Zoom lens and imaging apparatus

Abstract

To provide a zoom lens having better optical performance.SOLUTION: A zoom lens has a plurality of lens groups B1-B3. At least one lens group of the plurality of lens groups has a diffraction surface MOE with controlled wavelength dispersion. The Abbe number ν0 of the diffraction surface satisfies a condition of -0.28≤1 / ν0≤0.00.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a zoom lens suitable for imaging. [Background technology]

[0002] Patent Document 1 discloses a zoom lens that corrects chromatic aberration using a diffractive optical element. Patent Document 2 discloses a metasurface zoom lens that obtains a variable magnification effect by utilizing a phase change in a material. Patent Document 3 discloses a zoom lens that obtains a variable magnification effect by moving a metasurface lens in a direction perpendicular to the optical axis. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 09-197273 [Patent Document 2] U.S. Patent Publication No. 2021 / 333575 [Patent Document 3] U.S. Patent Publication No. 2021 / 231909 Summary of the Invention [Problem to be solved by the invention]

[0004] In the zoom lens described above, better optical performance is required. [Means for solving the problem]

[0005] A zoom lens according to one aspect of the present invention has a plurality of lens groups, and the spacing between adjacent lens groups changes during zooming. At least one of the lens groups has a diffractive surface with controlled wavelength dispersion, and the Abbe number ν of the diffractive surface is -0.28≦1 / ν0≦0.00 The Abbe number ν0 will be described later.

[0006] Another aspect of the present invention is a zoom lens having a plurality of lens groups, and the spacing between adjacent lens groups changes during zooming. At least one of the lens groups has a diffractive surface with controlled wavelength dispersion, and at least one of the lens groups has a refractive surface. The Abbe number of the diffractive surface is expressed as ν0, where ν0 is the diffractive surface's Abbe number, and ν0 is the refractive surface's Abbe number. 1 / ν0≦0.00 The present invention is characterized in that the following conditions are satisfied: An imaging device having the above zoom lens also constitutes another aspect of the present invention. [Effects of the Invention]

[0007] It is possible to provide a zoom lens having better optical performance than conventional zoom lenses. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view of a zoom lens according to a first embodiment. [Figure 2] 5A to 5C are aberration diagrams of the zoom lens of Example 1 at the wide-angle end, at the intermediate zoom position, and at the telephoto end. [Figure 3] FIG. 10 is a cross-sectional view of a zoom lens according to a second embodiment. [Figure 4] 10A to 10C are aberration diagrams of the zoom lens of Example 2 at the wide-angle end, at the intermediate zoom position, and at the telephoto end. [Figure 5] FIG. 10 is a cross-sectional view of a zoom lens according to a third embodiment. [Figure 6] 10A to 10C are aberration diagrams of the zoom lens of Example 3 at the wide-angle end, at the intermediate zoom position, and at the telephoto end. [Figure 7] FIG. 10 is a cross-sectional view of a zoom lens according to a fourth embodiment. [Figure 8] 10A to 10C are aberration diagrams of the zoom lens of Example 4 at the wide-angle end, at the intermediate zoom position, and at the telephoto end. [Figure 9] FIG. 10 is a cross-sectional view of a zoom lens according to a fifth embodiment. [Figure 10] 10A to 10C are aberration diagrams of the zoom lens of Example 5 at the wide-angle end, at the intermediate zoom position, and at the telephoto end. [Figure 11] FIG. 1 is a diagram showing an imaging device equipped with a zoom lens according to any one of Examples 1 to 5. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0010] Figures 1, 3, 5, 7, and 9 each show the configuration of the zoom lens of Examples 1 to 5 at the wide-angle end. O indicates the optical axis. Bi (i is the order counted from the object side) is the ith lens group, and MOE is a diffractive surface with controlled wavelength dispersion (hereinafter referred to as dispersion-controlled). The number on the left of the MOE indicates the lens group (ith lens group) that includes the diffractive surface, and 1 on the right indicates that the diffractive surface is the object-side surface of a diffractive optical element (lens), and 2 indicates that the diffractive surface is the image-side surface of a diffractive optical element.

[0011] SP denotes the aperture stop, and IP denotes the image plane, where the imaging surface (imaging surface) of an imaging element such as a CCD sensor or CMOS sensor, or the film surface (photosensitive surface) of a silver halide film, is located.

[0012] First, prior to the specific description of Examples 1 to 5, matters common to all Examples will be described.

[0013] The zoom lens of each embodiment has multiple lens groups. In each embodiment, the lens groups have a refractive power that refracts incident parallel light and provides a focusing or diverging effect. Furthermore, a lens group is a group of optical elements, such as one or more lenses, that may or may not move together during zooming, focusing, and image stabilization (image shake correction). The spacing between adjacent lens groups changes during zooming and focusing. The wide-angle end and telephoto end, which are the two ends of zooming, respectively indicate the maximum and minimum angles of view (shortest focal lengths) when the lens groups that move during zooming are positioned at the ends of their mechanically or controllably movable range on the optical axis. The lens groups may also include an aperture diaphragm.

[0014] In an imaging device in which the zoom lens of each embodiment is intended to be used, the lens groups are moved to minimize the spacing between them in order to reduce the overall size of the imaging device when the zoom lens is retracted. Since the thickness of the zoom lens in the optical axis direction when retracted in the imaging device (hereinafter referred to as the retracted zoom lens) is determined by the sum of the thicknesses of the lens groups, the thickness of each lens group must be reduced in order to further reduce the size of the imaging device.

[0015] On the other hand, to obtain good optical performance in a zoom lens, it is necessary to minimize the aberrations (chromatic aberration and geometric aberration) that occur in each lens group. However, if multiple lenses are used to minimize the aberrations of the lens groups, the thickness of the lens groups increases. As a result, the thickness of the zoom lens in the retracted state (and therefore the thickness of the imaging device in which the zoom lens is retracted) also increases.

[0016] In each zoom lens embodiment, at least one lens group includes a dispersion-controlled diffractive surface to reduce the aberrations occurring in that lens group while reducing the thickness of that lens group.

[0017] The diffractive optical element having a dispersion-controlled diffractive surface used in each embodiment is different from conventional blazed diffractive optical elements. The dispersion of the blazed diffractive optical element disclosed in Patent Document 1 is -3.45, expressed as an Abbe number at the d-line, which is extremely high. Therefore, increasing the refractive power of the diffractive surface will result in significant chromatic aberration. As described in Patent Document 1, the refractive power of a blazed diffractive optical element is limited to approximately 10% of the refractive power of the lens group.

[0018] Furthermore, the zoom lenses in Patent Documents 2 and 3 use metasurfaces to achieve the zoom effect, but require temperature control and displacement control of the lens group in a direction perpendicular to the optical axis, which is different from that of ordinary zoom lenses.

[0019] The zoom lens of each embodiment can solve these problems by using a dispersion-controlled diffractive surface.

[0020] In each embodiment, it is preferable that the diffractive optical element having a diffractive surface has negative dispersion. In a diffractive optical element having negative dispersion, when the diffractive surface is given the same refractive power as the lens group, it is possible to cancel chromatic aberrations generated by the other lens surfaces. As a result, it is possible to share part of the refractive power of the other lens surfaces and simultaneously achieve achromatism, thereby minimizing aberrations within the lens group.

[0021] In each embodiment, when the focal length of the lens group including the dispersion-controlled diffractive surface is fi and the focal length of the dispersion-controlled diffractive surface is fmi, it is preferable to satisfy the following formula (1):

[0022] 0.15≦fi / fmi≦10.00 (1) If the refractive power of the diffractive surface becomes too strong, such that fi / fmi exceeds the upper limit of formula (1), the structure of the diffractive surface becomes complicated, making it difficult to manufacture the diffractive surface, which is undesirable.If the refractive power of the diffractive surface becomes too weak, such that fi / fmi falls below the lower limit of formula (1), the refractive power contribution of the lens group including the diffractive surface decreases, and the refractive power of other lens surfaces in the lens group becomes strong, making it difficult to correct geometric aberrations, which is also undesirable.

[0023] Furthermore, it is preferable that the zoom lens of each embodiment satisfies the condition of the following formula (2), where ν0 is the Abbe number of the dispersion-controlled diffractive surface.

[0024] -0.28≦1 / ν0≦0.00 (2) The Abbe number ν0 of a dispersion-controlled diffractive surface is defined by the following formula: Here, the reference wavelength is the d-line (λ d =0.58756[μm]), and the main dispersion is F-line (λ F =0.48613[μm]) and C line (λ C =0.65627[μm]), and the optical path difference functions at the wavelengths of the d-line, F-line, and C-line are respectively ψ(λ d ), ψ(λ F ), ψ(λ C ) and the optical path difference dispersion of the surface at the wavelengths of the d-line, F-line, and C-line is P(λd ), P(λ F ), P(λ C ) In this case,

[0025]

number

[0026] is.

[0027] When a refractive power is imparted to an optical element, it can bend light of a specific wavelength in a specific direction, but chromatic aberration occurs unless the behavior of light of wavelengths other than the specific wavelength is controlled. Therefore, by setting the Abbe number ν0 of the diffractive surface to satisfy the condition of formula (2), chromatic aberration can be effectively corrected even if the refractive power of the lens group including the diffractive surface whose dispersion is controlled to satisfy the condition of formula (1) is largely shared by the diffractive surface.

[0028] If the dispersion of the diffractive surface becomes positive so that 1 / ν0 exceeds the upper limit of formula (2), chromatic aberration can be well corrected, but the refractive power becomes too weak. As a result, the diffractive surface is unable to share the refractive power of the lens group, making it difficult to simultaneously correct geometric aberration and chromatic aberration, which is undesirable. If the negative dispersion of the diffractive surface becomes too large so that 1 / ν0 falls below the lower limit of formula (2), the diffractive surface cannot be given refractive power, and the geometric aberration correction effect becomes insufficient, which is also undesirable.

[0029] However, if it is acceptable for the geometric aberration correction effect to be insufficient (for example, if geometric aberration correction is performed by image processing in an imaging device), 1 / ν0 may be below the lower limit of formula (2). In other words, it is sufficient to satisfy 1 / ν0≦0.00.

[0030] The zoom lens of each embodiment has the above configuration and satisfies the conditions of expressions (1) and (2), thereby making it possible to effectively correct chromatic aberration and geometric aberration while achieving a slim and compact image pickup device equipped with the zoom lens.

[0031] It is more preferable to set the numerical range of the formula (1) as follows:

[0032] 0.15≦fi / fmi≦7.00 (1a) Furthermore, it is more preferable to set the numerical range of formula (1) as follows:

[0033] 0.15≦fi / fmi≦3.00 (1b) Furthermore, it is more preferable to set the numerical range of the formula (2) as follows:

[0034] -0.15<1 / ν0≦0.00 (2a) Furthermore, it is more preferable to set the numerical range of the formula (2) as follows:

[0035] -0.10<1 / ν0≦0.00 (2b) Furthermore, it is preferable that the zoom lens of each embodiment has the following configuration and satisfies at least one of the conditions of expressions (3) to (7).

[0036] First, it is preferable that all surfaces of a zoom lens be refractive surfaces rather than diffractive surfaces. One reason for this is that if both surfaces of a diffractive optical element are diffractive surfaces, it becomes difficult to manufacture the diffractive optical element. Another reason is that if the diffractive optical element is a thin lens, there will be no significant difference in the position where light passes between the object-side surface and the image-side surface, resulting in insufficient flexibility in aberration correction. For this reason, it is preferable to provide the diffractive optical element with a sufficient thickness, with one surface being a diffractive surface and the other being a refractive surface, as in Example 5 described below. Furthermore, by making one surface a refractive surface, the difficulty of manufacturing the diffractive optical element can be reduced. Furthermore, to reduce the difficulty of manufacturing the diffractive surface, it is desirable to make the base surface on which the diffractive surface is formed a flat surface.

[0037] It is also preferable that the lens group including the dispersion-controlled diffractive surface be composed of two or fewer lenses. This is because if the lens group has three or more lenses and the thickness of the lens group increases, the thickness of the zoom lens in the retracted state will also increase. Furthermore, if all lens groups in the zoom lens can be composed of two or fewer lenses, this is preferable because it allows the thickness of the zoom lens in the retracted state to be kept small.

[0038] However, if the concave surface closest to the image of one lens group and the concave surface closest to the object of the adjacent lens group are arranged close to each other, the distance between the lens groups cannot be sufficiently reduced to prevent the peripheral portions of these concave surfaces from interfering with each other. As a result, the thickness of the zoom lens in the retracted state cannot be reduced. For this reason, it is preferable to avoid such a configuration.

[0039] It is also preferable that the zoom lens of each embodiment satisfy the condition of the following formula (3): Here, the sum of the thicknesses on the optical axis of all lens groups constituting the zoom lens is denoted by Dsum, and the focal lengths at the wide-angle end and telephoto end when the zoom lens is focused on an object at infinity (hereinafter referred to as the infinity focused state) are denoted by fw and ft, respectively.

[0040] 0.05≦Dsum / √(fw·ft)≦0.80 (3) The condition in equation (3) indicates an appropriate range for the total thickness Dsum of the lens group normalized by the focal lengths fw and ft of the zoom lens in order to keep the thickness of the zoom lens in the retracted state small. If the total thickness of the lens group becomes too large, such that Dsum / √(fw·ft) exceeds the upper limit of equation (3), the thickness of the zoom lens in the retracted state will be large, which is undesirable. If the total thickness of the lens group becomes too small, such that Dsum / √(fw·ft) falls below the lower limit of equation (3), the focal length of the zoom lens will become too large, increasing the overall length of the zoom lens and making it difficult to retract the zoom lens into the imaging device, which is also undesirable.

[0041] It is more preferable to set the numerical range of the formula (3) as follows:

[0042] 0.08≦Dsum / √(fw·ft)≦0.70 (3a) Furthermore, it is more preferable to set the numerical range of the formula (3) as follows:

[0043] 0.10≦Dsum / √(fw·ft)≦0.60 (3b) It is also preferable that the zoom lens of each embodiment satisfies the condition of the following formula (4): Here, the half angle of view of the zoom lens when focused at infinity and at the telephoto end is denoted as ωT.

[0044] 0.1≦Dsum / (ft·tanωT)≦2.0 (4) The condition in equation (4) indicates the appropriate range for the total thickness Dsum of the lens units normalized by the focal length ft at the telephoto end of the entire zoom lens system and the half angle of view ωT in order to reduce the thickness of the zoom lens in the retracted state. If the total thickness of the lens units increases so that Dsum / (ft tan ωT) exceeds the upper limit of equation (4), the thickness of the zoom lens in the retracted state will be too large, which is undesirable. On the other hand, if the total thickness of the lens units decreases so that Dsum / (ft tan ωT) falls below the lower limit of equation (4), the diameter of the image circle will be too large for the zoom lens. This can result in problems such as oblique incidence on the image sensor of an imaging device, or the increased size of the zoom lens makes it difficult to fit into the imaging device, which is undesirable.

[0045] It is more preferable to set the numerical range of the formula (4) as follows:

[0046] 0.15≦Dsum / (ft·tanωT)≦1.80 (4a) Furthermore, it is more preferable to set the numerical range of the formula (4) as follows:

[0047] 0.18≦Dsum / (ft·tanωT)≦1.50 (4b) It is also preferable that at least one pair of adjacent lens groups in the zoom lens of each embodiment satisfy the condition of the following formula (5). Here, the order of the lens groups when counted from the object side is i, the radius of curvature of the lens surface closest to the image in the i-th lens group is Ri2, and the radius of curvature of the lens surface closest to the object in the (i+1)-th lens group is R(i+1)1. Note that if the lens surface is aspherical, the radius of curvature is the radius of curvature of the reference spherical surface of that lens surface.

[0048] |(R(i+1)1-Ri2) / (R(i+1)1+Ri2)|≦2.0 (5) The condition of equation (5) indicates the appropriate range for the shape factor of the air lens between the ith lens group and the (i+1)th lens group. If the air lens has a biconvex shape (i.e., both lens surfaces of the air lens are concave), it is difficult to narrow the distance between the ith lens group and the (i+1)th lens group, even if the thicknesses of these lens groups are reduced, in order to avoid interference between the lenses on either side of the air lens. In contrast, if the air lens has a meniscus shape, the concave surface of one of the lenses on either side can be inserted into the convex surface of the other, which makes it possible to narrow the distance between the ith lens group and the (i+1)th lens group when the zoom lens is retracted.

[0049] If the shape factor of the air lens exceeds the upper limit of formula (5), the air lens will have a biconvex shape, and as mentioned above, even if the thicknesses of the ith lens group and the (i+1)th lens group are reduced, the distance between these lens groups cannot be narrowed, which is undesirable. Also, in terms of aberration correction, if the air lens has a biconvex (or biconcave) shape, the refractive power on both sides of the air lens will be large, which will increase the aberrations that occur on those sides and increase sensitivity in manufacturing, which is undesirable.

[0050] It is more preferable to set the numerical range of the formula (5) as follows:

[0051] |(R(i+1)1-Ri2) / (R(i+1)1+Ri2)|≦1.5 (5a) Furthermore, it is more preferable to set the numerical range of the formula (5) as follows:

[0052] |(R(i+1)1-Ri2) / (R(i+1)1+Ri2)|≦1.2 (5b) The zoom lenses of Examples 1, 4, and 5 are negative-lead type zoom lenses with a refractive power arrangement that has, in order from the object side to the image side, a first lens group with negative refractive power and a second lens group with positive refractive power. While this configuration makes it difficult to increase the zoom magnification, it is advantageous for shortening the overall length (downsizing) and achieving a wider angle of view. In such negative-lead zoom lenses, it is preferable to satisfy the following condition (6): Here, the focal lengths of the first lens group and the second lens group are defined as f1 and f2, respectively.

[0053] -2.1≦f1 / f2≦-1.0 (6) The condition of formula (6) indicates an appropriate refractive power arrangement for miniaturizing a zoom lens. When f1 / f2 exceeds the upper limit of formula (6), the refractive power of the first and second lens groups is strong, and the amount of movement of the second lens group is increased. Such strong refractive power of the first and second lens groups is undesirable because it makes it difficult to correct geometric aberrations and requires the refractive power of the diffractive surface to be strong. Furthermore, increasing the amount of movement of the second lens group is undesirable because it tends to increase the F-number (become darker) at the telephoto end. When f1 / f2 falls below the lower limit of formula (6), the overall length at the wide-angle end increases, resulting in a refractive power arrangement that tends to increase the diameter of the first lens group. As a result, the thickness of the first lens group increases, making it difficult to shorten the length of the zoom lens in the retracted state, which is undesirable.

[0054] It is more preferable to set the numerical range of the formula (6) as follows:

[0055] -2.0≦f1 / f2≦-1.1 (6a) Furthermore, it is more preferable to set the numerical range of the formula (6) as follows:

[0056] -1.95≦f1 / f2≦-1.20 (6b) The zoom lenses of Examples 2 and 3 are positive-lead zoom lenses with a refractive power arrangement that has, from the object side to the image side, a first lens group with positive refractive power and a second lens group with negative refractive power. This arrangement is advantageous for achieving a high zoom ratio of over 8x, and also makes it easy to shorten the overall length at the wide-angle end. In such positive-lead zoom lenses, it is preferable to satisfy the condition of the following equation (7):

[0057] -0.80≦f2 / ft≦-0.05 (7) The condition of equation (7) indicates the appropriate range of the focal length f2 of the second lens group relative to the focal length ft at the telephoto end of the entire zoom lens system. If the refractive power of the second lens group becomes too strong, such that f2 / ft exceeds the upper limit of equation (7), the zoom effect caused by its movement will be great, but the Petzval sum will become too negative, making it difficult to correct field curvature throughout the entire zoom range, which is undesirable. If the refractive power of the second lens group becomes too weak, such that f2 / ft falls below the lower limit of equation (7), either the required zoom ratio cannot be obtained or the overall length of the zoom lens at the telephoto end will increase, making it difficult to reduce the thickness of the zoom lens when retracted, which is also undesirable.

[0058] It is more preferable to set the numerical range of the formula (7) as follows:

[0059] -0.70≦f2 / ft≦-0.10 (7a) Furthermore, it is more preferable to set the numerical range of the formula (7) as follows:

[0060] -0.60≦f2 / ft≦-0.15 (7b) Below, Examples 1 to 5 will be specifically described. After Example 5, Numerical Examples 1 to 5 corresponding to Examples 1 to 5, respectively, are shown. [Example]

[0061] The zoom lens of Example 1 (Numerical Example 1) shown in FIG. 1 has a focal length of 9.06 to 17.72 mm, an F-number of 4.12 to 6.27, and a half angle of view of 35.52 to 24.01°. The zoom lens of this example is composed of, arranged in order from the object side to the image side, a first lens unit B1 with negative refractive power, a second lens unit B2 with positive refractive power, an aperture stop SP, and a third lens unit B3 with negative refractive power. During zooming, all of the lens units B1 to B3 move, changing the spacing between adjacent lens units. A glass block GB, such as a glass plate or UV / IR cut filter, that protects the image sensor is disposed between the third lens unit B3 and the image plane IP.

[0062] When zooming from the wide-angle end to the telephoto end, the first lens unit B1 moves along a locus convex toward the image so that it is positioned closer to the image at the telephoto end than at the wide-angle end. The second and third lens units B2 and B3 move toward the object. This movement of the first to third lens units B1 to B3 weakens the refractive power of the first and second lens units B1 and B2, making it easier to correct aberrations. Furthermore, when zooming from the wide-angle end to the telephoto end, the distance between the first lens unit B1 and the second lens unit B2 narrows, while the distance between the second lens unit B2 and the third lens unit B3 widens. By widening the distance between the second lens unit B2 and the third lens unit B3 at the intermediate zoom position, upper line flare of off-axial rays can be cut, allowing for good aberration correction.

[0063] The first lens group B1 is composed of one negative lens element and has, on its object side, a dispersion-controlled diffractive surface MOE 11. The diffractive surface MOE 11 has negative refractive power and corrects distortion and curvature of field while also correcting chromatic aberration that occurs on the image-side refractive surface.

[0064] The second lens group B2 is composed of one positive lens element and has, on its image side, a dispersion-controlled diffractive surface MOE 22. The diffractive surface MOE 22 has positive refractive power and corrects chromatic aberration that occurs on the object-side refractive surface while correcting coma and spherical aberration.

[0065] The third lens group B3 is composed of one negative lens element and has, on its image side, a dispersion-controlled diffractive surface MOE 32. The diffractive surface MOE 32 has negative refractive power and corrects chromatic aberrations that occur on the object-side refractive surface while correcting coma and field curvature.

[0066] Each of the lenses in the first to third lens groups B1 to B3 has a refractive surface with a curvature, and in order to correct chromatic aberration that occurs here, they are made of low-dispersion glass lenses with an Abbe number based on the d-line of 50 or more. The refractive surface on the image side of the first lens group B1 is concave, and the refractive surface on the object side of the second lens group B2 is convex, so that the distance between the first lens group B1 and the second lens group B2 is short when the zoom lens is retracted.

[0067] In addition, all refractive surfaces with curvature are aspherical, providing excellent correction for geometric aberrations. Furthermore, the use of high-order diffractive surfaces on all diffractive surfaces provides an aspherical effect, achieving both correction of geometric aberrations and correction of chromatic aberrations. All diffractive surfaces are formed on a flat base surface, which reduces the difficulty of manufacturing each lens.

[0068] When focusing from infinity to a close distance, the third lens group B3 is moved toward the image side. By configuring the third lens group B3 with a single lens, the weight of the third lens group B3 is reduced and the focus drive mechanism is simplified. For image stabilization, the second lens group B2 is moved (shifted) in a direction perpendicular to the optical axis. Note that other lens groups may also be moved for focusing and image stabilization.

[0069] By positioning the aperture stop SP between the second lens unit B2 and the third lens unit B3, it is possible to move the second lens unit B2, which has a large zoom effect, closer to the first lens unit B1 during zooming, thereby achieving both a high zoom ratio and high performance. [Example]

[0070] The zoom lens of Example 2 (Numerical Example 2) shown in FIG. 3 has a focal length of 4.30 to 41.75 mm, an F-number of 3.61 to 6.82, and a half angle of view of 37.44 to 5.30°. The zoom lens of this example is composed of, arranged in order from the object side to the image side, a first lens unit B1 with positive refractive power, a second lens unit B2 with negative refractive power, a lens unit B3 with positive refractive power including an aperture stop SP, and a fourth lens unit B4 with positive refractive power. During zooming, all of the lens units B1 to B4 move, changing the spacing between adjacent lens units. Similar to Example 1, a glass block GB is disposed between the fourth lens unit B4 and the image plane IP.

[0071] During zooming from the wide-angle end to the telephoto end, the first lens unit B1 moves to be positioned closer to the object than at the wide-angle end at the telephoto end. The second lens unit B2 moves once toward the image side so that it is positioned closer to the object than at the wide-angle end at the telephoto end, then moves toward the object side, and then moves toward the image side. The third lens unit B3 moves toward the object side. The fourth lens unit B4 moves once toward the object side so that it is positioned closer to the object than at the wide-angle end at the telephoto end, then moves toward the image side, and then moves toward the object side.

[0072] By moving the first through fourth lens groups B1 through B4 in this manner, the refractive power of each lens group can be weakened, making it easier to correct aberrations and increasing the zoom ratio. When zooming from the wide-angle end to the telephoto end, the distance between the first lens group B1 and the second lens group B2 increases, the distance between the second lens group B2 and the third lens group B3 decreases, and the distance between the third lens group B3 and the fourth lens group B4 increases. By moving the fourth lens group B4 in the above-described manner at the intermediate zoom position, the distance between the third lens group B3 and the fourth lens group B4 remains small, eliminating the upper line flare of off-axial rays and enabling good aberration correction.

[0073] The first lens group B1 is composed of a single positive lens element and has a dispersion-controlled diffractive surface MOE 12 on its image side. The diffractive surface MOE 12 has positive refractive power and effectively corrects chromatic aberration that occurs on the object-side refractive surface while correcting distortion and field curvature at the wide-angle end and spherical aberration at the telephoto end. By locating the diffractive surface MOE 12 on the image side, humans cannot touch the diffractive surface MOE 12 from the outside, eliminating the need for a protective window or the like.

[0074] The second lens group B2 is composed of one negative lens element and has a dispersion-controlled diffractive surface MOE 21 on its object side. The diffractive surface MOE 21 has negative refractive power and corrects distortion and field curvature at the wide-angle end while also correcting chromatic aberration that occurs on the image-side refractive surface.

[0075] The third lens group B3 is composed of one positive lens and one negative lens, and has a dispersion-controlled diffractive surface MOE32 on the image side of the positive lens. The diffractive surface MOE32 has positive refractive power and corrects coma and spherical aberrations throughout the zoom range while also correcting chromatic aberrations that occur on the object-side refractive surface.

[0076] The fourth lens group B4 is composed of one positive lens element and has, on its image side, a dispersion-controlled diffractive surface MOE 42. The diffractive surface MOE 42 has positive refractive power and corrects distortion and curvature of field while also correcting chromatic aberration that occurs on the object-side refractive surface.

[0077] Each of the lenses in the first through fourth lens groups B1-B4 has a refractive surface with a curvature, and in order to correct chromatic aberration that occurs here, it is composed of a low-dispersion glass lens with an Abbe number of 40 or more based on the d-line. Specifically, the second lens group B2, which contributes to compactness, and the fourth lens group B4, which has a low effect in correcting chromatic aberration, have a high refractive index at the expense of their Abbe numbers. By making the image-side refractive surface of the second lens group B2 concave and the object-side refractive surface of the third lens group B3 convex, it is possible to shorten the distance between the first lens group B1 and the second lens group B2 when the zoom lens is retracted.

[0078] Furthermore, it is preferable to make the refractive surface of the third lens unit B3, which has a large effect in correcting spherical aberration over the entire zoom range, aspherical, so that geometric aberrations can be corrected well.

[0079] In addition, the use of high-order diffractive surfaces on all diffractive surfaces creates an aspherical effect, correcting both geometric and chromatic aberrations. Furthermore, all diffractive surfaces are formed on a flat base surface, which reduces the difficulty of manufacturing each lens.

[0080] When focusing from infinity to close range, the fourth lens group B4 is moved toward the object. By configuring the fourth lens group B4 with a single lens, the weight of the fourth lens group B43 is reduced and the focus drive mechanism is simplified. For image stabilization, the third lens group B3 is shifted in a direction perpendicular to the optical axis. Note that other lens groups may also be moved for focusing and image stabilization.

[0081] By locating the aperture diaphragm SP within the third lens unit B3, it is possible to position the third lens unit B3, which has a large zoom effect, closer to the second lens unit B2, achieving both a high zoom ratio and high performance. Furthermore, a flare-cutting diaphragm is located on the image side of the third lens unit B3, which cuts off-axis upper flare throughout the entire zoom range, reducing aberrations. [Example]

[0082] The zoom lens of Example 3 (Numerical Example 3) shown in Figure 5 has a focal length of 9.19 to 17.69 mm, an F-number of 4.12 to 7.93, and a half angle of view of 34.50 to 24.04°. The zoom lens of this example is composed of, arranged in order from the object side to the image side, a first lens unit B1 including an aperture stop SP with positive refractive power, and a second lens unit B2 with positive refractive power. During zooming, all of the lens units B1 and B2 move, changing the spacing between adjacent lens units. As in Example 1, a glass block GB is arranged between the second lens unit B2 and the image plane IP.

[0083] When zooming from the wide-angle end to the telephoto end, the first lens unit B1 and the second lens unit B2 move toward the object so that the distance between them narrows. This movement of the first and second lens units B1 and B2 strengthens the refractive power of each lens unit and shortens the overall length of the zoom lens at the wide-angle end.

[0084] The first lens group B1 is composed of two lenses: one negative lens and one positive lens. The image side of the negative lens has a dispersion-controlled diffractive surface MOE12. The diffractive surface MOE12 has positive refractive power and corrects spherical aberration, coma, and field curvature while also correcting chromatic aberrations generated by other refractive surfaces. By locating the diffractive surface MOE12 on the image side, it is inaccessible to humans from the outside, eliminating the need for a protective window or similar.

[0085] The second lens group B2 is composed of one negative lens element and has, on its image side, a dispersion-controlled diffractive surface MOE 22. The diffractive surface MOE 22 has negative refractive power and corrects chromatic aberrations that occur on the object-side refractive surface while correcting field curvature and distortion.

[0086] Each of the lenses in the first and second lens groups B1 and B2 has a refractive surface with curvature, and in order to correct chromatic aberration that occurs on the refractive surface, the lenses are made of low-dispersion glass lenses with an Abbe number of 40 or more based on the d-line.

[0087] By making the image-side surface of the first lens group B1 a convex surface and the object-side surface of the second lens group B2 a concave surface, the distance between the first lens group B1 and the second lens group B2 can be shortened in the retracted state of the zoom lens.

[0088] All refractive surfaces with a curvature in the first lens group B1, except for the surface closest to the object, are aspherical, providing excellent correction for geometric aberrations. Furthermore, the use of high-order diffractive surfaces in all diffractive surfaces provides an aspherical effect, achieving both correction of geometric aberrations and correction of chromatic aberrations. Furthermore, all diffractive surfaces are formed on a flat base surface, which reduces the difficulty of manufacturing each lens.

[0089] When focusing from infinity to a close distance, the first lens unit B1 is moved toward the object side, that is, the first lens unit B1, which has a small lens diameter and is lightweight, is moved.

[0090] By disposing the aperture stop SP within the first lens unit B1, the diameter of the first lens unit B1 is reduced and oblique incidence is alleviated. [Example]

[0091] The zoom lens of Example 4 (Numerical Example 4) shown in Figure 7 has a focal length of 9.06 to 17.75 mm, an F-number of 4.12 to 5.78, and a half angle of view of 35.52 to 23.97°. The zoom lens of this example is composed of, arranged in order from the object side to the image side, a first lens unit B1 with negative refractive power, a second lens unit B2 with positive refractive power, an aperture stop SP, and a third lens unit B3 with negative refractive power. None of the first to third lens units B1 to B3 have curvature, but because they have a refractive effect due to their diffractive surfaces, they are treated as lens units in this example.

[0092] During zooming, all lens groups B1 to B3 move, changing the spacing between adjacent lens groups. When zooming from the wide-angle end to the telephoto end, the first lens group B1 moves along a convex path toward the image side, returning to the same position at the telephoto end as at the wide-angle end. The second and third lens groups B2 and B3 move toward the object side. By moving the first, second, and third lens groups B1 to B3 in this manner, the overall length of the zoom lens can be minimized while weakening the refractive power of the first and second lens groups B1 and B2. Furthermore, during zooming from the wide-angle end to the telephoto end, the spacing between the first lens group B1 and the second lens group B2 narrows, while the spacing between the second lens group B2 and the third lens group B3 widens. By widening the spacing between the second lens group B2 and the third lens group B3 at the intermediate zoom position, the upper line flare of off-axial rays can be reduced, effectively correcting aberrations.

[0093] The first lens group B1 is composed of a single negative lens, with dispersion-controlled diffractive surfaces MOE11 and MOE12 on its object and image sides, respectively. The object-side diffractive surface MOE11 has negative refractive power, while the image-side diffractive surface MOE12 has positive refractive power. This achieves a balance between correction of distortion and field curvature and correction of chromatic aberration.

[0094] The second lens group B2 is composed of one positive lens element and has a dispersion-controlled diffractive surface MOE 21 on its object side. The diffractive surface MOE 21 has positive refractive power and corrects chromatic aberration that occurs on the object-side surface while correcting coma and spherical aberration.

[0095] The third lens group B3 is composed of one negative lens element and has, on its image side, a dispersion-controlled diffractive surface MOE31. The diffractive surface MOE31 has negative refractive power and corrects chromatic aberrations that occur on the object-side surface while correcting coma and field curvature.

[0096] Each of the lenses in the first to third lens groups B1 to B3 has flat surfaces on both sides, and in order to correct chromatic aberration that occurs at each flat surface, they are made of low-dispersion glass lenses with an Abbe number, based on the d-line, of 60 or more. By making both the image-side surface of the first lens group B1 and the object-side surface of the second lens group B2 flat, the distance between the first lens group B1 and the second lens group B2 can be shortened when the zoom lens is retracted.

[0097] In addition, the use of high-order diffractive surfaces on all diffractive surfaces creates an aspherical effect, correcting both geometric and chromatic aberrations. Furthermore, all diffractive surfaces are formed on a flat base surface, which reduces the difficulty of manufacturing each lens.

[0098] When focusing from infinity to a close distance, the third lens group B3 is moved toward the image side. By configuring the third lens group B3 with a single lens, the weight of the third lens group B3 is reduced and the focus drive mechanism is simplified. For image stabilization, the second lens group B2 is shifted in a direction perpendicular to the optical axis. Note that other lens groups may also be moved for focusing and image stabilization.

[0099] By locating the aperture stop SP between the second lens group B2 and the third lens group B3, it is possible to position the second lens group B2, which has a large zoom effect, closer to the first lens group B1, thereby achieving both a high zoom ratio and high performance. [Example]

[0100] The zoom lens of Example 5 (Numerical Example 4) shown in Figure 9 has a focal length of 9.06 to 17.75 mm, an F-number of 4.12 to 6.21, and a half angle of view of 35.52 to 23.97°. The zoom lens of this example is composed of, arranged in order from the object side to the image side, a first lens unit B1 with negative refractive power, a second lens unit B2 with positive refractive power, and an aperture stop SP. Neither the first nor the second lens unit B1, B2 has a curvature, but because they have a refractive effect due to their diffractive surfaces, they are treated as lens units in this example.

[0101] During zooming, all lens groups B1 and B2 move, changing the spacing between adjacent lens groups. When zooming from the wide-angle end to the telephoto end, the first lens group B1 and the second lens group B2 move toward the object side to narrow the spacing between them. The first lens group B1 moves along a convex locus toward the image side, making a complete round trip to a position at the telephoto end that is equal to that at the wide-angle end, while the second lens group B2 moves toward the object side. By moving the first and second lens groups B1 and B2 in this way, the refractive power of the first and second lens groups B1 and B2 is weakened while the overall length of the zoom lens is shortened.

[0102] The first lens group B1 is composed of a single negative lens element, with dispersion-controlled diffractive surfaces MOE11 and MOE12 on its object and image sides, respectively. The object-side diffractive surface MOE11 has negative refractive power, while the image-side diffractive surface MOE12 has positive refractive power. This achieves a balance between the correction of distortion and field curvature and the correction of chromatic aberration.

[0103] The second lens group B2 is composed of a single positive lens element, with dispersion-controlled diffractive surfaces MOE21 and MOE22 on its object and image sides, respectively. These diffractive surfaces MOE21 and MOE22 have positive refractive power and correct chromatic aberration while also correcting coma and spherical aberration. Furthermore, by increasing the thickness of the lens, a difference is created between the positions at which light rays pass on the object-side surface and the image-side surface, allowing the aberration correction to be shared.

[0104] Both lenses in the first and second lens groups B1 and B2 have flat surfaces, and in order to correct chromatic aberration that occurs at each flat surface, they are constructed of low-dispersion glass lenses with an Abbe number of 60 or greater, based on the d-line. By making both the image-side surface of the first lens group B1 and the object-side surface of the second lens group B2 flat, the distance between the first lens group B1 and the second lens group B2 can be shortened when the zoom lens is retracted.

[0105] In addition, the use of high-order diffractive surfaces on all diffractive surfaces creates an aspherical effect, correcting both geometric and chromatic aberrations. Furthermore, all diffractive surfaces are formed on a flat base surface, which reduces the difficulty of manufacturing each lens.

[0106] When focusing from infinity to close range, the first lens unit B1 moves toward the object. By configuring the first lens unit B1 with a single lens, the weight of the first lens unit B1 is reduced and the focus drive mechanism is simplified.

[0107] By positioning the aperture stop SP closer to the image side than the second lens unit B2, it is possible to position the second lens unit B2, which has a large zoom effect, closer to the first lens unit B1, achieving both a high zoom ratio and high performance.

[0108] In each embodiment, the optical path difference function of the dispersion-controlled diffractive surface may be realized by a metasurface in which the meta-atoms are arranged so as to calculate the phase delay of the meta-atoms for each wavelength and control the wavelength dispersion characteristics of the surface. The metasurface may be a so-called single-layer metasurface consisting of one layer, or a so-called stacked metasurface consisting of multiple layers. Furthermore, aberrations generated by a zoom lens may be corrected by image processing in the imaging device.

[0109] Numerical Examples 1 to 5 are shown below. In each numerical example, surface number i indicates the order of the surface when counted from the object side. r is the radius of curvature (mm) of the ith surface from the object side, d is the lens thickness or air gap (mm) on the optical axis between the ith and (i+1)th surfaces, and nd is the refractive index at the d-line of the optical material between the ith and (i+1)th surfaces. νd is the Abbe number based on the d-line of the optical material between the ith and (i+1)th surfaces.

[0110] The Abbe number νd based on the d-line is given by the following, where the refractive indices at the d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm) are Nd, NF, and NC, respectively: νd=(Nd-1) / (NF-NC) It is expressed as:

[0111] BF stands for back focal length (mm). Back focal length is the distance on the optical axis from the surface of a zoom lens closest to the image (the final surface) to the paraxial image plane, expressed as an air-equivalent length. "Lens length" is the distance on the optical axis from the surface of a zoom lens closest to the object (the foreground) to the final surface plus the back focal length, and is also called the optical length.

[0112] An "*" next to a surface number indicates that the surface has an aspherical shape. The aspherical shape is expressed by the following formula, where x is the displacement from the vertex of the surface in the optical axis direction, h is the height from the optical axis in a direction perpendicular to the optical axis, the direction of light travel is positive, R is the paraxial radius of curvature, k is the conic constant, and A4, A6, A8, and A10 are aspherical coefficients. "e±M" is x 10 -M means.

[0113] x=(h 2 / R) / [1+{1-(1+k)(h / R) 2} 1 / 2 ] +A4·h 4 +A6·h 6 +A8·h 8 +A10·h 10 Furthermore, the optical path difference function ψ0 of the surface at the design wavelength is expressed by the following equation, where U2, U4, U6, U8, and U10 are coefficients of the optical path difference function of the surface.

[0114] ψ0=U2·h 2 +U4·h 4 +U6·h 6 +U8·h 8 +U10·h 10 (Diffraction) means a surface that has been optically designed according to the optical path difference function of the surface.

[0115] Table 1 shows the numerical values ​​relating to the conditions of the above-mentioned formulas (1) to (7) in Numerical Examples 1 to 5. Each of the Numerical Examples satisfies all of the conditions of formulas (1) to (7).

[0116] 2(a), (b), (c), 4(a), (b), (c), 6(a), (b), (c), 8(a), (b), (c), and 10(a), (b), (c) show longitudinal aberrations (spherical aberration, astigmatism, distortion, and chromatic aberration) of the zoom lenses of Numerical Examples 1 to 5, respectively, when focused at infinity and at (a) the wide-angle end, (b) the intermediate zoom position, and (c) the telephoto end. In the spherical aberration diagrams, Fno indicates the F-number, the solid line indicates spherical aberration at the d-line (wavelength 587.6 nm), and the two-dot chain line indicates spherical aberration at the g-line (wavelength 435.8 nm). In the astigmatism diagrams, the solid line S indicates astigmatism at the sagittal image plane, and the dashed line M indicates astigmatism at the meridional image plane. The distortion diagram shows distortion at the d-line. The chromatic aberration diagram shows lateral chromatic aberration at the g-line. ω is the half angle of view (°). [Numerical Example 1] Surface Data Surface number rd nd νd 1(diffraction) ∞ 0.70 1.58313 59.4 2* 12.744 (variable) 3* 5.061 1.71 1.49710 81.6 4(diffraction) ∞ 2.91 5 (Aperture) ∞ (Variable) 6* -15.686 0.50 1.49710 81.6 7 (diffraction) ∞ (variable) 8 ∞ 0.55 1.51633 64.1 9∞0.86 10 ∞ 0.50 1.51633 64.1 11 ∞ (variable) Image plane ∞ Aspheric data Surface 1 (diffractive surface) U 2= 1.16733e-02 U 4=-5.60771e-04 U 6= 4.53318e-05 U 8=-1.34827e-06 U10= 1.37813e-08 2nd side K =-7.39509e+00 A 4= 1.93534e-03 A 6=-1.02565e-04 A 8= 2.99088e-06 A10 = -1.55725e-08 Page 3 K = 0.00000e+00 A 4=-1.15177e-04 A 6= 7.58775e-05 A 8=-1.24957e-05 A10 = 1.88105e-06 Side 4 (folded side) U 2=-1.99346e-02 U 4= 1.17636e-04 U 6= 1.19021e-04 U 8=-2.14007e-05 U10 = 2.70008e-06 Page 6 K = 0.00000e+00 A 4=-1.40481e-03 A 6=-7.44242e-04 A 8= 1.46738e-04 A10 = -1.86344e-05 Side 7 (folded side) U 2= 5.70651e-03 U 4= 3.16597e-04 U 6=-2.52105e-04 U 8= 3.92598e-05 U10=-3.15610e-06 Surface optical path difference dispersion Page 1, Page 4, Page 7 P(λ) = 2266.41068·λ10 - 12144.39247·λ9 + 29486.82651·λ8 -42762.08537·λ7 + 41106.88437·λ6 - 27470.79737·λ5 + 13006.44877·λ4 -4356.52716·λ3 + 1009.95630·λ2 - 153.95668·λ + 13.87546 P(λd) = 1.0000 P(λC) = 0.9156 P(λF) = 1.1842 Various データ Zoom ratio 1.95 Wide-angle Mid-range Telephoto Focal length 9.06 14.28 17.72 F-number 4.12 5.33 6.27 Half angle of view (°) 35.52 28.92 24.01 Image height 6.47 7.89 7.89 Lens length 24.08 20.81 21.84 BF(in air) 8.15 9.17 12.13 d 2 8.80 3.22 1.94 d 5 0.95 2.24 1.60 d 7 5.40 6.42 9.37 d11 1.20 1.20 1.20 [Numerical Example 2] Surface Data Surface number rd nd νd 1 22.742 2.14 1.49700 81.5 2 (diffraction) ∞ (variable) 3(diffraction) ∞ 0.50 1.69680 55.5 4 9.825 (variable) 5* 3.718 1.40 1.76802 49.2 6(diffraction) ∞ 0.05 7 (Aperture) ∞ 0.00 8 10.508 0.30 1.64769 33.8 9 2.745 1.44 10 ∞ (variable) 11 20.394 1.40 1.83481 42.7 12 (diffraction) ∞ (variable) 13 ∞ 0.30 1.51633 64.1 14 ∞ 0.52 15 ∞ 0.50 1.51633 64.1 16 ∞ (variable) Image plane ∞ Aspheric data Surface 2 (diffractive surface) U 2=-3.90092e-03 U 4= 2.64576e-06 U 6= 1.00228e-07 U 8=-2.06308e-09 U10= 1.67417e-11 Surface 3 (diffractive surface) U 2= 4.03024e-02 U 4=-7.96691e-05 U 6= 8.85646e-07 U 8=-2.52786e-08 U10= 4.17985e-10 5th page K =-7.12564e-01 A 4= 4.72706e-04 A 6= 1.73220e-05 A 8=-2.35441e-05 Surface 6 (diffractive surface) U 2=-1.27570e-02 U 4= 6.99982e-04 U 6=-1.39118e-04 U 8=-9.03648e-06 Surface 12 (diffractive surface) U 2=-4.67880e-03 U 4=-4.66633e-05 U 6=-1.21998e-06 U 8= 1.91916e-08 Optical path difference dispersion of the surface 2nd side, 6th side, 12th side P(λ) = 2266.41068·λ10 - 12144.39247·λ9 + 29486.82651·λ8 - 42762.08537·λ7 + 41106.88437·λ6 - 27470.79737·λ5 + 13006.44877·λ4 - 4356.52716·λ3 + 1009.95630·λ2 - 153.95668·λ + 13.87546 P(λd) = 1.0000 P(λC) = 0.9156 P(λF) = 1.1842 3rd page P(λ) = 606.61668·λ10 - 3567.44539·λ9 + 9538.09656·λ8 - 15288.88750·λ7 + 16315.44261·λ6 - 12165.39383·λ5 + 6465.34198·λ4 - 2448.35587·λ3 + 647.33574·λ2 - 113.77083·λ + 11.97801 P(λd) = 1.0000 P(λC) = 0.9047 P(λF) = 1.1965 Various data Zoom ratio 9.70 Focal length 4.30 13.44 41.75 F-number 3.61 5.84 6.82 Half angle of view (°) 37.44 16.08 5.30 Image height 3.29 3.88 3.88 Lens length 35.68 43.08 55.50 Optical total length 35.94 43.34 55.76 BF(in air) 5.79 7.86 9.53 d 2 0.30 7.20 18.43 d 4 17.86 8.42 3.50 d10 4.75 12.64 17.07 d12 4.21 6.28 7.95 d16 0.53 0.53 0.53 [Numerical Example 3] Surface Data Surface number rd nd νd 1 -6.229 0.50 1.49710 81.6 2(diffraction) ∞ 0.94 3 (Aperture) ∞ 0.50 4* 19.242 2.58 1.49710 81.6 5* -3.518 (variable) 6* -8.433 0.50 1.80139 45.5 7 (diffraction) ∞ (variable) 8 ∞ 0.55 1.51633 64.1 9∞0.86 10 ∞ 0.50 1.51633 64.1 11 ∞ (variable) Image plane ∞ Aspheric data Surface 2 (diffractive surface) U 2=-2.49030e-02 U 4= 4.32303e-04 U 6=-4.02618e-04 U 8= 2.18493e-04 U10=-3.89805e-05 Side 4 K = 0.00000e+00 A 4=-4.13532e-03 A 6=-7.65827e-04 5th page K = 0.00000e+00 A 4= 1.12893e-03 A 6=-5.74274e-04 A 8= 8.73569e-05 A10=-1.10028e-05 Side 6 K =-2.33772e+01 A 4=-5.57520e-03 A 6= 5.34799e-04 A 8=-3.92900e-05 A10= 9.59231e-07 Surface 7 (diffractive surface) U 2= 8.54392e-03 U 4=-1.10035e-03 U 6= 1.38481e-04 U 8=-9.99651e-06 U10= 2.30160e-07 Optical path difference dispersion of the surface 2nd side P(λ) = 0.58756 / λ P(λd) = 1.0000 P(λC) = 0.8953 P(λF) = 1.2086 Side 7 P(λ) = 533.20107·λ10 - 3201.64587·λ9 + 8717.86553·λ8 - 14203.42791·λ7 + 15380.55257·λ6 - 11621.31727·λ5 + 6251.15666·λ4 - 2393.52390·λ3 + 639.27445·λ2 - 113.41301·λ + 12.03846 P(λd) = 1.0000 P(λC) = 0.9000 P(λF) = 1.2024 Various data Zoom ratio 1.93 Wide-angle Mid-range Telephoto Focal length 9.19 13.44 17.69 F-number 4.12 6.03 7.93 Half angle of view (°) 34.50 30.42 24.04 Image height 6.31 7.89 7.89 Lens length 12.79 16.42 21.03 BF 3.13 8.80 14.47 d 5 4.65 2.61 1.55 d 7 0.44 6.11 11.78 d11 1.14 1.14 1.14 [Numerical Example 4] Surface Data Surface number rd nd νd 1(diffraction) ∞ 0.50 1.51633 64.1 2 (diffraction) ∞ (variable) 3(diffraction) ∞ 0.50 1.51633 64.1 4∞0.00 5 (Aperture) ∞ (Variable) 6(Diffraction) ∞ 0.50 1.51633 64.1 7 ∞ (variable) Image plane ∞ Aspheric data Surface 1 (diffractive surface) U 2= 9.52759e-02 U 4= 1.92148e-03 U 6= 4.62097e-05 U 8=-1.22395e-05 U10= 4.94686e-07 Surface 2 (diffractive surface) U 2=-5.79118e-02 U 4=-1.48228e-03 U 6=-3.23889e-07 U 8= 7.49816e-06 U10=-3.21850e-07 Surface 3 (diffractive surface) U 2=-5.11424e-02 U 4= 2.30016e-05 U 6=-9.14201e-05 U 8= 2.82694e-05 U10=-3.43660e-06 Surface 6 (diffractive surface) U 2=-8.37514e-03 U 4= 2.08999e-04 U 6=-3.05321e-06 U 8= 2.51364e-07 U10=-6.82706e-09 Optical path difference dispersion of the surface 1st side, 2nd side, 3rd side, 6th side P(λ) = 0.58756 / λ P(λd) = 1.0000 P(λC) = 0.8953 P(λF) = 1.2086 Various data Zoom ratio 1.96 Wide-angle Mid-range Telephoto Focal length 9.06 12.98 17.75 F-number 4.12 4.92 5.78 Half angle of view (°) 35.52 31.30 23.97 Image height 6.47 7.89 7.89 Lens length 22.00 21.43 22.00 BF 11.49 11.33 13.45 d 2 6.85 3.01 0.30 d 5 2.17 5.60 6.75 d 7 11.49 11.33 13.45 [Numerical Example 5] Surface Data Surface number rd nd νd 1(diffraction) ∞ 1.54 1.51633 64.1 2 (diffraction) ∞ (variable) 3(diffraction) ∞ 5.39 1.51633 64.1 4(diffraction) ∞ 0.00 5 (Aperture) ∞ (Variable) Image plane ∞ Aspheric data Surface 1 (diffractive surface) U 2= 7.12979e-02 U 4= 1.51365e-03 U 6= 5.21235e-05 U 8=-4.85827e-06 U10= 1.47453e-08 Surface 2 (diffractive surface) U 2=-1.83870e-02 U 4=-1.00835e-03 U 6=-1.20402e-05 U 8= 4.64800e-06 U10=-7.44672e-08 Surface 3 (diffractive surface) U 2=-4.96083e-02 U 4=-5.36448e-05 U 6= 1.38943e-06 U 8=-5.63052e-06 U10= 8.02406e-07 Surface 4 (diffractive surface) U 2=-1.73067e-02 U 4= 3.39963e-04 U 6=-1.00376e-04 U 8= 4.34611e-05 U10=-6.13235e-06 Optical path difference dispersion of the surface 1st side, 2nd side, 3rd side, 4th side P(λ) = 0.58756 / λ P(λd) = 1.0000 P(λC) = 0.8953 P(λF) = 1.2086 Various data Zoom ratio 1.96 Wide-angle Mid-range Telephoto Focal length 9.06 13.41 17.75 F-number 4.12 5.29 6.46 Half angle of view (°) 35.52 30.48 23.97 Image height 6.47 7.89 7.89 Lens length 24.59 25.25 27.35 BF 12.81 16.40 19.99 d 2 4.85 1.92 0.43 d 5 12.81 16.40 19.99

[0117] [Table 1]

[0118] [Imaging device] 11 shows a digital still camera as an imaging device that uses the zoom lens of each of the above-described embodiments as an imaging optical system. 20 denotes the camera body, and 21 denotes the imaging optical system configured with any of the zoom lenses of Examples 1 to 5. 22 denotes a solid-state imaging element such as a CCD sensor or CMOS sensor that is built into the camera body 20 and photoelectrically converts the optical image (subject image) formed by the imaging optical system 21, i.e., captures the subject image through the imaging optical system 21. 23 denotes a recording unit that records image data generated by processing the imaging signal from the imaging element 22, and 24 denotes a rear display that displays the image data.

[0119] By using the zoom lens of each embodiment, a small camera with high optical performance can be obtained. In particular, chromatic aberration can be reduced and the angle of incidence on the image sensor 22 can be relaxed. The camera may be a single-lens reflex camera with a quick-turn mirror, or a mirrorless camera without a quick-turn mirror.

[0120] The above embodiment includes the following configurations.

[0121] (Configuration 1) A zoom lens having a plurality of lens groups, in which the spacing between adjacent lens groups changes during zooming, At least one of the plurality of lens groups has a diffractive surface with controlled wavelength dispersion, The Abbe number of the diffractive surface is ν0, the reference wavelength is d-line, and the primary dispersion is F-line and C-line. The optical path difference functions at the wavelengths of d-line, F-line, and C-line are respectively defined as ψ(λ d ), ψ(λ F ), ψ(λ C ), and the optical path difference dispersion of the surface at the wavelengths of the d-line, F-line, and C-line is P(λ d ), P(λ F ), P(λ C )year,

[0122]

number

[0123] When -0.28≦1 / ν0≦0.00 A zoom lens characterized by satisfying the following conditions: (Configuration 2) When the focal length of the lens group having the diffractive surface is fi and the focal length of the diffractive surface is fmi, 0.15≦fi / fmi≦10.00 3. The zoom lens according to configuration 1 or 2, characterized in that the following conditions are satisfied: (Configuration 3) When the sum of the thicknesses of the plurality of lens groups on the optical axis is Dsum, and the focal lengths of the zoom lens at the wide-angle end and the telephoto end when focused on an object at infinity are fw and ft, respectively, 0.05≦Dsum / √(fw·ft)≦0.80 4. The zoom lens according to any one of configurations 1 to 3, wherein the following condition is satisfied: (Configuration 4) When the sum of the thicknesses of the plurality of lens groups on the optical axis is Dsum, the focal length of the zoom lens at the telephoto end in a state where the zoom lens is focused on an object at infinity is ft, and the half angle of view of the zoom lens at the telephoto end in a state where the zoom lens is focused on an object at infinity is ωT, 0.1≦Dsum / (ft tanωT)≦2.0 5. The zoom lens according to any one of configurations 1 to 4, wherein the following condition is satisfied: (Configuration 5) When the radius of curvature of the lens surface closest to the image in the i-th lens group counting from the object side among the plurality of lens groups is Ri2 and the radius of curvature of the lens surface closest to the object side in the (i+1)-th lens group is R(i+1)1, |(R(i+1)1-Ri2) / (R(i+1)1+Ri2)|≦2.0 6. The zoom lens according to any one of configurations 1 to 5, wherein the following condition is satisfied: (Configuration 6) the plurality of lens groups include a first lens group having a negative refractive power and a second lens group having a positive refractive power, which are arranged in order from the object side to the image side; When the focal length of the first lens group is f1 and the focal length of the second lens group is f2, -2.1≦f1 / f2≦-1.0 7. The zoom lens according to any one of configurations 1 to 6, wherein the following condition is satisfied: (Configuration 7) the plurality of lens groups include a first lens group having a positive refractive power and a second lens group having a negative refractive power, which are arranged in order from the object side to the image side; When the focal length of the second lens group is f2 and the focal length of the zoom lens at the telephoto end in a state where the zoom lens is focused on an object at infinity is ft, -0.80≦f2 / ft≦-0.05 7. The zoom lens according to any one of configurations 1 to 6, wherein the following condition is satisfied: (Configuration 8) 9. A zoom lens according to any one of configurations 1 to 8, characterized in that it has at least one refractive surface. (Configuration 9) 10. The zoom lens according to any one of configurations 1 to 9, wherein the lens group having the diffractive surface is composed of two or less lenses. (Configuration 10) 11. The zoom lens according to any one of configurations 1 to 10, wherein each of the plurality of lens groups is composed of two or less lenses. (Configuration 11) The zoom lens according to configuration 1, wherein the diffractive surface is formed on a flat surface serving as a base surface. (Configuration 12) the plurality of lens groups are configured to include, in order from the object side to the image side, a first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group having negative refractive power; A zoom lens according to any one of configurations 1 to 6 and 8 to 11, wherein the first, second, and third lens groups move during zooming. (Configuration 13) the plurality of lens groups are configured to include, in order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power; A zoom lens according to any one of configurations 1 to 5 and 7 to 11, wherein the first, second, third and fourth lens groups move during zooming. (Configuration 14) the plurality of lens groups are configured by a first lens group having a positive refractive power and a second lens group having a positive refractive power, which are arranged in order from the object side to the image side, A zoom lens according to any one of configurations 1 to 6 and 9 to 12, wherein the first and second lens groups move during zooming. (Configuration 15) the plurality of lens groups are configured by a first lens group having negative refractive power and a second lens group having positive refractive power, which are arranged in order from the object side to the image side, A zoom lens according to any one of configurations 1 to 6 and 8 to 11, wherein the first and second lens groups move during zooming. (Configuration 16) A zoom lens having a plurality of lens groups, in which the spacing between adjacent lens groups changes during zooming, At least one of the plurality of lens groups has a diffractive surface with controlled wavelength dispersion, At least one of the plurality of lens groups has a refractive surface, The Abbe number of the diffractive surface is ν0, the reference wavelength is d-line, and the primary dispersion is F-line and C-line. The optical path difference functions at the wavelengths of d-line, F-line, and C-line are respectively defined as ψ(λ d ), ψ(λ F ), ψ(λ C ), and the optical path difference dispersion of the surface at the wavelengths of the d-line, F-line, and C-line is P(λ d ), P(λ F ), P(λ C )year,

[0124]

number

[0125] When 1 / ν0≦0.00 A zoom lens characterized by satisfying the following conditions: (Configuration 17) The zoom lens according to any one of configurations 1 to 16, and an image sensor for capturing an image of a subject through the zoom lens.

[0126] The embodiments described above are merely representative examples, and various modifications and alterations are possible to each embodiment when implementing the present invention. [Explanation of symbols]

[0127] Bi i-th lens group MOE dispersion-controlled diffractive surface SP aperture stop IP image plane

Claims

1. A zoom lens having a plurality of lens groups, in which the spacing between adjacent lens groups changes during zooming, At least one of the plurality of lens groups has a diffractive surface with controlled wavelength dispersion, The Abbe number of the diffractive surface is ν ０ , the reference wavelength is the d-line, the primary dispersion is the F-line and the C-line, and the optical path difference functions at the wavelengths of the d-line, F-line and C-line are respectively ψ(λ ｄ ), ψ(λ Ｆ ), ψ(λ Ｃ ), the optical path difference dispersion of the surface at the wavelengths of the d-line, F-line, and C-line is P(λ ｄ ), P(λ Ｆ ), P(λ Ｃ )year, [Equation 1] When -0.28≦1 / n ０ ≦0.00 A zoom lens characterized by satisfying the following conditions:

2. When the focal length of the lens group having the diffractive surface is fi and the focal length of the diffractive surface is fmi, 0.15≦fi / fmi≦10.00 2. The zoom lens according to claim 1, wherein the following condition is satisfied:

3. When the sum of the thicknesses of the plurality of lens groups on the optical axis is Dsum, and the focal lengths of the zoom lens at the wide-angle end and the telephoto end in a state where the zoom lens is focused on an object at infinity are fw and ft, respectively, 0.05≦Dsum / √(fw・ft)≦0.80 2. The zoom lens according to claim 1, wherein the following condition is satisfied:

4. When the sum of the thicknesses of the plurality of lens groups on the optical axis is Dsum, the focal length of the zoom lens at the telephoto end in a state where the zoom lens is focused on an object at infinity is ft, and the half angle of view of the zoom lens at the telephoto end in a state where the zoom lens is focused on an object at infinity is ωT, 0.1≦Dsum / (ft・tanωT)≦2.0 2. The zoom lens according to claim 1, wherein the following condition is satisfied:

5. When the radius of curvature of the lens surface closest to the image in the i-th lens group counting from the object side among the plurality of lens groups is Ri2 and the radius of curvature of the lens surface closest to the object side in the (i+1)-th lens group is R(i+1)1, |(R(i+1)1-Ri2) / (R(i+1)1+Ri2)|≦2.0 2. The zoom lens according to claim 1, wherein the following condition is satisfied:

6. the plurality of lens groups include a first lens group having a negative refractive power and a second lens group having a positive refractive power, which are arranged in order from the object side to the image side; When the focal length of the first lens group is f1 and the focal length of the second lens group is f2, -2.1≦f1 / f2≦-1.0 2. The zoom lens according to claim 1, wherein the following condition is satisfied:

7. the plurality of lens groups include a first lens group having a positive refractive power and a second lens group having a negative refractive power, which are arranged in order from the object side to the image side; When the focal length of the second lens group is f2 and the focal length of the zoom lens at the telephoto end in a state where the zoom lens is focused on an object at infinity is ft, -0.80≦f2 / ft≦-0.05 2. The zoom lens according to claim 1, wherein the following condition is satisfied:

8. 2. The zoom lens of claim 1, comprising at least one refractive surface.

9. 2. The zoom lens according to claim 1, wherein the lens group having the diffractive surface is composed of two or less lenses.

10. 2. The zoom lens according to claim 1, wherein each of the plurality of lens groups is composed of two or less lenses.

11. 2. The zoom lens according to claim 1, wherein the diffractive surface is formed on a flat surface serving as a base surface.

12. the plurality of lens groups are configured to include, in order from the object side to the image side, a first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group having negative refractive power; 2. The zoom lens according to claim 1, wherein the first, second and third lens groups move during zooming.

13. the plurality of lens groups are configured to include, in order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power; 2. The zoom lens according to claim 1, wherein the first, second, third and fourth lens groups move during zooming.

14. the plurality of lens groups are configured by a first lens group having a positive refractive power and a second lens group having a positive refractive power, which are arranged in order from the object side to the image side, 2. The zoom lens according to claim 1, wherein the first and second lens groups move during zooming.

15. the plurality of lens groups are configured by a first lens group having a negative refractive power and a second lens group having a positive refractive power, which are arranged in order from the object side to the image side, 2. The zoom lens according to claim 1, wherein the first and second lens groups move during zooming.

16. A zoom lens having a plurality of lens groups, in which the spacing between adjacent lens groups changes during zooming, At least one of the plurality of lens groups has a diffractive surface with controlled wavelength dispersion, At least one of the plurality of lens groups has a refractive surface, The Abbe number of the diffractive surface is ν ０ , the reference wavelength is the d-line, the primary dispersion is the F-line and the C-line, and the optical path difference functions at the wavelengths of the d-line, F-line and C-line are respectively ψ(λ ｄ ), ψ(λ Ｆ ), ψ(λ Ｃ ), the optical path difference dispersion of the surface at the wavelengths of the d-line, F-line, and C-line is P(λ ｄ ), P(λ Ｆ ), P(λ Ｃ )year, [Equation 2] When 1 / n ０ ≦0.00 A zoom lens characterized by satisfying the following conditions:

17. a zoom lens according to any one of claims 1 to 16; and an image sensor for capturing an image of a subject through the zoom lens.

Images