JP2011175280A - Optical system and imaging device using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical system, which can reduce its thickness while having a high variable power ratio and reduces influence of eccentricity to prevent deterioration in performance, and to provide an imaging device using the optical system. <P>SOLUTION: The optical system includes: a first lens group G1 having negative refractive power; a second lens group G2 having positive refractive power; and a cemented lens having positive refractive power as a whole and having cemented surfaces on the optical axis. Lenses constituting the cemented lens satisfy an expression (5): 40<νmax-νmin<80 and an expression (6): 23.7>νmin. In the expressions (5) and (6), νmax is a maximum Abbe number in the cemented lens, and νmin is a minimum Abbe number in the cemented lens. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical system and an image pickup apparatus using the optical system, and in particular, by devising the optical system part, it is possible to reduce the thickness even at a high zoom ratio, and suppress the influence of eccentricity to prevent performance deterioration. The present invention relates to a zoom lens having a configuration suitable for a digital camera and a video camera, and an imaging apparatus using the zoom lens.

  In recent years, zoom lenses, particularly digital camera zoom lenses, are increasingly required to be thin. Compared to a silver salt camera, a digital camera with a small imaging device can generally be designed with a small lens, but the manufacturing error of lens parts and the mounting error of the lens barrel become relatively large, and the performance is reduced by eccentricity. Since it deteriorates, it tends to reduce the yield. In addition, in order to reduce the camera thickness, it is necessary to reduce the number of lenses constituting the zoom lens. In many cases, aberration is corrected by using aspheric surfaces with a small number of lenses.

  However, in such an optical system, the imaging performance is likely to deteriorate due to the relative decentration between the aspheric lenses due to manufacturing errors, and it is difficult to achieve both mass production with good yield and thinning.

  Conventional examples include Patent Document 1, Patent Document 2, Patent Document 3, and the like. However, in Patent Document 1, performance deterioration (particularly off-axis aberration) may be large due to eccentricity caused by a manufacturing error of a single lens. Further, the Abbe number difference between the lenses constituting the cemented lens is small and correction of chromatic aberration is insufficient, and those of Patent Documents 2 and 3 are not sufficiently thinned because they do not use an aspherical surface.

JP 2004-102111 A JP 2002-350726 A JP 2004-198855 A

  The present invention has been made in view of such a problem of the prior art, and the object thereof is an optical which can be reduced in thickness even at a high zoom ratio, and the performance of deterioration is prevented by minimizing the influence of eccentricity. A system and an imaging apparatus using the system are provided.

In order to achieve the above object, the first optical system of the present invention includes, in order from the object side, a first lens group having a negative refractive power and a second lens group having a positive refractive power, and is positive as a whole. An optical system including a cemented lens having a refractive power and cementing three or more lenses including at least one negative lens,
The zoom ratio is 2 times or more, and is configured to satisfy the following conditional expression.

| F _co / F _ci | <0.95 (1)
0.05 <D _co / D _ci <20 (2)
Where F _co : focal length of the lens closest to the object side of the cemented lens,
F _ci : the focal length of the lens closest to the image plane of the cemented lens,
D _co : the thickness on the optical axis of the lens closest to the object side of the cemented lens,
D _ci : the thickness on the optical axis of the lens closest to the image plane of the cemented lens,
It is.

  The reason and action of the above configuration in the first optical system of the present invention will be described below.

  A thin zoom lens using two or more negative and positive lens groups and having three or more lenses having a positive refractive power cemented has been proposed in the past. The relative eccentricity of the surface greatly affects performance. Although there is a method of performing the center adjustment of the performance deterioration due to the manufacturing error by using one of the joint surfaces, only one of the performances of the deteriorated screen center and the screen periphery can be greatly improved.

  In the present invention, by appropriately arranging the power balance of the entrance-side and exit-side lenses constituting the cemented lens, it is possible to reduce performance deterioration at both the center and the periphery of the junction by adjusting the lens relative center. It becomes easy.

  Conditional expression (1) defines the balance of the lens power on the incident side and the exit side that constitute the cemented lens. When the upper limit of 0.95 is exceeded, it becomes difficult to perform center adjustment that improves both the central performance and the peripheral performance.

  In addition, the ratio of the thickness on the optical axis of the most object-side lens and the image-side lens constituting the cemented lens in manufacturing is out of the range of the conditional expression (2), that is, the upper limit is 20, and the lower limit is 0.05. In the case of exceeding the thickness, the thickness of the cemented lens itself increases, which hinders downsizing. Or chromatic aberration correction becomes difficult. Or the effect as a junction lens of three or more sheets will become small.

The second optical system of the present invention includes, in order from the object side, a first lens group having a negative refractive power and a second lens group having a positive refractive power, and has a positive refractive power as a whole. An optical system including a cemented lens in which three or more lenses including the negative lens are cemented,
The zoom ratio is 2 times or more, and is configured to satisfy the following conditional expression.

10 <| R ₁ / r ₁ | (3)
Where r ₁ : radius of curvature of the most object side surface of the cemented lens,
R ₁ : radius of curvature of the cemented surface closest to the object side of the cemented lens,
It is.

  The reason and action of the above configuration in the second optical system of the present invention will be described below.

  A thin zoom lens using two or more negative and positive lens groups and having three or more lenses having a positive refractive power cemented has been proposed in the past. The relative eccentricity of the surface greatly affects performance. Although there is a method of performing the center adjustment of the performance deterioration due to the manufacturing error by using one of the joint surfaces, only one of the performances of the deteriorated screen center and the screen periphery can be greatly improved.

In the present invention, by making the radius of curvature R ₁ of the cemented surface of the most incident side lens constituting the cemented lens sufficiently large, the change in the tilt (tilt) of the lens surface is reduced when adjusting the lens relative center. By correcting the relative center by shifting the lens surface, it becomes possible to simultaneously reduce the center and off-axis performance deterioration from the design value.

Conditional expression (3) is an expression that defines the shape of the lens on the most object side constituting the cemented lens,
By increasing the curvature radius of the contact surface R _1, since the tilt of the surface that occurs when adjusting the relative heart lenses is reduced, it is possible to prevent performance degradation.

The third optical system of the present invention includes, in order from the object side, a first lens group having a negative refractive power and a second lens group having a positive refractive power, and has a positive refractive power as a whole, and at least one piece. An optical system including a cemented lens in which three or more lenses including the negative lens are cemented,
The cemented lens has a convex shape on the object side, a zoom ratio of 2 or more, and is configured to satisfy the following conditional expression.

0.7 <| R ₂ / r ₂ | (4)
Where r ₂ : radius of curvature of the surface closest to the image plane of the cemented lens,
R ₂ : radius of curvature of the cemented surface closest to the image plane of the cemented lens,
It is.

  Hereinafter, the reason and action of the above configuration in the third optical system of the present invention will be described.

  A thin zoom lens using two or more negative and positive lens groups and having three or more lenses having a positive refractive power cemented has been proposed in the past. The relative eccentricity of the surface greatly affects performance. Although there is a method of performing the center adjustment of the performance deterioration due to the manufacturing error by using one of the joint surfaces, only one of the performances of the deteriorated screen center and the screen periphery can be greatly improved.

In the present invention, by sufficiently increasing the bonding surface R ₂ most of the exit-side lens of the cemented lens, to reduce the change in the tilt (tilt) of the lens surface when adjusting the lens relative heart, the lens surface By correcting the relative center by shifting, it is possible to simultaneously reduce the center and off-axis performance deterioration from the design value.

Condition (4) is an expression for defining the shape of the most image plane side lens of the cemented lens, by increasing the radius of curvature of the cemented surface R _2, occurs when adjusting the relative heart lenses Since the inclination of the surface to be reduced is reduced, performance deterioration can be prevented.

  A fourth optical system of the present invention is an optical system including a cemented lens having a cemented surface on the optical axis, and the lens constituting the cemented lens satisfies the following conditions. is there.

40 <ν _max −ν _min <80 (5)
23.7> ν _min (6)
Where ν _max is the maximum Abbe number in the cemented lens,
ν _min : the smallest Abbe number in the cemented lens,
It is.

  Hereinafter, the reason and action of the fourth optical system according to the present invention will be described.

  An optical system provided with a cemented lens, in which chromatic aberration is corrected according to the type of glass material of the constituting lens, has been proposed in the past. In any case, the Abbe of the lens constituting the cemented lens is proposed. Since the number is larger than the value shown in the conditional expression (6) and the glass material outside the range of the conditional expression (5) is used, it becomes difficult to obtain high optical performance over the entire zooming range.

  The present invention provides an optical system having an ability to particularly favorably correct chromatic aberration over the entire zoom range by appropriately setting the material of each lens constituting the cemented lens.

  Below the range of conditional expression (5), that is, 40 or less, correction of chromatic aberration is insufficient, and when above the range of conditional expression (5), that is, 80 or more, correction is excessive.

  The fifth optical system of the present invention is an optical system including a cemented lens having a cemented surface on the optical axis, and the lens constituting the cemented lens satisfies the following conditions. is there.

40 <ν _max −ν _min <80 (5)
23.7> ν _min (6)
60 <ν _max (7)
1.8 <n _dmax (8)
1.55> n _dmin (9)
Where ν _max is the maximum Abbe number in the cemented lens,
ν _min : the smallest Abbe number in the cemented lens,
n _dmax : maximum refractive index in the cemented lens,
n _dmin : minimum refractive index in the cemented lens,
It is.

  Hereinafter, the reason and action of the fifth optical system of the present invention having the above configuration will be described.

  An optical system provided with a cemented lens, in which an optical system that corrects chromatic aberration according to the type of glass material of the lens that has been proposed has been proposed, but in any case, the refraction of the lens that constitutes the cemented lens Since a glass material whose rate and Abbe number are outside the range of the conditional expressions (5) to (9) is used, it is mainly difficult to correct chromatic aberration, and it becomes difficult to obtain high optical performance over the entire zoom range. .

  The present invention provides an optical system having an ability to particularly favorably correct chromatic aberration over the entire zoom range by appropriately setting the material of each lens constituting the cemented lens.

  Below the range of conditional expression (5), that is, 40 or less, correction of chromatic aberration is insufficient, and when above the range of conditional expression (5), that is, 80 or more, correction is excessive.

  Further, when the condition is outside the range of the conditional expression (8), that is, when the maximum refractive index in the cemented lens is 1.8 or less, field curvature and spherical aberration occur.

  According to a sixth optical system of the present invention, in the fourth and fifth optical systems, the optical system has two groups of a negative refractive power lens group and a positive refractive power lens group. It is.

  The reason and action of the above configuration in the sixth optical system of the present invention will be described below.

  As described above, the configuration having the two groups of the negative refractive power lens group and the positive refractive power lens group is the minimum configuration for obtaining a high zoom ratio of 2 times or more while satisfactorily correcting the aberration. is there. In addition, when combined with a cemented lens that satisfies the conditions of the third optical system, the power of other lenses can be increased, so that further downsizing can be achieved.

  According to a seventh optical system of the present invention, in the first to sixth optical systems, at least one of the air contact surfaces on the light incident side and the light exit side of the cemented lens is an aspherical surface. Is.

  Hereinafter, the reason and operation of the seventh optical system of the present invention having the above configuration will be described.

  Since the lens element is reduced by cementing three or more lenses including at least one negative lens, the reduced aberration correction capability can be covered by making the air contact surface of the cemented lens aspherical, As a result, the entire optical system can be further reduced in thickness. In particular, by combining with conditional expression (1) or (3), it is possible to ensure that manufacturing tolerances become severe due to the arrangement of the aspheric surfaces, and that the ease of manufacturing can be ensured by enhancing the effect of center adjustment.

  The eighth optical system of the present invention is characterized in that, in the first to seventh optical systems, the cemented lens is composed of three lenses.

  The reason and action of the above configuration in the eighth optical system of the present invention will be described below.

  By using a lens in which three lenses are cemented, it is possible to sufficiently correct chromatic aberration, and it is easy to reduce the amount of decentering between lens elements by cementing three lenses. Can be reduced.

  According to a ninth optical system of the present invention, in the first to eighth optical systems, the second lens group includes a positive first lens, a negative second lens, and a positive third lens arranged from the object side. And a three-piece cemented lens.

  The reason and action of the ninth optical system according to the present invention will be described below.

  By using an optical system of an array of a positive first lens, a negative second lens, and a positive third lens in order from the object side in the second lens group, mainly axial aberration, field curvature, and chromatic aberration are excellent. Can be corrected.

  According to a tenth optical system of the present invention, in the first to ninth optical systems, the second lens group is composed of only a three-piece cemented lens.

  The reason and action of the above configuration in the tenth optical system of the present invention will be described below.

  By configuring the second lens group with only three cemented lenses, it becomes possible to make the lens compact while maintaining a good balance of aberrations centered on chromatic aberration.

  The eleventh optical system of the present invention is characterized in that in the first to tenth optical systems, focusing is performed by moving a group of lenses in the optical system.

  Hereinafter, the reason and action of the above-described configuration in the eleventh optical system of the present invention will be described.

  With this configuration, the mechanism is simple and the variation in aberration from the wide-angle end to the telephoto end can be reduced.

  In a twelfth optical system according to the present invention, in the first to eleventh optical systems, the second lens unit moves monotonically from the image plane side to the object side at the time of zooming from the wide angle end to the telephoto end. The first lens group moves along a locus that is convex toward the image plane side.

  The reason and action of the above configuration in the tenth optical system of the present invention will be described below.

If configured in this way, the mechanism is simple, the overall lens length at the time of photographing can be shortened, and when the aperture stop is arranged integrally with the second lens group, the entrance pupil position at the wide angle becomes shallow,
The diameter of the first lens group can be reduced.

  A thirteenth optical system of the present invention is characterized in that the first to third optical systems are configured to satisfy the following conditional expression.

40 <ν _max −ν _min <80 (5)
Where ν _max is the maximum Abbe number in the cemented lens,
ν _min : the smallest Abbe number in the cemented lens,
It is.

  The reason and action of the above configuration in the thirteenth optical system of the present invention will be described below.

  When the difference between the Abbe numbers of the lenses constituting the cemented lens satisfies the conditional expression (4), the chromatic aberration is mainly corrected well in the optical system, and the optical system is compact and has high optical performance over the entire zoom range. Is possible. In particular, in the case of a lens system composed of a cemented lens and another lens, the ability to correct chromatic aberration in the cemented lens can be increased, so that the power of other lenses can be increased with a small configuration, so that it can be a compact or variable magnification lens. If this is the case, high zooming becomes easy.

  The fourteenth optical system of the present invention is characterized in that, in the first to twelfth optical systems, the most object side lens and the most image side lens constituting the three-piece joint are made of the same glass material. It is.

  The reason and action of the above configuration in the fourteenth optical system of the present invention will be described below.

  By using the same glass material in this way, the types of glass materials to be used can be reduced. Therefore, production management is easy and cost reduction is possible.

  According to a fifteenth optical system of the present invention, in the first to third and sixth to fourteenth optical systems, the cemented lens has a convex shape on the object side, and further satisfies the following conditional expression: To do.

0.50 <D _n1 /Σd<0.95 (10)
Where D _{n1 is} the distance from the most object side surface in the cemented lens to the surface having the greatest negative refractive power,
Σd: total thickness of the cemented lens,
It is.

  The reason and action of the above configuration in the fifteenth optical system of the present invention will be described below.

  By satisfying the conditional expression (10) and appropriately separating the negative power in the cemented lens from the most object side surface having the positive power, the principal point position of the second lens unit at the telephoto end is corrected while the chromatic aberration is corrected. It can be close to one lens group, which is advantageous for high zoom ratio.

  If the upper limit of 0.95 in conditional expression (10) is exceeded, the thickness of the subsequent lens (on the image plane side with respect to the negative power surface in the cemented lens) becomes too thin, making it difficult to manufacture. If the lower limit of 0.50 is exceeded, the negative power will be too close to the incident surface (side surface of the most object), making it difficult to adjust the principal point position, making it difficult to achieve a high zoom ratio.

  The sixteenth optical system of the present invention is characterized in that, in the fifteenth optical system, the following conditional expression is further satisfied.

0.05 <D _n2 /Σd<0.35 (11)
Where D _{n2 is} the distance from the surface having the largest negative refractive power in the cemented lens to the surface closest to the image plane,
It is.

  The reason and action of the above configuration in the sixteenth optical system of the present invention will be described below.

  The principal point position of the second lens group is appropriately adjusted by satisfying the conditional expression (11) and suppressing the distance from the surface having negative power in the cemented lens to the exit surface (side surface of the most image surface). In addition to a high zoom ratio, the size can be reduced when retracted.

  If the upper limit of 0.35 in conditional expression (11) is exceeded, the cemented lens becomes too thick, which is disadvantageous for downsizing when retracted. Or, it becomes difficult to bring the principal point position at the telephoto end close to the first lens group, which is disadvantageous for high zoom ratio. When the lower limit of 0.05 is exceeded, the thickness of the lens from the negative power surface to the exit surface becomes too thin, making manufacturing difficult.

  According to a seventeenth optical system of the present invention, in the first to third and sixth to sixteenth optical systems, the cemented lens has a convex shape on the object side, and further satisfies the following conditional expression: To do.

−1.5 <(r ₁ + r ₂ ) / (r ₁ −r ₂ ) <− 0.5 (12)
Where r ₁ : radius of curvature of the most object side surface of the cemented lens,
r ₂ : radius of curvature of the surface closest to the image plane of the cemented lens,
It is.

  The reason and action of the above configuration in the seventeenth optical system of the present invention will be described below.

  Conditional expression (12) defines the shape of the cemented lens. In other words, the main positive power in the cemented lens is formed on the entrance surface (the most object side surface), and the configuration is advantageous for downsizing and high zoom ratio while maintaining the balance of various aberration corrections.

  If the upper limit of −0.5 of conditional expression (12) is exceeded, the power on the entrance surface will be weak (the power on the exit surface will be strong), and it will be difficult to adjust the principal point position, especially at the telephoto end. Alternatively, it is difficult to make the lens disposed near the image plane in the cemented lens thin, and it is difficult to reduce the size. When the lower limit of −1.5 is exceeded, the power of the entrance surface becomes too strong (or the power of the exit surface tends to be negative), and relative aberration correction becomes difficult.

  According to an eighteenth optical system of the present invention, in the first to third and sixth to seventeenth optical systems, the cemented lens has a convex shape on the object side, and the negative lens is the image surface of the lens on the most object side. And the following conditional expression is further satisfied.

−1.0 <R ₁ / F ₂ <−0.05 (13)
0.50 <D ₁ /Σd<0.95 (14)
Where R _{1 is the} radius of curvature of the cemented surface closest to the object side of the cemented lens,
F ₂ : focal length of the second lens group,
D ₁ : thickness on the optical axis of the lens closest to the object side of the cemented lens,
Σd: total thickness of the cemented lens,
It is.

  The reason and action of the above configuration in the 18th optical system of the present invention will be described below.

  The negative lens is cemented to the lens arranged on the most object side of the cemented lens, and the cemented lens on the most object side of the cemented lens has a negative power that satisfies the conditional expression (13), thereby reducing the size. The chromatic aberration (especially the longitudinal chromatic aberration) is also corrected well. Further, by separating the surface having negative power from the incident surface to the extent that the conditional expression (14) is satisfied, the principal point position of the second lens group at the telephoto end can be brought close to the first lens group. A high zoom ratio can be achieved while maintaining the balance of aberration correction.

  If the upper limit of −0.05 of the conditional expression (13) is exceeded, the curvature (power) of the joint surface on the most object side becomes too strong, and therefore the tilt (tilt) of the lens surface when adjusting the lens relative center. Even if the relative center is corrected by shifting the lens surface, the center or off-axis performance deterioration from the design value occurs. If the lower limit of −1.0 is exceeded, the curvature (power) of the joint surface on the most object side becomes too weak and it is difficult to correct chromatic aberration.

  If the upper limit of 0.95 in conditional expression (14) is exceeded, the thickness of the subsequent lens (image surface side relative to the most object side lens in the cemented lens) becomes too thin, making it difficult to manufacture, or It becomes difficult to reduce the size of the cemented lens. If the lower limit of 0.50 is exceeded, the negative power will be too close to the incident surface (side surface of the most object), making it difficult to adjust the principal point position, making it difficult to achieve a high zoom ratio.

  According to a nineteenth optical system of the present invention, in the first to third and sixth to seventeenth optical systems, the cemented lens has a convex shape on the object side, and the negative lens is closest to the image plane side of the cemented lens. The lens is cemented to the arranged lens and further satisfies the following conditional expression.

2.5 <| R ₁ / F ₂ | (15)
0.45 <R ₂ / F ₂ <2.3 (16)
Where R _{1 is the} radius of curvature of the cemented surface closest to the object side of the cemented lens,
F ₂ : focal length of the second lens group,
R ₂ : radius of curvature of the cemented surface closest to the image plane of the cemented lens,
It is.

  The reason and action of the above configuration in the nineteenth optical system of the present invention will be described below.

  By satisfying conditional expression (15) and setting the cemented surface on the most object side in the cemented lens to have a weak positive or negative power, the influence of decentering can be reduced. Further, since the cemented surface on the most object side can be brought closer to the plane while maintaining the power of the cemented lens, each radius of curvature of the lens arranged on the image plane side is made larger than the lens on the most object side (closer to the plane). )be able to. As a result, the subsequent lens (image surface side relative to the cemented surface on the most object side) can be made thinner, and the manufacture of the cemented lens is facilitated along with the reduction in size and thickness. Further, the chromatic aberration is corrected by satisfying the conditional expression (16) on the cemented lens on the most image surface side of the cemented lens so as to have a negative power, and at the cemented surface away from the incident surface (most object side surface). In particular, the principal point position of the second lens group at the telephoto end is brought close to the first lens group, which is advantageous for increasing the zoom ratio.

  If the lower limit value of 2.5 in the conditional expression (15) is exceeded, the curvature of the cemented surface on the most object side becomes too strong. Therefore, when adjusting the lens relative center, the change in tilt (tilt) of the lens surface is large. Thus, even if the relative center is corrected by the shift of the lens surface, the performance deterioration of the center or off-axis from the design value occurs.

If the upper limit of 2.3 in conditional expression (16) is exceeded, the curvature of the cemented surface on the most image side becomes weak, and chromatic aberration is difficult to correct. Alternatively, it is necessary to correct chromatic aberration by increasing the negative power of another lens surface (for example, the most object side cemented surface). In this case, the principal point position of the second lens group at the telephoto end is brought closer to the first lens group. In order to achieve a high zoom ratio, it is necessary to increase the lens thickness in order to keep the distance from the incident surface to the lens surface having the negative power appropriately, and it is difficult to reduce the size. If the lower limit of 0.45 is exceeded, the curvature of the joint surface on the most image surface side becomes too strong, and the curvature of the surface on the most image surface side must be strengthened to maintain the balance of various aberration corrections. As a result, the lens on the most image surface side tends to be thick. Alternatively, the surface on the most image surface side tends to have negative power, and it is necessary to increase the curvature of the most object side surface in order to maintain the power of the cemented lens. As a result, it is difficult to correct relative aberrations. Become.

  The twentieth optical system of the present invention is characterized in that the following conditional expression is satisfied in the nineteenth optical system.

−1.5 <(r ₁ + r ₂ ) / (r ₁ −r ₂ ) <− 0.5 (12)
0.05 <D ₃ /Σd<0.30 (17)
Where r ₁ : radius of curvature of the most object side surface of the cemented lens,
r ₂ : radius of curvature of the surface closest to the image plane of the cemented lens,
D ₃ : thickness on the optical axis of the lens closest to the image plane of the cemented lens,
Σd: total thickness of the cemented lens,
It is.

  The reason and action of the above configuration in the twentieth optical system of the present invention will be described below.

  By satisfying conditional expression (12), the main positive power in the cemented lens is borne on the incident surface (the most object side surface), and it is advantageous for downsizing and high zoom ratio while maintaining the balance of various aberration corrections. . Further, by satisfying conditional expressions (12) and (16), the lens on the most image side of the cemented lens can be made thin enough to satisfy conditional expression (17). Accordingly, since the surface following the cemented surface on the most image surface side having negative power can be brought close to the cemented surface on the most image surface side, the principal point position of the second lens group particularly at the telephoto end is set to the first lens group. A high zoom ratio can be achieved.

  If the upper limit of −0.5 of conditional expression (12) is exceeded, the power on the entrance surface will be weak (the power on the exit surface will be strong), and it will be difficult to adjust the principal point position, especially at the telephoto end. Alternatively, it is difficult to make the lens disposed near the image plane in the cemented lens thin, and it is difficult to reduce the size. When the lower limit of −1.5 is exceeded, the power on the entrance surface becomes too strong (or the power on the exit surface tends to be negative), and relative aberration correction becomes difficult.

  If the upper limit of 0.30 in conditional expression (17) is exceeded, the cemented lens tends to be thick and difficult to downsize. Alternatively, the curvature of the surface closest to the image plane becomes strong, and the principal point position adjustment becomes difficult. If the lower limit of 0.05 is exceeded, the surface on the most image side becomes too close to the cemented surface on the most image surface side, and the lens on the most image surface side becomes too thin, making manufacturing difficult.

  The twenty-first optical system of the present invention is characterized in that, in the first to third and sixth to twentieth optical systems, the following conditional expressions are further satisfied.

40 <ν _max −ν _min <80 (5)
23.7> ν _min (6)
Where ν _max is the maximum Abbe number in the cemented lens,
ν _min : the smallest Abbe number in the cemented lens,
It is.

  The reason and action of the above configuration in the twenty-first optical system of the present invention will be described below.

  An optical system provided with a cemented lens, in which chromatic aberration is corrected according to the type of glass material of the constituting lens, has been proposed in the past. In any case, the Abbe of the lens constituting the cemented lens is proposed. Since the number is larger than the value shown in the conditional expression (6) and the glass material outside the range of the conditional expression (5) is used, it becomes difficult to obtain high optical performance over the entire zooming range.

  The present invention provides an optical system having an ability to particularly favorably correct chromatic aberration over the entire zoom range by appropriately setting the material of each lens constituting the cemented lens.

  Below the range of conditional expression (5), that is, 40 or less, correction of chromatic aberration is insufficient, and when above the range of conditional expression (5), that is, 80 or more, correction is excessive.

  The twenty-second optical system of the present invention is characterized in that, in the twenty-first optical system, the following conditional expression is further satisfied.

60 <ν _max (7)
1.8 <n _dmax (8)
1.55> n _dmin (9)
Where ν _max is the maximum Abbe number in the cemented lens,
n _dmax : maximum refractive index in the cemented lens,
n _dmin : minimum refractive index in the cemented lens,
It is.

  The reason and action of the above configuration in the twenty-second optical system of the present invention will be described below.

  An optical system provided with a cemented lens, in which an optical system that corrects chromatic aberration according to the type of glass material of the lens that has been proposed has been proposed, but in any case, the refraction of the lens that constitutes the cemented lens Since a glass material whose rate and Abbe number are outside the range of the conditional expressions (5) to (9) is used, it is mainly difficult to correct chromatic aberration, and it becomes difficult to obtain high optical performance over the entire zoom range. .

  The present invention provides an optical system having an ability to particularly favorably correct chromatic aberration over the entire zoom range by appropriately setting the material of each lens constituting the cemented lens.

  Outside the range of conditional expression (8), that is, when the maximum refractive index in the cemented lens is 1.8 or less, field curvature and spherical aberration occur.

  According to a twenty-third optical system of the present invention, in the fourth and fifth optical systems, the cemented lens has at least one positive lens and one negative lens.

  The reason and action of the above-described configuration in the twenty-third optical system of the present invention will be described below.

  Chromatic aberration can be favorably corrected by including at least one positive lens and one negative lens in the cemented lens. In this case, the Abbe number of the negative lens is preferably smaller than the Abbe number of the positive lens.

  According to a twenty-fourth optical system of the present invention, in the first to twenty-third optical systems, the cemented lens has a biconvex shape in the vicinity of the optical axis.

  The reason and action of the above configuration in the twenty-fourth optical system of the present invention will be described below.

  By making the cemented lens biconvex, the entrance surface and exit surface of the cemented lens can be brought close to a symmetric system, and various aberration corrections can be easily balanced.

  A twenty-fifth optical system according to the present invention is characterized in that, in the seventh to twenty-fourth optical systems, the aspheric surface on the exit side is provided so that the diverging action is strong at the lens peripheral portion. is there.

  The reason and action of the above configuration in the twenty-fifth optical system of the present invention will be described below.

  By providing an aspherical surface in this manner, the on-axis and off-axis aberrations can be corrected in a balanced manner on the surface closest to the image plane.

  The present invention includes an image pickup apparatus that includes first to twenty-fifth optical systems, and further includes an electronic image pickup element for converting an optical image obtained by the optical system into an electric signal.

  This imaging apparatus can obtain the same effects as the above optical system.

  The more preferable ranges of the above conditional expressions (1) to (17) are shown below. When a plurality of numerical values are shown, the limit value is more preferable as the right numerical value.

Conditional expression Lower limit Upper limit (1)-0.93 / 0.85 / 0.80
(2) 1.0 / 2.0 / 2.5 15/10 / 7.5 / 5.5
(3) 12 / 14.5 / 20 −
(4) 0.75 / 0.80 −
(5)-70/60/55
(6)-23.0 / 22.5
(7) 63.5 / 64.0 −
(8)--
(9)--
(10) 0.60 / 0.68 0.90 / 0.85
(11) 0.08 / 0.10 / 0.12 0.32 / 0.30 / 0.25
(12) -1.3 / -1.0 -0.65 / -0.70 / -0.80 / -0.85
(13) -0.90 -0.25 / -0.35 / -0.50
(14) 0.55 / 0.60 0.85 / 0.80 / 0.75
(15) 3.0 / 4.5 / 5.0 −
/5.5 /6.5 /9.0
(16) 0.5 / 0.6 / 0.7 2.0 / 1.5
(17) 0.08 / 0.11 0.25 / 0.22
.

  According to the present invention, it is possible to reduce the thickness even at a high zoom ratio, and to obtain an optical system that suppresses the influence of eccentricity and prevents performance deterioration. Cameras and video cameras can be obtained.

FIG. 2 is a lens cross-sectional view at a wide-angle end (a), an intermediate state (b), and a telephoto end (c) when focusing on an object point at infinity according to Example 1 of the zoom optical system of the present invention. FIG. 6 is a view similar to FIG. 1 of Embodiment 2 of the zoom optical system of the present invention. It is the same figure as FIG. 1 of Example 3 of the zoom optical system of this invention. It is the same figure as FIG. 1 of Example 4 of the zoom optical system of this invention. It is the same figure as FIG. 1 of Example 5 of the zoom optical system of this invention. It is the same figure as FIG. 1 of Example 6 of the zoom optical system of this invention. It is the same figure as FIG. 1 of Example 7 of the zoom optical system of this invention. It is a figure similar to FIG. 1 of Example 8 of the zoom optical system of this invention. It is the same figure as FIG. 1 of Example 9 of the zoom optical system of this invention. It is a figure similar to FIG. 1 of Example 10 of the zoom optical system of this invention. FIG. 6 is an aberration diagram for Example 1 upon focusing on an object point at infinity. FIG. 6 is an aberration diagram for Example 2 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 3 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 4 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 5 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 6 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 7 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 8 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 9 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 10 upon focusing on an object point at infinity. It is a front perspective view which shows the external appearance of the digital camera by this invention. It is a back perspective view of the digital camera of FIG. It is sectional drawing of the digital camera of FIG.

  Examples 1 to 10 of the zoom optical system according to the present invention will be described below. FIGS. 1 to 10 show lens cross-sectional views of the wide-angle end (a), the intermediate state (b), and the telephoto end (c) when focusing on an object point at infinity in Examples 1 to 10, respectively. In the figure, the first lens group is G1, the aperture stop is S, the second lens group is G2, the third lens group is G3, and a parallel plate constituting a low-pass filter or the like with a wavelength band limiting coat that limits infrared light. Is denoted by F and the image plane is denoted by I.

  As shown in FIG. 1, the zoom optical system according to the first exemplary embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, and a second lens group G2 having a positive refractive power. When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves along a locus that is convex on the image plane side, and at the telephoto end is located closer to the image plane side than the wide-angle end. The aperture stop S and the second lens group G2 are moved monotonously to the object side.

  In order from the object side, the first lens group G1 includes a negative meniscus lens having a convex surface facing the object side and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 has a convex surface facing the object side. A positive meniscus lens, a negative meniscus lens having a convex surface facing the object side, and a biconvex positive lens. The aspherical surface is a surface on the image surface side of the negative meniscus lens in the first lens group G1, and The three lens cemented lenses of the second lens group G2 are used for the three surfaces of the most object side surface and the most image side surface.

  As shown in FIG. 2, the zoom optical system according to the second exemplary embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, and a second lens group G2 having a positive refractive power. When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves along a locus that is convex on the image plane side, and at the telephoto end is located closer to the image plane side than the wide-angle end. The aperture stop S and the second lens group G2 are moved monotonously to the object side.

  In order from the object side, the first lens group G1 includes a negative meniscus lens having a convex surface facing the object side and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 has a convex surface facing the object side. A positive meniscus lens, a negative meniscus lens having a convex surface facing the object side, and a biconvex positive lens. The aspherical surface is a surface on the image surface side of the negative meniscus lens in the first lens group G1, and The three lens cemented lenses of the second lens group G2 are used for the three surfaces of the most object side surface and the most image side surface.

  As shown in FIG. 3, the zoom optical system of Embodiment 3 includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, and a second lens group G2 having a positive refractive power. When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves along a locus that is convex on the image plane side, and at the telephoto end is located closer to the image plane side than the wide-angle end. The aperture stop S and the second lens group G2 are moved monotonously to the object side.

  In order from the object side, the first lens group G1 includes a negative meniscus lens having a convex surface facing the object side and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 has a convex surface facing the object side. The aspherical surface is composed of a negative meniscus lens surface of the first lens group G1, and a second lens group G2 of a cemented convex positive lens, a plano-concave negative lens, and a biconvex positive lens. The three-piece cemented lens is used on three surfaces, the most object side surface and the most image side surface.

  As shown in FIG. 4, the zoom optical system according to the fourth exemplary embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, and a second lens group G2 having a positive refractive power. When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves along a locus that is convex on the image plane side, and at the telephoto end is located closer to the image plane side than the wide-angle end. The aperture stop S and the second lens group G2 are moved monotonously to the object side.

  In order from the object side, the first lens group G1 includes a negative meniscus lens having a convex surface facing the object side, and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 includes a biconvex positive lens and both lenses. The aspherical surface is composed of a cemented lens composed of a concave negative lens and a biconvex positive lens. The aspherical surface is the surface of the negative meniscus lens of the first lens group G1 and the most cemented lens of the second lens group G2. It is used for the three surfaces of the object side surface and the most image surface side surface.

  As shown in FIG. 5, the zoom optical system according to the fifth exemplary embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, and a second lens group G2 having a positive refractive power. When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves along a locus that is convex on the image plane side, and at the telephoto end is located closer to the image plane side than the wide-angle end. The aperture stop S and the second lens group G2 are moved monotonously to the object side.

  In order from the object side, the first lens group G1 includes a negative meniscus lens having a convex surface directed toward the object side and a positive meniscus lens having a convex surface directed toward the object side. The second lens group G2 includes a biconvex positive lens and an image. The aspherical surface is a surface on the image plane side of the negative meniscus lens of the first lens group G1. And the three surfaces of the three-piece cemented lens of the second lens group G2, the most object side surface and the most image side surface.

  As shown in FIG. 6, the zoom optical system according to the sixth exemplary embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, and a second lens group G2 having a positive refractive power. When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves in a convex locus on the image plane side, and is located closer to the object side than the wide-angle end at the telephoto end. The aperture stop S and the second lens group G2 move monotonously as a unit to the object side.

  In order from the object side, the first lens group G1 includes a negative meniscus lens having a convex surface facing the object side and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 has a convex surface facing the object side. A positive meniscus lens, a negative meniscus lens having a convex surface facing the object side, and a biconvex positive lens. The aspherical surface is a surface on the image surface side of the negative meniscus lens in the first lens group G1, and The three lens cemented lenses of the second lens group G2 are used for the three surfaces of the most object side surface and the most image side surface.

  As shown in FIG. 7, the zoom optical system according to the seventh embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, and a second lens group G2 having a positive refractive power. When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves along a locus that is convex on the image plane side, and at the telephoto end is located closer to the image plane side than the wide-angle end. The aperture stop S and the second lens group G2 are moved monotonously to the object side.

  In order from the object side, the first lens group G1 includes a negative meniscus lens having a convex surface directed toward the object side and a positive meniscus lens having a convex surface directed toward the object side. The second lens group G2 includes a biconvex positive lens and an image. The aspherical surface is a surface on the image surface side of the negative meniscus lens of the first lens group G1. And two surfaces of the three-lens cemented lens of the second lens group G2 and the most image side surface.

  As shown in FIG. 8, the zoom optical system according to the eighth embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, and a second lens group G2 having a positive refractive power. When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves along a locus that is convex on the image plane side, and at the telephoto end is located closer to the image plane side than the wide-angle end. The aperture stop S and the second lens group G2 are moved monotonously to the object side.

  In order from the object side, the first lens group G1 includes a negative meniscus lens having a convex surface facing the object side and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 has a convex surface facing the object side. A positive meniscus lens, a negative meniscus lens having a convex surface facing the object side, and a biconvex positive lens. The aspherical surface is a surface on the image surface side of the negative meniscus lens in the first lens group G1, and The three lens cemented lenses of the second lens group G2 are used for the three surfaces of the most object side surface and the most image side surface.

  As shown in FIG. 9, the zoom optical system according to the ninth embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a weak lens. The third lens group G3 has a negative refractive power. When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves in a convex locus on the image plane side. The telephoto end is located closer to the image plane than the wide-angle end, the aperture stop S and the second lens group G2 move monotonously to the object side, and the third lens group G3 moves to the image plane side for image plane compensation. Moving.

  In order from the object side, the first lens group G1 includes a negative meniscus lens having a convex surface facing the object side and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 has a convex surface facing the object side. A positive meniscus lens, a negative cemented lens with a convex surface facing the object side, and a biconvex positive lens. The third lens group G2 is composed of a single negative meniscus lens with a convex surface facing the object side. The aspherical surface has three surfaces, that is, the image surface side surface of the negative meniscus lens of the first lens group G1, and the most object side surface and the most image surface side surface of the three-junction lens of the second lens group G2. Used.

As shown in FIG. 10, the zoom optical system according to the tenth embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a weak lens. The first lens unit G1 is composed of a third lens unit G3 having a positive refractive power. When zooming from the wide-angle end to the telephoto end, the first lens unit G1 moves in a convex locus on the image plane side. The telephoto end is located closer to the image plane side than the wide-angle end, the aperture stop S and the second lens group G2 are monotonously moved integrally to the object side, and the third lens group G3 is fixed.

  In order from the object side, the first lens group G1 includes a negative meniscus lens having a convex surface facing the object side and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 has a convex surface facing the object side. A positive meniscus lens, a negative meniscus lens having a convex surface facing the object side, and a biconvex positive lens. The third lens group G2 is composed of a single positive meniscus lens having a convex surface facing the object side. The aspherical surface has three surfaces, that is, the image surface side surface of the negative meniscus lens of the first lens group G1, and the most object side surface and the most image surface side surface of the three-junction lens of the second lens group G2. Used.

Hereinafter, numerical data of each embodiment described above, but the symbols are outside the above, f is the focal length, F _NO is the F-number, 2 [omega is field angle, WE denotes a wide angle end, ST intermediate state, TE is The telephoto end, r ₁ , r ₂ ... Is the radius of curvature of each lens surface, d ₁ , d ₂ ... _Are the distances between the lens surfaces, n _d1 , n _d2 are the refractive index of the d-line of each lens, ν _d1 , ν _d2 ... is the Abbe number of each lens. The aspherical shape is represented by the following formula, where x is an optical axis with the light traveling direction being positive, and y is a direction orthogonal to the optical axis.

x = (y ² / r) / [1+ {1- (K + 1) (y / r) ² } ^1/2 ]
+ A ₂ y ² + A ₄ y ⁴ + A ₆ y ⁶ + A ₈ y ⁸ + A ₁₀ y ¹⁰
Where r is a paraxial radius of curvature, K is a conic coefficient, and A ₂ , A ₄ , A ₆ , A ₈ , and A ₁₀ are secondary, fourth, sixth, eighth, and tenth aspherical coefficients, respectively. .

  In the numerical data of the following examples, the value indicating the length is the length in mm.

Example 1
r ₁ = 37.691 d ₁ = 1.20 n _d1 = 1.80495 ν _d1 = 40.93
r ₂ = 4.362 (aspherical surface) d ₂ = 2.33
r ₃ = 8.294 d ₃ = 1.62 n _d2 = 1.84666 ν _d2 = 23.78
r ₄ = 16.326 d ₄ = (variable)
r ₅ = ∞ (aperture) d ₅ = -0.26
r ₆ = 4.636 (aspherical surface) d ₆ = 4.02 n _d3 = 1.51635 ν _d3 = 64.02
r ₇ = 30.000 d ₇ = 1.14 n _d4 = 1.80810 ν _d4 = 22.76
r ₈ = 7.183 d ₈ = 1.29 n _d5 = 1.51635 ν _d5 = 64.02
r ₉ = -25.382 (aspherical surface) d ₉ = (variable)
r ₁₀ = ∞ d ₁₀ = 0.76 n _d6 = 1.54771 ν _d6 = 62.84
r ₁₁ = ∞ d ₁₁ = 0.50
r ₁₂ = ∞ d ₁₂ = 0.50 n _d7 = 1.51633 ν _d7 = 64.14
r ₁₃ = ∞ d ₁₃ = 0.37
r ₁₄ = ∞ (image plane)
Aspheric coefficient 2nd surface K = -0.704
A ₄ = 2.01910 × 10 ^-4
A ₆ = -1.91890 × 10 ^-7
A ₈ = 1.20310 × 10 ^-8
A ₁₀ = -7.41780 × 10 ^-10
6th surface K = -1.860
A ₄ = 1.68779 × 10 ^-3
A ₆ = 5.98250 × 10 ^-5
A ₈ = -9.36385 × 10 ^-6
A ₁₀ = 6.02976 × 10 ^-7
Surface 9 K = -10.683
A ₄ = 1.92469 × 10 ^-3
A ₆ = 3.36702 × 10 ^-4
A ₈ = -5.00279 × 10 ^-5
A ₁₀ = 5.80240 × 10 ^-6
Zoom data (∞)
WE ST TE
f (mm) 5.95 10.08 17.05
F _NO 3.15 3.98 5.39
2ω (°) 64.41 39.67 23.88
d ₄ 12.66 5.55 1.37
d ₉ 8.97 12.68 18.93.

Example 2
r ₁ = 37.691 d ₁ = 1.20 n _d1 = 1.80495 ν _d1 = 40.93
r ₂ = 4.362 (aspherical surface) d ₂ = 2.33
r ₃ = 8.294 d ₃ = 1.62 n _d2 = 1.84666 ν _d2 = 23.78
r ₄ = 16.326 d ₄ = (variable)
r ₅ = ∞ (aperture) d ₅ = -0.26
r ₆ = 4.623 (aspherical surface) d ₆ = 4.23 n _d3 = 1.51603 ν _d3 = 64.02
r ₇ = 100.000 d ₇ = 1.09 n _d4 = 1.80810 ν _d4 = 22.76
r ₈ = 8.719 d ₈ = 1.13 n _d5 = 1.51603 ν _d5 = 64.02
r ₉ = -25.844 (aspherical surface) d ₉ = (variable)
r ₁₀ = ∞ d ₁₀ = 0.76 n _d6 = 1.54771 ν _d6 = 62.84
r ₁₁ = ∞ d ₁₁ = 0.50
r ₁₂ = ∞ d ₁₂ = 0.50 n _d7 = 1.51633 ν _d7 = 64.14
r ₁₃ = ∞ d ₁₃ = 0.37
r ₁₄ = ∞ (image plane)
Aspheric coefficient 2nd surface K = -0.704
A ₄ = 2.01910 × 10 ^-4
A ₆ = -1.91890 × 10 ^-7
A ₈ = 1.20310 × 10 ^-8
A ₁₀ = -7.41780 × 10 ^-10
6th surface K = -3.132
A ₄ = 3.33055 × 10 ^-3
A ₆ = -4.83274 × 10 ^-5
A ₈ = -3.28992 × 10 ^-6
A ₁₀ = 4.12519 × 10 ^-7
The ninth side K = -10.671
A ₄ = 2.03797 × 10 ^-3
A ₆ = 3.37686 × 10 ^-4
A ₈ = -4.96072 × 10 ^-5
A ₁₀ = 5.80349 × 10 ^-6
Zoom data (∞)
WE ST TE
f (mm) 5.95 10.08 17.05
F _NO 3.15 3.98 5.39
2ω (°) 64.40 39.67 23.88
d ₄ 12.66 5.55 1.37
d ₉ 8.95 12.66 18.92.

Example 3
r ₁ = 37.691 d ₁ = 1.20 n _d1 = 1.80495 ν _d1 = 40.93
r ₂ = 4.362 (aspherical surface) d ₂ = 2.33
r ₃ = 8.294 d ₃ = 1.62 n _d2 = 1.84666 ν _d2 = 23.78
r ₄ = 16.326 d ₄ = (variable)
r ₅ = ∞ (aperture) d ₅ = -0.26
r ₆ = 4.607 (aspherical surface) d ₆ = 4.24 n _d3 = 1.51603 ν _d3 = 64.02
r ₇ = ∞ d ₇ = 1.10 n _d4 = 1.80810 ν _d4 = 22.76
r ₈ = 9.612 d ₈ = 1.13 n _d5 = 1.51603 ν _d5 = 64.02
r ₉ = -26.572 (aspherical surface) d ₉ = (variable)
r ₁₀ = ∞ d ₁₀ = 0.76 n _d6 = 1.54771 ν _d6 = 62.84
r ₁₁ = ∞ d ₁₁ = 0.50
r ₁₂ = ∞ d ₁₂ = 0.50 n _d7 = 1.51633 ν _d7 = 64.14
r ₁₃ = ∞ d ₁₃ = 0.37
r ₁₄ = ∞ (image plane)
Aspheric coefficient 2nd surface K = -0.704
A ₄ = 2.01910 × 10 ^-4
A ₆ = -1.91890 × 10 ^-7
A ₈ = 1.20310 × 10 ^-8
A ₁₀ = -7.41780 × 10 ^-10
6th surface K = -3.131
A ₄ = 3.37249 × 10 ^-3
A ₆ = -4.66743 × 10 ^-5
A ₈ = -3.92163 × 10 ^-6
A ₁₀ = 4.65697 × 10 ^-7
The ninth side K = -10.671
A ₄ = 2.08460 × 10 ^-3
A ₆ = 3.53565 × 10 ^-4
A ₈ = -5.49632 × 10 ^-5
A ₁₀ = 6.38510 × 10 ^-6
Zoom data (∞)
WE ST TE
f (mm) 5.95 10.08 17.05
F _NO 3.15 3.98 5.39
2ω (°) 64.40 39.67 23.88
d ₄ 12.66 5.55 1.37
d ₉ 8.94 12.65 18.91.

Example 4
r ₁ = 37.691 d ₁ = 1.20 n _d1 = 1.80495 ν _d1 = 40.93
r ₂ = 4.362 (aspherical surface) d ₂ = 2.33
r ₃ = 8.294 d ₃ = 1.62 n _d2 = 1.84666 ν _d2 = 23.78
r ₄ = 16.326 d ₄ = (variable)
r ₅ = ∞ (aperture) d ₅ = -0.26
r ₆ = 4.603 (aspherical surface) d ₆ = 4.24 n _d3 = 1.51603 ν _d3 = 64.02
r ₇ = -300.000 d ₇ = 1.10 n _d4 = 1.80810 ν _d4 = 22.76
r ₈ = 9.954 d ₈ = 1.13 n _d5 = 1.51603 ν _d5 = 64.02
r ₉ = -26.804 (aspherical surface) d ₉ = (variable)
r ₁₀ = ∞ d ₁₀ = 0.76 n _d6 = 1.54771 ν _d6 = 62.84
r ₁₁ = ∞ d ₁₁ = 0.50
r ₁₂ = ∞ d ₁₂ = 0.50 n _d7 = 1.51633 ν _d7 = 64.14
r ₁₃ = ∞ d ₁₃ = 0.38
r ₁₄ = ∞ (image plane)
Aspheric coefficient 2nd surface K = -0.704
A ₄ = 2.01910 × 10 ^-4
A ₆ = -1.91890 × 10 ^-7
A ₈ = 1.20310 × 10 ^-8
A ₁₀ = -7.41780 × 10 ^-10
6th surface K = -3.131
A ₄ = 3.38882 × 10 ^-3
A ₆ = -4.78149 × 10 ^-5
A ₈ = -3.72655 × 10 ^-6
A ₁₀ = 4.44776 × 10 ^-7
The ninth side K = -10.671
A ₄ = 2.10306 × 10 ^-3
A ₆ = 3.52644 × 10 ^-4
A ₈ = -5.41202 × 10 ^-5
A ₁₀ = 6.22955 × 10 ^-6
Zoom data (∞)
WE ST TE
f (mm) 5.95 10.08 17.05
F _NO 3.15 3.98 5.39
2ω (°) 64.40 39.67 23.88
d ₄ 12.66 5.55 1.37
d ₉ 8.93 12.64 18.90.

Example 5
r ₁ = 37.691 d ₁ = 1.20 n _d1 = 1.80495 ν _d1 = 40.93
r ₂ = 4.362 (aspherical surface) d ₂ = 2.33
r ₃ = 8.294 d ₃ = 1.62 n _d2 = 1.84666 ν _d2 = 23.78
r ₄ = 16.326 d ₄ = (variable)
r ₅ = ∞ (aperture) d ₅ = -0.26
r ₆ = 4.300 (aspherical surface) d ₆ = 4.31 n _d3 = 1.51742 ν _d3 = 52.43
r ₇ = -5.152 d ₇ = 1.20 n _d4 = 1.80810 ν _d4 = 22.76
r ₈ = -20.000 d ₈ = 0.95 n _d5 = 1.51603 ν _d5 = 64.02
r ₉ = -24.338 (aspherical surface) d ₉ = (variable)
r ₁₀ = ∞ d ₁₀ = 0.76 n _d6 = 1.54771 ν _d6 = 62.84
r ₁₁ = ∞ d ₁₁ = 0.50
r ₁₂ = ∞ d ₁₂ = 0.50 n _d7 = 1.51633 ν _d7 = 64.14
r ₁₃ = ∞ d ₁₃ = 0.37
r ₁₄ = ∞ (image plane)
Aspheric coefficient 2nd surface K = -0.704
A ₄ = 2.01910 × 10 ^-4
A ₆ = -1.91890 × 10 ^-7
A ₈ = 1.20310 × 10 ^-8
A ₁₀ = -7.41780 × 10 ^-10
6th surface K = -3.112
A ₄ = 4.54021 × 10 ^-3
A ₆ = -8.58413 × 10 ^-5
A ₈ = 2.62817 × 10 ^-6
A ₁₀ = 2.91567 × 10 ^-7
9th surface K = -10.670
A ₄ = 2.43162 × 10 ^-3
A ₆ = 3.02302 × 10 ^-4
A ₈ = -2.43703 × 10 ^-5
A ₁₀ = 3.51356 × 10 ^-6
Zoom data (∞)
WE ST TE
f (mm) 5.96 10.09 17.05
F _NO 3.16 3.98 5.39
2ω (°) 64.32 39.64 23.89
d ₄ 12.66 5.55 1.37
d ₉ 8.94 12.66 18.93.

Example 6
r ₁ = 51.401 d ₁ = 1.20 n _d1 = 1.80495 ν _d1 = 40.93
r ₂ = 4.250 (aspherical surface) d ₂ = 2.33
r ₃ = 8.280 d ₃ = 1.62 n _d2 = 1.84666 ν _d2 = 23.78
r ₄ = 16.031 d ₄ = (variable)
r ₅ = ∞ (aperture) d ₅ = -0.26
r ₆ = 4.690 (aspherical surface) d ₆ = 4.00 n _d3 = 1.51603 ν _d3 = 64.02
r ₇ = 48.276 d ₇ = 1.09 n _d4 = 1.80810 ν _d4 = 22.76
r ₈ = 8.996 d ₈ = 1.13 n _d5 = 1.51603 ν _d5 = 64.02
r ₉ = -32.723 (aspherical surface) d ₉ = (variable)
r ₁₀ = ∞ d ₁₀ = 0.76 n _d6 = 1.54771 ν _d6 = 62.84
r ₁₁ = ∞ d ₁₁ = 0.50
r ₁₂ = ∞ d ₁₂ = 0.50 n _d7 = 1.51633 ν _d7 = 64.14
r ₁₃ = ∞ d ₁₃ = 0.37
r ₁₄ = ∞ (image plane)
Aspheric coefficient 2nd surface K = -0.704
A ₄ = 2.01910 × 10 ^-4
A ₆ = -1.91890 × 10 ^-7
A ₈ = 1.20310 × 10 ^-8
A ₁₀ = -7.41780 × 10 ^-10
6th surface K = -3.132
A ₄ = 3.33772 × 10 ^-3
A ₆ = -4.81743 × 10 ^-5
A ₈ = -4.35927 × 10 ^-6
A ₁₀ = 5.17931 × 10 ^-7
The ninth side K = -10.671
A ₄ = 2.15229 × 10 ^-3
A ₆ = 3.18975 × 10 ^-4
A ₈ = -5.59975 × 10 ^-5
A ₁₀ = 6.63410 × 10 ^-6
Zoom data (∞)
WE ST TE
f (mm) 5.85 10.56 20.05
F _NO 3.32 4.39 6.58
2ω (°) 66.60 38.16 20.40
d ₄ 12.66 5.55 1.37
d ₉ 9.84 14.64 24.30.

Example 7
r ₁ = 37.691 d ₁ = 1.20 n _d1 = 1.80495 ν _d1 = 40.93
r ₂ = 4.450 (aspherical surface) d ₂ = 2.33
r ₃ = 8.294 d ₃ = 1.62 n _d2 = 1.84666 ν _d2 = 23.78
r ₄ = 16.326 d ₄ = (variable)
r ₅ = ∞ (aperture) d ₅ = -0.26
r ₆ = 4.441 d ₆ = 3.89 n _d3 = 1.51603 ν _d3 = 64.02
r ₇ = -9.298 d ₇ = 0.98 n _d4 = 1.80810 ν _d4 = 22.76
r ₈ = -279.238 d ₈ = 0.74 n _d5 = 1.51603 ν _d5 = 64.02
r ₉ = -60.000 (aspherical surface) d ₉ = (variable)
r ₁₀ = ∞ d ₁₀ = 0.76 n _d6 = 1.54771 ν _d6 = 62.84
r ₁₁ = ∞ d ₁₁ = 0.50
r ₁₂ = ∞ d ₁₂ = 0.50 n _d7 = 1.51633 ν _d7 = 64.14
r ₁₃ = ∞ d ₁₃ = 0.37
r ₁₄ = ∞ (image plane)
Aspheric coefficient 2nd surface K = -0.705
A ₂ = -5.57868 × 10 ^-3
A ₄ = 3.37216 × 10 ^-5
A ₆ = 4.60028 × 10 ^-5
A ₈ = -4.71414 × 10 ^-6
A ₁₀ = 1.61550 × 10 ^-7
Surface 9 K = -10.651
A ₄ = 3.53185 × 10 ^-3
A ₆ = 1.08265 × 10 ^-4
A ₈ = 2.25584 × 10 ^-5
A ₁₀ = -2.80053 × 10 ^-8
Zoom data (∞)
WE ST TE
f (mm) 6.66 10.88 17.35
F _NO 3.27 4.06 5.28
2ω (°) 58.61 36.89 23.47
d ₄ 12.66 5.55 1.37
d ₉ 9.80 13.25 18.54.

Example 8
r ₁ = 37.691 d ₁ = 1.20 n _d1 = 1.80400 ν _d1 = 46.57
r ₂ = 4.393 (aspherical surface) d ₂ = 2.33
r ₃ = 8.294 d ₃ = 1.62 n _d2 = 1.84666 ν _d2 = 23.78
r ₄ = 16.326 d ₄ = (variable)
r ₅ = ∞ (aperture) d ₅ = -0.26
r ₆ = 4.567 (aspherical surface) d ₆ = 3.01 n _d3 = 1.49700 ν _d3 = 81.54
r ₇ = 66.799 d ₇ = 1.67 n _d4 = 1.92286 ν _d4 = 18.90
r ₈ = 13.949 d ₈ = 1.11 n _d5 = 1.51603 ν _d5 = 64.02
r ₉ = -32.135 (aspherical surface) d ₉ = (variable)
r ₁₀ = ∞ d ₁₀ = 0.76 n _d6 = 1.54771 ν _d6 = 62.84
r ₁₁ = ∞ d ₁₁ = 0.50
r ₁₂ = ∞ d ₁₂ = 0.50 n _d7 = 1.51633 ν _d7 = 64.14
r ₁₃ = ∞ d ₁₃ = 0.37
r ₁₄ = ∞ (image plane)
Aspheric coefficient 2nd surface K = -0.704
A ₄ = 2.10637 × 10 ^-4
A ₆ = 1.07255 × 10 ^-6
A ₈ = -3.71750 × 10 ^-8
A ₁₀ = 5.72629 × 10 ^-9
6th surface K = -3.130
A ₄ = 4.08852 × 10 ^-3
A ₆ = -1.44925 × 10 ^-4
A ₈ = 1.73649 × 10 ^-6
A ₁₀ = 7.90457 × 10 ^-7
Surface 9 K = -10.672
A ₄ = 3.03679 × 10 ^-3
A ₆ = 1.53844 × 10 ^-4
A ₈ = -7.79567 × 10 ^-5
A ₁₀ = 1.49615 × 10 ^-5
Zoom data (∞)
WE ST TE
f (mm) 5.96 10.00 16.64
F _NO 3.13 3.92 5.24
2ω (°) 64.81 40.07 24.48
d ₄ 12.66 5.55 1.37
d ₉ 9.50 13.08 18.96.

Example 9
r ₁ = 37.691 d ₁ = 1.20 n _d1 = 1.80495 ν _d1 = 40.93
r ₂ = 4.362 (aspherical surface) d ₂ = 2.33
r ₃ = 8.294 d ₃ = 1.62 n _d2 = 1.84666 ν _d2 = 23.78
r ₄ = 16.326 d ₄ = (variable)
r ₅ = ∞ (aperture) d ₅ = -0.26
r ₆ = 4.538 (aspherical surface) d ₆ = 4.20 n _d3 = 1.51603 ν _d3 = 64.02
r ₇ = 96.074 d ₇ = 1.05 n _d4 = 1.80810 ν _d4 = 22.76
r ₈ = 8.579 d ₈ = 1.08 n _d5 = 1.51603 ν _d5 = 64.02
r ₉ = -28.441 (aspherical surface) d ₉ = (variable)
r ₁₀ = 211.718 d ₁₀ = 0.71 n _d6 = 1.49700 ν _d6 = 81.54
r ₁₁ = 102.523 d ₁₁ = (variable)
r ₁₂ = ∞ d ₁₂ = 0.76 n _d7 = 1.54771 ν _d7 = 62.84
r ₁₃ = ∞ d ₁₃ = 0.50
r ₁₄ = ∞ d ₁₄ = 0.50 n _d8 = 1.51633 ν _d8 = 64.14
r ₁₅ = ∞ d ₁₅ = 0.37
r ₁₆ = ∞ (image plane)
Aspheric coefficient 2nd surface K = -0.704
A ₄ = 2.01910 × 10 ^-4
A ₆ = -1.91890 × 10 ^-7
A ₈ = 1.20310 × 10 ^-8
A ₁₀ = -7.41780 × 10 ^-10
6th surface K = -3.131
A ₄ = 3.53969 × 10 ^-3
A ₆ = -5.76418 × 10 ^-5
A ₈ = -2.28407 × 10 ^-6
A ₁₀ = 3.73706 × 10 ^-7
The ninth side K = -10.671
A ₄ = 2.22302 × 10 ^-3
A ₆ = 3.59589 × 10 ^-4
A ₈ = -4.93117 × 10 ^-5
A ₁₀ = 6.01662 × 10 ^-6
Zoom data (∞)
WE ST TE
f (mm) 5.95 10.09 17.06
F _NO 3.16 3.98 5.40
2ω (°) 64.35 39.64 23.87
d ₄ 12.66 5.55 1.37
d ₉ 6.05 9.77 16.11
d ₁₁ 2.32 2.25 0.37.

Example 10
r ₁ = 37.691 d ₁ = 1.20 n _d1 = 1.80495 ν _d1 = 40.93
r ₂ = 4.362 (aspherical surface) d ₂ = 2.33
r ₃ = 8.294 d ₃ = 1.62 n _d2 = 1.84666 ν _d2 = 23.78
r ₄ = 16.326 d ₄ = (variable)
r ₅ = ∞ (aperture) d ₅ = -0.26
r ₆ = 4.526 (aspherical surface) d ₆ = 4.20 n _d3 = 1.51603 ν _d3 = 64.02
r ₇ = 92.786 d ₇ = 1.05 n _d4 = 1.80810 ν _d4 = 22.76
r ₈ = 8.550 d ₈ = 1.08 n _d5 = 1.51603 ν _d5 = 64.02
r ₉ = -30.010 (aspherical surface) d ₉ = (variable)
r ₁₀ = 110.638 d ₁₀ = 0.76 n _d6 = 1.49700 ν _d6 = 81.54
r ₁₁ = 123.617 d ₁₁ = 2.26
r ₁₂ = ∞ d ₁₂ = 0.76 n _d7 = 1.54771 ν _d7 = 62.84
r ₁₃ = ∞ d ₁₃ = 0.50
r ₁₄ = ∞ d ₁₄ = 0.50 n _d8 = 1.51633 ν _d8 = 64.14
r ₁₅ = ∞ d ₁₅ = 0.37
r ₁₆ = ∞ (image plane)
Aspheric coefficient 2nd surface K = -0.704
A ₄ = 2.01910 × 10 ^-4
A ₆ = -1.91890 × 10 ^-7
A ₈ = 1.20310 × 10 ^-8
A ₁₀ = -7.41780 × 10 ^-10
6th surface K = -3.131
A ₄ = 3.54289 × 10 ^-3
A ₆ = -4.52245 × 10 ^-5
A ₈ = -4.77798 × 10 ^-6
A ₁₀ = 5.17175 × 10 ^-7
The ninth side K = -10.671
A ₄ = 2.18272 × 10 ^-3
A ₆ = 4.27937 × 10 ^-4
A ₈ = -6.90882 × 10 ^-5
A ₁₀ = 7.84657 × 10 ^-6
Zoom data (∞)
WE ST TE
f (mm) 5.91 10.03 17.04
F _NO 3.13 3.96 5.39
2ω (°) 64.80 39.84 23.89
d ₄ 12.66 5.55 1.37
d ₉ 6.05 9.75 16.03.

  Aberration diagrams at the time of focusing on an object point at infinity in Examples 1 to 10 are shown in FIGS. In these aberration diagrams, (a) shows the spherical aberration, astigmatism, distortion and lateral chromatic aberration at the wide-angle end, (b) the intermediate state, and (c) the telephoto end. In each aberration diagram, “FIY” represents the image height.

The values of conditional expressions (1) to (17) in Examples 1 to 10 are as follows.

Conditional Example Example 1 Example 2 Example 3 Example 4 Example 5
(1) 0.92 0.72 0.65 0.62 -0.02
(2) 3.12 3.74 3.75 3.75 4.55
(3) 6.47 21.63 INF 65.18 1.20
(4) 0.283 0.337 0.362 0.371 0.822
(5) 41.26 41.26 41.26 41.26 41.26
(6) 22.76 22.76 22.76 22.76 22.76
(7) 64.02 64.02 64.02 64.02 64.02
(8) 1.80810 1.80810 1.80810 1.80810 1.80810
(9) 1.51635 1.51603 1.51603 1.51603 1.51603
(10) 0.80 0.82 0.83 0.83 0.67
(11) 1.29 1.13 1.13 1.13 0.33
(12) -0.69 -0.70 -0.70 -0.71 -0.70
(13) 3.12 10.39 INF -31.16 -0.54
(14) 0.62 0.66 0.66 0.66 0.67
(15) 3.12 10.39 INF 31.16 0.54
(16) 0.75 0.91 1.00 1.03 2.08
(17) 0.20 0.18 0.17 0.17 0.15

Conditional Example Example 6 Example 7 Example 8 Example 9 Example 10
(1) 0.71 0.04 0.51 0.70 0.70
(2) 3.54 5.27 2.72 3.91 3.91
(3) 10.29 2.09 14.63 21.17 20.45
(4) 0.275 4.654 0.434 0.084 0.069
(5) 41.26 41.26 45.12 41.26 41.26
(6) 22.76 22.76 18.90 22.76 22.76
(7) 64.02 64.02 64.02 64.02 64.02
(8) 1.80810 1.80810 1.92286 1.80810 1.80810
(9) 1.51603 1.51603 1.51603 1.51603 1.51603
(10) 0.82 0.69 0.81 0.83 0.83
(11) 1.13 0.31 1.11 1.08 1.08
(12) -0.75 -0.86 -0.75 -1.09 -1.08
(13) 5.01 -0.97 6.94 9.98 9.64
(14) 0.64 0.69 0.52 0.66 0.66
(15) 5.01 -0.97 6.94 9.98 9.64
(16) 0.93 29.00 1.45 0.89 0.89
(17) 0.18 0.13 0.19 0.17 0.17
.

  FIGS. 21 to 23 are conceptual diagrams of a configuration in which the zoom optical system according to the present invention is incorporated in a photographing optical system 41 of a digital camera. FIG. 21 is a front perspective view showing the external appearance of the digital camera 40, FIG. 22 is a rear front view thereof, and FIG. 23 is a schematic perspective plan view showing the configuration of the digital camera 40. However, in FIGS. 21 and 23, the photographing optical system 41 is not retracted. In this example, the digital camera 40 includes a photographing optical system 41 having a photographing optical path 42, a finder optical system 43 having a finder optical path 44, a shutter 45, a flash 46, a liquid crystal display monitor 47, a focal length change button 61, a setting. When the photographing optical system 41 is retracted, including the change switch 62, the photographing optical system 41, the finder optical system 43, and the flash 46 are covered with the cover 60 by sliding the cover 60. When the cover 60 is opened and the camera 40 is set to the photographing state, the photographing optical system 41 enters the non-collapsed state shown in FIG. 23. When the shutter 45 disposed on the upper portion of the camera 40 is pressed, the photographing optical system is linked. Photographing is performed through the system 41, for example, the zoom optical system of the first embodiment. An object image formed by the photographic optical system 41 is formed on the imaging surface of the CCD 49 via the low-pass filter F and the cover glass C subjected to IR cut coating. The object image received by the CCD 49 is displayed as an electronic image on the liquid crystal display monitor 47 provided on the back of the camera via the processing means 51. Further, the processing means 51 is connected to a recording means 52 so that a photographed electronic image can be recorded. The recording means 52 may be provided separately from the processing means 51, or may be configured to perform recording / writing electronically using a floppy disk, memory card, MO, or the like. Further, it may be configured as a silver salt camera in which a silver salt film is arranged in place of the CCD 49.

  Further, a finder objective optical system 53 is disposed on the finder optical path 44. The finder objective optical system 53 includes a plurality of lens groups (four groups in the figure) and two prisms, and includes a zoom optical system whose focal length changes in conjunction with the zoom lens of the photographing optical system 41. The object image formed by the finder objective optical system 53 is formed on the field frame 57 of the erecting prism 55 that is an image erecting member. Behind the erecting prism 55, an eyepiece optical system 59 for guiding the erect image to the observer eyeball E is disposed. A cover member 50 is disposed on the exit side of the eyepiece optical system 59.

  In the digital camera 40 configured in this manner, the photographing optical system 41 has a high performance and a small size and can be retracted, so that a high performance and a small size can be realized.

  The present invention may be applied not only to a so-called compact digital camera that captures a general subject as described above, but also to a surveillance camera that requires a wide angle of view and an interchangeable lens camera.

  The optical system of the present invention may have the following configuration in addition to the configuration of the claims.

    [1] The optical system according to any one of [1] to [25], wherein the optical system includes two lens groups as a whole.

    [2] The optical system according to any one of [1] to [25], wherein the optical system includes a total of three lens groups.

    [3] The optical system according to [2], wherein the lens group disposed closest to the image side among the three lens groups has a negative refractive power.

    [4] The optical system as set forth in [3], wherein among the three lens groups, the lens group arranged closest to the image side has a positive refractive power.

    [5] The optical system according to any one of [2] to [4], wherein the lens group disposed closest to the image side among the three lens groups is fixed at the time of zooming. system.

    [6] The optical system according to any one of [2] to [4], wherein among the three lens groups, the lens group disposed closest to the image side moves during zooming. .

    [7] The optical system according to [6], wherein the lens group disposed closest to the image side moves so as to be positioned closer to the image side at the telephoto end than at the wide angle end.

    [8] The optical system according to any one of [1] to [3], [6] to [26], and [1] to [7], wherein the cemented lens is included in the second lens group.

  According to the present invention, it is possible to reduce the thickness even at a high zoom ratio, and to obtain an optical system that suppresses the influence of eccentricity and prevents performance deterioration. Cameras and video cameras can be obtained.

G1 ... 1st lens group G2 ... 2nd lens group G3 ... 3rd lens group S ... Aperture stop F ... Parallel plate (low-pass filter)
C ... Cover glass I ... Image plane E ... Observer eyeball 40 ... Digital camera 41 ... Shooting optical system 42 ... Shooting optical path 43 ... Viewfinder optical system 44 ... Viewfinder optical path 45 ... Shutter button 46 ... Flash 47 ... Liquid crystal display monitor 49 ... CCD
DESCRIPTION OF SYMBOLS 50 ... Cover member 51 ... Processing means 52 ... Recording means 53 ... Viewfinder objective optical system 55 ... Erect prism 57 ... Field frame 59 ... Eyepiece optical system 60 ... Cover 61 ... Focal length change button 62 ... Setting change switch

Claims (29)

An optical system comprising a cemented lens having a cemented surface on the optical axis, wherein the lens constituting the cemented lens satisfies the following conditions.
40 <ν _max −ν _min <80 (5)
23.7> ν _min (6)
Where ν _max is the maximum Abbe number in the cemented lens,
ν _min : the smallest Abbe number in the cemented lens,
It is. The optical system according to claim 1, wherein the lens constituting the cemented lens satisfies the following condition.
60 <ν _max (7)
1.8 <n _dmax (8)
1.55> n _dmin (9)
Where n _dmax is the maximum refractive index in the cemented lens,
n _dmin : minimum refractive index in the cemented lens,
It is. The optical system includes two groups, a first lens group having a negative refractive power and a second lens group having a positive refractive power, or a first lens group having a negative refractive power and a positive refractive power in order from the object side. The optical system according to claim 1, wherein the second lens group includes a third lens group having a weak negative or weak positive refractive power, and the second lens group includes the cemented lens. 4. The optical system according to claim 1, wherein at least one of the air contact surfaces on the light incident side and the light exit side of the cemented lens is an aspherical surface. 5. The optical system according to any one of claims 1 to 4, wherein the cemented lens is a three-lens cemented lens including three lenses. The cemented lens in the second lens group is the three-lens cemented lens in which a positive first lens, a negative second lens, and a positive third lens are arranged from the object side. The optical system according to claim 3. 7. The optical system according to claim 3, wherein the second lens group includes only a three-piece cemented lens. 8. The optical system according to claim 3, wherein focusing is performed by moving a lens of the first lens group in the optical system. 9. At the time of zooming from the wide-angle end to the telephoto end, the second lens group moves monotonically from the image side to the object side, and the first lens group moves along a convex locus on the image side. The optical system according to any one of claims 3, 6, 7, and 8. 10. The cemented lens according to claim 1, wherein the cemented lens is composed of three cemented lenses, wherein the lens closest to the object side and the lens closest to the image plane are made of the same glass material. Optical system. The optical system according to claim 1, wherein the cemented lens has a convex shape on the object side and further satisfies the following conditional expression.
0.50 <D _n1 /Σd<0.95 (10)
Where D _{n1 is} the distance from the most object side surface in the cemented lens to the surface having the greatest negative refractive power,
Σd: total thickness of the cemented lens,
It is. The optical system according to claim 11, further satisfying the following conditional expression:
0.05 <D _n2 /Σd<0.35 (11)
Where D _{n2 is} the distance from the surface having the largest negative refractive power in the cemented lens to the surface closest to the image plane,
It is. The optical system according to claim 1, wherein the cemented lens has a convex shape on the object side and further satisfies the following conditional expression.
−1.5 <(r ₁ + r ₂ ) / (r ₁ −r ₂ ) <− 0.5 (12)
Where r ₁ : radius of curvature of the most object side surface of the cemented lens,
r ₂ : radius of curvature of the surface closest to the image plane of the cemented lens,
It is. The cemented lens has a convex shape on the object side, and the negative lens is cemented on the image plane side of the lens on the most object side, further satisfying the following conditional expression: 2. The optical system according to item 1.
−1.0 <R ₁ / F ₂ <−0.05 (13)
0.50 <D ₁ /Σd<0.95 (14)
Where R _{1 is the} radius of curvature of the cemented surface closest to the object side of the cemented lens,
F ₂ : focal length of the second lens group,
D ₁ : thickness on the optical axis of the lens closest to the object side of the cemented lens,
Σd: total thickness of the cemented lens,
It is. The cemented lens has a convex shape on the object side, and the negative lens is cemented to a lens disposed closest to the image plane of the cemented lens, further satisfying the following conditional expression: 14. The optical system according to any one of 14.
2.5 <| R ₁ / F ₂ | (15)
0.45 <R ₂ / F ₂ <2.3 (16)
Where R _{1 is the} radius of curvature of the cemented surface closest to the object side of the cemented lens,
F ₂ : focal length of the second lens group,
R ₂ : radius of curvature of the cemented surface closest to the image plane of the cemented lens,
It is. The optical system according to claim 15, wherein the following conditional expression is satisfied:
−1.5 <(r ₁ + r ₂ ) / (r ₁ −r ₂ ) <− 0.5 (12)
0.05 <D ₃ /Σd<0.30 (17)
Where r ₁ : radius of curvature of the most object side surface of the cemented lens,
r ₂ : radius of curvature of the surface closest to the image plane of the cemented lens,
D ₃ : thickness on the optical axis of the lens closest to the image plane of the cemented lens,
Σd: total thickness of the cemented lens,
It is. 3. The optical system according to claim 1, wherein the cemented lens has at least one positive lens and one negative lens. The optical system according to claim 1, wherein the cemented lens has a biconvex shape in the vicinity of the optical axis. The optical system according to any one of claims 4 to 18, wherein the aspherical surface on the exit side is provided so that a diverging action is strong at a lens peripheral portion. The optical system according to any one of claims 3, 6, 7, 8, and 9, wherein the optical system includes two lens groups as a whole. The optical system according to any one of claims 3, 6, 7, 8, and 9, wherein the optical system includes a total of three lens groups. The optical system according to claim 21, wherein the lens group disposed closest to the image side among the three lens groups has a negative refractive power. The optical system according to claim 21, wherein the lens group disposed closest to the image side among the three lens groups has a positive refractive power. 24. The optical system according to claim 21, wherein the lens group disposed closest to the image side among the three lens groups is fixed at the time of zooming. 23. The optical system according to claim 21, wherein the lens group disposed closest to the image side among the three lens groups moves for image plane compensation at the time of zooming. 26. The optical system according to claim 25, wherein the lens group arranged closest to the image side moves so as to be positioned closer to the image side at the telephoto end than at the wide-angle end. 27. An imaging apparatus comprising: the optical system according to claim 1; and an electronic imaging element for converting an optical image obtained by the optical system into an electrical signal. 27. The optical system according to any one of claims 3, 6, 7, 8, 9, and 20 to 26, wherein the optical system is configured to satisfy the following conditional expression.
10 <| R ₁ / r ₁ | (3)
Where r ₁ : radius of curvature of the most object side surface of the cemented lens,
R ₁ : radius of curvature of the cemented surface closest to the object side of the cemented lens,
It is. 29. Any one of claims 3, 6, 7, 8, 9, 20 to 26, 28, wherein the cemented lens has a convex shape on the object side and satisfies the following conditional expression: The optical system according to claim 1.
0.7 <| R ₂ / r ₂ | (4)
Where r ₂ : radius of curvature of the surface closest to the image plane of the cemented lens,
R ₂ : radius of curvature of the cemented surface closest to the image plane of the cemented lens,
It is.

Images