JP2023140093A - Optical system, lens unit, and image capturing device - Google Patents

Abstract

To provide an optical system which is suitable for producing a fisheye lens with an anti-shake function.SOLUTION: An optical system 101 is provided, comprising a front group 102, an aperture stop SP, and a rear group 103 having positive refractive power arranged in order from the object side to the image side. The rear group includes an anti-shake group with negative refractive power configured to move in a direction having a component perpendicular to an optical axis when anti-shake is enabled. A distance Dr1 from the aperture stop to a most object-side lens surface of the anti-shake group along the optical axis and a focal distance ftotal of the optical system satisfy a given condition expression.SELECTED DRAWING: Figure 1

Description

The present invention relates to an optical system and is suitable for imaging devices such as digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, and surveillance cameras.

In recent years, fisheye lenses have been used to create omnidirectional images and virtual reality (VR) content. When a virtual reality image is displayed on a head-mounted display or the like, the image is enlarged and displayed, so the blurring of the image becomes noticeable when viewing. Particularly in fisheye lenses, it is important to achieve a sufficient vibration isolation angle and to satisfactorily correct various aberrations during vibration isolation.

Patent Document 1 describes a VR image capturing device having a lens device including two fisheye lenses. In the imaging device described in Patent Document 1, two optical images are formed on one image sensor by bending the optical path using a reflective member.

Further, Patent Document 2 describes a single fisheye lens that has a function of performing image stabilization by moving a positive lens in a direction perpendicular to the optical axis.

Japanese Patent Application Publication No. 2020-008629 Japanese Patent Application Publication No. 2018-185386

However, the imaging device described in Patent Document 1 does not have an image stabilization function. Furthermore, in the imaging device described in Patent Document 2, as the vibration isolation angle increases, fluctuations in various aberrations increase.

The present invention provides an optical system suitable for realizing an image stabilization function in a fisheye lens.

An optical system according to one aspect of the present invention includes a front group, an aperture stop, and a rear group with positive refractive power, which are arranged in order from the object side to the image side, and the rear group has an anti-vibration function. In this case, the distance on the optical axis from the aperture stop to the lens surface closest to the object side of the image stabilization group is defined as Dr1. , when the focal length of the optical system is ftotal,
1.2<Dr1/ftotal<20.0
It is characterized by satisfying the following conditional expression.

Other objects and features of the invention are explained in the following embodiments.

According to the present invention, it is possible to provide an optical system suitable for realizing an image stabilization function in a fisheye lens.

3 is a cross-sectional view of a lens in the optical system of Example 1. FIG. 3 is an aberration diagram of the optical system of Example 1. FIG. FIG. 4 is a diagram of lateral aberration of the optical system of Example 1 when vibration isolating and when not vibration-proofing. FIG. 3 is a cross-sectional view of a lens in the optical system of Example 2. FIG. 7 is an aberration diagram of the optical system of Example 2. FIG. 7 is a lateral aberration diagram of the optical system of Example 2 when image stabilization is performed and when image stabilization is not performed. FIG. 7 is a cross-sectional view of a lens in the optical system of Example 3. FIG. 7 is a cross-sectional view of a main part of a lens device in which two optical systems of Example 3 are arranged in parallel, showing a state in which an optical path is bent by a reflecting member. A mechanical structure for holding together two vibration isolation groups in two optical systems is shown. This figure shows a structure that connects two vibration isolation groups in two optical systems. FIG. 7 is an aberration diagram of the optical system of Example 3. FIG. 7 is a lateral aberration diagram of the optical system of Example 3 when image stabilization is performed and when image stabilization is not performed. FIG. 4 is a cross-sectional view of a lens in the optical system of Example 4. FIG. 4 is an aberration diagram of the optical system of Example 4. FIG. 7 is a diagram of lateral aberration of the optical system of Example 4 when vibration isolating and when vibration is not damped. FIG. 1 is a schematic diagram of an imaging device.

Hereinafter, the optical system (fisheye lens) according to each embodiment will be explained based on the attached drawings.

1, 4, 7, and 13 are lens cross-sectional views of the optical system 101 of Examples 1 to 4 when focusing on infinity. The optical system 101 in each embodiment is an optical system used in an imaging device such as a digital video camera, a digital still camera, a broadcasting camera, a silver halide film camera, and a surveillance camera.

In each lens cross-sectional view, the left side is the object side (front), and the right side is the image side (back). The optical system 101 of each embodiment is configured to include a plurality of lens groups. Note that the lens group may be composed of one lens or a plurality of lenses. Furthermore, the lens group may include an aperture stop.

The optical system 101 of each embodiment includes a front group 102, an aperture stop SP, and a rear group 103 with positive refractive power, which are arranged in order from the object side to the image side. LIS represents a lens group included in the rear group 103 that moves in a direction including a component perpendicular to the optical axis during image stabilization. In other words, the LIS is a lens group that moves in a direction having a component perpendicular to the optical axis in order to move the imaging position in the direction perpendicular to the optical axis.

Further, SP is an aperture stop. IP is an image plane, and when the optical system 101 of each embodiment is used as a photographing optical system of a digital still camera or a digital video camera, the IP is an image plane of a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or a CMOS sensor. is placed. When the optical system of each embodiment is used as a photographing optical system of a silver halide film camera, a photosensitive surface corresponding to the film surface is placed on the image plane IP.

Further, in each lens cross-sectional view, coordinate axes are shown for expressing the movement direction and movement amount of the image stabilization group LIS. The x-axis is taken parallel to the optical axis of the optical system 101 from the object side to the image side. The y-axis is taken perpendicular to the x-axis from the bottom to the top of the paper. The z-axis is taken perpendicular to the page from the back of the page to the front. In each embodiment, the moving direction of the vibration isolation group LIS is set in the +y direction. In an optical system with rotational symmetry, the vibration isolation group LIS can be moved in the z direction, or may be moved in the y and z directions simultaneously. Further, an even larger vibration isolation angle may be secured by combining with other vibration isolation methods, such as vibration isolation in which the image sensor is shifted in response to a gyro signal, or vibration isolation in which a region is cut out from an image.

2, FIG. 5, FIG. 11, and FIG. 14 are aberration diagrams of the optical systems 101 of Examples 1 to 4 when focusing on infinity, respectively.

In the spherical aberration diagram, Fno is the F number and indicates the amount of spherical aberration for the d-line (wavelength 587.6 nm) and the g-line (wavelength 435.8 nm). In the astigmatism diagram, S indicates the amount of astigmatism on the sagittal image plane, and M indicates the amount of astigmatism on the meridional image surface. In the distortion aberration diagram, the amount of distortion for the d-line is shown, and the distortion for equidistant projection is shown. Equidistant projection is a projection method that satisfies y=fθ during image formation. Here, y is the image height (height) on the image plane IP, f is the focal length of the optical system 101, and θ is the angle of view (°). The chromatic aberration diagram shows the amount of chromatic aberration at the g-line. ω is the imaging half angle of view (°).

3, FIG. 6, FIG. 12, and FIG. 15 are lateral aberration diagrams of the optical systems 101 of Examples 1 to 4 when focusing at infinity, respectively, and show the lateral aberration diagrams at the same point on the image plane IP during image stabilization and non-vibration. This shows the change in performance during vibration isolation. The broken line (S) represents the sagittal image plane at the d-line, and the solid line (M) represents the astigmatism amount at the meridional image plane at the d-line.

Next, the characteristic configuration of the optical system 101 of each embodiment will be described.

The optical system 101 of each embodiment includes a front group 102, an aperture stop SP, and a rear group 103 with positive refractive power, which are arranged in order from the object side to the image side. The rear group 103 includes an anti-vibration group LIS with negative refractive power. The image stabilization group LIS moves in a direction that includes a component perpendicular to the optical axis during image stabilization, that is, in order to move the imaging position in a direction perpendicular to the optical axis, the image stabilization group LIS moves in a direction that includes a component perpendicular to the optical axis. This is a lens group that moves in a direction that has a component. In Patent Document 2, the vibration isolation group that moves for vibration isolation has positive refractive power. However, if an image stabilizing group with a positive refractive power is placed closer to the image side than the aperture stop, off-axis light beams are eclipsed during image stabilization, resulting in a decrease in the amount of peripheral light. This makes it difficult to ensure a sufficient vibration isolation angle. Alternatively, the diameter of the vibration isolation group is increased in order to avoid a decrease in peripheral light intensity, resulting in an increase in the size of the vibration isolation group. This makes high-speed vibration isolation difficult. On the other hand, if an anti-vibration group with positive refractive power is placed closer to the object than the aperture stop, a decrease in the amount of peripheral light can be avoided. However, in this case, fluctuations in field curvature during image stabilization become large. Therefore, in a fisheye lens, an anti-vibration group with negative refractive power should be placed closer to the image side than the aperture stop.

Furthermore, the optical system 101 of each example satisfies the following conditional expression (1).

1.2<Dr1/ftotal<20.0...(1)
Here, Dr1 is the distance on the optical axis from the aperture stop SP to the lens surface closest to the object side of the image stabilization group LIS. ftotal is the focal length of the optical system 101 at the d-line.

Conditional expression (1) is a condition for optimizing the position of the vibration isolation group LIS in the optical system 101. If the lower limit of conditional expression (1) is not reached, the distance between the image stabilization group LIS and the aperture stop SP becomes too close, and coma aberration that occurs during image stabilization becomes large. If the upper limit of conditional expression (1) is exceeded, the image stabilization group LIS becomes too far from the aperture stop SP, and the curvature of field and astigmatism that occur during image stabilization become large.

Furthermore, it is preferable that the numerical range of conditional expression (1) is the range of conditional expression (1a) below.

1.8<Dr1/ftotal<10.0...(1a)
Further, it is more preferable that the numerical range of conditional expression (1) is the range of conditional expression (1b) below.

2.0<Dr1/ftotal<5.0...(1b)
With the above configuration, it is possible to configure an optical system suitable for realizing an image stabilization function in a fisheye lens.

Next, a configuration that is preferably satisfied in the optical system 101 of each embodiment will be described.

In the optical system 101 of each example, the lens placed closest to the object side in the front group 102 and the lens placed second from the object side in the front group 102 are both negative lenses. It is preferable. Further, the lens disposed closest to the object side is preferably a negative meniscus lens with a convex surface facing the object side. In order to ensure the wide angle of view required of a fisheye lens, it is preferable to increase the refractive power of the negative lens. At this time, it is preferable to use two or more negative lenses in order to satisfactorily correct distortion and field curvature.

In the optical system 101 of each embodiment, the front group 102 preferably has negative refractive power. In a fisheye lens, the paraxial focal length is small in order to obtain a wide angle of view. In order to secure space for inserting lenses necessary for aberration correction, a so-called retrofocus configuration is adopted in which the front group 102 with negative refractive power and the rear group 103 with positive refractive power are arranged in order from the object side. is preferred.

In the optical system 101 of each embodiment, the rear group 103 preferably includes a lens group r1 with a positive refractive power disposed between the aperture stop SP and the image stabilization group LIS that moves during image stabilization. Since the vibration isolation group LIS has negative refractive power, the height of the off-axis light beam in the rear group 103 tends to become high. In order to downsize the image stabilization group LIS, it is preferable to arrange a lens group r1 having a positive refractive power closer to the object side than the image stabilization group LIS.

In the optical system 101 of each embodiment, the rear group 103 preferably has a lens group r2 with positive refractive power disposed between the image stabilization group LIS and the image plane IP. In order to increase the vibration isolation angle per amount of movement of the vibration isolation group LIS, it is preferable to arrange the lens closer to the image side than the vibration isolation group LIS. Furthermore, since the image stabilization group LIS has a negative refractive power, it is preferable to make the refractive power of the lens group r2 positive, since it is possible to reduce changes in the curvature of field during image stabilization.

In the optical system 101 of each embodiment, the vibration isolation group LIS preferably includes a positive lens having an Abbe number of 10 or more and 30 or less. In order to reduce the change in lateral chromatic aberration during image stabilization, it is preferable that chromatic aberration be well corrected in the image stabilization group LIS. On the other hand, it is preferable to increase the refractive power of the negative lens in order to reduce aberration fluctuations during image stabilization and to configure the image stabilization group LIS with a small number of lenses to make it smaller and lighter. At this time, it is preferable to use a high refractive material for the negative lens, and in this case, the negative lens has relatively high dispersion. Therefore, it is preferable that the image stabilization group LIS further includes a positive lens made of a highly dispersive material in order to correct chromatic aberration.

Next, conditions that are preferably satisfied by the optical system 101 of each example will be described. It is preferable that the optical system 101 of each embodiment satisfies at least one of the following conditional expressions (2) to (10).

5.0<Dtotal/fttotal<30.0...(2)
0.60<Dr1/fr1<3.00...(3)
1.50<fr1/ftotal<5.00 (4)
-10.00<fLIS/ftotal<-3.00...(5)
2.0<fr2/ftotal<20.0...(6)
0.10<fr1/fr2<1.00 (7)
1.30<βIS<6.00...(8)
0.10<βr2<1.00 (9)
160°<FOV<220°...(10)
Here, Dtotal is the distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side in the optical system 101. fr1 is the composite focal length at the d-line of the lens arranged between the aperture stop SP and the image stabilization group LIS. fLIS is the focal length of the vibration isolation group LIS at the d-line. fr2 is the composite focal length at the d-line of the lens placed between the image stabilization group LIS and the image plane. βIS is the lateral magnification of the vibration isolation group LIS. βr2 is the composite lateral magnification of the lens arranged between the image stabilization group LIS and the image plane. FOV is the total angle of view (°) of the optical system 101.

Conditional expression (2) defines the ratio between the total lens length of the optical system 101 and the focal length of the optical system 101. If the lower limit of conditional expression (2) is not reached, the total lens length of the optical system 101 becomes too short, making it difficult to insert the image stabilization group LIS, which is not preferable. Exceeding the upper limit of conditional expression (2) is not preferable because the optical system 101 becomes larger.

The numerical range of conditional expression (2) is more preferably within the range of conditional expression (2a) below, and even more preferably within the range of conditional expression (2b) below.

6.0<Dtotal/fttotal<25.0...(2a)
8.0<Dtotal/fttotal<20.0...(2b)
Conditional expression (3) defines the ratio between the distance on the optical axis from the aperture stop SP to the image stabilization group LIS and the composite focal length of the lens placed between the aperture stop SP and the image stabilization group LIS. It is. In order to capture a stereoscopic image necessary for a VR image, it is preferable to arrange two optical systems identical to the optical system 101 in parallel. If the lower limit of conditional expression (3) is not reached, the convergence effect on the off-axis light beam will be insufficient, and the image stabilization group LIS will become large, which is not preferable. Moreover, if the upper limit of conditional expression (3) is exceeded, the distance between the aperture stop SP and the image stabilization group LIS becomes too large, which is not preferable because the fluctuation of the curvature of field during image stabilization becomes large.

The numerical range of conditional expression (3) is more preferably within the range of conditional expression (3a) below, and even more preferably within the range of conditional expression (3b) below.

0.70<Dr1/fr1<2.50...(3a)
0.75<Dr1/fr1<2.00...(3b)
Conditional expression (4) defines the ratio between the composite focal length of the lenses arranged between the aperture stop SP and the image stabilization group LIS and the focal length of the optical system 101. If the lower limit of conditional expression (4) is exceeded, the positive refractive power of the lens group disposed between the aperture stop SP and the image stabilization group LIS becomes too strong, and spherical aberration and coma aberration become large, which is not preferable. Moreover, if the upper limit of conditional expression (4) is exceeded, the convergence effect on the off-axis light beam becomes too weak and the vibration isolation group LIS becomes large, which is not preferable.

The numerical range of conditional expression (4) is more preferably within the range of conditional expression (4a) below, and even more preferably within the range of conditional expression (4b) below.

2.00<fr1/ftotal<4.50...(4a)
2.50<fr1/ftotal<4.00...(4b)
Conditional expression (5) defines the ratio between the focal length of the image stabilization group LIS and the focal length of the optical system 101. If the lower limit of conditional expression (5) is not reached, the refractive power of the image stabilization group LIS becomes too strong, which is not preferable because the fluctuations in lateral chromatic aberration and curvature of field during image stabilization become large. Moreover, if the upper limit of conditional expression (5) is exceeded, the refractive power of the vibration isolation group LIS becomes too weak, making it difficult to secure a sufficient vibration isolation angle, which is not preferable.

The numerical range of conditional expression (5) is more preferably within the range of conditional expression (5a) below, and even more preferably within the range of conditional expression (5b) below.

-8.00<fLIS/ftotal<-3.50...(5a)
-7.00<fLIS/ftotal<-4.00...(5b)
Conditional expression (6) defines the ratio of the combined focal length of the lenses arranged between the image stabilizing group LIS and the image plane IP and the focal length of the optical system 101. If the lower limit of conditional expression (6) is not reached, the refractive power of the lens group disposed closer to the image side than the image stabilization group LIS will become too strong, making it difficult to secure the necessary back focus, which is not preferable. Furthermore, if the upper limit of conditional expression (6) is exceeded, the refractive power of the lens group placed on the image side of the image stabilization group LIS becomes too weak, making it difficult to secure a sufficient image stabilization angle, which is not preferable. .

The numerical range of conditional expression (6) is more preferably within the range of conditional expression (6a) below, and even more preferably within the range of conditional expression (6b) below.

3.0<fr2/ftotal<18.0...(6a)
4.0<fr2/ftotal<16.0...(6b)
Conditional expression (7) is the combined focal length of the lens placed between the aperture stop SP and the image stabilization group LIS, and the combined focal length of the lens placed between the image stabilization group LIS and the image plane IP. It defines the ratio. If the lower limit of conditional expression (7) is not reached, the refractive power of the lens group disposed between the aperture stop SP and the vibration isolation group LIS becomes too strong, which is not preferable because spherical aberration and coma aberration become large. Moreover, if the upper limit of conditional expression (7) is exceeded, the refractive power of the lens group arranged between the aperture diaphragm SP and the image stabilization group LIS becomes too weak, and the image stabilization group LIS becomes large, which is not preferable. .

The numerical range of conditional expression (7) is more preferably within the range of conditional expression (7a) below, and even more preferably within the range of conditional expression (7b) below.

0.15<fr1/fr2<0.90...(7a)
0.20<fr1/fr2<0.80...(7b)
Conditional expression (8) defines the lateral magnification of the vibration isolation group LIS. If the lower limit of conditional expression (8) is not reached, the relative movement amount of the image when moving the image stabilization group LIS becomes small, which is not preferable because the image stabilization effect becomes small. Moreover, if the upper limit of conditional expression (8) is exceeded, the amount of movement of the image relative to the amount of movement of the image stabilization group LIS becomes too large, making it difficult to precisely control the image stabilization group LIS, which is not preferable.

The numerical range of conditional expression (8) is more preferably within the range of conditional expression (8a) below, and even more preferably within the range of conditional expression (8b) below.

1.40<βIS<4.50...(8a)
1.50<βIS<4.00...(8b)
Conditional expression (9) defines the combined lateral magnification of the lenses arranged between the image stabilization group LIS and the image plane IP in the optical system 101. If the lower limit of conditional expression (9) is not reached, the relative movement amount of the image when moving the image stabilization group LIS becomes small, which is not preferable because the image stabilization effect becomes small. Moreover, if the upper limit of conditional expression (9) is exceeded, the amount of movement of the image relative to the amount of movement of the image stabilization group LIS becomes too large, making it difficult to precisely control the image stabilization group LIS, which is not preferable.

The numerical range of conditional expression (9) is more preferably within the range of conditional expression (9a) below, and even more preferably within the range of conditional expression (9b) below.

0.20<βr2<0.90...(9a)
0.30<βr2<0.80 (9b)
Conditional expression (10) defines the total angle of view (°) of the optical system 101. If the lower limit of conditional expression (10) is not reached, the angle of view becomes too small, making it impossible to ensure a sense of immersion, which is important in VR viewing, which is not preferable. Moreover, if the upper limit of conditional expression (10) is exceeded, the angle of view becomes too large and the relative resolution per unit angle of view is insufficient, resulting in a decrease in image quality during viewing, which is not preferable.

The numerical range of conditional expression (10) is more preferably within the range of conditional expression (10a) below, and even more preferably within the range of conditional expression (10b) below.

170°<FOV<205°...(10a)
175°<FOV<200°...(10b)
Next, the optical system 101 of each embodiment will be described in detail.

FIG. 1 is a cross-sectional view of a lens of an optical system 101 in Example 1. The optical system 101 of the first embodiment includes a front group 102, an aperture stop SP, and a rear group 103, which are arranged in order from the object side to the image side. The rear group 103 includes a lens group r1, an image stabilization group LIS, and a lens group r2, which are arranged in order from the object side to the image side. FIG. 2 is an aberration diagram of the optical system 101 of Example 1 when focusing on infinity. FIG. 3 is a lateral aberration diagram of the optical system 101 of Example 1 when focusing on infinity. The amount of movement of the anti-vibration group LIS is 0.40 mm, and the anti-vibration angle at this time, that is, the angular change on the object side of the principal ray of the luminous flux reaching the image point at height 0 is 2.7°.

Other examples different from Example 1 will be described below. Regarding the other embodiments, only the points different from the first embodiment will be described.

FIG. 4 is a cross-sectional view of the lens of the optical system 101 in Example 2. The optical system 101 of the second embodiment includes a front group 102, an aperture stop SP, and a rear group 103, which are arranged in order from the object side to the image side. The rear group 103 includes a lens group r1, an image stabilization group LIS, and a lens group r2, which are arranged in order from the object side to the image side. FIG. 5 is an aberration diagram of the optical system 101 of Example 2 when focusing on infinity. FIG. 6 is a lateral aberration diagram of the optical system 101 of Example 2 when focusing on infinity.

The second embodiment differs from the first embodiment in that the vibration isolation angle is larger. The amount of movement of the vibration isolation group LIS is 1.0 mm, and the vibration isolation angle at this time is 9.0°.

FIG. 7 is a cross-sectional view of the lens of the optical system 101 of Example 3. The optical system 101 of the third embodiment differs from the optical system 101 of the first embodiment in that a first reflecting member 201 and a second reflecting member 202 for bending the optical path are arranged. In FIG. 7, the folded optical path is shown unfolded. The position of the reflective surface is located exactly between the respective reflective members 201 and 202. In the third embodiment, a prism is used to bend the optical path, but a mirror may be used to bend the optical path.

The optical system 101 of the third embodiment includes a front group 102, an aperture stop SP, and a rear group 103, which are arranged in order from the object side to the image side. A first reflecting member 201 is arranged closest to the image side of the front group 102. The rear group 103 includes a lens group r1, an image stabilization group LIS, and a lens group r2, which are arranged in order from the object side to the image side. A second reflective member 202 is arranged in the lens group r1.

FIG. 8 is a cross-sectional view of a main part of a lens device 100 in which two optical systems 101 (a first optical system 101A and a second optical system 101B) of Example 3 are arranged in parallel. This shows a state in which the optical path is bent. Note that in FIG. 8 and the following description, the subscript A indicates the configuration of the first optical system 101A. The subscript B indicates the configuration of the second optical system 101B. In order to capture a VR image with a three-dimensional effect, it is preferable that the distance (baseline length) between the optical axes on the incident side of the two optical systems 101A and 101B be about the same as that of the human eye (about 60 to 65 mm). . By arranging two optical systems 101 of Embodiment 3 in parallel for one sensor surface, optical It is possible to perform vibration isolation.

FIG. 9 shows a mechanical structure that integrally holds two vibration isolation groups 301 and 302 (first vibration isolation group and second vibration isolation group) in two optical systems 101A and 101B. In the lens barrel 300, two vibration isolation groups 301 and 302 are arranged, corresponding to the two optical systems 101A and 101B, respectively. In the optical system 101 that bends the optical path as in the third embodiment, in order to easily realize optical image stabilization, the image stabilization group LIS is arranged between the image plane IP and the reflective surface closest to the image plane IP. It is preferable. Furthermore, it is preferable that the two optical systems 101A and 101B arranged in parallel have a mechanical structure in which the two vibration isolation groups 301 and 302 move together. In FIG. 9, two vibration isolation groups 301 and 302 are held by a holding mechanism 310, and when the holding mechanism 310 moves within the YZ plane relative to the lens barrel 300 during vibration isolation, the two vibration isolation groups 301 and 302 are The vibration isolation groups 301 and 302 move together.

FIG. 10 shows a modification of the structure for moving the two vibration isolation groups 301 and 302 together. FIG. 10 shows a structure that connects the vibration isolation groups 301 and 302 in the two optical systems 101A and 101B, and the vibration isolation groups 301 and 302 that are simultaneously driven by the structure. Similarly to FIG. 9, FIG. 10 also shows a structure for driving two vibration isolation groups 301 and 302 simultaneously.

FIG. 11 is an aberration diagram of the optical system 101 of Example 3 when focusing on infinity. FIG. 12 is a lateral aberration diagram of the optical system 101 of Example 3 when focusing on infinity. The amount of movement of the vibration isolation group LIS is 0.4 mm, and the vibration isolation angle at this time is 2.3°.

FIG. 13 is a cross-sectional view of the lens of the optical system 101 of Example 4. The optical system 101 of the fourth embodiment, like the optical system 101 of the third embodiment, includes a first reflecting member 201 and a second reflecting member 202 for bending the optical path. The folded optical path is shown expanded. Further, the position of the reflective surface is located exactly between the respective reflective members 201 and 202.

The optical system 101 of the fourth embodiment includes a front group 102, an aperture stop SP, and a rear group 103, which are arranged in order from the object side to the image side. A first reflecting member 201 is arranged closest to the image side of the front group 102. The rear group 103 includes a lens group r1, an image stabilization group LIS, and a lens group r2, which are arranged in order from the object side to the image side. A second reflective member 202 is arranged in the lens group r1.

FIG. 14 is an aberration diagram of the optical system 101 of Example 4 when focusing on infinity. FIG. 15 is a lateral aberration diagram of the optical system 101 of Example 4 when focusing on infinity. The amount of movement of the vibration isolation group LIS is 0.4 mm, and the vibration isolation angle at this time is 2.6°.

A lens device 100 in which two optical systems 101 each having a reflecting member that bends an optical path as in Examples 3 and 4 are arranged in parallel satisfies the following conditional expression (11).

0.05<Dout/Din<0.50 (11)
Here, Din is the distance between the surface vertices of the lens located closest to the object in the two optical systems 101A and 101B arranged in parallel. Dout is the distance between the surface vertices of the lenses arranged closest to the image side in the two optical systems 101A and 101B arranged in parallel. The value of Dout is taken so that the two image circles are circumscribed. Therefore, in Examples 3 and 4, Dout=17.1 mm. At this time, the value of Din is also determined from numerical examples described later, and Din=58.6 mm. However, in Examples 3 and 4, the angle at which the optical path is bent is 90°.

Conditional expression (11) defines the baseline length of the lens device 100 in which the two optical systems 101A and 101B are arranged in parallel. When the lower limit of conditional expression (11) is below, in the two optical systems 101A and 101B arranged in parallel, the distance between the rear group 103A of the first optical system 101A and the rear group 103B of the second optical system 101B becomes If it becomes too small, it becomes difficult to perform vibration isolation, which is undesirable. Furthermore, if the upper limit of conditional expression (11) is exceeded, the base line length will be insufficient, making it impossible to obtain a sufficient three-dimensional effect when viewing VR images, which is not preferable.

The numerical range of conditional expression (11) is more preferably within the range of conditional expression (11a) below, and even more preferably within the range of conditional expression (11b) below.

0.10<Dout/Din<0.45...(11a)
0.20<Dout/Din<0.40...(11b)
Numerical Examples 1 to 4 corresponding to Examples 1 to 4 are shown below.

In the surface data of each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the axial distance (distance on the optical axis) between the m-th surface and the (m+1)-th surface. . However, m is the number of the surface counted from the light incident side. Further, nd represents the refractive index of each optical member with respect to the d-line, and νd represents the Abbe number of the optical member. The Abbe number νd of a certain material is νd when the refractive index at the Fraunhofer line d line (587.6 nm), F line (486.1 nm), and C line (656.3 nm) is Nd, NF, and NC. It is expressed as =(Nd-1)/(NF-NC).

In each numerical example, d, focal length (mm), F number, and half angle of view (°) are all values when the optical system 101 of each example focuses on an object at infinity. "Back focus BF" is the distance on the optical axis from the final lens surface (the lens surface closest to the image side) to the paraxial image surface expressed in air equivalent length. The "total lens length" is the length obtained by adding the back focus to the distance on the optical axis from the frontmost surface (lens surface closest to the object) of the optical system to the final surface. A "lens group" is not limited to a case where it is composed of a plurality of lenses, but also includes a case where it is composed of a single lens.

Numerical Examples 1 to 4 employ a method in which the entire optical system 101 is extended when focusing from an object at infinity to an object at a short distance. However, in order to reduce the weight of the driving unit, it is also possible to perform focusing by driving some of the lenses of the optical system 101.

Furthermore, if the optical surface is an aspherical surface, an * symbol is attached to the right side of the surface number. The aspherical shape is expressed as follows: When A8 and A10 are the aspheric coefficients of each order,
x=(h ² /R)/[1+{1-(1+k)(h/R) ² } ^1/2 ]+A4×h ⁴ +A6×h ⁶ +A8×h ⁸ +A10×h ¹⁰
It is expressed as Note that "e±XX" in each aspheric coefficient means "x10±XX".

[Numerical Example 1]
Unit: mm

Surface data Surface number rd nd νd Effective diameter
1 37.494 2.30 1.76385 48.5 44.43
2 12.703 8.77 24.61
3* 31.891 1.50 1.76385 48.5 21.91
4* 9.084 6.68 15.72
5 -19.195 1.00 1.72916 54.7 14.88
6 43.904 1.89 14.68
7 -450.634 2.80 1.95375 32.3 14.84
8 -18.856 1.39 14.96
9 37.473 5.88 1.54814 45.8 12.34
10 -9.679 1.00 1.52841 76.5 9.93
11 97.644 5.86 8.37
12(Aperture) ∞ 2.89 6.26
13 -61.647 1.00 1.90525 35.0 6.52
14 12.714 3.01 1.59522 67.7 6.67
15 -15.555 0.50 8.33
16 -93.283 2.01 1.52841 76.5 9.28
17 -31.794 0.50 10.39
18 15.330 3.65 1.49700 81.6 12.25
19 -29.583 0.30 12.57
20 -278.618 1.20 1.85025 30.1 12.63
21 9.962 3.34 1.92286 20.9 12.84
22 23.300 0.62 12.82
23 20.056 1.00 2.00100 29.1 13.29
24 9.544 7.64 1.59282 68.6 13.05
25 -19.983 12.83 14.52
Image plane ∞

Aspheric data 3rd surface
K =-3.17249e+00 A 4=-7.28609e-06 A 6=-5.21032e-08 A 8= 3.07460e-10

Side 4
K =-1.75208e-01 A 4= 7.81192e-06 A 6=-1.85735e-07 A 8= 8.11459e-10

Various data

Focal length 4.98
F number 2.91
Half angle of view (°) 59.77
Image height 8.55
Lens total length 79.56
BF 12.83

Entrance pupil position 12.84
Exit pupil position -48.37
Front principal point position 17.42
Back principal point position 7.85

Lens group data group Starting surface Focal length Lens length Front principal point position Rear principal point position
1 1 -18.71 33.20 -0.69 -43.04
r1 12 15.35 13.57 8.82 -0.62
LIS 20 -28.46 4.54 2.55 0.15
r2 23 27.80 8.64 3.86 -1.79

Single lens data lens starting surface focal length
1 1 -26.20
2 3 -17.12
3 5 -18.20
4 7 20.57
5 9 14.68
6 10 -16.61
7 13 -11.57
8 14 12.24
9 16 90.26
10 18 20.88
11 20 -11.29
12 21 16.83
13 23 -19.10
14 24 12.06

[Numerical Example 2]
Unit: mm

Surface data Surface number rd nd νd Effective diameter
1 39.936 2.30 1.76385 48.5 45.31
2 12.593 9.10 24.43
3* 22.861 1.50 1.76385 48.5 21.95
4* 7.691 6.36 16.03
5 -26.679 1.00 1.72916 54.7 15.36
6 32.457 1.80 15.03
7 124.017 3.03 1.95375 32.3 15.22
8 -20.200 0.50 15.25
9 144.914 4.83 1.54814 45.8 13.37
10 -9.348 1.00 1.52841 76.5 11.97
11 -76.899 7.69 10.38
12(Aperture) ∞ 1.69 6.45
13 -41.827 1.00 1.90525 35.0 6.55
14 11.024 3.00 1.59522 67.7 6.73
15 -14.048 0.50 7.25
16 -71.503 1.95 1.52841 76.5 7.86
17 -28.389 0.50 8.94
18 18.162 3.19 1.49700 81.6 10.24
19 -19.558 0.30 10.74
20 -97.640 1.20 1.85025 30.1 10.88
21 8.688 3.18 1.92286 20.9 11.35
22 20.145 2.17 11.47
23 18.761 1.00 2.00100 29.1 13.40
24 10.372 7.56 1.59282 68.6 13.28
25 -19.396 13.50 14.75
Image plane ∞

Aspheric data 3rd surface
K =-1.71470e+01 A 4=-7.58301e-05 A 6= 5.33793e-07 A 8=-1.28688e-09

Side 4
K =-6.90385e-01 A 4=-1.80584e-04 A 6= 1.47952e-06 A 8=-2.13461e-10

Various data

Focal length 5.23
F number 2.91
Half angle of view (°) 58.56
Image height 8.55
Lens total length 79.85
BF 13.50

Entrance pupil position 12.70
Exit pupil position -50.81
Front principal point position 17.50
Back principal point position 8.27

Lens group data group Starting surface Focal length Lens length Front principal point position Rear principal point position
1 1 -30.21 31.42 -8.98 -69.10
r1 12 15.10 11.83 8.04 0.48
LIS 20 -21.55 4.38 2.15 -0.13
r2 23 23.47 8.56 3.37 -2.30

Single lens data lens starting surface focal length
1 1 -24.99
2 3 -15.85
3 5 -19.94
4 7 18.40
5 9 16.20
6 10 -20.24
7 13 -9.55
8 14 10.86
9 16 87.73
10 18 19.50
11 20 -9.33
12 21 14.61
13 23 -24.64
14 24 12.59

[Numerical Example 3]
Unit: mm

Surface data Surface number rd nd νd Effective diameter
1 42.226 1.90 1.76385 48.5 39.47
2 11.338 6.68 21.91
3 21.623 1.05 1.76385 48.5 20.34
4 10.485 7.15 16.50
5 -15.116 0.85 1.85150 40.8 15.57
6 89.063 1.76 16.07
7 -250.197 3.90 1.91650 31.6 16.63
8 -16.982 7.10 17.08
9 ∞ 13.40 1.51633 64.1 11.06
10 ∞ 2.28 10.00
11(Aperture) ∞ 1.47 8.17
12 40.529 0.50 1.94864 33.4 8.42
13 12.686 2.95 1.59303 44.1 8.39
14 -21.153 0.15 8.62
15 ∞ 13.40 1.51633 64.1 10.00
16 ∞ 1.00 12.40
17 18.761 3.31 1.43875 94.7 13.82
18 -25.862 0.50 13.97
19 163.171 1.00 1.91449 32.0 13.91
20 15.040 1.68 1.92286 20.9 13.76
21 26.978 1.00 13.70
22 20.059 1.87 1.52841 76.5 14.24
23 55.536 0.30 14.21
24 20.247 0.75 2.00100 29.1 14.32
25 9.413 6.75 1.49700 81.6 13.56
26 -42.378 12.83 14.37
Image plane ∞

Various data

Focal length 5.36
F number 2.91
Half angle of view (°) 57.91
Image height 8.55
Lens total length 95.54
BF 12.83

Entrance pupil position 11.55
Exit pupil position -49.78
Front principal point position 16.45
Back principal point position 7.47

Lens group data group Starting surface Focal length Lens length Front principal point position Rear principal point position
1 1 -12.89 43.80 1.59 -41.47
r1 11 18.89 22.78 11.79 -6.22
LIS 19 -36.02 2.68 1.71 0.30
r2 22 40.44 9.66 1.62 -5.13

Single lens data lens starting surface focal length
1 1 -20.85
2 3 -27.78
3 5 -15.12
4 7 19.72
5 9 0.00
6 12 -19.64
7 13 13.82
8 15 0.00
9 17 25.36
10 19 -18.17
11 20 34.50
12 22 58.36
13 24 -18.21
14 25 16.20

[Numerical Example 4]
Unit: mm

Surface data Surface number rd nd νd Effective diameter
1 42.952 1.90 1.76385 48.5 39.49
2 11.377 5.85 21.91
3 17.504 1.05 2.00100 29.1 20.34
4 10.673 7.50 16.99
5 -16.842 0.85 1.85150 40.8 15.64
6 45.129 2.93 15.85
7 275.574 3.90 1.91650 31.6 16.87
8 -18.746 7.10 17.19
9 ∞ 13.40 1.51633 64.1 11.18
10 ∞ 2.31 12.40
11(Aperture) ∞ 1.44 8.11
12 32.818 0.50 1.89163 39.6 8.32
13 11.946 2.95 1.52376 49.1 8.27
14 -20.382 0.15 8.47
15 ∞ 13.40 1.51633 64.1 12.40
16 ∞ 0.50 12.40
17 109.582 1.47 1.43875 94.7 12.83
18 -80.994 0.50 13.21
19 18.137 4.24 1.49700 81.6 14.29
20 -27.158 0.15 14.31
21 963.905 1.00 1.85025 30.1 14.02
22 14.625 1.65 1.92286 20.9 13.63
23 21.956 0.30 13.44
24 18.756 0.75 2.00100 29.1 13.57
25 9.344 6.73 1.49700 81.6 13.02
26 -29.601 12.83 14.03
Image plane ∞

Various data

Focal length 5.35
F number 2.91
Half angle of view (°) 57.97
Image height 8.55
Lens total length 95.35
BF 12.83

Entrance pupil position 11.44
Exit pupil position -46.60
Front principal point position 16.31
Back principal point position 7.48

Lens group data group Starting surface Focal length Lens length Front principal point position Rear principal point position
1 1 -15.03 44.47 -0.15 -48.38
r1 11 16.36 25.15 13.89 -6.45
LIS 21 -27.81 2.65 1.56 0.15
r2 24 59.08 7.48 3.73 -1.32

Single lens data lens starting surface focal length
1 1 -20.80
2 3 -29.60
3 5 -14.31
4 7 19.27
5 9 0.00
6 12 -21.31
7 13 14.85
8 15 0.00
9 17 106.40
10 19 22.58
11 21 -17.47
12 22 42.83
13 24 -19.38
14 25 15.16

Various values in each numerical example are summarized in Table 1 below.

[Imaging device]
Next, an embodiment of a digital still camera (imaging device) using the optical system 101 of the present invention as an imaging optical system will be described using FIG. 16. FIG. 16 is a schematic side view of the imaging device 400 of this embodiment. The imaging device 400 includes a camera body 420 having one imaging element 410, and a lens device 100 having an optical system 101 similar to any of Examples 1 to 4 described above. The lens device 100 and the camera body 420 may be configured integrally or may be configured to be detachable. The camera body 420 may be a so-called single-lens reflex camera with a quick turn mirror, or a so-called mirrorless camera without a quick turn mirror. The image sensor 410 is a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or a CMOS sensor that receives an optical image formed by the optical system 101 and converts it photoelectrically. Although only one optical system is shown in FIG. 16, two optical systems 101 configured to bend the optical path as in Examples 3 and 4 may be arranged in parallel in the depth direction.

In this embodiment, by having a lens device 100 equipped with an optical system 101 that is similar to any of the above-described embodiments 1 to 4, it is possible to provide an imaging device 400 with an image stabilization function. .

Note that the lens device 100 described above can be applied not only to the digital still camera shown in FIG. 16 but also to various imaging devices such as a broadcasting camera, a silver halide film camera, and a surveillance camera.

Although preferred embodiments and examples of the present invention have been described above, the present invention is not limited to these embodiments and examples, and various combinations, modifications, and changes can be made within the scope of the gist.

Optical system 101
Front group 102
Rear group 103
Aperture diaphragm SP
Anti-vibration group LIS

Claims (23)

An optical system consisting of a front group, an aperture stop, and a rear group with positive refractive power arranged in order from the object side to the image side,
The rear group includes a vibration isolation group with negative refractive power that moves in a direction including a component perpendicular to the optical axis during vibration isolation,
When the distance on the optical axis from the aperture stop to the lens surface closest to the object side of the image stabilization group is Dr1, and the focal length of the optical system is ftotal,
1.2<Dr1/ftotal<20.0
An optical system characterized by satisfying the following conditional expression. The lens arranged closest to the object side in the front group and the second lens arranged from the object side in the front group are negative lenses,
2. The optical system according to claim 1, wherein the lens disposed closest to the object side is a negative meniscus lens with a convex surface facing the object side. The optical system according to claim 1 or 2, wherein the front group has negative refractive power. 4. The optical system according to claim 1, wherein the rear group includes a lens group having a positive refractive power disposed between the aperture stop and the vibration isolation group. The optical system according to any one of claims 1 to 4, wherein the rear group includes a lens group with a positive refractive power disposed between the image stabilization group and an image plane. When the distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side in the optical system is Dtotal,
5.0<Dtotal/fttotal<30.0
6. The optical system according to claim 1, wherein the optical system satisfies the following conditional expression. When the composite focal length of the lens arranged between the aperture stop and the image stabilization group is fr1,
0.60<Dr1/fr1<3.00
7. The optical system according to claim 1, wherein the optical system satisfies the following conditional expression. When the composite focal length of the lens arranged between the aperture stop and the image stabilization group is fr1,
1.50<fr1/ftotal<5.00
8. The optical system according to claim 1, wherein the optical system satisfies the following conditional expression. When the focal length of the vibration isolation group is fLIS,
-10.00<fLIS/fttotal<-3.00
9. The optical system according to claim 1, wherein the optical system satisfies the following conditional expression. When the composite focal length of the lens arranged between the image stabilizing group and the image plane is fr2,
2.0<fr2/ftotal<20.0
10. The optical system according to claim 1, wherein the optical system satisfies the following conditional expression. When the composite focal length of the lens arranged between the aperture stop and the image stabilization group is fr1, and the composite focal length of the lens arranged between the image stabilization group and the image plane is fr2, 0.10 <fr1/fr2<1.00
11. The optical system according to claim 1, wherein the optical system satisfies the following conditional expression. 12. The optical system according to claim 1, wherein the image stabilization group includes a positive lens having an Abbe number of 10 or more and 30 or less. When the lateral magnification of the vibration isolation group is βIS,
1.30<βIS<6.00
13. The optical system according to claim 1, wherein the optical system satisfies the following conditional expression. When the composite lateral magnification of the lens arranged between the image stabilization group and the image plane is βr2,
0.10<βr2<1.00
14. The optical system according to claim 1, wherein the optical system satisfies the following conditional expression. When the entire angle of view of the optical system is FOV,
160°＜FOV＜220°
15. The optical system according to claim 1, wherein the optical system satisfies the following conditional expression. 16. The optical system according to claim 1, wherein a first reflecting member for bending an optical path is arranged in the front group. 17. The optical system according to claim 1, wherein a second reflecting member for bending an optical path is disposed in the rear group. Two optical systems: a first optical system as an optical system according to any one of claims 1 to 17, and a second optical system as an optical system according to any one of claims 1 to 17. A lens device characterized by having an optical system. 19. The lens device according to claim 18, wherein the two optical systems are arranged in parallel. When the distance between the surface vertices of the lens placed closest to the object side in the two optical systems is Din, and the distance between the surface vertices of the lens placed closest to the image side in the two optical systems is Dout,
0.05<Dout/Din<0.50
20. The lens device according to claim 18, wherein the lens device satisfies the following conditional expression. The first vibration isolation group, which is the vibration isolation group in the first optical system, and the second vibration isolation group, which is the vibration isolation group in the second optical system, are held by the same holding mechanism. 21. A lens device according to any one of claims 18 to 20. A lens device according to any one of claims 18 to 21;
An imaging device comprising: an imaging element that captures an optical image formed by the two optical systems. 23. The imaging device according to claim 22, wherein the optical images obtained by the two optical systems are captured by one image sensor.