JP2015138122A - Optical system and imaging device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical system that easily obtains high optical performance over an entire object distance with a wide angle of view.SOLUTION: An optical system comprises, in order from an object side to an image side, a front group having negative refractive power and a rear group having positive refractive power. The front group includes a first lens group having negative refractive power, the rear group includes, in order from the object side to the image side, a second lens group having positive refractive power and a third lens group having positive refractive power, and distances between adjacent lens groups change during zooming. The rear group has a lens system LF having positive refractive power that moves on an optical axis during focusing. The lens system LF has, in order from the object side to the image side, a lens unit GA having positive refractive power and a lens unit GB having positive or negative refractive power, and a lens surface of the lens unit GB closest to the object side is concave.

Description

  The present invention relates to an optical system, and is suitable for an imaging optical system of an imaging apparatus such as a digital still camera, a video camera, a TV camera, and a surveillance camera.

  An imaging device is required to have a wide angle of view, high optical performance over the entire screen, and a back focus of a predetermined length. As a wide-angle imaging optical system, Patent Document 1 is composed of a first lens unit having a negative refractive power, an aperture stop, and a second lens group having a positive refractive power. A wide-angle lens with a single focal length is disclosed. In Patent Document 1, focusing is performed by moving the first B lens group having a negative refractive power, which is a part of the first lens group.

  As a wide-angle imaging optical system, a negative lead type zoom lens in which a lens unit having a negative refractive power is disposed closest to the object side is known. Japanese Patent Application Laid-Open No. 2004-228561 includes two groups having a total angle of view of 114.7 degrees at the wide angle end and a zoom ratio of about 1.65, which includes a first lens group having a negative refractive power and a second lens group having a positive refractive power. A zoom lens is disclosed. In this zoom lens, focusing is performed by moving a part of the cemented lens having positive refractive power on the object side of the second lens group.

  In addition, Patent Document 2 includes a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power. A three-group zoom lens with a wide angle of view of 7 degrees and a zoom ratio of about 1.65 is disclosed. In this three-group zoom lens, focusing is performed by moving a part of the cemented lens having positive refractive power on the object side of the second lens group.

JP 2011-227124 A JP 2007-94174 A

  The imaging optical system used in the imaging device is required to have a wide angle of view, little aberration fluctuation during focusing, high resolution over the entire object distance from infinity to short distance, and high resolution over the entire screen. ing. The negative lead type imaging optical system described above can relatively easily obtain an optical system having a wide angle of view and a long back focus.

  However, in general, since the negative lead type imaging optical system has an asymmetric refractive power arrangement with respect to the aperture stop, it is difficult to correct off-axis aberrations such as field curvature and distortion. In particular, if the negative refractive power of the front group is increased in order to obtain a long back focus, it becomes difficult to correct off-axis aberrations. In addition, aberration fluctuations during focusing increase, making it difficult to obtain high resolution over the entire object distance.

  For this reason, in a negative lead imaging optical system, in order to reduce aberration fluctuations during focusing and obtain high optical performance at the entire object distance while widening the angle of view, the refractive power arrangement of each lens group is appropriately set. Setting is important. Furthermore, it is important to select a focusing lens system and to appropriately set the lens configuration of the focusing lens system.

  In Patent Document 1, the first lens group is divided into a first A lens group having a negative refractive power and a first B lens group having a negative refractive power, and the first B lens group is moved during focusing. However, since the focus lens group is provided in the first lens group having a large effective diameter, it is necessary to increase the size of the focus lens group and to secure a predetermined amount of space between the first A lens group and the focus first B lens group. Therefore, it is difficult to reduce the effective diameter of the front lens.

  In Patent Document 2, the second lens group is divided into a focus lens group having a positive refractive power and a fixed lens group having a positive refractive power, thereby achieving downsizing of the focus lens group. However, there has been a tendency for fluctuations in field curvature due to focusing to increase.

  An object of the present invention is to provide an optical system capable of obtaining a high optical performance at a wide angle of view and an entire object distance, and an imaging apparatus having the optical system.

  In order from the object side to the image side, a front group having a negative refractive power and a rear group having a positive refractive power, the front group including a first lens group having a negative refractive power, and the rear group, In the optical system which includes a second lens group having a positive refractive power and a third lens group having a positive refractive power in order from the object side to the image side, and in which an interval between adjacent lens groups changes during zooming, the rear group includes The lens system LF has a positive refractive power that moves on the optical axis during focusing. The lens system LF has a positive refractive power lens unit GA and a positive or negative refractive power in order from the object side to the image side. It has a lens unit GB, and the lens surface on the most object side of the lens unit GB is concave.

  In the optical system, which is composed of a front group having a negative refractive power and a rear group having a positive refractive power in order from the object side to the image side, the front group and the rear group move along different paths during zooming. The group includes a lens system LF having a positive refractive power that moves on the optical axis during focusing. The lens system LF sequentially has a lens unit GA having a positive refractive power and a positive or negative refractive power in order from the object side to the image side. The lens unit GB has a force, and the lens surface closest to the object side of the lens unit GB has a concave shape.

  In a single focal length optical system composed of a front group having a negative refractive power and a rear group having a positive refractive power in order from the object side to the image side with the largest air gap as the boundary, the rear group is focused. The lens system LF has a positive refractive power lens system LF that moves on the optical axis. The lens system LF sequentially has a positive refractive power lens unit GA and a positive or negative refractive power lens from the object side to the image side. A lens unit GB is provided, and the lens surface closest to the object side of the lens unit GB is concave.

  According to the present invention, an optical system having a wide field angle and high optical performance over the entire object distance can be obtained.

Lens cross-sectional view (object distance: infinity) at the wide-angle end (short focal length end) of the zoom lens of Example 1 (A), (B) Longitudinal aberration diagrams (object distance: infinity) at the wide-angle end and the telephoto end (long focal length end) of the zoom lens of Example 1 (A), (B) Longitudinal aberration diagrams at the wide-angle end and the telephoto end of the zoom lens of Example 1 (object distance: 0.28 m) Cross-sectional view of the zoom lens of Embodiment 2 at the wide-angle end (object distance: infinity) (A), (B) Longitudinal aberration diagrams at the wide-angle end and the telephoto end of the zoom lens of Example 2 (object distance: infinity) (A), (B) Longitudinal aberration diagrams at the wide-angle end and the telephoto end of the zoom lens of Example 2 (object distance: 0.28 m) Lens sectional view of an optical system having a single focal length in Example 3 (object distance: infinity) Longitudinal aberration diagram of the optical system having the single focal length in Example 3 (object distance: infinity) Longitudinal aberration diagram of the optical system having the single focal length in Example 3 (object distance: 0.28 m) Schematic diagram of essential parts of a camera (imaging device) provided with the optical system of the present invention.

  Examples of the optical system of the present invention and an image pickup apparatus having the optical system will be described below. The optical system of the present invention is a retrofocus type wide-angle single-focus-lens shooting lens or wide-angle zoom lens used in an imaging apparatus. When the optical system is a zoom lens, the entire system is a retrofocus type at the wide angle end.

When the optical system of the present invention is composed of a single focal length photographing optical system, it is the boundary from the object side to the image side with the largest air gap as the boundary, or in the case of a zoom lens, the largest air gap at the wide angle end. In this order, the lens unit is composed of a front group LA having a negative refractive power and a rear group LB having a positive refractive power. The rear group LB includes a lens system LF having a positive refractive power that moves on the optical axis during focusing.
The lens system LF includes, in order from the object side to the image side, a lens unit GA having a positive refractive power and a lens unit GB having a positive or negative refractive power, and the lens surface closest to the object side of the lens unit GB has a concave shape. is there. Here, the lens unit refers to a single lens or a cemented lens in which a plurality of lenses are cemented.

  The focal length of the entire system means a focal length when an object at infinity is in focus (during focusing) in an imaging optical system having a single focal length. In the case of a zoom lens, it means the focal length at the wide-angle end when an object at infinity is in focus.

  FIG. 1 is a lens cross-sectional view (object distance: infinity) at the wide-angle end (short focal length end) of the zoom lens according to the first exemplary embodiment. 2A and 2B are longitudinal aberration diagrams (object distance: infinity) at the wide-angle end and the telephoto end (long focal length end) of the zoom lens of Example 1. FIG. 3A and 3B are longitudinal aberration diagrams (object distance of 0.28 m) at the wide-angle end and the telephoto end of the zoom lens of Example 1. FIG. Here, the object distance is a distance from the image plane to the object plane when a numerical example described later is expressed in mm, and so on.

  FIG. 4 is a lens cross-sectional view (object distance: infinity) at the wide-angle end of the zoom lens according to the second exemplary embodiment. 5A and 5B are longitudinal aberration diagrams (object distance: infinity) at the wide-angle end and the telephoto end of the zoom lens of Example 2. FIGS. 6A and 6B are longitudinal aberration diagrams (object distance: 0.28 m) at the wide-angle end and the telephoto end of the zoom lens according to Embodiment 2. FIGS.

  FIG. 7 is a lens cross-sectional view (object distance: infinity) of the optical system having the single focal length according to the third embodiment. FIG. 8 is a longitudinal aberration diagram (object distance: infinity) of the optical system having the single focal length according to Example 3. FIG. 9 is a longitudinal aberration diagram (object distance 0.28 m) of the optical system having the single focal length according to Example 3. FIG. 10 is a schematic view of a main part of a camera (imaging device) including the optical system of the present invention.

  The zoom lens of each embodiment is a photographing lens system (imaging lens) used in an imaging apparatus such as a video camera, a digital camera, a TV camera, a surveillance camera, and a silver salt film camera. In the lens cross-sectional view, the left side is the object side (front), and the right side is the image side (rear). In the lens cross-sectional view, LA is a front group of negative refractive power (optical power = reciprocal of focal length). LB is a rear group having a positive refractive power. In each embodiment, the front group LA and the rear group LB are separated with the largest air interval as the boundary, or in the case of a zoom lens, with the largest air interval at the wide-angle end.

  SP is a variable aperture diameter photographic beam diameter determining member (hereinafter referred to as “aperture stop”) that controls the photographic beam diameter according to the aperture value at the time of shooting, and is disposed between the front group LA and the rear group LB. ing. FP1 and FP2 are flare cut stops for cutting unnecessary light. i indicates the order of the lens groups from the object side, and Li is the i-th lens group. LF is a lens system that moves during focusing.

  In the lens cross-sectional views of FIGS. 1 and 4, arrows indicate the movement trajectory of each lens group during zooming from the wide-angle end to the telephoto end. In the first and second embodiments, the wide-angle end and the telephoto end are zoom positions when the respective lens groups are positioned at both ends of a range in which the lens group can move on the optical axis. IP is an image plane. When used as a photographing optical system for a video camera or a digital still camera, an imaging surface of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor is arranged, and a camera for a silver salt film In this case, the film surface is arranged.

  In the zoom lens of Example 1 shown in FIG. 1, the front group LA includes a first lens unit L1 having a negative refractive power. The rear group LB includes a second lens unit L2 having a positive refractive power and a third lens unit L3 having a positive refractive power. The distance between adjacent lens units changes during zooming. Specifically, during zooming from the wide-angle end to the telephoto end, the first lens unit L1 moves along a convex locus toward the image side as indicated by an arrow. The second lens unit L2 moves toward the object side while reducing the distance from the first lens unit L1. The third lens unit L3 moves toward the object side while increasing the distance from the second lens unit L2.

  The aperture stop SP moves along a locus different from that of the third lens unit L3. Focusing is performed by a lens system LF including the second lens unit L2. During focusing from infinity to short distance, the lens system LF moves to the image side as indicated by the focus of the arrow.

  In the zoom lens of Example 2 shown in FIG. 4, the front group LA has a negative refractive power, and the rear group LB has a positive refractive power. During zooming, the front group LA and the rear group LB move along different tracks.

  Specifically, during zooming from the wide-angle end to the telephoto end, the front group LA moves along a locus convex to the image side, and the rear group LB moves toward the object side while reducing the distance from the front group LA. Yes. The aperture stop SP moves integrally with the rear group LB. Focusing is performed by a part of the lens system LF of the rear group LB. During focusing from infinity to short distance, the lens system LF moves to the image side as indicated by the focus of the arrow.

  In the single focal length imaging optical system of Example 3 in FIG. 7, the front group LA has a negative refractive power. The rear group LB has a positive refractive power. Focusing is performed by moving some lens systems LF of the rear group LB. During focusing from infinity to short distance, the lens system LF moves to the image side as indicated by the focus of the arrow.

  Each aberration diagram represents spherical aberration, astigmatism, distortion, and lateral chromatic aberration in order from the left. In the diagrams showing spherical aberration and lateral chromatic aberration, the solid line represents the d-line (587.6 nm), and the two-dot chain line represents the g-line (435.8 nm). In the diagram showing astigmatism, the solid line represents the sagittal direction of the d line, and the broken line represents the meridional direction of the d line. The figure showing the distortion represents the distortion at the d-line. Fno is an F number, and ω is a half angle of view (degrees).

  Next, features of each embodiment other than those described above will be described. When the optical system of each embodiment is composed of a photographing optical system with a single focal length, an image is taken from the object side with the largest air gap as the boundary, or in the case of a zoom lens, with the largest air gap at the wide angle end. In order to the side, there are a front group LA having a negative refractive power and a rear group LB having a positive refractive power.

  In the optical system of each embodiment, the rear group LB includes a lens system LF having a positive refractive power that moves on the optical axis and performs focusing. The lens system LF includes a lens unit GA having a positive refractive power and a lens unit GB having a positive or negative refractive power in order from the object side to the image side. The lens unit GB has a concave surface on the most object side. When designing an ultra-wide angle of view lens, it is important to obtain good optical performance over the entire screen while preventing the effective diameter of the front lens from increasing so much.

  In a retrofocus optical system, requiring a long back focus is equivalent to increasing the retro ratio. Moreover, a remarkably large retro ratio means that the negative refractive power (absolute value of the negative refractive power) of the front group of the negative refractive power is remarkably increased. If the balance of refractive power with the rear group of positive refractive power is lost, the optical performance deteriorates. In particular, the Petzval sum increases, and many off-axis aberrations such as field curvature and distortion occur, making it difficult to correct these various aberrations.

  As in each of the embodiments, when the focusing lens system LF having a positive refractive power is disposed in the rear group of the positive refractive power, the focusing lens system LF is imaged during focusing from infinity to a short distance. It moves to the surface side and the retro ratio becomes larger. For this reason, the angle of view at the wide-angle end is wider than that when focusing on an object at infinity, and off-axis rays passing through the front group with negative refractive power pass through the periphery of the lens more. As a result, the field curvature is over at the time of focusing to a short distance.

  In each embodiment, this problem is solved by devising the configuration of the focusing lens system LF. The focusing lens system LF includes, in order from the object side to the image side, a lens unit GA having a positive refractive power and a lens unit GB having a positive or negative refractive power. Since the focusing lens system LF moves to the image side during focusing from infinity to a short distance, off-axis rays pass through the periphery of the lens at a short distance compared to focusing at infinity.

  By utilizing this fact, the positive refracting power of the lens surface on the object side of the lens unit GA having a positive refractive power is decreased to increase the positive refractive power of the lens surface on the object side, and an image is obtained when focusing to a short distance. The effect of making the surface curvature under is increased. As a result, the curvature of field that occurs in the front group of negative refractive power, which increases during focusing to a short distance, is corrected.

  Further, spherical aberration generated by increasing the refractive power of the lens surface on the object side of the lens unit GA is corrected by making the lens surface on the object side of the lens unit GB concave. Making the object-side lens surface of the lens unit GB concave has a lens surface close to a concentric circle with respect to the aperture stop SP. Thus, the off-axis light beam incident on the lens unit GB passes through without being extremely refracted, thereby reducing the occurrence of field curvature. By adopting such a configuration for the focusing lens system LF, good optical performance is obtained at the entire object distance.

  When the optical system of each embodiment is a zoom lens, it is more preferable to satisfy one or more of the following conditional expressions. According to this, an effect corresponding to each conditional expression can be obtained. The focal length of the lens system LF is ffz, and the focal length of the entire system at the wide angle end is fw. Let R1az be the radius of curvature of the lens surface on the most object side of the lens unit GA. The radius of curvature of the lens surface closest to the object side of the lens unit GB is R1bz. The focal length of the air lens formed by the lens surface closest to the image side of the lens unit GA and the lens surface closest to the object side of the lens unit GB is fabz. The total lens length at the wide angle end is Lw.

  The lens unit GA is composed of a cemented lens GAA in which a negative lens and a positive lens are cemented in order from the object side to the image side. The refractive index of the material of the negative lens of the cemented lens GAA is Nnz, and the material of the positive lens of the cemented lens GAA. The refractive index is Npz. Let the focal length of the front group LA be fLAz. The focal length of the rear group LB is assumed to be fLBz.

At this time, one or more of the following conditional expressions should be satisfied.
3.0 <ffz / fw <15.0 (1a)
0.1 <R1az / ffz <0.5 (2a)
0.1 <| R1bz / ffz | <0.6 (3a)
0.3 <| fabz / ffz | <1.5 (4a)
8.0 <Lw / fw <20.0 (5a)
1.1 <Nnz / Npz <1.5 (6a)
1.0 <| fLAz / fw | <2.0 (7a)
2.0 <fLBz / fw <5.0 (8a)

  When the optical system of each embodiment has a single focal length, it is more preferable to satisfy one or more of the following conditional expressions. According to this, an effect corresponding to each conditional expression can be obtained. The focal length of the lens system LF is ff, and the focal length of the entire system is f. Let R1a be the radius of curvature of the lens surface closest to the object side of the lens unit GA. Let R1b be the radius of curvature of the lens surface closest to the object side of the lens unit GB. The focal length of the air lens formed by the lens surface closest to the image side of the lens unit GA and the lens surface closest to the object side of the lens unit GB is defined as fab. Let L be the total lens length.

  The lens unit GA is composed of a cemented lens GAA in which a negative lens and a positive lens are cemented in order from the object side to the image side. The refractive index of the material of the negative lens of the cemented lens GAA is Nn, and the material of the positive lens of the cemented lens GAA. The refractive index is Np. Let the focal length of the front group LA be fLA. Let the focal length of the rear group LB be fLB. At this time, one or more of the following conditional expressions should be satisfied.

3.0 <ff / f <15.0 (1b)
0.1 <R1a / ff <0.5 (2b)
0.1 <| R1b / ff | <0.6 (3b)
0.3 <| fab / ff | <1.5 (4b)
8.0 <L / f <20.0 (5b)
1.1 <Nn / Np <1.5 (6b)
1.0 <| fLA / f | <2.0 (7b)
2.0 <fLB / f <5.0 (8b)

  Here, the conditional expressions (1a) to (8a) and the conditional expressions (1b) to (8b) are differences in whether the optical system is a zoom lens or a single focal length. The technical contents of the conditional expressions corresponding to each other such as conditional expression (1a) and conditional expression (1b), conditional expression (2a) and conditional expression (2b) are the same. For example, what is meant by the focal length of the entire system and the total lens length in an optical system having a single focal length corresponds to the focal length of the entire system at the wide angle end and the total lens length at the wide angle end of the optical system of the zoom lens.

  Next, the technical meaning of each conditional expression described above will be described. Conditional expressions (1a) and (1b) are used to appropriately set the focal length of the focusing lens system LF. Satisfying conditional expressions (1a) and (1b) achieves good optical performance while reducing the size of the focusing lens system LF.

  If the positive refractive power of the focusing lens system LF becomes too weak beyond the upper limit of the conditional expressions (1a) and (1b), the amount of movement during focusing of the focusing lens system LF increases, and the short distance Aberration fluctuations when focusing on the lens become large. If the lower limit is exceeded and the positive refractive power of the focusing lens system LF becomes too strong, axial chromatic aberration and spherical aberration will increase and it will be difficult to correct these aberrations.

  Conditional expressions (2a) and (2b) appropriately set the radius of curvature of the lens surface on the most object side of the lens unit GA. Satisfying conditional expressions (2a) and (2b) makes it easy to obtain good optical performance over the entire object distance.

  If the radius of curvature of the lens surface on the most object side of the lens unit GA becomes too large beyond the upper limit of conditional expressions (2a) and (2b), a negative image surface generated in the lens system LF during focusing to a short distance Less curvature. For this reason, it becomes difficult to correct the positive curvature of field generated from the front group having a negative refractive power, which increases during focusing to a short distance. When the lower limit is exceeded and the radius of curvature of the surface closest to the object side of the lens unit GA becomes too small, spherical aberration increases and it becomes difficult to correct this aberration.

  Conditional expressions (3a) and (3b) appropriately set the radius of curvature of the lens surface closest to the object side of the lens unit GB. Satisfying conditional expressions (3a) and (3b) makes it easy to obtain good optical performance over the entire object distance.

  When the upper limit of conditional expressions (3a) and (3b) is exceeded, the radius of curvature of the lens surface closest to the object side of the lens unit GB becomes too large (the negative refractive power becomes too weak), and the lens unit GB is closest to the object side. The amount of positive spherical aberration that occurs on the lens surface is reduced. For this reason, it becomes difficult to correct negative spherical aberration occurring on the lens surface closest to the object side of the lens unit GA. If the lower limit is exceeded, if the radius of curvature of the lens surface closest to the object side of the lens unit GB becomes too small (negative refractive power becomes too strong), positive spherical aberration increases, and this spherical aberration is increased by other lenses. It becomes difficult to correct with.

  Conditional expressions (4a) and (4b) appropriately set the focal length of the air lens constituted by the lens surface closest to the image side of the lens unit GA and the lens surface closest to the object side of the lens unit GB. Satisfying conditional expressions (4a) and (4b) makes it easy to obtain good optical performance over the entire object distance.

  If the upper limit of conditional expressions (4a) and (4b) is exceeded, the negative or positive refractive power of the air lens becomes too weak (the absolute value of the refractive power becomes too small), and spherical aberration that occurs in the focusing lens system Is difficult to correct. If the lower limit is exceeded, the negative or positive refractive power of the air lens becomes too strong (the absolute value of the refractive power becomes too large), and the field curvature increases during focusing to a short distance, and this aberration is corrected. It becomes difficult.

  Conditional expressions (5a) and (5b) relate to the ratio of the focal length of the optical system to the total lens length. Conditional expressions (5a) and (5b) set the tele ratio appropriately. If the upper limit of conditional expressions (5a) and (5b) is exceeded and the total lens length becomes too long, it will be difficult to reduce the effective diameter of the front lens. If the lower limit of conditional expressions (5a) and (5b) is exceeded and the total lens length becomes too short, the Petzval sum becomes too large in the positive direction, and field curvature increases, making it difficult to correct this.

  Conditional expressions (6a) and (6b) are used to appropriately set the refractive index ratio between the negative lens material and the positive lens material of the cemented lens constituting the lens unit GA. By satisfying conditional expressions (6a) and (6b), spherical aberration is corrected well on the cemented lens surface. If the upper limit of conditional expressions (6a) and (6b) is exceeded, the refractive index ratio becomes too large, the Petzval sum increases in the positive direction, and it becomes difficult to correct field curvature. If the lower limit is exceeded, the action of correcting spherical aberration on the cemented lens surface becomes small, and correction of spherical aberration generated from the lens unit GA becomes difficult.

  Conditional expressions (7a) and (7b) appropriately set the negative focal length of the front group LA. If the upper limit of conditional expressions (7a) and (7b) is exceeded and the negative focal length of the front group LA becomes too long (the absolute value of the negative focal length becomes too large), the effective diameter of the front lens is reduced. It becomes difficult. In addition, it is difficult to ensure a long back focus. If the lower limit of conditional expressions (7a) and (7b) is exceeded and the negative focal length of the front group LA becomes too short (the absolute value of the negative focal length becomes too small), field curvature, distortion, etc. Is difficult to correct.

  Conditional expressions (8a) and (8b) define the focal length of the rear group LB. If the upper limit of conditional expressions (8a) and (8b) is exceeded and the focal length of the rear group LB becomes too long (the refractive power of the rear group LB becomes too small), it becomes difficult to reduce the effective diameter of the front lens. . In addition, it is difficult to ensure a long back focus. If the lower limit of conditional expressions (8a) and (8b) is exceeded and the focal length of the rear group LB becomes too short (the refractive power of the rear group LB becomes too strong), field curvature, distortion, etc. are corrected. It becomes difficult. In each embodiment, the numerical ranges of the conditional expressions (1a) to (8a) are preferably set as follows.

4.0 <ffz / fw <14.0 (1aa)
0.12 <R1az / ffz <0.40 (2aa)
0.12 <| R1bz / ffz | <0.50 (3aa)
0.4 <| fabz / ffz | <1.3 (4aa)
10.0 <Lw / fw <18.0 (5aa)
1.15 <Nnz / Npz <1.40 (6aa)
1.0 <fLAz / fw <1.7 (7aa)
2.5 <fLBz / fw <4.0 (8aa)

In the third embodiment, it is more preferable to set the numerical ranges of the conditional expressions (1b) to (8b) as follows.
4.0 <ff / f <14.0 (1bb)
0.12 <R1a / ff <0.40 (2bb)
0.12 <| R1b / ff | <0.50 (3bb)
0.4 <| fab / ff | <1.3 (4bb)
10.0 <L / f <18.0 (5bb)
1.15 <Nn / Np <1.40 (6bb)
1.0 <fLA / f <1.7 (7bb)
2.5 <fLB / f <4.0 (8bb)

  In each embodiment, the following configuration is preferably adopted. In each embodiment, the lens unit GB may have a negative refractive power. Since the lens unit GB has a negative refractive power, the refractive power of the lens unit GA having a positive refractive power can be increased, and the radius of curvature of the lens surface closest to the object side of the lens unit GA can be easily reduced. For this reason, it is easy to correct curvature of field during focusing to a short distance. In addition, the lens surface on the most object side of the lens unit GB can be easily concave, and it is easy to correct spherical aberration that occurs in the focusing lens system LF.

  The lens unit GA is preferably composed of a cemented lens of a negative lens and a positive lens in order from the object side to the image side. The lens surface on the most object side of the lens unit GA passes through a position where the axial light beam is high, and large spherical aberration and coma occur. Therefore, by arranging a negative lens having a convex surface on the object side, aberrations that occur largely on the object-side lens surface of the negative lens are corrected on the immediately following cemented surface. In addition, achromaticity is corrected with a negative lens and a positive lens, and axial chromatic aberration is corrected well. Furthermore, it is easy to achieve a retrofocus type refractive power arrangement, and it is easy to reduce the effective diameter of the front lens while widening the angle of view at the wide-angle end.

  As described above, according to each of the embodiments, an optical system that has a super-wide field angle exceeding 120 ° at the wide-angle end and a small overall system and good optical performance over the entire object distance can be obtained. It is done.

  Next, an embodiment of a single-lens reflex camera system (imaging device) using the optical system of the present invention will be described with reference to FIG. In FIG. 10, 10 is a single-lens reflex camera body, and 11 is an interchangeable lens equipped with an optical system according to the present invention. Reference numeral 12 denotes a recording unit such as a film or an image sensor for recording (receiving) a subject image obtained through the interchangeable lens 11. Reference numeral 13 denotes a finder optical system for observing the subject image from the interchangeable lens 11, and reference numeral 14 denotes a quick return mirror that rotates to switch the subject image formed by the interchangeable lens 11 to the recording means 12 and the finder optical system 13 for transmission. is there.

  When observing the subject image with the finder, the subject image formed on the focusing plate 15 via the quick return mirror 14 is made into an erect image with the pentaprism 16 and then magnified and observed with the eyepiece optical system 17. At the time of shooting, the quick return mirror 14 rotates in the direction of the arrow, and the subject image is formed and recorded on the recording means 12. Reference numeral 18 denotes a submirror, and 19 denotes a focus detection device.

  In this way, by applying the optical system of the present invention to an imaging apparatus such as an interchangeable lens such as a single-lens reflex camera, an imaging apparatus having high optical performance can be realized. The optical system of the present invention can be similarly applied to a camera without a quick return mirror. Further, the present invention can be similarly applied to a projection lens for a projector.

  Next, numerical examples of the respective embodiments of the present invention will be shown. In each numerical example, i indicates the order of the surfaces from the object side, ri is the radius of curvature of the lens surface, di is the lens thickness and air spacing between the i-th surface and the i + 1-th surface, and ndi and νdi are respectively The refractive index and Abbe number for the d-line are shown. BF is the back focus, and is indicated by the distance from the final lens surface to the image plane. The total lens length is the distance from the first lens surface to the image plane. The aspherical shape is the X axis in the optical axis direction, the H axis in the direction perpendicular to the optical axis, the light traveling direction is positive, R is the paraxial radius of curvature, K is the conic constant, A4, A6, A8, A10, A12, A14. Are respectively aspherical coefficients,

It is expressed by the following formula. [E + X] means [× 10 + ^X ], and [e−X] means [× 10 ^−X ]. An aspherical surface is indicated by adding * after the surface number. Further, the portion where the distance d between the optical surfaces is (variable) changes during zooming. Table 1 shows the relationship between the above-described conditional expressions and numerical examples.

[Numerical Example 1]

Unit mm

Surface data surface number rd nd νd Effective diameter
1 * 100.402 3.10 1.77250 49.6 83.99
2 32.787 10.70 62.10
3 42.207 3.20 1.58443 59.4 59.67
4 * 20.133 10.96 49.61
5 100.037 2.60 1.85000 40.3 46.09
6 * 47.753 5.77 36.38
7 313.541 1.30 1.59522 67.7 35.84
8 24.146 7.54 30.95
9 -76.811 1.15 1.43875 94.9 30.84
10 64.103 0.89 30.46
11 39.327 6.40 1.72047 34.7 30.67
12 -123.615 (variable) 29.97
13 ∞ (variable) 17.72 (flare cut aperture)
14 (Aperture) ∞ (Variable) 18.91
15 20.914 1.10 2.00100 29.1 20.11
16 15.600 7.47 1.57501 41.5 19.38
17 -34.531 2.04 19.13
18 -26.292 0.90 1.91082 35.3 18.24
19 68.346 2.28 1.80518 25.4 18.57
20 -87.663 (variable) 18.72
21 ∞ 0.00 18.98 (Flare cut aperture)
22 29.727 0.95 1.88300 40.8 19.07
23 14.164 6.33 1.51742 52.4 18.30
24 -97.092 0.95 1.83481 42.7 18.40
25 117.819 0.15 18.52
26 22.677 6.42 1.49700 81.5 19.06
27 -27.253 0.20 19.64
28 -210.616 1.10 1.88300 40.8 19.59
29 16.507 7.00 1.58313 59.4 19.72
30 * -89.025 (variable) 20.89
Image plane ∞

Aspheric data 1st surface
K = 0.00000e + 000 A 4 = 5.07039e-006 A 6 = -3.66524e-009
A 8 = 2.14684e-012 A10 = -1.59746e-016 A12 = -3.49877e-019
A14 = 1.41029e-022

4th page
K = -3.08703e + 000 A 4 = 3.79875e-005 A 6 = -6.27286e-008
A 8 = 1.29970e-011 A10 = 1.49707e-014

6th page
K = 0.00000e + 000 A 4 = 1.15171e-005 A 6 = -2.29358e-009
A 8 = 2.08815e-010 A10 = -7.57344e-013 A12 = 1.20672e-015

30th page
K = 0.00000e + 000 A 4 = 1.96961e-005 A 6 = 3.33943e-008
A 8 = 2.90343e-011 A10 = -2.00200e-013 A12 = 7.23046e-015

Various data Zoom ratio 2.05
Wide angle Medium telephoto focal length 11.33 17.32 23.28
F number 4.12 4.12 4.12
Half angle of view (degrees) 62.36 51.32 42.90
Image height 21.64 21.64 21.64
Total lens length 171.38 162.77 165.23
BF 39.88 52.64 65.40

d12 26.47 7.95 0.51
d13 9.51 6.65 3.80
d14 1.74 1.51 1.29
d20 3.29 3.52 3.74
d30 39.88 52.64 65.40

Zoom lens group data group Start surface Focal length
1 1 -18.23
2 13 ∞
3 14 ∞
4 15 70.93
5 21 56.82

[Numerical Example 2]

Unit mm

Surface data surface number rd nd νd Effective diameter
1 * 66.540 2.60 1.77250 49.6 69.99
2 25.367 8.07 49.58
3 28.749 2.60 1.58383 59.4 47.72
4 * 16.316 10.33 43.43
5 100.001 2.10 1.85400 40.4 40.57
6 * 32.421 6.16 30.66
7 189.979 1.30 1.59522 67.7 30.34
8 39.134 5.01 28.64
9 -53.880 1.20 1.43875 94.9 28.51
10 56.561 0.15 28.22
11 36.018 7.45 1.72047 34.7 28.40
12 -99.582 (variable) 27.43
13 ∞ (variable) 16.59
14 (Aperture) ∞ 1.74 17.77 (Flare cut aperture)
15 20.662 1.00 2.00100 29.1 19.04
16 15.022 7.90 1.61340 44.3 18.38
17 -32.080 1.45 18.05
18 -26.143 0.90 1.91082 35.3 17.34
19 26.601 3.61 1.85478 24.8 17.60
20 -105.795 3.69 17.76
21 ∞ 0.00 17.86 (Flare cut diaphragm)
22 29.922 0.95 1.88 300 40.8 17.89
23 14.726 6.00 1.49700 81.5 17.23
24 -106.579 0.14 17.26
25 -86.482 0.95 1.76421 50.4 17.26
26 81.303 0.15 17.35
27 21.584 6.24 1.49700 81.5 19.33
28 -28.319 0.20 19.84
29 -261.504 1.05 1.88300 40.8 19.82
30 19.182 5.48 1.58313 59.4 19.94
31 * -103.197 (variable) 20.67
Image plane ∞

Aspheric data 1st surface
K = 0.00000e + 000 A 4 = 6.42646e-006 A 6 = -8.86916e-009
A 8 = 1.26766e-011 A10 = -9.48216e-015 A12 = 3.74162e-018
A14 = -2.77582e-022

4th page
K = -1.00193e + 000 A 4 = 9.47246e-006 A 6 = -3.04033e-008
A 8 = -9.25956e-011 A10 = 1.29892e-013

6th page
K = 0.00000e + 000 A 4 = 2.20599e-005 A 6 = 2.45095e-008
A 8 = 5.49604e-010 A10 = -3.00594e-012 A12 = 8.33695e-015

No. 31
K = 0.00000e + 000 A 4 = 2.69196e-005 A 6 = 2.94334e-008
A 8 = 8.62945e-010 A10 = -6.99775e-012 A12 = 3.65541e-014

Various data Zoom ratio 1.88
Wide angle Medium telephoto focal length 12.36 17.82 23.28
F number 4.12 4.12 4.12
Half angle of view (degrees) 60.26 50.52 42.90
Image height 21.64 21.64 21.64
Total lens length 158.46 152.79 155.01
BF 40.01 51.17 62.34

d12 20.62 6.58 0.44
d13 9.40 6.60 3.80
d31 40.01 51.17 62.34


Zoom lens group data group Start surface Focal length
1 1 -18.23
2 13 ∞
3 14 37.27

[Numerical Example 3]

Unit mm

Surface data surface number rd nd νd Effective diameter
1 * 63.441 2.20 1.69680 55.5 59.00
2 25.442 5.52 45.91
3 28.300 2.20 1.58313 59.4 42.76
4 * 12.904 7.23 37.90
5 50.374 1.70 1.85000 40.3 31.20
6 * 24.947 4.05 22.99
7 59.522 0.85 1.59522 67.7 22.32
8 15.341 4.35 19.00
9 -64.807 0.80 1.43875 94.9 18.69
10 31.693 0.20 17.51
11 20.918 10.35 1.72047 34.7 17.21
12 547.908 1.48 12.19
13 ∞ 7.86 10.62 (Flare cut diaphragm)
14 (Aperture) ∞ 0.00 13.07
15 22.443 1.42 2.00 100 29.1 13.39
16 14.385 4.86 1.62004 36.3 13.07
17 -20.142 0.17 13.16
18 -20.527 0.80 1.91082 35.3 13.08
19 20.122 3.34 1.84666 23.8 13.46
20 -235.657 2.62 13.79
21 20.587 0.80 1.88300 40.8 14.78
22 12.875 6.84 1.51742 52.4 14.40
23 -13.416 0.80 1.83400 37.2 15.20
24 -160.886 0.15 17.31
25 40.147 6.23 1.49700 81.5 19.53
26 -19.300 0.20 20.70
27 54.325 1.10 1.88300 40.8 21.87
28 15.275 8.45 1.55332 71.7 21.64
29 * -48.549 22.86
Image plane ∞

Aspheric data 1st surface
K = 0.00000e + 000 A 4 = 5.33233e-006 A 6 = 1.54429e-009
A 8 = -8.67461e-013 A10 = 2.56875e-015 A12 = -1.67470e-018
A14 = 2.74451e-021

4th page
K = -1.68145e + 000 A 4 = -7.54012e-007 A 6 = -6.22445e-008
A 8 = 6.75757e-011 A10 = 2.02117e-014

6th page
K = 0.00000e + 000 A 4 = 7.63671e-005 A 6 = 1.39072e-007
A 8 = 4.35972e-010 A10 = -9.56156e-012 A12 = 8.97876e-014

29th page
K = 0.00000e + 000 A 4 = 2.00655e-005 A 6 = -5.66525e-009
A 8 = 3.94520e-010 A10 = -2.36003e-012 A12 = 5.91161e-015

Various data

Focal length 10.30
F number 2.88
Half angle of view (degrees) 64.54
Statue height 21.64
Total lens length 124.58
BF 38.00

LF Front group LR Rear group L1 First lens group L2 Second lens group L3 Third lens group La Front lens portion Lb Rear lens portion SP Aperture stop

Claims (27)

In order from the object side to the image side, it consists of a front group of negative refractive power and a rear group of positive refractive power,
The front group includes a first lens group having a negative refractive power, and the rear group includes, in order from the object side to the image side, a second lens group having a positive refractive power and a third lens group having a positive refractive power. In an optical system that is configured and the interval between adjacent lens groups changes during zooming,
The rear group includes a lens system LF having a positive refractive power that moves on the optical axis during focusing, and the lens system LF sequentially has a lens unit GA having a positive refractive power, a positive or negative lens unit in order from the object side to the image side. An optical system comprising a lens unit GB having a refractive power of 5 mm and a lens surface closest to the object side of the lens unit GB having a concave shape.   During zooming from the wide-angle end to the telephoto end, the first lens group moves along a convex locus toward the image side, and both the second lens group and the third lens group move toward the object side. The optical system according to claim 1.   The optical system according to claim 1, wherein the lens system LF is the second lens group. In order from the object side to the image side, it consists of a front group of negative refractive power and a rear group of positive refractive power,
In an optical system in which the front group and the rear group move along different trajectories during zooming, the rear group has a lens system LF having a positive refractive power that moves on the optical axis during focusing, and the lens system LF includes: In order from the object side to the image side, a lens unit GA having a positive refractive power and a lens unit GB having a positive or negative refractive power are provided, and the lens unit GB has a concave surface on the most object side. An optical system.   5. The optical system according to claim 4, wherein during zooming from the wide-angle end to the telephoto end, the front group moves along a convex locus toward the image side, and the rear group moves toward the object side.   6. The optical system according to claim 4, wherein the lens system LF is a part of the rear group. When the focal length of the lens system LF is ffz and the focal length of the entire system at the wide angle end is fw,
3.0 <ffz / fw <15.0
The optical system according to claim 1, wherein the following conditional expression is satisfied. When the radius of curvature of the lens surface closest to the object side of the lens unit GA is R1az and the focal length of the lens system LF is ffz,
0.1 <R1az / ffz <0.5
The optical system according to claim 1, wherein the following conditional expression is satisfied. When the radius of curvature of the lens surface closest to the object side of the lens unit GB is R1bz and the focal length of the lens system LF is ffz,
0.1 <| R1bz / ffz | <0.6
The optical system according to claim 1, wherein the following conditional expression is satisfied. When the focal length of the air lens formed by the lens surface closest to the image side of the lens unit GA and the lens surface closest to the object of the lens unit GB is fabz, and the focal length of the lens system LF is ffz,
0.3 <| fabz / ffz | <1.5
The optical system according to claim 1, wherein the following conditional expression is satisfied.   The optical system according to claim 1, wherein the lens unit GB has a negative refractive power. When the total lens length at the wide angle end is Lw and the focal length of the entire system at the wide angle end is fw,
8.0 <Lw / fw <20
The optical system according to claim 1, wherein the following conditional expression is satisfied. The lens unit GA is composed of a cemented lens GAA in which a negative lens and a positive lens are cemented in order from the object side to the image side. When the refractive index of the material is Npz,
1.1 <Nnz / Npz <1.5
The optical system according to claim 1, wherein the following conditional expression is satisfied. When the focal length of the front group is fLAz and the focal length of the entire system at the wide angle end is fw,
1.0 <| fLAz / fw | <2.0
The optical system according to claim 1, wherein the following conditional expression is satisfied. When the focal length of the rear group is fLBz and the focal length of the entire system at the wide angle end is fw,
2.0 <fLBz / fw <5.0
The optical system according to claim 1, wherein the following conditional expression is satisfied.   In a single focal length optical system composed of a front group having a negative refractive power and a rear group having a positive refractive power in order from the object side to the image side with the largest air gap as the boundary, the rear group is focused. The lens system LF has a positive refractive power lens system LF that moves on the optical axis. The lens system LF sequentially has a positive refractive power lens unit GA and a positive or negative refractive power lens from the object side to the image side. An optical system having a unit GB, wherein the lens surface closest to the object side of the lens unit GB has a concave shape. When the focal length of the lens system LF is ff and the focal length of the entire system is f,
3.0 <ff / f <15.0
The optical system according to claim 16, wherein the following conditional expression is satisfied. When the radius of curvature of the lens surface on the most object side of the lens unit GA is R1a and the focal length of the lens system LF is ff,
0.1 <R1a / ff <0.5
The optical system according to claim 16 or 17, wherein the following conditional expression is satisfied. When the radius of curvature of the lens surface closest to the object side of the lens unit GB is R1b and the focal length of the lens system LF is ff,
0.1 <| R1b / ff | <0.6
The optical system according to claim 16, wherein the following conditional expression is satisfied. When the focal length of the air lens formed by the most image side lens surface of the lens unit GA and the most object side lens surface of the lens unit GB is fab, and the focal length of the lens system LF is ff,
0.3 <| fab / ff | <1.5
The optical system according to claim 16, wherein the following conditional expression is satisfied.   The optical system according to any one of claims 16 to 20, wherein the lens unit GB has a negative refractive power. When the total lens length is L and the focal length of the entire system is f
8.0 <L / f <20
The optical system according to claim 16, wherein the following conditional expression is satisfied. The lens unit GA includes a cemented lens GAA in which a negative lens and a positive lens are cemented in order from the object side to the image side. The refractive index of the material of the negative lens of the cemented lens GAA is Nn, and the positive lens of the cemented lens GAA. When the refractive index of the material is Np,
1.1 <Nn / Np <1.5
The optical system according to claim 16, wherein the following conditional expression is satisfied. When the focal length of the front group is fLA and the focal length of the entire system is f,
1.0 <| fLA / f | <2.0
The optical system according to claim 16, wherein the following conditional expression is satisfied. When the focal length of the rear group is fLB and the focal length of the entire system is f,
2.0 <fLB / f <5.0
The optical system according to claim 16, wherein the following conditional expression is satisfied.   The optical system according to any one of claims 1 to 25, wherein an image is formed on a solid-state imaging device.   27. An imaging apparatus comprising: the optical system according to claim 1; and a solid-state imaging device that receives an image formed by the optical system.