JP4766929B2 - Image pickup apparatus having an optical path folding zoom lens - Google Patents

Description

The present invention relates to an image pickup apparatus including an optical path folding type zoom lens, and more particularly to an image pickup apparatus including a zoom lens including a reflecting surface that bends an optical path and having a thickness as small as possible in an incident optical axis direction.

  2. Description of the Related Art Conventionally, there are known optical path folding zoom lenses in which the thickness in the direction of the incident optical axis is minimized by bending the optical path. Such a zoom lens includes a moving group that has a reflecting surface in the first lens group and moves to the optical path after reflection upon zooming. Therefore, the moving optical path of the lens that moves at the time of zooming becomes the height direction or horizontal direction of the imaging device, and while suppressing the thickness in the camera thickness direction (direction from the subject to the photographer), the high zoom ratio Zoom lens and camera.

As such zoom lenses, for example, zoom lenses described in Patent Literature 1, Patent Literature 2, Patent Literature 3, Patent Literature 4, and Patent Literature 5 are known.
JP 2000-131610 A JP 2003-202500 A JP 2003-302576 A JP 2003-329932 A JP 2004-184627 A

  However, the optical path folding zoom lens shown in the prior art has a relatively large first lens group for bending the optical path. Therefore, the thickness direction at the optical path bending portion is not yet thinned. Alternatively, a thin and wide angle of view or a high zoom ratio cannot be achieved.

  Moreover, the optical system after bending is long, and consideration for downsizing of the image pickup apparatus in the height direction or the lateral direction is thin.

The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to perform imaging using an optical path folding zoom lens that can be made thinner in the thickness direction and sufficiently secure an angle of view. Is to provide a device.

  It is another object of the present invention to provide an image pickup apparatus using an optical path folding zoom lens that can shorten the height direction or the horizontal direction of the image pickup apparatus by downsizing the configuration after bending while maintaining a wide angle of view.

The first optical path bending zoom lens according to the present invention that achieves the above object, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a positive refraction. A third lens group having a power and a fourth lens group having a positive refractive power;
During zooming from the wide-angle end to the telephoto end, the first lens group is fixed, at least the second lens group and the third lens group move, and the third lens group and the fourth lens group The distance is changed, the second lens group is positioned on the image plane side at the telephoto end rather than the wide-angle end, and the third lens group is positioned on the object side at the telephoto end than the wide-angle end;
The first lens group includes a reflective optical element that bends the optical path by reflection;
The following conditional expression is satisfied.

0.5 <f _1G / f _w <3.5 (1)
Where f _1G is the focal length of the first lens group,
f _w is the focal length of the entire zoom lens system at the wide-angle end,
It is.

  The reason why the above configuration is adopted in the first optical path bending type zoom lens and the function and effect thereof will be described below.

  In the zoom lens according to the present invention, a thin zoom lens is configured by four lens groups of positive, negative, positive, and positive in order from the object, and the optical path is bent by reflection in the positive first lens group. The magnification is changed mainly by moving the second lens group and the third lens group.

  At this time, if the zooming action of the second lens group is large, the amount of movement of the second lens group becomes large, and the off-axis ray incident height to the first lens group at the wide-angle end tends to be high. It is difficult to reduce the lens diameter.

  Therefore, according to the present invention, the amount of movement of the second lens group can be reduced by giving the third lens group a zooming action and reducing the burden of the zooming action of the second lens group. As a result, the first lens group ray height can be reduced.

  In the present invention, the lens outer shape of the first lens group is reduced and the bent thickness is reduced by appropriately adjusting the power of the positive first lens group so as to satisfy the conditional expression (1). Is possible.

  If the lower limit of 0.5 of conditional expression (1) is exceeded, the power of the first lens group will increase, which is advantageous for downsizing of the first lens group. However, spherical aberration and astigmatism will occur in the first lens group. It occurs greatly and it becomes difficult to correct the aberration of the entire system.

  On the other hand, when the upper limit of 3.5 to conditional expression (1) is exceeded, the power of the first lens group is weakened, the amount of movement of the second lens group is increased, and the first lens group is likely to be enlarged. Alternatively, the positive refracting power in the third lens group is increased, and it becomes difficult to suppress aberration fluctuations due to movement of the third lens group with a small number of lenses.

  The second optical path folding zoom lens of the present invention is characterized in that the following conditional expression is satisfied in the first optical path folding zoom lens.

0.5 <| f _2G / f _w | <1.8 (2)
Where f _2G is the focal length of the second lens group,
It is.

  The reason why the above configuration is adopted in the second optical path bending type zoom lens and the function and effect thereof will be described below.

  Conditional expression (2) appropriately defines the power of the second lens group. If the power of the second lens group is increased beyond the lower limit of 0.5 in conditional expression (2), the amount of movement of the second lens group is reduced, which is advantageous for shortening the overall length, but astigmatism and distortion occur. This makes it difficult to correct aberrations of the entire system.

  When the upper limit of 1.8 to conditional expression (2) is exceeded, the amount of movement of the second lens group becomes too large, making it difficult to shorten the overall length.

  The third optical path folding zoom lens of the present invention is characterized in that the following conditional expressions are satisfied in the first and second optical path folding zoom lenses.

0.7 <m _2GZ / m _3GZ <1.2 (3)
However, m _2GZ is the ratio of the telephoto end magnification to the wide angle end magnification of the second lens group when focusing on an object point at infinity,
m _3GZ is the ratio of the telephoto end magnification to the wide-angle end magnification of the third lens group when focusing on an object point at infinity,
It is.

  The reason why the above configuration is adopted in the third optical path folding zoom lens and the function and effect thereof will be described below.

  Conditional expression (3) appropriately defines the variable magnification sharing of the second lens group and the third lens group. If the upper limit of 1.2 in conditional expression (3) is exceeded, the variable magnification share of the second lens group becomes large and the amount of movement of the second lens group becomes large, so the diameter of the first lens group tends to increase. Alternatively, the refractive power of the second lens group becomes large, and it becomes difficult to suppress aberration fluctuation due to movement.

  If the lower limit of 0.7 of conditional expression (3) is exceeded, the variable magnification share of the third lens group becomes large, the amount of movement of the third lens group tends to increase, and the total length tends to increase. Alternatively, the refractive power of the third lens group becomes large, and it is difficult to suppress aberration fluctuation due to movement.

  According to a fourth optical path folding zoom lens of the present invention, the first to third optical path folding zoom lenses satisfy the following conditional expressions.

-0.2 <f _w / R ₁ <0.2 (4)
Where R ₁ is the paraxial radius of curvature of the object side surface of the lens closest to the object side in the first lens group,
It is.

  The reason why the above-described configuration is adopted in the fourth optical path bending type zoom lens and the operation and effect thereof will be described below.

  Conditional expression (4) defines the paraxial radius of curvature of the object side surface of the lens closest to the object side in the first lens group. If the lower limit of −0.2 is exceeded, large negative distortion tends to occur at the wide angle end.

  Exceeding the upper limit of 0.2 in conditional expression (4) is advantageous for correcting off-axis aberrations, but on the other hand, the top of the lens surface tends to protrude toward the object side, making it difficult to reduce the thickness.

  According to a fifth optical path folding zoom lens of the present invention, in the first to fourth optical path folding zoom lenses, the first lens group includes, in order from the object side, a negative meniscus lens having a convex surface facing the object side, an optical path It is constituted by a reflective optical element for bending the lens and a positive lens group.

  The reason why the above configuration is adopted in the fifth optical path bending type zoom lens and the operation and effect thereof will be described below.

  If a reflective optical element for bending the optical path is provided in the first lens group, the entrance pupil position inevitably tends to be deep. Therefore, the diameter and size of each optical element constituting the first lens group are enlarged, and it is difficult to physically establish the optical path bending method. Therefore, the first lens group includes, in order from the object side, a negative meniscus lens having a convex surface directed toward the object side, a reflective optical element for bending the optical path, and a positive lens group, and is necessary for bending by the reflective optical element. It is preferable to keep the chief rays in the optical path close to parallel and suppress the enlargement of the diameter.

  Even if the positive lens group is a single positive lens, it is preferable in terms of miniaturization.

  In the present invention, the following configuration may be further satisfied.

  According to a sixth optical path folding zoom lens of the present invention, in the first to fifth optical path folding zoom lenses, the first lens group includes, in order from the object side, a negative lens group and a reflective optical element for folding the optical path. The negative lens group is configured by a positive lens group, and satisfies the following conditional expression.

0.5 <| f _L1 / f _w | <2.5 (5)
Where f _L1 is the focal length of the negative lens group of the first lens group,
It is.

  The reason why the above configuration is adopted in the sixth optical path bending type zoom lens and the function and effect thereof will be described below.

  In order to make the entrance pupil shallow and to allow optical path bending physically, it is preferable to increase the power of the negative lens unit of the first lens unit to be moderately strong as in the conditional expression (5).

  If the upper limit of 2.5 of conditional expression (5) is exceeded, the entrance pupil remains deep, and the diameter and size of each optical element constituting the first lens group will be enlarged if a certain angle of view is to be secured. The optical path bending is difficult to be physically established.

  If the lower limit of 0.5 of conditional expression (5) is exceeded, the possible magnification of the lens unit that moves for zooming that follows the first lens unit becomes close to zero, and the amount of movement increases or zoom ratio It is easy to cause a problem such as a decrease in the size of the lens, and it becomes difficult to correct off-axis aberrations such as distortion and chromatic aberration.

  According to a seventh optical path folding zoom lens of the present invention, in the first to sixth optical path folding zoom lenses, focusing on a short-distance object is performed by moving the fourth lens group to the object side. It is what.

  The reason why the above configuration is adopted in the seventh optical path bending type zoom lens and the function and effect thereof will be described below.

  By performing the focusing by moving the fourth lens group to the object side, the fluctuation of the off-axis aberration at a short distance may be small.

  In addition, it is preferable to configure the following imaging device using the above zoom lens.

  The first image pickup apparatus of the present invention is an image pickup having first to seventh optical path folding zoom lenses and a light receiving surface that is arranged on the image side and converts an optical image formed by the zoom lens into an electric signal. And satisfying the following conditional expression.

1.6 <f _w /ih<1.9 (6)
Where ih is the maximum image height in the effective shooting area of the light receiving surface,
It is.

  Hereinafter, the reason why the above-described configuration is adopted in the first imaging device and the operation and effect thereof will be described.

  Conditional expression (6) defines the focal length of the entire zoom lens system with respect to the maximum image height at the wide-angle end. If the lower limit of 1.6 of conditional expression (6) is exceeded, the angle of view at the wide-angle end becomes small, which is contrary to the purpose of wide angle of view.

  On the other hand, when the upper limit of 1.9 is exceeded, the angle of view becomes too wide, and the zoom lens becomes thick in order to secure a bent optical path.

The conditional expression (6) is also intended to define the scope of the wide angle end focal length f _w of the conditional expression (1) or the like.

  The effective imaging area on the light receiving surface means an area for obtaining image information used for printing, display, etc. on the light receiving surface on which an optical image is formed.

  The optical path bending type zoom lens of the present invention is advantageous for suppressing the thickness and the total length while having a wide angle.

  The imaging device is preferably configured as follows.

  The above-mentioned focal length condition for each group is re-specified by the maximum image height of the effective imaging area on the light receiving surface. A description of the effects already described is omitted.

A second imaging device of the present invention includes a zoom lens, and an imaging element having a light receiving surface that is arranged on the image side and converts an optical image formed by the zoom lens into an electrical signal,
The zoom lens includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive refractive power. A fourth lens group having
Upon zooming from the wide-angle end to the telephoto end, the first lens group is fixed with respect to the image plane on the light receiving surface, and at least the second lens group and the third lens group move, and the third lens The distance between the first lens group and the fourth lens group changes, the second lens group is positioned closer to the image plane at the telephoto end than the wide-angle end, and the third lens group is closer to the telephoto end than the wide-angle end. Located on the object side
The first lens group includes a reflective optical element that bends the optical path by reflection;
The following conditional expression is satisfied.

1.6 <f _w /ih<1.9 (6)
0.85 <f _1G /ih<6.0 (7)
Where f _1G is the focal length of the first lens group,
f _w is the focal length of the entire zoom lens system at the wide-angle end,
ih is the maximum image height in the effective shooting area of the light-receiving surface,
It is.

  The reason why the above-described configuration is adopted in the second imaging apparatus and the function and effect thereof will be described below.

  Conditional expression (6) defines the focal length at the wide-angle end by the maximum image height of the effective imaging region. If the lower limit of 1.6 of conditional expression (6) is exceeded, the angle of view at the wide-angle end becomes small, which is contrary to the purpose of wide angle of view.

  On the other hand, when the upper limit of 1.9 is exceeded, the angle of view becomes too wide, and the zoom lens becomes thick in order to secure a bent optical path.

  Conditional expression (7) defines the focal length of the first lens group with the maximum image height. If the lower limit of 0.85 in conditional expression (7) is exceeded, the power of the first lens group will increase, which is advantageous for downsizing of the first lens group. However, spherical aberration and astigmatism will occur in the first lens group. It occurs greatly and it becomes difficult to correct the aberration of the entire system.

  On the other hand, when the upper limit of 6.0 of the conditional expression (7) is exceeded, the power of the first lens group is weakened, the amount of movement of the second lens group is increased, and the first lens group is easily increased in size. Alternatively, the positive refracting power in the third lens group is increased, and it becomes difficult to suppress aberration fluctuations due to movement of the third lens group with a small number of lenses.

  The third imaging device of the present invention is characterized in that, in the second imaging device, the following conditional expression is satisfied.

0.85 <| f _2G /ih|<3.1 (8)
Where f _2G is the focal length of the second lens group,
It is.

  Hereinafter, the reason why the above-described configuration is adopted in the third imaging device and the operation and effect thereof will be described.

  Conditional expression (8) defines the power of the second lens group at the maximum image height. If the power of the second lens unit is increased beyond the lower limit of 0.85 in conditional expression (8), astigmatism and distortion will occur greatly, making it difficult to correct the aberration of the entire system.

  If the upper limit of 3.1 to conditional expression (8) is exceeded, the amount of movement of the second lens group becomes too large, and it becomes difficult to shorten the overall length.

  According to a fourth imaging device of the present invention, the second and third imaging devices satisfy the following conditional expressions.

0.7 <m _2GZ / m _3GZ <1.2 (3)
However, m _2GZ is the ratio of the telephoto end magnification to the wide angle end magnification of the second lens group when focusing on an object point at infinity,
m _3GZ is the ratio of the telephoto end magnification to the wide-angle end magnification of the third lens group when focusing on an object point at infinity,
It is.

  The reason why the above-described configuration is adopted in the fourth imaging apparatus and the operation and effects thereof are as described above.

  According to a fifth imaging device of the present invention, in the second to fourth imaging devices, the following conditional expression is satisfied.

−0.118 <ih / R ₁ <0.118 (9)
Where R ₁ is the paraxial radius of curvature of the object side surface of the lens closest to the object side in the first lens group,
It is.

  The reason why the above configuration is adopted in the fifth image pickup apparatus and the operation and effect thereof will be described below.

  Conditional expression (9) defines the paraxial radius of curvature of the object side surface of the lens closest to the object side in the first lens group at the maximum image height. Exceeding the lower limit of −0.118 tends to cause large negative distortion at the wide-angle end.

  Exceeding the upper limit of 0.118 in conditional expression (9) is advantageous for correcting off-axis aberrations, but on the other hand, the top of the lens surface tends to protrude to the object side, making it difficult to reduce the thickness.

  According to a sixth imaging device of the present invention, in the second to fifth imaging devices, the first lens group includes, in order from the object side, a negative meniscus lens having a convex surface directed toward the object side, and reflective optics for bending the optical path. It is composed of an element and a positive lens group.

  The reason why the above configuration is adopted in the sixth imaging apparatus and the operation and effects thereof are as described above.

  According to a seventh imaging device of the present invention, in the second to sixth imaging devices, the first lens group includes, in order from the object side, a negative lens group, a reflective optical element for bending an optical path, and a positive lens group. The negative lens unit is configured to satisfy the following conditional expression.

0.85 <| f _L1 /ih|<4.25 (10)
Where f _L1 is the focal length of the negative lens group of the first lens group,
It is.

  The reason why the above configuration is adopted in the seventh imaging apparatus and the operation and effect thereof will be described below.

  Conditional expression (10) defines the focal length of the negative lens group, which is the front group of the first lens group, by the maximum image height. The power of the negative lens group of the first lens group should be appropriately increased.

  If the upper limit of 4.25 of the conditional expression (10) is exceeded, the entrance pupil remains deep, and when trying to secure a certain angle of view, the diameter and size of each optical element constituting the first lens group are enlarged. The optical path bending is difficult to be physically established.

  If the lower limit of 0.85 in conditional expression (10) is exceeded, the magnification that can be taken by the lens unit that moves for zooming that follows the first lens unit becomes close to zero, and the amount of movement increases or the zoom ratio. It is easy to cause a problem such as a decrease in the size of the lens, and it becomes difficult to correct off-axis aberrations such as distortion and chromatic aberration.

  If the negative lens group is a single lens, it is preferable to reduce the size of the imaging device in the thickness direction.

  When the positive lens group is a single lens, it is preferable to reduce the size of the imaging device in the height direction or the lateral direction.

  According to an eighth imaging apparatus of the present invention, in the second to seventh imaging apparatuses, focusing on a short-distance object is performed by moving the fourth lens group to the object side.

  The reason why the above configuration is adopted in the eighth image pickup apparatus and the operation and effects thereof are as described above.

  According to a ninth imaging device of the present invention, in the seventh imaging device, the positive lens group of the first lens group satisfies the following condition.

1.5 <f _L2 /ih<4.0 (11)
Where f _L2 is the focal length of the positive lens group of the first lens group,
It is.

  Hereinafter, the reason why the above-described configuration is adopted in the ninth image pickup apparatus and the function and effect thereof will be described.

  Conditional expression (11) defines the focal length of the positive lens group, which is the rear group of the first lens group, with the maximum image height. The power of the negative lens group of the first lens group should be appropriately increased, but in this case, off-axis aberrations such as distortion tend to occur. For this reason, the positive lens group disposed near the negative lens group also has moderately strong power, so that it is easy to suppress the occurrence of aberrations, which is advantageous for downsizing.

  If the upper limit of 4.0 of conditional expression (11) is exceeded, the power of the positive lens group becomes small, which is disadvantageous for sufficient correction of off-axis aberrations.

  If the lower limit of 1.5 to conditional expression (11) is exceeded, the power of the positive lens group becomes too strong, and aberration correction with this lens group becomes difficult.

  According to a tenth imaging device of the present invention, in the second to ninth imaging devices, an aperture stop is disposed between the second lens group and the third lens group.

  Hereinafter, the reason why the above-described configuration is adopted in the tenth imaging apparatus and the operation and effect thereof will be described.

  This configuration is advantageous for making the exit pupil close to infinity while balancing the size of the entire lens system.

  In particular, the following configuration is desirable.

  An eleventh imaging apparatus of the present invention is characterized in that, in the tenth imaging apparatus, the position of the brightness stop at the wide angle end satisfies the following condition.

0.5 <D _2GS / D _S3G <1.0 (12)
However, D _2GS is the axial distance from the second lens group to the aperture stop at the wide-angle end,
_DS3G is the axial distance from the aperture stop to the third lens group at the wide-angle end,
It is.

  Hereinafter, the reason why the above-described configuration is adopted in the eleventh imaging apparatus and the operation and effect thereof will be described.

  It is more preferable that the stop position at the wide-angle end be arranged at a position close to the first lens group and the second lens group because the height of the light beam transmitted through the first lens group can be lowered. When the lower limit of 0.5 of conditional expression (12) is exceeded and the aperture is moved away from the third lens group, the outer diameter of the third lens group tends to increase, and aberration correction in the third lens group becomes difficult.

  When the upper limit of 1.0 of the conditional expression (12) is exceeded and the aperture is separated from the second lens group, it is difficult to make the first lens group small.

  According to a twelfth imaging device of the present invention, in the fifth, seventh, and ninth imaging devices, an aperture stop is disposed between the second lens group and the third lens group, and the third lens group. The surface closest to the image side is concave, and satisfies the following conditions.

0.5 <D _2GS / D _S3G <1.0 (12)
0.5 <R _3GE /ih<2.5 (13)
However, D _2GS is the axial distance from the second lens group to the aperture stop at the wide-angle end,
_DS3G is the axial distance from the aperture stop to the third lens group at the wide-angle end,
R _3GE is the paraxial radius of curvature of the concave surface closest to the image side of the third lens unit,
It is.

  The reason why the above configuration is adopted in the twelfth imaging apparatus and the operation and effect thereof will be described below.

  If the absolute value of the radius of curvature of the object side surface of the first lens group is made small, or if the power of the front group of negative refractive power is made negative, it is advantageous for reducing the thickness of the first lens group. On the other hand, off-axis aberrations on the wide angle side tend to occur.

  Conditional expression (12) specifies the position of the stop as described above, but is advantageous for reducing the incident height of the light beam to the first lens group. On the other hand, the incident height to the concave surface of the exit surface of the third lens unit having positive refractive power is also increased, and an effect of correcting off-axis aberrations on this concave surface can be provided.

  Conditional expression (13) defines the paraxial radius of curvature of the concave surface. If the lower limit of 0.5 is exceeded, the power of the concave surface becomes too strong, which is disadvantageous for aberration correction of the third lens group itself. Become. When the upper limit of 2.5 is exceeded, the power of the concave surface becomes weak and the function of correcting off-axis aberrations deteriorates.

  According to a thirteenth imaging device of the present invention, in the second to twelfth imaging devices, the fourth lens group satisfies the following conditions.

3.3 <f _4G /ih<6.6 (14)
Where f _4G is the focal length of the fourth lens group,
It is.

  The reason why the above-described configuration is adopted in the thirteenth imaging apparatus and the function and effect thereof will be described below.

  Conditional expression (14) defines an appropriate refractive power of the fourth lens group at the maximum image height. Since the fourth lens group is arranged close to the image plane, if the power exceeds the lower limit of 3.3 of conditional expression (14) and the power is too strong, aberrations are likely to occur and the number of lenses increases and the size tends to increase. On the other hand, if the power exceeds the upper limit of 6.6 and the power is too weak, it is difficult to ensure telecentricity, or the distance between the third lens group and the fourth lens group becomes long, which is disadvantageous for miniaturization.

  Further, in order to obtain an imaging apparatus that achieves downsizing and a high zoom ratio of the zoom lens after bending the optical path while ensuring the angle of view, the following configuration may be employed.

A fourteenth imaging device of the present invention includes a zoom lens, and an imaging element having a light receiving surface that is disposed on the image side and converts an optical image formed by the zoom lens into an electric signal,
The zoom lens includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive refractive power. A fourth lens group having
During zooming from the wide-angle end to the telephoto end, the first lens group is fixed, at least the second lens group and the third lens group move, and the third lens group and the fourth lens group The distance is changed, the second lens group is positioned on the image plane side at the telephoto end rather than the wide-angle end, and the third lens group is positioned on the object side at the telephoto end than the wide-angle end;
The first lens group includes a reflective optical element that bends the optical path by reflection;
The following conditional expression is satisfied.

1.6 <f _w /ih<1.9 (6)
0.85 <| f _2G /ih|<3.1 (8)
1.0 <f _3G /ih<3.7 (15)
0.7 <m _2GZ / m _3GZ <1.2 (3)
Where f _w is the focal length of the entire zoom lens system at the wide-angle end,
f _2G is the focal length of the second lens group,
f _3G is the focal length of the third lens group,
ih is the maximum image height in the effective shooting area of the light-receiving surface,
m _2GZ is the ratio of the telephoto end magnification to the wide-angle end magnification of the second lens group when focusing on an object point at infinity,
m _3GZ is the ratio of the telephoto end magnification to the wide-angle end magnification of the third lens group when focusing on an object point at infinity,
It is.

  Hereinafter, the reason why the above-described configuration is adopted in the fourteenth imaging device and the operation and effect thereof will be described.

  In the zoom lens according to the present invention, a thin zoom lens is configured by four lens groups of positive, negative, positive, and positive in order from the object, and the optical path is bent by reflection in the positive first lens group.

  At this time, if the zooming action of the second lens group is large, the amount of movement of the second lens group becomes large, and the off-axis ray incident height to the first lens group at the wide-angle end tends to be high. It is difficult to reduce the lens diameter.

  Therefore, in the present invention, the third lens group also has a zooming action, and the amount of movement of the second lens group is reduced by reducing the burden of the zooming action of the second lens group.

  In addition, by appropriately setting the focal lengths of the second lens group and the third lens group, the optical system after the optical path is bent is reduced in size.

  Conditional expression (6) defines the focal length at the wide-angle end by the maximum image height of the effective imaging region. If the lower limit of 1.6 of conditional expression (6) is exceeded, the angle of view at the wide-angle end becomes small, which is contrary to the purpose of wide angle of view. On the other hand, if the upper limit of 1.9 is exceeded, the angle of view becomes too wide, and the zoom lens becomes thick in order to secure a bent optical path.

  Conditional expression (8) defines the power of the second lens group at the maximum image height. If the power of the second lens unit is increased beyond the lower limit of 0.85 in conditional expression (8), astigmatism and distortion will occur greatly, making it difficult to correct the aberration of the entire system. If the upper limit of 3.1 to conditional expression (8) is exceeded, the amount of movement of the second lens group becomes too large, and it becomes difficult to shorten the overall length.

  Conditional expression (15) defines the power of the third lens group at the maximum image height. If the power of the third lens unit is increased beyond the lower limit of 1.0 in the conditional expression (15), astigmatism and distortion will occur greatly, making it difficult to correct the aberration of the entire system. If the upper limit of 3.7 to conditional expression (15) is exceeded, the amount of movement of the third lens group becomes too large, making it difficult to shorten the overall length.

  Conditional expression (3) appropriately defines the variable magnification sharing between the second lens group and the third lens group. If the lower limit of 0.7 of conditional expression (3) is exceeded, the variable magnification share of the second lens group becomes large and the amount of movement of the second lens group becomes large, so the diameter of the first lens group tends to increase. Alternatively, the refractive power of the second lens group becomes large, and it becomes difficult to suppress aberration fluctuation due to movement.

  If the lower limit of 0.7 of conditional expression (3) is exceeded, the variable magnification share of the third lens group becomes large, the amount of movement of the third lens group tends to increase, and the total length tends to increase. Alternatively, the refractive power of the third lens group becomes large, and it is difficult to suppress aberration fluctuation due to movement.

  In order to reduce the size and correct aberrations satisfactorily while giving a variable magnification burden to the second lens group and the third lens group, the following configuration is preferable.

  According to a fifteenth imaging device of the present invention, in the fourteenth imaging device, the second lens group is a single lens having a negative refractive power in which the image side surface is smaller in paraxial curvature radius absolute value than the object side surface in order from the object side. And a cemented lens of a biconcave negative lens and a biconvex positive lens, and the third lens group is composed of a plurality of positive lenses and one or two negative lenses in order from the object side. A lens and a negative lens are cemented together, and the fourth lens group is composed of two or less lenses.

  The reason why the above-described configuration is adopted in the fifteenth imaging apparatus and the operation and effect thereof will be described below.

  The second lens group is composed of two negative lenses and a biconvex positive lens in order from the object side, so that the principal point is closer to the object, which is advantageous for reducing the diameter of the first lens group and the second lens group. It becomes. Further, the main negative power of the second lens group is shared by the two negative lenses, so that aberration can be corrected satisfactorily. Further, by having a cemented lens of a negative lens and a biconvex positive lens, it becomes easy to correct chromatic aberration of the second lens group itself.

  The main positive power of the third lens group is shared by a plurality of positive lenses. Then, in order from the object side, a plurality of positive lenses and one or two negative lenses are configured, and by making the principal point closer to the object, it is possible to have a function of increasing the focal length at the telephoto end. Become.

  Then, by providing a cemented lens of a positive lens and a negative lens in the third lens group, it becomes easy to correct chromatic aberration.

  Since the fourth lens group is located closest to the image plane in the zoom lens, reducing the number of lenses is advantageous for downsizing. Therefore, it is preferable in terms of miniaturization to have a configuration with two or less lenses.

  It is more preferable that a plurality of the above-described structures are arbitrarily satisfied at the same time because the respective effects can be obtained simultaneously.

  For example, you may comprise as follows.

  The sixteenth imaging device of the present invention is characterized in that, in the fourteenth and fifteenth imaging devices, the following conditions are satisfied.

0.85 <f _1G /ih<6.0 (7)
Where f _1G is the focal length of the first lens group,
It is.

  The seventeenth imaging device of the present invention is characterized in that, in the fourteenth to sixteenth imaging devices, the following conditions are satisfied.

−0.118 <ih / R ₁ <0.118 (9)
Where R ₁ is the paraxial radius of curvature of the object side surface of the lens closest to the object side in the first lens group,
It is.

  According to an eighteenth imaging device of the present invention, in the fourteenth to seventeenth imaging devices, the first lens group includes, in order from the object side, a negative meniscus lens having a convex surface directed toward the object side, and reflective optics for bending the optical path. It is composed of an element and a positive lens group.

  According to a nineteenth imaging device of the present invention, in the fourteenth to eighteenth imaging devices, the first lens group includes, in order from the object side, a negative lens group, a reflective optical element for bending an optical path, and a positive lens group. The negative lens unit is configured to satisfy the following conditional expression.

0.85 <| f _L1 /ih|<4.25 (10)
Where f _L1 is the focal length of the negative lens group of the first lens group,
It is.

  In the nineteenth imaging device, as described above, it is advantageous in terms of downsizing if either one of the positive lens group and the negative lens group is a single lens.

  According to a twentieth imaging apparatus of the present invention, in the nineteenth imaging apparatus, the positive lens group of the first lens group satisfies the following condition.

1.5 <f _L2 /ih<4.0 (11)
Where f _L2 is the focal length of the positive lens group of the first lens group,
It is.

  According to a twenty-first imaging apparatus of the present invention, in the fourteenth to twentieth imaging apparatuses, an aperture stop is disposed between the second lens group and the third lens group.

  According to a twenty-second imaging apparatus of the present invention, in the twenty-first imaging apparatus, the position of the brightness stop at the wide-angle end satisfies the following condition.

0.5 <D _2GS / D _S3G <1.0 (12)
However, D _2GS is the axial distance from the second lens group to the aperture stop at the wide-angle end,
_DS3G is the axial distance from the aperture stop to the third lens group at the wide-angle end,
It is.

  According to a twenty-third imaging device of the present invention, in the seventeenth, nineteenth, and twentieth imaging devices, an aperture stop is disposed between the second lens group and the third lens group, and the third lens group. The surface closest to the image side is concave, and satisfies the following conditions.

0.5 <D _2GS / D _S3G <1.0 (12)
0.5 <R _3GE /ih<2.5 (13)
However, D _2GS is the axial distance from the second lens group to the aperture stop at the wide-angle end,
_DS3G is the axial distance from the aperture stop to the third lens group at the wide-angle end,
R _3GE is the paraxial radius of curvature of the concave surface closest to the image side of the third lens unit,
It is.

  According to a twenty-fourth imaging device of the present invention, in the fourteenth to twenty-third imaging devices, the fourth lens group satisfies the following conditions.

3.3 <f _4G /ih<6.6 (14)
Where f _4G is the focal length of the fourth lens group,
It is.

  In the above conditional expressions (1) to (15), it may be further limited as follows.

For conditional expression (1),
More preferably, the lower limit is 1.0, and more preferably 1.5.
It is more preferable that the upper limit value is 3.0, further 2.5.

For conditional expression (2),
It is more preferable that the lower limit value is 0.8, further 1.3.
It is more preferable that the upper limit value is 1.6, further 1.5.

Conditional expression (3)
The lower limit is more preferably 0.75, and even more preferably 0.77.
It is more preferable that the upper limit value is 1.1, further 1.05.

For conditional expression (4),
More preferably, the lower limit is -0.1, more preferably -0.05.
The upper limit is more preferably 0.15, and further preferably 0.1.

For conditional expression (5),
More preferably, the lower limit is 1.0, and more preferably 1.5.
It is more preferable that the upper limit value is 2.2, further 2.0.

For conditional expression (6),
It is more preferable that the lower limit value is 1.63, further 1.66.
It is more preferable that the upper limit value is 1.8, further 1.75.

For conditional expression (7),
It is more preferable that the lower limit value is 1.7, further 2.55.
It is more preferable that the upper limit value is 5.1, further 4.25.

Conditional expression (8)
More preferably, the lower limit is 1.36, more preferably 2.21.
It is more preferable that the upper limit value is 2.72, further 2.55.

Conditional expression (9)
More preferably, the lower limit is -0.059, more preferably -0.029.
More preferably, the upper limit value is 0.088, more preferably 0.059.

For conditional expression (10),
It is more preferable that the lower limit value is 1.7, further 2.55.
It is more preferable that the upper limit value is 3.74, further 3.4.

For conditional expression (11),
More preferably, the lower limit is 1.8, and more preferably 2.2.
More preferably, the upper limit value is 3.5, more preferably 3.0.

Conditional expression (12)
It is more preferable that the lower limit value is 0.6, further 0.65.
More preferably, the upper limit value is 0.95, more preferably 0.9.

For conditional expression (13),
It is more preferable that the lower limit value is 0.7, further 0.9.
More preferably, the upper limit value is 2.0, more preferably 1.5.

For conditional expression (14),
More preferably, the lower limit is 3.5, and even 3.7.
It is more preferable that the upper limit value is 5.5, further 5.3.

For conditional expression (15),
More preferably, the lower limit is 2.0, and more preferably 2.5.
More preferably, the upper limit is 3.4, and even 3.1.

  In addition, since each structure and conditional expression mentioned above have each effect by combining suitably, it is more effective.

  According to the present invention, it is possible to obtain an optical path folding zoom lens that can be made thinner in the thickness direction and sufficiently secure an angle of view, and an imaging device using the zoom lens. Further, by reducing the size of the configuration after bending while maintaining a wide angle of view, an optical path folding zoom lens that can shorten the height direction or the horizontal direction of the imaging device and an imaging device using the same can be obtained.

  Examples 1 to 4 of the optical path folding zoom lens according to the present invention will be described below. Lens cross-sectional views at 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 4 are shown in FIGS. In each figure, the first lens group is G1, the second lens group is G2, the diaphragm is S, the third lens group is G3, the fourth lens group is G4, the optical low-pass filter having an IR cut coat surface is F, and the electron A cover glass such as a CCD or CMOS which is an image pickup element is indicated by C, and an image surface (light receiving surface) of CCD, CMOS or the like is indicated by I. Further, a parallel plate in which the optical path bending prism in G1 in the first lens group is developed is indicated by P. As for the IR cut coat, the optical low-pass filter F may be directly coated as shown in the figure, or an IR cut absorption filter may be provided separately, or the IR plane may be provided on the incident surface of the transparent flat plate. You may use what was cut-coated.

  The optical path bending prism P is configured as a reflecting prism that bends the optical path by 90 °, for example, as shown in FIG. 5 which is a cross-sectional view of the zoom lens according to the first embodiment when the zoom lens is in focus at the wide-angle end infinity. In addition, the reflective position in Examples 1-4 is an intermediate | middle of the entrance plane of the parallel plate P, and an output surface. The reflection direction of the optical path bending prism P is the vertical direction of the imaging device, and the short side direction of the light receiving surface. The reflection direction may be the long side direction of the light receiving surface.

  As shown in FIG. 1, the zoom lens of Example 1 includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, an aperture stop S, and a positive The third lens group G3 having a refractive power of 4 and a fourth lens group G4 having a positive refractive power, and the first lens group G1 is fixed when zooming from the wide angle end to the telephoto end. The second lens group G2 moves to the image plane side, the aperture stop S is substantially fixed, the third lens group G3 moves to the object side, and the fourth lens group G4 widens the distance from the third lens group G3. However, it moves along a concave locus toward the object side, and is located closer to the image plane at the telephoto end than at the wide-angle end.

  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, an optical path bending prism P, and a biconvex positive lens. The second lens group G2 has a convex surface on the object side. A negative meniscus lens facing the lens, and a cemented lens of a biconcave negative lens and a biconvex positive lens. The third lens group G3 includes a biconvex positive lens, a positive meniscus lens having a convex surface facing the object side, and an object side. The fourth lens group G4 includes a negative meniscus lens having a convex surface directed toward the object side and a biconvex positive lens.

  The aspherical surfaces are used on both surfaces of the biconvex positive lens of the first lens group G1, both surfaces of the biconvex positive lens of the third lens group G3, and both surfaces of the biconvex positive lens of the fourth lens group G4.

  As shown in FIG. 2, the zoom lens according to the second embodiment includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, an aperture stop S, and a positive lens. The third lens group G3 having a refractive power of 4 and a fourth lens group G4 having a positive refractive power, and the first lens group G1 is fixed when zooming from the wide angle end to the telephoto end. The second lens group G2 moves to the image plane side, the aperture stop S is fixed, the third lens group G3 moves to the object side, and the fourth lens group G4 increases the distance from the third lens group G3. Move to the image plane 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, an optical path bending prism P, and a biconvex positive lens, and the second lens group G2 includes a biconcave negative lens. The third lens group G3 is composed of a biconvex positive lens, and a cemented lens of a biconvex positive lens and a biconcave negative lens. The fourth lens group is composed of a biconcave negative lens and a biconvex positive lens. G4 includes one biconvex positive lens.

  The aspherical surfaces are used on both surfaces of the biconvex positive lens of the first lens group G1, both surfaces of the biconvex positive lens of the third lens group G3, and both surfaces of the biconvex positive lens of the fourth lens group G4.

  As shown in FIG. 3, the zoom lens according to the third exemplary embodiment includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, an aperture stop S, and a positive lens. The third lens group G3 having a refractive power of 4 and a fourth lens group G4 having a positive refractive power, and the first lens group G1 is fixed when zooming from the wide angle end to the telephoto end. The second lens group G2 moves to the image plane side, the aperture stop S is fixed, the third lens group G3 moves to the object side, and the fourth lens group G4 increases the distance from the third lens group G3. Move to the image plane side.

  In order from the object side, the first lens group G1 includes a biconcave negative lens, an optical path bending prism P, and a biconvex positive lens. The second lens group G2 includes a negative meniscus lens having a convex surface facing the object side. The third lens group G3 is composed of two biconvex positive lenses and a cemented lens of a biconvex positive lens and a biconcave negative lens. The lens group G4 includes one biconvex positive lens.

  Aspherical surfaces are used on both surfaces of the biconvex positive lens of the first lens group G1, both surfaces of the object side biconvex positive lens of the third lens group G3, and both surfaces of the biconvex positive lens of the fourth lens group G4. ing.

  As shown in FIG. 4, the zoom lens of Example 4 includes, in order from the object side, a first lens unit G1 having a positive refractive power, a second lens unit G2 having a negative refractive power, an aperture stop S, and a positive lens unit. The third lens group G3 having a refractive power of 4 and a fourth lens group G4 having a positive refractive power, and the first lens group G1 is fixed when zooming from the wide angle end to the telephoto end. The second lens group G2 moves to the image plane side, the aperture stop S is fixed, the third lens group G3 moves to the object side, and the fourth lens group G4 increases the distance from the third lens group G3. It moves along a concave locus toward the object side, and is located closer to the image plane at the telephoto end than at the wide-angle end.

  In order from the object side, the first lens group G1 includes a negative meniscus lens having a convex surface facing the object side, an optical path bending prism P, and a biconvex positive lens, and the second lens group G2 includes a biconcave negative lens. The third lens group G3 includes a biconvex positive lens, a cemented lens of a biconvex positive lens and a biconcave negative lens, and a convex surface facing the object side. The fourth lens group G4 is composed of one biconvex positive lens.

  The aspherical surfaces are used on both surfaces of the biconvex positive lens of the first lens group G1, both surfaces of the biconvex positive lens of the third lens group G3, and both surfaces of the biconvex positive lens of the fourth lens group G4.

In the following, numerical data of the above embodiment is shown. Symbols are the above, f is the total focal length, _FNO is the F number, ω is the half angle of view, WE is the wide angle end, ST is the intermediate state, TE is telephoto end, r _1, r ₂ ... curvature radius of each lens surface, d _1, d ₂ ... the spacing between the lens surfaces, n _d1, n _d2 ... d-line refractive index of each lens, [nu _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 ₄ y ⁴ + A ₆ y ⁶ + A ₈ y ⁸ + A ₁₀ y ¹⁰
Here, r is a paraxial radius of curvature, K is a conical coefficient, and A ₄ , A ₆ , A ₈ , and A ₁₀ are fourth-order, sixth-order, eighth-order, and tenth-order aspherical coefficients, respectively.

Example 1
r ₁ = 295.026 d ₁ = 0.80 n _d1 = 1.92286 ν _d1 = 20.88
r ₂ = 11.061 d ₂ = 1.40
r ₃ = ∞ d ₃ = 7.40 n _d2 = 1.83400 ν _d2 = 37.16
r ₄ = ∞ d ₄ = 0.15
r ₅ = 16.187 (aspherical surface) d ₅ = 2.40 n _d3 = 1.77377 ν _d3 = 47.17
r ₆ = -15.754 (aspherical surface) d ₆ = (variable)
r ₇ = 144.141 d ₇ = 0.70 n _d4 = 1.88300 ν _d4 = 40.76
r ₈ = 14.573 d ₈ = 1.15
r ₉ = −10.681 d ₉ = 0.70 n _d5 = 1.88300 ν _d5 = 40.76
r ₁₀ = 15.091 d ₁₀ = 1.90 n _d6 = 1.92286 ν _d6 = 20.88
r ₁₁ = -29.145 d ₁₁ = (variable)
r ₁₂ = ∞ (aperture) d ₁₂ = (variable)
r ₁₃ = 8.042 (aspherical surface) d ₁₃ = 4.01 n _d7 = 1.58313 ν _d7 = 59.46
r ₁₄ = -22.780 (aspherical surface) d ₁₄ = 0.20
r ₁₅ = 6.659 d ₁₅ = 3.68 n _d8 = 1.49700 ν _d8 = 81.54
r ₁₆ = 74.227 d ₁₆ = 0.80 n _d9 = 1.84666 ν _d9 = 23.78
r ₁₇ = 4.449 d ₁₇ = (variable)
r ₁₈ = 27.385 d ₁₈ = 0.80 n _d10 = 1.84666 ν _d10 = 23.78
r ₁₉ = 12.421 d ₁₉ = 0.20
r ₂₀ = 10.830 (aspherical surface) d ₂₀ = 2.50 n _d11 = 1.48749 ν _d11 = 70.23
r ₂₁ = -12.101 (aspherical surface) d ₂₁ = (variable)
r ₂₂ = ∞ d ₂₂ = 0.88 n _d12 = 1.54771 ν _d12 = 62.84
r ₂₃ = ∞ d ₂₃ = 0.89
r ₂₄ = ∞ d ₂₄ = 0.50 n _d13 = 1.51633 ν _d13 = 64.14
r ₂₅ = ∞ d ₂₅ = 0.60
r ₂₆ = ∞ (image plane)
Aspheric coefficient Fifth surface K = 0.000
A ₄ = -8.31125 × 10 ^-5
A ₆ = -1.49859 × 10 ^-7
A ₈ = 1.31609 × 10 ^-7
A ₁₀ = -6.10430 × 10 ^-9
6th surface K = 0.000
A ₄ = -1.07939 × 10 ^-5
A ₆ = 2.74948 × 10 ^-6
A ₈ = -1.35732 × 10 ^-8
A ₁₀ = -3.44642 × 10 ^-9
Surface 13 K = 0.000
A ₄ = 7.10303 × 10 ^-6
A ₆ = 5.21257 × 10 ^-6
A ₈ = 8.01135 × 10 ^-7
A ₁₀ = -4.07370 × 10 ^-8
14th face K = 0.000
A ₄ = 4.85355 × 10 ^-4
A ₆ = 1.71401 × 10 ^-5
A ₈ = 2.37660 × 10 ^-8
A ₁₀ = 0
20th face K = 0.000
A ₄ = -3.10795 × 10 ^-4
A ₆ = 2.67988 × 10 ^-5
A ₈ = 2.65967 × 10 ^-8
A ₁₀ = -1.19394 × 10 ^-7
Side 21 K = 0.000
A ₄ = -4.20742 × 10 ^-4
A ₆ = 3.97404 × 10 ^-5
A ₈ = 1.06118 × 10 ^-9
A ₁₀ = -1.23676 × 10 ^-7
Zoom data (∞)
WE ST TE
f (mm) 6.898 11.557 19.670
F _NO 3.57 4.27 5.10
ω (°) 30.3 17.8 10.7
d ₆ 0.50 3.71 5.73
d ₁₁ 6.24 2.99 1.00
d ₁₂ 7.21 5.05 1.20
d ₁₇ 2.61 5.29 9.07
d ₂₁ 3.12 2.66 2.67.

Example 2
r ₁ = 92.883 d ₁ = 0.80 n _d1 = 1.92286 ν _d1 = 20.88
r ₂ = 9.863 d ₂ = 1.75
r ₃ = ∞ d ₃ = 7.40 n _d2 = 1.80100 ν _d2 = 34.90
r ₄ = ∞ d ₄ = 0.16
r ₅ = 14.947 (aspherical surface) d ₅ = 2.67 n _d3 = 1.77933 ν _d3 = 45.68
r ₆ = -14.846 (aspherical surface) d ₆ = (variable)
r ₇ = -39.260 d ₇ = 0.80 n _d4 = 1.88300 ν _d4 = 40.76
r ₈ = 17.909 d ₈ = 0.73
r ₉ = -18.959 d ₉ = 0.70 n _d5 = 1.87765 ν _d5 = 40.94
r ₁₀ = 11.087 d ₁₀ = 1.70 n _d6 = 1.92286 ν _d6 = 20.88
r ₁₁ = -122.735 d ₁₁ = (variable)
r ₁₂ = ∞ (aperture) d ₁₂ = (variable)
r ₁₃ = 7.900 (aspherical surface) d ₁₃ = 3.68 n _d7 = 1.58900 ν _d7 = 61.20
r ₁₄ = -18.676 (aspherical surface) d ₁₄ = 0.15
r ₁₅ = 8.530 d ₁₅ = 4.35 n _d8 = 1.49700 ν _d8 = 81.60
r ₁₆ = -27.187 d ₁₆ = 0.73 n _d9 = 1.84666 ν _d9 = 23.78
r ₁₇ = 4.740 d ₁₇ = (variable)
r ₁₈ = 16.474 (aspherical surface) d ₁₈ = 2.30 n _d10 = 1.49700 ν _d10 = 81.54
r ₁₉ = -13.740 (aspherical surface) d ₁₉ = (variable)
r ₂₀ = ∞ d ₂₀ = 0.88 n _d11 = 1.54771 ν _d11 = 62.84
r ₂₁ = ∞ d ₂₁ = 0.89
r ₂₂ = ∞ d ₂₂ = 0.50 n _d12 = 1.51633 ν _d12 = 64.14
r ₂₃ = ∞ d ₂₃ = 0.60
r ₂₄ = ∞ (image plane)
Aspheric coefficient Fifth surface K = 0.000
A ₄ = -9.52388 × 10 ^-5
A ₆ = 5.55144 × 10 ^-6
A ₈ = -3.08535 × 10 ^-7
A ₁₀ = 5.48257 × 10 ^-9
6th surface K = 0.000
A ₄ = 3.22716 × 10 ^-5
A ₆ = 4.78631 × 10 ^-6
A ₈ = -2.53119 × 10 ^-7
A ₁₀ = 4.52425 × 10 ^-9
Surface 13 K = 0.000
A ₄ = -4.91485 × 10 ^-5
A ₆ = -7.61719 × 10 ^-6
A ₈ = 1.21791 × 10 ^-6
A ₁₀ = -4.15023 × 10 ^-8
14th face K = 0.000
A ₄ = 4.05960 × 10 ^-4
A ₆ = 5.85350 × 10 ^-7
A ₈ = 8.56264 × 10 ^-7
A ₁₀ = -3.18996 × 10 ^-8
18th face K = 0.000
A ₄ = 6.29854 × 10 ^-4
A ₆ = -3.03281 × 10 ^-5
A ₈ = 4.96221 × 10 ^-7
A ₁₀ = -5.27261 × 10 ^-8
19th face K = 0.000
A ₄ = 5.31709 × 10 ^-4
A ₆ = -1.74744 × 10 ^-6
A ₈ = -1.63257 × 10 ^-6
A ₁₀ = 0
Zoom data (∞)
WE ST TE
f (mm) 6.810 11.526 19.654
F _NO 3.50 3.95 5.00
ω (°) 30.5 18.0 10.8
d ₆ 0.60 3.35 5.19
d ₁₁ 5.62 2.87 1.03
d ₁₂ 7.50 4.85 1.03
d ₁₇ 2.50 5.24 9.60
d ₁₉ 3.60 3.51 2.97.

Example 3
r ₁ = -205.452 d ₁ = 0.80 n _d1 = 1.84666 ν _d1 = 23.78
r ₂ = 10.665 d ₂ = 1.52
r ₃ = ∞ d ₃ = 7.40 n _d2 = 1.80610 ν _d2 = 40.92
r ₄ = ∞ d ₄ = 0.20
r ₅ = 15.074 (aspherical surface) d ₅ = 2.49 n _d3 = 1.76802 ν _d3 = 49.24
r ₆ = -14.697 (aspherical surface) d ₆ = (variable)
r ₇ = 153.510 d ₇ = 0.70 n _d4 = 1.88300 ν _d4 = 40.76
r ₈ = 13.647 d ₈ = 1.15
r ₉ = −11.094 d ₉ = 0.70 n _d5 = 1.88300 ν _d5 = 40.76
r ₁₀ = 16.398 d ₁₀ = 1.80 n _d6 = 1.92286 ν _d6 = 20.88
r ₁₁ = -32.399 d ₁₁ = (variable)
r ₁₂ = ∞ (aperture) d ₁₂ = (variable)
r ₁₃ = 9.297 (aspherical surface) d ₁₃ = 2.43 n _d7 = 1.58913 ν _d7 = 61.25
r ₁₄ = -24.419 (aspherical surface) d ₁₄ = 0.20
r ₁₅ = 9.855 d ₁₅ = 2.60 n _d8 = 1.49700 ν _d8 = 81.54
r ₁₆ = -150.333 d ₁₆ = 0.80
r ₁₇ = 19.700 d ₁₇ = 1.77 n _d9 = 1.60172 ν _d9 = 60.60
r ₁₈ = -32.398 d ₁₈ = 0.80 n _d10 = 1.84666 ν _d10 = 23.78
r ₁₉ = 4.457 d ₁₉ = (variable)
r ₂₀ = 15.828 (aspherical surface) d ₂₀ = 2.49 n _d11 = 1.52500 ν _d11 = 55.80
r ₂₁ = -15.755 (aspherical surface) d ₂₁ = (variable)
r ₂₂ = ∞ d ₂₂ = 0.88 n _d12 = 1.54771 ν _d12 = 62.84
r ₂₃ = ∞ d ₂₃ = 0.89
r ₂₄ = ∞ d ₂₄ = 0.50 n _d13 = 1.51633 ν _d13 = 64.14
r ₂₅ = ∞ d ₂₅ = 0.60
r ₂₆ = ∞ (image plane)
Aspheric coefficient Fifth surface K = 0.000
A ₄ = -1.26135 × 10 ^-4
A ₆ = 2.52905 × 10 ^-6
A ₈ = -4.00946 × 10 ^-8
A ₁₀ = -1.87589 × 10 ^-9
6th surface K = 0.000
A ₄ = -4.93971 × 10 ^-6
A ₆ = 3.84372 × 10 ^-6
A ₈ = -1.00573 × 10 ^-7
A ₁₀ = -6.58744 × 10 ^-10
Surface 13 K = 0.000
A ₄ = -2.02391 × 10 ^-4
A ₆ = -4.63863 × 10 ^-7
A ₈ = -2.67686 × 10 ^-8
A ₁₀ = -1.07522 × 10 ^-8
14th face K = 0.000
A ₄ = 1.06475 × 10 ^-4
A ₆ = 2.61409 × 10 ^-6
A ₈ = -3.62177 × 10 ^-7
A ₁₀ = 0
20th face K = 0.000
A ₄ = 4.10682 × 10 ^-4
A ₆ = -2.65177 × 10 ^-5
A ₈ = 1.17779 × 10 ^-6
A ₁₀ = -3.98281 × 10 ^-8
Side 21 K = 0.000
A ₄ = 3.52819 × 10 ^-4
A ₆ = -1.96304 × 10 ^-5
A ₈ = 7.23922 × 10 ^-7
A ₁₀ = -3.11244 × 10 ^-8
Zoom data (∞)
WE ST TE
f (mm) 6.813 11.525 19.653
F _NO 3.57 4.00 5.10
ω (°) 30.6 17.9 10.9
d ₆ 0.60 3.50 5.27
d ₁₁ 5.56 2.66 0.90
d ₁₂ 7.85 5.28 1.10
d ₁₉ 3.00 5.69 9.96
d ₂₁ 3.21 3.09 3.00.

Example 4
r ₁ = 131.601 d ₁ = 0.80 n _d1 = 1.92286 ν _d1 = 20.88
r ₂ = 10.274 d ₂ = 1.71
r ₃ = ∞ d ₃ = 7.40 n _d2 = 1.80100 ν _d2 = 34.90
r ₄ = ∞ d ₄ = 0.16
r ₅ = 16.442 (aspherical surface) d ₅ = 2.74 n _d3 = 1.78680 ν _d3 = 44.13
r ₆ = -15.303 (aspherical surface) d ₆ = (variable)
r ₇ = -32.168 d ₇ = 0.80 n _d4 = 1.88300 ν _d4 = 40.76
r ₈ = 20.848 d ₈ = 0.70
r ₉ = -22.286 d ₉ = 0.70 n _d5 = 1.88300 ν _d5 = 40.76
r ₁₀ = 11.716 d ₁₀ = 1.72 n _d6 = 1.92286 ν _d6 = 20.88
r ₁₁ = -119.952 d ₁₁ = (variable)
r ₁₂ = ∞ (aperture) d ₁₂ = (variable)
r ₁₃ = 8.583 (aspherical surface) d ₁₃ = 3.84 n _d7 = 1.59635 ν _d7 = 59.32
r ₁₄ = -14.212 (aspherical surface) d ₁₄ = 0.15
r ₁₅ = 8.450 d ₁₅ = 3.92 n _d8 = 1.49700 ν _d8 = 81.54
r ₁₆ = -33.510 d ₁₆ = 0.70 n _d9 = 1.84666 ν _d9 = 23.78
r ₁₇ = 5.517 d ₁₇ = 0.30
r ₁₈ = 6.321 d ₁₈ = 0.70 n _d10 = 1.84666 ν _d10 = 23.78
r ₁₉ = 4.809 d ₁₉ = (variable)
r ₂₀ = 17.254 (aspherical surface) d ₂₀ = 2.41 n _d11 = 1.49700 ν _d11 = 81.54
r ₂₁ = -12.397 (aspherical surface) d ₂₁ = (variable)
r ₂₂ = ∞ d ₂₂ = 0.88 n _d12 = 1.54771 ν _d12 = 62.84
r ₂₃ = ∞ d ₂₃ = 0.89
r ₂₄ = ∞ d ₂₄ = 0.50 n _d13 = 1.51633 ν _d13 = 64.14
r ₂₅ = ∞ d ₂₅ = 0.60
r ₂₆ = ∞ (image plane)
Aspheric coefficient Fifth surface K = 0.000
A ₄ = -8.88876 × 10 ^-5
A ₆ = -2.05062 × 10 ^-8
A ₈ = -4.57479 × 10 ^-8
A ₁₀ = -3.03644 × 10 ^-10
6th surface K = 0.000
A ₄ = 2.05704 × 10 ^-6
A ₆ = 7.72185 × 10 ^-9
A ₈ = -1.95829 × 10 ^-8
A ₁₀ = -8.08470 × 10 ^-10
Surface 13 K = 0.000
A ₄ = -2.57739 × 10 ^-4
A ₆ = -3.58372 × 10 ^-6
A ₈ = 2.27081 × 10 ^-7
A ₁₀ = -1.65528 × 10 ^-8
14th face K = 0.000
A ₄ = 1.53919 × 10 ^-4
A ₆ = 3.18624 × 10 ^-6
A ₈ = -2.93908 × 10 ^-7
A ₁₀ = -3.53209 × 10 ^-9
20th face K = 0.000
A ₄ = 5.82785 × 10 ^-4
A ₆ = -2.69526 × 10 ^-5
A ₈ = 3.96147 × 10 ^-7
A ₁₀ = -5.07160 × 10 ^-8
Side 21 K = 0.000
A ₄ = 4.65781 × 10 ^-4
A ₆ = -1.31534 × 10 ^-6
A ₈ = -1.58552 × 10 ^-6
A ₁₀ = 0
Zoom data (∞)
WE ST TE
f (mm) 6.818 11.526 19.653
F _NO 3.57 4.00 5.10
ω (°) 30.5 18.0 10.9
d ₆ 0.60 3.47 5.48
d ₁₁ 5.66 2.80 0.80
d ₁₂ 7.47 4.74 0.80
d ₁₉ 2.50 5.29 9.19
d ₂₁ 2.75 2.69 2.71.

  Aberration diagrams at the time of focusing on an object point at infinity in Examples 1 to 4 are shown in FIGS. In these aberration diagrams, (a) shows the wide-angle end, (b) the intermediate state, and (c) spherical aberration SA, astigmatism AS, distortion DT, and lateral chromatic aberration CC at the telephoto end. In the figure, “FIY” indicates the image height.

  Next, the values of the conditional expressions (1) to (15) of the above embodiments and the values of parameters related to the conditional expressions are shown.

Conditional Example Example 1 Example 2 Example 3 Example 4
(1) 2.387 1.991 2.080 2.213
(2) 1.458 1.362 1.394 1.476
(3) 0.997 0.797 0.885 0.974
(4) 0.023 0.073 -0.033 0.052
(5) 1.808 1.764 1.755 1.777
(6) 1.725 1.690 1.691 1.692
(7) 4.116 3.365 3.516 3.743
(8) 2.514 2.301 2.357 2.497
(9) 0.014 0.043 -0.020 0.031
(10) 3.117 2.981 2.966 3.006
(11) 2.667 2.468 2.495 2.599
(12) 0.865 0.749 0.708 0.758
(13) 1.112 1.176 1.106 1.193
(14) 5.222 3.837 3.836 3.702
(15) 2.858 2.927 2.956 2.827
Parameter f _w 6.898 6.810 6.813 6.818
f _1G 16.465 13.560 14.171 15.086
f _2G -10.056 -9.274 -9.500 -10.065
f _3G 11.432 11.796 11.912 11.395
f _4G 20.890 15.465 15.459 14.918
f _L1 -12.469 -12.013 -11.955 -12.114
f _L2 10.668 9.948 10.054 10.472
D _2GS 6.240 5.620 5.560 5.660
D _S3G 7.210 7.500 7.850 7.470
R ₁ 295.026 92.883 -205.452 131.601
R _3GE 4.449 4.740 4.457 4.809
ih 4.000 4.030 4.030 4.030
m _2GZ 1.670 1.839 1.784 1.716
m _3GZ 1.665 1.464 1.579 1.672.

  The optical path folding zoom lens according to the present invention as described above is an imaging apparatus that forms an object image with an imaging optical system including a zoom lens and receives the image on an image sensor such as a CCD or a silver salt film to perform imaging. In particular, it can be used for a digital camera, a video camera, a personal computer which is an example of an information processing device, a telephone, particularly a mobile phone which is convenient to carry. Hereinafter, an embodiment in which the optical path folding zoom lens of the present invention is used in a digital camera will be described.

  10 to 12 are conceptual diagrams of a configuration in which the optical path folding zoom lens according to the present invention is incorporated in a photographing optical system 41 of a digital camera. 10 is a front perspective view showing the appearance of the digital camera 40, FIG. 11 is a rear perspective view thereof, and FIG. 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, and the like. When the shutter 45 disposed in the position is pressed, photographing is performed through the photographing optical system 41, for example, the optical path folding zoom lens of the first embodiment in conjunction therewith. An object image formed by the photographing optical system 41 is formed on the imaging surface of the CCD 49 via an optical low-pass filter F having an IR cut coat surface. 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 object image formed by the finder objective optical system 53 is formed on the field frame 57 of the Porro prism 55 which is an image erecting member. Behind this polyprism 55 is an eyepiece optical system 59 that guides the erect image to the observer eyeball E. Note that cover members 50 are disposed on the incident side of the photographing optical system 41 and the finder objective optical system 53 and on the exit side of the eyepiece optical system 59, respectively.

  The digital camera 40 configured in this manner is a small and thin zoom lens in which the photographing optical system 41 has a wide angle of view, a high zoom ratio, a good aberration, is bright, and a filter can be disposed. , Small size, high performance and low cost.

  In the example of FIG. 12, a parallel plane plate is disposed as the cover member 50, but a lens having power may be used.

FIG. 3 is a lens cross-sectional view at the wide-angle end (a), the intermediate state (b), and the telephoto end (c) when focusing on an object point at infinity according to Example 1 of the optical path folding zoom lens of the present invention. FIG. 3 is a lens cross-sectional view similar to FIG. 1 of the optical path bending type zoom lens of Example 2. FIG. 6 is a lens cross-sectional view similar to FIG. 1 of the optical path bending type zoom lens of Example 3. FIG. 6 is a lens cross-sectional view similar to FIG. FIG. 3 is a cross-sectional view of the optical path folding zoom lens of Example 1 when folded at the time of focusing on an object point at infinity at the wide angle end. 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. It is a front perspective view which shows the external appearance of the digital camera incorporating the optical path bending type zoom lens 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.

Explanation of symbols

G1 ... 1st lens group G2 ... 2nd lens group G3 ... 3rd lens group G4 ... 4th lens group S ... Diaphragm F ... Optical low pass filter C with IR cut coat surface ... Cover glass I of electronic image sensor ... Electron Image plane of image sensor (light receiving surface)
P ... Optical path bending prism (parallel plate)
E ... Observer eye 40 ... Digital camera 41 ... Shooting optical system 42 ... Shooting optical path 43 ... Viewfinder optical system 44 ... Viewfinder optical path 45 ... Shutter 46 ... Flash 47 ... Liquid crystal display monitor 49 ... CCD
DESCRIPTION OF SYMBOLS 50 ... Cover member 51 ... Processing means 52 ... Recording means 53 ... Finder objective optical system 55 ... Porro prism 57 ... Field frame 59 ... Eyepiece optical system

Claims (15)

A zoom lens, and an image sensor having a light receiving surface that is disposed on the image side and converts an optical image formed by the zoom lens into an electrical signal;
The zoom lens includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive refractive power. A fourth lens group having
Upon zooming from the wide-angle end to the telephoto end, the first lens group is fixed with respect to the image plane on the light receiving surface , and at least the second lens group and the third lens group move, and the third lens The distance between the first lens group and the fourth lens group changes, the second lens group is positioned closer to the image plane at the telephoto end than the wide-angle end, and the third lens group is closer to the telephoto end than the wide-angle end. Located on the object side
The first lens group includes , in order from the object side, a negative lens group, a reflective optical element that bends the optical path by reflection , and a positive lens group.
An imaging apparatus provided with an optical path folding zoom lens characterized by satisfying the following conditional expression:
0.5 <f _1G / f _w <3.5 (1)
1.6 <f _w /ih<1.9 (6)
0.85 <f _1G /ih<6.0 (7)
0.85 <| f _L1 /ih|<4.25 (10)
1.5 <f _L2 /ih<4.0 (11)
Where f _1G is the focal length of the first lens group,
f _w is the focal length of the entire zoom lens system at the wide-angle end,
ih is the maximum image height in the effective shooting area of the light-receiving surface,
f _L1 is the focal length of the negative lens unit of the first lens unit,
f _L2 is the focal length of the positive lens group of the first lens group,
It is. The image pickup apparatus having the optical path bending zoom lens according to claim 1, wherein the following conditional expression is satisfied.
0.5 <| f _2G / f _w | <1.8 (2)
Where f _2G is the focal length of the second lens group,
It is. The image pickup apparatus provided with the optical path folding zoom lens according to claim 1, wherein the following conditional expression is satisfied.
0.7 <m _2GZ / m _3GZ <1.2 (3)
However, m _2GZ is the ratio of the telephoto end magnification to the wide angle end magnification of the second lens group when focusing on an object point at infinity,
m _3GZ is the ratio of the telephoto end magnification to the wide-angle end magnification of the third lens group when focusing on an object point at infinity,
It is. The imaging apparatus comprising the optical path folding zoom lens according to any one of claims 1 to 3, wherein the following conditional expression is satisfied.
-0.2 <f _w / R ₁ <0.2 (4)
Where R ₁ is the paraxial radius of curvature of the object side surface of the lens closest to the object side in the first lens group,
It is. The first lens group includes, in order from the object side, a negative meniscus lens having a convex surface directed toward the object side, a reflective optical element for bending an optical path, and a positive lens group. 5. An imaging apparatus comprising the optical path folding zoom lens according to any one of 4 above. The first lens group includes, in order from the object side, a negative lens group, a reflective optical element for bending an optical path, and a positive lens group, and the negative lens group satisfies the following conditional expression: An imaging apparatus comprising the optical path folding zoom lens according to claim 1.
0.5 <| f _L1 / f _w | <2.5 (5)
Where f _L1 is the focal length of the negative lens group of the first lens group,
It is. The imaging apparatus having an optical path folding zoom lens according to any one of claims 1 to 6, wherein focusing on a short-distance object is performed by moving the fourth lens group toward the object side. 8. An image pickup apparatus comprising the optical path folding zoom lens according to claim 1, wherein the following conditional expression is satisfied.
0.85 <| f _2G /ih|<3.1 (8)
Where f _2G is the focal length of the second lens group,
It is. An image pickup apparatus having an optical path bending type zoom lens according to any one of claims 1, characterized by satisfying the following conditional expression 8.
−0.118 <ih / R ₁ <0.118 (9)
Where R ₁ is the paraxial radius of curvature of the object side surface of the lens closest to the object side in the first lens group,
It is. An image pickup apparatus having an optical path bending type zoom lens according to any one of claims 1-9, characterized in that arranged an aperture stop between the second lens group and the third lens group. The image pickup apparatus having an optical path folding zoom lens according to claim 10, wherein the position of the aperture stop at the wide angle end satisfies the following condition.
0.5 <D _2GS / D _S3G <1.0 (12)
However, D _2GS is the axial distance from the second lens group to the aperture stop at the wide-angle end,
_DS3G is the axial distance from the aperture stop to the third lens group at the wide-angle end,
It is. An aperture stop is disposed between the second lens group and the third lens group, and the most image side surface of the third lens group is a concave surface, and the following conditions are satisfied. Item 12. An imaging device comprising the optical path bending zoom lens according to any one of Items 1 to 11 .
0.5 <D _2GS / D _S3G <1.0 (12)
0.5 <R _3GE /ih<2.5 (13)
However, D _2GS is the axial distance from the second lens group to the aperture stop at the wide-angle end,
_DS3G is the axial distance from the aperture stop to the third lens group at the wide-angle end,
R _3GE is the paraxial radius of curvature of the concave surface closest to the image side of the third lens unit,
It is. The image pickup apparatus having an optical path folding zoom lens according to any one of claims 1 to 12 , wherein the fourth lens group satisfies the following condition.
3.3 <f _4G /ih<6.6 (14)
Where f _4G is the focal length of the fourth lens group,
It is. An image pickup apparatus having an optical path bending type zoom lens according to any one of claims 1 to 13, characterized by satisfying the conditional expressions below.
0.85 <| f _2G /ih|<3.1 (8)
1.0 <f _3G /ih<3.7 (15)
0.7 <m _2GZ / m _3GZ <1.2 (3)
Where f _2G is the focal length of the second lens group,
f _3G is the focal length of the third lens group,
m _2GZ is the ratio of the telephoto end magnification to the wide-angle end magnification of the second lens group when focusing on an object point at infinity,
m _3GZ is the ratio of the telephoto end magnification to the wide-angle end magnification of the third lens group when focusing on an object point at infinity,
It is. The second lens group includes, in order from the object side, a single lens having a negative refractive power whose paraxial curvature radius absolute value is smaller on the image side surface than the object side surface, and a cemented lens of a biconcave negative lens and a biconvex positive lens. The third lens group includes, in order from the object side, a plurality of positive lenses and one or two negative lenses, and is formed by bonding adjacent positive lenses and negative lenses, and the fourth lens group. The image pickup apparatus having an optical path folding zoom lens according to claim 14, wherein the zoom lens is configured with two or less lenses.

Images