JP2016054371A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus comprising an imaging optical system where deterioration in resolution power is small even when negative distortion aberration is corrected electronically.SOLUTION: The imaging apparatus comprises: an imaging optical system; an imaging device which photodetects an image formed by the imaging optical system; and an image processor which corrects the distortion of an image obtained by the imaging device. The image processor sets each enlarging amount at each image height of 50%, 70% and 90% with respect to a maximum image height within the effective range of the imaging device so as to meet a predetermined condition expression.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an imaging apparatus such as a digital camera, a digital single-lens reflex camera, and a digital video camera.

  A technique for correcting distortion of a captured image by performing coordinate conversion processing of the captured image using an image processing unit of an imaging apparatus is known (Patent Document 1).

JP 2006-330675 A

  By correcting the negative distortion of the imaging optical system using the image processing unit of the imaging apparatus, it becomes easy to obtain a small imaging optical system with a wide angle of view. However, when correcting the negative distortion, if the curve shape of the distortion from the center of the screen to the periphery of the screen is inappropriate, the image quality is greatly reduced.

  An object of the present invention is to provide an image pickup apparatus having an image pickup optical system in which a decrease in resolution is small even when distortion is corrected.

The imaging apparatus according to the present invention includes an imaging optical system, an imaging element that receives an image formed by the imaging optical system, and an image processing unit that corrects distortion of an image obtained by the imaging element. The maximum image height is 100% of the effective range of the image sensor, and the image height [mm] at i% of the maximum image height before correcting the distortion is y1ai, and the pixel pitch [mm] of the image sensor is the image height y1ai The image height [mm] after adding y2ai, the image height [mm] after correcting the distortion at the image height y1ai is y1bi, the image height [mm] after correcting the distortion at the image height y2ai is y2bi, The extension amount kmi in the meridional direction at an image height that is 10% of the maximum image height.
kmi = (y2bi-y1bi) / (y2ai-y1ai)
When the maximum image height is 50%, 70%, and 90%, the stretch amounts km5, km7, and km9 are respectively
0.05 <km7-km5 <0.12
0.05 <km9-km5 <0.28
1.18 <km7 <1.4
It satisfies the following conditional expression.

  According to the present invention, it is possible to obtain an image pickup apparatus having an image pickup optical system with little reduction in resolving power even if distortion is corrected electronically.

Conceptual diagram of distortion correction in the meridional direction Conceptual diagram of distortion correction in the sagittal direction Conceptual diagram of distortion shape of the present invention Lens cross-sectional view at the wide-angle end of the zoom lens of Example 1 (A), (B) Aberration diagrams at the wide-angle end and the telephoto end of the zoom lens of Numerical Example 1 Lens cross-sectional view at the wide-angle end of the zoom lens of Example 2 (A), (B) Aberration diagrams at the wide-angle end and the telephoto end of the zoom lens of Numerical Example 2 Lens cross-sectional view at the wide-angle end of the zoom lens of Example 3 (A), (B) Aberration diagrams at the wide-angle end and the telephoto end of the zoom lens of Numerical Example 3 Lens cross-sectional view at the wide-angle end of the zoom lens according to Example 4 (A), (B) Aberration diagrams at the wide-angle end and the telephoto end of the zoom lens of Numerical Example 4 Schematic diagram of main parts of an imaging apparatus of the present invention

Examples of the present invention will be described below. The imaging apparatus of the present invention includes an imaging optical system, an imaging element that receives an image formed by the imaging optical system, and an image processing unit that corrects distortion of an image obtained by the imaging element. First, the mechanism by which the resolving power deteriorates when distortion occurs in the optical system will be described. Figures 1 (A) and 1 (B) show conceptual diagrams before and after distortion correction in the meridional direction. The x-axis is taken from the center of the screen to the diagonal image height. The length (image height) of the line segment from the center of the screen in the meridional direction before correction is L1 _m (x), and the length of the line segment of the minute area (pixel pitch) is ΔL1 _m (x).

It is assumed that the negative distortion occurring in FIG. 1 (A) is corrected to 0% in FIG. 1 (B). The length of the line segment after correction of the length L1 _m (x) of the line segment is L2 _m (x), and the line of the micro area after correction of the length ΔL1 _m (x) of the micro area before the correction Let the length of the minute be ΔL2 _m (x). Distortion in the length L1 _m correcting (x) the length L2 _m (x) and length .DELTA.L1 _m (x) is extended in length [Delta] L2 _m (x). Here, the coordinate transformation function V (x) is defined as follows.

  Since the stretching by distortion correction can be calculated by how much the line segment of the minute region is stretched, the stretching function xm (x) in the meridional direction can be defined as follows.

  here,

And Dist represents the amount of distortion expressed in%. y _r represents the actual image height, and y _i represents the ideal image height. This equation can be modified as follows.

Here, in order to improve the prospect, consider the case where the corrected distortion is 0%. Even when the distortion after correction is not 0%, only the correction term is entered, and the trends agree. Since the distortion after correction is 0%, this corresponds to the stretching in which the actual image height y _r before distortion correction becomes the ideal image height y _i after distortion correction.

It becomes. Since we want to know the relationship between stretching and distortion due to distortion correction in the meridional direction, the stretching function x _m (x) is expressed as a function of the distortion amount Dist. Since the corrected distortion is 0%, it can be deformed as follows.

  In other words, how much is stretched in the meridional direction is the amount of distortion Dist and the differential value of the distortion

Depends on. Since the resolution decreases as the amount of stretching increases, the differential value of distortion

The larger the value, the lower the resolution in the meridional direction. Since the difference value in the region ΔL1 _m (x) of about the pixel pitch can be regarded as a differential value, here, the distortion difference value is used.

  FIG. 2 shows a conceptual diagram when correcting distortion in the sagittal direction. Let ΔL1s be the line segment of the small area in the sagittal direction before distortion correction. Let ΔL2s be the line segment of the minute region after distortion correction. By correcting the distortion, the line segment ΔL1s is extended to the line segment ΔL2s. Since what is currently considered is a minute region, the line segment ΔL1s can be regarded as having the same size as the arc of radius L1 and angle θ. Similarly, the line segment ΔL2s can be regarded as having the same size as the arc having the radius L2 and the angle θ. Therefore, it becomes as follows.

Since the extension by distortion correction can be calculated by how much the line segment ΔL1s of the minute region is extended, the extension function x _s (x) in the sagittal direction can be defined as follows.

Considering the case where the distortion after correction is 0% as in the case of the meridional direction, this corresponds to the enlargement in which the image height yr before the distortion correction becomes the image height yi after the distortion correction. As in the case of the meridional direction, we want to know the relationship between stretching by distortion correction and distortion, so x _s (x) is expressed by a function of Dist.

  That is, the extension of how much can be extended in the sagittal direction is determined by the distortion amount Dist. The larger the negative distortion amount Dist, the larger the stretching amount and the lower the resolution in the sagittal direction. Here, the mechanism by which the resolving power at a high image height when the negative distortion is large will be described. If there is a negative distortion, the image at the periphery of the screen is compressed compared to the image at the center of the screen. For example, when the subject is a chart for evaluation of resolution of 100 lp / mm, the image at the center of the screen on the image sensor (sensor) is not compressed by distortion, so the chart is formed at 100 lp / mm.

  In contrast, the image at the periphery of the screen is formed by a spatial compression effect due to distortion, for example, a chart at 140 lp / mm. In general, the higher the spatial frequency is, the lower the resolving power is. Therefore, if there is a negative distortion, the resolving power at the periphery of the screen is lower than that at the center of the screen. For the above reasons, when distortion occurs, the meridional direction is the difference value of the distortion.

As the value increases, the resolution decreases. In the sagittal direction, when the amount of distortion Dist increases, the stretching function x _s (x) increases and the resolution decreases. In general, when distortion is increased, the amount of distortion tends to increase rapidly at the periphery of the screen. Therefore, the difference value of distortion at the periphery of the screen

Increases, and the stretching functions x _m (x) and x _s (x) increase. In particular, x _m (x) increases and the resolution in the meridional direction decreases greatly. Therefore, while producing large distortion (more than -10% at the maximum image height) to reduce the size of the entire optical system, the difference value of distortion

By setting a distortion curve so as to be small even in the peripheral portion, the resolution in the meridional direction is sequentially reduced so that the decrease in the resolution in the meridional direction is suppressed.

  A conceptual diagram of the distortion shape of the present invention is shown in FIG. A curve A in FIG. 3 is a distortion shape of a conventional optical system, and a curve B and a curve C are distortion shapes according to the optical system of the present invention. D is a linear distortion shape. In the conventional optical system, for example, the curve A is set, so that the resolving power at the periphery of the screen is reduced. On the other hand, the closer to the straight line D, the better the resolution at the periphery of the screen. However, since the straight line D causes large distortion from the center of the screen, the spherical aberration increases, and the resolution at the center of the screen decreases.

  Therefore, in the optical system of the present invention, distortions of shapes such as the curve B and the curve C are left in order to balance the resolving power and the spherical aberration. The optical system of the present invention is configured so that the distortion of the shape shown by the curve B or the curve C is generated in order to reduce the decrease in the resolving power when the distortion is corrected while reducing the size of the entire system. Yes.

  The present invention provides an image pickup apparatus that corrects electronic distortion in an image processing unit by actively remaining distortion aberration of an image pickup optical system from a relatively low image height in consideration of a mechanism in which the resolution is lowered. It is aimed. The variable power optical system of Patent Document 1 has a large distortion amount of about -20% at the maximum image height, which is advantageous for miniaturization of the entire system, but the resolution value in the meridional direction decreases because the difference value of distortion is large. There was a tendency to.

  An image pickup optical system used in the image pickup apparatus of the present invention aims at widening the angle of view and reducing the size of the entire system. The distortion curve shape at each image height at this time is set so that the distortion becomes 0% when electronically corrected at a predetermined image height with a predetermined stretch amount. That is, when the distortion of the imaging optical system is positively set, the distortion at each image height is set to 0% when electronically corrected with a predetermined stretch amount. At this time, the electronically corrected distortion is not limited to 0%, but may be a predetermined value (for example, within a range of 0% to 5%).

  The imaging optical system according to the present invention may be a zoom lens in addition to a single focal length optical system. In the case of a zoom lens, each constituent element may be set based on the zoom position at the wide-angle end.

The maximum image height is set to 100% of the effective range of the image sensor. Let y1ai be the image height [mm] at i% of the maximum image height before correcting the distortion. The image height [mm] obtained by adding the pixel pitch [mm] of the image sensor to the image height y1ai is y2ai, and the image height [mm] after correcting the distortion at the image height y1ai is y1bi. The image height [mm] after correcting the distortion at the image height y2ai is defined as y2bi. The extension amount kmi in the meridional direction at an image height that is 10% of the maximum image height.
kmi = (y2bi-y1bi) / (y2ai-y1ai)
And

At this time, the stretch amount km5, km7, and km9 at 50%, 70%, and 90% of the maximum image height is
0.05 <km7-km5 <0.12 (1)
0.05 <km9-km5 <0.28 (2)
1.18 <km7 <1.4 (3)
Is set to satisfy the following conditional expression.

  Conditional expression (1) defines the range of the difference between the 70% image height after distortion correction and the 50% image height after distortion correction of the extension amount kmi in the meridional direction. Exceeding the upper limit value of the conditional expression (1) and the stretching amount km7 becoming too large is not preferable because the resolution in the meridional direction at 70% image height becomes too great. If the lower limit value of conditional expression (1) is exceeded and the amount of extension km7 is too small, it is not preferable because it becomes difficult to downsize the entire system.

  Conditional expression (2) is for reducing degradation of resolution at 90% image height after distortion correction while reducing the size of the entire system. Conditional expression (2) defines the range of the difference between the extension amount km9 of 90% image height after distortion correction and the extension amount km5 of 50% image height after distortion correction. Exceeding the upper limit value of the conditional expression (2) and the stretching amount km9 becoming too large are not preferable because the resolution in the meridional direction at 90% image height becomes remarkable. If the lower limit value of conditional expression (2) is not reached, the extension amount km9 becomes too small, and it is difficult to downsize the entire system, which is not preferable.

  Conditional expression (3) is for maintaining a high resolving power while reducing the size of the entire system. Conditional expression (3) defines the range of the value of the stretch amount km7 at the 70% image height after distortion correction as described above. If the value of the extension amount km7 exceeds the upper limit value of the conditional expression (3), the resolution will be excessively deteriorated at an image height of 70%, which is not preferable. If the lower limit of conditional expression (3) is not reached, the amount of distortion becomes small and it is difficult to downsize the entire system, which is not preferable.

By satisfying conditional expressions (1), (2), and (3) at the same time, the amount of distortion required for miniaturization of the entire system can be obtained, and the resolution degradation when electronically correcting the amount of distortion produced To obtain a small digital camera (imaging device). More preferably, the numerical ranges of conditional expressions (1), (2), and (3) are set as follows.
0.06 <km7-km5 <0.12 (1a)
0.07 <km9-km5 <0.28 (2a)
1.2 <km7 <1.4 (3a)

In addition, the imaging device as one embodiment of the present invention has an extension amount km3, km5, km7 at each image height of 30%, 50%, and 70% of the maximum image height.
1.05 <km3 <1.15 (4)
1.1 <km5 <1.3 (5)
1.18 <km7 <1.40 (3)
The following conditional expression is satisfied.

  Conditional expressions (4), (5), and (3) respectively set the stretch amount km3, km5, and km7 in the meridional direction of 30% image height, 50% image height, and 70% image height appropriately, This is to reduce the decrease in resolution after distortion correction while reducing the size of the entire system.

  If the amount of enlargement at each image height deviates from either the lower limit value or the upper limit value of conditional expressions (3), (4), and (5), the resolution in the meridional direction is maintained well while reducing the size of the entire system. It becomes difficult to do. For example, when the upper limit is exceeded, the decrease in resolution increases. When the lower limit is exceeded, the amount of distortion decreases, making it difficult to downsize the entire system. More preferably, the numerical ranges of conditional expressions (4) and (5) should be set as follows.

1.06 <km3 <1.10 (4a)
1.13 <km5 <1.25 ・ ・ ・ (5a)
Stretching amount ksi in the sagittal direction at an image height that is i% of the maximum image height
ksi = y2bi / y2ai
In this case, the stretching amount ks9 at 90% of the maximum image height is
1.11 <ks9 <1.40 (6)
It is good to satisfy the following conditional expression.

  Conditional expression (6) defines the range of the enlargement amount ks9 at 90% image height after sagittal distortion correction. Exceeding the upper limit value of conditional expression (6) is not preferable because distortion becomes excessively large and deterioration of resolution at an image height of 90% becomes excessively large. If the lower limit of conditional expression (6) is not reached, the amount of distortion becomes small and it is difficult to downsize the entire system. More desirably, when the following conditional expression (6a) is satisfied, it becomes easy to maintain a high resolving power while downsizing the entire system.

1.11 <ks9 <1.35 (6a)
More preferably, the following conditional expression (6b) should be satisfied.
1.11 <ks9 <1.30 (6b)
More desirably, the following conditional expression (6c) should be satisfied.
1.11 <ks9 <1.25 (6c)
The stretch amounts km3 and km9 at 30% and 90% of the maximum image height are respectively
0.1 <km9-km3 <0.5 (7)
It is good to satisfy the following conditional expression.

  Conditional expression (7) is for reducing the degradation of the resolution on the entire screen. Conditional expression (7) defines the range of the difference between the stretch amount km9 of 90% image height after distortion correction and the stretch amount km3 of 30% image height after distortion correction. Exceeding the upper limit of conditional expression (7) is not preferable because the 90% image height enlargement amount km9 becomes too large, and the resolution in the meridional direction becomes significant at 90% image height. If the lower limit value of conditional expression (7) is not reached, the value of the stretch amount km3 becomes too large, and the resolution in the meridional direction at 30% image height becomes remarkable, which is not preferable.

More desirably, the following conditional expression (7a) is satisfied because the degradation of the resolution of the entire screen can be reduced.
0.10 <km9-km3 <0.45 ... (7a)

  Next, the lens configuration of each example will be described. Unless otherwise specified in the present invention, the distortion correction used in the calculation refers to a correction in which the distortion becomes 0% after the distortion correction. The values of stretch amounts kmi and ksi are calculated at the wide-angle end where distortion tends to be particularly noticeable. The distortion is calculated with the object distance at infinity. Each conditional expression must be satisfied at any zoom position of the zoom lens when the optical system is focused at infinity when the optical system has a single focal length, and must be satisfied throughout the entire zoom range. There is no.

  In the numerical examples, correction is performed so that the distortion after distortion correction is 0%, but the scope of the present invention is not limited to this. The values of the stretching amounts kmi and ksi are calculated when the distortion after distortion correction is 0%, but the distortion correction may be performed in a state where, for example, 0.5% of distortion is left in the embodiment. The distortion after distortion correction may be about 0 to 5%.

[Example 1]
Hereinafter, the lens configuration of the zoom lens according to Example 1 of the present invention will be described with reference to FIG. FIGS. 5A and 5B are aberration diagrams of the first embodiment at the wide-angle end and the telephoto end. In the aberration diagrams, d is the d-line and g is the g-line. ΔM is a meridional image plane, and ΔS is a sagittal image plane. The lateral chromatic aberration is shown for the g-line. Hereinafter, all aberration diagrams are the same.

  The zoom lens of Example 1 shown in FIG. 4 includes, in order from the object side to the image side, a first lens unit L1 having a negative refractive power, an aperture stop SP, a second lens unit L2 having a positive refractive power, and a flare-cut stop FC. The third lens unit L3 has a positive refractive power. GB is a glass block. The arrow indicates the moving direction during zooming from the wide-angle end to the telephoto end. The movement of each lens unit during zooming from the wide-angle end to the telephoto end is as follows.

  The first lens unit L1 moves along a locus convex toward the image side, and is positioned closer to the object side at the telephoto end than at the wide-angle end. The aperture stop SP and the second lens group L2 move together (with the same trajectory) toward the object side. The third lens unit L3 moves to the object side. The glass block GB does not move during zooming. As the object distance becomes closer to infinity, the third lens unit L3 moves to the object side. In Example 1, the maximum image height (100% image height) after distortion correction is calculated as 4.6285 mm. A sensor with an effective dimension of 5.55mm x 7.41mm is assumed as an image sensor. The pixel pitch is calculated as 2 μm.

  In a conventional optical system, if the maximum distortion amount is about 15% with priority given to the effect of miniaturization of the entire system, the extension amount km7 at 70% image height is generally about 1.4. Since the evaluation frequency in the meridional direction changes in proportion to the amount of stretching, for example, assuming that the evaluation frequency is 1001 p / mm, this is equivalent to evaluating at 1401 p / mm.

  The value of the stretch amount km7 in Example 1 is 1.28, and the evaluation is performed at 1281 p / mm. When calculating a monochromatic MTF with a wavelength of 587.6 nm and an image height of 3.26 mm, the MTF is improved by 20% in the meridional direction with a spatial frequency of 128 lp / mm and 15% in the meridional direction with a spatial frequency of 140 lp / mm. In general, when the evaluation frequency is lowered, the resolving power is increased. Therefore, it is understood that the deterioration of the resolving power can be reduced by paying attention to the difference value of the distortion.

[Example 2]
Hereinafter, the lens configuration of the zoom lens according to Example 2 of the present invention will be described with reference to FIG. FIGS. 7A and 7B are aberration diagrams of the second embodiment at the wide-angle end and the telephoto end. The zoom lens of Example 2 shown in FIG. 6 includes, in order from the object side to the image side, a first lens unit L1 having a negative refractive power, a second lens unit L2 having a positive refractive power, and a third lens having a negative refractive power. The lens unit includes a group L3 and a fourth lens unit L4 having a positive refractive power. The aperture stop SP is included in the second lens unit L2. The arrow indicates the moving direction during zooming from the wide-angle end to the telephoto end. The movement of each lens unit during zooming from the wide-angle end to the telephoto end is as follows.

  The first lens unit L1 moves along a locus convex toward the image side, and the second lens unit L2 moves toward the object side. The third lens unit L3 moves to the object side, and the fourth lens unit L4 moves to the object side. In Example 2, the maximum image height is 13.63 mm. A sensor of APS-C size (effective dimension 15.1mm x 22.7mm) is assumed as an image sensor. The pixel pitch is calculated as 4.3 μm.

  In Example 2, the value of the stretching amount km7 at the 70% image height is 1.27. For example, if the evaluation frequency is 30 lp / mm with a digital single-lens reflex camera without distortion, the evaluation frequency is 39.3 lp / mm. When the conventional optical system is considered in the same manner as in Example 1, the extension amount km7 is about 1.4, which is equivalent to evaluation at 421 p / mm. When calculating a monochromatic MTF with a wavelength of 587.6 nm and an image height of 9.6 mm, the MTF was improved by 29% in the meridional direction with a spatial frequency of 39.3 lp / mm and 26% in the meridional direction with a spatial frequency of 42 lp / mm. As in the case of the first embodiment, it can be seen that the deterioration of the resolution can be reduced by paying attention to the difference value of the distortion.

[Example 3]
Hereinafter, the lens configuration of the zoom lens according to Example 3 of the present invention will be described with reference to FIG. 9A and 9B are aberration diagrams of Example 3 at the wide-angle end and the telephoto end. The zoom lens of Example 3 shown in FIG. 8 is as follows in order from the object side to the image side. First lens unit L1 with positive refractive power, second lens unit L2 with negative refractive power, aperture stop SP, third lens unit L3 with positive refractive power, fourth lens unit L4 with negative refractive power, positive A fifth lens unit L5 having refractive power is included. GB is a glass block. The arrow indicates the moving direction during zooming from the wide-angle end to the telephoto end. The movement of each lens unit during zooming from the wide-angle end to the telephoto end is as follows.

  The first lens unit L1 moves along a locus convex toward the image side, and is positioned closer to the object side at the telephoto end than at the wide-angle end. The second lens unit L2 moves along a locus convex toward the image side, and is positioned closer to the image side than the wide-angle end at the telephoto end. The aperture stop SP moves independently of other lens groups (with different trajectories). The third lens unit L3 moves to the object side. The fourth lens unit L4 moves to the object side. The fifth lens unit L5 moves along a locus convex toward the object side. The glass block GB does not move during zooming.

  The third embodiment achieves a higher zoom ratio than the first embodiment. Generally, downsizing of the entire system is contrary to widening the angle of view and high zoom ratio of the optical system. For this reason, in order to reduce the size as much as possible, electronic distortion correction is introduced. Conditional expression (3) is the largest among the numerical examples 1 to 4, and the entire system is miniaturized to the maximum. In Example 3, the image sensor is assumed to be 1 / 2.3 type (effective size 4.65 mm × 6.2 mm), the maximum image height is 3.875 mm, and the pixel pitch is 1.4 μm.

  The value of the stretching amount km7 in Example 3 is 1.32. For example, if the evaluation frequency is 100 lp / mm with an undistorted digital camera, the evaluation frequency is 132 p / mm. When the conventional optical system is considered in the same manner as in Example 1, the extension amount km7 is about 1.4, which corresponds to evaluation at 1401 p / mm. When a monochromatic MTF with a wavelength of 587.6 nm and an image height of 2.73 mm is calculated, the MTF is improved by 17% in the meridional direction at a spatial frequency of 132 lp / mm and 16% in the meridional direction at a spatial frequency of 140 lp / mm. As in the case of the first embodiment, it can be seen that the deterioration of the resolution can be reduced by paying attention to the difference value of the distortion.

[Example 4]
Hereinafter, the lens configuration of the zoom lens according to Example 4 of the present invention will be described with reference to FIG. 11A and 11B are aberration diagrams at the wide-angle end and the telephoto end of Example 4. The zoom lens of Example 4 shown in FIG. 10 includes, in order from the object side to the image side, a first lens unit L1 having a negative refractive power, an aperture stop SP, a second lens unit L2 having a positive refractive power, and a flare-cut stop FC. The third lens unit L3 has a positive refractive power. GB is a glass block.

  The arrow indicates the moving direction during zooming from the wide-angle end to the telephoto end. The movement of each lens unit during zooming from the wide-angle end to the telephoto end is as follows. The first lens unit L1 moves along a locus convex toward the image side, and is positioned closer to the object side at the telephoto end than at the wide-angle end. The aperture stop SP and the second lens unit L2 move together to the object side. The third positive lens unit L3 moves to the image side during zooming. The glass block GB does not move during zooming. The third lens unit L3 moves to the object side during focusing when the object distance is close to infinity.

  Conditional expressions (1), (2), and (3) are the smallest among the numerical examples 1 to 4, and the degradation of the resolution is small. In Example 4, the maximum image height after distortion correction is calculated as 4.6285 mm. A sensor with an effective dimension of 5.55mm x 7.41mm is assumed as an image sensor. The pixel pitch is calculated as 2 μm.

  The value of the stretch amount km7 in Example 4 is 1.22. For example, if the evaluation frequency is 100 lp / mm with a digital camera without distortion, the evaluation frequency is 122 p / mm. When the conventional optical system is considered in the same manner as in Example 1, the extension amount km7 is about 1.4, which corresponds to evaluation at 1401 p / mm. When calculating a monochromatic MTF with a wavelength of 587.6 nm and an image height of 3.26 mm, the MTF is improved by 45% in the meridional direction at a spatial frequency of 122 lp / mm and 38% in the meridional direction at a spatial frequency of 140 lp / mm. As in the case of the first embodiment, it can be seen that the deterioration of the resolution can be reduced by paying attention to the difference value of the distortion.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

  Next, an embodiment in which the zoom lens shown in Embodiments 1 to 4 is applied to an imaging apparatus will be described with reference to FIG. The imaging apparatus of the present invention is an interchangeable lens apparatus including a zoom lens, and is detachably connected to the interchangeable lens apparatus via a camera mount unit, and receives an optical image formed by the zoom lens and converts it into an electrical image signal. And a camera body including an image pickup device.

  FIG. 12 is a schematic diagram of a main part of a single-lens reflex camera. In FIG. 12, reference numeral 10 denotes a photographing lens having the zoom lens 1 of the first to fourth embodiments. The zoom lens 1 is held by a lens barrel 2 that is a holding member. Reference numeral 20 denotes a camera body, which includes a quick return mirror 3 that reflects the light beam from the photographing lens 10 upward, and a focusing screen 4 that is disposed in the image forming apparatus of the photographing lens 10. Further, it is composed of a penta roof prism 5 for converting an inverted image formed on the focusing screen 4 into an erect image, an eyepiece 6 for observing the erect image, and the like.

  Reference numeral 7 denotes a photosensitive surface, on which a solid-state imaging device (photoelectric conversion device) and a silver salt film that receive an image formed by a zoom lens such as a CCD sensor or a CMOS sensor are arranged. At the time of photographing, the quick return mirror 3 is retracted from the optical path, and an image is formed on the photosensitive surface 7 by the photographing lens 10. The benefits described in the first to fourth embodiments are effectively enjoyed in the imaging apparatus disclosed in the present embodiment. The same applies to a mirrorless camera without the quick return mirror 3 as an imaging device.

  Next, numerical examples of the respective embodiments of the present invention will be shown. In each numerical example, i indicates the order of the surfaces from the object side, ri is the radius of curvature of the lens surface, di is the lens thickness and air spacing between the i-th surface and the i + 1-th surface, and ndi and νdi are respectively Indicates the refractive index and Abbe number for the d-line. BF is a back focus, and is represented by a distance in terms of air from the final lens surface to the image plane. The total lens length is a value obtained by adding back focus to the distance from the first lens surface to the final lens surface. The aspherical shape is the X axis in the optical axis direction, the H axis in the direction perpendicular to the optical axis, the light traveling direction is positive, R is the paraxial radius of curvature, K is the conic constant, A4, A6, A8, A10, A12 When the aspheric coefficient is used,

It is expressed by the following formula. [E + X] means [× 10 ^{+ x} ], and [e−X] means [× 10 ^{+ x} ]. An aspherical surface is indicated by adding * after the surface number. Also, the portion where the distance d between the optical surfaces is (variable) changes during zooming, and the surface distance corresponding to the focal length is shown in the separate table. Table 1 shows the relationship between the above-described conditional expressions of the present invention and numerical examples.

Numerical example 1
Unit mm

Surface data surface number rd nd νd Effective diameter
1 * -715.455 1.40 1.84954 40.1 14.29
2 * 6.510 2.68 10.94
3 * 11.638 1.90 1.94595 18.0 12.60
4 21.257 (variable) 12.20
5 (Aperture) ∞ 0.40 6.97
6 * 8.262 2.70 1.74330 49.3 7.77
7 * 162.365 0.20 7.54
8 7.747 1.95 1.51633 64.1 7.40
9 107.724 0.60 1.80518 25.4 6.90
10 5.319 3.15 6.10
11 17.548 1.65 1.72000 50.2 6.50
12 -39.308 0.35 6.50
13 ∞ (variable) 5.10
14 * 18.438 2.00 1.48749 70.2 10.80
15 50.327 (variable) 10.80
16 ∞ 1.96 1.51633 64.1 15.00
17 ∞ 0.61 15.00
Image plane ∞

Aspheric data 1st surface
K = -1.85357e + 004 A 4 = -4.16158e-004 A 6 = 1.82503e-005
A 8 = -2.61932e-007 A10 = 1.37270e-009

Second side
K = -2.20782e + 000 A 4 = 2.05194e-004 A 6 = 5.57972e-006
A 8 = 6.35090e-007 A10 = -1.08481e-008

Third side
K = 4.95770e-002 A 4 = -3.16117e-005 A 6 = -1.34160e-006
A 8 = 1.19908e-007 A10 = -1.52323e-009

6th page
K = -1.43493e-001 A 4 = -5.85079e-005 A 6 = 2.59082e-006
A 8 = 7.59699e-008 A10 = 1.90128e-009

7th page
K = -6.19299e + 003 A 4 = 2.41060e-004 A 6 = -7.08566e-006
A 8 = 8.19434e-007 A10 = -1.57781e-008

14th page
K = 4.39801e-001 A 4 = 1.45395e-004 A 6 = -1.59824e-005
A 8 = 6.09418e-007 A10 = -8.97900e-009

Various data Zoom ratio 3.53
Wide angle Medium Telephoto focal length 6.18 13.83 21.84
F number 2.50 3.78 5.49
Half angle of view (degrees) 33.39 18.51 11.96
Statue height 4.07 4.63 4.63
Total lens length 46.16 43.24 48.89
BF 4.75 3.63 2.51

d 4 17.19 5.00 1.38
d13 5.23 15.63 26.02
d15 2.85 1.73 0.61

Entrance pupil position 7.72 5.29 3.93
Exit pupil position -25.96 -49.23 -94.59
Front principal point position 12.46 15.28 20.76
Rear principal point position -5.57 -13.22 -21.24

Zoom lens group data group Start surface Focal length Lens configuration length Front principal point position Rear principal point position
1 1 -12.06 5.98 -0.03 -4.53
2 5 13.02 11.00 1.67 -8.37
3 14 58.49 2.00 -0.76 -2.08
4 16 ∞ 1.96 0.65 -0.65

Single lens Data lens Start surface Focal length
1 1 -7.59
2 3 24.81
3 6 11.63
4 8 16.06
5 9 -6.97
6 11 17.06
7 14 58.49
8 16 0.00

Numerical example 2

Unit mm

Surface data surface number rd nd νd Effective diameter
1 33.781 2.10 1.77250 49.6 44.84
2 19.506 7.27 34.52
3 * 47.969 1.80 1.85400 40.4 33.13
4 * 12.261 8.97 24.36
5 -81.369 1.20 1.49700 81.5 24.27
6 25.540 0.33 23.24
7 21.691 6.00 1.80610 33.3 23.42
8 219.669 (variable) 22.13
9 * 17.306 2.50 1.85135 40.1 10.31
10 -568.837 2.38 9.49
11 (Aperture) ∞ 2.51 7.63
12 -52.975 0.80 1.80610 33.3 7.12
13 8.429 3.00 1.59282 68.6 7.02
14 -30.911 0.20 7.14
15 133.860 1.50 1.48749 70.2 7.12
16 -19.488 (variable) 7.77
17 -189.040 1.01 1.60311 60.6 8.58
18 28.470 (variable) 9.27
19 319.925 3.00 1.48749 70.2 19.89
20 -40.785 0.30 20.65
21 -141.113 1.20 1.80518 25.4 21.26
22 509.921 4.00 1.55332 71.7 21.85
23 * -26.440 (variable) 22.55
Image plane ∞

Aspheric data 3rd surface
K = 3.22156e + 000 A 4 = 1.61064e-005 A 6 = -1.38171e-008
A 8 = -4.78782e-011 A10 = -5.48940e-013 A12 = 1.67078e-015

4th page
K = -1.94862e-001 A 4 = 1.80767e-006 A 6 = -8.13067e-008
A 8 = 3.12204e-009 A10 = -3.16628e-011 A12 = 5.07186e-014

9th page
K = -4.41308e-001 A 4 = -1.88740e-005 A 6 = 3.75387e-007
A 8 = -1.00553e-008 A10 = 7.26232e-011 A12 = 2.75905e-014

23rd page
K = -1.90837e-001 A 4 = 4.31184e-005 A 6 = -6.10361e-007
A 8 = 7.03104e-009 A10 = -3.32333e-011 A12 = -9.21025e-015
A13 = 4.76713e-015

Various data Zoom ratio 1.90
Wide angle Medium telephoto focal length 9.22 14.05 17.50
F number 3.39 4.04 4.63
Half angle of view (degrees) 53.07 44.12 37.91
Image height 12.27 13.63 13.63
Total lens length 89.68 83.60 86.84
BF 14.22 15.78 16.00

d 8 19.98 6.83 3.00
d16 0.73 3.17 4.00
d18 4.68 7.75 13.76
d23 14.22 15.78 16.00

Entrance pupil position 18.62 17.15 16.55
Exit pupil position -31.38 -51.83 -117.70
Front principal point position 25.98 28.28 31.76
Rear principal point position 5.00 1.73 -1.50

Zoom lens group data group Start surface Focal length Lens configuration length Front principal point position Rear principal point position
1 1 -17.71 27.67 6.15 -17.62
2 9 19.24 12.89 3.95 -8.09
3 17 -40.96 1.01 0.55 -0.08
4 19 36.28 8.50 4.53 -1.13

Single lens Data lens Start surface Focal length
1 1 -63.85
2 3 -19.75
3 5 -38.97
4 7 29.46
5 9 19.77
6 12 -8.97
7 13 11.50
8 15 35.01
9 17 -40.96
10 19 74.41
11 21 -137.16
12 22 45.55

Numerical example 3

Unit mm

Surface data surface number rd nd νd Effective diameter
1 108.129 1.80 1.72047 34.7 41.81
2 46.978 5.26 1.49700 81.5 37.75
3 -946.730 0.18 37.67
4 51.474 3.98 1.59282 68.6 37.18
5 280.718 (variable) 36.78
6 142.908 0.95 1.88300 40.8 19.48
7 * 9.032 4.03 14.13
8 466.957 0.80 1.80 400 46.6 13.77
9 19.862 1.99 13.22
10 -93.334 0.70 1.80 400 46.6 13.24
11 62.738 0.20 13.34
12 19.578 1.99 1.94595 18.0 13.68
13 111.681 (variable) 13.49
14 ∞ 0.00 8.81
15 (Aperture) ∞ 0.00 8.81
16 ∞ (variable) 8.81
17 * 12.974 2.93 1.55332 71.7 11.20
18 * 18242.199 0.20 11.13
19 13.658 2.51 1.43875 94.9 11.05
20 -126.223 0.32 10.67
21 17.766 0.60 1.83400 37.2 10.10
22 9.367 (variable) 9.48
23 21.414 0.70 1.90366 31.3 9.54
24 8.926 2.72 1.59263 41.7 9.31
25 60.848 (variable) 9.37
26 * 21.453 2.13 1.49680 63.2 11.51
27 -50.678 0.60 2.00069 25.5 11.52
28 -102.015 (variable) 11.57
29 ∞ 0.30 1.51633 64.1 30.00
30 ∞ 0.47 30.00
31 ∞ 0.50 1.51633 64.1 30.00
32 ∞ 0.52 30.00
Image plane ∞

Aspheric data 7th surface
K = -3.26846e-002 A 4 = 4.44730e-006 A 6 = 1.98474e-006
A 8 = -9.09294e-008 A10 = 1.04407e-009

17th page
K = -2.35583e + 000 A 4 = 8.02150e-005 A 6 = -6.01650e-007
A 8 = -1.22700e-008 A10 = 2.23374e-010

18th page
K = -1.89560e + 010 A 4 = 3.33961e-005 A 6 = -6.54026e-007

26th page
K = -8.62550e-001 A 4 = 4.05831e-005 A 6 = -5.46445e-006
A 8 = 3.46453e-007 A10 = -7.66379e-009

Various data Zoom ratio 55.73
Wide angle Medium Telephoto focal length 3.86 10.55 215.00
F number 2.87 5.00 7.07
Half angle of view (degrees) 40.82 20.17 1.03
Image height 3.33 3.88 3.88
Total lens length 104.64 99.63 150.63
BF 9.87 15.27 9.51

d 5 0.80 12.48 66.13
d13 31.78 21.47 1.69
d16 19.59 1.51 1.54
d22 2.06 1.53 5.01
d25 5.92 12.76 32.14
d28 8.36 13.75 7.99

Entrance pupil position 18.57 37.18 715.09
Exit pupil position 82.69 -57.35 10777.46
Front principal point 22.61 45.81 934.38
Rear principal point position -3.34 -10.03 -214.48

Zoom lens group data group Start surface Focal length Lens configuration length Front principal point position Rear principal point position
1 1 84.74 11.22 3.15 -4.13
2 6 -8.91 10.66 0.83 -7.94
SP 14 ∞ 0.00 0.00 -0.00
3 17 21.84 6.57 -2.41 -6.01
4 23 -640.72 3.42 21.30 18.59
5 26 43.50 2.73 0.12 -1.61
GB 29 ∞ 1.27 0.50 -0.50

Single lens Data lens Start surface Focal length
1 1 -116.74
2 2 90.21
3 4 105.64
4 6 -10.96
5 8 -25.82
6 10 -46.57
7 12 24.83
8 17 23.46
9 19 28.25
10 21 -24.56
11 23 -17.40
12 24 17.31
13 26 30.64
14 27 -101.23
15 29 0.00
16 31 0.00

Numerical example 4

Unit mm

Surface data surface number rd nd νd Effective diameter
1 * -12.772 1.40 1.84954 40.1 13.87
2 * 14.060 2.68 10.93
3 * 15.399 1.90 1.94595 18.0 12.60
4 * 38.111 (variable) 12.20
5 (Aperture) ∞ 0.40 7.10
6 * 7.325 2.70 1.74330 49.3 8.07
7 * 7993.996 0.20 7.78
8 10.302 1.95 1.51633 64.1 7.40
9 252.002 0.60 1.80518 25.4 6.90
10 5.032 3.15 6.10
11 13.505 1.65 1.72000 50.2 6.50
12 -116.500 0.35 6.50
13 ∞ (variable) 5.10
14 * 21.647 2.00 1.48749 70.2 10.80
15 * -70.118 (variable) 10.80
16 ∞ 1.96 1.51633 64.1 15.00
17 ∞ 0.60 15.00
Image plane ∞

Aspheric data 1st surface
K = -9.22800e + 000 A 4 = 7.20202e-004 A 6 = -1.03552e-005
A 8 = 8.21482e-008 A10 = -3.80566e-010

Second side
K = 3.20487e + 000 A 4 = 7.82725e-004 A 6 = -1.32225e-006
A 8 = 3.77284e-007 A10 = -1.20322e-008

Third side
K = -7.66165e-001 A 4 = -1.22270e-004 A 6 = 9.28959e-006
A 8 = -1.44673e-007 A10 = 6.65676e-010

4th page
K = -2.50168e + 000 A 4 = -4.73353e-006 A 6 = -6.35396e-008
A 8 = -4.30242e-009 A10 = 2.50050e-011

6th page
K = -2.85005e-001 A 4 = -1.09355e-004 A 6 = -5.93715e-006
A 8 = 5.18542e-007 A10 = -1.31579e-008

7th page
K = 3.62301e + 006 A 4 = -2.18903e-005 A 6 = -7.49735e-007
A 8 = 5.51846e-007 A10 = -2.06687e-008

14th page
K = -5.57156e + 000 A 4 = 1.52203e-004 A 6 = -2.10569e-005
A 8 = 1.13453e-006 A10 = -1.70610e-008

15th page
K = 1.34767e + 002 A 4 = -5.58926e-005 A 6 = 7.07720e-006
A 8 = 1.93192e-007 A10 = 3.33693e-010

Various data Zoom ratio 3.54
Wide angle Medium Telephoto focal length 6.18 13.70 21.84
F number 2.46 3.70 5.43
Half angle of view (degrees) 34.21 18.67 11.96
Image height 4.20 4.63 4.63
Total lens length 46.16 43.60 49.38
BF 4.74 3.66 2.57

d 4 17.11 5.06 1.35
d13 5.32 15.90 26.48
d15 2.85 1.77 0.68

Entrance pupil position 7.26 4.93 3.63
Exit pupil position -33.50 -113.93 504.18
Front principal point position 12.31 16.99 26.42
Rear principal point position -5.58 -13.10 -21.24

Zoom lens group data group Start surface Focal length Lens configuration length Front principal point position Rear principal point position
1 1 -12.53 5.98 -0.81 -5.54
2 5 13.45 11.00 0.94 -8.84
3 14 34.17 2.00 0.32 -1.03
4 16 ∞ 1.96 0.65 -0.65

Single lens Data lens Start surface Focal length
1 1 -7.69
2 3 26.25
3 6 9.86
4 8 20.75
5 9 -6.38
6 11 16.90
7 14 34.17
GB 16 0.00

L1 1st lens group L2 2nd lens group L3 3rd lens group L4 4th lens group
L5 5th lens group IP Image surface GB Glass block SP Aperture stop
FC flare-cut diaphragm

Claims (5)

In an imaging apparatus having an imaging optical system, an imaging element that receives an image formed by the imaging optical system, and an image processing unit that corrects distortion of an image obtained by the imaging element,
When correcting the distortion by the image processing unit, the maximum image height of the effective range of the image sensor is set to 100%, and the image height [mm] at i% of the maximum image height before correcting the distortion is y1ai, the image height Image height [mm] obtained by adding pixel pitch [mm] of the image sensor to y1ai, y2ai, distortion after image height y1ai was corrected, image height [mm] was corrected to y1bi, and distortion at image height y2ai was corrected The subsequent image height [mm] is y2bi, and the extension amount kmi in the meridional direction at the image height divided by i relative to the maximum image height.
kmi = (y2bi-y1bi) / (y2ai-y1ai)
When the maximum image height is 50%, 70%, and 90%, the stretch amounts km5, km7, and km9 are respectively
0.05 <km7-km5 <0.12
0.05 <km9-km5 <0.28
1.18 <km7 <1.4
An imaging device characterized by satisfying the following conditional expression: The stretch amounts km3, km5, and km7 at 30%, 50%, and 70% of the maximum image height are respectively
1.05 <km3 <1.15
1.1 <km5 <1.3
1.18 <km7 <1.40
The imaging apparatus according to claim 1, wherein the following conditional expression is satisfied. In an imaging apparatus having an imaging optical system, an imaging element that receives an image formed by the imaging optical system, and an image processing unit that corrects distortion of an image obtained by the imaging element,
When correcting the distortion by the image processing unit, the maximum image height of the effective range of the image sensor is set to 100%, and the image height [mm] at i% of the maximum image height before correcting the distortion is y1ai, the image height Image height [mm] obtained by adding pixel pitch [mm] of the image sensor to y1ai, y2ai, distortion after image height y1ai was corrected, image height [mm] was corrected to y1bi, and distortion at image height y2ai was corrected The subsequent image height [mm] is y2bi, and the extension amount kmi in the meridional direction at the image height divided by i relative to the maximum image height.
kmi = (y2bi-y1bi) / (y2ai-y1ai)
When the maximum image height is 30%, 50%, and 70%, the stretch amounts km3, km5, and km7 are respectively
1.05 <km3 <1.15
1.1 <km5 <1.3
1.18 <km7 <1.40
An imaging device characterized by satisfying the following conditional expression: The amount of stretching ksi in the sagittal direction at an image height that is i% of the maximum image height is
ksi = y2bi / y2ai
In this case, the stretching amount ks9 at 90% of the maximum image height is
1.11 <ks9 <1.40
The imaging apparatus according to claim 1, wherein the following conditional expression is satisfied. The stretch amounts km3 and km9 at 30% and 90% of the maximum image height are respectively
0.1 <km9-km3 <0.5
The imaging apparatus according to claim 1, wherein the following conditional expression is satisfied.