JP2016102897A - Wide-angle lens, lens barrel, and optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wide-angle lens which offers reduced size, weight and cost and increased view angle (preferably 140 degrees or greater), secures back focus, and suppresses back focus variation with temperature variation.SOLUTION: A wide-angle lens comprises a first lens group G1 having negative refractive power, an aperture stop SD having a prescribed diameter, and a second lens group G2 having positive refractive power arranged in order from the object side, the first and second lens groups having plastic lenses, and is configured to satisfy a conditional expression: 0<[Σ(Ki/fi)]/f<0.5, where fi represents a focal length of each lens constituting the first and second lens group, Ki represents a linear expansion coefficient of each lens constituting the first and second lens groups, and f represent a focal length of the entire lens system. An increased view angle, secured back focus, and suppression of back focus variation with temperature are thus realized.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a wide-angle lens and a lens barrel used in an optical apparatus such as a digital camera using a solid-state imaging device such as a CCD, and more particularly to a digital single-lens reflex camera, a mirrorless single-lens reflex camera, or a silver salt film. The present invention relates to a wide-angle lens and a lens barrel applied to a lens optical system such as a camera.

In recent years, in a compact digital camera, a digital single-lens reflex camera, a mirrorless single-lens reflex camera, and the like, an interchangeable lens camera that can freely exchange a lens (lens barrel) according to various shooting scenes has become mainstream. If these interchangeable lenses (lens barrels) are small and light, they can be easily carried and the burden on the user can be reduced.
Therefore, in interchangeable lenses (particularly, lens barrels equipped with wide-angle lenses), the lens diameter is reduced or the lens barrel is resinized while reducing the outer diameter, thereby reducing the size (downsizing), reducing the weight, and reducing the cost. In addition, when a lens or a lens barrel is made of resin, it is desired to suppress a change in a focus imaging position (back focus) due to a change in environmental temperature.

On the other hand, the conventional wide-angle lens includes a first lens group having a negative refractive power, an aperture stop, and a second lens group having a positive refractive power, which are arranged in order from the object side. The lens group is composed of two negative meniscus lenses arranged in order from the object side, two concave lenses, a cemented lens in which a negative meniscus lens and a biconvex lens are cemented, and a cemented lens in which a biconcave lens and a biconvex lens are cemented. The second lens group is arranged in order from the object side, and consists of a front group and a rear group that moves in focus with respect to the front group, and the front group is a cemented lens in which a biconvex lens and a biconcave lens are cemented, It consists of a biconvex lens, and the rear group consists of a cemented lens in which a biconcave lens and a biconvex lens are cemented, and a cemented lens in which a biconvex lens and a negative meniscus lens are cemented. , F2 Those having about 8 of large diameter are known (e.g., see Patent Document 1).
In this wide-angle lens, since the back focus is sufficiently secured, it can be applied to a digital single-lens reflex camera or the like, but the foremost lens (front lens) has a large diameter, and the number of lenses is large. All glass lenses and focusing mechanism are used, so it meets the demands for compactness (miniaturization), weight reduction, and cost reduction that can be easily carried and replaced. It is not possible.

The other wide-angle lens includes a first lens group having a negative refractive power, an aperture stop, and a second lens group having a positive refractive power, which are arranged in order from the object side. Is composed of a negative meniscus lens and a biconvex lens arranged in order from the object side, and the second lens group is composed of a biconvex lens and a cemented lens in which a biconvex lens and a biconcave lens are cemented. A field angle of about 80 to 90 degrees and a large aperture of about F2.0 are known (see, for example, Patent Document 2).
This wide-angle lens has five lenses and is more compact than the 15-lens wide-angle lens described above, but the foremost lens (front lens) has a larger diameter and is made of all glass lenses. It is used, and the angle of view is about 80 to 90 degrees, and the back focus is not enough, and it may be applicable as an in-vehicle camera or surveillance camera, but it is applicable to digital single-lens reflex cameras, etc. It is difficult to do.

Furthermore, as another wide-angle lens, the first lens group, the aperture stop, and the second lens group, which are arranged in order from the object side, are arranged, and the first lens group is arranged in order from the object side. 2 groups consisting of a negative meniscus lens, a biconcave lens, and a biconvex (or positive) lens, and a second lens group comprising a cemented lens and a biconvex lens in which a biconcave lens and a biconvex lens (or a biconvex lens and a biconcave lens) are cemented. A structure in which six lenses are used and two lenses (second lens and sixth or third lens) are formed of plastic (resin) is known (for example, see Patent Document 3). .
In this wide-angle lens, the number of lenses is 6, and the number of lenses is increased by one compared to the above-mentioned wide-angle lens of 5 lenses, the front lens (front lens) has a larger diameter, and the back focus is increased. However, it is difficult to apply it to a digital single-lens reflex camera or the like although it may be applicable as an in-vehicle camera or a surveillance camera.

JP 2005-316398 A JP 2009-75141 A JP-A-2005-221920

  The present invention has been made in view of the above circumstances, and its object is to achieve a wide diagonal angle of view while achieving compactness (miniaturization), weight reduction, cost reduction, and the like (preferably Wide angle lens that can secure a sufficient back focus, suppress fluctuations in the back focus with respect to environmental temperature changes, correct various aberrations, and is high performance, compact, and inexpensive. Another object is to provide a lens barrel and an optical apparatus.

The wide-angle lens of the present invention includes a first lens group having a negative refractive power, an aperture stop having a predetermined aperture, and a second lens group having a positive refractive power, which are arranged in order from the object side. The first lens group or the second lens group includes a plastic lens, and the focal length of each lens constituting the first lens group and the second lens group is fi, and each of the first lens group and the second lens group is configured. When the lens linear expansion coefficient is Ki and the focal length of the entire lens system is f, the following conditional expression (1)
(1) 0 <[Σ (Ki / fi)] / f <0.5
It is characterized by satisfying.
According to this configuration, in the entire lens system including the plastic lens, by satisfying the conditional expression (1), desired optical characteristics can be ensured while achieving weight reduction, size reduction, cost reduction, and the like. Ensures back focus and suppresses back focus fluctuations with respect to environmental temperature changes (specifically, it suppresses fluctuations in lens curvature, thickness, refractive index, etc. to reduce back focus fluctuations) In particular, it can be applied as an interchangeable lens that can be easily replaced in a digital single-lens reflex camera, a mirrorless single-lens reflex camera, or the like.

The lens surface of the lens used in the wide-angle lens of the present invention may be formed as a spherical surface, a flat surface, or an aspheric surface. It is preferable that the lens surface is a spherical surface or a flat surface because lens processing and assembly adjustment are facilitated, and deterioration of optical performance due to errors in processing and assembly adjustment can be prevented. When the lens surface is aspherical, any aspherical surface by grinding, a glass mold aspherical surface in which glass is formed into an aspherical shape, or a composite aspherical surface in which resin is formed in an aspherical shape on the glass surface It doesn't matter. If necessary, the lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or the like.
Also, in the entire lens system, the lens located on the outermost side (frontmost, rearmost) may be exposed to the outside during use, so various processing can be performed as necessary. It is. As an example of this processing, the surface portion may be hydrophilized with a photocatalyst or the like in order to prevent the lens body from fogging or water droplet formation.

In the wide-angle lens configured as described above, when the focal length of the plastic lens is fp and the focal length of the entire lens system is f, the following conditional expression (2)
(2) 0 <1 / fp <0.1
A configuration that satisfies the above can be adopted.
According to this configuration, by satisfying the conditional expression (2), in addition to the configuration satisfying the conditional expression (1), the back focus variation amount can be further suppressed with respect to the environmental temperature change (specifically, Can suppress fluctuations in the curvature, thickness, refractive index, and the like of the plastic lens, thereby minimizing fluctuations in the back focus.

In the wide-angle lens configured as described above, when the focal length of the first lens unit is f _G1 and the focal length of the entire lens system is f, the following conditional expression (3)
(3) -1.0 <f _G1 /f<-0.7
A configuration that satisfies the above can be adopted.
According to this configuration, by satisfying conditional expression (3), a sufficient back focus can be secured, and various aberrations, particularly field curvature and astigmatism can be corrected well.

In the wide-angle lens having the above configuration, when the distance on the optical axis from the object side surface of the first lens unit to the image plane on the optical axis is TL and the focal length of the entire lens system is f, the following conditional expression (4)
(4) 0.28 <f / TL <0.35
A configuration that satisfies the above can be adopted.
According to this configuration, by satisfying conditional expression (4), various aberrations can be corrected favorably, and downsizing (compacting) can be achieved. That is, conditional expression (4) is a conditional expression for defining the ratio of the focal length f of the entire lens system and the total length TL of the entire lens system in the optical axis direction (determining the size of the entire lens system). When the value of f / TL satisfies the upper limit value, various aberrations can be corrected favorably, and when the value of f / TL satisfies the lower limit value, downsizing (compacting) can be achieved.

In the wide-angle lens having the above configuration, the first lens group includes a first lens having a negative refractive power and a second lens having a positive refractive power, which are arranged in order from the object side. Is composed of a third lens having a positive refractive power, a fourth lens having a positive refractive power, and a fifth lens having a negative refractive power, which are arranged in order from the object side. A configuration that is a plastic lens can be adopted.
According to this configuration, by adopting a two-group five-lens configuration and employing a negative lens having a negative refractive power as the first lens and a plastic lens having a positive refractive power as the second lens, the above conditional expression ( In addition to the configuration satisfying 1) to (4) and the like, a wide angle of view (preferably a wide angle of view of 140 degrees or more can be secured) and a digital single-lens reflex camera equipped with an image sensor such as a CCD It is possible to secure a sufficiently long back focus to be applied, and by making the second lens a plastic lens, it achieves weight reduction and cost reduction, but also against environmental temperature changes A lens arrangement that can suppress the amount of back focus fluctuation can be obtained, various aberrations can be corrected well, and the entrance pupil position is positioned on the object side by using the lens arrangement described above. The height of the off-axis light beam incident on the first lens can be reduced, and therefore the effective diameter (ie, the outer diameter) of the first lens (front lens) can be reduced. Can be achieved.

In the wide-angle lens having the above configuration, the second lens and the third lens can adopt a configuration in which at least one of the object side and the image plane side is formed as an aspherical surface.
According to this configuration, by providing the aspherical surfaces on the second lens and the third lens adjacent to the aperture stop, particularly the spherical aberration and the coma aberration can be favorably corrected, and the height of the light ray incident on the first lens is increased. It is possible to achieve a reduction in size and a reduction in size (compression) while achieving a wide angle of view.

In the wide-angle lens having the above configuration, a configuration in which the fourth lens and the fifth lens are cemented lenses can be employed.
According to this configuration, by using the fourth lens and the fifth lens as a cemented lens, it is possible to particularly favorably correct chromatic aberration (axial chromatic aberration, lateral chromatic aberration) while achieving downsizing (compacting). .

In the wide-angle lens configured as described above, when the radius of curvature of the object side surface of the first lens is R1 and the radius of curvature of the image side surface is R2, the following conditional expression (5)
(5) 1.4 <(R1 + R2) / (R1-R2) <1.8
A configuration that satisfies the above can be adopted.
According to this configuration, by satisfying conditional expression (5), it is possible to secure a large angle of view of 140 degrees or more while suppressing an increase in the diameter of the first lens.

In the wide-angle lens having the above configuration, when the Abbe number of the first lens is ν1, the Abbe number of the fourth lens is ν4, and the Abbe number of the fifth lens is ν5, the following conditional expression (6)
(6) ν1 ≧ 45, ν4 ≧ 50, ν5 ≦ 30
A configuration that satisfies the above can be adopted.
According to this configuration, it is possible to satisfactorily correct chromatic aberration that affects resolution, that is, axial chromatic aberration and lateral chromatic aberration.

In the wide-angle lens having the above configuration, the first lens is a concave meniscus lens having a convex surface facing the object side and a concave surface facing the image surface side, and the second lens has a convex surface facing the object side and a convex surface facing the image surface side. Alternatively, the third lens is a biconvex lens or convex meniscus lens having a convex surface facing the object side and a convex surface facing the image surface side, and the fourth lens is a biconvex lens or convex meniscus lens having a concave surface. A biconvex lens or convex meniscus lens having a convex surface or concave surface facing the object side and a convex surface facing the image surface side, and the fifth lens is a concave meniscus lens having the concave surface facing the object side and the convex surface facing the image surface side. Certain configurations can be employed.
According to this configuration, by adopting the lenses having the above-described forms as the first lens to the fifth lens, the diagonal angle of view is achieved while achieving compactness (miniaturization), weight reduction, cost reduction, and the like. Wide (preferably 140 degrees or more), sufficient back focus can be secured, fluctuation amount of back focus can be suppressed against environmental temperature change, various aberrations are corrected well, high performance and small size An inexpensive wide-angle lens can be obtained.

In the wide-angle lens having the above-described configuration, the first lens and the fifth lens may be glass lenses.
According to this configuration, the first lens and the fifth lens located on the outermost side (frontmost and rearmost) in the entire lens system are made of glass lenses, thereby preventing deterioration of quality and performance due to dirt or scratches. Thus, the desired optical characteristics can be maintained. In other words, the outermost lens is more likely to become dirty or scratched when exposed to the external environment, for example, when sold in the market or when used, so there is a need to prevent deterioration in quality and performance. From this point of view, it is preferable to employ a glass lens.

The lens barrel of the present invention is a lens barrel including any one of the wide-angle lenses configured as described above and a lens barrel that holds the wide-angle lens, and the lens barrel is formed of a resin material. It is characterized by that.
According to this configuration, by combining the wide-angle lens having the above-described configuration and a resin lens barrel, a back focus variation amount due to a temperature change of the wide-angle lens including the plastic lens can be reduced. The lens barrel can be configured so as to cancel out with the amount of back focus fluctuation caused by the change in the interval, and the amount of change in the focus imaging position can be reduced over a wide range of temperature changes.
The method of combining the wide-angle lens and the lens barrel is performed by, for example, heat caulking, adhesion with an adhesive, insertion of a known presser ring or C ring.

In the lens barrel having the above-described configuration, the linear expansion coefficient in the temperature range of −40 ° C. to + 85 ° C. of the plastic lens included in the wide-angle lens is 60 to 70 (× 10 ⁻⁶ / ° C.). A configuration in which a linear expansion coefficient in a temperature range of ˜ + 85 ° C. is 60 to 70 (× 10 ⁻⁶ / ° C.) can be adopted.
According to this configuration, in a wide temperature range (for example, −40 ° C. to + 85 ° C.), the focus shift amount is within the range of −0.02 mm to +0.02 mm, and the focus shift amount is within the depth of field. A suppressed lens barrel can be obtained.

An optical apparatus according to the present invention includes any one of the wide-angle lenses configured as described above, or includes any one of the wide-angle lenses configured as described above and a resin barrel that holds the wide-angle lens. .
According to these configurations, while achieving downsizing (miniaturization), weight reduction, cost reduction, etc., the diagonal angle of view is wide (preferably 140 degrees or more), the back focus can be sufficiently secured, and the environmental It is possible to provide a high-performance, small, and inexpensive optical apparatus that can suppress the amount of back focus fluctuation with respect to a temperature change, correct various aberrations satisfactorily.
That is, the wide-angle lens and the lens barrel having the above-described configuration are, for example, optical devices such as cameras (consumer cameras such as digital cameras, in-vehicle cameras, surveillance cameras, endoscope cameras, medical cameras mounted on video cameras, and video shooting). It can be used for camcorders (movie cameras), various inspection cameras, robot cameras, and the like.

  According to the wide-angle lens having the above-described configuration, the diagonal angle of view is wide (preferably 140 degrees or more) and the back focus can be sufficiently secured while achieving compactness (miniaturization), weight reduction, and cost reduction. A high-performance, compact, and inexpensive wide-angle lens that can suppress back focus fluctuations with respect to environmental temperature changes and that corrects various aberrations can be obtained. A lens barrel and an optical instrument can be obtained.

It is a schematic block diagram which shows one Embodiment of the wide angle lens which concerns on this invention. FIG. 3 is an aberration diagram showing spherical aberration, astigmatism, and distortion (distortion) in the wide-angle lens (Example 1) shown in FIG. 1. It is a schematic block diagram which shows other embodiment of the wide angle lens which concerns on this invention. FIG. 4 is an aberration diagram showing spherical aberration, astigmatism, and distortion (distortion) in the wide-angle lens (Example 2) shown in FIG. 3. It is a schematic block diagram which shows other embodiment of the wide angle lens which concerns on this invention. FIG. 6 is an aberration diagram showing spherical aberration, astigmatism, and distortion (distortion) in the wide-angle lens (Example 3) shown in FIG. 5. It is sectional drawing which shows one Embodiment of the lens-barrel which concerns on this invention. 5 is a graph showing, together with a comparative example, an amount of focus deviation with respect to a change in environmental temperature in a lens barrel equipped with a wide-angle lens according to the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
As shown in FIG. 1, the wide-angle lens according to this embodiment includes a first lens group G1 having a negative refractive power, an aperture stop SD having a predetermined aperture, and a second lens group G2 having a positive refractive power. Are arranged in order from the object side to the image plane side on the optical axis L.
Here, the first lens group G1 includes a first lens 1 having a negative refractive power and a second lens 2 having a positive refractive power, which are arranged in order from the object side, and the second lens group G2. Consists of a third lens 3 having a positive refractive power, a fourth lens 4 having a positive refractive power, and a fifth lens 5 having a negative refractive power, which are arranged in order from the object side.
Further, in the above configuration, a glass filter 6 as a parallel plate (which hardly generates power) serving as an infrared cut filter, a low-pass filter or the like is disposed behind the fifth lens 5 (closer to the image plane side). An image plane P (which is an imaging plane such as a CCD as a solid-state imaging device) is disposed behind the glass filter 6.

Here, the first lens 1, the second lens 2, the aperture stop SD, the third lens 3, the fourth lens 4, the fifth lens 5, the glass filter 6, and the image plane P are along the optical axis L on the object side. 1, the respective surfaces are Si (i = 1 to 12) and the curvature radii of the respective surfaces Si are Ri (i = 1 to 12). ), The refractive index with respect to the d-line is Ni (i = 1 to 6), the Abbe number is νi (i = 1 to 6), and the distance (thickness) on each optical axis L from the first lens 1 to the image plane P , The air interval) is Di (i = 1 to 12), the back focus (air conversion distance) from the image plane side surface S10 to the image plane P of the fifth lens 5 is BF, and the foremost lens of the first lens group G1 ( The distance on the optical axis L from the object-side surface S1 of the first lens 1) to the image plane P is represented by TL.
The focal length of the entire lens system is f, the focal length of the first lens group G1 (the combined focal length of the first lens 1 and the second lens 2) is f _G1 , and the first lens group G1 and the second lens group G2 are used. The focal length of each lens (the first lens 1 to the fifth lens 5) constituting the lens is fi (i = 1 to 5), and the focal length of the glass lens included in the first lens group G1 or the second lens group G2 is fp. (Here, fp = f2), the linear expansion coefficient of each lens (the first lens 1 to the fifth lens 5) constituting the first lens group G1 and the second lens group G2 is Ki (i = 1 to 5). Represent.

The first lens 1 is a glass lens formed of a glass material, and a concave meniscus lens in which the object-side surface S1 is convex and the image-side surface S2 is concave so as to have negative refractive power. It is. Here, the surface S1 and the surface S2 are formed as spherical surfaces.
The second lens 2 is a plastic lens formed of a resin material, and a convex meniscus lens in which the object-side surface S3 is convex and the image-side surface S4 is concave so as to have positive refractive power. It is. Here, the surface S3 and the surface S4 are formed as aspherical surfaces.
In the configuration diagram shown in FIG. 1, the aperture stop SD is disposed between the third lens 3 and the fourth lens 4 and close to the third lens 3 (near the surface S4), and has a predetermined aperture. Both are shown as a surface S5 and a radius of curvature R5 (∞).
The third lens 3 is a glass lens formed of a glass material, and is a biconvex lens in which the object side surface S6 is a convex surface and the image surface side surface S7 is a convex surface so as to have a positive refractive index. is there. Here, the surface S6 and the surface S7 are formed as aspherical surfaces.
The fourth lens 4 is a glass lens formed of a glass material, and is a biconvex lens in which the object side surface S8 is a convex surface and the image surface side surface S9 is a convex surface so as to have a positive refractive index. is there. Here, the surface S8 and the surface S9 are formed as spherical surfaces.
The fifth lens 5 is formed of a glass material and is bonded to the image surface side surface S9 of the fourth lens 4, and the object side surface S9 is concave and has an image surface side so as to have negative refractive power. The surface is a concave meniscus lens having a convex surface. Here, the surface S10 is formed as a spherical surface.

As described above, by using the fourth lens 4 and the fifth lens 5 as cemented lenses, it is possible to particularly favorably correct chromatic aberration (axial chromatic aberration, lateral chromatic aberration) while achieving downsizing (compacting). .
The second lens 2 and the third lens 3 have at least one surface on the object side and the image surface side (here, S3, S4, S6, S7) formed as an aspheric surface, that is, an aperture stop SD. By providing an aspherical surface on the second lens 2 and the third lens 3 adjacent to each other, particularly spherical aberration and coma aberration can be corrected well, and the height of light incident on the first lens 1 can be reduced. While achieving angle of view, downsizing (compacting) and the like can be achieved.

Here, a formula representing an aspheric surface provided in the second lens 2 and the third lens 3 is defined by the following formula.
Z = Cy ² / [1+ (1-εC ² y ² ) ^1/2 ] + Dy ⁴ + Ey ⁶ + Fy ⁸ + Gy ¹⁰
Where Z: distance from the tangent plane at the apex of the aspheric surface to a point on the aspheric surface whose height from the optical axis L is y, y: height from the optical axis, C: curvature at the apex of the aspheric surface ( 1 / R), ε: conic constant, D, E, F, G: aspherical coefficients.

In the wide-angle lens having the above-described configuration, the focal length fi (i = 1 to 5) of each lens (the first lens 1 to the fifth lens 5) constituting the first lens group G1 and the second lens group G2, the first The relationship between the linear expansion coefficient Ki (i = 1 to 5) of each lens (the first lens 1 to the fifth lens 5) constituting the lens group G1 and the second lens group G2 and the focal length f of the entire lens system is as follows. Conditional expression (1)
(1) 0 <[Σ (Ki / fi)] / f <0.5
It is formed so as to satisfy.
Conditional expression (1) defines the relationship between the sum Σ (Ki / fi) of values obtained by multiplying the reciprocal of the focal length of each lens by its linear expansion coefficient and the focal length f of the entire lens system. When the value of Σ (Ki / fi)] / f satisfies the above range, the amount of back focus fluctuation can be reduced with respect to environmental temperature changes.
That is, in the entire lens system including the plastic lens (here, the second lens 2), by satisfying the conditional expression (1), a desired optical characteristic can be obtained while achieving weight reduction, size reduction, cost reduction, and the like. It is possible to ensure a sufficient back focus, and it is possible to suppress a back focus fluctuation amount with respect to a change in environmental temperature.

In the wide-angle lens having the above-described configuration, the relationship between the focal length fp (= f2) of the plastic lens (here, the second lens 2) and the focal length f of the entire lens system is conditional expression (2).
(2) 0 <1 / fp <0.1
It is formed so as to satisfy.
Conditional expression (2) defines a value related to the reciprocal (1 / fp) of the focal length of the plastic lens (second lens 2). When the value of the reciprocal (1 / fp) satisfies the above range, In addition to the configuration satisfying the conditional expression (1), it is possible to further reduce the back focus fluctuation amount with respect to the environmental temperature change.

In the wide-angle lens having the above-described configuration, the focal length f _G1 of the first lens group _G1, and the lens relation total focal length f of the conditional expressions (3)
(3) -1.0 <f _G1 /f<-0.7
It is formed so as to satisfy.
Condition (3), the relationship between the focal length f _G1 and the lens focal length f of the first lens group G1, i.e., a conditional expression for defining the optimum power arrangement of the entire lens system, f _When the value of _G1 / f satisfies the upper limit, various aberrations, particularly field curvature and astigmatism can be corrected favorably, and when the value of _fG1 / f satisfies the upper limit, sufficient back focus is ensured. be able to.

In the wide-angle lens having the above-described configuration, the distance TL on the optical axis L from the object-side surface S1 to the image plane P of the foremost lens (first lens 1) of the first lens group G1, and the entire lens system The relationship of the focal length f is conditional expression (4)
(4) 0.28 <f / TL <0.35
It is formed so as to satisfy.
Conditional expression (4) is a conditional expression for defining the ratio of the focal length f of the entire lens system and the total length TL of the entire lens system in the optical axis direction (determining the size of the entire lens system), and f / When the value of TL satisfies the upper limit value, various aberrations can be corrected favorably, and when the value of f / TL satisfies the lower limit value, downsizing (compacting) can be achieved. That is, by satisfying conditional expression (4), it is possible to achieve downsizing (compacting) while satisfactorily correcting various aberrations.

In the wide-angle lens having the above configuration, the relationship between the curvature radius R1 of the object-side surface S1 and the curvature radius R2 of the image-side surface S2 of the first lens 1 is conditional expression (5).
(5) 1.4 <(R1 + R2) / (R1-R2) <1.8
It is formed so as to satisfy.
Conditional expression (5) defines the relationship between the curvature radii of both the object side and the image plane side of the front lens, and by satisfying conditional expression (5), the increase in diameter of the first lens 1 is suppressed. However, a large angle of view of 140 ° or more can be ensured.

Furthermore, in the wide-angle lens having the above-described configuration, the Abbe number ν1 of the first lens 1, the Abbe number ν4 of the fourth lens 4, and the Abbe number ν5 of the fifth lens 5 are conditional expressions (6).
(6) ν1 ≧ 45, ν4 ≧ 50, ν5 ≦ 30
It is formed so as to satisfy.
By satisfying conditional expression (6), it is possible to satisfactorily correct chromatic aberration that affects resolution, that is, longitudinal chromatic aberration and lateral chromatic aberration.

According to the wide-angle lens having the above configuration, the first lens 1 has a negative lens having a negative refractive power and the second lens 2 has a positive refractive power (plastic lens). ) To ensure an appropriate wide angle of view with a diagonal angle of 140 degrees or more, and by adopting a retrofocus type, a digital single-lens reflex camera equipped with an image sensor such as a CCD, etc. It is possible to ensure a sufficiently long back focus to be applied to the lens, and by making the second lens 2 a plastic plastic lens, it is possible to reduce the weight and cost while maintaining the environmental temperature. It is possible to obtain a lens arrangement that can suppress the variation amount of the back focus with respect to the change, and it is possible to satisfactorily correct various aberrations.
Further, by adopting the lens arrangement described above, the height of the off-axis light beam incident on the first lens 1 can be lowered by positioning the entrance pupil position on the object side, and therefore, the first lens 1 (front lens) can be reduced. Since the effective diameter (that is, the outer diameter) can be reduced, the diameter can be reduced, the size can be reduced (compacted), and the like.
Furthermore, the first lens 1 and the fifth lens 5 located on the outermost side (frontmost and rearmost) in the entire lens system are made of glass lenses to prevent deterioration of quality and performance due to dirt, scratches, etc. The desired optical properties can be maintained.

In the above configuration, examples of the lens material include crown glass and flint glass as the glass lens material, and examples of the plastic lens material include resin materials such as acrylic and polycarbonate. The linear expansion coefficient of the glass lens material is in the range of 1 to 10 (× 10 ⁻⁶ / ° C.), and the linear expansion coefficient of the plastic lens material is 60 to 70 (× 10 ⁻⁶ / ° C.). ) Is preferably applied.

  Next, a specific numerical example of the wide-angle lens having the above-described configuration is shown as Example 1 below.

The lens configuration of the wide-angle lens is as shown in FIG. 1, and the main specifications of the first lens 1 to the fifth lens 5 and the glass filter 6, various numerical data (setting values), conditional expressions (1) to The numerical data of (6) is as follows.
<Specification specifications>
Object distance (mm) → ∞
Focal length of whole lens system (mm) → f = 9.145
Focal length (mm) of the first lens group G1 → f _G1 = −6.7
Focal length (mm) of the first lens 1 to the fifth lens 5 → f1 = −4.298, f2 (fp) = 14.57, f3 = 9.271, f4 = 9.2, f5 = −13.151
Linear expansion coefficients (× 10 ^{−6 /} ° C.) of the first lens 1 to the fifth lens 5 → K1 = 5.9, K2 = 66, K3 = 5.8, K4 = 5.7, K5 = 8.8
F number = 8.0
Angle of view (2ω) = 146 °
Exit pupil position (mm: ∞) → −28.71
Back focus (mm: air conversion) → BF = 15.550
The light beam passing height of the lens is the minimum value (mm) → H1 = 6.4
Maximum ray passing height of lens (mm) → H5 = 11.6
Distance from object side surface S1 to image surface P of first lens 1 (mm: air conversion) → TL = 30.955

<Curvature radius: mm>
R1 = 12,000, R2 = 2.415, R3 = 8.065 (aspheric surface), R4 = 58.737 (aspheric surface), R5 (aperture stop) = ∞, R6 = 28.620 (aspheric surface), R7 = −5.413 (aspherical surface), R8 = 260.845, R9 = −6.5528, R10 = −16.444, R11 = ∞, R12 = ∞
<Spacing on the optical axis: mm>
D1 = 0.800, D2 = 1.170, D3 = 1.270, D4 = 0.150, D5 = 0.700, D6 = 4.900, D7 = 0.150, D8 = 4.250, D9 = 0.6, D10 = 11.955, D11 = 4.00, D12 = 1.0
<Refractive index (Nd)>
N1 = 1.73, N2 = 1.64, N3 = 1.52, N4 = 1.70, N5 = 1.85, N6 = 1.52
<Abbe number (νd)>
ν1 = 54.7, ν2 = 24.0, ν3 = 64.1, ν4 = 55.5, ν5 = 23.8, ν6 = 64.2

<Numerical data of aspheric coefficient>
<S3 surface>
ε = 1.0000000, D = 6.6925 × 10 ⁻⁴ , E = 0, F = 0, G = 0
<S4 surface>
ε = 1.0000000, D = −4.567 × 10 ⁻⁴ , E = 0, F = 0, G = 0
<S6 surface>
ε = 1.0000000, D = 2.8458 × 10 ⁻³ , E = −2.839 × 10 ⁻⁴ , F = 1.7536 × 10 ⁻⁵ , G = 0
<S7 surface>
ε = 1.0000000, D = 8.0000 × 10 ⁻⁴ , E = 2.7688 × 10 ⁻⁵ , F = 3.1006 × 10 ⁻⁶ , G = 0
<Outer diameter of lens: mm>
The outer diameter (diameter) of the first lens 1 → 7.8, the outer diameter (diameter) of the second lens 2 → 6.1, the outer diameter (diameter) of the third lens 3 → 9.0, Outer diameter (diameter) → 10.7, outer diameter (diameter) of the fifth lens 5 → 13.0
<Value of conditional expression>
(1) [Σ (Ki / fi)] / f = 0.408
(2) 1 / fp = 0.69
(3) f _G1 /f=−0.733
(4) f / TL = 0.298
(5) R1 + R2) / (R1-R2) = 1.504
(6) ν1 = 54.7, ν4 = 55.5, ν5 = 23.8

The aberration diagrams regarding the spherical aberration, astigmatism, and distortion in Example 1 are as shown in FIG. In FIG. 2, g is a g line, F is an F line, e is an e line, d is a d line, C is a C line, S is an aberration on a sagittal plane, and M is an aberration on a meridional plane.
According to the lens specifications according to the first embodiment, the back focus BF is 15.550 mm and the angle of view (2ω) is 146 degrees, so that the fluctuation amount of the back focus can be suppressed with respect to the environmental temperature change, and various aberrations are caused. A well-corrected high-performance, compact and inexpensive wide-angle lens can be obtained.

The lens configuration of the wide-angle lens is as shown in FIG. 3. Main specifications of the first lens 1 to the fifth lens 5 and the glass filter 6, various numerical data (setting values), conditional expressions (1) to The numerical data of (6) is as follows.
In this wide-angle lens, as shown in FIG. 3, the second lens 2 is a biconvex lens in which the object side surface S3 is a convex surface and the image surface side surface S4 is a convex surface. The fourth surface 4 is a convex meniscus lens in which the surface S6 on the side is concave and the surface S7 on the image side is convex, and the fourth lens 4 is a convex surface in which the surface S8 on the object side is concave and the surface S9 on the image side is convex. The meniscus lens is otherwise the same as the lens configuration (such as irregularities) shown in FIG.

<Specification specifications>
Object distance (mm) → ∞
Focal length of whole lens system (mm) → f = 9.148
Focal length (mm) of the first lens group G1 → f _G1 = −8.60039
Focal length (mm) of the first lens 1 to the fifth lens 5 → f1 = −4.944, f2 (fp) = 14.569, f3 = 8.596, f4 = 9.543, f5 = −12.432
Linear expansion coefficient (× 10 ^{−6 /} ° C.) of the first lens 1 to the fifth lens 5 → K1 = 5.7, K2 = 66, K3 = 5.8, K4 = 5.7, K5 = 8.8
F number = 7.98
Angle of view (2ω) = 147 °
Exit pupil position (mm: ∞) → -25.048
Back focus (mm: air conversion) → BF = 14.87
The light beam passing height of the lens is the minimum value (mm) → H1 = 6.4
Maximum ray passing height of lens (mm) → H5 = 10.6
Distance from object side surface S1 to image surface P of first lens 1 (mm: air conversion) → TL = 27.89

<Curvature radius: mm>
R1 = 10.253, R2 = 2.496, R3 = 12.379 (aspherical surface), R4 = -35.479 (aspherical surface), R5 (aperture stop) = ∞, R6 = -53.158 (aspherical surface) ), R7 = −4.179 (aspherical surface), R8 = −36.306, R9 = −5.830, R10 = −13.737, R11 = ∞, R12 = ∞
<Spacing on the optical axis: mm>
D1 = 0.800, D2 = 1.240, D3 = 1.070, D4 = 0.150, D5 = 1.190, D6 = 3.150, D7 = 0.100, D8 = 3.300, D9 = 0.650, D10 = 11.150, D11 = 4.00, D12 = 1.0
<Refractive index (Nd)>
N1 = 1.70, N2 = 1.64, N3 = 1.52, N4 = 1.70, N5 = 1.85, N6 = 1.52
<Abbe number (νd)>
ν1 = 55.5, ν2 = 24.0, ν3 = 64.1, ν4 = 55.5, ν5 = 23.8, ν6 = 64.2

<Numerical data of aspheric coefficient>
<S3 surface>
ε = 1.0000000, D = −3.512 × 10 ⁻³ , E = 0, F = 0, G = 0
<S4 surface>
ε = 1.0000000, D = −3.878 × 10 ⁻³ , E = 0, F = 0, G = 0
<S6 surface>
ε = 1.0000000, D = 4.5556 × 10 ⁻⁴ , E = −2.861 × 10 ⁻⁴ , F = 0, G = 0
<S7 surface>
ε = 1.0000000, D = 7.5202 × 10 ⁻⁴ , E = 9.9988 × 10 ⁻⁵ , F = 0, G = 0
<Outer diameter of lens: mm>
The outer diameter (diameter) of the first lens 1 → 7.8, the outer diameter (diameter) of the second lens 2 → 6.1, the outer diameter (diameter) of the third lens 3 → 8.5, Outer diameter (diameter) → 9.7, outer diameter (diameter) of the fifth lens 5 → 12.0
<Value of conditional expression>
(1) [Σ (Ki / fi)] / f = 0.431
(2) 1 / fp = 0.69
(3) f _G1 /f=−0.941
(4) f / TL = 0.328
(5) R1 + R2) / (R1-R2) = 1.644
(6) ν1 = 55.5, ν4 = 55.5, ν5 = 23.8

The aberration diagrams relating to spherical aberration, astigmatism, and distortion (distortion) in Example 2 are as shown in FIG. In FIG. 4, g is a g line, F is an F line, e is an e line, d is a d line, C is a C line, S is an aberration on the sagittal plane, and M is an aberration on the meridional plane.
According to the lens specifications according to the second embodiment, the back focus BF is 14.87 mm and the angle of view (2ω) is 147 degrees, and the amount of fluctuation of the back focus can be suppressed with respect to the environmental temperature change. A well-corrected high-performance, compact and inexpensive wide-angle lens can be obtained.

The lens configuration of the wide-angle lens is as shown in FIG. 5. The main specifications of the first lens 1 to the fifth lens 5 and the glass filter 6, various numerical data (setting values), conditional expressions (1) to The numerical data of (6) is as follows. 5 is the same as the wide-angle lens shown in FIG. 1 (irregularities etc.).
<Specification specifications>
Object distance (mm) → ∞
Focal length of whole lens system (mm) → f = 9.149
Focal length (mm) of first lens group G1 → f _G1 = −6.7392
Focal length (mm) of the first lens 1 to the fifth lens 5 → f1 = −4.298, f2 (fp) = 14.569, f3 = 8.596, f4 = 9.543, f5 = −12.432
Linear expansion coefficient (× 10 ^{−6 /} ° C.) of the first lens 1 to the fifth lens 5 → K1 = 6.2, K2 = 66, K3 = 5.8, K4 = 7.2, K5 = 8.3
F number = 8.0
Angle of view (2ω) = 142 °
Exit pupil position (mm: ∞) → −28.69
Back focus (mm: air conversion) → BF = 15.55
Minimum value (mm) of light beam passing through lens → H1 = 6.2
Maximum ray passing height of lens (mm) → H5 = 11.6
Distance from the object-side surface S1 to the image plane P of the first lens 1 (mm: air conversion) → TL = 30.963

<Curvature radius: mm>
R1 = 9.852, R2 = 2.395, R3 = 8.899 (aspherical surface), R4 = 216.959 (aspherical surface), R5 (aperture stop) = ∞, R6 = 33.425 (aspherical surface), R7 = −5.329 (aspherical surface), R8 = 166.586, R9 = −6.696, R10 = −17.244, R11 = ∞, R12 = ∞
<Spacing on the optical axis: mm>
D1 = 0.800, D2 = 1.165, D3 = 1.260, D4 = 0.150, D5 = 0.690, D6 = 4.880, D7 = 0.150, D8 = 4.300, D9 = 0.6, D10 = 11.828, D11 = 4.14, D12 = 1.0
<Refractive index (Nd)>
N1 = 1.73, N2 = 1.64, N3 = 1.52, N4 = 1.70, N5 = 1.85, N6 = 1.52
<Abbe number (νd)>
ν1 = 49.6, ν2 = 24.0, ν3 = 63.8, ν4 = 55.3, ν5 = 22.8, ν6 = 64.2

<Numerical data of aspheric coefficient>
<S3 surface>
ε = 1.0000000, D = 4.8363 × 10 ⁻⁴ , E = −9.195 × 10 ⁻⁵ , F = 5.2639 × 10 ⁻⁵ , G = 0
<S4 surface>
ε = 1.0000000, D = -4.607 × 10 ⁻⁴ , E = 1.4603 × 10 ⁻⁴ , F = 1.8636 × 10 ⁻⁴ , G = 0
<S6 surface>
ε = 1.0000000, D = 3.2828 × 10 ⁻³ , E = −4.038 × 10 ⁻⁴ , F = 3.6290 × 10 ⁻⁵ , G = 0
<S7 surface>
ε = 1.0000000, D = 8.6833 × 10 ⁻⁴ , E = 2.9622 × 10 ⁻⁵ , F = 3.4541 × 10 ⁻⁶ , G = 0
<Outer diameter of lens: mm>
The outer diameter (diameter) of the first lens 1 → 7.6, the outer diameter (diameter) of the second lens 2 → 6.0, the outer diameter (diameter) of the third lens 3 → 9.0, Outer diameter (diameter) → 10.7, outer diameter (diameter) of the fifth lens 5 → 13.0
<Value of conditional expression>
(1) [Σ (Ki / fi)] / f = 0.421
(2) 1 / fp = 0.69
(3) f _G1 /f=−0.737
(4) f / TL = 0.295
(5) R1 + R2) / (R1-R2) = 1.443
(6) ν1 = 49.6, ν4 = 55.3, ν5 = 22.8

The aberration diagrams regarding the spherical aberration, astigmatism, and distortion in Example 3 are as shown in FIG. In FIG. 6, g is a g line, F is an F line, e is an e line, d is a d line, C is a C line, S is an aberration on the sagittal plane, and M is an aberration on the meridional plane.
According to the lens specification according to the first embodiment, the back focus BF is 15.55 mm, the field angle (2ω) is 142 degrees, and the amount of fluctuation of the back focus can be suppressed with respect to the environmental temperature change. A well-corrected high-performance, compact and inexpensive wide-angle lens can be obtained.

FIG. 7 shows a lens barrel in which the wide-angle lens having the above configuration is mounted on the lens barrel 10. Here, the first lens 1 to the fifth lens 5 constituting the wide-angle lens are plastic lenses in which the second lens 2 is formed of a resin material as shown in the first to third embodiments. It is the glass lens formed using.
The lens barrel 10 is formed using a resin material. Here, as the resin material forming the lens barrel 10, resin materials such as polycarbonate, polymethyl methacrylate, polyethylene, polypropylene, polyvinyl chloride, polystyrene, acrylonitrile butadiene styrene, and the like can be used. Here, the linear expansion coefficient of the resin material is preferably 60 to 70 (× 10 ⁻⁶ / ° C.).
That is, the linear expansion coefficient in the temperature range of −40 ° C. to + 85 ° C. of the glass lens included in the wide-angle lens is 1 to 10 (× 10 ⁻⁶ / ° C.), and the plastic lens is −40 ° C. to The linear expansion coefficient in the temperature range of + 85 ° C. is 60 to 70 (× 10 ⁻⁶ / ° C.), and the linear expansion coefficient of the lens barrel 10 in the temperature range of −40 ° C. to + 85 ° C. is 60 ~ 70 ( ^x10-6 / ° C) is applied.

FIG. 8 shows the environmental temperature change (−40 ° C. to + 85 ° C.) in each lens barrel formed by incorporating the wide-angle lenses according to Examples 1 to 3 into the resin and metal barrels 10 respectively. This is a comparison of back focus fluctuation amount (deviation amount) with respect to.
Here, examples in which the wide-angle lenses of Examples 1 to 3 are incorporated in a resin barrel are shown in Examples 1 to 3, and those in which the wide-angle lenses of Examples 1 to 3 are incorporated in a metal barrel are compared. Examples 1-3 are shown.
In addition, as a resin material used for the resin-made lens barrel 10 as Examples 1 to 3, in consideration of facilitating the desired processing and satisfying the desired strength, Polycarbonate is employed, and its linear expansion coefficient in the temperature range of −40 ° C. to + 85 ° C. is 60 to 70 (× 10 ⁻⁶ / ° C.).
Moreover, as a metal material used for the metal lens barrels as Comparative Examples 1 to 3, it is an aluminum material, and its linear expansion coefficient in a temperature range of −40 ° C. to + 85 ° C. is 23 (× 10 ⁻⁶ / ° C).
As is apparent from the results shown in FIG. 8, in the case of a lens barrel using a resin barrel, the amount of focus shift is -0.02 mm to a wide temperature range (for example, -40 ° C to + 85 ° C). It is possible to obtain a lens barrel that is within a range of +0.02 mm and that suppresses the amount of focus shift within the depth of field.
In this way, by combining a wide-angle lens and a plastic lens barrel, back focus fluctuation due to temperature changes of wide-angle lenses, including plastic lenses, is generated as the lens spacing changes due to deformation due to temperature changes of the lens barrel. Therefore, a lens barrel can be obtained in which the amount of change in the focus imaging position is reduced over a wide range of temperature changes.

That is, as shown in FIG. 8, in the embodiment of the present invention, the focus imaging position shifts to the image plane side due to the curvature variation of the second lens (plastic lens) 2 at a high temperature. A lens barrel in which the amount of change in the focus imaging position is reduced in a wide range of temperature changes is obtained by offsetting the focus imaging position by shifting to the object side due to the interval fluctuation due to the temperature change of the cylinder 10 or the thickness fluctuation of each lens. It is possible.
More specifically, since the plastic lens as the second lens 2 has a larger linear expansion coefficient than the glass lens, the variation of the curvature, thickness, refractive index, etc. at the time of temperature change may be increased. (2) By satisfying 0 <1 / fp <0.1, and further by satisfying conditional expression (1) 0 <[Σ (Ki / fi)] / f <0.5, back focus fluctuations are reduced. It can be suppressed.

  In the above embodiment, the first lens group G1 includes the first lens 1 and the second lens 2, and the second lens group G2 includes the third lens 3, the fourth lens 4, and the fifth lens 5. However, the present invention is not limited to this, and wide-angle lenses having other lens configurations are adopted as long as conditional expression (1) 0 <[Σ (Ki / fi)] / f <0.5 is satisfied. be able to. In the above embodiment, the second lens 2 included in the first lens group G1 is a plastic lens. However, the present invention is not limited to this, and a lens configuration in which other lenses are plastic lenses. May be adopted.

  As described above, the wide-angle lens of the present invention achieves downsizing (miniaturization), weight reduction, cost reduction, etc., and has a wide diagonal angle of view (preferably 140 degrees or more), and a back focus. A digital single-lens reflex camera can be secured as a high-performance, compact, and inexpensive device that can sufficiently secure, suppress back focus fluctuations against environmental temperature changes, and correct various aberrations. It can be applied as a wide-angle lens in a lens optical system such as a mirrorless single-lens reflex camera or a silver salt film camera, or as a wide-angle lens for other optical equipment such as an in-vehicle camera or a surveillance camera, or for other uses. It is also useful as a wide-angle lens for optical equipment used in the above.

L Optical axis G1 First lens group G2 Second lens group SD Aperture stop 1 First lens (front lens)
2 Second lens 3 3rd lens 4 4th lens 5 5th lens 6 Glass filter P Image surface f Focal length f of the entire lens system _G1 Focal length Ki of the 1st lens group linear expansion coefficient fi of each lens Focal point of each lens Distance νi Abbe number fp of each lens Focal length TL of the plastic lens Distance R1 on the optical axis from the object side surface of the first lens group to the image plane on the optical axis R2 Curvature radius R2 of the object side surface of the first lens Radius of curvature of the image side surface of one lens

Claims (15)

Arranged in order from the object side,
A first lens group having negative refractive power;
An aperture stop having a predetermined aperture;
A second lens group having a positive refractive power,
The first lens group or the second lens group includes a plastic lens,
The focal length of each lens constituting the first lens group and the second lens group is fi, the linear expansion coefficient of each lens constituting the first lens group and the second lens group is Ki, and the focal length of the entire lens system is where f is the following conditional expression (1)
(1) 0 <[Σ (Ki / fi)] / f <0.5
Satisfy,
A wide-angle lens characterized by that. When the focal length of the plastic lens is fp and the focal length of the entire lens system is f, the following conditional expression (2)
(2) 0 <1 / fp <0.1
Satisfy,
The wide-angle lens according to claim 1. When the focal length of the first lens group is f _G1 and the focal length of the entire lens system is f, the following conditional expression (3)
(3) -1.0 <f _G1 /f<-0.7
Satisfy,
The wide-angle lens according to claim 1, wherein the wide-angle lens is provided. When the distance on the optical axis from the object side surface of the first lens unit to the image plane on the optical axis is TL and the focal length of the entire lens system is f, the following conditional expression (4)
(4) 0.28 <f / TL <0.35
Satisfy,
The wide-angle lens according to any one of claims 1 to 3, characterized in that: The first lens group includes a first lens having a negative refractive power and a second lens having a positive refractive power, which are arranged in order from the object side.
The second lens group includes a third lens having a positive refractive power, a fourth lens having a positive refractive power, and a fifth lens having a negative refractive power, which are arranged in order from the object side. ,
The second lens is a plastic lens;
The wide-angle lens according to claim 1, wherein the wide-angle lens is provided. In the second lens and the third lens, at least one of the object side and the image side is formed as an aspheric surface,
The wide-angle lens according to claim 5. The fourth lens and the fifth lens are cemented lenses.
The wide-angle lens according to claim 5 or 6, characterized in that: When the radius of curvature of the object side surface of the first lens is R1 and the radius of curvature of the image side surface is R2, the following conditional expression (5)
(5) 1.4 <(R1 + R2) / (R1-R2) <1.8
Satisfy,
The wide-angle lens according to claim 5, wherein the wide-angle lens is provided. When the Abbe number of the first lens is ν1, the Abbe number of the fourth lens is ν4, and the Abbe number of the fifth lens is ν5, the following conditional expression (6)
(6) ν1 ≧ 45, ν4 ≧ 50, ν5 ≦ 30
Satisfy,
The wide-angle lens according to claim 5, wherein the wide-angle lens is provided. The first lens is a concave meniscus lens having a convex surface facing the object side and a concave surface facing the image surface side,
The second lens is a biconvex lens or a convex meniscus lens having a convex surface facing the object side and a convex surface or concave surface facing the image surface side,
The third lens is a biconvex lens or convex meniscus lens having a convex surface or concave surface facing the object side and a convex surface facing the image surface side,
The fourth lens is a biconvex lens or a convex meniscus lens having a convex surface or a concave surface facing the object side and a convex surface facing the image surface side,
The fifth lens is a concave meniscus lens having a concave surface facing the object side and a convex surface facing the image surface side.
The wide angle lens according to claim 5, wherein the wide angle lens is used. The first lens and the fifth lens are glass lenses,
The wide-angle lens according to any one of claims 5 to 10, wherein: A lens barrel comprising: the wide-angle lens according to any one of claims 1 to 11; and a lens barrel that holds the wide-angle lens,
The lens barrel is formed of a resin material.
A lens barrel characterized by that. The linear expansion coefficient in the temperature range of −40 ° C. to + 85 ° C. of the plastic lens included in the wide angle lens is 60 to 70 (× 10 ⁻⁶ / ° C.),
The linear expansion coefficient in the temperature range of −40 ° C. to + 85 ° C. of the lens barrel is 60 to 70 (× 10 ⁻⁶ / ° C.).
The lens barrel according to claim 12. Including the wide-angle lens according to claim 1,
An optical apparatus characterized by that. Including the lens barrel according to claim 12 or 13,
An optical apparatus characterized by that.

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