阅读说明：本技术 透镜装置和相机系统 (Lens apparatus and camera system ) 是由 小坂雄一 吉田真介 于 2019-08-27 设计创作，主要内容包括：公开了透镜装置和相机系统。透镜装置包括：光学系统,该光学系统包括前透镜组和后透镜组,该前透镜组具有正折光力并且被配置成在从无限远到近距离物体的聚焦期间向物侧移动,该后透镜组被布置在前透镜组的像侧并且被配置成在聚焦期间不移动；马达,被配置成使前透镜组移动；以及保持构件,在物侧包括在与光学系统的光轴垂直的方向上延伸的凸缘部,并且被配置成保持后透镜组的至少一部分,其中,马达包括线圈、容纳线圈的壳体以及在光学系统的光轴方向上从壳体延伸的轴部,并且马达被布置在壳体的像侧端面在光轴方向上相对于凸缘部处于物侧的位置。(Lens apparatus and camera systems are disclosed. The lens device includes: an optical system including a front lens group having a positive refractive power and configured to move to an object side during focusing from infinity to a close-distance object, and a rear lens group arranged on an image side of the front lens group and configured not to move during focusing; a motor configured to move the front lens group; and a holding member including a flange portion extending in a direction perpendicular to an optical axis of the optical system on the object side and configured to hold at least a part of the rear lens group, wherein the motor includes a coil, a housing accommodating the coil, and a shaft portion extending from the housing in the optical axis direction of the optical system, and the motor is disposed at a position of an image side end surface of the housing on the object side with respect to the flange portion in the optical axis direction.)

1. A lens apparatus, comprising:

an optical system including a front lens group having a positive refractive power and configured to move to an object side during focusing from infinity to a close-distance object, and a rear lens group arranged on an image side of the front lens group and configured not to move during focusing;

a motor configured to move the front lens group; and

a holding member including a flange portion extending in a direction perpendicular to an optical axis of the optical system on an object side and configured to hold at least a part of the rear lens group,

wherein the motor includes a coil, a housing accommodating the coil, and a shaft portion extending from the housing in an optical axis direction of the optical system, and the motor is disposed at a position of an image side end surface of the housing on an object side with respect to the flange portion in the optical axis direction.

2. The lens apparatus of claim 1, further comprising:

a guide barrel configured to guide movement of the front lens group; and

a cam cylinder configured to rotate relative to the guide cylinder by driving of a motor to move the front lens group,

wherein the motor is disposed at a position where the motor overlaps with at least one of the guide barrel and the cam barrel in the optical axis direction.

3. The lens device according to claim 1, wherein the following conditional expression is satisfied,

0.20＜Δ/L＜0.30

where Δ represents a moving distance of the front lens group during focusing from a state where the optical system is focused on an object at infinity to a state where the optical system has a lateral magnification of-0.5, and L represents a total lens length of the optical system focused on the object at infinity.

4. A lens apparatus, comprising:

an optical system including a front lens group having a positive refractive power and configured to move to an object side during focusing from infinity to a close-distance object, and a rear lens group arranged on an image side of the front lens group and configured not to move during focusing;

a motor configured to move the front lens group;

a guide barrel configured to guide movement of the front lens group; and

a cam cylinder configured to rotate relative to the guide cylinder by a driving motor to move the front lens group,

wherein the motor is disposed adjacent to the image side of the cam barrel, and

wherein the following conditional expressions are satisfied:

0.20＜Δ/L＜0.30

where Δ represents a moving distance of the front lens group during focusing from a state where the optical system is focused on an object at infinity to a state where the optical system has a lateral magnification of-0.5, and L represents a total lens length of the optical system focused at infinity.

5. The lens device according to claim 4, wherein the motor is disposed at a position where the motor overlaps at least one of the guide barrel and the cam barrel in an optical axis direction of the optical system.

6. The lens apparatus according to claim 1, wherein the following conditional expression is satisfied:

0.10＜LR/L＜0.50

where LR denotes a distance on an optical axis from a surface closest to the object side to a surface closest to the image side of the rear lens group, and L denotes a total lens length of an optical system focused at infinity.

7. The lens apparatus according to claim 1, wherein the following conditional expression is satisfied:

0.05＜f/|f2|＜0.40

where f denotes a focal length of the optical system focused at infinity, and f2 denotes a focal length of the rear lens group.

8. The lens apparatus according to claim 1, wherein the following conditional expression is satisfied:

0.80＜f1/f＜1.20

where f1 denotes a focal length of the front lens group, and f denotes a focal length of the optical system focused at infinity.

9. The lens apparatus according to claim 1, wherein the following conditional expression is satisfied:

0.50＜Lfh/LF＜1.00

where Lfh denotes a distance from a surface of the front lens group closest to the object side to a main plane of the front lens group, and LF denotes a distance on an optical axis from the surface of the front lens group closest to the object side to a surface closest to the image side.

10. The lens device according to claim 1, wherein at least a part of the object side surface of the housing and the image side surface of the housing is covered with a magnetic shield member.

11. The lens apparatus according to claim 1, wherein the motor is arranged in such a manner that a central axis of the coil is not parallel to the optical axis direction.

12. A camera system, comprising:

a lens apparatus, comprising:

an optical system including a front lens group having a positive refractive power and configured to move to an object side during focusing from infinity to a close-distance object, and a rear lens group arranged on an image side of the front lens group and configured not to move during focusing,

a motor configured to move the front lens group, an

A holding member including a flange portion extending in a direction perpendicular to an optical axis of the optical system on an object side, and configured to hold at least a part of the rear lens group; and

a light receiving element configured to receive an image formed by the optical system,

wherein the motor includes a coil, a housing accommodating the coil, and a shaft portion extending from the housing in an optical axis direction of the optical system, and the motor is disposed at a position of an image side end surface of the housing on an object side with respect to the flange portion in the optical axis direction.

13. A camera system, comprising:

a lens apparatus, comprising:

a front lens group having a positive refractive power and configured to move to an object side during focusing from infinity to a close-distance object, and a rear lens group arranged on an image side of the front lens group and configured not to move during focusing;

a motor configured to move the front lens group,

a guide barrel configured to guide movement of the front lens group, an

A cam cylinder configured to rotate relative to the guide cylinder by driving of a motor to move the front lens group; and

a light receiving element configured to receive an image formed by the optical system,

wherein the motor is disposed adjacent to the image side of the cam barrel, and

wherein the following conditional expressions are satisfied:

0.20＜Δ/L＜0.30

where Δ represents a moving distance of the front lens group during focusing from a state where the optical system is focused on an object at infinity to a state where the optical system has a lateral magnification of-0.5, and L represents a total lens length of the optical system focused at infinity.

Technical Field

The invention relates to a lens apparatus and a camera system.

Background

As an actuator for moving a part assembly in an optical system, a motor driven by energizing a coil, such as a stepping motor or a voice coil motor, is known. In the case where the amount of energization of the coil is large or the arrangement position of the motor is close to, for example, an image capturing element in a mirrorless camera, noise may be superimposed on an image signal generated by the image capturing element due to the influence of a magnetic field occurring due to energization of the coil.

U.S. patent application publication No.2012/0019680 discusses a technique of reducing noise superimposed on an image signal by changing the driving frequency of a driving device for an image capturing element when reading out electric charges from the image capturing element.

However, in U.S. patent application publication No.2012/0019680, when noise reduction measures are not taken on the camera side in an image pickup system including a replaceable lens device, the influence of a magnetic field occurring from the lens device cannot be reduced. In this case, regardless of the configuration of the optical system in the lens apparatus, simply arranging the motor at the position farthest from the image capturing element makes the lens apparatus likely to become large depending on the configuration of the optical system.

Disclosure of Invention

According to one aspect of the invention, a lens apparatus comprises: an optical system including a front lens group having a positive refractive power and configured to move to an object side during focusing from infinity to a close-distance object, and a rear lens group arranged on an image side of the front lens group and configured not to move during focusing; a motor configured to move the front lens group; and a holding member including a flange portion extending in a direction perpendicular to an optical axis of the optical system on the object side and configured to hold at least a part of the rear lens group, wherein the motor includes a coil, a housing accommodating the coil, and a shaft portion extending from the housing in the optical axis direction of the optical system, and the motor is disposed at a position of an image side end surface of the housing on the object side with respect to the flange portion in the optical axis direction.

According to another aspect of the present invention, a lens apparatus includes: an optical system including a front lens group having a positive refractive power and configured to move to an object side during focusing from infinity to a close-distance object, and a rear lens group arranged on an image side of the front lens group and configured not to move during focusing; a motor configured to move the front lens group; a guide barrel configured to guide movement of the front lens group; and a cam barrel configured to rotate relative to the guide barrel by driving the motor to move the front lens group, wherein the motor is disposed adjacent to an image side of the cam barrel, and wherein the following conditional expression is satisfied:

0.20＜Δ/L＜0.30

where Δ represents a moving distance of the front lens group during focusing from a state where the optical system is focused on an object at infinity to a state where the optical system has a lateral magnification of-0.5, and L represents a total lens length of the optical system focused at infinity.

Further features of the invention will become apparent from the following description of exemplary embodiments, with reference to the attached drawings.

Drawings

Fig. 1A and 1B each show a configuration of a lens apparatus and a camera.

Fig. 2 shows a peripheral configuration of the lens barrel.

Fig. 3 shows a peripheral configuration of the lens barrel.

Fig. 4 shows the configuration of the actuator.

Fig. 5 is a sectional view of an optical system according to the first exemplary embodiment.

Fig. 6A and 6B are aberration diagrams of the optical system according to the first exemplary embodiment.

Fig. 7 is a sectional view of an optical system according to a second exemplary embodiment.

Fig. 8A and 8B are aberration diagrams of an optical system according to the second exemplary embodiment.

Fig. 9 shows the configuration of the motor.

Detailed Description

A lens apparatus and a camera system according to exemplary embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The same components in the drawings are denoted by the same reference numerals, and thus their repetitive description will be omitted.

Fig. 1A and 1B illustrate a configuration of a camera 100 and a lens apparatus 200 attachable to the camera 100 and detachable from the camera 100 according to a first example embodiment. Referring to fig. 1A and 1B, the optical axis direction of the optical system OL in the lens apparatus 200 is defined as a Z-axis direction, and two directions, both of which are parallel to the outer shape of the image capturing element (light receiving element) 104 and orthogonal to each other, are defined as a Y-axis direction and an X-axis direction, respectively.

In the camera 100, the mirror 101 reflects a part of the light beam from the optical system OL to the pentaprism 105, and transmits the remaining light beam through the mirror 101. The pentaprism 105 guides incident light to the observation side by internal reflection. The mirror 102 guides the light transmitted through the mirror 101 to an Auto Focus (AF) optical system (not shown) for distance measurement. When the mirrors 101 and 102 are moved outside the optical path, the image capturing element 104 receives an image formed by the optical system OL of the lens apparatus 200 and generates an image signal of the received image.

Next, the configuration of the lens apparatus 200 will be described. The optical system OL includes a front lens group Lf having a positive refractive power and moving to the object side during focusing from infinity to a close-distance object, and a rear lens group Lr arranged on the image side (camera side) of the front lens group Lf and not moving during focusing. Fig. 1A shows the optical system OL focused on an object at infinity, and fig. 1B shows the optical system OL with a lateral magnification of-0.5. Referring to fig. 1A, the moving distance of the front lens group Lf is indicated by a symbol Δ. The front lens group Lf includes nine lenses of lenses L1 to L9, and the rear lens group Lr includes two lenses of lenses L10 and L11. An aperture stop 205 is disposed between the lens L4 and the lens L5, the aperture stop 205 being moved in a direction perpendicular to the optical axis OA when correcting image shake.

The lens barrel of the lens apparatus 200 includes a fixed barrel 212, an outer barrel 213, and a base 209. The mount 209, which is a coupling portion between the lens apparatus 200 and the camera 100, is connected to the fixed barrel 212 via the outer barrel 213. The mount 209 indirectly holds the guide barrel 201, the 1A lens barrel 203, and the 2B lens barrel 208 via the fixed barrel 212.

The holding mechanism of the front lens group Lf will be described. The 1A lens barrel 203 holds lenses L1 to L4. The 1B lens barrel 204 holds a lens L5 and an aperture stop 205. The 1C lens barrel 206 holds the lenses L6 to L9. The 1B lens barrel 204 and the 1C lens barrel 206 are fixed to the 1A lens barrel 203.

The motor 220 moves the 1A lens barrel 203 in the Z-axis direction via the guide barrel 201, the cam barrel 202 having the worm cam 210, and the cam follower 211. As described above, since the 1B lens barrel 204 and the 1C lens barrel 206 are fixed to the 1A lens barrel 203, when the 1A lens barrel 203 moves in the Z-axis direction, the 1B lens barrel 204 and the 1C lens barrel 206 move integrally with the 1A lens barrel 203. In other words, the motor 220 has a function of indirectly moving the front lens group Lf in the Z-axis direction.

The cam barrel 202 is disposed outside the guide barrel 201. The cam follower 211 fixed to the 1A lens barrel 203 is engaged with a translational guide groove (not shown) of the guide barrel 201 and a cam groove (not shown) included in the cam barrel 202 formed in the Z-axis direction. Rotating the cam cylinder 202 by the driving of the motor 220 causes the cam follower 211 to move along the translational guide groove of the guide cylinder 201, and thus the front lens group Lf moves with the movement of the cam follower 211.

The holding mechanism of the rear lens group Lr will be described. The 2A lens barrel 207 holds a lens L10, and the 2B lens barrel (holding member) 208 holds a lens L11 that is a part of the rear lens group Lr. Fig. 2 shows a peripheral configuration of the 2A lens barrel 207 and the 2B lens barrel 208, and is a sectional view of a section different from that of fig. 1A and 1B. The 2A lens barrel 207 includes, on the object side, a flange portion 207F extending in a direction perpendicular to the optical axis of the optical system OL (a direction perpendicular to the Z axis, for example, a radial direction of the optical system OL). The 2B lens barrel 208 includes a flange portion 208F extending in a direction perpendicular to the optical axis on the object side. The 2A lens barrel 207 is fixed to the 2B lens barrel 208 in such a manner that the flange portion 207F abuts against the object side of the flange portion 208F. The 2B lens barrel 208 is fixed to the guide barrel 201 via the flange portion 208F. However, the flange portion 207F and the flange portion 208F are not necessarily formed at the object side end portions of each of the 2A lens barrel 207 and the 2B lens barrel 208 as in the present exemplary embodiment. The flange portion 207F and the flange portion 208F only need to be formed at least on the object side with respect to respective intermediate positions in the Z-axis direction of the 2A lens barrel 207 and the 2B lens barrel 208.

The flange portions 207F and 208F are formed at different heights depending on the circumferential position. For example, fig. 3 is a cross-sectional view different from the cross-section of fig. 2. The lengths of the flange portions 207F and 208F in the cross-sectional view of fig. 3 in the direction perpendicular to the optical axis are formed shorter than the flange portions 207F and 208F in the cross-sectional view of fig. 2.

Arrangement and arrangement of motors

Next, the arrangement of the motor 220 applied to the above-described optical system OL in the present exemplary embodiment will be described.

The configuration and arrangement of the motor 220 will be described with reference to fig. 3, 4, and 9. According to the present exemplary embodiment, the kind of the motor 220 is a stepping motor. The motor 220 includes a magnet 220b, a coil 220a, a housing 220c, and a shaft portion 220 d. In the motor 220, four coils 220a (two coils are not shown) are arranged along the circumferential direction of the magnet 220b, and when the coils 220a are energized, the magnet 220b rotates with respect to the coils 220 a. The coil 220a and the magnet 220b are accommodated in a case 220 c. The housing 220c may have a cylindrical shape as shown in fig. 4 or may have a different shape. The shaft portion 220d, which is a portion extending from the housing 220c in the Z-axis direction, is rotationally driven with the rotation of the magnet 220 b. The generated rotational force is transmitted to the worm cam 210 via a pinion gear (not shown) and a gear set (not shown), which rotates the worm cam 210. Then, the rotation of the worm cam 210 rotates the cam cylinder 202. Then, the rotation of the cam barrel 202 relative to the guide barrel 201 moves the front lens group Lf in the Z-axis direction. In the case where the magnet 220b is rod-shaped, a portion of the magnet 220b may protrude outward from the housing 220 c.

An optical system OL generally used in a lens apparatus for close-range imaging has a feature that a lens diameter is large and a lens group closest to the object side has a relatively large moving distance during focusing. Therefore, it is preferable but optional that the motor 220 is disposed at a position that does not make the lens apparatus 200 large. Therefore, according to the present exemplary embodiment, the motor 220 is disposed at a position on the object side of the end face 220R on the image side of the housing 220c with respect to the flange portion 208F. The arrangement at this position makes it possible to reduce the size of the lens apparatus 200 and reduce noise for the image signal taken by the image capturing element 104, as compared with the case where the motor 220 is arranged at a different position.

For example, disposing the end face 220R of the motor 220 at a position on the image side with respect to the flange portion 208F causes the influence of noise due to a magnetic field to increase at the image capturing element 104. Disposing the end face 220R of the motor 220 outside the flange portion 208F in the direction perpendicular to the optical axis increases the diameter of the lens apparatus 200.

Further, in the present exemplary embodiment, the motor 220 is arranged at a position where the motor 220 overlaps the guide barrel 201 and the cam barrel 202 in the Z-axis direction. In this way, it is preferable but optional that the motor 220 overlaps with at least one of the guide barrel 201 and the cam barrel 202 in the Z-axis direction (viewed from the optical axis direction). In other words, it is preferable but optional that the motor 220 is not disposed outside the guide barrel 201. This arrangement enables: the diameter of the lens apparatus 200 is smaller than that in the case where the motor 220 is arranged outside the guide barrel 201 in the direction perpendicular to the optical axis of the optical system OL.

Further, in the present exemplary embodiment, the position at which the motor 220 is arranged is the image side with respect to the cam barrel 202 and the guide barrel 201. This arrangement makes it possible to avoid an increase in the diameter of the lens apparatus 200. If the motor 220 is disposed on the object side with respect to the guide lens barrel 201 and the cam lens barrel 202, there is a possibility that the motor 220 interferes with the front lens group Lf during focusing.

Further, in the present exemplary embodiment, the motor 220 is arranged such that the central axis of each coil 220a extends in the X-axis direction or the Y-axis direction. Preferably but optionally, the motor 220 is arranged such that the central axis of each coil 220a is not parallel to the Z-axis direction. This arrangement may prevent the main direction of the magnetic field generated when the coil 220a is energized from being directed to the image capturing element 104. Therefore, a noise signal generated due to a magnetic field on the image signal taken by the image capturing element 104 can be reduced.

Further, in the motor 220, as shown in fig. 4, a shield (magnetic shield member) 221 that reduces the magnetic flux passing through the surface may be provided on the surface of the housing 220 c. Preferably but optionally, at least a portion of the object side surface and the image side surface of the case 220c is covered by the shield member 221. This arrangement enables the strength of the magnetic field generated by the motor 220 to decay or change direction when the coil 220a is energized. Therefore, a noise signal on the image signal taken by the image capturing element 104 can be reduced.

Relationship between optical system and motor

Next, the configuration of the optical system OL in the lens apparatus 200 according to the present exemplary embodiment and the arrangement relationship between the optical system OL and the motor 220 will be described.

As described above, since the optical system OL includes a lens having a relatively large moving distance during focusing, disposing the motor 220 at an inappropriate position with respect to the image side of the cam barrel 202 makes it more likely that noise is superimposed on the image signal of the captured image. Meanwhile, spacing the motor 220 from the image capture element 104 very far in the Z-axis direction increases the diameter or overall length of the lens device 200.

In the case where the lateral magnification of the optical system OL has an absolute value of 0.5 or more, it is preferable but optional that the optical system OL satisfies the following conditional expression (1):

0.20＜Δ/L＜0.30…(1)

where Δ represents a moving distance of the front lens group Lf during focusing from a state where the optical system OL is focused on an object at infinity to a state where the optical system OL has a lateral magnification of-0.5, and L represents a total lens length of the optical system OL when focused on an object at infinity.

The motor 220 is disposed adjacent to the image side of the cam barrel 202. Here, the meaning of "adjacently disposed" is not limited to the case where the motor 220 abuts on the cam barrel 202, but also includes the case where the motor 220 is disposed at an air interval without any member.

The movement distance Δ is related to the lengths of the guide barrel 201 and the cam barrel 202 in the Z-axis direction. If the motor 220 is disposed adjacent to the image side of the cam barrel 202, appropriate determination of the movement distance Δ and the total lens length L causes appropriate determination of the disposition position (distance from the image plane) of the motor 220. Arranging the motor 220 adjacent to the image side of the cam barrel 202 enables the diameter of the lens apparatus 200 to be reduced. Ensuring that the moving distance Δ is at a predetermined level satisfying the conditional expression (1) enables reduction of noise signals on the image signal taken by the image capturing element 104 while achieving high optical performance.

In the case where the moving distance of the front lens group Lf is increased beyond the upper limit of conditional expression (1), the cam barrel 202 and the guide barrel 201 become long in the Z-axis direction. Accordingly, the distance between the motor 220 and the image capturing element 104 is reduced when focusing at infinity, and thus noise is more likely to be superimposed on the image signal generated by the image capturing element 104. Further, the lens apparatus 200 increases in weight, and the total length of the lens apparatus 200 when the front lens group Lf moves toward the object side increases. Below the lower limit of conditional expression (1), the front lens group Lf and the rear lens group Lr increase in refractive power, resulting in an increase in aberration. Therefore, this arrangement is not preferable.

Further, it is preferable but optional that the optical system OL satisfies at least one of the following conditional expressions (2) to (5). Satisfying at least one conditional expression enables at least one of the following: the lens device 200 is further reduced in size, the optical performance of the optical system OL is enhanced, and noise is reduced for a captured image.

0.10＜LR/L＜0.50…(2)

0.05＜f/|f2|＜0.40…(3)

0.80＜f1/f＜1.20…(4)

0.50＜Lfh/LF＜1.00…(5)

Where LF denotes a distance on an optical axis from a surface closest to the object side of the front lens group LF to a surface closest to the image side (hereinafter referred to as a thickness of the front lens group LF), and LR denotes a distance on an optical axis from a surface closest to the object side of the rear lens group LR to a surface closest to the image side (hereinafter referred to as a thickness of the rear lens group LR). L denotes the total lens length of the optical system OL focused on an object at infinity. f denotes a focal length of the optical system OL focused on an object at infinity, f1 denotes a focal length of the front lens group Lf, and f2 denotes a focal length of the rear lens group Lr. Lfh denotes a distance from a surface of the front lens group Lf closest to the object side to a main plane of the front lens group Lf.

Conditional expression (2) relates to a preferable range of the ratio between the thickness of the rear lens group Lr and the total lens length. In the case where the thickness of the rear lens group Lr is increased beyond the upper limit of conditional expression (2), the refractive power of the rear lens group Lr increases, and the refractive power of the front lens group Lf increases with this increase. Therefore, aberration increases, and aberration variation during focusing increases. In the case where the lower limit of the conditional expression (2) is insufficient to reduce the thickness of the rear lens group Lr, the cam barrel 202 is disposed closer to the image capturing element 104, and further the motor 220 is disposed at a position close to the image capturing element 104. Therefore, noise is more likely to be superimposed on the image signal generated by the image capturing element 104.

Conditional expression (3) relates to a preferable range of the absolute value of the focal length ratio between the rear lens group Lr and the optical system OL. In the case where the absolute value of the focal length of the rear lens group Lr is decreased and the refractive power of the rear lens group Lr is increased beyond the upper limit of conditional expression (3), various aberrations such as spherical aberration increase. In the case where the absolute value of the focal length of the rear lens group Lr is increased and the refractive power of the rear lens group Lr is decreased below the lower limit of conditional expression (3), the total lens length becomes long.

Conditional expression (4) relates to a preferable range of the focal length ratio between the front lens group Lf and the optical system OL. In the case where the focal length of the front lens group Lf is increased and the refractive power of the front lens group Lf is decreased beyond the upper limit of conditional expression (4), the total lens length of the optical system OL becomes long. In the case where the focal length of the front lens group Lf is decreased and the refractive power of the front lens group Lf is increased below the lower limit of conditional expression (4), various aberrations such as spherical aberration increase.

Conditional expression (5) relates to a preferable range of the position of the principal plane of the front lens group Lf. Satisfying the range of conditional expression (5) enables reducing the effective diameter of the lens relatively disposed on the object side of the optical system OL, thus reducing the size of the optical system OL. Above the upper limit of conditional expression (5), the principal plane of the front lens group Lf is rearward of the front lens group Lf. Therefore, the lens refractive power included in the front lens group Lf increases, and thus aberration increases. Below the lower limit of conditional expression (5), the lens L1 effective diameter increases. Therefore, the diameter of the optical system OL increases.

Preferably but alternatively, the numerical ranges of the conditional expressions (2) to (5) satisfy the following conditional expressions (2a) to (5a), respectively.

0.13＜LR/L＜0.40…(2a)

0.10＜f/|f2|＜0.35…(3a)

0.90＜f1/f＜1.10…(4a)

0.60＜Lfh/LF＜0.90…(5a)

More preferably, the numerical ranges of the conditional expressions (2) to (5) satisfy the following conditional expressions (2b) to (5b), respectively.

0.15＜LR/L＜0.35…(2b)

0.15＜f/|f2|＜0.30…(3b)

0.95＜f1/f＜1.05…(4b)

0.70＜Lfh/LF＜0.85…(5b)

Examples of the optical system OL will be described with reference to fig. 5 to 8B. Fig. 5 is a sectional view of the optical system OL according to the first exemplary embodiment. Fig. 6A and 6B are aberration diagrams of the optical system OL according to the first exemplary embodiment. Fig. 7 is a sectional view of the optical system OL according to the second exemplary embodiment. Fig. 8A and 8B are aberration diagrams of the optical system OL according to the second exemplary embodiment. Referring to fig. 5 and 7, each image plane IMG corresponds to an arrangement position of the image capturing element 104 in the camera 100. Each of the aberration diagrams shown in fig. 6A, 6B, 8A, and 8B indicates spherical aberration, astigmatism, distortion aberration, and chromatic aberration in order from left to right. In each spherical aberration diagram, a solid line indicates a d-line (wavelength 587.6nm) in the Fraunhofer line (Fraunhofer line), and a two-dot chain line indicates a g-line (wavelength 435.84nm) in the Fraunhofer line. In each astigmatism diagram, a broken line Δ S represents sagittal rays, and a solid line Δ M represents meridional rays. In each distortion aberration diagram, the solid line represents a d-line. In each color difference map, a two-dot chain line indicates a g-line. Each aberration diagram of fig. 6A and 8A results from the optical system OL focused on an object at infinity. Each aberration diagram of fig. 6B and 8B results from the optical system OL having a lateral magnification of-0.5.

The optical systems OL according to the first and second exemplary embodiments each include a front lens group Lf having a positive refractive power and moving toward the object side during focusing from infinity to a close-distance object, and a rear lens group Lr arranged on the image side of the front lens group Lf. The rear lens group Lr is not moved during focusing.

According to the above, the optical system having at least such a configuration is suitable as the optical system OL of the lens apparatus 200 according to the exemplary embodiment of the present invention. Therefore, the number of lenses included in each of the front lens group Lf and the rear lens group Lr, the arrangement of the aperture stop 205, and the shape of each lens included in the optical system OL are not limited to those of the optical system OL illustrated in fig. 1A and 1B, and are not limited to those of the respective optical systems OL according to the first and second exemplary embodiments. The values of the F-number are not limited to those according to the first exemplary embodiment and the second exemplary embodiment. The refractive power of the rear lens group Lr is not limited to being negative as in the first and second exemplary embodiments, and may be positive.

The optical system OL according to the first exemplary embodiment and the optical system OL according to the second exemplary embodiment are different in, for example, the number of lenses in the front lens group Lf, the position of the aperture stop 205, and the refractive index and the shape of each lens included in the optical system OL. Specifically, the optical system OL according to the first exemplary embodiment is an optical system indicated in [ first numerical example ] to be described below, and the optical system OL according to the second exemplary embodiment is an optical system indicated in [ second numerical example ] to be described below.

In [ first numerical example ] and [ second numerical example ], the surface number indicates the order of the optical surfaces from the object side. r denotes a radius of curvature (mm) of the optical surface, d denotes a space (mm) between adjacent optical surfaces, nd denotes a refractive index of a material of the optical member at d-line, and vd denotes an abbe number of the material of the optical member based on d-line. The abbe number vd is expressed by the following expression:

vd＝(Nd-1)/(NF-NC)

where NF, Nd and NC represent the refractive indices of the material at the F line (486.1nm), d line (587.6nm) and C line (656.3nm) in the fraunhofer line, respectively. BF denotes the back focus. The "back focal length" is represented by an air conversion length of a distance on the optical axis from the rearmost surface (lens surface closest to the image side) of the optical system OL to the paraxial image plane. The "total lens length" is the length of the back focal length plus the distance on the optical axis from the frontmost surface (lens surface closest to the object side) to the rearmost surface of the optical system OL.

In each numerical example, the surface number of the aspherical surface is marked with an asterisk ＊ on the right side of the surface number for an aspherical shape, when the optical axis direction is defined as the X axis, the direction perpendicular to the optical axis is defined as the H axis, the light traveling direction is defined as positive, R is defined as the paraxial radius of curvature, K is defined as a conic constant, and a4, a6, a8, a10, and a12 are defined as aspherical constants, the following expression is taken:

for each aspheric constant, "e ± x" means 10^±x。

Further, [ table 1] indicates respective values corresponding to conditional expressions (1) to (5) in the first numerical example and the second numerical example.

[ first numerical example ]

Unit mm

Surface data

Surface numbering	r	d	nd	vd	Effective diameter
						1	-101.398	1.20	1.80810	22.8	28.00
2	27.457	1.96			25.61
						3	43.072	4.35	2.00100	29.1	25.62
4	-76.107	4.94			25.21
						5	-43.452	1.34	1.51742	52.4	21.52
6	20.892	6.97	1.83400	37.2	22.63
						7	-57.860	2.00			22.44
8 (diaphragm)	∞	9.00			20.92
						9*	-46.158	2.00	1.58313	59.4	16.99
10	-22.244	0.49			17.10
						11	-25.258	4.23	1.83400	37.2	17.55
12	-10.915	1.00	1.80518	25.4	18.21
						13	219.604	5.99			22.59
14	394.851	3.23	1.58913	61.1	32.92
						15	-59.412	0.50			33.35
16	-138.542	5.23	1.80100	35.0	35.15
						17	-32.649	(variable)			35.80
18	191.652	3.64	1.69680	55.5	37.00
						19	-77.278	8.75			37.02
20	-34.676	1.00	1.58144	40.8	35.08
						21	99.122	11.65			36.86

Infinity image plane

Aspheric surface data

The ninth surface

K＝0.00000e+000 A4＝-3.86457e-005 A6＝-8.07285e-008

A8＝-1.41532e-010 A10＝-1.98576e-012

Various types of data

Lens group data

Group of	Starting surface	Focal length	Length of lens structure	Front principal point location	Rear principal point location
						1	1	37.13	54.43	36.51	-10.06
2	18	-135.27	13.39	30.80	15.75

Single lens data

Lens and lens assembly	Starting surface	Focal length
			1	1	-26.63
2	3	27.99
			3	5	-27.07
4	6	19.18
			5	9	71.43
6	11	20.32
			7	12	-12.89
8	14	87.89
			9	16	52.18
10	18	79.48
			11	20	-44.06

[ second numerical example ]

Unit mm

Surface data

Infinity image plane

Aspheric surface data

Second surface

K＝0.00000e+000 A4＝1.11348e-005 A6＝-6.54297e-009

A8＝1.45473e-010 A10＝-3.78548e-013 A12＝6.79599e-016

Sixteenth surface

K＝0.00000e+000 A4＝-4.25646e-006 A6＝7.76315e-008

A8-4.15916 e-010 a 10-1.07574 e-012 a 12-1.00091 e-015 various types of data

Lens group data

Group of	Starting surface	Focal length	Length of lens structure	Front principal point location	Rear principal point location
						1	1	41.96	38.48	24.57	-8.19
2	14	-139.74	18.17	33.03	14.10

Single lens data

Lens and lens assembly	Starting surface	Focal length
			1	1	-60.67
2	3	-54.17
			3	4	19.27
4	7	41.72
			5	8	-17.57
6	10	57.83
			7	12	49.55
8	14	102.36
			9	16	-52.33

[ Table 1]

	First numerical example	Second numerical example
			(1)	0.24	0.29
(2)	0.17	0.25
			(3)	-0.27	-0.30
(4)	1.03	1.00
			(5)	0.82	0.78

Camera system

The camera system according to the exemplary embodiment of the present invention includes a replaceable lens apparatus 200 and a camera 100 to which the lens apparatus 200 is attachable and detachable, or includes a camera including the lens apparatus 200 and the camera 100 integrally formed. The camera 100 may be a single lens reflex camera including mirrors 101 and 102 or may be a mirrorless camera without mirrors 101 and 102. In the case where the lens apparatus 200 and the camera 100 are integrally formed, the configuration of the camera 100 is substantially similar to that of the camera 100 shown in fig. 1A and 1B, except that the lens apparatus 200 is fixed to the camera 100 without the mirrors 101 and 102 and without the mount 209.

Additional example embodiments

The flange portions 207F and 208F can be formed highly uniformly regardless of the circumferential position. Alternatively, as long as a portion of not less than half of each of the flange portions 207F and 208F in the circumferential position extends in the direction perpendicular to the optical axis, the remaining portion does not need to extend in the direction perpendicular to the optical axis.

According to the above-described exemplary embodiment, the motor 220 as the stepping motor has been described. However, the motor 220 may be a different type of motor as long as the motor 220 serves as an actuator driven by energizing a coil. For example, the motor 220 may be a Direct Current (DC) motor. The motor 220 may be a lead screw motor, and may move the 1A lens barrel 203. The arrangement of the coils in the motor 220 is not limited to the arrangement according to the example embodiment, and thus the arrangement of the coils may be appropriately changed corresponding to the motor 220 or the optical system OL.

The 2B lens barrel 208 only needs to hold at least a part of the rear lens group Lr. For example, the 2B lens barrel 208 may also function as the 2A barrel 207, and may hold the lens L10 and the lens L11.

The optical system OL according to each numerical example having an absolute value of 0.5 as a maximum value of lateral magnification has been exemplified, but the characteristics of the optical system OL according to the exemplary embodiment of the present invention are not limited thereto. The maximum value of the lateral magnification absolute value may be lower than 0.5, but is preferably 0.5 or higher for good close-range imaging.

The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments. Accordingly, various modifications and changes may be made without departing from the spirit thereof.

While the present invention has been described with reference to the exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.