Imaging lens and imaging device
阅读说明：本技术 成像镜头及摄像装置 (Imaging lens and imaging device ) 是由 宫城岛峻介 于 2019-06-20 设计创作，主要内容包括：本发明提供一种可实现小型化、且畸变像差和倍率色差被充分地校正而具有良好的性能的成像镜头及具备该成像镜头的摄像装置。成像镜头从物体侧依次由正的第1透镜组(G1)、光圈、正的第2透镜组(G2)、负的第3透镜组(G3)构成。从物体侧起的第1个及第2个透镜均为将凸面朝向物体侧的负单透镜。第2透镜组(G2)包括由负透镜和正透镜构成的接合透镜。对焦时只有第2透镜组(G2)移动。在将第1透镜组(G1)、第2透镜组(G2)的焦点距离分别设为f1、f2的情况下,成像镜头满足0.7＜f1/f2＜2。(The invention provides an imaging lens which can realize miniaturization, and has good performance by fully correcting distortion aberration and magnification chromatic aberration, and an imaging device with the imaging lens. The imaging lens is composed of a positive 1 st lens group (G1), a diaphragm, a positive 2 nd lens group (G2), and a negative 3 rd lens group (G3) in this order from the object side. The 1 st and 2 nd lenses from the object side are both negative single lenses with the convex surface facing the object side. The 2 nd lens group (G2) includes a cemented lens composed of a negative lens and a positive lens. Only the 2 nd lens group (G2) moves upon focusing. When the focal distances of the 1 st lens group (G1) and the 2 nd lens group (G2) are respectively f1 and f2, the imaging lens satisfies 0.7 < f1/f2 < 2.)
1. An imaging lens includes, in order from an object side to an image side, a 1 st lens group having positive refractive power, a stop, a 2 nd lens group having positive refractive power, and a 3 rd lens group having negative refractive power,
the 1 st and 2 nd lenses from the object side of the 1 st lens group are each a single lens having a negative refractive power with a convex surface directed to the object side, the 1 st lens group includes at least 1 positive lens,
the 2 nd lens group includes a cemented lens in which 1 negative lens and 1 positive lens are cemented,
when focusing from an object at infinity to a nearest object is performed, only the 2 nd lens group is moved along the optical axis,
when the focal distance of the 1 st lens group is set to f1,
in the case where the focal distance of the 2 nd lens group is set to f2,
satisfy by
0.7＜f1/f2＜2 (1)
The conditional formula (1).
2. The imaging lens according to claim 1,
the partial dispersion ratio between the g-line and the F-line of the positive lens having the lowest refractive index in the 1 st lens group is set to θ gfPL,
the partial dispersion ratio between the g-line and the F-line of the negative lens having the lowest refractive index in the 1 st lens group is set to θ gfNL,
the abbe number of the d-line reference of the positive lens with the lowest refractive index in the 1 st lens group is defined as vpl,
when the abbe number of the negative lens having the lowest refractive index in the 1 st lens group is represented by v NL,
satisfy by
-0.015＜(θgfPL-θgfNL)/(v PL-v NL)＜0 (2)
The conditional formula (2).
3. The imaging lens according to claim 1 or 2,
the partial dispersion ratio between the g-line and the F-line of the positive lens having the highest refractive index in the 1 st lens group is set to θ gfPH,
when the partial dispersion ratio between the g-line and the F-line of the negative lens having the highest refractive index in the 1 st lens group is represented by θ gfNH,
satisfy by
-0.05＜θgfPH-θgfNH＜0 (3)
The conditional expression (3).
4. The imaging lens according to claim 1 or 2,
setting a back focal length of the imaging lens at an air converted distance to be Bf in a state of focusing on an object at infinity,
when TTL is defined as the sum of Bf and the distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side,
satisfy by
2.5＜TTL/Bf＜5.5 (4)
The conditional formula (4).
5. The imaging lens according to claim 1 or 2,
the 1 st and 2 nd lenses from the object side of the 1 st lens group are both meniscus lenses,
a single lens having a positive refractive power is disposed in series with the meniscus lens on an image side of the 2 nd meniscus lens from the object side of the 1 st lens group,
a cemented lens, which is composed of at least 1 negative lens and at least 1 positive lens cemented together and has a convex lens surface closest to the image side, is disposed closest to the image side of the 1 st lens group.
6. The imaging lens according to claim 1 or 2,
the 2 nd lens group includes, in order from the object side toward the image side:
the cemented lens is formed by sequentially cementing a biconcave lens and a biconvex lens from the object side; and
a biconvex shaped singlet lens.
7. The imaging lens according to claim 1 or 2,
the 3 rd lens group includes at least 1 negative lens and at least 1 positive lens.
8. The imaging lens according to claim 1 or 2,
the lens surface of the 3 rd lens group closest to the object side is a concave surface, and the lens surface of the 3 rd lens group closest to the image side is a convex surface.
9. The imaging lens according to claim 1 or 2,
the 1 st lens group is composed of 6 or 7 lenses.
10. The imaging lens according to claim 1 or 2,
the 2 nd lens group is composed of 3 lenses.
11. The imaging lens according to claim 1 or 2,
the 3 rd lens group is composed of 2 or 3 lenses.
12. The imaging lens according to claim 1,
satisfy by
1＜f1/f2＜1.8 (1-1)
The conditional formula (1-1).
13. The imaging lens according to claim 2,
satisfy by
-0.01＜(θgfPL-θgfNL)/(v PL-v NL)＜0 (2-1)
The conditional formula (2-1).
14. The imaging lens according to claim 3,
satisfy by
-0.04＜θgfPH-θgfNH＜0 (3-1)
The conditional formula (3-1).
15. The imaging lens according to claim 4,
satisfy by
3＜TTL/Bf＜4.8 (4-1)
The conditional formula (4-1).
16. An imaging device provided with the imaging lens according to any one of claims 1 to 15.
Technical Field
The present invention relates to an imaging lens and an imaging apparatus.
Background
Conventionally, as an imaging lens applicable to an imaging device such as a digital camera, for example, a lens system having a 3-group structure as described in
Patent document 1: japanese patent laid-open No. 2014-142604
Patent document 2: japanese patent laid-open publication No. 2013-125213
Patent document 3: japanese patent laid-open publication No. 2013-029658
In recent years, along with the miniaturization of imaging devices, miniaturization of imaging lenses mounted on imaging devices has been also demanded. Further, along with the miniaturization, higher performance is also required, and the level of the requirement is increasing year by year.
The correction of distortion aberration of the lens system described in
Disclosure of Invention
The present invention has been accomplished in view of the above circumstances. An object of one embodiment of the present invention is to provide an imaging lens that can be made compact and has good performance by sufficiently correcting distortion aberration and chromatic aberration of magnification, and an imaging apparatus including the imaging lens.
Specific methods for solving the above problems include the following.
An imaging lens according to
satisfies the conditional expression (1) represented by 0.7 < f1/f2 < 2 (1).
An imaging lens according to
satisfies the conditional formula (2) represented by-0.015 < (θ gfPL- θ gfNL)/(v PL-v NL) < 0 (2).
An imaging lens according to
satisfies the conditional expression (3) represented by-0.05 < theta gfPH-theta gfNH < 0 (3).
An imaging lens according to claim 4 is the imaging lens according to any one of
satisfies the conditional expression (4) represented by 2.5 < TTL/Bf < 5.5 (4).
An imaging lens according to claim 5 is the imaging lens according to any one of
An imaging lens according to claim 6 is the imaging lens according to any one of
An imaging lens according to claim 7 is the imaging lens according to any one of
An imaging lens according to
An imaging lens according to claim 9 is the imaging lens according to any one of
An imaging lens according to claim 10 is the imaging lens according to any one of
An imaging lens according to claim 11 is the imaging lens according to any one of
An imaging lens according to claim 12 is the imaging lens according to
satisfies the conditional expression (1-1) represented by 1 < f1/f2 < 1.8 (1-1).
An imaging lens according to claim 13 is the imaging lens according to
satisfies the conditional formula (2-1) represented by-0.01 < (θ gfPL- θ gfNL)/(v PL-v NL) < 0 (2-1).
An imaging lens according to
satisfies the conditional expression (3-1) represented by-0.04 < theta gfPH-theta gfNH < 0 (3-1).
An imaging lens according to claim 15 is the imaging lens according to claim 4,
satisfies the conditional expression (4-1) represented by 3 < TTL/Bf < 4.8 (4-1).
The imaging device according to claim 16 includes any one of the imaging lenses according to
In addition, "consisting of" and "consisting of" in the present specification mean that, in addition to the components listed above, the following components may be included: a lens having substantially no optical power; optical elements other than lenses, such as a diaphragm, a filter, and a cover glass; lens flanges, lens barrels, imaging elements, and mechanism parts such as a handshake correction mechanism.
In the present specification, "group having positive refractive power" means that the group as a whole has positive refractive power. Similarly, "group having negative refractive power" means that the group as a whole has negative refractive power. "lens having positive refractive power" and "positive lens" mean the same. "a lens having a negative refractive power" and "a negative lens" mean the same. The "lens group" is not limited to a configuration composed of a plurality of lenses, and may be a configuration composed of only 1 lens.
"singlet lens" refers to 1 lens that is not cemented. However, a compound aspherical lens (a spherical lens and an aspherical film formed on the spherical lens are integrated, and the lens functioning as 1 aspherical lens as a whole) is treated as 1 lens instead of being regarded as a cemented lens. The signs of refractive power and the surface shape of the lens surface relating to the lens including the aspherical surface are considered in the paraxial region unless otherwise specified.
The "focal distance" used in the conditional expression is a paraxial focal distance. The "back focus" used in the conditional expression is an air-converted distance on the optical axis from the lens surface closest to the image side to the focal position on the image side. The values used in the conditional expressions are values in the case where the d-line is used as a reference, except for the partial dispersion ratio. The partial dispersion ratio θ gF between g-line and F-line of a certain lens is defined by θ gF ═ (Ng-NF)/(NF-NC) when the refractive indices of the lens to g-line, F-line and C-line are Ng, NF and NC, respectively. The "d line", "C line", "F line" and "g line" described in the present specification are bright lines, the wavelength of the d line is 587.56nm (nm), the wavelength of the C line is 656.27nm (nm), the wavelength of the F line is 486.13nm (nm), and the wavelength of the g line is 435.84nm (nm).
Effects of the invention
According to an embodiment of the present invention, it is possible to provide an imaging lens that is small in size and has good performance by sufficiently correcting distortion aberration and chromatic aberration of magnification, and an imaging apparatus including the imaging lens.
Drawings
Fig. 1 is a sectional view showing a configuration of an imaging lens according to an embodiment of the present invention (an imaging lens according to example 1 of the present invention).
Fig. 2 is a sectional view showing the structure of an imaging lens of
Fig. 3 is a sectional view showing the structure of an imaging lens of
Fig. 4 is a sectional view showing the structure of an imaging lens of embodiment 4 of the present invention.
Fig. 5 is a sectional view showing the structure of an imaging lens of embodiment 5 of the present invention.
Fig. 6 is each aberration diagram of the imaging lens of
Fig. 7 is each aberration diagram of the imaging lens of
Fig. 8 is each aberration diagram of an imaging lens of
Fig. 9 is each aberration diagram of the imaging lens of embodiment 4 of the present invention.
Fig. 10 is each aberration diagram of the imaging lens of embodiment 5 of the present invention.
Fig. 11 is a front perspective view of an imaging device according to an embodiment of the present invention.
Fig. 12 is a perspective view of the back side of the imaging device according to the embodiment of the present invention.
Detailed Description
Hereinafter, a detailed description will be given with reference to embodiments of the imaging lens of the present disclosure. Fig. 1 is a cross-sectional view showing a structure of an imaging lens according to an embodiment of the present invention. The example shown in fig. 1 corresponds to an imaging lens of
The imaging lens of the present disclosure is composed of, in order from the object side toward the image side along the optical axis Z, a 1 St lens group G1 having positive refractive power, an aperture stop St, a 2 nd lens group G2 having positive refractive power, and a 3 rd lens group G3 having negative refractive power. In this way, the lens groups are arranged in order of positive, and negative refractive power from the object side toward the image side, which is advantageous in shortening the total length of the lens system. In addition, the aperture stop St shown in fig. 1 indicates a position on the optical axis Z.
For example, in the imaging lens shown in fig. 1, the 1 st lens group G1 is composed of 6 lenses of lenses L11 to L16 in order from the object side to the image side, the 2 nd lens group G2 is composed of 3 lenses of lenses L21 to L23 in order from the object side to the image side, and the 3 rd lens group G3 is composed of 2 lenses of lenses L31 to L32 in order from the object side to the image side. However, as in the embodiment described later, the number of lenses constituting each lens group may be different from that in the embodiment shown in fig. 1.
The imaging lens is constituted as follows: upon focusing from an infinity object to a closest object, only the 2 nd lens group G2 moves along the optical axis Z, and the 1 St lens group G1, aperture stop St, and 3 rd lens group G3 are fixed with respect to the image plane Sim. That is, a lens group (hereinafter, referred to as a focusing group) which moves in focusing is the 2 nd lens group G2. By configuring to move only the 2 nd lens group G2 at the time of focusing, the focusing unit that moves at the time of focusing can be made small and light in weight, and therefore, it is advantageous to reduce the load on the drive system that drives the focusing group and to increase the speed of focusing. Further, the 1 st lens group G1 and the 3 rd lens group G3 are fixed at the time of focusing, whereby dust-proof and drip-proof effects can be obtained.
In the example shown in fig. 1, the 2 nd lens group G2 moves to the object side in focusing from an infinity object to a closest object. The arrow toward the left direction below the 2 nd lens group G2 shown in fig. 1 indicates that the 2 nd lens group G2 is a focusing group that moves to the object side upon focusing from an infinity object to a closest object.
In this imaging lens, an aperture stop St is disposed between the 1 St lens group G1 and the 2 nd lens group G2. Since the aperture stop St is disposed just before the object side of the focus group, the height of the light beam incident on the focus group can be suppressed, and therefore, the diameter of the lens of the focus group can be reduced, which is advantageous for reducing the load of the drive system for driving the focus group and speeding up the focusing.
The 1 st and 2 nd lenses from the object side of the 1 st lens group G1 are both single lenses having a negative refractive power with the convex surface facing the object side. The 1 st lens group G1 includes at least 1 positive lens. By arranging 2 single lenses having negative refractive power with their convex surfaces facing the object side in series from the most object side, it is possible to easily correct distortion aberration and to reduce the size of the imaging lens in the radial direction while securing the angle of view. Further, by causing these 2 negative lenses and positive lenses to cooperate, chromatic aberration and distortion aberration can be corrected well.
The 1 st lens group G1 may be configured to have the above-described configuration and be composed of 6 or 7 lenses as a whole. In this case, the 1 st lens group G1 can be configured to include the number of lenses necessary for correcting distortion and chromatic aberration in a satisfactory manner while taking into consideration downsizing. In addition, in a lens system including 3 lens groups and having the aperture stop St disposed between the 1 St lens group G1 and the 2 nd lens group G2, the number of lenses in the 1 St lens group G1 is 6 or 7, which facilitates the aperture stop St to be positioned near the middle of the lens system, and thus facilitates the improvement of the object-side and image-side symmetry of the aperture stop St, which is advantageous for the correction of distortion aberration.
Preferably, the 1 st and 2 nd negative lenses from the object side of the 1 st lens group G1 are both meniscus lenses, and in this case, correction of distortion aberration becomes easy. Further, it is preferable that a single lens having a positive refractive power is disposed in the 1 st lens group G1 on the image side of the 2 nd meniscus lens from the object side, and a cemented lens in which at least 1 negative lens and at least 1 positive lens are cemented together and the lens surface closest to the image side is a convex surface is disposed on the most image side of the 1 st lens group G1. In this case, the 1 st lens group G1 including a combination of a positive lens and a negative lens can suppress the occurrence of chromatic aberration in the 1 st lens group G1, and further suppress the variation in chromatic aberration when the 2 nd lens group G2 moves in focus. Further, the most image side surface of the 1 st lens group G1 is a convex surface, whereby distortion aberration and astigmatism can be corrected. In addition, when at least 2 single lenses having positive refractive power are disposed in the image side of the 2 nd meniscus lens from the object side in the 1 st lens group G1, which is continuous with the meniscus lens, it is preferable to suppress the occurrence of chromatic aberration in the 1 st lens group G1.
Specifically, for example, the 1 st lens group G1 may be configured as a negative meniscus lens having 2 convex surfaces facing the object side, a single lens having a positive refractive power having 2 or 3 convex surfaces facing the object side, and a cemented lens in which a biconcave lens and a biconvex lens are cemented in this order from the object side to the image side. Alternatively, the 1 st lens group G1 may be composed of, in order from the object side to the image side, 3 negative meniscus lenses with convex surfaces facing the object side, a single lens with positive refractive power with convex surfaces facing the object side, and a cemented lens in which a biconcave lens and a biconvex lens are cemented in order from the object side.
The 2 nd lens group G2 is configured to include a cemented lens in which 1 negative lens and 1 positive lens are cemented. The 2 nd lens group G2 has 1 negative lens and 1 positive lens, and therefore chromatic aberration of the 2 nd lens group G2 alone can be appropriately suppressed, and an effect of suppressing distortion aberration is also obtained.
The 2 nd lens group G2 may be configured to have the above-described configuration and be composed of 3 lenses as a whole. In this case, while downsizing of the 2 nd lens group G2 which is a focusing group is achieved, it is advantageous to correct various aberrations including chromatic aberration well.
The 2 nd lens group G2 preferably includes, in order from the object side toward the image side, a cemented lens in which a biconcave lens and a biconvex lens are cemented together in order from the object side, and a biconvex single lens. In this case, by the combination of the biconcave lens and the biconvex lens, an effect of correcting the curvature of field and astigmatism can be obtained, and chromatic aberration can be corrected in the 2 nd lens group G2. Further, the effect of correcting spherical aberration and distortion aberration can be obtained by the biconvex single lens having positive refractive power.
In order to achieve both downsizing and good optical performance, the 2 nd lens group G2 is preferably composed of, in order from the object side to the image side, a cemented lens in which a biconcave lens and a biconvex lens are cemented in order from the object side, and a biconvex single lens.
The 3 rd lens group G3 may be constituted by 2 or 3 lenses as a whole. In this case, it is advantageous to correct various aberrations well while achieving miniaturization.
The 3 rd lens group G3 preferably includes at least 1 negative lens and at least 1 positive lens. The 3 rd lens group G3 is configured to include both negative and positive lenses, whereby in the lens group closest to the image plane Sim, suppression of chromatic aberration generated in the lens group alone can be obtained, which is advantageous for suppressing chromatic aberration.
Preferably, the lens surface closest to the object side in the 3 rd lens group G3 is a concave surface, and the lens surface closest to the image side in the 3 rd lens group G3 is a convex surface. The effect of correcting the curvature of image plane can be obtained by making the most object-side lens surface of the 3 rd lens group G3 concave. The occurrence of astigmatism can be suppressed by making the most image-side lens surface of the 3 rd lens group G3 convex.
For example, the 3 rd lens group G3 may be configured by a cemented lens in which a biconcave lens and a biconvex lens are cemented in this order from the object side. Alternatively, the 3 rd lens group G3 may be configured by a cemented lens formed by 2 positive meniscus lenses with the convex surface facing the image side and a negative meniscus lens with the convex surface facing the image side. Alternatively, the 3 rd lens group G3 may be configured by a cemented lens in which a biconcave lens, a biconvex lens, and a negative meniscus lens having a convex surface facing the image side are cemented in this order from the object side.
Next, the structure of the conditional expression will be described. The imaging lens of the present disclosure satisfies the following conditional expression (1) with the focal distance of the 1 st lens group G1 set to f1 and the focal distance of the 2 nd lens group G2 set to
0.7＜f1/f2＜2 (1)
1＜f1/f2＜1.8 (1-1)
Preferably, the following conditional expression (2) is satisfied where θ gfPL represents a partial dispersion ratio between G-line and F-line of the positive lens having the lowest refractive index in the 1 st lens group G1, θ gfNL represents a partial dispersion ratio between G-line and F-line of the negative lens having the lowest refractive index in the 1 st lens group G1, ν PL represents an abbe number of the positive lens having the lowest refractive index in the 1 st lens group G1, and ν NL represents an abbe number of the negative lens having the lowest refractive index in the 1 st lens group G1. By not being equal to or less than the lower limit of conditional expression (2), the difference between θ gfPL and θ gfNL is not excessively large, and the difference between v PL and v NL is not excessively small, so that a two-dimensional achromatic effect is sufficiently obtained, and a two-dimensional chromatic aberration of magnification can be corrected satisfactorily. By not being equal to or more than the upper limit of conditional expression (2), the difference between θ gfPL and θ gfNL does not become excessively small, and a combination of materials having low dispersion can be avoided when a positive lens and a negative lens are combined, so that a combination of materials effective for correction of two-dimensional chromatic aberration of magnification can be easily selected. Further, a configuration satisfying the following conditional expression (2-1) can provide better characteristics.
-0.015＜(θ gfPL-θgfNL)/(v PL-v NL)＜0 (2)
-0.01＜(θgfPL-θgfNL)/(v PL-v NL)＜0 (2-1)
It is preferable that the following conditional expression (3) is satisfied, where θ gfPH is a partial dispersion ratio between G-line and F-line of the positive lens having the highest refractive index in the 1 st lens group G1, and θ gfNH is a partial dispersion ratio between G-line and F-line of the negative lens having the highest refractive index in the 1 st lens group G1. Generally, an optical material having a high refractive index tends to have a large dispersion. By not being equal to or less than the lower limit of conditional expression (3), it is possible to reduce the two-dimensional chromatic aberration of magnification caused by the high-refractive-index positive lens and the high-refractive-index negative lens. By not being equal to or more than the upper limit of conditional expression (3), the refractive power of the negative lens in the 1 st lens group G1 can be ensured, and the radial miniaturization of the imaging lens can be facilitated. Further, a configuration satisfying the following conditional expression (3-1) can provide better characteristics.
-0.05＜θgfPH-θgfNH＜0 (3)
-0.04＜θgfPH-θgfNH＜0 (3-1)
Preferably, in a state of focusing on an object at infinity, the following conditional expression (4) is satisfied, where Bf is a back focal length of the imaging lens in an air-converted distance, and TTL is a sum of Bf and an optical axis distance from a lens surface closest to the object side to a lens surface closest to the image side. By not being equal to or less than the lower limit of conditional expression (4), the refractive power of the lens group closest to the image side does not become excessively weak, and correction of astigmatism becomes easy. By not being equal to or more than the upper limit of conditional expression (4), the total length of the lens system can be shortened. Further, a configuration satisfying the following conditional expression (4-1) can provide better characteristics.
2.5＜TTL/Bf＜5.5 (4)
3＜TTL/Bf＜4.8 (4-1)
The preferred structures and realizable structures described above can be combined arbitrarily and selected and used as appropriate according to the required specifications. According to the technique of the present disclosure, miniaturization can be achieved, distortion aberration and chromatic aberration of magnification are sufficiently corrected, and an imaging lens having good performance can be realized.
Next, a numerical example of the imaging lens of the present invention will be explained.
[ example 1]
A cross-sectional view showing the structure of the imaging lens of
The 1 st lens group G1 is composed of 6 lenses of lenses L11 to L16 in order from the object side toward the image side, the 2 nd lens group G2 is composed of 3 lenses of lenses L21 to L23 in order from the object side toward the image side, and the 3 rd lens group G3 is composed of 2 lenses of lenses L31 to L32 in order from the object side toward the image side.
Table 1 shows basic lens data of the imaging lens of example 1, table 2 shows various factors, and table 3 shows aspherical coefficients. In table 1, the column Sn shows the surface number in the case where the surface closest to the object side is the 1 st surface and the numbers are increased one by one toward the image side, the column R shows the radius of curvature of each surface, and the column D shows the surface interval on the optical axis between each surface and the surface adjacent to the image side. The refractive index of each component with respect to the d-line is shown in the Nd column, the abbe number of each component with respect to the d-line is shown in the vd column, and the partial dispersion ratio between the g-line and the F-line of each component is shown in the θ gF column.
In table 1, the sign of the radius of curvature of the surface of the shape in which the convex surface faces the object side is positive, and the sign of the radius of curvature of the surface of the shape in which the convex surface faces the image side is negative. Table 1 also shows the aperture stop St, and the surface number (St) and the phrase (St) are described in the column of the surface number corresponding to the surface of the aperture stop St. The value in the lowermost column of D in table 1 is the distance between the image plane Sim and the surface closest to the image side in the table.
In table 2, the values of the focal length F of the imaging lens, the back focus Bf at the air converted distance, the F number fno, and the maximum
In table 1, the numbers of the surfaces of the aspherical surfaces are denoted by x, and numerical values of paraxial radii of curvature are described in the column of radii of curvature of the aspherical surfaces. In table 3, the column Sn shows the surface number of the aspheric surface, and the columns KA and Am (m is 3, 4, 5, and …) show the numerical values of the aspheric surface coefficients of the aspheric surfaces. "E. + -. n" (n: integer) of numerical values of aspherical surface coefficients of Table 3 represents ". times.10±n". KA and Am are aspheric coefficients in an aspheric expression represented by the following expression.
Zd＝C×h2/{1+(1-KA×C2×h2)1/2}+∑Am×hm
Wherein, Zd: aspheric depth (length of perpendicular line from a point on the aspheric surface of height h, down to a plane perpendicular to the optical axis in contact with the aspheric apex)
h: height (distance from optical axis to lens surface)
C: reciprocal of paraxial radius of curvature
KA. Am, and (2): coefficient of aspheric surface
The aspherical Σ refers to the sum of m.
In the data of each table, the degree is used as an angle unit and mm (millimeter) is used as a length unit, but other appropriate units can be used because an optical system can be used even if it is scaled up or down. Each table shown below shows numerical values rounded by a predetermined number of digits.
[ Table 1]
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