WO2014199766A1

WO2014199766A1 - Converter lens, image capture optical assembly, and portable terminal

Info

Publication number: WO2014199766A1
Application number: PCT/JP2014/062792
Authority: WO
Inventors: 敦司山下
Original assignee: コニカミノルタ株式会社
Priority date: 2013-06-11
Filing date: 2014-05-14
Publication date: 2014-12-18

Abstract

Provided are a converter lens which, while having a conversion ratio of 0.7x or less, is sufficiently thin with respect to the thickness direction of an image capture device and has a small diameter as well, and an image capture optical assembly and an image capture device wherein said converter lens is employed. A converter lens (CL) is configured, in order from the object side, from a first lens (L1) having a negative refractive power, a second lens (L2) having a negative refractive power, and a third lens (L3) having a positive refractive power, and satisfies the following conditional formulae: 0.4<d4/d5<0.3 (1), 0.1<(R6+R5)/(R6-R5)<2.0 (2), where d4 is an axial air gap between the second lens and the third lens, d5 is an axial thickness of the third lens, R5 is a radius of curvature of the object-side face of the third lens, and R6 is a radius of curvature of the image-side face of the third lens.

Description

Converter lens, imaging optical system, and portable terminal

The present invention relates to a converter lens, an imaging optical system, and a mobile terminal that are mounted on the object side of the main lens and convert the photographing field angle of the main lens to the wide angle side.

In recent years, mobile terminals such as smartphones have been released, and the market is rapidly expanding. Such a portable terminal is generally mounted with an imaging device, and is used in various ways such as transferring an image captured by the imaging device or performing image processing on the portable terminal. However, since a general portable terminal is thin, an imaging device incorporated therein is strictly required to be compact. Accordingly, a single-focus optical system is usually mounted on an imaging device mounted on a conventional portable terminal. However, some users have a desire to image a wider range of subjects.

In response to such a demand, a converter lens that can change the focal length of the photographic lens to the wide-angle side by positioning it in front of the photographic lens (main lens) provided in the photographing apparatus is disclosed in Patent Documents 1 and 2. Is disclosed.

Japanese Patent No. 4557355 Japanese Patent No. 2997026

However, the converter lenses disclosed in Patent Documents 1 and 2 have a large overall optical system length and diameter, and it is difficult to say that they are sufficiently compact to be mounted on a portable terminal and used. In order to satisfy the compactness, it is necessary to suppress the overall length and diameter as much as possible.

In view of such a problem, the present invention provides a converter lens having a conversion ratio of 0.7 times or less and sufficiently thin in the thickness direction of the imaging device and having a small diameter, and an imaging optical system and an imaging device used therefor. The purpose is to provide.

In order to achieve at least one of the objects described above, a converter lens reflecting one aspect of the present invention is mounted on the object side of the main lens, and converts the shooting field angle of the main lens to the wide angle side. In
The converter lens includes, in order from the object side, a first lens having negative refractive power, a second lens having negative refractive power, and a third lens having positive refractive power,
The following conditional expression is satisfied.
0.04 <d4 / d5 <0.3 (1)
0.1 <(R6 + R5) / (R6-R5) <2.0 (2)
However,
d4: On-axis air space between the second lens and the third lens d5: On-axis thickness of the third lens R5: Curvature radius of the object side surface of the third lens R6: Radius of curvature of the image side surface of the third lens

Since this converter lens is mounted on the object side of the main lens to shorten the focal length of the combined optical system of the converter lens and the main lens, the refractive power arrangement of the negative lens group and the positive lens group in order from the object side. The so-called reverse Galileo type is adopted, and the angular magnification of the converter lens is 1 or less. At this time, in order to reduce the optical dimension such as the front lens diameter that tends to be the largest in the converter lens, the entrance pupil position is moved closer to the object side by increasing the refractive power of the negative lens group. Can be considered. However, if this negative lens group is composed of a single negative lens, various aberrations occurring here and aberration fluctuations due to manufacturing errors also increase. Therefore, by constructing the negative lens group from two negative lenses and dividing the refractive power, aberration and error sensitivity of each lens can be suppressed while suppressing the outer diameter of the converter lens.

Further, since the value of the expression (1) exceeds the lower limit, the second lens and the third lens are not too close to each other, so that the refractive power of each lens does not become too strong, and astigmatism and coma generated here. Can be suppressed. In addition, aberration variations due to manufacturing errors can be suppressed. On the other hand, since the value of the formula (1) is below the upper limit, the second lens and the third lens are not separated from each other. Therefore, it is possible to suppress an increase in the converter lens by suppressing the total length. The following (1) 'formula,
0.04 <d4 / d5 <0.26 (1) ′
It is more preferable to satisfy

Furthermore, when the value of the expression (2) exceeds the lower limit, the curvature radius of the image side surface of the third lens does not become too small, and various aberrations occurring on this surface can be suppressed. In addition, the front principal point position of the third lens is less likely to move toward the image side, the distance between the principal points of the second lens is not excessively widened, and as a result, miniaturization of the converter lens can be maintained by suppressing the overall length. It becomes possible. On the other hand, when the value of the expression (2) is below the upper limit, the radius of curvature of the object side surface of the third lens does not become too small, and various aberrations occurring on this surface can be suppressed. The following (2) 'formula,
0.15 <(R6 + R5) / (R6-R5) <1.5 (2) ′
More preferably, the following (2) ″ formula:
0.2 <(R6 + R5) / (R6-R5) <0.85 (2) ″
If it satisfies, it is more preferable.

The imaging optical system includes the converter lens and the main lens, and the main lens is provided with an aperture stop closer to the object side than the second lens from the object side of the main lens. .

It is preferable that the aperture stop of the main lens is disposed in the vicinity of the lens closest to the object side of the main lens, that is, the object side or the image side of the lens closest to the object side of the main lens. More preferably, by placing the front aperture on the object side of the lens closest to the object side, it is possible to keep the light beam passing through the converter lens of off-axis light low, so that the optical dimensions such as the front lens diameter Can be kept small. The main lens may be disposed closer to the image side than the position on the optical axis of the object side surface of the lens closest to the object side and closer to the object side than the most peripheral portion of the object side surface.

This mobile terminal is characterized in that the main lens and the image sensor are built in the main body, and the converter lens can be mounted.

It is possible to provide a portable terminal that can take a wider angle than the main lens with a compact appearance.

According to the present invention, it is possible to provide a converter lens that has a conversion ratio of 0.7 times or less and is sufficiently thin in the thickness direction of the imaging device and has a small diameter, and an imaging optical system and an imaging device used therefor. it can.

It is a perspective view which shows the state which attached the imaging optical system concerning this embodiment to the portable terminal. 1 is a cross-sectional view of an imaging optical system according to Example 1. FIG. FIG. 4 is an aberration diagram (spherical aberration (a), astigmatism (b), distortion (c)) of the imaging optical system of Example 1. FIG. 6 is an aberration diagram (spherical aberration (a), astigmatism (b), distortion aberration (c)) of the main lens. 6 is a cross-sectional view of an imaging optical system according to Example 2. FIG. FIG. 6 is an aberration diagram of Example 2 (spherical aberration (a), astigmatism (b), distortion (c)). 6 is a cross-sectional view of an imaging optical system according to Example 3. FIG. FIG. 6 is an aberration diagram of Example 3 (spherical aberration (a), astigmatism (b), distortion (c)). 6 is a cross-sectional view of an imaging optical system according to Example 4. FIG. FIG. 6 is an aberration diagram of Example 4 (spherical aberration (a), astigmatism (b), distortion (c)). 10 is a cross-sectional view of an imaging optical system according to Example 5. FIG. FIG. 6 is an aberration diagram of Example 5 (spherical aberration (a), astigmatism (b), distortion (c)). 10 is a cross-sectional view of an imaging optical system according to Example 6. FIG. FIG. 10 is an aberration diagram of Example 6 (spherical aberration (a), astigmatism (b), distortion (c)). FIG. 10 is a cross-sectional view of an image pickup optical system according to a seventh embodiment. FIG. 10 is an aberration diagram of Example 7 (spherical aberration (a), astigmatism (b), distortion (c)). 10 is a cross-sectional view of an image pickup optical system according to Example 8. FIG. FIG. 10 is an aberration diagram of Example 9 (spherical aberration (a), astigmatism (b), distortion (c)). 10 is a cross-sectional view of an image pickup optical system according to Example 9. FIG. FIG. 10 is an aberration diagram of Example 9 (spherical aberration (a), astigmatism (b), distortion (c)). FIG. 12 is a cross-sectional view of the imaging optical system according to Example 10. FIG. 10 is an aberration diagram of Example 10 (spherical aberration (a), astigmatism (b), distortion (c)).

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a state in which the imaging optical system according to the present embodiment is attached to a portable terminal. For example, the mobile terminal SF, which is a thin smartphone, has a built-in image pickup apparatus including a main lens ML and an image pickup device (not shown). The main lens ML has its subject side facing the front side (front side in FIG. 1) of the mobile terminal SF.

The converter lens CL is arranged in a cylindrical lens barrel HLD attached to a rectangular plate body (main body) BD of the mobile terminal SF. The lens barrel HLD is formed as a separate unit from the body BD and may be attached to the body BD or may be a part of the body BD. The optical axis of the converter lens CL is coincident with the optical axis of the main lens ML. The converter lens CL and the main lens ML constitute an imaging optical system.

The converter lens CL has negative refractive power in order from the object side, as shown in FIGS. 2, 5, 7, 9, 11, 13, 15, 15, 17, and 21, which will be described later. , A second lens L2 having a negative refractive power, and a third lens L3 having a positive refractive power, and satisfy the following conditional expressions (1) and (2).
0.04 <d4 / d5 <0.3 (1)
0.1 <(R6 + R5) / (R6-R5) <2.0 (2)
However,
d4: axial air space between the second lens L2 and the third lens L3 d5: axial thickness of the third lens L3 R5: radius of curvature of the object side surface of the third lens L3 R6: radius of curvature of the image side surface of the third lens L3

The parallel light beam incident on the converter lens CL is emitted as a parallel light beam and is incident on the main lens ML. The subject light that has passed through the converter lens CL and the main lens ML is received by the image sensor and converted into an electrical signal. Note that while the converter lens CL is removed, the subject can be imaged only with the main lens ML, but by attaching the converter lens CL, an imaging optical system capable of converting the photographic field angle to the wide angle side is obtained.

A monitor (not shown) on the back of the mobile terminal SF displays an image based on an electrical signal output from the image sensor, functions as an electronic viewfinder, and displays a captured image in almost real time. Furthermore, when a user performs a release operation at a timing at which still image shooting is desired, a still image is shot. As a result, the image data is recorded in the memory.

Hereinafter, preferred embodiments will be further described.

In the converter lens, it is preferable that the following conditional expression is satisfied.
n1> 1.7 (3)
However,
n1: Refractive index of the first lens

By satisfying the expression (3), a sufficiently high refractive index can be obtained in the first lens. Therefore, even with a lens having the same refractive power, the radius of curvature can be increased, and as a result, the outer diameter is suppressed. It becomes possible to suppress distortion, astigmatism, and the like that occur in the first lens. The following (3) 'formula,
n1> 1.8 (3) ′
It is more preferable to satisfy

Moreover, it is preferable to satisfy the following conditional expressions.
30 <ν1 <50 (4)
Where ν1: Abbe number of the first lens

Since the chromatic dispersion of the first lens does not become too large when the value of the expression (4) exceeds the lower limit, axial chromatic aberration that causes the short wavelength to be over or magnification that reduces the image height of the short wavelength. Chromatic aberration can be suppressed small. On the other hand, since the chromatic dispersion of the first lens does not become too small when the value of the expression (4) is below the upper limit, the axial chromatic aberration that causes the short wavelength to be under or the image height of the short wavelength is increased. The lateral chromatic aberration can be reduced. The following formula (4) ′, 35 <ν1 <45 (4) ′
More preferably, the following (4) ″ formula:
37 <ν1 <43 (4) ″
If it satisfies, it is more preferable.

Moreover, it is preferable to satisfy the following conditional expressions.
25 <ν3 <50 (5)
However,
ν3: Abbe number of the third lens

Since the chromatic dispersion of the third lens does not become too large because the value of the expression (5) exceeds the lower limit, axial chromatic aberration that causes the short wavelength to be under, and magnification that increases the image height of the short wavelength. Chromatic aberration can be suppressed small. On the other hand, since the chromatic dispersion of the third lens does not become too small when the value of the expression (5) is below the upper limit, the axial chromatic aberration that causes the short wavelength to be over or the image height of the short wavelength is reduced. Chromatic aberration of magnification can be kept small. The following (5) 'formula,
30 <ν3 <45 (5) ′
It is more preferable to satisfy

Moreover, it is preferable to satisfy the following conditional expressions.
0.05 <d2 / d35 <2.0 (6)
However,
d2: axial air space between the first lens and the second lens d35: axial distance from the object side surface of the second lens to the image side surface of the third lens

When the value of the expression (6) exceeds the lower limit, the first lens and the second lens are not too close to each other, so that the refractive power of each lens does not become too strong, and various aberrations occurring here can be suppressed. In addition, it is possible to suppress aberration fluctuations caused by manufacturing errors. On the other hand, since the value of the expression (6) is below the upper limit, the first lens and the second lens are not separated from each other, so the diameter of the first lens (front lens diameter) is increased, and the enlargement of the converter lens is prevented. be able to. The following formula (6) ′, 0.05 <d2 / d35 <1.5 (6) ′
More preferably, the following (6) ″ formula:
0.1 <d2 / d35 <0.95 (6) ″
If it satisfies, it is more preferable.

Moreover, it is preferable to satisfy the following conditional expressions.
0.5 <f2 / f1 <10 (7)
However,
f1: Focal length of the first lens f2: Focal length of the second lens

When the value of the expression (7) exceeds the lower limit, the refractive power of the second lens does not become too strong, so that various aberrations occurring here can be suppressed. In addition, aberration fluctuations caused by manufacturing errors can be reduced, and the front lens diameter can be reduced. On the other hand, since the refractive power of the first lens does not become too strong because the value of the expression (7) is below the upper limit, various aberrations occurring here can be suppressed. In addition, it is possible to reduce aberration fluctuations caused by manufacturing errors. The following (7) 'formula,
0.7 <f2 / f1 <8.5 (7) ′
More preferably, the following (7) ″ formula:
0.9 <f2 / f1 <7.7 (7) ″
If it satisfies, it is more preferable.

Moreover, it is preferable that the first lens has at least an aspheric surface on the object side surface and satisfies the following conditional expression.
-25 <APE1 / ASP1 <-5 (8)
However,
APE1: Effective radius of the object side surface of the first lens ASP1: Aspheric amount at an effective radius of the object side surface of the first lens

Here, the “aspheric amount” means an amount expressed by (sag amount of actual shape of lens surface) − (sag amount by lens surface spherical component). The value of the radius of curvature of the lens surface for obtaining the sag amount by the spherical component of the lens surface is the vicinity of the center of the lens (specifically, the center within 10% of the lens outer diameter) in the actual lens measurement scene. The shape measurement value in (region) can be regarded as the approximate radius of curvature when fitting by the method of least squares. For example, when a secondary aspherical coefficient is used, it can be considered that the radius of curvature takes into account the secondary aspherical coefficient in the reference curvature radius of the aspherical definition formula (for example, Matsui as a reference). (See pages 41-42 of Yoshiya's "Lens Design Method" (Kyoritsu Publishing Co., Ltd.)). Since the value of the equation (8) exceeds the lower limit, the aspherical amount of the object side surface of the first lens can be secured, so that distortion, astigmatism, etc. generated on this surface can be corrected well. On the other hand, since the amount of the aspherical surface does not increase excessively when the value of the expression (8) is less than the upper limit, fluctuations in aberrations when this surface is decentered can be suppressed. The following (8) 'formula,
−21 <APE1 / ASP1 <−7 (8) ′
It is more preferable to satisfy

The first lens preferably has at least an aspheric surface on the image side surface and satisfies the following conditional expression.
-90 <APE2 / ASP2 <-5 (9)
However,
APE1: Effective radius of the image side surface of the first lens ASP1: Aspheric amount at an effective radius of the image surface of the first lens

When the value of the expression (9) exceeds the lower limit, the aspheric amount on the image side surface of the first lens can be secured, and therefore, distortion aberration, astigmatism, etc. occurring on this surface can be corrected well. On the other hand, since the amount of the aspherical surface of the first lens does not increase too much because the value of the expression (9) is below the upper limit, it is possible to suppress aberration fluctuations when this surface is decentered. The following (9) 'formula,
-85 <APE2 / ASP2 <-8 (9) '
It is more preferable to satisfy

Further, it is preferable that the first lens has an aspheric surface on both the object side surface and the image side surface and satisfies the following conditional expression.
1 <ASP1 / ASP2 <8 (10)
However,
ASP1: Aspheric amount at effective radius of object side surface of first lens ASP2: Aspheric amount at effective radius of image side surface of first lens

Since the value of the expression (10) exceeds the lower limit, the amount of aspherical surface on the image side surface of the first lens does not increase excessively, so that aberration fluctuation when this surface is decentered can be suppressed. On the other hand, since the value of the expression (10) is less than the upper limit, the amount of aspherical surface on the object side surface of the first lens does not increase too much, so that aberration fluctuation when this surface is decentered can be suppressed. The following (10) 'formula,
1.4 <ASP1 / ASP2 <7.1 (10) ′
It is more preferable to satisfy

In addition, the description in the said embodiment and each Example is a suitable example which concerns on this invention, and is not limited to this. The imaging optical system can also be mounted on a digital still camera or a video camera.

(Example)
Next, examples suitable for the above-described embodiment will be described. However, the present invention is not limited to the following examples.
f: Focal length of the entire system (mm)
R: radius of curvature (mm)
d: Distance between shaft upper surfaces (mm)
nd: refractive index of lens material with respect to d-line νd: Abbe number of lens material

In each embodiment, the surface provided with * next to the surface number is a surface having an aspheric shape, and the shape of the aspheric surface has the vertex of the surface as the origin and the X-axis in the optical axis direction. The height in the direction perpendicular to the axis is represented by h as follows.

However,
Ai: i-th order aspherical coefficient R: reference radius of curvature K: conic constant Repeatedly, in the actual lens measurement scene, the radius of curvature of the lens surface in this specification is the vicinity of the center of the lens (specifically, The approximate radius of curvature when the shape measurement value in the central region within 10% of the lens outer diameter) is fitted by the method of least squares. For example, when a secondary aspheric coefficient is used, the reference radius of curvature of the aspheric definition formula also includes a curvature radius that takes into account the secondary aspheric coefficient.

(Example 1)
Table 1 shows lens data of Example 1. In the following (including the lens data in the table), a power of 10 (for example, 2.5 × 10 ⁻⁰² ) is expressed using E (for example, 2.5E-02). FIG. 2 is a sectional view of the image pickup optical system according to the first embodiment. In the figure, CL is a converter lens, and in order from the object side, a first lens L1 having a negative refractive power, a second lens L2 having a negative refractive power, and a third lens L3 having a positive refractive power. Composed. ML is a main lens (focal length f = 4.33 mm), and is composed of a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, and an eighth lens L8 in this order from the object side. S denotes an aperture stop provided on the object side from the position on the optical axis of the object side surface of the fourth lens L4 on the object side from the most peripheral part of the object side surface, and IM denotes an image pickup surface of the image pickup apparatus. . Further, CG is a cover glass of the main lens ML, and F is a parallel plate assuming an optical low-pass filter, an IR cut filter, a seal glass of a solid-state image sensor, and the like. The converter lens CL (surface numbers 1 to 6) and the main lens ML (surface numbers 7 to 22) constitute an imaging optical system. In the present embodiment, the converter lens CL includes only a spherical lens, and the main lens ML includes an aspheric lens.

[Table 1]
Example 1

Surface number (aspherical surface) R (mm) d (mm) nd νd Effective diameter (mm)
1 15.068 0.80 1.83481 42.7 10.90
2 4.905 3.25 8.14
3 42.025 0.70 1.83400 37.3 7.46
4 11.930 0.20 7.05
5 5.804 2.64 1.67270 32.2 6.91
6 -59.293 1.24 5.95
7 ∞ 0.79 1.51633 64.1 4.15
8 ∞ 1.24 3.51
9 ∞ 0.05 1.80
10 (Aperture) ∞ -0.24 1.80
11 * 1.676 0.63 1.54470 56.2 1.87
12 * -13.857 0.05 1.90
13 * 4.012 0.28 1.63469 23.9 1.92
14 * 1.559 0.57 1.90
15 * -36.876 0.31 1.63469 23.9 2.15
16 * -35.075 0.42 2.46
17 * -6.434 0.86 1.54470 56.2 3.72
18 * -0.965 0.23 4.08
19 * -2.637 0.45 1.53048 55.7 4.59
20 * 1.582 0.64 5.12
21 ∞ 0.30 1.51633 64.1 5.66
22 ∞ 0.40 5.78
image

Aspheric coefficient of main lens
11th surface 12th surface 13th surface 14th surface 15th surface
K -0.025 -29.823 -30.000 -6.295 30.000
A4 5.4737E-03 2.9864E-02 -4.4484E-02 4.7985E-02 -1.2218E-01
A6 1.8802E-03 3.6878E-02 1.4564E-01 5.1872E-02 -2.6536E-02
A8 -3.1928E-03 -4.3208E-02 -1.2728E-01 -1.8852E-02 6.2354E-02
A10 1.7037E-02 -2.3999E-02 -3.2604E-02 -6.3501E-03 2.0372E-02
A12 -2.1868E-02 2.7062E-02 7.7790E-02 -4.1075E-03 -1.8554E-02
A14 8.4210E-03 0.0000E + 00 -1.8876E-02 2.2070E-02 -6.3386E-04

16th surface 17th surface 18th surface 19th surface 20th surface
K 30.000 7.826 -4.059 -30.000 -12.523
A4 -1.0027E-01 -3.7724E-04 -4.3185E-02 -1.4223E-02 -3.6784E-02
A6 3.0627E-03 2.0421E-02 5.1578E-02 -1.5539E-03 7.2592E-03
A8 1.9106E-02 -1.1047E-03 -1.1842E-02 2.1085E-03 -1.4441E-03
A10 1.6054E-02 -1.6207E-03 6.5318E-04 -1.9864E-04 1.4444E-04
A12 -2.2771E-03 2.6445E-04 1.9046E-05 -2.5376E-05 -5.0337E-06
A14 -2.7944E-03 0.0000E + 00 0.0000E + 00 2.8800E-06 3.2341E-08

Values in the combined optical system of the converter lens and main lens
Focal length 3.03mm
F number 2.41
Half angle of view 47.7 °
Image height 3.02mm
Total lens length 15.82mm
Back focus 1.24mm
However, the total lens length is the distance from the side of the first lens subject to the main lens paraxial image point.
Main lens focal length 4.33mm
Converter magnification 0.70

FIG. 3 is an aberration diagram of Example 1 (spherical aberration (a), astigmatism (b), distortion aberration (c)), and the aberration diagram is a combination of the converter lens and the main lens. . FIG. 4 is an aberration diagram (spherical aberration (a), astigmatism (b), distortion (c)) of only the main lens. In the spherical aberration diagram, the dotted line represents the amount of spherical aberration with respect to the g line, and the solid line represents the amount of spherical aberration with respect to the d line. In the astigmatism diagram, the solid line S represents the sagittal plane, and the dotted line M represents the meridional plane (the same applies hereinafter).

In Example 1, the ratio of the effective diameter of the object side surface of the first lens L1 to the aperture stop diameter of the main lens ML is about 0.17, thereby realizing a compact imaging optical system.

(Example 2)
Table 2 shows lens data of Example 2. FIG. 5 is a sectional view of the image pickup optical system according to the second embodiment. In the figure, CL is a converter lens, and in order from the object side, a first lens L1 having a negative refractive power, a second lens L2 having a negative refractive power, and a third lens L3 having a positive refractive power. Composed. ML is a main lens, and is composed of a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, and an eighth lens L8 in this order from the object side. S denotes an aperture stop provided on the object side from the position on the optical axis of the object side surface of the fourth lens L4 on the object side from the most peripheral part of the object side surface, and IM denotes an image pickup surface of the image pickup apparatus. . Further, CG is a cover glass of the main lens ML, and F is a parallel plate assuming an optical low-pass filter, an IR cut filter, a seal glass of a solid-state image sensor, and the like. The converter lens CL (surface numbers 1 to 6) and the main lens ML (surface numbers 7 to 22) constitute an imaging optical system. In the present embodiment, the converter lens CL includes only a spherical lens, and the main lens ML includes an aspheric lens. Since the main lens ML used in the second embodiment is the same as that used in the first embodiment, the aspheric coefficient is omitted.

[Table 2]
Example 2

Surface number (aspherical surface) R (mm) d (mm) nd νd Effective diameter (mm)
1 14.298 0.80 1.88300 40.8 10.91
2 4.966 3.19 8.21
3 36.957 0.70 1.83481 42.7 7.58
4 12.156 0.20 7.18
5 5.774 2.84 1.64769 33.8 7.02
6 -53.069 1.24 5.97
7 ∞ 0.79 1.51633 64.1 4.15
8 ∞ 1.24 3.51
9 ∞ 0.05 1.80
10 (Aperture) ∞ -0.24 1.80
11 * 1.676 0.63 1.54470 56.2 1.87
12 * -13.857 0.05 1.90
13 * 4.012 0.28 1.63469 23.9 1.92
14 * 1.559 0.57 1.90
15 * -36.876 0.31 1.63469 23.9 2.15
16 * -35.075 0.42 2.46
17 * -6.434 0.86 1.54470 56.2 3.73
18 * -0.965 0.23 4.08
19 * -2.637 0.45 1.53048 55.7 4.59
20 * 1.582 0.64 5.12
21 ∞ 0.30 1.51633 64.1 5.66
22 ∞ 0.40 5.79
image

Values in the combined optical system of the converter lens and main lens
Focal length 3.04mm
F number 2.41
Half angle of view 47.4 °
Image height 3.02mm
Total lens length 15.95mm
Back focus 1.24mm
However, the total lens length is the distance from the side of the first lens subject to the main lens paraxial image point.
Main lens focal length 4.33mm
Converter magnification 0.70

FIG. 6 is an aberration diagram of Example 2 (spherical aberration (a), astigmatism (b), distortion aberration (c)), and the aberration diagram is a combination of the converter lens and the main lens. .

In Example 2, the ratio of the effective diameter of the object side surface of the first lens L1 to the aperture stop diameter of the main lens ML is about 0.17, thereby realizing a compact imaging optical system.

(Example 3)
Table 3 shows lens data of Example 3. FIG. 7 is a cross-sectional view of the image pickup optical system according to the third embodiment. In the figure, CL is a converter lens, and in order from the object side, a first lens L1 having a negative refractive power, a second lens L2 having a negative refractive power, and a third lens L3 having a positive refractive power. Composed. ML is a main lens, and is composed of a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, and an eighth lens L8 in this order from the object side. S denotes an aperture stop provided on the object side from the position on the optical axis of the object side surface of the fourth lens L4 on the object side from the most peripheral part of the object side surface, and IM denotes an image pickup surface of the image pickup apparatus. . Further, CG is a cover glass of the main lens ML, and F is a parallel plate assuming an optical low-pass filter, an IR cut filter, a seal glass of a solid-state image sensor, and the like. The converter lens CL (surface numbers 1 to 6) and the main lens ML (surface numbers 7 to 22) constitute an imaging optical system. In the present embodiment, the converter lens CL includes only a spherical lens, and the main lens ML includes an aspheric lens. Since the main lens ML used in the third embodiment is the same as that used in the first embodiment, the aspheric coefficient is omitted.

[Table 3]
Example 3

Surface number (aspherical surface) R (mm) d (mm) nd νd Effective diameter (mm)
1 11.812 0.80 1.83481 42.7 13.01
2 5.747 3.69 10.01
3 21.832 0.70 1.83481 42.7 9.07
4 7.327 0.84 8.18
5 6.198 3.29 1.62588 35.7 8.13
6 -36.168 1.96 7.11
7 ∞ 0.79 1.51633 64.1 4.15
8 ∞ 1.24 3.52
9 ∞ 0.05 1.80
10 (Aperture) ∞ -0.24 1.80
11 * 1.676 0.63 1.54470 56.2 1.87
12 * -13.857 0.05 1.90
13 * 4.012 0.28 1.63469 23.9 1.92
14 * 1.559 0.57 1.90
15 * -36.876 0.31 1.63469 23.9 2.15
16 * -35.075 0.42 2.46
17 * -6.434 0.86 1.54470 56.2 3.71
18 * -0.965 0.23 4.07
19 * -2.637 0.45 1.53048 55.7 4.58
20 * 1.582 0.64 5.11
21 ∞ 0.30 1.51633 64.1 5.66
22 ∞ 0.40 5.78
image

Values in the combined optical system of the converter lens and main lens
Focal length 3.04mm
F number 2.41
Half angle of view 45.9 °
Image height 3.02mm
Total lens length 18.26mm
Back focus 1.24mm
However, the total lens length is the distance from the side of the first lens subject to the main lens paraxial image point.
Main lens focal length 4.33mm
Converter magnification 0.70

FIG. 8 is an aberration diagram of Example 3 (spherical aberration (a), astigmatism (b), distortion aberration (c)), and the aberration diagram is a state where the converter lens and the main lens are combined. .

In Example 3, a compact imaging optical system is realized in which the ratio of the effective diameter of the object side surface of the first lens L1 to the aperture stop diameter of the main lens ML is about 0.14.

Example 4
Table 4 shows lens data of Example 4. FIG. 9 is a sectional view of the image pickup optical system according to the fourth embodiment. In the figure, CL is a converter lens, and in order from the object side, a first lens L1 having a negative refractive power, a second lens L2 having a negative refractive power, and a third lens L3 having a positive refractive power. Composed. ML is a main lens, and is composed of a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, and an eighth lens L8 in this order from the object side. S denotes an aperture stop provided on the object side from the position on the optical axis of the object side surface of the fourth lens L4 on the object side from the most peripheral part of the object side surface, and IM denotes an image pickup surface of the image pickup apparatus. . Further, CG is a cover glass of the main lens ML, and F is a parallel plate assuming an optical low-pass filter, an IR cut filter, a seal glass of a solid-state image sensor, and the like. The converter lens CL (surface numbers 1 to 6) and the main lens ML (surface numbers 7 to 22) constitute an imaging optical system. In the present embodiment, the converter lens CL includes only a spherical lens, and the main lens ML includes an aspheric lens. Since the main lens ML used in the second embodiment is the same as that used in the first embodiment, the aspheric coefficient is omitted.

[Table 4]
Example 4

Surface number (aspherical surface) R (mm) d (mm) nd νd Effective diameter (mm)
1 40.045 0.80 1.83481 42.7 10.83
2 5.128 2.53 8.05
3 19.828 0.70 1.83481 42.7 7.73
4 11.085 0.20 7.38
5 5.906 3.40 1.62588 35.7 7.31
6 -25.478 1.24 6.10
7 ∞ 0.79 1.51633 64.1 4.14
8 ∞ 1.24 3.50
9 ∞ 0.05 1.80
10 (Aperture) ∞ -0.24 1.80
11 * 1.676 0.63 1.54470 56.2 1.87
12 * -13.857 0.05 1.90
13 * 4.012 0.28 1.63469 23.9 1.92
14 * 1.559 0.57 1.90
15 * -36.876 0.31 1.63469 23.9 2.15
16 * -35.075 0.42 2.46
17 * -6.434 0.86 1.54470 56.2 3.72
18 * -0.965 0.23 4.07
19 * -2.637 0.45 1.53048 55.7 4.58
20 * 1.582 0.64 5.11
21 ∞ 0.30 1.51633 64.1 5.66
22 ∞ 0.40 5.78
image

Values in the combined optical system of the converter lens and main lens
Focal length 2.90mm
F number 2.41
Half angle of view 52.3 °
Image height 3.02mm
Total lens length 15.86mm
Back focus 1.24mm
However, the total lens length is the distance from the side of the first lens subject to the main lens paraxial image point.
Main lens focal length 4.33mm
Converter magnification 0.67

FIG. 10 is an aberration diagram of Example 4 (spherical aberration (a), astigmatism (b), distortion aberration (c)). The aberration diagram shows a state in which the converter lens and the main lens are combined. .

In Example 4, the ratio of the effective diameter of the object side surface of the first lens L1 to the aperture stop diameter of the main lens ML is about 0.17, thereby realizing a compact imaging optical system.

(Example 5)
Table 5 shows lens data of Example 5. FIG. 11 is a sectional view of the image pickup optical system according to the fifth embodiment. In the figure, CL is a converter lens, and in order from the object side, a first lens L1 having a negative refractive power, a second lens L2 having a negative refractive power, and a third lens L3 having a positive refractive power. Composed. ML is a main lens, and is composed of a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, and an eighth lens L8 in this order from the object side. S denotes an aperture stop provided on the object side from the position on the optical axis of the object side surface of the fourth lens L4 on the object side from the most peripheral part of the object side surface, and IM denotes an image pickup surface of the image pickup apparatus. . Further, CG is a cover glass of the main lens ML, and F is a parallel plate assuming an optical low-pass filter, an IR cut filter, a seal glass of a solid-state image sensor, and the like. The converter lens CL (surface numbers 1 to 6) and the main lens ML (surface numbers 7 to 22) constitute an imaging optical system. In the present embodiment, the converter lens CL includes only a spherical lens, and the main lens ML includes an aspheric lens. Since the main lens ML used in the fifth embodiment is the same as that used in the first embodiment, the aspheric coefficient is omitted.

[Table 5]
Example 5

Surface number (aspherical surface) R (mm) d (mm) nd νd Effective diameter (mm)
1 -30.000 0.75 1.83481 42.7 10.90
2 7.671 0.92 8.92
3 10.827 1.95 1.51742 52.2 8.83
4 7.184 0.20 7.86
5 6.713 4.50 1.61293 37.0 7.85
6 -15.723 1.24 6.28
7 ∞ 0.79 1.51633 64.1 4.13
8 ∞ 1.24 3.50
9 ∞ 0.05 1.80
10 (Aperture) ∞ -0.24 1.80
11 * 1.676 0.63 1.54470 56.2 1.87
12 * -13.857 0.05 1.90
13 * 4.012 0.28 1.63469 23.9 1.92
14 * 1.559 0.57 1.90
15 * -36.876 0.31 1.63469 23.9 2.15
16 * -35.075 0.42 2.47
17 * -6.434 0.86 1.54470 56.2 3.77
18 * -0.965 0.23 4.11
19 * -2.637 0.45 1.53048 55.7 4.61
20 * 1.582 0.64 5.14
21 ∞ 0.30 1.51633 64.1 5.68
22 ∞ 0.40 5.80
image

Values in the combined optical system of the converter lens and main lens
Focal length 3.02mm
F number 2.41
Half angle of view 58.9 °
Image height 3.02mm
Total lens length 16.54mm
Back focus 1.24mm
However, the total lens length is the distance from the side of the first lens subject to the main lens paraxial image point.
Main lens focal length 4.33mm
Converter magnification 0.70

FIG. 12 is an aberration diagram of Example 5 (spherical aberration (a), astigmatism (b), distortion aberration (c)), and the aberration diagram is a state where the converter lens and the main lens are combined. .

Example 5 realizes a compact imaging optical system in which the ratio of the effective diameter of the object side surface of the first lens L1 to the aperture stop diameter of the main lens ML is about 0.17.

(Example 6)
Table 6 shows lens data of Example 6. FIG. 13 is a sectional view of the image pickup optical system according to the sixth embodiment. In the figure, CL is a converter lens, and in order from the object side, a first lens L1 having a negative refractive power, a second lens L2 having a negative refractive power, and a third lens L3 having a positive refractive power. Composed. ML is a main lens, and is composed of a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, and an eighth lens L8 in this order from the object side. S denotes an aperture stop provided on the object side from the position on the optical axis of the object side surface of the fourth lens L4 on the object side from the most peripheral part of the object side surface, and IM denotes an image pickup surface of the image pickup apparatus. . Further, CG is a cover glass of the main lens ML, and F is a parallel plate assuming an optical low-pass filter, an IR cut filter, a seal glass of a solid-state image sensor, and the like. The converter lens CL (surface numbers 1 to 6) and the main lens ML (surface numbers 7 to 22) constitute an imaging optical system. In the present embodiment, the converter lens CL includes only a spherical lens, and the main lens ML includes an aspheric lens. Since the main lens ML used in the sixth embodiment is the same as that used in the first embodiment, the aspheric coefficient is omitted.

[Table 6]
Example 6

Surface number (aspherical surface) R (mm) d (mm) nd νd Effective diameter (mm)
1 -32.917 0.75 1.88300 40.8 10.89
2 7.522 0.93 8.90
3 10.606 2.08 1.48749 70.4 8.81
4 7.025 0.20 7.83
5 6.645 4.50 1.62004 36.3 7.83
6 -15.644 1.24 6.28
7 ∞ 0.79 1.51633 64.1 4.13
8 ∞ 1.24 3.50
9 ∞ 0.05 1.80
10 (Aperture) ∞ -0.24 1.80
11 * 1.676 0.63 1.54470 56.2 1.87
12 * -13.857 0.05 1.90
13 * 4.012 0.28 1.63469 23.9 1.92
14 * 1.559 0.57 1.90
15 * -36.876 0.31 1.63469 23.9 2.15
16 * -35.075 0.42 2.47
17 * -6.434 0.86 1.54470 56.2 3.77
18 * -0.965 0.23 4.11
19 * -2.637 0.45 1.53048 55.7 4.61
20 * 1.582 0.64 5.14
21 ∞ 0.30 1.51633 64.1 5.68
22 ∞ 0.40 5.80
image

Values in the combined optical system of the converter lens and main lens
Focal length 2.94mm
F number 2.41
Half angle of view 61.2 °
Image height 3.02mm
Total lens length 16.68mm
Back focus 1.24mm
However, the total lens length is the distance from the side of the first lens subject to the main lens paraxial image point.
Main lens focal length 4.33mm
Converter magnification 0.68

FIG. 14 is an aberration diagram of Example 6 (spherical aberration (a), astigmatism (b), distortion aberration (c)), and the aberration diagram is a state where the converter lens and the main lens are combined. .

In Example 6, the ratio of the effective diameter of the object side surface of the first lens L1 to the aperture stop diameter of the main lens ML is about 0.17, thereby realizing a compact imaging optical system.

(Example 7)
Table 7 shows lens data of Example 7. FIG. 15 is a sectional view of the image pickup optical system according to the seventh embodiment. In the figure, CL is a converter lens, and in order from the object side, a first lens L1 having a negative refractive power, a second lens L2 having a negative refractive power, and a third lens L3 having a positive refractive power. Composed. ML is a main lens, and is composed of a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, and an eighth lens L8 in this order from the object side. S denotes an aperture stop provided on the object side from the position on the optical axis of the object side surface of the fourth lens L4 on the object side from the most peripheral part of the object side surface, and IM denotes an image pickup surface of the image pickup apparatus. . Further, CG is a cover glass of the main lens ML, and F is a parallel plate assuming an optical low-pass filter, an IR cut filter, a seal glass of a solid-state image sensor, and the like. The converter lens CL (surface numbers 1 to 6) and the main lens ML (surface numbers 7 to 22) constitute an imaging optical system. In the present embodiment, in the converter lens CL, the first lens L1 is an aspheric lens, the other lenses are spherical lenses, and the main lens ML has an aspheric lens. Since the main lens ML used in the seventh embodiment is the same as that used in the first embodiment, the aspheric coefficient is omitted.

[Table 7]
Example 7

Surface number (aspherical surface) R (mm) d (mm) nd νd Effective diameter (mm)
1 * 25.425 0.75 1.88202 37.2 10.95
2 * 5.973 2.59 8.48
3 -114.874 0.70 1.78590 43.9 7.99
4 11.710 0.20 7.62
5 7.342 4.34 1.64769 33.8 7.65
6 -11.799 1.24 6.46
7 ∞ 0.79 1.51633 64.1 4.13
8 ∞ 1.24 3.50
9 ∞ 0.05 1.80
10 (Aperture) ∞ -0.24 1.80
11 * 1.676 0.63 1.54470 56.2 1.87
12 * -13.857 0.05 1.90
13 * 4.012 0.28 1.63469 23.9 1.92
14 * 1.559 0.57 1.90
15 * -36.876 0.31 1.63469 23.9 2.15
16 * -35.075 0.42 2.46
17 * -6.434 0.86 1.54470 56.2 3.74
18 * -0.965 0.23 4.09
19 * -2.637 0.45 1.53048 55.7 4.60
20 * 1.582 0.64 5.13
21 ∞ 0.30 1.51633 64.1 5.67
22 ∞ 0.40 5.80
image

Aspheric coefficient of converter lens
First side Second side
K 0.000 0.000
A4 -7.2151E-04 -5.8463E-04
A6 4.1528E-06 2.1826E-06
A8 2.2788E-07 -8.4479E-07
A10 -3.5985E-09 6.4026E-08

Values in the combined optical system of the converter lens and main lens
Focal length 2.72mm
F number 2.41
Half angle of view 70.8 °
Image height 3.02mm
Total lens length 16.80mm
Back focus 1.24mm
However, the total lens length is the distance from the side of the first lens subject to the main lens paraxial image point.
Main lens focal length 4.33mm
Converter magnification 0.63

FIG. 16 is an aberration diagram of Example 7 (spherical aberration (a), astigmatism (b), distortion aberration (c)), and the aberration diagram shows a state in which the converter lens and the main lens are combined. .

Example 7 realizes a compact imaging optical system in which the ratio of the effective diameter of the object side surface of the first lens L1 to the aperture stop diameter of the main lens ML is about 0.16.

(Example 8)
Table 8 shows lens data of Example 8. FIG. 17 is a cross-sectional view of the image pickup optical system according to the eighth embodiment. In the figure, CL is a converter lens, and in order from the object side, a first lens L1 having a negative refractive power, a second lens L2 having a negative refractive power, and a third lens L3 having a positive refractive power. Composed. ML is a main lens, and is composed of a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, and an eighth lens L8 in this order from the object side. S denotes an aperture stop provided on the object side from the position on the optical axis of the object side surface of the fourth lens L4 on the object side from the most peripheral part of the object side surface, and IM denotes an image pickup surface of the image pickup apparatus. . Further, CG is a cover glass of the main lens ML, and F is a parallel plate assuming an optical low-pass filter, an IR cut filter, a seal glass of a solid-state image sensor, and the like. The converter lens CL (surface numbers 1 to 6) and the main lens ML (surface numbers 7 to 22) constitute an imaging optical system. In the present embodiment, in the converter lens CL, the first lens L1 is an aspheric lens, the other lenses are spherical lenses, and the main lens ML has an aspheric lens. Since the main lens ML used in the eighth embodiment is the same as that used in the first embodiment, the aspheric coefficient is omitted.

[Table 8]
Example 8

Surface number (aspherical surface) R (mm) d (mm) nd νd Effective diameter (mm)
1 * 30.226 0.75 1.88202 37.2 10.96
2 * 6.282 2.58 8.48
3 -117.270 0.70 1.78590 43.9 7.98
4 11.258 0.20 7.60
5 7.256 4.34 1.64769 33.8 7.65
6 -11.702 1.24 6.46
7 ∞ 0.79 1.51633 64.1 4.13
8 ∞ 1.24 3.50
9 ∞ 0.05 1.80
10 (Aperture) ∞ -0.24 1.80
11 * 1.676 0.63 1.54470 56.2 1.87
12 * -13.857 0.05 1.90
13 * 4.012 0.28 1.63469 23.9 1.92
14 * 1.559 0.57 1.90
15 * -36.876 0.31 1.63469 23.9 2.15
16 * -35.075 0.42 2.46
17 * -6.434 0.86 1.54470 56.2 3.74
18 * -0.965 0.23 4.09
19 * -2.637 0.45 1.53048 55.7 4.60
20 * 1.582 0.64 5.13
21 ∞ 0.30 1.51633 64.1 5.67
22 ∞ 0.40 5.79
image

Aspheric coefficient of converter lens
First side Second side
K 0.000 0.000
A4 -4.7093E-04 -2.5021E-04
A6 -6.2283E-06 -1.1760E-06
A8 4.6488E-07 -1.0778E-06
A10 -5.7998E-09 8.0612E-08

Values in the combined optical system of the converter lens and main lens
Focal length 2.72mm
F number 2.41
Half angle of view 70.8 °
Image height 3.02mm
Total lens length 16.79mm
Back focus 1.24mm
However, the total lens length is the distance from the side of the first lens subject to the main lens paraxial image point.
Main lens focal length 4.33mm
Converter magnification 0.63

FIG. 18 is an aberration diagram of Example 8 (spherical aberration (a), astigmatism (b), distortion aberration (c)), and the aberration diagram shows a state in which the converter lens and the main lens are combined. .

In Example 8, the ratio of the effective diameter of the object side surface of the first lens L1 to the aperture stop diameter of the main lens ML is about 0.16, thereby realizing a compact imaging optical system.

Example 9
Table 9 shows lens data of Example 9. FIG. 19 is a cross-sectional view of the image pickup optical system according to the ninth embodiment. In the figure, CL is a converter lens, and in order from the object side, a first lens L1 having a negative refractive power, a second lens L2 having a negative refractive power, and a third lens L3 having a positive refractive power. Composed. ML is a main lens, and is composed of a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, and an eighth lens L8 in this order from the object side. S denotes an aperture stop provided on the object side from the position on the optical axis of the object side surface of the fourth lens L4 on the object side from the most peripheral part of the object side surface, and IM denotes an image pickup surface of the image pickup apparatus. . Further, CG is a cover glass of the main lens ML, and F is a parallel plate assuming an optical low-pass filter, an IR cut filter, a seal glass of a solid-state image sensor, and the like. The converter lens CL (surface numbers 1 to 6) and the main lens ML (surface numbers 7 to 22) constitute an imaging optical system. In the present embodiment, in the converter lens CL, the first lens L1 is an aspheric lens, the other lenses are spherical lenses, and the main lens ML has an aspheric lens. Since the main lens ML used in the ninth embodiment is the same as that used in the first embodiment, the aspheric coefficient is omitted.

[Table 9]
Example 9

Surface number (aspherical surface) R (mm) d (mm) nd νd Effective diameter (mm)
1 * 15.980 0.75 1.88202 37.2 10.97
2 * 5.172 2.67 8.48
3 -163.709 0.70 1.78590 43.9 7.99
4 11.289 0.20 7.61
5 7.267 4.34 1.64769 33.8 7.65
6 -11.787 1.24 6.46
7 ∞ 0.79 1.51633 64.1 4.13
8 ∞ 1.24 3.50
9 ∞ 0.05 1.80
10 (Aperture) ∞ -0.24 1.80
11 * 1.676 0.63 1.54470 56.2 1.87
12 * -13.857 0.05 1.90
13 * 4.012 0.28 1.63469 23.9 1.92
14 * 1.559 0.57 1.90
15 * -36.876 0.31 1.63469 23.9 2.15
16 * -35.075 0.42 2.46
17 * -6.434 0.86 1.54470 56.2 3.74
18 * -0.965 0.23 4.09
19 * -2.637 0.45 1.53048 55.7 4.60
20 * 1.582 0.64 5.13
21 ∞ 0.30 1.51633 64.1 5.67
22 ∞ 0.40 5.80
image

Aspheric coefficient of converter lens
First side Second side
K 0.000 0.000
A4 -1.4947E-03 -1.6461E-03
A6 3.0552E-05 1.5199E-06
A8 -2.9350E-07 1.9499E-08
A10 9.5095E-10 6.7781E-09

Values in the combined optical system of the converter lens and main lens
Focal length 2.72mm
F number 2.41
Half angle of view 70.8 °
Image height 3.02mm
Total lens length 16.88mm
Back focus 1.24mm
However, the total lens length is the distance from the side of the first lens subject to the main lens paraxial image point.
Main lens focal length 4.33mm
Converter magnification 0.63

FIG. 20 is an aberration diagram of Example 9 (spherical aberration (a), astigmatism (b), distortion aberration (c)), and the aberration diagram is a state where the converter lens and the main lens are combined. .

In the ninth embodiment, the ratio of the effective diameter of the object side surface of the first lens L1 to the aperture stop diameter of the main lens ML is about 0.16, thereby realizing a compact imaging optical system.

(Example 10)
Table 10 shows lens data of Example 10. FIG. 21 is a sectional view of the image pickup optical system according to the tenth embodiment. In the figure, CL is a converter lens, and in order from the object side, a first lens L1 having a negative refractive power, a second lens L2 having a negative refractive power, and a third lens L3 having a positive refractive power. Composed. ML is a main lens, and is composed of a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, and an eighth lens L8 in this order from the object side. S denotes an aperture stop provided on the object side from the position on the optical axis of the object side surface of the fourth lens L4 on the object side from the most peripheral part of the object side surface, and IM denotes an image pickup surface of the image pickup apparatus. . Further, CG is a cover glass of the main lens ML, and F is a parallel plate assuming an optical low-pass filter, an IR cut filter, a seal glass of a solid-state image sensor, and the like. The converter lens CL (surface numbers 1 to 6) and the main lens ML (surface numbers 7 to 22) constitute an imaging optical system. In the present embodiment, the converter lens CL has an aspheric object side surface of the first lens L1 and a spherical surface other than that, and the main lens ML has an aspheric lens. Since the main lens ML used in the tenth embodiment is the same as that used in the first embodiment, the aspheric coefficient is omitted.

[Table 10]
Example 10

Surface number (aspherical surface) R (mm) d (mm) nd νd Effective diameter (mm)
1 * 30.284 0.75 1.88202 37.2 10.94
2 5.990 2.76 8.41
3 -57.165 0.70 1.78590 43.9 7.92
4 14.450 0.20 7.61
5 7.692 4.17 1.64769 33.8 7.61
6 -11.791 1.24 6.46
7 ∞ 0.79 1.51633 64.1 4.13
8 ∞ 1.24 3.50
9 ∞ 0.05 1.80
10 (Aperture) ∞ -0.24 1.80
11 * 1.676 0.63 1.54470 56.2 1.87
12 * -13.857 0.05 1.90
13 * 4.012 0.28 1.63469 23.9 1.92
14 * 1.559 0.57 1.90
15 * -36.876 0.31 1.63469 23.9 2.15
16 * -35.075 0.42 2.47
17 * -6.434 0.86 1.54470 56.2 3.78
18 * -0.965 0.23 4.12
19 * -2.637 0.45 1.53048 55.7 4.62
20 * 1.582 0.64 5.14
21 ∞ 0.30 1.51633 64.1 5.68
22 ∞ 0.40 5.80
image

Aspheric coefficient of converter lens
First side
K 0.000
A4 -2.1950E-04
A6 -7.4033E-06
A8 2.4743E-07
A10 -2.8930E-09

Values in the combined optical system of the converter lens and main lens
Focal length 2.66mm
F number 2.41
Half angle of view 70.7 °
Image height 3.02mm
Total lens length 16.80mm
Back focus 1.24mm
However, the total lens length is the distance from the side of the first lens subject to the main lens paraxial image point.
Main lens focal length 4.33mm
Converter magnification 0.61

FIG. 22 is an aberration diagram of Example 10 (spherical aberration (a), astigmatism (b), distortion aberration (c)), and the aberration diagram shows a state in which the converter lens and the main lens are combined. .

Example 10 realizes a compact imaging optical system in which the ratio of the effective diameter of the object side surface of the first lens L1 to the aperture stop diameter of the main lens ML is about 0.16.

Table 11 shows values of each example corresponding to each conditional expression.

The present invention is not limited to the embodiments and examples described in the specification, and includes other embodiments, examples, and modified examples. It will be apparent to those skilled in the art from the technical idea. For example, even when a dummy lens having substantially no power is further provided, it is within the scope of the present invention.

BD body
HLD Lens CL Converter lens ML Main lens SF Mobile terminal L1-L8 Lens

Claims

In the converter lens that is mounted on the object side from the main lens and converts the shooting angle of view of the main lens to the wide angle side,
The converter lens includes, in order from the object side, a first lens having negative refractive power, a second lens having negative refractive power, and a third lens having positive refractive power,
A converter lens characterized by satisfying the following conditional expression:
0.04 <d4 / d5 <0.3 (1)
0.1 <(R6 + R5) / (R6-R5) <2.0 (2)
However,
d4: On-axis air space between the second lens and the third lens d5: On-axis thickness of the third lens R5: Curvature radius of the object side surface of the third lens R6: Radius of curvature of the image side surface of the third lens
The converter lens according to claim 1, wherein the following conditional expression is satisfied.
n1> 1.7 (3)
However,
n1: Refractive index of the first lens
The converter lens according to claim 1, wherein the following conditional expression is satisfied.
30 <ν1 <50 (4)
Where ν1: Abbe number of the first lens
The converter lens according to any one of claims 1 to 3, wherein the following conditional expression is satisfied.
25 <ν3 <50 (5)
However,
ν3: Abbe number of the third lens
The converter lens according to claim 1, wherein the following conditional expression is satisfied.
0.05 <d2 / d35 <2.0 (6)
However,
d2: axial air space between the first lens and the second lens d35: axial distance from the object side surface of the second lens to the image side surface of the third lens
The converter lens according to claim 1, wherein the following conditional expression is satisfied.
0.5 <f2 / f1 <10 (7)
However,
f1: Focal length of the first lens f2: Focal length of the second lens
The converter lens according to claim 1, wherein the first lens has an aspheric surface at least on the object side surface, and satisfies the following conditional expression.
-25 <APE1 / ASP1 <-5 (8)
However,
APE1: Effective radius of the object side surface of the first lens ASP1: Aspheric amount at an effective radius of the object side surface of the first lens
The converter lens according to claim 1, wherein the first lens has an aspheric surface at least on an image side surface, and satisfies the following conditional expression.
-90 <APE2 / ASP2 <-5 (9)
However,
APE1: Effective radius of the image side surface of the first lens ASP1: Aspheric amount at an effective radius of the image surface of the first lens
The converter lens according to claim 1, wherein the first lens has an aspheric surface on both the object side surface and the image side surface, and satisfies the following conditional expression.
1 <ASP1 / ASP2 <8 (10)
However,
ASP1: Aspheric amount at effective radius of object side surface of first lens ASP2: Aspheric amount at effective radius of image side surface of first lens
A converter lens according to any one of claims 1 to 9 and the main lens, wherein the main lens is provided with an aperture stop closer to the object side than the second lens from the object side of the main lens. An imaging optical system characterized by comprising:
10. A portable terminal comprising the main lens and an image sensor incorporated in a main body, wherein the converter lens according to claim 1 can be attached.