CN201773214U - Photographic lens and photographic device - Google Patents
Photographic lens and photographic device Download PDFInfo
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- CN201773214U CN201773214U CN2010201546072U CN201020154607U CN201773214U CN 201773214 U CN201773214 U CN 201773214U CN 2010201546072 U CN2010201546072 U CN 2010201546072U CN 201020154607 U CN201020154607 U CN 201020154607U CN 201773214 U CN201773214 U CN 201773214U
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Abstract
The utility model provides a photographic lens and a photographic device. The photographic lens has fine optical performance and higher resolution, and is aimed to be sufficiently miniaturized. The photographic lens is provided with a diaphragm, a first lens (L1) and a second lens (L2) sequentially from an objective side; two surfaces of the first lens (L1) are arranged into aspheric shapes; the center of the first lens has positive focal power; two surfaces of the second lens (L2) are arranged into aspheric shapes; and the center of the second lens has positive focal power. In the first lens (L1), the surface on the objective side is arranged into such a shape that a convex surface faces the objective side at the center and the positive focal power is weakened along with movement of the convex surface towards peripheral positions, and the surface on an image side is arranged into such a shape that the positive focal power is stronger at the peripheral positions than those at the center. Besides, a convex surface of the second lens (L2) in a crescent shape faces an objective side at the center.
Description
Technical Field
The present invention relates to an imaging lens and an imaging device, and more particularly to an imaging lens suitable for use in a small-sized camera for surveillance, a small-sized camera for authentication, or the like, and an imaging device provided with the imaging lens.
Background
Conventionally, small cameras have been used for various purposes such as: portable terminal devices such as mobile phones; a monitoring device mounted on a door video phone, a car, or the like; a discriminating device for reading a bar code or discriminating a bill/coin; and biometric identity verification devices that read biometric information such as the face, color of eyes, palm, and fingers of a person and perform verification. In recent years, with the progress of miniaturization and high-pixelation of imaging elements mounted in such compact cameras, there has been an increasing demand for miniaturization and high-pixelation of imaging lenses mounted thereon.
As for the small imaging lens, various lenses developed for portable terminals are available, but a relatively long lens having a total lens length (a distance from a lens vertex on the object side to an imaging surface) of 3mm to 5mm is mainly used. This is because a lens structure of 3 or more lenses is required for high resolution and a wide image circle. However, in order to meet the recent demand for downsizing, a method of reducing the number of constituent lenses of the imaging lens as much as possible is useful, and a method of constituting the imaging lens by 2 lenses is conceivable.
Patent document 1: japanese patent laid-open publication No. 2005-107254
Patent document 2: japanese patent laid-open publication No. 2006-189586
Patent document 3: japanese patent laid-open No. 2008-152004
Patent document 4: japanese patent laid-open publication No. 2004-170460
Patent document 1: japanese patent laid-open publication No. 2004-4620
However, there is an increasing demand for downsizing of imaging lenses mounted in small cameras in the above-mentioned fields, and specifically, there is a demand for an imaging lens having a total lens system length of 3mm or less. The total length of the lens systems of the optical systems described in patent documents 1, 2, and 5 exceeds 3mm, and the miniaturization required in recent years has not been achieved. The total length of the lens systems of the optical systems described in patent documents 3 and 4 is 3mm or less, but these imaging lenses have a vignetting (ケラレ) in the light flux around the imaging region, and therefore, when the angle of view is increased, a high peripheral light quantity ratio cannot be secured, and there is a problem that the resolution is poor. Further, the optical system described in patent document 3 has an F number as large as 3.5, and therefore does not have a high resolution that can cope with an imaging element with high definition.
Disclosure of Invention
In view of the above circumstances, an object of the present invention is to provide an imaging lens having high resolution and sufficient miniaturization while having good optical performance, and an imaging device including the imaging lens.
An imaging lens according to the present invention is characterized by comprising, in order from an object side: an aperture stop, a 1 st lens having both surfaces thereof formed in an aspherical shape and having a positive refractive power in a central portion, and a 2 nd lens having both surfaces thereof formed in an aspherical shape and having a positive refractive power in a central portion, wherein in the 1 st lens, a convex surface faces an object side in the central portion, the positive refractive power decreases as the lens moves from the central portion to a peripheral portion, and the negative refractive power in the peripheral portion, and a surface on the image side has a shape having a stronger positive refractive power in the peripheral portion than in the central portion; the 2 nd lens has a meniscus shape with a convex surface facing the object side in the center.
Regarding the aspherical surface on the object side of the 1 st lens, the aspherical shape of the aspherical surface on the object side of the 1 st lens may be expressed by the following aspherical surface equation, where Y represents the height in the direction perpendicular to the optical axis, zf (Y) represents the distance in the optical axis direction from the tangent plane to the vertex of the aspherical surface to the aspherical surface of the height Y, Cf represents the curvature of the paraxial region, Kf represents the aspherical coefficient, and Bfn represents the n-th aspherical coefficient (n is an integer of 2 or more).
Zf(Y)＝Cf·Y2/{1+(1-Kf·Cf2·Y2)1/2}+∑Bfn·|Y|n
In this case, in the imaging lens of the present invention, when the maximum value of 1-time differentiation of Y with respect to Zf (Y) in the effective diameter is Zf' max, it is preferable that the following conditional expression (1) is satisfied.
Zf’max＜0.5…(1)
In the imaging lens of the present invention, it is preferable that the following conditional expression (2) is satisfied where Zf is a 2-th differential with respect to Y in Zf (Y), Y1 is a height of a point where Zf ″ in the effective diameter is a maximum in a direction perpendicular to the optical axis, and ER1 is an effective radius of a surface on the object side of the 1 st lens.
Y1/ER1＜0.20…(2)
Similarly to the object-side aspheric surface, regarding the image-side aspheric surface of the 1 st lens, the height in the direction perpendicular to the optical axis is Y, the distance in the optical axis direction from the tangent plane at the vertex of the aspheric surface to the aspheric surface of the height Y is zr (Y), the curvature of the paraxial region is Cr, the aspheric coefficient is Kr, and the aspheric coefficient of degree n is Brn (n is an integer of 2 or more), and the aspheric shape of the image-side aspheric surface of the 1 st lens can be expressed by the following aspheric expression. Zr (Y) ═ Cr · Y2/{1+(1-Kr·Cr2·Y2)1/2}+∑Brn·|Y|n
In this case, in the imaging lens of the present invention, it is preferable that the following conditional expression (3) is satisfied where Zr ' is a 1 st differential of Zr (Y) with respect to Y, ER2 is an effective radius of the image-side surface of the 1 st lens, and | Zr ' | hmax is a maximum value of | Zr ' | in a range of Y < 0.5 × ER 2.
|Zr’|hmax＜0.25…(3)
In the imaging lens of the present invention, it is preferable that the following conditional expression (4) is satisfied where Zr ' is a 1-time differential of Zr (Y) with respect to Y, Y2 is a height in a direction perpendicular to the optical axis of a point where | Zr ' | is a value of 20% of a maximum value of | Zr ' | in the effective diameter, and ER2 is an effective radius of a surface on the image side of the 1 st lens.
0.50＜Y2/ER2…(4)
In the imaging lens of the present invention, it is preferable that the following conditional expression (5) is satisfied where TL is an optical axis distance from one of the stop and the object-side surface of the 1 st lens, which is closer to the object on the optical axis, to the image plane, and f is a focal length of the entire system.
1.05＜TL/f＜2.0…(5)
In the imaging lens of the present invention, it is preferable that the object-side surface of the 1 st lens has at least one inflection point in the effective diameter.
In the imaging lens of the present invention, it is preferable that the following conditional expression (6) is satisfied where f1 denotes a focal length of the 1 st lens and f denotes a focal length of the entire system.
1.10＜f1/f＜7.5…(6)
When the distance on the optical axis between the 1 st lens and the 2 nd lens is d3 and the focal length of the entire system is f, the following conditional expression (7) is preferably satisfied.
0.06＜d3/f＜0.6…(7)
In the imaging lens of the present invention, it is preferable that the following conditional expression (8) is satisfied where vd1 denotes the abbe number of the 1 st lens with respect to the d-line and vd2 denotes the abbe number of the 2 nd lens with respect to the d-line.
15＜vd1-vd2…(8)
In the imaging lens of the present invention, "in order from the object side" means that the order is not given based on the surface of the lens on the object side, but is given based on the center of the lens.
The "central portion" of the imaging lens of the present invention refers to the paraxial region.
In the imaging lens of the present invention, the refractive power at a point on the surface is represented by (N2 to N1)/R, where R is a radius of curvature at the point, N1 is a refractive index at the object side, and N2 is a refractive index at the image side. The curvature radius is defined, for example, by obtaining an intersection point between a normal line of a predetermined point of the surface and the optical axis, and defining a length of a line segment connecting the intersection point and the predetermined point as the curvature radius.
In the present invention, when the optical system is rotationally symmetric with respect to the optical axis, the diameter of a circle formed by the outermost points in each radial direction when the intersection point of the total light beam (including the on-axis light beam and the total image height) contributing to the image formation and the lens surface is considered is referred to as "effective diameter", and the radius of the circle is referred to as "effective radius".
In addition, when the above-mentioned "TL" is calculated, the rear intercept is divided into air-converted lengths.
The imaging device of the present invention is characterized by including the imaging lens of the present invention described above.
The imaging device of the present invention can be used for night vision monitoring, for imaging an image based on near-infrared light having a wavelength of 700nm to 1000nm, and for biometric authentication.
According to the imaging lens of the present invention, the number of lenses is set to at least 2, and an optical system configured by a combination of a positive lens and a positive lens is used, and an aspherical surface is applied, which is advantageous in that sufficient miniaturization is achieved. Further, according to the imaging lens of the present invention, by appropriately setting the surface shapes of the 2 lenses, it is possible to have good optical performance, in particular, it is possible to increase the peripheral light quantity ratio in the peripheral portion of the imaging region while having an optical system with a small F-number, and it is possible to realize an optical system with high resolution.
According to the imaging device of the present invention, since the imaging lens of the present invention is provided, a high-resolution image can be obtained with a small configuration.
Drawings
Fig. 1 is a sectional view showing a lens structure of an imaging lens according to embodiment 1 of the present invention.
Fig. 2 is a sectional view showing a lens structure of an imaging lens according to example 2 of the present invention.
Fig. 3 is a sectional view showing a lens structure of an imaging lens according to example 3 of the present invention.
Fig. 4 is a sectional view showing a lens structure of an imaging lens according to example 4 of the present invention.
Fig. 5 is a sectional view showing a lens structure of an imaging lens according to example 5 of the present invention.
Fig. 6 is a sectional view showing a lens structure of an imaging lens according to example 6 of the present invention.
Fig. 7 is each aberration diagram of the visible region of the imaging lens in example 1 of the present invention.
Fig. 8 is each aberration diagram of the visible region of the imaging lens in example 2 of the present invention.
Fig. 9 is each aberration diagram of the visible region of the imaging lens in example 3 of the present invention.
Fig. 10 is each aberration diagram of the visible region of the imaging lens in example 4 of the present invention.
Fig. 11 is each aberration diagram of the visible region of the imaging lens in example 5 of the present invention.
Fig. 12 is each aberration diagram of the visible region of the imaging lens in example 6 of the present invention.
Fig. 13 is a diagram showing aberrations in the near-infrared region of an imaging lens according to example 1 of the present invention.
Fig. 14 is a diagram showing aberrations in the near-infrared region of an imaging lens according to example 2 of the present invention.
Fig. 15 is a diagram showing aberrations in the near infrared region of an imaging lens according to example 3 of the present invention.
Fig. 16 is a diagram showing aberrations in the near-infrared region of an imaging lens according to example 4 of the present invention.
Fig. 17 is a diagram showing aberrations in the near infrared region of an imaging lens according to example 5 of the present invention.
Fig. 18 is a diagram showing aberrations in the near infrared region of an imaging lens according to example 6 of the present invention.
Fig. 19 is a diagram showing the relationship between Zf', Zf ", and Y of the imaging lens in example 1 of the present invention.
Fig. 20 is a diagram showing a relationship between | Zr' | and Y of the imaging lens in embodiment 1 of the present invention.
Fig. 21 is a diagram showing the relationship between Zf', Zf ", and Y of the imaging lens in example 2 of the present invention.
FIG. 22 is a diagram showing the relationship between | Zr' | and Y of an imaging lens according to example 2 of the present invention
Fig. 23 is a diagram showing the relationship between Zf', Zf ", and Y of the imaging lens in example 3 of the present invention.
Fig. 24 is a diagram showing a relationship between | Zr' | and Y of the imaging lens according to example 3 of the present invention.
Fig. 25 is a diagram showing the relationship between Zf', Zf ", and Y of the imaging lens in example 4 of the present invention.
Fig. 26 is a diagram showing the relationship between | Zr' | and Y of the imaging lens according to example 4 of the present invention.
Fig. 27 is a diagram showing the relationship between Zf', Zf ", and Y of the imaging lens in example 5 of the present invention.
Fig. 28 is a diagram showing the relationship between | Zr' | and Y of the imaging lens according to example 5 of the present invention.
Fig. 29 is a diagram showing the relationship between Zf', Zf ", and Y of the imaging lens in example 6 of the present invention.
Fig. 30 is a diagram showing the relationship between | Zr' | and Y of the imaging lens according to example 6 of the present invention.
Fig. 31 is a cross-sectional view showing a schematic configuration of an imaging apparatus for biometric authentication (also referred to as biometric authentication) according to an embodiment of the present invention.
Fig. 32 is an enlarged perspective view showing the inside of the living body feature authentication imaging device according to the embodiment of the present invention.
Fig. 33 is a perspective view showing a schematic configuration of an imaging device according to another embodiment of the present invention.
In the figure: 200, 300 camera, 220, 320 camera lens, 230, 330 camera, L1-1 St lens, L2-2 nd lens, PP optical component, Sim image plane, St aperture stop, Z-optical axis
Detailed Description
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Fig. 1 to 6 are sectional views showing the configuration of an imaging lens according to an embodiment of the present invention, and correspond to examples 1 to 6 described later. Since all basic configurations of embodiments 1 to 6 are the same and the method shown in fig. 1 to 6 is the same, the configuration of the imaging lens according to the embodiment of the present invention will be described below by taking the configuration of embodiment 1 shown in fig. 1 as an example.
As shown in fig. 1, an imaging lens according to an embodiment of the present invention includes, in order from an object side: aperture stop St, 1 St lens L1, and 2 nd lens L2. In fig. 1, the left side is the object side, the right side is the image side, and the aperture stop St in fig. 1 does not indicate the shape or size thereof but indicates the position thereof on the optical axis Z.
In fig. 1, an image pickup device 5 disposed on an image plane Sim of an image pickup lens is also illustrated in consideration of the case where the image pickup lens is applied to an image pickup apparatus. The imaging element 5 is an element that converts an optical image formed by the imaging lens into an electric signal, and for example, a CCD image sensor, a CMOS image sensor, or the like can be used.
When the imaging lens is applied to the imaging device, it is preferable to provide a protective glass sheet, a low-pass filter, an infrared cut filter, or the like depending on the configuration of the camera side on which the lens is mounted, and fig. 1 shows an example in which the optical member PP in the form of a parallel flat plate assumed to be arranged between the lens closest to the image side and the imaging element 5 (image plane Sim).
The imaging lens of the present embodiment is composed of 2 lenses, that is: the first lens L1 having aspherical surfaces on both sides and positive refractive power in the center, and the second lens L2 having aspherical surfaces on both sides and positive refractive power in the center. By adopting the 2-piece structure, it becomes advantageous for miniaturization. Further, by using the aspherical lens, the lens system can be downsized while maintaining high performance. In particular, in order to obtain high resolution while correcting chromatic aberration well, it is effective to form the lens from 2 or more aspherical lenses.
In the case where the lens system is provided in a 2-plate structure, the combination of powers of the 2-plate lenses can be considered in various cases. For example, in a retrofocus (retrofocus) formula formed by a combination of a lens having negative refractive power and a lens having positive refractive power, the back intercept can be made long, but miniaturization becomes difficult.
In addition, in the telescopic type configured by a combination of a lens having positive refractive power and a lens having negative refractive power, the back intercept is shorter than the focal length. In order to achieve a smaller size, it is necessary to achieve a shorter focal length, and when the optical element is used in combination with an image sensor such as a CCD, a protective glass sheet, various filters, and the like are arranged. In the telescopic type, when the focal length is shortened, the back focal length cannot be sufficiently obtained, and thus the degree of freedom in selecting a lens shape, a housing shape, an image pickup device, and the like is low.
Therefore, in the present embodiment, an optical system including a combination of a positive power lens and a positive power lens is used, and the arrangement is performed by appropriately setting the structures of these 2 lenses, thereby realizing a small-sized lens system having a relatively long back focal length.
The 1 st lens L1 of the imaging lens according to the present embodiment is configured such that the surface on the object side faces the convex surface toward the object side in the central portion of the lens, and positive power decreases as it moves from the central portion to the peripheral portion, and negative power is present in the peripheral portion; the image side surface is formed in a shape having a positive power in the peripheral portion thereof compared with the central portion of the lens. The 2 nd lens L2 of the imaging lens according to the present embodiment is configured such that the object-side surface thereof faces the convex surface toward the object side at the center of the lens and the image-side surface thereof faces the concave surface toward the image side at the center of the lens, that is, such that the lens has a meniscus shape with the convex surface facing the object side at the center of the lens.
The center portion of L2 of the 2 nd lens is defined as: in the meniscus shape with the convex surface facing the object side, the angle between the light beam which is gradually focused by each surface of the 1 st lens L1 and enters the 2 nd lens L2 and the normal line of each surface of the 2 nd lens can be reduced, and therefore, the spherical aberration remaining after passing through the 1 st lens L1 can be corrected satisfactorily without causing high-order aberration.
By configuring the aspherical shapes of the 1 st lens L1 and the 2 nd lens L2 in the above manner, an optical system having a small F number can be realized, high resolution is possible, and high definition of pixels of an image pickup element can be achieved. Further, by configuring the aspherical shapes of the 1 st lens L1 and the 2 nd lens L2 as described above, the angle of the light beam incident on the image plane at the periphery of the image forming region can be reduced, and the amount of light effective for the pixels of the image pickup element disposed on the image plane can be increased, thereby achieving high resolution. In the present imaging lens, the aperture stop St is disposed on the object side of the 1 St lens L1, which is advantageous in reducing the incident angle to the imaging element disposed on the image plane. As described above, according to the imaging lens of the present invention, a lens system having a high resolution and a sufficiently small size can be realized.
Here, regarding the aspherical surface of the 1 st lens L1 of the imaging lens on the object side, the height in the direction perpendicular to the optical axis Z is defined as Y, the distance in the optical axis Z direction from the tangent plane at the vertex of the aspherical surface to the aspherical surface of the height Y is defined as zf (Y), and the paraxial region is approximated to the aspherical surfaceThe curvature of (c) is Cf, the aspherical coefficient of (k) is Kf, and the aspherical coefficient of (n) th order is Bfn (n is an integer of 2 or more), and the aspherical shape can be expressed by the following aspherical expression. Zf (Y) Cf. Y2/{1+(1-Kf·Cf2·Y2)1/2}+∑Bfn·|Y|n
In this case, in the above formula Zf (Y), when 1-time differential of Zf (Y) with respect to Y is Zf ' and the maximum value of Zf ' in the effective diameter is Zf ' max, the following conditional formula (1) is preferably satisfied.
Zf’max＜0.5…(1)
The conditional expression (1) is one of expressions for defining an object-side aspherical shape of the 1 st lens L1. The condition (1) means that Zf' is less than 0.5 in the entire region within the effective diameter. By forming the object-side surface of the 1 st lens L1 so as to satisfy the conditional expression (1), it is possible to suppress the surface from being strongly convex, that is, the surface having strong positive power.
If the object-side surface of the 1 st lens L1 is strongly convex, the thickness (length in the optical axis direction) of the entire lens system increases, which is disadvantageous for downsizing. Further, if the object side surface of the 1 st lens L1 is strongly convex, large negative spherical aberration occurs, so that the spherical aberration must be corrected by another surface, and this burden is imposed on the other surface, so that the degree of freedom in design is reduced, and as a result, it is difficult to obtain good optical performance. In the case where a large negative spherical aberration occurs as described above, particularly in a lens system having a small F-number, it becomes more difficult to correct the aberration.
In order to further suppress an increase in the thickness of the entire lens system and the occurrence of large negative spherical aberration, the following conditional expression (1-1) is preferably satisfied.
Zf’max＜0.3…(1-1)
In order to satisfy the conditional expression (1) or the conditional expression (1-1), when Zf "is defined as 2-fold differentiation of Y with respect to Zf (Y), it is preferable that the maximum value of Zf" is located more inward than 20% of the effective diameter. That is, when the height of the point where Zf ″ is the maximum value in the effective diameter in the direction perpendicular to the optical axis is Y1 and the effective radius of the object-side surface of the 1 st lens L1 is ER1, the following conditional expression (2) is preferably satisfied.
Y1/ER1＜0.20…(2)
By satisfying the conditional expression (2), a shape having a required positive refractive power at the center of the 1 st lens L1 and a weakened positive refractive power at the peripheral portion can be obtained.
Further, it is preferable that the following conditional formula (2-1) is satisfied.
0.07＜Y1/ER1＜0.20…(2-1)
By setting the maximum value position of Zf ″ so as to satisfy the lower limit of conditional expression (2-1), the center portion of the object-side surface of the 1 st lens L1 can be further suppressed from becoming a strong convex shape. As a result, as described above, the problem that the object-side surface of the 1 st lens L1 has a strong convex shape can be suppressed, which is advantageous in terms of downsizing and makes it easier to obtain excellent optical performance.
Similarly to the above aspheric expression of the object-side surface of the 1 st lens L1, regarding the aspheric surface of the image-side surface of the 1 st lens L1, the aspheric shape can be expressed by the following aspheric expression, where Y represents a height in a direction perpendicular to the optical axis Z, zr (Y) represents a distance in the optical axis Z from a tangent plane to a vertex of the aspheric surface at the height Y, Cr represents a curvature of a paraxial region, Kr represents an aspheric coefficient, and Brn represents an n-order aspheric coefficient (n is an integer of 2 or more). Zr (Y) ═ Cr · Y2/{1+(1-Kr·Cr2·Y2)1/2}+∑Brn·|Y|n
The 1 st lens L1 preferably has a gentle curvature at the center and a strong convex shape toward the image side at the peripheral portion, that is, has strong positive power at the peripheral portion. In the above formula Zr (Y), it is preferable that the following conditional formula (3) is satisfied where Zr ' is a 1-time differential of Zr (Y) with respect to Y, ER2 is an effective radius of the image-side surface of the 1 st lens, and | Zr ' | hmax is a maximum value of Zr ' in a range satisfying Y < 0.5 × ER 2.
|Zr’|hmax＜0.25…(3)
The conditional expression (3) is an expression for making the center portion of the image-side surface of the 1 st lens L1 have a gentle curvature. Since the center portion of the image-side surface of the 1 st lens L1 has a gentle curvature, the light beam gently collected by the object-side surface of the 1 st lens L1 is again converged gently, and the light beam can be transmitted to the 2 nd lens L2 without generating a large spherical aberration. This can reduce the burden of correcting the spherical aberration of the 2 nd lens L2, and can increase the degree of freedom of correcting other aberrations.
Further, the image-side surface of the 1 st lens L1 is preferably formed in a convex shape whose peripheral portion is strong toward the image side. With this configuration, a lens having a large angle of view and no vignetting of the light flux can be obtained regardless of the optical system having a small F-number. In order to have a large angle of view in an optical system having a small F number, it is necessary to rapidly bend the peripheral rays of light toward the optical axis in the 1 st lens L1, but large spherical aberration is likely to occur in this case. In the imaging lens of the present embodiment, the image-side surface of the 1 st lens L1 is formed into a convex shape whose peripheral portion is strongly directed toward the image side, so that the function of the 1 st lens L1 for rapidly bending the peripheral light beam toward the optical axis side is held on the image-side surface of the 1 st lens L1, thereby suppressing the occurrence of large spherical aberration.
If the degree of refraction of the peripheral light beam in the 1 st lens L1 is insufficient, the interval between the 1 st lens L1 and the 2 nd lens L2 has to be increased, and therefore, the size reduction cannot be achieved. When the distance between the 1 st lens L1 and the 2 nd lens L2 is reduced unreasonably despite the insufficient refractive index of the light beam at the peripheral portion of the 1 st lens L1, the curvature of the concave shape of the peripheral portion of the object-side surface of the 2 nd lens L2 becomes steep, high-order coma aberration (also referred to as coma aberration) is likely to occur, and it is difficult to correct the high-order coma aberration.
In order to form the image-side surface of the 1 st lens L1 into a convex shape that is strong toward the image side in the peripheral portion, it is preferable that the position where | Zr '| has a value of 20% of the maximum value of | Zr' | in the effective diameter is located further outside than 50% of the effective diameter. That is, when Zr ' is a 1-time differential of Zr (Y) with respect to Y, Y2 is a height from the optical axis to the lens surface at a point where | Zr ' | takes a value of 20% of the maximum value of | Zr ' | in the effective diameter, and ER2 is an effective radius of the image-side surface of the 1 st lens, the following conditional expression (4) is preferably satisfied.
Y2/ER2＞0.50…(4)
When TL is an axial distance from one of the aperture stop St and the object-side surface of the 1 St lens L1, which is closer to the object on the optical axis, to the image plane Sim, and f is a focal length of the entire system, the following conditional expression (5) is preferably satisfied.
1.05＜TL/f＜2.0…(5)
Conditional expression (5) is an expression for downsizing the imaging lens system. If the condition is exceeded
(5) The upper limit of (b) is not sufficient for miniaturization, and when the lower limit is less than the lower limit, high-order aberration is generated, and high resolution cannot be obtained.
Further, it is preferable that the object side surface of L1 of the 1 st lens has at least 1 inflection point in the effective diameter. Since the inflection point is provided, the surface interval between the object-side surface and the image-side surface of the 1 st lens L1 can be set to a predetermined length or more in the effective diameter peripheral portion or the outer side thereof, and therefore, the problem of the 1 st lens L1 having an extremely narrow interval between the object-side surface and the image-side surface can be avoided in the effective diameter peripheral portion or the outer side thereof as compared with the central portion of the lens. Thus, when the lens is manufactured by injection molding, the material of the lens can be easily injected and fed uniformly into the molding die, and therefore, the moldability can be improved.
When the focal length of the 1 st lens L1 is f1 and the focal length of the entire system is f, the following conditional expression (6) is preferably satisfied.
1.10＜f1/f＜7.5…(6)
Conditional expression (6) is an expression for providing the 1 st lens L1 with an appropriate refractive power. If the refractive power of the 1 st lens L1 is too strong below the lower limit of the conditional expression (6), large negative spherical aberration occurs, and therefore, the degree of freedom for correcting other aberrations by the 2 nd lens L2 is reduced by correcting the spherical aberration by the 2 nd lens L2. If the upper limit of conditional expression (6) is exceeded, the refractive power of the 1 st lens L1 becomes weak, and the 2 nd lens L2 needs to have a strong refractive power in order to obtain a short focal length in the entire system, which is not preferable because a problem of an increase in negative spherical aberration occurs.
When the distance on the optical axis between the 1 st lens L1 and the 2 nd lens L2 is d3 and the focal length of the entire system is f, the following conditional expression (7) is preferably satisfied.
0.06＜d3/f＜0.6…(7)
Conditional expression (7) is an expression relating to downsizing and aberration correction of the imaging lens system. If the upper limit of conditional expression (7) is exceeded, the distance between lenses becomes wider, making miniaturization difficult. If the distance between the lenses is smaller than or equal to the lower limit of conditional expression (7), in order to achieve an optical system having a small F-number and a large angle of view while achieving miniaturization, it is necessary to bend the peripheral light beam very strongly toward the optical axis side in the image-side surface of the 1 st lens L1, and high-order coma aberration occurs, and good resolution cannot be obtained.
In order to achieve a short focal length for downsizing, it is desirable to secure a sufficient back focal length, and the sufficient back focal length can be obtained by appropriately maintaining the optical powers of the 1 st lens L1 and the 2 nd lens L2 so as to satisfy the conditional expression (6) and arranging the 1 st lens L1 and the 2 nd lens L2 at an appropriate interval so as to satisfy the conditional expression (7).
When importance is placed on downsizing, it is preferable to determine the interval between the 1 st lens L1 and the 2 nd lens L2 so as to satisfy the following conditional expression (7-1).
0.06＜d3/f＜0.3…(7-1)
When the abbe number of the 1 st lens L1 to the d-line is vd1 and the abbe number of the 2 nd lens L2 to the d-line is vd2, the following conditional expression (8) is preferably satisfied.
15＜vd1-vd2…(8)
The conditional expression (8) is an expression relating to correction of chromatic aberration. When the imaging lens of the present embodiment is used as an imaging lens for a color image, it is preferable that a material having a large abbe number is used for the 1 st lens L1 and a material having a small abbe number is used for the 2 nd lens L2, and the conditional expression (8) is satisfied. This further improves the chromatic aberration correction effect, and high resolution can be achieved.
In order to further improve the chromatic aberration correction effect and to achieve further high resolution, it is preferable that the following conditional expression (8-1) is satisfied.
25＜vd1-vd2…(8-1)
When the imaging lens of the present embodiment is used as an imaging lens for a monochrome image, for example, when imaging is performed using single-wavelength light such as LED light, the conditional expressions (8) and (8-1) are not necessarily satisfied, and high resolution can be obtained even if the conditional expressions (8) and (8-1) are not satisfied. When the imaging lens of the present embodiment is used as an imaging lens for a monochrome image or when imaging is performed using a single-wavelength light such as an LED light, it is preferable to use a material having a high refractive index for both the 1 st lens L1 and the 2 nd lens L2. By using a material having a high refractive index, the degree of freedom in design is improved, and the respective aberrations can be easily corrected while achieving miniaturization.
In the imaging lens of the present embodiment, it is preferable that imd be the air converted length from the most image side surface of the lens system to the image plane Sim in the use state, and that the following conditional expression (9) be satisfied.
0.25＜imd/f＜0.55…(9)
By satisfying conditional expression (9), it is possible to reduce the size of the image pickup device, to appropriately secure the distance from the surface closest to the image plane, to provide freedom in the lens shape, the housing shape, the selection of the image pickup device, and the like, and to sufficiently obtain adjustment amounts (adjustment しろ) for adjusting the focus offset due to manufacturing errors.
Preferably, the material of the 1 st lens L1 or the 2 nd lens L2 is plastic. By using plastic, it is possible to cope with a complicated lens shape, to improve the degree of freedom in design, and to further perform high-level aberration correction. Further, since it is relatively easy to transfer the shape of the mold with high accuracy by the plastic material and to process the mold, a lens with less manufacturing error can be manufactured. Therefore, a lens with high aberration correction can be manufactured with high accuracy, and thus a lens system with high resolution can be realized. Further, by using a plastic material, it is possible to realize an inexpensive and lightweight structure.
A light shielding member may be provided between the 1 st lens L1 and the 2 nd lens L2, and between the 2 nd lens L2 and the image plane Sim, in order to prevent stray light from outside each subject, flare light due to reflection at the edge (side) of each lens or the like, and the like. The light shielding member may be a spacer ring or the like, or a lens may be directly coated or coated to have the same effect, or an opaque plate material may be provided.
Next, a numerical example of the imaging lens of the present invention will be described. The lens cross-sectional views of examples 1 to 6 are shown in FIGS. 1 to 6, respectively. In each embodiment, reference numerals Ri, Di (i ═ 1, 2, 3, …) of the lens cross-sectional view correspond to Ri, Di of lens data described below.
Lens data of the imaging lens according to example 1 is shown in table 1, and aspherical data is shown in table 2. Similarly, lens data and aspherical surface data of the imaging lenses according to examples 2 to 6 are shown in tables 3 to 12, respectively. The meaning of the symbols in the table will be described below taking example 1 as an example, but the symbols in examples 2 to 6 are also basically the same.
In the lens data in table 1, the object plane and the image plane are also shown together. In the lens data in table 1, Si denotes the number of the ith (i is 1, 2, 3, …) surface that increases in order toward the image side with the surface of the most object-side factor as the 1 st surface, Ri denotes the radius of curvature of the ith surface, and Di denotes the surface interval on the optical axis Z between the ith surface and the (i + 1) th surface. The mark of the curvature radius is positive when it is convex on the object side and negative when it is convex on the image side.
In the lens data, Ndj represents a refractive index of the j-th (j is 1, 2, 3, …) optical factor with respect to the d-line (wavelength 587.6nm) which increases in order toward the image side with the 1 st lens located closest to the object side, and vdj represents an abbe number of the j-th optical factor with respect to the d-line. The lens data also includes a term indicating the aperture stop St and the optical member PP, and the term (aperture stop) is described in a column corresponding to the radius of curvature of the surface of the aperture stop St.
The unit of the radius of curvature, the surface spacing, is used herein as "mm". However, this is merely an example, and the optical system can obtain the same optical performance even when it is scaled up or down, and therefore other appropriate units may be used.
In the lens data in table 1, a number is attached to the surface number of the aspherical surface, and the curvature radius of the aspherical surface indicates a numerical value of a paraxial curvature radius (curvature radius of the central portion). The aspherical surface data in table 2 show the surface numbers of aspherical surfaces and aspherical surface coefficients relating to the respective aspherical surfaces. "E-0 m" (m: integer) of the numerical values of the aspherical surface data of Table 2 means ". times.10-m"," E +0m "(m: integer) means". times.10m". The aspherical surface coefficient is a value of each coefficient K, Bn (n is 2, 3, 4, … 20) when each aspherical surface is expressed by the following aspherical surface formula (a). Zd ═ C.Y2/{1+(1-K·C2·Y2)1/2}+∑Bn·|Y|n…(A)
Wherein,
and (d) is as follows: distance in the optical axis direction from the tangent plane at the apex of the aspherical surface to the aspherical surface with height Y
Y: height in a direction perpendicular to the optical axis
C: curvature of the proximal axis
K, Bn: aspheric coefficient (n ═ 2, 3, 4, … 20)
Regarding the aspherical surface of the 1 st lens L1 on the object side, Zd, C, K, and Bn in the formula (a) correspond to zf (y), Cf, Kf, and Bfn, respectively. Moreover, regarding the image-side aspheric surface of the 1 st lens L1, Zd, C, K, and Bn in the formula (a) correspond to zr (y), Cr, Kr, and Bfr, respectively.
[ Table 1]
Example 1 lens data
| Si | Ri | Di | Ndj | vdj |
| Object surface | ∞ | 17.000 | ||
| 1 | (Aperture diaphragm) | 0.046 | ||
| *2 | 1.0355 | 0.592 | 1.5311 | 56 |
| *3 | -4.6809 | 0.299 | ||
| *4 | 1.0101 | 0.538 | 1.6318 | 23 |
| *5 | 0.8356 | 0.350 | ||
| 6 | ∞ | 0.120 | 1.5168 | 64.2 |
| 7 | ∞ | 0.055 | ||
| Image plane | ∞ |
[ Table 2]
Example 1 aspheric data
| Si | *2 | *3 | *4 | *5 |
| K | 0.95398 | 4.99747 | 2.32480 | 1.12580 |
| B2 | 0.00000E+00 | 0.00000E+00 | 0.00000E+00 | 0.00000E+00 |
| B3 | -2.94709E-01 | 1.16577E+00 | 7.76862E-01 | -1.05943E+00 |
| B4 | 2.11816E+01 | -1.23311E+01 | -1.49264E+01 | 1.48414E+00 |
| B5 | -3.01727E+02 | 2.26197E+01 | 4.59233E+01 | 2.20179E+01 |
| B6 | 1.57917E+03 | 1.23628E+02 | 5.47649E+02 | -9.63301E+01 |
| B7 | -2.00081E+03 | -6.23770E+02 | -5.79309E+03 | -1.50557E+01 |
| B8 | -6.77717E+03 | 9.52499E+02 | 2.13596E+04 | 6.23520E+02 |
| B9 | 1.28523E+03 | -1.87192E+03 | -3.21550E+04 | -8.72130E+02 |
| B10 | 5.70994E+04 | 5.01951E+03 | 9.88512E+03 | -1.05161E+02 |
| B11 | 5.73441E+04 | -2.64808E+03 | -1.24971E+04 | -3.43790E+01 |
| B12 | -1.35530E+05 | 2.62994E+03 | 5.70573E+04 | 1.74369E+03 |
| B13 | -3.61338E+05 | -7.07756E+02 | 7.66132E+04 | -3.12344E+02 |
| B14 | -2.17160E+06 | -9.84378E+03 | -2.68122E+04 | -1.52408E+03 |
| B15 | -2.25283E+06 | -1.56352E+05 | -4.46866E+05 | -2.41178E+03 |
| B16 | 1.93311E+07 | -4.09278E+05 | -3.83022E+05 | 3.14635E+03 |
| B17 | 5.56797E+07 | 1.02895E+06 | 6.90594E+05 | 4.88438E+03 |
| B18 | -9.77465E+07 | 7.10458E+06 | 1.13804E+06 | -2.93667E+03 |
| B19 | -3.03627E+08 | -1.96905E+07 | 2.87312E+06 | -1.16212E+04 |
| B20 | 4.74117E+08 | 1.33806E+07 | -5.78180E+06 | 1.05228E+04 |
[ Table 3]
Example 2 lens data
| Si | Ri | Di | Ndj | vdj |
| Object surface | ∞ | 30.000 | ||
| 1 | (Aperture diaphragm) | 0.062 | ||
| *2 | 1.5453 | 0.592 | 1.5095 | 56 |
| *3 | -1.1603 | 0.230 | ||
| *4 | 0.9648 | 0.350 | 1.606 | 27 |
| *5 | 0.8624 | 0.332 |
| 6 | ∞ | 0.300 | 1.5168 | 64.2 |
| 7 | ∞ | 0.055 | ||
| Image plane | ∞ |
[ Table 4]
Example 2 aspherical data
| Si | *2 | *3 | *4 | *5 |
| K | 4.82578 | 5.00000 | 3.04886 | -4.99990 |
| B2 | 0.00000E+00 | 0.00000E+00 | 0.00000E+00 | 0.00000E+00 |
| B3 | 9.42486E-02 | 3.24941E+00 | 3.79641E+00 | 1.16965E+00 |
| B4 | 1.50462E+01 | -2.03097E+01 | -3.23546E+01 | -7.53155E+00 |
| B5 | -2.39006E+02 | 1.78140E+01 | 8.97840E+01 | 4.32713E+01 |
| B6 | 1.32412E+03 | 1.78526E+02 | 5.22938E+02 | -1.07942E+02 |
| B7 | -2.08868E+03 | -5.87680E+02 | -5.85182E+03 | -4.69846E+01 |
| B8 | -5.69043E+03 | 8.25938E+02 | 2.13142E+04 | 6.24433E+02 |
| B9 | 4.40648E+03 | -2.24256E+03 | -3.21028E+04 | -8.23360E+02 |
| B10 | 6.04848E+04 | 4.59628E+03 | 1.01198E+04 | -3.35513E+01 |
| B11 | 4.91481E+04 | -2.40389E+03 | -1.20593E+04 | -1.41104E+01 |
| B12 | -1.92951E+05 | 4.97249E+03 | 5.75950E+04 | 1.68455E+03 |
| B13 | -5.45050+05 | 5.43571E+03 | 7.65258E+04 | -5.34060E+02 |
| B14 | -2.59386E+06 | -3.29243E+02 | -2.90943E+04 | -1.78371E+03 |
| B15 | -2.66606E+06 | -1.52211E+05 | -4.53600E+05 | -2.49893E+03 |
| B16 | 2.13696E+07 | -4.37495E+05 | -3.92936E+05 | 3.45235E+03 |
| B17 | 6.97109E+07 | 9.17202E+05 | 6.94837E+05 | 5.69805E+03 |
| B18 | -5.05175E+07 | 6.85340E+06 | 1.16332E+06 | -1.85483E+03 |
| B19 | -2.35248E+08 | -1.99629E+07 | 2.81910E+06 | -1.14025E+04 |
| B20 | -2.95699E+07 | 1.50162E+07 | -5.61228E+06 | 7.75301E+03 |
[ Table 5]
Example 3 lens data
| Si | Ri | Di | Ndj | vdj |
| Object surface | ∞ | 40.000 | ||
| 1 | (Aperture diaphragm) | 0.027 | ||
| *2 | 1.0729 | 0.548 | 1.5311 | 56 |
| *3 | -4.895 | 0.266 | ||
| *4 | 1.0587 | 0.395 | 1.606 | 27 |
| *5 | 0.9661 | 0.339 | ||
| 6 | ∞ | 0.400 | 1.5168 | 64.2 |
| 7 | ∞ | 0.055 | ||
| Image plane | ∞ |
[ Table 6]
Example 3 aspherical data
| Si | *2 | *3 | *4 | *5 |
| K | -2.34557 | 4.71272 | -4.76635 | 1.18599 |
| B2 | 0.00000E+00 | 0.00000E+00 | 0.00000E+00 | 0.00000E+00 |
| B3 | -6.91763E-01 | 1.39541E+00 | 2.82115E+00 | 1.29993E+00 |
| B4 | 2.49971E+01 | -9.79690E+00 | -2.69125E+01 | -1.10610E+01 |
| B5 | -3.13832E+02 | -2.50001E+00 | 7.64218E+01 | 4.75446E+01 |
| B6 | 1.59686E+03 | 1.67608E+02 | 5.41277E+02 | -1.01305E+02 |
| B7 | -2.01097E+03 | -5.63874E+02 | -5.83828E+03 | -5.15576E+01 |
| B8 | -6.85942E+03 | 8.99352E+02 | 2.12922E+04 | 6.12707E+02 |
| B9 | 1.32337E+03 | -2.13310E+03 | -3.21787E+04 | -8.32843+02 |
| B10 | 5.78305E+04 | 4.63351E+03 | 1.00436E+04 | -3.27211E+01 |
| B11 | 5.92129E+04 | -2.73360E+03 | -1.19666E+04 | 5.74017E-01 |
| B12 | -1.35128E+05 | 3.73401E+03 | 5.79939E+04 | 1.71249E+03 |
| B13 | -3.64055E+05 | 2.74298E+03 | 7.76181E+04 | -5.00584E+02 |
| B14 | -2.22322E+06 | -3.85530E+03 | -2.78764E+04 | -1.75713E+03 |
| B15 | -2.41449E+06 | -1.51744E+05 | -4.54291E+05 | -2.50286E+03 |
| B16 | 1.92673E+07 | -4.18421E+05 | -3.99577E+05 | 3.38389E+03 |
| B17 | 5.65431E+07 | 9.81078E+05 | 6.73954E+05 | 5.52591E+03 |
| B18 | -9.57148E+07 | 6.98270E+06 | 1.14196E+06 | -2.12229E+03 |
| B19 | -2.97089E+08 | -1.99000E+07 | 2.82400E+06 | -1.15885E+04 |
| B20 | 4.53622E+08 | 1.41538E+07 | -5.44811E+06 | 8.59821E+03 |
[ Table 7]
Example 4 lens data
| Si | Ri | Di | Ndj | vdj |
| Object surface | ∞ | 300.000 |
| 1 | (Aperture diaphragm) | 0.033 | ||
| *2 | 1.1653 | 0.591 | 1.5311 | 56 |
| *3 | -3.1515 | 0.284 | ||
| *4 | 0.934 | 0.395 | 1.606 | 27 |
| *5 | 0.8101 | 0.308 | ||
| 6 | ∞ | 0.300 | 1.5168 | 64.2 |
| 7 | ∞ | 0.055 | ||
| Image plane | ∞ |
[ Table 8]
Example 4 aspherical data
| Si | *2 | *3 | *4 | *5 |
| K | 0.10804 | -2.44232 | 2.82676 | 1.33953 |
| B2 | 0.00000E+00 | 0.00000E+00 | 0.00000E+00 | 0.00000E+00 |
| B3 | -2.47528E-01 | 1.19133E+00 | 7.45821E-01 | -3.14862E-01 |
| B4 | 2.10700E+01 | -1.24035E+01 | -1.45932E+01 | -1.24612E+00 |
| B5 | -3.01574E+02 | 2.22914E+01 | 4.41567E+01 | 2.26535E+01 |
| B6 | 1.57956E+03 | 1.23536E+02 | 5.45483E+02 | -9.30806E+01 |
| B7 | -2.00046E+03 | -6.22797E+02 | -5.79326E+03 | -1.32370E+01 |
| B8 | -6.77752E+03 | 9.54999E+02 | 2.13641E+04 | 6.21839E+02 |
| B9 | 1.28327E+03 | -1.86841E+03 | -3.21462E+04 | -8.77217E+02 |
| B10 | 5.70868E+04 | 5.02112E+03 | 9.89784E+03 | -1.12016E+02 |
| B11 | 5.73170E+04 | -2.65657E+03 | -1.24868E+04 | -4.02912E+01 |
| B12 | -1.35544E+05 | 2.59756E+03 | 5.70548E+04 | 1.74229E+03 |
| B13 | -3.61347E+05 | -7.74157E+02 | 7.65471E+04 | -3.04996E+02 |
| B14 | -2.17156E+06 | -9.95638E+03 | -2.70082E+04 | -1.50438E+03 |
| B15 | -2.25263E+06 | -1.56481E+05 | -4.47306E+05 | -2.37824E+03 |
| B16 | 1.93316E+07 | -4.09284E+05 | -3.83860E+05 | 3.19010E+03 |
| B17 | 5.56814E+07 | 1.02933E+06 | 6.89233E+05 | 4.92412E+03 |
| B18 | -9.77429E+07 | 7.10576E+06 | 1.13694E+06 | -2.93777E+03 |
| B19 | -3.03617E+08 | -1.96878E++07 | 2.87611E+06 | -1.17262E+04 |
| B20 | 4.74116E+08 | 1.33808E+07 | -5.76112E+06 | 1.01892E+04 |
[ Table 9]
Example 5 lens data
| Si | Ri | Di | Ndj | vdj |
| Object surface | ∞ | 40.000 | ||
| 1 | (Aperture diaphragm) | 0.063 | ||
| *2 | 1.5018 | 0.673 | 1.6318 | 23 |
| *3 | 1.9163 | 0.121 | ||
| *4 | 0.4521 | 0.503 | 1.6318 | 23 |
| *5 | 0.6687 | 0.349 | ||
| 6 | ∞ | 0.100 | 1.5168 | 64.2 |
| 7 | ∞ | 0.055 | ||
| Image plane | ∞ |
[ Table 10]
Example 5 aspherical data
| Si | *2 | *3 | *4 | *5 |
| K | 2.99998 | 3.00000 | -0.80363 | 0.60092 |
| B2 | 0.00000E+00 | 0.00000E+00 | 0.00000E+00 | 0.00000E+00 |
| B3 | -7.68300E-02 | -8.12108E-01 | -2.12599E-01 | -4.72412E-02 |
| B4 | 3.55895E+00 | 4.25116E+00 | -4.19168E+00 | -9.93579E+00 |
| B5 | -3.70481E+01 | -8.17439E+01 | -7.94532E+01 | 8.34396E+01 |
| B6 | 1.57081E+02 | 3.25207E+02 | 1.16456E+03 | -2.51288E+02 |
| B7 | -5.50942E+02 | -4.97372E+02 | -6.75423E+03 | 5.52184E+01 |
| B8 | 1.25225E+03 | 7.14014E+02 | 1.99506E+04 | 9.60174E+02 |
| B9 | -4.15505E+01 | -2.80142E+03 | -2.97751E+04 | -1.14270E+03 |
| B10 | 5.44786E+03 | 3.67614E+03 | 1.83656E+04 | -5.22250E+02 |
| B11 | -4.90812E+04 | -2.03645E+03 | -7.29362E+03 | -3.69139E+02 |
| B12 | -2.01060E+04 | 1.05037E+04 | 1.21151E+04 | 2.94359E+03 |
| B13 | 4.51553E+05 | 1.81305E+04 | 3.20859E+04 | 3.06965E+02 |
| B14 | 2.32371E+03 | 6.31745E+03 | -1.43425E+04 | -1.35519E+03 |
| B15 | -2.76279E+06 | -2.03464E+05 | -2.52425E+05 | -3.59723E+03 |
| B16 | 3.48704E+05 | -5.85013E+05 | -1.20983E+04 | 6.20222E+02 |
| B17 | 1.45220E+07 | 6.29676E+05 | 1.18234E+06 | 2.22888E+03 |
| B18 | -2.21978E+07 | 7.40230E+06 | -4.59236E+05 | -2.06750E+03 |
| B19 | 3.11931E+07 | -1.64964E+07 | -2.16434E+06 | 8.85088E+03 |
| B20 | -4.68259E+07 | 9.89791E+06 | 1.76151E+06 | -6.93172E+03 |
[ Table 11]
Example 6 lens data
| Si | Ri | Di | Ndj | vdj |
| Object surface | ∞ | 56.500 | ||
| 1 | (Aperture diaphragm) | -0.013 | ||
| *2 | 0.7808 | 0.517 | 1.5311 | 56 |
| *3 | 3.0732 | 0.312 | ||
| *4 | 1.1249 | 0.337 | 1.606 | 27 |
| *5 | 1.0146 | 0.392 | ||
| 6 | ∞ | 0.400 | 1.5168 | 64.2 |
| 7 | ∞ | 0.055 | ||
| Image plane | ∞ |
[ Table 12]
Example 6 aspherical data
| Si | *2 | *3 | *4 | *5 |
| K | 1.56091 | 4.99929 | 4.65725 | 2.33747 |
| B2 | 0.00000E+00 | 0.00000E+00 | 0.00000E+00 | 0.00000E+00 |
| B3 | -3.44820E-01 | 1.16672E+00 | 6.93933E-01 | -6.60636E-01 |
| B4 | 2.14592E+01 | -1.19829E+01 | -1.41389E+01 | -8.58056E-02 |
| B5 | -3.02022E+02 | 2.26650E+01 | 4.38221E+01 | 2.16123E+01 |
| B6 | 1.57851E+03 | 1.23033E+02 | 5.44370E+02 | -9.35206E+01 |
| B7 | -2.00207E+03 | -6.25107E+02 | -5.79672E+03 | -1.26807E+01 |
| B8 | -6.77822E+03 | 9.49911E+02 | 2.13580E+04 | 6.21346E+02 |
| B9 | 1.28942E+03 | -1.87703E+03 | -3.21493E+04 | -8.80664E+02 |
| B10 | 5.71176E+04 | 5.00967E+03 | 9.91189E+03 | -1.18127E+02 |
| B11 | 5.74118E+04 | -2.66466E+03 | -1.24378E+04 | -4.56993E+01 |
| B12 | -1.35314E+05 | 2.61448E+03 | 5.71264E+04 | 1.74439E+03 |
| B13 | -3.60934E+05 | -6.68730E+02 | 7.64454E+04 | -2.87258E+02 |
| B14 | -2.17120E+06 | -9.60800E+03 | -2.79132E+04 | -1.46266E+03 |
| B15 | -2.25379E+06 | -1.55546E+05 | -4.50629E+05 | -2.30899E+03 |
| B16 | 1.93236E+07 | -4.07188E+05 | -3.92653E+05 | 3.27813E+03 |
| B17 | 5.56529E+07 | 1.03320E+06 | 6.71924E+05 | 4.99468E+03 |
| B18 | -9.78131E+07 | 7.10972E+06 | 1.11838E+06 | -2.98015E+03 |
| B19 | -3.03691E+08 | -1.97005E+07 | 2.91516E+06 | -1.20535E+04 |
| B20 | 4.74564E+08 | 1.32895E+07 | -5.40874E+06 | 9.24035E+03 |
Aberration diagrams of the visible regions of the imaging lenses of examples 1 to 6 are shown in fig. 7 to 12, respectively. Fig. 7 to 12 show aberration diagrams of spherical aberration (also referred to as spherical aberration), astigmatism and distortion aberration (also referred to as astigmatism) in the upper half and lateral aberration in the lower half. In fig. 7 to 12, the aberration is shown with the e-line (wavelength 546.07nm) as the reference wavelength, but the aberration is also shown in the g-line (wavelength 436nm) and the C-line (wavelength 656.27nm) in the spherical aberration diagram and the lateral aberration diagram. In the astigmatism diagram, the solid line represents the aberration in the sagittal direction, and the broken line represents the aberration in the meridional direction. The left aberration diagram of the lateral aberration diagram shows the aberration in the meridional direction, and the right aberration diagram shows the aberration in the sagittal direction. The F No. of the spherical aberration diagram indicates the F number, and ω of the other aberration diagrams indicates the half angle of view.
Fig. 13 to 18 show aberration diagrams in the near infrared region of the imaging lenses of examples 1 to 6. In fig. 13 to 18, the aberration with the wavelength of 900nm as the reference wavelength is shown, but in the spherical aberration diagram and the lateral aberration diagram, the aberration with the wavelength of 750nm and the aberration with the wavelength of 1000nm are also shown. In the astigmatism diagram, the solid line represents the aberration in the sagittal direction, and the broken line represents the aberration in the meridional direction. The left aberration diagram of the lateral aberration diagram shows the aberration in the meridional direction, and the right aberration diagram shows the aberration in the sagittal direction. The F No. of the spherical aberration diagram indicates the F number, and ω of the other aberration diagrams indicates the half angle of view.
Table 13 shows values of conditional expressions (1) to (9) corresponding to the imaging lenses of examples 1 to 6. Table 14 shows values of the conditional expressions.
[ Table 13]
| (6) Formula f1/f | 1.28 | 1.18 | 1.19 | 1.21 | 5.98 | 1.14 |
| (7) Formula d3/f | 0.23 | 0.19 | 0.19 | 0.20 | 0.11 | 0.19 |
| (8) Formula vd1-vd2 | 33 | 29 | 29 | 29 | 0 | 29 |
| (9) Formula imd/f | 0.373 | 0.489 | 0.459 | 0.402 | 0.417 | 0.442 |
[ Table 14]
In addition, the rear intercept point in TL in table 13 is expressed by air conversion. For example, in example 1, table 1 shows lens data when the lens is used with an object distance of 17mm, and the actual length (geometric length) on the optical axis including the thickness of the optical member PP from the surface closest to the object (the surface of the aperture stop St in example 1) to the image plane Sim is 1.999mm, and the length from the surface closest to the object to the image plane Sim is 1.958mm by air conversion of the optical member PP of 0.12 mm. TL in table 13 represents the value obtained by air-converting the optical member PP in this manner.
Fig. 19 shows the relationship between Zf' and Zf ″ of example 1 and the height Y as data on the above conditional expressions (1) and (2). The left vertical axis of fig. 19 indicates the value of Zf', and the right vertical axis of fig. 19 indicates the value of Zf ″. The abscissa of fig. 19 is Y/ER1, and the abscissa is a value obtained by normalizing the height Y by the effective radius of the surface on the object side. Fig. 20 shows the relationship between | Zr' | and the height Y in example 1 as data on the above conditional expressions (3) and (4). The abscissa of fig. 20 is Y/ER2, and the value normalized by the effective radius of the image-side surface as the height Y is taken as the abscissa. Similarly, the relationships between Zf 'and Zf ″ of examples 2 to 6 and the height Y are shown in fig. 21, 23, 25, 27, and 29, respectively, and the relationships between | Zr' | of examples 2 to 6 and the height Y are shown in fig. 22, 24, 26, 28, and 30, respectively.
As can be seen from the above data, the imaging lenses of examples 1 to 6 have a very compact structure in which the distance from the aperture stop St to the image plane Sim is 2mm or less or about 2mm, and have a relatively long back intercept, and the F-number is as small as 2.2 to 2.4, and the aberrations are well corrected, and have good optical performance, and are constituted by a small number of 2 lenses.
Next, an imaging device according to an embodiment of the present invention will be described. Fig. 31 is a sectional view showing a schematic configuration of an imaging device 200 of the 1 st embodiment using the imaging lens of the present invention. Fig. 32 is an enlarged perspective view showing an interior of the imaging device 200 of the 1 st embodiment. The imaging device 200 is a device for biometric authentication, and is a device for identifying an individual by observing a finger 201 of a person.
The imaging device 200 illuminates a finger 201 of a person with an infrared light lamp 210 that emits near-infrared light having a wavelength of 700nm to 1000nm, and forms an image near the surface of the finger 201 on a light-receiving surface of an imaging element 230 by passing the image through an imaging lens 220 and an infrared light transmission filter 225 that transmits infrared light and cuts visible light. Then, the image near the surface of the finger 201 formed on the light receiving surface is captured by the imaging element 230. The image captured by the image pickup device 230 is displayed on the display device 240.
The image showing the vicinity of the surface of the finger 201 displayed on the display device 240 allows the peripheral blood vessels of the veins in the vicinity of the surface of the skin of the finger 201 to be observed, thereby enabling the individual to be identified.
Fig. 33 is a perspective view showing a schematic configuration of the 2 nd imaging device 300 using the imaging lens of the present invention, and is a view showing the inside of the 2 nd imaging device 300. The imaging device 300 of the 2 nd can be used as a monitoring camera including a biometric authentication camera such as face verification or a door video phone camera, and can be used as an imaging device for identifying an individual by observing a face 301 of a person.
The imaging device 300 forms an image of the human face 301 on the light receiving surface of the imaging element 330 through the imaging lens 320 and the infrared cut filter 325 for transmitting visible light and cutting infrared light. Then, an image of the face hole 301 formed on the light receiving surface is captured by the imaging element 330. The image captured by the imaging element 330 is displayed on the display device 340. An individual can be identified based on the image representing the face 301 of the person displayed by the display device 340.
The imaging device to which the present invention can be applied is not limited to the above example, and may be an imaging device that reads biological information such as the color of a pupil, the shape of a palm vein, and a finger fingerprint, for example. In addition, as an image pickup device to which the present invention can be applied, there are an image pickup device that picks up an image based on near infrared light having a wavelength of 700nm to 1000nm and is used for night vision and night vision for night vision, dark places, and the like, an image pickup device that is mounted on a door video phone, a car, and the like for monitoring, an image pickup device that reads a barcode, recognizes a bill, a coin, and the like, an image pickup device for a portable terminal, and the like.
The embodiments and examples have been described above, but the present invention is not limited to the embodiments and examples described above, and various modifications can be made. For example, the values of the curvature radius, the surface interval, the refractive index, and the abbe number of each lens component are not limited to the values shown in the numerical examples, and may be other values.
Claims (15)
1. An imaging lens characterized in that,
the device comprises the following components in sequence from an object side: an aperture stop, a 1 st lens having both surfaces thereof formed in an aspherical shape and having positive refractive power in a central portion thereof, a 2 nd lens having both surfaces thereof formed in an aspherical shape and having positive refractive power in a central portion thereof,
in the above-described lens 1, the object-side surface has a shape in which the convex surface is directed toward the object side in the central portion, the positive power decreases as the convex surface moves from the central portion to the peripheral portion, and the image-side surface has a negative power in the peripheral portion, and the image-side surface has a positive power stronger than that in the central portion in the peripheral portion,
the 2 nd lens element has a meniscus shape with a convex surface directed to the object side in the center.
2. The imaging lens of claim 1,
the aspherical surface of the 1 st lens on the object side is expressed by the following aspherical surface formula, where Y represents the height in the direction perpendicular to the optical axis, zf (Y) represents the distance in the optical axis direction from the tangent plane to the vertex of the aspherical surface to the aspherical surface of the height Y, Cf represents the curvature of the paraxial region, Kf represents the aspherical coefficient, and Bfn represents the n-th-order aspherical coefficient,
Zf(Y)＝Cf·Y2/{1+(1-Kf·Cf2·Y2)1/2}+∑Bfn·|Y|n
wherein n is an integer of 2 or more,
and Zf' max is a maximum value of 1-time differential to Y in the effective diameter with respect to Zf (Y), the following conditional expression (1) is satisfied:
Zf’max＜0.5…(1)。
3. the imaging lens of claim 2,
when 2-time differential of Y with respect to Zf (Y) is Zf ", a height of a point where Zf ″ in the effective diameter is maximum in a direction perpendicular to the optical axis is Y1, and an effective radius of the object-side surface of the 1 st lens is ER1, the following conditional expression (2) is satisfied:
Y1/ER1＜0.20…(2)。
4. the imaging lens of claim 1,
the aspherical surface of the first lens element 1 on the object side is expressed by the following aspherical surface formula, where Y represents the height in the direction perpendicular to the optical axis, zf (Y) represents the distance in the optical axis direction from the tangent plane to the vertex of the aspherical surface to the aspherical surface, Cf represents the curvature of the paraxial region, Kf represents the aspherical coefficient, and Bfn represents the n-th-order aspherical coefficient,
Zf(Y)＝Cf·Y2/{1+(1-Kf·Cf2·Y2)1/2}+∑Bfn·|Y|n
wherein n is an integer of 2 or more,
when Zf is a 2-fold differential of Zf (Y) with respect to Y, Y1 is a height of a point where Zf' in an effective diameter is a maximum in a direction perpendicular to an optical axis, and ER1 is an effective radius of a surface on the object side of the 1 st lens, the following conditional expression (2) is satisfied
Y1/ER1＜0.20…(2)。
5. The imaging lens according to any one of claims 1 to 4,
regarding the aspherical surface on the image side of the 1 st lens, the aspherical shape is expressed by the following aspherical expression where Y represents the height in the direction perpendicular to the optical axis, zr (Y) represents the distance in the optical axis direction from the tangent plane to the vertex of the aspherical surface to the aspherical surface for the height Y, Cr represents the curvature of the paraxial region, Kr represents the aspherical coefficient, and Brn represents the n-th aspherical coefficient,
Zr(Y)＝Cr·Y2/{1+(1-Kr·Cr2·Y2)1/2}+∑Brn·|Y|n
wherein n is an integer of 2 or more,
and the following conditional expression (3) is satisfied where Zr ' is a 1-time differential of Zr (Y) with respect to Y, ER2 is an effective radius of the image-side surface of the 1 st lens, and | Zr ' | hmax is a maximum value of | Zr ' | in a range of Y < 0.5 × ER 2:
|Zr’|hmax＜0.25…(3)。
6. the imaging lens of claim 5,
when Zr (Y) is given as a 1-time differential with respect to Y, Y2 is given as a height in a direction perpendicular to the optical axis of a point where | Zr '| takes a value of 20% of a maximum value of | Zr' | in the effective diameter, and ER2 is given as an effective radius of a surface on the image side of the 1 st lens, the following conditional expression (4) is satisfied:
0.50＜Y2/ER2…(4)。
7. the imaging lens according to any one of claims 1 to 4,
regarding the aspherical surface on the image side of the 1 st lens, the aspherical shape is expressed by the following aspherical expression where Y represents the height in the direction perpendicular to the optical axis, zr (Y) represents the distance in the optical axis direction from the tangent plane to the vertex of the aspherical surface to the aspherical surface for the height Y, Cr represents the curvature of the paraxial region, Kr represents the aspherical coefficient, and Brn represents the n-th aspherical coefficient,
Zr(Y)＝Cr·Y2/{1+(1-Kr·Cr2·Y2)1/2}+∑Brn·|Y|n
wherein n is an integer of 2 or more,
and the following conditional expression (4) is satisfied where Zr ' is a 1-time differential of Y with respect to Zr (Y), Y2 is a height in a direction perpendicular to the optical axis of a point where | Zr ' | takes a value of 20% of a maximum value of | Zr ' | in the effective diameter, and ER2 is an effective radius of a surface on the image side of the 1 st lens:
0.50＜Y2/ER2…(4)。
8. the imaging lens according to any one of claims 1 to 4,
when TL is an optical axis distance from one of the aperture stop and the object-side surface of the 1 st lens, which is closer to the object on the optical axis, to the image plane, and f is a focal length of the entire system, the following conditional expression (5) is satisfied:
1.05＜TL/f＜2.0…(5)。
9. the imaging lens according to any one of claims 1 to 4,
the object-side surface of the 1 st lens has at least one inflection point in the effective diameter.
10. The imaging lens according to any one of claims 1 to 4,
when the focal length of the 1 st lens is f1 and the focal length of the entire system is f, the following conditional expression (6) is satisfied:
1.10＜f1/f＜7.5…(6)。
11. the imaging lens according to any one of claims 1 to 4,
when the distance between the 1 st lens and the 2 nd lens on the optical axis is d3 and the focal length of the entire system is f, the following conditional expression (7) is satisfied:
0.06＜d3/f＜0.6…(7)。
12. the imaging lens according to any one of claims 1 to 4,
when the abbe number of the 1 st lens to the d-line is ν d1 and the abbe number of the 2 nd lens to the d-line is ν d2, the following conditional expression (8) is satisfied:
15＜νd1-νd2…(8)。
13. an image pickup apparatus is characterized in that,
an imaging lens according to any one of claims 1 to 12.
14. A camera device for night vision surveillance, characterized in that,
the disclosed device is provided with:
the imaging lens according to any one of claims 1 to 12; and
an imaging element for imaging an image based on near-infrared light having a wavelength of 700nm to 1000 nm.
15. An imaging device for biometric authentication, characterized in that,
the disclosed device is provided with:
the imaging lens according to any one of claims 1 to 12; and
an imaging element for imaging an image based on near-infrared light having a wavelength of 700nm to 1000 nm.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2009-114403 | 2009-05-11 | ||
| JP2009114403A JP2010262218A (en) | 2009-05-11 | 2009-05-11 | Imaging lens and imaging apparatus |
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| CN201773214U true CN201773214U (en) | 2011-03-23 |
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| CN2010201546072U Expired - Lifetime CN201773214U (en) | 2009-05-11 | 2010-03-24 | Photographic lens and photographic device |
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| JP (1) | JP2010262218A (en) |
| CN (1) | CN201773214U (en) |
| TW (1) | TWM388793U (en) |
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| EP2643727B1 (en) * | 2010-11-23 | 2015-03-18 | Umicore | Super wide angle lens arrangement for infrared applications |
| TWI438476B (en) | 2012-01-12 | 2014-05-21 | Largan Precision Co Ltd | Image capturing system |
| US8675288B2 (en) | 2012-06-12 | 2014-03-18 | Samsung Electro-Mechanics Co., Ltd. | Lens module |
| CN103123414A (en) * | 2012-11-15 | 2013-05-29 | 玉晶光电(厦门)有限公司 | Portable electronic device and optical imaging lens of portable electronic device |
| JP2014167497A (en) * | 2013-01-31 | 2014-09-11 | Hitachi Maxell Ltd | Infrared lens device |
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| JP3717483B2 (en) * | 2003-02-19 | 2005-11-16 | フジノン株式会社 | Imaging lens |
| JP2007293176A (en) * | 2006-04-27 | 2007-11-08 | Konica Minolta Opto Inc | Imaging lens, imaging apparatus, and personal digital assistant equipped with imaging apparatus |
| KR100780240B1 (en) * | 2006-12-01 | 2007-11-27 | 삼성전기주식회사 | Ultra compact imaging optics |
-
2009
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