JP2019109539A - Optical system and imaging apparatus - Google Patents

Abstract

To provide a large-aperture optical system in which the size and weight of a vibration-proof optical system are reduced and which is excellent in optical performance during vibration proof and is bright.SOLUTION: The optical system comprises, in order from an object side, a first lens group Gf, a vibration-proof lens group Gvc, and a third lens group Gr. The vibration-proof lens group Gvc comprises a single lens unit and the third lens group Gr has at least one lens having negative refractive power. The optical system satisfies a properly set conditional expression.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical system and an imaging apparatus suitable as an imaging optical system, and more particularly to an optical system and an imaging apparatus having a vibration reduction function for reducing image blurring caused by vibration such as camera shake at the time of imaging.

  BACKGROUND ART Conventionally, imaging devices using solid-state imaging devices such as digital cameras and video cameras have become widespread. In recent years, with the miniaturization of optical systems in lens exchange systems, etc., the market for lens interchangeable type imaging devices such as single-lens reflex cameras and mirrorless single-lens cameras has significantly expanded, and a wide range of user groups use lens interchangeable type imaging devices It is getting to be done. With the expansion of such a user layer, there is a demand for brighter large-aperture optical systems as well as performance and miniaturization of optical systems in lens exchange systems. There is also a strong demand for reduction of image blurring caused by vibration such as camera shake at the time of imaging. Furthermore, cost reduction is also required along with these.

  Under such circumstances, for example, Patent Document 1 discloses a retrofocus type wide-angle lens provided with an anti-vibration optical system, and corrects image blurring caused by vibration such as camera shake at the time of imaging. It is assumed.

Patent No. 5196281 gazette

  However, although the optical system described in Patent Document 1 exhibits good optical performance, the vibration-proof optical system is constituted by a cemented lens, and further downsizing and weight reduction of the vibration-proof optical system are required. .

  Therefore, an object of the present invention is to provide a bright, large-aperture optical system excellent in optical performance at the time of vibration reduction, as well as achieving downsizing and weight reduction of the vibration-proof optical system.

  As a result of intensive studies, the present inventors have achieved the above object by adopting the following optical system.

  The optical system according to the present invention comprises, in order from the object side, a first lens group Gf, a vibration reduction lens group Gvc that moves in a direction perpendicular to the optical axis to change the image position, and a third lens group Gr. In the optical system, the vibration reduction lens group Gvc is configured of a single lens unit, the third lens group Gr includes at least one lens having negative refractive power, and satisfies the following conditional expression It is characterized by

0.90 <| fvc | / f <3.10 (1)
45 <d dvc ... (2) '
0.996 ≦ | fr | / f <1.80 (3) ′ ′ ′ ′
−0.1 <Cr1vc / ff (4) '
1.110 ≦ | ff / f | ... (6) ''
However, in each of the above equations,
fvc is a focal length of the anti-vibration lens group Gvc,
f is the focal length of the whole optical system,
d dvc is the Abbe number for the d-line of the single lens unit that constitutes the anti-vibration lens group Gvc
fr is a focal length of the third lens unit Gr,
Cr 1 vc is the radius of curvature of the surface of the anti-vibration lens group Gvc closest to the object,
ff is the focal length of the first lens group Gf.

  In the optical system according to the present invention, Fno of the entire system is preferably brighter than 2.8.

  In the optical system according to the present invention, the third lens group Gr preferably has a positive refractive power.

  In the optical system according to the present invention, it is preferable to satisfy the following conditional expression (5).

0.20 <| (1-βvc) × βr | <0.80 (5)
However, in the above equation (5),
βvc is a lateral magnification of the vibration reduction lens group Gvc,
β r is the lateral magnification of the third lens group Gr.

  An imaging device according to the present invention includes the optical system according to the present invention, and an imaging element provided on the image side of the optical system for converting an optical image formed by the optical system into an electrical signal. It is characterized by

  According to the present invention, downsizing and weight reduction of the vibration isolation optical system can be achieved, and a bright large aperture optical system having excellent optical performance even at the time of vibration isolation can be realized.

It is sectional drawing which shows the lens structural example of the optical system (fixed focus lens) of Example 1 of this invention. FIG. 6 shows a spherical aberration diagram, an astigmatism diagram and a distortion diagram of the optical system of Example 1 at infinity focusing. FIG. 6A is a lateral aberration diagram in a reference state at infinity focusing and an optical aberration of the optical system of Example 1 is a lateral aberration diagram at 0.3 ° angle blurring correction at infinity focusing. It is sectional drawing which shows the lens structural example of the optical system (fixed focus lens) of Example 2 of this invention. FIG. 8 shows a spherical aberration diagram, an astigmatism diagram and a distortion diagram of the optical system of the second embodiment at infinity focusing. FIG. 8A is a lateral aberration diagram in a reference state at infinity focusing and an optical aberration of the optical system in Example 2 is a lateral aberration diagram at 0.3 ° angle blurring correction at infinity focusing. It is sectional drawing which shows the lens structural example of the optical system (fixed focus lens) of Example 3 of this invention. They are a spherical-aberration figure at the time of infinity focusing of the optical system of Example 3, an astigmatism figure, and a distortion aberrational figure. FIG. 13A is a lateral aberration diagram in a reference state at infinity focusing and an optical aberration of the optical system of Example 3 is a lateral aberration diagram at 0.3 ° angle blurring correction at infinity focusing. It is sectional drawing which shows the lens structural example of the optical system (fixed focus lens) of Example 4 of this invention. They are a spherical-aberration figure at the time of infinity focusing of the optical system of Example 4, an astigmatism figure, and a distortion aberrational figure. FIG. 14A is a lateral aberration diagram in a reference state at infinity focusing and an optical aberration of the optical system of Example 4 is a lateral aberration diagram at 0.3 ° angle blurring correction at infinity focusing. It is sectional drawing which shows the lens structural example of the optical system (fixed focus lens) of Example 5 of this invention. FIG. 20 shows a spherical aberration, an astigmatism and a distortion diagram of the optical system of Example 5 at infinity focusing. FIG. 16A is a lateral aberration diagram in a reference state at the time of infinity focusing according to an embodiment 5 of the optical system of Example 5, and FIG. It is sectional drawing which shows the lens structural example of the optical system (fixed focus lens) of Example 6 of this invention. They are a spherical-aberration figure at the time of infinity focusing of the optical system of Example 6, an astigmatism figure, and a distortion aberrational figure. FIG. 18A is a lateral aberration diagram of the optical system of Example 6 in the reference state at infinity focusing, and FIG. 18B is a lateral aberration diagram at the time of 0.3 ° angle blurring correction at infinity focusing.

  Hereinafter, embodiments of an optical system and an imaging device according to the present invention will be described.

1-1. Configuration of Optical System First, the configuration of the optical system according to the present invention will be described. The optical system according to the present invention includes a first lens group Gf, an anti-vibration lens group Gvc that moves in a direction perpendicular to the optical axis to change an image position, and a third lens group Gr, which are disposed in order from the object side. The anti-vibration lens group Gvc is configured of a single lens unit, and the third lens group Gr includes at least one lens having negative refractive power, and the conditional expression (1) to the conditional expression described later. It is preferable to satisfy (4) and to satisfy conditional expressions (5) to (8). According to the present invention, it is possible to reduce the size and weight of the vibration isolation optical system, and provide a bright large aperture optical system (hereinafter referred to as "large aperture") having excellent optical performance (imaging performance) even during vibration isolation. Lens) can be realized. Hereinafter, the configuration and the conditional expression of the optical system will be described in order.

(1) First lens group Gf
As long as the first lens group Gf is configured to satisfy at least the conditional expression (1) to the conditional expression (4) in the optical system, the refractive power may be positive or negative. The typical lens configuration is also not particularly limited.

(2) Anti-vibration lens group Gvc
The anti-vibration lens group Gvc is composed of a single lens unit, and if it is configured to satisfy at least the conditional expressions (1) to (4), the refractive power and specifics of the anti-vibration lens group Gvc Typical lens configuration is not particularly limited. According to the present invention, the vibration reduction lens group Gvc is disposed between the first lens group Gf and the third lens group Gr, and at least the conditional expressions (1) to (4) are satisfied. The size and weight of the anti-vibration lens group Gvc can be reduced, and a bright large-aperture lens excellent in optical performance at the time of anti-vibration can be provided.

  Here, a single lens unit is a unit formed of a single lens, and a plurality of lenses such as a positive lens and a negative lens are adhered or adhered to each other on the optical surface thereof without an air layer interposed therebetween. A cemented lens and an integrated body in which an air layer is interposed between optical surfaces of a plurality of lenses are excluded.

  In addition, a single lens refers to a single lens (optical element) having an optical surface on the object side and an image side, and the optical surface is coated with various coatings such as an antireflective film and a protective film. Are also included in the single lens. The shape and the like of the optical surface of the single lens is not particularly limited, and may be either a spherical lens or an aspheric lens, and so-called compound non-spherical surface formed of a thin resin layer on the surface of the spherical lens. A spherical lens is also included, and one side may be flat. Further, the method of manufacturing the single lens is not particularly limited, and includes various lenses manufactured by polishing, molding, injection molding or the like. Further, the single lens may be either a glass lens made of a glass material or a resin lens made of a resin material, and the material of the single lens is not particularly limited.

  The anti-vibration lens group Gvc may be formed of a single lens unit, and its refractive power may be either positive or negative. However, from the viewpoint of further reducing the weight of the vibration reduction lens group Gvc, it is preferable that the refractive power of the vibration reduction lens group Gvc be negative. In order to realize a bright large aperture lens, it is required to configure the optical system with a lens having a large outer diameter in order to take in a large amount of light. For this reason, by making the refractive power of the anti-vibration lens group Gvc negative, it becomes easy to reduce the thickness of the lenses constituting the anti-vibration lens group Gvc, and the weight reduction of the anti-vibration lens group Gvc. Can be Along with this, it is possible to reduce the load of an actuator for driving the anti-vibration lens group Gvc, a drive motor and the like, and to miniaturize these anti-vibration drive mechanisms. For this reason, the outer diameter of the lens barrel that accommodates the optical system, the antivibration drive mechanism, and the like can be reduced.

(3) Third lens group Gr
As described above, if the third lens group Gr includes at least one lens having a negative refractive power, and is configured to satisfy at least conditional expressions (1) to (4), The refractive power of the third lens group Gr and the specific lens configuration are not limited. By disposing at least one lens having negative refractive power in the third lens group Gr, it is possible to reduce the chromatic aberration generated in the optical system by the third lens group Gr. Also, the refractive power of the third lens group Gr may be positive or negative, but from the viewpoint of downsizing of the large aperture lens, the third lens group Gr has positive refractive power. preferable. By making the refractive power of the third lens group Gr which is the final group in the optical system positive, the final group can be made to have a converging action and the magnification can be reduced, and the first lens group Gf which is the object side group The diameter of can be reduced.

1-2. Conditional Expressions Next, each conditional expression will be described. As described above, the optical system is characterized by satisfying the following conditional expression (1) to conditional expression (4). Hereinafter, each conditional expression will be described in order.

0.90 <| fvc | / f <3.10 (1)
35 <d dvc ... (2)
0.78 <| fr | / f <1.80 (3)
−0.4 <Cr1vc / ff (4)
However, in each of the above equations,
fvc is a focal length of the anti-vibration lens group Gvc,
f is the focal length of the whole optical system,
d dvc is the Abbe number for the d-line of the single lens unit that constitutes the anti-vibration lens group Gvc
fr is a focal length of the third lens unit Gr,
Cr 1 vc is the radius of curvature of the surface of the anti-vibration lens group Gvc closest to the object,
ff is the focal length of the first lens group Gf.

1-2-4. Conditional expression (1)
Conditional expression (1) defines the ratio of the focal length of the vibration reduction lens group Gvc to the focal length of the entire optical system. In the present invention, when vibration such as camera shake occurs, the vibration reduction lens group Gvc is moved in the direction perpendicular to the optical axis. That is, at the time of image stabilization, the image stabilization lens group Gvc is decentered, and the image moved due to vibration such as camera shake is returned to the original imaging position. In general, in the case of a large aperture lens, in addition to the tendency that the generation amount of coaxial aberration also tends to be large, when the vibration reduction lens group Gvc is decentered, the generation amount of aberration due to the eccentricity is large. The amount of generation of core coma aberration and decentering field curvature tends to be large. In the present invention, by setting the optical system to satisfy the conditional expression (1), the generation amount of decentering coma aberration and decentering image surface curvature is suppressed, and a large diameter bright aperture having excellent optical performance even at the time of image stabilization. A lens can be realized. Further, by setting the optical system to satisfy the conditional expression (1), the moving amount of the anti-vibration lens group Gvc at the time of anti-vibration can be made within the appropriate range. As a result, the anti-vibration lens group Gvc It is possible to suppress an increase in the size of the anti-vibration drive mechanism such as an actuator for driving, and to reduce the outer diameter of the lens barrel. As described above, since the excellent optical performance can be realized even when the optical system having a large aperture lens can be miniaturized with a small number of lenses, the large aperture lens can be miniaturized.

  When the numerical value of the conditional expression (1) becomes equal to or less than the lower limit value, the focal length of the vibration reduction lens group Gvc becomes too small, and decentering coma and decentration image surface accompanying decentration of the vibration reduction lens group Gvc at the time of vibration reduction The fluctuation of the curvature becomes large, and it becomes difficult to secure good optical performance at the time of vibration reduction with a small number of lenses.

  When the numerical value of the conditional expression (1) exceeds the upper limit value, the focal length of the vibration reduction lens group Gvc becomes too large, and the vertical movement amount of the vibration reduction lens group Gvc during vibration reduction exceeds the appropriate range. As a result, the anti-vibration drive mechanism becomes large and the outer diameter of the lens barrel also becomes large, which is not preferable in achieving the downsizing of the large aperture lens.

  In order to obtain the above effects, in the optical system, the vibration reduction lens group Gvc in the optical system more preferably satisfies the following conditional expression (1) ′, more preferably the following conditional expression (1) ′ ′, and the following conditions It is even more preferable to satisfy the formula (1) ′ ′ ′.

0.93 <| fvc | / f <3.00 ・ ・ ・ (1) '
0.98 <| fvc | / f <2.90 (1) '
0.98 <| fvc | / f <2.53 ... (1) ''

1-2-2. Conditional expression (2)
Conditional expression (2) defines the Abbe number of the d-line of the single lens unit constituting the vibration reduction lens group Gvc. By satisfying the conditional expression (2), it is possible to reduce the color shift when moving the vibration reduction lens group Gvc at the time of vibration reduction, and to realize excellent optical performance even at the time of vibration reduction.

  In order to obtain the above effect, it is preferable that the Abbe number of the d-line of the single lens unit constituting the vibration reduction lens group Gvc in the optical system satisfies the following conditional expression (2) ′, and the following conditional expression (2) ′ It is more preferable to satisfy ', and it is even more preferable to satisfy the following conditional expression (2)' ''.

40 <d dvc ... (2) '
45 <d dvc ... (2) '
54 <d dvc ... (2) ''

1-2-3. Conditional expression (3)
Conditional expression (3) defines the ratio of the focal length of the third lens unit Gr to the focal length of the entire optical system. By satisfying the conditional expression (3), it is possible to ensure excellent optical performance with a small number of lenses, to miniaturize the large aperture lens, and to suppress an increase in cost.

  When the numerical value of the conditional expression (3) becomes equal to or less than the lower limit value, the focal length of the third lens group Gr becomes too small, so the spherical aberration and the field curvature generated in the third lens group Gr become large. In order to correct these aberrations and ensure excellent optical performance, it is necessary to increase the number of lenses. As a result, the size and cost of the large aperture lens are increased, which is not preferable.

  In addition, when the numerical value of the conditional expression (3) exceeds the upper limit value, the focal length of the third lens group Gr becomes too large, so that the first lens group Gf or the first lens group Gf can be used to realize a large aperture lens with excellent optical performance. The amount of aberration correction to be assigned to the vibration reduction lens group Gvc becomes large, which causes deterioration of the optical performance at the time of vibration reduction and makes it difficult to make the optical system a large aperture lens.

  In order to obtain the above effect, the optical system preferably satisfies the following conditional expression (3) ′, and more preferably satisfies the following conditional expression (3) ′ ′, and the following conditional expression (3) ′ ′ ′ It is further preferable to satisfy the following condition (3) ′ ′ ′ ′.

0.80 <| fr | / f <1.78 (3) '
0.83 <| fr | / f <1.75 (3) ′ ′
0.94 <| fr | / f <1.75 (3) ''
0.996 ≦ | fr | / f <1.80 (3) ′ ′ ′ ′

1-2-4. Conditional expression (4)
Conditional expression (4) defines the ratio of the radius of curvature of the object-side surface (optical surface) of the vibration reduction lens group Gvc to the focal length of the first lens group Gf. By configuring the optical system so as to satisfy the conditional expression (4), the angle when the axial light beam is incident on the object side surface of the vibration reduction lens group Gvc from the first lens group Gf side is It becomes close to 0 ° or 0 °. As described above, by reducing the angle of the axial light beam incident on the object-side surface of the vibration reduction lens group Gvc, the decentering coma aberration generated substantially perpendicularly to the object-side surface can be reduced. It is possible to suppress the deterioration of the optical performance at the time of image stabilization.

  In order to obtain the above effect, the optical system preferably satisfies the following conditional expression (4) ′, and more preferably the following conditional expression (4) ′ ′.

-0.1 <Cr1 vc / ff (4) '
0.0 <Cr1vc / ff (4) ''

1-2-5. Conditional expression (5)
In the present invention, it is preferable to satisfy the following conditional expression (5) in addition to the conditional expressions (1) to (4).

0.20 <| (1-βvc) x βr | <0.80 (5)
However, in the above equation (5),
βvc is a lateral magnification of the vibration reduction lens group Gvc,
β r is the lateral magnification of the third lens group Gr.

  Conditional expression (5) defines the ratio between the amount of movement of the vibration reduction lens group Gvc in the vertical direction and the amount of movement of the image point on the image plane, that is, a shake correction coefficient. In the present invention, by setting the optical system to satisfy the conditional expression (5), the blur correction coefficient can be set to an appropriate range, and the generation amount of decentering coma aberration and decentering field curvature is suppressed to prevent It is possible to realize a bright large aperture lens having excellent optical performance even during shaking. As a result, even when the optical system is configured with a small number of lenses, excellent optical performance can be realized, so that the size of the large aperture lens can be further reduced.

  When the numerical value of the conditional expression (5) becomes equal to or less than the lower limit value, that is, when the shake correction coefficient decreases, the moving amount in the vertical direction of the vibration reduction lens group Gvc during vibration reduction increases and the vibration reduction lens group Gvc is driven. The anti-vibration drive mechanism such as the actuator for the As a result, as in the case of the conditional expression (1), the outer diameter of the lens barrel that accommodates these becomes large, which is not preferable in achieving the downsizing of the large aperture lens.

  In addition, when the numerical value of the conditional expression (5) exceeds the upper limit, that is, when the shake correction coefficient becomes large, the variation of decentering coma aberration and decentering field curvature at the time of image stabilization becomes large, and these corrections are difficult It becomes. For this reason, the optical performance at the time of vibration isolation may deteriorate, which is not preferable. In addition, when the shake correction coefficient is increased, the moving amount of the vibration reduction lens group Gvc at the time of vibration reduction is decreased, and precise drive control of the vibration reduction lens group Gvc is required. For this reason, the load of the electrical and mechanical accuracy becomes high, which is not preferable.

  In order to obtain the above effect, the optical system preferably satisfies the following conditional expression (5) ′, and more preferably the following conditional expression (5) ′ ′.

0.28 <| (1-βvc) x βr | <0.65 (5) '
0.35 <| (1−βvc) × βr | <0.60 (5) ′ ′

1-2-5. Conditional expression (6)
In the optical system according to the present invention, in addition to the conditional expression (1) to the conditional expression (4), it is also preferable to satisfy the following conditional expression (6).

  0.80 <| ff / f | (6)

  Conditional expression (6) defines the ratio of the focal length of the first lens group Gf to the focal length of the entire optical system. By satisfying the conditional expression (6), it is possible to suppress that the refractive power of the first lens group Gf becomes too strong, and it is possible to configure the optical system with a small number of lenses, and to miniaturize the optical system. In addition, an optical system having high optical performance can be obtained.

  In order to obtain the above effects, in the optical system, the first lens group Gf more preferably satisfies the following conditional expression (6) ′, and further preferably satisfies the following conditional expression (6) ′ ′ It is more preferable to satisfy the following conditional expression (6) ′ ′ ′.

0.87 <| ff / f | ... (6) '
0.92 <| ff / f | ... (6) '
1.110 ≦ | ff / f | ... (6) ''

1-2-7. Conditional expression (7)
In the optical system according to the present invention, it is effective for correcting the chromatic aberration that at least one negative lens included in the third lens group Gr satisfies the following conditional expression (7); It is more preferable to satisfy the) ', it is more preferable to satisfy the conditional expression (7)'', and it is still more preferable to satisfy the conditional expression (7)''', and the conditional expression (7) ''' It is most preferable to satisfy '.

71> dn dn (7)
64> dn dn (7) '
57> dn dn (7)
51> dn dn (7) ''
41> dn dn (7) ′ ′ ′ ′

1-2-8. Conditional expression (8)
In the optical system according to the present invention, at least one negative lens included in the third lens group Gr satisfying the following conditional expression (8) is effective for correcting the image surface property, and the conditional expression It is more preferable to satisfy (8) ′, and it is further preferable to satisfy the conditional expression (8) ′ ′.

1.48 <Ndn (8)
1.51 <Ndn (8) '
1.61 <Ndn (8) ''

1-3. Brightness The present invention is preferably applied to a large aperture lens in which the Fno of the entire optical system is brighter than 2.8. As described above, the vibration reduction lens group Gvc is disposed between the first lens group Gf and the third lens group Gr, and at least one negative lens is disposed in the third lens group, and at least the conditional expression (1 By satisfying the conditional expression (4), the movement amount of the vibration reduction lens group Gvc at the time of vibration reduction, the shake correction coefficient, the refractive power of each lens group, the paraxial magnification, etc. can be made appropriate. A large aperture lens having excellent optical performance even at the time of image stabilization can be obtained.

  In order to further ensure the effects of the present invention, the present invention is more preferably applied to an optical system in which the Fno of the entire optical system is brighter than 2.4, and is applied to an optical system in which the Fno is brighter than 2.0 It is more preferable to apply to an optical system with Fno brighter than 1.8. According to the present invention, in such a large aperture lens with Fno brighter than 2.8, it is possible to realize downsizing and weight reduction of the vibration reduction mechanism including the vibration reduction lens group Gvc and the vibration reduction drive mechanism, and less A bright large aperture lens excellent in optical performance at the time of vibration reduction can be obtained by the number of lenses.

2. Imaging Device Next, an imaging device according to the present invention will be described. An imaging device according to the present invention includes the optical system according to the present invention, and an imaging device provided on the image side of the optical system for converting an optical image formed by the optical system into an electrical signal. It is characterized by Here, the imaging device and the like are not particularly limited, and a solid-state imaging device such as a CCD sensor or a CMOS sensor can also be used, and the imaging device according to the present invention is a solid-state imaging device such as a digital camera or a video camera. It is suitable for the used imaging device. Further, the imaging device may be a lens fixed imaging device in which a lens is fixed to a housing, or may be a lens interchangeable imaging device such as a single-lens reflex camera or a mirrorless single-lens camera. Of course.

  Next, the present invention will be specifically described by showing Examples and Comparative Examples. However, the present invention is not limited to the following examples. The optical system of each of the embodiments described below is a photographing optical system used for an imaging apparatus (optical apparatus) such as a digital camera, a video camera, a silver halide film camera. Further, in the lens cross-sectional views (FIGS. 1, 4, 7, 10, 13 and 16), the left side is the object side and the right side is the image side in the drawings.

(1) Configuration of Optical System FIG. 1 is a lens sectional view showing the configuration of a fixed focus lens which is an optical system according to a first embodiment of the present invention. The fixed focus lens includes, in order from the object side, a first lens group Gf having positive refractive power, a vibration reduction lens group Gvc having negative refractive power, and a third lens group Gr having positive refractive power. It comprises and is comprised by these lens groups. The anti-vibration lens group moves in a direction perpendicular to the optical axis to change the image position, and the anti-vibration lens group Gvc reduces image blurring caused by vibration such as camera shake at the time of imaging. it can. In FIG. 1, “S” shown in the first lens group Gf is an aperture stop. In addition, “I” shown on the image side of the third lens group Gr is an image plane, and specifically, an imaging surface of a solid-state imaging device such as a CCD sensor or a CMOS sensor, or a film surface of a silver halide film Show. The specific lens configuration of each lens group is as shown in FIG. In addition, since these code | symbol shows the same thing also in FIG. 4, FIG. 7, FIG. 10, FIG. 13 and FIG. 16 shown by Example 2-Example 6, description is abbreviate | omitted below.

(2) Numerical Example Next, a numerical example to which a specific numerical value of the fixed focus lens is applied will be described. Table 1 shows lens data of the fixed focus lens. In Table 1, the surface number No. Is the order of the lens surface counted from the object side, R is the radius of curvature of the lens surface, D is the distance on the optical axis of the lens surface, Nd is the refractive index for d line (wavelength λ = 587.6 nm), ν d is d line The Abbe numbers for (wavelength λ = 587.6 nm) are shown. Also, the aperture stop (stop S) is shown with the surface number attached with STOP. Furthermore, when the lens surface is aspheric, the surface number indicates ASPH, and the column of radius of curvature R indicates paraxial radius of curvature. In addition, since these are the same also in Table 2, Table 3, Table 5, Table 7, and Table 9 shown in Example 2-Example 6, description is abbreviate | omitted below.

  FIG. 2 shows a longitudinal aberration diagram at the time of infinity focusing of the fixed focus lens. The respective longitudinal aberration diagrams represent spherical aberration, astigmatism and distortion in order from the left toward the drawing. In the diagrams showing spherical aberration, the solid line represents d-line (587.6 nm) and the broken line represents g-line (435.8 nm). In a diagram showing astigmatism, a solid line indicates the sagittal direction X of the d-line, and a broken line indicates the meridional direction Y of the d-line. The order in which these aberrations are displayed, the order in which they are displayed, and the solid lines and broken lines shown in the respective drawings are the same in FIGS. 5, 8, 11, 14 and 17 shown in the second to sixth embodiments. Because there is, the description will be omitted below.

  FIG. 3 is (a) lateral aberration at the time of focusing at infinity, in the reference state, and (b) lateral aberration at the time of 0.3 ° angle blurring correction at the time of infinity focusing. The axial aberration diagram at the center is shown at the center, and the transverse aberration diagram of the 70% image height is shown at the top and bottom. The d-line (587.6 nm) and the broken line represent the g-line (435.8 nm). The order in which these aberrations are displayed, and the solid lines and broken lines shown in the respective drawings are the same as in FIGS. 6, 9, 12, 15, and 18 shown in the second to sixth embodiments. The description is omitted below.

  The focal length (f), the large aperture ratio (Fno), and the angle of view (ω) of the fixed focus lens are respectively as follows. Further, the numerical values of the conditional expressions (1) to (8) are shown in Table 11.

  f = 87.5187 Fno = 1.4578 ω = 13.8585 °

(1) Configuration of Optical System FIG. 4 is a lens sectional view showing the configuration of a fixed focus lens which is an optical system according to a second embodiment of the present invention. The fixed focus lens includes, in order from the object side, a first lens group Gf having positive refractive power, a vibration reduction lens group Gvc having negative refractive power, and a third lens group Gr having positive refractive power. , And these lens groups. The function of the vibration reduction lens group Gvc is the same as that of the first embodiment. The specific lens configuration is as shown in FIG.

(2) Numerical Example Next, a numerical example to which a specific numerical value of the fixed focus lens is applied will be described. Table 2 shows lens data of the fixed focus lens. FIG. 5 is a longitudinal aberration diagram at the time of infinity focusing, and FIG. 6 is (a) a lateral aberration diagram of the reference state at the time of infinity focusing, and (b) 0.3 ° angle at the time of infinity focusing FIG. 7 is a lateral aberration diagram at the time of blur correction.

  Further, the focal length (f), the large aperture ratio (Fno), and the angle of view (ω) of the fixed focus lens are respectively as follows. Further, the numerical values of the conditional expressions (1) to (8) are shown in Table 11.

  f = 87.0 859 Fno = 1.4743 ω = 14.0419 °

(1) Configuration of Optical System FIG. 7 is a lens sectional view showing the configuration of a fixed focus lens which is an optical system according to a third embodiment of the present invention. The fixed focus lens includes, in order from the object side, a first lens group Gf having positive refractive power, a vibration reduction lens group Gvc having negative refractive power, and a third lens group Gr having positive refractive power. , And these lens groups. The function of the vibration reduction lens group Gvc is the same as that of the first embodiment. The specific lens configuration is as shown in FIG.

(2) Numerical Example Next, a numerical example to which a specific numerical value of the fixed focus lens is applied will be described. Table 3 shows lens data of the fixed focus lens. 8 is a longitudinal aberration diagram at the time of infinity focusing, and FIG. 9 is a horizontal aberration diagram of the reference state at the time of (a) infinity focusing, and (b) 0.3 at the time of infinity focusing. It is a lateral aberration figure at the time of ° angle blurring amendment.

  Further, the focal length (f), the large aperture ratio (Fno), and the angle of view (ω) of the fixed focus lens are respectively as follows. Further, the numerical values of the conditional expressions (1) to (8) are shown in Table 11.

  f = 82.8700 Fno = 1.4617 ω = 14.5834 °

  With respect to the aspheric surfaces shown in Table 3 above, the aspheric surface coefficients and the conical constants are shown in Table 4 when the shape is expressed by the following equation. The aspherical coefficients and the conical constants shown in Tables 6, 8 and 10 described later are also based on the following definitions.

Here, the aspheric surface is defined by the following equation.
z = ch2 / [1 + {1- (1 + k) c2 h 2} 1/2] + A 4 h 4 + A 6 h 6 + A 8 h 8 + A 10 h 10 ...
(Where c is the curvature (1 / r), h is the height from the optical axis, k is the conical coefficient, A4, A6, A8, A10,... Are aspheric coefficients of each order)

(1) Configuration of Optical System FIG. 10 is a lens sectional view showing the configuration of a fixed focus lens which is an optical system according to a fourth embodiment of the present invention. The fixed focus lens includes a first lens group Gf having negative refractive power in order from the object side, a vibration reduction lens group Gvc having negative refractive power, and a third lens group Gr having positive refractive power. , And these lens groups. The function of the vibration reduction lens group Gvc is the same as that of the first embodiment. The specific lens configuration is as shown in FIG.

(2) Numerical Example Next, a numerical example to which a specific numerical value of the fixed focus lens is applied will be described. Table 5 shows lens data of the fixed focus lens. 11 is a longitudinal aberration diagram at the time of infinity focusing, and FIG. 12 is (a) a lateral aberration diagram of the reference state at the time of infinity focusing, and (b) 0.3 at the time of infinity focusing. It is a lateral aberration figure at the time of ° angle blurring amendment.

  Further, the focal length (f), the large aperture ratio (Fno), and the angle of view (ω) of the fixed focus lens are respectively as follows. Further, the numerical values of the conditional expressions (1) to (8) are shown in Table 11.

  f = 35.3524 Fno = 1.8354 ω = 31.7460 °

  The aspheric coefficients and the conical constants of the aspheric surfaces shown in Table 5 are shown in Table 6.

(1) Configuration of Optical System FIG. 13 is a lens sectional view showing the configuration of a fixed focus lens which is an optical system according to a fifth embodiment of the present invention. The fixed focus lens includes a first lens group Gf having negative refractive power in order from the object side, a vibration reduction lens group Gvc having negative refractive power, and a third lens group Gr having positive refractive power. , And these lens groups. The function of the vibration reduction lens group Gvc is the same as that of the first embodiment. The specific lens configuration is as shown in FIG.

(2) Numerical Example Next, a numerical example to which a specific numerical value of the fixed focus lens is applied will be described. Table 7 shows lens data of the fixed focus lens. FIG. 14 is a longitudinal aberration diagram at the time of infinity focusing, and FIG. 15 is (a) a lateral aberration diagram of the reference state at the time of infinity focusing, and (b) 0.3 at the time of infinity focusing It is a lateral aberration figure at the time of ° angle blurring amendment.

  Further, the focal length (f), the large aperture ratio (Fno), and the angle of view (ω) of the fixed focus lens are respectively as follows. Further, the numerical values of the conditional expressions (1) to (8) are shown in Table 11.

  f = 35. 3498 Fno = 1.8352 ω = 31.9864 °

The aspheric coefficients and the conical constants of the aspheric surfaces shown in Table 7 are shown in Table 8.

(1) Configuration of Optical System FIG. 16 is a lens sectional view showing the configuration of a fixed focus lens which is an optical system according to a sixth embodiment of the present invention. The fixed focus lens includes, in order from the object side, a first lens group Gf having positive refractive power, a vibration reduction lens group Gvc having positive refractive power, and a third lens group Gr having positive refractive power. , And these lens groups. The function of the vibration reduction lens group Gvc is the same as that of the first embodiment. The specific lens configuration is as shown in FIG.

(2) Numerical Example Next, a numerical example to which a specific numerical value of the fixed focus lens is applied will be described. Table 9 shows lens data of the fixed focus lens. FIG. 17 is a longitudinal aberration diagram at the time of infinity focusing, and FIG. 17 is a horizontal aberration diagram of the reference state at the time of (a) infinity focusing, and (b) 0.3 at the time of infinity focusing. It is a lateral aberration figure at the time of ° angle blurring amendment.

  Further, the focal length (f), the large aperture ratio (Fno), and the angle of view (ω) of the fixed focus lens are respectively as follows. Further, the numerical values of the conditional expressions (1) to (8) are shown in Table 11.

  f = 35.8750 Fno = 2.3779 ω = 31.8711 °

  The aspheric coefficients and the conical constants of the aspheric surfaces shown in Table 9 are shown in Table 10.

  The numerical values of the conditional expressions in each numerical example are shown in Table 11.

  According to the present invention, downsizing and weight reduction of the vibration isolation optical system can be achieved, and a bright large aperture optical system having excellent optical performance even at the time of vibration isolation can be realized.

Gf: First lens group Gr: Third lens group Gvc: Anti-vibration lens group S: Aperture I: Image plane

Claims (5)

An optical system comprising, in order from the object side, a first lens group Gf, a vibration reduction lens group Gvc that moves in a direction perpendicular to the optical axis to change an image position, and a third lens group Gr,
The anti-vibration lens group Gvc is composed of a single lens unit,
The third lens group Gr includes at least one lens having negative refractive power.
An optical system characterized by satisfying the following conditional expression.
0.90 <| fvc | / f <3.10 (1)
45 <d dvc ... (2) '
0.996 ≦ | fr | / f <1.80 (3) ′ ′ ′ ′
−0.1 <Cr1vc / ff (4) '
1.110 ≦ | ff / f | ... (6) ''
However, in each of the above equations,
fvc is a focal length of the anti-vibration lens group Gvc,
f is the focal length of the whole optical system,
d dvc is the Abbe number for the d-line of the single lens unit that constitutes the anti-vibration lens group Gvc
fr is a focal length of the third lens unit Gr,
Cr 1 vc is the radius of curvature of the surface of the anti-vibration lens group Gvc closest to the object,
ff is the focal length of the first lens group Gf.   The optical system according to claim 1, wherein Fno of the whole system is brighter than 2.8.   The optical system according to claim 1, wherein the third lens group Gr has a positive refractive power. The optical system according to any one of claims 1 to 3, which satisfies the following conditional expression.
0.20 <| (1-βvc) × βr | <0.80 (5)
However, in the above equation (5),
βvc is a lateral magnification of the vibration reduction lens group Gvc,
β r is the lateral magnification of the third lens group Gr.   An optical system according to any one of claims 1 to 4 and an imaging device provided on the image side of the optical system for converting an optical image formed by the optical system into an electrical signal. An imaging apparatus characterized by comprising.

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