CN115685494A - Optical system and image pickup apparatus - Google Patents
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Abstract
The problem is to provide a small, large-diameter, and high-performance optical system and an imaging device. The solution is that the optical system is composed of a1 st lens group (G1), a 2 nd lens group (G2) and a 3 rd lens group (G3). Each lens group has positive power, and the 2 nd lens group (G2) is a focusing group. The 1 st lens group (G1) has at least 3 lenses 1 to 3 in order from the object side. The optical system has optical characteristics represented by a specific formula defined by the lens.
Description
Technical Field
The present invention relates to an optical system and an imaging apparatus.
Background
Optical systems used in video cameras, digital still cameras, and mirrorless single-lens cameras are required to be small and have high optical performance. An optical system is known which is composed of 3 lens groups of a1 st lens group, a 2 nd lens group, and a 3 rd lens group, wherein the 2 nd lens group is movable for focusing, and the 3 lens groups each have positive power (for example, refer to patent documents 1 to 3).
Prior art documents
Patent literature
[ patent document 1] Japanese patent laid-open publication No. 2019-66585
[ patent document 2] Japanese patent laid-open publication No. 2017-167327
[ patent document 3] International publication No. 2019/073744
Disclosure of Invention
Problems to be solved by the invention
However, the above-mentioned prior art still has a room for study from the viewpoint of the balance between miniaturization and high optical performance. For example, the techniques described in patent documents 1 and 2 are large-diameter optical systems, but the correction of chromatic aberration of magnification is insufficient. The technique described in patent document 3 has room for study on the arrangement of lenses in the 1 st lens group, and it has not been possible to achieve both a reduction in the total optical length and an improvement in performance.
The invention provides an optical system and an imaging device which are small, have a large diameter and have high performance.
Means for solving the problems
In order to solve the above problem, an optical system according to an aspect of the present invention includes, in order from an object side: a1 st lens group having positive power, a 2 nd lens group having positive power, and a 3 rd lens group having positive power, wherein the 2 nd lens group is movable along an optical axis to vary an interval between adjacent lens groups, the 1 st lens group having, in order from an object side, at least: a1 st lens, a 2 nd lens and a 3 rd lens, wherein the 1 st lens and the 2 nd lens have negative focal power and satisfy the following formula:
65<νd12max·····(1)
-1<(Rr+Rf)/(Rr-Rf)<1·····(2)
wherein,
ν d12max: a maximum value of Abbe numbers of the 1 st lens and the 2 nd lens corresponding to the d-line
Rf: a curvature radius of an image surface side surface of the 2 nd lens
Rr: a radius of curvature of an object-side surface of the 3 rd lens.
In order to solve the above problem, an imaging device according to an aspect of the present invention includes: the above optical system; and an imaging element that is provided on an image plane side of the optical system and converts an optical image formed by the optical system into an electric signal.
Effects of the invention
According to an aspect of the present invention, a compact, large-diameter, high-performance optical system and an imaging device can be provided.
Drawings
Fig. 1 is a diagram schematically showing an optical structure of an optical system of example 1 in infinity focusing.
Fig. 2 is a diagram showing longitudinal aberrations in infinity focus in the optical system of example 1.
Fig. 3 is a diagram schematically showing an optical structure of the optical system of example 2 in infinity focusing.
Fig. 4 is a diagram showing longitudinal aberrations in infinity focus in the optical system of example 2.
Fig. 5 is a diagram schematically showing an optical structure of the optical system of example 3 in infinity focus.
Fig. 6 is a diagram showing longitudinal aberration in infinity focusing in the optical system according to example 3.
Fig. 7 is a diagram schematically showing an optical structure of the optical system of example 4 in infinity focus.
Fig. 8 is a diagram showing longitudinal aberrations in infinity focus in the optical system of example 4.
Fig. 9 is a diagram schematically showing an optical structure of the optical system of example 5 in infinity focusing.
Fig. 10 is a diagram showing longitudinal aberration in infinity focusing in the optical system according to example 5.
Fig. 11 is a diagram schematically showing an example of the configuration of an imaging device according to an embodiment of the present invention.
Description of reference numerals:
1. no-reflector single-lens camera (pick-up device)
2. Main body
3. Lens barrel
21. CG protective glass
22 CCD sensor (Camera element)
30. Optical system
31. G1 the 1 st lens group
32. G2 lens group 2
33. G3 lens group
34. S diaphragm
IMG image plane
OA optical axis
Detailed Description
[ embodiment 1]
An embodiment of the present invention will be described in detail below. Embodiments of the present invention relate to an optical system suitable for use as an imaging optical system such as a film camera, a video camera, and a digital still camera, and an imaging apparatus including the optical system. The optical system and the imaging device to be described below are one embodiment of the optical system and the imaging device according to the present invention, and the optical system and the imaging device according to the present invention are not limited to the following embodiment. In the present specification, a structure expressed as "consisting of means including substantially only the structure.
1. Optical system
1-1. Optical structure
An optical system according to an embodiment of the present invention is composed of, in order from an object side, a1 st lens group having positive power, a 2 nd lens group having positive power, and a 3 rd lens group having positive power. Since each lens group has positive power, light beams are easily collected. Therefore, in the present embodiment, an optical system having a large diameter can be designed.
In the present specification, a "lens group" includes one or more lenses, and the interval between the lenses included in the lens group does not vary.
Further, in the present specification, the lens group may include a cemented lens. The number of lenses in the case where the lens group includes cemented lenses is counted for each cemented lens. As the cemented lens, for example, a cemented lens in which a plurality of lenses are integrated and which has no air space therebetween can be cited. In this case, only a plurality of lenses constituting the cemented lens are counted. Another example of the cemented lens is a cemented lens in which a plurality of lenses are bonded together with a layer of an adhesive agent having a very thin thickness and having no substantial influence on the optical properties, and the plurality of lenses are integrated. In this case, the layer of adhesive does not count the number of lenses.
Further, the lens group may include a compound lens in which 1 lens and a resin are integrated. For example, a compound lens in which 1 lens and a resin are integrated is counted as 1 lens.
(1) Group 1 lens
The 1 st lens group is a lens group located closest to the object side among the 3 lens groups constituting the optical system of the present embodiment. And a1 st lens group having positive refractive power as a whole. The 1 st lens group includes at least a1 st lens, a 2 nd lens, and a 3 rd lens in this order from the object side, and the 1 st lens and the 2 nd lens have negative refractive power. In this manner, the 1 st lens group is a lens (negative lens) having negative refractive power from the most object-side lens to the 2 nd lens. In the present embodiment, with such a configuration, radial miniaturization can be achieved, and a wider angle can be achieved.
More preferably, the 1 st lens and the 2 nd lens are negative meniscus lenses having convex surfaces directed toward the object side. This structure is preferable from the viewpoint of correcting distortion and coma, achieving radial miniaturization, and achieving a wide angle.
Further, it is preferable that at least 1 cemented lens is included in the 1 st lens group. This configuration is preferable from the viewpoint of favorably correcting the axial chromatic aberration and chromatic aberration of magnification that occur in the entire optical system. This structure is preferable from the viewpoint of reducing the lens interval to further shorten the total optical length of the optical system.
(2) Group 2 lens
The 2 nd lens group is a lens group positioned at the center of the 3 lens groups constituting the optical system of the present embodiment. And a 2 nd lens group having positive refractive power as a whole. The 2 nd lens group is movable along the optical axis so as to vary the interval between adjacent lens groups, and in the optical system of the present embodiment, the 2 nd lens group is a focusing group as described later.
Preferably, the 2 nd lens group is composed of 3 or less lenses. This configuration is preferable from the viewpoint of downsizing the driving device such as an actuator for moving the 2 nd lens group, and downsizing the optical system of the present embodiment including the entire lens barrel.
In the 2 nd lens group, it is preferable that a most object side lens of the 2 nd lens group has a concave surface facing the object side. This structure is preferable from the viewpoint of correcting well the image plane variation occurring at the time of focusing.
(3) Group 3 lens
The 3 rd lens group is a lens group located on the most image surface side among the 3 lens groups constituting the optical system of the present embodiment. And a 3 rd lens group having positive focal power as a whole.
Preferably, the 3 rd lens group is composed of 3 or less lenses. This structure is preferable from the viewpoint of reducing the number of lens pieces to shorten the total optical length. Also, it is preferable that the 3 or less lenses include at least 1 negative lens, but not an aspherical lens. This structure is preferable from the viewpoint of good correction of chromatic aberration and image quality.
(4) Other constructions
An optical system according to an embodiment of the present invention includes, in order from an object, only 3 lens groups, i.e., a1 st lens group, a 2 nd lens group, and a 3 rd lens group. The 1 st lens group and the 2 nd lens group, the 2 nd lens group and the 3 rd lens group, and the 3 rd lens group are not included on the image surface side. The optical system according to the embodiment of the present invention may further include other optical elements than the lens group, within a range in which the effects of the present embodiment can be obtained.
Preferably, the optical system has a diaphragm. Here, the stop as used herein means a stop that defines the beam diameter of the optical system, that is, a stop that defines the F-number of the optical system. From the viewpoint of downsizing the aperture unit, it is preferable to dispose the aperture between the 1 st lens group and the 2 nd lens group.
1-2 actions during focusing
In an embodiment of the present invention, the 2 nd lens group is movable along the optical axis to vary the interval between adjacent lens groups. The 2 nd lens group functions as a so-called focusing group, and moves in the optical axis direction when focusing from infinity to a finite distance object. In the configuration in which the 2 nd lens group is the focusing group, focusing is performed by moving only a part of the lens groups (only one lens group) among the lens groups constituting the optical system, and therefore the optical system including the entire lens barrel can be downsized.
1-3 formula representing conditions of optical system
Preferably, the optical system according to the present embodiment satisfies at least 1 or more of the following expressions at the same time by adopting the above-described configuration.
65<νd12max·····(1)
Wherein,
ν d12max: the maximum value among the abbe numbers of the 1 st lens and the 2 nd lens corresponding to the d-line.
The expression (1) specifies the maximum value of abbe numbers corresponding to d-lines of the 1 st lens and the 2 nd lens. From the viewpoint of using a material with low dispersion to achieve good correction of chromatic aberration of magnification, it is preferable to satisfy formula (1). ν d12max is an abbe number of the 1 st lens which is larger than an abbe number corresponding to the d-line and an abbe number of the 2 nd lens which is larger than the d-line. If ν d12max is equal to or less than the lower limit of expression (1), correction of chromatic aberration of magnification and the like becomes difficult. From the above viewpoint, ν d12max is preferably greater than 67, more preferably greater than 70. From the above viewpoint, ν d12max does not need to be particularly limited to the upper limit value, but may be less than 120, for example, from the viewpoint of sufficiently exhibiting the effects from the above viewpoint.
Preferably, the optical system according to the present embodiment satisfies the following condition:
-1<(Rr+Rf)/(Rr-Rf)<1·····(2)
wherein,
rf: radius of curvature of image surface side surface of 2 nd lens
Rr: radius of curvature of the object-side surface of the 3 rd lens.
Equation (2) defines the shape of the air lens between the 2 nd lens and the 3 rd lens. From the viewpoint of being able to maintain the curvature radius of the lens that can be manufactured while suppressing the variation in each aberration, it is preferable to satisfy equation (2). When (Rr + Rf)/(Rr-Rf) is equal to or less than the lower limit of formula (2) or equal to or more than the upper limit of formula (2), the variation in curvature of field and distortion aberration becomes large, which is not preferable from the viewpoint of improving the performance of the optical system. From the above viewpoint, (Rr + Rf)/(Rr-Rf) is more preferably more than-0.60, and still more preferably more than-0.40. From the above viewpoint, (Rr + Rf)/(Rr-Rf) is more preferably less than 0.60, and still more preferably less than 0.40.
Preferably, the optical system according to the present embodiment satisfies the following condition:
0.54<f1/f2<3.74·····(3)
wherein,
f1: focal length of the 1 st lens group
f2: focal length of the 2 nd lens group.
Equation (3) specifies the focal length of the 1 st lens group and the focal length of the 2 nd lens group. From the viewpoint of achieving miniaturization of the optical system and good correction of aberrations, it is preferable that the formula (3) is satisfied. If f1/f2 is not less than the upper limit of formula (3), the power of the 1 st lens group is weakened, resulting in an increase in the size of the entire optical system. If f1/f2 is equal to or less than the lower limit of formula (3), the power of the 1 st lens group becomes strong, which is advantageous for downsizing, but the amount of coma and the like generated in the 1 st lens group becomes large, which makes correction difficult. From the viewpoint of correcting aberrations such as coma aberration well, f1/f2 is more preferably more than 0.62, and still more preferably more than 0.70. From the viewpoint of downsizing the optical system, f1/f2 is more preferably less than 3.46, and still more preferably less than 3.17.
Preferably, the optical system according to the present embodiment satisfies the following condition:
0.78<f3/f1<7.33·····(4)
wherein,
f1: focal length of the 1 st lens group
f3: focal length of lens group 3.
Equation (4) specifies the focal length of the 3 rd lens group and the focal length of the 1 st lens group. From the viewpoint of achieving miniaturization in the radial direction of the optical system and good correction of aberrations, it is preferable to satisfy equation (4). If f3/f1 is below the lower limit of formula (4), the power of the 3 rd lens group becomes strong and the power of the 1 st lens group becomes weak. Therefore, the incident height of the off-axis light to the 3 rd lens group becomes high, and the diameter of the 3 rd lens group becomes large. If f3/f1 is above the upper limit of formula (4), the power of the 3 rd lens group weakens, and the power of the 1 st lens group strengthens. Therefore, although it is advantageous for the diameter of the 3 rd lens group to become small, the amount of generation of coma and the like generated in the 1 st lens group becomes large, causing difficulty in correction. From the above viewpoint, f3/f1 is more preferably greater than 0.89, and still more preferably greater than 1.00. From the above viewpoint, f3/f1 is more preferably less than 6.77, and still more preferably less than 6.20.
Preferably, the optical system according to the present embodiment satisfies the following condition:
0.12<β2<0.58·····(5)
wherein,
beta 2: lateral magnification of the 2 nd lens group at infinity focusing.
Equation (5) defines the lateral magnification of the 2 nd lens group. From the viewpoint of achieving miniaturization of the optical system and good correction of aberrations, it is preferable that the formula (5) is satisfied. If β 2 is equal to or more than the upper limit of formula (5), the focal length of the combination of the 1 st lens group and the 2 nd lens group becomes long, and the focal power becomes weak, resulting in an increase in the size of the entire optical system. If β 2 is equal to or less than the lower limit of formula (5), the combined power of the 1 st lens group and the 2 nd lens group becomes strong, which is advantageous for downsizing, but it becomes difficult to correct coma aberration generated in the 1 st group, or it becomes difficult to correct the coma aberration due to large aberration variation at focusing. From the above viewpoint, β 2 is more preferably more than 0.13, and still more preferably more than 0.15. From the above viewpoint, β 2 is more preferably less than 0.53, and still more preferably less than 0.49.
Preferably, the optical system according to the present embodiment satisfies the following conditions:
Nd3<1.7·····(6)
wherein,
nd3: refractive index of the 3 rd lens corresponding to d-line.
The formula (6) defines the refractive index of the 3 rd lens corresponding to the d-line. From the viewpoint of improving the performance of the optical system, it is preferable to satisfy the formula (6). If Nd3 is equal to or more than the upper limit of formula (6), the refractive power of the 3 rd lens becomes strong, and it becomes difficult to design a lens shape that is advantageous for correcting aberrations such as curvature of field, and therefore it is not preferable from the viewpoint of high performance. From the above viewpoint, nd3 is more preferably less than 1.65, and still more preferably less than 1.60. From the above viewpoint, the Nd3 does not need to be particularly limited to the lower limit value, but may be larger than 1.30, for example, from the viewpoint of sufficiently exhibiting the effects from the above viewpoint.
Preferably, the optical system according to the present embodiment satisfies the following condition:
60<νd2max·····(7)
wherein,
ν d2max: maximum value among abbe numbers corresponding to d-lines of the lenses of the 2 nd lens group.
Equation (7) specifies the abbe number of the lens in the 2 nd lens group corresponding to the d-line. Vd 2max is the highest value among abbe numbers corresponding to d-lines of the respective lenses constituting the 2 nd lens group. From the viewpoint of correcting aberrations well, it is preferable to satisfy equation (7). If vd 2max is equal to or less than the lower limit of formula (7), it becomes difficult to use a material having low dispersion in the 2 nd lens group, and therefore, it becomes difficult to correct axial chromatic aberration, chromatic aberration of magnification, and the like. From the above viewpoint, ν d2max is more preferably greater than 70, and still more preferably greater than 80. From the above viewpoint, ν d2max does not need to particularly define the upper limit value, but may be less than 120, for example, from the viewpoint of sufficiently exhibiting the effects from the above viewpoint.
Preferably, the optical system according to the present embodiment satisfies the following conditions:
νd123min<45·····(8)
wherein,
ν d123min: the minimum value among abbe numbers corresponding to d-lines of the 1 st lens, the 2 nd lens and the 3 rd lens.
Equation (8) defines the lowest abbe number of the corresponding d-line among the 1 st lens, the 2 nd lens, and the 3 rd lens. From the viewpoint of correcting aberrations well, it is preferable to satisfy equation (8). If ν d123min is equal to or larger than the upper limit of expression (8), correction of chromatic aberration of magnification and the like becomes difficult. From the above viewpoint, ν d123min is more preferably less than 40, and still more preferably less than 36. From the above viewpoint, ν d123min does not need to have a lower limit value particularly specified, but is preferably more than 10, for example, from the viewpoint of sufficiently exhibiting the effects from the above viewpoint.
Preferably, the optical system according to the present embodiment satisfies the following conditions:
60<νd321max·····(9)
wherein,
ν d321max: the maximum value among Abbe numbers corresponding to d-lines of the (m-2) th lens, the (m-1) th lens and the m-th lens.
The expression (9) specifies the highest abbe number corresponding to the d-line of 3 lenses in order from the most image surface side among the lenses included in the 3 rd lens group. ν d321max is the highest value among abbe numbers corresponding to d-lines of the 3 lenses located on the most image plane side in the 3 rd lens group. M is the total number of lenses of the optical system, and is preferably an integer of 7 or more. From the viewpoint of correcting aberrations well, it is preferable to satisfy equation (9). If ν d321max is equal to or less than the lower limit of expression (9), correction of chromatic aberration of magnification and the like becomes difficult. From the above viewpoint, ν d321max is more preferably greater than 65, and still more preferably greater than 70. From the above viewpoint, ν d321max does not need to particularly define the upper limit value, but is preferably less than 120, for example, from the viewpoint of sufficiently exhibiting the effects from the above viewpoint.
Preferably, the optical system according to the present embodiment satisfies the following condition:
0.5<(1-β2 2 )×β3 2 <1.5·····(10)
wherein,
beta 2: transverse magnification of 2 nd lens group in infinite focusing
Beta 3: lateral magnification of the 3 rd lens group at infinity focusing.
Expression (10) represents the amount of movement of the image forming surface and the movement of the 2 nd lens group in the optical axis directionThe ratio of the amounts. From the viewpoint of downsizing the optical system and correcting aberrations well, it is preferable that expression (10) is satisfied. If (1-. Beta.2) 2 )×β3 2 When the lower limit of the expression (10) is less, the total optical length becomes longer due to an increase in the moving amount of the 2 nd lens group. If (1-. Beta.2) 2 )×β3 2 If the upper limit of the expression (10) is not less than the upper limit, the focus group (the 2 nd lens group) can be reduced in size, but the aberration variation during focusing becomes large, which makes the correction difficult. (1-. Beta.2) from the viewpoint of shortening the total optical length 2 )×β3 2 More preferably, it is more than 0.7, and still more preferably more than 0.9. Further, (1-. Beta.2) is preferable from the viewpoint of suppressing aberration variation at the time of focusing 2 )×β3 2 More preferably less than 1.3, and still more preferably less than 1.1.
2. Image pickup apparatus
Next, an imaging device according to an embodiment of the present invention will be described. The imaging device includes: the optical system according to the above embodiment; and an imaging element that is provided on an image plane side of the optical system and converts an optical image formed by the optical system into an electric signal. The optical system in the present embodiment is, for example, a single focus lens (single focus lens).
The imaging element is not limited to a specific one, and a solid-state imaging element such as a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor, a silver halide thin film, or the like can be used. The imaging device according to the present embodiment is suitable for an imaging device using the solid-state imaging element, such as a digital camera or a video camera. The imaging device may be a lens-fixed type in which a lens is fixed to a housing, or may be a lens-interchangeable type such as a single lens reflex camera or a mirrorless single lens camera.
Fig. 11 is a diagram schematically showing an example of the configuration of the imaging device according to the present embodiment. As shown in fig. 11, the mirrorless single-lens camera 1 includes a main body 2 and a lens barrel 3 that is attachable to and detachable from the main body 2. The mirrorless single-lens camera 1 is one mode of an image pickup apparatus.
The lens barrel 3 has an optical system 30. The optical system 30 includes a1 st lens group 31, a 2 nd lens group 32, and a 3 rd lens group 33. The 1 st lens group 31, the 2 nd lens group 32, and the 3 rd lens group 33 are all configured to have positive power. The 1 st lens group 31 includes at least a1 st lens, a 2 nd lens, and a 3 rd lens in this order from the object side. Further, the optical system 30 is configured to satisfy the above equations (1) and (2), for example. Further, a stop 34 is disposed between the 1 st lens group 31 and the 2 nd lens group 32.
The main body 2 includes a cover glass 21 as an image pickup device and a CCD sensor 22. The CCD sensor 22 is disposed at a position in the main body 2 where an optical axis OA of the optical system 30 in the lens barrel 3 attached to the main body 2 becomes a central axis of the CCD sensor 22. The main body 2 may have an optical element having no substantial power such as an infrared cut filter, instead of the protective glass 21.
The optical system according to the embodiment of the present invention is configured as a short-overall-length large-diameter, small-sized, and high-performance optical system by appropriately adjusting the power arrangement of the optical system and the movable group at the time of focusing. Further, the imaging device according to the embodiment of the present invention is provided with such an optical system, and therefore is suitable for imaging devices that require high-performance imaging with a short length in the optical axis direction, such as digital input/output devices such as an in-vehicle camera and an unmanned aerial vehicle-mounted camera.
The present invention is not limited to the above embodiments, and various modifications can be made within the scope of the claims. Embodiments obtained by appropriately combining technical means disclosed in the different embodiments are also included in the technical scope of the present invention.
[ examples ] A method for producing a compound
An embodiment of the present invention will be explained below. In the tables below, all units of length are "mm", and all units of angle of view are "°". Further, "E-a" represents ". Times.10 -a ". In example 1, the drawings and the tables are described, but the drawings and the tables in example 1 are similar to those in other examples.
The optical system shown below in embodiments 1 to 5 is constituted by, in order from the object side, a1 st lens group G1 having positive power, a stop S, a 2 nd lens group G2 having positive power, and a 3 rd lens group G3 having positive power. In focusing from infinity to a finite distance object, the 1 st lens group G1 and the 3 rd lens group G3 are always fixed and do not move with respect to the image plane IMG, and the 2 nd lens group G2 moves toward the object side along the optical axis.
[ example 1]
Fig. 1 is a diagram schematically showing an optical structure of an optical system of example 1 in infinity focus. "CG" shown in fig. 1 is a cover glass, and "IMG" is an image plane (imaging plane). The arrow in the figure indicates the case where the 2 nd lens group G2 moves at the time of focusing. The arrow indicates that the 2 nd lens group G2 moves substantially linearly within a range corresponding to the optical axis direction of the arrow for focusing.
The 1 st lens group is composed of, in order from the object side, a negative meniscus lens having a convex surface facing the object side, a biconcave lens, a biconvex lens, a cemented lens in which a biconcave lens and a biconvex lens are cemented, and a positive meniscus lens having a convex surface facing the object side.
The 2 nd lens group is composed of, in order from the object side, a negative meniscus lens having a concave surface facing the object side, and a biconvex lens.
The 3 rd lens group is composed of a biconcave lens, a biconvex lens, and a biconvex lens in this order from the object side.
Next, the optical characteristics of the optical system will be explained. Table 1 is surface data of the optical system of example 1.
In the embodiment, "surface number" indicates the number of lens surfaces when the lens surfaces of the optical system are counted from the object side, "R" indicates the radius of curvature of the lens surfaces, "D" indicates the interval of the lens surfaces on the optical axis, "Nd" indicates the refractive index of the lens corresponding to the D-line (wavelength λ =587.56 nm), and "ABV" indicates the abbe number of the lens corresponding to the D-line. "D (n)" (n is an integer) means that the interval of the lens surfaces on the optical axis is a variable interval that changes at the time of focusing. Note that "STOP" attached to the surface number indicates that it is an aperture, and "ASPH" indicates that the lens surface is an aspherical surface. Further, "0.0000" in the column of the curvature radius represents a plane.
[ Table 1]
Table 2 shows a parameter table of the optical system of example 1. The parameter table shows numerical values of optical characteristics corresponding to respective imaging distances. In the parameter table, "F" represents the focal length of the optical system corresponding to each imaging distance, "Fno" represents the F value, and "W" represents the half field angle. Further, "D (0)" means a photographing distance. In addition, the shooting distance refers to the distance from the object to the 1 st surface.
[ Table 2]
| F | 13.1301 | 13.1331 | 13.1412 |
| Fno | 1.8023 | 1.8197 | 1.8812 |
| W | 48.5322 | 48.4523 | 48.1981 |
| D(0) | ∞ | 380.8913 | 113.4998 |
| D(15) | 7.8693 | 7.4458 | 6.5654 |
| D(19) | 2.4107 | 2.8341 | 3.7146 |
Table 3 is a table showing aspheric coefficients of the respective aspheric surfaces in the optical system of example 1. "K, A4, A6, A8, a10, and a12" in the table are coefficients when the aspherical surface shape of each aspherical surface is defined by the following expression. In the following formula, "Z" represents a displacement amount from a reference plane in An optical axis direction, "r" represents a paraxial radius of curvature, "h" represents a height from the optical axis in a direction perpendicular to the optical axis, "K" represents a conic coefficient, and "An" represents An aspherical coefficient of degree n.
[ mathematical formula 1]
[ Table 3]
| Noodle number | K | A4 | | A8 | A10 | |
| 1 | 0.00000E+00 | -4.16892E-05 | 1.43140E-07 | -3.97690E-10 | 4.09977E-13 | |
| 2 | -5.88114E-01 | -1.90902E-05 | -2.24085E-07 | 2.86434E-09 | -1.18741E-11 | |
| 5 | -3.66353E-01 | -9.82977E-06 | 3.44722E-09 | -1.57233E-09 | 1.48100E-11 | |
| 16 | 8.84990E-01 | 3.79704E-05 | 9.21787E-07 | -6.13394E-09 | 4.78012E-12 | |
| 17 | 5.50000E-01 | 7.13104E-05 | 9.53551E-07 | -6.27805E-09 | 1.76430E-11 | |
| | A12 | |||||
| 1 | 0.00000E+00 | |||||
| 2 | 0.00000E+00 | |||||
| 5 | -8.80257E-14 | |||||
| 16 | 0.00000E+00 | |||||
| 17 | 0.00000E+00 |
Fig. 2 is a diagram showing longitudinal aberrations in infinity focusing in the optical system of example 1. In fig. 2, spherical aberration (mm), astigmatism (mm), and distortion aberration (%) are shown in this order from the left side toward the drawing.
In the graph showing the spherical aberration, the ordinate represents the ratio to the open F value, and the abscissa represents the defocus. In the graph indicating spherical aberration, the solid line indicates the longitudinal aberration corresponding to the d-line (wavelength λ =587.56 nm), the broken line indicates the longitudinal aberration corresponding to the F-line (wavelength λ =486.13 nm), and the dotted line indicates the longitudinal aberration corresponding to the C-line (wavelength λ =656.28 nm).
In the graph showing astigmatism, the vertical axis indicates a half field angle (°), and the horizontal axis indicates defocus. In the graph showing astigmatism, a solid line indicates a sagittal image plane (S) with respect to a d-line (wavelength λ =587.56 nm), and a four-dot chain line indicates a meridional image plane (T) with respect to the d-line.
In the graph showing distortion aberration, the vertical axis shows half field angle (°), and the horizontal axis shows distortion (%).
[ example 2]
Fig. 3 schematically shows an optical structure of the optical system of example 2 at infinity focus, and fig. 4 shows longitudinal aberrations of the optical system of example 2 at infinity focus. Table 4 shows surface data of the optical system of example 2, table 5 shows a parameter table of the optical system of example 2, and table 6 shows aspheric coefficients of the aspheric surfaces in the optical system of example 2.
[ Table 4]
| Noodle number | R | D | Nd | ABV |
| 1ASPH | 39.9427 | 1.4000 | 1.49700 | 81.61 |
| 2ASPH | 9.4265 | 3.5775 | ||
| 3 | 15.9638 | 1.2000 | 1.72916 | 54.67 |
| 4 | 12.1785 | 9.2777 | ||
| 5ASPH | -19.4383 | 0.9000 | 1.59270 | 35.45 |
| 6 | 71.4435 | 0.1500 | ||
| 7 | 40.9154 | 2.3521 | 1.87070 | 40.73 |
| 8 | 140.7261 | 0.1500 | ||
| 9 | 137.8193 | 0.8000 | 1.83848 | 24.02 |
| 10 | 22.5023 | 5.4755 | 1.87071 | 40.73 |
| 11 | -27.9632 | 0.1500 | ||
| 12 | 38.8117 | 2.0050 | 1.92177 | 22.80 |
| 13 | 84.5581 | 10.0187 | ||
| 14Stop | 0.0000 | 0.0000 | ||
| 15 | 0.0000 | D(15) | ||
| 16ASPH | -19.6307 | 1.1000 | 1.76802 | 49.24 |
| 17ASPH | -20.0000 | 0.1612 | ||
| 18 | 48.9442 | 7.5498 | 1.43700 | 95.10 |
| 19 | -15.5927 | D(19) | ||
| 20 | -42.4005 | 0.8000 | 1.75520 | 27.53 |
| 21 | 29.8838 | 1.5408 | ||
| 22 | 41.3057 | 4.3006 | 1.49700 | 81.61 |
| 23 | -87.0548 | 0.1500 | ||
| 24 | 51.5872 | 5.9567 | 1.68806 | 57.08 |
| 25 | -41.5968 | 13.2537 | ||
| 26 | 0.0000 | 2.0000 | 1.51680 | 64.20 |
| 27 | 0.0000 | 1.0000 |
[ Table 5]
| F | 13.1309 | 13.1614 | 13.2276 |
| Fno | 1.8017 | 1.8128 | 1.8390 |
| W | 48.5308 | 48.4333 | 48.1354 |
| D(0) | ∞ | 382.1085 | 113.4998 |
| D(15) | 8.8183 | 8.3915 | 7.4867 |
| D(19) | 2.4124 | 2.8390 | 3.7440 |
[ Table 6]
| Noodle numbering | K | A4 | | A8 | A10 | |
| 1 | 0.00000E+00 | -2.63074E-05 | 9.71165E-08 | -2.59247E-10 | 2.65454E-13 | |
| 2 | -5.78918E-01 | -1.02442E-05 | -3.81024E-07 | 3.85330E-09 | -1.82641E-11 | |
| 5 | -3.66780E-01 | -1.00568E-05 | -3.73377E-09 | -1.08659E-09 | 9.56013E-12 | |
| 16 | 7.60554E-01 | -4.68705E-06 | 8.38846E-07 | -2.69831E-09 | -2.07884E-11 | |
| 17 | 5.50000E-01 | 4.34719E-05 | 9.06822E-07 | -1.65054E-09 | -1.19366E-11 | |
| | A12 | |||||
| 1 | 0.00000E+00 | |||||
| 2 | 0.00000E+00 | |||||
| 5 | -5.32552E-14 | |||||
| 16 | 0.00000E+00 | |||||
| 17 | 0.00000E+00 |
[ example 3]
Fig. 5 schematically shows an optical structure of the optical system of example 3 at infinity focus, and fig. 6 shows longitudinal aberrations of the optical system of example 3 at infinity focus. Table 7 shows surface data of the optical system of example 3, table 8 shows a parameter table of the optical system of example 3, and table 9 shows aspheric coefficients of the aspheric surfaces in the optical system of example 3.
[ Table 7]
[ Table 8]
| F | 13.1290 | 13.0909 | 13.0150 |
| Fno | 1.8022 | 1.8083 | 1.8469 |
| W | 48.5355 | 48.5173 | 48.4082 |
| D(0) | ∞ | 380.2174 | 113.4996 |
| D(15) | 7.9822 | 7.5614 | 6.6977 |
| D(19) | 2.4112 | 2.8319 | 3.6958 |
[ Table 9]
| Noodle numbering | K | A4 | | A8 | A10 | |
| 1 | 0.00000E+00 | -4.79612E-05 | 1.67934E-07 | -5.27689E-10 | 5.80644E-13 | |
| 2 | -7.16272E-01 | -1.77836E-06 | -1.36013E-07 | 3.43195E-09 | -1.36534E-11 | |
| 5 | -3.05266E-01 | -1.13786E-05 | 1.07416E-08 | -2.51781E-09 | 2.41116E-11 | |
| 16 | 1.00000E+00 | 2.78886E-05 | 4.56250E-07 | -7.05197E-09 | 1.83092E-11 | |
| 17 | 5.50000E-01 | 6.51795E-05 | 5.26657E-07 | -6.57651E-09 | 2.56628E-11 | |
| | A12 | |||||
| 1 | 0.00000E+00 | |||||
| 2 | 0.00000E+00 | |||||
| 5 | -1.40214E-13 | |||||
| 16 | 0.00000E+00 | |||||
| 17 | 0.00000E+00 |
[ example 4]
Fig. 7 schematically shows an optical structure of the optical system of example 4 in infinity focusing, and fig. 8 shows longitudinal aberrations of the optical system of example 4 in infinity focusing. Table 10 shows surface data of the optical system of example 4, table 11 shows a parameter table of the optical system of example 4, and table 12 shows aspheric coefficients of the respective aspheric surfaces in the optical system of example 4.
[ Table 10]
| Noodle number | R | D | Nd | ABV |
| 1ASPH | 24.4437 | 1.4000 | 1.59201 | 67.02 |
| 2ASPH | 9.2285 | 6.3698 | ||
| 3 | 21.9555 | 1.2000 | 1.48749 | 70.44 |
| 4 | 13.7405 | 9.4893 | ||
| 5ASPH | -17.7551 | 0.9264 | 1.59270 | 35.45 |
| 6 | 137.5973 | 0.1500 | ||
| 7 | 45.1277 | 1.8729 | 1.87070 | 40.73 |
| 8 | 74.9548 | 0.1500 | ||
| 9 | 69.0416 | 0.8000 | 1.85817 | 25.35 |
| 10 | 18.6049 | 5.2498 | 1.84834 | 41.68 |
| 11 | -33.8920 | 3.5478 | ||
| 12 | 49.5046 | 2.3872 | 1.90366 | 31.31 |
| 13 | -111.2074 | 7.2102 | ||
| 14Stop | 0.0000 | 0.0000 | ||
| 15 | 0.0000 | D(15) | ||
| 16ASPH | -22.4464 | 1.1000 | 1.76802 | 49.24 |
| 17ASPH | -34.8800 | 0.2040 | ||
| 18 | 67.9726 | 3.0543 | 1.49700 | 81.61 |
| 19 | -32.5687 | 0.1500 | ||
| 20 | -145.9427 | 3.2076 | 1.43700 | 95.10 |
| 21 | -20.0615 | D(21) | ||
| 22 | -30.1711 | 0.8000 | 1.76156 | 27.83 |
| 23 | 32.8685 | 1.0836 | ||
| 24 | 39.7302 | 5.0153 | 1.49700 | 81.61 |
| 25 | -35.6853 | 0.1500 | ||
| 26 | 45.5078 | 4.7492 | 1.57672 | 67.23 |
| 27 | -61.0327 | 13.1000 | ||
| 28 | 0.0000 | 2.0000 | 1.51680 | 64.20 |
| 29 | 0.0000 | 1.0000 |
[ Table 11]
| F | 13.1293 | 13.1031 | 13.0508 |
| Fno | 1.8022 | 1.8097 | 1.8640 |
| W | 48.5340 | 48.4860 | 48.3097 |
| D(0) | ∞ | 380.6584 | 113.4996 |
| D(15) | 7.7212 | 7.2994 | 6.4280 |
| D(21) | 2.4115 | 2.8331 | 3.7048 |
[ Table 12]
[ example 5]
Fig. 9 schematically shows an optical structure of the optical system of example 5 at the time of infinity focusing, and fig. 10 shows longitudinal aberration of the optical system of example 5 at the time of infinity focusing. Table 13 shows surface data of the optical system of example 5, table 14 shows a parameter table of the optical system of example 5, and table 15 shows aspheric coefficients of the aspheric surfaces in the optical system of example 5.
[ Table 13]
[ Table 14]
| F | 13.1302 | 13.1368 | 13.1524 |
| Fno | 1.8023 | 1.8204 | 1.8826 |
| W | 48.5321 | 48.4357 | 48.1458 |
| D(0) | ∞ | 381.1838 | 113.4998 |
| D(15) | 7.9047 | 7.4808 | 6.5959 |
| D(19) | 2.4111 | 2.8349 | 3.7199 |
[ Table 15]
| Noodle number | K | A4 | | A8 | A10 | |
| 1 | 0.00000E+00 | -4.38587E-05 | 1.34673E-07 | -3.76469E-10 | 3.65763E-13 | |
| 2 | -5.57678E-01 | -2.37021E-05 | -2.57490E-07 | 2.83090E-09 | -1.33215E-11 | |
| 5 | -3.97521E-01 | -9.00257E-06 | -3.49117E-09 | -1.34181E-09 | 1.21248E-11 | |
| 16 | 9.46745E-01 | 2.20281E-05 | 8.30470E-07 | -2.19335E-09 | -1.71584E-11 | |
| 17 | 5.50000E-01 | 5.49863E-05 | 8.58563E-07 | -2.92236E-09 | -1.47224E-12 | |
| | A12 | |||||
| 1 | 0.00000E+00 | |||||
| 2 | 0.00000E+00 | |||||
| 5 | -6.84220E-14 | |||||
| 16 | 0.00000E+00 | |||||
| 17 | 0.00000E+00 |
Table 16 and table 17 show the values calculated by the above equations in examples 1 to 5 and the numerical values used in the equations.
[ Table 16]
[ Table 17]
| Example 1 | Example 2 | Example 3 | Example 4 | Example 5 | |
| (1)νd12max | 70.44 | 81.60 | 70.44 | 70.44 | 63.85 |
| (2)(Rr+Rf)/(Rr-Rf) | 0.18 | 0.23 | 0.07 | 0.13 | 0.18 |
| (3)f1/f2 | 1.36 | 2.89 | 0.77 | 0.97 | 1.47 |
| (4)f3/f1 | 2.16 | 1.10 | 5.51 | 4.24 | 2.01 |
| (5)β2 | 0.31 | 0.16 | 0.45 | 0.38 | 0.29 |
| (6)Nd3 | 1.59 | 1.59 | 1.59 | 1.59 | 1.59 |
| (7)νd2max | 95.1 | 95.1 | 95.1 | 95.1 | 95.1 |
| (8)νd123min | 35.4 | 35.4 | 35.4 | 35.4 | 35.4 |
| (9)νd321max | 81.6 | 81.6 | 81.6 | 81.6 | 81.6 |
| (10)(1-β2 2 )×β3 2 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 |
Claims (15)
1. An optical system comprising, in order from an object side: a1 st lens group having positive power, a 2 nd lens group having positive power, and a 3 rd lens group having positive power, wherein the 2 nd lens group is movable along an optical axis to vary an interval between adjacent lens groups,
the 1 st lens group includes, in order from an object side: a1 st lens, a 2 nd lens and a 3 rd lens, wherein the 1 st lens and the 2 nd lens have negative focal power and satisfy the following formula:
65<νd12max·····(1)
-1<(Rr+Rf)/(Rr-Rf)<1·····(2)
wherein,
ν d12max: a maximum value of Abbe numbers of the 1 st lens and the 2 nd lens corresponding to the d-line
Rf: a curvature radius of an image surface side surface of the 2 nd lens
Rr: a radius of curvature of an object-side surface of the 3 rd lens.
2. The optical system of claim 1, satisfying the following equation:
0.54<f1/f2<3.74·····(3)
wherein,
f1: focal length of the 1 st lens group
f2: focal length of the 2 nd lens group.
3. The optical system of claim 1 or 2, satisfying the following equation:
0.78<f3/f1<7.33·····(4)
wherein,
f3: a focal length of the 3 rd lens group.
4. The optical system according to any one of claims 1 to 3, satisfying the following formula:
0.12<β2<0.58·····(5)
wherein,
beta 2: and the transverse magnification of the 2 nd lens group in the infinite focusing.
5. The optical system according to any one of claims 1 to 4, satisfying the following formula:
Nd3<1.7·····(6)
wherein,
nd3: a refractive index of the 3 rd lens corresponding to the d-line.
6. The optical system according to any one of claims 1 to 5, satisfying the following formula:
60<νd2max·····(7)
wherein,
ν d2max: a maximum value among abbe numbers of the lenses of the 2 nd lens group corresponding to the d-line.
7. The optical system according to any one of claims 1 to 6, satisfying the following formula:
νd123min<45·····(8)
wherein,
ν d123min: a minimum value among abbe numbers corresponding to d-lines of the 1 st lens, the 2 nd lens, and the 3 rd lens.
8. The optical system according to any one of claims 1 to 7, wherein the 3 rd lens group has at least an (m-2) th lens, an (m-1) th lens, and an m-th lens when the total number of lenses of the optical system is m, and satisfies the following expression:
60<νd321max·····(9)
wherein,
ν d321max: a maximum value among Abbe numbers corresponding to d-lines of the (m-2) th lens, the (m-1) th lens, and the m-th lens.
9. The optical system according to any one of claims 1 to 8, satisfying the following formula:
0.5<(1-β2 2 )×β3 2 <1.5·····(10)
wherein,
beta 3: and the transverse magnification of the 3 rd lens group in infinite focusing.
10. The optical system according to any one of claims 1 to 9,
the 1 st lens and the 2 nd lens are both negative meniscus lenses having convex surfaces facing the object side.
11. The optical system according to any one of claims 1 to 10,
the 2 nd lens group is composed of 3 or less lenses.
12. The optical system according to any one of claims 1 to 11,
the 1 st lens group has at least 1 cemented lens.
13. The optical system according to any one of claims 1 to 12,
the most object-side lens of the 2 nd lens group has a concave surface facing the object side.
14. The optical system according to any one of claims 1 to 13,
the 3 rd lens group is composed of 3 or less lenses, includes at least 1 negative lens, and does not include an aspherical lens.
15. An imaging device includes:
an optical system as claimed in any one of claims 1 to 14; and
and an image pickup device that is provided on an image plane side of the optical system and converts an optical image formed by the optical system into an electric signal.
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