Patent Grant
11249290
The aspect of the embodiments relates to a zoom lens and an image pickup apparatus including the same, which are suitable for an image pickup optical system to be used with an image pickup apparatus using an image pickup element, such as a video camera, an electronic still camera, a broadcasting camera, or a monitoring camera.
It is required of an image pickup optical system to be used with image pickup apparatus to be a zoom lens having a short total length (distance from the first lens surface to an image plane), being compact as the entire system of the zoom lens, and having a high zoom ratio and high optical performance over the entire zoom range. As a zoom lens satisfying those requirements, there is known a positive-lead type zoom lens, in which a lens unit having a positive refractive power is arranged closest to an object side (Japanese Patent Application Laid-Open No. H11-202202).
In Japanese Patent Application Laid-Open No. H11-202202, the zoom lens consists of, in order from the object side to an image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a fourth lens unit having a negative refractive power.
According to at least one embodiment of the disclosure, there is provided a zoom lens including, in order from an object side to an image side: a first lens unit having a positive refractive power; a second lens unit having a negative refractive power; a third lens unit having a positive refractive power; and a fourth lens unit having a negative refractive power, wherein an interval between each pair of adjacent lens units is changed during zooming, wherein the first lens unit is configured not to move for zooming, and wherein the following inequalities are satisfied:
0.30<DT/fT<0.85;
0.02<BW/DW<0.14; and
0.145<f3/fT<0.450,
where DT is a total length of the zoom lens at a telephoto end, fT is a focal length of the zoom lens at the telephoto end, BW is a distance of a back focus at a wide-angle end, DW is a total length of the zoom lens at the wide-angle end, and f3 is a focal length of the third lens unit.
According to at least one embodiment of the disclosure, there is provided an image pickup apparatus including: a zoom lens; and an image pickup element configured to receive an optical image formed through the zoom lens, the zoom lens including, in order from an object side to an image side: a first lens unit having a positive refractive power; a second lens unit having a negative refractive power; a third lens unit having a positive refractive power; and a fourth lens unit having a negative refractive power, wherein an interval between each pair of adjacent lens units is changed during zooming, wherein the first lens unit is configured not to move for zooming, and wherein the following inequalities are satisfied:
0.30<DT/fT<0.85;
0.02<BW/DW<0.14; and
0.145<f3/fT<0.450,
Further features of the disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Now, exemplary embodiments of the disclosure are described with reference to the attached drawings.
The zoom lens of each of Embodiment of the disclosure includes, in order from an object side to an image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a fourth lens unit having a negative refractive power. An interval between each pair of adjacent lens units is changed during zooming. The first lens unit is configured not to move for zooming.
In the lens cross-sectional views of Embodiment 1 of
The second lens unit L2 and the fourth lens unit L4 are configured to move along mutually different loci for zooming. At the telephoto end as compared to the wide-angle end, the second lens unit L2 is configured to move toward an image side, and the fourth lens unit L4 is configured to move toward an object side. Further, during focusing from infinity to close distance, the fourth lens unit L4 is configured to move toward the image side.
Further, the third lens unit L3 is moved (shifted) in a direction having a component perpendicular to an optical axis to perform image stabilization.
In the lens cross-sectional views of Embodiment 3 of
In the lens cross-sectional views of Embodiment 4 of
In Embodiment 3 and Embodiment 4, the second lens unit L2 and the fourth lens unit L4 are configured to move along mutually different loci for zooming. At the telephoto end as compared to the wide-angle end, the second lens unit L2 is configured to move toward an image side, and the fourth lens unit L4 is configured to move toward an object side. Further, during focusing from infinity to close distance, the fourth lens unit L4 is configured to move toward the image side.
Further, the third lens unit L3 is moved (shifted) in a direction having a component perpendicular to an optical axis to perform image stabilization.
In the lens cross-sectional views, an optical block GB, for example, an optical low-pass filter or an infrared cut filter, is illustrated. At an image plane IP, an image pickup surface of an image pickup element (photoelectric conversion element), for example, a CCD sensor or a CMOS sensor, is arranged when the zoom lens is used as an image pickup optical system of a video camera or a digital still camera. An f-number determining member (aperture stop) SP serves as an aperture stop configured to determine (restrict) a light flux at the open f-number (Fno). An optical axis OA is also illustrated.
In spherical aberration diagrams of the longitudinal aberration diagrams, the solid line “d” indicates a d-line (wavelength: 587.6 mm), and the two-dot chain line “g” indicates a g-line (wavelength: 435.8 mm). In astigmatism diagrams, the broken line M indicates a meridional image plane, and the solid line S indicates a sagittal image plane. In chromatic-aberration-of-magnification diagrams, the two-dot chain line “g” is shown for the g-line.
Further, the lateral aberration diagrams show aberrations at respective image heights, and are aberration diagrams of the d-line at image heights of +100%, +70%, center, −70%, and −100% in order from the above. The broken line indicates a sagittal image plane, and the solid line indicates a meridional image plane.
The zoom lens of each of Embodiment 1 and 2 includes, in order from the object side to the image side, a first lens unit L1 having a positive refractive power, a second lens unit L2 having a negative refractive power, a third lens unit L3 having a positive refractive power, and a fourth lens unit LA having a negative refractive power.
The zoom lens of each of Embodiment 3 and 4 include, in order from the object side to the image side, a first lens unit L1 having a positive refractive power, a second lens unit L2 having a negative refractive power, a third lens unit L3 having a positive refractive power, and a fourth lens unit L4 having a negative refractive power. The zoom lens further includes a fifth lens unit L5 having a positive or negative refractive power arranged adjacent to, and on the image side of, the fourth lens unit LA. The fifth lens unit L5 has a positive refractive power in Embodiment 3, and the fifth lens unit L5 has a negative refractive power in Embodiment 4. By adopting the above-mentioned lens configuration, the entire zoom lens has a compact and simple configuration, and achieves a high zoom ratio and good optical performance.
Further, in the zoom lens of each of Embodiment, the first lens unit L1 is configured not to move with respect to the image plane for zooming. With this configuration, it is not required to drive the first lens unit L1, which tends to be increased in size, in particular, and a driving mechanism is simplified.
In each of Embodiment, the following inequalities are satisfied:
0.30<DT/fT<0.85 (1);
0.02<BW/DW<0.14 (2); and
0.145<f3/fT<0.450 (3),
where DT is a total length (value obtained by adding a value of an air-equivalent back focus to a distance from the first lens surface to the last lens surface) of the zoom lens at the telephoto end, fT is a focal length of the zoom lens at the telephoto end, BW is a distance of the back focus at the wide-angle end, DW is a total length of the zoom lens at the wide-angle end, and f3 is a focal length of the third lens unit L3.
Next, the technical meanings of the above-mentioned inequalities are described.
When the ratio of the inequality (1) exceeds the upper limit value of the inequality (1), a value of the total length DT of the zoom lens becomes much larger, and the entire zoom lens is increased in size. When the ratio falls below the lower limit value of the inequality (1), the value of the total length DT of the zoom lens becomes much smaller, and refractive powers of the respective lens units become much stronger (absolute values of refractive powers becomes much larger), with the result that it becomes difficult to correct various aberrations.
When the ratio of the inequality (2) exceeds the upper limit value of the inequality (2), a value of the back focus BW becomes much larger, and the entire zoom lens is increased in size. When the ratio falls below the lower limit value of the inequality (2), the value of the back focus BW becomes much smaller, and the zoom lens and the image pickup surface tend to interfere with each other.
When the ratio of the inequality (3) exceeds the upper limit value of the inequality (3), a value of the focal length f3 of the third lens unit L3 becomes much larger, and the positive refractive power of the third lens unit L3 becomes much weaker, with the result that the entire zoom lens is increased in size. When the ratio falls below the lower limit value of the inequality (3), the value of the focal length f3 becomes much smaller, and the positive refractive power of the third lens unit L3 becomes much stronger, with the result that it becomes difficult to correct spherical aberration and comatic aberration. Alternatively, when the third lens unit L3 is moved (shifted) in a direction perpendicular to the optical axis to perform image stabilization, it becomes difficult to correct decentering aberration.
In each of Embodiment, the numerical ranges of the inequality (1) to the inequality (3) are set as follows.
0.32<DT/fT<0.85 (1a)
0.03<BW/DW<0.13 (2a)
0.150<f3/fT<0.430 (3a)
Moreover, in each of Embodiment, the numerical ranges of the inequality (1a) to the inequality (3a) are set as follows.
0.35<DT/fT<0.84 (1b)
0.04<BW/DW<0.12 (2b)
0.155<f3/fT<0.400 (3b)
In each of the Embodiment, one or more of the following inequalities are satisfied:
−2.0<f3/f4<−0.4 (4)
0.31<f3/f1<0.80 (5)
−1.50<f3/f2<−0.70 (6)
−0.60<f4/fT<−0.08 (7)
where f4 is a focal length of the fourth lens unit L4, f1 is a focal length of the first lens unit L1, and f2 is a focal length of the second lens unit L2.
Next, the technical meanings of the above-mentioned inequalities are described.
When the ratio of the inequality (4) exceeds the upper limit value of the inequality (4), the value of the focal length f3 becomes much smaller, and the positive refractive power of the third lens unit L3 becomes much stronger, with the result that it becomes difficult to correct spherical aberration and comatic aberration. Alternatively, when the third lens unit L3 is moved (shifted) in the direction having the component perpendicular to the optical axis to perform image stabilization, it becomes difficult to correct decentering aberration. When the ratio falls below the lower limit value of the inequality (4), the value of the focal length f3 becomes much larger, and the positive refractive power of the third lens unit L3 becomes much weaker, with the result that the entire zoom lens is increased in size.
When the ratio of the inequality (5) exceeds the upper limit value of the inequality (5), the value of the focal length f3 becomes much larger, and the positive refractive power of the third lens unit L3 becomes much weaker, with the result that the entire zoom lens is increased in size. When the ratio falls below the lower limit value of the inequality (5), the value of the focal length f3 becomes much smaller, and the positive refractive power of the third lens unit L3 becomes much stronger, with the result that it becomes difficult to correct spherical aberration and comatic aberration. Alternatively, when the third lens unit L3 is moved (shifted) in the direction having the component perpendicular to the optical axis to perform image stabilization, it becomes difficult to correct decentering aberration.
When the ratio of the inequality (6) exceeds the upper limit value of the inequality (6), the value of the focal length f3 becomes much smaller, and the positive refractive power of the third lens unit L3 becomes much stronger, with the result that it becomes difficult to correct spherical aberration and comatic aberration. Alternatively, when the third lens unit L3 is moved (shifted) in the direction having the component perpendicular to the optical axis to perform image stabilization, it becomes difficult to correct decentering aberration. When the ratio falls below the lower limit value of the inequality (6), the value of the focal length f3 becomes much larger, and the positive refractive power of the third lens unit L3 becomes much weaker, with the result that the entire zoom lens is increased in size.
When the ratio of the inequality (7) exceeds the upper limit value of the inequality (7), the absolute value of the focal length f4 becomes much smaller, and the negative refractive power of the fourth lens unit L4 becomes much stronger, with the result that it becomes difficult to correct curvature of field and distortion. Alternatively, variations in various aberrations caused when the fourth lens unit L4 is moved along the optical axis to perform focusing becomes much larger. When the ratio falls below the lower limit value of the inequality (7), the absolute value of the focal length f4 becomes much larger, and the negative refractive power of the fourth lens unit L4 becomes much weaker, with the result that the entire zoom lens is increased in size.
Furthermore, in one Embodiment, the numerical ranges of the inequality (4) to the inequality (7) are set as follows.
−1.9<f3/f4<−0.5 (4a)
0.32<f3/f1<0.75 (5a)
−1.40<f3/f2<−0.80 (6a)
−0.55<f4/fT<−0.09 (7a)
Moreover, in one Embodiment, the numerical ranges of the inequality (4a) to the inequality (7a) are set as follows.
−1.8<f3/f4<−0.6 (4b)
0.33<f3/f1<0.70 (5b)
−1.30<f3/f2<−0.90 (6b)
−0.50<f4/fT<−0.10 (7b)
In each of Embodiment, a part or the whole of the third lens unit L3 is configured to move in the direction having the component perpendicular to the optical axis to perform image stabilization. With this configuration, it becomes easier to satisfactorily correct decentering aberration generated during the image stabilization.
The third lens unit L3 includes, in order from the object side to the image side, a cemented lens formed by cementing a positive lens and a negative lens, and a positive lens. With this configuration, spherical aberration and comatic aberration can be satisfactorily corrected, in particular. Alternatively, decentering aberration generated when the third lens unit L3 is moved (shifted) in the direction having the component perpendicular to the optical axis to perform image stabilization can be satisfactorily corrected.
In one embodiment, the third lens unit L3 include the aperture stop SP. With this configuration, the entire zoom lens can be made compact. Also, the third lens unit L3 is to be configured not to move with respect to the image plane for zooming. With this configuration, it becomes easier to simplify the driving mechanism configured to perform zooming.
In one embodiment, a part or the whole of the fourth lens unit L4 is to be configured to move along the optical axis to perform focusing. With this configuration, it becomes easier to suppress variations in various aberrations caused when the focusing is performed.
In one embodiment, the fourth lens unit L4 includes, in order from the object side to the image side, a positive lens and a negative lens. With this configuration, curvature of field and distortion can be satisfactorily corrected, in particular. Alternatively, it becomes easier to suppress the variations in various aberrations caused when the fourth lens unit L4 is moved along the optical axis to perform focusing.
As described above, according to each of Embodiment, the zoom lens having good image forming performance and good image stabilization with the compact and simple configuration can be obtained.
Next, referring to
In
Next, each of Numerical Embodiment, which correspond to each of Embodiment of the disclosure, respectively, is described. In each of Numerical Embodiment, Symbol “i” represents the order of a surface counted from the object side.
In each of Numerical Embodiment, Symbol ri represents a radius of curvature of an i-th lens surface in order from the object side. Symbol di represents a lens thickness and an air gap between an i-th surface and an (i+1)th surface in order from the object side. Symbols ndi and vdi represent a refractive index and an Abbe number with respect to the d-line of a material between the i-th surface and the (i+1)th surface in order from the object side, respectively.
Symbol BF is back focus, which is a value represented by an air-converted length from a final lens surface to a paraxial image plane. A total lens length is obtained by adding the length corresponding to the back focus BF to a distance from a forefront lens surface to the final lens surface.
The total length DT of the zoom lens at the telephoto end, the total length DW of the zoom lens at the wide-angle end, and the back focus BW at the wide-angle end described above also follow the above-mentioned definitions.
Moreover, a relationship between the conditional expressions described above and Embodiment is shown in Table 1.
(Numerical Data 1)
(Numerical Data 2)
(Numerical Data 3)
(Numerical Data 4)
While the disclosure has been described with reference to exemplary embodiments, it is to be understood that the disclosure 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. 2019-057699, filed Mar. 26, 2019, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2019-057699 | Mar 2019 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 8405915 | Hayakawa | Mar 2013 | B2 |
| 8611016 | Imaoka | Dec 2013 | B2 |
| 10432870 | Yamazoe | Oct 2019 | B2 |
| Number | Date | Country |
|---|---|---|
| H11-202202 | Jul 1999 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20200310089 A1 | Oct 2020 | US |
