CN107703606B - Objective optical system for endoscope and endoscope - Google Patents
Objective optical system for endoscope and endoscope Download PDFInfo
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- CN107703606B CN107703606B CN201710666063.4A CN201710666063A CN107703606B CN 107703606 B CN107703606 B CN 107703606B CN 201710666063 A CN201710666063 A CN 201710666063A CN 107703606 B CN107703606 B CN 107703606B
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/001—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
- G02B13/0015—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design
- G02B13/002—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design having at least one aspherical surface
- G02B13/004—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design having at least one aspherical surface having four lenses
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B1/00—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor
- A61B1/00064—Constructional details of the endoscope body
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B1/00—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor
- A61B1/00163—Optical arrangements
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/06—Panoramic objectives; So-called "sky lenses" including panoramic objectives having reflecting surfaces
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- G—PHYSICS
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- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/18—Optical objectives specially designed for the purposes specified below with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration
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Abstract
Provided are an objective optical system for an endoscope and an endoscope, which solve the problem that it is difficult to design a small-sized and wide-field-angle endoscope while maintaining good optical performance. The objective optical system for an endoscope includes, in order from an object side, a first lens group having negative power and a second lens group having positive power, the first lens group including, in order from the object side, a negative lens having a concave surface facing the image side and a positive lens having a convex surface facing the image side, and the second lens group including, in order from the object side, at least a positive lens having a convex surface facing the image side and a cemented lens obtained by cementing the negative lens and the positive lens, and satisfies a predetermined condition.
Description
Technical Field
The present invention relates to an endoscopic objective optical system and an endoscope incorporating the endoscopic objective optical system.
Background
As a device for diagnosing a body cavity of a patient, an endoscope (a fiberscope or an electron microscope) is generally known and put to practical use. The distal end portion of such an endoscope is preferably designed to be small (small in diameter and short in overall length) so as to be smoothly inserted even in a small slit.
The minimum design-possible outer shape of the distal end portion of the endoscope is actually limited by the large-sized mounting member. The large-sized mounting member includes, for example, an objective optical system for an endoscope. Selecting a small-sized objective optical system for an endoscope as a mounting member is an effective means for achieving downsizing of the distal end portion of the endoscope.
In order to reduce the operator's leakage of the lesion, the objective optical system for an endoscope is preferably designed to have a wide observation angle, i.e., a wide angle of view.
For example, in an endoscopic objective optical system for digestive organs, the field angle is generally about 140 °. At this angle of view, when observing the back side of the wall or the fold in the large intestine, the bending portion of the endoscope needs to be bent to change the orientation of the distal end portion of the endoscope. However, for example, when the lumen diameter is small, the movement of the endoscope distal end portion is restricted, and therefore the endoscope distal end portion may not be changed to a desired orientation.
For example, patent documents 1 and 2 disclose objective optical systems for endoscopes that are designed to have a wider field angle than 140 °. The field angle of the objective optical system for an endoscope is designed to be wider, and the tube wall in the large intestine, the back surface of the plica, and the like can be easily observed without changing the orientation of the distal end portion of the endoscope.
Prior art documents
Patent document
Patent document 1: japanese patent No. 4819203
Patent document 2: patent No. 5750618.
Disclosure of Invention
Problems to be solved by the invention
The objective optical system for an endoscope described in patent document 1 has a wide angle of view exceeding 180 °. However, in the objective optical system for an endoscope described in patent document 1, since the petzval sum is large, when observing a lumen such as a digestive tract, for example, the peripheral resolution varies depending on the observation direction. Further, since the incident angle to the lens surface disposed closest to the object side in the objective optical system for an endoscope is large, the amount of incident light decreases. In the objective optical system for an endoscope described in patent document 2, the negative power of the lens disposed closest to the object side in the objective optical system for an endoscope needs to be increased to enlarge the angle of view, and therefore the radius of curvature of each lens surface in the objective optical system for an endoscope becomes small, and correction of coma aberration and astigmatism is insufficient. That is, according to the objective optical systems for endoscopes described in patent documents 1 and 2, at least optical performance is sacrificed in order to realize a wide field angle.
The present invention has been made in view of the above circumstances, and an object thereof is to provide an objective optical system for an endoscope and an endoscope having excellent optical performance and designed to be small and have a wide angle of view.
Means for solving the problems
An endoscopic objective optical system according to an embodiment of the present invention includes, in order from an object side, a first lens group having negative power and a second lens group having positive power. The first lens group comprises negative lenses with concave surfaces facing the image side in sequence from the object sideA lens and a positive lens having a convex surface facing the image side. The second lens group includes, in order from the object side, at least a positive lens having a convex surface facing the image side and a cemented lens obtained by cementing a negative lens and the positive lens. According to the endoscopic objective optical system of an embodiment of the present invention, a focal length of the negative lens positioned closest to the object side in the first lens group is defined as f1(unit: mm), and a focal length positioning instrument f of the first lens groupF(unit: mm), the effective diameter in the maximum image height of the surface located closest to the object side in the first lens group is positioned as ED (unit: mm), and the combined focal length of the first lens group and the second lens group is defined as f (unit: mm), the following two conditions are satisfied:
0.2＜f1/fF＜0.5
4.0＜ED/f＜5.0。
further, the objective optical system for an endoscope according to the embodiment of the present invention may be configured such that, when a stop is provided between the first lens group and the second lens group, and a focal length of a positive lens positioned on the side closest to the stop in the first lens group is positioned at f2 (unit: mm), the following condition is satisfied:
0.5＜∣f2/fF∣＜2.0。
in one embodiment of the present invention, the positive lens in the first lens group has a planar object-side surface, for example.
Further, the objective optical system for an endoscope according to the embodiment of the present invention may be configured to satisfy the following condition when the maximum image height on the image formation plane is defined as y (unit: mm):
3.0＜ED/y＜4.0。
further, the objective optical system for an endoscope according to the embodiment of the present invention may be configured such that the angle of view exceeds 180 °.
In the endoscope objective optical system according to the first aspect of the present invention, the lens surfaces of all the lenses included in the first lens group and the second lens group may be spherical.
Further, an endoscope according to an embodiment of the present invention is an apparatus in which the above-described objective optical system for an endoscope is assembled at a distal end.
Effects of the invention
According to an embodiment of the present invention, it is possible to provide an objective optical system for an endoscope and an endoscope having excellent optical performance and designed to be small and have a wide angle of view.
Drawings
Fig. 1 is an external view showing an external appearance of an electron microscope according to an embodiment of the present invention.
Fig. 2 is a sectional view showing the arrangement of an objective optical system for an endoscope and optical components arranged at the rear side thereof according to an embodiment (example 1) of the present invention.
A, B, C, D in FIG. 3 are various aberration diagrams of the objective optical system for an endoscope according to an embodiment (example 1) of the present invention.
Fig. 4 is a sectional view showing the arrangement of the objective optical system for an endoscope and optical components arranged at the rear side thereof according to example 2 of the present invention.
A, B, C, D in FIG. 5 are various aberration diagrams of the objective optical system for an endoscope according to example 2 of the present invention.
Fig. 6 is a sectional view showing the arrangement of an objective optical system for an endoscope and optical components arranged at the rear side thereof according to example 3 of the present invention.
A, B, C, D in FIG. 7 are various aberration diagrams of the objective optical system for an endoscope according to example 3 of the present invention.
Fig. 8 is a sectional view showing the arrangement of an objective optical system for an endoscope and optical components arranged at the rear side thereof according to example 4 of the present invention.
A, B, C, D in FIG. 9 are various aberration diagrams of the objective optical system for an endoscope according to example 4 of the present invention.
Fig. 10 is a sectional view showing the arrangement of an objective optical system for an endoscope and optical components arranged at the rear side thereof according to example 5 of the present invention.
A, B, C, D in FIG. 11 are various aberration diagrams of the objective optical system for an endoscope according to example 5 of the present invention.
Fig. 12 is a sectional view showing the arrangement of an objective optical system for an endoscope and optical components arranged at the rear side thereof according to example 6 of the present invention.
A, B, C, D in FIG. 13 are various aberration diagrams of the objective optical system for an endoscope according to example 6 of the present invention.
Description of the symbols
1. An electron microscope 100 and an objective optical system for an endoscope.
Detailed Description
An endoscopic objective optical system and an electronic microscope incorporating the endoscopic objective optical system according to an embodiment of the present invention will be described below with reference to the drawings.
Fig. 1 is an external view showing an external appearance of an electron microscope 1 according to an embodiment of the present invention. As shown in fig. 1, the galvano-mirror 1 includes an insertion portion flexible tube 11, and the insertion portion flexible tube 11 is enclosed by a flexible sheath 11 a. The distal end portion (bent portion 14) of the insertion portion flexible tube 11 is bent in accordance with a remote operation from the remote operation portion 13 (specifically, a rotation operation of the bending operation knob 13 a) coupled to the base end of the insertion portion flexible tube 11. The bending mechanism is a known mechanism incorporated in a general endoscope, and bends the bending portion 14 by pulling an operation wire in conjunction with a rotational operation of the bending operation handle 13 a. The proximal end of the distal end portion 12, which is sealed by a case made of a hard resin, is connected to the distal end of the bending portion 14. The direction of the distal end portion 12 changes in accordance with the bending operation by the rotating operation of the bending operation knob 13a, and the imaging region of the galvano-mirror 1 moves.
An objective optical system 100 for an endoscope (a block shown by a broken line in fig. 1) is assembled inside a resin case of the distal end portion 12. The objective optical system 100 for an endoscope images light from an object on a light receiving surface of a solid-state imaging device (not shown in the figure) in order to extract image data of the object in an imaging area. As the solid-state imaging Device, for example, a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor may be cited.
Fig. 2 is a sectional view showing the arrangement of the objective optical system 100 for an endoscope and optical components arranged at the rear side thereof according to example 1 (which will be described later in detail) of the present invention. Next, an objective optical system 100 for an endoscope according to an embodiment of the present invention will be described in detail with reference to fig. 2.
As shown in fig. 2, the endoscopic objective optical system 100 includes at least a first lens group G1, a stop S, and a second lens group G2 in this order from the object (subject) side. Each of the optical lenses constituting the first lens group G1 and the second lens group G2 has a shape rotationally symmetric about the optical axis AX of the objective optical system 100 for an endoscope. A color correction filter F for a solid-state imaging device is disposed behind the second lens group G2. The color correction filter F is bonded to a glass cover (not shown in the drawings) that protects the solid-state imaging device.
The reason why the above is limited to "at least having" is that there may be a configuration example in which other optical elements are added within the scope of the technical idea of the present invention. For example, the following configuration example is possible: the objective optical system for an endoscope according to the present invention is added with a configuration example of a parallel flat plate that does not substantially contribute to optical performance, or a configuration example of another optical element in a case where the configuration and effects of the objective optical system for an endoscope according to the present invention are maintained. For the same reason, the first lens group G1 and the second lens group G2 are also described as "having at least".
The first lens group G1 is a lens group disposed on the object side more than the stop S. The first lens group G1 includes, in order from the object side, at least a negative lens L1 having a concave surface facing the image side and a positive lens L2 having a convex surface facing the image side. The first lens group G1 has negative power as a whole, and thereby realizes a wide field angle of the endoscopic objective optical system 100, i.e., a wide range of an object to be captured.
If the power of the negative lens L1 is strengthened in order to achieve wide field of view, the asymmetry of the first lens group G1 and the second lens group G2 becomes strong, it becomes difficult to achieve correction of distortion aberration, and the curvature of the negative refractive surface becomes large, and therefore, various aberrations such as coma aberration and chromatic aberration increase. Therefore, in the present embodiment, the positive lens L2 is disposed in front of the stop S, and the strong negative power of the negative lens L1 is eliminated in the first lens group G1.
In order to effectively suppress a decrease in resolution around the observation field of view due to image tilt that tends to occur when the wide field of view of the negative lens L1 is widened, and a decrease in resolution around the observation field of view due to the occurrence of distortion aberration, the object-side surface of the positive lens L2 is preferably a flat surface.
The second lens group G2 is a lens group disposed on the image side of the stop S. The second lens group G2 has, in order from the object side, at least a positive lens L3, a cemented lens CL cemented with a negative lens L4 and a positive lens L5. The second lens group G2 has positive power as a whole, and performs imaging of a wide range of subjects taken in by the first lens group G1 on the light receiving surface of the solid-state imaging device.
When a lens having a concave surface facing the image side is used as the positive lens L3 in the second lens group G2 having positive power, the exit angle becomes large. Therefore, it is difficult to secure a sufficient exit pupil distance. To avoid this problem, in the present embodiment, the positive lens L3 is disposed so that its convex surface faces the image side.
The more the negative power of the first lens group G1 is strengthened to make the field of view wider, the larger the chromatic aberration of magnification occurs in the first lens group G1. In order to effectively correct chromatic aberration of magnification occurring in the first lens group G1, the present embodiment employs a configuration in which a cemented lens CL is disposed in the second lens group G2 where off-axis light passes through the highest position.
For convenience of description, the object-side surface and the image-side surface of each optical member will be referred to as a first surface and a second surface, respectively. The stop S is a plate-shaped member having a predetermined circular opening centered on the optical axis AX, or a light-shielding film applied to a lens surface (the second surface r4 of the positive lens L2 in the configuration example of fig. 2) of the stop S closest to the first lens group G1, outside a predetermined circular region centered on the optical axis AX. The thickness of the diaphragm S is extremely small compared to the thickness of each optical lens such as the negative lens L1 or the positive lens L2, and there is no problem at all in calculating the optical performance of the objective optical system 100 for an endoscope. Therefore, in the present specification, the thickness of the diaphragm S is described as 0.
The focal length of the negative lens L1 located closest to the object side in the first lens group G1 of the objective optical system 100 for an endoscope is defined as f1(unit: mm), the focal length of the first lens group G1 is defined as fF(unit: mm), when the effective diameter in the maximum image height of the surface located closest to the object side (the first surface r1 of the negative lens L1) within the first lens group G1 is defined as ED (unit: mm), and the focal length (of the combination of the first lens group G1 and the second lens group G2) of the entire system is defined as f (unit: mm), the following two conditions (1) and (2) are satisfied:
0.2＜f1/fF＜0.5 (1)
4.0＜ED/f＜5.0 (2)。
condition (1) defines the focal length f of the negative lens L1 located closest to the object side within the first lens group G11Focal length f of the first lens group G1FThe ratio of (a) to (b). By satisfying the condition (1), a suitably large angle of view (for example, an angle of view exceeding 180 °) when the first lens group G1 and the second lens group G2 are combined can be obtained, while the effective diameter of the negative lens L1 located closest to the object side can be suppressed.
In the condition (1), "f1/fFIf "the value on the right side (0.5 or more)," various aberrations such as coma aberration can be corrected well, but the effective diameter ED of the negative lens L1 becomes large, so the diameter of the objective optical system 100 for an endoscope cannot be made small. Since the objective optical system 100 for an endoscope needs to be incorporated into the distal end portion 12 of the electron microscope 1, the distal end portion 12 cannot be designed to have a small diameter, or the degree of freedom in designing the distal end portion 12 is greatly limited. Further, since the magnification of the positive lens L2 is too large, it is difficult to suppress the image tilt when the positive lens L2 is decentered (displaced in the vertical direction with respect to the optical axis AX) in combination.
In the condition (1), "f1/fF"the effective diameter ED of the negative lens L1 is reduced to reduce the diameter of the endoscopic objective optical system 100 when the value on the left side (0.2 or less), but the power of the negative lens L1 is too strong, and therefore, it is difficult to achieve both wide field angle and aberration (mainly, coma aberration and chromatic aberration) correctionIs positive. Further, since the magnification of the second lens group G2 has to be set high, it is difficult to suppress the deviation of the angle of view due to the gap error between the first lens group G1 and the second lens group G2 at the time of assembly.
The condition (2) defines a ratio of the effective diameter ED in the maximum image height of the surface located closest to the object side (the first surface r1 of the negative lens L1) within the first lens group G1 to the focal length f of the entire system. By satisfying the condition (2), the negative lens L1 can be formed into a shape that is easy to handle without increasing the size of the endoscopic objective optical system 100 (i.e., increasing the diameter and increasing the overall length of the endoscopic objective optical system 100) (in other words, reducing the size of the endoscopic objective optical system 100 can be achieved).
The first surface r1 of the negative lens L1 is exposed outward on the distal end surface of the distal end portion 12 of the galvano-mirror 1. When the condition (2) is satisfied, since the diameter of the first face r1 is small, the cleaning range of the negative lens L1 is small, and the amount of protrusion of the first face r1 on the front end face is small. Therefore, the negative lens L1 is formed in an easily handled shape that suppresses a reduction in the cleaning performance of the distal end portion 12 and suppresses the risk of damage to the first surface r1 due to collision with other structures and the like when the electron microscope 1 is managed.
In the condition (2), if "ED/f" is equal to or larger than the value on the right side (5.0), the amount of projection of the first surface r1 on the distal end surface increases. Therefore, the cleaning performance of the tip end portion 12 is reduced (for example, it is difficult to remove stains when cleaning the tip end surface), and there is a large risk that the first surface r1 collides with other structures and the like and is damaged when the electron microscope 1 is managed. The amount of protrusion of the first face r1 is defined as the distance in the optical axis AX direction between the tangent plane on the optical axis AX of the first face r1 and the outermost edge of the effective diameter of the first face r 1.
In the condition (2), when "ED/f" is equal to or less than the left value (═ 4.0), the amount of projection of the first surface r1 on the distal end surface becomes smaller as the effective diameter ED of the negative lens L1 becomes smaller. However, the amount of light reflected by the surface increases on the first surface r1, and the loss of light amount is large. Further, the entire length of the objective optical system 100 for an endoscope becomes long. Since the endoscope objective optical system 100 having a long overall length needs to be incorporated into the distal end portion 12 of the electron microscope 1, it is difficult to keep the overall length of the distal end portion 12 short. The tip portion 12 having a hard property is long in the entire length, and thus, for example, the insertability (ease of insertion) into the scope 1 in the body cavity is reduced or the load on the patient is increased when the scope 1 is inserted.
As described above, the objective optical system 100 for an endoscope satisfies the conditions (1) and (2) in the above-described lens arrangement (the first lens group G1 and the second lens group G2) at the same time, thereby having good optical performance, realizing downsizing and wide field angle (for example, a wide field angle exceeding 180 ° when applied to lumen observation), and becoming, for example, used in combination with a high-definition solid-state imaging device.
Further, since the objective optical system 100 for an endoscope does not necessarily require an aspherical lens when correcting various aberrations, the burden of design and development is reduced, and the processing is easy. In the embodiments of the present invention, lens surfaces of all the lenses included in the first lens group G1 and the second lens group G2 are spherical.
The focal length of the positive lens L2 located closest to the stop in the first lens group G1 of the endoscopic objective optical system 100 is defined as f2(unit: mm), the following condition (3) is satisfied:
0.5＜∣f2/fF∣＜2.0 (3)。
condition (3) defines the focal length f of the positive lens L2 located on the closest diaphragm side within the first lens group G12Focal length f of the first lens group G1FThe ratio of (a) to (b). By satisfying the condition (3), deterioration of optical performance around the observation field, which is feared when the wide field of view is made wide, can be more suitably suppressed.
In condition (3), "| f2/fFWhen | is equal to or greater than the value on the right side (═ 2.0), for example, when observing a lumen, an image with less distortion from the center of the observation field to the periphery of the observation field can be obtained. However, since the magnification in the vicinity of the center of the observation field of view is reduced, when, for example, a lesion is found and then the center of the observation field of view is moved closer, the lesion cannot be imaged at a high resolution.
In condition (3), "| f2/fF| below the left value (═ 0.5), e.g. to view a lumenIn this case, the object-side resolution around the observation field of view is decreased as the distortion degree of the image around the observation field of view is increased.
When the maximum image height on the image forming surface is defined as y (unit: mm), the objective optical system 100 for an endoscope satisfies the following condition (4):
3.0＜ED/y＜4.0 (4)。
the condition (4) defines a ratio of the effective diameter ED in the maximum image height of the surface located closest to the object side (the first surface r1 of the negative lens L1) within the first lens group G1 to the maximum image height y in the imaging plane. By satisfying the condition (4), the negative lens L1 can be formed into a shape that is easy to handle without increasing the size of the endoscopic objective optical system 100 (in other words, the endoscopic objective optical system 100 can be made smaller).
In the condition (4), if "ED/y" is equal to or larger than the right value (4.0), the amount of projection of the first surface r1 on the distal end surface of the distal end portion 12 of the electron microscope 1 decreases. However, the amount of light reflected by the surface increases on the first surface r1, and the light amount loss increases. Further, the entire length of the objective optical system 100 for an endoscope becomes long. Since the endoscope objective optical system 100 having a long overall length needs to be incorporated into the distal end portion 12 of the electron microscope 1, it is difficult to keep the overall length of the distal end portion 12 short. The tip portion 12 having a hard property is long in the entire length, and thus, for example, the insertability into the body cavity of the scope 1 is reduced or the load on the patient is increased when the scope 1 is inserted.
In the condition (4), "ED/y" is equal to or less than the left value (═ 3.0), the amount of projection of the first surface r1 on the distal end surface increases. Therefore, the cleaning performance of the tip end portion 12 is reduced, and the risk of the first surface r1 colliding with another structure or the like and being damaged increases when the electron microscope 1 is managed.
Next, six specific numerical examples of the endoscope objective optical system 100 described above will be described. The objective optical system 100 for an endoscope according to each of the numerical embodiments 1 to 6 is assembled to the distal end portion 12 of the electron microscope 1 shown in fig. 1.
[ example 1 ]
As described above, the configuration of the objective optical system 100 for an endoscope according to embodiment 1 of the present invention is shown in fig. 2.
Table 1 shows specific numerical configurations (design values) of the objective optical system 100 for an endoscope (and optical components arranged at the rear thereof) according to example 1. The face number NO shown in the upper column (face data) of table 1 corresponds to the face mark rn (n is a natural number) in fig. 2, except for the face number 5 corresponding to the diaphragm S. In the upper column of Table 1, R (unit: mm) represents the radius of curvature of each surface of the optical member, D (unit: mm) represents the thickness of the optical member or the interval between the optical members on the optical axis AX, N (D) represents the refractive index of D-line (wavelength 588nm), and vd represents the Abbe number of D-line. The lower column (various data) of table 1 shows the specifications (effective F number, focal length (unit: mm) of the entire system, optical magnification, half field angle (unit: degree), image height (unit: mm)) of the objective optical system 100 for an endoscope according to example 1.
[ TABLE 1 ]
Numerical example 1
Surface data
Various data
A list of values calculated when the conditions (1) to (4) are applied to the endoscopic objective optical system 100 according to example 1 is shown.
Condition (1): f. of1/fF＝0.35
Condition (2): ED/f 4.17
Condition (3): | f2/fF∣＝1.10
Condition (4): ED/y 3.11
Graphs a to D in fig. 3 are various aberration diagrams of the endoscopic objective optical system 100 according to example 1. Graph A shows spherical aberration on the d-line, g-line (wavelength 436nm), C-line (wavelength 656nm), and chromatic aberration on the axis. Graph B shows the chromatic aberration of magnification at d-line, g-line, and C-line. In the graph A, B, the solid line indicates the aberration of the d-line, the broken line indicates the aberration of the g-line, and the one-dot chain line indicates the aberration of the C-line. Graph C shows astigmatism. In graph C, the solid line represents the sagittal component and the broken line represents the meridional component. Graph D represents distortion aberration. The ordinate of each of the graphs a to C indicates the image height, and the abscissa indicates the amount of aberration. The vertical axis of the graph D represents the image height, and the horizontal axis represents the distortion rate. The description about the graphs in the present embodiment 1 also applies to the graphs mentioned in the following embodiments.
[ example 2 ]
Fig. 4 is a sectional view showing the arrangement of the optical components including the objective optical system 100 for an endoscope according to example 2 of the present invention. Graphs a to D in fig. 5 are graphs of various aberrations (spherical aberration, axial chromatic aberration, chromatic aberration of magnification, astigmatism, and distortion aberration) of the objective optical system 100 for an endoscope according to example 2. Table 2 shows specific numerical configurations and specifications of the objective optical system 100 for an endoscope according to example 2.
[ TABLE 2 ]
Numerical example 2
Surface data
Various data
A list of values calculated when the conditions (1) to (4) are applied to the endoscopic objective optical system 100 according to example 2 is shown.
Condition (1): f. of1/fF＝0.37
Condition (2): ED/f 4.07
Condition (3): | f2/fF∣＝1.34
Condition (4): ED/y is 3.07
[ example 3 ]
Fig. 6 is a sectional view showing the arrangement of the optical components including the objective optical system 100 for an endoscope according to example 3 of the present invention. Graphs a to D in fig. 7 are graphs of various aberrations (spherical aberration, axial chromatic aberration, chromatic aberration of magnification, astigmatism, and distortion aberration) of the objective optical system 100 for an endoscope according to example 3. Table 3 shows specific numerical configurations and specifications of the objective optical system 100 for an endoscope according to example 3.
[ TABLE 3 ]
Numerical example 3
Surface data
Various data
A list of values calculated when the conditions (1) to (4) are applied to the endoscopic objective optical system 100 according to example 3 is shown.
Condition (1): f. of1/fF＝0.23
Condition (2): ED/f 4.14
Condition (3): | f2/fF∣＝0.67
Condition (4): ED/y is 3.07
[ example 4 ]
Fig. 8 is a sectional view showing the arrangement of the optical components including the objective optical system 100 for an endoscope according to example 4 of the present invention. Graphs a to D in fig. 9 are graphs of various aberrations (spherical aberration, axial chromatic aberration, chromatic aberration of magnification, astigmatism, and distortion aberration) of the objective optical system 100 for an endoscope according to example 4. Table 4 shows specific numerical configurations and specifications of the objective optical system 100 for an endoscope according to example 4.
[ TABLE 4 ]
Numerical example 4
Surface data
Various data
A list of values calculated when the conditions (1) to (4) are applied to the objective optical system 100 for an endoscope according to example 4 is shown.
Condition (1): f. of1/fF＝0.37
Condition (2): ED/f 4.46
Condition (3): | f2/fF∣＝1.22
Condition (4): ED/y 3.33
[ example 5 ]
Fig. 10 is a sectional view showing the arrangement of the optical components including the objective optical system 100 for an endoscope according to example 5 of the present invention. Graphs a to D in fig. 11 are graphs of various aberrations (spherical aberration, axial chromatic aberration, chromatic aberration of magnification, astigmatism, and distortion aberration) of the objective optical system 100 for an endoscope according to example 5. Table 5 shows specific numerical configurations and specifications of the objective optical system 100 for an endoscope according to example 5.
[ TABLE 5 ]
Numerical value example 5
Surface data
Various data
A list of values calculated when the conditions (1) to (4) were applied to the endoscopic objective optical system 100 according to example 5 is shown.
Condition (1): f. of1/fF＝0.41
Condition (2): ED/f 4.29
Condition (3): | f2/fF∣＝1.45
Condition (4): ED/y 3.25
[ example 6 ]
Fig. 12 is a sectional view showing the arrangement of the optical components of the objective optical system 100 for an endoscope according to example 6 of the present invention. Graphs a to D in fig. 13 are graphs of various aberrations (spherical aberration, axial chromatic aberration, chromatic aberration of magnification, astigmatism, and distortion aberration) of the objective optical system 100 for an endoscope according to example 6. Table 6 shows specific numerical configurations and specifications of the objective optical system 100 for an endoscope according to example 6.
[ TABLE 6 ]
Numerical value example 6
Surface data
Various data
A list of values calculated when the conditions (1) to (4) are applied to the endoscopic objective optical system 100 according to example 6 is shown.
Condition (1): f. of1/fF＝0.47
Condition (2): ED/f 4.75
Condition (3): | f2/fF∣＝1.83
Condition (4): ED/y is 3.45
(comparison verification)
As comparative examples to examples 1 to 6, a first example of patent document 1 is exemplified. The objective optical system for an endoscope according to the comparative example includes a front group having negative power (a group including a negative meniscus lens having a convex surface facing the object side and a negative meniscus lens having a concave surface facing the object side, which are arranged in this order from the object side) and a rear group having positive power (a group including a plano-convex lens (positive lens) having a convex surface facing the image side, a biconvex lens as a positive lens, and a cemented lens having a concave surface facing the negative meniscus lens) arranged in this order from the object side), and does not satisfy all of the conditions (1) to (4). Therefore, the objective optical system for an endoscope according to the comparative example cannot realize a wide field angle and sufficient miniaturization. In order to realize a wide field angle, some optical characteristics such as peripheral resolution and incident light amount are sacrificed.
For reference, a list of values calculated when the conditions (1) to (4) are applied to the objective optical system for an endoscope according to the comparative example is shown.
Condition (1): f. of1/fF＝1.38
Condition (2): ED/f 2.98
Condition (3): | f2/fF∣＝4.75
Condition (4): ED/y 2.31
In contrast, the endoscopic objective optical system 100 according to each of examples 1 to 6 includes the first lens group G1 having negative power (a lens group including at least a negative lens having a concave surface facing the image side and a positive lens having a convex surface facing the image side in this order from the object side) and the second lens group G2 having positive power (a lens group including at least a positive lens having a convex surface facing the image side and a cemented lens obtained by cementing the negative lens and the positive lens in this order from the object side), and is configured to satisfy the conditions (1) and (2). Therefore, as shown in the tables and the various aberration diagrams, the objective optical system 100 for an endoscope according to the embodiments has excellent optical performance, and realizes downsizing and wide field angle.
The objective optical system 100 for an endoscope according to each of the embodiments 1 to 6 is configured to satisfy the condition (3) and the condition (4). According to each of embodiments 1 to 6, further effects can be achieved by satisfying the conditions (3) and (4).
The foregoing is a description of exemplary embodiments of the invention. The embodiments of the present invention are not limited to the above description, and various modifications are possible within the scope of the technical idea of the present invention. For example, the embodiments exemplarily illustrated in the description or the obvious embodiments and the like are also included in the embodiments of the present application, where appropriate.
Claims (6)
1. An objective optical system for an endoscope, characterized in that,
includes, in order from an object side, a first lens group having negative power and a second lens group having positive power,
the first lens group comprises a negative lens with a concave surface facing to the image side and a positive lens with a convex surface facing to the image side in sequence from the object side,
the second lens group includes, in order from an object side, at least a positive lens having a convex surface facing the image side and a cemented lens in which a negative lens and the positive lens are cemented,
defining a focal length of the negative lens positioned closest to the object side within the first lens group as f1Defining a focal length of the first lens group as fFWhen an effective diameter in a maximum image height of a face located closest to the object side within the first lens group is positioned as ED and a combined focal length of the first lens group and the second lens group is defined as f, the following two conditions are satisfied:
0.2＜f1/fF＜0.5
4.0＜ED/f＜5.0
wherein f is1、fFThe units of ED, f are mm,
when the maximum image height in the imaging plane is defined as y, the following condition is satisfied:
3.0＜ED/y＜4.0，
wherein y is in mm.
2. The endoscopic objective optical system according to claim 1,
an aperture stop is provided between the first lens group and the second lens group,
defining a focal length of the positive lens positioned at the side closest to an aperture stop within the first lens group as f2Then, the following conditions are satisfied:
0.5＜∣f2/fF∣＜2.0，
wherein f is2The unit of (d) is mm.
3. The objective optical system for an endoscope according to claim 1 or 2,
a surface of the positive lens in the first lens group that satisfies the object side is a plane.
4. The objective optical system for an endoscope according to claim 1 or 2,
the field angle of the objective optical system for an endoscope exceeds 180 °.
5. The objective optical system for an endoscope according to claim 1 or 2,
lens surfaces of all the lenses included in the first lens group and the second lens group are spherical surfaces.
6. An endoscope having the objective optical system for an endoscope according to any one of claims 1 to 5 assembled at a distal end thereof.
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| JP2016155329A JP6774811B2 (en) | 2016-08-08 | 2016-08-08 | Objective optical system for endoscopes and endoscopes |
| JP2016-155329 | 2016-08-08 |
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| JP7126868B2 (en) * | 2018-06-04 | 2022-08-29 | 株式会社タムロン | Imaging lens and imaging device |
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| JPH08122634A (en) * | 1994-10-25 | 1996-05-17 | Asahi Optical Co Ltd | Objective for endoscope |
| JP3851417B2 (en) * | 1997-06-24 | 2006-11-29 | ペンタックス株式会社 | Endoscope objective optical system |
| JP4150565B2 (en) * | 2002-09-25 | 2008-09-17 | Ｈｏｙａ株式会社 | Endoscope objective lens system |
| JP4426236B2 (en) * | 2003-09-17 | 2010-03-03 | Ｈｏｙａ株式会社 | Endoscope objective optical system |
| JP2006146016A (en) * | 2004-11-24 | 2006-06-08 | Matsushita Electric Ind Co Ltd | Wide angle lens |
| US7885010B1 (en) * | 2008-01-14 | 2011-02-08 | Integrated Medical Systems International | Endoscope objective lens and method of assembly |
| CN101630058B (en) * | 2008-07-18 | 2011-03-23 | 上海澳华光电内窥镜有限公司 | Objective lens of endoscope |
| JP5668059B2 (en) * | 2010-06-01 | 2015-02-12 | Hoya株式会社 | Endoscope objective lens and endoscope |
| JP2013238684A (en) * | 2012-05-14 | 2013-11-28 | Tamron Co Ltd | Fisheye lens |
| WO2014088104A1 (en) * | 2012-12-07 | 2014-06-12 | オリンパス株式会社 | Objective lens and observation device equipped with same |
| TWI491915B (en) * | 2014-04-01 | 2015-07-11 | Sintai Optical Shenzhen Co Ltd | Wide-angle lens |
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| CN107703606A (en) | 2018-02-16 |
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