IMAGING OPTICAL SYSTEM, LENS UNIT AND IMAGING DEVICE

CROSS-REFERENCE TO RELATED APPLICATIONS

The entire disclosure of Chinese Patent Application No. 202210899228.3 filed on Jul. 28, 2022 is incorporated herein by reference.

BACKGROUND
Technical Field

The present invention relates to an imaging optical system, a lens unit and an imaging device.

Description of Related Art

Chinese Patent Application Laid-Open No. 105204144 and Chinese Patent Application Laid-Open No. 103529538 disclose an imaging optical system configured by six lenses with a relatively wide angle of view.

In the optical system disclosed in Example 4 of Chinese Patent Application Laid-Open No. 105204144, the angle of view is 68.5°, which is wide, but the F-number is 2.43, which is relatively large, and also the total track length with respect to the focal length is relatively long.

In the optical system disclosed in Chinese Patent Application Laid-Open No. 103529538, the F-number is 2.15, which is relatively small, and also the total track length with respect to the focal length is relatively short, but the angle of view is 40.7°, which is relatively narrow.

SUMMARY

One or more embodiments of the present invention achieve high optical performance and small dimensions while maintaining a small F-number and a wide angle of view.

According to an aspect of the present invention, there is provided an imaging optical system including:

- in order from an object side,
- a first lens that has negative power and an object side surface having a convex shape;
- a second lens that has positive power and a meniscus shape being convex toward the object side;
- a third lens that has positive power;
- a fourth lens that hays negative power;
- a fifth lens that is a biconvex lens having positive power; and
- a sixth lens that has positive or negative power, has an image side surface, and has an extreme value other than an intersection point with an optical axis on the image side surface of the sixth lens, wherein
- the imaging optical system satisfies the following conditional expression (1):

1.5<f2/f<3.5 (1)

- where f2 represents a focal length of the second lens, and f represents a focal length of the imaging optical system.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages and features provided by one or more embodiments of the invention will become more fully understood from the detailed description given hereinbelow and the appended drawings which are given by way of illustration only, and thus are not intended as a definition of the limits of the present invention, wherein:

FIG. 1 is a schematic sectional view of an imaging device according to one or more embodiments;

FIG. 2 is a block diagram showing a schematic control configuration of the imaging device according to one or more embodiments;

FIG. 3A is a sectional view of an imaging optical system of Example 1;

FIG. 3B shows longitudinal aberrations of the imaging optical system of Example 1;

FIG. 4A is a sectional view of the imaging optical system of Example 2;

FIG. 4B shows longitudinal aberrations of the imaging optical system of Example 2;

FIG. 5A is a sectional view of the imaging optical system of Example 3;

FIG. 5B shows longitudinal aberrations of the imaging optical system of Example 3;

FIG. 6A is a sectional view of the imaging optical system of Example 4; and

FIG. 6B shows longitudinal aberrations of the imaging optical system of Example 4.

DETAILED DESCRIPTION

Description will hereinafter be given for embodiments of the present invention with reference to drawings. However, the scope of the present invention is not limited to the disclosed embodiments.

[Overall Configuration of Imaging Device]

FIG. 1 is a schematic sectional view of an imaging device 100 according to one or more embodiments.

As shown in this figure, the imaging device 100 includes a camera module 30 for forming an image signal.

The camera module 30 includes a lens unit 40 having therein an imaging optical system 10, and a sensor section 50 that converts a subject image formed by the imaging optical system 10 into an image signal.

The lens unit 40 comprises the imaging optical system 10 and a lens barrel 41 in which the imaging optical system 10 is incorporated.

The imaging optical system 10 includes first to sixth lenses L1 to L6 and an optical filter F. Details of a configuration of the imaging optical system 10 will be given later.

The lens barrel 41 is formed of resin, metal, a mixture of resin and glass fiber, or the like, and houses the imaging optical system 10 and the like therein. The lens barrel 41 has an opening OP through which light from the object side enters the lens barrel 41. The lens barrel 41 directly or indirectly holds the first to sixth lenses L1 to L6 and the optical filter F constituting the imaging optical system 10. The lens barrel 41 positions these with respect to the direction of the optical axis Ax of the imaging optical system 10 and the direction perpendicular to the optical axis Ax.

The sensor section 50 includes an imaging element (solid-state image sensor) 51 that detects and photoelectrically converts a subject image formed by the imaging optical system 10.

The imaging element 51 is, for example, a CMOS image sensor. The imaging element 51 is fixed in a state of being positioned with respect to the optical axis Ax. The imaging element 51 has a photoelectric conversion section serving as an imaging surface (image plane) I. A signal processing circuit (not shown) is formed around the photoelectric conversion section. In the photoelectric conversion section, pixels, that is, photoelectric conversion elements, are two dimensionally arranged. Note that the imaging element 51 is not limited to the above-described CMOS image sensor, and hence may be another imaging element, such as a CCD image sensor.

FIG. 2 is a block diagram showing a schematic control configuration of the imaging device 100.

As shown in this figure, the imaging device 100 comprises a processing unit 60 that causes the camera module 30 to operate.

The processing unit 60 comprises an element drive section 62, an input section 63, a storage section 64, an image processing section 65, a display part 66, and a controller 67.

The element drive section 62 receives supply of a voltage or a clock signal for driving the imaging element 51 from the controller 67 and outputs the voltage or the clock signal to a circuit associated with the imaging element 51. Thus, the element drive section 62 causes the imaging element 51 to operate.

The input section 63 receives a user operation or a command from an external device.

The storage section 64 stores information necessary for the operation of the imaging device 100, image data obtained by the camera module 30, lens correction data used for image processing, and the like.

The image processing section 65 performs image processing, such as color correction, tone correction or zooming, on the image signal output from the imaging element 51.

The display part 66 displays information to be presented to a user, a captured image, and the like. Note that the display part 66 can also function as the input section 63.

The controller 67 comprehensively controls operations of the element drive section 62, the input section 63, the storage section 64, the image processing section 65, the display part 66, and the like. The controller 67 performs various kinds of image processing on, for example, the image data obtained by the camera module 30.

[Specific Configuration of Imaging Optical System]

Next, the imaging optical system 10 will be described in more detail.

As shown in FIG. 1, in one or more embodiments, the imaging optical system 10 comprises a first lens L1, a second lens L2, an aperture stop S, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, and an optical filter F in this order from the object side.

Among these, the optical filter F is a parallel plate that is assumed, in one or more embodiments, to be an optical low-pass filter, an infrared cut filter, seal glass of the imaging element 51 or the like. Arrangement (provision) of the optical filter F may be omitted by providing its function to one of the lens surfaces configuring the imaging optical system 10. For example, arrangement of the optical filter F may be omitted by providing an infrared cut coating as an infrared cut filter on the surface of at least one lens.

The first lens L1 has negative power (refractive power).

The first lens L1 has a convex surface as its object side surface. Therefore, an incident angle of an off-axis light flux to the object side surface can be made small, so that aberrations that occur on the object side surface can be suppressed and favorable optical performance can be obtained.

The second lens L2 has positive power.

The second lens L2 has a meniscus shape being convex toward the object side. Therefore, the principal point distance can be made shorter than that in a case where the second lens L2 is a biconvex lens. Further, the power of the combined system of the first lens L1 and the second lens L2 becomes small, and aberrations that occur on the first lens L1 and the second lens L2 can be made small.

The third lens L3 has positive power.

The fourth lens L4 has negative power.

The object side surface of each of the third lens L3 and the fourth lens L4 has a convex shape. That is, at least part of the object side surface of each of the third lens L3 and the fourth lens L4 is convex.

The fifth lens L5 has positive power.

The fifth lens L5 is a biconvex lens having convex surfaces on both the object side and the image side. Therefore, the power of the fifth lens L5 can be made relatively strong, and chromatic aberration and the like can be effectively corrected.

The sixth lens L6 has positive or negative power.

The sixth lens L6 has, at least on its image side surface, an extreme value (inflection point) other than an intersection point with the optical axis Ax. The “extreme value” is a point on an aspheric surface, the point where a tangent line of the aspheric surface becomes a line segment perpendicular to the optical axis Ax, in a case of considering a curve of a sectional shape of the sixth lens L6 including, in a surface/plane, the optical axis Ax within an effective radius. Therefore, even in a case where the imaging element 51 needs a large ray incidence angle or needs a non-linear incidence angle characteristic with respect to the image height, the chief ray angle corresponds to the imaging element 51 while the optical performance is maintained.

Further, the imaging optical system 10 satisfies the following conditional expression (1).

1.5<f2/f<3.5 (1)

The “f2” represents the focal length of the second lens L2. The “f” represents the focal length of the entire imaging optical system 10.

The conditional expression (1) is a conditional expression for appropriately setting the focal length of the second lens L2.

If f2/f exceeds the lower limit of the conditional expression (1), the refractive power of the second lens L2 does not become too strong. As a result, it is possible to suppress spherical aberration, coma, axial chromatic aberration and the like that occur on the second lens L2. In addition, it is possible to suppress deterioration in optical performance due to a shape error or an eccentricity error of the second lens L2.

If f2/f falls below the upper limit of the conditional expression (1), the refractive power of the second lens L2 does not become too weak. As a result, it is possible to suppress increase in size of the imaging optical system 10.

Further, the imaging optical system 10 may satisfy the following conditional expression (2).

0.35<CT5/f<0.60 (2)

The “CT5” represents the center thickness (thickness on the optical axis Ax) of the fifth lens L5. The “f” represents the focal length of the entire imaging optical system 10.

The conditional expression (2) is a conditional expression for appropriately setting the thickness of the fifth lens L5 in the axial direction.

If CT5/f falls below the upper limit of the conditional expression (2), the fifth lens L5 does not become too thick. Therefore, it is possible to suppress over field curvature that occurs in a case where the fifth lens L5 becomes thick, and also it is possible to suppress increase in size of the imaging optical system 10.

If CT5/f exceeds the lower limit of the conditional expression (2), the fifth lens L5 does not become too thin. Therefore, it is possible to suppress under field curvature that occurs in a case where the fifth lens L5 becomes thin, and also it is possible to secure the rigidity of the fifth lens L5. Further, the imaging optical system 10 may satisfy the following conditional expression (3).

-1.25<f1/f<−0.30 (3)

The “f1” represents the focal length of the first lens L1. The “f” represents the focal length of the entire imaging optical system 10.

The conditional expression (3) is a conditional expression for appropriately setting the focal length of the first lens L1.

If f1/f falls below the upper limit of the conditional expression (3), the negative refractive power of the first lens L1 does not become strong more than necessary. Therefore, it is possible to reduce coma and distortion in the peripheral portion.

If f1/f exceeds the lower limit of the conditional expression (3), the negative refractive power of the first lens L1 can be appropriately maintained. Therefore, effects in reducing the Petzval sum and correcting field curvature can be obtained.

Further, the imaging optical system 10 may satisfy the following conditional expression (4).

1.5<f5/f<2.5 (4)

The “f5” represents the focal length of the fifth lens L5. The “f” represents the focal length of the entire imaging optical system 10.

The conditional expression (4) is a conditional expression for appropriately setting the focal length of the fifth lens L5.

If f5/f falls below the upper limit of the conditional expression (4), the refractive power of the fifth lens L5 does not become strong more than necessary. Therefore, it is possible to reduce coma and distortion in the peripheral portion.

If f5/f exceeds the lower limit of the conditional expression (4), the refractive power of the fifth lens L5 can be appropriately maintained. Therefore, the total track length does not become too long, and the imaging optical system 10 can be downsized.

Further, the imaging optical system 10 may satisfy the following conditional expression (5).

0.40<r3/r4<0.80 (5)

The “r3” represents the curvature radius of the object side surface of the second lens L2. The “r4” represents the curvature radius of the image side surface of the second lens L2.

The conditional expression (5) is a conditional expression for appropriately setting the ratio of the curvature radii of the object side surface and the image side surface of the second lens L2.

If r3/r4 falls within the range of the conditional expression (5), the refractive index of the second lens L2 can be appropriately set. Therefore, it is possible to prevent increase in size of the imaging optical system 10, and also it is possible to reduce various aberrations and error sensitivity that occur on the second lens L2.

Further, the imaging optical system 10 may satisfy the following conditional expression (6).

−3.0<r10/f<−1.0 (6)

The “r10” represents the curvature radius of the image side surface of the fifth lens L5. The “f” represents the focal length of the entire imaging optical system 10.

The conditional expression (6) is a conditional expression for appropriately setting the curvature radius of the image side surface of the fifth lens L5.

If r10/f falls below the upper limit of the conditional expression (6), the refractive power of the fifth lens L5 does not become strong more than necessary. Therefore, it is possible to reduce coma and distortion in the peripheral portion.

If r10/f exceeds the lower limit of the conditional expression (6), the refractive power of the first lens L1 can be appropriately maintained. Therefore, the total track length does not become too long, and the imaging optical system 10 can be downsized.

Further, the imaging optical system 10 may satisfy the following conditional expression (7).

v3−v4>30.0 (7)

The “v3” represents the Abbe number of the third lens L3. The “v4” represents the Abbe number of the fourth lens L4.

The conditional expression (7) is a conditional expression for appropriately setting the Abbe numbers of the third lens L3 and the fourth lens L4.

If v3-v4 falls within the range of the conditional expression (7), chromatic aberration and field curvature of the entire imaging optical system 10 can be favorably corrected.

As described above, according to one or more embodiments, the first lens L1 has a convex surface as its object side surface. Therefore, an incident angle of an off-axis light flux to the object side surface can be made small, so that aberrations that occur on the object side surface can be suppressed and favorable optical performance can be obtained.

Further, the second lens L2 has a meniscus shape being convex toward the object side. Therefore, the principal point distance can be made shorter than that in a case where the second lens L2 is a biconvex lens. Further, the power of the combined system of the first lens L1 and the second lens L2 becomes small, and aberrations that occur on the first lens L1 and the second lens L2 can be made small.

Further, the fifth lens L5 is a biconvex lens. Therefore, the power of the fifth lens L5 can be made relatively strong, and chromatic aberration and the like can be effectively corrected.

Further, the sixth lens L6 has, at least on its image side surface, an extreme value other than an intersection point with the optical axis Ax. Therefore, the CRA (chief ray angle) can be made to correspond to the imaging element 51 while the optical performance is maintained.

Further, by the power arrangement (negative, positive, positive, negative, positive, positive or negative) of the first to sixth lenses L1 to L6, various aberrations can be adjusted in a well-balanced manner and the optical performance can be improved.

Further, the imaging optical system 10 satisfies the above conditional expression (1), which is about f2/f. Hence, the refractive power of the second lens L2 can be suitably set. Therefore, it is possible to, while maintaining a small F-number and a wide angle of view, suppress various aberrations that occur on the second lens L2, deterioration of the optical performance, and increase in size of the imaging optical system 10.

Therefore, it is possible to achieve high optical performance and small dimensions while maintaining a small F-number and a wide angle of view.

In the above, embodiments of the present invention has been described. However, embodiments to which the present invention can be applied are not limited to the above-described embodiments and its modification examples, and hence can be appropriately modified without departing from the scope of the present invention.

EXAMPLES

Examples of the imaging optical system of one or more embodiments of the present invention are shown below. Symbols used in Examples are as follows.

- f: Focal Length of Entire Imaging Optical System
- F: F-number 2ω: Entire Angle of View
- TTL: Total Track Length (Length from Most Convex Point (Vertex) of Lens Surface on Object Side of First Lens to Imaging Element)
- R: Curvature Radius
- D: On-axis Surface Distance
- Nd: Refractive Index of Lens Material with respect to d Line
- vd: Abbe Number of Lens Material

In Examples, surfaces with “*” after their surface numbers of lens surface data shown in Tables below are surfaces having an aspheric shape. The shape of an aspheric surface is expressed with the vertex of a surface being the origin, the X-axis being the optical axis direction, and the height in the direction perpendicular to the optical axis being h, and expressed by Formula 1 below.

$\begin{matrix} X = \frac{h^{2} / R}{1 + \sqrt{1 - (1 + K) h^{2} / R^{2}}} + \sum A_{i} h^{i} & [Formula 1] \end{matrix}$

where A, represents an i^thorder aspheric coefficient, R represents a curvature radius, and K represents a conic constant.

Example 1

FIG. 3A and FIG. 3B show a sectional view and longitudinal aberrations (spherical aberration, astigmatism and distortion) of the imaging optical system of Example 1.

Overall specifications of the imaging optical system of Example 1 are shown below.

- f=1.73 mm
- F=2.04
- 2ω=150.0°
- TTL=5.9 mm

Data on the lens surfaces of Example 1 is shown in Table 1 below.

TABLE 1

SURFACE NUMBER
R (mm)
D (mm)
Nd
νd

1*
2580.0787
0.48
1.53504
55.7

2
1.108932
0.80

3*
1.1926927
0.46
1.66100
21.3

4*
1.8032878
0.26

5 (STOP)
1.02E+18
−0.01

6*
4.3824659
0.86
1.53504
55.7

7*
−1.067065
0.03

8*
11.56849
0.30
1.66100
21.3

9*
1.6973581
0.07

10*
5.1161978
0.78
1.53504
55.7

11*
−3.665262
0.38

12*
1.4459061
0.47
1.53504
55.7

13*
1.1591615
0.63

Aspheric coefficients of the lens surfaces of Example 1 are shown in Table 2 below. Hereinafter (lens data in Tables included), a power of 10 may be expressed by using “E”. For example, “2.5×10⁻²” is expressed by “2.5E-02”.

TABLE 2

1^stSURFACE
K=
0

A4=
−0.00242742

A6=
0.009545748

A8=
−0.00404049

A10=
0.000952315

A12=
−0.00013147

A14=
9.85E−06

A16=
−3.09E−07

2^ndSURFACE
K=
−1.09079061

A4=
0.034566562

A6=
−0.04591726

A8=
0.108052258

A10=
−0.02438065

A12=
−0.08046088

A14=
0.08132455

A16=
−0.02355121

3^rdSURFACE
K=
−0.21268048

A4=
−0.02145139

A6=
−0.09425657

A8=
0.129056979

A10=
−0.29299395

A12=
0.127525581

A14=
0

A16=
0

4^thSURFACE
K=
2.321884228

A4=
0.122436352

A6=
−0.45440473

A8=
2.495283657

A10=
−6.45936837

A12=
6.720748904

A14=
0

A16=
0

6^thSURFACE
K=
15.9679931

A4=
0.039698746

A6=
−0.16866858

A8=
0.572595159

A10=
−0.50837093

A12=
−1.35457263

A14=
2.377342084

A16=
0

7^thSURFACE
K=
−0.47440706

A4=
0.13537278

A6=
−0.21215528

A8=
0.075701707

A10=
−0.09019501

A12=
−0.10463828

A14=
0.246174201

A16=
0

8^thSURFACE
K=
0

A4=
−0.3034561

A6=
0.475277279

A8=
−0.76261923

A10=
0.288417262

A12=
0.163636697

A14=
−0.23710317

A16=
0

9^thSURFACE
K=
−15.4288732

A4=
−0.06472756

A6=
0.07007514

A8=
−0.0344727

A10=
−0.03355805

A12=
0.029103243

A14=
−0.00645211

A16=
0

10^thSURFACE
K=
−53.3101441

A4=
0.136143101

A6=
−0.31002606

A8=
0.444635064

A10=
−0.37736957

A12=
0.185063521

A14=
−0.04832812

A16=
0.005147943

11^thSURFACE
K=
−11.5321884

A4=
−0.03377538

A6=
0.07673631

A8=
−0.06679749

A10=
−0.01696666

A12=
0.045036587

A14=
−0.01890159

A16=
0.00249193

12^thSURFACE
K=
−0.6669685

A4=
−0.29657584

A6=
0.206260512

A8=
−0.11441985

A10=
0.04277499

A12=
−0.01066955

A14=
0.001544403

A16=
−9.39E−05

13^thSURFACE
K=
−0.73733527

A4=
−0.33126204

A6=
0.198617664

A8=
−0.10173145

A10=
0.035453812

A12=
−0.00815137

A14=
0.001067116

A16=
−5.98E−05

Single lens data of Example 1 is shown in Table 3 below.

TABLE 3

LENS
START SURFACE
FOCAL LENGTH (mm)

1
1
−2.07

2
3
4.07

3
6
1.69

4
8
−3.02

5
10
4.10

6
12
−25.78

Numerical values of the conditional expressions (1) to (7) in the imaging optical system of Example 1 are shown below.

- Conditional Expression (1): f2/f=2.36
- Conditional Expression (2): CT5/f=0.45
- Conditional Expression (3): f1/f=−1.20
- Conditional Expression (4): f5/f=2.38
- Conditional Expression (5): r3/r4=0.66
- Conditional Expression (6): r10/f=−2.12
- Conditional Expression (7): v3−v4=34.37

Example 2

FIG. 4A and FIG. 4B show a sectional view and longitudinal aberrations (spherical aberration, astigmatism and distortion) of the imaging optical system of Example 2.

Overall specifications of the imaging optical system of Example 2 are shown below.

- f=1.73 mm
- F=2.04
- 2ω=150.0°
- TTL=5.8 mm

Data on the lens surfaces of Example 2 is shown in Table 4 below.

TABLE 4

SURFACE NUMBER
R (mm)
D (mm)
Nd
νd

1*
10000
0.30
1.53504
55.7

2
1.0900833
0.83

3*
1.4523543
0.72
1.65100
21.5

4*
2.8162231
0.18

5 (STOP)
1.02E+18
0.01

6*
4.89748589
0.72
1.53504
55.7

7*
−1.061015
0.03

8*
8.4907025
0.30
1.66100
21.3

9*
1.5657104
0.12

10*
10.804379
0.75
1.53504
55.7

11*
−2.517102
0.50

12*
1.5653394
0.50
1.53504
55.7

13*
1.1661707
0.55

Aspheric coefficients of the lens surfaces of Example 2 are shown in Table 5 below.

TABLE 5

1^stSURFACE
K=
0

A4=
0.393974518

A6=
−0.03690375

A8=
−0.02156268

A10=
0.00070405

A12=
−0.00777927

A14=
−0.001566

A16=
−0.00180962

2^ndSURFACE
K=
−1.08511998

A4=
0.031880318

A6=
−0.05506238

A8=
0.113693925

A10=
−0.02565916

A12=
−0.08046088

A14=
0.08132455

A16=
−0.02355121

3^rdSURFACE
K=
−0.25737498

A4=
−0.0956141

A6=
−0.00784549

A8=
0.000414932

A10=
0.000294061

A12=
−6.7057E−05

A14=
0

A16=
0

4^thSURFACE
K=
−0.73332385

A4=
0.013849339

A6=
0.004301036

A8=
0.002491363

A10=
0.000752775

A12=
0.000338081

A14=
0

A16=
0

6^thSURFACE
K=
14.38061683

A4=
0.001443764

A6=
0.000119971

A8=
0.000288209

A10=
7.25705E−05

A12=
−2.6036E−05

A14=
1.15076E−05

A16=
0

7^thSURFACE
K=
−0.60973E+00

A4=
0.20923E−01

A6=
−0.95888E−02

A8=
0.56649E−02

A10=
0.59833E−03

A12=
0.87891E−03

A14=
0.74953E−04

A16=
0.00000E+00

8^thSURFACE
K=
0

A4=
−0.18731381

A6=
−0.01816674

A8=
0.002085001

A10=
−0.00035265

A12=
0.000706661

A14=
−0.0002929

A16=
0

9^thSURFACE
K=
−14.704445

A4=
−0.10789532

A6=
−0.02515989

A8=
0.000499958

A10=
−0.00250383

A12=
0.000447355

A14=
−0.000624

A16=
0

10^thSURFACE
K=
−35.6048477

A4=
0.082630439

A6=
−0.01320302

A8=
−0.00062313

A10=
−0.00335456

A12=
−0.00125442

A14=
−0.00105968

A16=
−0.00026841

11^thSURFACE
K=
−4.04272691

A4=
−0.02516081

A6=
0.061622118

A8=
0.006272709

A10=
−0.00437964

A12=
−0.00441623

A14=
−0.0002118

A16=
0.000277271

12^thSURFACE
K=
−0.54322036

A4=
−1.55439595

A6=
0.180017323

A8=
−0.04570088

A10=
0.014991565

A12=
−0.00712738

A14=
0.000666549

A16=
0.000258687

13^thSURFACE
K=
0.73529984

A4=
−2.71674235

A6=
0.12954875

A8=
−0.0934601

A10=
0.018190227

A12=
−0.01389108

A14=
−0.00263317

A16=
−0.00119992

Single lens data of Example 2 is shown in Table 6 below.

TABLE 6

LENS
START SURFACE
FOCAL LENGTH (mm)

1
1
−2.04

2
3
3.84

3
6
1.70

4
8
−2.97

5
10
3.90

6
12
−15.19

Numerical values of the conditional expressions (1) to (7) in the imaging optical system of Example 2 are shown below.

- Conditional Expression (1): f2/f=2.22
- Conditional Expression (2): CT5/f=0.43
- Conditional Expression (3): f1/f=−1.18
- Conditional Expression (4): f5/f=2.25
- Conditional Expression (5): r3/r4=0.52
- Conditional Expression (6): r10/f=−1.45
- Conditional Expression (7): v3−v4=34.37

Example 3

FIG. 5A and FIG. 5B show a sectional view and longitudinal aberrations (spherical aberration, astigmatism and distortion) of the imaging optical system of Example 3.

The overall specifications of the imaging optical system of Example 3 are shown below.

- f=1.73 mm
- F=2.04
- 2ω=150.0°
- TTL=5.8 mm

Data on the lens surfaces of Example 3 is shown in Table 7 below.

TABLE 7

SURFACE NUMBER
R (mm)
D (mm)
Nd
νd

1*
10000
0.42
1.53504
55.7

2
1.1223659
0.84

3*
1.2674305
0.52
1.65100
21.5

4*
2.0747341
0.24

5 (STOP)
1.02E+18
0.01

6*
4.6006482
0.72
1.53504
55.7

7*
−1.100098
0.03

8*
12.986845
0.30
1.66100
21.3

9*
1.7397167
0.12

10*
12.405706
0.75
1.53504
55.7

11*
−2.338837
0.39

12*
1.5614784
0.52
1.53504
55.7

13*
1.170936
0.64

Aspheric coefficients of the lens surfaces of Example 3 are shown in Table 8 below.

TABLE 8

1^stSURFACE
K=
0

A4=
0.357644071

A6=
−0.02332452

A8=
−0.01477712

A10=
0.005328196

A12=
−0.00502852

A14=
0.000558512

A16=
−0.00130312

2^ndSURFACE
K=
−1.15488778

A4=
0.031347046

A6=
−0.04113438

A8=
0.116253553

A10=
−0.03014871

A12=
−0.08046088

A14=
0.08132455

A16=
−0.02355121

3^rdSURFACE
K=
−0.17215806

A4=
−0.08689828

A6=
−0.01441409

A8=
−0.00179427

A10=
−2.59E−06

A12=
−4.46E−05

A14=
0

A16=
0

4^thSURFACE
K=
1.20856504

A4=
0.017479426

A6=
0.001229587

A8=
0.001196234

A10=
0.000386851

A12=
0.000232777

A14=
0

A16=
0

6^thSURFACE
K=
6.138776434

A4=
−0.00036901

A6=
−0.0012522

A8=
−2.61E−05

A10=
−6.86E−05

A12=
2.44E−06

A14=
−1.06E−06

A16=
0

7^thSURFACE
K=
−0.40849837

A4=
0.011008831

A6=
−0.01624538

A8=
0.000507967

A10=
−0.00093368

A12=
2.97131E−05

A14=
−0.00012856

A16=
0

8^thSURFACE
K=
0

A4=
−0.1579378

A6=
−0.01604397

A8=
−0.00237027

A10=
−0.00111463

A12=
−8.55E−05

A14=
−0.00024479

A16=
0

9^thSURFACE
K=
−15.3203943

A4=
−0.08447904

A6=
−0.0107875

A8=
0.00048063

A10=
−0.00068425

A12=
−1.39E−05

A14=
−0.00025021

A16=
0

10^thSURFACE
K=
−23.4902818

A4=
0.0882402

A6=
−0.01538441

A8=
0.001878818

A10=
−0.0014766

A12=
−0.00011311

A14=
−0.00036417

A16=
−6.22E−05

11^thSURFACE
K=
−6.15069034

A4=
−0.01357687

A6=
0.04017082

A8=
−0.00174916

A10=
6.19E−05

A12=
−0.00200554

A14=
0.00025047

A16=
0.000123577

12^thSURFACE
K=
−0.54232092

A4=
−1.51645424

A6=
0.184072467

A8=
−0.05016377

A10=
0.015857068

A12=
−0.00694098

A14=
0.000894519

A16=
4.39E−05

13^thSURFACE
K=
−0.73649442

A4=
−2.70737062

A6=
0.159854164

A8=
−0.08896012

A10=
0.022296562

A12=
−0.01109379

A14=
−0.00102011

A16=
−0.00122504

Single lens data of Example 3 is shown in Table 9 below.

TABLE 9

LENS
START SURFACE
FOCAL LENGTH (mm)

1
1
−2.10

2
3
3.99

3
6
1.74

4
8
−3.07

5
10
3.74

6
12
−16.21

Numerical values of the conditional expressions (1) to (7) in the imaging optical system of Example 3 are shown below.

- Conditional Expression (1): f2/f=2.30
- Conditional Expression (2): CT5/f=0.43
- Conditional Expression (3): f1/f=−1.21
- Conditional Expression (4): f5/f=2.16
- Conditional Expression (5): r3/r4=0.61
- Conditional Expression (6): r10/f=−1.35
- Conditional Expression (7): v3−v4=34.37

Example 4

FIG. 6A and FIG. 6B show a sectional view and longitudinal aberrations (spherical aberration, astigmatism and distortion) of the imaging optical system of Example 4.

Overall specifications of the imaging optical system of Example 4 are shown below.

- f=1.73 mm
- F=2.04
- 2ω=150.0°
- TTL=5.8 mm

Data on the lens surfaces of Example 4 is shown in Table 10 below.

TABLE 10

SURFACE NUMBER
R (mm)
D (mm)
Nd
νd

1*
10000
0.41
1.53504
55.7

2
1.1086262
0.83

3*
1.2740841
0.53
1.65100
21.5

4*
2.1331468
0.24

5 (STOP)
1.02E+18
0.01

6*
4.8536396
0.72
1.53504
55.7

7*
−1.072688
0.04

8*
16.710801
0.30
1.66100
21.3

9*
1.7183159
0.12

10*
10.840048
0.75
1.53504
55.7

11*
−2.392496
0.39

12*
1.531843
0.52
1.53504
55.7

13*
1.1616288
0.64

Aspheric coefficients of the lens surfaces of Example 4 are shown in Table 11 below.

TABLE 11

1^stSURFACE
K=
0

A4=
0.353164874

A6=
−0.02201199

A8=
−0.0209059

A10=
0.003589651

A12=
−0.00688606

A14=
−0.0003549

A16=
−0.0017433

2^ndSURFACE
K=
−1.18120834

A4=
0.027669842

A6=
−0.04563049

A8=
0.115390019

A10=
−0.02786608

A12=
−0.08046088

A14=
0.08132455

A16=
−0.02355121

3^rdSURFACE
K=
−0.17178249

A4=
−0.08845882

A6=
−0.01223123

A8=
−0.00125192

A10=
−9.91E−05

A12=
−0.00010228

A14=
0

A16=
0

4^thSURFACE
K=
1.261603874

A4=
0.017808329

A6=
0.00207065

A8=
0.00145813

A10=
0.000415932

A12=
0.000231349

A14=
0

A16=
0

6^thSURFACE
K=
1.776505856

A4=
−0.00104734

A6=
−0.00141319

A8=
−2.30E−05

A10=
−9.39E−05

A12=
1.98E−05

A14=
−1.40E−05

A16=
0

7^thSURFACE
K=
−0.39063626

A4=
0.00982878

A6=
−0.01664006

A8=
4.26424E−05

A10=
−0.00092788

A12=
−2.653E−05

A14=
−0.00015164

A16=
0

8^thSURFACE
K=
0

A4=
−0.1587176

A6=
−0.01672472

A8=
−0.00301287

A10=
−0.00118401

A12=
−0.00010263

A14=
−0.00031264

A16=
0

9^thSURFACE
K=
−14.7283254

A4=
−0.08245009

A6=
−0.01158722

A8=
−0.00161748

A10=
−0.00095065

A12=
4.12E−06

A14=
−0.00031998

A16=
0

10^thSURFACE
K=
−13.9149463

A4=
0.088078342

A6=
−0.01724877

A8=
0.001777085

A10=
−0.00284895

A12=
−0.00022275

A14=
−0.00057069

A16=
−0.00025292

11^thSURFACE
K=
−6.61947522

A4=
−0.01928023

A6=
0.038508893

A8=
0.000524209

A10=
−4.52E−05

A12=
−0.0029069

A14=
0.000179457

A16=
0.000109516

12^thSURFACE
K=
−0.54709115

A4=
−1.50757638

A6=
0.184972921

A8=
−0.05082234

A10=
0.015149743

A12=
−0.00790394

A14=
0.001234387

A16=
−0.00010698

13^thSURFACE
K=
−0.73553411

A4=
−2.70864044

A6=
0.168306523

A8=
−0.09158475

A10=
0.017331136

A12=
−0.01599413

A14=
−0.00197755

A16=
−0.00139094

Single lens data of Example 4 is shown in Table 12 below.

TABLE 12

LENS
START SURFACE
FOCAL LENGTH (mm)

1
1
−2.07

2
3
3.91

3
6
1.71

4
8
−2.92

5
10
3.74

6
12
−17.46

Numerical values of the conditional expressions (1) to (7) in the imaging optical system of Example 4 are shown below.

- Conditional Expression (1): f2/f=2.26
- Conditional Expression (2): CT5/f=0.43
- Conditional Expression (3): f1/f=−1.20
- Conditional Expression (4): f5/f=2.16
- Conditional Expression (5): r3/r4=0.60
- Conditional Expression (6): r10/f=−1.38
- Conditional Expression (7): v3−v4=34.37

Although the disclosure has been described with respect to only a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that various other embodiments may be devised without departing from the scope of the present invention. Accordingly, the scope of the invention should be limited only by the attached claims.

IMAGING OPTICAL SYSTEM, LENS UNIT AND IMAGING DEVICE

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Original Assignees

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Abstract

Description

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