Lens apparatus and image pickup apparatus

Abstract

To provide an inexpensive and high-performance photographic lens.SOLUTION: It is possible to obtain a first lens system including a 1A lens group closest to the object side and a positive lens group on the image side of the 1A lens group, and a second lens system in which the entire system focal distance is set to the telephoto side by disposing a 1B lens group instead of the center lens group, and the following conditional expressions are satisfied. 0.01<, 0.01<, 0.02<Σ1 / (fP / f1A) <0.3, and 0.001 <Σ1 / (fP / f1B) <0.2, where fP is a focal distance of the positive lens unit, f1A is a focal distance of the first A lens unit, and f1B is a focal distance of the first B lens unit (at the time of focusing on infinity). fPi is a focal length of each lens arranged in the positive lens group, and Ni is a refractive index of the lens.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure is suitable for a lens device, an imaging device, and a method for manufacturing a lens device. [Background technology]

[0002] In recent years, there has been a demand for optical systems with various focal lengths and apertures depending on the application in imaging devices such as digital still cameras and video cameras that use solid-state imaging elements. Among these, prime lenses have fewer moving lens groups than zoom lenses, making their structure easier to strengthen and offering greater design flexibility, making them small, high-performance, and inexpensive. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 129612 / 1983 Summary of the Invention [Problem to be solved by the invention]

[0004] In the prior art disclosed in Patent Document 1, the rear group has a weak negative refractive power, and therefore plays a small role in correcting aberrations in the entire system. The present disclosure aims to provide an inexpensive, high-performance photographic lens and a manufacturing method thereof. [Means for solving the problem]

[0005] An imaging lens according to one aspect of the present disclosure can provide a first lens system having a 1A lens group closest to the object and a positive lens group on the image side thereof, and a second lens system having a total system focal length on the telephoto side by disposing a 1B lens group in place of the 1A lens group, and satisfies the following conditional expression:

[0006] 0.01<|fP / f1A|<0.3 0.01<|fP / f1B|<0.3 0.20<Σ1 / (fPi·Ni)<1.0 where fP is the focal length of the positive lens group, f1A is the focal length of the 1A lens group, and f1B is the focal length of the 1B lens group (when focused at infinity). fPi is the focal length of each lens in the positive lens group, and Ni is the refractive index of that lens.

[0007] A manufacturing method according to one aspect of the present disclosure is a manufacturing method for manufacturing a first lens device and a second lens device, the second lens device having a focal length longer than that of the first lens device, The first lens device comprises a first partial optical system, a first aperture stop, and a second partial optical system, arranged in that order from the object side to the image side, and the second lens device comprises a third partial optical system, a second aperture stop, and a fourth partial optical system, arranged in that order from the object side to the image side, wherein the total number of positive lenses arranged in the second partial optical system is equal to the total number of positive lenses arranged in the fourth partial optical system, the total number of negative lenses arranged in the second partial optical system is equal to the total number of negative lenses arranged in the fourth partial optical system, and the following conditional expression is satisfied:

[0008] 0.01<|fP / f1A|<0.30 0.01<|fP / f1B|<0.30 0.02<Σ1 / (fPi·Ni)<0.10 0.90 <f2 / f4<1.10 Here, the focal length of the first partial optical system is f1A, the focal length of the third partial optical system is f1B, the focal length of each lens arranged in the second partial optical system is fPi, the refractive index is Ni, the focal length of the second partial optical system is f2, and the focal length of the fourth partial optical system is f4. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide an inexpensive, high-performance photographic lens. [Brief explanation of the drawings]

[0010] [Figure 1]1 is an optical cross-sectional view of a first lens system and a second lens system of a photographing lens according to a first embodiment. [Figure 2] 4A to 4C are aberration diagrams of the first and second lens systems of the photographing lens of Example 1 when focusing on an object at infinity. [Figure 3] FIG. 10 is an optical cross-sectional view of a first lens system and a second lens system of a photographing lens according to a second embodiment. [Figure 4] 10A and 10B are aberration diagrams of the first and second lens systems of the photographing lens of Example 2 when focusing at infinity. [Figure 5] FIG. 11 is an optical cross-sectional view of the first lens system and the second lens system of the photographic lens of Example 3. [Figure 6] 10A to 10C are aberration diagrams of the first and second lens systems of the photographing lens of Example 3 when focusing at infinity. [Figure 7] 1 is a schematic diagram of an imaging device according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] The photographic lens of the present disclosure, an imaging device including the same, and a manufacturing method thereof will be described below.

[0012] In one aspect of the photographic lens of the present disclosure, by exchanging a portion of the optical system, it is possible to switch between two different focal lengths, a first lens system and a second lens system. The first lens system is composed of, from the object side, a 1A lens group with weak refractive power and a second lens group with positive refractive power. The second lens system is composed of, from the object side, a 1B lens group with weak refractive power and a second lens group with positive refractive power. The second lens group has a common configuration, and by exchanging the 1A lens group and the 1B lens group, it is possible to switch between two different focal lengths.

[0013] Here, when exchanging a part of an optical system according to the present disclosure, the definition of a group is that the lens group before and after the lens group that is exchanged during switching is defined as one group each. In other words, with regard to optical systems that operate a part of a group, such as partial group focusing, in which focusing is performed using some of the lenses in the group, or partial group image stabilization, in which image stabilization is performed using some of the lenses in the group, these are not separated into groups, but will be described in terms of group classification based on exchange.

[0014] In addition, in the manufacturing method of the present disclosure, the first lens device corresponds to the first lens system and the second lens device corresponds to the second lens system, and the lenses arranged in the first lens device and the second lens device are not common but are different products.

[0015] 1A and 1B are optical cross-sectional views of the first and second lens systems of the photographic lens of Example 1. Figures 2A and 2B are aberration diagrams of the first and second lens systems of the photographic lens of Example 1 when focused at infinity.

[0016] Figures 3A and 3B are optical cross-sectional views of the first and second lens systems of the photographic lens of Example 2. Figures 4A and 4B are aberration diagrams of the first and second lens systems of the photographic lens of Example 2 when focused at infinity.

[0017] Figures 5A and 5B are optical cross-sectional views of the first and second lens systems of the photographic lens of Example 3. Figures 6A and 6B are aberration diagrams of the first and second lens systems of the photographic lens of Example 3 when focused at infinity.

[0018] 7 is a schematic diagram of the main components of a camera (image capture device) equipped with a photographic lens according to the present invention. The photographic lenses of the respective embodiments are photographic lens systems used in image capture devices such as video cameras, digital cameras, and silver halide film cameras. In the lens cross-sectional view, the left side is the subject side (object side) (front) and the right side is the image side (rear). In the lens cross-sectional view, i indicates the order of the lens groups from the object side, and Bi is the ith lens group.

[0019] In the lens cross-sectional views of each embodiment, B1A is the 1A lens group, B1B is the 1B lens group, and B2 is the 2nd lens group.

[0020] In each embodiment, SP denotes an aperture stop, which is located on the object side of the second lens group. By locating the aperture stop midway between the first and second lens systems, the optical system is arranged symmetrically, making it possible to correct distortion and curvature of field, which is advantageous for improving performance. Furthermore, by positioning the aperture stop away from the solid-state image sensor, the angle of incidence onto the solid-state image sensor can be made gentler, which is advantageous for suppressing image degradation due to shading and the like, thereby improving image quality. In this embodiment, the aperture stop is located on the object side of the second lens group, but it is also possible to place a lens on the object side of the stop, in which case the stop may be located within the second lens group.

[0021] The GB is an optical block equivalent to an optical filter, a faceplate, a crystal low-pass filter, an infrared cut filter, etc.

[0022] IP is the image plane, and when used as the shooting optical system of a video camera or digital still camera, it is placed on the imaging surface of a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or CMOS sensor, and in the case of a silver halide film camera, it is placed on the photosensitive surface corresponding to the film surface.

[0023] In each aberration diagram, d and g represent the d-line and g-line, ΔM and ΔS represent the meridional image plane and sagittal image plane, and lateral chromatic aberration is represented by the g-line. ω is the half angle of view (half the photographic angle of view), and fno is the F-number.

[0024] In each embodiment, the first lens system of the partially shared photographic lens, which is one aspect of the present disclosure, is composed of a 1A lens group and a second lens group with an aperture stop sandwiched between them. The second lens system is composed of a 1B lens group and a second lens group with an aperture stop sandwiched between them. The second lens group has positive refractive power. By sharing the second lens group located on the image side and replacing the 1A lens group in front of the aperture stop with the 1B lens group, the focal lengths of the first lens system and the second lens system can be changed, making it possible to switch the photographic angle of view.

[0025] In each embodiment, when focusing from infinity to close range, in Example 1, focusing is performed by moving the fourth lens from the object side in the second lens group in the optical axis direction. This lens has negative refractive power and is retracted toward the image side during focusing. In Example 2, focusing is performed by moving the third lens from the object side in the second lens group in the optical axis direction. This lens has positive refractive power and is retracted toward the object side during focusing. By configuring the focus group with a single lens as in Examples 1 and 2, lightweight focusing is possible. Furthermore, by placing the focus group in the shared second lens group, a configuration that is easy for users to replace can be realized. Alternatively, even when manufacturing as separate lenses, the focus mechanism can be shared, improving development efficiency and enabling low prices. In Example 3, focusing is performed by extending the entire first or second lens system. Example 3 is designed using a resin lens, making use of lightweight materials. Since the entire lens is extended, aberrations are corrected, which has the advantage of achieving high performance.

[0026] In each embodiment, the 1A lens group is composed of two to five lenses. In all embodiments, the 1A lens group is composed of one to two more lenses than the 1B lens group. This is because the first lens system has a wider angle of view than the second lens system, and because the wider-angle lens passes through the outer periphery of the lens, the number of lenses is increased to correct the curvature of field of peripheral rays.

[0027] Furthermore, the 1A lens group and the 1B lens group each have at least one positive lens and at least one negative lens, in order to correct chromatic aberration in the interchangeable lens groups and to improve performance when switching lenses.

[0028] The second lens group has positive refractive power and is composed of five lenses. As will be described later, because the 1A lens group and the 1B lens group have weak refractive power, the second lens group bears the majority of the refractive power of the first and second lens systems as a whole. For this reason, it is preferable that the number of lenses constituting the shared second lens group be equal to or greater than the number of lenses in the 1A lens group and the 1B lens group. However, in the case of a pan-focus lens that does not include a focus mechanism, the design difficulty is reduced, and it is possible to further reduce the number of lenses.

[0029] Furthermore, since the second lens group is a shared lens group, it is desirable to use aspherical lenses in the second lens group and to use as many spherical lenses as possible in the 1A lens group and the 1B lens group. The second lens group provides the majority of the refractive power of the first and second lens systems, so its refractive power is strong. Therefore, using an aspherical lens in the second lens group to efficiently correct aberrations can achieve a compact overall system. Furthermore, assuming the lenses are manufactured as separate lenses, using aspherical lenses in the shared lens group increases the production volume of aspherical lenses, thereby creating the benefit of low cost through mass production. In this embodiment, too, the second lens group contains more aspherical lenses than the 1A lens group and the 1B lens group. In this way, another advantage of this proposal is that it can reduce the overall cost of the lens by concentrating costly components, such as aspherical lenses, aperture diaphragms, focus mechanisms, and vibration isolation mechanisms, in shared areas and increasing the number of these components.

[0030] The key point of the present invention is to set the refractive power of the 1A lens group in the first lens system or the 1B lens group in the second lens system to be weak, and to make the Petzval sum large on the negative side.

[0031] Achieving a compact optical system requires a positive group with strong power, but a positive group with strong power results in a large Petzval sum on the positive side. If the group closest to the object is a strong negative group, the change in spacing during lens interchange changes the height of the pupil paraxial ray, causing spherical aberration and curvature of field. When switching lenses, simply fine-tuning the spacing is not enough to simultaneously correct both spherical aberration and curvature of field. In this invention, by weakening the refractive power of the 1A lens group and the 1B lens group, the effect on spherical aberration is reduced, making it possible to provide a photographic lens configured to correct only curvature of field through fine adjustment of the spacing.

[0032] In the manufacturing method, the first lens system (first lens device) and the second lens system (second lens device) are not common to each other, and the first lens device comprises a first partial optical system, a first aperture stop, and a second partial optical system, arranged in this order from the object side to the image side. Furthermore, the second lens device has a longer focal length than the first lens device, and comprises a first partial optical system, a first aperture stop, and a second partial optical system, arranged in this order from the object side to the image side. The second lens device comprises a third partial optical system, a second aperture stop, and a fourth partial optical system, arranged in this order from the object side to the image side. The total number of positive lenses arranged in the second partial optical system is equal to the total number of positive lenses arranged in the fourth partial optical system. The total number of negative lenses arranged in the second partial optical system is equal to the total number of negative lenses arranged in the fourth partial optical system. Furthermore, when the focal length of the second partial optical system is f2 and the focal length of the fourth partial optical system is f4, 0.90 <f2 / f4<1.10 ···(10) This allows the lens of the fourth partial optical system to be used for the second partial optical system, or allows the mold type to be standardized or can be manufactured by fine-tuning the mold type, making it easy to manufacture high-performance lenses at low cost.

[0033] More preferably, the numerical range of conditional expression (10) should be set as follows:

[0034] 0.95 <f2 / f4<1.05 ···(10a) It is more preferable to set the numerical range of conditional expression (10) as follows:

[0035] 0.97 <f2 / f4<1.03 ···(10a) In the manufacturing method below, the 1A lens group corresponds to the first partial optical system, the 1B lens group corresponds to the third partial optical system, and the positive lens group corresponds to the second or fourth partial optical system.

[0036] In Examples 1 to 3, when focusing at infinity, the focal length of the positive lens group is fP, the focal length of the 1A lens group is f1A, and the focal length of the 1B lens group is f1B. When the focal length of each lens arranged in the positive lens group is fPi and the refractive index of that lens is Ni, 0.01<|fP / f1A|<0.30 (1) 0.01<|fP / f1B|<0.30 (2) 0.02<Σ1 / (fPi·Ni)<0.10···(3) The following condition is satisfied.

[0037] Conditional formula (1) defines the ratio of the focal length of the 1A lens group to the focal length of the 2nd lens group in the first lens system. As mentioned above, the refractive power of the 1A lens group is weak, and the refractive power of the 2nd lens group is positively strong.

[0038] If the value falls below the lower limit of conditional formula (1), the refractive power of the second lens group will be too strong relative to the refractive power of the first lens group. If the refractive power of the second lens group is too strong, significant curvature of field will occur in the second lens group. To counteract this, the Petzval sum of the first lens group must also be set to a large negative value. This is undesirable because it makes the sensitivity of spacing adjustments when switching lenses too high. Alternatively, the number of lenses will increase in order to correct the curvature of field in the second lens group, which is undesirable because it results in an increase in the size of the optical system.

[0039] If the value exceeds the upper limit of conditional expression (1), the refractive power of the 1A lens group becomes too strong relative to the refractive power of the 2nd lens group, and as a result, the change in spacing when switching lenses changes the spherical aberration and curvature of field, making it difficult to adjust the two aberrations simultaneously, and thus making it difficult to achieve high performance.

[0040] Conditional formula (2) defines the ratio of the focal length of the 1B lens group to the focal length of the 2nd lens group in the 2nd lens system. As mentioned above, the refractive power of the 1B lens group is weak, and the refractive power of the 2nd lens group is positively strong.

[0041] If the value falls below the lower limit of conditional formula (2), the refractive power of the second lens group will be too strong relative to the refractive power of the first lens group B. If the refractive power of the second lens group is too strong, significant curvature of field will occur in the second lens group. To counteract this, the Petzval sum of the first lens group B must also be set to a large negative value. This is undesirable because it makes the sensitivity of spacing adjustments when switching lenses too high. Alternatively, the number of lenses will increase in order to correct the curvature of field in the second lens group, which is undesirable because it results in an increase in the size of the optical system.

[0042] If the value exceeds the upper limit of conditional expression (2), the refractive power of the 1B lens group becomes too strong relative to the refractive power of the 2nd lens group, and as a result, spherical aberration and curvature of field change due to the change in spacing when switching lenses, making it difficult to adjust the two aberrations simultaneously and making it difficult to achieve high performance.

[0043] Condition (3) defines the Betzval sum of the second lens group.

[0044] If the value falls below the lower limit of conditional formula (3), the focal length of the 1A lens group must be set to f1A, and the Petzval sum must be corrected in each of the 1B lens group and the 2nd lens group, resulting in an increase in the number of lenses and a larger optical system. This increases the number of lenses in the 2nd lens group, which has particularly strong refractive power. This corresponds to the case where a converter lens is attached to the object side of a normal photographic lens, but many lenses are required to achieve a high-performance lens.

[0045] If the value exceeds the upper limit of conditional expression (3), the amount of field curvature generated in each group becomes too large, which is undesirable because it makes the sensitivity of spacing adjustment when switching lenses too high.

[0046] In order to realize a more compact, high-performance photographic lens with an interchangeable front group, it is more preferable to set the numerical ranges of conditional expressions (1) to (3) as follows:

[0047] 0.10<|fP / f1A|<0.30 (1a) 0.05<|fP / f1A|<0.25 (2a) 0.02<Σ1 / (fPi·Ni)<0.08···(3a) It is more preferable to set the numerical ranges of the conditional expressions (1) to (3) as follows:

[0048] 0.15<|fP / f1A|<0.30 (1b) 0.09<|fP / f1A|<0.23 (2b) 0.02<Σ1 / (fPi·Ni)<0.07···(3b) In the present invention, it is more preferable that one or more of the following conditions be satisfied.

[0049] 0.01<|ff1 / f1A|<0.20 (4) 0.01<|ff2 / f1B|<0.20 (5) 0.3 <LP / L1<0.8 ···(6) 0.8 <N2aveP / N2aveN<1.5···(7) 0.15 <D1A / DP<1.5 ···(8) 0.05 <BFinair / L1<0.3 ···(9) where ff1 is the focal length of the first lens system when focused at infinity, and ff2 is the focal length of the second lens system when focused at infinity. LP is the distance from the object-side surface of the second lens group to the image plane, and L1 is the distance from the surface of the first lens system closest to the object to the image plane. N2aveP and N2aveN are the average refractive indices of the positive and negative lenses in the second lens group, respectively.

[0050] Conditional expression (4) defines the ratio between the focal length of the first lens system and the focal length of the 1A lens group in the first lens system.

[0051] If the value falls below the lower limit of conditional expression (4), the refractive power of the 1A lens group will be too weak for the focal length of the first lens system, so the refractive power of the 2A lens group must be strengthened. Stronger refractive power in the 2A lens group results in greater curvature of field in the 2A lens group. To counteract this, the Petzval sum of the 1A lens group must also be set to a large negative value. This is undesirable because it makes the adjustment of the spacing when switching lenses too sensitive. Alternatively, the number of lenses must be increased to correct the curvature of field in the 2A lens group, which results in an increase in the size of the optical system, which is also undesirable.

[0052] If the value exceeds the upper limit of conditional expression (4), the refractive power of the 1A lens group becomes too strong relative to the refractive power of the entire first lens system, which causes changes in the spacing when switching lenses in the first lens system, resulting in changes in spherical aberration and curvature of field, making it difficult to adjust the two aberrations simultaneously and making it difficult to achieve high performance.

[0053] Conditional expression (5) defines the ratio of the focal length of the 1B lens group to the focal length of the second lens group in the second lens system.

[0054] If the value falls below the lower limit of conditional expression (5), the focal length of the second lens system will be too weak compared to the refractive power of the 1B lens group, so the refractive power of the 2B lens group must be strengthened. Stronger refractive power in the 2B lens group results in greater curvature of field in the 2B lens group. To counteract this, the Petzval sum of the 1B lens group must also be set to a large negative value. This is undesirable because it makes the spacing adjustment when switching lenses too sensitive. Alternatively, the number of lenses must be increased to correct the curvature of field in the 2B lens group, which results in an increase in the size of the optical system, which is also undesirable.

[0055] If the value exceeds the upper limit of conditional expression (5), the refractive power of the 1B lens group becomes too strong relative to the refractive power of the entire second lens system, which causes changes in the spacing when switching lenses in the second lens system, resulting in changes in spherical aberration and curvature of field, making it difficult to adjust the two aberrations simultaneously and making it difficult to achieve high performance.

[0056] Conditional expression (6) defines the ratio of the thickness of the second lens unit to the overall length of the first lens system.

[0057] If the value falls below the lower limit of conditional expression (6), the second lens group becomes too thin. As mentioned above, since the aperture stop is located on the image side of the first-A lens group, the aperture stop is too close to the image plane, shortening the exit pupil and sharpening the angle of incidence on the sensor. This is undesirable because it causes color shading and other issues.

[0058] If the value exceeds the upper limit of conditional expression (6), the second lens group becomes too thick. As the second lens group becomes thicker, the first lens group becomes thinner, and the distance from the aperture stop to the surface of the first lens group closest to the object becomes shorter. This reduces the height of the paraxial ray of light passing through the first lens group, making it difficult to correct distortion and curvature of field, resulting in poor performance. Alternatively, it becomes necessary to reduce the number of lenses constituting the first lens group, making it difficult to correct chromatic aberration.

[0059] Conditional expression (7) defines the ratio of the average refractive index of the positive lens and the negative lens that make up the second lens group.

[0060] If the value falls below the lower limit of condition (7), the average refractive index of the positive lenses becomes too small, causing the Petzval sum to become positive and large. This undesirably increases the sensitivity of the spacing adjustment when switching lenses.

[0061] If the value exceeds the upper limit of conditional expression (7), the average refractive index of the positive lens can be increased, which is advantageous in terms of field curvature, but it also means that only high-dispersion lenses can be used, which is undesirable because chromatic aberration correction becomes insufficient.

[0062] Conditional expression (8) defines the ratio of the thickness of the 1A lens group to the thickness of the 2A lens group.

[0063] If the value falls below the lower limit of condition (8), the positive lens becomes too thick, and the overall system becomes large.

[0064] If the value exceeds the upper limit of conditional expression (8), the positive lens with strong refractive power is thin, and therefore a lens for correcting curvature of field cannot be arranged, resulting in a deterioration in performance.

[0065] Conditional expression (9) defines the ratio of the back focal length to the overall length of the first lens system, and also defines compactness. The photographic lens of the present invention is characterized by a configuration in which the object-side lens group is switched, and is therefore suitable for a lens with a short back focal length. By satisfying the range of conditional expression, it is possible to make the entire photographic lens compact. However, if the back focal length is too close, scratches or dust on the lens surface will be captured on the image sensor, which is not desirable.

[0066] Even more preferably, the numerical ranges of the conditions (4) to (6) should be set as follows:

[0067] 0.05<|ff1 / f1A|<0.20 (4a) 0.05<|ff2 / f1B|<0.20 ···(5a) 0.4 <LP / L1<0.75 ···(6a) 0.9 <N2aveP / N2aveN<1.2 ···(7a) 0.3 <D1A / DP<1.3 ···(8a) 0.08 <BFinair / L1<0.2 ···(9a) In the present invention, it is more preferable that one or more of the following conditions be satisfied.

[0068] 0.08<|ff1 / f1A|<0.195 ···(4b) 0.08<|ff2 / f1B|<0.195 ···(5b) 0.5 <LP / L1<0.72 ···(6b) 0.92 <N2aveP / N2aveN<1.15···(7b) 0.5 <D1A / DP<1.1 ···(8b) 0.1 <BFinair / L1<0.15 ···(9b) Next, Numerical Examples 1 to 3 corresponding to Examples 1 to 3 of the present invention, respectively, are shown. In each Numerical Example, i indicates the order of the optical surfaces from the object side. ri indicates the radius of curvature of the ith optical surface (ith surface), di indicates the distance between the ith surface and the (i+1)th surface, and ndi and vdi indicate the refractive index and Abbe number of the material of the ith optical member for the d-line, respectively.

[0069] Furthermore, when k is the eccentricity, A4, A6, A8, and A10 are aspheric coefficients, and the displacement in the optical axis direction at a position of height h from the optical axis is x with the vertex of the surface as the reference, the aspheric shape is x=(h 2 / R) / [1+[1-(1+k)(h / R) 2 ] 1 / 2 ]+A4h 4 +A6h 6 +A8h 8 +A10h 10 where R is the paraxial radius of curvature. For example, "EZ" is displayed as "10 -Z" means. In the numerical examples, the last two surfaces are surfaces of an optical block such as a filter or faceplate. In each example, the back focus (BF) is the distance, converted into air, from the surface nearest to the image of the lens group nearest to the image side, which has refractive power, to the paraxial image plane. Table 1 shows the correspondence between each numerical example and the above-mentioned conditional expressions.

[0070] (Numerical Example 1) First lens unit Surface Data Surface number rd nd vd Effective diameter 1 28.532 0.80 2.00100 29.1 18.00 2 9.738 2.38 13.50 3 35.887 0.60 1.72916 54.7 12.80 4 8.390 0.97 10.40 5 14.069 2.27 1.77830 23.9 10.20 6 -48.500 0.87 9.20 7 -13.342 0.50 1.69350 53.2 6.70 8* 4.585 1.57 5.40 9 8.236 2.00 1.59270 35.3 5.00 10 -7.313 (variable) 4.50 11 (Aperture) ∞ 0.86 3.62 12* 9.763 2.16 1.49710 81.6 4.00 13* -15.297 0.10 5.00 14 -10.490 0.35 1.77830 23.9 5.10 15 10.490 0.25 5.60 16* 7.230 1.79 1.76802 49.2 5.80 17* -7.324 1.97 6.30 18 -23.609 0.40 1.76182 26.5 7.90 19 15.979 2.12 8.50 20* 36.613 2.41 1.63560 23.9 12.10 21* -27.501 (variable) 12.30 22 ∞ 1.00 1.51633 64.1 14.00 23 ∞ (variable) 14.00 Image plane ∞ Aspheric data Side 8 K = 0.00000e+000 A 4= 4.27645e-004 A 6= 1.01149e-004 A 8=-1.26872e-005 A10= 2.04569e-007 Side 12 K = 0.00000e+000 A 4=-2.93772e-003 A 6= 2.15270e-004 A 8=-1.06245e-004 A10= 1.17246e-005 A12=-1.47530e-006 Page 13 K = 0.00000e+000 A 4=-1.72367e-002 A 6= 2.14408e-003 A 8=-2.10511e-004 A10= 9.85190e-006 A12=-5.30549e-007 Page 16 K = 0.00000e+000 A 4=-8.72413e-003 A 6= 7.34397e-004 A 8=-2.99277e-005 A10= 1.75556e-007 Page 17 K = 0.00000e+000 A 4= 1.30281e-003 A 6=-3.06018e-004 A 8= 3.66480e-005 A10=-1.32288e-006 Page 20 K = 0.00000e+000 A 4= 2.40907e-003 A 6=-2.28373e-004 A 8= 1.21252e-005 A10=-3.42829e-007 A12= 5.04162e-009 A14=-3.08266e-011 Page 21 K = 0.00000e+000 A 4= 3.02717e-003 A 6=-2.34941e-004 A 8= 8.48720e-006 A10=-1.41285e-007 A12= 8.67693e-010 Various data Zoom ratio 1.00 Focal length 4.52 F-number 2.94 Angle of view 55.08 Image height 6.47 Lens length 29.56 BF(in air) 3.37 d10 1.47 d21 1.71 d23 1.00 Second lens system Surface Data Surface number rd nd vd Effective diameter 1 10.588 5.70 1.53775 74.7 17.80 2 26.320 1.09 14.10 3 12.615 0.50 1.91082 35.3 9.40 4 4.185 3.20 6.90 5* -12.183 0.50 1.68948 31.0 5.40 6 5.000 0.34 4.80 7 6.327 1.87 2.00069 25.5 4.80 8 -14.235 (variable) 4.20 9 (Aperture) ∞ 0.86 3.62 10* 9.763 2.16 1.49710 81.6 4.00 11* -15.297 0.10 5.00 12 -10.490 0.35 1.77830 23.9 5.10 13 10.490 0.25 5.60 14* 7.230 1.79 1.76802 49.2 5.80 15* -7.324 1.97 6.30 16 -23.609 0.40 1.76182 26.5 7.90 17 15.979 2.12 8.50 18* 36.613 2.41 1.63560 23.9 12.10 19* -27.501 (variable) 12.30 20 ∞ 1.00 1.51633 64.1 14.00 21 ∞ (variable) 14.00 Image plane ∞ Aspheric data 5th page K =-9.49305e+000 A 4=-6.01723e-004 A 6=-2.45714e-005 A 8= 4.60567e-006 Side 10 K = 0.00000e+000 A 4=-2.93772e-003 A 6= 2.15270e-004 A 8=-1.06245e-004 A10= 1.17246e-005 A12=-1.47530e-006 Page 11 K = 0.00000e+000 A 4=-1.72367e-002 A 6= 2.14408e-003 A 8=-2.10511e-004 A10= 9.85190e-006 A12=-5.30549e-007 Side 14 K = 0.00000e+000 A 4=-8.72413e-003 A 6= 7.34397e-004 A 8=-2.99277e-005 A10= 1.75556e-007 Page 15 K = 0.00000e+000 A 4= 1.30281e-003 A 6=-3.06018e-004 A 8= 3.66480e-005 A10=-1.32288e-006 Page 18 K = 0.00000e+000 A 4= 2.40907e-003 A 6=-2.28373e-004 A 8= 1.21252e-005 A10=-3.42829e-007 A12= 5.04162e-009 A14=-3.08266e-011 Page 19 K = 0.00000e+000 A 4= 3.02717e-003 A 6=-2.34941e-004 A 8= 8.48720e-006 A10=-1.41285e-007 A12= 8.67693e-010 Various data Zoom ratio 1.00 Focal length 8.53 F-number 2.88 Angle of view 37.18 Image height 6.47 Lens length 30.63 BF(in air) 3.37 d81.31 d19 1.71 d21 1.00

[0071] (Numerical Example 2) First lens unit Surface Data Surface number rd nd vd Effective diameter 1 -39.417 0.50 1.49700 81.5 7.70 2 4.131 1.66 6.00 3 8.146 2.00 1.88300 40.8 5.50 4 -18.336 0.68 4.70 5 -8.135 0.40 2.00100 29.1 3.60 6 15.682 1.57 1.59270 35.3 3.70 7 -5.528 (variable) 4.00 8 (Aperture) ∞ 0.72 3.88 9 15.876 1.74 2.00100 29.1 4.50 10 -6.459 0.16 4.90 11 -5.870 0.50 1.92286 18.9 4.80 12 38.746 3.57 5.30 13 -49.996 1.61 1.85135 40.1 8.30 14* -8.656 1.61 8.70 15 -8.203 0.50 1.59270 35.3 9.10 16 28.695 0.10 10.50 17 20.020 1.95 2.00100 29.1 11.20 18 991.458 (variable) 11.50 19 ∞ 1.00 1.51633 64.1 16.00 20 ∞ (variable) 16.00 Image plane ∞ Aspheric data Side 14 K =-4.96723e+000 A 4=-6.36810e-004 A 6= 1.72414e-005 A 8=-1.66807e-007 Various data Zoom ratio 1.00 Focal length 8.41 F-number 2.88 Angle of view: 37.57 Image height 6.47 Lens length 23.34 BF(in air) 3.24 d 7 0.50 d18 1.58 d20 1.00 Second lens system Surface Data Surface number rd nd vd Effective diameter 1 -21.959 0.50 1.59270 35.3 5.30 2 5.138 0.28 4.60 3 6.342 1.33 1.95375 32.3 4.60 4 -319.485 (variable) 4.00 5 (Aperture) ∞ 0.72 3.88 6 15.876 1.74 2.00100 29.1 4.50 7 -6.459 0.16 4.90 8 -5.870 0.50 1.92286 18.9 4.80 9 38.746 3.57 5.30 10 -49.996 1.61 1.85135 40.1 8.30 11* -8.656 1.61 8.70 12 -8.203 0.50 1.59270 35.3 9.10 13 28.695 0.10 10.50 14 20.020 1.95 2.00100 29.1 11.20 15 991.458 (variable) 11.50 16 ∞ 1.00 1.51633 64.1 16.00 17 ∞ (variable) 16.00 Image plane ∞ Aspheric data Page 11 K =-4.96723e+000 A 4=-6.36810e-004 A 6= 1.72414e-005 A 8=-1.66807e-007 Various data Zoom ratio 1.00 Focal length 10.98 F-number 2.88 Angle of view 30.51 Image height 6.47 Lens length 20.19 BF(in air) 3.24 d 4 2.05 d15 1.58 d17 1.00

[0072] (Numerical Example 3) First lens unit Surface Data Surface number rd nd vd Effective diameter 1* -4.513 0.30 1.53110 55.9 3.50 2* 2.519 0.45 2.20 3* 2.449 0.45 1.63560 23.9 2.00 4* 3.264 0.24 2.20 5* 9.626 0.71 1.53110 55.9 2.40 6* -3.077 (variable) 2.50 7 (Aperture) ∞ 0.00 2.42 8* 2.830 0.81 1.53110 55.9 2.50 9* -3.182 0.31 2.30 10* -1.823 0.25 1.67070 19.3 2.40 11* -3.148 0.30 2.60 12* 7.979 0.40 1.67070 19.3 3.10 13* 5.151 0.37 3.70 14* -13.080 0.57 1.53110 55.9 3.80 15* -2.535 0.36 4.30 16* -5.613 0.61 1.53110 55.9 4.90 17* 3.432 (variable) 6.50 18 ∞ 0.50 1.51633 64.1 8.00 19 ∞ (variable) 8.00 Image plane ∞ Aspheric data Front page K = 0.00000e+000 A 4= 7.89744e-002 A 6=-2.94228e-002 A 8= 8.24147e-003 A10=-1.60682e-003 A12= 1.45539e-004 2nd side K = 0.00000e+000 A 4= 4.71755e-002 A 6= 4.56983e-002 A 8=-3.98462e-002 A10= 3.55135e-002 A12=-9.43780e-003 3rd page K = 0.00000e+000 A 4=-9.21224e-002 A 6= 8.31161e-003 A 8=-2.20693e-002 A10= 1.43813e-002 A12=-6.41808e-003 Side 4 K = 0.00000e+000 A 4=-6.13004e-003 A 6=-2.62918e-002 A 8= 1.98964e-002 A10=-2.68404e-002 A12= 9.28136e-003 5th page K = 0.00000e+000 A 4= 4.41146e-002 A 6=-1.31930e-003 A 8=-3.65416e-003 A10=-1.75153e-003 A12=-1.97985e-003 Page 6 K = 0.00000e+000 A 4=-1.46227e-002 A 6= 3.46387e-003 A 8=-1.58619e-003 A10= 5.77662e-003 A12=-4.53954e-003 Page 8 K = 0.00000e+000 A 4=-2.53143e-003 A 6= 2.42501e-003 A 8=-7.05389e-004 A10= 1.40080e-003 A12=-3.28669e-004 Page 9 K = 0.00000e+000 A 4=-2.65470e-002 A 6= 7.21846e-003 A 8= 1.13827e-002 A10=-3.88763e-003 A12= 1.50814e-004 Page 10 K = 0.00000e+000 A 4= 8.86329e-002 A 6= 3.77122e-002 A 8=-3.35627e-002 A10= 1.24171e-002 A12=-2.53504e-003 Page 11 K = 0.00000e+000 A 4= 9.93444e-002 A 6= 3.59588e-002 A 8=-2.90860e-002 A10= 9.17142e-003 A12=-1.27442e-003 Page 12 K = 0.00000e+000 A 4=-6.73654e-002 A 6= 1.71258e-002 A 8=-5.17064e-003 A10= 2.52327e-003 A12=-6.17873e-004 Page 13 K = 0.00000e+000 A 4=-7.29890e-002 A 6= 2.02941e-002 A 8=-6.15148e-003 A10= 1.95317e-003 A12=-2.96023e-004 Side 14 K = 0.00000e+000 A 4=-5.35027e-002 A 6= 2.03321e-002 A 8=-5.00558e-003 A10= 6.55710e-004 A12=-3.47856e-005 Page 15 K = 0.00000e+000 A 4= 1.40884e-002 A 6= 1.50063e-003 A 8= 1.47795e-003 A10=-5.17366e-004 A12= 4.99945e-005 Page 16 K = 0.00000e+000 A 4=-1.79942e-003 A 6=-8.21842e-003 A 8= 2.00600e-003 A10=-9.82724e-005 A12=-3.69235e-006 Page 17 K = 0.00000e+000 A 4=-4.05291e-002 A 6= 4.61670e-003 A 8=-4.32837e-004 A10= 2.30741e-005 A12=-9.39199e-007 Various data Zoom ratio 1.00 Focal length 3.37 F-number 2.06 Angle of view 49.03 Image height 3.88 Lens length 7.51 BF(in air) 1.09 d6 0.10 d17 0.36 d19 0.40 Second lens system Surface Data Surface number rd nd vd Effective diameter 1* -5.680 0.50 1.63560 23.9 3.40 2* 15.064 0.66 2.50 3* 2.197 0.86 1.61550 25.8 1.80 4* 4.874 (variable) 1.70 5 (Aperture) ∞ 0.00 1.62 6* 2.830 0.81 1.53110 55.9 2.50 7* -3.182 0.31 2.30 8* -1.823 0.25 1.67070 19.3 2.40 9* -3.148 0.30 2.60 10* 7.979 0.40 1.67070 19.3 3.10 11* 5.151 0.37 3.70 12* -13.080 0.57 1.53110 55.9 3.80 13* -2.535 0.36 4.30 14* -5.613 0.61 1.53110 55.9 4.90 15* 3.432 (variable) 6.50 16 ∞ 0.50 1.51633 64.1 8.00 17 ∞ (variable) 8.00 Image plane ∞ Aspheric data Front page K = 0.00000e+000 A 4= 1.24548e-001 A 6=-4.90804e-002 A 8= 1.71391e-002 A10=-3.50156e-003 A12= 2.85105e-004 2nd side K = 0.00000e+000 A 4= 1.64816e-001 A 6=-2.23879e-002 A 8=-3.21306e-003 A10= 1.81730e-002 A12=-5.57023e-003 3rd page K = 0.00000e+000 A 4= 3.09562e-002 A 6= 2.58767e-003 A 8=-2.82627e-003 A10= 6.77709e-003 A12=-9.17677e-004 Page 4 K = 0.00000e+000 A 4= 1.63288e-002 A 6=-2.64447e-002 A 8= 9.64590e-002 A10=-9.67115e-002 A12= 4.76898e-002 Page 6 K = 0.00000e+000 A 4=-2.53143e-003 A 6= 2.42501e-003 A 8=-7.05389e-004 A10= 1.40080e-003 A12=-3.28669e-004 Page 7 K = 0.00000e+000 A 4=-2.65470e-002 A 6= 7.21846e-003 A 8= 1.13827e-002 A10=-3.88763e-003 A12= 1.50814e-004 Page 8 K = 0.00000e+000 A 4= 8.86329e-002 A 6= 3.77122e-002 A 8=-3.35627e-002 A10= 1.24171e-002 A12=-2.53504e-003 Page 9 K = 0.00000e+000 A 4= 9.93444e-002 A 6= 3.59588e-002 A 8=-2.90860e-002 A10= 9.17142e-003 A12=-1.27442e-003 Page 10 K = 0.00000e+000 A 4=-6.73654e-002 A 6= 1.71258e-002 A 8=-5.17064e-003 A10= 2.52327e-003 A12=-6.17873e-004 Page 11 K = 0.00000e+000 A 4=-7.29890e-002 A 6= 2.02941e-002 A 8=-6.15148e-003 A10= 1.95317e-003 A12=-2.96023e-004 Side 12 K = 0.00000e+000 A 4=-5.35027e-002 A 6= 2.03321e-002 A 8=-5.00558e-003 A10= 6.55710e-004 A12=-3.47856e-005 Page 13 K = 0.00000e+000 A 4= 1.40884e-002 A 6= 1.50063e-003 A 8= 1.47795e-003 A10=-5.17366e-004 A12= 4.99945e-005 Side 14 K = 0.00000e+000 A 4=-1.79942e-003 A 6=-8.21842e-003 A 8= 2.00600e-003 A10=-9.82724e-005 A12=-3.69235e-006 Page 15 K = 0.00000e+000 A 4=-4.05291e-002 A 6= 4.61670e-003 A 8=-4.32837e-004 A10= 2.30741e-005 A12=-9.39199e-007 Various data Zoom ratio 1.00 Focal length 4.32 F-number 2.89 Angle of view: 41.87 Image height 3.88 Lens length 7.84 BF(in air) 1.09 d 4 0.56 d15 0.36 d17 0.40

[0073] [Table 1]

[0074] Next, an embodiment of a digital still camera using the photographing lens shown in each example as a photographing optical system will be described with reference to FIG.

[0075] In Fig. 7, 20 denotes a camera body, and 21 denotes a photographing optical system constituted by any of the photographing lenses described in Examples 1 to 3. 22 denotes a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or CMOS sensor that is built into the camera body and receives the subject image formed by the photographing optical system 21. 23 denotes a memory that records information corresponding to the subject image photoelectrically converted by the solid-state image sensor 22. 24 denotes a finder constituted by a liquid crystal display panel or the like, for observing the subject image formed on the solid-state image sensor 22.

[0076] In this way, by applying the photographic lens of the present invention to an imaging device such as a digital still camera, it is possible to realize an imaging device having a compact, high-performance photographic lens that can switch between two specifications. [Explanation of symbols]

[0077] B1A 1A lens group B1B 1B lens group B2 Second lens group dd wire gg line ΔM meridional image plane ΔS sagittal image plane IP imaging surface SP Aperture GB Glass blocks for CCD force plates and low-pass filters ω Half angle of view fno F-number

Claims

1. A photographic lens that can provide a first lens system having a 1A lens group closest to the object and a positive lens group on the image side thereof, and a second lens system in which the focal length of the entire system is on the telephoto side by disposing a 1B lens group in place of the 1A lens group, and that satisfies the following conditional expression: 0.01<|fP / f1A|<0.30 0.01<|fP / f1B|<0.30 0.02<Σ1 / (fPi・Ni)<0.10 where fP is the focal length of the positive lens group, f1A is the focal length of the 1A lens group, and f1B is the focal length of the 1B lens group (when focusing at infinity), fPi is the focal length of each lens arranged in the positive lens group, and Ni is the refractive index of that lens.

2. 2. The photographic lens according to claim 1, wherein the photographic lens satisfies the following conditional expression: 0.01<|ff1 / f1A|<0.20 0.01<|ff2 / f1B|<0.20 Here, ff1 and ff2 are the focal lengths of the first and second lens systems when focused at infinity, respectively.

3. 2. The photographic lens according to claim 1, wherein the photographic lens satisfies the following conditional expression: 3<LP / L1<0.8 Here, LP is the distance from the object side surface of the positive lens unit to the image plane, and L1 is the distance from the surface of the first lens system closest to the object side to the image plane.

4. 2. The photographic lens according to claim 1, wherein the photographic lens satisfies the following conditional expression: 0.8<N2aveP / N2aveN<1.5 N2aveP and N2aveN are the average refractive indices of the positive lens and the negative lens included in the second lens group, respectively.

5. 2. The photographic lens according to claim 1, wherein the photographic lens has an aperture stop on the image side of the 1A lens group in the first lens system or the 1B lens group in the second lens system.

6. 2. The photographic lens according to claim 1, wherein at least a part of the positive lens group moves during focusing.

7. 2. The photographic lens according to claim 1, wherein the number of lenses in the first A lens group is greater than the number of lenses in the first B lens group.

8. 2. The photographic lens according to claim 1, wherein the number of aspherical lenses in the positive lens group is greater than that in the first A lens group.

9. 2. The photographic lens according to claim 1, wherein the number of aspherical lenses in the positive lens group is greater than that in the first B lens group.

10. 2. The photographic lens according to claim 1, wherein the first A lens group of the photographic lens has at least one positive lens and at least one negative lens.

11. 2. The photographic lens according to claim 1, wherein the first B lens group of the photographic lens has at least one positive lens and at least one negative lens.

12. 2. The photographic lens according to claim 1, wherein the positive lens group of the photographic lens has at least one positive lens and at least one negative lens, and also has an aspherical lens.

13. 2. The photographic lens according to claim 1, wherein the photographic lens satisfies the following conditional expression: 0.15<D1A / DP<1.5 Here, D1A is the distance on the optical axis from the most object-side surface to the most image-side surface of the 1A lens group, and DP is the distance on the optical axis from the most object-side surface to the most image-side surface of the positive lens group.

14. 2. The photographic lens according to claim 1, wherein the photographic lens satisfies the following conditional expression: 05<BFinair / L1<0.3 Here, BFinair is the air-equivalent back focal length of the first lens system, and L1 is the distance from the surface of the first lens system closest to the object to the image plane.

15. A manufacturing method for manufacturing a first lens device and a second lens device, comprising: the second lens arrangement has a longer focal length than the first lens arrangement; the first lens device comprises a first partial optical system, a first aperture stop, and a second partial optical system, which are arranged in this order from the object side to the image side; the second lens device comprises a third partial optical system, a second aperture stop, and a fourth partial optical system, which are arranged in this order from the object side to the image side; the total number of positive lenses arranged in the second partial optical system is equal to the total number of positive lenses arranged in the fourth partial optical system, the total number of negative lenses arranged in the second partial optical system is equal to the total number of negative lenses arranged in the fourth partial optical system, 0.01<|fP / f1A|<0.30 0.01<|fP / f1B|<0.30 0.02<Σ1 / (fPi・Ni)<0.10 0.90<f2 / f4<1.10 Here, the focal length of the first partial optical system is f1A, the focal length of the third partial optical system is f1B, the focal length of each lens arranged in the second partial optical system is fPi, the refractive index is Ni, the focal length of the second partial optical system is f2, and the focal length of the fourth partial optical system is f4.

Images