LENS OPTICAL SYSTEM, LIGHT RECEIVING DEVICE, AND DISTANCE MEASURING SYSTEM

The present disclosure relates to a lens optical system, a light receiving device, and a distance measuring system capable of providing a highly efficient lens optical system while achieving reduction in size and height. A lens optical system includes, in order from an object side, a first lens group having a negative refractive power, and a second lens group having a positive refractive power, in which the first lens group includes a first lens having a negative refractive power, the second lens group includes a second lens having a positive or negative refractive power, a third lens having a positive refractive power, and a fourth lens having a positive refractive power, and the lens optical system has a positive refractive power as a whole. The present disclosure can be applied to, for example, a distance measuring system that detects a distance to a subject in a depth direction, and the like.

TECHNICAL FIELD

The present disclosure relates to a lens optical system, a light receiving device, and a distance measuring system, and particularly relates to a lens optical system, a light receiving device, and a distance measuring system capable of providing a highly efficient lens optical system while achieving reduction in size and height.

BACKGROUND ART

Imaging devices such as a camera-equipped mobile phone and a digital still camera using an imaging element such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) image sensor are known. In such an imaging device, further downsizing, height reduction, high efficiency, and high output power are required, and also in an imaging lens to be mounted, in addition to downsizing and height reduction, it is required to reduce a decrease in peripheral light amount ratio that tends to occur in height reduction. By increasing the peripheral light amount ratio, light beams can be collected more efficiently, and a load of image processing in the subsequent stage is also reduced.

Furthermore, for the imaging lens, a bright lens with a large aperture, that is, an opening with a bright Fno is required in order to achieve a faster shutter speed and secure an absolute light amount incident on the optical system while preventing deterioration of image quality due to noise in imaging in a dark place. As such a small and highly efficient imaging lens, a lens optical system having a configuration of four or more lenses is required.

For example, the lens optical systems of Patent Documents 1 to 4 have been proposed as an optical system with a four-lens configuration.

CITATION LIST

Patent Document

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

The lens optical system of Patent Document 1 has an Fno of about 2.4 in a four-lens configuration, and various aberrations, particularly spherical aberration and field curvature, are well corrected and good performance can be secured. However, a barrel-shaped distortion aberration cannot be corrected, and the barrel-shaped distortion aberration occurs largely. Furthermore, the second lens has a shape with a convex surface facing an object side and a distance to the first lens is long, and thus the total length becomes long, impairing performance in terms of miniaturization and height reduction.

The lens optical system of Patent Document 2 also has a four-lens configuration and has an Fno of about 2.0, and it can be seen that light beams can be efficiently collected. However, also in this lens optical system, the second lens has a shape with a convex surface facing the object side and the distance to the first lens is long, and thus the total length is long, impairing the performance in terms of miniaturization and height reduction. From these lens optical systems, it is expected that aberration correction, particularly correction of spherical aberration and coma aberration, will be difficult if downsizing and height reduction or enlargement of the Fno aperture are further advanced in the future.

The lens optical system of Patent Document 3 also has a four-lens configuration and has an Fno of about 2.4. This lens optical system has a small size and a low height with a short interval between the respective lenses including the interval between the first lens and the second lens. It can be seen that the second lens has a concave surface facing the object side and can collect light with high efficiency. However, the distance from the final lens to the light receiving element is long, and efficiency of peripheral light beams and light beams incident on a peripheral portion of the light receiving element is low there. Furthermore, the distortion aberration is largely generated in a barrel shape.

The lens optical system of Patent Document 4 also has a four-lens configuration, and Fno is a numerical value from 2.4 to 2.8. A negative first lens, a positive second lens, a positive third lens, and a negative fourth lens are provided, and each lens interval including an interval between the first lens and the second lens or the like is close, which is considered to be suitable for miniaturization and height reduction. Furthermore, it can be seen that the second lens has a concave surface facing the object side and can collect light with high efficiency. However, it is conceivable that this lens optical system splashes the light beams incident on the peripheral portion of the light receiving element from the shape of the final surface of the fourth lens, thereby decreasing efficiency of the peripheral light beams.

The present disclosure has been made in view of such a situation, and an object thereof is to provide a highly efficient lens optical system while achieving reduction in size and height.

Solutions to Problems

A lens optical system according to a first aspect of the present disclosure includes,

in order from an object side:

a first lens group having a negative refractive power; and

a second lens group having a positive refractive power, in which

the first lens group includesa first lens having a negative refractive power,

the second lens group includesa second lens having a positive or negative refractive power,a third lens having a positive refractive power, anda fourth lens having a positive refractive power, and

the lens optical system has a positive refractive power as a whole.

A light receiving device according to a second aspect of the present disclosure includes:

a lens optical system; and

a light receiving element that receives light from an object side collected by the lens optical system, in which

the lens optical system has a positive refractive power as a whole, and includes,in order from the object side,a first lens group having a negative refractive power, anda second lens group having a positive refractive power,

the first lens group includesa first lens having a negative refractive power, and

the second lens group includesa second lens having a positive or negative refractive power,a third lens having a positive refractive power, anda fourth lens having a positive refractive power.

A distance measuring system according to a third aspect of the present disclosure includes:

a lighting device that emits irradiation light; and

a light receiving device that receives reflected light in which the irradiation light is reflected by an object, in which

the light receiving device includesa lens optical system, anda light receiving element that receives light beams from an object side collected by the lens optical system, and

the lens optical system has a positive refractive power as a whole, and includes,in order from the object side,a first lens group having a negative refractive power, anda second lens group having a positive refractive power,

the first lens group includesa first lens having a negative refractive power, and

the second lens group includesa second lens having a positive or negative refractive power,a third lens having a positive refractive power, anda fourth lens having a positive refractive power.

In the first to third aspects of the present disclosure, as the lens optical system, in order from an object side a first lens group having a negative refractive power, and a second lens group having a positive refractive power are provided, in which the first lens group includes a first lens having a negative refractive power, the second lens group includes a second lens having a positive or negative refractive power, a third lens having a positive refractive power, and a fourth lens having a positive refractive power, and the lens optical system has a positive refractive power as a whole.

A lens optical system according to a fourth aspect of the present disclosure includes,

in order from an object side:

a first lens group having a negative refractive power; and

a second lens group having a positive refractive power, in which

the first lens group includesa first lens having a negative refractive power,

the second lens group includesa second lens having a positive refractive power,a third lens having a positive or negative refractive power, anda fourth lens having a positive refractive power, and

the lens optical system has a positive refractive power as a whole.

A light receiving device according to a fifth aspect of the present disclosure includes:

a lens optical system; and

a light receiving element that receives light from an object side collected by the lens optical system, in which

the lens optical system has a positive refractive power as a whole, and includes,in order from the object side,a first lens group having a negative refractive power, anda second lens group having a positive refractive power,

the first lens group includesa first lens having a negative refractive power, and

the second lens group includesa second lens having a positive refractive power,a third lens having a positive or negative refractive power, anda fourth lens having a positive refractive power.

A distance measuring system according to a sixth aspect of the present disclosure includes:

a lighting device that emits irradiation light; and

a light receiving device that receives reflected light in which the irradiation light is reflected by an object, in which

the light receiving device includesa lens optical system, anda light receiving element that receives light beams from an object side collected by the lens optical system, and

the lens optical system has a positive refractive power as a whole, and includes,in order from the object side,a first lens group having a negative refractive power, anda second lens group having a positive refractive power,

the first lens group includesa first lens having a negative refractive power, and

the second lens group includesa second lens having a positive refractive power,a third lens having a positive or negative refractive power, and

a fourth lens having a positive refractive power.

In the fourth to sixth aspects of the present disclosure, as the lens optical system, in order from an object side a first lens group having a negative refractive power, and a second lens group having a positive refractive power are provided, in which the first lens group includes a first lens having a negative refractive power, the second lens group includes a second lens having a positive refractive power, a third lens having a positive or negative refractive power, and a fourth lens having a positive refractive power, and the lens optical system has a positive refractive power as a whole.

The lens optical system, the light receiving device, and the distance measuring system may be independent devices, or may be modules incorporated in other devices.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, modes for carrying out the present disclosure (hereinafter, it is referred to as an embodiment) will be described with reference to the accompanying drawings. Note that in the description and the drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant descriptions are omitted. The description will be made in the following order.

1. First Embodiment of Lens Optical System

2. Second Embodiment of Lens Optical System

3. Application Example to Distance Measuring System

4. Application Example to Electronic Device

5. Application Example to Mobile Object

1. First Embodiment of Lens Optical System

First, a lens optical system according to a first embodiment of the present disclosure will be described with reference to a lens optical system1-1inFIG.1. The lens optical system1-1inFIG.1is a first configuration example of a lens optical system1in the first embodiment.

The lens optical system1according to the first embodiment of the present disclosure includes a first lens L1having a negative refractive power, a second lens L2having a positive or negative refractive power, a third lens L3having a positive refractive power, and a fourth lens L4having a positive refractive power in order from an object side around an optical axis Z1of a one-dot chain line, and has a positive refractive power as a whole. The first lens L1closer to the object side than an aperture stop STO constitutes a first lens group and has a negative refractive power. The second lens L2to the fourth lens L4on an image side of the aperture stop STO constitute a second lens group and have a positive refractive power. The first lens group is also referred to as a front group, and the second lens group is also referred to as a rear group.

In the lens optical system1, the aperture stop STO is disposed between the first lens L1and the second lens L2, and a sealing glass SG is disposed between the fourth lens L4and an image plane IMG. The sealing glass SG can have a filter function such as an infrared cut filter and a band pass filter, an antireflection function, and the like, in addition to a function of protecting a light receiving element. Note that the sealing glass SG may be omitted.

The lens optical system1collects light beams from the object side on a photoelectric conversion section of the light receiving element arranged at the position of the image plane IMG and forms an image.

The lens optical system1has negative (first lens L1), positive or negative (second lens L2), positive (third lens L3), and positive (fourth lens L4) refractive powers in order from the first lens L1on the object side, and has a positive refractive power as a whole, so that the angle of view is widened, the range on the object side can thereby be widened, and the light beams from the object side can be efficiently collected and guided to the light receiving element. Moreover, in addition to good collecting performance and optical performance, it is possible to shorten the total optical length, and it is possible to meet the need for reduction in size and height.

In the lens optical system1, by configuring each lens so as to satisfy at least one conditional expression, preferably two or more conditional expressions in combination described below, it is possible to achieve a lens optical system having good collecting performance and optical performance, and having a reduced size and a reduced height.

Note that, in the following description, a surface on the object side of the first lens L1is assumed as “1”, and a lens surface is denoted by “Si” with a number i so as to sequentially increase toward the image side. Furthermore, a paraxial curvature radius (mm) of the lens surface “Si” is represented by “Ri”.

First, for the lens optical system1, a first conditional expression is that the lens shape of the second lens L2on the object side is concave toward the object side. That is, a curvature radius R3of a lens surface S3satisfies the following conditional expression (1).

Next, for the lens optical system1, a second conditional expression is that the lens shape of the fourth lens L4on the object side is convex toward the object side. That is, a curvature radius R7of a lens surface S7satisfies the following conditional expression (2).

Since the lens shape of the second lens L2on the object side is concave toward the object side, the light beams from the object side can be efficiently collected up to the peripheral edge portion of the light receiving element, and a shading characteristic is improved.

Next, the lens optical system1satisfies the following conditional expression (3).

In the conditional expression (3), f represents a focal length (mm) of the entire lens optical system1at a d-line (wavelength 587.6 nm), fa1represents a focal length (mm) of the first lens group (front group) at the d-line (wavelength 587.6 nm), and fa2represents a focal length (mm) of the second lens group (rear group) at the d-line (wavelength 587.6 nm).

The conditional expression (3) is an expression relating to an appropriate power distribution of the first lens group and the second lens group with respect to the power of lens of the entire optical system. The absolute value is used in the conditional expression (3) because the first lens group has negative power. When the conditional expression (3) exceeds an upper limit, the power of the first lens group becomes too small with respect to the power of lens of the entire optical system and the power of the second lens group, and it becomes difficult to widen the angle of view.

In consideration of securing the angle of view and the viewing angle, the conditional expression (3) more preferably satisfies the following conditional expression (3)′.

Next, the lens optical system1satisfies the following conditional expression (4).

In the conditional expression (4), f2represents a focal length (mm) of the second lens L2at the d-line (wavelength 587.6 nm), and f3represents a focal length (mm) of the third lens L3at the d-line (wavelength 587.6 nm).

The conditional expression (4) is an expression relating to an appropriate power distribution of the combined power of the second lens L2and the third lens L3with respect to the power of lens of the entire optical system. When the conditional expression (4) exceeds an upper limit, the combined power of the second lens L2and the third lens L3becomes excessively large with respect to the power of lens of the entire optical system, and it becomes difficult to collect the light beams up to the peripheral angle of view while securing the angle of view and to secure the peripheral light amount ratio. On the other hand, when the conditional expression (4) exceeds a lower limit, the power of lens of the entire optical system becomes excessively large with respect to the combined power of the second lens L2and the third lens L3, and although it is easy to widen the angle of view, it becomes difficult to correct each aberration, particularly coma aberration, and it becomes difficult to secure performance.

In consideration of securing the angle of view and the viewing angle, the conditional expression (4) more preferably satisfies the following conditional expression (4)′.

Next, the lens optical system1satisfies the following conditional expression (5).

In the conditional expression (5), FOV represents an object-side capturing angle of the lens optical system1, what is called an angle of view, and corresponds to an angle of view2ω on both sides. D12represents an inter-lens distance between the first lens L1and the second lens L2. TL represents the total optical length of the lens optical system1.

The conditional expression (5) is a conditional expression indicating the relationship among the angle of view FOV, the inter-lens distance D12between the first lens L1and the second lens L2, and the total optical length TL of the lens optical system1. When the conditional expression (5) exceeds an upper limit, the total optical length TL of the lens optical system1becomes too short with respect to the relationship between the angle of view FOV and the length D12from the first lens L1to the second lens L2, and it becomes difficult to secure necessary optical performance in a state where the angle of view FOV is maintained. On the other hand, when the conditional expression (5) falls below a lower limit, the total optical length TL of the lens optical system1becomes too long with respect to the angle of view FOV and the length D12from the first lens L1to the second lens L2, and is no longer small in size.

In consideration of securing the angle of view and the viewing angle, the conditional expression (5) more preferably satisfies the following conditional expression (5)′.

Next, the lens optical system1satisfies the following conditional expression (6).

The conditional expression (6) expresses the relationship of the lens curvature radius R2of an image-side surface S2of the first lens L1with the lens curvature radius R1of an object-side surface S1of the first lens L1by the conditional expression. When the conditional expression (6) falls below a lower limit, in a case where the object-side surface S1of the first lens L1is a concave surface, the curvature radius R2of the image-side surface S2becomes too large with respect to the curvature radius R1of the object-side surface S1, and in a case where the object-side surface S1of the first lens L1is a convex surface, the curvature radius R2of the image-side surface S2becomes too small with respect to the curvature radius R1of the object-side surface S1, so that it becomes difficult to efficiently collect the light beams up to the peripheral edge portion of the light receiving element. On the other hand, when the conditional expression (6) exceeds an upper limit, the curvature radius R2of the image-side surface S2becomes too small with respect to the curvature radius R1of the object-side surface S1of the first lens L1, and it becomes difficult to efficiently collect the light beams up to the peripheral edge portion of the light receiving element.

In consideration of efficiently collecting light up to the peripheral edge portion of the light receiving element, the conditional expression (6) more preferably satisfies the following conditional expression (6)′.

Next, the lens optical system1satisfies the following conditional expression (7).

The conditional expression (7) expresses the relationship of the lens curvature radius R4of the image-side surface S4of the second lens L2with the lens curvature radius R3of the object-side surface S3of the second lens L2. When the conditional expression (7) falls below a lower limit, the lens curvature radius R4of the image-side surface S4becomes too large with respect to the curvature radius R3of the object-side surface S3of the second lens L2, and it becomes difficult to efficiently cause the light beams collected by the first lens L1to reach the peripheral edge portion of the light receiving element. On the other hand, when the conditional expression (7) exceeds an upper limit, the curvature radius R4of the image-side surface S4becomes too small with respect to the curvature radius R3of the object-side surface S3of the second lens L2, and it becomes difficult to efficiently cause the light beams collected by the first lens L1to reach the peripheral edge portion of the light receiving element.

In consideration of efficiently collecting light up to the peripheral edge portion of the light receiving element, the conditional expression (7) more preferably satisfies the following conditional expression (7)′.

Next, the lens optical system1satisfies the following conditional expression (8).

The conditional expression (8) expresses the relationship of the lens curvature radius R8of the image-side surface S8of the fourth lens L4with the lens curvature radius R7of the object-side surface S7of the fourth lens L4. When the conditional expression (8) falls below a lower limit, the lens curvature radius R8of the image-side surface S8becomes too small with respect to the lens curvature radius R7of the object-side surface S7of the fourth lens L4, which adversely affects aberration correction, particularly distortion aberration correction. On the other hand, when the conditional expression (8) exceeds an upper limit, the lens curvature radius R8of the image-side surface S8becomes too large with respect to the lens curvature radius R7of the object-side surface S7of the fourth lens L4, and similarly, aberration correction, particularly correction of distortion aberration becomes difficult, making it difficult to obtain an appropriate correction effect.

In consideration of the aberration correction effect, the conditional expression (8) more preferably satisfies the following conditional expression (8)′.

Hereinafter, a configuration example in which specific numerical values are applied to the lens optical system1in the first embodiment will be described.

<1.1 First Configuration Example of First Embodiment>

FIG.1illustrates a first configuration example (Example 1) of the lens optical system1in the first embodiment.

The lens optical system1-1inFIG.1includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.2illustrates specific characteristic data of the lens optical system1-1and lens data of the first lens L1to the fourth lens L4.

InFIG.2, “FNo” represents the F-number of the lens optical system1-1, “f” represents the focal length (mm) of the entire lens system of the lens optical system1-1, and “2ω” represents a diagonal total angle of view (°).

Furthermore, “Si” represents the i-th surface counted from the object side to the image side, “Ri” represents a paraxial curvature radius of the i-th surface Si, “Di” represents an interval on the optical axis between the i-th surface S1and the (i+1)-th surface S(i+1), “Ndi” represents a refractive index at the d-line (wavelength 587.6 nm) of the lens starting from the i-th surface Si, and “νdi” represents the Abbe number at the d-line of the lens starting from the i-th surface Si.

An aspherical shape of each surface S1of the lens optical system1-1is expressed by the following Formula (1). In Formula (1), Z represents a depth of the aspherical surface, and Y represents a height from the optical axis (a position in a direction perpendicular to the optical axis). Furthermore, K represents a conic constant, and Ai represents an i-th order (i is an integer of 3 or more) aspherical coefficient. R is a paraxial curvature radius. The meaning of each symbol is similar in other configuration examples (examples) described later.

FIG.3illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system1-1and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.4is a diagram illustrating aberration performance of the lens optical system1-1, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

In the spherical aberration diagram, T represents spherical aberration in a lens normal direction, and S represents spherical aberration in a lens tangential direction. T and S are similarly used in spherical aberration diagrams of other configuration examples (examples) described later.

As can be seen from each aberration diagram, the lens optical system1-1has various aberrations corrected well and has excellent image forming performance.

<1.2 Second Configuration Example of First Embodiment>

FIG.5illustrates a second configuration example (Example 2) of the lens optical system1in the first embodiment.

A lens optical system1-2inFIG.5includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.6illustrates specific characteristic data of the lens optical system1-2and lens data of the first lens L1to the fourth lens L4.

FIG.7illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system1-2and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai. In the value of the aspherical coefficient Ai, a numerical value including a symbol “E” is an expression by an exponential function with a base of 10, and for example, “1.0E-05” indicates “1.0×10−5”.

FIG.8is a diagram illustrating aberration performance of the lens optical system1-2, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system1-2has various aberrations corrected well and has excellent image forming performance.

<1.3 Third Configuration Example of First Embodiment>

FIG.9illustrates a third configuration example (Example 3) of the lens optical system1in the first embodiment.

A lens optical system1-3inFIG.9includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.10illustrates specific characteristic data of the lens optical system1-3and lens data of the first lens L1to the fourth lens L4.

FIG.11illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system1-3and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.12is a diagram illustrating aberration performance of the lens optical system1-3, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system1-3has various aberrations corrected well and has excellent image forming performance.

<1.4 Fourth Configuration Example of First Embodiment>

FIG.13illustrates a fourth configuration example (Example 4) of the lens optical system1in the first embodiment.

A lens optical system1-4inFIG.13includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, negative, positive, and positive refractive power, respectively, in order from the first lens L1on the object side. Therefore, the second lens L2has a positive refractive power in the lens optical systems1-1to1-3described above, but has a negative refractive power in the lens optical system1-4.

FIG.14illustrates specific characteristic data of the lens optical system1-4and lens data of the first lens L1to the fourth lens L4.

FIG.15illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system1-4and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.16is a diagram illustrating aberration performance of the lens optical system1-4, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system1-4has various aberrations corrected well and has excellent image forming performance.

<1.5 Fifth Configuration Example of First Embodiment>

FIG.17illustrates a fifth configuration example (Example 5) of the lens optical system1in the first embodiment.

A lens optical system1-5inFIG.17includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.18illustrates specific characteristic data of the lens optical system1-5and lens data of the first lens L1to the fourth lens L4.

FIG.19illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system1-5and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.20is a diagram illustrating aberration performance of the lens optical system1-5, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system1-5has various aberrations corrected well and has excellent image forming performance.

<1.6 Sixth Configuration Example of First Embodiment>

FIG.21illustrates a sixth configuration example (Example 6) of the lens optical system1in the first embodiment.

A lens optical system1-6inFIG.21includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.22illustrates specific characteristic data of the lens optical system1-6and lens data of the first lens L1to the fourth lens L4.

FIG.23illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system1-6and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.24is a diagram illustrating aberration performance of the lens optical system1-6, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system1-6has various aberrations corrected well and has excellent image forming performance.

<1.7 Seventh Configuration Example of First Embodiment>

FIG.25illustrates a seventh configuration example (Example 7) of the lens optical system1in the first embodiment.

A lens optical system1-7inFIG.25includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.26illustrates specific characteristic data of the lens optical system1-7and lens data of the first lens L1to the fourth lens L4.

FIG.27illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system1-7and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.28is a diagram illustrating aberration performance of the lens optical system1-7, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system1-7has various aberrations corrected well and has excellent image forming performance.

<1.8 Eighth Configuration Example of First Embodiment>

FIG.29illustrates an eighth configuration example (Example 8) of the lens optical system1in the first embodiment.

A lens optical system1-8inFIG.29includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.30illustrates specific characteristic data of the lens optical system1-8and lens data of the first lens L1to the fourth lens L4.

FIG.31illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system1-8and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.32is a diagram illustrating aberration performance of the lens optical system1-8, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system1-8has various aberrations corrected well and has excellent image forming performance.

<1.9 Ninth Configuration Example of First Embodiment>

FIG.33illustrates a ninth configuration example (Example 9) of the lens optical system1in the first embodiment.

A lens optical system1-9inFIG.33includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.34illustrates specific characteristic data of the lens optical system1-9and lens data of the first lens L1to the fourth lens L4.

FIG.35illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system1-9and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.36is a diagram illustrating aberration performance of the lens optical system1-9, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system1-9has various aberrations corrected well and has excellent image forming performance.

<1.10 Tenth Configuration Example of First Embodiment>

FIG.37illustrates a tenth configuration example (Example 10) of the lens optical system1in the first embodiment.

A lens optical system1-10inFIG.37includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.38illustrates specific characteristic data of the lens optical system1-10and lens data of the first lens L1to the fourth lens L4.

FIG.39illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system1-10and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.40is a diagram illustrating aberration performance of the lens optical system1-10, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system1-10has various aberrations corrected well and has excellent image forming performance.

<1.11 11th Configuration Example of First Embodiment>

FIG.41illustrates an 11th configuration example (Example 11) of the lens optical system1in the first embodiment.

A lens optical system1-11inFIG.41includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.42illustrates specific characteristic data of the lens optical system1-11and lens data of the first lens L1to the fourth lens L4.

FIG.43illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system1-11and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.44is a diagram illustrating aberration performance of the lens optical system1-11, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system1-11has various aberrations corrected well and has excellent image forming performance.

<1.12 12th Configuration Example of First Embodiment>

FIG.45illustrates a 12th configuration example (Example 12) of the lens optical system1in the first embodiment.

A lens optical system1-12inFIG.45includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.46illustrates specific characteristic data of the lens optical system1-12and lens data of the first lens L1to the fourth lens L4.

FIG.47illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system1-12and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.48is a diagram illustrating aberration performance of the lens optical system1-12, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system1-12has various aberrations corrected well and has excellent image forming performance.

<1.13 13th Configuration Example of First Embodiment>

FIG.49illustrates a 13th configuration example (Example 13) of the lens optical system1in the first embodiment.

A lens optical system1-13inFIG.49includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.50illustrates specific characteristic data of the lens optical system1-13and lens data of the first lens L1to the fourth lens L4.

FIG.51illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system1-13and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.52is a diagram illustrating aberration performance of the lens optical system1-13, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system1-13has various aberrations corrected well and has excellent image forming performance.

<1.14 14th Configuration Example of First Embodiment>

FIG.53illustrates a 14th configuration example (Example 14) of the lens optical system1in the first embodiment.

A lens optical system1-14inFIG.53includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.54illustrates specific characteristic data of the lens optical system1-14and lens data of the first lens L1to the fourth lens L4.

FIG.55illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system1-14and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.56is a diagram illustrating aberration performance of the lens optical system1-14, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system1-14has various aberrations corrected well and has excellent image forming performance.

<1.15 15th Configuration Example of First Embodiment>

FIG.57illustrates a 15th configuration example (Example 15) of the lens optical system1in the first embodiment.

A lens optical system1-15inFIG.57includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.58illustrates specific characteristic data of the lens optical system1-15and lens data of the first lens L1to the fourth lens L4.

FIG.59illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system1-15and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.60is a diagram illustrating aberration performance of the lens optical system1-15, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system1-15has various aberrations corrected well and has excellent image forming performance.

<1.16 16th Configuration Example of First Embodiment>

FIG.61illustrates a 16th configuration example (Example 16) of the lens optical system1in the first embodiment.

A lens optical system1-16inFIG.61includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.62illustrates specific characteristic data of the lens optical system1-16and lens data of the first lens L1to the fourth lens L4.

FIG.63illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system1-16and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.64is a diagram illustrating aberration performance of the lens optical system1-16, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system1-16has various aberrations corrected well and has excellent image forming performance.

<1.17 17th Configuration Example of First Embodiment>

FIG.65illustrates a 17th configuration example (Example 17) of the lens optical system1in the first embodiment.

A lens optical system1-17inFIG.65includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.66illustrates specific characteristic data of the lens optical system1-17and lens data of the first lens L1to the fourth lens L4.

FIG.67illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system1-17and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.68is a diagram illustrating aberration performance of the lens optical system1-17, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system1-17has various aberrations corrected well and has excellent image forming performance.

<1.18 18th Configuration Example of First Embodiment>

FIG.69illustrates an 18th configuration example (Example 18) of the lens optical system1in the first embodiment.

A lens optical system1-18inFIG.69includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.70illustrates specific characteristic data of the lens optical system1-18and lens data of the first lens L1to the fourth lens L4.

FIG.71illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system1-18and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.72is a diagram illustrating aberration performance of the lens optical system1-18, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system1-18has various aberrations corrected well and has excellent image forming performance.

<1.19 19th Configuration Example of First Embodiment>

FIG.73illustrates a 19th configuration example (Example 19) of the lens optical system1in the first embodiment.

A lens optical system1-19inFIG.73includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.74illustrates specific characteristic data of the lens optical system1-19and lens data of the first lens L1to the fourth lens L4.

FIG.75illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system1-19and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.76is a diagram illustrating aberration performance of the lens optical system1-19, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system1-19has various aberrations corrected well and has excellent image forming performance.

<1.20 20th Configuration Example of First Embodiment>

FIG.77illustrates a 20th configuration example (Example 20) of the lens optical system1in the first embodiment.

A lens optical system1-20inFIG.77includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.78illustrates specific characteristic data of the lens optical system1-20and lens data of the first lens L1to the fourth lens L4.

FIG.79illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system1-20and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.80is a diagram illustrating aberration performance of the lens optical system1-20, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system1-20has various aberrations corrected well and has excellent image forming performance.

<1.21 21st Configuration Example of First Embodiment>

FIG.81illustrates a 21st configuration example (Example 21) of the lens optical system1in the first embodiment.

A lens optical system1-21inFIG.81includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.82illustrates specific characteristic data of the lens optical system1-21and lens data of the first lens L1to the fourth lens L4.

FIG.83illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system1-21and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.84is a diagram illustrating aberration performance of the lens optical system1-21, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system1-21has various aberrations corrected well and has excellent image forming performance.

<1.22 22nd Configuration Example of First Embodiment>

FIG.85illustrates a 22nd configuration example (Example 22) of the lens optical system1in the first embodiment.

A lens optical system1-22inFIG.85includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, negative, positive, and positive refractive power, respectively, in order from the first lens L1on the object side. Therefore, in the lens optical system1-22, similarly to the lens optical system1-4inFIG.13described above, the second lens L2has a negative refractive power.

FIG.86illustrates specific characteristic data of the lens optical system1-22and lens data of the first lens L1to the fourth lens L4.

FIG.87illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system1-22and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.88is a diagram illustrating aberration performance of the lens optical system1-22, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system1-22has various aberrations corrected well and has excellent image forming performance.

<1.23 23rd Configuration Example of First Embodiment>

FIG.89illustrates a 23rd configuration example (Example 23) of the lens optical system1in the first embodiment.

A lens optical system1-23inFIG.89includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, negative, positive, and positive refractive power, respectively, in order from the first lens L1on the object side. Therefore, in the lens optical system1-23, similarly to the lens optical system1-22inFIG.85described above, the second lens L2has a negative refractive power.

FIG.90illustrates specific characteristic data of the lens optical system1-23and lens data of the first lens L1to the fourth lens L4.

FIG.91illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system1-23and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.92is a diagram illustrating aberration performance of the lens optical system1-23, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system1-23has various aberrations corrected well and has excellent image forming performance.

<1.24 24th Configuration Example of First Embodiment>

FIG.93illustrates a 24th configuration example (Example 24) of the lens optical system1in the first embodiment.

A lens optical system1-24inFIG.93includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, negative, positive, and positive refractive power, respectively, in order from the first lens L1on the object side. Therefore, in the lens optical system1-24, similarly to the lens optical system1-23inFIG.89described above, the second lens L2has a negative refractive power.

FIG.94illustrates specific characteristic data of the lens optical system1-24and lens data of the first lens L1to the fourth lens L4.

FIG.95illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system1-24and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.96is a diagram illustrating aberration performance of the lens optical system1-24, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system1-24has various aberrations corrected well and has excellent image forming performance.

<1.25 25th Configuration Example of First Embodiment>

FIG.97illustrates a 25th configuration example (Example 25) of the lens optical system1in the first embodiment.

A lens optical system1-25inFIG.97includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.98illustrates specific characteristic data of the lens optical system1-25and lens data of the first lens L1to the fourth lens L4.

FIG.99illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system1-25and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.100is a diagram illustrating aberration performance of the lens optical system1-25, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system1-21has various aberrations corrected well and has excellent image forming performance.

<1.26 Conditional Expression Data of Lens Optical System According to First Embodiment>

FIGS.101to103illustrate values obtained by calculating the conditional expressions (1) to (8) and original data required for calculating the respective conditional expressions in the lens optical systems1-1to1-25illustrated inFIGS.1to100.

As illustrated inFIGS.101to103, the lens optical systems1-1to1-25satisfy all of the conditional expressions (1) to (8). Furthermore, the lens optical systems1-1to1-25also satisfy the conditional expressions (3)′ to (8)′ which are more preferable conditions.

With the lens optical systems1-1to1-25satisfying the conditional expressions (1) to (8), more preferably the conditional expressions (3)′ to (8)′, Fno is bright, the light beams including peripheral light beams can be captured with high efficiency, and reduction in size and height can be achieved.

<2. Second Embodiment of Lens Optical System>

Next, a lens optical system according to a second embodiment of the present disclosure will be described with reference to a lens optical system2-1inFIG.104. The lens optical system2-1inFIG.104is a first configuration example of the lens optical system2in the second embodiment.

The lens optical system2according to the second embodiment of the present disclosure includes a first lens L1having a negative refractive power, a second lens L2having a positive refractive power, a third lens L3having a positive or negative refractive power, and a fourth lens L4having a positive refractive power in order from the object side around the optical axis Z1of a one-dot chain line, and has a positive refractive power as a whole. The first lens L1closer to the object side than an aperture stop STO constitutes a first lens group and has a negative refractive power. The second lens L2to the fourth lens L4on an image side of the aperture stop STO constitute a second lens group and have a positive refractive power. The first lens group is also referred to as a front group, and the second lens group is also referred to as a rear group.

In the lens optical system2, the aperture stop STO is disposed between the first lens L1and the second lens L2, and a sealing glass SG is disposed between the fourth lens L4and an image plane IMG. The sealing glass SG can have a filter function such as an infrared cut filter and a band pass filter, an antireflection function, and the like, in addition to a function of protecting a light receiving element.

The lens optical system2collects the light beams from the object side on a photoelectric conversion section of the light receiving element arranged at the position of the image plane IMG and forms an image.

The lens optical system2has negative (first lens L1), positive (second lens L2), positive or negative (third lens L3), and positive (fourth lens L4) refractive powers in order from the first lens L1on the object side, and has a positive refractive power as a whole, so that the angle of view is widened, the range on the object side can thereby be widened, and the light beams from the object side can be efficiently collected and guided to the light receiving element. Moreover, in addition to good collecting performance and optical performance, it is possible to shorten the total optical length, and it is possible to meet the need for reduction in size and height.

In the lens optical system2, by configuring each lens so as to satisfy at least one conditional expression, preferably two or more conditional expressions in combination described below, it is possible to achieve a lens optical system having good collecting performance and optical performance, and having a reduced size and a reduced height.

Note that, also in the second embodiment, the meaning of each symbol and each symbol are similar to that of the first embodiment.

First, for the lens optical system2, a first conditional expression is that the lens shape of the third lens L3on the object side is concave toward the object side. That is, a curvature radius R5of a lens surface S5satisfies the following conditional expression (1).

Next, for the lens optical system2, a second conditional expression is that the lens shape of the fourth lens L4on the object side is convex toward the object side. That is, a curvature radius R7of a lens surface S7satisfies the following conditional expression (2).

Since the lens shape of the third lens L3on the object side is concave toward the object side, the light beams from the object side can be efficiently collected up to the peripheral edge portion of the light receiving element, and a shading characteristic is improved.

Next, the lens optical system2satisfies the following conditional expression (3).

In the conditional expression (3), f represents a focal length (mm) of the entire lens optical system2at a d-line (wavelength 587.6 nm), fa1represents a focal length (mm) of the first lens group (front group) at the d-line (wavelength 587.6 nm), and fa2represents a focal length (mm) of the second lens group (rear group) at the d-line (wavelength 587.6 nm).

The conditional expression (3) is an expression relating to an appropriate power distribution of the first lens group and the second lens group with respect to the power of lens of the entire optical system. The absolute value is used in the conditional expression (3) because the first lens group has negative power. When the conditional expression (3) exceeds an upper limit, the power of the first lens group becomes too small with respect to the power of lens of the entire optical system and the power of the second lens group, and it becomes difficult to widen the angle of view.

In consideration of securing the angle of view and the viewing angle, the conditional expression (3) more preferably satisfies the following conditional expression (3)′.

Next, the lens optical system2satisfies the following conditional expression (4).

In the conditional expression (4), f2represents a focal length (mm) of the second lens L2at the d-line (wavelength 587.6 nm), and f3represents a focal length (mm) of the third lens L3at the d-line (wavelength 587.6 nm).

The conditional expression (4) is an expression relating to an appropriate power distribution of the power of the entire optical system with respect to the combined power of the second lens L2and the third lens L3. When the conditional expression (4) exceeds an upper limit, the power of the second lens L2and the third lens L3becomes too weak with respect to the power of the entire optical system, and it becomes difficult to efficiently collect light up to the peripheral edge portion of the light receiving element and to perform appropriate aberration correction while maintaining the wide angle of view.

In consideration of securing the angle of view and the aberration correction, the conditional expression (4) more preferably satisfies the following conditional expression (4)′.

Next, the lens optical system2satisfies the following conditional expression (5).

FOV represents an object-side capturing angle of the lens optical system2, what is called an angle of view, and corresponds to an angle of view2ω on both sides. D12represents an inter-lens distance between the first lens L1and the second lens L2. TL represents the total optical length of the lens optical system2.

The conditional expression (5) is a conditional expression indicating the relationship among the angle of view FOV, the inter-lens distance D12between the first lens L1and the second lens L2, and the total optical length TL of the lens optical system2. When the conditional expression (5) exceeds an upper limit, the total optical length TL of the lens optical system2becomes too short with respect to the relationship between the angle of view FOV and the length D12from the first lens L1to the second lens L2, and it becomes difficult to secure necessary optical performance in a state where the angle of view FOV is maintained. On the other hand, when the conditional expression (5) falls below a lower limit, the total optical length TL of the lens optical system2becomes too long with respect to the angle of view FOV and the length D12from the first lens L1to the second lens L2, and is no longer small in size.

In consideration of securing the angle of view and the viewing angle, the conditional expression (5) more preferably satisfies the following conditional expression (5)′.

Next, the lens optical system2satisfies the following conditional expression (6).

The conditional expression (6) expresses the relationship of the lens curvature radius R6of the image-side surface S6of the third lens L3with the lens curvature radius R5of the object-side surface S5of the third lens L3by the conditional expression. When the conditional expression (6) falls below a lower limit, the lens curvature radius R6of the image-side surface S6becomes too large with respect to the curvature radius R5of the object-side surface S5of the third lens L3, and it becomes difficult to efficiently collect the light beams up to the peripheral edge portion of the light receiving element. On the other hand, when the conditional expression (6) exceeds an upper limit, the lens curvature radius R6of the image-side surface S6of the third lens L3becomes too small with respect to the lens curvature radius R5of the object-side surface S5of the third lens L3, and it becomes difficult to efficiently collect the light beams up to the peripheral edge portion of the light receiving element. Furthermore, when both the lower limit and the upper limit are out of the range of the conditional expression, the aberration correction effect, particularly the correction effect on the field curvature and the coma aberration is impaired.

In consideration of efficiently collecting light up to the peripheral edge portion of the light receiving element and securing the aberration correction, the conditional expression (6) more preferably satisfies the following conditional expression (6)′.

Next, the lens optical system2satisfies the following conditional expression (7).

The conditional expression (7) expresses the relationship of the lens curvature radius R8of the image-side surface S8of the fourth lens L4with the lens curvature radius R7of the object-side surface S7of the fourth lens L4. When the conditional expression (7) falls below a lower limit, the lens curvature radius R8of the image-side surface S8becomes too small with respect to the lens curvature radius R7of the object-side surface S7of the fourth lens L4, which adversely affects aberration correction, particularly distortion aberration correction. On the other hand, when the conditional expression (7) exceeds an upper limit, the lens curvature radius R8of the image-side surface S8of the fourth lens L4becomes too large with respect to the lens curvature radius R7of the object-side surface S7of the fourth lens L4, and similarly, aberration correction, particularly correction of distortion aberration becomes difficult, making it difficult to obtain an appropriate correction effect.

In consideration of the aberration correction effect, the conditional expression (7) more preferably satisfies the following conditional expression (7)′.

Hereinafter, a configuration example in which specific numerical values are applied to the lens optical system2in the second embodiment will be described.

<2.1 First Configuration Example of Second Embodiment>

FIG.104illustrates a first configuration example (Example 1) of the lens optical system2in the second embodiment.

The lens optical system2-1inFIG.104includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.105illustrates specific characteristic data of the lens optical system2-1and lens data of the first lens L1to the fourth lens L4.

InFIG.105, “FNo” represents the F-number of the lens optical system2-1, “f” represents the focal length (mm) of the entire lens system of the lens optical system2-1, and “2ω” represents a diagonal total angle of view)(°.

Furthermore, “Si” represents the i-th surface counted from the object side to the image side, “Ri” represents a paraxial curvature radius of the i-th surface Si, “Di” represents an interval on the optical axis between the i-th surface S1and the (i+1)-th surface S(i+1), “Ndi” represents a refractive index at the d-line (wavelength 587.6 nm) of the lens starting from the i-th surface Si, and “νdi” represents the Abbe number at the d-line of the lens starting from the i-th surface Si.

The aspherical shape of each surface S1of the lens optical system2-1is expressed by the above-described formula (1). In Formula (1), Z represents the depth of the aspherical surface, and Y represents the height from the optical axis (the position in the direction perpendicular to the optical axis). Furthermore, K represents a conic constant, and Ai represents the i-th order (i is an integer of 3 or more) aspherical coefficient. R is a paraxial curvature radius. The meaning of each symbol is similar in other configuration examples (examples) described later.

FIG.106illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system2-1and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.107is a diagram illustrating aberration performance of the lens optical system2-1, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

In the spherical aberration diagram, T represents spherical aberration in the lens normal direction, and S represents spherical aberration in the lens tangential direction. T and S are similarly used in spherical aberration diagrams of other configuration examples (examples) described later.

As can be seen from each aberration diagram, the lens optical system2-1has various aberrations corrected well and has excellent image forming performance.

<2.2 Second Configuration Example of Second Embodiment>

FIG.108illustrates a second configuration example (Example 2) of the lens optical system2in the second embodiment.

A lens optical system2-2inFIG.108includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, negative, and positive refractive powers, respectively, in order from the first lens L1on the object side. Therefore, the third lens L3has a positive refractive power in the lens optical system2-1described above, but has a negative refractive power in the lens optical system2-2.

FIG.109illustrates specific characteristic data of the lens optical system2-2and lens data of the first lens L1to the fourth lens L4.

FIG.110illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system2-2and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.111is a diagram illustrating aberration performance of the lens optical system2-2, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system2-2has various aberrations corrected well and has excellent image forming performance.

<2.3 Third Configuration Example of Second Embodiment>

FIG.112illustrates a third configuration example (Example 3) of the lens optical system2in the second embodiment.

A lens optical system2-3inFIG.112includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.113illustrates specific characteristic data of the lens optical system2-3and lens data of the first lens L1to the fourth lens L4.

FIG.114illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system2-3and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.115is a diagram illustrating aberration performance of the lens optical system2-3, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system2-3has various aberrations corrected well and has excellent image forming performance.

<2.4 Fourth Configuration Example of Second Embodiment>

FIG.116illustrates a fourth configuration example (Example 4) of the lens optical system2in the second embodiment.

A lens optical system2-4inFIG.116includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, negative, and positive refractive powers, respectively, in order from the first lens L1on the object side. Therefore, the third lens L3has a positive refractive power in the lens optical system2-3described above, but has a negative refractive power in the lens optical system2-4.

FIG.117illustrates specific characteristic data of the lens optical system2-4and lens data of the first lens L1to the fourth lens L4.

FIG.118illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system2-4and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.119is a diagram illustrating aberration performance of the lens optical system2-4, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system2-4has various aberrations corrected well and has excellent image forming performance.

<2.5 Fifth Configuration Example of Second Embodiment>

FIG.120illustrates a fifth configuration example (Example 5) of the lens optical system2in the second embodiment.

A lens optical system2-5inFIG.120includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.121illustrates specific characteristic data of the lens optical system2-5and lens data of the first lens L1to the fourth lens L4.

FIG.122illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system2-5and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.123is a diagram illustrating aberration performance of the lens optical system2-5, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system2-5has various aberrations corrected well and has excellent image forming performance.

<2.6 Sixth Configuration Example of Second Embodiment>

FIG.124illustrates a sixth configuration example (Example 6) of the lens optical system2in the second embodiment.

A lens optical system2-6inFIG.124includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, negative, and positive refractive powers, respectively, in order from the first lens L1on the object side. Therefore, the third lens L3has a positive refractive power in the lens optical system2-5described above, but has a negative refractive power in the lens optical system2-6.

FIG.125illustrates specific characteristic data of the lens optical system2-6and lens data of the first lens L1to the fourth lens L4.

FIG.126illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system2-6and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.127is a diagram illustrating aberration performance of the lens optical system2-6, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system2-6has various aberrations corrected well and has excellent image forming performance.

<2.7 Seventh Configuration Example of Second Embodiment>

FIG.128illustrates a seventh configuration example (Example 7) of the lens optical system2in the second embodiment.

A lens optical system2-7inFIG.128includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.129illustrates specific characteristic data of the lens optical system2-7and lens data of the first lens L1to the fourth lens L4.

FIG.130illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system2-7and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.131is a diagram illustrating aberration performance of the lens optical system2-7, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system2-7has various aberrations corrected well and has excellent image forming performance.

<2.8 Eighth Configuration Example of Second Embodiment>

FIG.132illustrates an eighth configuration example (Example 8) of the lens optical system2in the second embodiment.

A lens optical system2-8inFIG.132includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.133illustrates specific characteristic data of the lens optical system2-8and lens data of the first lens L1to the fourth lens L4.

FIG.134illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system2-8and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.135is a diagram illustrating aberration performance of the lens optical system2-8, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system2-8has various aberrations corrected well and has excellent image forming performance.

<2.9 Ninth Configuration Example of Second Embodiment>

FIG.136illustrates a ninth configuration example (Example 9) of the lens optical system2in the second embodiment.

A lens optical system2-9inFIG.136includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.137illustrates specific characteristic data of the lens optical system2-9and lens data of the first lens L1to the fourth lens L4.

FIG.138illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system2-9and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.139is a diagram illustrating aberration performance of the lens optical system2-9, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system2-9has various aberrations corrected well and has excellent image forming performance.

<2.10 Tenth Configuration Example of Second Embodiment>

FIG.140illustrates a tenth configuration example (Example 10) of the lens optical system2in the second embodiment.

A lens optical system2-10inFIG.140includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.141illustrates specific characteristic data of the lens optical system2-10and lens data of the first lens L1to the fourth lens L4.

FIG.142illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system2-10and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.143is a diagram illustrating aberration performance of the lens optical system2-10, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system2-10has various aberrations corrected well and has excellent image forming performance.

<2.11 11th Configuration Example of Second Embodiment>

FIG.144illustrates an 11th configuration example (Example 11) of the lens optical system2in the second embodiment.

A lens optical system2-11inFIG.144includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.145illustrates specific characteristic data of the lens optical system2-11and lens data of the first lens L1to the fourth lens L4.

FIG.146illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system2-11and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.147is a diagram illustrating aberration performance of the lens optical system2-11, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system2-11has various aberrations corrected well and has excellent image forming performance.

<2.12 12th Configuration Example of Second Embodiment>

FIG.148illustrates a 12th configuration example (Example 12) of the lens optical system2in the second embodiment.

A lens optical system2-12inFIG.148includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.149illustrates specific characteristic data of the lens optical system2-12and lens data of the first lens L1to the fourth lens L4.

FIG.150illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system2-12and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.151is a diagram illustrating aberration performance of the lens optical system2-12, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system2-12has various aberrations corrected well and has excellent image forming performance.

<2.13 13th Configuration Example of Second Embodiment>

FIG.152illustrates a 13th configuration example (Example 13) of the lens optical system2in the second embodiment.

A lens optical system2-13inFIG.152includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.153illustrates specific characteristic data of the lens optical system2-13and lens data of the first lens L1to the fourth lens L4.

FIG.154illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system2-13and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.155is a diagram illustrating aberration performance of the lens optical system2-13, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system2-13has various aberrations corrected well and has excellent image forming performance.

<2.14 14th Configuration Example of Second Embodiment>

FIG.156illustrates a 14th configuration example (Example 14) of the lens optical system2in the second embodiment.

A lens optical system2-14inFIG.156includes the first lens group having a negative refractive power and the second lens group having a positive refractive power, and has a positive refractive power as a whole. The first lens L1to the fourth lens L4has negative, positive, positive, and positive refractive powers, respectively, in order from the first lens L1on the object side.

FIG.157illustrates specific characteristic data of the lens optical system2-14and lens data of the first lens L1to the fourth lens L4.

FIG.158illustrates a conic constant K of Formula (1) for specifying the aspherical shape of each surface S1of the lens optical system2-14and a value of the i-th order (i is an integer of 3 or more) aspherical coefficient Ai.

FIG.159is a diagram illustrating aberration performance of the lens optical system2-14, and illustrates a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram.

As can be seen from each aberration diagram, the lens optical system2-14has various aberrations corrected well and has excellent image forming performance.

<2.15 Conditional Expression Data of Lens Optical System According to Second Embodiment>

FIGS.160and161illustrate values obtained by calculating the conditional expressions (1) to (7) and original data required for calculating the respective conditional expressions in the lens optical systems2-1to2-14illustrated inFIGS.104to159.

As illustrated inFIGS.160and161, the lens optical systems2-1to2-14satisfy all of the conditional expressions (1) to (7). Furthermore, the lens optical systems2-1to2-14also satisfy the conditional expressions (3)′ to (7)′ which are more preferable conditions.

With the lens optical systems2-1to2-14satisfying the conditional expressions (1) to (7), more preferably the conditional expressions (3)′ to (7)′, Fno is bright, the light beams including peripheral light beams can be captured with high efficiency, and reduction in size and height can be achieved.

<3. Application Example to Distance Measuring System>

FIG.162illustrates a configuration example of a distance measuring system equipped with the lens optical system1according to the first embodiment or the lens optical system2according to the second embodiment described above.

A distance measuring system100inFIG.162includes a lighting device141that irradiates a predetermined object as a subject with irradiation light and a light receiving device142that receives reflected light returned after the irradiation light is reflected by the object.

The lighting device141includes a light emission control circuit111, a light emitting element112, and a light emitting side optical system113, and the light receiving device142includes a light receiving side optical system114and a light receiving element115.

The light emission control circuit111, the light emitting element112, and the light receiving element115are disposed on a same circuit board116, the light emission control circuit111is electrically connected to the circuit board116via a plurality of solder balls121, the light emitting element112is electrically connected to the circuit board116via a plurality of solder balls122, and the light receiving element115is electrically connected to the circuit board116via a plurality of solder balls123.

The light emission control circuit111generates a light emission timing signal for controlling a timing at which the light emitting element112emits irradiation light, and supplies the light emission timing signal to the light emitting element112and the light receiving element115via the circuit board116.

The light emitting element112includes, for example, a VCSEL array in which a plurality of vertical cavity surface emitting lasers (VCSEL) is arranged in a matrix. The light emitting element112turns on/off light emission (irradiation light) on the basis of the light emission timing signal supplied from the light emission control circuit111via the circuit board116.

The light emitting side optical system113includes a collimator lens131and a diffractive optical element132, and a lens holder133that holds them. The collimator lens131converts light emitted from the light emitting element112at a predetermined divergence angle into parallel light and outputs the parallel light. The diffractive optical element132enlarges an irradiation area by replicating a light emission pattern (light emission surface) of a predetermined region having passed through the collimator lens131in a direction perpendicular to the optical axis direction.

The light receiving side optical system114includes the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the sealing glass SG, and a lens holder LH that holds them. Furthermore, although not illustrated, the aperture stop STO is disposed between the first lens L1and the second lens L2. Note that the sealing glass SG may be omitted.

The light receiving side optical system114has a positive refractive power as a whole of a four-lens configuration with the first lens L1to the fourth lens L4, collects reflected light from the object side, and forms an image on the photoelectric conversion section of the light receiving element115. As the light receiving side optical system114, the lens optical system1according to the first embodiment described above or the lens optical system2according to the second embodiment can be employed.

The light receiving element115has a pixel array in which pixels are two-dimensionally arranged in a matrix in a row direction and a column direction. The pixel of the light receiving element115includes, for example, a single photon avalanche diode (SPAD), an avalanche photodiode (APD), or the like as the photoelectric conversion section.

The light receiving element115receives the reflected light collected by the light receiving side optical system114. Then, the light receiving element115performs an operation of obtaining the distance to the subject on the basis of a digital count value obtained by counting the time from when the light emitting element112emits the irradiation light to when the light receiving element115receives the irradiation light and the light speed, and generates and outputs a distance image in which the operation result is stored in each pixel. The light emission timing signal indicating a light emission timing of the light emitting element112is supplied from the light emission control circuit111via the circuit board116.

By employing the lens optical system1according to the first embodiment or the lens optical system2according to the second embodiment as the light receiving side optical system114, the angle of view is widened, so that the range on the object side can be widened, and the light beams from the object side can be efficiently collected and guided to the light receiving element115. Moreover, in addition to good light collecting performance and optical performance, the total optical length can be shortened, and reduction in size and height are achieved.

The light receiving element115described above is a ToF sensor of a direct ToF method that directly counts the time from when the light emitting element112emits the irradiation light to when the light receiving element115receives the irradiation light by the digital count value, but may be a ToF sensor of an indirect ToF method that detects the time from when the light emitting element112emits the irradiation light to when the light receiving element115receives the irradiation light as a phase difference. That is, the lens optical system1according to the first embodiment and the lens optical system2according to the second embodiment described above can be applied to the lens optical system of the ToF sensor of either the direct ToF method or the indirect ToF method. Furthermore, a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) image sensor can be applied as the light receiving element115instead of the ToF sensor. That is, the light receiving side optical system114can also be applied to an image forming lens of an image sensor for image generation.

<4. Application Example to Electronic Apparatus>

The above-described distance measuring system100can be mounted on, for example, electronic devices such as a smartphone, a tablet terminal, a mobile phone, a personal computer, a game device, a television receiver, a wearable terminal, a digital still camera, and a digital video camera.

FIG.163is a block diagram illustrating a configuration example of a smartphone as an electronic device equipped with the distance measuring system100.

As illustrated inFIG.163, a smartphone201is configured by connecting a distance measuring module202, an imaging device203, a display204, a speaker205, a microphone206, a communication module207, a sensor unit208, a touch panel209, and a control unit210via a bus211. Furthermore, the control unit210has functions as an application processing section221and an operation system processing section222by the CPU executing a program.

The distance measuring system100inFIG.162is applied to the distance measuring module202. For example, the distance measuring module202is arranged on the front surface of the smartphone201, and performs distance measurement for the user of the smartphone201, so that it is possible to output a distance image of a surface shape of a face, a hand, a finger, or the like of the user as a distance measurement result.

The imaging device203is arranged in front of the smartphone201, and performs imaging with the user of the smartphone201as a subject to acquire an image in which the user is captured. Note that, although not illustrated, a configuration may be employed in which the imaging device203is also disposed on the back surface of the smartphone201.

The display204displays an operation screen for performing processing by the application processing section221and the operation system processing section222, an image captured by the imaging device203, and the like. The speaker205and the microphone206output the voice of the other party and collect the voice of the user, for example, when making a call using the smartphone201.

The communication module207performs communication via a communication network. The sensor unit208senses speed, acceleration, proximity, and the like, and the touch panel209acquires a touch operation by the user on an operation screen displayed on the display204.

The application processing section221performs processing for providing various services by the smartphone201. For example, the application processing section221can perform processing of creating a face by computer graphics virtually reproducing the expression of the user on the basis of a depth map supplied from the distance measuring module202and displaying the face on the display204. Furthermore, the application processing section221can perform processing of creating, for example, three-dimensional shape data of an arbitrary three-dimensional object on the basis of the depth map supplied from the distance measuring module202.

The operation system processing section222performs processing for achieving basic functions and operations of the smartphone201. For example, the operation system processing section222can perform processing of authenticating the user's face, and unlocking the smartphone201on the basis of the depth map supplied from the distance measuring module202. Furthermore, the operation system processing section222can perform, for example, processing of recognizing a gesture of the user on the basis of the depth map supplied from the distance measuring module202, and processing of inputting various operations according to the gesture.

In the smartphone201configured as described above, for example, the distance image can be generated with high accuracy and at high speed by applying the above-described distance measuring system100. Thus, the smartphone201can more accurately detect the distance measurement information.

<5. Application Example to Mobile Object>

The technology according to the present disclosure (the present technology) can be applied to various products. For example, the technology according to the present disclosure may be achieved as a device mounted on any type of mobile object such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, a personal mobility, an airplane, a drone, a ship, a robot, and the like.

FIG.164is a block diagram illustrating a schematic configuration example of a vehicle control system which is an example of a mobile object control system to which the technology according to the present disclosure can be applied.

The vehicle control system12000includes a plurality of electronic control units connected to each other via a communication network12001. In the example depicted inFIG.164, the vehicle control system12000includes a driving system control unit12010, a body system control unit12020, an outside-vehicle information detecting unit12030, an in-vehicle information detecting unit12040, and an integrated control unit12050. Furthermore, as a functional configuration of the integrated control unit12050, a microcomputer12051, a sound/image output section12052, and an onboard network interface (I/F)12053are illustrated.

The imaging section12031is an optical sensor that receives light, and which outputs an electric signal corresponding to a received light amount of the light. The imaging section12031can output the electrical signal as an image or as distance measurement information. In addition, the light received by the imaging section12031may be visible light, or may be invisible light such as infrared rays or the like.

The in-vehicle information detecting unit12040detects information about the inside of the vehicle. The in-vehicle information detecting unit12040is, for example, connected with a driver state detecting section12041that detects the state of a driver. The driver state detecting section12041includes, for example, a camera that captures an image of the driver, and the in-vehicle information detecting unit12040may calculate the degree of fatigue or the degree of concentration of the driver, or determine whether or not the driver has fallen asleep on the basis of detection information input from the driver state detecting section12041.

FIG.165is a view illustrating an example of the installation position of the imaging section12031.

The imaging sections12101,12102,12103,12104, and12105are provided, for example, at positions such as a front nose, a side mirror, a rear bumper, a back door, and an upper part of a windshield in the cabin of the vehicle12100. The imaging section12101provided on the front nose and the imaging section12105provided above the windshield in the cabin mainly obtain a forward image of the vehicle12100. The imaging sections12102and12103provided in the side mirrors mainly obtain images of sides of the vehicle12100. The imaging section12104provided in a rear bumper or a back door mainly obtains an image behind the vehicle12100. The forward image obtained by the imaging sections12101and12105are mainly used for detecting a preceding vehicle, a pedestrian, an obstacle, a traffic light, a traffic sign, a lane, and the like.

Incidentally,FIG.165illustrates an example of imaging ranges of the imaging sections12101to12104. An imaging range12111represents the imaging range of the imaging section12101provided on the front nose, imaging ranges12112and12113represent the imaging ranges of the imaging sections12102and12103provided in the side mirrors, respectively, and an imaging range12114represents the imaging range of the imaging section12104provided in the rear bumper or the back door. A bird's-eye image of the vehicle12100as viewed from above is obtained by superimposing image data imaged by the imaging sections12101to12104, for example.

For example, the microcomputer12051can classify three-dimensional object data on three-dimensional objects into three-dimensional object data of a two-wheeled vehicle, a standard-sized vehicle, a large-sized vehicle, a pedestrian, a utility pole, and other three-dimensional objects on the basis of the distance information obtained from the imaging sections12101to12104, extract the classified three-dimensional object data, and use the extracted three-dimensional object data for automatic avoidance of an obstacle. For example, the microcomputer12051identifies obstacles around the vehicle12100as obstacles that the driver of the vehicle12100can recognize visually and obstacles that are difficult for the driver of the vehicle12100to recognize visually. Then, the microcomputer12051determines a collision risk indicating the risk of collision with each obstacle, and when the collision risk is equal to or higher than a set value and there is a possibility of collision, the microcomputer12051can output a warning to the driver via the audio speaker12061and the display section12062, or perform forced deceleration or avoidance steering via the driving system control unit12010, to thereby perform assistance in driving for collision avoidance.

The example of the vehicle control system to which the technology according to the present disclosure can be applied has been described above. The technology according to the present disclosure can be applied to the outside-vehicle information detecting unit12030and the in-vehicle information detecting unit12040among the above-described configurations. Specifically, by using the distance measurement by the distance measuring system100as the outside-vehicle information detecting unit12030and the in-vehicle information detecting unit12040, processing of recognizing the gesture of the driver is performed, and various operations (for example, an audio system, a navigation system, and an air conditioning system) according to the gesture can be executed, or the state of the driver can be detected more accurately. Furthermore, unevenness of the road surface can be recognized using the distance measurement by the distance measuring system1and reflected in control of the suspension.

The embodiments of the present disclosure are not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present disclosure.

The plurality of present technologies which has been described in the present description can be each implemented independently as a single unit as long as no contradiction occurs. Of course, any plurality of the present technologies can also be used and implemented in combination. Furthermore, part or all of any of the above-described present technologies can be implemented by using together with another technology that is not described above.

Further, for example, a configuration described as one device (or processing section) may be divided and configured as a plurality of devices (or processing sections). Conversely, configurations described above as a plurality of devices (or processing sections) may be combined and configured as one device (or processing section). Furthermore, a configuration other than those described above may of course be added to the configuration of each device (or each processing section). Moreover, if the configuration and operation of the entire system are substantially the same, a part of the configuration of a certain device (or processing section) may be included in the configuration of another device (or another processing section).

Moreover, in the present description, a system means a set of a plurality of components (devices, modules (parts), and the like), and it does not matter whether or not all components are in the same housing. Therefore, both of a plurality of devices housed in separate housings and connected via a network and a single device in which a plurality of modules is housed in one housing are systems.

Note that the effects described in the present description are merely examples and are not limited, and effects other than those described in the present description may be provided.

Note that the present disclosure can have the following configurations.

A lens optical system including,

in order from an object side:

a first lens group having a negative refractive power; and

a second lens group having a positive refractive power, in which

the first lens group includesa first lens having a negative refractive power,

the second lens group includesa second lens having a positive or negative refractive power,a third lens having a positive refractive power, anda fourth lens having a positive refractive power, and

the lens optical system has a positive refractive power as a whole.

The lens optical system according to (1) above, in which

a conditional expression (1) as follows is satisfied

where R3represents a curvature radius of an object-side surface of the second lens.

The lens optical system according to (1) or (2) above, in which

a conditional expression (2) as follows is satisfied

where R7represents a curvature radius of an object-side surface of the fourth lens.

The lens optical system according to any one of (1) to (3) above, in which

a conditional expression (3) as follows is satisfied

where f represents a focal length of the lens optical system at a d-line (wavelength 587.6 nanometers),

fa1represents a focal length of the first lens group at the d-line (wavelength 587.6 nanometers), and

fa2represents a focal length of the second lens group at the d-line (wavelength 587.6 nanometers).

The lens optical system according to any one of (1) to (4) above, in which

a conditional expression (4) as follows is satisfied

where f represents a focal length of the lens optical system at a d-line (wavelength 587.6 nanometers),

f2represents a focal length of the second lens at the d-line (wavelength 587.6 nanometers), and

f3represents a focal length of the third lens at the d-line (wavelength 587.6 nanometers).

The lens optical system according to any one of (1) to (5) above, in which

a conditional expression (5) as follows is satisfied

where TL represents a total optical length of the lens optical system,

FOV represents an angle of view, and

D12represents an inter-lens distance between the first lens and the second lens.

The lens optical system according to any one of (1) to (6) above, in which

a conditional expression (6) as follows is satisfied

where R1represents a lens curvature radius of an object-side surface of the first lens, and

R2represents a lens curvature radius of an image-side surface of the first lens.

The lens optical system according to any one of (1) to (7) above, in which

a conditional expression (7) as follows is satisfied

where R3represents a lens curvature radius of an object-side surface of the second lens, and

R4represents a lens curvature radius of an image-side surface of the second lens.

The lens optical system according to any one of (1) to (8) above, in which

a conditional expression (8) as follows is satisfied

where R7represents a lens curvature radius of an object-side surface of the fourth lens, and

R8represents a lens curvature radius of an image-side surface of the fourth lens.

A light receiving device including:

a lens optical system; and

a light receiving element that receives light from an object side collected by the lens optical system, in which

the lens optical system has a positive refractive power as a whole, and includes,in order from the object side,a first lens group having a negative refractive power, anda second lens group having a positive refractive power,

the first lens group includesa first lens having a negative refractive power, and

the second lens group includesa second lens having a positive or negative refractive power,a third lens having a positive refractive power, anda fourth lens having a positive refractive power.

A distance measuring system including:

a lighting device that emits irradiation light; and

a light receiving device that receives reflected light in which the irradiation light is reflected by an object, in which

the light receiving device includesa lens optical system, anda light receiving element that receives light beams from an object side collected by the lens optical system, and

the lens optical system has a positive refractive power as a whole, and includes,in order from the object side,a first lens group having a negative refractive power, anda second lens group having a positive refractive power,

the first lens group includesa first lens having a negative refractive power, and

the second lens group includesa second lens having a positive or negative refractive power,a third lens having a positive refractive power, anda fourth lens having a positive refractive power.

A lens optical system including,

in order from an object side:

a first lens group having a negative refractive power; and

a second lens group having a positive refractive power, in which

the first lens group includesa first lens having a negative refractive power,

the second lens group includesa second lens having a positive refractive power,a third lens having a positive or negative refractive power, anda fourth lens having a positive refractive power, and

the lens optical system has a positive refractive power as a whole.

The lens optical system according to (12) above, in which

a conditional expression (1) as follows is satisfied

where R5represents a curvature radius of an object-side surface of the third lens.

The lens optical system according to (12) or (13) above, in which

a conditional expression (2) as follows is satisfied

where R7represents a curvature radius of an object-side surface of the fourth lens.

The lens optical system according to any one of (12) to (14) above, in which

a conditional expression (3) as follows is satisfied

where f represents a focal length of the lens optical system at a d-line (wavelength 587.6 nanometers),

fa1represents a focal length of the first lens group at the d-line (wavelength 587.6 nanometers), and

fa2represents a focal length of the second lens group at the d-line (wavelength 587.6 nanometers).

The lens optical system according to any one of (12) to (15) above, in which

a conditional expression (4) as follows is satisfied

where f represents a focal length of the lens optical system at a d-line (wavelength 587.6 nanometers),

f2represents a focal length of the second lens at the d-line (wavelength 587.6 nanometers), and

f4represents a focal length of the fourth lens at the d-line (wavelength 587.6 nanometers).

The lens optical system according to any one of (12) to (16) above, in which

a conditional expression (5) as follows is satisfied

where TL represents a total optical length of the lens optical system,

FOV represents an angle of view, and

D12represents an inter-lens distance between the first lens and the second lens.

The lens optical system according to any one of (12) to (17) above, in which

a conditional expression (6) as follows is satisfied

where R5represents a lens curvature radius of an object-side surface of the third lens, and

R6represents a lens curvature radius of an image-side surface of the fourth lens.

The lens optical system according to any one of (12) to (18) above, in which

a conditional expression (7) as follows is satisfied

where R7represents a lens curvature radius of an object-side surface of the fourth lens, and

R8represents a lens curvature radius of an image-side surface of the fourth lens.

A light receiving device including:

a lens optical system; and

a light receiving element that receives light from an object side collected by the lens optical system, in which

the lens optical system has a positive refractive power as a whole, and includes,in order from the object side,a first lens group having a negative refractive power, anda second lens group having a positive refractive power,

the first lens group includesa first lens having a negative refractive power, and

the second lens group includesa second lens having a positive refractive power,a third lens having a positive or negative refractive power, anda fourth lens having a positive refractive power.

A distance measuring system including:

a lighting device that emits irradiation light; and

a light receiving device that receives reflected light in which the irradiation light is reflected by an object, in which

the light receiving device includesa lens optical system, anda light receiving element that receives light beams from an object side collected by the lens optical system, and

the lens optical system has a positive refractive power as a whole, and includes,in order from the object side,a first lens group having a negative refractive power, anda second lens group having a positive refractive power,

the first lens group includesa first lens having a negative refractive power, and

the second lens group includesa second lens having a positive refractive power,a third lens having a positive or negative refractive power, anda fourth lens having a positive refractive power.

REFERENCE SIGNS LIST