JP4814746B2 - Endoscope objective optical system - Google Patents

Description

  The present invention relates to an endoscope objective optical system for medical use or industrial use, and particularly to an endoscope objective optical system suitable for perspective or side view provided with an optical member that changes the viewing direction.

  In recent years, image sensors such as CCDs have become compact and high in image quality due to advances in pixel size miniaturization technology. As a result, in endoscope systems using image sensors such as CCDs, high performance and compact objective optics A system is needed. In particular, a perspective or side-view optical system using a field-of-view conversion optical element is larger in size than the direct-view optical system. Therefore, this type of perspective or side view optical system is required to be further miniaturized.

As such a perspective or side-view objective optical system using a field conversion element, an optical system described in the following document is known.
JP 2000-89105 A JP 2004-226722 A Among these conventional examples, the optical system described in Patent Document 1 is a high-definition image sensor such as a high-definition CCD in the trend of improving the image quality of endoscope systems in recent years. A small objective optical system with high performance. This objective optical system has been reduced in size by reducing the number of lenses, but because it does not use a cemented lens, it has difficulty in correcting chromatic aberration and cannot cope with higher pixel counts. It is a system. In addition, the optical system described in Patent Document 2 is small, but an angle of view of about 100 ° is not a sufficient angle of view.

  Furthermore, although the optical system described in Patent Document 3 has an angle of view of about 120 °, the overall length is large and the scope is enlarged.

The present invention is for eliminating the disadvantages of the conventional example, and is an endoscope objective optical system using a visual field direction conversion element, which has a wide angle of view, a short overall length, a small and high-definition optical system The present invention provides a high-performance objective optical system that can cope with the above.

  The endoscope objective optical system according to the present invention includes, in order from the object side, a negative first group, a diaphragm, and a positive second group, and a visual field between the first group and the second group. An optical member for changing the direction is arranged so that the following conditions (1), (2), and (3) are satisfied.

(1) -0.8 <F1 / F <-0.4
(2) 1.0 <F2 / F ≦ 1.333
(3) 0.9 <D / F <1.6
Where F is the focal length of the entire objective optical system, F1 is the focal length of the first group, F2 is the focal length of the second group, and D is the air-converted length from the first lens to the stop.

  In general, an endoscope objective optical system needs to be screened in a living body in order to find a lesion, and therefore it is desired to have a wide angle of view. However, the objective optical system in perspective or side view requires an arrangement of optical members for changing the viewing direction, and a space for arranging the optical members must be provided behind the first lens. Therefore, if the distance from the entrance surface of the first lens to the stop becomes long and the field angle is too wide, the principal ray height of the off-axis light beam in the first lens becomes undesirably high. Therefore, many endoscope objective optical systems for perspective and side views have an angle of view of about 100 °. In the endoscope objective optical system of the present invention, the focal length F1 of the first group satisfies the above condition (1) in order to keep the ray height in the first lens low while having a wide angle of view.

  In this condition (1), when the value of F1 / F exceeds the lower limit of −0.8, the power of the first group becomes weak, and a sufficient space is provided for arranging an optical member for optical path conversion such as a prism. In addition to this, the height of the light beam in the first lens increases, the diameter of the lens increases and the size increases, and it becomes difficult to secure a wide angle of view.

  Further, if F1 / F exceeds the upper limit of −0.4 in condition (1), the power of the first lens unit becomes too strong, which is not preferable because the field curvature becomes large.

  In the objective optical system of the present invention, it is preferable from the viewpoint of aberration correction or the like that the focal length F2 of the second group satisfies the condition (2).

Under this condition (2), if the value of F2 / F exceeds the lower limit of 1.0, the power of the second group becomes too strong and it becomes difficult to correct spherical aberration and further coma. Further, if the value of F2 / F exceeds the upper limit of 1.333 , the total length of the optical system becomes long, which is not preferable.

  In addition, since the objective optical system of the present invention is a perspective or side-view endoscope objective optical system, an optical member for converting the viewing direction is necessary. As this optical member, a prism or a mirror is used, but it is necessary to secure a space for arranging these optical members between the first group and the stop.

  The condition (3) is a condition necessary for that.

  In this condition (3), when the value of D / F exceeds the lower limit of 0.9, it becomes impossible to secure a space for arranging the viewing direction converting optical member. In particular, when the viewing direction conversion angle is about 30 ° to 60 °, it is necessary to provide a twice-reflecting prism or mirror, but it is difficult to ensure the optical path length for that purpose.

  In the condition (3), if the D / F value exceeds the upper limit of 1.6, a sufficient space for arranging the optical member for changing the viewing direction can be secured. The distance to the 1st reflective surface of a direction change optical member becomes long, and the diameter of the endoscope front-end | tip becomes large, and is unpreferable.

In the endoscope objective optical system of the present invention having such a configuration, it is desirable that the second group is composed of at least a positive lens and a cemented lens in order to correct chromatic aberration and the like. Furthermore, it is more desirable for correction of chromatic aberration if the cemented lens in the second group has a configuration in which a positive lens and a negative lens are bonded together and the following conditions (4) and (5) are satisfied.

(4) 1.0 <f1 / F <2.0
(5) -1.8 <f2 / F <-0.8
Here, f1 is the focal length of the positive lens of the cemented lens, f2 is the focal length of the negative lens of the cemented lens, and F is the focal length of the entire objective optical system.

  These conditions (4) and (5) are conditions necessary for correcting chromatic aberration, and if the value of f1 / F is 1.0 or less of the lower limit value in condition (4), the power of the positive lens of the cemented lens Increases, the amount of axial chromatic aberration increases, and causes color flare. On the other hand, if the value of f1 / F exceeds 2.0, which is the upper limit value of the condition (4), the power of the positive lens becomes weak, leading to an increase in the overall length of the optical system.

  Further, in condition (5), when the value of f2 / F becomes smaller than the lower limit value of −1.8, the power of the negative lens of the cemented lens becomes weak, and the chromatic aberration of magnification cannot be corrected. Further, in the condition (5), when the value of f2 / F becomes larger than the upper limit value of −0.8, the power of the negative lens of the cemented lens becomes strong, and the field angle of the entire system cannot be secured.

  In the optical system of the present invention, it is desirable for aberration correction or the like if the first group is constituted by a negative lens and the second group is constituted by at least a positive lens and a cemented lens as described above.

  In this case as well, it is more desirable that the cemented lens of the second group is formed by bonding a positive lens and a negative lens so as to satisfy the conditions (4) and (5).

  In the endoscope objective optical system of the present invention, it is desirable to satisfy the following condition (6) in order to reduce the size of the optical system.

(6) ENP / F <0.7
Here, ENP is the distance from the first lens surface to the entrance pupil position.

  Further, in the optical system configured by the first group and the second group, the second group has at least a positive lens and a cemented lens including a positive lens and a negative lens, or the first group is a negative lens. It is more preferable that the second group has a cemented lens by bonding at least a positive lens and a negative lens, and satisfies the conditions (4), (5), and (6).

  In this condition (6), if the entrance pupil position (distance from the first lens surface to the entrance pupil) ENP does not satisfy the condition (6), that is, if it exceeds the upper limit of 0.7, the angle of view is secured. Although it is easy, the diameter of the lens becomes large, which is not preferable.

  In the optical system of the present invention, it is preferable that the lens disposed closest to the object side in the second group satisfies the following condition (7) in terms of chromatic aberration correction and lens processing.

(7) | (R1 + R2) / (R1-R2) | <0.2
Here, R1 and R2 are the radii of curvature of the object-side and image-side surfaces of the most object-side lens in the second group, respectively.

  If this condition (7) is not satisfied, that is, if the value of | (R1 + R2) / (R1−R2) | exceeds 0.2, it is difficult to correct axial chromatic aberration. In addition, a sufficient lens edge cannot be secured, resulting in processing problems.

  Further, in the optical system of the present invention, the angle of view ω preferably satisfies the following condition (8).

(8) ω> 50 °
However, ω is a half angle of view at the time of observation.

  In order to perform sufficient screening at the time of endoscopy, it is preferable that the half angle of view ω satisfies the above conditions.

  If the half angle of view ω is not within the range of the above condition (8), it cannot be said that a sufficient field of view range is secured as an endoscope objective optical system, and it is convenient for a user of an optical system such as a doctor. It is no longer a good optical system.

  The endoscope objective optical system of the present invention described above has a configuration suitable for arranging the visual field direction changing optical member in the optical system.

  However, it is possible to use the optical system without disposing the visual field direction changing optical member.

  That is, the endoscope objective optical system according to the present invention includes, in order from the object side, a negative first group, a diaphragm, and a positive second group. The following conditions (1), (2), and (3) are satisfied. It is characterized by satisfaction.

(1) -0.8 <F1 / F <-0.4
(2) 1.0 <F2 / F ≦ 1.333
(3) 0.9 <D / F <1.6

  The endoscope objective optical system of the present invention can secure a space in which the visual field direction changing optical member can be arranged, and can achieve high performance with a wide angle of view with a small configuration.

  Next, an embodiment of the present invention will be described based on each example.

Example 1 of the endoscope objective optical system of the present invention has the following data with the configuration as shown in FIG.

Object distance 18.0mm, focal length 1.960mm, Fno 9.55
r1 = ∞ d1 = 0.572 n1 = 1.88814 ν1 = 40.78
r2 = 1.2745 d2 = 0.667
r3 = ∞ d3 = 3.435 n2 = 1.88815 ν2 = 40.76
r4 = ∞ d4 = 0
r5 = ∞ (aperture) d5 = 0.295
r6 = 3.6694 d6 = 0.850 n3 = 1.59667 ν3 = 35.31
r7 = -2.5653 d7 = 0.541
r8 = 6.6560 d8 = 1.098 n4 = 1.48915 ν4 = 70.23
r9 = -1.4225 d9 = 0.240 n5 = 1.85504 ν5 = 23.78
r10 = -4.8425 d10 = 0.895
r11 = ∞ d11 = 0.620 n6 = 1.51564 ν6 = 75.00
r12 = ∞ d12 = 1.536
r13 = ∞ d13 = 1.500 n7 = 1.51825 ν7 = 64.14
r14 = ∞ d14 = 1.230 n8 = 1.52207 ν8 = 60.00
r15 = ∞ d15 = 0

F1 / F = −0.732
F2 / F = 1.315
D / F = 1.269
f1 / F = 1.28
f2 / F = −1.242
ENP / F = 0.619
| (R1 + R2) / (R1-R2) | = 0.177
ω = 60.3 °

In the above data, r1, r2,... Are the radius of curvature of each lens surface, d1, d2,... Are the thickness and air spacing of each lens, and n1, n2,. Refractive indexes, ν1, ν2,... Are Abbe numbers on the d-line of each lens. The unit of length in the data is mm.

  As shown in FIG. 1, in Example 1, in order from the object side, the first group G1 (r1 to r2) having a negative refractive power, the visual field direction changing optical member L02 (r3 to r4), and the aperture S (r5) are arranged. ) And a second group G2 (r6 to r10) having a positive refractive power.

  The first group G1 includes only negative lenses L01 (r1 to r2), and the second group G2 includes positive lenses L03 (r6 to r7), positive lenses L04 (r8 to r9), and negative lenses L05 (r9 to r10). ).

  Further, the plane parallel plate L02 described between the first group G1 and the second group G2 in FIG. 1 is shown by developing a prism which is a visual field direction converting optical member. The aperture stop S is disposed on the image side surface (r4) of the visual field direction conversion prism.

  Further, the plane parallel plate L06 (r11 to r12) arranged on the image side of the second group G2 is a treatment laser for specific wavelengths such as YAG laser 1060 nm, semiconductor laser 810 nm, other semiconductors, PDT, KTP, etc. It is a filter for cutting the infrared region. The parallel flat plates L07 (r13 to r14) and L08 (r14 to r15) are CCD cover glasses, and the image side surface (r15) of the CCD cover glass L08 is a CCD imaging surface.

  The optical system of Example 1 satisfies the conditions (1) to (7) as shown in the data. Further, the half angle of view ω is 60.3 °, and has a wide angle of view in the range indicated by the condition (8).

In addition, the aberration situation of Example 1 is as shown in FIG. 9, and each aberration including chromatic aberration is corrected well.
[Reference example]

The reference example of the endoscope objective optical system according to the present invention has the following data with the configuration shown in FIG.

Object distance 16.0mm, focal length 1.950mm, Fno 9.49
r1 = ∞ d1 = 0.560 n1 = 1.88814 ν1 = 40.78
r2 = 1.2615 d2 = 0.719
r3 = ∞ d3 = 4.018 n2 = 1.88815 ν2 = 40.76
r4 = ∞ d4 = 0
r5 = ∞ (aperture) d5 = 0.292
r6 = 4.2584 d6 = 0.850 n3 = 1.58482 ν3 = 40.75
r7 = -2.9926 d7 = 0.216
r8 = 4.1617 d8 = 1.800 n4 = 1.48915 ν4 = 70.23
r9 = -1.5651 d9 = 0.360 n5 = 1.85504 ν5 = 23.78
r10 = -6.9213 d10 = 0.654
r11 = ∞ d11 = 0.620 n6 = 1.51564 ν6 = 75.00
r12 = ∞ d12 = 1.818
r13 = ∞ d13 = 1.500 n7 = 1.51825 ν7 = 64.14
r14 = ∞ d14 = 1.230 n8 = 1.52207 ν8 = 60.00
r15 = ∞ d15 = 0

F1 / F = −0.729
F2 / F = 1.378
D / F = 1.461
f1 / F = 1.331
f2 / F = −1.253
ENP / F = 0.639
| (R1 + R2) / (R1-R2) | = 0.175
ω = 61.5 °

In this reference example , as shown in FIG. 2, in order from the object side, the first group G1 (r1 to r2) having a negative refractive power, the viewing direction converting optical member L02 (r3 to r4), and the positive refractive power. The second group G2 (r6 to r10).

  The first group G1 includes only negative lenses L01 (r1 to r2). The second group G2 includes a cemented lens (r8 to r10) in which a positive lens L03 (r6 to r7), a positive lens L04 (r8 to r9), and a negative lens L05 (r9 to r10) are bonded together.

In addition, the plane parallel plate L02 in the drawing is a visual field direction changing optical member, and is shown by developing a prism. An aperture stop S (r5) is arranged between the first group G1 and the second group G2, and in this reference example, it is arranged on the image side surface (r4) of the prism L02 which is a field direction changing optical member. .

  Further, the plane parallel plate L06 (r11 to r12) arranged on the image side of the second group G2 has a specific wavelength, for example, YAG laser 1060 nm, semiconductor laser 810 nm, other semiconductors, treatment lasers such as PDT, KTP, or the like. This is a filter for cutting the infrared region.

  The plane parallel plates L07 (r13 to r14) and L08 (r14 to r15) are CCD cover glasses, and the image side surface (r15) of the cover glass L08 is a CCD imaging surface.

The optical system of this reference example satisfies the conditions (1) to (7) as shown in the data. The half angle of view ω is 61.5 °, which is a wide angle of view within the range of condition (8).

In addition, the aberration situation of the reference example is as shown in FIG.

Example 2 of the endoscope objective optical system of the present invention has the following data with the configuration as shown in FIG.

Object distance 19.3mm, focal length 2.070mm, Fno 8.24
r1 = ∞ d1 = 0.580 n1 = 1.88814 ν1 = 40.78
r2 = 1.3197 d2 = 0.706
r3 = ∞ d3 = 4.020 n2 = 1.88815 ν2 = 40.76
r4 = ∞ d4 = 0
r5 = ∞ (aperture) d5 = 0.296
r6 = 3.5919 d6 = 0.850 n3 = 1.59667 ν3 = 35.31
r7 = -4.2215 d7 = 0.086
r8 = 4.7796 d8 = 0.762 n4 = 1.48915 ν4 = 70.23
r9 = -10.7218 d9 = 0.182
r10 = 17.4473 d10 = 1.164 n5 = 1.488915 ν5 = 70.23
r11 = -1.4437 d11 = 0.260 n6 = 1.85504 ν6 = 23.78
r12 = -9.4550 d12 = 0.240
r13 = ∞ d13 = 0.620 n7 = 1.51564 ν7 = 75.00
r14 = ∞ d14 = 1.965
r15 = ∞ d15 = 1.500 n8 = 1.51825 ν8 = 64.14
r16 = ∞ d16 = 1.230 n9 = 1.52207 ν9 = 60.00
r17 = ∞ d17 = 0

F1 / F = −0.718
F2 / F = 1.255
D / F = 1.37
f1 / F = 1.344
f2 / F = −0.977
ENP / F = 0.619
| (R1 + R2) / (R1-R2) | = 0.081
ω = 55.5 °

As shown in FIG. 3, the objective optical system of Example 2 has, in order from the object side, a first group G1 (r1 to r2) having a negative refractive power, a visual field direction changing optical member L02 (r3 to r4), It is composed of a second group G2 (r6 to r12) having a positive refractive power.

The first group G1 of Example 2 is composed of only the negative lens L01 (r1 to r2). The second group G2 includes a cemented lens (a cemented lens) in which a positive lens L03 (r6 to r7), a positive lens L04 (r8 to r9), a positive lens L05 (r10 to r11), and a negative lens L06 (r11 to r12) are bonded. r10 to r12).

  The plane parallel plate L02 is a visual field direction changing optical member, and is shown by developing a prism.

  Further, the aperture stop S (r5) disposed between the first group G1 and the second group G2 is disposed on the image side surface (r4) of the prism L02 which is a visual field direction converting optical member.

  The parallel flat plate L07 (r13 to r14) arranged on the image side of the second group G2 has a specific wavelength, for example, YAG laser 1060 nm, semiconductor laser 810 nm, other semiconductors, treatment lasers such as PDT, KTP, or infrared region. It is a filter for cutting.

  The parallel flat plates L08 (r15 to r16) and L09 (r16 to r17) are CCD cover glasses, and the image side surface (r17) of the cover glass L09 is a CCD imaging surface.

In Example 2 , as shown in the data, the conditions (1) to (7) are satisfied. The half angle of view ω is 55.5 °, which is a wide angle of view defined by the condition (8).

The aberration state of Example 2 is as shown in FIG. 11, and the aberration is corrected well.

Example 3 of the endoscope objective optical system of the present invention has a configuration as shown in FIG. 4 and has the following data.

Object distance 18.0mm, focal length 2.187mm, Fno 9.92
r1 = ∞ d1 = 0.572 n1 = 1.88814 ν1 = 40.78
r2 = 1.4698 d2 = 0.667
r3 = ∞ d3 = 3.559 n2 = 1.88815 ν2 = 40.76
r4 = ∞ d4 = 0
r5 = ∞ (aperture) d5 = 0.300
r6 = 3.7365 d6 = 0.850 n3 = 1.59667 ν3 = 35.31
r7 = -3.3509 d7 = 0.844
r8 = 5.4689 d8 = 0.240 n4 = 1.85504 ν4 = 23.78
r9 = 1.9757 d9 = 1.098 n5 = 1.48915 ν5 = 70.23
r10 = -6.0345 d10 = 0.202
r11 = ∞ d11 = 0.620 n6 = 1.51564 ν6 = 75.00
r12 = ∞ d12 = 2.739
r13 = ∞ d13 = 1.500 n7 = 1.51825 ν7 = 64.14
r14 = ∞ d14 = 1.230 n8 = 1.52207 ν8 = 60.00
r15 = ∞ d15 = 0

F1 / F = −0.757
F2 / F = 1.333
D / F = 1.167
f1 / F = -1.708
f2 / F = 1.457
ENP / F = 0.597
| (R1 + R2) / (R1-R2) | = 0.054
ω = 56.8 °

As shown in FIG. 4, the optical system of Example 3 includes, in order from the object side, a first group G1 (r1 to r2) having a negative refractive power, a visual field direction changing optical member L02 (r3 to r4), a positive And a second group G2 (r6 to r10) of refractive power.

In Example 3 , the first group G1 includes only negative lenses L01 (r1 to r2), and the second group G2 includes positive lenses L03 (r6 to r7) and negative lenses L04 (r8 to r9). It consists of a cemented lens (r8 to r10) to which a lens L05 (r9 to r10) is bonded.

  A plane-parallel plate L02 illustrated between the first group G1 and the second group G2 is a development of a prism that is a visual field direction conversion optical member. Further, an aperture stop S (r5) is disposed between the first group G1 and the second group G2, and in this embodiment, on the image side surface (r4) of the prism L02 which is a visual field direction changing optical member. Has been placed.

  In addition, the plane parallel plate L06 (r11 to r12) arranged on the image side of the second group G2 has a specific wavelength, for example, YAG laser of 1060 nm, semiconductor laser of 810 nm, other semiconductor, treatment laser such as PDT, KTP, or the like. This is a filter for cutting the infrared region.

  The plane parallel plates L07 (r13 to r14) and L08 (r14 to r15) are CCD cover glasses, and the image side surface (r15) of L08 is a CCD imaging surface.

The optical system of Example 3 satisfies the conditions (1) to (7) as shown in the data. The half angle of view ω is 56.8 °, which is a wide angle of view within the range defined by the condition (8).

The aberration status of Example 3 is as shown in FIG. 12, and all aberrations are corrected well.

Embodiment 4 of the endoscope objective optical system according to the present invention has a configuration as shown in FIG. 5 and has the following data.

Object distance 19.3mm, focal length 2.074mm, Fno 8.57
r1 = ∞ d1 = 0.570 n1 = 1.88814 ν1 = 40.78
r2 = 1.3293 d2 = 0.667
r3 = ∞ d3 = 4.013 n2 = 1.88815 ν2 = 40.76
r4 = ∞ d4 = 0
r5 = ∞ (aperture) d5 = 0.296
r6 = 3.4527 d6 = 0.850 n3 = 1.59667 ν3 = 35.31
r7 = -3.2862 d7 = 0.346
r8 = 4.5666 d8 = 1.635 n4 = 1.48915 ν4 = 70.23
r9 = -1.4197 d9 = 0.240 n5 = 1.85504 ν5 = 23.78
r10 = -6.3309 d10 = 0.934
r11 = ∞ d11 = 0.620 n6 = 1.51564 ν6 = 75.00
r12 = ∞ d12 = 1.511
r13 = ∞ d13 = 1.500 n7 = 1.51825 ν7 = 64.14
r14 = ∞ d14 = 1.230 n8 = 1.52207 ν8 = 60.00
r15 = ∞ d15 = 0

F1 / F = −0.722
F2 / F = 1.281
D / F = 1.346
f1 / F = 1.173
f2 / F = −1.056
ENP / F = 0.615
| (R1 + R2) / (R1-R2) | = 0.025
ω = 55.5 °

As shown in FIG. 5, the optical system of Example 4 includes, in order from the object side, a first group G1 (r1 to r2) having a negative refractive power, a visual field direction changing optical member L02 (r3 to r4), The second group G2 (r6 to r10) having a positive refractive power.

  The first group G1 includes only negative lenses L01 (r1 to r2). The second group G2 includes a positive lens L03 (r6 to r7), a cemented lens (r8 to r10) in which a positive lens L04 (r8 to r9) and a negative lens L05 (r9 to r10) are bonded. ing.

  Further, the plane parallel plate L02 between the first group G1 and the second group G2 is shown by developing a prism which is a visual field direction changing optical member. Further, the aperture stop S (r5) disposed between the first group G1 and the second group G2 is disposed on the image side surface (r4) of the prism L02 which is a visual field direction converting optical member.

  The parallel flat plate L06 (r11 to r12) arranged on the image side of the second group G2 has a specific wavelength, for example, YAG laser 1060 nm, semiconductor laser 810 nm, other semiconductors, treatment lasers such as PDT, KTP, or infrared region. It is a filter for cutting.

  The plane parallel plates L07 (r13 to r14) and L08 (r14 to r15) are CCD cover glasses, and the image side surface (r15) of the cover glass L08 is a CCD imaging surface.

In Example 4 , the conditions (1) to (7) are satisfied. The half field angle ω is 55.5 °, which is a wide field angle within the range of the condition (8).

The aberration status of Example 4 is as shown in FIG. 13, and all aberrations are also corrected favorably.

The fifth embodiment of the endoscope objective optical system according to the present invention has a configuration as shown in FIG.

Object distance 16.0mm, focal length 1.943mm, Fno 9.45
r1 = ∞ d1 = 0.560 n1 = 1.88814 ν1 = 40.78
r2 = 1.2154 d2 = 2.600
r3 = ∞ (aperture) d3 = 0.200
r4 = 3.7172 d4 = 0.850 n2 = 1.72794 ν2 = 37.95
r5 = -4.2087 d5 = 0.358
r6 = 5.6186 d6 = 1.800 n3 = 1.48915 ν3 = 70.23
r7 = -1.2563 d7 = 0.2800 n4 = 1.85504 ν4 = 23.78
r8 = -3.8247 d8 = 0.9700
r9 = ∞ d9 = 0.6200 n5 = 1.51564 ν5 = 75.00
r10 = ∞ d10 = 1.530
r11 = ∞ d11 = 1.5000 n6 = 1.51825 ν6 = 64.14
r12 = ∞ d12 = 1.2300 n7 = 1.52207 ν7 = 60.00
r13 = ∞ d13 = 0

F1 / F = −0.704
F2 / F = 1.32
D / F = 1.338
f1 / F = 1.182
f2 / F = −1.186
ENP / F = 0.614
| (R1 + R2) / (R1-R2) | = 0.062
ω = 62.3 °

As shown in FIG. 6, the optical system of the fifth embodiment has a negative refractive power first group G1 (r1 to r2) and a positive refractive power second group G2 (r4 to r8) in order from the object side. ) And.

  The first group G1 includes only negative lenses L01 (r1 to r2), and the second group G2 includes positive lenses L02 (r4 to r5), positive lenses L03 (r6 to r7), and negative lenses L04 (r7). To r8) and a cemented lens (r6 to r8) bonded together.

  An aperture stop S (r3) is disposed between the first group G1 and the second group G2.

In Example 5 , a parallel plane plate (viewing direction changing optical member) is not disposed between the first group G1 and the second group G2. Therefore, as in the first to fifth embodiments, the optical path length is shorter than that of the optical system provided with the visual field direction conversion prism.

  However, a space in which the visual field direction conversion optical system can be disposed is provided between the first group G1 and the stop S. For this reason, for example, when a single mirror is disposed and the angle of visual field direction conversion is relatively large, such as about 90 °, the space is sufficient to dispose the mirror.

The plane parallel plate L05 (r9 to r10) arranged on the image side of the second group G2 of the fifth embodiment has a specific wavelength such as YAG laser of 1060 nm, semiconductor laser of 810 nm, other semiconductors, PDT, KTP, etc. This is a filter for cutting the laser or infrared region.

  The plane parallel plates L06 (r11 to r12) and L07 (r12 to r13) are CCD cover glasses, and the image side surface (r13) of the plane parallel plate L07 is a CCD imaging surface.

This Example 5 satisfies the conditions (1) to (7). The half field angle ω is 62.3 °, which is a wide field angle within the range of the condition (8).

In addition, the aberration situation of the fifth embodiment is as shown in FIG. 14, and the aberration is corrected well.

Example 6 of the endoscope objective optical system of the present invention has the following data with the configuration shown in FIG.

Object distance 16.0mm, focal length 1.973mm, Fno 9.69
r1 = ∞ d1 = 0.560 n1 = 1.88300 ν1 = 40.78
r2 = 1.010 d2 = 0.380
r3 = ∞ d3 = 4.050 n2 = 1.88300 ν2 = 40.76
r4 = ∞ d4 = 0
r5 = ∞ (aperture) d5 = 0.295
r6 = 3.946 d6 = 0.850 n3 = 1.58144 ν3 = 40.75
r7 = -2.951 d7 = 0.753
r8 = 2.446 d8 = 1.210 n4 = 1.48749 ν4 = 70.23
r9 = -1.648 d9 = 0.120 n5 = 1.84666 ν5 = 23.78
r10 = -78.500 d10 = 0.550
r11 = ∞ d11 = 0.620 n6 = 1.51400 ν6 = 75.00
r12 = ∞ d12 = 2.451
r13 = ∞ d13 = 1.500 n7 = 1.51633 ν7 = 64.14
r14 = ∞ d14 = 1.230 n8 = 1.52000 ν8 = 60.00
r15 = ∞ d15 = 0

F1 / F = −0.58
F2 / F = 1.263
D / F = 1.283
f1 / F = 1.134
f2 / F = −1.009
ENP / F = 0.550
| (R1 + R2) / (R1-R2) | = 0.144
ω = 61.7 °

As shown in FIG. 7, the optical system of the sixth embodiment has, in order from the object side, a first group G1 (r1 to r2) having a negative refractive power and a second group G2 (r6 to r10) having a positive refractive power. ) And.

  The first group G1 includes only negative lenses L01 (r1 to r2), and the second group G2 includes positive lenses L03 (r6 to r7), positive lenses L04 (r8 to r9), and negative lenses L05 ( It consists of a cemented lens (r8 to r10) to which r9 to r10) are bonded.

  The parallel flat plate L02 (r3 to r4) on the image side of the first group G1 is a development of a prism that is a visual field direction converting optical member.

  An aperture stop S (r5) is disposed between the first group G1 and the second group G2, and is provided on the image side surface (r4) of the prism L02 which is a visual field direction converting optical member.

  In addition, the plane parallel plate L06 (r11 to r12) arranged on the image side of the second group G2 has a specific wavelength, for example, YAG laser of 1060 nm, semiconductor laser of 810 nm, other semiconductor, treatment laser such as PDT, KTP, or the like. This is a filter for cutting the infrared region.

  The plane parallel plates L07 (r13 to r14) and L08 (r14 to r15) are CCD cover glasses, and the image side surface (r15) of the cover glass L08 is a CCD imaging surface.

This Example 6 satisfies the conditions (1) to (7). The half angle of view ω is 61.7 °, which is a wide angle of view within the range of condition (8).

The aberration status of Example 6 is as shown in FIG. 15, and each aberration is corrected well.

Example 7 of the endoscope objective optical system of the present invention has the following data with the configuration as shown in FIG.

Object distance 16.0mm, focal length 1.987mm, Fno 9.49
r1 = ∞ d1 = 0.360 n1 = 1.88300 ν1 = 40.78
r2 = 0.880 d2 = 0.508
r3 = ∞ d3 = 3.020 n2 = 1.88300 ν2 = 40.76
r4 = ∞ d4 = 0
r5 = ∞ (aperture) d5 = 0.300
r6 = 3.799 d6 = 0.850 n3 = 1.58144 ν3 = 40.75
r7 = -2.883 d7 = 1.240
r8 = 2.222 d8 = 1.215 n4 = 1.48749 ν4 = 70.23
r9 = -1.634 d9 = 0.240 n5 = 1.84666 ν5 = 23.78
r10 = -33.015 d10 = 0.335
r11 = ∞ d11 = 0.620 n6 = 1.51400 ν6 = 75.00
r12 = ∞ d12 = 2.63
r13 = ∞ d13 = 1.500 n7 = 1.51633 ν7 = 64.14
r14 = ∞ d14 = 1.230 n8 = 1.52000 ν8 = 60.00
r15 = ∞ d15 = 0

F1 / F = −0.501
F2 / F = 1.197
D / F = 1.063
f1 / F = 1.084
f2 / F = −1.025
ENP / F = 0.437
| (R1 + R2) / (R1-R2) | = 0.137
ω = 62.5 °

As shown in FIG. 8, the optical system of the seventh embodiment has, in order from the object side, a first group G1 (r1 to r2) having a negative refractive power and a second group G2 (r6 to r10) having a positive refractive power. ) And.

  The first group G1 of this embodiment consists of only the negative lens L01 (r1 to r2), and the second group G2 includes a positive lens L03 (r6 to r7), a positive lens L04 (r8 to r9), and a negative lens. And a cemented lens (r8 to r10) to which L05 (r9 to r10) is bonded.

  The plane parallel plate L02 (r3 to r4) is a development of a prism that is a visual field direction converting optical member. Further, the aperture stop S (r5) disposed between the first group G1 and the second group G2 is provided on the image side surface (r4) of the plane parallel plate L02. The parallel flat plate L06 (r11 to r12) arranged on the image side of the second group G2 has a specific wavelength, for example, YAG laser 1060 nm, semiconductor laser 810 nm, other semiconductors, treatment lasers such as PDT, KTP, or infrared region. It is a filter for cutting.

  The plane parallel plates L07 (r13 to r14) and L08 (r14 to r15) are CCD cover glasses, and the image side surface (r15) of L08 is a CCD imaging surface.

The optical system of Example 7 satisfies the conditions (1) to (7). The half angle of view ω is 62.5 °, which is a wide angle of view within the range of condition (8).

The aberration status of Example 7 is as shown in FIG. 16, and various aberrations are corrected favorably.

  In the embodiments described above, all of the embodiments using the visual field direction converting optical member are shown as parallel plane plates in the drawing, and only the entrance surface and the exit surface are included in the data. It is described.

  An example of the configuration of the viewing direction converting optical member is as shown in FIGS. Each of these figures shows a state of being arranged in the objective optical system of the present invention. Among them, FIG. 17 shows a view direction which is for perspective view converted by 45 °, and FIG. The viewing direction is converted by 90 ° for side viewing.

  The endoscope objective optical system of the present invention is used for medical or industrial endoscopes, can be used in perspective or side view, and has various angles including chromatic aberration over a wide angle of view. Observation with a good image in which aberrations are sufficiently corrected can be performed.

The figure which shows the structure of Example 1 of this invention. The figure which shows the structure of the reference example of this invention The figure which shows the structure of Example 2 of this invention. The figure which shows the structure of Example 3 of this invention. The figure which shows the structure of Example 4 of this invention. The figure which shows the structure of Example 5 of this invention. The figure which shows the structure of Example 6 of this invention. The figure which shows the structure of Example 7 of this invention. Aberration diagram of Example 1 of the present invention Aberration diagram of the reference example Aberration diagram of Example 2 of the present invention Aberration diagram of Example 3 of the present invention Aberration diagram of Example 4 of the present invention Aberration diagram of embodiment 5 of the present invention Aberration diagram of Embodiment 6 of the present invention Aberration diagram of Example 7 of the present invention The figure which shows the structure of a 45 degree perspective type with the optical system of this invention The figure which shows the structure of a 90 degree perspective type with the optical system of this invention.

Claims (5)

In order from the object side, a negative first group, a stop, and a positive second group are configured, and an optical member for changing the viewing direction is disposed between the first group and the second group, and the following conditions are satisfied. An endoscope objective optical system that satisfies (1), (2), and (3).
(1) -0.8 <F1 / F <-0.4
(2) 1.0 <F2 / F ≦ 1.333
(3) 0.9 <D / F <1.6
Here, F1 and F2 are the focal lengths of the first group and the second group, F is the focal length of the entire objective optical system, and D is the air-converted length from the image side surface of the first lens to the stop.   The endoscope objective optical system according to claim 1, wherein the second group includes at least a positive lens and a cemented lens in which a positive lens and a negative lens are cemented. The endoscope objective optical system according to claim 2, wherein the following conditions (4), (5), and (6) are satisfied.
(4) 1.0 <f1 / F <2.0
(5) -1.8 <f2 / F <-0.8
(6) ENP / F <0.7
Where f1 and f2 are the focal lengths of the positive and negative lenses of the second lens group, F is the focal length of the entire objective optical system, and ENP is the distance from the first surface of the optical system to the entrance pupil position. is there.   The endoscope objective optical system according to claim 1, wherein the first group is configured by a negative lens, and the second group is a cemented lens of at least a positive lens, a positive lens, and a negative lens. The endoscope objective optical system according to claim 4, wherein the cemented lens of the second group satisfies the following conditions (4), (5), and (6).
(4) 1.0 <f1 / F <2.0
(5) -1.8 <f2 / F <-0.8
(6) ENP / F <0.7
Where f1 and f2 are the focal lengths of the positive and negative lenses of the second lens group, F is the focal length of the entire objective optical system, and ENP is the distance from the first surface of the optical system to the entrance pupil position. is there.

Images