JP2021107893A - Wide-angle lens - Google Patents

Abstract

To provide a wide-angle lens which offers good imaging performance at each wavelength within a wide wavelength range.SOLUTION: A wide-angle lens 50 is provided, comprising first lens L1 having a convex surface on the object side, a second lens L2 having high positive power and a large Abbe number, a third lens L3 having low power, a fourth lens L4 having positive power, and a fifth lens L5 having negative power, arranged in order from the object side. A focal length of each lens f1-f5 and Abbe numbers νd1-νd5 satisfy each of the following conditional expressions: -2.5<f1/f<-0.5, 1.0<f2/f<4.0, 18<|f3/f|, 0.7<|f4/f5|<1.5, 1.0<d23/f<4.0, 2.0<νd4/νd5<5.0, 45.0<νd2, 35.0<νd1, where f represents a focal length of the entire lens system and d23 represents a distance between the first lens and the second lens.SELECTED DRAWING: Figure 1A

Description

The present invention relates to a wide-angle lens, and more particularly to a wide-angle lens capable of supporting a wide range of wavelengths from a visible light region (λ = 436 nm to 656 nm) to near ultraviolet rays (λ = 385 nm) and an infrared region (λ = 800 nm to 900 nm).

The range of use for wide-angle lenses is wide, and it covers a wide range of areas such as security and mounting in automobiles or drones. For this reason, the characteristics required for wide-angle lenses must meet various requirements such as miniaturization, weight reduction, cost reduction, high performance (for example, 4K support), and ultraviolet and infrared support. There is. In particular, the so-called multi-wave type wide-angle lens in which the visible light region (λ = 436 nm to 656 nm) to the infrared region (λ = 800 nm to 900 nm) are combined on almost the same focus plane and the characteristics are covered by a wide-angle lens. Difficult demands such as lenses are also increasing. For example, Patent Documents 1 and 2 propose wide-angle lenses corresponding to a wide range of wavelengths from visible light to infrared light.

JP-A-2017-102353 Japanese Unexamined Patent Publication No. 2008-83735

In a wide-angle lens, in order to satisfy each of the above requirements, it is common practice to increase the number of constituent lenses and adopt an aspherical lens to improve the performance and reduce the size. However, if the number of components is increased, it becomes difficult to reduce the size and weight, and it becomes a factor of high cost.

The adoption of an aspherical lens can be considered as one of the methods for obtaining high performance with a small number of components. Therefore, asphericalization using a glass lens or asphericalization using a plastic lens can be considered, but it is known that both of them have problems.

That is, the aspherical surface formed by glass molding makes the manufacturing cost of the mold and the molding cost of the aspherical lens extremely high, which leads to an increase in the cost of the product.

Aspherical lenses made of plastic are effective in reducing costs and weight, but the refractive index changes significantly due to temperature changes, and the optical system used in automobiles and drones changes in temperature due to the external environment (generally). Therefore, it is required to respond to a temperature change of about −10 ° to + 80 °), which causes the in-focus focus surface to move, making it unsuitable for a high-performance wide-angle lens. Therefore, as a means for obtaining good imaging performance for each wavelength in a wide wavelength band (near ultraviolet ray λ = 385 nm to near infrared ray λ = 900 nm), a material having a large Abbe number is often used and an aspherical lens is used. It corresponds by combining.

In view of these points, an object of the present invention is to provide a wide-angle lens capable of obtaining high performance by using an aspherical lens having a weak power and having a small focus movement.

In order to solve the above problems, the wide-angle lens of the present invention has a first lens having a negative power with a convex surface facing the object side from the object side toward the image plane side, and a positive power. A second lens with aspherical surface, a third lens with positive or negative power, a fourth lens with positive power, and a fifth lens with negative power are arranged in this order. There is.

The wide-angle lens according to the embodiment of the present invention has a lens configuration of four lenses including four glass spherical lenses and one plastic aspherical lens. With the first glass spherical lens (L1) having negative power, in order from the object side, the convex surface is directed toward the object side; A glass aspherical lens (L2) with a large Abbe number (νd) and a plastic aspherical lens (L3) with a weak power; a glass aspherical lens (L4) with a positive power, and a negative power. A glass spherical lens (L5) to be held is arranged.

Due to the composite lens (L45) consisting of the fourth lens (glass spherical lens L4) and the fifth lens (glass spherical lens L5), the correction between the first lens (L1) and the third lens (L3) became insufficient. The chromatic aberration on the axis and the chromatic aberration of the magnification are appropriately corrected.

That is, in the wide-angle lens of the present invention, the focal length and Abbe number of each lens are set so as to satisfy the following conditional expressions 1 to 8. In the following conditional expression, f is the focal length of the entire lens system, f1 to f5 are the focal lengths of the first to fifth lenses, d2 is the lens spacing between the first lens and the second lens, and νd1 to νd5 are the first. ~ Represents the Abbe number for the d-line of the 5th lens.

Conditional expression 1: -2.5 <f1 / f <-0.5
Conditional expression 2: 1.0 <f2 / f <4.0
Conditional expression 3:18 << | f3 / f |
Conditional expression 4: 0.7 << f4 / f5 | <1.5
Conditional expression 5: 1.0 <d2 / f <4.0
Conditional expression 6: 2.0 <νd4 / νd5 <5.0
Conditional expression 7: 45.0 <νd2
Conditional expression 8: 35.0 <νd1

Conditional expression 1: -2.5 <f1 / f <-0.5
Conditional expression 1 relates to securing astigmatism, chromatic aberration of magnification, coma, and back focus (bf). If the upper limit value exceeds −0.5, the astigmatism increases and the off-axis chromatic aberration also increases, which hinders good imaging performance. Further, since the power of each lens constituting the wide-angle lens becomes stronger, it becomes difficult to correct the coma aberration of off-axis light. On the other hand, if it is below the lower limit of -2.5, it is effective for correcting chromatic aberration, but it becomes difficult to secure the back focus (bf) and the S (Sagittal) plane of astigmatism is curved toward the object. , This correction becomes difficult.

Conditional expression 2: 1.0 <f2 / f <4.0
Conditional expression 2 relates to curvature of field, astigmatism or chromatic aberration, and CRA (primary ray incident angle). If the upper limit value exceeds 4.0, it is effective for changing the low angle of CRA, but the off-axis image plane is curved toward the object side and the chromatic aberration of magnification is increased. On the other hand, if it is less than the lower limit of 1.0, it is effective for correcting curvature of field and astigmatism, but not only it becomes difficult to secure the back focus (bf), but also the angle of CRA is increased. , Shading correction is required, which causes high cost. Here, in addition to these factors, considering the processing error and the like, it is desirable to set the conditional expression 2 in the following range.
2.0 <f2 / f <3.5

Conditional expression 3:18 << | f3 / f |
Conditional expression 3 is a condition for controlling the change of the best imaging point due to the temperature change. If this condition is not met, the change in the imaging point in an environment with a large temperature change (-10 ° to + 80 °) is large, making it unsuitable for a high-definition lens. In the examples described later, this condition is controlled to 22.0 << | f3 / f |, whereby the amount of change in the best imaging point is ± 0.01 mm or less.

Further, the third lens is designed to be compact and lightweight and has high definition, and is made of an aspherical surface made of plastic. This makes it possible to compensate for the insufficient correction of spherical aberration and coma by the spherical lens, and obtains good imaging characteristics even though it is a lightweight and compact lens system. The third lens L3 can also be a glass aspherical lens.

Conditional expression 4: 0.7 << f4 / f5 | <1.5
Conditional expression 4 relates to chromatic aberration and spherical aberration, curvature of field, and CRA. If the upper limit value exceeds 1.5, the chromatic aberration will be overcorrected and the spherical aberration will also be overcorrected. Further, the curvature of field is also curved toward the imaging side, which is so-called overcorrection, which hinders good imaging performance. On the other hand, if it is less than the lower limit value of 0.7, it is effective for lowering the angle of the CRA, but not only the chromatic aberration and the spherical aberration are insufficiently corrected, but also the curvature of field is also insufficiently corrected.

Conditional expression 5: 1.0 <d2 / f <4.0
Conditional expression 5 relates to miniaturization of the lens system and astigmatism, chromatic aberration and coma. If it exceeds the upper limit of 4.0, astigmatism will increase and it will be unsuitable for miniaturization of the lens system. In addition, chromatic aberration of magnification also increases, which hinders good imaging performance. On the other hand, if it is less than the lower limit of 1.0, it is effective for miniaturization, but it causes an increase in astigmatism and an increase in coma, which hinders a good image.

Conditional expression 6: 2.0 <νd4 / νd5 <5.0
Conditional expression 6 relates to color correction. If the upper limit value of 5.0 is exceeded, the chromatic aberration of the magnification of the axial light is overcorrected (the short wavelength increases in the (+) direction with respect to the reference wavelength), which hinders good imaging. On the other hand, if it falls below the lower limit of 2.0, on the contrary, the chromatic aberration of the magnification of the on-axis light and the off-axis light becomes insufficiently corrected (increases in the short wavelength (−) direction with respect to the reference wavelength). Here, it is desirable to set this condition in the range of 3.0 <νd4 / νd5 <4.0 because good imaging performance can be obtained.

Conditional expression 7: 45.0 <νd2
Conditional expression 7 is for maintaining good chromatic aberration over the near-ultraviolet ray λ = 385 nm to the near-infrared ray λ = 850 nm. If this condition is not met, chromatic aberration increases in the (−) direction for near-ultraviolet rays and in the (+) direction for near-infrared rays with respect to the reference wavelength, making color correction in a wide wavelength band difficult.

Conditional expression 8: 35.0 <νd1
The conditional expression 8 defines the Abbe number of the first lens (L1) constituting the first group. This is related to the correction of chromatic aberration in a wide wavelength band, and if this condition is not met, the amount of deviation of the imaging point in the wavelength band related to the near-infrared λ = 400 nm to the near-infrared λ = 850 nm with respect to the reference wavelength λ = 546 nm. Increases, and the axial chromatic aberration when the visible light is satisfactorily corrected increases in the (-) direction in the near-infrared ray and in the (+) direction in the near-infrared ray. Further, the chromatic aberration of magnification also increases in the (−) direction in the near ultraviolet rays and in the (+) direction in the near infrared rays, which makes it unsuitable for the development of the wide wavelength band type lens which is the object of the present invention. This condition,
40.0 <νd1
This is desirable because good optical characteristics can be obtained.

It is explanatory drawing which shows the structure of the lens optical system of the wide-angle lens of Example 1 to which this invention was applied. It is an aberration diagram of the wide-angle lens of Example 1. FIG. It is explanatory drawing which shows the structure of the lens optical system of the wide-angle lens of Example 2 to which this invention was applied. It is an aberration diagram of the wide-angle lens of Example 2. (A) and (b) are lists showing the lens data of the wide-angle lenses of Examples 1 and 2, and (c) is a list showing the values of each conditional expression of the wide-angle lenses of Examples 1 and 2. ..

Hereinafter, examples of a wide-angle lens to which the present invention is applied will be described with reference to the drawings.

1A and 2A are block diagrams of wide-angle lenses according to Examples 1 and 2 of the present invention, and FIGS. 1B and 2B are aberration diagrams of wide-angle lenses of Examples 1 and 2. As shown in FIGS. 1A and 2A, the basic configurations of the wide-angle lenses 50 and 60 of Examples 1 and 2 are the same, and the first lens L1 and the second lens L2 are directed from the object side to the image plane side. The third lens L3, the fourth lens L4, and the fifth lens L5 are arranged in this order. The diaphragm 6 is arranged on the object side of the second lens L2. Further, a low-pass filter (not shown) and a cover glass 7 are arranged between the fifth lens L5 and the image plane IM (light receiving surface of the light receiving element).

The first lens L1 is a glass spherical lens having a negative power with a convex surface facing the object side. The second lens L2 is a glass spherical lens having a positive power. The third lens L3 is a plastic aspherical lens having a positive or negative power and having an aspherical surface. The fourth lens L4 is a glass spherical lens having a positive power. The fifth lens L5 is a glass spherical lens having a negative power.

The meanings of the respective symbols in Examples 1 and 2 are as follows.
f: Focal length of the entire imaging lens Fno: F number f1: Focal length of the first lens f2: Focal length of the second lens f3: Focal length of the third lens f4: Focal length of the fourth lens f5: Fifth lens Focal length ω: Half-angle i: Surface number of the lens surface counted from the object side (Asterisk "*" after the surface number indicates that it is an aspherical surface)
r: Radius of curvature d: Distance between lens surfaces on the optical axis (plane spacing)
nd: Refractive index νd1 to νd5: Abbe number for the d-line of the first to fifth lenses νd6: Abbe number for the d-line of the cover glass

Here, in FIGS. 1A and 1A, the surface numbers i of the lens surfaces counted from the object side are shown as (1), (2), (3), and so on. An asterisk "*" after the surface number indicates that it is an aspherical surface. Further, the distance d (plane spacing) between the lens surfaces on the optical axis is shown as d1, d2, d3 ... In order from the object side.

Further, in the wide-angle lenses 50 and 60 of each embodiment, the shapes adopted for the aspherical surface of the lens surface are Z for the axis in the optical axis direction, H for the height in the direction orthogonal to the optical axis, K for the conical coefficient, and aspherical surface. When the coefficients are A4, A6, A8, A10, A12, and A14, it is expressed by the following formula.

<Lens data of each example>
The lens data of the wide-angle lenses 50 and 60 of Examples 1 and 2 are shown below.

非球面データ
第６面
Ｋ＝０．０
Ａ４＝−３．０６８７９４Ｅ−０３
Ａ６＝４．０４１３３６Ｅ−０４
Ａ８＝−５．０８２８７３Ｅ−０４
Ａ１０＝６．０４６１２８Ｅ−０５

第７面
Ｋ＝０．０
Ａ４＝−１．２０６４３７Ｅ−０３
Ａ６＝６．１１９５５２Ｅ−０４
Ａ８＝−３．４５７３３５Ｅ−０４
Ａ１０＝３．２８３９９３Ｅ−０５ (Lens data of Example 1)
f = 2.957 mm, Fno = 2.2, ω = 75.0 °
f1 = -3.0966 mm
f2 = 5.5556 mm
f3 = -1722.8500 mm
f4 = 4.6037 mm
f5 = -6.085mm
f45 = 16.9501 mm
d2 = 3.8434 mm

Aspherical data 6th surface K = 0.0
A4 = -3.068794E-03
A6 = 4.041336E-04
A8 = -5.082873E-04
A10 = 6.046128E-05

Side 7 K = 0.0
A4 = -1.206437E-03
A6 = 6.119552E-04
A8 = -3.457335E-04
A10 = 3.283939E-05

非球面データ
第６面
Ｋ＝１．２０４８８６
Ａ４＝−９．６９６７２８Ｅ−０３
Ａ６＝６．４４３７２２Ｅ−０４
Ａ８＝−５．２０２７４８Ｅ−０４
Ａ１０＝８．２２９６７２Ｅ−０５

第７面
Ｋ＝４．９５６８５２Ｅ−０１
Ａ４＝−１．２９６８４９Ｅ−０３
Ａ６＝９．８１１１６５Ｅ−０４
Ａ８＝−１．０８５０１５Ｅ−０４
Ａ１０＝１．１５５０３１Ｅ−０５
Ａ１２＝２．８３１３０６Ｅ−０６ (Lens data of Example 2)
f = 3.100 mm, Fno = 2.2, ω = 65.3 °
f1 = -3.0529mm
f2 = 4.3975mm
f3 = 103.9513mm
f4 = 5.0760mm
f5 = -5.9188 mm
f45 = 25.3750mm
d2 = 3.4367 mm

Aspherical data 6th surface K = 1.204886
A4 = -9.696728E-03
A6 = 6.443722E-04
A8 = -5.202748E-04
A10 = 8.229672E-05

7th surface K = 4.965852E-01
A4 = -1.296849E-03
A6 = 9.811165E-04
A8 = -1.085015E-04
A10 = 1.155031E-05
A12 = 2.831306E-06

(Action effect)
1B and 2B show the aberrations of the wide-angle lenses 50 and 60 of Examples 1 and 2. Further, FIGS. 3 (a) and 3 (b) collectively show the main lens data of the wide-angle lenses 50 and 60 of Examples 1 and 2, and FIG. 3 (c) shows each conditional expression (1) in each of the examples. ) To (8) are shown.

As can be seen from these figures, the wide-angle lenses 50 and 60 of Examples 1 and 2 satisfy all of the conditional equations 1 to 8 and have a wide wavelength band (near ultraviolet rays λ = 385 nm to near infrared rays λ = 900 nm). It was confirmed that good imaging performance can be obtained for each wavelength.

50, 60 Wide-angle lens L1 1st lens L2 2nd lens L3 3rd lens L4 4th lens L5 5th lens IM Imaging surface 6 Aperture 7 Cover glass (1) to (12) Lens surface surface numbers d1 to d6 Optical Distance between lens surfaces on the axis (plane spacing)

The present invention relates to a wide-angle lens, and more particularly to a wide-angle lens capable of supporting a wide range of wavelengths from a visible light region (λ = 436 nm to 656 nm) to near ultraviolet rays (λ = 385 nm) and an infrared region (λ = 800 nm to 900 nm).

The range of use for wide-angle lenses is wide, and it covers a wide range of areas such as security and mounting in automobiles or drones. For this reason, the characteristics required for wide-angle lenses must meet various requirements such as miniaturization, weight reduction, cost reduction, high performance (for example, 4K support), and ultraviolet and infrared support. There is. In particular, the so-called multi-wave type wide-angle lens in which the visible light region (λ = 436 nm to 656 nm) to the infrared region (λ = 800 nm to 900 nm) are combined on almost the same focus plane and the characteristics are covered by a wide-angle lens. Difficult demands such as lenses are also increasing. For example, Patent Documents 1 and 2 propose wide-angle lenses corresponding to a wide range of wavelengths from visible light to infrared light.

JP-A-2017-102353 Japanese Unexamined Patent Publication No. 2008-83735

In a wide-angle lens, in order to satisfy each of the above requirements, it is common practice to increase the number of constituent lenses and adopt an aspherical lens to improve the performance and reduce the size. However, if the number of components is increased, it becomes difficult to reduce the size and weight, and it becomes a factor of high cost.

The adoption of an aspherical lens can be considered as one of the methods for obtaining high performance with a small number of components. Therefore, asphericalization using a glass lens or asphericalization using a plastic lens can be considered, but it is known that both of them have problems.

That is, the aspherical surface formed by glass molding makes the manufacturing cost of the mold and the molding cost of the aspherical lens extremely high, which leads to an increase in the cost of the product.

Aspherical lenses made of plastic are effective in reducing costs and weight, but the refractive index changes significantly due to temperature changes, and the optical system used in automobiles and drones changes in temperature due to the external environment (generally). Therefore, it is required to respond to a temperature change of about −10 ° to + 80 °), which causes the in-focus focus surface to move, making it unsuitable for a high-performance wide-angle lens. Therefore, as a means for obtaining good imaging performance for each wavelength in a wide wavelength band (near ultraviolet ray λ = 385 nm to near infrared ray λ = 900 nm), a material having a large Abbe number is often used and an aspherical lens is used. It corresponds by combining.

In view of these points, an object of the present invention is to provide a wide-angle lens capable of obtaining high performance by using an aspherical lens having a weak power and having a small focus movement.

In order to solve the above problems, the wide-angle lens of the present invention has a first lens having a negative power with a convex surface facing the object side from the object side toward the image plane side, and a positive power. A second lens with aspherical surface, a third lens with positive or negative power, a fourth lens with positive power, and a fifth lens with negative power are arranged in this order. There is.

The wide-angle lens according to the embodiment of the present invention has a lens configuration of four lenses including four glass spherical lenses and one plastic aspherical lens. With the first glass spherical lens (L1) having negative power, in order from the object side, the convex surface is directed toward the object side; the convex surface is directed toward the object side through a predetermined distance (d 23) from the first lens, and is strong. A glass aspherical lens (L2) having a positive power and a large Abbe number (νd); a plastic aspherical lens (L3) with a weak power; a glass aspherical lens (L4) having a positive power, and a negative power. A glass spherical lens (L5) with a lens (L5) is arranged.

Due to the composite lens (L45) consisting of the fourth lens (glass spherical lens L4) and the fifth lens (glass spherical lens L5), the correction between the first lens (L1) and the third lens (L3) became insufficient. The chromatic aberration on the axis and the chromatic aberration of the magnification are appropriately corrected.

That is, in the wide-angle lens of the present invention, the focal length and Abbe number of each lens are set so as to satisfy the following conditional expressions 1 to 8. In the following conditional expressions, f is the focal length of the entire lens system, f1 to f5 is the focal length of the fifth lens, d 23 the lens distance between the first lens and the second lens, the νd1~νd5 first It represents the Abbe number for the d-line of the 1st to 5th lenses.

Conditional expression 1: -2.5 <f1 / f <-0.5
Conditional expression 2: 1.0 <f2 / f <4.0
Conditional expression 3:18 << | f3 / f |
Conditional expression 4: 0.7 << f4 / f5 | <1.5
Conditional expression 5: 1.0 <d 23 / f <4.0
Conditional expression 6: 2.0 <νd4 / νd5 <5.0
Conditional expression 7: 45.0 <νd2
Conditional expression 8: 35.0 <νd1

Conditional expression 1: -2.5 <f1 / f <-0.5
Conditional expression 1 relates to securing astigmatism, chromatic aberration of magnification, coma, and back focus (bf). If the upper limit value exceeds −0.5, the astigmatism increases and the off-axis chromatic aberration also increases, which hinders good imaging performance. Further, since the power of each lens constituting the wide-angle lens becomes stronger, it becomes difficult to correct the coma aberration of off-axis light. On the other hand, if it is below the lower limit of -2.5, it is effective for correcting chromatic aberration, but it becomes difficult to secure the back focus (bf) and the S (Sagittal) plane of astigmatism is curved toward the object. , This correction becomes difficult.

Conditional expression 2: 1.0 <f2 / f <4.0
Conditional expression 2 relates to curvature of field, astigmatism or chromatic aberration, and CRA (primary ray incident angle). If the upper limit value exceeds 4.0, it is effective for changing the low angle of CRA, but the off-axis image plane is curved toward the object side and the chromatic aberration of magnification is increased. On the other hand, if it is less than the lower limit of 1.0, it is effective for correcting curvature of field and astigmatism, but not only it becomes difficult to secure the back focus (bf), but also the angle of CRA is increased. , Shading correction is required, which causes high cost. Here, in addition to these factors, considering the processing error and the like, it is desirable to set the conditional expression 2 in the following range.
2.0 <f2 / f <3.5

Conditional expression 3:18 << | f3 / f |
Conditional expression 3 is a condition for controlling the change of the best imaging point due to the temperature change. If this condition is not met, the change in the imaging point in an environment with a large temperature change (-10 ° to + 80 °) is large, making it unsuitable for a high-definition lens. In the examples described later, this condition is controlled to 22.0 << | f3 / f |, whereby the amount of change in the best imaging point is ± 0.01 mm or less.

Further, the third lens is designed to be compact and lightweight and has high definition, and is composed of an aspherical surface made of plastic. This makes it possible to compensate for the insufficient correction of spherical aberration and coma by the spherical lens, and obtains good imaging characteristics even though it is a lightweight and compact lens system. The third lens L3 can also be a glass aspherical lens.

Conditional expression 4: 0.7 << f4 / f5 | <1.5
Conditional expression 4 relates to chromatic aberration and spherical aberration, curvature of field, and CRA. If the upper limit value exceeds 1.5, the chromatic aberration will be overcorrected and the spherical aberration will also be overcorrected. Further, the curvature of field is also curved toward the imaging side, which is so-called overcorrection, which hinders good imaging performance. On the other hand, if it is less than the lower limit value of 0.7, it is effective for lowering the angle of the CRA, but not only the chromatic aberration and the spherical aberration are insufficiently corrected, but also the curvature of field is also insufficiently corrected.

Conditional expression 5: 1.0 <d 23 / f <4.0
Conditional expression 5 relates to miniaturization of the lens system and astigmatism, chromatic aberration and coma. If it exceeds the upper limit of 4.0, astigmatism will increase and it will be unsuitable for miniaturization of the lens system. In addition, chromatic aberration of magnification also increases, which hinders good imaging performance. On the other hand, if it is less than the lower limit of 1.0, it is effective for miniaturization, but it causes an increase in astigmatism and an increase in coma, which hinders a good image.

Conditional expression 6: 2.0 <νd4 / νd5 <5.0
Conditional expression 6 relates to color correction. If the upper limit value of 5.0 is exceeded, the chromatic aberration of the magnification of the axial light is overcorrected (the short wavelength increases in the (+) direction with respect to the reference wavelength), which hinders good imaging. On the other hand, if it falls below the lower limit of 2.0, on the contrary, the chromatic aberration of the magnification of the on-axis light and the off-axis light becomes insufficiently corrected (increases in the short wavelength (−) direction with respect to the reference wavelength). Here, it is desirable to set this condition in the range of 3.0 <νd4 / νd5 <4.0 because good imaging performance can be obtained.

Conditional expression 7: 45.0 <νd2
Conditional expression 7 is for maintaining good chromatic aberration over the near-ultraviolet ray λ = 385 nm to the near-infrared ray λ = 850 nm. If this condition is not met, chromatic aberration increases in the (−) direction for near-ultraviolet rays and in the (+) direction for near-infrared rays with respect to the reference wavelength, making color correction in a wide wavelength band difficult.

Conditional expression 8: 35.0 <νd1
The conditional expression 8 defines the Abbe number of the first lens (L1) constituting the first group. This is related to the correction of chromatic aberration in a wide wavelength band, and if this condition is not met, the amount of deviation of the imaging point in the wavelength band related to the near-infrared λ = 400 nm to the near-infrared λ = 850 nm with respect to the reference wavelength λ = 546 nm. Increases, and the axial chromatic aberration when the visible light is satisfactorily corrected increases in the (-) direction in the near-infrared ray and in the (+) direction in the near-infrared ray. Further, the chromatic aberration of magnification also increases in the (−) direction in the near ultraviolet rays and in the (+) direction in the near infrared rays, which makes it unsuitable for the development of the wide wavelength band type lens which is the object of the present invention. This condition,
40.0 <νd1
This is desirable because good optical characteristics can be obtained.

It is explanatory drawing which shows the structure of the lens optical system of the wide-angle lens of Example 1 to which this invention was applied. It is an aberration diagram of the wide-angle lens of Example 1. FIG. It is explanatory drawing which shows the structure of the lens optical system of the wide-angle lens of Example 2 to which this invention was applied. It is an aberration diagram of the wide-angle lens of Example 2. (A) and (b) are lists showing the lens data of the wide-angle lenses of Examples 1 and 2, and (c) is a list showing the values of each conditional expression of the wide-angle lenses of Examples 1 and 2. ..

Hereinafter, examples of a wide-angle lens to which the present invention is applied will be described with reference to the drawings.

1A and 2A are block diagrams of wide-angle lenses according to Examples 1 and 2 of the present invention, and FIGS. 1B and 2B are aberration diagrams of wide-angle lenses of Examples 1 and 2. As shown in FIGS. 1A and 2A, the basic configurations of the wide-angle lenses 50 and 60 of Examples 1 and 2 are the same, and the first lens L1 and the second lens L2 are directed from the object side to the image plane side. The third lens L3, the fourth lens L4, and the fifth lens L5 are arranged in this order. The diaphragm 6 is arranged on the object side of the second lens L2. Further, a low-pass filter (not shown) and a cover glass 7 are arranged between the fifth lens L5 and the image plane IM (light receiving surface of the light receiving element).

The first lens L1 is a glass spherical lens having a negative power with a convex surface facing the object side. The second lens L2 is a glass spherical lens having a positive power. The third lens L3 is a plastic aspherical lens having a positive or negative power and having an aspherical surface. The fourth lens L4 is a glass spherical lens having a positive power. The fifth lens L5 is a glass spherical lens having a negative power.

The meanings of the respective symbols in Examples 1 and 2 are as follows.
f: Focal length of the entire imaging lens Fno: F number f1: Focal length of the first lens f2: Focal length of the second lens f3: Focal length of the third lens f4: Focal length of the fourth lens f5: Fifth lens Focal length ω: Half-angle i: Surface number of the lens surface counted from the object side (Asterisk "*" after the surface number indicates that it is an aspherical surface)
r: Radius of curvature d: Distance between lens surfaces on the optical axis (plane spacing)
nd: Refractive index νd1 to νd5: Abbe number for the d-line of the first to fifth lenses νd6: Abbe number for the d-line of the cover glass

Here, in FIGS. 1A and 1A, the surface numbers i of the lens surfaces counted from the object side are shown as (1), (2), (3), and so on. An asterisk "*" after the surface number indicates that it is an aspherical surface. Further, the distance d (plane spacing) between the lens surfaces on the optical axis is shown as d1, d2, d3 ... In order from the object side.

Further, in the wide-angle lenses 50 and 60 of each embodiment, the shapes adopted for the aspherical surface of the lens surface are Z for the axis in the optical axis direction, H for the height in the direction orthogonal to the optical axis, K for the conical coefficient, and aspherical surface. When the coefficients are A4, A6, A8, A10, A12, and A14, it is expressed by the following formula.

<Lens data of each example>
The lens data of the wide-angle lenses 50 and 60 of Examples 1 and 2 are shown below.

非球面データ
第６面
Ｋ＝０．０
Ａ４＝−３．０６８７９４Ｅ−０３
Ａ６＝４．０４１３３６Ｅ−０４
Ａ８＝−５．０８２８７３Ｅ−０４
Ａ１０＝６．０４６１２８Ｅ−０５

第７面
Ｋ＝０．０
Ａ４＝−１．２０６４３７Ｅ−０３
Ａ６＝６．１１９５５２Ｅ−０４
Ａ８＝−３．４５７３３５Ｅ−０４
Ａ１０＝３．２８３９９３Ｅ−０５ (Lens data of Example 1)
f = 2.957 mm, Fno = 2.2, ω = 75.0 °
f1 = -3.0966 mm
f2 = 5.5556 mm
f3 = -1722.8500 mm
f4 = 4.6037 mm
f5 = -6.085mm
f45 = 16.9501 mm
d 23 = 3.8434 mm = (d2 + d3)

Aspherical data 6th surface K = 0.0
A4 = -3.068794E-03
A6 = 4.041336E-04
A8 = -5.082873E-04
A10 = 6.046128E-05

Side 7 K = 0.0
A4 = -1.206437E-03
A6 = 6.119552E-04
A8 = -3.457335E-04
A10 = 3.283939E-05

非球面データ
第６面
Ｋ＝１．２０４８８６
Ａ４＝−９．６９６７２８Ｅ−０３
Ａ６＝６．４４３７２２Ｅ−０４
Ａ８＝−５．２０２７４８Ｅ−０４
Ａ１０＝８．２２９６７２Ｅ−０５

第７面
Ｋ＝４．９５６８５２Ｅ−０１
Ａ４＝−１．２９６８４９Ｅ−０３
Ａ６＝９．８１１１６５Ｅ−０４
Ａ８＝−１．０８５０１５Ｅ−０４
Ａ１０＝１．１５５０３１Ｅ−０５
Ａ１２＝２．８３１３０６Ｅ−０６ (Lens data of Example 2)
f = 3.100 mm, Fno = 2.2, ω = 65.3 °
f1 = -3.0529mm
f2 = 4.3975mm
f3 = 103.9513mm
f4 = 5.0760mm
f5 = -5.9188 mm
f45 = 25.3750mm
d 23 = 3.9878 mm = (d2 + d3)

Aspherical data 6th surface K = 1.204886
A4 = -9.696728E-03
A6 = 6.443722E-04
A8 = -5.202748E-04
A10 = 8.229672E-05

7th surface K = 4.965852E-01
A4 = -1.296849E-03
A6 = 9.811165E-04
A8 = -1.085015E-04
A10 = 1.155031E-05
A12 = 2.831306E-06

(Action effect)
1B and 2B show the aberrations of the wide-angle lenses 50 and 60 of Examples 1 and 2. Further, FIGS. 3 (a) and 3 (b) collectively show the main lens data of the wide-angle lenses 50 and 60 of Examples 1 and 2, and FIG. 3 (c) shows each conditional expression (1) in each of the examples. ) To (8) are shown.

As can be seen from these figures, the wide-angle lenses 50 and 60 of Examples 1 and 2 satisfy all of the conditional equations 1 to 8 and have a wide wavelength band (near ultraviolet rays λ = 385 nm to near infrared rays λ = 900 nm). It was confirmed that good imaging performance can be obtained for each wavelength.

50, 60 Wide-angle lens L1 1st lens L2 2nd lens L3 3rd lens L4 4th lens L5 5th lens IM Imaging surface 6 Aperture 7 Cover glass (1) to (12) Lens surface surface numbers d1 to d6 Optical Distance between lens surfaces on the axis (plane spacing)
d23 Lens spacing between the first lens and the second lens

Claims (6)

From the object side to the image plane side,
The first lens, which has a negative power and has a convex surface facing the object side,
The second lens with positive power and
A third lens with positive or negative power with an aspherical surface,
The 4th lens with positive power and
The fifth lens with negative power is arranged in this order,
The focal length of the entire lens system is f, the focal length of the first to fifth lenses is f1 to f5, the lens spacing between the first lens and the second lens is d2, and the d line of the first to fifth lenses. If the Abbe number for is νd1 to νd5,
Conditional expression 1: -2.5 <f1 / f <-0.5
Conditional expression 2: 1.0 <f2 / f <4.0
Conditional expression 3:18 << | f3 / f |
Conditional expression 4: 0.7 << f4 / f5 | <1.5
Conditional expression 5: 1.0 <d2 / f <4.0
Conditional expression 6: 2.0 <νd4 / νd5 <5.0
Conditional expression 7: 45.0 <νd2
Conditional expression 8: 35.0 <νd1
A wide-angle lens characterized by satisfying. In the wide-angle lens according to claim 1,
The first, second, fourth and fifth lenses are glass spherical lenses.
The third lens is a wide-angle lens which is a plastic aspherical lens. In the wide-angle lens according to claim 1 or 2.
The value of f2 / f satisfying the conditional expression 2 is
2.0 <f2 / f <3.5
Wide-angle lens that is a value within the range of. In the wide-angle lens according to claim 1, 2 or 3.
The value of | f3 / f | that satisfies the conditional expression 3 is
22.0 << | f3 / f |
Wide-angle lens that is a value within the range of. In the wide-angle lens according to any one of claims 1 to 4.
The value of νd4 / νd5 that satisfies the conditional expression 6 is
3.0 <νd4 / νd5 <4.0
Wide-angle lens that is a value within the range of. In the wide-angle lens according to any one of claims 1 to 5.
The value of νd1 satisfying the conditional expression 8 is
40.0 <νd1
Wide-angle lens that is a value within the range of.

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