Optical system and imaging device having the same

Abstract

To provide a compact, wide-angle optical system that has good optical performance on the periphery of a screen.SOLUTION: An optical system L0 has, in order from an object side to an image side, a front group LP having a positive refractive power, an intermediate group LF, and a rear group LR. In focusing from infinity to a close range, the intermediate group LF moves so that the interval between the front group LP and the intermediate group LF and the interval between the intermediate group LF and the rear group LR are changed. The focal distance of the front group LP and the effective diameter of the most image-side lens surface in the rear group LR satisfy a predetermined conditional expression.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an optical system and is suitable for imaging devices such as digital video cameras, digital still cameras, broadcast cameras, and cameras for silver halide film. [Background technology]

[0002] 2. Description of the Related Art In recent years, there has been a demand for small wide-angle lenses that have good optical performance around the periphery of the screen and a short overall length in optical systems used in imaging devices using solid-state imaging elements, such as digital still cameras and video cameras.

[0003] To achieve this, it is necessary to increase the positive refractive power of the optical system, but increasing the positive refractive power tends to result in a large positive Petzval sum, which makes it difficult to correct the curvature of field. It also makes it difficult to correct astigmatism. As such, in wide-angle optical systems, the optical performance at the periphery of the screen tends to deteriorate, and it is necessary to effectively correct these.

[0004] Patent Document 1 discloses an optical system including, from the object side, a lens group with positive refractive power, a lens group with negative refractive power, and a lens group with positive refractive power. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2010-176096 A Summary of the Invention [Problem to be solved by the invention]

[0006] In the technology disclosed in Patent Document 1, the positive refractive power of the lens group closer to the object than the group that moves with focusing is weaker, making it difficult to make the optical system a wide angle. Even if the refractive power of this lens group were to be increased, it would be difficult to correct the field curvature and astigmatism that would occur at that time.

[0007] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a compact wide-angle optical system with good optical performance around the periphery of the screen. [Means for solving the problem]

[0008] The optical system of the present invention includes, in order from the object side to the image side, Placed , positive refractive power front group, middle group, rear group Consists of the intermediate group LF moves so that a distance between the front group and the intermediate group and a distance between the intermediate group and the rear group change during focusing from infinity to a close distance; the front group includes a first subgroup, an aperture stop, and a second subgroup, arranged in this order from the object side to the image side, the first subgroup having a biconvex air lens; The focal length of the front group is fLP, and the effective diameter of the lens surface closest to the image side of the rear group is E A, the thickness of the air lens on the optical axis is Dair, the distance from the lens surface closest to the object side to the lens surface closest to the image side of the optical system is L, and the focal length of the second sub group is fL2. 0.01 <fLP / EA<0.80 0.11 <Dair / L<0.22 0.40 <fL2 / EA<1.10 The present invention is characterized in that the following conditional expression is satisfied: Effect of the Invention

[0009] According to the present invention, it is possible to realize a small-sized wide-angle optical system with good optical performance around the periphery of the screen. [Brief description of the drawings]

[0010] [Figure 1] 1 is a lens sectional view of an optical system according to a first embodiment. [Diagram 2] 4A to 4C are aberration diagrams of the optical system of Example 1. [Diagram 3] FIG. 11 is a cross-sectional view of a lens of an optical system according to a second embodiment. [Figure 4] 11A to 11C are aberration diagrams of the optical system of Example 2. [Diagram 5] FIG. 11 is a lens sectional view of the optical system of Example 3. [Figure 6] 11A to 11C are aberration diagrams of the optical system of Example 3. [Figure 7] FIG. 11 is a lens sectional view of the optical system of Example 4. [Figure 8] 11A to 11C are aberration diagrams of the optical system of Example 4. [Figure 9]FIG. 13 is a lens sectional view of the optical system of Example 5. [Figure 10] 13A to 13C are aberration diagrams of the optical system of Example 5. [Figure 11] FIG. 13 is a lens cross-sectional view of the optical system of Example 6. [Figure 12] 13A to 13C are aberration diagrams of the optical system of Example 6. [Figure 13] FIG. 13 is a lens cross-sectional view of the optical system of Example 7. [Figure 14] 13A to 13C are aberration diagrams of the optical system of Example 7. [Figure 15] FIG. 1 is a schematic diagram showing an imaging device. [Figure 16] FIG. 2 is a schematic diagram showing a lens device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of an optical system and an image pickup apparatus having the same according to the present invention will be described with reference to the accompanying drawings.

[0012] 1, 3, 5, 7, 9, 11, and 13 are cross-sectional views of the optical system L0 of Examples 1 to 7 when focused at infinity. The optical system L0 of each Example is an optical system used in imaging devices such as digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, surveillance cameras, and vehicle-mounted cameras.

[0013] In each lens cross-sectional view, the left side is the object side and the right side is the image side. The optical system L0 of each embodiment may be used as a projection lens for a projector, etc. In this case, the left side is the screen side and the right side is the projected image side.

[0014] The optical system L0 in each embodiment has a positive front group LP, an intermediate group LF, and a rear group LR, which are arranged in this order from the most object side to the image side.

[0015] The optical system L0 in each embodiment is configured to have multiple lenses. In this specification, the front group LP, the middle group LF, and the rear group LR are groups of lenses that move or remain stationary as a whole during focusing. Each group may be composed of one lens or multiple lenses. Each group may also include an aperture stop.

[0016] The rear group LR is a group of all lenses on the image side of the intermediate group LF. The rear group LR does not include parallel plate glass or the like that has no refractive power. However, it may include optical elements that have no paraxial refractive power but have an aspheric or Fresnel shape in the peripheral area, resulting in the convergence or divergence of light rays.

[0017] The front group LP may have a first subgroup L1 and a second subgroup L2. The first subgroup L1 and the second subgroup L2 are two subgroups separated by an aperture stop SP in the front group LP. The middle group LF may also be referred to as a third lens group L3. The rear group LR may also be referred to as a fourth lens group L4.

[0018] The arrows in each lens cross-sectional view indicate the direction of movement of the lens group during focusing from infinity to a close distance. In the optical system L0 of each embodiment, the middle group LF moves during focusing from infinity to a close distance so that the distance between the front group LP and the middle group LF and the distance between the middle group LF and the rear group LR change. Note that lens groups other than the middle group LF may also be moved during focusing.

[0019] In each lens cross-sectional view, SP is an aperture stop. IP is an image plane, and when the optical system of each embodiment is used as a photographing optical system for a digital still camera or digital video camera, the imaging surface of a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or CMOS sensor is disposed thereon. When the optical system of each embodiment is used as a photographing optical system for a silver halide film camera, a photosensitive surface equivalent to the film surface is disposed on the image plane IP.

[0020] Also, FL is an optical block equivalent to an optical filter, a face plate, a crystal low-pass filter, an infrared cut filter, or the like.

[0021] Furthermore, Gj (j is a natural number) represents the j-th lens, which is the j-th lens counted from the object side.

[0022] 2, 4, 6, 8, 10, 12, and 14 are aberration diagrams of the optical systems of Examples 1 to 7, respectively. In each aberration diagram, (A) is an aberration diagram when focusing at infinity, and (B) is an aberration diagram when focusing at a distance where the paraxial lateral magnification of the optical system L0 is −0.1.

[0023] In the spherical aberration diagram, Fno is the F-number, and shows the amount of spherical aberration for the d-line (wavelength 587.6 nm) and g-line (wavelength 435.8 nm). In the astigmatism diagram, S shows the amount of aberration on the sagittal image plane, and M shows the amount of aberration on the meridional image plane. In the distortion diagram, the amount of distortion for the d-line is shown. In the chromatic aberration diagram, the amount of lateral chromatic aberration for the g-line is shown. ω is the half angle of view (°).

[0024] Next, the characteristic configuration of the optical system of each embodiment will be described.

[0025] The optical system L0 of each embodiment is constructed so as to satisfy the following conditional expression: where fLP is the focal length of the front group LP, and EA is the effective diameter of the lens surface closest to the image side in the rear group LR. 0.01 <fLP / EA<0.80 ···(1)

[0026] By configuring the optical system L0 to have, in order from the object side to the image side, a positive front group LP, an intermediate group LF, and a rear group LR, the strong refractive power of the positive front group LP makes it possible to make the optical system L0 have a sufficiently wide angle, while inner focusing can be performed by the intermediate group LF. By using a configuration in which inner focusing is performed by the intermediate group LF, the overall length of the optical system does not change during focusing, so the overall length of the optical system L0 can be made compact.

[0027] Furthermore, by positioning the rear group LR on the image side of the intermediate group LF, even if the refractive power of the intermediate group LF is increased, it is possible for the rear group LR to correct aberrations generated in the intermediate group LF, thereby achieving both a wider angle of view for the optical system and improved performance at the periphery of the image.

[0028] Furthermore, by increasing the refractive power of the intermediate group LF, the focus sensitivity of the intermediate group LF (the ratio of the movement amount of the image plane to the movement amount of the intermediate group LF) can be increased. This allows the movement amount of the intermediate group LF during focusing to be reduced, and the air gap required for focusing before and after the intermediate group LF can be reduced. This allows the optical system L0 to be made more compact. Incidentally, reducing the movement amount of the intermediate group LF during focusing is also preferable in order to enable high-speed AF (autofocus).

[0029] Next, the technical meaning of the above-mentioned conditional formula (1) will be explained.

[0030] Conditional formula (1) prescribes the ratio of the focal length fLP of the front group LP to the effective diameter EA of the surface of the rear group LR closest to the image, which indicates that it is best to make fLP small and EA large, within the range that satisfies conditional formula (1).

[0031] By reducing fLP, the focal length of the optical system L0 can be reduced, and the optical system L0 can have a wider angle.

[0032] In addition, generally, both the on-axis light beam and the off-axis light beam are sufficiently converged on the surface closest to the image side of the optical system, and the effective diameter of the lens surface closest to the image side is determined by the height from the optical axis of the position where the off-axis light beam passes through that lens surface. In other words, the effective diameter of the lens surface closest to the image side is determined by the passing positions of the on-axis light beam and the off-axis light beam, which are determined by the power arrangement of the optical system. Therefore, a large effective diameter of the surface closest to the image side of the optical system means that the off-axis light beam passes through the surface while being sufficiently separated from the on-axis light beam in the direction perpendicular to the optical axis.

[0033] If the off-axis light beam is sufficiently separated from the on-axis light beam in the direction perpendicular to the optical axis and passes through the lens surface closest to the image side, it is possible to correct off-axis curvature of field and astigmatism without affecting spherical aberration and coma aberration to a great extent. This makes it possible to improve the optical performance around the periphery of the screen without affecting the center of the screen.

[0034] The effective diameter EA is the diameter of the area on the lens surface where light is incident. In other words, the effective diameter EA of a lens surface is the diameter of the area determined by the position of incidence of the light ray that passes through the position farthest from the optical axis in the direction perpendicular to the optical axis among the light rays incident on the lens surface.

[0035] If fLP falls below the lower limit of condition (1) and becomes small, this is advantageous for making the optical system wider-angle, but it is undesirable because the spherical aberration and curvature of field generated in the front group LP become too large in the under direction.Also, if EA falls below the lower limit of condition (1) and becomes large, the diameter of the lens in the rear group LR becomes too large, which is undesirable because the optical system becomes large in the radial direction.

[0036] If fLP increases beyond the upper limit of conditional formula (1), it becomes difficult to make the optical system wider-angle, which is not preferable.If EA decreases beyond the upper limit of conditional formula (1), the on-axis light beam and the off-axis light beam passing through the surface of the rear group LR closest to the image side do not separate sufficiently in the direction perpendicular to the optical axis, which makes it difficult to selectively correct curvature of field and astigmatism, which is not preferable.

[0037] It is preferable that at least one of the upper limit and the lower limit of the numerical range of conditional formula (1) satisfies the range of the following conditional formula (1a). 0.10 <fLP / EA<0.75 ···(1a)

[0038] It is even more preferable that at least one of the upper limit and the lower limit of the numerical range of conditional formula (1) is set to the range of the following conditional formula (1b). 0.20 <fLP / EA<0.68 ···(1b)

[0039] Furthermore, if at least one of the upper limit value or the lower limit value of the numerical range of conditional formula (1) is set within the range of the following conditional formula (1c), the effects of each of the above-mentioned conditional formulas can be maximized. 0.30 <fLP / EA<0.60 ···(1c)

[0040] Next, a description will be given of configurations that are preferably satisfied in the optical system of each embodiment.

[0041] The front group LP of the optical system L0 in each embodiment has, in order from the object side, a first subgroup L1, an aperture stop SP, and a positive second subgroup L2. By arranging the lens groups (subgroups) in front of and behind the aperture stop SP, it becomes possible to pass off-axis light beams through the lens surfaces approximately symmetrically in front of and behind the aperture stop SP, which is preferable in terms of correcting field curvature and distortion aberration. In addition, by arranging the lens groups on the object side of the aperture stop SP, it is possible to generate so-called coma aberration of the pupil and increase the aperture efficiency for off-axis light beams (the ratio of the cross-sectional area perpendicular to the optical axis of the on-axis incident light beam to the cross-sectional area perpendicular to the optical axis of the off-axis incident light beam). This makes it possible to increase the peripheral illumination ratio (image surface illuminance ratio), which is an issue in wide-angle optical systems.

[0042] Moreover, the first sub-group L1 has three lenses, in order from the object side, a meniscus lens with negative refractive power, a lens with negative refractive power, and a lens with positive refractive power. In the first to sixth embodiments, the lenses G1 to G3 correspond to these lenses. As shown in the seventh embodiment, another lens may be disposed on the object side of the three lenses. Moreover, in the first sub-group L1, a lens may be disposed on the image side of the three lenses.

[0043] At least one surface of the three lenses in the first partial group L1 may be aspheric, which makes it possible to effectively correct field curvature and distortion.

[0044] In the seventh embodiment, as shown in FIG. 13, lenses G2 to G4 correspond to the three lenses of the first partial group L1 described above, and a positive lens G1 is further disposed on the object side thereof.

[0045] The two negative lenses included in the first partial group L1 make the Petzval sum negative, so that the positive Petzval sum of the entire optical system L0 can be reduced. This allows for excellent correction of the curvature of field. This also allows for excellent correction of distortion.

[0046] Moreover, the negative lens and positive lens included in the first partial unit L1 make it possible to effectively correct lateral chromatic aberration.

[0047] In addition, the first sub-unit L1 has a biconvex air lens Lair. In a wide-angle optical system, barrel distortion is likely to occur due to strong positive refractive power, but by disposing the air lens Lair in the first sub-unit L1, barrel distortion and field curvature can be effectively corrected due to the strong negative refractive power of the air lens Lair.

[0048] Furthermore, it is preferable to set the air gap constituting the air lens Lair to the maximum among the air gaps between the surface closest to the object side and the surface closest to the image side of the optical system L0 (if the optical system L0 is a zoom lens, the air gap that is maximum either at the wide-angle end or the telephoto end). This means that a strong negative refractive power is obtained by the air lens Lair while other air gaps are made small. This allows the optical system L0 to be made compact while satisfactorily correcting aberrations.

[0049] The positive second sub-group L2 has at least two lenses Gp with positive refractive power and at least one lens Gn with negative refractive power. The second sub-group L2, which is located immediately behind the aperture stop SP, mainly corrects axial chromatic aberration and spherical aberration. Therefore, for example, by combining a positive lens with small dispersion and a negative lens with large dispersion, axial chromatic aberration can be effectively corrected.

[0050] Furthermore, in order to make the optical system L0 wide-angle, the second sub-unit L2 tends to have a strong positive refractive power, which tends to cause under-correction of spherical aberration. Therefore, by arranging at least two lenses Gp with positive refractive power in the second sub-unit L2, the necessary positive refractive power can be shared by multiple positive lenses, and the absolute value of the radius of curvature of the positive lenses can be made large. This makes it possible to further suppress the occurrence of spherical aberration.

[0051] Furthermore, if at least one surface of the lens Gp with positive refractive power has an aspheric shape, the effect of correcting spherical aberration is enhanced, which is preferable. In particular, it is even more preferable to have a shape in which the curvature at the periphery of the lens surface is gentler than the paraxial radius of curvature.

[0052] In addition, it is preferable that the intermediate group LF has a single lens having a concave surface on the object side and negative refractive power, or a cemented lens having a negative refractive power as a whole. The intermediate group LF moves during focusing, and at this time, fluctuations in curvature of field are likely to become a problem. Therefore, by disposing a single lens having a negative refractive power and a concave surface on the object side, or a cemented lens having a negative refractive power as a whole, in the intermediate group LF, it is possible to make light incident at an angle close to perpendicular to the concave surface. When light is incident at an angle close to perpendicular to the surface, the light beam is not significantly refracted by the surface, so that fluctuations in curvature of field can be reduced even if the intermediate group LF moves during focusing.

[0053] Moreover, it is preferable that the rear group LR has a single lens with positive refractive power, which makes it possible to refract off-axis rays near the image plane, ensure telecentricity within a range compatible with solid-state imaging devices, and correct astigmatism.

[0054] Furthermore, in the optical system L0 of each embodiment, image blur correction may be performed by moving one or more lenses in a direction perpendicular to the optical axis.

[0055] Next, conditions that the optical system L0 of each embodiment should preferably satisfy will be described.

[0056] It is preferable that the optical system L0 in each embodiment satisfies the following condition, where DSP is the distance from the aperture stop SP to the lens surface in the rear group LR closest to the image side, and T is the distance from the aperture stop SP to the image plane IP. 0.20 <DSP / T<1.00 ···(2)

[0057] Furthermore, it is preferable that the optical system L0 in each embodiment satisfies the following conditional expression, where the focal length of the first partial group L1 is fL1 and the focal length of the second partial group L2 is fL2. 0.00 <fL2 / |fL1|<0.80 ···(3)

[0058] Furthermore, it is preferable that the optical system L0 in each embodiment satisfies the following condition, where the focal length of the intermediate group LF is fLF. 0.00<|fLF| / |fL1|<1.50 ···(4)

[0059] Furthermore, it is preferable that the optical system L0 in each embodiment satisfies the following conditional expression, where f is the focal length of the entire optical system and ω is the half angle of view of the optical system L0. 0.30 <fLP / (f×tanω)<1.50 ···(5)

[0060] In the optical system L0 of each embodiment, it is preferable that the following condition be satisfied, where the lateral magnification of the middle group LF when focusing at infinity is βLF and the lateral magnification of the rear group when focusing at infinity is βLR. -1.50<(1-βLF 2 ) × βLR 2 <-0.40 ···(6)

[0061] Furthermore, when the Abbe number of the lens Gp with positive refractive power in the second sub-group L2 is vp and the Abbe number of the lens Gn with negative refractive power in the second sub-group L2 is vn, it is preferable that the optical system L0 satisfies the following conditional expression, which should be satisfied by at least one of the positive lenses and at least one of the negative lenses Gn in the second sub-group L2. 55<νp<120 (7) 15<νn<35 (8)

[0062] In addition, when the amount of movement of the intermediate group LF when the optical system L0 is focused at a distance where the paraxial lateral magnification is -0.1 with respect to the time when focused at infinity as a reference is taken as MF, it is preferable to satisfy the following conditional expression, where the sign of the amount of movement is positive in the traveling direction of light (direction from the object side to the image side). 0.02 <MF / DSP<0.15 ···(9)

[0063] It is also preferable that the following conditional expression be satisfied: 0.20 <fLP / DSP<0.80 ···(10) 0.30 <fL2 / EA<1.20 ···(11)

[0064] Furthermore, when the focal length of the air lens Lair of the first subgroup L1 is fLair, it is preferable that the following conditional expression be satisfied. -0.50 <fLair / |fL1|<0.00 ···(12)

[0065] Furthermore, when the air spacing (thickness on the optical axis) constituting the air lens Lair of the first subgroup L1 is Dair (the maximum value if Dair is variable), and the distance from the surface closest to the object side to the surface closest to the image side of the optical system L0 is L, it is preferable to satisfy the following conditional expression. 0.05 <Dair / L<0.30 ···(13)

[0066] The radius of curvature of the surface closest to the object of the single lens having negative refractive power or the cemented lens having negative refractive power as a whole included in the intermediate group LF is defined as R. The distance from the aperture stop SP to the surface closest to the object of the single lens having negative refractive power or the cemented lens having negative refractive power as a whole included in the intermediate group LF when focusing at infinity is defined as S. In this case, it is preferable to satisfy the following conditional expression. -1.00

[0067] It is also preferable that the following conditional expression be satisfied: -3.00 <fLF / f<-1.00 ···(15)​

[0068] Furthermore, when the focal length of a single lens having positive refractive power included in the rear group LR is taken as fLRp, it is preferable that the following condition be satisfied: 0.00 <fLRp / |fL1|<1.50 ···(16)

[0069] Next, the technical meanings of the above-mentioned conditional expressions (2) to (16) will be explained.

[0070] Conditional formula (2) prescribes the ratio of the distance DSP from the aperture stop SP to the lens surface of the rear group LR closest to the image side to the distance T from the aperture stop SP to the image surface. This indicates that it is advisable to make DSP larger than T and to locate the lens surface closest to the image side at a position farther away from the aperture stop SP, within the range that satisfies the conditional formula. At a position farther away from the aperture stop SP to the image side, the light beam sufficiently converges and the diameter of the light beam becomes smaller, making it easier to correct other aberrations without affecting spherical aberration and coma aberration. In addition, at a position farther away from the aperture stop SP to the image side, the distance in the direction perpendicular to the optical axis of the light beam through which the on-axis light beam and the off-axis light beam pass increases, making it easier to correct astigmatism, field curvature, and distortion aberration.

[0071] If DSP becomes small below the lower limit of condition (2), the distance from the aperture stop SP to the lens surface of the rear group LR closest to the image becomes too small, reducing the effect of correcting aberrations as described above.

[0072] If DSP increases beyond the upper limit of conditional expression (2), the above-mentioned correction effect increases, but it becomes difficult to arrange the optical block FL, such as an infrared cut filter or a low-pass filter.

[0073] Conditional formula (3) specifies the ratio of the absolute value of the focal length fL1 of the first sub-group L1 to the positive focal length fL2 of the second sub-group L2. By making fL2 small and |fL1| large within the range that satisfies the conditional formula, it is possible to realize an optical system that has a small variation in optical performance due to manufacturing errors and is easy to manufacture while widening the angle of the optical system L0. When |fL1| is large, the axial light beam emitted from the first sub-group L1 becomes approximately parallel (the first sub-group L1 becomes closer to an afocal system). As a result, even if the distance between the first sub-group L1 and the second sub-group L2 changes due to manufacturing errors or the like, the variation in spherical aberration is small, making it possible to realize a high-performance optical system even if manufacturing errors occur. In addition, by utilizing this, for example, the field curvature caused by the manufacturing errors of other lenses can be corrected without affecting the spherical aberration by intentionally changing the distance between the first sub-group L1 and the second sub-group L2. Moreover, by reducing fL2, it is possible to obtain the strong positive refractive power required for a wide angle.

[0074] If fL2 falls below the lower limit of condition (3) and becomes small, this is advantageous for achieving a wider angle, but is not preferable because it becomes difficult to correct the spherical aberration, curvature of field, and barrel distortion that occur in the second subunit L2.

[0075] If fL2 becomes large beyond the upper limit of conditional expression (3), it becomes difficult to make the optical system L0 wider-angle, which is not preferable, and if |fL1| becomes small beyond the upper limit of conditional expression (3), the spherical aberration fluctuation due to the above-mentioned manufacturing error and the like becomes large, which is not preferable.

[0076] Conditional formula (4) prescribes the ratio of the absolute value of the focal length fLF of the intermediate group LF to the absolute value of the focal length fL1 of the first partial group L1. By reducing |fLF| within the range that satisfies the conditional formula, the focus sensitivity of the intermediate group LF (the ratio of the movement amount of the image plane to the movement amount of the intermediate group LF) can be increased. Furthermore, by increasing |fL1| within the range that satisfies the conditional formula, the variation in spherical aberration due to manufacturing errors, etc. can be reduced.

[0077] If |fLF| becomes small by going below the lower limit of condition (4), the refractive power of the intermediate group LF becomes too strong, which is undesirable as it increases the variation in curvature of field during focusing.

[0078] If |fLF| becomes large, exceeding the upper limit of conditional expression (4), the focusing sensitivity of the middle group LF decreases, and the amount of movement of the middle group LF during focusing increases, resulting in an increase in the overall length of the optical system L0. Also, if |fL1| becomes small, exceeding the upper limit of conditional expression (4), then spherical aberration fluctuations due to manufacturing errors and the like increase, which is undesirable.

[0079] Conditional formula (5) specifies the ratio of the focal length fLP of the front group LP to the ideal image height in central projection (without taking into account changes in image height due to distortion). By reducing fLP within the range that satisfies conditional formula (5), it is possible to achieve a wide angle of view for optical system L0 while providing excellent correction for spherical aberration, curvature of field, and distortion.

[0080] If fLP falls below the lower limit of condition (5) and becomes small, this is advantageous for achieving a wider angle of view for the optical system, but it is undesirable because the spherical aberration and curvature of field generated in the front group LP become too large in the under-focus direction.

[0081] If fLP increases beyond the upper limit of condition (5), it becomes difficult to make the optical system have a wide angle, which is not preferable.

[0082] Condition (6) represents the focus sensitivity of the intermediate lens unit LF. By making the value smaller (increasing the absolute value) within the range in which the condition is satisfied, the amount of movement of the intermediate lens unit LF associated with focusing can be reduced, and the optical system L0 can be made more compact.

[0083] If the value falls below the lower limit of condition (6), the amount of movement of the intermediate group LF during focusing can be reduced, and the optical system L0 can be made more compact. However, this is not desirable because the refractive power of the intermediate group LF becomes too strong, causing large fluctuations in aberrations during focusing.

[0084] If the value exceeds the upper limit of condition (6), the amount of movement of the intermediate group LF during focusing becomes too large, and the overall length of the optical system L0 becomes large, which is undesirable.

[0085] Conditional expression (7) defines the Abbe number νp of the lens Gp in the second subunit L2. At least one positive lens in the second subunit L2 satisfies conditional expression (7). By increasing νp within a range that satisfies the conditional expression, it is possible to reduce axial chromatic aberration.

[0086] If νp becomes small below the lower limit of condition (7), the correction of axial chromatic aberration for the g-line becomes insufficient, which is not preferable.

[0087] If νp increases beyond the upper limit of condition (7), the axial chromatic aberration for the g-line will be overcorrected, which is not preferable.

[0088] Conditional formula (8) defines the Abbe number vn of the lens Gn in the second subgroup L2. At least one negative lens in the second subgroup L2 satisfies conditional formula (8). By making vn small within a range that satisfies the conditional formula, axial chromatic aberration can be reduced.

[0089] If vn becomes small below the lower limit of condition (8), the longitudinal chromatic aberration for the g-line will be overcorrected, which is not preferable.

[0090] If vn becomes large beyond the upper limit of condition (8), the correction of axial chromatic aberration for the g-line becomes insufficient, which is undesirable.

[0091] By making MF smaller within the range that satisfies conditional expression (9), the amount of movement of the intermediate group LF associated with focusing can be reduced, thereby making it possible to reduce the overall length of the optical system L0. Also, by making DSP larger within the range that satisfies conditional expression, the surface closest to the image side can be located at a position farthest from the aperture stop SP, making it easier to correct other aberrations (astigmatism, field curvature, and distortion) without affecting spherical aberration and coma.

[0092] If MF becomes small by going below the lower limit of condition (9), the refractive power of the middle group LF becomes too strong, which undesirably increases the fluctuation in aberrations during focusing, and if DSP becomes large by going below the lower limit of condition (9), the overall length of the optical system L0 becomes large, which undesirably.

[0093] If MF becomes large beyond the upper limit of condition (9), the amount of movement of the middle group LF during focusing becomes too large, and the overall length of the optical system L0 becomes large, which is not preferable. If DSP becomes small beyond the upper limit of condition (9), the effect of correcting aberrations described above becomes small, which is not preferable.

[0094] Conditional formula (10) prescribes the ratio of the focal length fLP of the front group LP to the distance DSP from the aperture stop SP to the surface of the rear group LR closest to the image. By reducing fLP within the range that satisfies the conditional formula, the optical system L0 can be made to have a wide angle while satisfactorily correcting spherical aberration, curvature of field, and distortion. Furthermore, by increasing DSP within the range that satisfies the conditional formula, it becomes easier to correct astigmatism, curvature of field, and distortion, as explained in conditional formula (9).

[0095] If fLP falls short of the lower limit of condition (10) and becomes small, this is advantageous for making the optical system wider-angle, but it is not preferable because the spherical aberration and curvature of field generated by the front group LP become too large in the under-focus direction. Also, if DSP falls short of the lower limit of condition (10) and becomes large, it is not preferable because the overall length of the optical system L0 becomes large.

[0096] If fLP increases beyond the upper limit of condition (10), it becomes difficult to make the optical system wider-angle, which is not preferable.If DSP decreases beyond the upper limit of condition (10), the effect of correcting astigmatism, curvature of field, and distortion becomes smaller, which is not preferable.

[0097] Conditional expression (11) defines the ratio of the focal length fL2 of the positive second subunit L2 to the effective aperture (diameter) EA of the surface of the rear unit LR that is closest to the image side.

[0098] If fLP falls short of the lower limit of condition (11) and becomes small, this is advantageous for making the optical system wider-angle, but it is undesirable because the spherical aberration and curvature of field generated by the front group LP become too large in the under direction.If EA falls short of the lower limit of condition (11) and becomes large, it is undesirable because the radial size of the optical system L0 becomes large.

[0099] If fLP becomes small by exceeding the upper limit of condition (11), it becomes difficult to make the optical system L0 wider-angle, which is not preferable. If EA becomes small by exceeding the upper limit of condition (11), the effect of correcting curvature of field, etc. in the rear group LR becomes small, which is not preferable.

[0100] Conditional expression (12) prescribes the ratio of the absolute value of the focal length fLair of the biconvex air lens Lair in the first subgroup L1 to the focal length fL1 of the first subgroup L1. If fLair is increased (the absolute value of fLair is reduced) within the range that satisfies the conditional expression, the Petzval sum of the air lens becomes negative, and the positive Petzval sum of the entire optical system L0 can be corrected to close to 0, thereby reducing the curvature of field.

[0101] If fLair becomes small by falling below the lower limit of condition (12), the correction of curvature of field becomes insufficient, which is not preferable.

[0102] If fLair becomes large beyond the upper limit of conditional expression (12), the air lens will not have a biconvex shape, and further the Petzval sum of the air lens will become positive, making it difficult to bring the Petzval sum of the entire optical system L0 close to 0, which is not preferable.

[0103] Conditional expression (13) defines the ratio of the maximum air spacing Dair of the biconvex air lens Lair in the first partial unit L1 to the distance L from the surface closest to the object side to the surface closest to the image side in the optical system L0.

[0104] If Dair becomes small by falling below the lower limit of conditional expression (13), it becomes necessary to reduce the curvature of the object-side and image-side surfaces that constitute the air lens Lair. As a result, the negative refractive power of the air lens becomes too small, and correction of field curvature becomes insufficient, which is not preferable.

[0105] If Dair increases beyond the upper limit of condition (13), the overall length of the optical system L0 increases, which is not preferable.

[0106] Conditional formula (14) prescribes the ratio between the radius of curvature R of the surface closest to the object side of a single lens with negative refractive power or a cemented lens with negative refractive power as a whole, the object-side surface of which is a concave surface in the intermediate group LF, and the distance S from the aperture stop SP to the object side surface when focusing to infinity. By setting this ratio within a range that satisfies the conditional formula, an off-axis light beam entering the intermediate group LF is incident at an angle close to perpendicular to the concave surface. When the light beam is incident at an angle close to perpendicular to the surface, it is not refracted significantly by the surface, which is preferable because it reduces the variation in field curvature even if the intermediate group LF moves with focusing.

[0107] If the lower or upper limit of condition (14) is exceeded, off-axis light beams will be incident on the concave surface at an angle tilted from the perpendicular, causing the light beams to be largely refracted and resulting in large fluctuations in field curvature during focusing, which is undesirable.

[0108] Conditional formula (15) prescribes the ratio of the focal length fLF of the intermediate group LF to the focal length f of the optical system L0. By increasing fLF (reducing its absolute value) within the range that satisfies the conditional formula, the amount of movement of the intermediate group LF that accompanies focusing can be reduced, making it possible to make the optical system L0 more compact. In addition, the intermediate group LF can significantly deflect off-axis light beams and guide them to the image plane, making it possible to shorten the overall length.

[0109] If fLF becomes small by going below the lower limit of condition (15), the amount of movement of the intermediate group LF during focusing becomes large, and the overall length of the optical system L0 becomes large, which is not preferable.

[0110] If fLF becomes large beyond the upper limit of condition (15), the refractive power of the intermediate lens unit LF becomes too strong, which is undesirable because it causes excessive fluctuations in aberrations such as curvature of field during focusing.

[0111] Condition (16) defines the ratio of the focal length fLRp of the single lens with positive refractive power in the rear group LR to the absolute value of the focal length fL1 of the first partial group L1. By reducing fLRp within the range that satisfies the condition, off-axis rays can be refracted near the image plane, ensuring telecentricity and correcting astigmatism.

[0112] If fLRp becomes small by going below the lower limit of condition (16), distortion on the barrel side will become large, which is undesirable.

[0113] If the upper limit of condition (16) is exceeded and fLRp becomes large, it becomes difficult to ensure sufficient telecentricity, which is undesirable.

[0114] It is also preferable that at least one of the upper limit and lower limit of the numerical range of conditional expressions (2) to (16) be within the range of the following conditional expressions (2a) to (16a). 0.25 <DSP / T<0.90 ···(2a) 0.01 <fL2 / |fL1|<0.70 ···(3a) 0.01<|fLF| / |fL1|<1.40 ···(4a) 0.40 <fLP / (f×tanω)<1.40 ···(5a) -1.40<(1-βLF 2 ) × βLR 2 <-0.50 (6a) 57<νp<115 (7a) 15<νn<33 (8a) 0.03 <MF / DSP<0.13 ···(9a) 0.25 <fLP / DSP<0.70 ···(10a) 0.40 <fL2 / EA<1.10 ···(11a) -0.45 <fLair / |fL1|<0.05 ···(12a) 0.07 <Dair / L<0.28 ···(13a) -0.90 -2.90 <fLF / f<-1.20 ···(15a) 0.00 <fLRp / |fL1|<1.45 ···(16a)

[0115] It is even more preferable that at least one of the upper limit and lower limit of the numerical range of conditional expressions (2) to (16) satisfies the range of the following conditional expressions (2b) and (16b). 0.40 <DSP / T<0.89 ···(2b) 0.01 <fL2 / |fL1|<0.60 ···(3b) 0.01<|fLF| / |fL1|<1.25 (4b) 0.45 <fLP / (f×tanω)<1.25 ···(5b) -1.30<(1-βLF 2 ) × βLR 2 <-0.60 (6b) 59<νp<110 (7b) 15<νn<32 (8b) 0.04 <MF / DSP<0.12 ···(9b) 0.30 <fLP / DSP<0.60 ···(10b) 0.50 <fL2 / EA<1.00 ···(11b) -0.40 <fLair / |fL1|<0.00 ···(12b) 0.09 <Dair / L<0.26 ···(13b) -0.80 -2.80 <fLF / f<-1.40 ···(15b) 0.00 <fLRp / |fL1|<1.40 ···(16b)

[0116] ​​In addition, if at least one of the upper limit and lower limit values ​​of the numerical range of conditional expressions (2) to (16) is set to the range of the following conditional expressions (2c) and (16c), the effects represented by the above-mentioned conditional expressions can be maximized. 0.50 <DSP / T<0.88 ···(2c) 0.02 <fL2 / |fL1|<0.50 ···(3c) 0.02<|fLF| / |fL1|<1.05 (4c) 0.55 <fLP / (f×tanω)<1.00 ···(5c) -1.20<(1-βLF 2 ) × βLR 2 <-0.65 ···(6c) 62<νp<100 (7c) 16<νn<31 (8c) 0.045 <MF / DSP<0.10 ···(9c) 0.35 <fLP / DSP<0.55 ···(10c) 0.55 <fL2 / EA<0.90 ···(11c) -0.30 <fLair / |fL1|<-0.01 ···(12c) 0.11 <Dair / L<0.22 ···(13c) -0.60 -2.70 <fLF / f<-1.60 ···(15c) 0.05 <fLRp / |fL1|<1.30 ···(16c)

[0117] Next, the optical system L0 of each embodiment will be described in further detail.

[0118] In the first to seventh embodiments, the first subunit L1 has a cemented lens made up of a positive lens and a negative lens, which reduces lateral chromatic aberration and reduces fluctuations in field curvature and one-sided blur caused by manufacturing errors in the first subunit L1.

[0119] ​In addition, in Examples 1 to 7, at least one positive lens in the second sub-unit L2 has an aspheric shape. Since the second sub-unit L2 requires strong positive refractive power to achieve a wide angle, by making the positive lens aspheric, it becomes possible to easily correct spherical aberration and coma aberration.

[0120] In addition, in the first to seventh embodiments, the intermediate group LF is composed of one negative lens or one cemented lens that is negative overall. It is preferable to configure the intermediate group LF with a small number of lenses, since this reduces the weight of the lens group and enables high-speed AF. Note that the intermediate group LF may include other lens elements as long as high-speed AF is possible. In addition, at least one surface of the intermediate group LF may be aspheric in order to suppress aberration fluctuations accompanying focusing.

[0121] In addition, in Examples 1 to 7, the rear lens group LR has a positive lens having an aspheric surface. Making the surface of the positive lens aspheric is preferable for effectively correcting astigmatism.

[0122] In the sixth embodiment, the rear group LR includes a negative lens G9 having an aspheric surface. The aspheric surface has an inflection point and a stationary point. Here, the stationary point is a point where h is such that, when X is the amount of displacement from the apex of the surface in the optical axis direction, h is the height from the optical axis in a direction perpendicular to the optical axis, and the aspheric shape is expressed as X(h), the value of the first derivative obtained by differentiating X(h) once with respect to h is 0. Similarly, the inflection point is a point where h is such that the value of the second derivative obtained by differentiating X(h) twice with respect to h is 0.

[0123] By having an inflection point or a stationary point, the magnitude and sign of the refractive power at the periphery of the lens surface can be changed independently of the paraxial refractive power, making it easier to correct astigmatism.

[0124] Numerical examples 1 to 7 corresponding to the first to seventh embodiments, respectively, are shown below.

[0125] In the surface data of each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the axial spacing (distance on the optical axis) between the mth surface and the (m+1)th surface. Here, m is the surface number counted from the light incident side. In addition, 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 given by Nd, NF, NC, and Ng, respectively, when the refractive indices at the Fraunhofer lines d-line (587.6 nm), F-line (486.1 nm), C-line (656.3 nm), and g-line (wavelength 435.8 nm) are νd=(Nd-1) / (NF-NC) It is expressed as:

[0126] In each numerical example, d, focal length (mm), F-number, and half angle of view (°) are all values ​​when the optical system of each example is focused on an object at infinity. The back focus BF is the air-equivalent distance from the final lens surface to the image surface. The total lens length is the value obtained by adding the back focus to the distance from the first lens surface to the final lens surface (not including optical blocks FL equivalent to optical filters, faceplates, crystal low-pass filters, infrared cut filters, etc.).

[0127] If the optical surface is aspheric, a * symbol is added to the right of the surface number. The aspheric shape is expressed as follows, where X is the displacement from the apex of the surface in the optical axis direction, h is the height from the optical axis in a direction perpendicular to the optical axis, R is the paraxial radius of curvature, k is the conic constant, and A4, A6, A8, A10, A12, ... 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 +A12×h 12 +··· In addition, "e±XX" in each aspheric coefficient is "×10± XX " It means.

[0128] [Numerical Example 1] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 6.878 0.35 1.83400 37.2 2 3.173 2.74 3 -7.178 0.35 1.51742 52.2 4 6.654 1.63 1.95375 32.3 5 -10.952 0.98 6(Aperture) ∞ 0.87 7* 8.549 2.24 1.49710 81.6 8* -12.398 0.10 9 -10.934 0.35 1.80809 22.8 10 9.261 0.26 11* 6.769 1.67 1.76802 49.2 12* -9.127 (variable) 13 -19.912 0.40 1.67300 38.3 14 23.670 (variable) 15* 52.176 2.21 1.63560 23.9 16* -22.467 0.50 12.00 17 ∞ 0.50 1.51633 64.1 18∞0.71 19 ∞ 1.20 1.51633 64.1 20 ∞ (variable) Image plane ∞ Aspheric Data Side 7 K = 0.00000e+000 A 4=-2.55136e-003 A 6= 1.30530e-004 A 8=-9.41662e-005 A10= 1.30876e-005 A12=-1.81088e-006 Side 8 K = 0.00000e+000 A 4=-1.79707e-002 A 6= 2.61764e-003 A 8=-3.01330e-004 A10= 1.86977e-005 A12=-9.24451e-007 Page 11 K = 0.00000e+000 A 4=-9.15823e-003 A 6= 8.44821e-004 A 8=-3.46287e-005 Side 12 K = 0.00000e+000 A 4= 1.20425e-003 A 6=-3.58145e-004 A 8= 5.11906e-005 A10=-2.11763e-006 Page 15 K = 0.00000e+000 A 4= 2.94889e-003 A 6=-3.11085e-004 A 8= 1.66513e-005 A10=-4.63985e-007 A12= 6.67079e-009 A14=-3.98198e-011 Page 16 K = 0.00000e+000 A 4= 4.06056e-003 A 6=-3.37557e-004 A 8= 1.25655e-005 A10=-2.13357e-007 A12= 1.34436e-009 Various data Focal length 6.75 F-number: 2.88 Half angle of view (°) 49.445 Image height 6.47 Lens length 21.56 BF 3.07 When focused at infinity When focused at close range (horizontal magnification -0.1) d12 2.05 2.86 d14 2.29 1.48 Lens Group Data Lens group Focal length Lens length 1 1 -118.32 5.07 2 7 7.97 4.62 3 13 -16.01 0.40 4 15 25.00 2.21 5 17 ∞ 1.71 Single lens data Lens starting surface focal length 1 1 -7.38 2 3 -6.62 3 4 4.55 4 7 10.55 5 9 -6.16 6 11 5.30 7 13 -16.01 8 15 25.00 9 17 0.00 10 19 0.00

[0129] [Numerical Example 2] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 55.072 0.40 1.59522 67.7 2 3.851 2.66 3 -8.092 0.40 1.51823 58.9 4 6.019 1.90 1.81600 46.6 5 -12.534 1.19 6(Aperture) ∞ 1.00 7 4.224 2.11 1.43700 95.1 8 58.578 0.10 9 6.033 1.47 1.49700 81.6 10 -29.754 0.40 1.75211 25.0 11 8.536 0.82 12* 23.704 0.50 1.85135 40.1 13* 200.010 (variable) 14 -17.843 0.40 1.81600 46.6 15 77.842 (variable) 16* 24.815 2.89 1.85135 40.1 17 -62.373 0.50 13.18 18 ∞ 0.59 1.51633 64.1 19∞0.71 20 ∞ 0.50 1.51633 64.1 21∞1.20 Image plane ∞ Aspheric Data Side 12 K = 0.00000e+000 A 4=-2.25054e-003 A 6=-7.60820e-004 A 8=-1.64662e-005 Page 13 K = 0.00000e+000 A 4= 1.38431e-003 A 6=-6.25380e-004 A 8=-1.06729e-005 A10= 4.98781e-006 Page 16 K = 0.00000e+000 A 4= 2.93176e-004 A 6=-4.11486e-006 A 8= 8.39650e-008 A10=-6.67871e-010 Various data Focal length 7.72 F-number: 2.88 Half angle of view (°) 45.746 Image height 6.39 Lens length 23.43 BF 3.13 When focused at infinity When focused at close range (horizontal magnification -0.1) d13 1.40 2.44 d15 2.65 1.61 Lens Group Data Lens group Focal length Lens length 1 1 -17.94 5.36 2 7 8.21 5.40 3 14 -17.76 0.40 4 16 21.17 2.89 Single lens data Lens starting surface focal length 1 1 -6.98 2 3 -6.60 3 4 5.22 4 7 10.30 5 9 10.23 6 10 -8.78 7 12 31.54 8 14 -17.76 9 16 21.17 10 18 0.00 11 20 0.00

[0130] [Numerical Example 3] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 7.089 0.40 1.80610 33.3 2 3.222 2.80 3 -7.163 0.35 1.51742 52.2 4 6.932 1.53 1.95375 32.3 5 -10.766 0.81 6(Aperture) ∞ 0.96 7* 9.525 2.36 1.49710 81.6 8* -10.752 0.11 9 -10.304 0.35 1.80809 22.8 10 10.304 0.28 11* 7.838 1.66 1.85135 40.1 12* -9.229 (variable) 13 -37.501 0.40 1.80809 22.8 14 15.368 (variable) 15* 27.898 2.41 1.63550 23.9 16* -42.069 0.50 12.30 17 ∞ 0.50 1.51633 64.1 18∞0.71 19 ∞ 0.50 1.51633 64.1 20∞1.20 Image plane ∞ Aspheric Data Side 7 K = 0.00000e+000 A 4=-2.51395e-003 A 6= 2.21434e-004 A 8=-1.51537e-004 A10= 2.79256e-005 A12=-2.99479e-006 Side 8 K = 0.00000e+000 A 4=-1.50953e-002 A 6= 1.69573e-003 A 8=-1.22171e-004 Page 11 K = 0.00000e+000 A 4=-7.10328e-003 A 6= 5.30705e-004 A 8=-1.37005e-005 A10=-3.50415e-007 Side 12 K = 0.00000e+000 A 4= 8.78035e-004 A 6=-2.63596e-004 A 8= 3.43946e-005 A10=-1.28653e-006 Page 15 K = 0.00000e+000 A 4= 1.69451e-003 A 6=-1.75727e-004 A 8= 9.58955e-006 A10=-2.69538e-007 A12= 3.89994e-009 A14=-2.32853e-011 Page 16 K = 0.00000e+000 A 4= 2.18456e-003 A 6=-1.87718e-004 A 8= 6.93398e-006 A10=-1.15675e-007 A12= 7.18190e-010 Various data Focal length 6.80 F-number: 2.88 Half angle of view (°) 49.289 Image height 6.47 Lens length 21.56 BF 3.07 When focused at infinity When focused at close range (horizontal magnification -0.1) d12 1.81 2.47 d14 2.24 1.59 Lens Group Data Lens group Focal length Lens length 1 1 -157.87 5.08 2 7 7.55 4.77 3 13 -13.44 0.40 4 15 26.75 2.41 Single lens data Lens starting surface focal length 1 1 -7.68 2 3 -6.75 3 4 4.62 4 7 10.57 5 9 -6.33 6 11 5.21 7 13 -13.44 8 15 26.75 9 17 0.00 10 19 0.00

[0131] [Numerical Example 4] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 10.242 0.40 1.88300 40.8 2 3.541 3.65 3 -13.689 0.35 1.49700 81.6 4 6.727 1.82 1.95375 32.3 5 -21.979 0.80 6 (Aperture) ∞ 0.82 7* 6.613 2.38 1.59201 67.0 8* -5.869 0.10 9 -5.405 0.35 1.80809 22.8 10 19.222 0.40 11* 10.211 1.08 1.85135 40.1 12* -15.940 (variable) 13 -16.670 0.40 1.63980 34.5 14 15.775 1.10 1.49700 81.6 15 34.716 (variable) 16* 38.126 1.91 1.67070 19.3 17* -22.882 0.50 11.06 18 ∞ 0.50 1.51633 64.1 19∞0.71 20 ∞ 0.50 1.51633 64.1 21∞1.20 Image plane ∞ Aspheric Data Side 7 K = 0.00000e+000 A 4=-7.20609e-004 A 6= 2.51245e-004 A 8=-1.65099e-004 A10= 3.41574e-005 A12=-3.88816e-006 Side 8 K = 0.00000e+000 A 4=-1.05929e-002 A 6= 1.69234e-003 A 8=-1.53149e-004 Page 11 K = 0.00000e+000 A 4=-8.68169e-003 A 6= 6.06804e-004 A 8= 3.27045e-005 A10=-3.01469e-006 Side 12 K = 0.00000e+000 A 4=-1.27865e-003 A 6=-2.01475e-004 A 8= 7.66873e-005 A10=-2.42045e-006 Page 16 K = 0.00000e+000 A 4= 1.48847e-003 A 6=-2.07594e-004 A 8= 1.30900e-005 A10=-4.07412e-007 A12= 6.30006e-009 A14=-3.93673e-011 Page 17 K = 0.00000e+000 A 4= 2.87532e-003 A 6=-2.51549e-004 A 8= 1.12199e-005 A10=-2.36244e-007 A12= 1.86665e-009 Various data Focal length 6.30 F-number: 2.88 Half angle of view (°) 51.417 Image height 6.47 Lens length 22.69 BF 3.07 When focused at infinity When focused at close range (horizontal magnification -0.1) d12 2.09 2.87 d15 1.98 1.19 Lens Group Data Lens group Focal length Lens length 1 1 -31.62 6.23 2 7 7.93 4.30 3 13 -16.01 1.50 4 16 21.59 1.91 Single lens data Lens starting surface focal length 1 1 -6.31 2 3 -9.02 3 4 5.57 4 7 5.65 5 9 -5.19 6 11 7.45 7 13 -12.61 8 14 57.07 9 16 21.59 10 18 0.00 11 20 0.00

[0132] [Numerical Example 5] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 7.472 0.40 1.49700 81.6 2 3.164 3.39 3 -5.114 0.35 1.59551 39.2 4 7.737 1.53 1.88300 40.8 5 -7.814 0.96 6 (Aperture) ∞ 1.02 7* 7.875 2.63 1.59201 67.0 8* -18.641 0.42 9 -30.537 0.35 1.75211 25.0 10 8.499 1.27 1.85135 40.1 11* -24.696 (variable) 12 -52.424 0.40 1.86966 20.0 13 24.787 (variable) 14* 35.850 2.17 1.63560 23.9 15* -40.892 0.50 11.95 16 ∞ 0.50 1.51633 64.1 17 ∞ 0.71 18 ∞ 0.50 1.51633 64.1 19∞1.20 Image plane ∞ Aspheric Data Side 7 K = 0.00000e+000 A 4=-2.08566e-004 A 6= 3.53007e-006 A 8=-2.76678e-007 Side 8 K = 0.00000e+000 A 4=-2.16111e-003 A 6= 7.84238e-005 A 8=-8.06643e-007 Page 11 K = 0.00000e+000 A 4= 2.63801e-003 A 6=-1.92920e-005 Side 14 K = 0.00000e+000 A 4= 6.84700e-004 A 6=-1.65324e-005 A 8= 1.74589e-007 Page 15 K = 0.00000e+000 A 4= 5.07011e-004 A 6=-6.54251e-006 A 8=-1.50520e-007 A10= 3.05170e-009 Various data Focal length 7.56 F-number: 2.88 Half angle of view (°) 46.247 Image height 6.47 Lens length 22.46 BF 3.07 When focused at infinity When focused at close range (horizontal magnification -0.1) d11 1.70 2.75 d13 2.79 1.74 Lens Group Data Lens group Focal length Lens length 1 1 -51.04 5.68 2 7 8.48 4.67 3 12 -19.31 0.40 4 14 30.39 2.17 Single lens data Lens starting surface focal length 1 1 -11.39 2 3 -5.12 3 4 4.62 4 7 9.71 5 9 -8.81 6 10 7.56 7 12 -19.31 8 14 30.39 9 16 0.00 10 18 0.00

[0133] [Numerical Example 6] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 8.240 0.40 1.51742 52.4 2 3.506 3.66 3 -7.157 0.35 1.51742 52.4 4 8.131 1.37 1.90043 37.4 5 -10.178 0.80 6(Aperture) ∞ 0.80 7* 12.736 2.80 1.59201 67.0 8* -7.907 0.14 9 -11.376 0.35 1.80809 22.8 10 11.376 0.57 11* 14.397 1.37 1.85135 40.1 12* -9.529 (variable) 13 -34.193 0.40 1.96300 24.1 14 23.172 (variable) 15* 45.086 2.29 1.67070 19.3 16* -40.653 0.50 17* 11.289 0.80 1.53160 55.8 18* 7.387 0.60 12.70 19 ∞ 0.50 1.51633 64.1 20∞1.20 Image plane ∞ Aspheric Data Side 7 K = 0.00000e+000 A 4=-1.75746e-003 A 6=-4.64106e-006 A 8=-2.08667e-005 Side 8 K = 0.00000e+000 A 4=-5.39088e-003 A 6= 3.46820e-004 A 8=-2.18984e-005 Page 11 K = 0.00000e+000 A 4=-3.25242e-003 Side 12 K = 0.00000e+000 A 4= 7.18016e-005 A 6=-1.64095e-004 A 8= 7.39502e-006 A10=-2.03249e-007 Page 15 K = 0.00000e+000 A 4= 1.64948e-003 A 6=-1.11437e-004 A 8= 4.29921e-006 A10=-9.36440e-008 A12= 1.10782e-009 A14=-5.68321e-012 Page 16 K = 0.00000e+000 A 4= 1.79573e-003 A 6=-1.15037e-004 A 8= 2.82313e-006 A10=-2.42846e-008 A12= 8.10346e-012 Page 17 K = 0.00000e+000 A 4=-4.54637e-003 A 6= 1.22575e-004 A 8=-1.07025e-006 Side 18 K = 0.00000e+000 A 4=-5.80361e-003 A 6= 1.52777e-004 A 8=-1.63066e-006 Various data Focal length 8.00 F-number: 2.88 Half angle of view (°) 44.623 Image height 6.47 Lens length 22.83 BF 2.13 When focused at infinity When focused at close range (horizontal magnification -0.1) d12 1.70 2.43 d14 2.40 1.68 Lens Group Data Lens group Focal length Lens length 1 1 85.93 5.78 2 7 8.43 5.22 3 13 -14.29 0.40 4 15 100.70 3.59 Single lens data Lens starting surface focal length 1 1 -12.14 2 3 -7.30 3 4 5.20 4 7 8.68 5 9 -6.99 6 11 6.92 7 13 -14.29 8 15 32.22 9 17 -43.28 10 19 0.00

[0134] [Numerical Example 7] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 14.048 0.95 1.90043 37.4 2 18.980 0.36 3 15.515 0.40 1.49700 81.6 4 3.442 3.44 5 -7.034 0.35 1.63980 34.5 6 9.868 1.78 1.88300 40.8 7 -8.501 0.80 8(Aperture) ∞ 0.80 9* 9.932 3.16 1.55332 71.7 10* -11.300 0.55 11 -11.094 0.35 1.69895 30.1 12 16.182 0.33 13* 10.346 1.84 1.76802 49.2 14* -13.304 (variable) 15 -169.196 0.40 1.95375 32.3 16 20.160 (variable) 17* 28.135 2.70 1.53160 55.8 18 -135.241 0.50 12.95 19 ∞ 0.50 1.51633 64.1 20∞0.71 21 ∞ 0.50 1.51633 64.1 22∞1.20 Image plane ∞ Aspheric Data 9th page K = 0.00000e+000 A 4=-1.28833e-003 A 6= 1.11092e-005 A 8=-1.34891e-005 Side 10 K = 0.00000e+000 A 4=-5.99816e-003 A 6= 3.16302e-004 A 8=-1.55071e-005 Page 13 K = 0.00000e+000 A 4=-3.63957e-003 A 6= 1.34216e-004 A 8= 1.35269e-006 Side 14 K = 0.00000e+000 A 4= 6.12152e-004 A 6=-4.63321e-005 A 8= 6.85976e-006 A10=-3.34102e-008 Page 17 K = 0.00000e+000 A 4= 2.70834e-004 A 6= 6.68230e-007 Various data Focal length 8.15 F-number: 2.88 Half angle of view (°) 44.143 Image height 6.75 Lens length 25.66 BF 3.07 When focused at infinity When focused at close range (horizontal magnification -0.1) d14 1.66 2.65 d16 2.72 1.73 Lens Group Data Lens group Focal length Lens length 1 1 -53.28 7.28 2 9 8.70 6.22 3 15 -18.87 0.40 4 17 44.06 2.70 Single lens data Lens starting surface focal length 1 1 55.00 2 3 -9.00 3 5 -6.37 4 6 5.42 5 9 10.09 6 11 -9.37 7 13 7.84 8 15 -18.87 9 17 44.06 10 19 0.00 11 21 0.00

[0135] The table below gives various values ​​for each example.

[0136] [Table 1]

[0137] [Imaging device] Next, an embodiment of a digital still camera (imaging device) using the optical system of the present invention will be described with reference to Fig. 15. In Fig. 15, 10 is a camera body, and 11 is a lens device including any of the optical systems L0 described in any of the first to seventh embodiments.

[0138] Reference numeral 12 denotes a solid-state image pickup element (photoelectric conversion element) such as a CCD sensor or a CMOS sensor that is built into the camera body and receives and photoelectrically converts an optical image formed by the lens device 11. The camera body 10 may be a so-called single-lens reflex camera having a quick-turn mirror, or a so-called mirrorless camera having no quick-turn mirror.

[0139] In this way, by applying the optical system L0 of the present invention to an imaging device such as a digital still camera, it is possible to obtain a small, wide-angle imaging device with good optical performance around the periphery of the screen.

[0140] [Lens device] Fig. 16 is a schematic diagram showing the appearance of a lens device according to the present invention. The lens device in Fig. 16 is a so-called interchangeable lens that is detachably attached to a camera body (not shown).

[0141] The lens device 20 includes a photographing optical system 21 similar to any one of the above-mentioned embodiments 1 to 7. The lens device 20 includes a focus operation means 22 and an operation means 23 for changing the photographing mode.

[0142] When the user operates the focus operation means 22, the arrangement of the intermediate group LF of the photographic optical system 21 is changed mechanically or electrically, thereby changing the focal position.

[0143] Also, the photographing optical system 21 may be configured so that the user operates the operation means 23 for a purpose other than focusing. For example, the operation means 23 may be used to change the aperture diameter of the aperture diaphragm SP.

[0144] Although the 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 are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0145] L0 optical system LP front group LF intermediate group LR rear group

Claims

1. It is composed of a front group, an intermediate group, and a rear group, all of which have positive refractive power, arranged in that order from the object side to the image side. said intermediate group moves so that a distance between said front group and said intermediate group and a distance between said intermediate group and said rear group change during focusing from infinity to a close distance; the front group includes a first subgroup, an aperture stop, and a second subgroup, arranged in this order from the object side to the image side; The first subgroup includes a biconvex air lens, Let fLP be the focal length of the front group, EA be the effective diameter of the lens surface of the rear group closest to the image side, D be the thickness of the air lens on the optical axis, L be the distance from the lens surface closest to the object side to the lens surface closest to the image side of the optical system, and fL2 be the focal length of the second sub group. 0.01<fLP / EA<0.80 0.11<Dair / L<0.22 0.40<fL2 / EA<1.10 An optical system characterized in that the following condition is satisfied:

2. Let DSP be the distance from the aperture stop to the lens surface of the rear group closest to the image side, and T be the distance from the aperture stop to the image plane. 0.20<DSP / T<1.00 2. The optical system according to claim 1, wherein the following condition is satisfied:

3. When the focal length of the first subgroup is fL1, 0.00<fL2 / |fL1|<0.80 3. The optical system according to claim 1, wherein the following condition is satisfied:

4. When the focal length of the first subgroup is fL1 and the focal length of the intermediate group is fLF, 0.00<|fLF| / |fL1|<1.50 4. The optical system according to claim 1, wherein the following condition is satisfied:

5. Let βLF be the lateral magnification of the intermediate group when focusing at infinity, and βLR be the lateral magnification of the rear group when focusing at infinity. -1.50<(1-βLF ２ )×βLR ２ <-0.40 5. The optical system according to claim 1, wherein the following condition is satisfied:

6. The second subgroup has a lens Gp having a positive refractive power and a lens Gn having a negative refractive power, When the Abbe number of the lens Gp is ​​vp and the Abbe number of the lens Gn is vn, 55<νp<120 15<vn<35 6. The optical system according to claim 1, wherein the following condition is satisfied:

7. Let DSP be the distance from the aperture stop to the lens surface of the rear group closest to the image side, and MF be the amount of movement of the intermediate group from focusing at infinity to focusing at a distance where the lateral magnification of the optical system is −0.

1. 0.02<MF / DSP<0.15 7. The optical system according to claim 1, wherein the following condition is satisfied:

8. Let DSP be the distance from the aperture stop to the lens surface of the rear group closest to the image side, 0.20<fLP / DSP<0.80 8. The optical system according to claim 1, wherein the following condition is satisfied:

9. When the focal length of the air lens is fLair and the focal length of the first subgroup is fL1, -0.50<fLair / |fL1|<0.00 9. The optical system according to claim 1, wherein the following condition is satisfied:

10. the intermediate group has a single lens having a negative refractive power, the lens surface facing the object side being concave, or a cemented lens having a negative refractive power as a whole, Let R be the radius of curvature of the lens surface of the single lens or the cemented lens included in the intermediate group closest to the object, and S be the distance from the aperture stop to the lens surface of the single lens or the cemented lens included in the intermediate group closest to the object during infinity focusing, -1.00<S / R<0.00 10. The optical system according to claim 1, wherein the following condition is satisfied:

11. Let f be the focal length of the intermediate group and f be the focal length of the optical system. -3.00<fLF / f<-1.00 11. The optical system according to claim 1, wherein the following condition is satisfied:

12. the rear group has a single lens having a positive refractive power, When the focal length of the first subgroup is fL1 and the focal length of the single lens of the rear group is fLRp, 0.00<fLRp / |fL1|<1.50 12. The optical system according to claim 1, wherein the following condition is satisfied:

13. An optical system described in any one of claims 1 to 12, characterized in that the first subgroup has three lenses, in order from the object side: a meniscus lens with negative refractive power, a lens with negative refractive power, and a lens with positive refractive power.

14. An optical system described in any one of claims 1 to 13, characterized in that the second subgroup has at least two lenses of positive refractive power and at least one lens of negative refractive power.

15. 15. The optical system according to claim 1, wherein the intermediate group has a negative refractive power, and the rear group has a positive refractive power.

16. 16. An imaging apparatus comprising: the optical system according to claim 1; and an imaging element that receives an image formed by the optical system.

17. When the focal length of the optical system is f and the half angle of view of the optical system is ω, 0.30<fLP / (f×tanω)<1.50 17. The imaging apparatus according to claim 16, wherein the following condition is satisfied:

Images