JP5845887B2 - Zoom lens and imaging device - Google Patents

Description

The present invention relates's Murenzu and imaging device.

  In recent years, various zoom types have been proposed as the performance of zoom lenses increases. Particularly, in a zoom lens for electronic image equipment such as a video camera and a digital still camera, a four-group configuration type zoom lens having positive, negative, positive, and positive refractive power arrangements in order from the object side has been conventionally used. (For example, see Patent Document 1).

JP 2000-147379 A

  However, with conventional zoom lenses, it has been extremely difficult to achieve both excellent imaging performance, high zoom ratio (high zoom ratio), miniaturization, and the like.

According to an aspect illustrating the present invention, the zoom lens includes 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 along the optical axis. A zoom lens having a third lens group having a positive refractive power and a final lens group having a positive refractive power arranged closest to the image side, when zooming from the wide-angle end state to the telephoto end state The first lens group moves toward the object side, the distance between the first lens group and the second lens group changes, the distance between the second lens group and the third lens group changes, Each of the first lens group and the final lens group has a diffractive optical surface, and the diffractive optical surface is formed at an interface having a refractive index difference of 0.45 or less, and a zoom ratio is 9 or more. it satisfies the equation.
0.5 <(C1 + CL) / fw <10.0
0.1 <fL / f1 ≦ 0.45233
However,
C1: effective diameter of the diffractive optical surface in the first lens group,
CL: effective diameter of the diffractive optical surface in the final lens group,
fw: focal length in the wide-angle end state of the zoom lens,
f1: the focal length of the first lens group,
fL: focal length of the final lens group.

According to an aspect of the present invention, the imaging apparatus is an imaging apparatus that includes a zoom lens that forms an image of an object on a predetermined surface, and the zoom lens is the zoom lens described above. It shall be the.

It is a figure which shows the lens structure and zoom track | orbit in the wide-angle end state of the zoom lens which concerns on 1st Example. It is a figure which shows the lens structure in the telephoto end state of the zoom lens which concerns on 1st Example. FIG. 6 is a longitudinal aberration diagram in the wide-angle end state of the zoom lens according to Example 1; FIG. 3 is a longitudinal aberration diagram in the telephoto end state of the zoom lens according to Example 1; FIG. 6 is a lateral aberration diagram in the wide-angle end state of the zoom lens according to Example 1; FIG. 6 is a lateral aberration diagram in the telephoto end state of the zoom lens according to Example 1; It is a figure which shows the lens structure and zoom track | orbit in the wide-angle end state of the zoom lens which concerns on 2nd Example. It is a figure which shows the lens structure in the telephoto end state of the zoom lens which concerns on 2nd Example. It is a longitudinal aberration diagram in the wide angle end state of the zoom lens according to Example 2. FIG. 6 is a longitudinal aberration diagram in a telephoto end state of a zoom lens according to Example 2; It is a lateral aberration diagram in the wide-angle end state of the zoom lens according to Example 2. FIG. 6 is a lateral aberration diagram in a telephoto end state of a zoom lens according to Example 2; It is sectional drawing of a digital single-lens reflex camera.

  Hereinafter, preferred embodiments of the present application will be described with reference to the drawings. First, as a general theory, the characteristics of a zoom lens having a multi-group configuration will be described. Since at least two lens groups are required to form a zoom lens, the multi-group configuration in the following description refers to a lens configuration having three or more lens groups. First, in a zoom lens having a multi-group configuration, the number of lens groups responsible for zooming increases, so it is possible to increase the magnification. In addition, when the number of lens groups is increased, the burden of the amount of aberration generated in each lens group can be easily equalized, so that excellent imaging performance can be achieved. Further, if the rearmost lens group, that is, the lens group closest to the image plane is made movable and moved to the object side during zooming from the wide-angle end to the telephoto end, there is an advantage that it is easy to increase the magnification. Although there has been a problem such as a complicated structure of the lens barrel due to an increase in the number of lens groups that can be moved along the optical axis, this problem is being overcome by recent advances in lens barrel technology.

  In the present embodiment, based on the technical basis and background of the zoom lens having a multi-group configuration as described above, the lens has positive, negative, and positive refractive power arrangements in order from the object side, and is the most positive lens on the image side. The structure which has a group is adopted. That is, in this embodiment, increasing the number of lens groups increases the degree of freedom of aberration correction including the degree of freedom of movement of each lens group. As a result, a high-power zoom lens can be realized, and excellent imaging performance can be obtained even in an intermediate focal length state other than the wide-angle end and the telephoto end. For example, a high-magnification zoom lens suitable for a high-resolution digital still camera can be obtained. Even when applied to a film camera photographing lens, excellent imaging performance can be obtained.

Next, the diffractive optical surface will be described. In general, refraction and reflection are known as a method of bending a light beam, but diffraction is known as a third method. A diffractive optical element is an optical element that utilizes a diffraction phenomenon of light, and is known to exhibit behavior different from refraction and reflection. Specifically, a diffraction grating and a Fresnel zone plate are conventionally known. Even natural light or white light usually has a coherent length of several λ. Therefore, if a wavelength-order structure is formed, a clear diffraction phenomenon can be produced as a result of the interference action of light waves. A surface having such a diffraction effect will be referred to as a diffractive optical surface. As a property of this diffractive optical surface, it is known that when the diffractive optical surface has a positive power, it has a negative dispersion value and is extremely effective for correcting chromatic aberration. On the other hand, it is known that when the diffractive optical surface has a negative power, it has a positive dispersion value and is extremely effective for correcting chromatic aberration. For this reason, it is possible to correct chromatic aberration that cannot be achieved with ordinary glass and can be achieved only with expensive special low dispersion glass.

  In this embodiment, on the surface of an optical member such as glass or plastic, a surface having an action of bending a light beam by applying a diffraction phenomenon, such as a diffraction grating or a Fresnel zone plate, is created, and the optical performance is improved by the action. Is to get. A surface having a function of bending a light beam by applying a diffraction phenomenon is called a diffractive optical surface, and an optical element having such a surface is generally called a diffractive optical element. The diffractive optical elements and the like are detailed in “Introduction to diffractive optical elements” (supervised by the Optical Society of Japan, Applied Physics Society, published in 2007, revised and revised)

  In general, it is preferable that the angle of light passing through the diffractive optical surface of the optical system is as small as possible. This is because when the ray angle is increased, flare is likely to occur from the cliff portion of the grating of the diffractive optical surface and the image quality is impaired. In order to obtain a good image without much influence of the flare, in the case of the present optical system, it is desirable that the light beam angle is 30 degrees or less. If such a condition can be satisfied, the diffractive optical surface may be disposed anywhere in the zoom lens.

  In the present embodiment, a plurality of diffractive optical elements are applied to the above-described zoom lens having a multi-group structure, thereby achieving high performance. The conventional zoom lens has a long overall length with respect to the image height, a large front lens diameter, and is not suitable for miniaturization. In addition, the conventional zoom lens has excellent imaging performance (especially with little color shift and flare) and high image performance corresponding to recent advances in imaging technology such as the finer pixel pitch and higher sensitivity of image sensors. It has been extremely difficult to achieve both zooming (high zoom ratio) and downsizing. In particular, this lack of performance was significant in a region called a high-power zoom lens. Conventionally, it has been common to use one diffractive optical element in the optical system. However, the performance of the diffractive optical element is improved, and it is becoming possible to use a plurality of diffractive optical elements in the optical system. .

  For example, as shown in FIG. 1, the zoom lens ZL of the present embodiment includes a first lens group G1 having a positive refractive power and a second lens having a negative refractive power, which are arranged in order from the object side along the optical axis. The lens group G2 includes a third lens group G3 having a positive refractive power and a fourth lens group G4 having a positive refractive power. In this case, the final lens group disposed closest to the image side is the fourth lens group G4. During zooming from the wide-angle end state to the telephoto end state, the first lens group G1 moves to the object side, the distance between the first lens group G1 and the second lens group G2 changes, The distance between the second lens group G2 and the third lens group G3 changes.

  The first lens group G1 and the final lens group each have a diffractive optical surface, and the diffractive optical surfaces of the first lens group G1 and the final lens group are respectively formed at interfaces having a refractive index difference of 0.45 or less. Yes. This refractive index difference is preferably set to 0.45 or less in order to suppress reflection at the interface and suppress stray light and to loosen the error sensitivity of the diffraction grating groove height. Is preferably 0.20 or less. Providing the first lens group G1 with a diffractive optical surface is effective for correcting chromatic aberration in the telephoto end state. Providing a diffractive optical surface in the final lens group has a great effect in suppressing chromatic aberration fluctuations during zooming because the final lens group has a large magnification change during zooming. Since the first lens group G1 and the final lens group are positioned farthest and symmetrically with respect to the stop, it is possible to particularly preferably correct lateral chromatic aberration.

  In the zoom lens ZL having such a configuration, it is preferable that the condition expressed by the following conditional expression (1) is satisfied.

0.5 <(C1 + CL) / fw <10.0 (1)
However,
C1: effective diameter of the diffractive optical surface in the first lens group G1,
CL: effective diameter of the diffractive optical surface in the final lens group,
fw: focal length in the wide-angle end state of the zoom lens ZL.

  Conditional expression (1) normalizes the sum of the effective diameters (diameters) of the diffractive optical surfaces in the first lens group G1 and the final lens group by the focal length in the wide-angle end state of the zoom lens ZL, and sets an appropriate range thereof. It is specified. If the condition exceeds the upper limit value of conditional expression (1), the sum of effective diameters becomes too large, making it difficult to manufacture the diffractive optical surface, leading to an increase in cost. In addition, harmful light from the outside tends to enter the diffractive optical surface, and the image quality is likely to deteriorate due to flare or the like. On the other hand, when the condition is less than the lower limit value of the conditional expression (1), the appropriate effective diameter of the lens having the diffractive optical surface becomes too small, and the tendency of the grating pitch of the diffractive optical surface to become small increases, and the diffractive optical surface This makes it difficult to manufacture and increases costs. In addition, the amount of flare generated by the grating of the diffractive optical surface is increased, and image quality is likely to be deteriorated. In addition, a sufficient amount of light cannot be obtained and a dark image tends to be obtained.

  In addition, in order to fully demonstrate the effect of this embodiment, it is desirable to set the upper limit of conditional expression (1) to 8.0. On the other hand, in order to fully demonstrate the effect of the present embodiment, it is desirable to set the lower limit of conditional expression (1) to 1.0. Further, at least in a zoom lens having a zoom ratio of 7 or more, by satisfying the condition expressed by the conditional expression (1), both high zoom ratio (high zoom ratio) and miniaturization can be achieved. .

  In the zoom lens ZL of the present embodiment, the diffractive optical surfaces of the first lens group G1 and the final lens group are close-contact multilayer diffractive optical surfaces and satisfy the condition represented by the following conditional expression (2). It is preferable.

1.0 <Lt / fw <30.0 (2)
However,
Lt: Total length of the zoom lens ZL in the telephoto end state.

  Conditional expression (2) defines an appropriate ratio between the total length of the zoom lens ZL in the telephoto end state (the length from the first surface of the zoom lens ZL to the image plane I) and the focal length in the wide-angle end state. . When the condition exceeds the upper limit value of conditional expression (2), the total length of the zoom lens ZL in the telephoto end state is too long compared to the focal length in the wide-angle end state, so the front lens diameter of the zoom lens ZL becomes large. Various aberrations including distortion become large. On the other hand, when the condition is lower than the lower limit value of the conditional expression (2), the total length of the zoom lens ZL in the telephoto end state is too short compared to the focal length in the wide-angle end state, which is suitable for downsizing the zoom lens ZL. In addition, distortion occurs on the positive side at the telephoto end.

  In addition, in order to fully demonstrate the effect of this embodiment, it is desirable to set the upper limit of conditional expression (2) to 18.0. On the other hand, in order to fully demonstrate the effect of this embodiment, it is desirable to set the lower limit of conditional expression (2) to 3.0.

  In the zoom lens ZL of the present embodiment, it is preferable that the condition represented by the following conditional expression (3) is satisfied.

0.02 <(p1 + pL) / fw <4.0 (3)
However,
p1: the minimum pitch of the diffractive optical surface in the first lens group G1,
pL: Minimum pitch of the diffractive optical surface in the final lens group.

Conditional expression (3) defines the appropriate range by normalizing the sum of the minimum pitches of the diffractive optical surfaces in the first lens group G1 and the final lens group with the focal length in the wide-angle end state of the zoom lens ZL. It is. When the condition exceeds the upper limit value of conditional expression (3), the sum of the minimum pitches becomes too large, so that the achromatic action by the diffractive optical surface is not sufficient, and good imaging performance cannot be obtained. On the other hand, when the condition is lower than the lower limit value of the conditional expression (3), the minimum pitch becomes too small, so that not only is it difficult to make, but also diffraction flare is likely to occur, and good image quality cannot be obtained.

  In order to fully demonstrate the effect of this embodiment, it is desirable to set the upper limit of conditional expression (3) to 1.0. On the other hand, in order to fully demonstrate the effect of this embodiment, it is desirable to set the lower limit of conditional expression (3) to 0.03.

  In the zoom lens ZL of the present embodiment, it is preferable that the zoom ratio is 9 or more and the condition represented by the following conditional expression (4) is satisfied.

0.1 <fL / f1 <5.0 (4)
However,
f1: Focal length of the first lens group G1
fL: focal length of the last lens group.

  Conditional expression (4) defines an appropriate range for the ratio of the focal length of the first lens group G1 to the focal length of the final lens group. If the condition exceeds the upper limit value of conditional expression (4), the focal length of the first lens group G1 becomes too small, so that the distortion at the telephoto end tends to shift to the positive side. In addition, the Petzval sum of the entire system shifts to the positive side, and negative field curvature is likely to occur, so that excellent imaging performance cannot be obtained. On the other hand, when the condition is lower than the lower limit value of the conditional expression (4), the focal length of the final lens group becomes too small, so that the Petzval sum of the entire system shifts to the positive side, and negative field curvature occurs. This is likely to occur and excellent imaging performance cannot be obtained. Furthermore, the principal ray passing through the first lens group G1 is easily separated from the optical axis, and as a result, the front lens diameter is increased, leading to an increase in the size of the entire optical system.

  In addition, in order to fully demonstrate the effect of this embodiment, it is desirable to set the upper limit of conditional expression (4) to 2.0. On the other hand, in order to fully demonstrate the effect of the present embodiment, it is desirable to set the lower limit of conditional expression (4) to 0.2.

  In the zoom lens ZL of the present embodiment, the zoom ratio is 15 or more, the final lens group has a negative lens and a positive lens, and satisfies the condition expressed by the following conditional expression (5). Is preferred.

0.2 <Lt / (y × Z) <8.0 (5)
However,
y: maximum image height,
Z: zoom ratio,
Lt: Total length of the zoom lens ZL in the telephoto end state.

Conditional expression (5) indicates that the ratio of the total length (the length from the first surface of the zoom lens ZL to the image plane I) and the maximum image height in the telephoto end state of the zoom lens ZL depends on the zoom ratio (zoom ratio). It defines the appropriate range. When the condition exceeds the upper limit value of the conditional expression (5), the total length of the zoom lens ZL in the telephoto end state becomes too large, leading to an increase in the lens diameter. On the other hand, when the condition is lower than the lower limit value of the conditional expression (5), the total length of the zoom lens ZL in the telephoto end state is too small, and it is difficult to achieve sufficient back focus. Further, the Petzval sum of the entire system shifts to the positive side, and the field curvature is likely to occur largely on the negative side, so that good imaging performance cannot be obtained.

  In addition, in order to fully demonstrate the effect of this embodiment, it is desirable to set the upper limit of conditional expression (5) to 3.0. On the other hand, in order to fully demonstrate the effect of this embodiment, it is desirable to set the lower limit of conditional expression (5) to 0.25.

  In the zoom lens ZL of the present embodiment, it is preferable that the condition represented by the following conditional expression (6) is satisfied.

0.07 <(PR1-1) / (PRL-1) <3.0 (6)
However,
PR1: a numerical value obtained by dividing the refractive power of the diffractive optical surface in the first lens group G1 by the refractive power of the first lens group G1,
PRL: A value obtained by dividing the refractive power of the diffractive optical surface in the final lens group by the refractive power of the final lens group.

  Conditional expression (6) shows an appropriate distribution of the power of the diffractive optical surface in the first lens group G1 and the final lens group. When the condition exceeds the upper limit value of conditional expression (6), the positive power of the diffractive optical surface in the first lens group G1 becomes too strong, so that it is difficult to correct chromatic aberration at the telephoto end. In particular, among the longitudinal chromatic aberration at the telephoto end, the long wavelength side tends to be excessive on the negative side. On the other hand, when the condition is less than the lower limit value of conditional expression (6), the positive power of the diffractive optical surface in the final lens group becomes too strong, making it difficult to correct chromatic aberration at the wide-angle end. In particular, among the lateral chromatic aberration at the wide-angle end, the long wavelength side tends to become excessive on the negative side.

  In order to fully demonstrate the effect of the present embodiment, it is desirable to set the upper limit of conditional expression (6) to 1.5. On the other hand, in order to fully demonstrate the effect of the present embodiment, it is desirable to set the lower limit of conditional expression (6) to 0.1.

  In the zoom lens ZL of the present embodiment, it is preferable that the condition represented by the following conditional expression (7) is satisfied.

  1.5 <C1 / CL <5.0 (7)

  Conditional expression (7) defines the ratio of the effective diameters (diameters) of the diffractive optical surfaces in the first lens group G1 and the final lens group. When the condition exceeds the upper limit value of the conditional expression (7), the effective diameter of the diffractive optical surface in the first lens group G1 becomes too large, so that not only the lens diameter increases, but also stray light easily enters. In addition, the minimum pitch of the grating tends to be fine, and flare tends to occur. In addition, since the effective diameter of the diffractive optical surface in the final lens group becomes too small, it is difficult to secure the peripheral light amount. On the other hand, when the condition is lower than the lower limit value of the conditional expression (7), the effective diameter of the diffractive optical surface in the final lens group becomes too large, which not only increases the lens diameter but also makes the minimum pitch of the grating fine. Therefore, flare tends to occur. In addition, since the effective diameter of the diffractive optical surface in the first lens group G1 becomes too small, it is difficult to secure the peripheral light amount.

  In addition, in order to fully demonstrate the effect of this embodiment, it is desirable to set the upper limit of conditional expression (7) to 3.5. On the other hand, in order to fully demonstrate the effect of this embodiment, it is desirable to set the lower limit of conditional expression (7) to 2.0.

  In the zoom lens ZL of the present embodiment, it is preferable that the condition represented by the following conditional expression (8) is satisfied.

0.008 <hd / p1 <1.0 (8)
However,
p1: the minimum pitch of the diffractive optical surface in the first lens group G1,
hd: grating height of the diffractive optical surface.

  Conditional expression (8) defines an appropriate aspect ratio (hd / p1) of the diffractive optical surface. This condition is important for manufacturing and for measures to reduce flare. When the condition exceeds the upper limit value of the conditional expression (8), the aspect ratio becomes too large, and manufacturing becomes difficult. Furthermore, the amount of diffraction flare generated becomes large, and good imaging performance cannot be obtained. On the other hand, when the condition is lower than the lower limit value of the conditional expression (8), the pitch of the diffraction grating grooves constituting the diffractive optical surface becomes too loose, and as a result, the achromatic action cannot be sufficiently obtained.

  In addition, in order to fully demonstrate the effect of this embodiment, it is desirable to set the upper limit of conditional expression (8) to 0.5. On the other hand, in order to fully demonstrate the effect of this embodiment, it is desirable to set the lower limit value of conditional expression (8) to 0.01.

  In the zoom lens ZL of this embodiment, it is preferable that the condition represented by the following conditional expression (9) is satisfied.

0.15 <ΔN <0.7 (9)
However,
ΔN: difference in refractive index of the bonded lenses in the first lens group G1.

  Conditional expression (9) defines an appropriate range of the refractive index difference of the cemented lenses in the first lens group G1. When there are a plurality of bonded lenses in the first lens group G1, the lens on the most object side is indicated. When the condition is less than the lower limit value of conditional expression (9), the refractive index difference becomes too small, and the spherical aberration at the telephoto end tends to be on the negative side. Similarly, the field curvature at the telephoto end is likely to be negative. On the other hand, if the condition exceeds the upper limit value of conditional expression (9), the refractive index difference of the bonded lens becomes too large, so that the occurrence of high-order spherical aberration and high-order chromatic aberration on the cemented surface increases and the image quality deteriorates. Inconvenience is likely to occur.

  In order to fully demonstrate the effect of the present embodiment, it is desirable to set the upper limit of conditional expression (9) to 0.50. On the other hand, in order to fully demonstrate the effect of this embodiment, it is desirable to set the lower limit of conditional expression (9) to 0.20.

  In the zoom lens ZL of the present embodiment, it is preferable that the condition expressed by the following conditional expression (10) is satisfied.

0.001 <d1 / fw <1.0 (10)
However,
d1: Thickness on the optical axis of the low refractive index side material of the close-contact multilayer element in the first lens group G1.

Conditional expression (10) standardizes the thickness on the optical axis of the low refractive index side material of the contact multilayer element (diffractive optical element) in the first lens group G1 with the focal length in the wide-angle end state of the zoom lens ZL. To define the appropriate range. When the condition exceeds the upper limit value of conditional expression (10), the thickness on the optical axis of the low refractive index side material of the contact multilayer element (diffractive optical element) becomes too large, and thus light absorption on the short wavelength side Becomes larger and the transmittance on the short wavelength side of the entire optical system tends to deteriorate. On the other hand, when the condition is lower than the lower limit value of conditional expression (10), the thickness on the optical axis of the low refractive index side material of the contact multilayer element (diffractive optical element) becomes too small. It becomes difficult to mold.

  In addition, in order to fully demonstrate the effect of this embodiment, it is desirable to set the upper limit of conditional expression (10) to 0.5. On the other hand, in order to fully demonstrate the effect of this embodiment, it is desirable to set the lower limit of conditional expression (10) to 0.002.

  Thus, according to the present embodiment, it is possible to obtain a zoom lens ZL having a high zoom ratio and a small size and excellent imaging performance.

  When actually configuring the zoom lens ZL, it is desirable to further satisfy the requirements described below.

  The angle of light passing through the diffractive optical surface of the optical system is preferably 30 degrees or less at the wide-angle end and 10 degrees or less at the telephoto end. If it can do in this way, a diffractive optical surface can be provided in any lens in the first lens group G1 and the final lens group. The lens provided with the diffractive optical surface may be a positive lens or a negative lens. However, in order to satisfactorily correct chromatic aberration, it is preferable to provide a bonded lens in the first lens group G1.

  The first lens group G1 preferably includes a cemented lens composed of a positive lens and a negative lens in order to correct a secondary spectrum that cannot be corrected by the diffractive optical surface.

  The second lens group G2 preferably has one positive lens, and preferably has at least three negative lenses. When actually configuring a zoom lens, the second lens group G2 can be fixed at the time of zooming. At this time, the structure is simplified from the viewpoint of mechanical configuration, and the influence of manufacturing errors can be reduced, which is preferable in terms of production technology.

  Focusing from an infinitely distant object to a short distance (finite distance) object may be performed by a so-called front focus method in which the first lens group G1 is extended to the object side. Further, from the viewpoint of realizing the inner focus, it is desirable that the use imaging magnification of the second lens group G2 does not exceed the same magnification (−1 ×) when zooming from the wide angle end to the telephoto end.

  The third lens group G3 preferably has a biconvex lens or a positive meniscus lens in the vicinity of the stop. Furthermore, it is preferable that the third lens group G3 has a cemented lens made up of a biconvex lens and a concave lens in order to satisfactorily correct chromatic aberration.

  The final lens group preferably has at least one convex lens component and one concave lens component.

  In the example of FIG. 1, the final lens group is the fourth lens group G4, but is not limited to this. A fourth lens group having a relatively weak negative refractive power may be sandwiched between the last lens group and the third lens group G3. In this case, the final lens group is a fifth lens group having a positive refractive power. In this way, during zooming (magnification), the fourth lens group changes the distance between the third lens group G3 and the last lens group to contribute not only to magnification but also to aberration correction. The effect can be demonstrated.

Next, the imaging apparatus according to the present embodiment will be described. A digital single-lens reflex camera CAM is shown in FIG. 13 as an imaging apparatus according to the present embodiment. In the digital single-lens reflex camera CAM shown in FIG. 13, light from an object (subject) (not shown) is collected by a photographing lens (zoom lens ZL) and imaged on a focusing screen F via a quick return mirror M. Is done. The light imaged on the focusing screen F is reflected a plurality of times in the pentaprism P and guided to the eyepiece lens E. Thus, the photographer can observe the image of the object (subject) as an erect image through the eyepiece lens E.

  When a release button (not shown) is pressed by the photographer, the quick return mirror M is retracted out of the optical path, and the light from the object (subject) collected by the photographing lens (zoom lens ZL) is captured by the image sensor C. The image is formed on the object to form an image of the subject. As a result, light from the object (subject) is imaged on the image sensor C, picked up by the image sensor C, and recorded in a memory (not shown) as an image of the object (subject). In this way, the photographer can photograph an object (subject) with the digital single-lens reflex camera CAM. Even a mirrorless camera that does not have the quick return mirror M can achieve the same effects as the camera CAM. The digital single-lens reflex camera CAM shown in FIG. 13 may be configured to detachably hold the photographing lens (zoom lens ZL), and is configured integrally with the photographing lens (zoom lens ZL). Also good.

  The photographing lens includes the zoom lens ZL according to the above-described embodiment. Therefore, as described above, it is possible to realize a small and excellent imaging performance while having a high zoom ratio.

(First embodiment)
Embodiments of the present application will be described below with reference to the accompanying drawings. First, a first embodiment of the present application will be described with reference to FIGS. FIG. 1 is a diagram showing the lens configuration and zoom trajectory of the zoom lens ZL (ZL1) according to the first example in the wide-angle end state, and FIG. 2 is the telephoto of the zoom lens ZL (ZL1) according to the first example. It is a figure which shows the lens structure in an end state. The zoom lens ZL1 according to the first example includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, arranged in order from the object side along the optical axis, and an aperture. It comprises a stop S, a third lens group G3 having a positive refractive power, and a fourth lens group G4 having a positive refractive power. In the zoom lens ZL1 according to Example 1, the last lens unit disposed closest to the image side is the fourth lens unit G4.

  During zooming from the wide-angle end state (W) to the telephoto end state (T), the distance between the first lens group G1 and the second lens group G2 changes, and the second lens group G2 and the second lens group G2 The first lens group G1, the second lens group G2, the third lens group G3, and the fourth lens group G4 each move toward the object side along the optical axis so that the distance from the third lens group G3 changes. The first lens group G1 and the fourth lens group G4 (final lens group) each have a diffractive optical surface, and the diffractive optical surfaces of the first lens group G1 and the fourth lens group G4 (final lens group) are In the contact multilayer type diffractive optical element, the refractive index difference is formed at the interface of 0.45 or less.

  The first lens group G1 is arranged in order from the object side along the optical axis, a cemented lens of a negative meniscus lens L11 having a convex surface facing the object side, and a biconvex positive lens L12, and a convex surface facing the object side. And a positive meniscus lens L13. A diffractive optical surface (sixth surface) is formed on the image surface I side lens surface of the positive meniscus lens L13 of the first lens group G1. The second lens group G2 includes, in order from the object side along the optical axis, a negative meniscus lens L21 having a convex surface facing the object side, a biconcave first negative lens L22, and a biconvex positive lens. L23 and a biconcave second negative lens L24. An aspheric surface (eighth surface) is formed on the object-side lens surface of the negative meniscus lens L21 of the second lens group G2.

The third lens group G3 includes a biconvex first positive lens L31 arranged in order from the object side along the optical axis, a positive meniscus lens L32 having a convex surface facing the object side, and a biconvex second lens. This is composed of a cemented lens of a positive lens L33 and a biconcave negative lens L34, and a cemented negative lens L35 having a biconcave shape. An aspheric surface (26th surface) is formed on the object side lens surface of the cemented negative lens L35 of the third lens group G3. The fourth lens group G4 includes a biconvex cemented positive lens L41 arranged in order from the object side along the optical axis, a first positive meniscus lens L42 having a convex surface directed toward the object side, and a convex surface directed toward the object side. Further, it is composed of a cemented lens with the negative meniscus lens L43 and a second positive meniscus lens L44 having a convex surface facing the object side. An aspheric surface (30th surface) is formed on the object-side lens surface of the cemented positive lens L41 of the fourth lens group G4, and diffraction is performed on the image surface-side I lens surface of the negative meniscus lens L43 of the fourth lens group G4. An optical surface (36th surface) is formed.

  The aperture stop S is disposed in the vicinity of the object side of the first positive lens L31 located closest to the object side in the third lens group G3, and at the time of zooming from the wide-angle end state to the telephoto end state. The third lens group G3 moves together with the third lens group G3.

In each embodiment, the height of the aspheric surface in the direction perpendicular to the optical axis (incident height) is y, and the optical surface extends from the tangential plane at the apex of the aspheric surface to the position on the aspheric surface at height y. The distance (sag amount) is S (y), the radius of curvature of the reference sphere (paraxial radius of curvature) is r, the cone coefficient is κ, and the nth order (n = 4, 6, 8, 10, 12). When the aspheric coefficient is An, it is represented by the following aspheric expression (a). In [Aspherical data], “En” indicates “× 10 ⁻ⁿ ”. In [Aspherical Data], coefficients other than the eighth surface in Table 2 use coefficients from A4 to A10 (terms from the fourth order to the tenth order), and omit the description of A12.

(Aspherical type)
S (y) = (y ² / r) / {1+ (1−κ × y ² / r ² ) ^1/2 }
^{+ A4 × y 4 + A6 ×} y 6 + A8 × y 8 + A10 × y 10 + A12 × y 12 ... (a)

  In each example, the phase difference of the diffractive optical surface was calculated using a phase function method. That is, the shape S (x, y) of the diffractive optical surface is represented by the following phase difference function equation (phase polynomial) (b).

(Phase difference function formula)
S (x, y) = ΣCj × x ^m × y ⁿ (b)
(However, j = 2, 4, 6, 8, 10)

  Here, in the above formula (b), j, m, and n are natural numbers and satisfy the following formula (c).

j = [(m + n) ² + m + 3n] / 2 (c)

  In each embodiment, since it is rotationally symmetric with respect to the optical axis, the above phase difference function equation, and further the optical path difference function equation, when the height from the optical axis is h, the following equation (d ) To (f).

(Phase difference function formula)
φ (h) = (2π / λ) × ψ (h) (d)
(Optical path difference function)
ψ (h) = C2 × h ² + C4 × h ⁴ + C6 × h ⁶ + C8 × h ⁸ + C10 × h ¹⁰ (e)
h = √ (x ² + y ² ) (f)

The data of the diffractive optical surface expressed in each example represents the phase difference added by the diffractive optical surface in the coefficient of the optical path difference function equation. In [Diffraction optical surface data], “E-
“n” indicates “× 10 ⁻ⁿ ”.

  In each embodiment, the spectral lines of the d-line, C-line, F-line, and g-line are used as aberration characteristic calculation targets. The wavelengths of these spectral lines are as follows.

Wavelength (nm)
d line 587.562
g-line 435.835
C line 656.273
F line 486.133

  Tables 1 and 2 are shown below, and these are the tables listing the values of the specifications of the zoom lenses according to the first to second examples. In [Lens data] in each table, the first column N indicates the order of the lens surfaces counted from the object side, the second column R indicates the radius of curvature of the lens surfaces, the third column D indicates the distance between the lens surfaces, The column nC indicates the refractive index for the C line, the fifth column nd indicates the refractive index for the d line, the sixth column nF indicates the refractive index for the F line, and the seventh column ng indicates the refractive index for the g line. Note that * attached to the right of the first column indicates that the lens surface is an aspherical surface, and ** attached to the right of the first column indicates that the lens surface is a diffractive optical surface. The curvature radius “∞” indicates a plane, and the description of the refractive index of air is omitted.

  [Variable interval data] indicates the focal length f from the wide-angle end to the telephoto end and the value of each variable interval. [Zoom lens group data] indicates the focal length of each lens group. It should be noted that “mm” is generally used as a unit of focal length f, radius of curvature R, surface interval D, and other lengths listed in all the following specification values. However, since the optical system can obtain the same optical performance even when proportionally enlarged or reduced, the unit is not limited to “mm”. In addition, the same reference numerals as in this embodiment are also used in the specification values of the second embodiment described later.

  Table 1 below shows specifications in the first embodiment. In addition, the curvature radius R of the 1st surface-39th surface in Table 1 respond | corresponds to the code | symbol R1-R39 attached | subjected to the 1st surface-39th surface (except the 18th surface which is a virtual surface) in FIG. Yes.

(Table 1)
[Lens specifications]
N R D nC nd nF ng
Object plane ∞ ∞
1 102.3346 1.0000 1.83649 1.84666 1.8721 1.89419
2 71.1956 9.0000 1.49514 1.497 1.50123 1.50451
3 -353.1978 0.1000
4 65.1129 4.8500 1.61504 1.618 1.62479 1.6301
5 124.0808 0.2000 1.5233 1.5278 1.5391 1.5491
6 ** 124.0808 0.2000 1.5538 1.5571 1.565 1.5713
7 121.7572 (D7)
8 * 118.1529 0.2000 1.5538 1.5571 1.565 1.5713
9 83.2686 1.0000 1.79882 1.804 1.81608 1.82569
10 16.7583 8.7217
11 -39.8074 1.0000 1.79882 1.804 1.81608 1.82569
12 42.9160 0.1000
13 33.1535 5.3000 1.83649 1.84666 1.8721 1.89419
14 -24.3571 0.1738
15 -22.7051 1.0000 1.87656 1.883 1.89822 1.9105
16 148.0818 (D16)
17 ∞ 1.0063 (Aperture stop S)
18 26.6145 0.0000
19 29.4675 3.7000 1.48534 1.48749 1.49228 1.49596
20 -237.9309 0.1000
21 36.0251 2.8000 1.48534 1.48749 1.49228 1.49596
22 119.5595 0.1000
23 22.7076 5.3000 1.49514 1.497 1.50123 1.50451
24 -45.0316 1.0000 1.82738 1.834 1.84982 1.86278
25 79.7006 1.9000
26 * -66.8407 0.2000 1.7678 1.7725 1.78337 1.79197
27 ∞ 1.8000 1.7678 1.7725 1.78337 1.79197
28 ∞ 0.0000 1.7678 1.7725 1.78337 1.79197
29 64.7918 (D29)
30 * 44.4399 1.2000 1.48534 1.48749 1.49228 1.49596
31 ∞ 3.8000 1.48534 1.48749 1.49228 1.49596
32 -24.4749 0.1000
33 39.7765 2.2500 1.48534 1.48749 1.49228 1.49596
34 81.8058 1.0000 1.79882 1.804 1.81608 1.82569
35 31.6631 0.1500 1.5233 1.5278 1.5391 1.5491
36 ** 31.6631 0.1500 1.5538 1.5571 1.565 1.5713
37 30.5100 1.1500
38 40.3147 2.2500 1.48534 1.48749 1.49228 1.49596
39 61.8148 (BF)
Image plane ∞ 0.0000
[Aspherical data]
8th surface κ = -1.300910780158308
A4 = 0.3474318028296278E-5
A6 = -0.7943461468710651E-9
A8 = -0.20745880341211E-10
A10 = 0.6678339621431103E-13
26th surface κ = -1.848278803382846
A4 = 0.8290335964147937E-5
A6 = -0.7700241803188065E-8
A8 = 0.1933525797659676E-9
A10 = -0.9187642743401549E-12
30th surface κ = -7.007942584925146
A4 = -0.403517605031337E-4
A6 = -0.1277509665115196E-7
A8 = -0.1195176970779431E-9
A10 = 0.964351667418942E-12
[Diffraction optical surface data]
6th surface C2 = -0.163619322814288E-4
C4 = 0.101873102883396E-8
C6 = 0.282604675094399E-10
C8 = -0.4365903845627951E-13
C10 = 0.237279434308552E-16
36th surface C2 = -0.59394589717945E-4
C4 = 0.200753386668359E-5
C6 = -0.234486562858558E-7
C8 = 0.8805868156283849E-10
C10 = 0.5376448265974231E-12
[Variable interval data]
Wide-angle end Telephoto end f = 18.500 288.000
D7 = 0.80000 64.14343
D16 = 27.59403 1.00000
D29 = 5.80415 1.00000
BF = 38.00006 106.92207
[Zoom lens group data]
Group number Group first surface Group focal length
G1 1 107.203
G2 8 -13.602
G3 19 50.143
G4 30 37.268

  FIG. 3 is a longitudinal aberration diagram in the wide-angle end state of the zoom lens ZL1 according to the first example. FIG. 4 is a longitudinal aberration diagram in the telephoto end state of the zoom lens ZL1 according to the first example. FIG. 5 is a lateral aberration diagram in the wide-angle end state of the zoom lens ZL1 according to the first example. FIG. 6 is a lateral aberration diagram in the telephoto end state of the zoom lens ZL1 according to the first example. In the longitudinal aberration diagrams, d indicates the d-line, g indicates the g-line, C indicates the C-line, and F indicates the aberration on the F-line. In the aberration diagrams showing astigmatism, the solid line shows the sagittal image plane, and the broken line shows the meridional image plane. The description of the aberration diagrams is the same in the other examples.

  From the respective aberration diagrams, it can be seen that in the first example, various aberrations are well corrected in each focal length state from the wide-angle end state to the telephoto end state, and the optical performance is excellent. As a result, by mounting the zoom lens ZL1 of the first embodiment, excellent optical performance can be secured even in the digital single-lens reflex camera CAM.

(Second embodiment)
Next, a second embodiment of the present application will be described with reference to FIGS. FIG. 7 is a diagram showing the lens configuration and zoom trajectory of the zoom lens ZL (ZL2) according to the second example in the wide-angle end state, and FIG. 8 is the telephoto of the zoom lens ZL (ZL2) according to the second example. It is a figure which shows the lens structure in an end state. The zoom lens ZL2 according to the second example includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, arranged in order from the object side along the optical axis, and an aperture. It comprises a stop S, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a negative refractive power, and a fifth lens group G5 having a positive refractive power. In the zoom lens ZL2 according to Example 2, the last lens unit disposed closest to the image side is the fifth lens unit G5.

During zooming from the wide-angle end state (W) to the telephoto end state (T), the distance between the first lens group G1 and the second lens group G2 changes, and the second lens group G2 and the second lens group G2 The first lens group G1, the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 are each along the optical axis so that the distance from the third lens group G3 changes. Move to the object side. The first lens group G1 and the fifth lens group G5 (final lens group) each have a diffractive optical surface, and the diffractive optical surfaces of the first lens group G1 and the fifth lens group G5 (final lens group) are In the contact multilayer type diffractive optical element, the refractive index difference is formed at the interface of 0.45 or less.

  The first lens group G1 is arranged in order from the object side along the optical axis, a cemented lens of a negative meniscus lens L11 having a convex surface facing the object side, and a biconvex positive lens L12, and a convex surface facing the object side. And a positive meniscus lens L13. A diffractive optical surface (sixth surface) is formed on the image surface I side lens surface of the positive meniscus lens L13 of the first lens group G1. The second lens group G2 is arranged in order from the object side along the optical axis, the first negative meniscus lens L21 having a convex surface facing the object side, a biconcave negative lens L22, and a biconvex positive lens. L23 and a second negative meniscus lens L24 having a convex surface directed toward the image plane I side. An aspheric surface (eighth surface) is formed on the object-side lens surface of the first negative meniscus lens L21 of the second lens group G2.

  The third lens group G3 includes a biconvex first positive lens L31, a biconvex second positive lens L32, and a biconcave negative lens L33 arranged in order from the object side along the optical axis. And a cemented lens of a negative meniscus lens L34 having a convex surface facing the object side and a positive meniscus lens L35 having a convex surface facing the object side. The fourth lens group G4 includes a cemented lens of a biconcave negative lens L41 and a biconvex positive lens L42 arranged in order from the object side along the optical axis, and a negative with a convex surface facing the image plane I side. And a meniscus lens L43. An aspheric surface (30th surface) is formed on the object side lens surface of the negative meniscus lens L43 of the fourth lens group G4.

  The fifth lens group G5 has a biconvex first positive lens L51, a biconvex second positive lens L52, and a convex surface facing the image plane I side, which are arranged in order from the object side along the optical axis. Further, the lens is composed of a cemented lens with a negative meniscus lens L53 and a biconcave negative lens L54. An aspheric surface (38th surface) is formed on the object side lens surface of the negative lens L54 of the fifth lens group G5, and a diffractive optical surface (40th surface) is formed on the image surface I side lens surface of the negative lens L54. It is formed. The aperture stop S is disposed in the vicinity of the object side of the first positive lens L31 located closest to the object side in the third lens group G3, and at the time of zooming from the wide-angle end state to the telephoto end state. The third lens group G3 moves together with the third lens group G3.

  Table 2 below shows specifications in the second embodiment. In addition, the curvature radius R of the 1st surface-the 41st surface in Table 2 respond | corresponds to code | symbol R1-R41 attached | subjected to the 1st surface-the 41st surface (except the 29th surface which is a virtual surface) in FIG. Yes.

(Table 2)
[Lens specifications]
N R D nC nd nF ng
Object plane ∞ ∞
1 112.2139 2.1909 1.84666 1.89419 1.83649 1.8721
2 77.2119 9.0000 1.49782 1.50526 1.49598 1.50201
3 -430.1991 0.1500
4 66.5449 5.9000 1.593189 1.604034 1.590539 1.599279
5 172.8593 0.2000 1.5278 1.5491 1.5233 1.5391
6 ** 169.8693 0.2000 1.5571 1.5713 1.5538 1.565
7 166.9747 (D7)
8 * 123.6263 0.1000 1.55389 1.57284 1.54968 1.56422
9 72.2944 1.2000 1.76684 1.78746 1.76192 1.77831
10 16.9117 6.2589
11 -38.9754 1.2000 1.804 1.8257 1.79882 1.81608
12 55.7998 0.2000
13 37.0975 4.1000 1.80809 1.85576 1.797996 1.83346
14 -44.9444 1.2000
15 -23.6768 1.2000 1.804 1.8257 1.79882 1.81608
16 -63.9397 (D16)
17 ∞ 0.5000 (Aperture stop S)
18 41.6427 2.9000 1.755 1.77296 1.75062 1.76506
19 -174.4771 0.1000
20 26.5732 5.2000 1.49782 1.50526 1.49598 1.50201
21 -84.9850 1.2000 1.84666 1.89419 1.83649 1.8721
22 192.1345 0.1000
23 41.4925 1.2000 1.83481 1.85953 1.82897 1.84851
24 14.0249 5.0000 1.51823 1.52915 1.51555 1.52435
25 55.8886 (D25)
26 -119.5895 1.2000 1.7725 1.79197 1.7678 1.78337
27 39.0655 2.4000 1.85026 1.8845 1.842588 1.86888
28 -99.5460 1.7788
29 ∞ 1.8553
30 * -23.2473 0.2000 1.55389 1.57284 1.54968 1.56422
31 -24.4180 1.2000 1.72916 1.7457 1.7251 1.73844
32 -54.7175 (D32)
33 46.2207 5.0000 1.51823 1.52915 1.51555 1.52435
34 -32.1748 0.1000
35 45.9978 5.2000 1.51742 1.52983 1.51444 1.52433
36 -42.8722 1.2000 1.90366 1.94134 1.89525 1.92415
37 -109.3669 0.7479
38 * -83.1124 1.2000 1.8208 1.84517 1.81506 1.83431
39 76.4511 0.2000 1.5278 1.5491 1.5233 1.5391
40 ** 76.4511 0.2000 1.5571 1.5713 1.5538 1.565
41 81.8421 (BF)
Image plane ∞ 0.0000
[Aspherical data]
8th surface κ = 3.766655656584851
A4 = 0.5693103970365781E-5
A6 = -0.3454278342709255E-8
A8 = -0.3215108468949865E-10
A10 = 0.1642947435970673E-12
A12 = 0.6145600000000001E-16
30th surface κ = 0.1089358940381225
A4 = 0.1303723767773823E-4
A6 = 0.3212762801800071E-7
A8 = 0.2770314401882783E-10
A10 = 0.4666443088834457E-13
38th surface κ = 1.193568249491222
A4 = -0.1409912055980126E-4
A6 = -0.2506261173660796E-7
A8 = 0.1714697415630599E-9
A10 = -0.383046862397599E-12
[Diffraction optical surface data]
6th surface C2 = -0.00003
C4 = 0.111527786298072E-7
C6 = 0.216068817353999E-11
C8 = -0.801818010846745E-14
C10 = 0.45455923956056731E-17
40th surface C2 = -0.0001
C4 = 0.165040914528812E-5
C6 = -0.216122250166198E-7
C8 = 0.117690363978525E-9
C10 = -0.220082967025765E-12
[Variable interval data]
Wide angle end Telephoto end f = 28.800 288.000
D7 = 1.54938 58.15003
D16 = 29.68319 1.50000
D25 = 2.19987 6.90876
D32 = 7.44513 1.50000
BF = 44.85387 96.27356
[Zoom lens group data]
Group number Group first surface Group focal length
G1 1 103.636
G2 8 -17.184
G3 18 38.222
G4 26 -57.563
G5 33 46.877

  FIG. 9 is a longitudinal aberration diagram in the wide-angle end state of the zoom lens ZL2 according to the second example. FIG. 10 is a longitudinal aberration diagram in the telephoto end state of the zoom lens ZL2 according to the second example. FIG. 11 is a lateral aberration diagram in the wide-angle end state of the zoom lens ZL2 according to the second example. FIG. 12 is a lateral aberration diagram in the telephoto end state of the zoom lens ZL2 in the second example. From the respective aberration diagrams, it can be seen that in the second example, various aberrations are well corrected in each focal length state from the wide-angle end state to the telephoto end state, and the optical performance is excellent. As a result, by mounting the zoom lens ZL2 of the second embodiment, excellent optical performance can be secured even in the digital single-lens reflex camera CAM.

  Table 3 below shows the values corresponding to the conditional expressions in the respective examples.

(Table 3)
First Example Second Example C1 51.349 54.938
CL 19.984 24.568
fw 18.500 28.800
Lt 235.867 236.114
p1 0.12401 0.65994
pL 1.60453 0.58338
f1 107.203 103.636
fL 37.2683 46.8772
Z 15.568 10.000
y 14.5 21.6
PR1 1.00328 1.00578
PRL 1.00389 1.03563
hd 0.0200533 0.0200533
d1 0.2 0.2
First Example Second Example Conditional Expression (1) (C1 + CL) /fw=3.8558 2.7606
Conditional expression (2) Lt / fw = 12.750 8.1984
Conditional expression (3) (p1 + pL) /fw=0.09343 0.04051
Conditional expression (4) fL / f1 = 0.34764 0.45233
Conditional expression (5) Lt / (y × Z) = 1.04488 1.09812
Conditional expression (6) (PR1-1) / (PRL-1) = 0.84319 0.16222
Conditional expression (7) C1 / CL = 2.56878 2.23606
Conditional expression (8) hd / p1 = 0.16171 0.03039
Conditional expression (9) ΔN = 0.34966 0.34884
Conditional expression (10) d1 / fw = 0.01081 0.00694

  Thus, it can be seen that each of the above-described conditional expressions is satisfied in each embodiment. As described above, according to each embodiment, it is possible to realize a zoom lens ZL and an image pickup apparatus (digital single-lens reflex camera CAM) that are small and have excellent imaging performance while having a high zoom ratio.

  In the above-described embodiment, in order to actually create a diffractive optical surface, it is easy to produce a grating structure that is rotationally symmetric with respect to the optical axis on the lens surface, such as a Fresnel zone plate. First, it is preferable. In this case, fine grinding or glass molding is possible as in the case of manufacturing an ordinary aspheric lens. Further, a lattice structure may be formed with a thin resin layer on the surface of the lens. In addition, the grating is not limited to a simple single layer structure such as kinoform, but if a plurality of grating structures are stacked, the wavelength characteristic and the angle of view characteristic of diffraction efficiency can be improved, which is advantageous.

  Further, in the zoom lens according to the present embodiment, an appropriate blur correction is performed based on the blur detection unit that detects the blur of the photographing lens, the signal from the blur detection unit, and the signal from the control unit that controls the operation sequence of the camera. An image stabilization lens system can be configured by combining an image stabilization control device that determines the amount and a drive mechanism that moves the image stabilization lens group based on the image stabilization amount. In this case, it is preferable that a part of the third lens group or a part of the fourth lens group is an anti-vibration lens group.

  It goes without saying that even better optical performance can be obtained by using a gradient index lens, an aspherical lens, or the like for each lens constituting the zoom lens of the present embodiment.

  In the zoom lens according to the present embodiment, the zoom ratio is about 7 to 30, but the zoom ratio is more preferably about 7 to 20.

CAM digital single-lens reflex camera (imaging device)
ZL zoom lens G1 first lens group G2 second lens group G3 third lens group G4 fourth lens group G5 fifth lens group S aperture stop I image plane

Claims (9)

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, arranged in order from the object side along the optical axis, and the most image A zoom lens having a final lens group having a positive refractive power disposed on the side,
During zooming from the wide-angle end state to the telephoto end state, the first lens group moves toward the object side, the distance between the first lens group and the second lens group changes, and the second lens group The distance from the third lens group changes,
The first lens group and the final lens group each have a diffractive optical surface;
The diffractive optical surface is formed at an interface having a refractive index difference of 0.45 or less,
The zoom ratio is 9 or more,
A zoom lens satisfying the following conditional expression:
0.5 <(C1 + CL) / fw <10.0
0.1 <fL / f1 ≦ 0.45233
However,
C1: effective diameter of the diffractive optical surface in the first lens group,
CL: effective diameter of the diffractive optical surface in the final lens group,
fw: focal length in the wide-angle end state of the zoom lens ,
f1: the focal length of the first lens group,
fL: focal length of the final lens group. The diffractive optical surface is a multi-contact diffractive optical surface,
The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
1.0 <Lt / fw <30.0
However,
Lt: Total length of the zoom lens in the telephoto end state. The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
0.02 <(p1 + pL) / fw <4.0
However,
p1: the minimum pitch of the diffractive optical surface in the first lens group,
pL: Minimum pitch of the diffractive optical surface in the final lens group. The zoom ratio is 15 or more,
The final lens group includes a negative lens and a positive lens,
The zoom lens according to any one of claims 1 to 3, wherein the following conditional expression is satisfied.
0.2 <Lt / (y × Z) <8.0
However,
y: maximum image height,
Z: the zoom ratio,
Lt: Total length of the zoom lens in the telephoto end state. The zoom lens according to any one of claims 1 to 4, wherein the following conditional expression is satisfied.
0.07 <(PR1-1) / (PRL-1) <3.0
However,
PR1: A numerical value obtained by dividing the refractive power of the diffractive optical surface in the first lens group by the refractive power of the first lens group,
PRL: a numerical value obtained by dividing the refractive power of the diffractive optical surface in the final lens group by the refractive power of the final lens group. The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
1.5 <C1 / CL <5.0 The zoom lens according to any one of claims 1 to 6, wherein the final lens group is a fourth lens group having a positive refractive power and disposed on the image side of the third lens group. . A fourth lens group having negative refractive power disposed on the image side of the third lens group;
The zoom lens according to claim 1, wherein the final lens group is a fifth lens group having a positive refractive power and disposed on the image side of the fourth lens group. . An imaging device including a zoom lens that forms an image of an object on a predetermined surface,
The zoom device according to claim 1, wherein the zoom lens is the zoom lens according to claim 1.

Images