JP2013003267A - Imaging optical system and endoscope device including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging optical system capable of sufficiently generating axial chromatic aberration while suppressing generation of chromatic aberration of magnification.SOLUTION: The imaging optical system comprises in order from an object side, a front group, an aperture, and a rear group. The front group includes a positive lens and a negative lens, and satisfies all of the following conditional expressions: 30≤|νd-νd|; 0.1≤y/y≤0.7; and -0.4≤Δf/f≤-0.1, where νdis the Abbe number of the positive lens, νdis the Abbe number of the negative lens, yis a maximum height of a principal ray in the positive lens or the negative lens, yis the height of an image, Δfis the axial chromatic aberration of light (g line) with a wavelength of 435 nm when using light (e line) with the wavelength of 546nm as a criterion, and f is a focal length of an entire system in the light (e line) with the wavelength of 546nm.

Description

  The present invention relates to an imaging optical system suitable for an imaging apparatus that performs image processing for increasing the depth of field, and an endoscope apparatus including the imaging optical system.

  Patent Document 1 discloses a method of performing image processing on an acquired image and expanding the depth of field. The image processing method described in Patent Document 1 is a method that utilizes the fact that the focal length of transmitted light differs depending on the wavelength in the imaging optical system, that is, the occurrence of chromatic aberration. Specifically, two or more colors are acquired in a predetermined region, and image processing is performed so as to recover a color having a low resolution (sharpness) among these colors.

  As an imaging optical system used in an apparatus for carrying out the image processing method described in Patent Document 1, for example, a sufficient axis as in the imaging optical system described in Patent Document 2 is used. Those in which upper chromatic aberration occurs are preferable.

JP 2008-532449 A JP 2006-141711 A

  However, in the image processing method described in Patent Document 1, the only chromatic aberration required for performing the image processing is axial chromatic aberration, and no lateral chromatic aberration is required.

  However, a general imaging optical system as described in Patent Document 2 generates lateral chromatic aberration along with axial chromatic aberration.

  Therefore, when an imaging optical system as described in Patent Document 2 is used in an apparatus for carrying out the image processing method described in Patent Document 1, the image quality is increased due to lateral chromatic aberration generated along with axial chromatic aberration. There was a problem that would deteriorate. In particular, when a high-pixel image sensor with a narrow pixel pitch is used in the apparatus, there is a problem that as the angle of view increases, the color blurs and the deterioration of the image becomes severe.

  The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide an imaging optical that can sufficiently generate axial chromatic aberration while suppressing the occurrence of lateral chromatic aberration. A system and an endoscope apparatus using the system are provided.

In order to achieve the above object, an imaging optical system of the present invention is an imaging optical system including a front group, a stop, and a rear group in order from the object side, wherein the front group is a positive lens. It has a negative lens and satisfies all of the following conditional expressions.
30 ≦ | νd _p −νd _n |
0.1 ≤ y _pn / y _i ≤ 0.7
−0.4 ≦ Δf _g /f≦−0.1
However, [nu] d _p is the Abbe number of the positive lens, [nu] d _n is the Abbe number of the negative lens, y _pn is the positive lens or maximum ray height of the chief ray in the negative lens, y _i denotes an image height, Delta] f _g is the wavelength On-axis chromatic aberration of light (g line) having a wavelength of 435 nm when f 546 nm light (e line) is used as a reference, and f is the focal length of the entire system of light (e line) having a wavelength of 546 nm.

In order to achieve the above object, the imaging optical system according to the present invention is an imaging optical system including a front group, a stop, and a rear group in order from the object side. It has a lens and a negative lens, and satisfies all of the following conditional expressions.
40 ≦ | νd _p −νd _n |
0.6 ≤ y _pn / y _i ≤ 1.2
−0.6 ≦ Δf _g /f≦−0.1
However, [nu] d _p is the Abbe number of the positive lens, [nu] d _n is the Abbe number of the negative lens, y _pn is the positive lens or maximum ray height of the chief ray in the negative lens, y _i denotes an image height, Delta] f _g is the wavelength On-axis chromatic aberration of light (g line) having a wavelength of 435 nm when f 546 nm light (e line) is used as a reference, and f is the focal length of the entire system of light (e line) having a wavelength of 546 nm.

In order to achieve the above object, the imaging optical system according to the present invention is an imaging optical system including a front group, a stop, and a rear group in order from the object side. It has a lens and a negative lens, and satisfies all of the following conditional expressions.
40 ≦ | νd _p −νd _n |
0.1 ≤ y _pn / y _i ≤ 0.6
0.1 ≦ Δf _g / f ≦ 1
However, [nu] d _p is the Abbe number of the positive lens, [nu] d _n is the Abbe number of the negative lens, y _pn is the positive lens or maximum ray height of the chief ray in the negative lens, y _i denotes an image height, Delta] f _g is the wavelength On-axis chromatic aberration of light (g line) having a wavelength of 435 nm when f 546 nm light (e line) is used as a reference, and f is the focal length of the entire system of light (e line) having a wavelength of 546 nm.

In order to achieve the above object, the imaging optical system of the present invention is an imaging optical system including a front group, a stop, and a rear group in order from the object side. It has a lens and a negative lens, and satisfies all of the following conditional expressions.
20 ≦ | νd _p −νd _n |
0.2 ≤ y _pn / y _i ≤ 0.4
0.1 ≦ Δf _g / f ≦ 1
However, [nu] d _p is the Abbe number of the positive lens, [nu] d _n is the Abbe number of the negative lens, y _pn is the positive lens or maximum ray height of the chief ray in the negative lens, y _i denotes an image height, Delta] f _g is the wavelength On-axis chromatic aberration of light (g line) having a wavelength of 435 nm when f 546 nm light (e line) is used as a reference, and f is the focal length of the entire system of light (e line) having a wavelength of 546 nm.

  The imaging optical system according to the present invention preferably includes a positive lens and a negative lens in each of the front group and the rear group.

  In the imaging optical system of the present invention, it is preferable that the positive lens and the negative lens are cemented.

  In order to achieve the above object, an endoscope apparatus according to the present invention includes any one of the imaging optical systems described above.

  According to the present invention, it is possible to provide an imaging optical system capable of sufficiently generating axial chromatic aberration while suppressing the occurrence of lateral chromatic aberration, and an endoscope apparatus using the same.

It is a figure which shows MTF of the defocus direction of the imaging optical system of this invention. It is a figure which shows MTF of the defocus direction of the conventional imaging optical system. 2 is a cross-sectional view along the optical axis showing the configuration and optical path of the imaging optical system according to Example 1. FIG. FIG. 4 is a cross-sectional view along the optical axis showing details of a lens constituting the imaging optical system shown in FIG. 3. 4A and 4B are aberration diagrams of the imaging optical system illustrated in FIG. 3, in which (a) illustrates spherical aberration, (b) illustrates field curvature aberration, (c) illustrates distortion, and (d) illustrates lateral chromatic aberration. FIG. 6 is a cross-sectional view along the optical axis showing the configuration and optical path of an imaging optical system according to Example 2. It is sectional drawing which follows the optical axis which shows the detail of the lens which comprises the imaging optical system shown in FIG. FIG. 7A is an aberration diagram of the imaging optical system shown in FIG. 6, where (a) shows spherical aberration, (b) shows field curvature aberration, (c) shows distortion aberration, and (d) shows lateral chromatic aberration. FIG. 6 is a cross-sectional view along the optical axis showing the configuration and optical path of an imaging optical system according to Example 3. It is sectional drawing which follows the optical axis which shows the detail of the lens which comprises the imaging optical system shown in FIG. FIG. 10 is an aberration diagram of the imaging optical system shown in FIG. 9, where (a) shows spherical aberration, (b) shows field curvature aberration, (c) shows distortion aberration, and (d) shows lateral chromatic aberration. FIG. 6 is a cross-sectional view along the optical axis showing the configuration and optical path of an imaging optical system according to Example 4. It is sectional drawing which follows the optical axis which shows the detail of the lens which comprises the imaging optical system shown in FIG. FIGS. 13A and 12B are aberration diagrams of the imaging optical system illustrated in FIG. 12, in which FIG. 12A illustrates spherical aberration, FIG. 12B illustrates field curvature aberration, FIG. 12C illustrates distortion, and FIG. FIG. 10 is a cross-sectional view along the optical axis showing the configuration and optical path of an imaging optical system according to Example 5. It is sectional drawing which follows the optical axis which shows the detail of the lens which comprises the imaging optical system shown in FIG. FIG. 16 is an aberration diagram of the imaging optical system shown in FIG. 15, where (a) shows spherical aberration, (b) shows field curvature aberration, (c) shows distortion aberration, and (d) shows lateral chromatic aberration. FIG. 10 is a cross-sectional view along the optical axis showing the configuration and optical path of an imaging optical system according to Example 6. It is sectional drawing which follows the optical axis which shows the detail of the lens which comprises the imaging optical system shown in FIG. FIG. 19 is an aberration diagram of the imaging optical system shown in FIG. 18, where (a) shows spherical aberration, (b) shows field curvature aberration, (c) shows distortion aberration, and (d) shows lateral chromatic aberration. FIG. 10 is a cross-sectional view along the optical axis showing the configuration and optical path of an imaging optical system according to Example 7. It is sectional drawing which follows the optical axis which shows the detail of the lens which comprises the imaging optical system shown in FIG. FIG. 22 shows aberration diagrams of the imaging optical system shown in FIG. 21, where (a) shows spherical aberration, (b) shows field curvature aberration, (c) shows distortion, and (d) shows lateral chromatic aberration. FIG. 10 is a sectional view taken along the optical axis showing the configuration and optical path of an imaging optical system according to Example 8. FIG. 25 is a cross-sectional view taken along the optical axis, showing details of a lens constituting the imaging optical system shown in FIG. 24. FIG. 25 is aberration diagrams of the imaging optical system shown in FIG. 24, where (a) shows spherical aberration, (b) shows field curvature aberration, (c) shows distortion aberration, and (d) shows lateral chromatic aberration. FIG. 10 is a sectional view taken along the optical axis showing the configuration and optical path of an imaging optical system according to Example 9. It is sectional drawing which follows the optical axis which shows the detail of the lens which comprises the imaging optical system shown in FIG. FIG. 28 is an aberration diagram of the imaging optical system shown in FIG. 27, where (a) shows spherical aberration, (b) shows field curvature aberration, (c) shows distortion aberration, and (d) shows lateral chromatic aberration. FIG. 12 is a cross-sectional view along the optical axis showing the configuration and optical path of an imaging optical system according to Example 10. It is sectional drawing which follows the optical axis which shows the detail of the lens which comprises the imaging optical system shown in FIG. FIG. 31 is an aberration diagram of the imaging optical system shown in FIG. 30, where (a) shows spherical aberration, (b) shows field curvature aberration, (c) shows distortion aberration, and (d) shows lateral chromatic aberration. 14 is a cross-sectional view along the optical axis showing the configuration and optical path of an imaging optical system according to Example 11. FIG. It is sectional drawing which follows the optical axis which shows the detail of the lens which comprises the imaging optical system shown in FIG. FIG. 34 is an aberration diagram of the imaging optical system shown in FIG. 33, where (a) shows spherical aberration, (b) shows field curvature aberration, (c) shows distortion aberration, and (d) shows lateral chromatic aberration. FIG. 16 is a cross-sectional view along the optical axis showing the configuration and optical path of an imaging optical system according to Example 12. FIG. 37 is a cross-sectional view along the optical axis showing details of a lens constituting the imaging optical system shown in FIG. 36. FIG. 37 is an aberration diagram of the imaging optical system shown in FIG. 36, where (a) shows spherical aberration, (b) shows field curvature aberration, (c) shows distortion aberration, and (d) shows lateral chromatic aberration. FIG. 14 is a cross-sectional view along the optical axis showing the configuration and optical path of an imaging optical system according to Example 13. It is sectional drawing which follows the optical axis which shows the detail of the lens which comprises the imaging optical system shown in FIG. FIG. 40 is an aberration diagram of the imaging optical system shown in FIG. 39, where (a) shows spherical aberration, (b) shows field curvature aberration, (c) shows distortion aberration, and (d) shows lateral chromatic aberration. 1 is an overall view of an endoscope apparatus including an imaging optical system according to the present invention.

  Prior to the description of the embodiments of the imaging optical system of the present invention and the endoscope apparatus using the same, the function and effect of the present invention will be described. It should be noted that when specifically describing the operational effects of the present invention, embodiments of the present invention will also be described with specific examples. However, these exemplified modes are just a part of the modes included in the present invention as in the case of the embodiments described later, and there are actually many variations. Accordingly, the present invention is not limited to those illustrated embodiments.

The imaging optical system according to the present invention is an imaging optical system including a front group, a stop, and a rear group in order from the object side. The front group includes a positive lens and a negative lens, and the following conditions are satisfied. All the expressions are satisfied.
30 ≦ | νd _p −νd _n | ... (1-1)
0.1 ≦ y _pn / y _i ≦ 0.7 (2-1)
−0.4 ≦ Δf _g /f≦−0.1 ... (3-1)
However, [nu] d _p is the Abbe number of the positive lens, [nu] d _n is the Abbe number of the negative lens, y _pn is the positive lens or maximum ray height of the chief ray in the negative lens, y _i denotes an image height, Delta] f _g is the wavelength On-axis chromatic aberration of light (g line) having a wavelength of 435 nm when f 546 nm light (e line) is used as a reference, and f is the focal length of the entire system of light (e line) having a wavelength of 546 nm.

  Thus, when a lens pair consisting of a positive lens and a negative lens is arranged in the front group, all of the above conditional expressions (1-1), (2-1), and (3-1) must be satisfied simultaneously. Thus, in this imaging optical system, it is possible to obtain axial chromatic aberration with insufficient correction while suppressing the occurrence of lateral chromatic aberration.

  Since this imaging optical system is configured to satisfy the conditional expressions (1-1) and (2-1), it is possible to effectively correct the lateral chromatic aberration. Therefore, even if axial chromatic aberration within the range of conditional expression (3-1) is generated, the image quality is not deteriorated.

In addition, it is more preferable to configure so as to satisfy any of the following conditional expressions (1-1) ′ and (1-1) ″ instead of the conditional expression (1-1).
35 ≦ | νd _p −νd _n | ... (1-1) '
40 ≦ | νd _p −νd _n | ... (1-1) "

Further, it is more preferable to configure so as to satisfy one of the following conditional expressions (2-1) ′ and (2-1) ″ instead of the conditional expression (2-1).
0.2 ≦ y _pn / y _i ≦ 0.6 (2-1) ′
0.25 ≦ y _pn / y _i ≦ 0.55 (2-1) ”
The upper limit value or lower limit value of conditional expression (2-1) ′ may be the upper limit value or lower limit value of conditional expression (2-1), or the upper limit value or lower limit value of conditional expression (2-1) ″. May be the upper limit value or lower limit value of conditional expressions (2-1) and (2-1) ′.

Furthermore, it is more preferable to configure so as to satisfy one of the following conditional expressions (3-1) ′ and (3-1) ″ instead of the conditional expression (3-1).
−0.35 ≦ Δf _g /f≦−0.13 ... (3-1) '
−0.30 ≦ Δf _g /f≦−0.15 ... (3-1) "
The upper limit value or lower limit value of conditional expression (3-1) ′ may be the upper limit value or lower limit value of conditional expression (3-1), or the upper limit value or lower limit value of conditional expression (3-1) ″. May be the upper limit value or lower limit value of conditional expressions (3-1) and (3-1) ′.

  Here, the adaptability of this imaging optical system and the conventional imaging optical system to image processing for expanding the depth of field will be compared using FIG. 1 and FIG. 2.

  FIG. 1 is a diagram showing MTF (imaging performance) in the defocus direction (focus amount) of this imaging optical system. FIG. 2 is a diagram showing the MTF in the defocus direction of the conventional imaging optical system. 1 and 2, the vertical axis represents the MTF, and the horizontal axis represents the defocus amount.

  As can be seen from these figures, this imaging optical system (FIG. 1) has a significantly different MTF peak value for each color as compared with the conventional imaging optical system (FIG. 2). That is, when the position where the MTF is less than 10% is the depth end, the position is greatly different for each color.

  An image processing method for enlarging the depth of field as described in Patent Document 1 is based on color information with a high resolution (sharpness), and a color recovery process with a low resolution (sharpness). Is to do. Therefore, when this image processing is performed, the depth of field is enlarged according to the position of the depth end of the color with high resolving power (sharpness).

  Therefore, in an apparatus that performs image processing as described in Patent Document 1, it is possible to greatly expand the depth of field by using this imaging optical system rather than using a conventional imaging optical system. In addition, image quality deterioration due to an increase in lateral chromatic aberration can be suppressed.

Further, the imaging optical system of the present invention is an imaging optical system including a front group, a stop, and a rear group in order from the object side, and the rear group includes a positive lens and a negative lens. It is characterized by satisfying all the conditional expressions.
40 ≦ | νd _p −νd _n | ... (1-2)
0.6 ≦ y _pn / y _i ≦ 1.2 (2-2)
−0.6 ≦ Δf _g /f≦−0.1 ... (3-2)
However, [nu] d _p is the Abbe number of the positive lens, [nu] d _n is the Abbe number of the negative lens, y _pn is the positive lens or maximum ray height of the chief ray in the negative lens, y _i denotes an image height, Delta] f _g is the wavelength On-axis chromatic aberration of light (g line) having a wavelength of 435 nm when f 546 nm light (e line) is used as a reference, and f is the focal length of the entire system of light (e line) having a wavelength of 546 nm.

  Thus, when a lens pair consisting of a positive lens and a negative lens is arranged in the rear group, all of the above conditional expressions (1-2), (2-2), and (3-2) are satisfied simultaneously. Thus, in this imaging optical system, it is possible to obtain axial chromatic aberration with insufficient correction while suppressing the occurrence of lateral chromatic aberration.

In addition, it is more preferable to configure so as to satisfy one of the following conditional expressions (1-2) ′ and (1-2) ″ instead of the conditional expression (1-2).
45 ≦ | νd _p −νd _n | ... (1-2) '
50 ≦ | νd _p −νd _n | ... (1-2) "

Further, it is more preferable to configure so as to satisfy any of the following conditional expressions (2-2) ′ and (2-2) ″ instead of the conditional expression (2-2).
0.7 ≦ y _pn / y _i ≦ 1.1 (2-2) ′
0.8 ≦ y _pn / y _i ≦ 1.05 (2-2) ”
The upper limit value or lower limit value of conditional expression (2-2) ′ may be used as the upper limit value or lower limit value of conditional expression (2-2), or the upper limit value or lower limit value of conditional expression (2-2) ″. May be the upper limit value or lower limit value of conditional expressions (2-2) and (2-2) ′.

Furthermore, it is more preferable to configure so as to satisfy one of the following conditional expressions (3-2) ′ and (3-2) ″ instead of the conditional expression (3-2).
−0.5 ≦ Δf _g /f≦−0.13 ... (3-2) '
−0.45 ≦ Δf _g /f≦−0.15 ... (3-2) "
The upper limit value or lower limit value of conditional expression (3-2) ′ may be the upper limit value or lower limit value of conditional expression (3-2), or the upper limit value or lower limit value of conditional expression (3-2) ″. May be the upper limit value or lower limit value of conditional expressions (3-2) and (3-2) ′.

Further, the imaging optical system of the present invention is an imaging optical system including a front group, a stop, and a rear group in order from the object side, and the rear group includes a positive lens and a negative lens. It is characterized by satisfying all the conditional expressions.
40 ≦ | νd _p −νd _n | ... (1-3)
0.1 ≦ y _pn / y _i ≦ 0.6 (2-3)
0.1 ≦ Δf _g / f ≦ 1 ... (3-3)
However, [nu] d _p is the Abbe number of the positive lens, [nu] d _n is the Abbe number of the negative lens, y _pn is the positive lens or maximum ray height of the chief ray in the negative lens, y _i denotes an image height, Delta] f _g is the wavelength On-axis chromatic aberration of light (g line) having a wavelength of 435 nm when f 546 nm light (e line) is used as a reference, and f is the focal length of the entire system of light (e line) having a wavelength of 546 nm.

  Thus, when a lens pair consisting of a positive lens and a negative lens is arranged in the rear group, all of the above conditional expressions (1-3), (2-3), and (3-3) are satisfied simultaneously. By doing so, in this imaging optical system, it is possible to obtain axial chromatic aberration in an overcorrected state while suppressing the occurrence of lateral chromatic aberration.

In addition, it is more preferable to configure so as to satisfy one of the following conditional expressions (1-3) ′ and (1-3) ″ instead of the conditional expression (1-3).
50 ≦ | νd _p −νd _n | ... (1-3) '
55 ≦ | νd _p −νd _n | ... (1-3) "

Further, it is more preferable to configure so as to satisfy one of the following conditional expressions (2-3) ′ and (2-3) ″ instead of the conditional expression (2-3).
0.2 ≦ y _pn / y _i ≦ 0.55 (2-3) ′
0.25 ≦ y _pn / y _i ≦ 0.5 (2-3) ”
The upper limit value or lower limit value of conditional expression (2-3) ′ may be the upper limit value or lower limit value of conditional expression (2-3), or the upper limit value or lower limit value of conditional expression (2-3) ″. May be the upper limit value or lower limit value of conditional expressions (2-3) and (2-3) ′.

Furthermore, it is more preferable to configure so as to satisfy one of the following conditional expressions (3-3) ′ and (3-3) ″ instead of the conditional expression (3-3).
0.13 ≦ Δf _g /f≦0.95 ... (3-3) '
0.15 ≦ Δf _g /f≦0.9 ... (3-3) "
The upper limit value or lower limit value of conditional expression (3-3) ′ may be set as the upper limit value or lower limit value of conditional expression (3-3), or the upper limit value or lower limit value of conditional expression (3-3) ″. May be the upper limit value or lower limit value of conditional expressions (3-3) and (3-3) ′.

Further, the imaging optical system of the present invention is an imaging optical system including a front group, a stop, and a rear group in order from the object side, wherein the front group includes a positive lens and a negative lens, It is characterized by satisfying all the conditional expressions.
20 ≦ | νd _p −νd _n | ... (1-4)
0.2 ≦ y _pn / y _i ≦ 0.4 (2-4)
0.1 ≦ Δf _g / f ≦ 1 ... (3-4)
However, [nu] d _p is the Abbe number of the positive lens, [nu] d _n is the Abbe number of the negative lens, y _pn is the positive lens or maximum ray height of the chief ray in the negative lens, y _i denotes an image height, Delta] f _g is the wavelength On-axis chromatic aberration of light (g line) having a wavelength of 435 nm when f 546 nm light (e line) is used as a reference, and f is the focal length of the entire system of light (e line) having a wavelength of 546 nm.

  Thus, when a lens pair consisting of a positive lens and a negative lens is arranged in the front group, all of the above conditional expressions (1-4), (2-4), and (3-4) are satisfied simultaneously. By doing so, in this imaging optical system, it is possible to obtain axial chromatic aberration in an overcorrected state while suppressing the occurrence of lateral chromatic aberration.

  In the imaging optical system of the present invention, it is preferable that the positive lens and the negative lens are cemented.

  By cementing the positive and negative lenses that make up the lens pair into a cemented lens, the cemented surface can be made to have a large curvature without causing total reflection, effectively correcting chromatic aberration of magnification. can do.

  In addition, an endoscope apparatus according to the present invention includes the imaging optical system according to any one of the above-described inventions.

  In general, in an endoscope apparatus, it is preferable to acquire an image having a large depth of field. Therefore, when using an image processing method as described in Patent Document 1 as means for expanding the depth of field, any one of the above-described imaging optical systems may be used. Further, since this imaging optical system can be a retrofocus type optical system, it is easy to reduce the size, and in this respect, it is also suitable for an endoscope apparatus.

  Hereinafter, embodiments of the imaging optical system of the present invention and an endoscope apparatus using the imaging optical system of the present invention will be described with reference to the drawings.

In the optical system sectional views r ₁ , r ₂ ,... And d ₁ , d ₂ ,..., The numbers shown as subscripts correspond to the surface numbers 1, 2,. is doing.

  In the numerical data, s is the surface number, r is the radius of curvature of each surface, d is the surface spacing, nd is the refractive index at the d-line (wavelength 587.56 nm), and νd is the Abbe number at the d-line. Yes.

  Hereinafter, the imaging optical system according to Example 1 will be described in detail with reference to FIGS.

  FIG. 3 is a cross-sectional view along the optical axis showing the configuration and optical path of the imaging optical system. FIG. 4 is a cross-sectional view along the optical axis showing the details of the lens constituting the imaging optical system shown in FIG. 5A and 5B are aberration diagrams of the imaging optical system shown in FIG. 3, where FIG. 5A shows spherical aberration, FIG. 5B shows field curvature aberration, FIG. 5C shows distortion aberration, and FIG. 5D shows lateral chromatic aberration. ing.

  As shown in FIGS. 3 and 4, the imaging optical system includes, in order from the object side, a front group FG, a diaphragm S, and a rear group RG, which are arranged on the optical axis Lc.

The front group FG has, in order from the object side, a lens L ₁ that is a plano-concave lens having negative refractive power and a concave surface facing the image side, a lens L ₂ that is a flat lens, and has negative refractive power on the image side. It is composed of L ₃ which is a plano-concave lens having a concave surface and a lens L ₄ which is a biconvex lens having a positive refractive power. Note that the lens L ₃ and the lens L ₄ form a lens pair including a negative lens and a positive lens. The lens L ₃ and the lens L ₄ are cemented.

The rear group RG includes, in order from the object side, a lens L ₅ that is a biconvex lens having positive refractive power and a lens L ₆ that is a plano-convex lens having positive refractive power and having a convex surface facing the object side. .

Numerical data 1
Unit mm
Surface data Surface number Curvature radius Surface spacing Refractive index Abbe number s r d nd νd
1 ∞ 0.50 1.88300 40.76
2 1.444 1.15
3 ∞ 0.31 1.51633 64.14
4 ∞ 0.20
5 ∞ 0.81 1.51633 64.14
6 5.020 1.60 1.84666 23.78
7 -3.423 0.90
8 (Aperture) ∞ 0.35
9 14.280 1.40 1.72916 54.68
10 -10.484 2.42
11 3.301 1.40 1.61800 63.33
12 ∞ 0.73

Various data Abbe number νd _p of positive lens of lens pair: 64.140
Abbe number νd _n of the negative lens of the lens pair: 23.780
Maximum ray height y _pn of the principal ray in the lens pair: 0.766
Image height y _i : 1.500
G-axis axial chromatic aberration Δf _g with respect to e-line: −0.236
Total system focal length f (mm) : 1.497

Condition _{(1-1) 30 ≦ | νd p} -νd n | : 40.360
_{(2-1) 0.1 ≦ y pn /} y i ≦ 0.7: 0.511
(3-1) −0.4 ≦ Δf _g /f≦−0.1 : -0.158

  Hereinafter, the imaging optical system according to Example 2 will be described in detail with reference to FIGS.

  FIG. 6 is a cross-sectional view along the optical axis showing the configuration and optical path of the imaging optical system. FIG. 7 is a cross-sectional view along the optical axis showing the details of the lenses constituting the imaging optical system shown in FIG. 8A and 8B are aberration diagrams of the imaging optical system shown in FIG. 6, in which FIG. 8A shows spherical aberration, FIG. 8B shows field curvature aberration, FIG. 8C shows distortion aberration, and FIG. 8D shows lateral chromatic aberration. ing.

  As shown in FIGS. 6 and 7, the imaging optical system is composed of a front group FG, a stop S, and a rear group RG in order from the object side, and these are arranged on the optical axis Lc.

The front group FG has, in order from the object side, a lens L ₁ that is a plano-concave lens having negative refractive power and a concave surface facing the image side, a lens L ₂ that is a flat lens, and has negative refractive power on the image side. It is composed of L ₃ which is a plano-concave lens having a concave surface and a lens L ₄ which is a biconvex lens having a positive refractive power. Note that the lens L ₃ and the lens L ₄ form a lens pair including a negative lens and a positive lens.

The rear group RG includes, in order from the object side, a lens L ₅ that is a biconvex lens having positive refractive power and a lens L ₆ that is a meniscus lens having positive refractive power and having a convex surface facing the object side. .

Numerical data 2
Unit mm
Surface data Surface number Curvature radius Surface spacing Refractive index Abbe number s r d nd νd
1 ∞ 0.50 1.88300 40.76
2 1.427 1.03
3 ∞ 0.31 1.51633 64.14
4 ∞ 0.20
5 ∞ 0.50 1.51633 64.14
6 4.866 0.20
7 4.760 2.35 1.84666 23.78
8 -3.872 0.70
9 (Aperture) ∞ 0.39
10 5.924 0.65 1.72916 54.68
11 -230.883 3.15
12 2.866 0.80 1.61800 63.33
13 11.660 0.81

Various data Abbe number νd _p of positive lens of lens pair: 64.140
Abbe number νd _n of the negative lens of the lens pair: 23.780
Maximum ray height y _pn of the principal ray in the lens pair: 0.755
Image height y _i : 1.500
G-axis longitudinal chromatic aberration Δf _g with respect to e-line: −0.248
Total system focal length f (mm) : 1.500

Condition _{(1-1) 30 ≦ | νd p} -νd n | : 40.360
(2-1) 0.1 ≦ y _pn / y _i ≦ 0.7: 0.503
(3-1) −0.4 ≦ Δf _g /f≦−0.1 : -0.165

  The imaging optical system according to Example 3 will be described in detail below with reference to FIGS.

  FIG. 9 is a cross-sectional view along the optical axis showing the configuration and optical path of the imaging optical system. FIG. 10 is a cross-sectional view along the optical axis showing the details of the lenses constituting the imaging optical system shown in FIG. FIG. 11 is an aberration diagram of the imaging optical system shown in FIG. 9, where (a) shows spherical aberration, (b) shows field curvature aberration, (c) shows distortion, and (d) shows lateral chromatic aberration. ing.

  As shown in FIGS. 9 and 10, this imaging optical system is composed of a front group FG, a stop S, and a rear group RG in order from the object side, and these are arranged on the optical axis Lc.

The front group FG includes, in order from the object side, a lens L ₁ that is a plano-concave lens having negative refractive power and a concave surface facing the image side, a lens L ₂ that is a flat lens, and a biconcave lens having negative refractive power. It is constituted by a certain L ₃ and a lens L ₄ which is a biconvex lens having a positive refractive power. Note that the lens L ₃ and the lens L ₄ form a lens pair including a negative lens and a positive lens. The lens L ₃ and the lens L ₄ are cemented.

The rear group RG includes, in order from the object side, a lens L ₅ that is a biconvex lens having positive refractive power and a lens L ₆ that is a meniscus lens having positive refractive power and having a convex surface facing the object side. .

Numerical data 3
Unit mm
Surface data Surface number Curvature radius Surface spacing Refractive index Abbe number s r d nd νd
1 ∞ 0.50 1.88300 40.76
2 1.680 1.15
3 ∞ 0.31 1.51633 64.14
4 ∞ 1.42
5 -7.211 0.56 1.49700 81.54
6 4.780 0.83 1.92286 18.90
7 -3.600 0.62
8 (Aperture) ∞ 2.35
9 24.437 0.42 1.77250 49.60
10 -14.827 1.61
11 2.525 0.83 1.49700 81.54
12 11.074 1.28

Various data Abbe number νd _p of positive lens of lens pair: 81.540
Abbe number νd _n of the negative lens of the lens pair: 18.900
Maximum ray height y _pn of the principal ray in the lens pair: 0.478
Image height y _i : 1.500
G-axis axial chromatic aberration Δf _g with respect to e-line: −0.436
Total system focal length f (mm) : 1.500

Condition _{(1-1) 30 ≦ | νd p} -νd n | : 62.640
(2-1) 0.1 ≦ y _pn / y _i ≦ 0.7: 0.318
(3-1) −0.4 ≦ Δf _g /f≦−0.1 : -0.291

  The imaging optical system according to Example 4 will be described in detail below with reference to FIGS.

  FIG. 12 is a cross-sectional view along the optical axis showing the configuration and optical path of the imaging optical system. FIG. 13 is a cross-sectional view along the optical axis showing the details of the lens constituting the imaging optical system shown in FIG. FIG. 14 is an aberration diagram of the imaging optical system shown in FIG. 12, where (a) shows spherical aberration, (b) shows curvature of field aberration, (c) shows distortion, and (d) shows chromatic aberration of magnification. ing.

  As shown in FIGS. 12 and 13, this imaging optical system includes a front group FG, a diaphragm S, and a rear group RG in order from the object side, and these are arranged on the optical axis Lc.

The front group FG includes, in order from the object side, a lens L ₁ that is a plano-concave lens having negative refractive power and a concave surface facing the image side, a lens L ₂ that is a flat lens, and a biconvex lens having positive refractive power. It is constituted by a certain L ₃ and a lens L ₄ which is a biconcave lens having negative refractive power. The lens L ₃ and the lens L ₄ form a lens pair composed of a positive lens and a negative lens. The lens L ₃ and the lens L ₄ are cemented.

The rear group RG is, in order from the object side, a lens L ₅ that is a meniscus lens having negative refractive power and having a convex surface facing the object side, and a lens L ₆ that is a meniscus lens having positive refractive power and directing the convex surface to the object side. It is comprised by.

Numerical data 4
Unit mm
Surface data Surface number Curvature radius Surface spacing Refractive index Abbe number s r d nd νd
1 ∞ 0.50 1.88300 40.76
2 1.652 1.15
3 ∞ 0.31 1.51633 64.14
4 ∞ 1.83
5 3.535 0.50 1.92286 18.90
6 -4.330 0.48 1.49700 81.54
7 6.373 0.37
8 (Aperture) ∞ 1.67
9 4.327 1.23 1.77250 49.60
10 13.590 1.38
11 2.601 0.70 1.49700 81.54
12 13.251 0.94

Various data Abbe number νd _p of positive lens of lens pair: 18.900
Abbe number νd _n of the negative lens of the lens pair: 81.540
Maximum ray height y _pn of the principal ray in the lens pair: 0.405
Image height y _i : 1.500
G-axis axial chromatic aberration Δf _g with respect to e-line: −0.416
Total system focal length f (mm) : 1.501

Condition _{(1-1) 30 ≦ | νd p} -νd n | : 62.640
(2-1) 0.1 ≦ y _pn / y _i ≦ 0.7: 0.270
(3-1) −0.4 ≦ Δf _g /f≦−0.1 : -0.277

  Hereinafter, the imaging optical system according to Example 5 will be described in detail with reference to FIGS.

  FIG. 15 is a cross-sectional view along the optical axis showing the configuration and optical path of the imaging optical system. FIG. 16 is a cross-sectional view along the optical axis showing the details of the lenses constituting the imaging optical system shown in FIG. FIG. 17 is an aberration diagram of the imaging optical system shown in FIG. 15, where (a) shows spherical aberration, (b) shows field curvature aberration, (c) shows distortion, and (d) shows lateral chromatic aberration. ing.

  As shown in FIGS. 15 and 16, the imaging optical system includes, in order from the object side, a front group FG, a stop S, and a rear group RG, which are arranged on the optical axis Lc.

The front group FG has, in order from the object side, a lens L ₁ that is a plano-concave lens having negative refractive power and a concave surface facing the image side, a lens L ₂ that is a flat lens, and has positive refractive power on the image side. And L ₃ which is a meniscus lens having a convex surface.

The rear group RG is, in order from the object side, a lens L ₄ that is a biconvex lens having a positive refractive power, a lens L ₅ that is a biconvex lens having a positive refractive power, and a biconcave lens having a negative refractive power. It is composed of a lens L _6. Note that the lens L ₅ and the lens L ₆ form a lens pair including a positive lens and a negative lens. The lens L ₅ and the lens L ₆ are cemented.

Numerical data 5
Unit mm
Surface data Surface number Curvature radius Surface spacing Refractive index Abbe number s r d nd νd
1 ∞ 0.50 1.88300 40.76
2 1.240 1.55
3 ∞ 0.31 1.51633 64.14
4 ∞ 0.60
5 -31.409 1.59 1.84666 23.78
6 -3.028 0.39
7 (Aperture) ∞ 0.92
8 6.010 0.60 1.77250 49.60
9 -67.508 3.00
10 3.187 0.89 1.49700 81.54
11 -2.676 0.30 1.84666 23.78
12 20.151 1.00

Various data Abbe number νd _p of positive lens of lens pair: 81.540
Abbe number νd _n of the negative lens of the lens pair: 23.780
Maximum ray height y _pn of the principal ray in the lens pair: 1.244
Image height y _i : 1.500
G-axis axial chromatic aberration Δf _g with respect to e-line: −0.291
Total system focal length f (mm) : 1.500

Conditional expressions _{(1-2) 40 ≦ | νd p} -νd n | : 57.760
(2-2) 0.6 ≦ y _pn / y _i ≦ 1.2: 0.829
(3-2) −0.6 ≦ Δf _g /f≦−0.1 : -0.194

  The imaging optical system according to Example 6 will be described below in detail with reference to FIGS.

  FIG. 18 is a cross-sectional view along the optical axis showing the configuration and optical path of the imaging optical system. FIG. 19 is a cross-sectional view along the optical axis showing the details of the lenses constituting the imaging optical system shown in FIG. 20A and 20B are aberration diagrams of the imaging optical system shown in FIG. 18. FIG. 20A shows spherical aberration, FIG. 20B shows curvature of field aberration, FIG. 20C shows distortion aberration, and FIG. 20D shows lateral chromatic aberration. ing.

  As shown in FIGS. 18 and 19, this imaging optical system includes, in order from the object side, a front group FG, a stop S, and a rear group RG, which are arranged on the optical axis Lc.

The front group FG includes, in order from the object side, a lens L ₁ that is a plano-concave lens having negative refractive power and a concave surface facing the image side, a lens L ₂ that is a flat lens, and a biconvex lens having positive refractive power. It is constituted by a certain L ₃ .

The rear group RG includes, in order from the object side, a lens L ₄ that is a biconvex lens having a positive refractive power, a lens L ₅ that is a biconvex lens having a positive refractive power, and a convex surface having negative refractive power on the image side. And a lens L ₆ which is a meniscus lens facing the lens. Note that the lens L ₅ and the lens L ₆ form a lens pair including a positive lens and a negative lens.

Numerical data 6
Unit mm
Surface data Surface number Curvature radius Surface spacing Refractive index Abbe number s r d nd νd
1 ∞ 0.50 1.88300 40.76
2 1.327 1.06
3 ∞ 0.31 1.51633 64.14
4 ∞ 1.57
5 21.973 0.56 1.84666 23.78
6 -3.207 1.23
7 (Aperture) ∞ 1.04
8 8.574 0.60 1.77250 49.60
9 -120.617 2.34
10 4.063 0.81 1.49700 81.54
11 -3.742 0.25
12 -2.826 0.52 1.84666 23.78
13 -3.669 0.79

Various data Abbe number νd _p of positive lens of lens pair: 81.540
Abbe number νd _n of the negative lens of the lens pair: 23.780
Maximum ray height y _pn of the principal ray in the lens pair: 1.482
Image height y _i : 1.500
G-axis axial chromatic aberration Δf _g with respect to e-line: −0.271
Total system focal length f (mm) : 1.501

Conditional expressions _{(1-2) 40 ≦ | νd p} -νd n | : 57.760
(2-2) 0.6 ≦ y _pn / y _i ≦ 1.2: 0.988
(3-2) −0.6 ≦ Δf _g /f≦−0.1 : -0.181

  The imaging optical system according to Example 7 will be described in detail below with reference to FIGS.

  FIG. 21 is a cross-sectional view along the optical axis showing the configuration and optical path of the imaging optical system. FIG. 22 is a cross-sectional view along the optical axis showing the details of the lens constituting the imaging optical system shown in FIG. FIG. 23 is an aberration diagram of the imaging optical system shown in FIG. 21, where (a) shows spherical aberration, (b) shows field curvature aberration, (c) shows distortion, and (d) shows lateral chromatic aberration. ing.

  As shown in FIGS. 21 and 22, this imaging optical system is composed of a front group FG, a stop S, and a rear group RG in this order from the object side, and these are arranged on the optical axis Lc.

The front group FG includes, in order from the object side, a lens L ₁ that is a plano-concave lens having negative refractive power and a concave surface facing the image side, a lens L ₂ that is a flat lens, and a biconvex lens having positive refractive power. It is constituted by a certain L ₃ .

The rear group RG includes, in order from the object side, a lens L ₄ that is a biconvex lens having a positive refractive power, a meniscus lens L ₅ that has a negative refractive power and has a convex surface facing the object side, and both lenses having a positive refractive power. The lens L ₆ is a convex lens. Note that the lens L ₅ and the lens L ₆ form a lens pair including a negative lens and a positive lens.

Numerical data 7
Unit mm
Surface data Surface number Curvature radius Surface spacing Refractive index Abbe number s r d nd νd
1 ∞ 0.50 1.88300 40.76
2 1.326 1.06
3 ∞ 0.31 1.51633 64.14
4 ∞ 1.57
5 12.633 0.66 1.84666 23.78
6 -3.583 1.36
7 (Aperture) ∞ 0.85
8 8.814 0.60 1.77250 49.60
9 -62.617 2.23
10 3.383 0.52 1.84666 23.78
11 2.647 0.25
12 4.068 0.88 1.49700 81.54
13 -3.820 0.88

Various data Abbe number νd _p of positive lens of lens pair: 81.540
Abbe number νd _n of the negative lens of the lens pair: 23.780
Maximum ray height y _pn of the principal ray in the lens pair: 1.409
Image height y _i : 1.500
G-axis axial chromatic aberration Δf _g with respect to e-line: −0.275
Total system focal length f (mm) : 1.501

Conditional expressions _{(1-2) 40 ≦ | νd p} -νd n | : 57.760
(2-2) 0.6 ≦ y _pn / y _i ≦ 1.2: 0.939
(3-2) −0.6 ≦ Δf _g /f≦−0.1 : -0.183

  The imaging optical system according to Example 8 will be described in detail below with reference to FIGS.

  FIG. 24 is a cross-sectional view along the optical axis showing the configuration and optical path of the imaging optical system. FIG. 25 is a cross-sectional view along the optical axis showing the details of the lens constituting the imaging optical system shown in FIG. FIG. 26 is an aberration diagram of the imaging optical system shown in FIG. 24. (a) shows spherical aberration, (b) shows field curvature aberration, (c) shows distortion, and (d) shows lateral chromatic aberration. ing.

  As shown in FIGS. 24 and 25, the imaging optical system includes a front group FG, a stop S, and a rear group RG in order from the object side, and these are arranged on the optical axis Lc.

The front group FG includes, in order from the object side, a lens L ₁ that is a plano-concave lens having negative refractive power and a concave surface facing the image side, a lens L ₂ that is a flat lens, and a biconvex lens having positive refractive power. It is constituted by a certain L ₃ .

The rear group RG includes, in order from the object side, a lens L ₄ that is a meniscus lens having negative refractive power and a convex surface facing the image side, a lens L ₅ that is a biconvex lens having positive refractive power, and negative refraction. The lens L ₆ is a meniscus lens having a force and a convex surface facing the image side. Note that the lens L ₅ and the lens L ₆ form a lens pair including a positive lens and a negative lens. The lens L ₅ and the lens L ₆ are cemented.

Numerical data 8
Unit mm
Surface data Surface number Curvature radius Surface spacing Refractive index Abbe number s r d nd νd
1 ∞ 0.50 1.88300 40.76
2 1.467 1.10
3 ∞ 0.31 1.51633 64.14
4 ∞ 2.22
5 2.722 0.77 1.92286 18.90
6 -3.567 0.10
7 (Aperture) ∞ 0.33
8 -1.633 1.22 1.77250 49.60
9 -5.682 2.06
10 3.019 1.50 1.49700 81.54
11 -1.810 0.68 1.92286 18.90
12 -3.039 1.10

Various data Abbe number νd _p of positive lens of lens pair: 81.540
Abbe number νd _n of the negative lens of the lens pair: 18.900
Maximum ray height y _pn of the principal ray in the lens pair: 1.537
Image height y _i : 1.500
G-axis axial chromatic aberration Δf _g with respect to e-line: −0.608
Total system focal length f (mm) : 1.501

Conditional expressions _{(1-2) 40 ≦ | νd p} -νd n | : 62.640
(2-2) 0.6 ≦ y _pn / y _i ≦ 1.2: 1.025
(3-2) −0.6 ≦ Δf _g /f≦−0.1 : -0.405

  The imaging optical system according to Example 9 will be described in detail below with reference to FIGS.

  FIG. 27 is a cross-sectional view along the optical axis showing the configuration and optical path of the imaging optical system. FIG. 28 is a cross-sectional view along the optical axis showing the details of the lenses constituting the imaging optical system shown in FIG. 29 is an aberration diagram of the imaging optical system shown in FIG. 27, where (a) shows spherical aberration, (b) shows field curvature aberration, (c) shows distortion, and (d) shows lateral chromatic aberration. ing.

  As shown in FIGS. 27 and 28, the imaging optical system includes, in order from the object side, a front group FG, a stop S, and a rear group RG, which are arranged on the optical axis Lc.

The front group FG has, in order from the object side, a lens L ₁ that is a plano-concave lens having negative refractive power and a concave surface facing the image side, a lens L ₂ that is a flat lens, and has negative refractive power on the image side. And L ₃ which is a meniscus lens having a convex surface.

The rear group RG includes, in order from the object side, a lens L ₄ that is a biconvex lens having a positive refractive power, a lens L ₅ that is a biconvex lens having a positive refractive power, and a convex surface having negative refractive power on the image side. And a lens L ₆ which is a meniscus lens facing the lens. Note that the lens L ₅ and the lens L ₆ form a lens pair including a positive lens and a negative lens. The lens L ₅ and the lens L ₆ are cemented.

Numerical data 9
Unit mm
Surface data Surface number Curvature radius Surface spacing Refractive index Abbe number s r d nd νd
1 ∞ 0.50 1.88300 40.76
2 2.910 0.99
3 ∞ 0.31 1.51633 64.14
4 ∞ 1.58
5 -1.439 0.63 1.84666 23.78
6 -10.597 0.32
7 (Aperture) ∞ 0.34
8 3.187 1.57 1.69680 55.53
9 -2.719 0.10
10 3.210 0.93 1.49700 81.54
11 -1.514 0.40 1.84666 23.78
12 -6.662 4.77

Various data Abbe number νd _p of positive lens of lens pair: 81.540
Abbe number νd _n of the negative lens of the lens pair: 23.780
Maximum ray height y _pn of the principal ray in the lens pair: 0.592
Image height y _i : 1.500
G-axis longitudinal chromatic aberration Δf _g with respect to e-line: 0.326
Total system focal length f (mm) : 1.583

Conditional expression (1-3) 40 ≦ | νd _p −νd _n | : 57.760
(2-3) 0.1 ≦ y _pn / y _i ≦ 0.6: 0.395
(3-3) 0.1 ≦ Δf _g / f ≦ 1 : 0.206

  The imaging optical system according to Example 10 will be described in detail below with reference to FIGS.

  FIG. 30 is a cross-sectional view along the optical axis showing the configuration and optical path of the imaging optical system. FIG. 31 is a cross-sectional view along the optical axis showing the details of the lenses constituting the imaging optical system shown in FIG. FIG. 32 is an aberration diagram of the imaging optical system shown in FIG. 30. (a) shows spherical aberration, (b) shows field curvature aberration, (c) shows distortion, and (d) shows lateral chromatic aberration. ing.

  As shown in FIGS. 30 and 31, this imaging optical system includes a front group FG, a stop S, and a rear group RG in order from the object side, and these are arranged on the optical axis Lc.

The front group FG has, in order from the object side, a lens L ₁ that is a plano-concave lens having negative refractive power and a concave surface facing the image side, a lens L ₂ that is a flat lens, and has negative refractive power on the image side. And L ₃ which is a meniscus lens having a convex surface.

The rear group RG includes, in order from the object side, a lens L ₄ that is a biconvex lens having positive refractive power, a lens L ₅ that is a meniscus lens having negative refractive power and a convex surface facing the object side, and positive refractive power. And a lens L ₆ which is a biconvex lens having Note that the lens L ₅ and the lens L ₆ form a lens pair including a negative lens and a positive lens. The lens L ₅ and the lens L ₆ are cemented.

Numerical data 10
Unit mm
Surface data Surface number Curvature radius Surface spacing Refractive index Abbe number s r d nd νd
1 ∞ 0.50 1.88300 40.76
2 1.659 0.99
3 ∞ 0.31 1.51633 64.14
4 ∞ 1.04
5 -2.737 1.14 1.84666 23.78
6 -6.321 0.28
7 (Aperture) ∞ 0.29
8 3.767 0.52 1.69680 55.53
9 -4.756 0.22
10 2.748 0.40 1.84666 23.78
11 1.125 0.66 1.49700 81.54
12 -5.461 4.53

Various data Abbe number νd _p of positive lens of lens pair: 81.540
Abbe number νd _n of the negative lens of the lens pair: 23.780
Maximum ray height y _pn of the principal ray in the lens pair: 0.393
Image height y _i : 1.500
G-axis longitudinal chromatic aberration Δf _g with respect to e-line: 0.231
Total system focal length f (mm) : 1.502

Conditional expression (1-3) 40 ≦ | νd _p −νd _n | : 57.760
(2-3) 0.1 ≦ y _pn / y _i ≦ 0.6: 0.262
(3-3) 0.1 ≦ Δf _g / f ≦ 1 : 0.154

  The imaging optical system according to Example 11 will be described in detail below with reference to FIGS.

  FIG. 33 is a cross-sectional view along the optical axis showing the configuration and optical path of the imaging optical system. FIG. 34 is a cross-sectional view along the optical axis showing the details of the lenses constituting the imaging optical system shown in FIG. FIG. 35 is an aberration diagram of the imaging optical system shown in FIG. 33, where (a) shows spherical aberration, (b) shows curvature of field aberration, (c) shows distortion, and (d) shows chromatic aberration of magnification. ing.

  As shown in FIGS. 33 and 34, this imaging optical system includes, in order from the object side, a front group FG, a stop S, and a rear group RG, which are arranged on the optical axis Lc.

The front group FG has, in order from the object side, a lens L ₁ that is a plano-concave lens having negative refractive power and a concave surface facing the image side, a lens L ₂ that is a flat lens, and has negative refractive power on the image side. And L ₃ which is a meniscus lens having a convex surface.

The rear group RG includes, in order from the object side, a lens L ₄ that is a biconvex lens having a positive refractive power, a lens L ₅ that is a biconvex lens having a positive refractive power, and a convex surface having negative refractive power on the image side. And a lens L ₆ which is a meniscus lens facing the lens. Note that the lens L ₅ and the lens L ₆ form a lens pair including a positive lens and a negative lens.

Numerical data 11
Unit mm
Surface data Surface number Curvature radius Surface spacing Refractive index Abbe number s r d nd νd
1 ∞ 0.50 1.88300 40.76
2 2.109 0.99
3 ∞ 0.31 1.51633 64.14
4 ∞ 1.78
5 -3.248 0.65 1.84666 23.78
6 -9.385 0.52
7 (Aperture) ∞ 0.14
8 2.955 1.53 1.69680 55.53
9 -4.246 0.10
10 2.875 0.62 1.49700 81.54
11 -1.433 0.15
12 -1.208 0.81 1.92286 18.90
13 -3.974 3.69

Various data Abbe number νd _p of positive lens of lens pair: 81.540
Abbe number νd _n of the negative lens of the lens pair: 18.900
Maximum ray height y _pn of the principal ray in the lens pair: 0.597
Image height y _i : 1.500
G-axis longitudinal chromatic aberration Δf _g with respect to e-line: 0.291
Total system focal length f (mm) : 1.519

Conditional expression (1-3) 40 ≦ | νd _p −νd _n | : 62.640
(2-3) 0.1 ≦ y _pn / y _i ≦ 0.6: 0.398
(3-3) 0.1 ≦ Δf _g / f ≦ 1 : 0.194

  The imaging optical system according to Example 12 will be described in detail below with reference to FIGS.

  FIG. 36 is a cross-sectional view along the optical axis showing the configuration and optical path of the imaging optical system. FIG. 37 is a cross-sectional view along the optical axis showing the details of the lenses constituting the imaging optical system shown in FIG. FIG. 38 is an aberration diagram of the imaging optical system shown in FIG. 36. (a) shows spherical aberration, (b) shows field curvature aberration, (c) shows distortion, and (d) shows chromatic aberration of magnification. ing.

  As shown in FIGS. 36 and 37, the imaging optical system includes a front group FG, a stop S, and a rear group RG in order from the object side, and these are arranged on the optical axis Lc.

The front group FG includes, in order from the object side, a lens L ₁ that is a plano-concave lens having negative refractive power and a concave surface facing the image side, a lens L ₂ that is a flat lens, and a biconvex lens having positive refractive power. there L _3, is constituted by the L ₄ is a biconcave lens having a negative refractive power. The lens L ₃ and the lens L ₄ form a lens pair composed of a positive lens and a negative lens. The lens L ₃ and the lens L ₄ are cemented.

The rear group RG includes, in order from the object side, a lens L ₅ that is a biconvex lens having positive refractive power, a lens L ₆ that is a biconvex lens having positive refractive power, and a convex surface having negative refractive power on the image side. And a lens L ₇ which is a meniscus lens facing the lens. Note that the lens L ₆ and the lens L ₇ form a lens pair including a positive lens and a negative lens. The lens L ₆ and the lens L ₇ are cemented.

Numerical data 12
Unit mm
Surface data Surface number Curvature radius Surface spacing Refractive index Abbe number s r d nd νd
1 ∞ 0.50 1.88300 40.76
2 1.955 0.86
3 ∞ 0.31 1.51633 64.14
4 ∞ 2.07
5 18.048 1.47 1.72916 54.68
6 -0.919 0.30 1.92286 18.90
7 9.546 0.05
8 (Aperture) ∞ 0.62
9 2.238 0.66 1.69680 55.53
10 -2.864 0.10
11 2.821 1.17 1.49700 81.54
12 -0.986 0.30 1.84666 23.78
13 -23.210 3.73

Various data Abbe number νd _p of positive lens of lens pair: 81.540
Abbe number νd _n of the negative lens of the lens pair: 23.780
Maximum ray height y _pn of the principal ray in the lens pair: 0.488
Image height y _i : 1.500
G-axis longitudinal chromatic aberration Δf _g with respect to e-line: 1.331
Total system focal length f (mm) : 1.500

Conditional expression (1-3) 40 ≦ | νd _p −νd _n | : 57.760
(2-3) 0.1 ≦ y _pn / y _i ≦ 0.6: 0.325
(3-3) 0.1 ≦ Δf _g / f ≦ 1 : 0.887

  The imaging optical system according to Example 13 will be described in detail below with reference to FIGS.

  FIG. 39 is a cross-sectional view along the optical axis showing the configuration and optical path of the imaging optical system. FIG. 40 is a cross-sectional view along the optical axis showing the details of the lenses constituting the imaging optical system shown in FIG. 41 is an aberration diagram of the imaging optical system shown in FIG. 39, where (a) shows spherical aberration, (b) shows field curvature aberration, (c) shows distortion, and (d) shows chromatic aberration of magnification. ing.

  As shown in FIGS. 39 and 40, the imaging optical system includes, in order from the object side, a front group FG, a stop S, and a rear group RG, which are arranged on the optical axis Lc.

The front group FG has, in order from the object side, a lens L ₁ that is a plano-concave lens having negative refractive power and a concave surface facing the image side, a lens L ₂ that is a flat lens, and has positive refractive power on the image side. It is composed of L ₃ which is a meniscus lens having a convex surface and L ₄ which is a biconcave lens having negative refractive power. The lens L ₃ and the lens L ₄ form a lens pair composed of a positive lens and a negative lens. The lens L ₃ and the lens L ₄ are cemented.

The rear group RG includes, in order from the object side, a lens L ₅ that is a biconvex lens having positive refractive power, a lens L ₆ that is a biconvex lens having positive refractive power, and a convex surface having negative refractive power on the image side. And a lens L ₇ which is a meniscus lens facing the lens. Note that the lens L ₆ and the lens L ₇ form a lens pair including a positive lens and a negative lens. The lens L ₆ and the lens L ₇ are cemented.

Numerical data 13
Unit mm
Surface data Surface number Curvature radius Surface spacing Refractive index Abbe number s r d nd νd
1 ∞ 0.50 1.88300 40.76
2 1.942 1.18
3 ∞ 0.31 1.51633 64.14
4 ∞ 0.38
5 -13.726 1.46 1.71999 50.23
6 -0.909 0.44 1.92286 18.90
7 30.100 0.11
8 (Aperture) ∞ 0.35
9 3.949 1.11 1.69680 55.53
10 -2.395 0.68
11 2.664 1.03 1.49700 81.54
12 -1.441 0.40 1.84666 23.78
13 -7.200 3.83

Various data Abbe number νd _p of positive lens of lens pair: 81.540
Abbe number νd _n of the negative lens of the lens pair: 23.780
Maximum ray height y _pn of the principal ray in the lens pair: 0.694
Image height y _i : 1.500
G-axis longitudinal chromatic aberration Δf _g with respect to e-line: 0.731
Total system focal length f (mm) : 1.519

Conditional expression (1-3) 40 ≦ | νd _p −νd _n | : 57.760
(2-3) 0.1 ≦ y _pn / y _i ≦ 0.6: 0.463
(3-3) 0.1 ≦ Δf _g / f ≦ 1 : 0.481

  Note that the imaging optical system of the present invention may be used in an endoscope apparatus as shown in FIG. The endoscope apparatus includes an insertion unit 1 for insertion into a patient's body, an endoscope operation unit 2, a control unit 3 having a light source unit and an image processing unit therein, and a control unit 3. And a monitor 4 for displaying the output image. And the insertion part 11 is equipped with the imaging optical system for endoscopes of this invention in the front-end | tip part 1a.

FG Front group RG Rear group LC Optical axis L ₁ , L ₂ , L ₃ , L ₄ , L ₅ , L ₆ , L ₇ Lens S Aperture 1 Insertion section 1a Tip section 2 Endoscope operation section 3 Control unit 4 Monitor

Claims (8)

In order from the object side, in the imaging optical system comprising the front group, the stop, and the rear group,
The front group includes a positive lens and a negative lens;
An imaging optical system characterized by satisfying all of the following conditional expressions:
30 ≦ | νd _p −νd _n |
0.1 ≤ y _pn / y _i ≤ 0.7
−0.4 ≦ Δf _g /f≦−0.1
However, [nu] d _p is the Abbe number of the positive lens, [nu] d _n is the Abbe number of the negative lens, y _pn is the positive lens or maximum ray height of the chief ray in the negative lens, y _i denotes an image height, Delta] f _g is the wavelength On-axis chromatic aberration of light (g line) having a wavelength of 435 nm when f 546 nm light (e line) is used as a reference, and f is the focal length of the entire system of light (e line) having a wavelength of 546 nm. In order from the object side, in the imaging optical system comprising the front group, the stop, and the rear group,
The rear group includes a positive lens and a negative lens;
An imaging optical system characterized by satisfying all of the following conditional expressions:
40 ≦ | νd _p −νd _n |
0.6 ≤ y _pn / y _i ≤ 1.2
−0.6 ≦ Δf _g /f≦−0.1
However, [nu] d _p is the Abbe number of the positive lens, [nu] d _n is the Abbe number of the negative lens, y _pn is the positive lens or maximum ray height of the chief ray in the negative lens, y _i denotes an image height, Delta] f _g is the wavelength On-axis chromatic aberration of light (g line) having a wavelength of 435 nm when f 546 nm light (e line) is used as a reference, and f is the focal length of the entire system of light (e line) having a wavelength of 546 nm. In order from the object side, in the imaging optical system comprising the front group, the stop, and the rear group,
The rear group includes a positive lens and a negative lens;
An imaging optical system characterized by satisfying all of the following conditional expressions:
40 ≦ | νd _p −νd _n |
0.1 ≤ y _pn / y _i ≤ 0.6
0.1 ≦ Δf _g / f ≦ 1
However, [nu] d _p is the Abbe number of the positive lens, [nu] d _n is the Abbe number of the negative lens, y _pn is the positive lens or maximum ray height of the chief ray in the negative lens, y _i denotes an image height, Delta] f _g is the wavelength On-axis chromatic aberration of light (g line) having a wavelength of 435 nm when f 546 nm light (e line) is used as a reference, and f is the focal length of the entire system of light (e line) having a wavelength of 546 nm. In order from the object side, in the imaging optical system comprising the front group, the stop, and the rear group,
The front group includes a positive lens and a negative lens;
An imaging optical system characterized by satisfying all of the following conditional expressions:
20 ≦ | νd _p −νd _n |
0.2 ≤ y _pn / y _i ≤ 0.4
0.1 ≦ Δf _g / f ≦ 1
However, [nu] d _p is the Abbe number of the positive lens, [nu] d _n is the Abbe number of the negative lens, y _pn is the positive lens or maximum ray height of the chief ray in the negative lens, y _i denotes an image height, Delta] f _g is the wavelength On-axis chromatic aberration of light (g line) having a wavelength of 435 nm when f 546 nm light (e line) is used as a reference, and f is the focal length of the entire system of light (e line) having a wavelength of 546 nm.   The imaging optical system according to claim 1, wherein the rear group includes a positive lens and a negative lens.   The imaging optical system according to claim 2, wherein the front group includes a positive lens and a negative lens.   The imaging optical system according to any one of claims 1 to 6, wherein the positive lens and the negative lens are cemented.   An endoscope apparatus comprising the imaging optical system according to any one of claims 1 to 5.

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