JP5542375B2 - 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.

Furthermore, in the optical systems disclosed in the above-mentioned Patent Documents to Patent Documents 3, large lateral chromatic aberration and coma aberration are generated when focusing on a short distance object.

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 to solve the above-described problem, the first invention of the present application includes, 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, and a positive refractive power. And a fourth lens unit L4 having negative refractive power, and at least the third lens unit L3 is moved to the object side when focusing from an infinite object to a close object. At the same time, the second lens unit L2 is moved in an arbitrary direction on the optical axis, and the distance on the optical axis between the first lens unit L1 and the second lens unit L2 is changed, and at the same time, the second lens unit L2 is changed. The distance on the optical axis between the lens group L2 and the third lens group L3 is reduced, and at the same time, the distance on the optical axis between the third lens group L3 and the fourth lens group L4 is increased from infinity to the same magnification. a possible close object at any magnification of the fourth lens group 4 includes a front group 4a lens unit L4a having a negative refractive power and a rear group 4b lens unit L4b having a positive refractive power in order from the object side, and the optical system is vibrated. An inner focus type macro lens having an anti-shake function characterized in that image blur correction is performed by moving the fourth lens group L4a in a direction substantially perpendicular to the optical axis, and satisfies the following conditional expression: provide.
(1) 2.0 <(Δx / ΔH)
(2) −2.0 <β2mod <−0.2
However,
ΔH is the amount of movement of the 4a lens unit L4a in the direction perpendicular to the optical axis Δx is the amount of movement of the image formation position on the image plane when the 4a lens unit L4a is moved ΔH in the direction perpendicular to the optical axis β2mod is the imaging magnification of the second lens unit L2 when focused on the object at the shortest distance

In the second invention of the present application, the first lens unit L1 and the fourth lens unit L4 are fixed in the optical axis direction with respect to the image plane when focusing from an infinitely distant object to a close object. An inner focus type macro lens having a vibration isolating function according to the first aspect of the present 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: To do.
(3) 0.0 <(f / R2r-f / R3f) <1.0
(4) -1.0 <(f / R4ar-f / R4bf) <0.0
However,
R2r is the radius of curvature R3f of the lens surface closest to the image plane of the second lens unit L2, and R4ar is the radius of curvature R4ar of the lens surface closest to the object side of the third lens unit L3 is closest to the image plane of the fourth lens unit L4a. The radius of curvature R4bf of the lens surface is the radius of curvature f of the lens surface closest to the object side of the 4b lens unit L4b, and the focal length of the entire optical system when focusing on an object at infinity.

Further, the present invention preferably satisfies the following conditional expression.
(5) 0.5 <f1 / f <1.0
(6) 0.35 <| f2 / f | <0.7
(7) 0.25 <f3 / f <0.5
(8) 0.4 <| f4 / f | <0.8
(9) 0.1 <| f4a / f | <0.25
(10) 0.15 <f4b / f <0.5
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 f4a of the fourth lens unit L4 is the fourth lens. The focal length f4b of the group L4a is the focal length f of the fourth lens group L4b. The focal length of the entire optical system when focusing on an object at infinity.

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 preferably disposed between the third lens unit L3 and the fourth lens unit L4 or between the second lens unit L2 and the third lens unit L3 because of the structure. .

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

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 when the 4a lens unit L4a is moved by 0.35 mm in the direction perpendicular to the optical axis and the image forming position is moved by an angle of view equivalent to 0.36 degrees during image stabilization. The lateral aberration curves of .141 mm and -15.141 mm are shown.

FIG. 5 is a transverse aberration diagram when focusing on a short-distance object (1.0 ×) according to Example 1 of the present invention. FIG. 5A shows a real image height of 0.0 mm to 21.63 mm at the time of non-vibration prevention. The lateral aberration curve, (b) shows the real image height when the 4a lens unit L4a is moved by 0.35 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.

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 0.25 mm in the direction perpendicular to the optical axis and the image forming position is moved by an angle of view equivalent to 0.31 degrees during image stabilization. The lateral aberration curves of .141 mm and -15.141 mm are shown.

FIG. 10 is a lateral aberration diagram when focusing on a short-distance object (1.0 ×) according to Example 2 of the present invention. FIG. 10 (a) shows a real image height of 0.0 mm to 21.63 mm at the time of non-vibration prevention. The lateral aberration curve, (b) shows the real image height when the 4a lens unit L4a is moved 0.25 mm in the direction perpendicular to the optical axis and the imaging position is moved by an angle of view equivalent to 0.31 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 0.25 mm in the direction perpendicular to the optical axis and the image forming position is moved by an angle of view equivalent to 0.31 degrees during image stabilization. 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. 15A is a diagram illustrating a real image height of 0.0 mm to 21.63 mm at the time of non-vibration prevention. The lateral aberration curve, (b) shows the real image height when the 4a lens unit L4a is moved 0.25 mm in the direction perpendicular to the optical axis and the imaging position is moved by an angle of view equivalent to 0.31 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 image stabilization coefficient of the image stabilization lens group. The image stabilization coefficient is a numerical value obtained by dividing the amount of movement of the imaging position on the image plane caused by camera shake or the like by the amount of movement of the image stabilizing lens group to be moved for image stabilization.

When the lower limit of conditional expression (1) is exceeded and the image stabilization coefficient of the image stabilization lens group becomes smaller, the amount of movement of the 4a lens group L4a necessary for correcting camera shake increases, and the image stabilization lens group drive mechanism Since it enlarges, it is not preferable.

Conditional expression (2) defines the imaging magnification of the second lens unit L2 when focusing on the object at the shortest distance.

If the upper limit of conditional expression (2) is exceeded and the imaging magnification of the second lens unit L2 increases, various aberrations such as coma aberration in the third lens unit L3 while suppressing the overall length of the lens system and the maximum diameter of the open stop. It becomes difficult to perform correction. If the lower limit of conditional expression (2) is exceeded and the imaging magnification of the second lens unit L2 is reduced, the lower values in the second lens unit L2 and the third lens unit L3 when the object at the shortest distance is in focus are obtained. The distance from the optical axis of the light beam is shortened, and it becomes difficult to correct lateral chromatic aberration and coma aberration with these lens groups. Further, the lateral aberration correction burden on the image surface at the time of focusing on a short distance object is only applied to the first lens unit L1, which is not preferable.

Conditional expression (3) defines the difference between the radius of curvature of the lens surface closest to the image plane of the second lens unit L2 and the radius of curvature of the lens surface closest to the object side of the third lens unit L3. .

When the upper limit of conditional expression (3) is exceeded and the ratio of R3f to R2r increases, large coma and astigmatism generated on the lens surface closest to the image plane of the second lens unit L2 are caused by the third lens unit L3. It becomes difficult to cancel the lens surface closest to the object. When the lower limit of conditional expression (3) is exceeded and the ratio of R3f to R2r becomes small, it becomes impossible to maintain the lower light beam from the lens surface of R2r to the lens surface of R3f at a strong angle, and focus on short-distance objects Sometimes, it becomes difficult to maintain a state exceeding the lower limit value of the conditional expression (2) while ensuring the distance between the second lens unit L2 and the third lens unit L3.

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 upper limit of conditional expression (4) is exceeded and the ratio of R4bf to R4ar becomes large, off-axis rays jumped at a strong angle with respect to the optical axis on the lens surface of R4ar will be undercorrected, and the lens system This is not preferable because the total length of the is enlarged.
If the lower limit of conditional expression (4) is exceeded and the ratio of R4bf to R4ar becomes small, large coma and astigmatism generated on the lens surface closest to the image plane of the 4a lens unit L4a will be reduced to the 4b lens unit. The action of canceling with the lens surface closest to the object of L4b is broken.

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

If the upper limit of conditional expression (5) is exceeded and the focal length of the first lens unit L1 is increased, it is advantageous for aberration correction, but the total length of the lens system and the maximum diameter of the aperture stop are increased. If the lower limit of conditional expression (5) is exceeded and the focal length of the first lens unit L1 is shortened, it is difficult to satisfactorily correct axial chromatic aberration and lateral chromatic aberration.

Conditional expression (6) defines the focal length of the second lens unit L2, and is intended to achieve both the numerical range of conditional expression (2) and good aberration correction.

If the upper limit of conditional expression (6) is exceeded and the focal length of the second lens unit L2 is increased in absolute value, it is difficult to satisfy conditional expression (2) while suppressing the total length of the lens system and the maximum diameter of the aperture stop. become. If the lower limit of conditional expression (6) is exceeded and the focal length of the second lens unit L2 is shortened in absolute value, variations in various aberrations depending on the focused object distance become severe, and astigmatism and coma are infinite. It becomes difficult to correct well in the entire focusing range from a distant object to a close object near the same magnification.

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 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 photographing magnification increases, and the total length of the lens system increases. End up. When the lower limit of conditional expression (7) is exceeded and the focal length of the third lens unit L3 is shortened, various aberrations such as spherical aberration and coma increase, and in addition, the third lens unit L3 and the fourth lens unit L3. It is difficult to ensure a distance from the lens unit L4.

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.

If the upper limit of conditional expression (8) is exceeded and the focal length of the fourth lens unit L4 is increased in absolute value, it is advantageous for aberration correction, but the image stabilization is performed while suppressing the diameter of the lens closest to the image plane. It becomes difficult to obtain a sufficient anti-vibration coefficient for the lens group. When the lower limit of conditional expression (8) is exceeded and the focal length of the fourth lens unit L4 becomes shorter in absolute value, the image stabilization is performed after securing the interval between the third lens unit L3 and the fourth lens unit L4. It becomes difficult to obtain a sufficient anti-vibration coefficient for the lens group.

Conditional expression (9) defines the focal length of the 4a lens unit L4a, and is intended to achieve both a sufficient anti-vibration coefficient of the anti-vibration lens unit and aberration correction during image stabilization. is there.

When the lower limit of conditional expression (9) 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 axial chromatic aberration, Astigmatism correction becomes difficult. If the upper limit of conditional expression (9) is exceeded and the focal length of the 4a lens unit L4a 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 (10) 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 (10) is exceeded and the focal length of the 4b lens unit L4b becomes short, it becomes difficult to give sufficient refractive power to the lens unit that moves during the focusing operation. If the upper limit of conditional expression (10) is exceeded and the focal length of the 4b lens unit L4b is increased, a sufficient amount of vibration-proof lens unit is ensured while ensuring the interval between the 4a lens unit L4a and the 4b lens unit L4b. It becomes difficult to obtain an anti-vibration coefficient.

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)

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,
When focusing from an object at infinity to an object at a short distance, at least the third lens unit L3 is moved to the object side and at the same time the second lens unit L2 is moved in an arbitrary direction on the optical axis; and The distance on the optical axis between the first lens group L1 and the second lens group L2 changes, 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. The distance on the optical axis between the third lens unit L3 and the fourth lens unit L4 is increased,
Close-up photography is possible at any magnification from infinity to 1x ,
The fourth lens unit L4 includes, in order from the object side, a front group 4a lens unit L4a having a negative refractive power and a rear group 4b lens unit L4b having a positive refractive power, and an optical system. When the lens 4 is vibrated, image blur correction is performed by moving the fourth lens unit L4a in a direction substantially perpendicular to the optical axis, and the following conditional expression is satisfied. Focus macro lens.
(1) 2.0 <(Δx / ΔH)
(2) −2.0 <β2mod <−0.2
However,
ΔH is the amount of movement of the 4a lens unit L4a in the direction perpendicular to the optical axis Δx is the amount of movement of the image formation position on the image plane when the 4a lens unit L4a is moved ΔH in the direction perpendicular to the optical axis β2mod is the imaging magnification of the second lens unit L2 when focused on the object at the shortest distance The first lens unit L1 and the fourth lens unit L4 are fixed in the optical axis direction with respect to the image plane when focusing from an infinitely distant object to a close object. Inner focus type macro lens with anti-vibration function. The inner focus type macro lens having an image stabilization function according to claim 1, wherein the following conditional expression is satisfied.
(3) 0.0 <(f / R2r-f / R3f) <1.0
(4) -1.0 <(f / R4ar-f / R4bf) <0.0
However,
R2r is the radius of curvature R3f of the lens surface closest to the image plane of the second lens unit L2, and R4ar is the radius of curvature R4ar of the lens surface closest to the object side of the third lens unit L3 is closest to the image plane of the fourth lens unit L4a. The radius of curvature R4bf of the lens surface is the radius of curvature f of the lens surface closest to the object side of the 4b lens unit L4b, and the focal length of the entire optical system when focusing on an object at infinity.

Images