIG. 25 is a sectional view, and FIG. 26 is a front view as seen from the entrance side. is there. The rigid endoscope includes an outer tube 1 and an inner tube 2 arranged concentrically with each other, and a light guide fiber bundle 5 for illumination is sandwiched between them. The first lens L ₁ of the objective optical system is manufactured by polishing or the like, and thereafter, is coated with a metal coating on the outer peripheral surface, and is fixed to the tip of the inner cylinder 2 by soldering. Meanwhile the third lens L ₃ of the objective optical system is fixed by bonding or the like to the holding cylinder 3, the second lens L ₂ through the third lens L ₃ to the holding cylinder 3 is bonded and fixed to the third lens L ₃ indirectly Is maintained. Further, other lenses and relay lenses of the objective optical system are attached to the lens holding cylinder 3 via the spacing ring 4 although not shown in FIG. Further, the lens holding cylinder 3 is inserted into the inner cylinder 2 from the eyepiece side of a rigid endoscope (not shown),
The first lens L ₁ and second lens L ₂ is fixed at a position a predetermined distance.

Next, FIG. 27 is a sectional view showing a distal end portion of a rigid mirror incorporating the oblique objective optical system of the present invention. A field conversion prism P ₂ and a third lens L ₃ are fixed to a holding cylinder 3. While holding the second lens L ₂ to the front surface of the object side of the prism, is basically the same as the structure shown in FIG. 25.

The structure as shown in FIGS. 25 and 27 improves the assemblability and repairability.

As described above, the first lens L ₁ plays a role as a cover glass in addition to securing a wide field of view and the like. In order to prevent high-temperature and high-pressure water vapor from entering the lenses subsequent to the lens L ₁ , the first lens L ₁ is used. It is soldered to the cylinder 2. To this way to with the lens L ₁ to the inner cylinder 2 soldering, its outer (edge) is are subjected to metallic coating after polishing. For applying the metal-based coating so good, when the lens L ₁ at crystal composed mainly of Al ₂ O _3, the crystal axis direction is processed to have 90 ° to the optical axis It is desirable. Also there is a possibility of occurrence of flare by applying a metal coating, 25, on the periphery of the first lens L ₁ indicated by reference character a in FIG. 27, applying a black paint such as black aqueous pen and ink Is preferred.

Next, the aspherical surface used in the embodiment is
It is expressed by the following equation.

Here, x and y are coordinate systems in which the optical axis is taken as the x-axis and the direction of the image is taken as positive, and the direction perpendicular to the optical axis is taken as the y-axis, and the origin is at the intersection of the plane and the optical axis. Are coordinate values.
R is the radius of curvature at the top of the aspheric surface, p is the conic constant,
E, F, G,... Are fourth-order, sixth-order, eighth-order,... Aspherical coefficients, respectively.

[0036]

The objective optical system for a rigid endoscope according to the present invention is used for a rigid endoscope for transmitting an object image using a relay lens, and the front group converging system is replaced by at least two negative lenses.
With this configuration, a wide viewing angle can be provided and resistance to sterilization by high-temperature and high-pressure steam can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an objective optical system according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of a rigid endoscope optical system according to a second embodiment of the present invention.

FIG. 3 is a diagram illustrating a configuration of a rigid endoscope optical system according to a third embodiment of the present invention.

FIG. 4 is a sectional view of an objective optical system according to a fourth embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of a rigid endoscope optical system according to a fifth embodiment of the present invention.

FIG. 6 is a sectional view of an objective optical system according to a sixth embodiment of the present invention.

FIG. 7 is a sectional view of an objective optical system according to a seventh embodiment of the present invention.

FIG. 8 is a diagram showing a configuration of a rigid endoscope optical system according to an eighth embodiment of the present invention.

FIG. 9 is a diagram showing a configuration of a rigid endoscope optical system according to a ninth embodiment of the present invention.

FIG. 10 is a sectional view of an objective optical system according to a tenth embodiment of the present invention.

FIG. 11 is a diagram showing a configuration of a rigid endoscope optical system according to an eleventh embodiment of the present invention.

FIG. 12 is a sectional view of an objective optical system according to a twelfth embodiment of the present invention.

FIG. 13 is an aberration curve diagram of the first embodiment.

FIG. 14 is an aberration curve diagram of the second embodiment.

FIG. 15 is an aberration curve diagram of the third embodiment.

FIG. 16 is an aberration curve diagram of the fourth embodiment.

FIG. 17 is an aberration curve diagram of the fifth embodiment.

FIG. 18 is an aberration curve diagram of the sixth embodiment.

FIG. 19 is an aberration curve diagram of the seventh embodiment.

FIG. 20 is an aberration curve diagram of the eighth embodiment.

FIG. 21 is an aberration curve diagram of the ninth embodiment.

FIG. 22 is an aberration curve diagram of the tenth embodiment.

FIG. 23 is an aberration curve diagram of the eleventh embodiment.

FIG. 24 is an aberration curve diagram of the twelfth embodiment.

FIG. 25 is a sectional view of a distal end of a rigid endoscope provided with the objective optical system of the present invention.

FIG. 26 is a front view of the distal end of the rigid endoscope.

FIG. 27 is a cross-sectional view of a rigid endoscope provided with an objective optical system in which a field conversion prism according to the present invention is arranged.

FIG. 28 is a diagram showing a configuration of a conventional rigid endoscope optical system.

FIG. 29 is a diagram showing a configuration of another conventional rigid endoscope optical system.

FIG. 30 is a diagram showing a state of light rays when two negative lenses at the tip of the rigid endoscope objective optical system are arranged.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 9/00-17/08 G02B 21/02-21/04 G02B 23/24-23/26 A61B 1 / 00

Claims (7)

(57) [Claims] In order from 1. A object side, an objective optical system, the rigid endoscope optical system comprising a relay lens for transmitting an object image, the objective optical system is a negative front group in order from the object side down
Retriever and a positive rear group, the order the front group from the object side,
Image side is concave and made of crystal mainly composed of Al ₂ O ₃
A first concave lens, and a second concave lens having a concave surface on the image side.
The rear group consists of at least two positive lens components , and satisfies the following condition (1).
Rigid endoscope KagamiHikari science system that foot. (1) −0.5 ≦ r ₂ / r ₁ ≦ 0.5 , where r ₁ and r ₂ are the object side of the first concave lens and
And the radius of curvature of the image-side surface. 2. The object-side surface of the first concave lens is flat.
The rigid endoscope optical system according to claim 1, wherein 3. The method according to claim 1, wherein the following condition (2) is satisfied.
Is a rigid endoscope optical system of 2. (2) 1 ≦ f ₁  / F _Two  ≤25 Where f ₁  , F _Two  Are the first concave lens and the front, respectively.
This is the focal length of the second concave lens. 4. A contract satisfying the following conditions (3) and (4):
The rigid endoscope optical system according to claim 3. (3) 0.5 ≦ | f _F  /F|≦0.8 (4) 2 ≦ f _R  /F≦4.5 Where f _F  , F _R  Are the focuses of the front group and the rear group, respectively.
The point distance, f, is the focal length of the entire objective optical system. 5. An objective optical system and an object image in order from an object side.
Endoscope optical system consisting of a relay lens that transmits light
In this case, the objective optical system is arranged in order from the object side to the negative front group and the aperture.
And a positive rear group, wherein the front group is in order from the object side,
A first concave lens whose image side is concave, and a concave lens whose image side is concave
A second concave lens and a second concave lens,
Consists of at least two positive lens components, and
(1)- A rigid endoscope optical system satisfying (4). (1) -0.5 ≦ r _Two  / R ₁  ≤0.5 (2) 1 ≦ f ₁  / F _Two  ≤25 (3) 0.5 ≦ | f _F  /F|≦0.8 (4) 2 ≦ f _R  /F≦4.5 Where r ₁  , R _Two  Are the object side of the first concave lens and
Radius of curvature of the image-side surface, f ₁  , F _Two  Are the first recesses, respectively.
The focal length of the lens and the second concave lens, f _F  , F
_R  Is the focal length of the front group and the rear group, respectively, and f is the objective
This is the focal length of the entire optical system. 6. fixing the first concave lens at the distal end of the cylindrical rigid endoscope body including a light guide, a lens holding cylinder lens component other than said first concave lens of the objective optical system fixed to and disposed within the rigid endoscope main body at a first concave lens a predetermined distance, claims
2. Rigid endoscope optical system . 7. The rigid endoscope optics according to claim 6 , wherein the first concave lens has a metal coating on an outer peripheral surface and is fixed to a distal end portion of the rigid endoscope main body by soldering. System .