JP2011186256A - Zoom optical system and electronic imaging apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom optical system in which while entire length is kept short in a both state of a collapsible state and a non-collapsible state, aberrations are satisfactorily corrected, and the variation of the aberrations when varying power from a wide angle end to a telephoto end is small, and also to provide an electronic imaging apparatus using the zoom optical system. <P>SOLUTION: In the zoom optical system which is composed of a plurality of lens groups and varies power by properly changing space between the plurality of lens groups, a first positive lens group, a second negative lens group, a third positive lens group and a fourth positive lens group are arranged in order from an object side. A surface nearest to the object side in the first lens group has such a shape that a convex surface turns to the object side. The zoom optical system satisfies an expression (1): SF<SB>G4</SB>=(r<SB>G4o</SB>+r<SB>G4i</SB>)/(r<SB>G4o</SB>-r<SB>G4i</SB>)>0. In the expression (1), SF<SB>G4</SB>is a shaping factor of the fourth lens group, r<SB>G4o</SB>is a radius of curvature of a surface nearest to the object side in the fourth lens group, and r<SB>G4i</SB>is a radius of curvature of a surface nearest to an image side in the fourth lens group. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a zoom optical system and an electronic imaging apparatus using the same.

  In recent years, in order to reduce the thickness of a compact camera, an optical system that is retracted and accommodated in a camera housing in a non-shooting state is known. In order to further reduce the thickness of such a compact camera, it is necessary to reduce the retractable thickness of the optical system.

  By the way, as a structure for retracting the optical system, there is known a structure in which a lens frame that holds the optical system is divided into a plurality of parts so that the optical system can be expanded and contracted. However, in order to reduce the retractable thickness of the optical system in such a configuration, it is necessary to increase the number of divisions of the lens frame. As a result, the weight of the entire lens frame increases, and the lens frames divided in the non-collapsed state are not easily arranged on the same axis, and the optical system is likely to be decentered. Therefore, when such a configuration is adopted, it is necessary to reduce the number of divisions while shortening the interval for dividing the lens frame.

  In order to satisfy these requirements, it is preferable to shorten the overall length of the optical system in both the retracted state and the non-collapsed state. An example of such an optical system is described in Patent Document 1 below. In the optical system described in Patent Document 1, the first lens group on the most object side is constituted by a cemented lens made up of a negative lens and a positive lens, thereby suppressing the occurrence of chromatic aberration and the first lens group. Is to reduce the thickness.

JP 2007-271711 A

  However, the optical system described in Patent Document 1 assumes a zoom magnification of about 5 to 7 times. For this reason, if the zoom magnification is to be increased to 10 times or more, it is necessary to increase the variation in the distance between the first lens group and the second lens group, so that there is a problem that the total length of the optical system at the telephoto end becomes long. . In this case, there is also a problem that fluctuations in various aberrations at the time of zooming from the wide-angle end to the telephoto end also become large.

  On the other hand, if it is attempted to increase the zoom magnification to 10 times or more without increasing the total length of the optical system at the telephoto end, it is necessary to increase the refractive power of each lens or lens group. There is a problem that aberrations become large and fluctuations in various aberrations at the time of zooming from the wide-angle end to the telephoto end become large.

  The present invention has been made in view of such problems of the prior art, and the object of the present invention is to provide a high zoom ratio of 10 times or more in both a retracted state and a non-collapsed state. Provided are a zoom optical system in which various aberrations are favorably corrected while keeping the overall length short in a state, and small fluctuations in various aberrations when zooming from the wide-angle end to the telephoto end, and an electronic imaging device using the same That is.

In order to achieve the above object, a zoom optical system according to the present invention is composed of a plurality of lens groups, and the zoom optical system performs zooming by appropriately changing the interval between the plurality of lens groups. In order from the side, a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group are arranged, and the most object side of the first lens group Is a shape with a convex surface facing the object side, and satisfies the following conditional expression (1).
SF _G4 = (r _G4o + r _G4i ) / (r _G4o -r _G4i )> 0 ... (1)
However, SF _G4 is the fourth lens group from the shaping factor, r _G4o is the radius of curvature of the most object-side surface of the fourth lens group, r _G4i the radius of curvature of the surface on the most image side of the fourth lens group is there.

In the zoom optical system of the present invention, it is preferable that the following conditional expression (2) is satisfied.
0.2 ≦ SF _G4 ≦ 5.0 ... (2)

  In the zoom optical system according to the present invention, it is preferable that the third lens group includes, in order from the object side, a positive single lens and a cemented lens including a positive lens and a negative lens.

  In the zoom optical system of the present invention, it is preferable that the first lens group includes only one lens component.

In the zoom optical system of the present invention, it is preferable that the following conditional expressions (3) and (4) are satisfied.
SF _G1o-G4i = (r _G1o + r _G4i ) / (r _G1o -r _G4i ) (3)
0 ≦ SF _G1o-G4i ≦ 0.4 ... (4)
Where SF _G1o-G4i is the shaping factor of the surface closest to the object side of the first lens group and the surface of the fourth lens group closest to the image side, and r _G1o is the radius of curvature of the surface closest to the object side of the first lens group. R _G4i is the radius of curvature of the most image-side surface of the fourth lens group.

In the zoom optical system of the present invention, it is preferable that the following conditional expression (5) is satisfied.
0.2 ≦ ΔD _w−w10 / L _t ≦ 0.35 ... (5)
Where ΔD _w−w10 is the amount of change in the distance between the first lens group and the second lens group from the wide-angle end to the state where the focal length is at least 10 times the focal length at the wide-angle end, and L _t is the telephoto end. Is the total length of the optical system.

  In the zoom optical system of the present invention, it is preferable that the second lens group includes a negative single lens, a negative cemented lens, and a positive single lens in order from the object side.

In the zoom optical system according to the present invention, when the second lens group includes a negative single lens, a negative cemented lens, and a positive single lens in order from the object side, the second lens It is preferable that the cemented lens of the group includes a negative lens and a positive lens, and satisfies the following conditional expression (6).
0.1 ≦ φ _G2n2 / φ _G2n1 ≦ 1.0 ... (6)
Where φ _G2n2 is the refractive power of the negative lens in the cemented lens of the second lens group, and φ _G2n1 is the refractive power of the negative single lens of the second lens group.

In the zoom optical system according to the present invention, when the second lens group includes, in order from the object side, a negative single lens, a negative cemented lens, and a positive single lens, the following conditional expression It is preferable to satisfy (7).
0.15 ≦ | φ _G2p2 / φ _G2n1 | ≦ 0.45 ... (7)
Where φ _G2p2 is the refractive power of the positive single lens of the second lens group, and φ _G2n1 is the refractive power of the negative single lens of the second lens group.

In the zoom optical system according to the present invention, when the second lens group includes a negative single lens, a negative cemented lens, and a positive single lens in order from the object side, the second lens It is preferable that the cemented lens of the group includes a negative lens and a positive lens, and satisfies the following conditional expression (8).
0.05 ≦ nd _{G2n2 −nd G2p1} ≦ 0.2 ... (8)
Here, nd _G2n2 is the refractive index at the d-line of the negative lens of the cemented lens of the second lens group, and nd _G2p1 is the refractive index at the d-line of the positive lens of the cemented lens of the second lens group.

In the zoom optical system according to the present invention, when the second lens group includes a negative single lens, a negative cemented lens, and a positive single lens in order from the object side, the second lens It is preferable that the cemented lens of the group includes a negative lens and a positive lens, and satisfies the following conditional expression (9).
20 ≦ νd _G2n2 −νd _G2p1 ≦ 50 ... (9)
Where νd _G2n2 is the Abbe number in the d-line of the negative lens of the cemented lens of the second lens group, and νd _G2p1 is the Abbe number in the d-line of the positive lens of the cemented lens in the second lens group.

In the zoom optical system of the present invention, the focal length of the entire optical system at the wide-angle end is f _w , the focal length of the entire optical system at the telephoto end is f _t , and the focal length of the entire optical system in the intermediate state is √ When (f _w × _ft ), it is preferable that the position of the second lens group in the intermediate state is closer to the object side than the positions at the wide-angle end and the telephoto end.

In the zoom optical system of the present invention, the focal length of the entire optical system at the wide-angle end is f _w , the focal length of the entire optical system at the telephoto end is f _t , and the focal length of the entire optical system in the intermediate state is √ when a (f _w × f _t), the position of the second lens group in the intermediate state, when of a position at the wide angle end and the telephoto end is the object side and satisfies the following conditional expression (10) .
−7.0 ≦ ΔV _G2w-m / ΔV _G2m-t ≦ −1.2 ... (10)
However, ΔV _G2w-m is represented by | V _G2m -V _G2w |, ΔV _G2m-t is represented by | V _G2t -V _G2m |, and V _G2w is the position of the second lens group at the wide angle end, V _G2m Is the position of the second lens group in the intermediate state, V _G2t is the position of the second lens group at the telephoto end, and the _signs of ΔV _G2w-m and ΔV _G2m-t are the image side of the second lens group The case of moving from to the object side is positive.

  In the zoom optical system of the present invention, it is preferable that the position of the second lens group at the telephoto end is closer to the object side than the position of the second lens group at the wide-angle end.

  In the zoom optical system according to the present invention, when the second lens group includes a negative single lens, a negative cemented lens, and a positive single lens in order from the object side, the second lens It is preferable that the cemented surface of the cemented lens of the group is an aspherical surface.

  In the zoom optical system according to the present invention, when the second lens group includes a negative single lens, a negative cemented lens, and a positive single lens in order from the object side, the second lens It is preferable that all surfaces of the cemented lens in the group are aspheric surfaces.

  In the zoom optical system according to the present invention, the second lens group includes, in order from the object side, a negative single lens, a negative cemented lens, and a positive single lens. When all the surfaces of the cemented lens are aspherical surfaces, when the direction from the object side to the image side on the optical axis is positive, the effective diameter of all the surfaces of the cemented lens in the second lens group is not The spherical amount is preferably a negative value.

In the zoom optical system according to the present invention, the second lens group includes, in order from the object side, a negative single lens, a negative cemented lens, and a positive single lens. When all surfaces of the cemented lens are aspheric surfaces, it is preferable that the following conditional expression (11) is satisfied.
10 ≦ (ASP _22c × | Δνd ₂₂ |) / (ASP _22o + ASP _22i ) ≦ 90
(11)
Where ASP _22c is the aspherical amount of the effective diameter of the cemented surface of the cemented lens of the second lens group, Δνd ₂₂ is the difference between the Abbe numbers of the two lenses constituting the cemented lens of the second lens group, and ASP _22o is An aspheric amount at the effective diameter of the object side surface of the cemented lens of the second lens group, and ASP _22i is an aspheric amount at the effective diameter of the image side surface of the cemented lens of the second lens group. The effective diameter is the smallest effective diameter of the effective diameters of the surfaces of the cemented lens of the second lens group.

  In the zoom optical system of the present invention, it is preferable that the fourth lens group includes only one lens component.

  In the zoom optical system of the present invention, it is preferable that when the fourth lens group is composed of only one lens component, the fourth lens group is composed of only one positive single lens.

In the zoom optical system according to the present invention, it is preferable that the following conditional expression (12) is satisfied.
0 ≦ | ΔV _G4w-t / f _w | ≦ 0.1 (12)
However, ΔV _G4w-t is represented by | V _G4t -V _G4w |
V _G4W the position of the fourth lens group at the wide-angle end, V _G4t the position of the fourth lens group at the telephoto end, f _w is the focal length of the entire optical system at the wide angle end, the [Delta] V _G4W-t The sign is positive when the fourth lens group moves from the image side to the object side.

  In the zoom optical system of the present invention, it is preferable that the fourth lens group does not move during zooming from the wide angle end to the telephoto end.

  In order to achieve the above object, an electronic image pickup apparatus of the present invention includes any one of the zoom optical systems described above.

  According to the present invention, the zoom magnification is a high magnification of 10 times or more, and various aberrations are favorably corrected while keeping the entire length short in both the retracted state and the non-collapsed state. It is possible to provide a zoom optical system in which fluctuations in various aberrations when zooming to the telephoto end is small, and an electronic imaging apparatus using the zoom optical system.

FIG. 2 is a cross-sectional view along the optical axis showing the optical configuration of the zoom optical system according to Embodiment 1 of the present invention when focusing on an object point at infinity, where (a) is a wide angle end, (b) is an intermediate, and (c) is an intermediate view. Each state at the telephoto end is shown. FIG. 2 is a diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration when the zoom optical system shown in FIG. 1 is focused on an object point at infinity, where (a) is the wide-angle end, (b) is the middle, (c ) Shows the state at the telephoto end. 2A and 2B are diagrams illustrating lateral coma aberration when the zoom optical system illustrated in FIG. 1 is focused on an object point at infinity, in which FIG. 1A illustrates a state at a wide-angle end, FIG. 1B illustrates an intermediate state, and FIG. Show. FIG. 4 is a cross-sectional view along an optical axis showing an optical configuration when focusing on an object point at infinity of a zoom optical system according to Embodiment 2 of the present invention, where (a) is a wide angle end, (b) is an intermediate, and (c) is an intermediate view. Each state at the telephoto end is shown. FIG. 5 is a diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration when the zoom optical system shown in FIG. 4 is focused on an object point at infinity, where (a) is the wide-angle end, (b) is the middle, ) Shows the state at the telephoto end. 5A and 5B are diagrams illustrating lateral coma aberration when the zoom optical system illustrated in FIG. 4 is focused on an object point at infinity, where FIG. 5A illustrates a state at a wide-angle end, FIG. 4B illustrates an intermediate state, and FIG. Show. FIG. 6 is a cross-sectional view along an optical axis showing an optical configuration when focusing on an object point at infinity of a zoom optical system according to Embodiment 3 of the present invention, where (a) is a wide angle end, (b) is an intermediate, and (c) is an intermediate view. Each state at the telephoto end is shown. FIG. 8 is a diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration when the zoom optical system shown in FIG. 7 is focused on an object point at infinity, where (a) is the wide angle end, (b) is the middle, (c ) Shows the state at the telephoto end. FIG. 8 is a diagram showing lateral coma aberration when the zoom optical system shown in FIG. 7 is focused on an object point at infinity, where (a) shows a state at a wide angle end, (b) shows an intermediate state, and (c) shows a state at a telephoto end, respectively. Show. FIG. 6 is a cross-sectional view along an optical axis showing an optical configuration at the time of focusing on an object point at infinity of a zoom optical system according to Embodiment 4 of the present invention, where (a) is a wide angle end, (b) is an intermediate, and (c). Indicates the state at the telephoto end. FIG. 11 is a diagram illustrating spherical aberration, astigmatism, distortion, and lateral chromatic aberration when the zoom optical system illustrated in FIG. 10 is focused on an object point at infinity, where (a) is a wide angle end, (b) is an intermediate, ) Shows the state at the telephoto end. It is a figure which shows the horizontal coma aberration at the time of infinity object point focusing of the zoom optical system shown in FIG. 10, (a) is a wide angle end, (b) is a middle, (c) is a state in a telephoto end, respectively. Show. FIG. 10 is a cross-sectional view along an optical axis showing an optical configuration when focusing on an object point at infinity of a zoom optical system according to Example 5 of the present invention, where (a) is a wide angle end, (b) is an intermediate, and (c) is Each state at the telephoto end is shown. FIG. 14 is a diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration when the zoom optical system shown in FIG. 13 is focused on an object point at infinity, where (a) is a wide-angle end, (b) is an intermediate, ) Shows the state at the telephoto end. It is a figure which shows the horizontal coma aberration at the time of an infinite object point focusing of the zoom optical system shown in FIG. 13, (a) is a wide angle end, (b) is an intermediate | middle, (c) is a state in a telephoto end, respectively. Show. FIG. 10 is a cross-sectional view along an optical axis showing an optical configuration at the time of focusing on an object point at infinity of a zoom optical system according to Example 6 of the present invention, where (a) is a wide angle end, (b) is an intermediate, and (c) is a cross-sectional view. Each state at the telephoto end is shown. FIG. 17 is a diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration when the zoom optical system shown in FIG. 16 is focused on an object point at infinity, where (a) is the wide-angle end, (b) is the middle, ) Shows the state at the telephoto end. FIG. 17 is a diagram showing lateral coma aberration when the zoom optical system shown in FIG. 16 is focused on an object point at infinity, where (a) shows the state at the wide-angle end, (b) shows the middle, and (c) shows the state at the telephoto end, respectively. Show. It is sectional drawing in alignment with the optical axis which shows the optical structure at the time of infinity object point focusing of the zoom optical system which concerns on Example 7 of this invention, (a) is a wide angle end, (b) is an intermediate | middle, (c) is Each state at the telephoto end is shown. FIG. 20 is a diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration when the zoom optical system shown in FIG. 19 is focused on an object point at infinity, where (a) is the wide-angle end, (b) is the middle, (c ) Shows the state at the telephoto end. FIG. 20 is a diagram showing lateral coma aberration when the zoom optical system shown in FIG. 19 is focused on an object point at infinity, where (a) shows a state at a wide angle end, (b) shows an intermediate state, and (c) shows a state at a telephoto end, respectively. Show. FIGS. 9A and 9B are cross-sectional views along an optical axis showing an optical configuration at the time of focusing on an object point at infinity of a zoom optical system according to Example 8 of the present invention, where FIG. Each state at the telephoto end is shown. FIG. 23 is a diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration when the zoom optical system shown in FIG. 22 is focused on an object point at infinity, where (a) is a wide-angle end, (b) is an intermediate, ) Shows the state at the telephoto end. FIG. 23 is a diagram showing lateral coma aberration when the zoom optical system shown in FIG. 22 is focused on an object point at infinity, where (a) shows a state at a wide angle end, (b) shows an intermediate state, and (c) shows a state at a telephoto end, respectively. Show. 1 is a front perspective view showing an external appearance of a digital camera incorporating a zoom optical system of the present invention. FIG. 26 is a rear front view of the digital camera shown in FIG. 25. It is a schematic diagram which shows the internal structure of the digital camera shown in FIG.

  Prior to the description of the zoom optical system of the present embodiment, the configuration of the zoom optical system of the present embodiment and the function and effect thereof will be described.

The zoom optical system according to the present embodiment includes a plurality of lens groups. In the zoom optical system that performs zooming by appropriately changing the interval between the plurality of lens groups, the positive first is sequentially arranged from the object side. A lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group are arranged, and the most object side surface of the first lens group is convex on the object side. And satisfying the following conditional expression (1).
SF _G4 = (r _G4o + r _G4i ) / (r _G4o -r _G4i )> 0 ... (1)
However, SF _G4 is the fourth lens group from the shaping factor, r _G4o is the radius of curvature of the most object-side surface of the fourth lens group, r _G4i the radius of curvature of the surface on the most image side of the fourth lens group is there.

  In general, many optical systems have a lens surface with a concave surface facing the stop, that is, a lens surface with a spherical center on the stop side. And as the configuration of these lens surfaces is closer to symmetry between the object side and the image side across the stop, the angle formed between the light ray incident on each lens surface and the normal line of each lens surface becomes smaller, aberration, In particular, the occurrence of distortion and coma is suppressed, and fluctuations thereof are also reduced. In particular, the most object-side surface and the most image-side surface of the optical system have a high ray height of incident light. Therefore, if these surfaces are concave with respect to the stop, the effect of reducing aberrations is great.

  Therefore, in the zoom optical system of the present embodiment, the most object-side surface of the first lens group has a shape with the convex surface facing the object side, and the shaping factor of the fourth lens group is a positive value, that is, the fourth lens group. The most image side surface of the lens group is configured to have a convex surface facing the image side.

  Due to such a configuration, the zoom optical system of the present embodiment can suppress the occurrence and fluctuation of various aberrations such as distortion and coma. Therefore, even when the zoom ratio is increased, aberrations at the telephoto end and in the vicinity thereof can be suppressed.

  With this configuration, the principal point of the fourth lens group is on the image side as compared with the case where the shaping factor is a negative value. As a result, the distance between the fourth lens group and the filters can be reduced without widening the distance from the filters (infrared cut filter, low-pass filter, sensor cover glass, etc.) arranged on the image side of the fourth lens group. The distance between the principal points can be increased, and the overall length of the optical system can be shortened. Therefore, when the zoom ratio is increased, not only the aberration at the telephoto end and its vicinity can be suppressed, but also the entire length of the optical system can be kept short.

In the zoom optical system according to the present embodiment, it is preferable that the following conditional expression (2) is satisfied.
0.2 ≦ SF _G4 ≦ 5.0 ... (2)

  As described above, when the zoom optical system according to the present embodiment satisfies the conditional expression (2), the total length of the optical system can be easily shortened without generating a large aberration on the most image side surface of the fourth lens group. .

  If the upper limit of conditional expression (2) is exceeded, the radius of curvature of the surface closest to the image side of the fourth lens group becomes too small, and the aberration generated on that surface tends to increase. On the other hand, if the lower limit value of conditional expression (2) is not reached, the principal point of the fourth lens group will be closer to the object side, and it will be difficult to ensure the distance between the fourth lens group and the filters.

  In the zoom optical system of the present embodiment, it is preferable that the third lens group includes, in order from the object side, a positive single lens and a cemented lens including a positive lens and a negative lens. .

  In the zoom optical system configured as in the present embodiment, as the third lens group, in order from the object side, a positive single lens, a cemented lens composed of a positive lens and a negative lens, a positive single lens, and The structure consisting of is often used. With such a configuration, coma aberration can be corrected satisfactorily.

  Here, in order from the object side, the third lens group is configured by a positive single lens and a cemented lens including a positive lens and a negative lens, and the fourth lens group is configured by only the positive single lens. The combination of the third lens group and the fourth lens group makes it easy to correct coma, particularly coma that occurs on the wide-angle end side where the distance between these lens groups is narrow.

  In addition, if the most image-side positive single lens is not arranged in the third lens group, the positive principal point of the third lens group is closer to the object side, and the main of the negative lens of the cemented lens of the third lens group The distance between the dots can be increased. As a result, the angle of the light beam incident on the negative lens of the cemented lens of the third lens group becomes gentle, and it becomes unnecessary to bend the light beam greatly with the negative lens, thereby suppressing the occurrence of spherical aberration and coma aberration. It becomes easy.

  Further, in the third lens group, the off-axis light beam having a high image height and the on-axis light beam pass through a close position from the wide-angle end to the telephoto end. Therefore, by arranging a cemented lens in the third lens group, spherical aberration and axial chromatic aberration can be favorably corrected on the cemented surface.

  In the zoom optical system of the present embodiment, it is preferable that the first lens group includes only one lens component.

  In the zoom optical system configured as in the present embodiment, since the incident angle of the light beam incident on the first lens group is large and the light beam height is also high, off-axis aberrations, particularly coma aberration, in the first lens group. In many cases, it has a role of correcting the above. For this purpose, it is necessary to arrange a plurality of lenses in the first lens group. On the other hand, since the height of light incident on the first lens group is high, the lenses constituting the first lens group are often large and thick.

  As a result, the total length becomes long in both the retracted state and the non-collapsed state. Further, since the weight of the first lens group also becomes heavy, it is necessary to increase the size of a motor or the like for moving the lens group, and the apparatus using the optical system itself becomes large.

  Therefore, it is desirable to reduce the number of lenses in the first lens group as much as possible, reduce the thickness of the group, and reduce the weight. Therefore, in the zoom optical system according to the present embodiment, it is preferable that the first lens group includes only one lens component. Note that even if the first lens group is composed of only one lens component, coma aberration does not occur greatly.

In the zoom optical system according to the present embodiment, it is preferable that the following conditional expressions (3) and (4) are satisfied.
SF _G1o-G4i = (r _G1o + r _G4i ) / (r _G1o -r _G4i ) (3)
0 ≦ SF _G1o-G4i ≦ 0.4 ... (4)
Where SF _G1o-G4i is the shaping factor of the most object side surface of the first lens group and the most image side surface of the fourth lens group, and r _G1o is the _curvature of the most object side surface of the first lens group. The radius, r _G4i, is the radius of curvature of the most image side surface of the fourth lens group.

  Thus, in the zoom optical system of the present embodiment, the shaping factor of the most object side surface of the first lens group and the most image side surface of the fourth lens group defined by the conditional expression (3) is a conditional expression. (4) is satisfied, that is, the radius of curvature of the surface closest to the object side of the first lens unit is equal to the radius of curvature of the surface of the fourth lens unit closest to the image side, or the first lens unit It is preferable that the radius of curvature of the most object-side surface of the fourth lens group be slightly larger than the radius of curvature of the most image-side surface of the fourth lens unit.

  With this configuration, the most object-side surface of the first lens group and the most image-side surface of the fourth lens group are close to symmetry with respect to the radius of curvature with respect to the diaphragm. Variations in coma aberration can be suppressed, and generation of large aberrations can be suppressed at and near the telephoto end where the magnification is high.

  If the upper limit of conditional expression (4) is exceeded, the difference in the radius of curvature between the most object side surface of the first lens group and the most image side surface of the fourth lens group becomes large, and the symmetry of the optical system is increased. Therefore, it is difficult to suppress fluctuations in coma during zooming, and it is difficult to suppress the occurrence of large aberrations at the telephoto end where the magnification is high and in the vicinity thereof. On the other hand, if the lower limit value of conditional expression (4) is not reached, the radius of curvature of the surface closest to the object side of the first lens group becomes small, so that the aberration generated on that surface becomes large.

In the zoom optical system according to the present embodiment, it is preferable that the following conditional expression (5) is satisfied.
0.2 ≦ ΔD _w−w10 / L _t ≦ 0.35 ... (5)
Where ΔD _w−w10 is the amount of change in the distance between the first lens group and the second lens group from the wide-angle end to the state where the focal length is at least 10 times the focal length at the wide-angle end, and L _t is the telephoto end. Is the total length of the optical system.

  In the configuration such as the zoom optical system of the present embodiment, in order to shorten the total length of the optical system in the retracted state and the non-collapsed state, it is desirable that the first lens group is configured with as few lens components as possible. In particular, it is preferable to use only one lens component. However, if the first lens group is composed of only one lens component, when the zoom ratio is high, the aberration cannot be corrected by the first lens group, and the aberration generated in the first lens group becomes large. Even if the aberration is corrected by the second lens group, if the variation in the distance between the first lens group and the second lens group is large, the variation in aberration at the wide-angle end and the telephoto end becomes large.

  Therefore, the zoom optical system of the present embodiment satisfies the conditional expression (5), that is, the amount of change in the distance between the first lens group and the second lens group even in a high zoom ratio of 10 times or more, It is configured to be shorter than the entire length of the optical system at the telephoto end.

  With this configuration, the variation in aberration at the wide-angle end and the telephoto end is small. In addition, since the correction of aberration can be shared between the first lens group and the second lens group, the aberration can be corrected satisfactorily. Furthermore, the total length of the optical system on the telephoto end side can be shortened.

  If the upper limit of conditional expression (5) is exceeded, the amount of variation in the distance between the first lens group and the second lens group becomes too large, and it is difficult to shorten the total length of the optical system on the telephoto end side. In addition, the amount of aberration variation at the time of zooming from the wide-angle end to the telephoto end tends to increase. On the other hand, if the lower limit of conditional expression (5) is not reached, the amount of fluctuation between the first lens group and the second lens group during zooming becomes too small, making it difficult to achieve a high zoom ratio.

  In the zoom optical system of the present embodiment, it is preferable that the second lens group includes a negative single lens, a negative cemented lens, and a positive single lens in order from the object side.

  With this configuration, since the cemented lens is included in the second lens group, when the zoom ratio is set to a high magnification of 10 times or more while keeping the total length of the optical system short, it mainly occurs at the telephoto end and its vicinity. It is easy to correct the chromatic aberration.

In the zoom optical system according to the present embodiment, when the second lens group includes, in order from the object side, a negative single lens, a negative cemented lens, and a positive single lens, It is preferable that the cemented lens of the lens group includes a negative lens and a positive lens and satisfies the following conditional expression (6).
0.1 ≦ φ _G2n2 / φ _G2n1 ≦ 1.0 ... (6)
Where φ _G2n2 is the refractive power of the negative lens in the cemented lens of the second lens group, and φ _G2n1 is the refractive power of the negative single lens of the second lens group.

  As described above, the zoom optical system according to the present embodiment satisfies the conditional expression (6), that is, the refractive power of the negative single lens disposed closest to the object side in the second lens group is within the cemented lens. It is preferable to be configured to be stronger than the refractive power of the negative lens.

  With this configuration, in the zoom optical system according to the present embodiment, since the principal point of the second lens group is closer to the object side, the first lens group and the second lens group can be brought closer to each other. Can be shortened. Further, when the principal point of the second lens group is closer to the object side, the entrance pupil is also closer to the object side, so that the light ray height in the first lens group is reduced, and the diameter of the first lens group can be reduced. As a result, the first lens group having a large amount of movement at the time of zooming can be reduced in size and weight, so that the entire optical system can be reduced in size and the motor for moving the first lens group can be reduced in size. You can also

  If the upper limit value of conditional expression (6) is exceeded, the refractive power of the negative single lens becomes weak, the principal point of the second lens group moves closer to the image side, and the first lens group and the second lens group It is difficult to reduce the overall length of the optical system. In addition, the entrance pupil is closer to the image side, the diameter of the first lens group is increased, and it is difficult to reduce the size of the entire optical system. On the other hand, if the lower limit of conditional expression (6) is not reached, the refractive power of the negative lens in the cemented lens becomes weak, the balance of the refractive power with the positive lens in the cemented lens is lost, and chromatic aberration is improved. Difficult to correct.

In the zoom optical system according to the present embodiment, when the second lens group includes, in order from the object side, a negative single lens, a negative cemented lens, and a positive single lens, the following conditions are satisfied. It is preferable to satisfy Formula (7).
0.15 ≦ | φ _G2p2 / φ _G2n1 | ≦ 0.45 ... (7)
Where φ _G2p2 is the refractive power of the positive single lens of the second lens group, and φ _G2n1 is the refractive power of the negative single lens of the second lens group.

  Thus, the zoom optical system of the present embodiment satisfies the conditional expression (7), that is, in the second lens group, the absolute value of the refractive power of the positive single lens is the refractive power of the negative single lens. It is preferable to be configured to be smaller than the absolute value.

  With this configuration, in the zoom optical system according to the present embodiment, the light beam is gently bent by the positive single lens. Therefore, the variation in aberration that occurs in the positive single lens during zooming from the wide-angle end to the telephoto end. Can be kept small.

  If the upper limit of conditional expression (7) is exceeded, the refractive power of the positive single lens becomes too strong, and the variation in aberrations during zooming tends to increase. On the other hand, if the lower limit value of conditional expression (7) is not reached, the refractive power of the positive single lens becomes too weak, and it is difficult to correct aberration occurring in the second lens group.

In the zoom optical system according to the present embodiment, when the second lens group includes, in order from the object side, a negative single lens, a negative cemented lens, and a positive single lens, It is preferable that the cemented lens of the lens group includes a negative lens and a positive lens and satisfies the following conditional expression (8).
0.05 ≦ nd _{G2n2 −nd G2p1} ≦ 0.2 ... (8)
Here, nd _G2n2 is the refractive index at the d-line of the negative lens of the cemented lens of the second lens group, and nd _G2p1 is the refractive index at the d-line of the positive lens of the cemented lens of the second lens group.

  As described above, the zoom optical system according to the present embodiment satisfies the conditional expression (8). That is, in the negative cemented lens of the second lens group, the refractive index of the negative lens at the d-line is higher than that of the positive lens. It is preferable to be configured to be higher. If comprised in this way, it is easy to suppress Petzval sum small.

  If the upper limit value of conditional expression (8) is exceeded, the refractive index of the negative lens becomes too high, the Petzval sum becomes large negative, and a large curvature of field tends to occur. On the other hand, if the lower limit value of conditional expression (8) is not reached, the refractive power of the negative lens becomes too low, the Petzval sum cannot be kept small, and a large curvature of field tends to occur.

In the zoom optical system according to the present embodiment, when the second lens group includes, in order from the object side, a negative single lens, a negative cemented lens, and a positive single lens, It is preferable that the cemented lens of the lens group includes a negative lens and a positive lens, and satisfies the following conditional expression (9).
20 ≦ νd _G2n2 −νd _G2p1 ≦ 50 ... (9)
Where νd _G2n2 is the Abbe number in the d-line of the negative lens of the cemented lens of the second lens group, and νd _G2p1 is the Abbe number in the d-line of the positive lens of the cemented lens in the second lens group.

  As described above, the zoom optical system of the present embodiment satisfies the conditional expression (5), that is, is configured so that the difference in Abbe number between the negative lens and the positive lens constituting the cemented lens is large. Is preferred. If constituted in this way, it is easy to correct chromatic aberration favorably.

  In addition, if it exceeds the upper limit of conditional expression (5), the material which can be used will be restricted and it will be difficult to manufacture. On the other hand, if the lower limit of conditional expression (5) is not reached, the Abbe number difference becomes too small, and it is difficult to correct chromatic aberration well.

In the zoom optical system of the present embodiment, the focal length of the entire optical system at the wide angle end is f _w , the focal length of the entire optical system at the telephoto end is f _t , and the focal length of the entire optical system in the intermediate state is When √ (f _w × f _t ), it is preferable that the position of the second lens group in the intermediate state is closer to the object side than the positions at the wide-angle end and the telephoto end.

  In the configuration of the zoom optical system of the present embodiment, the height of the off-axis principal ray in the first lens group increases from the wide-angle end to the intermediate state, and in particular, the shorter the focal length at the wide-angle end, the higher the ray height. Cheap. Even if the focal length at the wide-angle end is the same, the light beam height in the first lens group tends to increase as the distance between the first lens group and the second lens group increases. For this reason, in a configuration in which the distance between the first lens group and the second lens group suddenly widens during zooming from the wide-angle end to the intermediate state, it is necessary to increase the lens outer diameter of the first lens group. It is necessary to increase the lens thickness. As a result, the total length tends to be long in both the retracted state and the non-collapsed state.

  Therefore, the zoom optical system of the present embodiment is preferably configured such that the position of the second lens group in the intermediate state is closer to the object side than the positions at the wide-angle end and the telephoto end. With this configuration, the variation in the distance between the first lens group and the second lens group is small from the wide-angle end to the intermediate state and large from the intermediate state to the telephoto end. As a result, at the time of zooming from the wide-angle end to the intermediate state, the distance between the first lens group and the second lens group does not increase rapidly, and the ray height of the off-axis principal ray in the first lens group is difficult to increase. Therefore, it is not necessary to enlarge the first lens group, and it is easy to shorten the overall length in both the retracted state and the non-collapsed state.

In the zoom optical system of the present embodiment, the focal length of the entire optical system at the wide angle end is f _w , the focal length of the entire optical system at the telephoto end is f _t , and the focal length of the entire optical system in the intermediate state is When √ (f _w × f _t ), when the position of the second lens group in the intermediate state is closer to the object side than the positions at the wide angle end and the telephoto end, the following conditional expression (10) may be satisfied. preferable.
−7.0 ≦ ΔV _G2w-m / ΔV _G2m-t ≦ −1.2 ... (10)
However, ΔV _G2w-m is represented by | V _G2m -V _G2w |, ΔV _G2m-t is represented by | V _G2t -V _G2m |, and V _G2w is the position of the second lens group at the wide angle end, V _G2m Is the position of the second lens group in the intermediate state, V _G2t is the position of the second lens group at the telephoto end, and the _signs of ΔV _G2w-m and ΔV _G2m-t are the image side of the second lens group The case of moving from to the object side is positive.

  As described above, the zoom optical system according to the present embodiment satisfies the conditional expression (10), that is, the second lens group shifts from the wide-angle end to the intermediate state than when zooming from the intermediate state to the telephoto end. It is preferable that the zoom lens is configured to move more greatly during zooming.

  With this configuration, when changing the magnification from the wide-angle end to the intermediate state, the variation in the distance between the first lens group and the second lens group does not become too large, and the ray height in the first lens group does not become too high. . Also, with this configuration, the position of the second lens group at the wide-angle end and the telephoto end is compared, and the position at the telephoto end is located on the object side. As a result, the third lens group responsible for zooming easily moves to the object side at the telephoto end, and a high-magnification optical system is easily realized.

  If the upper limit of conditional expression (10) is exceeded, the positions of the second lens group at the wide-angle end and the telephoto end are closer, or the position at the telephoto end is closer to the image side than the wide-angle end. It becomes difficult for the third lens group to move to the object side, and it becomes difficult to realize a high-magnification optical system. On the other hand, if the lower limit of conditional expression (10) is not reached, the amount of movement of the second lens group from the wide-angle end to the intermediate state increases, and the variation in the distance between the first lens group and the second lens group becomes too small. It becomes difficult to scale.

  In the zoom optical system of the present embodiment, it is preferable that the position of the second lens group at the telephoto end is closer to the object side than the position of the second lens group at the wide-angle end.

  If comprised in this way, the 3rd lens group which bears zooming will move easily to the object side in a telephoto end. As a result, it is easy to achieve a high zoom ratio.

  In the zoom optical system according to the present embodiment, when the second lens group includes, in order from the object side, a negative single lens, a negative cemented lens, and a positive single lens, The cemented surface of the cemented lens of the lens group is preferably an aspherical surface.

  On the wide angle side, the off-axis light beam having a high image height is incident on the second lens group at a position where the light beam height is high. Thus, with this configuration, it is easy to satisfactorily correct off-axis aberrations on the wide-angle side, particularly lateral chromatic aberration.

  In the zoom optical system according to the present embodiment, when the second lens group includes, in order from the object side, a negative single lens, a negative cemented lens, and a positive single lens, It is preferable that all surfaces of the cemented lens in the lens group are aspherical surfaces.

  On the wide angle side, the off-axis light beam having a high image height is incident on the second lens group at a position where the light beam height is high. Thus, with this configuration, it is easy to satisfactorily correct off-axis aberrations such as coma on the wide angle side. On the telephoto side, since the second lens group approaches the diaphragm, a light flux of any image height is incident on a position close to the negative cemented lens. Therefore, with this configuration, it is easy to satisfactorily correct axial aberrations such as spherical aberration.

  In the zoom optical system according to the present embodiment, the second lens group includes, in order from the object side, a negative single lens, a negative cemented lens, and a positive single lens. When all the surfaces of the cemented lens in the group are aspherical surfaces, when the direction from the object side to the image side on the optical axis is positive, the effective diameter of all the surfaces of the cemented lens in the second lens group is The aspheric amount is preferably a negative value.

  In the zoom optical system configured as in the present embodiment, the cemented lens of the second lens group has a weak negative refractive power on the most object-side surface and a most image-side surface in consideration of paraxial power arrangement. It is desirable that the negative refractive power of the surface is strong. With such a configuration, the principal point of the cemented lens is closer to the image side, and the interval between the cemented lens and the positive lens disposed adjacent to the image side can be shortened. The thickness can be reduced. In addition, since the negative refractive power of the second lens group can be increased, the overall length of the optical system can also be shortened.

  However, if the light beam is greatly bent on only one surface, a large aberration occurs in a region having a high image height or a region having a high ray height of the axial light beam. In particular, astigmatism and coma aberration, and spherical aberration and the like greatly occur near the telephoto end. In order to suppress the occurrence of such aberration and gently bend the light beam, the surface closest to the object side of the cemented lens has a strong negative refractive power in a region away from the optical axis, and the surface closest to the image side from the optical axis. It is necessary to arrange the refractive power of the cemented lens in a well-balanced manner so that the negative refractive power becomes weak in the distant region.

  Therefore, in the cemented lens of the second lens group, a negative aspheric amount is given to a region farthest from the optical axis of the surface closest to the object side to increase the negative refractive power, and from the optical axis of the surface closest to the image side. It is preferable to give a negative aspherical amount to a distant area to weaken the negative refractive power. Further, at this time, unless a negative aspherical amount is given to the cemented surface to achieve a balance, the occurrence of chromatic aberration in a region where the beam height of the axial light beam is high becomes large. Therefore, it is preferable to give a negative aspheric amount to the joint surface in a region away from the optical axis as well.

In the zoom optical system according to the present embodiment, the second lens group includes, in order from the object side, a negative single lens, a negative cemented lens, and a positive single lens. When all the surfaces of the cemented lens in the group are aspheric surfaces, it is preferable that the following conditional expression (11) is satisfied.
10 ≦ (ASP _22c × | Δνd ₂₂ |) / (ASP _22o + ASP _22i ) ≦ 90
(11)
Where ASP _22c is the aspherical amount of the effective diameter of the cemented surface of the cemented lens of the second lens group, Δνd ₂₂ is the difference between the Abbe numbers of the two lenses constituting the cemented lens of the second lens group, and ASP _22o is An aspheric amount at the effective diameter of the object side surface of the cemented lens of the second lens group, and ASP _22i is an aspheric amount at the effective diameter of the image side surface of the cemented lens of the second lens group. The effective diameter is the smallest effective diameter of the effective diameters of the surfaces of the cemented lens of the second lens group.

  Since the cemented surface of the cemented lens is a lens on both the object side and the image side, the refractive index difference between the medium of the lens on the object side and the image side of the cemented surface is smaller than a surface where one of them is air. . That is, even if the same amount of aspheric surface is given, the refractive power due to the aspheric surface is smaller on the bonding surface than on the surface where either one is air. For this reason, in order to give the joint surface the same refractive power as that of the surface where one of the surfaces is air, it is necessary to increase the amount of aspherical surface given to the joint surface. Considering the balance between chromatic aberration correction on the cemented surface and other aberration corrections, when the difference in Abbe number of the materials of the two lenses constituting the cemented lens is large, compared to the case where the difference in Abbe number is small, It is desirable to reduce the amount of aspheric surfaces of the joint surfaces.

  Therefore, the zoom optical system according to the present embodiment is preferably configured to satisfy the conditional expression (11). If configured so as to satisfy this conditional expression (11), the aspheric amount of the cemented surface of the cemented lens becomes larger than the aspheric amount of the object side surface and the image side surface. In addition, if the difference in Abbe number between the materials of the two lenses constituting the cemented lens is small, the aspheric amount of the cemented surface increases, and if the difference in Abbe number is large, the aspheric amount of the cemented surface decreases. And coma aberration, lateral chromatic aberration, coma chromatic aberration, and the like can be corrected in a balanced manner.

  If the upper limit of conditional expression (11) is exceeded, the amount of aspheric surfaces on the cemented surface becomes too large, and various aberrations, particularly lateral chromatic aberration and coma chromatic aberration, are likely to occur. In addition, the difference in Abbe number between the materials of the two lenses constituting the cemented lens becomes too large, and the materials that can be used are limited, making it difficult to manufacture. On the other hand, if the lower limit value of conditional expression (11) is not reached, the aspheric amount of the cemented surface becomes too small, and it becomes difficult to correct various aberrations, particularly lateral chromatic aberration and coma chromatic aberration. Further, the difference in Abbe number between the materials of the two lenses constituting the cemented lens becomes too small, making it difficult to correct chromatic aberration.

  In the zoom optical system according to the present embodiment, it is preferable that the fourth lens group includes only one lens component.

  If comprised in this way, the thickness of a 4th lens group can be made thin. As a result, it is easy to shorten the overall length in both the retracted state and the non-collapsed state.

  In the zoom optical system according to the present embodiment, when the fourth lens group includes only one lens component, it is preferable that the fourth lens group includes only one positive single lens.

  If comprised in this way, the thickness of a 4th lens group can be made still thinner. As a result, it is easy to further shorten the overall length in both the retracted state and the non-collapsed state. Further, since this single positive single lens has a positive shaping factor, that is, the radius of curvature of the image side surface is smaller than that of the object side surface, the light beam incident on the image side surface and the image side surface The angle formed by the normal of the surface is reduced, and aberrations are less likely to occur.

In the zoom optical system according to the present embodiment, it is preferable that the following conditional expression (12) is satisfied.
0 ≦ | ΔV _G4w-t / f _w | ≦ 0.1 (12)
However, ΔV _G4w-t is | V _G4t -V _G4w | in expressed, V _G4W the position of the fourth lens group at the wide-angle end, V _G4t the position of the fourth lens group at the telephoto end, f _w is wide The focal length of the entire optical system at the end, and the sign of ΔV _G4w-t is positive when the fourth lens group moves from the image side to the object side.

  As described above, the zoom optical system according to the present embodiment satisfies the conditional expression (12), that is, the position change of the fourth lens group at the wide-angle end and the telephoto end is extremely small. preferable. If comprised in this way, it will be easy to suppress the fluctuation | variation of the curvature of field at the time of zooming small.

  If the upper limit of conditional expression (12) is exceeded, the amount of movement of the fourth lens group becomes too large, and the total length of the optical system tends to be long. In addition, the variation in field curvature during zooming tends to be large.

  In the zoom optical system of the present embodiment, it is preferable that the fourth lens group does not move during zooming from the wide angle end to the telephoto end.

  With this configuration, since the fourth lens unit does not move during zooming from the wide-angle end to the telephoto end, it is easy to suppress fluctuations in field curvature during zooming.

  Also, with this configuration, a mechanism for moving the fourth lens group is not necessary. Even when the fourth lens group is used as a focus group, a simple mechanism is sufficient because it only moves for focusing. As a result, the lens barrel and the motor can be reduced, and the entire optical system can be easily miniaturized.

  An electronic imaging apparatus according to the present embodiment includes any of the zoom optical systems described above.

  As described above, the zoom optical system of the present embodiment has a high magnification, a short overall length in both a retracted state and a non-collapsed state, various aberrations are corrected well, and from the wide-angle end to the telephoto end. Since variations in various aberrations when zooming is small, a high-quality image can be obtained by using such an optical system, and a thin and high-magnification electronic imaging apparatus can be obtained.

  Hereinafter, optical systems according to Examples 1 to 8 will be described with reference to the drawings.

The numbers shown as subscripts in the optical system sectional views r ₁ , r ₂ ,... And d ₁ , d ₂ ,. is doing.

In the numerical data, s is the surface number, r is the radius of curvature of each surface, d is the surface spacing, nd is the refractive index at the d-line (wavelength 587.56 nm), νd is the Abbe number at the d-line, and k is the cone. Coefficients A ₄ , A ₆ , A ₈ , A ₁₀ and A ₁₂ indicate aspheric coefficients, respectively.

In the aspherical coefficient of the numerical data, E represents a power of 10. For example, “E-10” represents 10 minus the first power. Each aspheric shape is expressed by the following equation using each aspheric coefficient described in the numerical data. However, the coordinate in the direction along the optical axis with the direction from the object side to the image side being positive is Z, and the coordinate in the direction perpendicular to the optical axis is Y.
Z = (Y ² / r) / [1+ {1− (1 + k) · (Y / r) ² } ^1/2 ]
+ A ₄ Y ⁴ + A ₆ Y ⁶ + A ₈ Y ⁸ + A ₁₀ Y ¹⁰ + A ₁₂ Y ¹² +.

  The zoom optical system according to Example 1 will be described below in detail with reference to FIGS.

  FIG. 1 is a cross-sectional view along the optical axis showing the optical configuration of the zoom optical system according to the present embodiment when focusing on an object point at infinity, where (a) is the wide-angle end, (b) is the middle, c) shows the state at the telephoto end. 2A and 2B are diagrams showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration when the zoom optical system shown in FIG. 1 is focused on an object point at infinity. FIG. 2A is a wide-angle end, and FIG. In the middle, (c) shows the state at the telephoto end. 3A and 3B are diagrams illustrating lateral coma aberration when the zoom optical system illustrated in FIG. 1 is focused on an object point at infinity, where FIG. 3A is a wide-angle end, FIG. 3B is an intermediate end, and FIG. 3C is a telephoto end. Each state is shown.

  First, the optical configuration of the zoom optical system of the present embodiment will be described with reference to FIG. In the description of the aspheric lens, the shape of the lens is a shape in the vicinity of the optical axis of light from the front object side.

In the zoom optical system of the present embodiment, on the optical axis Lc, in order from the object side, a positive first lens group G ₁ , a negative second lens group G ₂ , a positive third lens group G ₃ , and a positive first lens group G _{3 are} arranged. Four lens groups G ₄ are arranged. _On the object side of the third lens group G ₃ , an aperture stop S is provided so as to move integrally with the third lens group G ₃ . Note that an imaging element having a low-pass filter LF, a CCD cover glass CG, and an imaging surface IM is arranged on the image side of the fourth lens group G ₄ in order from the object side.

The first lens group G ₁ is composed of, in order from the object side, a positive lens L ₁₁ that is a negative meniscus lens having a convex surface facing the object side and a lens L ₁₂ that is a biconvex lens having an aspheric surface on the image side. It consists only of cemented lenses.

The second lens group G ₂ includes, in order from the object side, a lens L ₂₁ that is a negative meniscus lens having a convex surface facing the object side, and a lens that is a negative meniscus lens having both surfaces aspherical and the convex surface facing the object side. A negative cemented lens composed of L ₂₂ and a lens L ₂₃ which is a positive meniscus lens having both surfaces aspherical and having a convex surface facing the object side; and a lens L ₂₄ which is a positive meniscus lens having a convex surface facing the object side and It is comprised by.

The third lens group G ₃ includes, in order from the object side, a lens L ₃₁ that is a biconvex lens having both aspheric surfaces, a negative cemented lens that includes a lens L ₃₂ that is a biconvex lens, and a lens L ₃₃ that is a biconcave lens. It is comprised by.

Incidentally, the cemented lens constituting the third lens group G _3, all of the surface has a spherical surface. Therefore, the lens L ₃₂ and the lens L ₃₃ constituting the cemented lens can be manufactured by polishing, which is less expensive than an aspheric lens manufactured by glass molding or the like.

The fourth lens group G ₄ includes only a lens L ₄₁ that is a biconvex lens having both aspheric surfaces.

  Next, the movement of each lens unit of the zoom optical system of the present embodiment at the time of zooming will be described.

At the time of zooming from the wide angle end to the telephoto end, the first lens group G ₁ moves to the object side. The second lens group G ₂ reciprocates on the optical axis Lc so as to move first to the object side and then to the image side while increasing the distance from the first lens group G ₁ . The third lens group G ₃ moves together with the aperture stop S along the optical axis Lc toward the object side while narrowing the distance from the second lens group G ₂ . The fourth lens group G ₄ reciprocates on the optical axis Lc so as to move first to the image side and then to the object side while widening the distance from the third lens group G ₃ .

  Next, numerical data relating to the lenses constituting the zoom optical system of the present embodiment will be shown.

Numerical data 1
Unit mm
Surface data Surface number Curvature radius Surface spacing Refractive index Abbe number Effective diameter s r d nd νd
0 (object surface) ∞ ∞
1 20.0151 0.9000 1.94595 17.98 9.600
2 16.5455 3.8000 1.59201 67.02 9.123
3 (Aspherical surface) -608.4103 D3 8.850
4 50.2354 0.8000 1.88300 40.76 6.508
5 5.9863 3.2849 4.717
6 (Aspherical) 5620.2668 0.7000 1.69350 53.21 4.545
7 (Aspherical surface) 6.1973 0.8500 1.63387 23.38 4.432
8 (Aspherical) 13.2950 0.3000 4.419
9 11.1530 1.7900 1.92286 18.90 4.451
10 18.9979 D10 4.700
11 (Aperture) ∞ -0.1000 2.317
12 (Aspherical) 6.1358 3.3200 1.59201 67.02 2.395
13 (Aspherical surface) -13.3699 0.1400 2.356
14 6.9314 1.8800 1.49700 81.54 2.270
15 -8.5935 0.3900 1.61293 37.00 2.027
16 3.8417 D16 1.850
17 (Aspherical surface) 58542.8664 2.7200 1.53071 55.69 4.693
18 (Aspherical) -11.2254 D18 4.869
19 ∞ 0.3000 l.51633 64.14 4.264
20 ∞ 0.5000 4.241
21 ∞ 0.5000 1.51633 64.14 4.193
22 ∞ 0.3700 4.162
23 (Image plane) ∞

Aspherical data Surface number Radius of curvature Conical coefficient s r k
3 -608.410 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
8.55615e-06 -3.58742e-09 -7.49370e-12 2.26300e-13 -1.46640e-15
Surface number Curvature radius Conical coefficient s r k
6 5620.267 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
-1.32033e-03 2.12952e-05 -1.78021e-07 1.18290e-08 -2.17830e-10
Surface number Curvature radius Conical coefficient s r k
7 6.197 0.000
Aspheric coefficient
A ₄ A ₆ A ₈
-2.71239e-03 2.66916e-05 -1.63840e-08
Surface number Curvature radius Conical coefficient s r k
8 13.295 0.000
Aspheric coefficient
A ₄ A ₆ A ₈
-1.27786e-03 2.66916e-05 -1.63840e-08
Surface number Curvature radius Conical coefficient s r k
12 6.136 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
-4.75567e-04 -1.36226e-05 1.26882e-06 -1.30670e-07 4.87140e-09
Surface number Curvature radius Conical coefficient s r k
13 -13.370 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
4.07860e-04 -1.08520e-05 2.13300e-06 -2.60270e-07 1.08720e-08
Surface number Curvature radius Conical coefficient s r k
17 58542.866 0.000
Aspheric coefficient
A ₄ A ₆
-1.35928e-06 -8.57460e-07
Surface number Curvature radius Conical coefficient s r k
18 -11.225 0.000
Aspheric coefficient
A ₄ A ₆ A ₈
-4.46926e-05 -2.76328e-06 1.10000e-08

Various data Zoom ratio 11.518
Wide angle Medium telephoto 10 times the wide angle end
Focal length position Focal length 5.086 17.107 58.579 50.601
F number 3.257 5.446 6.300 6.252
Full angle of view 75.610 25.785 7.716 8.940
Image height 3.830 3.830 3.830 3.830
Total lens length 43.802 55.487 65.719 65.463
BF 5.994 5.388 5.412 5.516
Object distance ∞ ∞ ∞ ∞
D3 0.300 9.064 20.197 19.281
D10 13.620 6.523 1.685 2.459
D16 3.113 13.737 17.650 17.431
D18 4.596 3.991 4.015 4.119
Diaphragm diameter 2.317 2.317 2.317 2.317
Entrance pupil position 11.878 32.211 108.820 97.193
Exit pupil position -11.283 -120.092 620.677 869.645
Front principal point position 15.467 46.986 172.977 151.757
Rear principal point position -4.716 -16.737 -58.209 -50.231

Single lens data
lens Start focal length L ₁₁ 1 -115.459
L ₁₂ 2 27.270
L ₂₁ 4 -7.763
L ₂₂ 6 -8.947
L ₂₃ 7 17.501
L ₂₄ 9 26.378
L ₃₁ 12 7.584
L ₃₂ 14 8.043
L ₃₃ 15 -4.280
L ₄₁ 17 21.148

Zoom lens group data
group Start surface Group focal length Group length Front principal point position Rear principal point position G ₁ 1 36.727 4.700 -0.261 -3.112
G ₂ 4 -6.054 7.725 1.196 -4.151
G ₃ 11 9.945 5.630 -3.334 -4.964
G ₄ 17 21.148 2.720 1.777 -0.000

Group magnification
Wide angle Medium telephoto 10 times the wide angle end
Position to be the focal length G ₁ 0.000 0.000 0.000 0.000
G ₂ -0.232 -0.350 -0.981 -0.855
G ₃ -0.832 -1.786 -2.184 -2.181
G ₄ 0.717 0.745 0.744 0.739

Data related to the above conditional expression Conditional expression (1)
SF _G4 = (r _G4o + r _G4i ) / (r _G4o -r _G4i ): 1.000
Conditional expression (2)
SF _G4 : 1.000
Conditional expressions (3), (4)
SF _G1o-G4i = (r _G1o + r _G4i ) / (r _G1o -r _G4i ): 0.281
Conditional expression (5)
ΔD _w-w10 / L _t : 0.288
Conditional expression (6)
φ _G2n2 / φ _G2n1 ： 0.868
Conditional expression (7)
| Φ _G2p2 / φ _G2n1 |: 0.443
Conditional expression (8)
nd _{G2n2 -nd G2p1} : 0.060
Conditional expression (9)
νd _G2n2 −νd _G2p1 : 29.83
Conditional expression (10)
_ΔVG2w-m / _ΔVG2m-t : −3.24
Conditional expression (11)
(ASP _22c × | Δνd ₂₂ |) / (ASP _22o + ASP _22i ): 39.0
Conditional expression (12)
| ΔV _G4w-t / f _w |: 0.013

  The zoom optical system according to Example 2 will be described in detail below with reference to FIGS. Note that the optical configuration of the zoom optical system of the present embodiment and the movement of each lens group during zooming are substantially the same as those of the zoom optical system of Embodiment 1, so members having substantially the same configuration have the same reference numerals. And a detailed description thereof will be omitted.

  FIG. 4 is a cross-sectional view along the optical axis showing the optical configuration of the zoom optical system according to the present embodiment at the time of focusing on an object point at infinity, where (a) is the wide-angle end, (b) is the middle, c) shows the state at the telephoto end. 5A and 5B are diagrams showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration when the zoom optical system shown in FIG. 4 is focused on an object point at infinity. FIG. 5A is a wide-angle end, and FIG. In the middle, (c) shows the state at the telephoto end. 6A and 6B are diagrams illustrating lateral coma aberration when the zoom optical system illustrated in FIG. 4 is focused on an object point at infinity. FIG. 6A is a wide-angle end, FIG. 6B is an intermediate end, and FIG. 6C is a telephoto end. Each state is shown.

  Numerical data relating to the lenses constituting the zoom optical system of the present embodiment will be shown below.

Numerical data 2
Unit mm
Surface data Surface number Curvature radius Surface spacing Refractive index Abbe number Effective diameter s r d nd νd
0 (object surface) ∞ ∞
1 20.8522 0.9000 1.92286 20.88 9.600
2 16.6388 3.8000 1.59201 67.02 9.105
3 (Aspherical) -235.3898 D3 8.850
4 365.1222 0.8000 1.88300 40.76 5.695
5 5.6598 2.5701 4.251
6 (Aspherical) 26151.9145 0.7000 1.74250 49.27 4.183
7 (Aspherical surface) 8.1614 0.7164 1.63387 23.38 4.140
8 (Aspherical) 13.5155 0.3000 4.141
9 11.2152 1.7900 1.92286 18.90 4.206
10 28.4287 D10 4.700
11 (Aperture) ∞ -0.1000 2.321
12 (Aspherical) 6.0735 3.3200 1.59201 67.02 2.411
13 (Aspherical) -16.2836 0.1400 2.365
14 5.7093 1.8800 1.49700 81.54 2.288
15 -8.5126 0.3900 1.61293 37.00 2.049
16 3.5665 D16 1.850
17 (Aspherical surface) 15198.3952 2.7200 1.53071 55.69 4.698
18 (Aspherical) -10.6465 D18 4.883
19 ∞ 0.3000 l.51633 64.14 4.279
20 ∞ 0.5000 4.261
21 ∞ 0.5000 1.51633 64.14 4.217
22 ∞ 0.4100 4.193
23 (Image plane) ∞

Aspherical data Surface number Radius of curvature Conical coefficient s r k
3 -235.390 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
8.44752e-06 -7.65080e-09 -7.49370e-12 2.26300e-13 -1.46640e-15
Surface number Curvature radius Conical coefficient s r k
6 26151.915 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
-5.95515e-04 1.04365e-05 -3.25540e-07 1.18290e-08 -2.17830e-10
Surface number Curvature radius Conical coefficient s r k
7 8.161 0.000
Aspheric coefficient
A ₄ A ₆
-7.36856e-04 5.17862e-06
Surface number Curvature radius Conical coefficient s r k
8 13.515 0.000
Aspheric coefficient
A ₄ A ₆
-7.36856e-04 5.17862e-06
Surface number Curvature radius Conical coefficient s r k
12 6.074 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
-3.15931e-04 -1.13586e-05 9.94380e-07 -1.30670e-07 4.87140e-09
Surface number Curvature radius Conical coefficient s r k
13 -16.284 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
4.76102e-04 -1.08520e-05 2.13300e-06 -2.60270e-07 1.08720e-08
Surface number Curvature radius Conical coefficient s r k
17 15 198.395 0.000
Aspheric coefficient
A ₄ A ₆
-1.67790e-05 -8.57460e-07
Surface number Curvature radius Conical coefficient s r k
18 -10.646 0.000
Aspheric coefficient
A ₄ A ₆ A ₈
1.45469e-05 -1.98510e-06 1.10000e-08

Various data Zoom ratio 11.525
Wide angle Medium telephoto 10 times the wide angle end
Focal length position Focal length 5.096 17.159 58.731 50.642
F number 3.266 5.452 6.300 6.082
Full angle of view 75.469 25.238 7.561 8.731
Image height 3.830 3.830 3.830 3.830
Total lens length 41.957 55.165 65.758 65.491
BF 5.979 5.341 5.373 6.446
Object distance ∞ ∞ ∞ ∞
D3 0.300 9.861 21.131 20.323
D10 12.583 6.212 1.598 2.035
D16 3.168 13.824 17.730 16.761
D18 4.542 3.904 3.935 5.008
Diaphragm diameter 2.321 2.321 2.321 2.321
Entrance pupil position 10.636 32.341 110.693 100.267
Exit pupil position -11.626 -177.623 234.777 465.261
Front principal point position 14.257 47.891 184.461 156.653
Rear principal point position -4.686 -16.749 -58.321 -44.323

Single lens data
lens Start focal length L ₁₁ 1 -99.420
L ₁₂ 2 26.398
L ₂₁ 4 -6.517
L ₂₂ 6 -10.995
L ₂₃ 7 30.898
L ₂₄ 9 19.117
L ₃₁ 12 7.909
L ₃₂ 14 7.192
L ₃₃ 15 -4.051
L ₄₁ 17 20.048

Zoom lens group data
group Start surface Group focal length Group length Front principal point position Rear principal point position G ₁ 1 36.902 4.700 -0.076 -2.947
G ₂ 4 -5.951 6.877 0.660 -4.219
G ₃ 11 9.729 5.630 -3.454 -4.963
G ₄ 17 20.048 2.720 1.776 -0.001

Group magnification
Wide angle Medium telephoto 10 times the wide angle end
Position to be the focal length G ₁ 0.000 0.000 0.000 0.000
G ₂ -0.220 -0.340 -0.958 -0.848
G ₃ -0.894 -1.862 -2.270 -2.392
G ₄ 0.702 0.734 0.732 0.678

Data related to the above conditional expression Conditional expression (1)
SF _G4 = (r _G4o + r _G4i ) / (r _G4o -r _G4i ): 0.999
Conditional expression (2)
SF _G4 : 0.999
Conditional expressions (3), (4)
SF _G1o-G4i = (r _G1o + r _G4i ) / (r _G1o -r _G4i ): 0.324
Conditional expression (5)
ΔD _w-w10 / L _t : 0.303
Conditional expression (6)
φ _G2n2 / φ _G2n1 : 0.593
Conditional expression (7)
| Φ _G2p2 / φ _G2n1 |: 0.211
Conditional expression (8)
nd _{G2n2 -nd G2p1} : 0.109
Conditional expression (9)
νd _G2n2 −νd _G2p1 : 25.89
Conditional expression (10)
_ΔVG2w-m / _ΔVG2m-t : −5.39
Conditional expression (11)
(ASP _22c × | Δνd ₂₂ |) / (ASP _22o + ASP _22i ): 15.0
Conditional expression (12)
| ΔV _G4w-t / f _w |: 0.014

  The zoom optical system according to Example 3 will be described below in detail with reference to FIGS. Note that the optical configuration of the zoom optical system of the present embodiment and the movement of each lens group at the time of zooming are substantially the same as those of the zoom optical system of Embodiments 1 and 2, and therefore, members having substantially the same configuration are the same. And a detailed description thereof will be omitted.

  FIG. 7 is a cross-sectional view along the optical axis showing the optical configuration of the zoom optical system according to the present embodiment when focusing on an object point at infinity, where (a) is a wide angle end, (b) is an intermediate, c) shows the state at the telephoto end. FIG. 8 is a diagram showing spherical aberration, astigmatism, distortion aberration, and chromatic aberration of magnification when the zoom optical system shown in FIG. 7 is focused on an object point at infinity, where (a) is the wide-angle end, and (b) is In the middle, (c) shows the state at the telephoto end. FIG. 9 is a diagram showing lateral coma aberration when the zoom optical system shown in FIG. 7 is focused on an object point at infinity, where (a) is a wide angle end, (b) is an intermediate end, and (c) is a telephoto end. Each state is shown.

  Numerical data relating to the lenses constituting the zoom optical system of the present embodiment will be shown below.

Numerical data 3
Unit mm
Surface data Surface number Curvature radius Surface spacing Refractive index Abbe number Effective diameter s r d nd νd
0 (object surface) ∞ ∞
1 20.8017 0.9000 1.92286 20.88 9.600
2 16.6932 3.8000 1.59201 67.02 9.105
3 (Aspherical surface) -319.7700 D3 8.850
4 46.1252 0.8000 1.88300 40.76 6.473
5 6.4033 3.4783 4.828
6 (Aspherical surface) 311235.9057 0.7000 1.74250 49.27 4.567
7 (Aspherical surface) 7.1050 0.5292 1.63387 23.38 4.481
8 (Aspherical) 13.6297 0.3000 4.478
9 11.9340 1.7900 1.92286 18.90 4.523
10 22.8900 D10 4.700
11 (Aperture) ∞ -0.1000 2.320
12 (Aspherical) 6.2026 3.3200 1.59201 67.02 2.390
13 (Aspherical surface) -14.1286 0.1400 2.339
14 7.1625 1.8800 1.49700 81.54 2.259
15 -10.2598 0.3900 1.61293 37.00 2.015
16 3.8991 D16 1.850
17 (Aspherical) 63517.1399 2.7200 1.53071 55.69 4.676
18 (Aspherical) -11.1448 D18 4.855
19 ∞ 0.3000 l.51633 64.14 4.269
20 ∞ 0.5000 4.251
21 ∞ 0.5000 1.51633 64.14 4.205
22 ∞ 0.4100 4.175
23 (Image plane) ∞

Aspherical data Surface number Radius of curvature Conical coefficient s r k
3 -319.770 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
8.22246e-06 -7.65080e-09 -7.49370e-12 2.26300e-13 -1.46640e-15
Surface number Curvature radius Conical coefficient s r k
6 311235.906 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
-1.65912e-03 2.92159e-05 -1.86409e-07 1.18290e-08 -2.17830e-10
Surface number Curvature radius Conical coefficient s r k
7 7.105 0.000
Aspheric coefficient
A ₄ A ₆ A ₈
-2.62854e-03 3.59697e-05 -3.84445e-08
Surface number Curvature radius Conical coefficient s r k
8 13.630 0.000
A ₄ A ₆ A ₈
-1.55353e-03 3.59697e-05 -3.84445e-08
Surface number Curvature radius Conical coefficient s r k
12 6.203 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
-4.28096e-04 -1.14287e-05 1.26882e-06 -1.30670e-07 4.87140e-09
Surface number Curvature radius Conical coefficient s r k
13 -14.129 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
4.52974e-04 -1.08520e-05 2.13300e-06 -2.60270e-07 1.08720e-08
Surface number Curvature radius Conical coefficient s r k
17 63517.140 0.000
Aspheric coefficient
A ₄ A ₆
4.15743e-06 -8.57460e-07
Surface number Curvature radius Conical coefficient s r k
18 -11.145 0.000
A ₄ A ₆ A ₈
-5.47643e-05 -1.45284e-06 1.10000e-08

Various data Zoom ratio 11.532
Wide angle Medium telephoto 10 times the wide angle end
Focal length position Focal length 5.096 17.165 58.771 50.785
F number 3.253 5.438 6.300 6.142
Full angle of view 75.467 25.600 7.667 8.870
Image height 3.830 3.830 3.830 3.830
Total lens length 44.927 55.669 65.757 65.465
BF 5.972 5.332 5.360 5.956
Object distance ∞ ∞ ∞ ∞
D3 0.300 8.940 20.406 19.550
D10 14.832 6.916 1.600 2.281
D16 3.175 13.833 17.742 17.031
D18 4.535 3.895 3.922 4.518
Diaphragm diameter 2.320 2.320 2.320 2.320
Entrance pupil position 12.368 31.903 105.916 96.660
Exit pupil position -11.509 -130.799 459.647 1520.706
Front principal point position 15.979 46.904 172.290 149.148
Rear principal point position -4.686 -16.755 -58.361 -44.830

Single lens data
lens Start focal length L ₁₁ 1 -102.343
L ₁₂ 2 26.911
L ₂₁ 4 -8.501
L ₂₂ 6 -9.569
L ₂₃ 7 22.700
L ₂₄ 9 25.053
L ₃₁ 12 7.752
L ₃₂ 14 8.802
L ₃₃ 15 -4.562
L ₄₁ 17 20.996

Zoom lens group data
group Start surface Group focal length Group length Front principal point position Rear principal point position G ₁ 1 37.510 4.700 -0.148 -3.013
G ₂ 4 -6.453 7.597 1.257 -4.124
G ₃ 11 10.316 5.630 -3.430 -5.056
G ₄ 17 20.996 2.720 1.777 -0.000

Group magnification
Wide angle Medium telephoto 10 times the wide angle end
Position to be the focal length G ₁ 0.000 0.000 0.000 0.000
G ₂ -0.244 -0.362 -1.011 -0.892
G ₃ -0.779 -1.696 -2.080 -2.119
G ₄ 0.716 0.746 0.745 0.716

Data related to the above conditional expression Conditional expression (1)
SF _G4 = (r _G4o + r _G4i ) / (r _G4o -r _G4i ): 1.000
Conditional expression (2)
SF _G4 : 1.000
Conditional expressions (3), (4)
SF _G1o-G4i = (r _G1o + r _G4i ) / (r _G1o -r _G4i ): 0.302
Conditional expression (5)
ΔD _w-w10 / L _t : 0.292
Conditional expression (6)
φ _G2n2 / φ _G2n1 : 0.889
Conditional expression (7)
| Φ _G2p2 / φ _G2n1 |: 0.375
Conditional expression (8)
nd _{G2n2 -nd G2p1} : 0.109
Conditional expression (9)
νd _G2n2 −νd _G2p1 : 25.89
Conditional expression (10)
_ΔVG2w-m / _ΔVG2m-t : -1.52
Conditional expression (11)
(ASP _22c × | Δνd ₂₂ |) / (ASP _22o + ASP _22i ): 25.7
Conditional expression (12)
| ΔV _G4w-t / f _w |: 0.014

  The zoom optical system according to Example 4 will be described in detail below with reference to FIGS. Note that the optical configuration of the zoom optical system of the present embodiment and the movement of each lens group during zooming are substantially the same as those of the zoom optical system of Embodiments 1 to 3, and therefore, the members having substantially the same configuration are the same. And a detailed description thereof will be omitted.

  FIG. 10 is a cross-sectional view along the optical axis showing the optical configuration of the zoom optical system according to the present embodiment when focusing on an object point at infinity, where (a) is a wide angle end, (b) is an intermediate, c) shows the state at the telephoto end. 11A and 11B are diagrams showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration when the zoom optical system shown in FIG. 10 is focused on an object point at infinity. FIG. 11A is a wide-angle end, and FIG. In the middle, (c) shows the state at the telephoto end. 12A and 12B are diagrams illustrating lateral coma aberration when the zoom optical system illustrated in FIG. 10 is focused on an object point at infinity. FIG. 12A is a wide-angle end, FIG. 12B is an intermediate end, and FIG. 12C is a telephoto end. Each state is shown.

  Numerical data relating to the lenses constituting the zoom optical system of the present embodiment will be shown below.

Numerical data 4
Unit mm
Surface data Surface number Curvature radius Surface spacing Refractive index Abbe number Effective diameter s r d nd νd
0 (object surface) ∞ ∞
1 20.4547 0.9000 1.92286 20.88 9.600
2 16.3748 3.8000 1.59201 67.02 9.114
3 (Aspherical) -303.0106 D3 8.850
4 37.0720 0.8000 1.88300 40.76 6.242
5 5.8165 3.3069 4.524
6 (Aspherical) 12019.2977 0.7000 1.69350 53.21 4.273
7 (Aspherical) 6.1926 0.7000 1.63387 23.38 4.165
8 (Aspherical) 12.9491 0.3000 4.159
9 11.2636 1.7900 1.92286 18.90 4.183
10 18.5001 D10 4.700
11 (Aperture) ∞ -0.1000 2.290
12 (Aspherical) 6.1785 3.3200 1.59201 67.02 2.361
13 (Aspherical surface) -11.1135 0.1400 2.330
14 8.1838 1.8800 1.49700 81.54 2.242
15 -7.7822 0.3900 1.61293 37.00 2.008
16 4.0990 D16 1.850
17 (Aspherical surface) 63697.7428 2.7200 1.53071 55.69 4.679
18 (Aspherical) -11.1066 D18 4.853
19 ∞ 0.3000 l.51633 64.14 4.260
20 ∞ 0.5000 4.242
21 ∞ 0.5000 1.51633 64.14 4.196
22 ∞ 0.4000 4.165
23 (Image plane) ∞

Aspherical data Surface number Radius of curvature Conical coefficient s r k
3 -303.011 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
8.68825e-06 -7.65080e-09 -7.49370e-12 2.26300e-13 -1.46640e-15
Surface number Curvature radius Conical coefficient s r k
6 12019.298 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
-1.95119e-03 2.58482e-05 7.62847e-08 1.18290e-08 -2.17830e-10
Surface number Curvature radius Conical coefficient s r k
7 6.193 0.000
Aspheric coefficient
A ₄ A ₆ A ₈
-3.26104e-03 3.69617e-05 2.40345e-07
Surface number Curvature radius Conical coefficient s r k
8 12.949 0.000
Aspheric coefficient
A ₄ A ₆ A ₈
-1.88857e-03 3.69617e-05 2.40345e-07
Surface number Curvature radius Conical coefficient s r k
12 6.178 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
-6.14264e-04 -1.17654e-05 1.26882e-06 -1.30670e-07 4.87140e-09
Surface number Curvature radius Conical coefficient s r k
13 -11.113 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
4.27589e-04 -1.08520e-05 2.13300e-06 -2.60270e-07 1.08720e-08
Surface number Curvature radius Conical coefficient s r k
17 63697.743 0.000
Aspheric coefficient
A ₄ A ₆
1.70710e-05 -8.57460e-07
Surface number Curvature radius Conical coefficient s r k
18 -11.107 0.000
Aspheric coefficient
A ₄ A ₆ A ₈
-3.71076e-05 -1.65799e-06 1.10000e-08

Various data Zoom ratio 11.514
Wide angle Medium telephoto 10 times the wide angle end
Focal length position Focal length 5.102 17.151 58.740 50.824
F number 3.252 5.432 6.300 6.167
Full angle of view 75.411 25.621 7.674 8.871
Image height 3.830 3.830 3.830 3.830
Total lens length 43.094 55.284 65.746 65.462
BF 5.972 5.344 5.364 5.908
Object distance ∞ ∞ ∞ ∞
D3 0.300 9.226 20.410 19.557
D10 13.010 6.255 1.597 2.204
D16 3.165 13.812 17.728 17.146
D18 4.545 3.916 3.937 4.480
Diaphragm diameter 2.290 2.290 2.290 2.290
Entrance pupil position 11.786 32.432 109.557 99.295
Exit pupil position -11.583 -134.232 421.087 876.434
Front principal point position 15.405 47.476 176.597 153.086
Rear principal point position -4.702 -16.751 -58.340 -44.916

Single lens data
lens Start focal length L ₁₁ 1 -99.490
L ₁₂ 2 26.358
L ₂₁ 4 -7.908
L ₂₂ 6 -8.934
L ₂₃ 7 18.000
L ₂₄ 9 27.891
L ₃₁ 12 7.223
L ₃₂ 14 8.353
L ₃₃ 15 -4.326
L ₄₁ 17 20.925

Zoom lens group data
group Start surface Group focal length Group length Front principal point position Rear principal point position G ₁ 1 36.855 4.700 -0.141 -3.007
G ₂ 4 -5.952 7.597 1.298 -3.952
G ₃ 11 9.777 5.630 -3.062 -4.845
G ₄ 17 20.925 2.720 1.777 -0.000

Group magnification
Wide angle Medium telephoto 10 times the wide angle end
Position to be the focal length G ₁ 0.000 0.000 0.000 0.000
G ₂ -0.226 -0.343 -0.962 -0.845
G ₃ -0.856 -1.824 -2.228 -2.273
G ₄ 0.715 0.745 0.744 0.718

Data related to the above conditional expression Conditional expression (1)
SF _G4 = (r _G4o + r _G4i ) / (r _G4o -r _G4i ): 1.000
Conditional expression (2)
SF _G4 : 1.000
Conditional expressions (3), (4)
SF _G1o-G4i = (r _G1o + r _G4i ) / (r _G1o -r _G4i ): 0.296
Conditional expression (5)
ΔD _w-w10 / L _t : 0.292
Conditional expression (6)
φ _G2n2 / φ _G2n1 : 0.885
Conditional expression (7)
| Φ _G2p2 / φ _G2n1 |: 0.440
Conditional expression (8)
nd _{G2n2 -nd G2p1} : 0.060
Conditional expression (9)
νd _G2n2 −νd _G2p1 : 29.83
Conditional expression (10)
_ΔVG2w-m / _ΔVG2m-t : −4.52
Conditional expression (11)
(ASP _22c × | Δνd ₂₂ |) / (ASP _22o + ASP _22i ): 29.1
Conditional expression (12)
| ΔV _G4w-t / f _w |: 0.014

  The zoom optical system according to Example 5 will be described in detail below with reference to FIGS. The optical configuration of the zoom optical system of the present embodiment and the movement of each lens group during zooming except for the fourth lens group are substantially the same as those of the zoom optical system of Embodiments 1 to 4, and thus have substantially the same configuration. The members having the same reference numerals are given, and detailed descriptions thereof are omitted.

  FIG. 13 is a cross-sectional view along the optical axis showing the optical configuration at the time of focusing on an object point at infinity of the zoom optical system according to the present embodiment, where (a) is the wide-angle end, (b) is the middle, c) shows the state at the telephoto end. 14A and 14B are diagrams showing spherical aberration, astigmatism, distortion aberration, and lateral chromatic aberration when the zoom optical system shown in FIG. 13 is focused on an object point at infinity. FIG. 14A is a wide-angle end, and FIG. In the middle, (c) shows the state at the telephoto end. 15A and 15B are diagrams illustrating lateral coma aberration when the zoom optical system illustrated in FIG. 13 is focused on an object point at infinity. FIG. 15A is a wide-angle end, FIG. 15B is an intermediate end, and FIG. 15C is a telephoto end. Each state is shown.

  First, the movement of each lens unit of the zoom optical system of the present embodiment at the time of zooming will be described.

At the time of zooming from the wide angle end to the telephoto end, the first lens group G ₁ moves to the object side. The second lens group G ₂ reciprocates on the optical axis Lc so as to move first to the object side and then to the image side while increasing the distance from the first lens group G ₁ . The third lens group G ₃ moves together with the aperture stop S along the optical axis Lc toward the object side while narrowing the distance from the second lens group G ₂ . The fourth lens group G ₄ does not move.

  Next, numerical data relating to the lenses constituting the zoom optical system of the present embodiment will be shown.

Numerical data 5
Unit mm
Surface data Surface number Curvature radius Surface spacing Refractive index Abbe number Effective diameter s r d nd νd
0 (object surface) ∞ ∞
1 19.9393 0.9000 1.94595 17.98 9.600
2 16.5045 3.8000 1.59201 67.02 9.130
3 (Aspherical surface) -1023.5356 D3 8.850
4 57.8193 0.8000 1.88300 40.76 6.346
5 6.0512 3.0813 4.657
6 (Aspherical) 13937.0727 0.7000 1.69350 53.21 4.504
7 (Aspherical surface) 6.0041 0.8500 1.63387 23.38 4.369
8 (Aspherical) 12.3693 0.3000 4.353
9 10.9029 1.7900 1.92286 18.90 4.389
10 19.3733 D10 4.700
11 (Aperture) ∞ -0.1000 2.306
12 (Aspherical) 5.9431 3.3200 1.59201 67.02 2.398
13 (Aspherical surface) -14.3881 0.1400 2.358
14 6.3074 1.8800 1.49700 81.54 2.276
15 -8.0245 0.3900 1.61293 37.00 2.038
16 3.6314 D16 1.850
17 (Aspherical surface) 34988.2749 2.7200 1.53071 55.69 4.895
18 (Aspherical surface) -10.5779 D18 5.037
19 ∞ 0.3000 l.51633 64.14 4.296
20 ∞ 0.5000 4.271
21 ∞ 0.5000 1.51633 64.14 4.208
22 ∞ 0.4100 4.170
23 (Image plane) ∞

Aspherical data Surface number Radius of curvature Conical coefficient s r k
3 -1023.536 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
8.35195e-06 -2.29098e-09 -7.49370e-12 2.26300e-13 -1.46640e-15
Surface number Curvature radius Conical coefficient s r k
6 13937.073 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
-1.37173e-03 3.18973e-05 -4.05423e-07 1.18290e-08 -2.17830e-10
Surface number Curvature radius Conical coefficient s r k
7 6.004 0.000
Aspheric coefficient
A ₄ A ₆ A ₈
-2.83242e-03 3.83610e-05 -3.39659e-07
Surface number Curvature radius Conical coefficient s r k
8 12.369 0.000
Aspheric coefficient
A ₄ A ₆ A ₈
-1.33210e-03 3.83610e-05 -3.39659e-07
Surface number Curvature radius Conical coefficient s r k
12 5.943 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
-4.24607e-04 -1.37556e-05 1.26882e-06 -1.30670e-07 4.87140e-09
Surface number Curvature radius Conical coefficient s r k
13 -14.388 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
4.80281e-04 -1.08520e-05 2.13300e-06 -2.60270e-07 1.08720e-08
Surface number Curvature radius Conical coefficient s r k
17 34988.275 0.000
Aspheric coefficient
A ₄ A ₆
1.15108e-04 -8.57460e-07
Surface number Curvature radius Conical coefficient s r k
18 -10.578 0.000
Aspheric coefficient
A ₄ A ₆ A ₈
6.41007e-05 -2.25212e-06 1.10000e-08

Various data Zoom ratio 11.585
Wide angle Medium telephoto 10 times the wide angle end
Focal length position Focal length 5.083 17.168 58.893 50.830
F number 3.245 5.407 6.300 6.285
Full angle of view 75.649 25.822 7.762 9.004
Image height 3.830 3.830 3.830 3.830
Total lens length 43.015 54.979 65.792 65.522
BF 5.593 5.597 5.601 5.597
Object distance ∞ ∞ ∞ ∞
D3 0.300 9.193 20.456 19.485
D10 13.255 6.212 1.598 2.378
D16 3.296 13.406 17.565 17.491
D18 4.160 4.160 4.160 4.160
Diaphragm diameter 2.306 2.306 2.306 2.306
Entrance pupil position 11.700 32.120 109.109 97.896
Exit pupil position -12.003 -150.773 236.494 245.574
Front principal point 15.314 47.403 183.024 159.493
Rear principal point position -4.677 -16.758 -58.479 -45.233

Single lens data
lens Start focal length L ₁₁ 1 -116.070
L ₁₂ 2 27.474
L ₂₁ 4 -7.710
L ₂₂ 6 -8.662
L ₂₃ 7 17.500
L ₂₄ 9 24.533
L ₃₁ 12 7.564
L ₃₂ 14 7.429
L ₃₃ 15 -4.028
L ₄₁ 17 19.926

Zoom lens group data
group Start surface Group focal length Group length Front principal point position Rear principal point position G ₁ 1 37.042 4.700 -0.306 -3.153
G ₂ 4 -5.985 7.521 1.170 -4.008
G ₃ 11 9.669 5.630 -3.461 -4.967
G ₄ 17 19.926 2.720 1.776 -0.001

Group magnification
Wide angle Medium telephoto 10 times the wide angle end
Position to be the focal length G ₁ 0.000 0.000 0.000 0.000
G ₂ -0.226 -0.341 -0.953 -0.826
G ₃ -0.843 -1.889 -2.320 -2.312
G ₄ 0.719 0.719 0.719 0.719

Data related to the above conditional expression Conditional expression (1)
SF _G4 = (r _G4o + r _G4i ) / (r _G4o -r _G4i ): 0.999
Conditional expression (2)
SF _G4 : 0.999
Conditional expressions (3), (4)
SF _G1o-G4i = (r _G1o + r _G4i ) / (r _G1o -r _G4i ): 0.307
Conditional expression (5)
ΔD _w-w10 / L _t : 0.290
Conditional expression (6)
φ _G2n2 / φ _G2n1 : 0.891
Conditional expression (7)
| Φ _G2p2 / φ _G2n1 |: 0.315
Conditional expression (8)
nd _{G2n2 -nd G2p1} : 0.060
Conditional expression (9)
νd _G2n2 −νd _G2p1 : 29.83
Conditional expression (10)
_ΔVG2w-m / _ΔVG2m-t : −6.75
Conditional expression (11)
(ASP _22c × | Δνd ₂₂ |) / (ASP _22o + ASP _22i ): 41.8
Conditional expression (12)
| ΔV _G4w-t / f _w |: _0.00

  The zoom optical system according to Example 6 will be described in detail below with reference to FIGS. The optical configuration excluding the third lens group of the zoom optical system of the present embodiment and the movement of each lens group at the time of zooming are substantially the same as those of the zoom optical system of Embodiments 1 to 5, and therefore have substantially the same configuration. The members having the same reference numerals are given, and detailed descriptions thereof are omitted.

  FIG. 16 is a cross-sectional view along the optical axis showing the optical configuration of the zoom optical system according to the present embodiment when focusing on an object point at infinity, where (a) is a wide angle end, (b) is an intermediate, c) shows the state at the telephoto end. FIG. 17 is a diagram showing spherical aberration, astigmatism, distortion, and chromatic aberration of magnification when the zoom optical system shown in FIG. 16 is focused on an object point at infinity, where (a) is the wide-angle end, and (b) is In the middle, (c) shows the state at the telephoto end. 18A and 18B are diagrams illustrating lateral coma aberration when the zoom optical system illustrated in FIG. 16 is focused on an object point at infinity. FIG. 18A is a wide-angle end, FIG. 18B is an intermediate end, and FIG. 18C is a telephoto end. Each state is shown.

  First, the optical configuration of the zoom optical system of the present embodiment will be described with reference to FIG. In the description of the aspheric lens, the shape of the lens is a shape in the vicinity of the optical axis of light from the front object side.

In the zoom optical system of the present embodiment, on the optical axis Lc, in order from the object side, a positive first lens group G ₁ , a negative second lens group G ₂ , a positive third lens group G ₃ , and a positive first lens group G _{3 are} arranged. Four lens groups G ₄ are arranged. _On the object side of the third lens group G ₃ , an aperture stop S is provided so as to move integrally with the third lens group G ₃ . Note that an imaging element having a low-pass filter LF, a CCD cover glass CG, and an imaging surface IM is arranged on the image side of the fourth lens group G ₄ in order from the object side.

The first lens group G ₁ is composed of, in order from the object side, a positive lens L ₁₁ that is a negative meniscus lens having a convex surface facing the object side and a lens L ₁₂ that is a biconvex lens having an aspheric surface on the image side. It consists only of cemented lenses.

The second lens group G ₂ includes, in order from the object side, a lens L ₂₁ that is a negative meniscus lens having a convex surface facing the object side, and a lens that is a negative meniscus lens having both surfaces aspherical and the convex surface facing the object side. A negative cemented lens composed of L ₂₂ and a lens L ₂₃ which is a positive meniscus lens having both surfaces aspherical and having a convex surface facing the object side; and a lens L ₂₄ which is a positive meniscus lens having a convex surface facing the object side and It is comprised by.

The third lens group G ₃ includes, in order from the object side, a lens L ₃₁ that is a biconvex lens having both aspheric surfaces, a lens L ₃₂ that is a biconvex lens, and a lens L ₃₃ that is a biconcave lens having an aspheric surface on the image side. And a negative cemented lens.

Incidentally, the cemented lens constituting the third lens group G _3, only the surface of the most image side is aspherical. Therefore, coma aberration, spherical aberration, and the like generated in the third lens group can be effectively corrected by this aspherical surface to be kept small.

The fourth lens group G ₄ includes only a lens L ₄₁ that is a biconvex lens having both aspheric surfaces.

  Next, numerical data relating to the lenses constituting the zoom optical system of the present embodiment will be shown.

Numerical data 6
Unit mm
Surface data Surface number Curvature radius Surface spacing Refractive index Abbe number Effective diameter s r d nd νd
0 (object surface) ∞ ∞
1 20.8145 0.9000 1.92286 20.88 9.600
2 16.5877 3.8000 1.59201 67.02 9.119
3 (Aspherical surface) -225.6054 D3 8.850
4 69.9769 0.8000 1.88300 40.76 6.258
5 6.0251 3.0241 4.594
6 (Aspherical) 863.6638 0.7000 1.74250 49.27 4.444
7 (Aspherical surface) 6.6265 0.8451 1.63387 23.38 4.350
8 (Aspherical) 15.2235 0.3000 4.345
9 11.6966 1.7900 1.92286 18.90 4.378
10 21.5616 D10 4.700
11 (Aperture) ∞ -0.1000 2.310
12 (Aspherical) 6.0023 3.3200 1.59201 67.02 2.395
13 (Aspherical surface) -13.8703 0.1400 2.353
14 7.1798 1.8800 1.49700 81.54 2.266
15 -8.1988 0.3900 1.61293 37.00 2.025
16 (Aspherical) 3.9435 D16 1.850
17 (Aspherical surface) 104006.0363 2.7200 1.53071 55.69 4.733
18 (Aspherical) -10.9002 D18 4.907
19 ∞ 0.3000 l.51633 64.14 4.296
20 ∞ 0.5000 4.273
21 ∞ 0.5000 1.51633 64.14 4.222
22 ∞ 0.4100 4.190
23 (Image plane) ∞

Aspherical data Surface number Radius of curvature Conical coefficient s r k
3 -225.605 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
8.62567e-06 -7.65080e-09 -7.49370e-12 2.26300e-13 -1.46640e-15
Surface number Curvature radius Conical coefficient s r k
6 863.664 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
-1.23855e-03 1.19059e-05 1.01518e-07 1.18290e-08 -2.17830e-10
Surface number Curvature radius Conical coefficient s r k
7 6.627 0.000
Aspheric coefficient
A ₄ A ₆ A ₈
-2.20526e-03 1.46140e-05 3.55363e-07
Surface number Curvature radius Conical coefficient s r k
8 15.223 0.000
Aspheric coefficient
A ₄ A ₆ A ₈
-1.17262e-03 1.46140e-05 3.55363e-07
Surface number Curvature radius Conical coefficient s r k
12 6.002 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
-5.17903e-04 -2.08079e-05 1.26882e-06 -1.30670e-07 4.87140e-09
Surface number Curvature radius Conical coefficient s r k
13 -13.870 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
1.94464e-04 -1.08520e-05 2.13300e-06 -2.60270e-07 1.08720e-08
Surface number Curvature radius Conical coefficient s r k
16 3.943 0.000
Aspheric coefficient
A ₄ A ₆ A ₈
5.34119e-04 2.65221e-05 5.33697e-07
Surface number Curvature radius Conical coefficient s r k
17 104006.036 0.000
Aspheric coefficient
A ₄ A ₆
-2.41581e-06 -8.57460e-07
Surface number Curvature radius Conical coefficient s r k
18 -10.900 0.000
Aspheric coefficient
A ₄ A ₆ A ₈
-5.48318e-05 -1.48866e-06 1.10000e-08

Various data Zoom ratio 11.559
Wide angle Medium telephoto 10 times the wide angle end
Focal length position Focal length 5.086 17.164 58.787 50.691
F number 3.258 5.440 6.300 6.226
Full angle of view 75.577 25.530 7.660 8.878
Image height 3.830 3.830 3.830 3.830
Total lens length 43.194 55.494 65.760 65.454
BF 5.988 5.332 5.350 5.499
Object distance ∞ ∞ ∞ ∞
D3 0.300 9.415 20.551 19.652
D10 13.237 6.404 1.597 2.361
D16 3.160 13.833 17.752 17.433
D18 4.550 3.895 3.912 4.061
Diaphragm diameter 2.310 2.310 2.310 2.310
Entrance pupil position 11.454 32.426 108.965 98.582
Exit pupil position -11.606 -151.781 307.214 386.524
Front principal point position 15.070 47.715 179.200 156.017
Rear principal point position -4.676 -16.754 -58.377 -45.193

Single lens data
lens Start focal length L ₁₁ 1 -98.586
L ₁₂ 2 26.253
L ₂₁ 4 -7.510
L ₂₂ 6 -8.997
L ₂₃ 7 17.832
L ₂₄ 9 25.482
L ₃₁ 12 7.545
L ₃₂ 14 8.028
L ₃₃ 15 -4.292
L ₄₁ 17 20.537

Zoom lens group data
group Start surface Group focal length Group length Front principal point position Rear principal point position G ₁ 1 36.738 4.700 -0.066 -2.938
G ₂ 4 -6.040 7.459 1.050 -4.130
G ₃ 11 9.895 5.630 -3.312 -4.960
G ₄ 17 20.537 2.720 1.777 -0.000

Group magnification
Wide angle Medium telephoto 10 times the wide angle end
Position to be the focal length G ₁ 0.000 0.000 0.000 0.000
G ₂ -0.229 -0.349 -0.981 -0.856
G ₃ -0.854 -1.807 -2.206 -2.202
G ₄ 0.708 0.740 0.739 0.732

Data related to the above conditional expression Conditional expression (1)
SF _G4 = (r _G4o + r _G4i ) / (r _G4o -r _G4i ): 1.000
Conditional expression (2)
SF _G4 : 1.000
Conditional expressions (3), (4)
SF _G1o-G4i = (r _G1o + r _G4i ) / (r _G1o -r _G4i ): 0.313
Conditional expression (5)
ΔD _w-w10 / L _t : _0.293
Conditional expression (6)
φ _G2n2 / φ _G2n1 : 0.835
Conditional expression (7)
| Φ _G2p2 / φ _G2n1 |: 0.295
Conditional expression (8)
nd _{G2n2 -nd G2p1} : 0.109
Conditional expression (9)
νd _G2n2 −νd _G2p1 : 25.89
Conditional expression (10)
_ΔVG2w-m / _ΔVG2m-t : −3.66
Conditional expression (11)
(ASP _22c × | Δνd ₂₂ |) / (ASP _22o + ASP _22i ): 27.5
Conditional expression (12)
| ΔV _G4w-t / f _w |: 0.015

  The zoom optical system according to Example 7 will be described in detail below with reference to FIGS. Note that the optical configuration of the zoom optical system of the present embodiment and the movement of each lens group during zooming are substantially the same as those of the zoom optical systems of Embodiments 1 to 6, and therefore, members having substantially the same configuration are the same. And a detailed description thereof will be omitted.

  FIG. 19 is a cross-sectional view along the optical axis showing the optical configuration of the zoom optical system according to the present embodiment when focusing on an object point at infinity, where (a) is a wide angle end, (b) is an intermediate, c) shows the state at the telephoto end. FIG. 20 is a diagram showing spherical aberration, astigmatism, distortion, and chromatic aberration of magnification when the zoom optical system shown in FIG. 16 is focused on an object point at infinity, (a) is the wide-angle end, and (b) is In the middle, (c) shows the state at the telephoto end. FIG. 21 is a diagram showing lateral coma aberration when the zoom optical system shown in FIG. 16 is focused on an object point at infinity, where (a) is a wide-angle end, (b) is an intermediate end, and (c) is a telephoto end. Each state is shown.

  Numerical data relating to the lenses constituting the zoom optical system of the present embodiment will be shown below.

Numerical data 7
Unit mm
Surface data Surface number Curvature radius Surface spacing Refractive index Abbe number Effective diameter s r d nd νd
0 (object surface) ∞ ∞
1 19.8397 0.9000 1.94595 17.98 9.600
2 16.4175 3.8000 1.59201 67.02 9.126
3 (Aspherical surface) -1225.7535 D3 8.850
4 105.5527 0.8000 1.88300 40.76 6.802
5 6.4409 3.1624 5.013
6 (Aspherical surface) 5249.4851 0.7000 1.76802 49.24 4.893
7 (Aspherical) 6.3406 0.8500 1.72151 29.23 4.725
8 (Aspherical) 12.0206 0.3000 4.687
9 9.8776 1.7900 1.92286 18.90 4.798
10 21.6457 D10 4.700
11 (Aperture) ∞ -0.1000 2.401
12 (Aspherical) 5.9463 3.3200 1.59201 67.02 2.482
13 (Aspherical) -16.1041 0.1400 2.395
14 6.7027 1.8800 1.49700 81.54 2.299
15 -8.0019 0.3900 1.61293 37.00 2.048
16 3.6794 D16 1.850
17 (Aspherical) 116072.0079 2.7200 1.53071 55.69 4.755
18 (Aspherical) -11.0105 D18 4.934
19 ∞ 0.3000 l.51633 64.14 4.278
20 ∞ 0.5000 4.257
21 ∞ 0.5000 1.51633 64.14 4.206
22 ∞ 0.3900 4.172
23 (Image plane) ∞

Aspheric data
  Surface number Curvature radius Conical coefficient
    s r k
     3 -1225.754 0.000
          Aspheric coefficient
               A_Four          A₆          A₈          A_Ten          A₁₂    
           8.21105e-06 -2.71619e-09 -7.49370e-12  2.26300e-13 -1.46640e-15
  Surface number Curvature radius Conical coefficient
    s r k
     6 5249.485 0.000
          Aspheric coefficient
               A_Four          A₆          A₈          A_Ten          A₁₂    
          -5.04493e-04  1.29174e-05 -2.29383e-07  1.18290e-08 -2.17830e-10
  Surface number Curvature radius Conical coefficient
    s r k
     7 6.341 0.000
          Aspheric coefficient
               A_Four          A₆          A₈
          -2.07755e-03  1.23964e-05 -4.35883e-08
  Surface number Curvature radius Conical coefficient
    s r k
     8 12.021 0.000
          Aspheric coefficient
               A_Four          A₆          A₈
          -4.31903e-04  1.23964e-05 -4.35883e-08
  Surface number Curvature radius Conical coefficient
    s r k
    12 5.946 0.000
          Aspheric coefficient
               A_Four          A₆          A₈          A_Ten          A₁₂    
          -4.13390e-04 -1.55189e-05  1.26882e-06 -1.30670e-07  4.87140e-09
  Surface number Curvature radius Conical coefficient
    s r k
    13 -16.104 0.000
          Aspheric coefficient
               A_Four          A₆          A₈          A_Ten          A₁₂    
           3.77763e-04 -1.08520e-05  2.13300e-06 -2.60270e-07  1.08720e-08
  Surface number Curvature radius Conical coefficient
    s r k
    17 116072.008 0.000
          Aspheric coefficient
               A_Four          A₆
          -1.50949e-05 -8.57460e-07
  Surface number Curvature radius Conical coefficient
    s r k
    18 -11.010 0.000
          Aspheric coefficient
               A_Four          A₆          A₈
          -5.38393e-05 -2.22443e-06  1.10000e-08

Various data Zoom ratio 11.579
Wide angle Medium telephoto 10 times the wide angle end
Focal length position Focal length 5.086 17.170 58.890 50.691
F number 3.206 5.505 6.300 6.226
Full angle of view 75.610 25.781 7.681 8.904
Image height 3.830 3.830 3.830 3.830
Total lens length 45.589 55.703 65.728 65.498
BF 5.924 5.318 5.284 6.027
Object distance ∞ ∞ ∞ ∞
D3 0.300 8.174 19.938 19.085
D10 15.568 7.186 1.780 2.437
D16 3.145 14.373 18.074 17.296
D18 4.506 3.900 3.866 4.609
Diaphragm diameter 2.401 2.401 2.401 2.401
Entrance pupil position 12.214 29.417 103.017 93.783
Exit pupil position -11.340 -176.189 304.743 603.766
Front principal point position 15.802 44.963 173.488 148.970
Rear principal point position -4.696 -16.780 -58.500 -44.833

Single lens data
lens Start focal length L ₁₁ 1 -115.366
L ₁₂ 2 27.396
L ₂₁ 4 -7.798
L ₂₂ 6 -8.266
L ₂₃ 7 17.500
L ₂₄ 9 18.348
L ₃₁ 12 7.771
L ₃₂ 14 7.664
L ₃₃ 15 -4.061
L ₄₁ 17 20.745

Zoom lens group data
group Start surface Group focal length Group length Front principal point position Rear principal point position G ₁ 1 36.985 4.700 -0.317 -3.164
G ₂ 4 -6.559 7.602 0.961 -4.368
G ₃ 11 10.483 5.630 -3.928 -5.267
G ₄ 17 20.745 2.720 1.777 -0.000

Group magnification
Wide angle Medium telephoto 10 times the wide angle end
Position to be the focal length G ₁ 0.000 0.000 0.000 0.000
G ₂ -0.252 -0.362 -1.031 -0.909
G ₃ -0.763 -1.725 -2.072 -2.132
G ₄ 0.714 0.744 0.745 0.709

Data related to the above conditional expression Conditional expression (1)
SF _G4 = (r _G4o + r _G4i ) / (r _G4o -r _G4i ): 1.000
Conditional expression (2)
SF _G4 : 1.000
Conditional expressions (3), (4)
SF _G1o-G4i = (r _G1o + r _G4i ) / (r _G1o -r _G4i ): 0.286
Conditional expression (5)
ΔD _w-w10 / L _t : 0.285
Conditional expression (6)
φ _G2n2 / φ _G2n1 : 0.944
Conditional expression (7)
| Φ _G2p2 / φ _G2n1 |: _0.425
Conditional expression (8)
nd _{G2n2 -nd G2p1} : 0.047
Conditional expression (9)
νd _G2n2 −νd _G2p1 : 20.01
Conditional expression (10)
_ΔVG2w-m / _ΔVG2m-t : -1.29
Conditional expression (11)
(ASP _22c × | Δνd ₂₂ |) / (ASP _22o + ASP _22i ): 83.6
Conditional expression (12)
| ΔV _G4w-t / f _w |: 0.014

  The zoom optical system according to Example 8 will be described in detail below with reference to FIGS. The optical configuration excluding the second lens group of the zoom optical system of the present embodiment and the movement of each lens group during zooming are substantially the same as those of the zoom optical system of Embodiments 1 to 6, and therefore have substantially the same configuration. The members having the same reference numerals are given, and detailed descriptions thereof are omitted.

  FIG. 22 is a cross-sectional view along the optical axis showing the optical configuration at the time of focusing on an object point at infinity of the zoom optical system according to the present embodiment, where (a) is the wide-angle end, (b) is the middle, c) shows the state at the telephoto end. FIG. 23 is a diagram showing spherical aberration, astigmatism, distortion aberration, and lateral chromatic aberration when the zoom optical system shown in FIG. 22 is focused on an object point at infinity, where (a) is the wide-angle end, and (b) is In the middle, (c) shows the state at the telephoto end. FIG. 24 is a diagram showing lateral coma aberration when the zoom optical system shown in FIG. 22 is focused on an object point at infinity, where (a) is a wide-angle end, (b) is an intermediate end, and (c) is a telephoto end. Each state is shown.

  First, the optical configuration of the second lens group of the zoom optical system of the present embodiment will be described with reference to FIG. In the description of the aspheric lens, the shape of the lens is a shape in the vicinity of the optical axis of light from the front object side.

The second lens group G ₂ of the zoom optical system according to the present exemplary embodiment includes, in order from the object side, a lens L ₂₁ that is a negative meniscus lens having a convex surface directed toward the object side, and a convex surface directed toward the object side having both aspheric surfaces. A lens L ₂₂ that is a negative meniscus lens, a lens L ₂₃ that is a positive meniscus lens having a convex surface facing the object side that is aspheric on both sides, and a lens L that is a positive meniscus lens having a convex surface facing the object side _{And 24} .

  Next, numerical data relating to the lenses constituting the zoom optical system of the present embodiment will be shown.

Numerical data 8
Unit mm
Surface data Surface number Curvature radius Surface spacing Refractive index Abbe number Effective diameter s r d nd νd
0 (object surface) ∞ ∞
1 19.8964 0.9000 1.94595 17.98 9.600
2 16.5301 3.8000 1.59201 67.02 9.132
3 (Aspherical) -1470.7525 D3 8.850
4 89.7363 0.8000 1.88300 40.76 6.683
5 6.4923 3.0472 4.950
6 (Aspherical) 3533.2262 0.7000 1.77377 47.17 4.821
7 (Aspherical) 6.4369 0.2000 4.733
8 (Aspherical surface) 6.5 171 0.8500 1.72151 29.23 4.744
9 (Aspherical) 12.7331 0.3000 4.740
10 9.7949 1.7900 1.92286 18.90 4.860
11 18.3686 D11 4.700
12 (Aperture) ∞ -0.1000 2.382
13 (Aspherical) 5.9399 3.3200 1.59201 67.02 2.473
14 (Aspherical surface) -16.8713 0.1400 2.387
15 6.5405 1.8800 1.49700 81.54 2.297
16 -8.4790 0.3900 1.61293 37.00 2.045
17 3.6221 D17 1.850
18 (Aspherical) 126339.7743 2.7200 1.53071 55.69 4.743
19 (Aspherical surface) -10.9935 D19 4.919
20 ∞ 0.3000 1.51633 64.14 4.272
21 ∞ 0.5000 4.252
22 ∞ 0.5000 1.51633 64.14 4.201
23 ∞ 0.4100 4.167
24 (Image plane) ∞

Aspherical data Surface number Radius of curvature Conical coefficient s r k
3 -1470.752 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
8.34805e-06 -2.36501e-09 -7.49370e-12 2.26300e-13 -1.46640e-15
Surface number Curvature radius Conical coefficient s r k
6 3533.226 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
-1.21192e-04 -2.12253e-05 2.33239e-07 1.18290e-08 -2.17830e-10
Surface number Curvature radius Conical coefficient s r k
7 6.437 0.000
Aspheric coefficient
A ₄ A ₆ A ₈
-1.79232e-03 -2.61352e-05 6.28232e-07
Surface number Curvature radius Conical coefficient s r k
8 6.517 0.000
Aspheric coefficient
A ₄
-2.16063e-03
Surface number Curvature radius Conical coefficient s r k
9 12.733 0.000
Aspheric coefficient
A ₄
-4.97586e-04
Surface number Curvature radius Conical coefficient s r k
13 5.940 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
-3.96232e-04 -1.62403e-05 1.26882e-06 -1.30670e-07 4.87140e-09
Surface number Curvature radius Conical coefficient s r k
14 -16.871 0.000
Aspheric coefficient
A ₄ A ₆ A ₈ A ₁₀ A ₁₂
3.81327e-04 -1.08520e-05 2.13300e-06 -2.60270e-07 1.08720e-08
Surface number Curvature radius Conical coefficient s r k
18 126339.774 0.000
Aspheric coefficient
A ₄ A ₆
1.00640e-05 -8.57460e-07
Surface number Curvature radius Conical coefficient s r k
19 -10.993 0.000
Aspheric coefficient
A ₄ A ₆ A ₈
-3.00176e-05 -2.64213e-06 1.10000e-08

Various data Zoom ratio 11.579
Wide angle Medium telephoto 10 times the wide angle end
Focal length position Focal length 5.086 17.170 58.890 50.691
F number 3.251 5.452 6.300 6.226
Full angle of view 75.619 25.700 7.698 8.920
Image height 3.830 3.830 3.830 3.830
Total lens length 45.787 56.159 65.731 65.507
BF 5.980 5.332 5.317 5.980
Object distance ∞ ∞ ∞ ∞
D3 0.300 8.860 20.143 19.305
D11 15.630 7.390 1.796 2.493
D17 3.139 13.840 17.739 16.991
D19 4.542 3.894 3.879 4.542
Diaphragm diameter 2.382 2.382 2.382 2.382
Entrance pupil position 12.221 31.797 105.762 96.495
Exit pupil position -11.311 -138.373 377.555 964.162
Front principal point position 15.811 46.916 173.968 150.060
Rear principal point position -4.676 -16.760 -58.480 -44.882

Single lens data
lens Start focal length L ₁₁ 1 -118.713
L ₁₂ 2 27.638
L ₂₁ 4 -7.962
L ₂₂ 6 -8.335
L ₂₃ 8 17.500
L ₂₄ 10 20.668
L ₃₁ 13 7.845
L ₃₂ 15 7.751
L ₃₃ 16 -4.091
L ₄₁ 18 20.713

Zoom lens group data
group Start surface Group focal length Group length Front principal point position Rear principal point position G ₁ 1 37.077 4.700 -0.324 -3.170
G ₂ 4 -6.568 7.687 0.953 -4.479
G ₃ 12 10.549 5.630 -4.010 -5.305
G ₄ 18 20.713 2.720 1.777 -0.000

Group magnification
Wide angle Medium telephoto 10 times the wide angle end
Position to be the focal length G ₁ 0.000 0.000 0.000 0.000
G ₂ -0.252 -0.375 -1.052 -0.928
G ₃ -0.766 -1.664 -2.031 -2.079
G ₄ 0.711 0.743 0.743 0.711

Data related to the above conditional expression Conditional expression (1)
SF _G4 = (r _G4o + r _G4i ) / (r _G4o -r _G4i ): 1.000
Conditional expression (2)
SF _G4 : 1.000
Conditional expressions (3), (4)
SF _G1o-G4i = (r _G1o + r _G4i ) / (r _G1o -r _G4i ): 0.288
Conditional expression (5)
ΔD _w-w10 / L _t : 0.288
Conditional expression (10)
_ΔVG2w-m / _ΔVG2m-t : −1.06
Conditional expression (12)
| ΔV _G4w-t / f _w |: 0.014

In the above Examples 1 to 7, the lens L ₂₃ is a positive meniscus lens constituting the negative cemented lens in the second lens group G ₂ includes, also be formed by a glass material, is formed of a resin material It may be.
If the lens L ₂₃ is made of a glass material, there are many types compared to the resin material, and the positive lens and negative lens material constituting the negative cemented lens can be selected from a larger number of combinations. Optimal optical performance can be obtained. In addition, an optical system can be obtained in which changes in optical characteristics are small with respect to changes in temperature and humidity, and performance deterioration due to environmental changes is unlikely to occur.

On the other hand, if the lens L ₂₃ with the resin material, on the image side of the lens L ₂₂ is a negative meniscus lens constituting the negative cemented lens may be formed by directly molding a lens L ₂₃ (such a lens Is called a compound lens).

  In such direct molding, one lens portion is formed by applying or discharging a liquid resin on the other lens and then curing, so that compared with the case where a cemented lens is produced alone, Thickness and edge can be made very thin. Therefore, a cemented lens manufactured using direct molding can be approximately the thickness of one lens.

Therefore, the lens L ₂₃ be formed of a resin material, it is possible to shorten the overall length of the optical system in the collapsed state, of both the non-collapsed state condition.

  In addition, the resin material is advantageous in that it is lighter and cheaper than the glass material.

  In addition, it is preferable to use energy curable resin etc. as a resin material used for direct shaping | molding. If an energy curable resin is used, a composite lens can be easily produced simply by applying or discharging resin onto one lens and then applying the energy by pushing the resin with a mold.

  The energy curable resin may be any type such as a thermosetting type or an ultraviolet curable type, and an ultraviolet curable type is particularly preferable. If an ultraviolet curable energy curable resin is used, the resin can be cured without heating, and therefore, a material having low thermal durability such as plastic can be used for the lens serving as the base material. Also, the molding apparatus can be reduced in size.

Further, in the above embodiments, the lens L ₄₁ both sides constituting the fourth lens group G ₄ is biconvex aspheric, it is preferably formed of a resin material.

In general, the fourth lens group G _{4 as} the final lens group is often a focusing group, and in such a case, it is necessary to move it frequently. If such a focusing group is lightweight, the motor can be reduced in size and power consumption can be reduced.

Therefore, it is preferable that the lens L ₄₁ constituting the fourth lens group G ₄ is made of a light resin material compared to the glass material.

  Further, in each of the above embodiments, the optical system is a zoom optical system, but it may be used as a single focus optical system.

  Further, the zoom optical system of the present embodiment may be configured as follows.

  In the zoom optical system of the present embodiment, a flare stop may be disposed in addition to the brightness stop in order to cut off harmful light beams such as ghosts and flares. The flare stop is disposed at the object side of the first lens group, between the first lens group and the second lens group, between the second lens group and the third lens group, and between the third lens group and the fourth lens group. Any position between the lens group and between the fourth lens group and the imaging surface may be used. Further, the flare stop may be configured using a frame member, or may be configured using another member. Furthermore, the flare stop may be configured by printing directly on the optical member, or may be configured using a paint, an adhesive seal, or the like. Further, the shape of the flare stop may be any shape such as a circle, an ellipse, a rectangle, a polygon, or a shape surrounded by a function curve. Further, the flare stop may cut not only harmful light flux but also light flux such as coma flare around the screen.

  In addition, each lens constituting the zoom optical system of the present embodiment may be provided with an antireflection coating to reduce ghost and flare. In that case, in order to further effectively reduce ghost and flare, it is desirable that the antireflection coat to be applied is a multi-coat. Further, the infrared cut coat may be applied not to the low-pass filter but to the lens surface of each lens, a cover glass, or the like.

  In addition, in order to prevent the occurrence of ghosts and flares, a lens that is used alone is generally applied with an antireflection coating on the air contact surface of the lens. On the other hand, if the adhesive used for bonding has a high refractive index, the cemented lens plays the same role as an anti-reflection coating in which the phase formed by the adhesive has a reflectance equivalent to or less than that of a single-layer coating. For this reason, it is rare that the joint surface is coated. However, if an anti-reflection coating is positively applied to the cemented surface of the cemented lens, ghosts and flares can be further reduced, and a better image can be obtained.

  In particular, recently, high refractive index glass materials with high aberration correction effects have become widespread and are widely used in camera optical systems. However, when high refractive index glass materials are used as cemented lenses, Reflection on the surface can no longer be ignored. In such a case, it is particularly effective to provide an antireflection coating on the joint surface.

The effective usage of such a bonding surface coat is disclosed in JP-A-2-27301, JP-A-2001-324676, JP-A-2005-92115, USP 7116482, and the like. Yes. As the coating material to be used, Ta ₂ O ₅ , TiO ₂ , Nb ₂ O ₅ , ZrO ₂ , HfO ₂ , relatively high refractive index depending on the refractive index of the lens serving as the base material and the refractive index of the adhesive. A coating material such as CeO ₂ , SnO ₂ , In ₂ O ₃ , ZnO, and Y ₂ O ₃ , a coating material such as MgF ₂ , SiO ₂ , and Al ₂ O ₃ having a relatively low refractive index is appropriately selected, and phase conditions The film thickness may be set so as to satisfy the above.

  As a matter of course, the joint surface coat may be a multi-coat as well as the coating on the air contact surface of the lens. By appropriately combining two or more layers of coating materials and film thicknesses, it is possible to further reduce the reflectance and control the spectral characteristics and angular characteristics of the reflectance.

  In the zoom lens according to the present embodiment, it is preferable that focusing for adjusting the focus is performed in the fourth lens group, but any one of the first lens group, the second lens group, and the third lens group is used. You may carry out by a group and you may carry out by a some lens group. The focusing may be performed by moving the entire zoom lens or by moving a part of the lenses.

  In the zoom optical system according to the present embodiment, the decrease in brightness at the periphery of the image may be reduced by shifting the micro lens of the CCD. For example, the design of the CCD microlens may be changed according to the incident angle of the light beam at each image height. Further, the amount of decrease in brightness at the periphery of the image may be corrected by image processing.

  The zoom optical system according to the present embodiment as described above is used for a photographing apparatus, particularly a digital camera or a video camera, which performs photographing by forming an object image formed by the zoom optical system on an image sensor such as a CCD. Can do. The specific example is illustrated below.

  19, 20 and 21 are conceptual views showing the configuration of a digital camera using the zoom optical system of the present embodiment, and FIG. 19 is a front perspective view showing the appearance of the digital camera. FIG. 21 is a rear plan view, and FIG. 21 is a perspective plan view schematically showing the configuration of the digital camera. However, FIGS. 19 and 21 show the zoom lens when it is not retracted.

  The digital camera 10 includes a zoom optical system 11 disposed on the photographing optical path 12, a finder optical system 13 disposed on the finder optical path 14, a shutter button 15, a flash light emitting unit 16, a liquid crystal display monitor 17, and a focal length change. A button 18 and a setting change switch 19 are provided. Further, when the zoom lens 11 is retracted, the cover 20 slides to cover the zoom lens 11 and the viewfinder optical system 13.

  When the cover 20 is opened and the digital camera 10 is set to the photographing state, the zoom lens 11 is in the non-collapsed state shown in FIG. In this state, when the shutter button 15 disposed on the upper part of the digital camera 10 is pressed, shooting is performed through the zoom lens 11, for example, the zoom optical system 11 as described in the first embodiment, in conjunction therewith. The object image is formed on the imaging surface IM of the solid-state imaging device via the zoom optical system 11, the low pass filter LF, and the cover glass CG. Although it does not specifically limit as a solid-state image sensor, CCD, CMOS, etc. are mentioned. Image information of the object image formed on the imaging surface IM of the solid-state imaging device is recorded in the recording unit 22 via the processing unit 21. The recorded image information can be taken out by the processing means 21 and displayed as an electronic image on the liquid crystal display monitor 17 provided on the back of the camera. The recording unit 22 may be provided separately from the processing unit 21 or may be configured to perform recording and writing electronically and magnetically by a flexible disk, a memory card, an MO, or the like. Moreover, it may replace with a solid-state image sensor, and you may comprise as a silver salt camera which has arrange | positioned the silver salt film.

  Further, a finder objective optical system 23 is disposed on the finder optical path 14. The finder objective optical system 23 includes a plurality of lens groups (three groups in the figure) and two prisms, and the focal length changes in conjunction with the zoom optical system 11. The finder objective optical system 23 forms an object image on a field frame 25 of an erecting prism 24 that is an image erecting member. An eyepiece optical system 26 that guides the erect image to the observer's eyeball E is disposed behind the erecting prism 24. A cover member 27 is disposed on the exit side of the eyepiece optical system 26.

  In the digital camera 10 configured in this way, the zoom optical system 11 has a high zoom ratio, is small, and can be retracted. Miniaturization can be realized.

G ₁ first lens group G ₂ the second lens group G ₃ third lens group G ₄ fourth lens group _{L 11, L 12, L 21} , L 22, L 23, L 24, L 31, L 32, L 33 , L ₄₁ lens Lc optical axis S brightness stop LF low pass filter CG cover glass IM imaging surface E observer's eyeball 10 digital camera 11 zoom optical system 12 imaging optical path 13 finder optical system 14 finder optical path 15 shutter button 16 flash emission Section 17 Liquid crystal display monitor 18 Focal length change button 19 Setting change switch 20 Cover 19 Cover member 21 Processing means 22 Recording means 23 Viewfinder objective optical system 24 Erecting prism 25 Field frame 26 Eyepiece optical system 27 Cover member

Claims (23)

In a zoom optical system that is configured by a plurality of lens groups and performs zooming by appropriately changing the interval between the plurality of lens groups,
In order from the object side, a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group are arranged,
The most object side surface of the first lens group has a shape with a convex surface facing the object side,
The zoom optical system according to claim 1, wherein the following conditional expression (1) is satisfied.
SF _G4 = (r _G4o + r _G4i ) / (r _G4o -r _G4i )> 0 ... (1)
However, SF _G4 is the fourth lens group from the shaping factor, r _G4o is the radius of curvature of the most object-side surface of the fourth lens group, r _G4i the radius of curvature of the surface on the most image side of the fourth lens group is there. The zoom optical system according to claim 1, wherein the following conditional expression (2) is satisfied.
0.2 ≦ SF _G4 ≦ 5.0 ... (2)   2. The zoom optical system according to claim 1, wherein the third lens group includes, in order from the object side, a positive single lens and a cemented lens including a positive lens and a negative lens. .   The zoom optical system according to claim 1, wherein the first lens group includes only one lens component. The zoom optical system according to claim 1, wherein the following conditional expressions (3) and (4) are satisfied.
SF _G1o-G4i = (r _G1o + r _G4i ) / (r _G1o -r _G4i ) (3)
0 ≦ SF _G1o-G4i ≦ 0.4 ... (4)
Where SF _G1o-G4i is the shaping factor of the most object side surface of the first lens group and the most image side surface of the fourth lens group, and r _G1o is the _curvature of the most object side surface of the first lens group. The radius, r _G4i, is the radius of curvature of the most image side surface of the fourth lens group. The zoom optical system according to claim 1, wherein the following conditional expression (5) is satisfied.
0.2 ≦ ΔD _w−w10 / L _t ≦ 0.35 ... (5)
Where ΔD _w−w10 is the amount of change in the distance between the first lens group and the second lens group from the wide-angle end to the state where the focal length is at least 10 times the focal length at the wide-angle end, and L _t is the telephoto end. Is the total length of the optical system.   2. The zoom optical system according to claim 1, wherein the second lens group includes a negative single lens, a negative cemented lens, and a positive single lens in order from the object side. The cemented lens of the second lens group comprises a negative lens and a positive lens;
The zoom optical system according to claim 7, wherein the following conditional expression (6) is satisfied.
0.1 ≦ φ _G2n2 / φ _G2n1 ≦ 1.0 ... (6)
Where φ _G2n2 is the refractive power of the negative lens in the cemented lens of the second lens group, and φ _G2n1 is the refractive power of the negative single lens of the second lens group. The zoom optical system according to claim 7, wherein the following conditional expression (7) is satisfied.
0.15 ≦ | φ _G2p2 / φ _G2n1 | ≦ 0.45 ... (7)
Where φ _G2p2 is the refractive power of the positive single lens of the second lens group, and φ _G2n1 is the refractive power of the negative single lens of the second lens group. The cemented lens of the second lens group comprises a negative lens and a positive lens;
The zoom optical system according to claim 7, wherein the following conditional expression (8) is satisfied.
0.05 ≦ nd _{G2n2 −nd G2p1} ≦ 0.2 ... (8)
Here, nd _G2n2 is the refractive index at the d-line of the negative lens of the cemented lens of the second lens group, and nd _G2p1 is the refractive index at the d-line of the positive lens of the cemented lens of the second lens group. The cemented lens of the second lens group comprises a negative lens and a positive lens;
The zoom optical system according to claim 7, wherein the following conditional expression (9) is satisfied.
20 ≦ νd _G2n2 −νd _G2p1 ≦ 50 ... (9)
Where νd _G2n2 is the Abbe number in the d-line of the negative lens of the cemented lens of the second lens group, and νd _G2p1 is the Abbe number in the d-line of the positive lens of the cemented lens in the second lens group. When the focal length of the entire optical system at the wide-angle end is f _w , the focal length of the entire optical system at the telephoto end is f _t , and the focal length of the entire optical system in the intermediate state is √ (f _w × f _t ) The zoom optical system according to claim 1, wherein the position of the second lens group in the intermediate state is closer to the object side than the positions at the wide-angle end and the telephoto end. The zoom optical system according to claim 12, wherein the following conditional expression (10) is satisfied.
−7.0 ≦ ΔV _G2w-m / ΔV _G2m-t ≦ −1.2 ... (10)
However, ΔV _G2w-m is represented by | V _G2m -V _G2w |, ΔV _G2m-t is represented by | V _G2t -V _G2m |, and V _G2w is the position of the second lens group at the wide angle end, V _G2m Is the position of the second lens group in the intermediate state, V _G2t is the position of the second lens group at the telephoto end, and the _signs of ΔV _G2w-m and ΔV _G2m-t are the image side of the second lens group The case of moving from to the object side is positive.   2. The zoom optical system according to claim 1, wherein the position of the second lens group at the telephoto end is closer to the object side than the position of the second lens group at the wide-angle end.   The zoom lens according to claim 7, wherein a cemented surface of the cemented lens of the second lens group is an aspherical surface.   The zoom lens according to claim 7, wherein all surfaces of the cemented lens of the second lens group are aspherical surfaces.   The aspheric amount at the effective diameter of all surfaces of the cemented lens of the second lens group is a negative value when the direction from the object side to the image side on the optical axis is positive. Item 17. The zoom optical system according to Item 16. The zoom optical system according to claim 16, wherein the following conditional expression (11) is satisfied.
10 ≦ (ASP _22c × | Δνd ₂₂ |) / (ASP _22o + ASP _22i ) ≦ 90
(11)
Where ASP _22c is the aspherical amount of the effective diameter of the cemented surface of the cemented lens of the second lens group, Δνd ₂₂ is the difference between the Abbe numbers of the two lenses constituting the cemented lens of the second lens group, and ASP _22o is An aspheric amount at the effective diameter of the object side surface of the cemented lens of the second lens group, and ASP _22i is an aspheric amount at the effective diameter of the image side surface of the cemented lens of the second lens group. The effective diameter is the smallest effective diameter of the effective diameters of the surfaces of the cemented lens of the second lens group.   The zoom optical system according to claim 1, wherein the fourth lens group includes only one lens component.   The zoom optical system according to claim 19, wherein the fourth lens group includes only one positive single lens. The zoom optical system according to claim 1, wherein the following conditional expression (12) is satisfied.
0 ≦ | ΔV _G4w-t / f _w | ≦ 0.1 (12)
However, ΔV _G4w-t is | V _G4t -V _G4w | in expressed, V _G4W the position of the fourth lens group at the wide-angle end, V _G4t the position of the fourth lens group at the telephoto end, f _w is wide The focal length of the entire optical system at the end, and the sign of ΔV _G4w-t is positive when the fourth lens group moves from the image side to the object side.   2. The zoom optical system according to claim 1, wherein the fourth lens group does not move during zooming from the wide-angle end to the telephoto end.   An electronic imaging apparatus comprising the zoom optical system according to any one of claims 1 to 22.

Images