JP6811088B2 - Imaging lens and imaging device - Google Patents

Description

The present invention relates to an image pickup lens particularly suitable for an in-vehicle camera, and an image pickup device provided with the image pickup lens.

In recent years, a camera has been mounted on a vehicle and used to assist in confirming blind spot areas such as the side and / or rear of the driver, and used for image recognition of vehicles, pedestrians, and / or obstacles around the vehicle. It's coming.

As an image pickup lens that can be used in such an in-vehicle camera for photographing the periphery of a vehicle, for example, those described in Patent Documents 1 and 2 below are known. Patent Documents 1 and 2 disclose a 7-element lens system.

JP-A-2016-62021 Japanese Patent Application No. 2015-92550

It has been proposed that the in-vehicle camera be equipped with a camera specialized for wide-angle, intermediate, or telephoto depending on the shooting distance to improve the accuracy of image recognition. Of these, cameras specialized for telephoto are expected to be used mainly for monitoring the front side of a car, and the total angle of view is 40 ° or less and the shooting distance is expected to be several hundred meters (meters). ..

Such an in-vehicle camera for long-distance monitoring on the front side is generally installed behind the rear mirror on the ceiling inside the vehicle, but this space enters the driver's overhead front view, and the installation of objects gives the driver a feeling of oppression. As an image pickup lens having a small outer diameter and a small size, it is required to reduce the feeling of oppression given to the driver. Further, in order to improve the accuracy of image recognition, high imaging performance is also required.

However, the image pickup lenses of Patent Documents 1 and 2 all have a wide total angle of view of about 70 ° or more, and the number of pixels of the image sensor cannot be sufficiently allocated to each subject during long-distance shooting, so that the image recognition accuracy is lowered. There is a risk of doing so.

The present invention has been made in view of the above circumstances, and in an imaging lens suitable for an in-vehicle camera for distant surveillance, it has an angle of view suitable for distant photography, high imaging performance, and suppresses an increase in size in the radial direction. It is an object of the present invention to provide a small image pickup lens and an image pickup apparatus provided with the image pickup lens.

The imaging lens of the present invention has a first lens having a negative refractive power and a convex surface facing the object side, a second lens having a positive refractive power, and a third lens having a positive refractive power in order from the object side. From a lens, an aperture, a fourth lens having a negative refractive power, a fifth lens having a positive refractive power, a sixth lens having a positive refractive power, and a seventh lens having a negative refractive power. Therefore, it is characterized in that the following conditional expression (1) is satisfied.
-0.6 <f4 / f <-0.3 ... (1)
However,
f4: Focal length of the 4th lens f: Focal length of the whole system.

It is preferable that the following conditional expression (1-1) is satisfied.
-0.5 <f4 / f <-0.39 ... (1-1)

The image pickup lens of the present invention preferably satisfies the following conditional expression (2).
-2.9 <f1 / f <-1.7 ... (2)
However,
f1: Focal length of the first lens f: Focal length of the whole system.

Further, it is preferable to satisfy the following conditional expression (3).
0.7 <f2 / f <1.3 ... (3)
However,
f2: Focal length of the second lens f: Focal length of the whole system.

Further, it is preferable to satisfy the following conditional expression (4).
0.6 <f123 / f <0.8 ... (4)
However,
f123: Combined focal length of the first lens, the second lens, and the third lens f: The focal length of the entire system.

Further, it is preferable to satisfy the following conditional expression (5).
4.0 <f4567 / f <6.8 ... (5)
However,
f4567: Combined focal length of the 4th lens, the 5th lens, the 6th lens, and the 7th lens f: The focal length of the entire system.

Further, it is preferable to satisfy the following conditional expression (6).
20 <2ω <30 ... (6)
However,
2ω: Total angle of view, but the unit is °
And.

Further, it is preferable to satisfy the following conditional expression (7).
1.0 <TTL / f <2.0 ... (7)
However,
TTL: The distance on the optical axis from the surface of the first lens on the object side to the image plane, where the back focus is the air equivalent length f: the focal length of the entire system.

The imaging apparatus of the present invention is characterized by including the imaging lens of the present invention described above.

In addition to the components listed above, "consisting of" means a lens that has substantially no power, an optical element other than a lens such as an aperture, a mask, a cover glass, or a filter, a lens flange, and a lens. It is intended that a barrel, an image sensor, and / or a mechanical part such as a camera shake correction mechanism may be included.

Further, the code of the surface shape and the refractive power of the above lens shall be considered in the paraxial region when the aspherical surface is included.

The imaging lens of the present invention has a first lens having a negative refractive power and a convex surface facing the object side, a second lens having a positive refractive power, and a third lens having a positive refractive power in this order from the object side. From a lens, an aperture, a fourth lens having a negative refractive power, a fifth lens having a positive refractive power, a sixth lens having a positive refractive power, and a seventh lens having a negative refractive power. Therefore, since the following conditional expression (1) is satisfied, a small image pickup lens having an image angle suitable for long-distance photography and high imaging performance, and suppressing the increase in size in the radial direction, and this image pickup lens are provided. An imaging device can be provided.
-0.6 <f4 / f <-0.3 ... (1)

Sectional drawing which shows the lens structure of the image pickup lens (common with Example 1) which concerns on one Embodiment of this invention. Sectional drawing which shows the lens structure of the image pickup lens of Example 2 of this invention. Sectional drawing which shows the lens structure of the image pickup lens of Example 3 of this invention. Sectional drawing which shows the lens structure of the image pickup lens of Example 4 of this invention. Sectional drawing which shows the lens structure of the image pickup lens of Example 5 of this invention. Each aberration diagram of the image pickup lens of Example 1 of this invention Each aberration diagram of the image pickup lens of Example 2 of this invention Each aberration diagram of the image pickup lens of Example 3 of this invention Each aberration diagram of the image pickup lens of Example 4 of this invention Each aberration diagram of the image pickup lens of Example 5 of this invention Schematic configuration of the imaging apparatus according to the embodiment of the present invention

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing a lens configuration of an imaging lens according to an embodiment of the present invention. The configuration example shown in FIG. 1 is the same as the configuration of the image pickup lens of the first embodiment described later. In FIG. 1, the left side is the object side and the right side is the image side, and the aperture diaphragm St shown does not necessarily represent the size and / or shape, but shows the position of the diaphragm on the optical axis Z. .. In addition, the axial luminous flux w and the luminous flux wb having the maximum angle of view are also shown.

The imaging lens of the present embodiment has a first lens L1 having a negative refractive power and a convex surface facing the object side, a second lens L2 having a positive refractive power, and a positive refractive power in order from the object side. The third lens L3, the aperture aperture St, the fourth lens L4 having a negative refractive power, the fifth lens L5 having a positive refractive power, the sixth lens L6 having a positive refractive power, and the negative It is composed of a seventh lens L7 having a refractive power.

By using the first lens L1 on the most object side as a negative lens, it becomes easy to secure the back focus, and it becomes easy to miniaturize the lens system in the radial direction. Further, by using the first lens L1 as a lens having a convex surface facing the object side, it becomes easy to correct the distortion.

Spherical aberration and astigmatism are corrected by continuously arranging a second lens L2 and a third lens L3 having a positive refractive power as positive lenses following the first lens L1 and dispersing the positive refractive power. Becomes easier.

The fourth lens L4 arranged adjacent to the image side of the aperture stop St is used as a negative lens, and the light rays after passing through the aperture stop St are separated to cause the aberrations of the fifth lens L5 to the seventh lens L7. Correction becomes easy.

Spherical aberration and astigmatism are corrected by continuously arranging a fifth lens L5 and a sixth lens L6 having a positive refractive power as positive lenses following the fourth lens L4 and dispersing the positive refractive power. Becomes easier.

By using the 7th lens L7 on the image side as a negative lens, the light incident angle characteristic (CRA: Chief Ray Angle) to the image sensor arranged on the image plane Sim can be appropriately corrected, so that the peripheral illumination can be reduced. Can be prevented.

Further, the image pickup lens of the present embodiment is configured to satisfy the following conditional expression (1). By not exceeding the upper limit of the conditional expression (1), it is possible to refract the light rays after passing through the aperture stop St in the direction away from the optical axis without causing high-order aberrations particularly in the luminous flux in the peripheral portion. .. Further, by appropriately suppressing the refractive power, when the image pickup lens of the present embodiment is mounted on the vehicle-mounted camera, the fluctuation of the refractive power is excessive in a wide operating temperature range (for example, about -40 ° C to 105 ° C) peculiar to the vehicle. Since it is possible to suppress the fluctuation of the focus position, it is possible to suppress the fluctuation of the focus position. By making sure that the light rays do not fall below the lower limit of the conditional expression (1), the light rays after passing through the aperture stop St can be strongly separated, so that each aberration can be easily corrected by the fifth lens L5 to the seventh lens L7. It becomes. By satisfying the following conditional expression (1-1), better characteristics can be obtained.
-0.6 <f4 / f <-0.3 ... (1)
-0.5 <f4 / f <-0.39 ... (1-1)
However,
f4: Focal length of the 4th lens f: Focal length of the whole system.

The image pickup lens of the present invention preferably satisfies the following conditional expression (2). By not exceeding the upper limit of the conditional expression (2), it is possible to prevent the refractive power of the first lens L1 from becoming too strong, so that astigmatism can be easily corrected. By making sure that the value does not fall below the lower limit of the conditional expression (2), it is possible to prevent the refractive power of the first lens L1 from becoming too weak, so that it becomes easy to secure the back focus.
-2.9 <f1 / f <-1.7 ... (2)
However,
f1: Focal length of the first lens f: Focal length of the whole system.

Further, it is preferable to satisfy the following conditional expression (3). By not exceeding the upper limit of the conditional expression (3), it is possible to prevent the refractive power of the second lens L2 from becoming too weak, so that astigmatism, spherical aberration and distortion can be easily corrected. By making sure that the value does not fall below the lower limit of the conditional expression (3), it is possible to prevent the refractive power of the second lens L2 from becoming too strong, so that it is easy to suppress the error sensitivity of the second lens L2 to the eccentricity. Become.
0.7 <f2 / f <1.3 ... (3)
However,
f2: Focal length of the second lens f: Focal length of the whole system.

Further, it is preferable to satisfy the following conditional expression (4). By not exceeding the upper limit of the conditional equation (4), it is possible to prevent the combined focal length of the first lens L1 to the third lens L3 from becoming too large with a positive value, so that astigmatism and spherical surface are prevented. It becomes easy to suppress the aberration. By making sure that the value does not fall below the lower limit of the conditional expression (4), it is possible to prevent the combined focal length of the first lens L1 to the third lens L3 from becoming too small with a positive value, so that wide-angle lensing is easy. Become.
0.6 <f123 / f <0.8 ... (4)
However,
f123: Combined focal length of the first lens, the second lens, and the third lens f: The focal length of the entire system.

Further, it is preferable to satisfy the following conditional expression (5). By not exceeding the upper limit of the conditional expression (5), it is possible to prevent the combined focal length of the fourth lens L4 to the seventh lens L7 from becoming too large with a positive value, so that spherical aberration and astigmatism are not observed. It becomes easy to correct aberration or chromatic aberration of magnification. By making sure that the value does not fall below the lower limit of the conditional expression (5), it is possible to prevent the combined focal length of the fourth lens L4 to the seventh lens L7 from becoming too small with a positive value, so that wide-angle lensing is easy. Or, it becomes easy to correct the chromatic aberration on the axis.
4.0 <f4567 / f <6.8 ... (5)
However,
f4567: Combined focal length of the 4th lens, the 5th lens, the 6th lens, and the 7th lens f: The focal length of the entire system.

Further, it is preferable to satisfy the following conditional expression (6). By not exceeding the upper limit of the conditional expression (6), the number of pixels of the image sensor can be sufficiently allocated to each subject during long-distance shooting, so that the image recognition accuracy can be improved. By not exceeding the lower limit of the conditional expression (6), an appropriate shooting range can be secured during long-distance shooting.
20 <2ω <30 ... (6)
However,
2ω: Total angle of view, but the unit is °
And.

Further, it is preferable to satisfy the following conditional expression (7). By not exceeding the upper limit of the conditional expression (7), the total length can be shortened in addition to the miniaturization in the radial direction of the lens, so that the degree of freedom of installation can be increased. The curvature of field can be suppressed by not falling below the lower limit of the conditional expression (7).
1.0 <TTL / f <2.0 ... (7)
However,
TTL: The distance on the optical axis from the surface of the first lens on the object side to the image plane, where the back focus is the air equivalent length f: the focal length of the entire system.

When the present imaging lens is used in a harsh environment, it is preferable to apply a protective multilayer coating. Further, in addition to the protective coat, an antireflection coat may be applied to reduce ghost light during use.

Further, when applying this imaging lens to an imaging device, it is preferable to arrange various filters such as a cover glass, a prism, an infrared cut filter and a low-pass filter between the lens system and the image plane Sim. Here, an example is shown in which the parallel flat plate-shaped optical members PP1 and PP2 assuming these are arranged between the lens system and the image plane Sim. Instead of arranging these various filters between the lens system and the image plane Sim, these various filters may be arranged between each lens, or various filters may be arranged on the lens surface of any lens. A coat having a similar effect may be applied.

Next, numerical examples of the image pickup lens of the present invention will be described.
First, the image pickup lens of Example 1 will be described. FIG. 1 shows a cross-sectional view showing the lens configuration of the image pickup lens of the first embodiment. In FIGS. 1 and 2 to 5 corresponding to Examples 2 to 5 described later, the left side is the object side and the right side is the image side, and the illustrated aperture stop St does not necessarily have a size and / or shape. It does not represent the position of the diaphragm on the optical axis Z.

Table 1 shows the basic lens data of the imaging lens of Example 1, and Table 2 shows the data related to the specifications. In the following, the meanings of the symbols in the table will be described by taking the one of Example 1 as an example, but the same is basically the same for Examples 2 to 5.

In the lens data of Table 1, the surface number column shows the surface number of the component on the object side as the first surface, and the surface number gradually increases toward the image side, and the radius of curvature column shows the radius of curvature of each surface. In the column of surface spacing, the distance between each surface and the next surface on the optical axis Z is shown. Further, the n column shows the refractive index of each optical element with respect to the d line (wavelength 587.6 nm (nanometers)), and the ν column shows the Abbe number of each optical element with respect to the d line (wavelength 587.6 nm). Shown.

Here, the sign of the radius of curvature is positive when the surface shape is convex toward the object side and negative when the surface shape is convex toward the image side. The basic lens data includes the aperture stop St. In the column of the surface number of the surface corresponding to the aperture stop St, the word (aperture) is described together with the surface number.

In the data related to the specifications in Table 2, the focal length f'and F number FNo. , The value of the total angle of view 2ω, and the value of TTL in the conditional expression (7) are shown.

In the basic lens data and data related to specifications, degrees are used as the unit of angle and mm is used as the unit of length, but the optical system can be used even if it is expanded or contracted proportionally, so other suitable Units can also be used.

Each aberration diagram of the image pickup lens of Example 1 is shown in FIG. In addition, spherical aberration, astigmatism, distortion, and chromatic aberration of magnification are shown in order from the left side in FIG. These aberration diagrams show the state when the object distance is set to infinity. Each aberration diagram showing spherical aberration, astigmatism, and distortion shows aberrations with the d-line (wavelength 587.6 nm) as a reference wavelength. In the spherical aberration diagram, the aberrations for the d line (wavelength 587.6 nm), the C line (wavelength 656.3 nm), and the F line (wavelength 486.1 nm) are shown by solid lines, long dashed lines, and short dashed lines, respectively. The astigmatism diagram shows the aberrations in the sagittal and tangential directions with solid lines and short dashed lines, respectively. The chromatic aberration of magnification diagram shows the aberrations for line C (wavelength 656.3 nm) and line F (wavelength 486.1 nm) with long and short dashed lines, respectively. The FNo. Of the spherical aberration diagram. Means the F value, and ω in the other aberration diagrams means a half angle of view.

Unless otherwise specified, the symbols, meanings, and description methods of the data described in the above description of the first embodiment are the same as those of the following examples. Therefore, duplicate description will be omitted below.

Next, the image pickup lens of Example 2 will be described. FIG. 2 shows a cross-sectional view showing the lens configuration of the image pickup lens of the second embodiment. Further, the basic lens data of the image pickup lens of the second embodiment is shown in Table 3, the data related to the specifications is shown in Table 4, and each aberration diagram is shown in FIG.

Next, the image pickup lens of Example 3 will be described. FIG. 3 shows a cross-sectional view showing the lens configuration of the image pickup lens of the third embodiment. Table 5 shows the basic lens data of the image pickup lens of Example 3, Table 6 shows the data related to the specifications, and FIG. 8 shows each aberration diagram.

Next, the image pickup lens of Example 4 will be described. FIG. 4 shows a cross-sectional view showing the lens configuration of the image pickup lens of the fourth embodiment. Table 7 shows the basic lens data of the image pickup lens of Example 4, Table 8 shows the data related to the specifications, and FIG. 9 shows each aberration diagram.

Next, the image pickup lens of Example 5 will be described. A cross-sectional view showing the lens configuration of the image pickup lens of Example 5 is shown in FIG. Further, the basic lens data of the image pickup lens of Example 5 is shown in Table 9, the data related to the specifications is shown in Table 10, and each aberration diagram is shown in FIG.

Table 11 shows the values corresponding to the conditional expressions (1) to (7) of the imaging lenses of Examples 1 to 5. In all the examples, the d line is used as the reference wavelength, and the values shown in Table 11 below are at this reference wavelength.

From the above data, all the imaging lenses of Examples 1 to 5 satisfy the condition equations (1) to (7), have an angle of view suitable for long-distance photography, high imaging performance, and are in the radial direction. It can be seen that it is a small image pickup lens that suppresses the increase in size.

Next, the image pickup apparatus according to the embodiment of the present invention will be described. Here, an example when applied to an in-vehicle camera as an embodiment of the imaging device of the present invention will be described. FIG. 11 shows a state in which an in-vehicle camera is mounted on an automobile.

In FIG. 11, the automobile 100 is attached to the back surface of the rear-view mirror and includes an in-vehicle camera 101 (imaging device) for photographing the front side of the driver in the distance. The in-vehicle camera 101 includes an image pickup lens according to an embodiment of the present invention and an image pickup element that converts an optical image formed by the image pickup lens into an electric signal.

Although the present invention has been described above with reference to embodiments and examples, the present invention is not limited to the above embodiments and examples, and various modifications are possible. For example, the values of the radius of curvature, the interplanar spacing, the refractive index, the Abbe number, and the like of each lens component are not limited to the values shown in the above numerical examples, and other values can be taken.

Further, the imaging device according to the embodiment of the present invention is particularly preferably an in-vehicle camera for outside-vehicle photography, and is not limited to the above-mentioned in-vehicle camera for vehicle front photography, but also as an in-vehicle camera for vehicle rear photography. Good. In addition to the in-vehicle camera, various modes such as a surveillance camera can be used.

100 Automobile 101 In-vehicle camera L1 1st lens L2 2nd lens L3 3rd lens L4 4th lens L5 5th lens L6 6th lens L7 7th lens PP1, PP2 Optical member Sim Image plane St Aperture diaphragm wa Axial light beam wb Maximum Angle of view light beam Z optical axis

Claims (6)

From the object side, the first lens having a negative refractive power and the convex surface facing the object side, the second lens having a positive refractive power, the third lens having a positive refractive power, the aperture, and the negative It is composed of a fourth lens having a positive refractive power, a fifth lens having a positive refractive power, a sixth lens having a positive refractive power, and a seventh lens having a negative refractive power.
An imaging lens characterized by satisfying the following conditional expressions (1), (4), (5) and (6).
-0.6 <f4 / f <-0.3 ... (1)
0.6 <f123 / f <0.8 ... (4)
4.0 <f4567 / f <6.8 ... (5)
20 <2ω <30 ... (6)
However,
f4: Focal length of the fourth lens f: Focal length of the whole system
f123: Combined focal distance of the first lens, the second lens, and the third lens f4567: Combined focal distance of the fourth lens, the fifth lens, the sixth lens, and the seventh lens.
2ω: Total angle of view, but the unit is °
And. The following conditional expression (7) An imaging lens according to claim 1, wherein satisfying the.
1.0 <TTL / f <2.0 ... (7)
However,
TTL: The distance on the optical axis from the surface of the first lens on the object side to the image plane, where the back focus is the air equivalent length. The imaging lens according to claim 1, which satisfies the following conditional expression (1-1).
-0.5 <f4 / f <-0.39 ... (1-1) The imaging lens according to any one of claims 1 to 3, which satisfies the following conditional expression (2).
-2.9 <f1 / f <-1.7 ... (2)
However,
f1: Let it be the focal length of the first lens. The imaging lens according to any one of claims 1 to 4 , which satisfies the following conditional expression (3).
0.7 <f2 / f <1.3 ... (3)
However,
f2: Let it be the focal length of the second lens. An image pickup apparatus comprising the image pickup lens according to any one of claims 1 to 5 .