Patent Application
20230119358
The present application claims the priority of Japanese Patent Application No. 2020-053082 filed on Mar. 24, 2020, the disclosure of which is hereby incorporated by reference in its entirety.
The present disclosure relates to an image-capturing optical system, an image-capturing device, and a vehicle.
There is a need for surveillance cameras and vehicle-mounted cameras to have both a wide image-capturing area and a high resolving power. Although increasing the number of pixels of an image-capturing device contributes to improvement of resolving power, it also increases the cost of the image-capturing device. Accordingly, there is a concept of setting a central region of an image to have a higher definition than the peripheral region of the image by emulating human visual function as an efficient structure in terms of the amount of information in an image. As an image-capturing lens that achieves this concept, PTL 1 discloses an image-capturing optical system capable of obtaining, in a central region of a screen, an enlarged image having a high definition that is equivalent to that of an image obtained by a telephoto lens while ensuring a wide angle of view by generating a large negative distortion.
However, in PTL 1, the back focus is very short, and it is difficult to ensure a high resolving power without high-precision adjustment.
PTL 1: Japanese Unexamined Patent Application Publication No. 2005-010521
An image-capturing lens according to an embodiment of the present disclosure includes a first lens group that includes a first lens having a positive refractive power, a second lens having a negative refractive power, and a third lens having a positive refractive power arranged in this order starting from an object side or that includes a first lens having a negative refractive power and a second lens having a positive refractive power arranged in this order starting from the object side, the first lens group having a negative refractive power as a whole, at least one on-axis luminous flux regulating diaphragm, and a second lens group that has a positive refractive power. A surface of at least one of the lens that are included in the first lens group and that have the negative refractive power, the surface being located on the object side, is a convex surface in a paraxial region and has an aspherical surface having a shape with which convex power decreases with increasing distance from an optical axis. A surface of the second lens group on the most image side has a convex shape toward the image side in a paraxial region. The image-capturing lens satisfies the following conditional expressions (1) to (3).
−1.30<fn/f<−0.6 (1)
Di/tan ω/100<−0.4 (2)
2ω≤120° (3)
where f is a focal length of an entire lens system, fn is a focal length of a negative lens of the first lens group, Di is a distortion at a maximum angle of view (unit: %), and ω: an incident angle of a maximum angle of view light beam on the object side.
An image-capturing device according to an embodiment of the present disclosure includes an image-capturing optical system that includes a first lens group that includes a first lens having a positive refractive power, a second lens having a negative refractive power, and a third lens having a positive refractive power arranged in this order starting from an object side or that includes a first lens having a negative refractive power and a second lens having a positive refractive power arranged in this order starting from the object side, the first lens group having a negative refractive power as a whole, at least one on-axis luminous flux regulating diaphragm, and a second lens group that has a positive refractive power, in which a surface of at least one of the lens that are included in the first lens group and that have the negative refractive power, the surface being located on the object side, is a convex surface in a paraxial region and has an aspherical surface having a shape with which convex power decreases with increasing distance from an optical axis and in which a surface of the second lens group on the most image side has a convex shape toward the image side in a paraxial region, the image-capturing optical system satisfying conditional expressions (1) to (3) described below, and an image-capturing device that converts an optical image, which is formed through the image-capturing optical system, into an electrical signal.
−1.30<fn/f<−0.6 (1)
Di/tan ω/100<−0.4 (2)
2ω≤120° (3)
where:
A vehicle according to an embodiment of the present disclosure is equipped with an image-capturing device including an image-capturing optical system that includes a first lens group that includes a first lens having a positive refractive power, a second lens having a negative refractive power, and a third lens having a positive refractive power arranged in this order starting from an object side or that includes a first lens having a negative refractive power and a second lens having a positive refractive power arranged in this order starting from the object side, the first lens group having a negative refractive power as a whole, at least one on-axis luminous flux regulating diaphragm, and a second lens group that has a positive refractive power, in which a surface of at least one of the lens that are included in the first lens group and that have the negative refractive power, the surface being located on the object side, is a convex surface in a paraxial region and has an aspherical surface having a shape with which convex power decreases with increasing distance from an optical axis and in which a surface of the second lens group on the most image side has a convex shape toward the image side in a paraxial region, the image-capturing optical system satisfying conditional expressions (1) to (3) described below, and an image-capturing device that converts an optical image, which is formed through the image-capturing optical system, into an electrical signal.
−1.30<fn/f<−0.6 (1)
Di/tan ω/100<−0.4 (2)
2ω≤120° (3)
where:
According to the present embodiment, an image-capturing optical system, an image-capturing device, and a vehicle that achieve both a wide angle of view and a high definition in a central region of a screen at low cost can be provided.
The present embodiment will be described below with reference to the drawings. The drawings that will be referred to in the following description are schematic diagrams. The dimensional ratios and so forth of the objects illustrated in the drawings may sometimes be different from those of the actual objects.
A lens configuration of a six-element image-capturing optical system 100 according to an embodiment will be described with reference to
A lens configuration of a six-element wide angle image-capturing optical system 100 according to another embodiment will be described with reference to
A lens configuration of a seven-element wide angle image-capturing optical system 100 according to an embodiment will be described with reference to
Refractive power arrangements of the first lens group L1 and the second lens group L2 of the present embodiment will be described. In an imaging optical system of the present embodiment, in order to generate a large negative distortion, the power of a lens that is included in the first lens group L1 and that has a negative refractive power is set to be large.
In the imaging optical system of the present embodiment, a surface of a lens that is included in the first lens group L1 and that has a negative refractive power, the surface being located on the object side, was a convex surface facing an object in a paraxial region and an aspherical surface having a shape with which convex power decreases with increasing distance from an optical axis. As a result, a large distortion can be generated while spherical aberration and coma are suppressed. However, it is desirable that the surface of the lens, which is included in the first lens group L1 and which has a negative refractive power, on the object side have no inflection point for processing and appearance reasons.
In addition, it is desirable that the focal length of the lens, which is included in the first lens group L1 and which has a negative refractive power, satisfy the following conditional expressions in order to generate a large negative distortion while efficiently correcting various aberrations.
−1.30<fn/f<−0.6 (1)
Di/tan ω/100<−0.4 (2)
2ω≤120° (3)
where:
The conditional expression (1) specifies a preferable range of the ratio of the focal length of the lens, which is included in the first lens group L1 and which has a negative refractive power, to the focal length of the entire lens system for generating a large negative distortion while efficiently correcting various aberrations including spherical aberration. If the lower limit of the conditional expression (1) is exceeded, the focal length of the negative lens of the first lens group L1 becomes long for the entire system, and a sufficiently large distortion cannot be generated. If the upper limit of the conditional expression (1) is exceeded, the refractive power of the negative lens of the first lens group L1 becomes too large, which makes it difficult to correct spherical aberration and coma. Preferably, the range of the conditional expression (1) is set as follows, so that an advantageous effect of the present embodiment can be further easily obtained.
−1.20<fn/f<−0.7 (1)′
The conditional expression (2) specifies the relationship between distortion at the maximum image height for obtaining fovea centralis projection characteristics of the lens and the angle of incidence on the object side at that time. If a negative distortion becomes too large for a desired angle of view, the peripheral image becomes smaller than the central image, so that the viewability deteriorates, making it difficult to recognize an object. If the negative distortion becomes too small for the desired angle of view, an object at the center of a screen cannot be sufficiently enlarged, and the advantageous effect of the present embodiment cannot be sufficiently obtained. Preferably, the range of the conditional expression (2) is set as follows, so that the advantageous effect of the present embodiment can be obtained with higher certainty.
Di/tan ω/100<−0.5 (2)′
The present disclosure can further achieve size reduction while efficiently correcting various aberrations by satisfying the following conditional expression (4).
0.8<fpf/fb<2.2 (4)
where:
The conditional expression (4) specifies the range of the ratio of the focal length of a positive refractive power lens on the most image side in the first lens group L1 to the composite focal length of the positive refractive power lens on the most image side in the first lens group L1 and the second lens group. If the upper limit of the conditional expression (4) is exceeded, and the focal length of a lens that has a positive refractive power and that is located on the most diaphragm side in the first lens group L1 is increased, the entire lens length becomes long, which is not suitable for size reduction. Contrary to this, if the lower limit of the conditional expression (4) is exceeded, and the focal length of a lens that has a positive refractive power and that is located on the most diaphragm side in the first lens group L1 is decreased, spherical aberration and coma occur, and it becomes difficult to increase the diameter. Preferably, the range of the conditional expression (4) is set as follows, so that the advantageous effects of the present disclosure can be obtained with higher certainty.
1.0<fpf/fb<2.0 (4)′
Examples 1 to 11 based on specific numerical values of an image-capturing lens 100 will be described below. In Numerical Examples of Examples 1 to 11, the focal length, the F-value number, the maximum image height, the entire lens length, and the numerical data of each conditional expression are illustrated in the following Table 1.
Various Data Items
As illustrated in
The first lens group L1 has a negative refractive power. The second lens group L2 has a positive refractive power. A surface of the lens L11 having the negative refractive power, the surface being located on the object side (hereinafter referred to as “object-side surface”), is a convex surface in a paraxial region and has an aspherical surface having a shape with which convex power decreases with increasing distance from an optical axis. The amount of sag of the object-side surface of the lens L11 and the amount of sag of a surface of the lens L11 that is located on the image side (hereinafter referred to as “image-side surface”) both have no extrema within the effective diameter.
The second lens group L2 includes the lens L21 having a positive refractive power, the lens L22 having a negative refractive power, the lens L23 having a positive refractive power, and the lens L24 having a positive refractive power that are arranged in this order starting from the object side. The lens L22 and the lens L23 forms a doublet lens. The lens L24 has a predetermined aspherical shape. A surface of the lens L24 on the most image side has a convex shape toward the image side in a paraxial region. The amount of sag of the object-side surface of the lens L24 and the amount of sag of the image-side surface of the lens L24 both have no extrema within the effective diameter.
In a configuration diagram of an optical system, the flat plate 120 that is disposed closest to the imaging plane 130 is a filter. The filter is an optical filter such as an IR cut filter or a low-pass filter and its characteristics are suitably selected in accordance with an image-capturing device to which the imaging optical system according to the present embodiment is applied.
Table 2 illustrates a diaphragm, a curvature radius r (mm), a distance d (mm), a refractive index N (d), an Abbe number νd, and an effective diameter of each of the lenses corresponding to the surface numbers of the image-capturing optical system 100A in Example 1. In Table 2, the symbol “*” is given to some of the surface numbers, and this indicates that the corresponding surface has an aspherical shape. As illustrated in Table 2, the two surfaces of the lens L11 and the two surfaces of the lens L24 are aspherical surfaces (the same applies to the following Examples). Table 3 illustrates the aspheric coefficients of some of the surfaces. In the case of an aspherical surface, the curvature radius r indicates the paraxial radius of curvature. The distance d indicates the distance between the surface with the corresponding surface number and the surface with the next surface number. Thus, the distance d in the column of the surface number 1 indicates the distance between the surface R1 and the surface R2 in
Aspherical Data
As illustrated in
The first lens group L1 has a negative refractive power. The second lens group L2 has a positive refractive power. The object-side surface of the lens L11 having the negative refractive power is a convex surface in a paraxial region and has an aspherical surface having a shape with which convex power decreases with increasing distance from the optical axis. The amount of sag of the object-side surface of the lens L11 and the amount of sag of the image-side surface of the lens L11 both have no extrema within the effective diameter.
The second lens group L2 includes the lens L21 having a positive refractive power, the lens L22 having a negative refractive power, the lens L23 having a positive refractive power, and the lens L24 having a positive refractive power that are arranged in this order starting from the object side. The lens L22 and the lens L23 forms a doublet lens. The lens L24 has a predetermined aspherical shape. The surface of the lens L24 on the most image side has a convex shape toward the image side in a paraxial region. The amount of sag of the object-side surface of the lens L24 and the amount of sag of the image-side surface of the lens L24 both have no extrema within the effective diameter.
In a configuration diagram of an optical system, the flat plate 120 that is disposed closest to the imaging plane 130 is a filter. The filter is an optical filter such as an IR cut filter or a low-pass filter and its characteristics are suitably selected in accordance with an image-capturing device to which the imaging optical system according to the present embodiment is applied.
Table 4 illustrates the diaphragm, the curvature radius r (mm), the distance d (mm), the refractive index N (d), the Abbe number νd, and the effective diameter of each of the lenses corresponding to the surface numbers of the image-capturing optical system 100B in Example 1. In Table 4, the symbol “*” is given to some of the surface numbers, and this indicates that the corresponding surface has an aspherical shape. As illustrated in Table 4, the two surfaces of the lens L11 and the two surfaces of the lens L24 are aspherical surfaces. Table 5 illustrates the aspheric coefficients of some of the surfaces. In the case of an aspherical surface, the curvature radius r indicates the paraxial radius of curvature. The distance d indicates the distance between the surface with the corresponding surface number and the surface with the next surface number. Thus, the distance d in the column of the surface number 1 indicates the distance between the surface R1 and the surface R2 in
Aspherical Data
As illustrated in
The first lens group L1 has a negative refractive power. The second lens group L2 has a positive refractive power. The object-side surface of the lens L11 having the negative refractive power is a convex surface in a paraxial region and has an aspherical surface having a shape with which convex power decreases with increasing distance from an optical axis. The amount of sag of the object-side surface of the lens L11 and the amount of sag of the image-side surface of the lens L11 both have no extrema within the effective diameter.
The second lens group L2 includes the lens L21 having a positive refractive power, the lens L22 having a negative refractive power, the lens L23 having a positive refractive power, and the lens L24 having a positive refractive power that are arranged in this order starting from the object side. The lens L22 and the lens L23 forms a doublet lens. The lens L24 has a predetermined aspherical shape. The surface of the lens L24 on the most image side has a convex shape toward the image side in a paraxial region. The amount of sag of the object-side surface of the lens L24 and the amount of sag of the image-side surface of the lens L24 both have no extrema within the effective diameter.
In a configuration diagram of an optical system, the flat plate 120 that is disposed closest to the imaging plane 130 is a filter. The filter is an optical filter such as an IR cut filter or a low-pass filter and its characteristics are suitably selected in accordance with an image-capturing device to which the imaging optical system according to the present embodiment is applied.
Table 6 illustrates the diaphragm, the curvature radius r (mm), the distance d (mm), the refractive index N (d), the Abbe number νd, and the effective diameter of each of the lenses corresponding to the surface numbers of the image-capturing optical system 100C in Example 1. In Table 6, the symbol “*” is given to some of the surface numbers, and this indicates that the corresponding surface has an aspherical shape. As illustrated in Table 6, the two surfaces of the lens L11 and the two surfaces of the lens L24 are aspherical surfaces. Table 7 illustrates the aspheric coefficients of some of the surfaces. In the case of an aspherical surface, the curvature radius r indicates the paraxial radius of curvature. The distance d indicates the distance between the surface with the corresponding surface number and the surface with the next surface number. Thus, the distance d in the column of the surface number 1 indicates the distance between the surface R1 and the surface R2 in
Aspherical Data
As illustrated in
The first lens group L1 has a negative refractive power. The second lens group L2 has a positive refractive power. The object-side surface of the lens L11 having the negative refractive power is a convex surface in a paraxial region and has an aspherical surface having a shape with which convex power decreases with increasing distance from an optical axis. The amount of sag of the object-side surface of each of the lenses L11 and L12 and the amount of sag of the image-side surface of each of the lenses L11 and L12 both have no extrema within the effective diameter.
The second lens group L2 includes the lens L21 having a positive refractive power, the lens L22 having a negative refractive power, the lens L23 having a positive refractive power, and the lens L24 having a positive refractive power that are arranged in this order starting from the object side. The lens L22 and the lens L23 forms a doublet lens. The lens L24 has a predetermined aspherical shape. The surface of the lens L24 on the most image side has a convex shape toward the image side in a paraxial region. The amount of sag of the object-side surface of the lens L24 and the amount of sag of the image-side surface of the lens L24 both have no extrema within the effective diameter.
In a configuration diagram of an optical system, the flat plate 120 that is disposed closest to the imaging plane 130 is a filter. The filter is an optical filter such as an IR cut filter or a low-pass filter and its characteristics are suitably selected in accordance with an image-capturing device to which the imaging optical system according to the present embodiment is applied.
Table 8 illustrates the diaphragm, the curvature radius r (mm), the distance d (mm), the refractive index N (d), the Abbe number νd, and the effective diameter of each of the lenses corresponding to the surface numbers of the image-capturing optical system 100D in Example 1. In Table 8, the symbol “*” is given to some of the surface numbers, and this indicates that the corresponding surface has an aspherical shape. As illustrated in Table 8, the two surfaces of the lens L11, the two surfaces of the lens L12, and the two surfaces of the lens L24 are aspherical surfaces. Table 9 illustrates the aspheric coefficients of some of the surfaces. In the case of an aspherical surface, the curvature radius r indicates the paraxial radius of curvature. The distance d indicates the distance between the surface with the corresponding surface number and the surface with the next surface number. Thus, the distance d in the column of the surface number 1 indicates the distance between the surface R1 and the surface R2 in
Aspherical Data
As illustrated in
The first lens group L1 has a negative refractive power. The second lens group L2 has a positive refractive power. The object-side surface of the lens L12 having the negative refractive power is a convex surface in a paraxial region and has an aspherical surface having a shape with which convex power decreases with increasing distance from an optical axis. The amount of sag of the object-side surface of the lens L12 and the amount of sag of the image-side surface of the lens L12 both have no extrema within the effective diameter.
The second lens group L2 includes the lens L21 having a positive refractive power, the lens L22 having a negative refractive power, the lens L23 having a positive refractive power, and the lens L24 having a positive refractive power that are arranged in this order starting from the object side. The lens L22 and the lens L23 forms a doublet lens. The lens L24 has a predetermined aspherical shape. The surface of the lens L24 on the most image side has a convex shape toward the image side in a paraxial region. The amount of sag of the object-side surface of the lens L24 and the amount of sag of the image-side surface of the lens L24 both have no extrema within the effective diameter.
In a configuration diagram of an optical system, the flat plate 120 that is disposed closest to the imaging plane 130 is a filter. The filter is an optical filter such as an IR cut filter or a low-pass filter and its characteristics are suitably selected in accordance with an image-capturing device to which the imaging optical system according to the present embodiment is applied.
Table 10 illustrates the diaphragm, the curvature radius r (mm), the distance d (mm), the refractive index N (d), the Abbe number νd, and the effective diameter of each of the lenses corresponding to the surface numbers of the image-capturing optical system 100E in Example 5. In Table 10, the symbol “*” is given to some of the surface numbers, and this indicates that the corresponding surface has an aspherical shape. As illustrated in Table 10, the two surfaces of the lens L12 and the two surfaces of the lens L24 are aspherical surfaces. Table 11 illustrates the aspheric coefficients of some of the surfaces. In the case of an aspherical surface, the curvature radius r indicates the paraxial radius of curvature. The distance d indicates the distance between the surface with the corresponding surface number and the surface with the next surface number. Thus, the distance d in the column of the surface number 1 indicates the distance between the surface R1 and the surface R2 in
Aspherical Data
As illustrated in
The first lens group L1 has a negative refractive power. The second lens group L2 has a positive refractive power. The object-side surface of the lens L11 having the negative refractive power is a convex surface in a paraxial region and has an aspherical surface having a shape with which convex power decreases with increasing distance from an optical axis. The amount of sag of the object-side surface of the lens L11 and the amount of sag of the image-side surface of the lens L11 both have no extrema within the effective diameter.
The second lens group L2 includes the lens L21 having a positive refractive power, the lens L22 having a negative refractive power, the lens L23 having a positive refractive power, and the lens L24 having a positive refractive power that are arranged in this order starting from the object side. The lens L22 and the lens L23 forms a doublet lens. The lens L24 has a predetermined aspherical shape. The surface of the lens L24 on the most image side has a convex shape toward the image side in a paraxial region. The amount of sag of the object-side surface of the lens L24 and the amount of sag of the image-side surface of the lens L24 both have no extrema within the effective diameter.
In a configuration diagram of an optical system, the flat plate 120 that is disposed closest to the imaging plane 130 is a filter. The filter is an optical filter such as an IR cut filter or a low-pass filter and its characteristics are suitably selected in accordance with an image-capturing device to which the imaging optical system according to the present embodiment is applied.
Table 12 illustrates the diaphragm, the curvature radius r (mm), the distance d (mm), the refractive index N (d), the Abbe number νd, and the effective diameter of each of the lenses corresponding to the surface numbers of the image-capturing optical system 100A in Example 6. In Table 12, the symbol “*” is given to some of the surface numbers, and this indicates that the corresponding surface has an aspherical shape. As illustrated in Table 12, the two surfaces of the lens L11 and the two surfaces of the lens L24 are aspherical surfaces. Table 13 illustrates the aspheric coefficients of some of the surfaces. In the case of an aspherical surface, the curvature radius r indicates the paraxial radius of curvature. The distance d indicates the distance between the surface with the corresponding surface number and the surface with the next surface number. Thus, the distance d in the column of the surface number 1 indicates the distance between the surface R1 and the surface R2 in
Aspherical Data
As illustrated in
The first lens group L1 has a negative refractive power. The second lens group L2 has a positive refractive power. The object-side surface of the lens L11 having the negative refractive power is a convex surface in a paraxial region and has an aspherical surface having a shape with which convex power decreases with increasing distance from an optical axis. The amount of sag of the object-side surface of the lens L11 and the amount of sag of the image-side surface of the lens L11 both have no extrema within the effective diameter.
The second lens group L2 includes the lens L21 having a positive refractive power, the lens L22 having a negative refractive power, the lens L23 having a positive refractive power, and the lens L24 having a positive refractive power that are arranged in this order starting from the object side. The lens L22 and the lens L23 forms a doublet lens. The lens L24 has a predetermined aspherical shape. The surface of the lens L24 on the most image side has a convex shape toward the image side in a paraxial region. The amount of sag of the object-side surface of the lens L24 and the amount of sag of the image-side surface of the lens L24 both have no extrema within the effective diameter.
In a configuration diagram of an optical system, the flat plate 120 that is disposed closest to the imaging plane 130 is a filter. The filter is an optical filter such as an IR cut filter or a low-pass filter and its characteristics are suitably selected in accordance with an image-capturing device to which the imaging optical system according to the present embodiment is applied.
Table 14 illustrates the diaphragm, the curvature radius r (mm), the distance d (mm), the refractive index N (d), the Abbe number νd, and the effective diameter of each of the lenses corresponding to the surface numbers of the image-capturing optical system 100A in Example 7. In Table 14, the symbol “*” is given to some of the surface numbers, and this indicates that the corresponding surface has an aspherical shape. As illustrated in Table 14, the two surfaces of the lens L11 and the two surfaces of the lens L24 are aspherical surfaces. Table 15 illustrates the aspheric coefficients of some of the surfaces. In the case of an aspherical surface, the curvature radius r indicates the paraxial radius of curvature. The distance d indicates the distance between the surface with the corresponding surface number and the surface with the next surface number. Thus, the distance d in the column of the surface number 1 indicates the distance between the surface R1 and the surface R2 in
Aspherical Data
As illustrated in
The first lens group L1 has a negative refractive power. The second lens group L2 has a positive refractive power. The object-side surface of the lens L12 having the negative refractive power is a convex surface in a paraxial region and has an aspherical surface having a shape with which convex power decreases with increasing distance from an optical axis. The amount of sag of the object-side surface of the lens L12 and the amount of sag of the image-side surface of the lens L12 both have no extrema within the effective diameter.
The second lens group L2 includes the lens L21 having a positive refractive power, the lens L22 having a negative refractive power, the lens L23 having a positive refractive power, and the lens L24 having a positive refractive power that are arranged in this order starting from the object side. The lens L22 and the lens L23 forms a doublet lens. The lens L24 has a predetermined aspherical shape. The surface of the lens L24 on the most image side has a convex shape toward the image side in a paraxial region. The amount of sag of the object-side surface of the lens L24 and the amount of sag of the image-side surface of the lens L24 both have no extrema within the effective diameter.
In a configuration diagram of an optical system, the flat plate 120 that is disposed closest to the imaging plane 130 is a filter. The filter is an optical filter such as an IR cut filter or a low-pass filter and its characteristics are suitably selected in accordance with an image-capturing device to which the imaging optical system according to the present embodiment is applied.
Table 16 illustrates the diaphragm, the curvature radius r (mm), the distance d (mm), the refractive index N (d), the Abbe number νd, and the effective diameter of each of the lenses corresponding to the surface numbers of the image-capturing optical system 100E in Example 8. In Table 16, the symbol “*” is given to some of the surface numbers, and this indicates that the corresponding surface has an aspherical shape. As illustrated in Table 16, the two surfaces of the lens L12 and the two surfaces of the lens L24 are aspherical surfaces. Table 17 illustrates the aspheric coefficients of some of the surfaces. In the case of an aspherical surface, the curvature radius r indicates the paraxial radius of curvature. The distance d indicates the distance between the surface with the corresponding surface number and the surface with the next surface number. Thus, the distance d in the column of the surface number 1 indicates the distance between the surface R1 and the surface R2 in
Aspherical Data
As illustrated in
The first lens group L1 has a negative refractive power. The second lens group L2 has a positive refractive power. The object-side surface of the lens L12 having the negative refractive power is a convex surface in a paraxial region and has an aspherical surface having a shape with which convex power decreases with increasing distance from an optical axis. The amount of sag of the object-side surface of the lens L12 and the amount of sag of the image-side surface of the lens L12 both have no extrema within the effective diameter. The object-side surface of the lens L13 has a predetermined aspherical shape, and the amount of sag of the object-side surface of the lens L13 is set in such a manner that the object-side surface has a concave surface shape toward the object side in a paraxial region and a convex surface shape in a peripheral region.
The second lens group L2 includes the lens L21 having a positive refractive power, the lens L22 having a negative refractive power, the lens L23 having a positive refractive power, and the lens L24 having a positive refractive power that are arranged in this order starting from the object side. The lens L22 and the lens L23 forms a doublet lens. The lens L24 has a predetermined aspherical shape. The surface of the lens L24 on the most image side has a convex shape toward the image side in a paraxial region. The amount of sag of the object-side surface of the lens L24 and the amount of sag of the image-side surface of the lens L24 both have no extrema within the effective diameter.
In a configuration diagram of an optical system, the flat plate 120 that is disposed closest to the imaging plane 130 is a filter. The filter is an optical filter such as an IR cut filter or a low-pass filter and its characteristics are suitably selected in accordance with an image-capturing device to which the imaging optical system according to the present embodiment is applied.
Table 18 illustrates the diaphragm, the curvature radius r (mm), the distance d (mm), the refractive index N (d), the Abbe number νd, and the effective diameter of each of the lenses corresponding to the surface numbers of the image-capturing optical system 100E in Example 9. In Table 18, the symbol “*” is given to some of the surface numbers, and this indicates that the corresponding surface has a shape. As illustrated in Table 18, the two surfaces of the lens L12, the two surfaces of the lens L24, and the object-side surface of the lens L13 are aspherical surfaces. Table 19 illustrates the aspheric coefficients of some of the surfaces. In the case of an aspherical surface, the curvature radius r indicates the paraxial radius of curvature. The distance d indicates the distance between the surface with the corresponding surface number and the surface with the next surface number. Thus, the distance d in the column of the surface number 1 indicates the distance between the surface R1 and the surface R2 in
Aspherical Data
As illustrated in
The first lens group L1 has a negative refractive power. The second lens group L2 has a positive refractive power. The object-side surface of the lens L12 having the negative refractive power is a convex surface in a paraxial region and has an aspherical surface having a shape with which convex power decreases with increasing distance from an optical axis. The amount of sag of the object-side surface of the lens L12 and the amount of sag of the image-side surface of the lens L12 both have no extrema within the effective diameter, and the amount of sag of the object-side surface of the lens L13 and the amount of sag of the image-side surface of the lens L13 both have no extrema within the effective diameter.
The second lens group L2 includes the lens L21 having a negative refractive power, the lens L22 having a positive refractive power, and the lens L23 having a positive refractive power that are arranged in this order starting from the object side. The lens L21 and the lens L22 forms a doublet lens. The lens L23 has a predetermined aspherical shape. The surface of the lens L23 on the most image side has a convex shape toward the image side in a paraxial region. The amount of sag of the object-side surface of the lens L23 and the amount of sag of the image-side surface of the lens L23 both have no extrema within the effective diameter.
In a configuration diagram of an optical system, the flat plate 120 that is disposed closest to the imaging plane 130 is a filter. The filter is an optical filter such as an IR cut filter or a low-pass filter and its characteristics are suitably selected in accordance with an image-capturing device to which the imaging optical system according to the present embodiment is applied.
Table 20 illustrates the diaphragm, the curvature radius r (mm), the distance d (mm), the refractive index N (d), the Abbe number νd, and the effective diameter of each of the lenses corresponding to the surface numbers of the image-capturing optical system 100E in Example 10. In Table 20, the symbol “*” is given to some of the surface numbers, and this indicates that the corresponding surface has an aspherical shape. As illustrated in Table 20, the two surfaces of the lens L12, the two surfaces of the lens L13, and the two surfaces of the lens L23 are aspherical surfaces. Table 21 illustrates the aspheric coefficients of some of the surfaces. In the case of an aspherical surface, the curvature radius r indicates the paraxial radius of curvature. The distance d indicates the distance between the surface with the corresponding surface number and the surface with the next surface number. Thus, the distance d in the column of the surface number 1 indicates the distance between the surface R1 and the surface R2 in
Aspherical Data
As illustrated in
The first lens group L1 has a negative refractive power. The second lens group L2 has a positive refractive power. The object-side surface of the lens L11 having the negative refractive power is a convex surface in a paraxial region and has an aspherical surface having a shape with which convex power decreases with increasing distance from an optical axis. The amount of sag of the object-side surface of the lens L11 and the amount of sag of the image-side surface of the lens L11 both have no extrema within the effective diameter.
The second lens group L2 includes the lens L21 having a positive refractive power, the lens L22 having a negative refractive power, the lens L23 having a positive refractive power, and the lens L24 having a positive refractive power that are arranged in this order starting from the object side. The lens L22 and the lens L23 forms a doublet lens. The lens L24 has a predetermined aspherical shape. The surface of the lens L24 on the most image side has a convex shape toward the image side in a paraxial region. The amount of sag of the object-side surface of the lens L24 and the amount of sag of the image-side surface of the lens L24 both have no extrema within the effective diameter.
In a configuration diagram of an optical system, the flat plate 120 that is disposed closest to the imaging plane 130 is a filter. The filter is an optical filter such as an IR cut filter or a low-pass filter and its characteristics are suitably selected in accordance with an image-capturing device to which the imaging optical system according to the present embodiment is applied.
Table 22 illustrates the diaphragm, the curvature radius r (mm), the distance d (mm), the refractive index N (d), the Abbe number νd, and the effective diameter of each of the lenses corresponding to the surface numbers of the image-capturing optical system 100A in Example 11. In Table 22, the symbol “*” is given to some of the surface numbers, and this indicates that the corresponding surface has an aspherical shape. As illustrated in Table 22, the two surfaces of the lens L11 and the two surfaces of the lens L24 are aspherical surfaces. Table 23 illustrates the aspheric coefficients of some of the surfaces. In the case of an aspherical surface, the curvature radius r indicates the paraxial radius of curvature. The distance d indicates the distance between the surface with the corresponding surface number and the surface with the next surface number. Thus, the distance d in the column of the surface number 1 indicates the distance between the surface R1 and the surface R2 in
Aspherical Data
Although the image-capturing lens according to the present embodiment has been described above, the present disclosure is not limited to the image-capturing lenses of the above Examples, and various modifications can be made within the gist of the disclosure. For example, the specifications of the image-capturing lenses 100 of Examples 1 to 11 are examples, and various parameters can be changed within the gist of the present disclosure.
According to the present embodiment, a wide-angle image-capturing lens such as a surveillance camera or a vehicle-mounted camera that can be installed in various places, that has a favorable imaging performance over the entire screen while ensuring a wide field of view, and that has a high optical performance can be provided.
A subject image that is captured by the image-capturing lens 100 and focused on the light receiving surface of the image-capturing device 210 is converted into an electrical signal by a photoelectric conversion function of the image-capturing device 210 and output as an image signal from the image-capturing device 200.
The vehicle-mounted camera 310 outputs a captured image to the image processing apparatus 320 via a communication unit in the vehicle 300. The image processing apparatus 320 includes a memory that stores a dedicated processor for image processing, such as an image processing application specific integrated circuit (ASIC) or digital signal processing (DSP), and various information items and performs processing such as white balance adjustment, exposure adjustment processing, color interpolation, brightness correction, or gamma correction on images that are output by the vehicle-mounted camera 310 and other vehicle-mounted cameras. The image processing apparatus 320 performs processing such as switching of images, combination of images captured by a plurality of vehicle-mounted cameras, clipping of some images, or superimposing of a symbol, a character, a line that represents forecast trajectory, or the like onto an image and outputs an image signal according to the specifications of a display device 330. The vehicle-mounted camera 310 may have some or all of the functions of the image processing apparatus 320.
The display device 330 is disposed in or on a dashboard or the like of the vehicle 300 and displays image information processed by the image processing apparatus 320 to a driver of the vehicle 300.
As described above, the image-capturing lens 100 enables, at low cost, obtaining an image with a high definition and favorable viewability in a central region of a screen while ensuring a wide angle of view. As a result, the image-capturing lens 100 is suitable for various image-capturing devices and surveillance cameras and vehicle cameras that use such image-capturing devices.
100, 100A to 100K image-capturing optical system
L1 first lens group
L2 second lens group
L11 first lens of first lens group L1
L12 second lens of first lens group L1
L13 third lens of first lens group L1
L21 first lens of second lens group L2
L22 second lens of second lens group L2
L23 third lens of second lens group L2
L23 fourth lens of second lens group L2
110 on-axis luminous flux regulating diaphragm
120 flat plate
130 imaging plane
210 image-capturing device
220 housing
200 image-capturing device
300 vehicle
310 vehicle-mounted camera
320 image processing apparatus
330 display device
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-053082 | Mar 2020 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/008473 | 3/4/2021 | WO |
