JP5542374B2 - Inner focus type macro lens with anti-vibration function - Google Patents

Description

The present invention is an inner focus type macro lens, characterized in that it can shoot from an object at infinity to an object at a near distance close to the same magnification, and is further anti-vibration for correcting a shift in imaging position due to camera shake or the like. The present invention relates to an inner focus type macro lens having an anti-vibration function particularly suitable for digital cameras, silver halide cameras, video cameras, and the like.

2. Description of the Related Art Conventionally, in an optical device such as a photographic camera or a video camera, there are some which are classified as a macro lens or a micro lens (hereinafter referred to as “macro lens”) as a photographing lens mainly for photographing a short distance object.

Among these, in the so-called telephoto macro lens having an object-side incident angle of view of about 12 to 25 degrees suitable for a single-lens reflex camera for 35 mm film, the most object-side lens group is arranged in the optical axis direction during the focusing operation. There has been proposed one that is fixed without moving and has an anti-vibration function.

For example, in Patent Document 1 and Patent Document 2, the most image side lens group fixed in the optical axis direction is divided, and the negative lens group is moved in a direction substantially perpendicular to the optical axis. A macro lens that corrects image blur is described.

Further, for example, in Patent Document 3, the most object side lens group fixed in the optical axis direction is divided into a first A lens group and a first B lens group in order from at least the object to the image side. A macro lens that corrects image blur by moving the 1B lens group in a direction substantially perpendicular to the optical axis is described.

JP2003-329919A

JP 2006-106112 A

JP2005-062211

Generally, it is desirable that the amount of movement for moving the image stabilizing lens group for correcting image blur in the direction perpendicular to the optical axis is sufficiently small. That is, it is preferable that the maximum amount of movement of the image stabilizing lens unit be as small as possible in consideration of quick correction of image blur and limitation of the movable range of the image stabilizing lens unit.

Therefore, in order to reduce the movement amount of the image stabilizing lens group, it is desirable to set a so-called image stabilization coefficient sufficiently large. The image stabilization coefficient is a ratio between the amount of movement ΔH when the image stabilization lens group is moved in the direction perpendicular to the optical axis and the amount of movement Δx of the image formation position on the image plane, that is, Δx / ΔH. Indicates.

When focusing on an object at infinity, an optical system with a longer focal length has a larger image plane compared to an optical system with a shorter focal length, even if the same amount of camera shake occurs. Therefore, the image stabilization position needs to be set larger.

In the optical systems disclosed in Patent Literature 1 and Patent Literature 2 described above, the image stabilization coefficient is about 1.0, and application to a macro lens having a longer focal length is difficult. In addition, in the optical systems disclosed in Patent Document 1 and Patent Document 2 described above, since large astigmatism occurs during image stabilization, the optical characteristics when image blur is corrected are deteriorated.

Further, in the optical system disclosed in Patent Document 3 above, the problem of aberration that occurs during image stabilization is solved, but the value of the image stabilization coefficient is not sufficiently large, and during image stabilization. Since the anti-vibration lens group to be moved is arranged in the lens group closest to the object side, the weight of the anti-vibration lens group increases, which is not preferable in terms of mechanical mechanism. In addition, in the optical system disclosed in Patent Document 3 described above, a large on-axis chromatic aberration, curvature of the image surface, and astigmatism are generated particularly when focusing on an object at infinity, so that the optical characteristics deteriorate. ing.

The present invention makes it possible to correct a large amount of image blur with a small amount of movement of the anti-vibration lens group at the time of anti-vibration after correcting various aberrations over the entire in-focus region. An object of the present invention is to provide an inner focus type macro lens having an anti-vibration function capable of maintaining the performance.

In order from the object side, a first lens unit L1 having a positive refractive power, a second lens unit L2 having a negative refractive power, a third lens unit L3 having a positive refractive power, and a fourth lens having a negative refractive power A group L4, and at the time of focusing from an object at infinity to an object at a short distance, at least the second lens group L2 is moved to the image plane side and at the same time the third lens group L3 is moved to the object side, In addition, the distance on the optical axis between the first lens group L1 and the second lens group L2 is increased, and the distance on the optical axis between the second lens group L2 and the third lens group L3 is simultaneously reduced. At the same time, the distance on the optical axis between the third lens unit L3 and the fourth lens unit L4 is increased, and short-distance shooting is possible at any magnification from infinity to equal magnification, and the fourth lens unit L4. Are, in order from the object side, the front group L4a having a negative refractive power, and a positive The fourth lens unit front unit L4a includes at least one lens having a positive refractive power and one lens having a negative refractive power, and is configured to vibrate when the optical system vibrates. Moving the front group L4a in a direction substantially perpendicular to the optical axis to correct image blur;
An optical system satisfying the following conditional expression:
0.15 <| f4a / f | <0.4 (1)
0.3 <f4b / f <0.8 (2)
0.2 <| ΔS3 / ΔS2 | <1.0 (3)
However,
f4a is the focal length f4b of the fourth group front group L4a is the focal length f of the fourth group rear group L4b is the focal length ΔS2 of the entire optical system when focusing on an object at infinity. The amount of movement ΔS3 of the second lens unit L2 when focusing on the object is the amount of movement of the third lens unit L3 when focusing from an object at infinity to an object at a short distance.

The second invention of the present application is characterized in that the first lens unit L1 and the fourth lens unit L4 are fixed in the optical axis direction when focusing from an object at infinity to an object at a short distance. An inner focus type macro lens having the image stabilization function of the first invention is provided.

According to a third aspect of the present invention, there is provided an inner focus type macro lens having an image stabilization function according to the first aspect or the second aspect of the invention, wherein the following conditional expression is satisfied.
(4) 0 <f / R4ar-f / R4bf <2.0
However,
R4ar is the radius of curvature R4bf of the lens surface closest to the image plane of the 4a lens unit L4a, and the radius of curvature f of the lens surface closest to the object side of the 4b lens unit L4b is the optical system when focusing on an object at infinity. Focal length of the entire system

Further, the present invention preferably satisfies the following conditional expression.
(4a) 0 <f / R4ar-f / R4bf <1.0
However,
R4ar is the radius of curvature R4bf of the lens surface closest to the image plane of the 4a lens unit L4a, and the radius of curvature f of the lens surface closest to the object side of the 4b lens unit L4b is the optical system when focusing on an object at infinity. Focal length of the entire system

Further, the present invention preferably satisfies the following conditional expression.
(5) 0.4 <f1 / f <0.6
(6) 0.3 <| f2 / f | <0.4
(7) 0.2 <f3 / f <0.5
(8) 0.3 <| f4 / f | <0.7
However,
f1 is the focal length f2 of the first lens unit L1, the focal length f3 of the second lens unit L2, the focal length f4 of the third lens unit L3, and the focal length f of the fourth lens unit L4 is an infinite object. Focal length of the entire optical system when focused

Further, the present invention preferably satisfies the following conditional expression.
(9) 1.5 <(Δx / ΔH) <2.5
However,
ΔH is a moving amount Δx in the direction perpendicular to the optical axis of the 4a lens group L4a, and Δx is an imaging position on the image plane corresponding to the moving amount ΔH in the direction perpendicular to the optical axis of the fourth a lens group L4a. Amount of movement

Furthermore, in the present invention, it is preferable that the aperture diameter of the aperture stop changes during focusing from an object at infinity to a near object. This is because the marginal ray height is lowered when focusing on an object at a short distance compared to when focusing on an object at infinity.

The aperture stop is structurally disposed between the second lens unit L2 and the third lens unit L3 or between the third lens unit L3 and the fourth lens unit L4, and is an object at infinity. It is preferable to be fixed with respect to the image plane at the time of focusing on a short-distance object. By fixing the aperture stop at the time of focusing, it is not necessary to move the mechanism for changing the aperture of the open aperture at the time of focusing, and quick focusing can be performed.

According to the present invention, various aberrations are corrected well in an in-focus range from an object at infinity to a close object near the same magnification, and at the time of image stabilization, a sufficiently large image blur is caused by a small movement amount of the image stabilization lens unit. It is possible to provide an inner focus type macro lens having an anti-vibration function capable of correcting and maintaining good imaging performance.

FIG. 1 is a lens configuration diagram of Example 1 of the present invention. Longitudinal aberration diagram at the time of focusing on an object at infinity according to Example 1 of the present invention Longitudinal aberration diagram at the time of focusing on a short distance object (1.0 ×) in Example 1 of the present invention FIG. 6 is a lateral aberration diagram when focusing on an object at infinity according to Example 1 of the present invention, and a lateral aberration diagram when focusing on an object at infinity during image stabilization. FIG. 6 is a lateral aberration diagram when focusing on a short-distance object (1.0 times) and a lateral aberration diagram when focusing on a short-distance object (1.0 times) during image stabilization. FIG. 6 is a lens configuration diagram of Example 2 of the present invention. Longitudinal aberration diagram when focusing on an object at infinity according to Example 2 of the present invention Longitudinal aberration diagram at the time of focusing on a short distance object (1.0 ×) in Example 2 of the present invention Lateral aberration diagram when focusing on an object at infinity according to Example 2 of the present invention and lateral aberration diagram when focusing on an object at infinity during image stabilization Lateral aberration diagram at the time of focusing on a short distance object (1.0 times) and lateral aberration diagram at the time of focusing on a short distance object (1.0 times) of the image stabilization according to the second embodiment of the present invention Lens configuration diagram of Embodiment 3 of the present invention Longitudinal aberration diagram of Example 3 of the present invention when focusing on an object at infinity Longitudinal aberration diagram at the time of focusing on a short distance object (1.0 ×) in Example 3 of the present invention Lateral aberration diagram when focusing on an object at infinity according to Example 3 of the present invention and lateral aberration diagram when focusing on an object at infinity during image stabilization Lateral aberration diagram at the time of focusing on a short distance object (1.0 times) and lateral aberration diagram at the time of focusing on a short distance object (1.0 times) in the image stabilization according to Embodiment 3 of the present invention Lens configuration diagram of Embodiment 4 of the present invention Longitudinal aberration diagram of Example 4 of the present invention when focusing on an object at infinity Longitudinal aberration diagram at the time of focusing on a short distance object (1.0 ×) in Example 4 of the present invention Lateral aberration diagram when focusing on an object at infinity according to Example 4 of the present invention and lateral aberration diagram when focusing on an object at infinity during image stabilization Lateral aberration diagram at the time of focusing on a short distance object (1.0 times) and lateral aberration diagram at the time of focusing on a short distance object (1.0 times) in the image stabilization of Example 4 of the present invention Lens configuration diagram of Embodiment 5 of the present invention Longitudinal aberration diagram at the time of focusing on an object at infinity according to Example 5 of the present invention Longitudinal aberration diagram at the time of focusing on a short distance object (1.0 ×) in Example 5 of the present invention Lateral aberration diagram when focusing on an object at infinity according to Example 5 of the present invention and lateral aberration diagram when focusing on an object at infinity during image stabilization Lateral aberration diagram at the time of focusing on a short distance object (1.0 times) and lateral aberration diagram at the time of focusing on a short distance object (1.0 times) in the image stabilization according to Embodiment 5 of the present invention Lens configuration diagram of Embodiment 6 of the present invention Longitudinal aberration diagram of Example 6 of the present invention when focusing on an object at infinity Longitudinal aberration diagram at the time of focusing on a short distance object (1.0 ×) in Example 6 of the present invention Lateral aberration diagram when focusing on an object at infinity according to Example 6 of the present invention and lateral aberration diagram when focusing on an object at infinity during image stabilization Lateral aberration diagram at the time of focusing on a short distance object (1.0 times) and lateral aberration diagram at the time of focusing on a short distance object (1.0 times) in the image stabilization according to Embodiment 6 of the present invention

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIGS. 1A and 1B are lens configuration diagrams of Example 1 according to the present invention, in which FIG. 1A shows a focused state with respect to an object at infinity, and FIG. Yes.

2 is a longitudinal aberration diagram when focusing on an object at infinity according to Example 1 of the present invention, and FIG. 3 is when focusing on a short distance object (1.0 ×) according to Example 1 of the present invention. FIG.

FIG. 4 is a transverse aberration diagram when focusing on an object at infinity according to Example 1 of the present invention. FIG. 4A is a transverse aberration curve from a real image height of 0.0 mm to 21.63 mm at the time of non-vibration prevention. b) shows a real image height of 0.0 mm and 15 mm when the 4a lens unit L4a is moved by 0.6 mm in the direction perpendicular to the optical axis during image stabilization and the image forming position is moved by an angle corresponding to an angle of view of 0.37 degrees. The lateral aberration curves of .141 mm and -15.141 mm are shown.

FIG. 5 is a lateral aberration diagram when focusing on a short-distance object (1.0 ×) according to Example 1 of the present invention. FIG. The lateral aberration curve, (b) shows the real image height when the 4a lens unit L4a is moved by 0.6 mm in the direction perpendicular to the optical axis and the imaging position is moved by an angle of view equivalent to 0.37 degrees during image stabilization. The lateral aberration curves of 0.0 mm, 15.141 mm, and -15.141 mm are shown.

FIGS. 6A and 6B are lens configuration diagrams of Example 2 according to the present invention, in which FIG. 6A shows a focused state with respect to an object at infinity, and FIG. Yes.

FIG. 7 is a longitudinal aberration diagram when focusing on an object at infinity according to Example 2 of the present invention, and FIG. 8 is when focusing at a short distance object (1.0 times) according to Example 2 of the present invention. FIG.

FIG. 9 is a transverse aberration diagram when focusing on an object at infinity according to Example 2 of the present invention. FIG. 9A is a transverse aberration curve from a real image height of 0.0 mm to 21.63 mm when non-vibration-proof, b) shows a real image height of 0.0 mm and 15 mm when the 4a lens unit L4a is moved by 0.6 mm in the direction perpendicular to the optical axis during image stabilization and the image forming position is moved by an angle corresponding to an angle of view of 0.37 degrees. The lateral aberration curves of .141 mm and -15.141 mm are shown.

FIG. 10 is a transverse aberration diagram when focusing on a short-distance object (1.0 ×) according to Example 2 of the present invention. FIG. The lateral aberration curve, (b) shows the real image height when the 4a lens unit L4a is moved by 0.6 mm in the direction perpendicular to the optical axis and the imaging position is moved by an angle of view equivalent to 0.37 degrees during image stabilization. The lateral aberration curves of 0.0 mm, 15.141 mm, and -15.141 mm are shown.

FIG. 11 is a lens configuration diagram of Example 3 according to the present invention, where (a) shows a focused state with respect to an object at infinity, and (b) shows a focused state with respect to a short-range object (1.0 times). Yes.

FIG. 12 is a longitudinal aberration diagram when focusing on an object at infinity according to Example 3 of the present invention, and FIG. 13 is when focusing on a short-distance object (1.0 ×) according to Example 3 according to the present invention. FIG.

FIG. 14 is a lateral aberration diagram when focusing on an object at infinity according to Example 3 of the present invention. FIG. 14A is a lateral aberration curve from a real image height of 0.0 mm to 21.63 mm when non-vibration-proof. b) shows a real image height of 0.0 mm and 15 mm when the 4a lens unit L4a is moved by 0.6 mm in the direction perpendicular to the optical axis during image stabilization and the image forming position is moved by an angle corresponding to an angle of view of 0.37 degrees. The lateral aberration curves of .141 mm and -15.141 mm are shown.

FIG. 15 is a lateral aberration diagram when focusing on a short-distance object (1.0 ×) in Example 3 according to the present invention, and FIG. The lateral aberration curve, (b) shows the real image height when the 4a lens unit L4a is moved by 0.6 mm in the direction perpendicular to the optical axis and the imaging position is moved by an angle of view equivalent to 0.37 degrees during image stabilization. The lateral aberration curves of 0.0 mm, 15.141 mm, and -15.141 mm are shown.

FIG. 16 is a lens configuration diagram of Example 4 according to the present invention, where (a) shows a focused state with respect to an object at infinity, and (b) shows a focused state with respect to a close object (1.0 times). Yes.

FIG. 17 is a longitudinal aberration diagram when focusing on an object at infinity according to Example 4 of the present invention, and FIG. 18 is when focusing on a short distance object (1.0 ×) according to Example 4 of the present invention. FIG.

FIG. 19 is a lateral aberration diagram when focusing on an object at infinity according to Example 4 of the present invention. FIG. 19A is a lateral aberration curve from a real image height of 0.0 mm to 21.63 mm when non-vibration-proof. b) shows a real image height of 0.0 mm and 15 mm when the 4a lens unit L4a is moved by 0.4 mm in the direction perpendicular to the optical axis and the imaging position is moved by an angle corresponding to an angle of view of 0.37 degrees during image stabilization. The lateral aberration curves of .141 mm and -15.141 mm are shown.

FIG. 20 is a lateral aberration diagram when focusing on a short-distance object (1.0 ×) in Example 4 according to the present invention. FIG. The lateral aberration curve, (b) shows the real image height when the 4a lens unit L4a is moved by 0.4 mm in the direction perpendicular to the optical axis and the image forming position is moved by an angle corresponding to 0.37 degrees in view of vibration. The lateral aberration curves of 0.0 mm, 15.141 mm, and -15.141 mm are shown.

FIGS. 21A and 21B are lens configuration diagrams of Example 5 according to the present invention, in which FIG. Yes.

FIG. 22 is a longitudinal aberration diagram when focusing on an object at infinity according to Example 5 of the present invention, and FIG. 23 is when focusing on a short distance object (1.0 times) according to Example 5 of the present invention. FIG.

FIG. 24 is a lateral aberration diagram when focusing on an object at infinity according to Example 5 of the present invention. FIG. 24A is a lateral aberration curve from a real image height of 0.0 mm to 21.63 mm when non-vibration is corrected. b) shows a real image height of 0.0 mm and 15 mm when the 4a lens unit L4a is moved by 0.5 mm in the direction perpendicular to the optical axis and the image forming position is moved by an angle corresponding to an angle of view of 0.36 degrees. The lateral aberration curves of .141 mm and -15.141 mm are shown.

FIG. 25 is a lateral aberration diagram when focusing on a short-distance object (1.0 ×) according to Example 5 of the present invention. FIG. The lateral aberration curve, (b) shows the real image height when the 4a lens unit L4a is moved by 0.5 mm in the direction perpendicular to the optical axis and the imaging position is moved by an angle of view equivalent to 0.36 degrees during image stabilization. The lateral aberration curves of 0.0 mm, 15.141 mm, and -15.141 mm are shown.

FIG. 26 is a lens configuration diagram of Example 6 according to the present invention, where (a) shows a focused state with respect to an object at infinity, and (b) shows a focused state with respect to a short-range object (1.0 times). Yes.

27 is a longitudinal aberration diagram when focusing on an object at infinity according to Example 6 of the present invention. FIG. 28 is when focusing on a short distance object (1.0 ×) according to Example 6 of the present invention. FIG.

FIG. 29 is a lateral aberration diagram when focusing on an object at infinity according to Example 6 of the present invention. FIG. 29A is a lateral aberration curve from a real image height of 0.0 mm to 21.63 mm at the time of non-vibration prevention. b) shows a real image height of 0.0 mm and 15 mm when the 4a lens unit L4a is moved by 0.6 mm in the direction perpendicular to the optical axis and the image forming position is moved by an angle of view equivalent to 0.32 degrees during image stabilization. The lateral aberration curves of .141 mm and -15.141 mm are shown.

FIG. 30 is a lateral aberration diagram when focusing on a short-distance object (1.0 ×) in Example 6 according to the present invention. FIG. The horizontal aberration curve, (b) shows the actual image height when the 4a lens unit L4a is moved by 0.6 mm in the direction perpendicular to the optical axis and the imaging position is moved by an angle of view equivalent to 0.32 degrees during image stabilization. The lateral aberration curves of 0.0 mm, 15.141 mm, and -15.141 mm are shown.

Next, the technical meaning of each conditional expression will be described.

Conditional expression (1) defines the focal length of the 4a lens unit L4a as the image stabilizing lens unit, and ensures sufficient image stabilizing coefficient of the image stabilizing lens unit and corrects the aberration during image stabilization. It is for making it compatible.

If the lower limit of conditional expression (1) is exceeded and the focal length of the 4a lens unit L4a is shortened, aberrations caused by the movement of the 4a lens unit L4a in the direction perpendicular to the optical axis, particularly non- Correction of point aberration becomes difficult. If the focal length of the 4a lens unit L4a is increased by exceeding the upper limit value of the conditional expression (1), it is advantageous for aberration correction, but the diameter of the lens unit closest to the image plane is kept small. However, it is difficult to obtain a sufficient anti-vibration coefficient for the anti-vibration lens group.

Conditional expression (2) defines the focal length of the 4b lens unit L4b, and is for ensuring both a sufficient anti-vibration coefficient of the anti-vibration lens unit and correction of aberrations during image stabilization. .

If the lower limit of conditional expression (2) is exceeded and the focal length of the 4b lens unit L4b is shortened, it is difficult to give sufficient refractive power to the lens unit that moves during focusing while ensuring the back focus. Become. If the upper limit of conditional expression (2) is exceeded and the focal length of the 4b lens group L4b is increased, sufficient anti-vibration lens group protection is ensured while ensuring the distance between the 4a lens group L4a and the 4b lens group L4b. It becomes difficult to obtain a vibration coefficient.

Conditional expression (3) relates to the ratio between the amount of movement of the second lens unit L2 and the amount of movement of the third lens unit L3 during focusing.

When the lower limit value of conditional expression (3) is exceeded and the ratio of the moving amount of the third lens unit L3 to the moving amount of the second lens unit L2 becomes small, the unit movement of the third lens unit L3 with respect to the second lens unit L2 The amount of aberration generated per unit amount becomes excessive, making it difficult to correct good aberrations in the entire in-focus region, particularly to correct axial chromatic aberration and coma aberration, and the third lens unit L3 and the fourth lens unit L4a. It is difficult to secure the interval. If the upper limit of conditional expression (3) is exceeded and the ratio of the movement amount of the third lens group L3 to the movement amount of the second lens group L2 increases, the refractive power of the third lens group L3 with respect to the entire lens decreases. , it is difficult to obtain a sufficient vibration reduction coefficient of the vibration reduction lens group.

Conditional expression (4) defines the difference between the radius of curvature of the lens surface closest to the image plane of the 4a lens unit L4a and the radius of curvature of the lens surface closest to the object side of the 4b lens unit L4b. .

When the lower limit of conditional expression (4) is exceeded and the ratio of R4bf to R4ar becomes small, the lens diameter closest to the image plane is suppressed, and the distance between the third lens unit L3 and the fourth lens unit L4a is secured. It becomes difficult to obtain a sufficient anti-vibration coefficient for the anti-vibration lens group. Further, when the ratio of R4bf to R4ar increases when the upper limit is exceeded, large coma and astigmatism generated on the lens surface closest to the image plane of the 4a lens unit L4a are reduced to the most object side of the 4b lens unit L4b. The action of canceling with the lens surface will be lost.

In addition, when an aspheric surface is not used for any arbitrary surface of the fourth lens unit L4, correction of coma and astigmatism is not easy, so the upper limit range of conditional expression (4) is further increased. It is preferable to be regulated within the range of conditional expression (4a).

Conditional expression (5) defines the focal length of the first lens unit L1, and is intended to achieve both a reduction in lens size and good aberration correction.

When the lower limit value of conditional expression (5) is exceeded and the focal length of the first lens unit L1 is shortened, axial chromatic aberration and coma aberration are corrected well over the entire focus range from an infinitely distant object to a close object near the same magnification. It becomes difficult. If the upper limit of conditional expression (5) is exceeded and the focal length of the first lens unit L1 is increased, this is advantageous for aberration correction, but the total length of the lens system and the maximum diameter of the aperture stop are increased. End up.

Conditional expression (6) defines the focal length of the second lens unit L2, and is intended to achieve both reduction in the size of the lens system and good aberration correction.

When the lower limit of conditional expression (6) is exceeded and the focal length of the second lens unit L2 is shortened, various aberrations fluctuate greatly depending on the object distance to be focused, and coma aberration is reduced from an object at infinity to a near-distance object near the same magnification. It becomes difficult to correct well over the entire focusing range. When the upper limit of conditional expression (6) is exceeded and the focal length of the second lens unit L2 is increased, the amount of movement of the focus lens unit to ensure a constant shooting magnification increases, and the total length of the lens system increases. turn into.

Conditional expression (7) defines the focal length of the third lens unit L3, and is intended to achieve both a reduction in the size of the lens system and good aberration correction.

When the lower limit of conditional expression (7) is exceeded and the focal length of the third lens unit L3 is shortened, various aberrations including coma become large, and in addition, the third lens unit L3 and the fourth lens unit L4. It is difficult to ensure the interval. If the upper limit of conditional expression (7) is exceeded and the focal length of the third lens unit L3 is increased, the amount of movement of the focus lens unit to ensure a constant shooting magnification increases, and the total length of the lens system increases. turn into.

Conditional expression (8) defines the focal length of the fourth lens unit L4, and is for ensuring both a sufficient anti-vibration coefficient of the anti-vibration lens unit and correction of aberrations during image stabilization. is there.

When the lower limit value of conditional expression (8) is exceeded and the focal length of the fourth lens unit L4 is shortened, it becomes difficult to reduce the maximum diameter of the aperture stop while suppressing the refractive power of the third lens unit L3. If the upper limit of conditional expression (8) is exceeded and the focal length of the fourth lens unit L4 is increased, it is advantageous for aberration correction, but the image stabilizing lens is suppressed while suppressing the diameter of the lens closest to the image plane. It becomes difficult to obtain a sufficient anti-vibration coefficient for the group.

Conditional expression (9) defines the image stabilization coefficient of the image stabilization lens group.

If the lower limit of conditional expression (9) is exceeded and the image stabilization coefficient of the image stabilization lens unit becomes small, correction of aberrations caused by movement in the direction perpendicular to the optical axis of the 4a lens unit L4a becomes easy. This is not preferable because the amount of movement of the 4a lens unit L4a necessary for correcting image blur increases and the drive mechanism of the image stabilizing lens unit increases. If the upper limit of conditional expression (9) is exceeded and the image stabilization coefficient of the image stabilization lens unit becomes large, it becomes difficult to correct aberrations that occur due to the movement of the 4a lens unit L4a in the direction perpendicular to the optical axis.

In each embodiment, it is preferable to further set the numerical range of conditional expression (3) as follows.
(3a) 0.25 <| ΔS3 / ΔS2 | <0.7

Hereinafter, Numerical Example 1 to Numerical Example 6 of the present invention will be described.

In each numerical example, f in [general specifications] represents a focal length, Fno represents an F number, and 2ω represents an angle of view (unit: degree). In the [lens specifications], the number N in the first row is the surface number of the lens surface counted from the object side, the second row R is the radius of curvature of the lens surface, the third row D is the lens surface spacing, and the fourth row. nd represents the refractive index with respect to the d-line (wavelength λ = 587.6 nm), and the fifth column νd represents the Abbe number with respect to the d-line (wavelength λ = 587.6 nm). R = 0.0000 represents a plane, Bf represents back focus, “aperture” represents a diaphragm surface, “flare cut diaphragm” represents a flare cut diaphragm surface, “*” represents an aspheric surface, and air refraction. The description of the rate nd = 1.0000 is omitted. [Variable interval] indicates a variable interval for each shooting distance .

Further, d-line, g-line, and C-line in the figure are aberrations with respect to the respective wavelengths, ΔS represents a sagittal image plane, and ΔM represents a meridional image plane.

[Aspheric coefficient] represents an aspheric coefficient when the aspheric shape of the lens surface with the surface number N is expressed by the following equation.

Here, z indicates the amount of deviation in the optical axis direction at the position of the height y from the optical axis with respect to the vertex of the lens surface, K indicates the conic coefficient, and A4, A6, A8, and A10 are An aspheric coefficient is indicated, and r indicates a radius of curvature of the reference sphere. Further, “E-n” indicates “× 10 ⁻ⁿ ”, for example “−4.7168E-06” indicates “−4.7168 × 10 ⁻⁶ ”.

Hereinafter, in all the numerical examples, “mm” is used unless otherwise specified for the focal length, the radius of curvature, the lens surface interval, and other length units that are described, but the optical system is proportional. The unit is not limited to “mm” because the same optical performance can be obtained even when the magnification is enlarged or proportionally reduced.

(Numerical example 1)

(Numerical example 2)

(Numerical Example 3)

(Numerical example 4)

(Numerical example 5)

(Numerical example 6)

L1 1st lens group L2 2nd lens group L3 3rd lens group L4 4th lens group L4a 4a lens group L4b of the front group which constitutes the 4th lens group 4b lens group of the back group which constitutes the 4th lens group S aperture stop I image plane d d line C C line g g line Fno F number ΔS sagittal image plane ΔM meridional image plane Y image height

Claims (3)

In order from the object side, a first lens unit L1 having a positive refractive power, a second lens unit L2 having a negative refractive power, a third lens unit L3 having a positive refractive power, and a fourth lens having a negative refractive power Consisting of group L4,
At the time of focusing from an object at infinity to an object at a short distance, at least the second lens unit L2 is moved to the image side, and at the same time, the third lens unit L3 is moved to the object side, and the first lens The distance on the optical axis between the group L1 and the second lens group L2 is increased, and at the same time, the distance on the optical axis between the second lens group L2 and the third lens group L3 is reduced, and at the same time, the third lens group. The distance on the optical axis between L3 and the fourth lens unit L4 is increased,
Close-up photography is possible at any magnification from infinity to 1x ,
The fourth lens group L4 includes, in order from the object side, a front group L4a having a negative refractive power and a rear group L4b having a positive refractive power, and the fourth lens group front group L4a is at least positively refracted. Each lens has a power lens and a lens having a negative refractive power. When the optical system vibrates, the front group L4a is moved in a direction substantially perpendicular to the optical axis to correct image blurring. ,
An optical system satisfying the following conditional expression:
0.15 <| f4a / f | <0.4 (1)
0.3 <f4b / f <0.8 (2)
0.2 <| ΔS3 / ΔS2 | <1.0 (3)
However,
f4a is the focal length f4b of the fourth group front group L4a is the focal length f of the fourth group rear group L4b is the focal length ΔS2 of the entire optical system when focusing on an object at infinity. The amount of movement ΔS3 of the second lens unit L2 when focusing on the object is the amount of movement of the third lens unit L3 when focusing from an object at infinity to an object at a short distance. 2. The image stabilization function according to claim 1, wherein the first lens unit L <b> 1 and the fourth lens unit L <b> 4 are fixed in the optical axis direction when focusing from an object at infinity to an object at a short distance. Inner focus type macro lens. The inner focus type macro lens having an image stabilization function according to claim 1, wherein the following conditional expression is satisfied.
(4) 0 <f / R4ar-f / R4bf <2.0
However,
R4ar is the radius of curvature R4bf of the lens surface closest to the image plane of the 4a lens unit L4a, and the radius of curvature f of the lens surface closest to the object side of the 4b lens unit L4b is the optical system when focusing on an object at infinity. Focal length of the entire system

Images