JP6066272B2 - Photographing lens, optical device, and method for adjusting photographing lens - Google Patents

Description

  The present invention relates to a photographic lens, an optical device, and a method for adjusting a photographic lens.

  Conventionally, various photographing lenses suitable for photographic cameras, electronic still cameras, video cameras, and the like have been proposed (see, for example, Patent Document 1).

JP 2009-237542 A

  However, in the case of a conventional photographic lens, if an eccentric error occurs during manufacturing, the imaging performance deteriorates. In order to prevent such deterioration of the imaging performance, it was necessary to increase the shape accuracy of each lens, lens chamber, and mechanism to reduce the eccentric error. However, it is difficult to reduce the cost because the processing accuracy must be increased. There was a problem that there was.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a low-cost photographic lens that can achieve good optical performance, an optical device having the photographic lens, and a method for adjusting the photographic lens. .

In order to solve the above-described problems, the photographing lens according to the present invention includes substantially two lenses, a first lens group having a positive refractive power and a second lens group having a positive refractive power in order from the object side. The first lens group and the second lens group are arranged on the optical axis so that the distance between the first lens group and the second lens group is enlarged when focusing from a long distance object to a short distance object. along with the movement, the first lens group comprises, in order from the object side, a front group having positive refractive power and a rear group having positive refractive power, at least a part of the group of the first lens group It is characterized by having a position adjusting mechanism that shifts eccentrically in a direction including a component orthogonal to the optical axis.

  An optical apparatus according to the present invention includes any one of the above-described photographing lenses.

In addition, the method for adjusting a photographic lens according to the present invention includes, in order from the object side, substantially two lens groups, a first lens group having a positive refractive power and a second lens group having a positive refractive power. The first lens group and the second lens so that the distance between the first lens group and the second lens group is enlarged when focusing from a long distance object to a short distance object. The group moves along the optical axis, and the first lens group includes, in order from the object side, a front group having a positive refractive power and a rear group having a positive refractive power. At least a part of the group is shifted in a direction including a component orthogonal to the optical axis.

  According to the present invention, it is possible to provide a low-cost photographic lens that can achieve good optical performance, an optical device having the photographic lens, and a method for adjusting the photographic lens.

It is sectional drawing which shows the lens structure of the imaging lens which concerns on 1st Example. It is sectional drawing which showed typically the position adjustment mechanism of the said imaging lens. It is a top view of the said photographic lens, Comprising: (a) shows the case where it sees from the object side, (b) shows the case where it sees from the image surface side. FIG. 6 is a diagram illustrating an MTF when an eccentricity error does not occur during manufacturing in the photographing lens according to the first example, where (a) shows an MTF for an image height of 5.6 mm, and (b) shows an MTF for an image height of 0 mm. (C) shows the MTF for an image height of −5.6 mm. FIG. 6 is a diagram illustrating an MTF when a predetermined eccentricity error occurs during manufacturing in the photographing lens according to the first example, where (a) shows an MTF for an image height of 5.6 mm, and (b) shows an MTF for an image height of 0 mm. (C) shows the MTF for an image height of −5.6 mm. FIG. 7 is a diagram illustrating the MTF when the photographic lens according to the first example is adjusted using the position adjustment mechanism from the state shown in FIG. 6, and (a) shows the MTF for an image height of 5.6 mm, (b) ) Shows the MTF for an image height of 0 mm, and (c) shows the MTF for an image height of -5.6 mm. It is sectional drawing which shows the lens structure of the imaging lens which concerns on 2nd Example. FIG. 6 is a diagram illustrating an MTF when an eccentric error does not occur during manufacturing in the photographing lens according to the second example, where (a) shows an MTF for an image height of 5.6 mm, and (b) shows an MTF for an image height of 0 mm. (C) shows the MTF for an image height of −5.6 mm. FIG. 6 is a diagram illustrating an MTF when a predetermined eccentricity error occurs during manufacture in the photographing lens according to the second example, where (a) shows an MTF for an image height of 5.6 mm, and (b) shows an MTF for an image height of 0 mm. (C) shows the MTF for an image height of −5.6 mm. FIG. 11 is a diagram illustrating the MTF when the photographic lens according to the second example is adjusted using a position adjustment mechanism from the state shown in FIG. 10, and (a) shows the MTF for an image height of 5.6 mm, (b) ) Shows the MTF for an image height of 0 mm, and (c) shows the MTF for an image height of -5.6 mm. It is sectional drawing of the camera carrying the said imaging lens.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. First, the configuration of the taking lens SL according to the present embodiment will be described with reference to FIG. The photographic lens SL includes, in order from the object side, a first lens group G1 having a positive refractive power and a second lens group G2 having a positive refractive power. Further, the first lens group G1 includes, in order from the object side, a front group G1F having a positive refractive power and a rear group G1R having a positive refractive power. As will be described in detail later, the photographing lens SL is configured so that at least a part of the rear group G1R of the first lens group G1 (for example, the second partial lens group G1Rb of the rear group G1R) includes a component orthogonal to the optical axis. It has a position adjusting mechanism capable of adjusting the position for shifting eccentricity. With this configuration, the photographing lens SL shifts and decenters at least a part of the rear group G1R of the first lens group G1 in a direction including a component orthogonal to the optical axis, thereby adjusting an eccentric error during manufacturing. Can be corrected. For this reason, since the decentration aberration caused by the decentration error can be corrected, it is possible to eliminate the deterioration of the imaging performance caused by the decentration aberration, and to achieve good optical performance. In particular, the eccentric coma aberration can be corrected satisfactorily. Further, it is not necessary to increase the processing accuracy of the lens component and the mechanism component in order to reduce the occurrence of the eccentric error, and the cost can be reduced. The second partial lens group G1Rb that shifts and decenters in a direction that includes a component orthogonal to the optical axis is preferably the most image-side lens of the rear group G1R. With this configuration, only decentration coma is corrected with a small shift decentering amount, and other aberrations are not deteriorated.

  In addition, it is desirable that the position adjustment mechanism of the photographic lens SL is configured to change the air gap between the front group G1F and the rear group G1R constituting the first lens group G1. With this configuration, the photographic lens SL can satisfactorily correct various aberrations such as spherical aberration due to manufacturing errors of each part.

  In addition, the position adjustment mechanism of the photographic lens SL tilts the entire system (the entire photographic lens SL) with respect to an attachment surface to which the photographic lens SL is attached (or an imaging surface of an optical device to which the photographic lens SL is attached). It is desirable that the lens is decentered (the angle formed by the mounting surface or imaging surface and the optical axis of the photographing lens SL is changed). With this configuration, the photographing lens SL can satisfactorily correct image plane tilt (so-called one-sided blur).

  The front group G1F constituting the first lens group G1 of the photographing lens SL includes a first lens L11 having a positive refractive power, a second lens L12 having a positive refractive power, and a positive refractive power in order from the object side. And a fourth lens L14 having negative refractive power, and the position adjustment mechanism is configured to change the air gap between the third lens L13 and the fourth lens L14. It is desirable. With this configuration, the photographic lens SL can satisfactorily correct curvature of field due to manufacturing errors of each part.

  In addition, the photographing lens SL increases the distance between the first lens group G1 and the second lens group G2 when focusing from a long-distance object (infinity) to a short-distance object (closest). It is desirable that G1 and G2 be configured to move to the object side along the optical axis. With such a configuration, it is possible to satisfactorily correct lateral chromatic aberration and curvature of field.

  The photographing lens SL preferably has an aperture stop S in the first lens group G1. With such a configuration, coma can be corrected well.

  Now, conditions for configuring such a photographing lens SL will be described. The photographic lens SL desirably satisfies the following conditional expression (1).

0.30 <yG2 / yG1 <0.80 (1)
However,
yG1: of the first lens group G1 when focusing from infinity to a photographing magnification of -0.01 times
This represents the amount of movement on the optical axis, and is negative when moving to the object side. YG2: The second lens group G2 when focusing from infinity to a photographing magnification of -0.01 times
Represents the amount of movement on the optical axis, negative when moving to the object side

  Conditional expression (1) is a conditional expression for defining an appropriate range of the moving ratio in focusing at the intermediate shooting distance (shooting magnification -0.01 times) of the first lens group G1 and the second lens group G2. is there. If the lower limit value of the conditional expression (1) is not reached, the lateral chromatic aberration generated in the second lens group G2 alone is deteriorated, which is not preferable. In order to secure the effect of the present application, it is preferable to set the lower limit of conditional expression (1) to 0.35. If the upper limit value of conditional expression (1) is exceeded, coma aberration and field curvature will be overcorrected, which is not preferable. In order to secure the effect of the present application, it is preferable to set the upper limit of conditional expression (1) to 0.60.

  Next, the position adjustment mechanism 40 of the photographic lens SL will be described with reference to FIGS. The position adjustment mechanism 40 of the photographic lens SL includes a first holding member 41, a second holding member 42, a third holding member 43, and a fourth holding member 44 that hold the photographic lens SL. As shown in FIG. 2, 44 is held by a cylindrical cam cylinder member 21. Further, the cam cylinder member 21 is held by a cylindrical fixed cylinder member 22, and the cam cylinder member 21 and the fixed cylinder member 22 are accommodated in a cylindrical lens barrel 20. The rear group G1R constituting the first lens group G1 of the photographic lens SL is composed of a first partial lens group G1Ra and a second partial lens group G1Rb in this order from the object side. In FIG. 2, the lens barrel 20 and the position adjusting mechanism 40 show only the upper half of the optical axis.

  The front group G1F constituting the first lens group G1 of the photographic lens SL is held by a cylindrical first holding member 41. Further, the first partial lens group G1Ra in the rear group G1R constituting the first lens group G1 is held by a cylindrical second holding member 42, and the second partial lens group G1Rb is a cylindrical third lens. It is held by the holding member 43. The second lens group G2 is held by a cylindrical fourth holding member 44. Further, the third holding member 43 is held by the second holding member 42 described above.

  Here, the third holding member 43 is fixed and attached to a plurality of locations (for example, three locations) on the rear end surface of the second holding member 42 with screws 48. The diameter of the hole through which the screw 48 of the third holding member 43 is inserted is formed to be larger than the diameter of the shaft of the screw 48. Therefore, after loosening all the screws 48 and adjusting the position of the third holding member 43 in the direction orthogonal to the optical axis with respect to the second holding member 42, the screws 48 are tightened to fix the third holding member 42 to the third holding member 42. By fixing the holding member 43, the second partial lens group G1Rb of the rear group G1R can be shifted and decentered in a direction including a component orthogonal to the optical axis. With such a configuration, the decentration coma aberration of the photographic lens SL can be corrected.

  The first holding member 41 and the second holding member 42 are arranged side by side in the optical axis direction, and a washer 45 is provided between the surfaces where the first holding member 41 and the second holding member 42 are in contact with each other. Is arranged. Therefore, the axial air gap d89 between the front group GF and the rear group GR can be changed by replacing the washer 45 with a washer having a different thickness in the optical axis direction, and thereby the spherical aberration of the photographing lens SL. Can be corrected.

  Further, a mount member 23 for attaching the photographing lens SL to the camera is attached to the rear end portion of the fixed cylinder member 22, and the mount member 23 is attached to a plurality of locations (for example, the fixed cylinder member 22). It is fixed with screws 47 at three places. In addition, for example, three washers 46 are arranged between the fixed cylinder member 22 and the mount member 23 corresponding to each of the screws 47. Therefore, the angles of the cylindrical axes of the cam cylinder member 21 and the fixed cylinder member 22 with respect to the mount member 23 can be changed by replacing the three washers 46 with washers having different thicknesses in the optical axis direction. That is, since the angle of the optical axis of the photographic lens SL held by the cam cylinder member 21 and the fixed cylinder member 22 with respect to the mount member 23 can be changed, the photographic lens SL can be moved relative to the mounting surface or the imaging surface. Therefore, the photographic lens SL can be arranged and fixed at a position to correct the eccentric image plane tilt (so-called one-sided blur), and the eccentric image plane tilt can be corrected satisfactorily. The washer 46 can correct back focus fluctuations caused by manufacturing errors such as the curvature of the lens, the lens thickness, the lens interval, and the refractive index of the lens constituting the photographing lens SL.

  Further, in the photographic lens SL configured as shown in FIG. 1, a third lens (positive) included in the front group G1F of the first lens group G1 held by the first holding member 41 by the first holding member 41. The curvature of field can be corrected by changing the air distance d6 between the meniscus lens L13 and the fourth lens (negative meniscus lens) L14.

  The second holding member 42 and the fourth holding member 44 configured as described above are held by the cylindrical cam cylinder member 21 via a cam mechanism (not shown). The cam cylinder member is held by a cylindrical fixed cylinder member 22 so as to be rotatable about the optical axis. As described above, the mount member 23 is attached to the image side end portion of the fixed cylinder member 22, and is configured to be detachable from a camera body (not shown) or the like.

  Here, when the cam cylinder member 21 is rotated by a drive mechanism (not shown), the second and fourth holding members 42 and 44 are moved in the optical axis direction within the cam cylinder member 21 by the cam mechanism (not shown). It is configured. Thereby, when focusing from a long distance object (infinity) to a short distance object (closest), the distance between the first lens group G1 and the second lens group G2 is increased, and each lens group G1, G2 is moved. It can be moved to the object side.

  Further, a camera which is an optical device including the photographing lens SL according to the present embodiment will be described with reference to FIG. This camera 1 is a so-called mirrorless camera of an interchangeable lens provided with a photographic lens SL according to this embodiment as a photographic lens 2. The photographing lens 2 is provided with the position adjustment mechanism 40 described above. In this camera 1, light from an object (subject) (not shown) is collected by the taking lens 2 and is an OLPF (Optical low pass filter: optical low-pass filter, not shown). The filter group FL shown in FIG. The subject image is formed on the imaging surface of the imaging unit 3 via Then, the subject image is photoelectrically converted by the photoelectric conversion element provided in the imaging unit 3 to generate an image of the subject. This image is displayed on an EVF (Electronic view finder) 4 provided in the camera 1. Thus, the photographer can observe the subject via the EVF 4.

  Further, when a release button (not shown) is pressed by the photographer, an image photoelectrically converted by the imaging unit 3 is stored in a memory (not shown). In this way, the photographer can shoot the subject with the camera 1. In this embodiment, an example of a mirrorless camera has been described. However, the photographic lens SL according to this embodiment is mounted on a single-lens reflex camera that has a quick return mirror in the camera body and observes a subject with a finder optical system. Even in this case, the same effect as the camera 1 can be obtained.

  The contents described below can be appropriately adopted as long as the optical performance is not impaired.

  In the present embodiment, the photographic lens SL having the two-group configuration is shown, but the above-described configuration conditions and the like can be applied to other group configurations such as the three-group configuration. Further, a configuration in which a lens or a lens group is added to the most object side or a configuration in which a lens or a lens group is added to the most image side may be used. The lens group refers to a portion having at least one lens separated by an air interval that changes during focusing.

  Further, it may be a focusing lens group that performs focusing from a long distance object (infinity) to a short distance object by moving a single lens group, a plurality of lens groups, or a partial lens group in the optical axis direction. In this case, the focusing lens group can be applied to autofocus, and is also suitable for driving a motor for autofocus (such as an ultrasonic motor).

  Also, by moving the lens group or partial lens group so that it has a component in the direction perpendicular to the optical axis, or rotating (swinging) in the in-plane direction including the optical axis, image blur caused by camera shake is corrected. An anti-vibration lens group may be used. In particular, it is preferable that the most image-side lens (for example, L17 in FIG. 1) of the first lens group G1 is the anti-vibration lens group.

  Further, the lens surface may be formed as a spherical surface, a flat surface, or an aspheric surface. It is preferable that the lens surface is a spherical surface or a flat surface because lens processing and assembly adjustment are facilitated, and deterioration of optical performance due to errors in processing and assembly adjustment is prevented. Further, even when the image plane is deviated, it is preferable because there is little deterioration in drawing performance. When the lens surface is an aspheric surface, the aspheric surface is an aspheric surface by grinding, a glass mold aspheric surface made of glass with an aspheric shape, or a composite aspheric surface made of resin with an aspheric shape on the glass surface. Any aspherical surface may be used. The lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

  As described above, the aperture stop S is preferably arranged in the first lens group G1, but the role of the aperture stop S may be substituted by a lens frame without providing a member as an aperture stop.

  Further, each lens surface may be provided with an antireflection film having a high transmittance in a wide wavelength region in order to reduce flare and ghost and achieve high optical performance with high contrast.

  In addition, the photographing lens SL according to the present embodiment has a focal length in terms of 35 mm film size of about 60 mm to 150 mm, preferably about 80 mm to 90 mm. In addition, the photographing lens SL according to the present embodiment is on the optical axis from the image plane side to the image plane I of a lens disposed on the most image side that does not include a filter group FL such as a low-pass filter in terms of 35 mm film size. It is desirable that the distance (back focus) is about 8 mm to 30 mm, preferably about 10 mm to 20 mm.

  Hereinafter, each example of the present application will be described with reference to the drawings. 1 and 7 are cross-sectional views showing the configuration and refractive power distribution of the photographic lenses SL (SL1, SL2) according to the respective examples. Further, in the lower part of the sectional views of the photographing lenses SL2 and SL2, the moving direction along the optical axis of each of the lens groups G1 to G2 when focusing on an object at a close distance from infinity (∞) is shown. Shown with an arrow. As shown in FIGS. 1 and 7, the photographing lenses SL1 and SL2 according to the first and second examples include, in order from the object side, the first lens group G1 having a positive refractive power and the positive refractive power. And a second lens group G2. Further, the first lens group G1 includes, in order from the object side, a front group G1F having a positive refractive power and a rear group G1R having a positive refractive power. Then, focusing from a long-distance object (infinity) to a short-distance object (closest) is performed by separately extending the first lens group G1 and the second lens group G2 to the object side. That is, the first and second lens groups G1 and G2 move toward the object side along the optical axis so that the air gap between the first lens group G1 and the second lens group G2 increases and the back focus increases. . The aperture stop S is disposed in the first lens group G1 and moves together with the first lens group G1 during focusing.

[First embodiment]
FIG. 1 is a diagram illustrating a configuration of a photographic lens SL1 according to the first example. In the photographing lens SL1 shown in FIG. 1, the front group G1F of the first lens group G1 has a positive meniscus lens (first lens) L11 having a convex surface directed toward the object side and a convex surface directed toward the object side in order from the object side. The lens includes a positive meniscus lens (second lens) L12, a positive meniscus lens (third lens) L13 having a convex surface facing the object side, and a negative meniscus lens (fourth lens) L14 having a convex surface facing the object side. . The rear group G1R of the first lens group G1 has a first partial lens group G1Ra composed of a cemented lens CL1 in which a biconcave lens L15 and a biconvex lens L16 are cemented in order from the object side, and a concave surface directed toward the object side. The lens unit includes a second partial lens group G1Rb including a positive meniscus lens L17. The second lens group G2 includes a cemented lens CL2 in which a biconvex lens (positive lens) L21 and a biconcave lens (negative lens) L22 are cemented in order from the object side. The aperture stop S is disposed between the front group G1F and the rear group G1R of the first lens group G1. A filter group FL including a low-pass filter and an infrared cut filter is disposed between the photographing lens SL1 and the image plane I. Further, the image plane I is imaged on an image sensor (eg, film, CCD, CMOS, etc.).

  Table 1 below lists values of specifications of the first embodiment. In Table 1, f shown in the overall specifications is the focal length, FNo is the F number, 2ω is the angle of view [°], Y is the image height, and TL is the total length. These values are those when focusing on infinity. The total length TL is the distance on the optical axis from the lens surface (first surface) closest to the object side of the photographic lens SL1 to the image plane I. Further, the surface number shown in the lens data indicates the order of the lens surfaces from the object side along the direction of travel of the light beam, the surface interval indicates the interval on the optical axis from each optical surface to the next optical surface, the refractive index and The Abbe numbers indicate values for the d-line (λ = 587.6 nm). The surface numbers 1 to 19 shown in Table 1 correspond to the numbers 1 to 19 shown in FIG. The lens group focal length indicates the start surface and focal length of each of the first to second lens groups G1 to G2. Here, “mm” is generally used for the focal length, radius of curvature, surface interval, and other length units listed in all the following specification tables, but the optical system is proportionally enlarged or reduced. However, the same optical performance can be obtained, and the present invention is not limited to this. The radius of curvature “0.0000” indicates a plane or an opening. Further, the description of the refractive index “1.00000” of air is omitted. The description of these symbols and the description of the specification table are the same in the following embodiments.

(Table 1)
[Overall specifications]
f = 32.4
FNo = 1.24
2ω = 26.19
Image height = 8.19
TL = 52.60

[Lens data]
Surface number Curvature radius Surface spacing nd νd
1 33.0214 4.40 1.6968 55.52
2 637.5014 0.10
3 18.2318 4.00 1.6030 65.44
4 25.6174 0.10
5 20.9000 3.10 1.7950 45.31
6 30.0000 0.90
7 55.2655 1.20 1.7174 29.57
8 10.8367 5.20
9 0.0000 4.70 Aperture stop S
10 -12.2930 1.20 1.6727 32.19
11 85.0000 4.00 1.8830 40.66
12 -19.6365 0.30
13 -49.0000 2.10 1.7725 49.62
14 -23.4000 (d14)
15 30.8466 4.10 1.8348 42.73
16 -38.7000 1.20 1.7552 27.57
17 85.2086 (d17)
18 0.0000 2.79 1.5168 63.88
19 0.0000 2.11

[Lens focal length]
Lens group Start surface Focal length 1st lens group 1 51.86
Second lens group 15 47.97

  Further, as described above, in the photographing lens SL1 according to the first embodiment, the first lens group G1 and the second lens group G2 are used when focusing from a long distance object (infinity) to a short distance object (closest). Moves on the optical axis, so that the on-axis air distance d14 between the first lens group G1 and the second lens group G2, the on-axis air distance d17 between the second lens group G2 and the filter group FL, and the back focus Bf. Changes. Table 2 below shows the variable intervals in the infinite focus state, the intermediate shooting distance focus state, and the short distance focus state. In Table 2, the intermediate shooting distance is a shooting distance of a shooting magnification of -0.01 times, and the near shooting distance is a shooting distance of a shooting magnification of -0.07 times. The back focus Bf represents the distance on the optical axis from the lens surface (17th surface) closest to the image side of the second lens group G2 to the image surface I. Further, the axial air intervals d14 and d17 shown in Table 2 can be changed by replacing the washers 45 and 46 of the position adjusting mechanism 40 with washers having different thicknesses in the optical axis direction. Indicates a value before adjustment (before replacement). This description is the same in the following embodiments.

(Table 2)
Lens condition Infinity Medium distance Short distance d14 0.90 1.13 2.67
d17 10.20 10.43 11.97
Bf 15.10 15.33 16.87

  Table 3 below shows values corresponding to the conditional expressions in the first embodiment. In Table 3, yG1 represents the amount of movement on the optical axis of the first lens group G1 when focusing from infinity to the photographing magnification of -0.01 times, and the value when moving toward the object side is a negative value. yG2 represents the amount of movement of the second lens group G2 on the optical axis when focusing from infinity to a photographing magnification of -0.01 times, and a negative value when moving to the object side. The description of these symbols is the same in the following embodiments.

(Table 3)
yG1 = −0.47
yG2 = −0.23
(1) yG2 / yG1 = 0.50

  Thus, the photographic lens SL1 according to the first example satisfies the conditional expression (1).

  Here, in the photographic lens SL1 according to the first embodiment, the decentration error at the time of manufacture is corrected, thereby correcting the decentration aberration and eliminating the deterioration of the imaging performance. The description will be given with reference.

  FIG. 4 is a diagram showing an MTF (Modulation Transfer Function) in the case where no decentration error occurs during manufacturing in the photographic lens SL1 according to the first example, and FIG. 4A shows an image height of 5.6 mm. 4B shows the MTF for an image height of 0 mm (center), and FIG. 4C shows the MTF for an image height of −5.6 mm. Here, FIG. 4 shows the wave optical MTF for 60 lines / mm of the d line (λ = 587.6 nm), the vertical axis indicates the MTF value, and the horizontal axis indicates the defocus amount with respect to the Gaussian image plane. Respectively. In FIGS. 4A and 4C, the solid line represents the sagittal image MTF, and the dotted line represents the meridional image MTF. The description for these MTF diagrams is the same in the following.

  On the other hand, FIG. 5 is an MTF when a predetermined eccentricity error occurs during manufacturing. 5A shows the MTF for an image height of 5.6 mm, FIG. 5B shows the MTF for an image height of 0 mm (center), and FIG. 5C shows the MTF for an image height of −5.6 mm. . FIG. 6 shows a state in which the distance d89 between the front group G1F and the rear group G1R in the first lens group G1 is changed by −0.03 mm from the state shown in FIG. The second partial lens group G1Rb (positive meniscus lens L17) of the rear group G1R is decentered by −0.015 mm in a direction perpendicular to the optical axis, and the entire photographing lens SL1 is decentered by +0.7 ′ tilt, FIG. 10 is an MTF diagram when the distance d6 between the third lens (positive meniscus lens) L13 and the fourth lens (negative meniscus lens) L14 in the first lens group G1 is changed by +0.02 mm. As for the sign of shift eccentricity, the upward movement in FIG.

  4 to 6, the second partial lens group G1Rb (positive meniscus lens L17) in the first lens group G1 is shifted and decentered, and the distance between the front group G1F and the rear group G1R in the first lens group G1 is determined. When the position of the third lens L13 and the fourth lens L14 in the first lens group G1 is adjusted, the decentration aberration caused by the decentration error is adjusted. It can be seen that the image forming performance at the center (center) and the periphery of the image capturing screen is improved satisfactorily and the image forming performance is improved satisfactorily.

  As described above, according to the first embodiment, it is possible to realize the low-cost photographing lens SL1 that achieves good optical performance by correcting the eccentricity error generated during the manufacturing.

[Second Embodiment]
FIG. 7 is a diagram illustrating a configuration of the photographic lens SL2 according to the second example. In the photographing lens SL2 shown in FIG. 7, the front group G1F of the first lens group G1 has a positive meniscus lens (first lens) L11 having a convex surface directed toward the object side and a convex surface directed toward the object side in order from the object side. The lens includes a positive meniscus lens (second lens) L12, a positive meniscus lens (third lens) L13 having a convex surface facing the object side, and a negative meniscus lens (fourth lens) L14 having a convex surface facing the object side. . Further, the rear group G1R of the first lens group G1 is composed of a cemented lens CL1 in which, from the object side, a negative meniscus lens L15 having a concave surface facing the object side and a positive meniscus lens L16 having a concave surface facing the object side are cemented. The lens includes a first partial lens group G1Ra and a second partial lens group G1Rb including a positive meniscus lens L17 having a concave surface facing the object side. The second lens group G2 includes a cemented lens CL2 in which a biconvex lens (positive lens) L21 and a biconcave lens (negative lens) L22 are cemented in order from the object side. The aperture stop S is disposed between the front group G1F and the rear group G1R of the first lens group G1. A filter group FL including a low-pass filter and an infrared cut filter is disposed between the photographing lens SL2 and the image plane I. Further, the image plane I is imaged on an image sensor (eg, film, CCD, CMOS, etc.).

  Table 4 below shows values of specifications of the second embodiment. The surface numbers 1 to 19 shown in Table 4 correspond to the numbers 1 to 19 shown in FIG.

(Table 4)
[Overall specifications]
f = 32.0
FNo = 1.24
2ω = 25.87
Image height = 8.10
TL = 57.42

[Lens data]
Surface number Curvature radius Surface spacing nd νd
1 35.2535 4.80 1.6968 55.52
2 207.9092 0.10
3 30.5964 4.60 1.5932 67.90
4 62.5231 0.10
5 19.6000 4.70 1.8160 46.59
6 23.2000 1.00
7 50.5339 1.60 1.7552 27.57
8 11.9667 4.82
9 0.0000 4.80 Aperture stop S
10 -11.6552 1.40 1.6889 31.16
11 -297.7087 4.00 1.9027 35.73
12 -19.5086 0.10
13 -86.7505 3.40 1.7725 49.62
14 -24.9468 (d14)
15 28.9738 4.90 1.8830 40.66
16 -25.0000 1.60 1.7847 25.64
17 65.1950 (d17)
18 0.0000 2.79 1.5168 63.88
19 0.0000 2.11

[Lens focal length]
Lens group Start surface Focal length First lens group 1 55.36
Second lens group 15 42.77

  In the second embodiment, the axial air distance d14 between the first lens group G1 and the second lens group G2, the axial air distance d17 between the second lens group G2 and the filter group FL, and the back focus Bf are: It changes at the time of focusing. Table 5 below shows each group interval in the infinitely focused state, the intermediate distance focused state, and the short distance focused state. As described in the first embodiment, the axial air intervals d14 and d17 shown in Table 5 are changed by replacing the washers 45 and 46 of the position adjusting mechanism 40 with washers having different thicknesses in the optical axis direction. In Table 5, values before adjustment (before replacement) are shown.

(Table 5)
Lens condition Infinity Medium distance Short distance d14 1.20 1.40 3.41
d17 9.40 9.65 11.07
Bf 14.30 14.55 15.97

  Table 6 below shows values corresponding to the conditional expressions in the second embodiment.

(Table 6)
yG1 = −0.45
yG2 = −0.25
(1) yG2 / yG1 = 0.56

  Thus, the photographic lens SL2 according to the second example satisfies the conditional expression (1).

  Here, in the photographic lens SL2 according to the second example, the decentration error at the time of manufacture is corrected, and thereby the decentration aberration is corrected and the deterioration of the imaging performance is eliminated. The description will be given with reference.

  FIG. 8 is a diagram showing the MTF when no decentration error occurs during manufacture in the photographic lens SL2 according to the second example. FIG. 8A shows the MTF for an image height of 5.6 mm. 8 (b) shows the MTF for an image height of 0 mm (center), and FIG. 8 (c) shows the MTF for an image height of −5.6 mm.

  On the other hand, FIG. 9 shows the MTF when a predetermined eccentricity error occurs during manufacturing. 9A shows the MTF for an image height of 5.6 mm, FIG. 9B shows the MTF for an image height of 0 mm (center), and FIG. 9C shows the MTF for an image height of −5.6 mm. . FIG. 10 shows that the distance d89 between the front group G1F and the rear group G1R in the first lens group G1 is set to −0.0 from the state shown in FIG. 9 by using the same position adjustment mechanism 40 as in the first example. The second lens group G1Rb (positive meniscus lens L17) is shifted by -0.015 mm in the direction orthogonal to the optical axis, the entire taking lens SL2 is decentered by +0.7 'tilt, and the first lens group is changed by 03 mm. FIG. 14 is an MTF diagram when the distance d6 between the third lens (positive meniscus lens) L13 and the fourth lens (negative meniscus lens) L14 in G1 is changed by +0.02 mm. As for the sign of shift eccentricity, the upward movement in FIG.

  8 to 10, the second partial lens group G1b (positive meniscus lens L17) in the first lens group G1 is shifted and decentered, and the distance between the front group G1F and the rear group G1R in the first lens group G1 is set. When the position is adjusted, the entire photographing lens SL2 is tilt-adjusted, and the position of the distance between the third lens L13 and the fourth lens L14 in the first lens group G1 is adjusted, the decentration aberration caused by the decentration error is reduced. It can be seen that the imaging performance at the center (center) and the periphery of the shooting screen has been improved satisfactorily with good correction.

  As described above, according to the second embodiment, it is possible to realize a low-cost photographing lens that achieves good optical performance by correcting the eccentricity error that occurs during manufacturing.

SL (SL1, SL2) Shooting lens G1 First lens group G1F Front group L11 First lens L12 Second lens L13 Third lens L14 Fourth lens G1R Rear group G2 Second lens group S Aperture stop 1 Camera (optical device) 40 Position adjustment mechanism

Claims (10)

In order from the object side, the first lens group having a positive refractive power and a second lens group having a positive refractive power are substantially composed of two lens groups,
When focusing from a long distance object to a short distance object, the first lens group and the second lens group are aligned along the optical axis so that the distance between the first lens group and the second lens group is increased. Move and
The first lens group includes, in order from the object side, a front group having a positive refractive power and a rear group having a positive refractive power,
An imaging lens, comprising: a position adjusting mechanism that shifts and decenters at least a part of the rear group of the first lens group in a direction including a component orthogonal to an optical axis.   The photographing lens according to claim 1, wherein at least a part of the rear group that is shifted and decentered by the position adjusting mechanism is a lens closest to the image side of the rear group.   3. The photographing lens according to claim 1, wherein the first lens group and the second lens group move toward the object side along the optical axis when focusing from a long distance object to a short distance object. 4. . The photographic lens according to any one of claims 1 to 3, wherein a condition of the following formula is satisfied.
0.30 <yG2 / yG1 <0.80
However,
yG1: represents the amount of movement of the first lens unit on the optical axis when focusing from infinity to a photographing magnification of -0.01 times, and a negative value when moving to the object side. yG2: photographing magnification from infinity This represents the amount of movement of the second lens group on the optical axis when focusing on -0.01 times, and a negative value when moving to the object side   5. The photographic lens according to claim 1, wherein the position adjusting mechanism changes an air gap between the front group and the rear group of the first lens group.   The photographic lens according to claim 1, wherein the position adjustment mechanism tilts the entire system with respect to a mounting surface or an imaging surface. The front group of the first lens group includes, in order from the object side, a first lens having a positive refractive power, a second lens having a positive refractive power, a third lens having a positive refractive power, and a negative refractive power. A fourth lens having
The photographic lens according to claim 1, wherein the position adjustment mechanism changes an air gap between the third lens and the fourth lens.   The photographic lens according to claim 1, further comprising an aperture stop in the first lens group.   An optical apparatus comprising the photographing lens according to claim 1. In order from the object side, there is provided a method for adjusting a photographic lens substantially consisting of two lens groups, a first lens group having a positive refractive power and a second lens group having a positive refractive power,
When focusing from a long distance object to a short distance object, the first lens group and the second lens group are aligned along the optical axis so that the distance between the first lens group and the second lens group is increased. Move and
The first lens group includes, in order from the object side, a front group having a positive refractive power and a rear group having a positive refractive power, and at least a part of the rear group of the first lens group has an optical axis. A method for adjusting a photographic lens, characterized in that the lens is shifted decentered in a direction including a component orthogonal to.

Images