JP6693814B2 - Endoscope objective optical system and endoscope - Google Patents

Description

  The present invention relates to an endoscope objective optical system.

  For example, in a transnasal endoscope, it is desired that the scope has a small diameter. Therefore, it is desirable that the objective optical system mounted on the transnasal endoscope is small. However, in recent years, even in the case of a transnasal endoscope that requires a small diameter, not only high image quality but also a focus function is mounted, and there is an increasing market need to further improve the observation performance. Endoscope objective optical systems having a focus function have been proposed in Patent Documents 1, 2, and 3, for example.

JP 2008-107391 A International Publication No. 10/137238 JP, 2004-21158, A

  Although the objective optical systems proposed in Patent Documents 1, 2, and 3 have a focusing function, it is not sufficient to reduce the total length and outer diameter of the optical system.

  The present invention has been made in view of the above, and provides an endoscope objective optical system that has a small overall length and outer diameter, has good optical performance, and is capable of mounting a focusing mechanism (lens moving mechanism). The purpose is to provide.

In order to solve the above-mentioned problems and to achieve the object, an endoscope objective optical system according to at least some embodiments of the present invention includes, in order from the object side, a first group including one negative lens and a brightness. a second group of positive with-drawn, is constructed from a third group of positive with at least two cemented lenses, it is by riff Okashingu to moving only the second group,
It is characterized in that the following conditional expression (1) is satisfied .
2 <| f3R / f3L | <16 (1)
here,
f3L is the focal length of the cemented lens closest to the object side among the cemented lenses of the third group,
f3R is the focal length of the cemented lens closest to the image plane among the cemented lenses of the third group,
Is.
An endoscope according to at least some embodiments of the present invention is characterized by including the above-mentioned endoscope objective optical system.

  INDUSTRIAL APPLICABILITY The present invention has an effect of providing an endoscope objective optical system having a small overall length and outer diameter, good optical performance, and capable of mounting a lens moving mechanism.

It is a figure which shows the cross-sectional structure of the endoscope objective optical system which concerns on one Embodiment of this invention, (a) is sectional drawing in a normal observation state, (b) is a sectional view in a close-up observation state. It is a figure which shows the cross-sectional structure of the endoscope objective optical system which concerns on Example 1 of this invention, (a) is sectional drawing in a normal observation state, (b) is a sectional view in a close-up observation state. 3 is an aberration diagram showing spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) of Example 1. FIG. It is a figure which shows the cross-sectional structure of the endoscope objective optical system which concerns on Example 2 of this invention, (a) is sectional drawing in a normal observation state, (b) is a sectional view in a close-up observation state. 9 is an aberration diagram showing spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) of Example 2. FIG. It is a figure which shows the cross-sectional structure of the endoscope objective optical system which concerns on Example 3 of this invention, (a) is sectional drawing in a normal observation state, (b) is a sectional view in a close-up observation state. FIG. 8 is an aberration diagram showing spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration (CC) of Example 3; It is a figure which shows the cross-sectional structure of the endoscope objective optical system which concerns on Example 4 of this invention, (a) is sectional drawing in a normal observation state, (b) is a sectional view in a close-up observation state. 9 is an aberration diagram showing spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) of Example 4. FIG. It is a figure which shows the cross-sectional structure of the endoscope objective optical system which concerns on Example 5 of this invention, (a) is sectional drawing in a normal observation state, (b) is a sectional view in a close-up observation state. 16 is an aberration diagram showing spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration (CC) of Example 5. FIG. It is a figure which shows the cross-sectional structure of the endoscope objective optical system which concerns on Example 6 of this invention, (a) is sectional drawing in a normal observation state, (b) is a sectional view in a close-up observation state. 16 is an aberration diagram illustrating spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration (CC) of Example 6. FIG. It is a figure which shows the cross-sectional structure of the endoscope objective optical system which concerns on Example 7 of this invention, (a) is sectional drawing in a normal observation state, (b) is a sectional view in a close-up observation state. 17 is an aberration diagram illustrating spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration (CC) of Example 7. FIG. It is a figure which shows the cross-sectional structure of the endoscope objective optical system which concerns on Example 8 of this invention, (a) is sectional drawing in a normal observation state, (b) is a sectional view in a close-up observation state. 16 is an aberration diagram showing spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) of Example 8. FIG. It is a figure which shows the cross-sectional structure of the endoscope objective optical system which concerns on Example 9 of this invention, (a) is sectional drawing in a normal observation state, (b) is a sectional view in a close-up observation state. 17 is an aberration diagram illustrating spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) of Example 9. FIG. It is a figure which shows the cross-sectional structure of the endoscope objective optical system which concerns on Example 10 of this invention, (a) is sectional drawing in a normal observation state, (b) is a sectional view in a close-up observation state. 21 is an aberration diagram illustrating spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) of Example 10. FIG. It is a figure which shows the cross-sectional structure of the endoscope objective optical system which concerns on Example 11 of this invention, (a) is sectional drawing in a normal observation state, (b) is a sectional view in a close-up observation state. 21 is an aberration diagram showing spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration (CC) of Example 11. FIG. It is a figure which shows the cross-sectional structure of the endoscope objective optical system which concerns on Example 12 of this invention, (a) is sectional drawing in a normal observation state, (b) is a sectional view in a close-up observation state. 16 is an aberration diagram illustrating spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration (CC) of Example 12. FIG. It is a figure which shows the cross-sectional structure of the endoscope objective optical system which concerns on Example 13 of this invention, (a) is sectional drawing in a normal observation state, (b) is a sectional view in a close-up observation state. 16 is an aberration diagram showing spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) of Example 13. FIG. It is a figure which shows the cross-sectional structure of the endoscope objective optical system which concerns on Example 14 of this invention, (a) is sectional drawing in a normal observation state, (b) is a sectional view in a close-up observation state. 20 is an aberration diagram illustrating spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) of Example 14. FIG.

  Hereinafter, the endoscope objective optical system according to the embodiment will be described in detail with reference to the drawings. The present invention is not limited to this embodiment.

  1A and 1B are views showing a sectional configuration of an endoscope objective optical system according to an embodiment of the present invention. FIG. 1A is a sectional view in a normal observation state, and FIG. ..

  The present embodiment includes, in order from the object side, a first group G1 including one negative lens L1, a positive second group G2 having an aperture stop S, and at least two cemented lenses CL1 and CL2. The positive third lens group G3 is included, and only the second lens group G2 is movable to perform focusing.

  In the following, the reason and operation of having such a configuration in the present embodiment will be described. In order to form the movable lens group while reducing the size of the lens, a large surface distance is required before and after the movable lens group with respect to the entire length of the optical system. Furthermore, in order to reduce the total lens length, the number of lenses must be reduced as much as possible.

  In order to achieve this, the first group G1 is composed of one lens, and the second group G2 is a movable group with a large front-to-back surface spacing. However, with this configuration, the aberrations generated in the first group G1 and the second group G2 remain as they are.

  Therefore, the third group G3 is configured to use at least two cemented lenses, and the role of one cemented lens is to specialize in spherical aberration correction, and the role of the other cemented lens is chromatic aberration. Specialize in correction. By adopting this configuration, it is possible to achieve an endoscope objective optical system having good aberration performance even when there are large restrictions on the diameter and the total length.

Moreover, according to a preferable aspect of the present embodiment, it is desirable that the following conditional expression (1) is satisfied.
2 <| f3R / f3L | <16 (1)
here,
f3L is the focal length of the cemented lens CL1 closest to the object among the cemented lenses of the third group G3,
f3R is the focal length of the cemented lens CL2 closest to the image plane among the cemented lenses of the third group G3,
Is.

  In the following, the reason and operation of having such a configuration in the present embodiment will be described. In order to fully exert the role of the cemented lenses CL1 and CL2 of the third group G3, it is important to balance the power (refractive power) distribution of each cemented lens.

  In this configuration, the cemented lens CL1 arranged closest to the object side of the third group G3 is a lens having a strong power in order to specialize in spherical aberration correction.

  Further, the cemented lens CL2 disposed closest to the image plane side is a lens having a weak power in order to specialize in correction of chromatic aberration. If only the above is taken into consideration, it suffices to increase the power of one cemented lens and decrease the power of one, but in reality, even for a lens specializing in spherical correction, chromatic aberration correction is also performed although it is small. And vice versa.

  Therefore, it is desirable to satisfy the conditional expression (1). Conditional expression (1) relates to an appropriate ratio of f3R and f3L.

  When the value goes below the lower limit of conditional expression (1), the power of the lens arranged on the object side becomes weak and spherical aberration cannot be corrected sufficiently, or chromatic aberration is excessively corrected.

  If the upper limit of conditional expression (1) is exceeded, chromatic aberration cannot be corrected sufficiently, or spherical aberration will be corrected excessively.

Further, according to a preferable aspect of the present embodiment, it is desirable that the following conditional expression (2) is satisfied.
2 <f2 / L13 <10 (2)
here,
f2 is the focal length of the second lens group G2,
L13 is a distance from the lens of the first group G1 to the lens surface of the third group G3 closest to the object side.

  In the following, the reason and operation of having such a configuration in the present embodiment will be described. The second group G2 needs to be provided with a certain amount of power for focusing. Here, if the power is set to be strong, various aberrations occur largely, and correction becomes difficult. Therefore, it is necessary to secure a sufficient lens movement amount while reducing the sensitivity of aberration.

  Therefore, it is required to satisfy the conditional expression (2). Conditional expression (2) relates to an appropriate ratio of f2 and L13.

  When the value goes below the lower limit of conditional expression (2), the aberration sensitivity of the second lens group G2 increases, and it becomes difficult to correct the aberration of the third lens group G3.

  When the value exceeds the upper limit of conditional expression (2), the aberration sensitivity becomes small and the aberration correction becomes easy, but it becomes difficult to provide a sufficient lens stroke.

Further, according to a preferable aspect of the present embodiment, it is desirable that the following conditional expressions (3) and (4) are satisfied.
1.0 <ΔνR / ΔνL <3.0 (3)
35 <ΔνR (4)
here,
ΔνL is the Abbe's number difference between the positive lens and the negative lens forming the cemented lens CL1 closest to the object among the cemented lenses of the third group G3,
ΔνR is the Abbe's number difference between the positive lens and the negative lens forming the cemented lens CL2 closest to the image plane among the cemented lenses of the third group G3,
Is.

  In the following, the reason and operation of having such a configuration in the present embodiment will be described. In the configuration of the third group G3, in order to sufficiently perform the chromatic aberration correction, it is preferable that the conditional expressions (3) and (4) are satisfied in addition to the conditional expression (1). Conditional expression (3) relates to an appropriate ratio of ΔνR and ΔνL. Conditional expression (4) relates to an appropriate range of ΔνR.

  In the third group G3, chromatic aberration can be favorably corrected by increasing the Abbe number difference of the cemented lens CL2 closest to the image plane, but as described above, the cemented lens CL1 closest to the object plane also Although small, chromatic aberration is corrected.

  Therefore, chromatic aberration is favorably corrected by controlling the Abbe number difference between the cemented lenses CL1 and CL2. If the conditional expression (4) is not satisfied, the sensitivity for chromatic aberration correction cannot be sufficiently provided in the first place.

Further, it is desirable to satisfy the conditional expression (3), but if the lower limit value of the conditional expression (3) is exceeded, excessive chromatic aberration correction will occur in the cemented lens closest to the object surface. If the upper limit of conditional expression (3) is exceeded, excessive chromatic aberration correction will occur in the cemented lens CL2 closest to the image plane, which is not preferable.

  Further, according to a preferable aspect of the present embodiment, it is desirable that the third group G3 be composed of, in order from the object side, a positive cemented lens CL1, a positive single lens L5, and a cemented lens CL2. ..

  In the following, the reason and operation of having such a configuration in the present embodiment will be described. In this configuration, various aberrations are corrected in the third group G3, and for this reason, two or more cemented lenses CL1 and CL2 are provided to correct aberrations.

  However, when the power of the first group G1 composed of one negative lens L1 becomes large, either the spherical aberration correction or the chromatic aberration correction of the cemented lenses CL1 and CL2 of the third group G3 is excessively corrected, and one of them is sufficiently corrected. There is a problem that they cannot be corrected or both cannot be corrected sufficiently.

  Therefore, instead of specializing in spherical aberration correction or chromatic aberration correction, by inserting a single lens L5 for correcting each of them evenly between the cemented lenses CL1 and CL2, a balance of aberration correction is obtained. It becomes possible to realize good aberration correction.

Further, according to a preferable aspect of the present embodiment, it is desirable that the following conditional expression (5) is satisfied.
0.55 <| f1 / f3 | <0.75 (5)
here,
f1 is the focal length of the first group G1,
f3 is the focal length of the third lens group G3,
Is.

  In the following, the reason and operation of having such a configuration in the present embodiment will be described. In this configuration, all the aberrations generated in the first group G1 are absorbed by the third group G3. Therefore, it is necessary to appropriately set the power ratio of the first group G1 and the power of the third group G3, and it is desirable to satisfy the conditional expression (5).

When the value goes below the lower limit of conditional expression (5), spherical aberration is not sufficiently corrected, and a good image cannot be obtained.
If the upper limit of conditional expression (5) is exceeded, spherical aberration will be favorably corrected, but astigmatism will largely occur. When astigmatism occurs, the appearance of the image changes between the center and the periphery, which makes it difficult to obtain a good image, which is not preferable.

(Example 1)
The endoscope objective optical system according to Example 1 will be described. 2A is a cross-sectional view of the endoscope objective optical system according to the present embodiment in a normal observation state (far-distance object point), and FIG. 2B is a cross-section in the close-up observation state (near-distance object point). It is a figure.

  This embodiment has, in order from the object side, a first group G1 having a negative refractive power, a second group G2 having a positive refractive power, and a third group G3 having a positive refractive power.

  The first group G1 has, in order from the object side, a plano-concave negative lens L1 having a plane facing the object side. The second group G2 includes, in order from the object side, a positive meniscus lens L2 having a convex surface directed toward the image side, an aperture stop S, and a parallel plate F1. The third group G3 includes, in order from the object side, a biconvex positive lens L3, a negative meniscus lens L4 having a convex surface facing the image side, a plano-convex positive lens L5 having a plane surface facing the image side, and a biconvex positive lens L6. And a biconcave negative lens L7.

  The positive lens L3 and the negative meniscus lens L4 are cemented to form a cemented lens CL1. The positive lens L6 and the negative lens L7 are cemented to form a cemented lens CL2.

  The parallel plate F1 has a YAG laser cut coating on the object side of the infrared absorption filter and an LD laser cut coating on the image side. As described above, the parallel plate F1 does not directly affect various aberration performances, but functions as an infrared cut filter that blocks light on the long wavelength side unnecessary for observation.

  Further, on the image pickup surface I of the image pickup device (not shown), a parallel flat plate (cover glass) CG2 is attached to prevent scratches and the like from entering the image pickup device. Further, a centering cover glass CG1 for sticking out the center of the image sensor and the center of the optical axis AX is attached to the parallel plate CG2. The cover glass CG1 has a plano-convex shape with a flat surface facing the image side. The shape of the cover glass CG1 may be a parallel plate as in the example described later. These configurations are the same in other embodiments.

  Further, the second group G2 moves toward the image (image plane I) side when focusing from the normal observation state (FIG. 2A) to the close-up observation state (FIG. 2B).

3A, 3B, 3C, and 3D show spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the normal observation state of this embodiment. ) Is shown.
3E, 3F, 3G, and 3H show spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the close-up observation state of this embodiment. ) Is shown.
These aberration charts are shown for each wavelength of 656.27 nm (C line), 587.56 nm (d line) and 435.84 nm (g line). Further, in each figure, “Fno” indicates an F number and “ω” indicates a half angle of view. The same applies to the aberration diagrams below.

(Example 2)
An endoscope objective optical system according to Example 2 will be described. FIG. 4A is a cross-sectional view of the endoscope objective optical system according to the present embodiment in a normal observation state (far-distance object point), and FIG. 4B is a cross-section in the close-up observation state (near-distance object point). It is a figure.

  This embodiment has, in order from the object side, a first group G1 having a negative refractive power, a second group G2 having a positive refractive power, and a third group G3 having a positive refractive power.

  The first group G1 has, in order from the object side, a plano-concave negative lens L1 having a plane facing the object side. The second group G2 includes, in order from the object side, a negative meniscus lens L2 having a convex surface directed toward the image side, an aperture stop S, and a positive meniscus lens L3 having a convex surface directed toward the image side. The third group G3 has, in order from the object side, a biconvex positive lens L4, a negative meniscus lens L5 having a convex surface directed toward the image side, a parallel plate F1, a biconvex positive lens L6, and a convex surface directed toward the image side. And a negative meniscus lens L7. The cover glass CG1 has a plano-convex shape with a flat surface facing the image side.

  The positive lens L4 and the negative meniscus lens L5 are cemented to form a cemented lens CL1. The positive lens L6 and the negative meniscus lens L7 are cemented to form a cemented lens CL2.

  The parallel plate F1 has a YAG laser cut coating on the object side of the infrared absorption filter and an LD laser cut coating on the image side. As described above, the parallel plate F1 does not directly affect various aberration performances, but functions as an infrared cut filter that blocks light on the long wavelength side unnecessary for observation.

  Further, the second group G2 moves toward the image (image plane I) side when focusing from the normal observation state (FIG. 4A) to the close-up observation state (FIG. 4B).

5A, 5B, 5C, and 5D show spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the normal observation state of this embodiment. ) Is shown.
5E, 5F, 5G, and 5H show spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the close-up observation state of this embodiment. ) Is shown.

(Example 3)
An endoscope objective optical system according to Example 3 will be described. FIG. 6A is a cross-sectional view of the endoscope objective optical system according to the present embodiment in a normal observation state (far-distance object point), and FIG. 6B is a cross-section in the close-up observation state (near-distance object point). It is a figure.

  This embodiment has, in order from the object side, a first group G1 having a negative refractive power, a second group G2 having a positive refractive power, and a third group G3 having a positive refractive power.

  The first group G1 has, in order from the object side, a plano-concave negative lens L1 having a plane facing the object side. The second group G2 includes, in order from the object side, a parallel plate F1, an aperture stop S, and a positive meniscus lens L2 having a convex surface directed toward the image side. The third group G3 includes, in order from the object side, a biconvex positive lens L3, a negative meniscus lens L4 having a convex surface directed to the image side, a biconvex positive lens L5, and a concave plano negative lens L6 having a plane surface directed to the image side. And have. The cover glass CG1 is a parallel plate.

  The positive lens L3 and the negative meniscus lens L4 are cemented to form a cemented lens CL1. The positive lens L5 and the negative lens L6 are cemented to form a cemented lens CL2.

  The parallel plate F1 has a YAG laser cut coating on the object side of the infrared absorption filter and an LD laser cut coating on the image side. As described above, the parallel plate F1 does not directly affect various aberration performances, but functions as an infrared cut filter that blocks light on the long wavelength side unnecessary for observation.

  Further, the second group G2 moves to the image (image plane I) side when focusing from the normal observation state (FIG. 6A) to the close-up observation state (FIG. 6B).

7A, 7B, 7C, and 7D show spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the normal observation state of this embodiment. ) Is shown.
7E, 7F, 7G, and 7H show spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the close-up observation state of this embodiment. ) Is shown.

(Example 4)
An endoscope objective optical system according to Example 4 will be described. 8A is a cross-sectional view of the endoscope objective optical system according to the present embodiment in a normal observation state (far-distance object point), and FIG. 8B is a cross-section in the close-up observation state (near-distance object point). It is a figure.

  This embodiment has, in order from the object side, a first group G1 having a negative refractive power, a second group G2 having a positive refractive power, and a third group G3 having a positive refractive power.

  The first group G1 has, in order from the object side, a plano-concave negative lens L1 having a plane facing the object side. The second group G2 includes, in order from the object side, a positive meniscus lens L2 having a convex surface directed toward the image side, an aperture stop S, and a negative meniscus lens L3 having a convex surface directed toward the object side. The third group G3 includes, in order from the object side, a biconvex positive lens L4, a positive meniscus lens L5 having a convex surface facing the image side, a biconvex positive lens L6, and a negative meniscus lens L7 having a convex surface facing the image side. , With. The cover glass CG1 is a parallel plate.

  The positive lens L4 and the negative meniscus lens L5 are cemented to form a cemented lens CL1. The positive lens L6 and the negative meniscus lens L7 are cemented to form a cemented lens CL2.

  The parallel plate F1 is arranged on the image side of the third group G3. The parallel plate F1 has a YAG laser cut coating on the object side of the infrared absorption filter and an LD laser cut coating on the image side. As described above, the parallel plate F1 does not directly affect various aberration performances, but functions as an infrared cut filter that blocks light on the long wavelength side unnecessary for observation.

  Further, the second group G2 moves toward the image (image plane I) side when focusing from the normal observation state (FIG. 8A) to the close-up observation state (FIG. 8B).

9A, 9B, 9C, and 9D show spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the normal observation state of this embodiment. ) Is shown.
9E, 9F, 9G, and 9H show spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the close-up observation state of this embodiment. ) Is shown.

(Example 5)
An endoscope objective optical system according to Example 5 will be described. 10A is a cross-sectional view of the endoscope objective optical system according to the present embodiment in a normal observation state (far-distance object point), and FIG. 10B is a cross-section in the close-up observation state (near-distance object point). It is a figure.

  This embodiment has, in order from the object side, a first group G1 having a negative refractive power, a second group G2 having a positive refractive power, and a third group G3 having a positive refractive power.

  The first group G1 has, in order from the object side, a plano-concave negative lens L1 having a plane facing the object side. The second group G2 includes, in order from the object side, a positive meniscus lens L2 having a convex surface directed toward the image side, an aperture stop S, and a negative meniscus lens L3 having a convex surface directed toward the object side. The third group G3 includes, in order from the object side, a plano-convex positive lens L4 having a plane directed toward the image side, a plano-convex positive lens L5 having a plane directed toward the object side, a biconvex positive lens L6, and a biconcave negative lens. L7 and. The cover glass CG1 has a plano-convex shape with a flat surface facing the image side.

  The positive lens L4 and the positive lens L5 are cemented to form a cemented lens CL1. The positive lens L6 and the negative lens L7 are cemented to form a cemented lens CL2.

  The parallel plate F1 is arranged on the image side of the third group G3. The parallel plate F1 has a YAG laser cut coating on the object side of the infrared absorption filter and an LD laser cut coating on the image side. As described above, the parallel plate F1 does not directly affect various aberration performances, but functions as an infrared cut filter that blocks light on the long wavelength side unnecessary for observation.

  Further, the second group G2 moves toward the image (image plane I) side when focusing from the normal observation state (FIG. 10A) to the close-up observation state (FIG. 10B).

11A, 11B, 11C, and 11D show spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the normal observation state of this embodiment. ) Is shown.
11E, 11F, 11G, and 11H show spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the close-up observation state of this embodiment. ) Is shown.

(Example 6)
An endoscope objective optical system according to Example 6 will be described. 12A is a cross-sectional view of the endoscope objective optical system according to the present embodiment in a normal observation state (far-distance object point), and FIG. 12B is a cross-section in the close-up observation state (near-distance object point). It is a figure.

  This embodiment has, in order from the object side, a first group G1 having a negative refractive power, a second group G2 having a positive refractive power, and a third group G3 having a positive refractive power.

  The first group G1 has, in order from the object side, a plano-concave negative lens L1 having a plane facing the object side. The second group G2 includes, in order from the object side, a plano-convex positive lens L2 having a flat surface facing the image side, a parallel plate F1, an aperture stop S, and a negative meniscus lens L3 having a convex surface facing the object side. Have. The third group G3 includes, in order from the object side, a biconvex positive lens L4, a negative meniscus lens L5 having a convex surface directed toward the image side, a plano-convex positive lens L6 having a flat surface directed toward the image side, and a biconvex positive lens L7. And a biconcave negative lens L8. The cover glass CG1 is a parallel plate.

  The positive lens L4 and the negative meniscus lens L5 are cemented to form a cemented lens CL1. The positive lens L7 and the negative lens L8 are cemented to form a cemented lens CL2.

  The parallel plate F1 has a YAG laser cut coating on the object side of the infrared absorption filter and an LD laser cut coating on the image side. As described above, the parallel plate F1 does not directly affect various aberration performances, but functions as an infrared cut filter that blocks light on the long wavelength side unnecessary for observation.

  Further, the second group G2 moves toward the image (image plane I) side when focusing from the normal observation state (FIG. 12A) to the close-up observation state (FIG. 12B).

13A, 13B, 13C, and 13D show spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the normal observation state of this example. ) Is shown.
13E, 13F, 13G, and 13H show spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the close-up observation state of this embodiment. ) Is shown.

(Example 7)
An endoscope objective optical system according to Example 7 will be described. FIG. 14A is a cross-sectional view of the endoscope objective optical system according to the present embodiment in a normal observation state (far-distance object point), and FIG. 14B is a cross-section in the close-up observation state (near-distance object point). It is a figure.

  This embodiment has, in order from the object side, a first group G1 having a negative refractive power, a second group G2 having a positive refractive power, and a third group G3 having a positive refractive power.

  The first group G1 has, in order from the object side, a plano-concave negative lens L1 having a plane facing the object side. The second group G2 includes, in order from the object side, a positive meniscus lens L2 having a convex surface directed toward the image side, an aperture stop S, and a plano-concave negative lens L3 having a flat surface directed toward the object side. The third group G3 includes, in order from the object side, a biconvex positive lens L4, a negative meniscus lens L5 having a convex surface directed toward the image side, a biconvex positive lens L6, a biconvex positive lens L7, and a convex surface directed toward the image side. And a negative meniscus lens L8 facing the lens. The cover glass CG1 is a parallel plate.

  The positive lens L4 and the negative meniscus lens L5 are cemented to form a cemented lens CL1. The positive lens L7 and the negative meniscus lens L8 are cemented to form a cemented lens CL2.

  The parallel plate F1 is arranged on the image side of the third group G3. The parallel plate F1 has a YAG laser cut coating on the object side of the infrared absorption filter and an LD laser cut coating on the image side. As described above, the parallel plate F1 does not directly affect various aberration performances, but functions as an infrared cut filter that blocks light on the long wavelength side unnecessary for observation.

  Further, the second group G2 moves toward the image (image plane I) side when focusing from the normal observation state (FIG. 14A) to the close-up observation state (FIG. 14B).

15 (a), (b), (c), and (d) show spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the normal observation state of this example. ) Is shown.
15E, 15F, 15G, and 15H show spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the close-up observation state of this example. ) Is shown.

(Example 8)
An endoscope objective optical system according to Example 8 will be described. 16A is a cross-sectional view of the endoscope objective optical system according to the present embodiment in a normal observation state (far-distance object point), and FIG. 16B is a cross-section in the close-up observation state (near-distance object point). It is a figure.

  This embodiment has, in order from the object side, a first group G1 having a negative refractive power, a second group G2 having a positive refractive power, and a third group G3 having a positive refractive power.

  The first group G1 has, in order from the object side, a plano-concave negative lens L1 having a plane facing the object side. The second group G2 includes, in order from the object side, a plano-convex positive lens L2 having a flat surface directed toward the image side, an aperture stop S, and a negative meniscus lens L3 having a convex surface directed toward the object side. The third group G3 includes, in order from the object side, a biconvex positive lens L4, a negative meniscus lens L5 having a convex surface directed toward the image side, a plano-convex positive lens L6 having a flat surface directed toward the image side, and a biconvex positive lens L7. And a biconcave negative lens L8. The cover glass CG1 is a parallel plate.

  The positive lens L4 and the negative meniscus lens L5 are cemented to form a cemented lens CL1. The positive lens L7 and the negative lens L8 are cemented to form a cemented lens CL2.

  The parallel plate F1 is arranged on the image side of the third group G3. The parallel plate F1 has a YAG laser cut coating on the object side of the infrared absorption filter and an LD laser cut coating on the image side. As described above, the parallel plate F1 does not directly affect various aberration performances, but functions as an infrared cut filter that blocks light on the long wavelength side unnecessary for observation.

  Further, the second group G2 moves toward the image (image plane I) side when focusing from the normal observation state (FIG. 16A) to the close-up observation state (FIG. 16B).

17 (a), (b), (c), and (d) show spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the normal observation state of this example. ) Is shown.
17E, 17F, 17G, and 17H are spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the close-up observation state of the present embodiment. ) Is shown.

(Example 9)
An endoscope objective optical system according to Example 9 will be described. FIG. 18A is a cross-sectional view of the endoscope objective optical system according to the present embodiment in a normal observation state (distance object point), and FIG. 18B is a cross-section in a close-up observation state (short distance object point). It is a figure.

  This embodiment has, in order from the object side, a first group G1 having a negative refractive power, a second group G2 having a positive refractive power, and a third group G3 having a positive refractive power.

  The first group G1 has, in order from the object side, a plano-concave negative lens L1 having a plane facing the object side. The second group G2 includes, in order from the object side, an aperture stop S, and a negative meniscus lens L2 having a convex surface directed toward the object side. The third group G3 includes, in order from the object side, a plano-convex positive lens L3 having a flat surface facing the object side, a negative meniscus lens L4 having a convex surface facing the image side, a biconvex positive lens L5, and a biconvex positive lens L6. And a biconcave negative lens L7. The cover glass CG1 is a parallel plate.

  The positive lens L3 and the negative meniscus lens L4 are cemented to form a cemented lens CL1. The positive lens L6 and the negative lens L7 are cemented to form a cemented lens CL2.

  The parallel plate F1 is arranged on the image side of the third group G3. The parallel plate F1 is arranged on the image side of the third group G3. It is arranged on the image side of the third group G3. The object side of the infrared absorption filter is YAG laser cut coated, and the image side is LD laser cut coated. As described above, the parallel plate F1 does not directly affect various aberration performances, but functions as an infrared cut filter that blocks light on the long wavelength side unnecessary for observation.

  Further, the second group G2 moves toward the image (image plane I) side when focusing from the normal observation state (FIG. 18A) to the close-up observation state (FIG. 18B).

19 (a), (b), (c), and (d) show spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the normal observation state of this example. ) Is shown.
19E, 19F, 19G, and 19H show spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the close-up observation state of this example. ) Is shown.

(Example 10)
An endoscope objective optical system according to Example 10 will be described. 20A is a cross-sectional view of the endoscope objective optical system according to the present embodiment in a normal observation state (far-distance object point), and FIG. 20B is a cross-section in the close-up observation state (near-distance object point). It is a figure.

  This embodiment has, in order from the object side, a first group G1 having a negative refractive power, a second group G2 having a positive refractive power, and a third group G3 having a positive refractive power.

  The first group G1 has, in order from the object side, a plano-concave negative lens L1 having a plane facing the object side. The second group G2 includes, in order from the object side, a negative meniscus lens L2 having a convex surface directed toward the image side, an aperture stop S, and a parallel plate F1. The third group G3 includes, in order from the object side, a biconvex positive lens L3, a negative meniscus lens L4 having a convex surface directed toward the image side, a plano-convex positive lens L5 having a flat surface directed toward the object side, and a biconvex positive lens L6. And a biconcave negative lens L7. The cover glass CG1 has a plano-convex shape with a flat surface facing the image side.

  The positive lens L3 and the negative meniscus lens L4 are cemented to form a cemented lens CL1. The positive lens L6 and the negative lens L7 are cemented to form a cemented lens CL2.

  The parallel plate F1 has a YAG laser cut coating on the object side of the infrared absorption filter and an LD laser cut coating on the image side. As described above, the parallel plate F1 does not directly affect various aberration performances, but functions as an infrared cut filter that blocks light on the long wavelength side unnecessary for observation.

  Further, the second group G2 moves to the image (image plane I) side when focusing from the normal observation state (FIG. 20A) to the close-up observation state (FIG. 20B).

21A, 21B, 21C, and 21D show spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the normal observation state of this example. ) Is shown.
21E, 21F, 21G, and 21H show spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the close-up observation state of this example. ) Is shown.

(Example 11)
An endoscope objective optical system according to Example 11 will be described. 22A is a cross-sectional view of the endoscope objective optical system according to the present example in a normal observation state (far-distance object point), and FIG. 22B is a cross-section in the close-up observation state (near-distance object point). It is a figure.

  This embodiment has, in order from the object side, a first group G1 having a negative refractive power, a second group G2 having a positive refractive power, and a third group G3 having a positive refractive power.

  The first group G1 has, in order from the object side, a plano-concave negative lens L1 having a plane facing the object side. The second group G2 includes, in order from the object side, a positive meniscus lens L2 having a convex surface directed toward the image side, an aperture stop S, and a negative meniscus lens L3 having a convex surface directed toward the object side. The third group G3 includes, in order from the object side, a positive meniscus lens L4 having a convex surface directed toward the object side, a biconvex positive lens L5, a biconvex positive lens L6, and a negative meniscus lens L7 having a convex surface directed toward the image side. , With. The cover glass CG1 has a plano-convex shape with a flat surface facing the image side.

  The positive meniscus lens L4 and the positive lens L5 are cemented to form a cemented lens CL1. The positive lens L6 and the negative meniscus lens L7 are cemented to form a cemented lens CL2.

  The parallel plate F1 is arranged on the image side of the third group G3. The parallel plate F1 has a YAG laser cut coating on the object side of the infrared absorption filter and an LD laser cut coating on the image side. As described above, the parallel plate F1 does not directly affect various aberration performances, but functions as an infrared cut filter that blocks light on the long wavelength side unnecessary for observation.

  Further, the second group G2 moves toward the image (image plane I) side when focusing from the normal observation state (FIG. 22a) to the close-up observation state (FIG. 22 (b)).

23A, 23B, 23C, and 23D show spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the normal observation state of this example. ) Is shown.
23 (e), (f), (g), and (h) show spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the close-up observation state of this example. ) Is shown.

(Example 12)
An endoscope objective optical system according to Example 12 will be described. FIG. 24A is a cross-sectional view of the endoscope objective optical system according to the present embodiment in a normal observation state (far-distance object point), and FIG. 24B is a cross-section in the close-up observation state (near-distance object point). It is a figure.

  This embodiment has, in order from the object side, a first group G1 having a negative refractive power, a second group G2 having a positive refractive power, and a third group G3 having a positive refractive power.

  The first group G1 has, in order from the object side, a plano-concave negative lens L1 having a plane facing the object side. The second group G2 includes, in order from the object side, a plano-convex positive lens L2 having a flat surface facing the image plane, an aperture stop S, and a negative meniscus lens L3 having a convex surface facing the object side. The third group G3 includes, in order from the object side, a biconvex positive lens L4, a negative meniscus lens L5 having a convex surface directed toward the image side, a biconvex positive lens L6, a biconvex positive lens L7, and a biconcave negative lens L8. And have. The cover glass CG1 is a parallel plate.

  The positive lens L4 and the negative meniscus lens L5 are cemented to form a cemented lens CL1. The positive lens L7 and the negative lens L8 are cemented to form a cemented lens CL2.

  Further, the second group G2 moves toward the image (image plane I) side when focusing from the normal observation state (FIG. 24a) to the close-up observation state (FIG. 24 (b)).

  In addition, the plano-convex positive lens L2 having a plane surface facing the image plane has a YAG laser cut coating on the object side of the infrared absorption filter and an LD laser cut coating on the image side. In this way, the plano-convex positive lens L2 whose plane is directed toward the image plane corrects various aberrations and functions as an infrared cut filter that blocks light on the long wavelength side unnecessary for observation.

25A, 25B, 25C, and 25D show spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the normal observation state of this example. ) Is shown.
25E, 25F, 25G, and 25H show spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the close-up observation state of the present embodiment. ) Is shown.

(Example 13)
An endoscope objective optical system according to Example 13 will be described. FIG. 26A is a cross-sectional view of the endoscope objective optical system according to the present embodiment in a normal observation state (far-distance object point), and FIG. 26B is a cross-section in the close-up observation state (near-distance object point). It is a figure.

  This embodiment has, in order from the object side, a first group G1 having a negative refractive power, a second group G2 having a positive refractive power, and a third group G3 having a positive refractive power.

  The first group G1 has, in order from the object side, a plano-concave negative lens L1 having a plane facing the object side. The second group G2 includes, in order from the object side, a positive meniscus lens L2 having a convex surface directed toward the image side, an aperture stop S, and a parallel lithographic plate F1. The third group G3 includes, in order from the object side, a biconvex positive lens L3, a negative meniscus lens L4 having a convex surface directed toward the image side, a plano-convex positive lens L5 having a flat surface directed toward the image side, and a biconvex positive lens L6. And a biconcave negative lens L7. The cover glass CG1 has a plano-convex shape with a flat surface facing the image side.

  The positive lens L3 and the negative meniscus lens L4 are cemented to form a cemented lens CL1. The positive lens L6 and the negative lens L7 are cemented to form a cemented lens CL2.

  The parallel plate F1 has a YAG laser cut coating on the object side of the infrared absorption filter and an LD laser cut coating on the image side. As described above, the parallel plate F1 does not directly affect various aberration performances, but functions as an infrared cut filter that blocks light on the long wavelength side unnecessary for observation.

  Further, the second group G2 moves toward the image (image plane I) side when focusing from the normal observation state (FIG. 26a) to the close-up observation state (FIG. 26 (b)).

27A, 27B, 27C, and 27D show spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the normal observation state of this example. ) Is shown.
27E, 27F, 27G, and 27H show spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the close-up observation state of the present embodiment. ) Is shown.

(Example 14)
An endoscope objective optical system according to Example 14 will be described. 28A is a cross-sectional view of the endoscope objective optical system according to the present embodiment in a normal observation state (far-distance object point), and FIG. 28B is a cross-section in the close-up observation state (near-distance object point). It is a figure.

  This embodiment has, in order from the object side, a first group G1 having a negative refractive power, a second group G2 having a positive refractive power, and a third group G3 having a positive refractive power.

  The first group G1 has, in order from the object side, a plano-concave negative lens L1 having a plane facing the object side. The second group G2 includes, in order from the object side, a plano-convex positive lens L1 having a flat surface facing the object side, a parallel lithographic plate F1, an aperture stop S, and a negative meniscus lens L3 having a convex surface facing the object side. Have. The third group G3 includes, in order from the object side, a biconvex positive lens L4, a negative meniscus lens L5 having a convex surface directed toward the image side, a biconvex positive lens L6, a biconvex positive lens L7, and a biconcave negative lens L8. And have. The cover glass CG1 is a parallel plate.

  The positive lens L4 and the negative meniscus lens L5 are cemented to form a cemented lens CL1. The positive lens L7 and the negative lens L8 are cemented to form a cemented lens CL2.

  The parallel plate F1 has a YAG laser cut coating on the object side of the infrared absorption filter and an LD laser cut coating on the image side. As described above, the parallel plate F1 does not directly affect various aberration performances, but functions as an infrared cut filter that blocks light on the long wavelength side unnecessary for observation.

  Further, the second group G2 moves toward the image (image plane I) side when focusing from the normal observation state (FIG. 28a) to the close-up observation state (FIG. 28 (b)).

29A, 29B, 29C, and 29D show spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the normal observation state of this example. ) Is shown.
29E, 29F, 29G, and 29H show spherical aberration (SA), astigmatism (AS), distortion (DT), and chromatic aberration of magnification (CC) in the close-up observation state of this example. ) Is shown.

The numerical data of each of the above examples are shown below. The symbol is r, the radius of curvature of each lens surface, d is the distance between the lens surfaces, nd is the refractive index of the d line of each lens, and νd is the Abbe number of each lens. Further, S is a brightness diaphragm.
Numerical Example 1
Unit: mm

Surface data Surface number rd nd νd
Object plane ∞ variable
1 ∞ 0.25 1.883 40.76
2 0.6928 Variable
3 -1.5346 0.25 1.95906 17.47
4 -1.5327 0
5 (aperture) ∞ 0.03
6 ∞ 0.25 1.521 65.13
7 ∞ variable
8 4.7889 0.6629 1.755 52.32
9 -2.3563 0.25 1.72825 28.46
10 -2.5887 0.0798
11 2.0771 0.43 1.48749 70.23
12 ∞ 0.03
13 1.9933 0.6448 1.48749 70.23
14 -1.9922 0.25 1.95906 17.47
15 3.6914 0.7872
16 2.5 0.45 1.51633 64.14
17 ∞ 0.3 1.5051 63.26
18 (image plane) ∞

Various data
Normal observation state Close-up observation state Focal length 0.546 0.531
Enabled Fno 3.78 4.09
Angle of view (ω) 65.2 69.0
d0 16 4
d2 1.3872 1.6372
d7 0.78 0.53

Other figures
f3R -5.04
f3L 2.35
f2 19.73
L13 2.70
ΔνR 52.76
ΔνL 23.86
f1 -0.78
f3 1.66

Numerical value example 2
Unit: mm

Surface data Surface number rd nd νd
Object plane ∞ variable
1 ∞ 0.25 1.883 40.76
2 0.7939 Variable
3 -0.744 0.25 1.95906 17.47
4 -0.9028 0
5 (aperture) ∞ 0.03
6 -3.8319 0.25 1.95906 17.47
7 -3.1094 variable
8 4.3993 0.5115 1.755 52.32
9 -1.3114 0.25 1.72825 28.46
10 -2.4982 0.06
11 ∞ 0.29 1.521 65.13
12 ∞ 0.03
13 1.8762 0.5651 1.48749 70.23
14 -1.8743 0.25 1.95906 17.47
15 -14.0844 1.2043
16 2.5 0.45 1.51633 64.14
17 ∞ 0.3 1.5051 63.26
18 (image plane) ∞

Various data
Normal observation state Close-up observation state Focal length 0.544 0.524
Effective Fno 3.34 3.54
Angle of view (ω) 66.2 71.4
d0 16 4
d2 1.528 1.778
d7 0.78 0.53

Other figures
f3R 10.62
f3L 2.17
f2 34.06
L13 2.84
ΔνR 52.76
ΔνL 23.86
f1 -0.90
f3 1.92

Numerical Example 3
Unit: mm

Surface data Surface number rd nd νd
Object plane ∞ variable
1 ∞ 0.25 1.883 40.76
2 ∞ variable
3 0.7325 0.25 1.521 65.13
4 ∞ 0
5 (aperture) ∞ 0.08
6 ∞ 0.25 1.95906 17.47
7 -2.4192 Variable
8 -2.3737 0.6644 1.755 52.32
9 2.5905 0.25 1.72825 28.46
10 -2.2056 0.09
11 -2.4438 0.8394 1.48749 70.23
12 1.516 0.25 1.95906 17.47
13 -1.1897 0.7
14 -11.1363 0.45 1.51633 64.14
15 ∞ 0.3 1.5051 63.26
16 (image plane) ∞

Various data
Normal observation state Close-up observation state Focal length 0.538 0.526
Effective Fno 3.25 3.53
Angle of view (ω) 67.7 70.4
d0 16 6
d2 1.3781 1.6281
d7 0.78 0.53

Other figures
f3R 14.79
f3L 1.80
f2 35.67
L13 2.74
ΔνR 52.76
ΔνL 23.86
f1 -0.83
f3 1.43

Numerical Example 4
Unit: mm

Surface data Surface number rd nd νd
Object plane ∞ variable
1 ∞ 0.25 1.883 40.76
2 0.7727 Variable
3 -3.7458 0.25 1.883 40.76
4 -2.4737 0
5 (aperture) ∞ 0.03
6 1.0761 0.25 1.95906 17.47
7 0.9288 Variable
8 2.4387 0.6997 1.58913 61.14
9 -2.2502 0.268 1.5927 35.31
10 -2.1596 0.09
11 1.4757 0.8499 1.497 81.54
12 -1.4954 0.25 1.95906 17.47
13 -5.4826 0.03
14 ∞ 0.3 1.521 65.13
15 ∞ 0.4418
16 ∞ 0.45 1.51633 64.14
17 ∞ 0.01 1.51 64.05
18 ∞ 0.3 1.5051 63.26
19 (image plane) ∞

Various data
Normal observation state Close-up observation state Focal length 0.551 0.540
Enabled Fno 3.38 3.64
Angle of view (ω) 67.7 68.6
d0 16 4
d2 1.6719 1.9219
d7 0.78 0.53

Other figures
f3R 4.42
f3L 2.11
f2 7.98
L13 2.98
ΔνR 64.07
ΔνL 25.83
f1 -0.88
f3 1.47

Numerical Example 5
Unit: mm

Surface data Surface number rd nd νd
Object plane ∞ variable
1 ∞ 0.25 1.883 40.76
2 0.7962 variable
3 -2.0938 0.25 1.883 40.76
4 -1.6457 0
5 (aperture) ∞ 0.03
6 1.571 0.25 1.95906 17.47
7 1.3424 Variable
8 2.259 0.698 1.58913 61.14
9 ∞ 0.5 1.5927 35.31
10 -1.9954 0.09
11 1.334 0.8581 1.497 81.54
12 -1.3826 0.25 1.95906 17.47
13 11.6902 0.1
14 ∞ 0.3 1.521 65.13
15 ∞ 0.2717
16 2.5 0.45 1.51633 64.14
17 ∞ 0.3 1.5051 63.26
18 (image plane) ∞

Various data
Normal observation state Close-up observation state Focal length 0.548 0.536
Effective Fno 3.36 3.60
Angle of view (ω) 65.9 68.4
d0 16 4
d2 1.6738 1.9238
d7 0.78 0.53

Other figures
f3R 21.58
f3L 2.00
f2 9.32
L13 2.98
ΔνR 64.07
ΔνL 25.83
f1 -0.90
f3 1.59

Numerical Example 6
Unit: mm

Surface data Surface number rd nd νd
Object plane ∞ variable
1 ∞ 0.25 1.883 40.76
2 0.74 variable
3 3.301 0.3 1.72825 28.46
4 ∞ 0.03
5 ∞ 0.4 1.521 65.13
6 ∞ 0
7 (Aperture) ∞ 0.03
8 1.717 0.25 1.95906 17.47
9 1.354 Variable
10 2.908 0.56 1.755 52.32
11 -2.211 0.25 1.72825 28.46
12 -3.32 0.03
13 1.762 0.39 1.48749 70.23
14 ∞ 0.03
15 1.354 0.65 1.48749 70.23
16 -2.211 0.25 1.95906 17.47
17 3.543 0.2666
18 ∞ 0.45 1.51633 64.14
19 ∞ 0.3 1.5051 63.26
20 (image plane) ∞

Various data
Normal observation state Close-up observation state Focal length 0.507 0.503
Effective Fno 2.97 3.27
Angle of view (ω) 67.1 65.4
d0 14.5 4.32
d2 1.23 1.49
d9 0.79 0.53

Other figures
f3R -24.06
f3L 2.16
f2 6.57
L13 3.03
ΔνR 52.76
ΔνL 23.86
f1 -0.84
f3 1.18

Numerical Example 7
Unit: mm

Surface data Surface number rd nd νd
Object plane ∞ variable
1 ∞ 0.25 1.883 40.76
2 0.74 variable
3 -2.3707 0.25 1.95906 17.47
4 -1.9033 0
5 (aperture) ∞ 0.03
6 ∞ 0.25 1.51633 64.14
7 7.6937 Variable
8 2.4209 0.5813 1.755 52.32
9 -3.0078 0.25 1.72825 28.46
10 -5.9576 0.03
11 3.4041 0.3819 1.48749 70.23
12 -4.1003 0.03
13 1.7236 0.6172 1.48749 70.23
14 -1.3518 0.25 1.95906 17.47
15 -12.6443 0.3066
16 ∞ 0.3 1.521 65.13
17 ∞ 0.03
18 ∞ 0.45 1.51633 64.14
19 ∞ 0.3 1.5051 63.26
20 (image plane) ∞

Various data
Normal observation state Close-up observation state Focal length 0.488 0.476
Effective Fno 3.08 3.33
Angle of view (ω) 67.0 70.1
d0 14.5 4.5
d2 1.484 1.734
d7 0.78 0.53

Other figures
f3R 23.75
f3L 2.36
f2 17.72
L13 2.79
ΔνR 52.76
ΔνL 23.86
f1 -0.84
f3 1.39

Numerical Example 8
Unit: mm

Surface data Surface number rd nd νd
Object plane ∞ variable
1 ∞ 0.25 1.883 40.76
2 0.74 variable
3 4.7197 0.25 1.95906 17.47
4 ∞ 0
5 (aperture) ∞ 0.03
6 2.7357 0.25 1.95906 17.47
7 1.9796 variable
8 3.627 0.5557 1.755 52.32
9 -1.6079 0.25 1.72825 28.46
10 -3.1485 0.03
11 1.8635 0.3519 1.48749 70.23
12 ∞ 0.2595
13 1.3795 0.596 1.48749 70.23
14 -2.0598 0.25 1.95906 17.47
15 5.5927 0.05
16 ∞ 0.3 1.521 65.13
17 ∞ 0.03
18 ∞ 0.45 1.51633 64.14
19 ∞ 0.3 1.5051 63.26
20 (image plane) ∞

Various data
Normal observation state Close-up observation state Focal length 0.499 0.491
Effective Fno 3.11 3.40
Angle of view (ω) 66.6 67.4
d0 14.5 4.5
d2 1.5159 1.7659
d7 0.78 0.53

Other figures

f3R 76.43
f3L 2.31
f2 9.33
L13 2.83
ΔνR 52.76
ΔνL 23.86
f1 -0.84
f3 1.26

Numerical Example 9
Unit: mm

Surface data Surface number rd nd νd
Object plane ∞ variable
1 ∞ 0.25 1.883 40.76
2 0.7136 Variable
3 (aperture) ∞ 0.03
4 1.0966 0.25 1.51633 64.14
5 1.13 Variable
6 ∞ 0.6495 1.6968 55.53
7 -2.6028 0.25 1.84666 23.78
8 -2.5096 0.03
9 1.8975 0.504 1.48749 70.23
10 -4.2056 0.03
11 1.5142 0.7998 1.57135 52.95
12 -2.0785 0.25 1.95906 17.47
13 2.4247 0.2956
14 ∞ 0.3 1.521 65.13
15 ∞ 0.03
16 ∞ 0.45 1.51633 64.14
17 ∞ 0.3 1.5051 63.26
18 (image plane) ∞

Various data
Normal observation state Close-up observation state Focal length 0.494 0.495
Effective Fno 3.22 3.57
Angle of view (ω) 68.6 67.6
d0 14.5 8.95
d2 1.5871 1.8371
d5 0.78 0.53

Other figures
f3R -12.27
f3L 3.54
f2 20.24
L13 2.65
ΔνR 35.48
ΔνL 31.75
f1 -0.81
f3 1.26

Numerical Example 10
Unit: mm

Surface data Surface number rd nd νd
Object plane ∞ variable
1 ∞ 0.25 1.883 40.76
2 0.7192 Variable
3 -1.9027 0.25 1.95906 17.47
4 -1.8912 0
5 (aperture) ∞ 0.03
6 ∞ 0.25 1.521 65.13
7 ∞ variable
8 3.9803 0.6627 1.755 52.32
9 -2.2502 0.25 1.62004 36.26
10 -2.9877 0.0783
11 2.4266 0.43 1.48749 70.23
12 ∞ 0.03
13 1.8329 0.8387 1.497 81.54
14 -1.6266 0.25 1.95906 17.47
15 4.8855 0.5797
16 2.22 0.45 1.51633 64.14
17 ∞ 0.3 1.5051 63.26
18 (image plane) ∞

Various data
Normal observation state Close-up observation state Focal length 0.540 0.528
Effective Fno 3.41 3.71
Angle of view (ω) 66.3 69.4
d0 16 5.22
d2 1.3617 1.6117
d7 0.78 0.53

Other figures
f3R -7.38
f3L 2.32
f2 28.00
L13 2.67
ΔνR 64.07
ΔνL 16.06
f1 -0.81
f3 1.59

Numerical Example 11
Unit: mm

Surface data Surface number rd nd νd
Object plane ∞ variable
1 ∞ 0.25 1.883 40.76
2 0.7002 Variable
3 -1.6408 0.25 1.883 40.76
4 -1.4096 0
5 (aperture) ∞ 0.03
6 1.64 0.25 1.95906 17.47
7 1.4213 Variable
8 2.0388 0.6605 1.56883 56.36
9 5.8073 0.5 1.5927 35.31
10 -2.2622 0.09
11 1.4669 0.8274 1.497 81.54
12 -1.2763 0.25 1.95906 17.47
13 -8.1746 0.5463
14 ∞ 0.3 1.521 65.13
15 ∞ 0.03
16 3.6194 0.45 1.51633 64.14
17 ∞ 0.3 1.5051 63.26
18 (image plane) ∞

Various data
Normal observation state Close-up observation state Focal length 0.552 0.539
Effective Fno 3.33 3.62
Angle of view (ω) 65.4 67.9
d0 16 3.61
d2 1.3903 1.6403
d7 0.78 0.53

Other figures
f3R 7.18
f3L 2.04
f2 9.78
L13 2.70
ΔνR 64.07
ΔνL 21.05
f1 -0.79
f3 1.62

Numerical Example 12
Unit: mm

Surface data Surface number rd nd νd
Object plane ∞ variable
1 ∞ 0.25 1.883 40.76
2 0.7033 variable
3 4.0521 0.25 1.521 65.13
4 ∞ 0
5 (aperture) ∞ 0.03
6 0.9342 0.25 1.95906 17.47
7 0.8073 Variable
8 34.0497 0.6623 1.788 47.37
9 -1.4657 0.25 1.69895 30.13
10 -3.5091 0.03
11 1.8582 0.5124 1.48749 70.23
12 -4.3261 0.03
13 1.3211 0.8092 1.497 81.54
14 -2.5128 0.25 1.95906 17.47
15 7.217 0.2934
16 ∞ 0.45 1.51633 64.14
17 ∞ 0.3 1.5051 63.26
18 (image plane) ∞

Various data
Normal observation state Close-up observation state Focal length 0.457 0.455
Effective Fno 3.46 3.84
Angle of view (ω) 67.2 65.3
d0 14.5 4.5
d2 1.3623 1.6123
d7 0.78 0.53

Other figures
f3R 7.83
f3L 3.59
f2 7.02
L13 2.67
ΔνR 64.07
ΔνL 17.24
f1 -0.80
f3 1.19

Numerical Example 13
Unit: mm

Surface data Surface number rd nd νd
Object plane ∞ variable
1 ∞ 0.25 1.883 40.76
2 0.6695 Variable
3 -2.3615 0.25 1.95906 17.47
4 -2.3481 0
5 (aperture) ∞ 0.03
6 ∞ 0.25 1.521 65.13
7 ∞ variable
8 15.3307 0.6704 1.755 52.32
9 -1.7977 0.25 1.72825 28.46
10 -2.3221 0.0799
11 1.9806 0.43 1.48749 70.23
12 ∞ 0.03
13 1.4367 0.8197 1.48749 70.23
14 -2.9756 0.25 1.95906 17.47
15 2.0646 0.3212
16 1.7688 0.7 1.51633 64.14
17 ∞ 0.3 1.5051 63.26
18 (image plane) ∞

Various data
Normal observation state Close-up observation state Focal length 0.440 0.433
Effective Fno 3.03 3.32
Angle of view (ω) 66.7 69.0
d0 16 5.9
d2 1.3801 1.6301
d7 0.78 0.53

Other figures
f3R -6.46
f3L 2.71
f2 42.60
L13 2.69
ΔνR 52.76
ΔνL 23.86
f1 -0.76
f3 1.40

Numerical Example 14
Unit: mm

Surface data Surface number rd nd νd
Object plane ∞ variable
1 ∞ 0.25 1.883 40.76
2 0.74 variable
3 3.8327 0.3 1.72825 28.46
4 ∞ 0.03
5 ∞ 0.4 1.521 65.13
6 ∞ 0
7 (Aperture) ∞ 0.03
8 1.5474 0.25 1.95906 17.47
9 1.2589 Variable
10 3.4686 0.5576 1.755 52.32
11 -2.1971 0.25 1.72825 28.46
12 -3.1268 0.03
13 1.7753 0.4109 1.48749 70.23
14 -16.6469 0.03
15 1.3669 0.7113 1.48749 70.23
16 -2.4408 0.25 1.95906 17.47
17 2.75 0.2456
18 ∞ 0.45 1.51633 64.14
19 ∞ 0.3 1.5051 63.26
20 (image plane) ∞

Various data
Normal observation state Close-up observation state Focal length 0.503 0.500
Effective Fno 3.00 3.32
Angle of view (ω) 68.0 66.0
d0 14.5 4.95
d2 1.2492 1.5092
d9 0.79 0.53

Other figures
f3R -11.89
f3L 2.28
f2 7.44
L13 3.05
ΔνR 52.76
ΔνL 23.86
f1 -0.84
f3 1.16

The values corresponding to the conditional expressions in each example are shown below.

(1) | f3R / f3L |
(2) f2 / L13
(3) ΔνR / ΔνL
(4) ΔνR
(5) | f1 / f3 |

Conditional Expression Example 1 Example 2 Example 3 Example 4 Example 5
(1) 2.15 4.88 8.20 2.09 10.78
(2) 7.32 12.00 13.03 2.68 3.12
(3) 2.21 2.21 2.21 2.48 2.48
(4) 52.8 52.8 52.8 64.1 64.1
(5) 0.47 0.47 0.58 0.60 0.57

Conditional Expression Example 6 Example 7 Example 8 Example 9 Example 10
(1) 11.15 10.06 33.04 3.46 3.17
(2) 2.17 6.34 3.30 7.65 10.48
(3) 2.21 2.21 2.21 1.12 3.99
(4) 52.8 52.8 52.8 35.5 64.1
(5) 0.71 0.60 0.67 0.64 0.51

Conditional Expression Example 11 Example 12 Example 13 Example 14
(1) 3.52 2.18 2.38 5.21
(2) 3.62 2.63 15.83 2.44
(3) 3.04 3.72 2.21 2.21
(4) 64.1 64.1 52.8 52.8
(5) 0.49 0.67 0.54 0.72

  The above-mentioned endoscope optical system may simultaneously satisfy a plurality of configurations. This is preferable for obtaining a good endoscope. Also, the combination of preferable configurations is arbitrary. Further, for each conditional expression, only the upper limit value or the lower limit value of the numerical range of the more limited conditional expression may be limited.

  Although various embodiments of the present invention have been described above, the present invention is not limited to these embodiments only, and is configured by appropriately combining the configurations of these embodiments without departing from the spirit thereof. The form is also within the scope of the present invention.

  INDUSTRIAL APPLICABILITY As described above, the present invention is useful for an endoscope objective optical system having a small overall length and outer diameter, good optical performance, and a mountable lens mechanism.

G1 1st group G2 2nd group G3 3rd group L1-L7 lens F1, CG1, CG2 parallel plate S brightness diaphragm CL1, CL2 cemented lens I image surface (imaging surface)
AX optical axis

Claims (6)

In order from the object side, it is composed of a first group consisting of one negative lens, a positive second group having an aperture stop, and a positive third group having at least two cemented lenses. then by riff Okashingu to be moved only a group,
An endoscope objective optical system that satisfies the following conditional expression (1) .
2 <| f3R / f3L | <16 (1)
here,
f3L is a focal length of the cemented lens closest to the object side among the cemented lenses of the third group,
f3R is a focal length of the cemented lens closest to the image plane among the cemented lenses of the third group,
Is.   The endoscope objective optical system according to claim 1, wherein the following conditional expression (2) is satisfied.
  2 <f2 / L13 <10 (2)
  here,
  f2 is the focal length of the second group,
  L13 is a distance from the image side surface of the negative lens of the first group to the lens surface of the third group closest to the object side,
Is.   The endoscope objective optical system according to claim 1 or 2, wherein the following conditional expressions (3) and (4) are satisfied.
  1.0 <ΔνR / ΔνL <3.0 (3)
  35 <ΔνR (4)
  here,
  ΔνL is the difference in Abbe number between the positive lens and the negative lens forming the cemented lens closest to the object among the cemented lenses of the third group,
  ΔνR is the difference in Abbe number between the positive lens and the negative lens forming the cemented lens closest to the image plane among the cemented lenses of the third group,
Is.   The third group includes, in order from the object side, a positive cemented lens, a positive single lens, and a cemented lens.
The endoscope objective optical system according to any one of claims 1 to 3, wherein the objective optical system is an endoscope objective optical system.   The endoscope objective optical system according to any one of claims 1 to 4, wherein the following conditional expression (5) is satisfied.
  0.55 <| f1 / f3 | <0.75 (5)
  here,
  f1 is the focal length of the first group,
  f3 is the focal length of the third lens unit,
Is. An endoscope comprising the endoscope objective optical system according to any one of claims 1 to 5 .

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