JPH07294806A - Objective lens of oblique view type side view endscope - Google Patents

Abstract

PURPOSE:To provide an objective lens whose aberrations including magnified chromatic aberration are well compensated by providing a first lens group, a second lens group and a reflection member specified altogether. CONSTITUTION:This lens is composed of a first lens group L1 of a negative lens, a reflection member P for changing an optical path having a light beam transmitting part such as a prism and a beam reflection surface and a second lens group L2 of a positive power having image forming function. In this case, the negative lens of the first lens group L1 is made to be eccentric by DELTAy to the second lens group L2, the angle of the reflection surface of the reflection member P is set to be an angle other than 45 deg. to the optical gis of the second lens group L2 or both methods are utilized. Furthermore in this optical system, the conditions; nuA>55 nuB>55 are satisfied, where nuA is the Abbe number of the first lens group L1 and nuB is the Abbe number of the reflection member P.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an objective lens for a medical and industrial side-viewing endoscope, and more particularly to an objective lens for a perspective side-viewing endoscope.

[0002]

2. Description of the Related Art As an endoscope, a side-viewing type endoscope for observing a distal end side portion of a tubular portion inserted into a body cavity or a tube is known. This side-viewing endoscope is further divided into a direct-viewing side-viewing type in which a direction orthogonal to the axis of the distal end tubular portion is the center of the observation visual field, and a perspective side-viewing type in which the visual field center is different from the orthogonal direction. Be divided. In the case of the latter perspective-type side-viewing endoscope, the following optical system can be considered in order to realize this.

For example, in (A) an objective lens system, a reflecting prism having a reflecting surface forming an angle of 45 ° with respect to the axis of the distal end cylindrical portion is arranged, and a lens group located on the object side of this reflecting prism is arranged. An eccentric optical system, (B) an optical system in which the angle of the reflecting surface of the reflecting prism with respect to the axis of the distal end cylindrical portion is set to an angle other than 45 °, and the visual field direction is determined by the angle.
(C) An optical system combining (A) and (B), (D)
An optical system in which two reflecting surfaces are provided on the reflecting prism, and the direction of the visual field center is determined by the combination of the angles of the two reflecting surfaces, (E)
In the optical system of the above (A), instead of decentering the lens group located closer to the object side than the reflecting prism, an optical system in which a fiber located on the image plane or a CCD light receiving element is decentered with respect to the optical axis of the objective lens. System etc.

Of these optical systems, (D) has a complicated prism shape and is expensive to process. Also, (E)
Means that the fiber bundle or CCD element is displaced in the direction perpendicular to the optical axis of the objective lens having an optical axis parallel to the axial direction of the tip tubular portion, so the diameter of the entire tip tubular portion is Has the drawback of becoming larger. Therefore, from the viewpoint of processing cost and downsizing, (A) to (C) are good choices.

On the other hand, it is preferable that the optical axis of the most object-side surface of the optical system is perpendicular to the tip cylindrical portion. That is,
When only the first lens unit L1 and the optical path changing prism P are illustrated, a state in which the optical axis O1 of the first lens L1 is inclined with respect to the side surface 13 of the distal end tubular portion 11 as shown in FIG. 1 (that is, the first lens). The state in which the optical axis O1 of L1 is not orthogonal to the axis 12 of the distal end tubular portion 11 is not preferable, and FIGS.
Is parallel to the axis 12 of the tip tubular portion 11 (that is, the optical axis O1 of the first lens L1 is the axis 1 of the tip tubular portion 11).
2 is preferable). In this case, the shape of the prism P may be such that the incident surface and the reflecting surface form a right angle as shown in FIG. 2 or the shape that does not form a right angle as shown in FIG. As described above, it is preferable that the incident surface and the reflecting surface are at a right angle. In the figure, the surface closest to the object side of the first lens L1 is shown as a plane for ease of explanation, but the same applies to a curved surface if a tangent line or an optical axis is taken into consideration.

In this case, chromatic aberration occurs due to the decentering effect of the lens or the triangular prism effect. Although a glass material having a high refractive index can be used for the optical path changing prism because of the advantages of shortening the optical path length and the condition of total reflection of the light flux, the glass material having a high refractive index generally has a small Abbe number, that is, a large dispersion. The greater the dispersion of the glass material, the greater the degree of deterioration of lateral chromatic aberration on the image plane, and the greater the influence on the deterioration of the imaging performance.Therefore, such a high refractive index and high dispersion glass material is not preferable. is there.

Further, like the optical systems of (B) and (C),
When an optical path changing prism whose reflection surface is at an angle other than 45 ° with respect to the axis of the tip cylindrical portion is used, if the chromatic aberration due to the triangular prism effect is not generated, the entrance surface and the exit surface of the prism will not be at right angles. Therefore, the difficulty of processing increases, which is not preferable.

Further, in the optical systems of (A) and (C), since a part of the lens groups of the optical system is decentered as described above, a chromatic aberration of magnification occurs due to the same prism effect and the image forming performance is deteriorated. It's easy to do.

[0009]

The object of the present invention is to provide these (A) to (C).
Optical system, that is, a first lens group having an optical axis orthogonal to the axis of the tubular distal end portion of the endoscope; and a reflection member for changing the optical path having a light flux transmission portion through which a light flux passes and a reflection surface for reflection. ;
A second lens group having an optical axis parallel to the axis of the tubular tip portion on which the light flux reflected by the reflecting surface of the reflecting member is incident; and at least one of the first lens group and the reflecting member is the second lens group.
A perspective-type side-view endoscope provided such that the optical axis of the lens group is extended to the first lens side via the reflecting member and the optical axis of the first lens group does not coincide with each other. It is an object of the present invention to provide an objective lens in which various aberrations including chromatic aberration of magnification are favorably corrected.

[0010]

SUMMARY OF THE INVENTION In the objective lens of a perspective side-view endoscope of the present invention, in the above optical system, the first lens group consists of one negative lens and the second lens group consists of a positive lens group. And satisfies the following conditional expressions (1) and (2). (1) ν _A > 55 (2) ν _B > 55 where ν _{A is} the Abbe number of the first lens group, and ν _B is the Abbe number of the reflecting member.

The second lens group of the endoscope objective lens of the present invention preferably includes at least one positive lens and at least one set of positive and negative cemented lenses.

Further, this objective lens preferably satisfies the following conditional expressions (3) to (7). _{(3) -3.2 <f 1 /f<-1.3} (4) 0.65 <| R B | / f <1.25 (5) ν 2P> 35 (6) ν 2N <30 (7 ) -0.7 <m ₂ <-0.2 where, f: focal length of the entire optical system, f _1: focal length of the first lens group, R _B: bonding of cemented lens second lens group Radius of curvature of surface, ν _2P : average Abbe number of positive lens in second lens group, ν _2N : Abbe number of negative lens in second lens group, m ₂ : imaging magnification of second lens group, Is.

The second lens group is more preferably composed of one positive lens and one set of positive and negative cemented lenses.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The lens system of the present invention mainly comprises a first lens unit L1 of a negative lens used for the purpose of enlarging a viewing angle, a light beam transmitting portion P1 such as a prism and a light beam reflecting surface P2.
And a second lens unit having a positive power and having an image forming function. The reflecting member P may be any member as long as it has the light flux transmitting portion P1 and the reflecting surface P2, and in addition to the triangular prism, a reflecting prism having a roof surface for changing the optical path is also used for double-sided correction. And, the positional relationship where the optical axis of the second lens group and the optical axis of the first lens group do not coincide with the optical axis of the second lens group that is extended to the first lens side via the reflecting member, which is necessary for the perspective side-viewing endoscope, is inexpensive. In order to obtain a small size and a small size, the negative lens of the first lens unit L1 is decentered by Δy with respect to the second lens unit L2 (FIG. 4), or the reflecting member P
Of the reflection surface P2 of the second lens unit L2 with respect to the optical axis
It is configured by setting an angle other than 5 degrees (FIG. 5) or using both of them.

As described above, in such a structure, lateral chromatic aberration occurs. This is particularly a factor for deteriorating the image quality when the diameter of the fiber used in the endoscope and the image size of the CCD element used in the electronic endoscope become smaller and higher definition is required. It becomes a problem. Therefore, it is necessary to pay attention to the selection of the Abbe number of the glass material used for the first lens and the reflecting prism.

Conditional expressions (1) and (2) are conditions for this. If these conditions are not met, the above eccentric effect,
The chromatic aberration due to the triangular prism effect, particularly the chromatic aberration of magnification, deteriorates, and the image quality deteriorates.

The second lens group is a group having an image forming effect for condensing the light flux which has become divergent light from the first lens group on the image plane. Since the light flux emitted from the first lens group has spherical aberration, chromatic aberration, and astigmatism that are all over, it is necessary to appropriately correct these in the second lens group. Therefore, it is preferable that the second lens group includes at least one positive lens and at least one set of positive and negative cemented lenses.

In order to correct these various aberrations to a higher degree, it is preferable to satisfy the following conditional expressions (3) to (7).

Conditional expression (3) relates to the focal length or the power of the first lens. The power of this lens should be strong to some extent to reduce the Petzval sum, and conversely to weak to suppress the increase in chromatic aberration due to decentering and the asymmetry of aberration, it is necessary to set it in an appropriate range.
When the value exceeds the upper limit, the power becomes too strong, the amount of chromatic aberration increases, and the image quality deteriorates, and the symmetry of the performance in the screen collapses, and the image quality cannot be maintained uniform. On the other hand, if the value goes below the lower limit, the power becomes too weak, the Petzval sum cannot be reduced, and the field curvature cannot be corrected. It will be inappropriate.

Conditional expression (4) relates to the radius of curvature of the cemented surface of the cemented lens in the second lens group. This is a condition necessary to keep the chromatic aberration of the entire lens system small together with the following conditional expressions (5) and (6). If the upper limit is exceeded, the radius of curvature becomes too large and the surface power weakens, making it impossible to correct chromatic aberration, especially lateral chromatic aberration.
When the value goes below the lower limit, on the contrary, the radius of curvature becomes too small, and the chromatic aberration, particularly the axial chromatic aberration increases too much, and the shape becomes difficult to process as a lens.

Conditional expressions (5) and (6) relate to the Abbe number of the glass material in the second lens group. If neither of these conditions is satisfied, both axial chromatic aberration and lateral chromatic aberration cannot be corrected sufficiently.

Conditional expression (7) relates to the imaging magnification in the second lens group. In the lens system of the present invention, as described above, the first
Chromatic aberration occurs in the lens group and the reflecting member. This chromatic aberration inevitably occurs because of the perspective type, and there is no way to correct it to zero. Therefore, it is necessary to select the magnification of the second lens group so as not to increase this chromatic aberration but to reduce it.

When the value goes below the lower limit of the conditional expression (7), the magnification becomes large and the aberration increases, which is not preferable. On the contrary, if the upper limit is exceeded, the distance between the first lens group and the second lens group becomes large, and the total lens length increases, or it becomes necessary to increase the power of the second lens group in order to prevent the total length increase. Spherical aberration, chromatic aberration, and curvature of field occur, degrading optical performance.

Considering the cost of the lens, the second
It is desirable that the lens group be composed of one positive lens and one set of positive and negative cemented lenses.

To further improve the optical performance, it is preferable to satisfy the following conditional expressions (8) and (9). (8) n _2PA > 1.6 (9) ν _2PB > 37 where n _{2PA is} the refractive index of the positive lens not cemented in the second lens group, and ν _2PB is the positive lens cemented in the second lens group. Abbe number.

Conditional expression (8) is a condition for reducing the Petzval sum in the entire lens system and better correcting the field curvature. In the lens system of the present invention, as indicated by the conditional expression (3), the power of the first lens group is relatively weak.
Therefore, since the Petzval sum tends to be large, it is preferable to reduce the Petzval sum by selecting the refractive index of the non-bonded positive lens in the second lens group so as to satisfy the conditional expression (8).

Conditional expression (9) is a condition for correcting chromatic aberration, particularly lateral chromatic aberration, to a higher degree. The Abbe number of the glass material used for the positive lens in the second lens group is set by the conditional expression (5). However, the positive lens attached to the second lens group may further satisfy the conditional expression (9). desirable.

Specific numerical examples will be described below. In each of Examples 1 to 7 below, one negative lens forming the first lens group has a flat incident surface side. In each case, the negative lens of the first lens unit L1 is decentered by Δy with respect to the second lens unit L2, and the angle α of the reflecting surface P2 of the reflecting member P is the optical axis of the second lens unit L2. Is an embodiment in which the present invention is applied to a perspective side-viewing endoscope in which the type of FIG. 5 is set to an angle other than 45 degrees. S is a diaphragm.

[Embodiment 1] FIG. 6 is a lens configuration diagram of a first embodiment of the present invention. Table 1 shows specific numerical data of this lens system, FIG. 7 shows lateral aberrations, and FIG. 8 shows lateral chromatic aberrations.
Shown in. In the lateral aberration diagram, Y represents the image height, DS represents the amount of curvature of field of the sagittal light flux, and DM represents the amount of curvature of field of the meridional light flux.

In the table and drawings, F _NO is F number, f is focal length, M is lateral magnification, ω is total angle of view, Y is image height, r _i is radius of curvature of each lens surface, and d _i is lens thickness. Alternatively, the lens spacing, N is the refractive index of the d line, and ν is the Abbe number of the d line.
It should be noted that the numerical data of any of the examples includes data of the cover glass and the adhesive of the CCD light receiving element formed by bonding two parallel plane plates to the final surface. However, the present invention can of course be applied even when there is no cover glass or adhesive.

[0031]

[Table 1] Δy = -0.15 α = 45.56. (Reflecting surface is the fourth surface) F _NO = 1: 5.6 f = 1.83 M = -0.258 Y = ± 1.209 ω = 72.2 ° surface NO rd N ν 1 ∞ 0.35 1.51633 64.1 2 1.773 0.77--3 ∞ 1.20 1.48749 70.2 4 ∞ 1.20 1.48749 70.2 5 ∞ 0.32--6 5.157 2.14 1.83400 37.2 7 -2.393 0.18--8 11.516 0.30 1.92286 21.3 9 1.469 1.73 1.70200 40.1 10 -28.125 1.71--11 ∞ 0.60 1.53000 60.0 12 ∞ 0.40 1.54000 40.0 13 ∞-- -

[Embodiment 2] FIG. 9 is a lens configuration diagram of a second embodiment of the present invention. Specific numerical data of this lens system are shown in Table 2, lateral aberrations are shown in FIG. 10, and lateral chromatic aberrations are shown in FIG.

[0033]

[Table 2] Δy = -0.15 α = 45.56. (Reflective surface is the fourth surface) F _NO = 1: 5.6 f = 1.30 M = -0.171 Y = ± 1.209 ω = 122.3 ° surface NO rd N ν 1 ∞ 0.30 1.51633 64.1 2 1.758 1.34--3 ∞ 2.31 1.48749 70.2 4 ∞ 1.20 1.48749 70.2 5 ∞ 0.32--6 4.841 1.37 1.83400 37.2 7 -2.415 0.33--8 12.226 0.30 1.92286 21.3 9 1.433 1.18 1.73400 51.5 10 -22.781 1.14--11 ∞ 0.60 1.53000 60.0 12 ∞ 0.40 1.54000 40.0 13 ∞-- -

[Embodiment 3] FIG. 12 is a lens configuration diagram of a third embodiment of the present invention. Specific numerical data of this lens system are shown in Table 3, lateral aberrations are shown in FIG. 13, and lateral chromatic aberrations are shown in FIG.

[0035]

[Table 3] Δy = -0.15 α = 45.56. (Reflective surface is the fourth surface) F _NO = 1: 5.6 f = 1.45 M = -0.200 Y = ± 1.209 ω = 96.6 ° surface NO rd N ν 1 ∞ 0.30 1.51633 64.1 2 1.687 1.01--3 ∞ 1.20 1.48749 70.2 4 ∞ 1.68 1.48749 70.2 5 ∞ 0.32--6 4.043 1.23 1.83400 37.2 7 -2.517 0.16--8 8.691 0.30 1.92286 21.3 9 1.297 1.29 1.70200 40.1 10 -22.836 1.32--11 ∞ 0.60 1.53000 60.0 12 ∞ 0.40 1.54000 40.0 13 ∞-- -

[Embodiment 4] FIG. 15 is a lens configuration diagram of a fourth embodiment of the present invention. Specific numerical data of this lens system are shown in Table 4, lateral aberrations are shown in FIG. 16, and lateral chromatic aberrations are shown in FIG.

[0037]

[Table 4] Δy = -0.15 α = 45.56. (Reflection surface is the fourth surface) F _NO = 1: 5.6 f = 1.26 M = -0.168 Y = ± 1.209 ω = 118.4 ° surface NO rd N ν 1 ∞ 0.30 1.51633 64.1 2 1.809 1.28--3 ∞ 1.20 1.48749 70.2 4 ∞ 1.94 1.48749 70.2 5 ∞ 0.32--6 4.142 1.21 1.83400 37.2 7 -2.511 0.20--8 8.021 0.30 1.92286 21.3 9 1.176 0.76 1.70154 41.2 10 -8.679 1.27--11 ∞ 0.60 1.53000 60.0 12 ∞ 0.40 1.54000 40.0 13 ∞-- -

[Embodiment 5] FIG. 18 is a lens configuration diagram of a fifth embodiment of the present invention. Table 5 shows specific numerical data of this lens system, FIG. 19 shows lateral aberrations, and FIG. 20 shows chromatic aberration of magnification.

[0039]

[Table 5] Δy = -0.20 α = 46.84. (Reflection surface is the fourth surface) F _NO = 1: 5.6 f = 1.48 M = -0.193 Y = ± 1.209 ω = 101.5 ° surface NO rd N ν 1 ∞ 0.40 1.51633 64.1 2 1.787 1.07--3 ∞ 1.26 1.51633 64.1 4 ∞ 2.20 1.51633 64.1 5 ∞ 0.99--6 7.469 0.78 1.72916 54.7 7 -2.230 0.20--8 19.154 1.29 1.60311 60.7 9 -1.333 0.40 1.76182 26.5 10 -9.322 1.73--11 ∞ 0.60 1.53000 60.0 12 ∞ 0.40 1.54000 40.0 13 ∞- --

[Sixth Embodiment] FIG. 21 is a lens configuration diagram of a sixth embodiment of the present invention. Specific numerical data of this lens system are shown in Table 6, lateral aberrations are shown in FIG. 22, and lateral chromatic aberrations are shown in FIG.

[0041]

[Table 6] Δy = -0.20 α = 46.84. (Reflection surface is the fourth surface) F _NO = 1: 5.6 f = 1.43 M = -0.187 Y = ± 1.209 ω = 100.7 ° surface NO rd N ν 1 ∞ 0.80 1.48749 70.2 2 1.589 1.00--3 ∞ 1.20 1.48749 70.2 4 ∞ 1.94 1.48749 70.2 5 ∞ 0.63--6 6.785 0.61 1.83400 37.2 7 -2.508 0.52--8 5.841 0.30 1.84666 23.8 9 1.320 0.50 1.61800 63.4 10 -19.555 1.71--11 ∞ 0.60 1.53000 60.0 12 ∞ 0.40 1.54000 40.0 13 ∞-- -

[Embodiment 7] FIG. 24 is a lens configuration diagram of the seventh embodiment of the present invention. Table 7 shows specific numerical data of this lens system, FIG. 25 shows lateral aberrations, and FIG. 26 shows chromatic aberration of magnification.

[0043]

[Table 7] Δy = -0.20 α = 46.84. (Reflecting surface is the fourth surface) F _NO = 1: 5.6 f = 1.45 M = -0.189 Y = ± 1.209 ω = 102.0 ° surface NO rd N ν 1 ∞ 0.40 1.51633 64.1 2 1.803 1.33--3 ∞ 1.27 1.48749 70.2 4 ∞ 2.20 1.48749 70.2 5 ∞ 0.46--6 5.794 1.51 1.83400 37.2 7 -2.322 0.11--8 10.399 0.30 1.92286 21.3 9 1.483 1.50 1.69680 55.5 10 479.027 1.51--11 ∞ 0.60 1.53000 60.0 12 ∞ 0.40 1.54000 40.0 13 ∞---

Table 8 shows the values corresponding to the conditional expressions of Examples 1 to 7.

[Table 8] Conditional expression (1) Conditional expression (2) Conditional expression (3) Conditional expression (4) Conditional expression (5) Example 1 64.1 70.2 -1.880 0.804 38.7 Example 2 64.1 70.2 -2.619 1.102 46.0 Example 3 64.1 70.2 -2.256 0.896 38.7 Example 4 64.1 70.2 -2.772 0.930 39.2 Example 5 64.1 64.1 -2.345 0.903 57.7 Example 6 70.2 70.2 -2.272 0.920 50.3 Example 7 70.2 70.2 -2.442 1.037 46.4 Conditional expression (6) Conditional expression ( 7) Conditional Expression (8) Conditional Expression (9) Example 1 21.3 -0.532 1.834 40.1 Example 2 21.3 -0.382 1.834 54.8 Example 3 21.3 -0.443 1.834 40.1 Example 4 21.3 -0.361 1.834 41.2 Example 5 26.5 -0.426 1.72916 60.7 Example 6 23.8 -0.440 1.834 63.4 Example 7 21.3 -0.414 1.834 55.5

As is apparent from Table 8, the numerical values of Examples 1 to 7 all satisfy the conditional expressions (1) to (9).

[0046]

According to the present invention, it is possible to obtain an objective lens for a perspective side-viewing endoscope in which various aberrations including lateral chromatic aberration have been satisfactorily corrected.

[Brief description of drawings]

FIG. 1 is an optical configuration diagram of a main part showing an arrangement example of optical elements in a distal end tubular portion of a perspective side-view endoscope.

FIG. 2 is an optical configuration diagram of a main part showing another arrangement example.

FIG. 3 is an optical configuration diagram of a main part showing still another arrangement example.

FIG. 4 is a first perspective side view endoscope according to the present invention;
It is an optical block diagram which shows the example of arrangement | positioning of a 2nd lens group and a reflection member.

FIG. 5 is a first perspective side view endoscope according to the present invention;
It is an optical block diagram which shows another example of arrangement | positioning of a 2nd lens group and a reflection member.

FIG. 6 is a lens configuration diagram showing a first example of the perspective side-viewing endoscope objective lens according to the present invention.

FIG. 7 is a lateral aberration diagram of the lens system of FIG.

8 is a lateral chromatic aberration diagram of the lens system of FIG.

FIG. 9 is a lens configuration diagram showing a second example of the perspective side-viewing endoscope objective lens according to the present invention.

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

11 is a lateral chromatic aberration diagram of the lens system of FIG.

FIG. 12 is a lens configuration diagram showing a third embodiment of the perspective side-viewing endoscope objective lens according to the present invention.

13 is a lateral aberration diagram of the lens system in FIG.

14 is a lateral chromatic aberration diagram of the lens system of FIG.

FIG. 15 is a lens configuration diagram showing a fourth example of the perspective side-viewing endoscope objective lens according to the present invention.

16 is a lateral aberration diagram of the lens system in FIG.

17 is a lateral chromatic aberration diagram of the lens system of FIG.

FIG. 18 is a lens configuration diagram showing a fifth example of the perspective side-viewing endoscope objective lens according to the present invention.

FIG. 19 is a lateral aberration diagram of the lens system in FIG.

20 is a lateral chromatic aberration diagram of the lens system in FIG. 18.

FIG. 21 is a lens configuration diagram showing a sixth example of the perspective side-viewing endoscope objective lens according to the present invention.

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

23 is a lateral chromatic aberration diagram of the lens system in FIG. 21. FIG.

FIG. 24 is a lens configuration diagram showing a seventh example of the perspective side-viewing endoscope objective lens according to the present invention.

25 is a lateral aberration diagram of the lens system in FIG. 24.

FIG. 26 is a lateral chromatic aberration diagram of the lens system of FIG. 24.

[Explanation of symbols]

 L1 First lens group L2 Second lens group P Prism

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[Procedure amendment]

[Submission date] June 15, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

[0009]

The object of the present invention is to provide these (A) to (C).
Optical system, that is, a first lens group having an optical axis orthogonal to the axis of the tubular distal end portion of the endoscope; and a reflection member for changing the optical path having a light flux transmission portion through which a light flux passes and a reflection surface for reflection. ;
A second lens group having an optical axis parallel to the axis of the tubular tip portion on which the light flux reflected by the reflecting surface of the reflecting member is incident; and the optical axis of the first lens group is the light of the second lens group. and the axis of the extension of the axis to the first lens side through the reflecting member, in perspective-type objective lens side viewing endoscope provided so that the positional relationship do not match, the aberrations including the chromatic aberration of magnification The objective is to provide a well-corrected objective lens.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction content]

[0031]

[Table 1] Δy = -0.15 α = 45.56 ° (Reflection surface is the 4th surface) F _NO = 1: 5.6 f = 1.83 M = -0.258 Y = ± 1.209 ω = 72.2 ° surface NO r _i d _i N ν 1 ∞ 0.35 1.51633 64.1 2 1.773 0.77--3 ∞ 1.20 1.48749 70.2 4 ∞ 1.20 1.48749 70.2 5 ∞ 0.32--6 5.157 2.14 1.83400 37.2 7 -2.393 0.18--8 11.516 0.30 1.92286 21.3 9 1.469 1.73 1.70200 40.1 10 -28.125 1.71- -11 ∞ 0.60 1.53000 60.0 12 ∞ 0.40 1.54000 40.0 13 ∞---

[Submission date] June 15, 1995

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0033

[Correction method] Change

[Correction content]

[0033]

[Table 2] Δy = -0.15 α = 45.56 ° (Reflection surface is the fourth surface) F _NO = 1: 5.6 f = 1.30 M = -0.171 Y = ± 1.209 ω = 122.3 ° surface NO r _i d _i N ν 1 ∞ 0.30 1.51633 64.1 2 1.758 1.34--3 ∞ 2.31 1.48749 70.2 4 ∞ 1.20 1.48749 70.2 5 ∞ 0.32--6 4.841 1.37 1.83400 37.2 7 -2.415 0.33--8 12.226 0.30 1.92286 21.3 9 1.433 1.18 1.73400 51.5 10 -22.781 1.14- -11 ∞ 0.60 1.53000 60.0 12 ∞ 0.40 1.54000 40.0 13 ∞---

[Submission date] June 15, 1995

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0035

[Correction method] Change

[Correction content]

[0035]

[Table 3] Δy = -0.15 α = 45.56 ° (reflection surface is the fourth surface) F _NO = 1: 5.6 f = 1.45 M = -0.200 Y = ± 1.209 ω = 96.6 ° surface NO r _i d _i N ν 1 ∞ 0.30 1.51633 64.1 2 1.687 1.01--3 ∞ 1.20 1.48749 70.2 4 ∞ 1.68 1.48749 70.2 5 ∞ 0.32--6 4.043 1.23 1.83400 37.2 7 -2.517 0.16--8 8.691 0.30 1.92286 21.3 9 1.297 1.29 1.70200 40.1 10 -22.836 1.32- -11 ∞ 0.60 1.53000 60.0 12 ∞ 0.40 1.54000 40.0 13 ∞---

[Submission date] June 15, 1995

[Procedure correction 6]

[Document name to be amended] Statement

[Name of item to be corrected] 0037

[Correction method] Change

[Correction content]

[0037]

[Table 4] Δy = -0.15 α = 45.56 ° (Reflection surface is the fourth surface) F _NO = 1: 5.6 f = 1.26 M = -0.168 Y = ± 1.209 ω = 118.4 ° surface NO r _i d _i N ν 1 ∞ 0.30 1.51633 64.1 2 1.809 1.28--3 ∞ 1.20 1.48749 70.2 4 ∞ 1.94 1.48749 70.2 5 ∞ 0.32--6 4.142 1.21 1.83400 37.2 7 -2.511 0.20--8 8.021 0.30 1.92286 21.3 9 1.176 0.76 1.70154 41.2 10 -8.679 1.27- -11 ∞ 0.60 1.53000 60.0 12 ∞ 0.40 1.54000 40.0 13 ∞---

[Submission date] June 15, 1995

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0039

[Correction method] Change

[Correction content]

[0039]

[Table 5] Δy = -0.20 α = 46.84 ° (Reflective surface is the 4th surface) F _NO = 1: 5.6 f = 1.48 M = -0.193 Y = ± 1.209 ω = 101.5 ° surface NO r _i d _i N ν 1 ∞ 0.40 1.51633 64.1 2 1.787 1.07--3 ∞ 1.26 1.51633 64.1 4 ∞ 2.20 1.51633 64.1 5 ∞ 0.99--6 7.469 0.78 1.72916 54.7 7 -2.230 0.20--8 19.154 1.29 1.60311 60.7 9 -1.333 0.40 1.76182 26.5 10 -9.322 1.73 --11 ∞ 0.60 1.53000 60.0 12 ∞ 0.40 1.54000 40.0 13 ∞---

[Submission date] June 15, 1995

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0041

[Correction method] Change

[Correction content]

[0041]

[Table 6] Δy = -0.20 α = 46.84 ° (Reflecting surface is the 4th surface) F _NO = 1: 5.6 f = 1.43 M = -0.187 Y = ± 1.209 ω = 100.7 ° surface NO r _i d _i N ν 1 ∞ 0.80 1.48749 70.2 2 1.589 1.00--3 ∞ 1.20 1.48749 70.2 4 ∞ 1.94 1.48749 70.2 5 ∞ 0.63--6 6.785 0.61 1.83400 37.2 7 -2.508 0.52--8 5.841 0.30 1.84666 23.8 9 1.320 0.50 1.61800 63.4 10 -19.555 1.71- -11 ∞ 0.60 1.53000 60.0 12 ∞ 0.40 1.54000 40.0 13 ∞---

[Submission date] June 15, 1995

[Procedure Amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0043

[Correction method] Change

[Correction content]

[0043]

[Table 7] Δy = -0.20 α = 46.84 ° (Reflection surface is the 4th surface) F _NO = 1: 5.6 f = 1.45 M = -0.189 Y = ± 1.209 ω = 102.0 ° surface NO r _i d _i N ν 1 ∞ 0.40 1.51633 64.1 2 1.803 1.33--3 ∞ 1.27 1.48749 70.2 4 ∞ 2.20 1.48749 70.2 5 ∞ 0.46--6 5.794 1.51 1.83400 37.2 7 -2.322 0.11--8 10.399 0.30 1.92286 21.3 9 1.483 1.50 1.69680 55.5 10 479.027 1.51-- 11 ∞ 0.60 1.53000 60.0 12 ∞ 0.40 1.54000 40.0 13 ∞---

Claims (4)

[Claims] 1. A first lens group consisting of a single negative lens having an optical axis orthogonal to the axis of the tubular tip portion of the endoscope; and a light flux transmitting portion for transmitting a light flux and a reflecting surface for reflecting the light flux. A reflecting member for changing the optical path; a second lens group having a positive power and having an optical axis parallel to the axis of the cylindrical tip portion on which the light flux reflected by the reflecting surface of the reflecting member is incident; At least one of the first lens group and the reflecting member is the second lens.
Objective lens of the perspective endoscope provided such that the optical axis of the lens group is extended to the first lens side via the reflecting member and the optical axis of the first lens group does not coincide with each other. In, an objective lens of a perspective side-view endoscope that satisfies the following conditional expressions (1) and (2). (1) ν _A > 55 (2) ν _B > 55 where ν _{A is} the Abbe number of the first lens group, and ν _{B is} the Abbe number of the reflecting member. 2. The objective lens for a perspective side-viewing endoscope according to claim 1, wherein the second lens group includes at least one positive lens and at least one set of positive and negative cemented lenses. 3. The objective lens for a perspective side-view endoscope according to claim 2, wherein the following conditional expressions (3) to (7) are satisfied. _{(3) -3.2 <f 1 /f<-1.3} (4) 0.65 <| R B | / f <1.25 (5) ν 2P> 35 (6) ν 2N <30 (7 ) -0.7 <m ₂ <-0.2 where, f: focal length of the entire optical system, f _1: focal length of the first lens group, R _B: adhesion of cemented lens in the second lens group Radius of curvature of mating surface, ν _2P : average Abbe number of positive lens in second lens group, ν _2N : Abbe number of negative lens in second lens group, m ₂ : imaging magnification of second lens group . 4. The objective lens for a perspective side-view endoscope according to claim 3, wherein the second lens group is composed of one positive lens and one set of positive and negative cemented lenses.