JP2008070433A - Teleconverter lens and imaging apparatus with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a teleconverter lens which can provide an image of excellent optical performance because variation in the aberration of the entire system is small even when the teleconverter lens is mounted on a master lens. <P>SOLUTION: The teleconverter lens mounted on the object side of the master lens is composed of the front group having a positive refractive power and the rear group having a negative refractive power across an air distance being largest in an optical axis direction, in order from the object side to an image side. The front group is composed of a first cemented lens which is obtained by cementing an eleventh lens having a negative refractive power and a twelfth lens having a positive refractive power and has a positive refractive power as a whole, and a thirteenth lens having a positive refractive power. The rear group is composed of a second cemented lens which is obtained by cementing a twenty-first lens having a positive refractive power and a twenty-second lens having a negative refractive power and has a negative refractive power as a whole. When the Abbe numbers of the materials of the eleventh lens and the twelfth lens are defined as ν11 and ν12 respectively, conditions of 30<ν11<50 and 25<ν12-ν11 are satisfied. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is detachably mounted on the object side of a photographing lens (master lens) used in a digital still camera, a video camera, a broadcasting camera, etc., and the focal length of the entire system is compared with the original focal length of the master lens. This is related to a teleconverter lens that changes to a longer one.

  In general, as a method of shifting the focal length of the master lens (photographing lens) to the telephoto side (shifting to the longer side), a front-type teleconverter lens in which an afocal lens is detachably attached to the object side of the master lens is known. ing. This method has an advantage that the F number of the master lens is not sacrificed (not changed) even if the focal length is changed.

  In recent years, in a digital camera and a video camera, a solid-state imaging device such as a CCD sensor has been increased in pixels, and a photographing lens used for them has been required to have high optical performance including chromatic aberration.

  Therefore, the same high optical performance is required for the teleconverter lens to be attached to the photographing lens.

  Furthermore, the teleconverter lens is required to have a higher afocal magnification (high magnification).

  As this front-type teleconverter lens, a lens composed of a front group having a positive refractive power and a rear group having a negative refractive power in order from the object side to the image side is known.

Among these, there is known a teleconverter lens in which the front group includes one negative lens and two positive lenses, and the rear group includes a positive lens and a negative lens (Patent Documents 1 to 3).
Japanese Patent Laid-Open No. 10-197792 JP 2001-228393 A JP 2002-82367 A

  The teleconverter lens is required to have less aberration fluctuation in order to maintain high optical performance when mounted on the master lens.

  Generally, when a teleconverter lens is mounted on the object side of a master lens and the focal length of the entire system is shifted to the longer side, spherical aberration, axial chromatic aberration, lateral chromatic aberration, and the like greatly change on the telephoto side.

  Here, the telephoto side means an enlarged focal length when the master lens has a single focal length. The same applies hereinafter.

  In the teleconverter lens shown in Example 4 of Patent Document 1, the front group having a positive refractive power is composed of, in order from the object side, a cemented lens of a negative lens and a positive lens, a biconvex lens, and a positive lens. It is divided into two.

  However, the refractive power of an air lens formed between two positive lenses is extremely weak, and it cannot be said that the positive refractive power of the front group is effectively shared by a plurality of positive lenses.

  In such a configuration, the spherical aberration and the curvature of field when the refractive power of the front group is increased are insufficiently corrected.

  In the teleconverter lens disclosed in Patent Document 2, the front group having a positive refractive power is composed of a positive lens and a cemented lens of a positive lens and a negative lens in order from the object side. As the configuration of the cemented lens, since the effective diameter of the positive lens is larger than that of the negative lens and the positive lens in this order, the size of the cemented lens is easily increased.

  In the teleconverter lens disclosed in Patent Document 3, the front group having a positive refractive power is composed of a cemented lens of a negative lens and a positive lens and a positive lens in order from the object side, and an afocal magnification is 1.9. The above has been achieved.

  However, the axial chromatic aberration of the g-line in the entire system when the teleconverter lens is mounted is greatly deteriorated as compared with the case of the master lens alone.

  It is an object of the present invention to provide a teleconverter lens that has high optical performance with little variation in various aberrations when mounted on a master lens, in particular, small g-axis axial chromatic aberration, little blue blur.

The teleconverter lens of the present invention is a teleconverter lens to be mounted on the object side of the master lens,
In order from the object side to the image side, consisting of a front group of positive refractive power and a rear group of negative refractive power, with the widest air interval in the optical axis direction as a boundary,
The front group includes a first cemented lens having a positive refractive power and a 13th lens having a positive refractive power as a whole, in which an eleventh lens having a negative refractive power and a twelfth lens having a positive refractive power are cemented.
The rear group includes a second cemented lens having a negative refractive power as a whole, in which a 21st lens having a positive refractive power and a 22nd lens having a negative refractive power are cemented.
When the Abbe numbers of the materials of the eleventh lens and the twelfth lens are ν11 and ν12, respectively, 30 <ν11 <50
25 <ν12−ν11
It is characterized by satisfying the following conditions.

  According to the present invention, it is possible to obtain a teleconverter lens in which aberration variation of the entire system is small even when attached to a master lens, and an image with good optical performance can be obtained.

  Hereinafter, the teleconverter lens of the present invention, an imaging system when it is mounted on a master lens (main lens system), and an imaging apparatus using the imaging system will be described. The teleconverter lens according to the present invention is a lens that can be mounted on the object side of either a master lens integrally formed with the camera body or an interchangeable lens that can be attached to and detached from the camera body.

  FIG. 1 is a lens cross-sectional view of the teleconverter lens of Example 1 of the present invention.

  FIG. 2 is a lens cross-sectional view at the wide-angle end of a master lens M having a zooming action selected as an example in which the teleconverter lens of the present invention is detachably mounted.

  The master lens M may be a photographing lens having a single focal length.

  FIG. 3 is a lens cross-sectional view at the telephoto end zoom position when the teleconverter lens of Example 1 of the present invention is mounted on the object side of the master lens M.

  FIGS. 4 and 5 are aberration diagrams at an intermediate zoom position and a telephoto end zoom position when the teleconverter lens according to the first embodiment of the present invention is mounted on the object side of the master lens M. FIGS.

  6 and 7 are aberration diagrams at the intermediate zoom position of the master lens M alone and the zoom position at the telephoto end.

  FIG. 8 is a lens cross-sectional view of the teleconverter lens of Example 2 of the present invention.

  9 and 10 are aberration diagrams at the intermediate zoom position and the telephoto end zoom position when the teleconverter lens according to the second embodiment of the present invention is mounted on the object side of the master lens M. FIG.

  FIG. 11 is a lens cross-sectional view of the teleconverter lens of Example 3 of the present invention.

  12 and 13 are aberration diagrams at an intermediate zoom position and a telephoto end zoom position when the teleconverter lens according to the third embodiment of the present invention is mounted on the object side of the master lens M. FIG.

  FIG. 14 is a lens cross-sectional view of a teleconverter lens according to Example 4 of the present invention.

  FIGS. 15 and 16 are aberration diagrams at the intermediate zoom position and the telephoto end zoom position when the teleconverter lens according to the fourth embodiment of the present invention is mounted on the object side of the master lens M. FIGS.

  FIG. 17 is an explanatory diagram of an imaging apparatus having the teleconverter lens of the present invention.

  In the lens cross-sectional view, T is a teleconverter lens, and M is a master lens.

  In the lens cross-sectional view, the left side is the object side, and the right side is the image side.

  In the aberration diagrams, ΔM is represented by a meridional image surface, ΔS is represented by a sagittal image surface, and lateral chromatic aberration is represented by a g-line.

  fno is an F number. ω is a half angle of view.

  The teleconverter lens T of each embodiment is mounted on the object side of the master lens M, and the focal length of the entire system is changed in a direction in which it is enlarged compared to the focal length of the master lens alone.

  The teleconverter lens T of each embodiment constitutes an afocal system. Then, the front group LF having a positive refractive power (the reciprocal of the focal length, optical power) and the rear group LR having a negative refractive power at the widest air interval in order from the object side to the image side. Yes.

  The configuration of the teleconverters of the first, third, and fourth embodiments shown in FIGS. 1, 11, and 14 will be described.

  The front lens group LF includes, in order from the object side to the image side, a meniscus eleventh lens 11 having a convex surface facing the object side (hereinafter abbreviated as “negative”) and a positive surface having a convex surface facing the object side. A first cemented lens 1C having a positive refractive power as a whole joined with the twelfth lens 12 is provided. Furthermore, it has a positive thirteenth lens 13 with the convex surface facing the object side.

  The rear group LR includes a second cemented lens 2C having a negative refractive power as a whole, in which the positive 21st lens 21 and the negative 22nd lens 22 are cemented in order from the object side to the image side.

  A configuration of the teleconverter according to the second embodiment illustrated in FIG. 8 will be described. The teleconverter lens T of Example 2 is configured by a first cemented lens 2C in which the rear group LR is cemented with a negative 21st lens 21a and a positive 22nd lens 22a in order from the object side to the image side. Different from 1, 2, 3.

  In the teleconverter lens T of each embodiment, the front group LF and the rear group LR both have at least one positive lens and one negative lens.

  With this configuration, the axial chromatic aberration and lateral chromatic aberration of the entire system when mounted on the master lens M are corrected in a well-balanced manner.

  The positive refractive power of the front group LF is shared by the first cemented lens 1C and the positive thirteenth lens 13 behind the first cemented lens 1C, so that spherical aberration and curvature of field are corrected well.

  Such a configuration is particularly effective in strengthening the refractive power of the front lens group LF to achieve both high afocal magnification and compactness.

  Further, the first cemented lens 1C constituting the front group LF is composed of a negative eleventh lens 11 and a positive twelfth lens 12 in order from the object side to the image side. Thereby, compared with the case where it comprises in reverse order, the positive 12th lens 12 can be brought close to the master lens M side, and the effective diameter of the whole lens system can be made small.

  In general, it is necessary for a positive lens to ensure a certain edge thickness (edge thickness) in terms of lens processing.

  When the lens is thinned as much as possible by setting the edge thickness to the minimum dimension required for processing, the effective diameter can be reduced as the positive lens is brought closer to the master lens M. As a result, the central wall thickness can be reduced, and the lens can be made smaller and lighter.

  Although the effective diameter of the negative eleventh lens 11 is larger than that of the positive lens and the negative lens in this order, the negative eleventh lens 11 is not particularly limited if the strength can be maintained because there is no restriction on the edge thickness in processing. There is no need to worry about wall thickness.

  As a result, the first cemented lens 1C as a whole can be reduced in size and weight as compared with the case where the negative lens and the positive lens are arranged in reverse order from the object side to the image side.

  The angle of view 2ω at the telephoto end of the master lens portion M shown in FIG. 2 is 12.1 °.

  In the teleconverter lens T attached to the master lens M having such an angle of view, the image side surface of the second cemented lens 2C of the rear group LR is preferably concave as shown in FIG. And it is preferable to make the shape of the air lens between the teleconverter lens T and the master lens M a shape close to concentric.

  In such a configuration, since the exit angle of the off-axis light beam does not become extremely large on the image side lens surface of the second cemented lens 2C of the rear lens group LR, generation of high-order components of astigmatism and lateral chromatic aberration is reduced. There is a merit that

  The configuration of the zoom lens used as the master lens M in FIG. 2 is as follows.

  In the lens cross-sectional view of FIG. 2, L1 is a first lens group having a positive refractive power (optical power = reciprocal of focal length), L2 is a second lens group having a negative refractive power, and L3 is a third lens having a positive refractive power. The lens group L4 is a fourth lens group having a positive refractive power. SP is an aperture stop, which is located on the object side of the third lens unit L3.

  G is an optical block corresponding to an optical filter, a face plate, or the like. IP is an image plane, and when used as an imaging optical system for a video camera or a digital camera, the imaging surface of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor is used for imaging optics of a silver salt film camera. When used as a system, it corresponds to the film surface.

  During zooming from the wide-angle end to the telephoto end, as indicated by the arrows, the first lens unit L1 and the third lens unit move so as to be positioned closer to the object side at the telephoto end than at the wide-angle end. The second lens unit L2 moves to have a convex locus on the image side, and the fourth lens unit L4 moves to have a convex locus on the object side.

  Further, a rear focus type is employed in which the fourth lens unit L4 is moved on the optical axis to perform focusing. A solid curve 4a and a dotted curve 4b relating to the fourth lens unit L4 are movement trajectories for correcting image plane fluctuations accompanying zooming when focusing on an object at infinity and an object at close distance, respectively.

  Further, when focusing from an object at infinity to an object at a short distance at the telephoto end, the fourth lens unit L4 is moved forward as indicated by an arrow 4c.

In each embodiment, the Abbe numbers of the materials of the negative eleventh lens 11 and the positive twelfth lens 12 are ν11 and ν12, respectively. At this time, 30 <ν11 <50 (1)
25 <ν12−ν11 (2)
Is satisfied.

  Conditional expression (1) defines the Abbe number of the material of the negative eleventh lens 11 constituting the first cemented lens 1C of the front group LF.

  Generally, when a teleconverter lens T that is sufficiently achromatic is mounted on the master lens M, the axial chromatic aberration is an amount obtained by multiplying the aberration amount of the master lens M by the afocal magnification of the teleconverter.

  Therefore, if the afocal magnification of the teleconverter lens T is increased, the axial chromatic aberration, which is not a problem with the master lens M alone, increases by the afocal magnification when the teleconverter lens T is mounted, and this causes a problem of color bleeding. It becomes.

  The refractive index of the glass material has a large change in refractive index per unit wavelength on the short wavelength side. For this reason, in a master lens that has been achromatic so that the axial chromatic aberration is the same between the general C line and the f line, the axial chromatic aberration of the g line is positive (over).

  This residual axial chromatic aberration is corrected to such an extent that it does not normally cause a problem with the master lens M alone.

  Assume that the teleconverter lens T is attached to the master lens M. At this time, even if it is assumed that the ideal achromaticity with zero axial chromatic aberration generated by the teleconverter lens T alone is performed, the axial chromatic aberration of the g-line in the entire system is the residual axial chromatic aberration of the master lens M. It is a value obtained by multiplying the afocal magnification of the teleconverter lens T.

  For this reason, blue blurring on the axis, which was not a problem with the master lens M alone, is enlarged by the installation of the teleconverter lens T.

  Since this enlargement is proportional to the afocal magnification, it appears more prominently when the high-power teleconverter lens T is mounted, and causes deterioration in image quality called blue flare or purple fringe.

  In each embodiment, when the teleconverter lens T is attached to the master lens, the axial chromatic aberration of the g-line generated in the teleconverter lens T is generated on the underside of the master lens M. This reduces the blue blur on the axis.

  When the Abbe number becomes too small beyond the lower limit of the conditional expression (1), that is, when the dispersion is too large, the g-line generated in the negative eleventh lens 11 constituting the first cemented lens 1C of the front group LF Axial chromatic aberration increases on the over side.

  For this reason, it becomes difficult to correct axial chromatic aberration and lateral chromatic aberration at the same time.

  Conditional expression (1) is also important from the viewpoint of correcting the on-axis secondary spectrum generated in the negative eleventh lens 11. In order to reduce the on-axis secondary spectrum, it is necessary to appropriately select the glass material in relation to the Abbe number and the partial dispersion ratio θg, F.

  For example, a graph is used in which the vertical axis represents the partial dispersion ratio θg, F and the horizontal axis represents the Abbe number νd. At this time, the product name PBM2 (νd = 36.26, θg, F = 0.5828) manufactured by OHARA INC. And the product name NSL7 (νd = 60.49, θg, F) manufactured by OHARA INC. = 0.5436) is a reference line.

  As for the distribution of the optical glass on this graph, many high-dispersion glasses having an Abbe number νd smaller than about 35 are located above the reference line.

  Therefore, if the Abbe number of the material of the negative eleventh lens 11 is too small beyond the lower limit of conditional expression (1), the on-axis secondary spectrum at the g-line also increases to the over side, and on-axis at other wavelengths While correcting the chromatic aberration, it is difficult to cause the axial chromatic aberration of the g line to occur on the under side.

  Further, if the Abbe number is too large beyond the upper limit, the Abbe number difference from the material of the positive twelfth lens 12 cannot be taken sufficiently, and the achromaticity at the first cemented lens 1C becomes insufficient. not good.

  Conditional expression (2) defines the Abbe number difference between the materials of the negative eleventh lens 11 and the positive twelfth lens 12 constituting the first cemented lens 1C of the front lens group LF. If the Abbe number difference is too small beyond the lower limit of conditional expression (2), correction will be insufficient in achromatization in the front group LF, so that correction of chromatic aberration is performed even if the front group LF is used as the first cemented lens 1c. It's not good because the effect fades.

  Conditional expression (1) may be set as follows in order to enhance the achromatic effect in the first cemented lens 1C and the correction effect of the secondary spectrum of axial chromatic aberration.

30 <ν11 <45 (1a)
More preferably, the following is satisfied.

32 <ν11 <40 (1b)
Further, in the conditional expression (2), in order to sufficiently correct the chromatic aberration in the first cemented lens 1C, the achromatic effect in the cemented lens 1C increases as the Abbe number difference increases. For this reason, there is no particular upper limit, but if it is set from the currently known range of Abbe numbers of glass materials, it is preferable to set as follows.

28 <ν12−ν11 <60 (2a)
More preferably, the following should be satisfied.

28 <ν12−ν11 <40 (2b)
Let ΦF be the refractive power of the front group LF. Let Φc be the refractive power of the cemented surface of the first cemented lens 1C of the front group LF.

  At this time, the teleconverter lens of each example satisfies the following conditional expressions.

0.2 (1 / mm) <ΦF · ν11 <0.6 (1 / mm) (3)
−1.0 (1 / mm) <Φc / (1 / ν11−1 / ν12) <− 0.3 (1 / mm) (4)
Conditional expression (3) defines the relationship between the refractive power (power) of the front lens group LF and the Abbe number of the material of the negative eleventh lens 11.

  If the refractive power ΦF of the front group LF becomes too small beyond the lower limit of the conditional expression (3), the teleconverter lens will become large, which is not good.

  If the refractive power ΦF of the front group LF becomes too large exceeding the upper limit of the conditional expression (3), various aberrations generated in the front group LF become large, and it is difficult to correct this in the rear group LR.

  Conditional expression (3) is preferably set as follows, considering the achievement of compactness and the balance of optical performance.

0.25 (1 / mm) <ΦF · ν11 <0.5 (1 / mm) (3a)
More preferably, the following should be satisfied.

0.3 (1 / mm) <ΦF · ν11 <0.4 (1 / mm) (3b)
In addition, it is preferable that the conditional expression (3) satisfies the conditional expression (6) considering the distance dF from the most object-side surface vertex of the front lens group LF to the most image-side surface vertex.

5.0 <ΦF · dF · ν11 <15.0 (6)
If the refractive power ΦF of the front group LF becomes too small beyond the lower limit of the conditional expression (6), the teleconverter lens will be enlarged, which is not good. In addition, dF becomes too small, and a sufficient effective diameter cannot be ensured because a sufficient thickness cannot be given to the lens constituting the front group LF.

  When the refractive power ΦF of the front group LF becomes too large beyond the upper limit of the conditional expression (6), various aberrations generated in the front group LF become large, and it is difficult to correct this in the rear group LR. In addition, dF becomes too large, which leads to an increase in the size of the teleconverter lens.

  Conditional expression (6) should be set as follows, considering the achievement of compactness and the balance of optical performance.

7.0 <ΦF · dF · ν11 <13.0 (6a)
More preferably, the following should be satisfied.

9.0 <ΦF · dF · ν11 <11.0 (6b)
Conditional expression (4) is an expression that defines the relationship between divergent power and chromatic dispersion at the cemented surface of the first cemented lens 1C of the front lens group LF. The refractive power Φc of the cemented surface of the first cemented lens 1C is defined by the following equation.

Φc = (n2-n1) / R12
Where n1: the refractive index of the material of the negative eleventh lens 11 of the first cemented lens 1C,
n2: refractive index of the material of the positive twelfth lens 12 of the first cemented lens 1C,
R12: radius of curvature of the cemented surface of the first cemented lens 1C,
It is.

  In each embodiment, n1> n2 and R12> 0, and the refractive power Φc takes a negative value. Therefore, the cemented surface of the first cemented lens 1C is a divergent cemented surface having a negative refractive power.

  When the lower limit of conditional expression (4) is exceeded and the refractive power Φc becomes too small, it is difficult to perform sufficient achromatic action on the cemented surface of the first cemented lens 1C, making it difficult to achieve both axial chromatic aberration and lateral chromatic aberration. Not good.

  Also, if the refractive power Φc is too large beyond the upper limit of conditional expression (4), the divergent power of the light beam at the cemented surface becomes strong and high-order aberrations occur, resulting in excessive astigmatism and lateral chromatic aberration. This is not good because off-axis performance deteriorates.

  If conditional expression (4) is more preferably set as follows, both axial chromatic aberration and off-axis performance are corrected well.

−0.85 (1 / mm) <Φc / (1 / ν11−1 / ν12) <− 0.3 (1 / mm) (4a)
More preferably, the following should be satisfied.
−0.65 (1 / mm) <Φc / (1 / ν11−1 / ν12) <− 0.35 (1 / mm) (4b)
In addition, it is preferable to satisfy the conditional expression (7) in consideration of the refractive power φ1c of the first cemented lens 1C.
−1.6 <(Φc / Φ1c) / (1 / ν11−1 / ν12) / 1000 <−0.01 (7)
When the ratio of the refractive power Φc of the cemented surface to the refractive power Φ1c of the entire cemented lens becomes too small beyond the lower limit of the conditional expression (7), sufficient achromatic action can be performed on the cemented surface of the first cemented lens 1C. This makes it difficult to achieve both axial chromatic aberration and lateral chromatic aberration.

  If the ratio of the refractive power Φc to the refractive power Φ1c is too large beyond the upper limit of the conditional expression (7), the divergent power of the light beam at the cemented surface becomes strong and high-order aberrations occur, and astigmatism and magnification It is not good because excessive chromatic aberration occurs and the off-axis performance deteriorates.

If conditional expression (7) is more preferably set as follows, both axial chromatic aberration and off-axis performance are corrected well.
−1.3 <(Φc / Φ1c) / (1 / ν11−1 / ν12) / 1000 <−0.04 (7a)
More preferably, the following should be satisfied.
−1.0 <(Φc / Φ1c) / (1 / ν11−1 / ν12) / 1000 <−0.08 (7b)
When the teleconverter lens of each embodiment is mounted on a master lens and used as an imaging device, it is preferable that both satisfy the following conditional expression.

  Let δsk (M) be the axial chromatic aberration of the g-line with respect to the d-line in an object at infinity at the long focal length of the master lens alone.

  Let δsk (T) be the axial chromatic aberration of the g-line with respect to the d-line for an object at infinity at a long focal length when the teleconverter lens T is attached to the master lens M.

  Let β be the afocal magnification of the teleconverter lens.

  However, when the master lens is a zoom lens, the longitudinal chromatic aberration is a value at the telephoto end.

At this time,
0.4 <δsk (T) / (δsk (M) × β) <1.0 (5)
Is to satisfy.

  Conditional expression (5) is an expression that defines the effect of correcting the axial chromatic aberration of the g-line by the teleconverter lens T. When the axial chromatic aberration of the g-line when the teleconverter lens T is mounted on the master lens M exceeds the lower limit of the conditional expression (5), the axial chromatic aberration of wavelengths other than the g-line increases and the axial chromatic aberration is increased. It is difficult to balance and it is not good.

  Further, when the axial chromatic aberration of the g-line when the teleconverter lens T is mounted on the master lens M exceeds the upper limit of the conditional expression (5), blue blurring on the axis becomes remarkable, which is not good.

  If conditional expression (5) is more preferably set as follows, the axial chromatic aberration of the g-line and other wavelengths may be corrected in a well-balanced manner.

0.5 <δsk (T) / (δsk (M) × β) <0.9 (5a)
Next, numerical examples 1 to 4 corresponding to the teleconverter lenses according to the first to fourth embodiments of the present invention and numerical examples of the master lens will be described.

  In each numerical example, i indicates the order of the optical surfaces from the object side, Ri is the radius of curvature of the i-th optical surface (i-th surface), Di is the distance between the i-th surface and the i + 1-th surface, Ni and νi indicate the refractive index and Abbe number of the material of the i-th optical member with respect to the d-line, respectively. Also, when k is the eccentricity, B, C, D, and E are aspheric coefficients, and the displacement in the optical axis direction at the position of the height h from the optical axis is x with respect to the surface vertex, the aspheric shape is ,

Is displayed.

Where R is the radius of curvature. Also for example, a display of the "E-Z" means ^{"10 -Z".} Table 1 shows the correspondence with the above-described conditional expressions in each numerical example. f represents a focal length, Fno represents an F number, and ω represents a half angle of view.

  In the numerical example of the teleconverter lens, f, Fno, and 2ω are values at the telephoto end when the teleconverter lens is attached to the master lens.

  Next, an embodiment of a digital still camera (imaging device) in which the teleconverter lens of the present invention is attached to a master lens and used as a photographing optical system will be described with reference to FIG.

  In FIG. 17, reference numeral 20 denotes a camera body, and 21 denotes a photographing optical system in which the teleconverter lens of the present invention is attached to a master lens.

  Reference numeral 22 denotes a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor that receives a subject image formed by the photographing optical system 21 and is built in the camera body.

  A memory 23 stores information corresponding to the subject image photoelectrically converted by the image sensor 22. Reference numeral 24 is a finder for observing a subject image formed on the solid-state image sensor 22, which includes a liquid crystal display panel or the like.

  As described above, the imaging optical system of the present invention is applied to an imaging apparatus such as a digital still camera, thereby realizing a small imaging apparatus having high optical performance.

Lens sectional view of the teleconverter lens of Example 1 Cross section of the master lens Lens sectional view of the teleconverter lens and master lens of Example 1 at the telephoto end zoom position Aberration diagram at the zoom position between the teleconverter lens and the master lens of Example 1 Aberration diagram at telephoto end of teleconverter lens and master lens of Example 1 Aberration diagram at the middle zoom position of the master lens Aberration diagram at the zoom position of the telephoto end of the master lens Lens sectional view of the teleconverter lens of Example 2 Aberration diagram at zoom position intermediate between teleconverter lens and master lens of Example 2 Aberration diagram at telephoto end of teleconverter lens and master lens of Example 2 Lens cross section of the teleconverter lens of Example 3 Aberration diagram at zoom position intermediate between tele-converter lens and master lens of Example 3 Aberration diagram at telephoto end of teleconverter lens and master lens of Example 3 Lens cross section of the teleconverter lens of Example 4 Aberration diagram at zoom position midway between teleconverter lens and master lens of Example 4 Aberration diagram at telephoto end of teleconverter lens and master lens of Example 4 Schematic diagram of imaging device of the present invention

Explanation of symbols

LF: Teleconverter lens front group LR: Teleconverter lens rear group T: Teleconverter lens M: Master lens L1: Master lens first lens group L2: Master lens second lens group L3: Master lens third lens Lens group L4: Fourth lens group SP of the master lens: Aperture stop fno: F-number ω: Half angle of view ΔS: Sagittal image plane ΔM: Meridional image plane

Claims (8)

A teleconverter lens mounted on the object side of the master lens,
In order from the object side to the image side, consisting of a front group of positive refractive power and a rear group of negative refractive power, with the widest air interval in the optical axis direction as a boundary,
The front group includes a first cemented lens having a positive refractive power and a 13th lens having a positive refractive power as a whole, in which an eleventh lens having a negative refractive power and a twelfth lens having a positive refractive power are cemented.
The rear group includes a second cemented lens having a negative refractive power as a whole, in which a 21st lens having a positive refractive power and a 22nd lens having a negative refractive power are cemented.
When the Abbe numbers of the materials of the eleventh lens and the twelfth lens are ν11 and ν12, respectively, 30 <ν11 <50
25 <ν12−ν11
A teleconverter lens characterized by satisfying the following conditions: When the refractive power of the front group is ΦF,
0.2 (1 / mm) <ΦF · ν11 <0.6 (1 / mm)
The teleconverter lens according to claim 1, wherein the following condition is satisfied. When the refractive power of the front group is ΦF, and the distance from the most object-side surface vertex of the front group to the most image-side surface vertex is dF,
5.0 <ΦF · dF · ν11 <15.0
The teleconverter lens according to claim 1 or 2, wherein the following condition is satisfied. When the power of the cemented surface of the first cemented lens is Φc,
−1.0 (1 / mm) <Φc / (1 / ν11−1 / ν12) <− 0.3 (1 / mm)
The teleconverter lens according to claim 1, wherein the following condition is satisfied. When the power of the cemented surface of the first cemented lens is Φc and the refractive power of the first cemented lens is Φ1c,
−1.6 <(Φc / Φ1c) / (1 / ν11−1 / ν12) / 1000 <−0.01
The teleconverter lens according to claim 1, wherein the following condition is satisfied.   6. The image pickup apparatus having a master lens and a solid-state image sensor that receives an image formed by the master lens can be attached to the object side of the master lens. Teleconverter lens.   A master lens, the teleconverter lens according to any one of claims 1 to 6, which can be mounted on the object side of the master lens, and a solid-state imaging device that receives an image formed by the teleconverter lens and the master lens; An imaging device comprising: The difference between the axial chromatic aberrations of the d-line and the g-line with respect to an infinite object in the entire system in which the master lens and the tele-converter lens are mounted on the master lens are set as δsk (M) and δsk (T), respectively. When the lens afocal magnification is β,
0.4 <δsk (T) / (δsk (M) × β) <1.0
The imaging apparatus according to claim 7, wherein the following condition is satisfied.
However, when the master lens is a zoom lens, the axial chromatic aberration is a value at the telephoto end.

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