Patent Grant
11789249
The present invention relates to a zoom lens and an image pickup apparatus.
One of the known zoom lenses having a wide angle of view and a high zoom ratio is a positive lead type zoom lens in which a first lens unit having a positive refractive power is disposed closest to the object. Japanese Patent Laid-Open No. (“JP”) 2016-173481 discloses a zoom lens having a high zoom ratio of about 7 and including, in order from an object side to an image side, a first lens unit having a positive refractive power, second to fifth lens units configured to move during zooming (a magnification variation), and a sixth lens unit. The fifth lens unit includes a diaphragm (aperture stop). JP 2020-160262 discloses a zoom lens having a zoom ratio of about 3 as a zoom lens that can support a full-size image sensor mage pickup element) and has a wide angle of view, and this zoom lens includes, in order from the object side to the image side, a first lens unit having a positive refractive power, second to fourth lens units configured to move during zooming, and a fifth lens unit. The fourth lens unit includes a diaphragm.
In order to realize a high optical performance, a wide angle of view, and a small size in the positive lead type zoom lenses, it is important to properly set a diaphragm position and a focal length of each lens unit. For a wider angle of view; a lens diameter of the first lens unit, which is determined by a height of an off-axis ray at the wide-angle end, increases and the zoom lens becomes larger, or the focal length of the first lens unit needs to be short and thus it becomes difficult to achieve a good optical performance (imaging performance) from the central portion to the periphery.
In the zoom lens disclosed in JP 2016-173481, a moving amount of the lens unit including the diaphragm is small, and the lens diameter of the first lens unit increases when the angle of view is made wider. In the zoom lens disclosed in JP 2020-160262, the lens unit including the diaphragm includes three or more lenses, which is disadvantageous in achieving a bright aperture diameter ratio, a small size, and a light weight.
An aspect of the disclosure provides, for example, a zoom lens beneficial in a wide angle of view, a small size and a light weight, and a high optical performance over an entire zoom range thereof.
A zoom lens according to the disclosure includes, in order from an object side to an image side, a first lens unit having a positive refractive power, and a subsequent unit including a plurality of lens units. The first lens unit is configured not to move for zooming. A distance between each pair of adjacent lens units changes in zooming. The subsequent unit includes, in order from the image side to the object side, a lens unit having a positive refractive power and configured not to move for zooming, a moving positive lens unit consisting of one or two lenses, having a positive refractive power, and configured to move in zooming, and a diaphragm configured to move in zooming. The diaphragm is closer to the object side at the wide-angle end than at the telephoto end. The following condition is satisfied:
0.01≤Lwt/Td≤0.25
where Lwt is a distance on an optical axis between a position of the diaphragm at the wide-angle end and a position of the diaphragm at the telephoto end, and Td is a distance on the optical axis from a surface closest to the object side of the zoom lens to an image plane of the zoom lens at the wide-angle end.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Referring now to the accompanying drawings, a description will be given of embodiments according to the present invention.
Prior to specific explanations according to Examples 1 to 6, matters common to each example will be explained. In the zoom lens according to each example, in order to obtain a wide angle of view (overall angle of view 2ω is about 54 to 100°), a zoom ratio (magnification variation ratio) of about 2 to 13, a small size, a light weight, and a high optical performance over the entire zoom range, a moving amount of the diaphragm relative to the overall length and a configuration of a lens unit that is moved during zooming are properly set.
The zoom lens according to each example includes, in order from the object side to the image side, a first lens unit (U1) having a positive refractive power, and a subsequent unit including a plurality of lens units (U2 to U5 or U6). The zoom lens according to each example is a positive lead type zoom lens in which a lens unit having a positive refractive power is disposed closest to the object.
The zoom lens according to each example provides zooming by changing a distance between adjacent lens units, The first lens unit does not move (is fixed or immobile) for zooming. The subsequent unit includes, in order from the image side to the object side, a final lens unit that has a positive refractive power and is not moved for zooming, a finally-moving positive lens unit that includes (consists of) one or two lenses, has a positive refractive power, is moved during zooming. in each example, one lens means a single lens, and a cemented lens in which two lenses are joined together is considered to be two lenses. This is because both the cemented lens and the two non-cemented lenses can exhibit similar chromatic aberration correcting effects.
The subsequent unit includes an diaphragm (SP) that is moved during zooming.
A focal length conversion optical system that includes an insertable or detachable lens unit, and converts a focal length of the entire zoom lens system may be disposed before and after the final lens unit. A driving mechanism may be provided that suppresses a focus movement during zooming in the entire zoom range by slightly moving the final lens unit along the optical axis wholly or partially.
In the zoom lens according to each example, the diaphragm is closer to the object at the wide-angle end than at the telephoto end. A condition expressed by the following expression (inequality) (1) is satisfied:
0.01≤Lwt/Td≤0.25 (1)
where Lwt is a distance on the optical axis between the positions of the diaphragm at the wide-angle end and the position of the diaphragm at the telephoto end, and Td is a distance on the optical axis from the surface closest to the object in the first lens unit (that is, the zoom lens) at the wide-angle end to the image plane.
The distance Lwt corresponds to a moving amount of the diaphragm during zooming from the wide-angle end to the telephoto end when a direction in which the diaphragm is moved to the image side is set positive from the wide-angle end to the telephoto end. Even if the moving direction of the diaphragm changes during zooming, it is determined only by the position of the diaphragm at the wide-angle end and the position of the diaphragm at the telephoto end.
A description will now be given of a relationship between the moving amount of the diaphragm and the first lens unit. Upper and lower figures in
The expression (1) defines a condition regarding a relationship between the moving amount on the optical axis of the diaphragm placed in the subsequent unit during zooming from the telephoto end to the wide-angle end, and a distance on the optical axis (overall lens length) from the surface closest to the object to the image plane at the wide-angle end. When Lwt/Td satisfies the condition expressed in the expression (1), the zoom lens can be made small. If Lwt/Td is higher than the upper limit in the expression (1), a space necessary for zooming in the subsequent unit becomes long, and it becomes difficult to make small the zoom lens. If Lwt/Td is lower than the lower limit in the expression (1), the effect of moving the entrance pupil by the diaphragm at the wide-angle end toward the object side becomes small, and it becomes difficult to make small the zoom lens.
The numerical range of the expression (1) may be set as follows:
0.02≤Lwt/Td≤0.20 (1a)
The numerical range of the expression (1) may be set as follows:
0.03≤Lwt/Td≤0.15 (1b)
The numerical range of the expression (1) may be set as follows:
0.04≤Lwt/Td≤0.07 (1c)
The zoom lens according to each example may satisfy at least one of the conditions expressed by the following expressions (2) to (13), in addition to the condition of the expression (1).
The subsequent unit in the zoom lens according to each example includes a finally-moving negative lens unit m2 that has a negative refractive power, includes (consists of) one or two lenses, and is moved during zooming, in addition to the final lens unit (designated by r hereinafter) and the finally-moving positive lens unit (designated by m1 hereinafter). The condition expressed by the following expression (2) may be satisfied:
−2.0×10−3≤(θ m1−θm2)/(vm2−vm1)≤2.5×10−3 (2)
where vm1 is an average value of Abbe numbers based on the d-line of optical materials of all positive lenses included in the finally-moving positive lens unit m1, θm1 is an average value of partial dispersion ratios with respect to the g-line and the F-line, vm2 is an average value of Abbe numbers based on the d-line of optical materials of all negative lenses included in the finally-moving negative lens unit m2, and θm2 is an average value of partial dispersion ratios with respect to the g-line and the F-line.
The finally-moving positive lens unit m1 is adjacent to the final lens unit r, and the smaller (brighter) the aperture diameter ratio of the zoom lens becomes, the larger the lens diameter of the finally-moving positive lens unit m1 becomes. In order to reduce the size and weight of the lens unit that is moved during zooming, it is effective to reduce the number of lenses constituting this lens unit. In each example, the finally-moving positive lens unit m1 includes (consists of) one or two lenses. in addition, by arranging the finally-moving positive lens unit m1 and the finally-moving negative lens unit m2 close to each other and by correcting the chromatic aberration using the relationship of the characteristics of the glass materials between the moving lens units, the chromatic aberration can be satisfactorily corrected over the entire zoom range.
The Abbe number vd (vm1, vm2) based on the d-line of the optical material in the expression (2) and the partial dispersion ratio θgF (θm1, θm2) with respect to the g-line and F-line are expressed by the following expressions (a) and (b), respectively. In each expression, Ng, NF, Nd, and NC, respectively, are refractive indexes of the optical material for the g-line (wavelength 435.8 nm), the F-line (wavelength 486.1 nm), the d-line (wavelength 587.6 am), and the C-line (wavelength 656.3 nm) in the Fraunhofer lines:
vd=(Nd−1)/(NF−NC) (a)
θgF=(Ng−NF)/(NF−NC) (b)
A description will now be given of a relationship regarding the chromatic aberration correction between the finally-moving positive lens unit m1 and the finally-moving negative lens unit m2. As illustrated in
L=h×h×(Φp/vp+Φn/vn) (c)
T=h×H×(Φp/vp+θn/vn) (d)
Φp+Φn=Φ (e)
The on-axis paraxial ray and the pupil paraxial ray are rays defined as follows, The on-axis paraxial ray is a paraxial ray incident on the zoom lens while the focal length of the entire zoom lens system at the wide-angle end is normalized to 1, and the incident height is set to 1 in parallel with the optical axis. The pupil paraxial ray is a paraxial ray that passes through an intersection of the entrance pupil of the zoom lens and the optical axis among light rays incident on the maximum image height of the imaging plane, while the focal length of the entire zoom lens system at the wide-angle end is normalized to 1.
The refractive power of each lens in the expressions (c) and (d) is normalized so that Φ=1 in the expression (e). This is similarly applied to three or more lenses. In the expressions (c) and (d), when L=0 and T=0, the imaging positions on the optical axis and the image plane coincide with each other between the C-line and the F-line. The chromatic aberration correction for two specific wavelengths in this way is generally called two-wavelength achromatism (primary spectrum correction). In particular, in a high-magnification zoom lens, the chromatic aberration of each lens unit, that is, L and T, is corrected to nearly 0 in order to suppress the chromatic aberration fluctuation along with zooming.
Assume that a secondary spectral amount Δs of the longitudinal chromatic aberration and a secondary spectral amount Δy of the lateral chromatic aberration are a shift amount of the longitudinal chromatic aberration of the g-line to the F-line and a shift amount of the lateral chromatic aberration of the g-line relative to the F-line, in the infinity-focused state, that is, the state where the light beam is incident on the zoom lens with the object distance at infinity, respectively. Then, they are expressed by the following expressions (f) and (g):
Δs=−h×h×(θp−θn)/(vp−vn)×f (f)
Δy=−h×H×(θp−θn)/(vp−vn)×Y (g)
where f is a focal length of the entire zoom lens system, and Y is an image height.
The chromatic aberration correction for three specific wavelengths by adding a specific wavelength to the above two wavelengths in this way is generally called three-wavelength achromatism (secondary spectrum correction).
Since the focal length f of the expression (f) increases as the zoom lens has a higher zoom ratio, it becomes difficult to reduce the secondary spectrum of longitudinal chromatic aberration. As the angle of view of the zoom lens is made wider, the pupil paraxial ray H in the expression (g) increases, and it becomes difficult to reduce the secondary spectrum of the lateral chromatic aberration at the wide-angle end. Each example particularly makes wider the angle of view of the zoom lens, and satisfactorily corrects the primary and secondary spectra of the lateral and longitudinal chromatic aberrations over the entire zoom range.
Satisfying the condition expressed in the expression (2) can provide proper differences in Abbe number and partial dispersion ratio between the finally-moving positive lens unit m1 and the finally-moving negative lens unit m2, and becomes advantageous in correcting the chromatic aberration over the entire zoom range. When (θm1−θm2)/(vm2−vm1) is higher than the upper limit or lower than the lower limit in the expression (2), it becomes difficult to provide the finally-moving positive lens unit m1 and the finally-moving negative lens unit m2 with proper chromatic aberration correcting powers. Moreover, it is difficult to achieve a good optical performance over the entire zoom range.
The numerical range of expression (2) may be set as follows:
−1.0×10−3≤(θm1−−θm2)/(vm2−vm1)≤2.2×10−3 (2a)
The numerical range of expression (2) may be set as follows:
−0.5×10−3≤(θm1−θm2)/(vm2−vm1)≤1.9×10−3 (2b)
The numerical range of expression (2) may be set as follows:
0≤(θm1−θm2)/(vm2−vm1)≤1.9×10−3 (2c)
The numerical range of expression (2) may be set as follows:
0.2×10−3≤(θm1−θm2)/(vm2−vm1)≤1.5×10−3 (2d)
The numerical range of expression (2) may be set as follows:
0.5×10−3≤(θm1−θm2)/(vm2−vm1)≤1.3×10−3 (2e)
The zoom lens according to each example may satisfy a condition expressed by the following expression (3):
0.01≤Dm12/fm1≤0.50 (3)
where Dm12 is a maximum air distance (spacing) between the finally-moving positive lens unit m1 and the finally-moving negative lens unit m2 in the entire zoom range from the wide-angle end to the telephoto end, and fm1 is a focal length of the finally-moving positive lens unit m1.
In the zoom lens according to each example, in order to reduce the weight of the finally-moving positive lens unit m1 and the finally-moving negative lens unit m2, it is unnecessary to correct the chromatic aberration by the positive lens and the negative lens in each lens unit. By properly selecting optical materials of the lenses in the finally-moving positive lens unit m1 and the finally-moving negative lens unit m2 adjacent to the finally-moving positive lens unit m1 and by correcting the chromatic aberration between the lens units, the chromatic aberration may be satisfactorily corrected in the entire zoom range. In the zoom lens according to each example, the aberration correction ability in the middle zoom range is improved by moving the finally-moving positive lens unit m1 and the finally-moving negative lens unit m2 so as to draw different moving loci during zooming. Since the chromatic aberration correction capability fluctuates at the same time, it is basically necessary for the finally-moving positive lens unit m1 and the finally-moving negative lens unit m2 to maintain a close relationship to each other in the entire zoom range.
The expression (3) defines a condition regarding a relationship between the maximum air spacing during zooming between the finally-moving positive lens unit m1 and the finally-moving negative lens unit m2 and the focal length fm1 of the finally-moving positive lens unit m1. By satisfying the condition expressed in the expression (3), the finally-moving positive lens unit m1 and the finally-moving negative lens unit m2 can be properly brought close to each other in the entire zoom range, and the chromatic aberration correction ability in the entire zoom range can be sufficiently restrained from fluctuating. When Dm12/fm1 is higher than the upper limit in the expression (3), the finally-moving positive lens unit m1 and the finally-moving negative lens unit m2 are separated from each other, and it becomes difficult to satisfactorily correct the chromatic aberration in the entire zoom range. When Dm12/fm1 is lower than the lower limit in the expression (3), the fluctuation of the distance between the finally-moving positive lens unit m1 and the finally-moving negative lens unit m2 is almost eliminated, and it is difficult to divide the lens unit to correct an aberration other than chromatic aberration.
The numerical range of the expression (3) may be set as follows:
0.02≤Dm12/fm1≤0.45 (3a)
The numerical range of the expression (3) may be set as follows:
0.03≤Dm12/fm1≤0.40 (3b)
The numerical range of the expression (3) may be set as follows:
0.04≤Dm12/fm1≤0.35 (3c)
The numerical range of the expression (3) may be set as follows:
0.05≤Dm12/fm1≤0.30 (3d)
The zoom lens according to each example may satisfy a condition expressed by the following expression (4):
−5.0≤fm2/fm1≤−0.7 (4)
where fm1 is a focal length of the finally-moving positive lens unit m1, and fm2 is a focal length of the finally-moving negative lens unit m2.
Satisfying the conditional expressed in the expression (4) can make smaller the zoom lens. If fm2/fm1 is higher than the upper limit in the expression (4), the refractive power of the finally-moving negative lens unit m2 becomes strong, the lens diameter of the subsequent unit becomes large, and it becomes difficult to make smaller the zoom lens. If fm2/fm1 is lower than the lower limit in the expression (4), the refractive power of the finally-moving negative lens unit m2 becomes weak, the moving amount of the finally-moving negative lens unit m2 during zooming becomes large, and it becomes difficult to make smaller the zoom lens.
The numerical range of the expression (4) may be set as follows:
−4.7≤fm2/fm1≤−0.8 (4a)
The numerical range of the expression (4) may be set as follows:
−3.2≤fm2/fm1≤−0.9 (4b)
The numerical range of the expression (4) may be set as follows:
−2.4≤fm2/fm1≤−1.0 (4c)
In the zoom lens according to each example, the finally-moving positive lens unit m1 includes (consists of) a single positive lens, and the conditions expressed by the following expressions (5) and (6) may be satisfied:
28≤vm1u≤60 (5)
0.540≤θm1u≤0.600 (6)
where vm1u is an Abbe number based on the d-line of the optical material of the single positive lens, and θm1u is a partial dispersion ratio of the optical material of the single positive lens with respect to the g-line and the F-line.
Satisfying the expressions (5) and (6) can make smaller the zoom lens and provide a high optical performance. The expressions (5) and (6) define conditions relating to ranges of the dispersion (Abbe number) and the partial dispersion ratio which are advantageous in correcting the lateral chromatic aberration that tends to increase at a wider angle of view when the finally-moving positive lens unit m1 includes (consists of) a single positive lens. If vm1u is lower than the lower limit in the expression (5) or θm1u is higher than the upper limit in the expression (6), the positive lens using the existing optical material has an excessively high dispersion and an excessively high partial dispersion ratio, and it becomes difficult to achieve a satisfactory optical performance in the entire zoom range. If vm1u is higher than the upper limit in expression (5) or θm1u is lower than the lower limit in expression (6), the positive lens has an excessively high partial dispersion ratio, and it becomes difficult to achieve a satisfactory optical performance in the entire zoom range.
The numerical ranges of the expressions (5) and (6) may be set as follows:
29≤vm1u≤59 (5a)
0.542≤θm1u≤0.595 (6a)
The numerical ranges of the expressions (5) and (6) may be set as follows:
31≤vm1u≤56 (5b)
0.543≤θm1u≤0.590 (6b)
The numerical ranges of the expressions (5) and (6) may be set as follows:
33≤vm1u≤50 (5c)
0.550≤θm1u≤0.585 (6c)
The zoom lens according to each example may satisfy conditions expressed by the following expressions (7) and (8) when the finally-moving negative lens unit m2 includes (consists of) a single negative lens:
60≤vm2u≤110 (7)
0.520≤θm2u≤0.550 (8)
where vm2u is an Abbe number based on the d-line of the optical material of the single negative lens, and θm2u is a partial dispersion ratio of the optical material of the single negative lens with respect to the g-line and the F-line.
Satisfying the conditions of expressions (7) and (8) can make smaller the zoom lens and provide a high optical performance. The expressions (7) and (8) define conditions under which a proper chromatic aberration correction relationship can be established with the finally-moving positive lens unit m1 when the finally-moving negative lens unit m2 includes (consists of) a single negative lens. Satisfying these conditions is advantageous in correcting the lateral chromatic aberration that particularly tends to increase at a wider angle of view. If vm2u is lower than the lower limit in the expression (7), the primary chromatic aberration caused by the movement of the finally-moving negative lens unit m2 along with zooming significantly fluctuates, and it becomes difficult to achieve a good optical performance in the entire zoom range. If θm2u is higher than the upper limit in the expression (8), the secondary chromatic aberration caused by the movement of the finally-moving negative lens unit m2 along with zooming significantly fluctuates, and it becomes difficult to achieve a good optical performance in the entire zoom range. If vm2u is higher than the upper limit in the expression (7), or if θm2u is lower than the lower limit in the expression (8), it becomes difficult to select a glass material.
The numerical ranges of the expressions (7) and (8) may be set as follows:
63≤vm2u≤107 (7a)
0.522≤θm2u≤0.545 (8a)
The numerical ranges of the expressions (7) and (8) may be set as follows:
70≤vm2u≤102 (7b)
0.524≤θm2u≤0.543 (8b)
The numerical ranges of the expressions (7) and (8) may be set as follows:
74≤vm2u≤97 (7c)
0.526≤θm2u≤0.540 (8c)
The numerical ranges of the expressions (7) and (8) may be set as follows:
80≤vm2u≤95 (7d)
0.528≤θmu2≤0.538 (8d)
The zoom lens according to each example may satisfy the condition expressed by the following expression (9):
|/βm1|≤0.2 (9)
where βm1 is a lateral magnification of the finally-moving positive lens unit m1 at the wide-angle end in the infinity in-focus state.
Satisfying the condition of the expression (9) can bring the light ray emitted from the finally-moving positive lens unit m1 close to parallel to reduce the change is higher than the upper limit in the expression (9), the emitted light beam from the finally moving positive lens unit m1 has an angle, the aperture diameter significantly changes during zooming, and the control mechanism becomes complicated.
The numerical range of the expression (9) may be set as follows:
|1/βm1|≤0.15 (9a)
The numerical range of the expression (9) may be set as follows:
|1/βm1|≤0.13 (9b)
The numerical range of the expression (9) may be set as follows:
|1/βm1≤0.11 (9c)
The numerical range of the expression (9) may be set as follows:
|1/βm1≤0.04 (9d)
The one or two n-th moving lens units configured to move during zooming in the subsequent unit of the zoom lens according to each example includes a lens unit having a negative refractive power (negative lens unit). Then, the conditions expressed by the following expressions (10) and (11) may be satisfied:
−5.0≤f1/fn≤−0.8 (10)
−2.5≤fm1/fn≤−1.2 (11)
where fn is a combined focal length of the one or two n-th moving lens units in the infinity in-focus state at the wide-angle end, and f1 is a focal length of the first lens unit.
The expressions (10) and (11) define conditions regarding the power arrangement of the lens units for a further miniaturization and a higher performance of the zoom lens. The focal length of the zoom lens is a product value of the focal length of the first lens unit and the lateral magnification of the lens units in the subsequent unit. In order to achieve a wide angle of view, it is necessary to properly set the focal length of the first lens unit. If f1/fn is higher than the upper limit in the expression (10), the refractive power of the first lens unit becomes strong and it becomes difficult to correct the aberration fluctuation. In addition, since the refractive power of the n-th moving lens unit is insufficient for the first lens unit, it is disadvantageous in reducing the size and weight of the zoom lens. If f1/fn is lower than the lower limit in the expression (10), the refractive power of the first lens unit is insufficient, and it becomes difficult to widen the angle of view and reduce the size and weight.
The numerical range of the expression (10) may be set as follows:
−4.0≤f1/fn≤−0.9 (10a)
The numerical range of the expression (10) may be set as follows:
−3.5≤f1/fn≤−1.0 (10b)
The numerical range of the expression (10) may be set as follows:
−3.0≤f1/fn≤−1.3 (10c)
Satisfying the condition expressed in the expression (11) can make smaller the zoom lens. If fm1/fn is higher than the upper limit in the expression (11), the refractive power of the negative lens unit in the subsequent unit becomes weak, the moving amount of the negative lens unit during zooming becomes large, and it becomes difficult to make small the zoom lens. If fm1 /fn is lower than the lower limit in the expression (11), the refractive power of the positive lens unit in the subsequent unit becomes weak, the lens diameter of the subsequent unit becomes large, and it becomes difficult to make small the zoom lens.
The numerical range of the expression (11) may be set as follows:
−2.4≤fm1/fn≤−1.3 (11a)
The numerical range of the expression (11) may be set as follows:
−2.3≤fm1/fn≤−1.4 (11b)
The numerical range of the expression (11) may be set as follows:
−2.1≤fm1/fn≤−1.5 (11c)
The zoom lens according to each example may satisfy a condition expressed by the following expression (12):
0.6≤(βtn/βwn)/Zwt≤4.0 (12)
where βnw and βnt are lateral magnifications of the n-th moving lens unit at the wide-angle end and at the telephoto end, respectively, and Zwt is a zoom ratio from the wide-angle end to the telephoto end of the entire zoom lens system.
The condition of the expression (12) defines a condition regarding a share of the n-th moving lens unit in a zoom ratio from the wide-angle end to the telephoto end of the zoom lens. Satisfying the condition expressed in the expression (12) can establish a proper zoom share, and is further advantageous for the miniaturization and high performance of the zoom lens. If (βtn/βwn)/Zwt is higher than the upper limit in the expression (12), the share of the n-th moving lens unit in the zoom ratio is too lame, and it is difficult to suppress the aberration fluctuation along with the movement of the n-th lens unit. If (βtn/βwn)/Zwt is lower than the lower limit in the expression (12), the zoom share of the lens unit after the n-th moving lens unit increases, which has a relatively simple configuration, and the high performance becomes difficult.
The numerical range of the expression (12) may be set as follows:
0.7≤(βtn/βwn)/Zwt≤3.1 (12a)
The numerical range of the expression (12) may be set as follows:
0.8≤(βtn/βwn)/Zwt≤2.0 (12b)
The numerical range of the expression (12) may be set as follows:
0.9≤(βtn/βwn)/Zwt≤1.4 (12c)
The numerical range of the expression (12) may be set as follows:
0.9≤(βtn/βwn)/Zwt≤1.2. (12d)
The zoom lens according to each example may satisfy a condition expressed by the following expression (13):
−1.0×10−3≤(θnp−θnn)/(vnn−vnp)≤3.0×10−3 (13)
where vnp and vnn are average values of Abbe numbers based on the d-line of optical materials of all positive lenses and all negative lenses included in the negative lens unit included in the n-th moving lens unit, respectively, and θnp and θnn are average values of partial dispersion ratios of the optical materials with respect to the 2-line and the F-line, respectively.
Satisfying the condition of the expression (13) can provide a difference in each of the Abbe number and partial dispersion ratio which is advantageous in correcting the lateral chromatic aberration in the negative lens unit, which particularly tends to increase at a wider angle of view: If (θnp−θnn)/(vnn−vnp) is higher than the upper limit in the expression (13), the chromatic aberration correction in the negative lens unit becomes insufficient, and it becomes difficult to achieve a good optical performance.
The numerical range of the expression (13) may be set as follows:
−0.5×10−3≤(θnp−θnn)/(vnn−vnp)≤2.7×10−3 (13a)
The numerical range of the expression (13) may be set as follows:
0≤(θnp−θnn)/(vnn−vnp)≤2.5×10−3 (13b)
The numerical range of the expression (13) may be set as follows:
0≤(θnp−θnn)/(vnn−vnp)≤2.4×10−3 (13c)
The numerical range of the expression (13) may be set as follows:
0.5×10−3≤(θnp−θnn)/(vnn−vnp)≤2.2×10−3 (13d)
The numerical range of the expression (13) may be set as follows:
1.0×10−3≤(θnp−θnn)/(vnn−vnp)≤2.1×10−3 (13e)
A description will now be given of Examples 1 to 6 and numerical examples 1 to 6 corresponding to them.
A zoom lens according to Example 1 (numerical example 1) illustrated in
In this example, the second lens unit U2 corresponds to the n-th moving lens unit, the third lens unit U3 corresponds to the finally-moving negative lens unit m2, the fourth lens unit U4 corresponds to the finally-moving positive lens unit m1, and the fifth lens unit U5 corresponds to the final lens unit r. The diaphragm SP is included in the fourth lens unit U4, and is closest to the object in the fourth lens unit U4.
In the numerical example 1, a surface number i denotes the order of the surfaces counted from the object side. r denotes a radius of curvature (mm) of an i-th surface counted from the object side, d denotes a lens thickness or air spacing (mm) on the optical axis between an i-th surface and an (i+1)-th surface, and nd denotes a refractive index of an optical material between an i-th surface and an (i+1)-th surface for the d-line. vd is an Abbe number based on the d-line of the optical material between an i-th surface and an (i+1)-th surface. θgF denotes a partial dispersion ratio with respect to the g-line and the F-line of the optical material between an i-th surface and an (i+1)-th surface, Numerical example l also illustrates the effective diameter (mm) and focal length (mm) of each surface.
BF denotes a backfocus (mm). The backfocus is a distance on the optical axis from the final surface of the zoom lens (the lens surface closest to the image plane) to the paraxial image plane and is converted into an air equivalent length. The overall lens length is a length obtained by adding the backfocus to the distance on the optical axis from the frontmost surface (lens surface closest to the object) to the final surface in the zoom lens, and the overall lens length al the wide-angle end corresponds to the distance Td illustrated in the expression (1).
An asterisk “*” attached to a surface number means that the surface has an aspherical shape. The aspherical shape is expressed as follows:
where an X-axis is set to an optical axis direction, an H-axis is set to a direction orthogonal to the optical axis, a light traveling direction is set positive, R is a paraxial radius of curvature, k is a conical constant, and A3 to A16 are aspherical coefficients. “e-z” means “×10−Z.”
The description regarding this numerical example is similarly applied to other numerical examples described later.
In numerical example 1, the first lens unit U1 corresponds to first to sixteenth surfaces. The second lens unit U2 corresponds to seventeenth to twenty-third surfaces. The third lens unit U3 corresponds to twenty-fourth and twenty-fifth surfaces. The fourth lens unit U4 corresponds to twenty-sixth to twenty-eighth surfaces. The fifth lens unit U5 corresponds to twenty-ninth to forty-first surfaces.
The first lens unit U1 includes a first lens subunit (first to seventh surface) that has a negative refractive power and is not moved for focusing, a second lens subunit (eighth and ninth surfaces) that has a positive refractive power, and is moved to the image side during focusing from the infinity object to the short-distance object, and a third lens subunit (tenth to sixteenth surfaces) that has a positive refractive power and is not moved for focusing, In numerical example 1. the maximum air spacing mD12 between the third lens unit U3 and the fourth lens unit U4 is a distance obtained at a focal length of 35 mm.
Table 1 summarizes the values of the conditions expressed in the expressions (1) to (13) in Example 1 (numerical example 1). The zoom lens according to Example 1 satisfies each condition, and has a small size, a light weight, a wide angle of view, and a high optical performance in the entire zoom range. In particular, in this example, the third lens unit U3 includes (consists of) a single negative lens and the fourth lens unit U4 includes (consists of) a single positive lens, so that the zoom lens has a wide angle of view, a small size, a light weight, a bright aperture diameter ratio, and a high optical performance.
A zoom lens according to Example 2 (numerical example 2) illustrated in
In this example, the second lens unit U2 corresponds to the n-th moving lens unit, the third lens unit U3 corresponds to the finally-moving negative lens unit m2, the fourth lens unit U4 corresponds to the finally-moving positive lens unit m1, and the fifth lens unit. U5 corresponds to the final lens unit r. The diaphragm SP is included in the fourth lens unit U4, and is closest to the object in the fourth lens unit U4.
In numerical example 2, the first lens unit U1 corresponds to first to fourteenth surfaces. The second lens unit U2 corresponds to fifteenth to twenty-first surfaces. The third lens unit U3 corresponds to twenty-second and twenty-third surfaces. The fourth lens unit U4 corresponds to twenty-fourth to twenty-sixth surfaces. The fifth lens unit U5 corresponds to twenty-seventh to thirty-ninth surfaces.
The first lens unit U1 includes a first lens subunit (first to fourth surfaces) that has a negative refractive power and is not moved for focusing, a second lens subunit (fifth to seventh surfaces) that has a negative refractive power and is moved to the image side during focusing from the infinity object to the short-distance object, and a third lens subunit (eighth to fourteenth surfaces) that has a positive refractive power and is not moved for focusing. In numerical example 2, the maximum air spacing mD12 between the third lens unit U3 and the fourth lens unit U4 is a distance obtained at a focal length of 67 mm.
Table 1 summarizes the values of the conditions expressed in the expressions (1) to (13) in Example 2 (numerical example 2). The zoom lens according to Example 2 satisfies each condition, and has a small size, a light weight, a wide angle of view, and a high optical performance in the entire zoom range. In particular, in this example, the third lens unit U3 includes (consists of) a single negative lens and the fourth lens unit U4 includes (consists of) a single positive lens, so that the zoom lens has a wide angle of view, a small size, a light weight, a bright aperture diameter ratio, and a high optical performance.
A zoom lens according to Example 3 (numerical example 3) illustrated in
In this example, the second lens unit U2 corresponds to the n-th moving lens unit, the third lens unit U3 corresponds to the finally-moving negative lens unit m2, the fourth lens unit U4 corresponds to the finally-moving positive lens unit m1, and the fifth lens unit U5 corresponds to the final lens unit r. The diaphragm SP is included in the fourth lens unit U4, and is closest to the object in the fourth lens unit U4.
In numerical example 3, the first lens unit U1 corresponds to first to twenty-first surfaces. The second lens unit U2 corresponds to twenty-second to thirtieth surfaces. The third lens unit U3 corresponds to thirty-first to thirty-third surfaces.
The fourth lens unit U4 corresponds to thirty-fourth to thirty-eighth surfaces. The fifth lens unit U5 corresponds to thirty-ninth to forty-eighth surfaces. The dummy glass DG corresponds to the forty-ninth to fifty-first surfaces.
The first lens unit U1 includes a first lens subunit (first to eighth surfaces) that has a negative refractive power and is not moved for focusing, a second lens subunit (ninth and tenth surfaces) that has a negative refractive power and is moved to the image side during focusing from the infinity object to the short-distance object, and a third lens subunit (eleventh to twenty-first surfaces) that has a positive refractive power and is not moved during focusing. In numerical example 3, the maximum air spacing mD12 between the third lens unit U3 and the fourth lens unit U4 is a distance obtained at a focal length of 16 mm.
Table 1 summarizes the values of the conditions expressed in the expressions (1) to (13) in Example 3 (numerical example 3). The zoom lens according to Example 3 satisfies each condition, and has a small size, a light weight, a wide angle of view, and a high optical performance in the entire zoom range. In particular, in this example, the third lens unit U3 includes (consists of) two lenses or a single negative lens and a single positive lens, and the fourth lens unit U4 includes (consists of) two positive lenses, so that the zoom lens has a wide angle of view, a small size, a light weight, a bright aperture diameter ratio, and a high optical performance.
A zoom lens according to Example 4 (numerical example 4) illustrated in
In this example, the second lens unit U2 and the third lens unit U3 correspond to the n-th moving lens unit, the fourth lens unit U4 corresponds to the finally-moving negative lens unit m2, the fifth lens unit U5 corresponds to the finally-moving positive lens unit m1, and the sixth lens unit U6 corresponds to the final lens unit r. The diaphragm SP is included in the third lens unit U3, and is closest to the image plane in the third lens unit U3.
In numerical example 4, the first lens unit U1 corresponds to first to sixteenth surfaces. The second lens unit U2 corresponds to seventeenth to twenty-second surfaces. The third lens unit U3 corresponds to twenty-third to twenty-fifth surfaces. The fourth lens unit U4 corresponds to twenty-sixth to twenty-eighth surfaces. The fifth lens unit U5 corresponds to twenty-ninth and thirtieth surfaces. The sixth lens unit U6 corresponds to thirty-first to forty-third surfaces,
The first lens unit U1 includes a first lens subunit (first to sixth surfaces) that has a negative refractive power and is not moved for focusing, a second lens subunit (seventh and eighth surfaces) that has a negative refractive power and is moved to the image side during focusing from the infinity object to the short-distance object, and a third lens subunit (ninth to sixteenth surfaces) having a positive refractive power that is not moved during focusing. In numerical example 4, the maximum air spacing mD12 between the fourth lens unit U4 and the fifth lens unit U5 is a distance obtained at a focal length of 22.6 mm.
Table 1 summarizes the values of the conditions expressed in the expressions (1) to (13) in Example 4 (numerical example 4). The zoom lens according to Example 4 satisfies each condition, and has a small size, a light weight, a wide angle of view; and a high optical performance in the entire zoom range. In particular, in this example, the third lens unit U3 includes (consists of) two lenses or a single negative lens and a single positive lens, and the fourth lens unit U4 includes (consists of) a single positive lens, so that the zoom lens has a wide angle of view a small size, a light weight, a bright aperture diameter ratio, and a high optical performance.
A zoom lens according to Example 5 (numerical example 5) illustrated in
In this example, the second lens unit U2 corresponds to the n-th moving lens unit, the third lens unit U3 corresponds to the finally-moving negative lens unit m2, the fourth lens unit U4 corresponds to the finally-moving positive lens unit m1, and the fifth lens unit. U5 corresponds to the final lens unit r. The diaphragm SP is disposed between the third lens unit U3 and the fourth lens unit U4, and is moved independently of these lens units during zooming.
In numerical example 5, the first lens unit U1 corresponds to first to eighteenth surfaces. The second lens unit U2 corresponds to nineteenth to twenty-fifth surfaces. The third lens unit U3 corresponds to twenty-sixth and twenty-eighth surfaces. The diaphragm SP corresponds to a twenty-ninth surface. The fourth lens unit U4 corresponds to thirtieth and thirty-first surfaces. The fifth lens unit US corresponds to thirty-second to forty-eighth surfaces.
The first lens unit U1 includes a first lens subunit (first to sixth surfaces) that has a negative refractive power and is not moved for focusing, a second lens subunit (seven and eighth surfaces) that has a negative refractive power and is moved to the image side during focusing from the infinity object to the short-distance object, and a third lens subunit (ninth to eighteenth surfaces) that has a positive refractive power and is not moved during focusing. In numerical example 5, the maximum air spacing mD12 between the third lens unit U3 and the fourth lens unit U4 is a distance obtained at a focal length of 28.5 mm.
Table 1 summarizes the values of the conditions expressed in the expressions (1) to (13) in Example 5 (numerical example 5). The zoom lens according to Example 5 satisfies each condition, and has a small size, a light weight, a wide angle of view, and a high optical performance in the entire zoom range. In particular, in this example, the fourth lens unit U4 includes (consists of) two lenses or a single negative lens a single positive lens, and the fifth lens unit U5 includes (consists of) a single positive lens, so that the zoom lens has a wide angle of view, a small size, a light weight, a bright aperture diameter ratio, and a high optical performance. The diaphragm SP is moved independently of other lens units, and thus the zoom lens becomes smaller and lighter and the degree of freedom is improved in the aberration correction.
A zoom lens according to Example 6 (numerical example 6) illustrated in
In this example, the second lens unit U2 corresponds to the n-th moving lens unit, the third lens unit U3 corresponds to the finally-moving negative lens unit m2, the fourth lens unit U4 corresponds to the finally-moving positive lens unit m1, and the fifth lens unit. US corresponds to the final lens unit r. The diaphragm SP is disposed between the second lens unit U2 and the third lens unit U3, and is moved independently of these lens units during zooming.
In numerical example 6, the first lens unit U1 corresponds to first to thirteenth surfaces. The second lens unit U2 corresponds to fourteenth to twentieth surfaces. The diaphragm SP corresponds to a twenty-first surface. The third lens unit U3 corresponds to twenty-second and twenty-third surfaces. The fourth lens unit U4 corresponds to twenty-fourth to twenty-sixth surfaces. The fifth lens unit US corresponds to twenty-seventh to thirty-eighth surfaces.
The first lens unit U1 includes a first lens subunit (first to sixth surfaces) that has a negative refractive power and is not moved for focusing, a second lens subunit (seventh and eighth surfaces) that has a negative refractive power and is moved to the image side during focusing from the infinity object to the short-distance object, and a third lens subunit (ninth to thirteenth surfaces) that has a positive refractive power and is not moved during focusing. In numerical example 6, the maxim wn air spacing mD12 between the third lens unit U3 and the fourth lens unit U4 is a distance obtained at a focal length of 27 mm.
Table 1 summarizes the values of the conditions expressed in the expressions (1) to (13) in Example 6 (numerical example 6). The zoom lens according to Example 6 satisfies each condition, and has a small size, a light weight, a wide angle of view, and a high optical performance in the entire zoom range. In particular, in this example, the third lens unit U3 includes (consists of) a single negative lens and the fourth lens unit U4 includes (consists of) two lenses or a single negative lens and a single positive lens, so that the zoom lens has a wide angle of view; a small size, a light weight, a bright aperture diameter ratio, and a high optical performance. Moreover, the diaphragm SP is moved independently of other lens units, and thus the zoom lens becomes smaller and lighter and the degree of freedom is improved in the aberration correction.
(Numerical Example 1)
(Numerical Example 2)
(Numerical Example 3)
(Numerical Example 4)
(Numerical Example 5)
(Numerical Example 6)
The zoom lens 101 includes a first lens unit F, a zooming unit LZ included in the subsequent unit, and a rear unit R used for imaging. The first lens unit F is a lens unit that is moved during focusing. The zooming unit LZ includes a plurality of lens units that are moved during zooming. The diaphragm SP is moved during zooming. Reference numerals 114 and 115 denote driving mechanisms such as a helicoid and a cam that drive lens units included in the first lens unit F and the zooming unit LZ in the optical axis direction, respectively.
Reference numerals 116 to 118 denote motors that drive the driving mechanisms 114 and 115 and the diaphragm SP. Reference numerals 119 to 121 denote detectors such as an encoder, a potentiometer, or a photosensor, each of which detects a position of the first lens unit F, the zooming unit LZ, or the diaphragm SP in the optical axis direction, or an aperture diameter of the diaphragm SP.
In the camera 124, reference numeral 109 denotes a glass block corresponding to an optical filter and a color separating optical system, and reference numeral 110 denotes an image sensor (an image pickup element or a photoelectric conversion element), such as a CCD sensor and CMOS sensor, that receives an object image formed by the zoom lens 101. Reference numerals 111 and 122 denote CPUs that control the camera 124 and the zoom lens 101.
Using the zoom lens according to each example in this way can provide an image pickup apparatus having a high optical performance.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2021-020779, filed on Feb. 12, 2021, which is hereby incorporated by reference herein in its entirety.
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