Patent Application
20240201475
The present invention relates to a zoom optical system, an optical apparatus, and a method for manufacturing the zoom optical system.
Conventionally, a zoom optical system that is suitable for a photographing camera, an electronic still camera, a video camera, and the like has been proposed (for example, refer to Patent literature 1). With such a zoom optical system, it is difficult to achieve bright and favorable optical performance with a small size.
A zoom optical system according to a first invention consists of a first lens group having positive refractive power and a rear group comprising a plurality of lens groups, the lens groups being arranged in order from an object side along an optical axis, a space between the lens groups adjacent to each other changes upon zooming, the plurality of lens groups in the rear group include a second lens group having positive refractive power and disposed closest to the object side in the rear group, and the following conditional expression is satisfied,
0.15<f2/f1<0.80
A zoom optical system according to a second invention consists of a first lens group having positive refractive power and a rear group comprising a plurality of lens groups, the lens groups being arranged in order from an object side along an optical axis, upon zooming from a wide-angle end state to a telephoto end state, the first lens group moves to the object side along the optical axis and the space between the lens groups adjacent to each other changes, the first lens group comprises a front fixed group having a position fixed relative to an image surface upon focusing and a front focusing group that moves along the optical axis upon focusing, the groups being arranged in order from the object side along the optical axis, and the following conditional expressions are satisfied,
0.60<fP1/(−fF1)<1.00
0.80<(−fF1)/fw<1.40
An optical apparatus according to the present invention comprises the above-described zoom optical system.
A first method for manufacturing a zoom optical system consisting of a first lens group having positive refractive power and a rear group comprising a plurality of lens groups, the lens groups being arranged in order from an object side along an optical axis,
0.15<f2/f1<0.80
A second method for manufacturing a zoom optical system consisting of a first lens group having positive refractive power and a rear group comprising a plurality of lens groups, the lens groups being arranged in order from an object side along an optical axis,
0.60<fP1/(−fF1)<1.00
0.80<(−fF1)/fw<1.40
Preferable embodiments according to the present invention will be described below. First, a camera (optical apparatus) comprising a zoom optical system according to the present embodiment will be described below with reference to
Light from an object is collected by the zoom optical system ZL of the photographing lens 3 and incident on an image surface I of the image capturing element 4. After being incident on the image surface I, the light from the object is photoelectrically converted by the image capturing element 4 and recorded as digital image data in a non-shown memory. The digital image data recorded in the memory can be displayed on the liquid crystal screen 5 in accordance with an operation by a user. Note that the camera may be a mirrorless camera or may be a single-lens reflex type camera including a quick return mirror. The zoom optical system ZL shown in
A zoom optical system according to a first embodiment will be described below. As shown in
With the above-described configuration, the zoom optical system ZL according to the first embodiment satisfies the following Conditional Expression (1).
0.15<f2/f1<0.80 (1)
According to the first embodiment, it is possible to obtain a zoom optical system having a small size and bright and favorable optical performance, and an optical apparatus comprising the zoom optical system. The zoom optical system ZL according to the first embodiment may be a zoom optical system ZL (2) shown in
Conditional Expression (1) defines an appropriate relation between the focal length of the first lens group G1 and the focal length of the second lens group G2. Note that the focal length of the first lens group G1 is the focal length of the first lens group G1 upon focusing on infinity. When Conditional Expression (1) is satisfied, it is possible to obtain favorable optical performance in the entire range of zooming.
When the correspondence value of Conditional Expression (1) is out of the above-described range, it is difficult to obtain favorable optical performance in at least part of the range of zooming. It is possible to secure the advantageous effect of the present embodiment by setting the upper limit value of Conditional Expression (1) to 0.75, 0.70, 0.65, 0.60, 0.55, 0.50, 0.45, and 0.40. Moreover, it is possible to secure the advantageous effect of the present embodiment by setting the lower limit value of Conditional Expression (1) to 0.18, 0.20, 0.23, 0.25, 0.28, and 0.30.
A zoom optical system according to a second embodiment will be described below. As shown in
With the above-described configuration, the zoom optical system ZL according to the second embodiment satisfies the following Conditional Expressions (2) and (3).
0.60<fP1/(−fF1)<1.00 (2)
0.80<(−fF1)/fw<1.40 (3)
According to the second embodiment, it is possible to obtain a zoom optical system having a small size and bright and favorable optical performance, and an optical apparatus comprising the zoom optical system. The zoom optical system ZL according to the second embodiment may be the zoom optical system ZL (2) shown in
Conditional Expression (2) defines an appropriate relation between the focal length of the front fixed group GP1 and the focal length of the front focusing group GF1. Conditional Expression (3) defines an appropriate relation between the focal length of the front focusing group GF1 and the focal length of the zoom optical system ZL in the wide-angle end state. When Conditional Expressions (2) and (3) are satisfied, it is possible to have a small size and favorable optical performance upon focusing on a close distance object.
When the correspondence value of Conditional Expression (2) is out of the above-described range, it is difficult to obtain favorable optical performance upon focusing on a close distance object. It is possible to secure the advantageous effect of the present embodiment by setting the upper limit value of Conditional Expression (2) to 0.98, 0.96, 0.95, 0.93, 0.90, 0.88, and 0.85. Moreover, it is possible to secure the advantageous effect of the present embodiment by setting the lower limit value of Conditional Expression (2) to 0.63, 0.65, 0.68, 0.70, 0.73, 0.75, 0.76, and 0.80.
When the correspondence value of Conditional Expression (3) is out of the above-described range, as well, it is difficult to obtain favorable optical performance upon focusing on a close distance object. It is possible to secure the advantageous effect of the present embodiment by setting the upper limit value of Conditional Expression (3) to 1.35, 1.33, 1.30, 1.26, 1.25, 1.23, and 1.20. Moreover, it is possible to secure the advantageous effect of the present embodiment by setting the lower limit value of Conditional Expression (3) to 0.83, 0.85, 0.88, 0.90, 0.93, 0.95, 0.96, and 1.00.
The zoom optical system ZL according to any of the first and second embodiments preferably satisfies the following Conditional Expression (4).
1.20<ft/fw<2.00 (4)
Conditional Expression (4) defines an appropriate range of the zooming ratio of the zoom optical system ZL. When Conditional Expression (4) is satisfied, it is possible to excellently correct a variety of aberrations such as curvature of field in the entire range of zooming.
When the correspondence value of Conditional Expression (4) exceeds the upper limit value, it is difficult to correct curvature of field in at least part of the range of zooming. It is possible to secure the advantageous effect of each embodiment by setting the upper limit value of Conditional Expression (4) to 1.90, 1.80, 1.70, and 1.60.
When the correspondence value of Conditional Expression (4) is below the lower limit value, the zooming ratio of the zoom optical system ZL is too small and thus the zoom optical system ZL cannot function as a zoom optical system (zoom lens). It is possible to secure the advantageous effect of each embodiment by setting the lower limit value of Conditional Expression (4) to 1.25, 1.30, 1.35, 1.40, 1.43, 1.45, and 1.48.
The zoom optical system ZL according to any of the first and second embodiments preferably satisfies the following Conditional Expression (5).
0.01<Bfw/TLw<0.20 (5)
Conditional Expression (5) defines an appropriate relation between the back focus of the zoom optical system ZL in the wide-angle end state and the entire length of the zoom optical system ZL in the wide-angle end state. When Conditional Expression (5) is satisfied, it is possible to excellently correct curvature of field.
When the correspondence value of Conditional Expression (5) exceeds the upper limit value, the relative length of the back focus the zoom optical system ZL relative to the entire length thereof is too long and thus it is difficult to correct curvature of field. It is possible to secure the advantageous effect of each embodiment by setting the upper limit value of Conditional Expression (5) to 0.18, 0.15, 0.12, and 0.10.
When the correspondence value of Conditional Expression (5) is below the lower limit value, the entire length of the zoom optical system ZL is long and thus it is difficult to have the zoom optical system ZL in a small size and correct curvature of field. It is possible to secure the advantageous effect of each embodiment by setting the lower limit value of Conditional Expression (5) to 0.02, 0.04, 0.05, 0.06, and 0.07.
The zoom optical system ZL according to any of the first and second embodiments preferably satisfies the following Conditional Expression (6).
0.60<YLE/IHw<1.00 (6)
Conditional Expression (6) defines an appropriate relation between the effective diameter of the lens disposed closest to the image side in the zoom optical system ZL and the maximum image height of the zoom optical system ZL in the wide-angle end state. Hereinafter, the lens disposed closest to the image side in the zoom optical system ZL is also referred to as a final lens. In each embodiment, the effective diameter of the final lens is the effective diameter of a lens surface of the final lens on the image side in the wide-angle end state. When Conditional Expression (6) is satisfied, it is possible to excellently correct curvature of field.
When the correspondence value of Conditional Expression (6) exceeds the upper limit value, the effective diameter of the final lens is large and thus it is difficult to have the zoom optical system ZL in a small size and correct curvature of field. It is possible to secure the advantageous effect of each embodiment by setting the upper limit value of Conditional Expression (6) to 0.96, 0.95, 0.93, 0.90, 0.88, and 0.85.
When the correspondence value of Conditional Expression (6) is below the lower limit value, the effective diameter of the final lens is small and thus it is difficult to correct curvature of field. It is possible to secure the advantageous effect of each embodiment by setting the lower limit value of Conditional Expression (6) to 0.65, 0.70, 0.73, 0.75, 0.78, and 0.80.
The zoom optical system ZL according to any of the first and second embodiments preferably satisfies the following Conditional Expression (7).
FNOw<2.8 (7)
Conditional Expression (7) defines an appropriate range of the F-number of the zoom optical system ZL in the wide-angle end state. Conditional Expression (7) is preferably satisfied because a bright zoom optical system is obtained. It is possible to secure the advantageous effect of each embodiment by setting the upper limit value of Conditional Expression (7) to 2.50, 2.40, 2.20, 2.00, and 1.90. The lower limit value of Conditional Expression (7) may be 1.20, 1.40, 1.50, 1.80 or larger.
The zoom optical system ZL according to any of the first and second embodiments preferably satisfies the following Conditional Expression (8).
10.00°<2ωw<35.00° (8)
Conditional Expression (8) defines an appropriate range of the full angle of view of the zoom optical system ZL in the wide-angle end state. Conditional Expression (8) is preferably satisfied because a zoom optical system in an intermediate telephoto range is obtained. It is possible to secure the advantageous effect of each embodiment by setting r limit value of Conditional Expression (8) to 32.00°, 30.00°, 29.00°, and 28.00°. It is possible to secure the advantageous effect of each embodiment by setting the lower limit value of Conditional Expression (8) to 15.00°, 20.00°, 24.00°, and 27.00°.
The zoom optical system ZL according to any of the first and second embodiments preferably satisfies the following Conditional Expression (9).
0.30<fw/f1<0.70 (9)
Conditional Expression (9) defines an appropriate relation between the focal length of the zoom optical system ZL in the wide-angle end state and the focal length of the first lens group G1. When Conditional Expression (9) is satisfied, it is possible to excellently correct spherical aberration in the entire range of zooming.
When the correspondence value of Conditional Expression (9) exceeds the upper limit value, the refractive power (power) of the first lens group G1 is too strong and thus it is difficult to correct spherical aberration. It is possible to secure the advantageous effect of each embodiment by setting the upper limit value of Conditional Expression (9) to 0.68, 0.65, 0.62, 0.58, and 0.55.
When the correspondence value of Conditional Expression (9) is below the lower limit value, the refractive power of the first lens group G1 is too weak and thus the zoom optical system ZL needs to be large. Thus, it is difficult to have the zoom optical system ZL in a small size and correct spherical aberration. It is possible to secure the advantageous effect of each embodiment by setting the lower limit value of Conditional Expression (9) to 0.33, 0.35, 0.38, 0.42, and 0.45.
In the zoom optical system ZL according to each of the first and second embodiments, the plurality of lens groups in the rear group GR preferably include the second lens group G2 having positive refractive power and disposed closest to the object side in the rear group GR, and the following Conditional Expression (10) is preferably satisfied.
0.30<f2/fRw<0.65 (10)
Conditional Expression (10) defines s an appropriate relation between the focal length of the second lens group G2 and the combined focal length of the rear group GR in the wide-angle end state. When Conditional Expression (10) is satisfied, it is possible to excellently correct spherical aberration in the entire range of zooming.
When the correspondence value of Conditional Expression (10) exceeds the upper limit value, the refractive power (power) of the second lens group G2 is too weak and thus it is difficult to correct curvature of field. It is possible to secure the advantageous effect of each embodiment by setting the upper limit value of Conditional Expression (10) to 0.62, 0.60, 0.58, 0.55, and 0.52.
When the correspondence value of Conditional Expression (10) is below the lower limit value, the refractive power of the second lens group G2 is too strong and thus it is difficult to correct spherical aberration. It is possible to secure the advantageous effect of each embodiment by setting the lower limit value of Conditional Expression (10) to 0.32, 0.34, 0.35, 0.36, 0.38, and 0.40.
In the zoom optical system ZL according to each of the first and second embodiments, the plurality of lens groups in the rear group GR preferably include a final lens group GE disposed closest to the image side in the rear group GR, and the following Conditional Expression (11) is preferably satisfied.
0.50<(−fGE)/fw<1.00 (11)
Conditional Expression (11) defines an appropriate relation between the focal length of the final lens group GE and the focal length of the zoom optical system ZL in the wide-angle end state. When Conditional Expression (11) is satisfied, the zoom optical system ZL can have a small size and excellently correct curvature of field.
When the correspondence value of Conditional Expression (11) exceeds the upper limit value, the refractive power (power) of the final lens group GE is too weak and thus it is difficult to correct curvature of field. It is possible to secure the advantageous effect of each embodiment by setting the upper limit value of Conditional Expression (11) to 0.98, 0.95, 0.93, 0.90, 0.88, 0.85, 0.83, and 0.80.
When the correspondence value of Conditional Expression (11) is below the lower limit value, the refractive power of the final lens group GE is too strong and thus it is difficult to correct distortion and chromatic aberration of magnification. It is possible to secure the advantageous effect of each embodiment by setting the lower limit value of Conditional Expression (11) to 0.53, 0.55, 0.58, 0.60, 0.63, 0.65, 0.68, 0.70, and 0.72.
The zoom optical system ZL according to any of the first and second embodiments preferably satisfies the following Conditional Expression (12).
1.00<(L1r2+L1r1)/(L1r2−L1r1)<2.50 (12)
Conditional Expression (12) defines an appropriate range of a shape factor of the lens disposed closest to the object side in the zoom optical system ZL. When Conditional Expression (12) is satisfied, it is possible to excellently correct a variety of aberrations such as coma aberration in the entire range of zooming.
When the correspondence value of Conditional Expression (12) exceeds the upper limit value, it is difficult to correct spherical aberration. It is possible to secure the advantageous effect of each embodiment by setting the upper limit value of Conditional Expression (12) to 2.40, 2.25, 2.10, 2.00, 1.95, 1.90, 1.85, and 1.80.
When the correspondence value of Conditional Expression (12) is below the lower limit value, it is difficult to correct coma aberration. It is possible to secure the advantageous effect of each embodiment by setting the lower limit value of Conditional Expression (12) to 1.05, 1.10, 1.15, 1.20, 1.25, 1.30, 1.35, and 1.40.
The zoom optical system ZL according to any of the first and second embodiments preferably satisfies the following Conditional Expression (13).
1.50<(LEr2+LEr1)/(LEr2−LEr1)<3.00 (13)
where,
Conditional Expression (13) defines an appropriate range of a shape factor of the lens (final lens) disposed closest to the image side in the zoom optical system ZL. When Conditional Expression (13) is satisfied, it is possible to excellently correct a variety of aberrations such as curvature of field in the entire range of zooming.
When the correspondence value of Conditional Expression (13) exceeds the upper limit value, it is difficult to correct spherical aberration. It is possible to secure the advantageous effect of each embodiment by setting the upper limit value of Conditional Expression (13) to 2.90, 2.80, 2.70, 2.60, 2.50, 2.45, 2.40, 2.35, and 2.30.
When the correspondence value of Conditional Expression (13) is below the lower limit value, it is difficult to correct coma aberration. It is possible to secure the advantageous effect of each embodiment by setting the lower limit value of Conditional Expression (13) to 1.60, 1.65, 1.75, 1.80, 1.85, 1.90, 1.95, and 2.00.
The zoom optical system ZL according to any of the first and second embodiments preferably satisfies the following Conditional Expression (14).
1.00<f1/fRw<1.80 (14)
Conditional Expression (14) defines an appropriate relation between the focal length of the first lens group G1 and the combined focal length of the rear group GR in the wide-angle end state. When Conditional Expression (14) is satisfied, it is possible to excellently correct spherical aberration in the entire range of zooming.
When the correspondence value of Conditional Expression (14) exceeds the upper limit value, the refractive power (power) of the first lens group G1 is too weak and thus the zoom optical system ZL needs to be large. Thus, it is difficult to have the zoom optical system ZL in a small size and correct spherical aberration. It is possible to secure the advantageous effect of each embodiment by setting the upper limit value of Conditional Expression (14) to 1.75, 1.70, 1.68, 1.65, 1.63, and 1.60.
When the correspondence value of Conditional Expression (14) is below the lower limit value, the refractive power of the first lens group G1 is too strong and thus it is difficult to correct spherical aberration. It is possible to secure the advantageous effect of each embodiment by setting the lower limit value of Conditional Expression (14) to 1.03, 1.05, 1.08, and 1.10.
In the zoom optical system ZL according to each of the first and second embodiments, the plurality of lens groups in the rear group GR preferably include the second lens group G2 having positive refractive power and disposed closest to the object side in the rear group GR, and a third lens group G3 disposed side by side on the image side of the second lens group G2, and the space between the second lens group G2 and the third lens group G3 preferably decreases upon zooming from the wide-angle end state to the telephoto end state.
The zoom optical system ZL according to any of the first and second embodiments preferably comprises an aperture stop S disposed between the first lens group G1 and the rear group GR, and the first lens group G1 preferably moves along the optical axis together with the aperture stop S upon zooming.
In the zoom optical system ZL according to each of the first and second embodiments, the first lens group G1 preferably comprises the front focusing group GF1 that moves along the optical axis upon focusing, the rear group GR preferably comprises a rear focusing group GF2 that moves along the optical axis with a locus different from that of the front focusing group GF1 upon focusing, and at least part of any one of the plurality of lens groups in the rear group GR is preferably included in the rear focusing group GF2.
In the zoom optical system ZL according to each of the first and second embodiments, the front focusing group GF1 and the rear focusing group GF2 may satisfy the following Conditional Expression (15).
−0.30<fF2/fF1<0.30 (15)
Conditional Expression (15) defines an appropriate relation between the focal length of the front focusing group GF1 and the focal length of the rear focusing group GF2. When Conditional Expression (15) is satisfied, it is possible to excellently prevent variation in curvature of field upon focusing in the entire range of zooming.
When the correspondence value of Conditional Expression (15) exceeds the upper limit value, it is difficult to prevent variation in curvature of field upon focusing. It is possible to secure the advantageous effect of each embodiment by setting the upper limit value of Conditional Expression (15) to 0.28, 0.25, 0.23, 0.20, and 0.18.
When the correspondence value of Conditional Expression (15) is below the lower limit value, as well, it is difficult to prevent variation in curvature of field upon focusing. It is possible to secure the advantageous effect of each embodiment by setting the lower limit value of Conditional Expression (15) to −0.25, −0.15, −0.10, −0.05, −0.01, 0.01, and 0.02.
In the zoom optical system ZL according to each of the first and second embodiments, the front focusing group GF1 and the rear focusing group GF2 may satisfy the following Conditional Expression (16).
0.01<fF2/(−fF1)<0.30 (16)
Conditional Expression (16) defines an appropriate relation between the focal length of the front focusing group GF1 and the focal length of the rear focusing group GF2. When Conditional Expression (16) is satisfied, it is possible to excellently prevent variation in curvature of field upon focusing in the entire range of zooming.
When the correspondence value of Conditional Expression (16) exceeds the upper limit value, it is difficult to prevent variation in curvature of field upon focusing. It is possible to secure the advantageous effect of each embodiment by setting the upper limit value of Conditional Expression (16) to 0.28, 0.25, 0.23, 0.20, and 0.18.
When the correspondence value of Conditional Expression (16) is below the lower limit value, as well, it is difficult to prevent variation in curvature of field upon focusing. It is possible to secure the advantageous effect of each embodiment by setting the lower limit value of Conditional Expression (16) to 0.02.
An outline of a method for manufacturing the zoom optical system ZL according to the first embodiment will be described below with reference to
An outline of a method for manufacturing the zoom optical system ZL according to the second embodiment will be described below with reference to
The zoom optical system ZL according to an example of each embodiment will be described below with reference to the accompanying drawings.
In
Among Tables 1 to 4 below, Table 1 is a table listing various data in the first example, Table 2 is a table listing various data in the second example, Table 3 is a table listing various data in the third example, and Table 4 is a table listing various data in the fourth example. In each example, aberration characteristics are calculated for the d-line (wavelength=587.6 nm) and the g-line (wavelength=435.8 nm).
In each table of [General Data], f represents the focal length of the entire lens system, FNO represents the F-number, 2ω represents the angle of view (in the unit of ° (degrees); ω represents the half angle of view), and Ymax represents the maximum image height. In addition, TL represents a distance as the sum of BF and the distance from a frontmost lens surface to a final lens surface on the optical axis upon focusing on infinity, and BF represents the distance (back focus) from the final lens surface to the image surface I on the optical axis upon focusing on infinity. Note that these values are listed for each of the zooming states of the wide-angle end (W) and the telephoto end (T).
In each table of [General Data], the value of YLE represents the effective diameter of the lens (final lens) disposed closest to the image side in the zoom optical system. The value of IHw represents the maximum image height of the zoom optical system in the wide-angle end state. The value of fP1 represents the focal length of the front fixed group. The value of fF1 represents the focal length of the front focusing group. The value of fRw represents the combined focal length of the rear group in the wide-angle end state. The value of fF2 represents the focal length of the rear focusing group.
In each table of [Lens Data], a surface number represents the order of an optical surface from the object side in a direction in which a light beam proceeds, R represents the radius of curvature (defined to have a positive value for a surface having a curvature center positioned on the image side) of an optical surface, D represents a surface distance that is the distance on the optical axis from an optical surface to the next optical surface (or the image surface), nd represents the refractive index of the material of an optical member at the d-line, and vd represents the Abbe number of the material of an optical member with reference to the d-line. The symbol “∞” for the radius of curvature indicates a flat surface or an opening, and “(aperture stop S)” represents an aperture stop S. Notation of the refractive index nd of air=1.00000 is omitted. When an optical surface is aspherical, the symbol “*” is attached to the surface number, and the paraxial radius of curvature is listed in the column of the radius R of curvature.
In each table of [Aspherical Surface Data], the shape of each aspherical surface listed in [Lens Specifications] is expressed by Expression (A) below. In the expression, X(y) represents a distance (sag amount) in the optical axis direction from a tangent plane at the apex of the aspherical surface to a position on the aspherical surface at a height y, R represents the radius of curvature (paraxial radius of curvature) of a reference spherical surface, k represents a conic constant, and Ai represents the i-th order aspherical coefficient. The notation “E−n” represents “×10−n”. For example, 1.234E−05 represents 1.234×10−5. Note that the secondary aspherical coefficient A2 is zero, and notation thereof is omitted.
X(y)=(y2/R)/{1+(1−κxy2/R2)1/2}+A4xy4+A6xy6+A8xy8+A10xy10 (A)
Each table of [Variable Distance Data] lists surface distance for a surface number i of the surface distance “Di” in the table of [Lens Specifications]. Each table of [Variable Distance Data] lists the surface distance upon focusing on infinity and the surface distance upon focusing on a close distance object state.
Each table of [Lens Group Data] lists the starting surface (surface closest to the object side) and focal length of each lens group.
Unless otherwise stated, the unit “mm” is typically used for all data values such as the focal length f, the radius R of curvature, the surface distance D, and other lengths listed in the tables below, but each optical system can obtain equivalent optical performance when proportionally scaled up or down, and thus the values are not limited to the unit.
The above description of the tables is common to all examples, and any duplicate description is omitted below.
The first example will be described below with reference to
The first lens group G1 comprises a positive meniscus lens L11 having a convex surface toward the object side, a cemented lens formed by cementing a positive meniscus lens L12 having a convex surface toward the object side and a negative meniscus lens L13 having a convex surface toward the object side, a positive meniscus lens L14 having a convex surface toward the object side, and a cemented lens formed by cementing a biconvex positive lens L15 and a biconcave negative lens L16, the lenses being arranged in order from the object side along the optical axis.
The second lens group G2 comprises a biconcave negative lens L21, a biconvex positive lens L22, and a cemented lens formed by cementing a biconvex positive lens L23 and a negative meniscus lens L24 having a concave surface toward the object side, the lenses being arranged in order from the object side along the optical axis. The positive lens L23 has an aspherical lens surface on the object side.
The third lens group G3 comprises a cemented lens formed by cementing a positive meniscus lens L31 having a concave surface toward the object side and a biconcave negative lens L32, and a negative meniscus lens L33 having a concave surface toward the object side, the lenses being arranged in order from the object side along the optical axis. The negative lens L32 has an aspherical surface lens on the image side. The image surface I is disposed on the image side of the third lens group G3.
In the present example, the second lens group G2 and the third lens group G3 serve as the rear group GR having positive refractive power as a whole. The third lens group G3 corresponds to the final lens group GE disposed closest to the image side in the rear group GR. The negative meniscus lens L33 in the third lens group G3 corresponds to the final lens. The positive meniscus lens L11, the cemented lens formed by cementing the positive meniscus lens L12 and the negative meniscus lens L13, and the positive meniscus lens L14 in the first lens group G1 serve as the front fixed group GP1 having a position fixed relative to the image surface I upon focusing. The cemented lens formed by cementing the positive lens L15 and the negative lens L16 in the first lens group G1 serves as the front focusing group GF1 that moves along the optical axis upon focusing. Upon focusing on from an infinite distance object to a close distance object, the front focusing group GF1 (cemented lens formed by cementing the positive lens L15 and the negative lens L16 in the first lens group G1) moves to the image side along the optical axis.
Table 1 below lists data values of the zoom optical system according to the first example.
From the variety of aberration diagrams, it can be understood that the zoom optical system according to the first example has a variety of aberrations excellently corrected in both the wide-angle end state and the telephoto end state and has excellent imaging performance.
The second example will be described below with reference to
The first lens group G1 comprises a positive meniscus lens L11 having a convex surface toward the object side, a cemented lens formed by cementing a biconvex positive lens L12 and a biconcave negative lens L13, a positive meniscus lens L14 having a convex surface toward the object side, and a cemented lens formed by cementing a biconvex positive lens L15 and a biconcave negative lens L16, the lenses being arranged in order from the object side along the optical axis.
The second lens group G2 comprises a biconcave negative lens L21, a biconvex positive lens L22, and a cemented lens formed by cementing a biconvex positive lens L23 and a negative meniscus lens L24 having a concave surface toward the object side, the lenses being arranged in order from the object side along the optical axis. The positive lens L23 has an aspherical lens surface on the object side.
The third lens group G3 comprises a cemented lens formed by cementing a positive meniscus lens L31 having a concave surface toward the object side and a biconcave negative lens L32, and a negative meniscus lens L33 having a concave surface toward the object side, the lenses being arranged in order from the object side along the optical axis. The negative lens L32 has an aspherical surface lens on the image side. The image surface I is disposed on the image side of the third lens group G3.
In the present example, the second lens group G2 and the third lens group G3 serve as the rear group GR having positive refractive power as a whole. The third lens group G3 corresponds to the final lens group GE disposed closest to the image side in the rear group GR. The negative meniscus lens L33 in the third lens group G3 corresponds to the final lens. The positive meniscus lens L11, the cemented lens formed by cementing the positive lens L12 and the negative lens L13, and the positive meniscus lens L14 in the first lens group G1 serve as the front fixed group GP1 having a position fixed relative to the image surface I upon focusing. The cemented lens formed by cementing the positive lens L15 and the negative lens L16 in the first lens group G1 serves as the front focusing group GF1 that moves along the optical axis upon focusing. The cemented lens formed by cementing the positive lens L23 and the negative meniscus lens L24 in the second lens group G2 serves as the rear focusing group GF2 that moves along the optical axis upon focusing. Upon focusing on from an infinite distance object to a close distance object, the front focusing group GF1 (cemented lens formed by cementing the positive lens L15 and the negative lens L16 in the first lens group G1) moves to the image side along the optical axis and the rear focusing group GF2 (cemented lens formed by cementing the positive lens L23 and the negative meniscus lens L24 in the second lens group G2) moves to the object side along the optical axis.
Table 2 below lists data values of the zoom optical system according to the second example.
The third example will be described below with reference to
The first lens group G1 comprises a positive meniscus lens L11 having a convex surface toward the object side, a cemented lens formed by cementing a biconvex positive lens L12 and a biconcave negative lens L13, a biconvex positive lens L14, and a cemented lens formed by cementing a positive meniscus lens L15 having a concave surface toward the object side and a biconcave negative lens L16, the lenses being arranged in order from the object side along the optical axis.
The second lens group G2 comprises a biconcave negative lens L21, a biconvex positive lens L22, and a cemented lens formed by cementing a biconvex positive lens L23 and a negative meniscus lens L24 having a concave surface toward the object side, the lenses being arranged in order from the object side along the optical axis. The positive lens L23 has an aspherical lens surface on the object side.
The third lens group G3 comprises a cemented lens formed by cementing a positive meniscus lens L31 having a concave surface toward the object side and a negative meniscus lens L32 having a concave surface toward the object side, the lenses being arranged in order from the object side along the optical axis. The negative meniscus lens L32 has an aspherical surface lens on the image side.
The fourth lens group G4 comprises a negative meniscus lens L41 having a concave surface toward the object side. The image surface I is disposed on the image side of the fourth lens group G4.
In the present example, the second lens group G2, the third lens group G3, and the fourth lens group G4 serve as the rear group GR having positive refractive power as a whole. The fourth lens group G4 corresponds to the final lens group GE disposed closest to the image side in the rear group GR. The negative meniscus lens L41 in the fourth lens group G4 corresponds to the final lens. The positive meniscus lens L11 in the first lens group G1, the cemented lens formed by cementing the positive lens L12 and the negative lens L13, and the positive lens L14 serve as the front fixed group GP1 having a position fixed relative to the image surface I upon focusing. The cemented lens formed by cementing the positive meniscus lens L15 and the negative lens L16 in the first lens group G1 serves as the front focusing group GF1 that moves along the optical axis upon focusing. The entire third lens group G3 serves as the rear focusing group GF2 that moves along the optical axis upon focusing. Upon focusing on from an infinite distance object to a close distance object, the front focusing group GF1 (cemented lens formed by cementing the positive meniscus lens L15 and the negative lens L16 in the first lens group G1) moves to the image side along the optical axis and the rear focusing group GF2 (entire third lens group G3) moves to the image side along the optical axis with a locus (moving amount) different from that of the front focusing group GF1.
Table 3 below lists data values of the zoom optical system according to the third example.
The fourth example will be described below with reference to
The first lens group G1 comprises a positive meniscus lens L11 having a convex surface toward the object side, a cemented lens formed by cementing a positive meniscus lens L12 having a convex surface toward the object side and a negative meniscus lens L13 having a convex surface toward the object side, a positive meniscus lens L14 having a convex surface toward the object side, and a cemented lens formed by cementing a biconvex positive lens L15 and a biconcave negative lens L16, the lenses being arranged in order from the object side along the optical axis.
The second lens group G2 comprises a biconcave negative lens L21, a biconvex positive lens L22, and a cemented lens formed by cementing a biconvex positive lens L23 and a negative meniscus lens L24 having a concave surface toward the object side, the lenses being arranged in order from the object side along the optical axis. The positive lens L23 has an aspherical lens surface on the object side.
The third lens group G3 comprises a cemented lens formed by cementing a positive meniscus lens L31 having a concave surface toward the object side and a biconcave negative lens L32, and a negative meniscus lens L33 having a concave surface toward the object side, the lenses being arranged in order from the object side along the optical axis. The negative lens L32 has an aspherical surface lens on the image side. The image surface I is disposed on the image side of the third lens group G3.
In the present example, the second lens group G2 and the third lens group G3 serve as the rear group GR having positive refractive power as a whole. The third lens group G3 corresponds to the final lens group GE disposed closest to the image side in the rear group GR. The negative meniscus lens L33 in the third lens group G3 corresponds to the final lens. The positive meniscus lens L11, the cemented lens formed by cementing the positive meniscus lens L12 and the negative meniscus lens L13, and the positive meniscus lens L14 in the first lens group G1 serve as the front fixed group GP1 having a position fixed relative to the image surface I upon focusing. The cemented lens formed by cementing the positive lens L15 and the negative lens L16 in the first lens group G1 serves as the front focusing group GF1 that moves along the optical axis upon focusing. Upon focusing on from an infinite distance object to a close distance object, the front focusing group GF1 (cemented lens formed by cementing the positive lens L15 and the negative lens L16 in the first lens group G1) moves to the image side along the optical axis.
Table 4 below lists data values of the zoom optical system according to the fourth example.
The following presents a table of [Conditional expression correspondence value]. The table collectively lists values corresponding to Conditional Expressions (1) to (16) for all examples (first to fourth examples).
Acct each above-described example, it is possible to achieve a zoom optical system having a small size and bright and favorable optical performance.
The above-described examples are specific examples of the present application invention, and the present application invention is not limited thereto.
Contents of the following description may be applied as appropriate without losing the optical performance of a zoom optical system of the present embodiment.
Each above-described example of the zoom optical system of the present embodiment has a three-group configuration or a four-group configuration, but the present application is not limited thereto and the zoom optical system may have any other group configuration (for example, a five-group). Specifically, a lens or a lens group may be added closest to the object side or the image surface side in the zoom optical system of the present embodiment. Note that a lens group means a part including at least one lens and separated at an air distance that changes upon zooming.
The focusing lens groups may perform focusing on from an infinite distance object to a close distance object by moving one or a plurality of lens groups or a partial lens group in the optical axis direction. The focusing lens groups are also applicable to automatic focusing and also suitable for automatic focusing motor drive (using an ultrasonic wave motor or the like).
A lens group or a partial lens group may be moved with a component in a direction orthogonal to the optical axis or may be rotationally moved (swung) in an in-plane direction including the optical axis, thereby achieving a vibration-proof lens group that corrects image blur caused by camera shake.
A lens surface may be so formed as to be a spherical surface, a flat surface, or an aspherical surface. In the case where a lens surface is a spherical or flat surface, the lens is readily processed, assembled, and adjusted, whereby degradation in the optical performance due to errors in the lens processing, assembly, and adjustment is preferably avoided. Further, even when an image plane is shifted, the amount of degradation in drawing performance is preferably small.
In the case where the lens surface is an aspherical surface, the aspherical surface may be any of a ground aspherical surface, a glass molded aspherical surface that is a glass surface so molded in a die as to have an aspheric shape, and a composite aspherical surface that is a glass surface on which aspherically shaped resin is formed. The lens surface may instead be a diffractive surface, or the lenses may be any of a distributed index lens (GRIN lens) or a plastic lens.
The aperture stop is preferably disposed between the first lens group and the second lens group, but no member as an aperture stop may be provided and the frame of a lens may serve as the aperture stop.
Each lens surface may be provided with an antireflection film having high transmittance over a wide wavelength range to achieve good optical performance that reduces flare and ghost and achieves high contrast.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-211906 | Dec 2020 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/040485 | 11/4/2021 | WO |
