JP5137715B2 - Teleconverter lens and imaging apparatus having the same - Google Patents

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 even if the focal length is changed, the F number at the telephoto end of the master lens is not sacrificed (not changed).

  In recent years, digital cameras and video cameras have been downsized and the number of pixels of a solid-state imaging device such as a CCD sensor has been increased, and a photographing lens used for them has to be small and have high optical performance with good correction of chromatic aberration. Has been.

  Therefore, the teleconverter lens to be mounted on the photographing lens is also required to have a small size and high optical performance.

  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.

  In the front teleconverter, a small teleconverter lens is known in which each of the front group having a positive refractive power and the rear group having a negative refractive power is configured by one lens (for example, Patent Document 1).

  There is also known a small teleconverter lens in which the front group having a positive refractive power is composed of two positive lenses and the rear group is composed of one or two lenses (for example, Patent Documents 2 and 3). .

In addition, a teleconverter lens is known in which the front group includes one negative lens and one positive lens, and the rear group includes a positive lens and a negative lens (Patent Document 4).
JP 55-32046 A JP-A-4-191717 JP 2005-331851 A Japanese Patent Laid-Open No. 10-197792

  Teleconverter lenses have a short optical total length (length from the first lens surface to the final lens surface), are small in size, and have a small number of lenses so that high optical performance can be maintained when mounted on a master lens, and There is a demand for small aberration fluctuations.

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

  In addition, when the master lens is a zoom lens, it is also important to suppress fluctuations in various aberrations accompanying zooming.

  To maintain high optical performance while downsizing the entire teleconverter lens, it is important to set the lens configuration of the front group with positive refractive power and the rear group with negative refractive power appropriately. . For example, unless the number of lenses constituting the entire lens and the lens shape of each lens constituting the front group of positive refractive power are not set appropriately, it is difficult to maintain good optical performance while reducing the size of the entire system. It becomes.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a teleconverter lens having a short optical total length and a small variation in various aberrations when mounted on a master lens and having high optical performance.

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 plane side, it is composed of a front group of positive refractive power and a rear group of negative refractive power,
The front group includes a first meniscus positive lens having a convex object side surface and a second meniscus positive lens having a convex object side surface,
The rear group consists of one positive lens and a negative lens whose surface on the image side is concave,
When the radius of curvature of the object-side and image-side surfaces of the first lens is R11 and R12, respectively, and the radius of curvature of the object-side and image-side surfaces of the second lens is R21 and R22, respectively 1.0 < (R11 + R12) / (R12-R11) <20.0
1.0 <(R21 + R22) / (R22-R21) <20.0
It is characterized by satisfying the following conditions.

  According to the present invention, it is possible to obtain a teleconverter lens having a short optical total length and a small variation in various aberrations when mounted on a master lens and having high optical performance.

  Hereinafter, a teleconverter lens (teleconverter) according to the present invention, an imaging system when the lens 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.

  The teleconverter lens according to the present invention includes, in order from the object side to the image plane side, a front group having a positive refractive power and a rear group having a negative refractive power. The front group includes a first meniscus positive lens having a convex object side surface and a second meniscus positive lens having a convex object side surface. The rear group includes one positive lens and one negative lens having a concave surface on the image plane side.

  FIGS. 1A and 1B are a telephoto end (long focal length end) and a wide angle end (short focal length end) when the teleconverter lens of Example 1 of the present invention is mounted on the object side of the master lens M. It is lens sectional drawing in the zoom position.

  2 and 3 are aberration diagrams at the zoom positions of the telephoto end and the wide-angle end when the teleconverter lens of Example 1 of the present invention is mounted on the object side of the master lens M. FIG.

  FIG. 4 is a lens cross-sectional view of the teleconverter lens of Example 2 of the present invention.

  FIGS. 5 and 6 are aberration diagrams at the zoom positions of the telephoto end and the wide-angle end when the teleconverter lens of Example 2 of the present invention is mounted on the object side of the master lens M. FIGS.

  FIG. 7 is a lens cross-sectional view of the teleconverter lens of Example 3 of the present invention.

  8 and 9 are aberration diagrams at the telephoto end and wide-angle end zoom positions when the teleconverter lens of Example 3 of the present invention is mounted on the object side of the master lens M. FIG.

  FIG. 10 is a lens cross-sectional view of a teleconverter lens according to Example 4 of the present invention.

  11 and 12 are aberration diagrams at the telephoto end and wide-angle end zoom positions when the teleconverter lens of Example 4 of the present invention is mounted on the object side of the master lens M. FIG.

  FIG. 13 is a lens cross-sectional view of the teleconverter lens of Example 5 of the present invention.

  14 and 15 are aberration diagrams at the telephoto end and wide-angle end zoom positions when the teleconverter lens of Example 5 of the present invention is mounted on the object side of the master lens M. FIG.

  FIG. 16 is a lens cross-sectional view of a teleconverter lens according to Example 6 of the present invention.

  FIGS. 17 and 18 are aberration diagrams at the telephoto end and wide-angle end zoom positions when the teleconverter lens of Example 6 of the present invention is mounted on the object side of the master lens M. FIGS.

  FIG. 19 is a lens cross-sectional view of a teleconverter lens according to Example 7 of the present invention.

  20 and 21 are aberration diagrams at the zoom positions at the telephoto end and the wide-angle end when the teleconverter lens according to the seventh embodiment of the present invention is mounted on the object side of the master lens M. FIG.

  FIG. 22 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, d and g are d-line and g-line. ΔM and ΔS are a meridional image surface and a sagittal image surface. Lateral chromatic aberration is represented by the 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 a substantially 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 principal point interval between the front group LF and the rear group LR is substantially equal to the sum of the focal lengths of the front group LF and the rear group LR, thereby constituting an afocal system as a whole.

  The front group LF includes a positive first meniscus lens G1 having a convex surface on the object side and a positive second lens G2 having a convex surface on the object side and a meniscus shape.

  The rear group LR includes one positive lens G3 and a negative lens G4 having a concave surface on the image plane side.

  The master lens M is composed of a zoom lens. FIG. 1 shows a lens cross-sectional view at the wide-angle end (W) and the telephoto end (T) that are in a practical range when the teleconverter lens T is attached.

  Here, the practical range refers to a range that can be used in a state in which the maximum image height of the master lens M is sufficient to secure a sufficient amount of light and so-called “scratch” is small.

Further, by using only the center portion of the screen that is not lost, it is possible to use it on the wide angle side.

The configuration of the master lens M is as follows.

  In the lens cross-sectional view of FIG. 1, 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. FP is a flare stop, which is disposed on the image side of the third lens unit L3 and cuts flare light.

  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 telephoto end to the wide-angle end, as indicated by arrows, the first lens unit L1, the second lens unit L2, and the third lens unit L3 move so as to be positioned on the image side at the wide-angle end compared to the telephoto end. The fourth lens unit L4 moves so as to form a locus convex toward 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. When focusing from an object at infinity to a near object, the fourth lens unit L4 is extended forward.

In each embodiment, in the teleconverter lens, the curvature radii of the object-side surface and the image-side surface of the first lens G1 in the front group LF are R11 and R12, respectively. The curvature radii of the object side and the image plane side of the second lens G2 are R21 and R22, respectively. At this time, 1.0 <(R11 + R12) / (R12−R11) <20.0 (1)
1.0 <(R21 + R22) / (R22−R21) <20.0 (2)
Is satisfied.

  Next, the technical meaning of conditional expressions (1) and (2) will be described.

  Conditional expression (1) relates to the lens shape of the positive lens G1 of the front group LF.

  When the value of conditional expression (1) exceeds 1, a meniscus shape with a convex surface facing the object side, when 1.0, a plano-convex lens shape with a convex surface facing the object side, a range of -1.0 to 1.0 When taking a value, it becomes a biconvex shape.

  If the positive lens G1 of the front lens group LF exceeds the lower limit of the conditional expression (1) and the surface on the image plane side is flat or convex on the image side, the exit angle of the off-axis light beam becomes too large. As a result, higher-order components of field curvature and lateral chromatic aberration generated by the positive lens G1 increase, and it becomes difficult to correct these by the rear group LR.

  Further, since the main point interval of the front group LF shifts to the image plane side, the air interval between the front group LF and the rear group LR is increased, and the optical total length of the teleconverter lens T (the distance from the first lens surface to the final lens surface). ) Will increase.

  Conversely, if the positive lens G1 of the front lens group LF exceeds the upper limit of the conditional expression (1) and the radius of curvature of the object side surface becomes too small, spherical aberration generated on the entrance surface of the positive lens G1 increases. Is difficult to correct with the rear group LR. As a result, when the teleconverter lens T is attached to the master lens M, it becomes difficult to obtain good optical characteristics.

  Conditional expression (2) relates to the lens shape of the positive lens G2 of the front group LF.

  If the positive lens G2 of the front lens group LF exceeds the lower limit of the conditional expression (2) and the image side surface is flat or convex toward the image side, the exit angle of the off-axis light beam becomes too large. As a result, higher-order components of field curvature and lateral chromatic aberration generated by the positive lens G2 increase, and it becomes difficult to correct this with the rear group LR.

  Further, since the main point interval of the front group LF is shifted to the image plane side, the air interval between the front group LF and the rear group LR is enlarged, and the optical total length of the teleconverter lens T is increased.

  Conversely, if the positive lens G2 of the front lens group LF exceeds the upper limit of the conditional expression (2) and the radius of curvature of the object side surface becomes too small, the spherical aberration generated on the incident surface of the positive lens G2 increases. Is difficult to correct with the rear group LR. As a result, when the teleconverter lens T is attached to the master lens M, it becomes difficult to obtain good optical characteristics.

  By configuring as described above, various aberrations such as longitudinal chromatic aberration, lateral chromatic aberration, spherical aberration, and curvature of field are well corrected, and a high-performance and compact teleconverter compatible with high-pixel digital cameras and video cameras. The lens is realized.

In each embodiment, it is more preferable that one or more of the following conditions be satisfied.
The Abbe numbers of the materials of the first lens G1 and the second lens G2 are νd1 and νd2, respectively.
The Abbe numbers of the materials of the positive lens G3 and the negative lens G4 in the rear group LR are νd3 and νd4, respectively.
The focal lengths of the first lens G1 and the second lens G2 are f1 and f2, respectively.
The focal lengths of the positive lens G3 and the negative lens G4 in the rear group LR are f3 and f4, respectively.
The air gap between the front group LF and the rear group LR is D, and the distance along the optical axis from the lens surface vertex of the rear group LR closest to the object side to the lens surface vertex closest to the image plane is DR. .
The total thickness along the optical axis of all the lenses constituting the teleconverter lens T is Dglass, and the total distance along the optical axis of all air intervals is Dair.
Let R31 be the radius of curvature of the object side surface of the rear group positive lens G3 (the most object side surface of the rear group LR), and let R42 be the radius of curvature of the image side surface of the negative lens G4 of the rear group.
The radius of curvature of the image side surface of the second lens G2 is R22.

At this time, 55 <νd1 (3)
55 <νd2 (4)
0.05 <| f4 / f3 | <0.80 (5)
0.1 <D / DR <1.5 (6)
−8.0 <(R31 + R42) / (R42−R31) <− 0.5 (7)
0.2 <f1 / f2 <2.5 (8)
0.05 <Dair / Dglass <0.70 (9)
5.0 <| νd3−νd4 | <30.0 (10)
0.1 <R22 / R31 <3.0 (11)
It is preferable to satisfy one or more of the following conditions.

  Next, the technical meaning of each conditional expression described above will be described.

  Conditional expression (3) defines the material of the first lens G1.

  If the lower limit of conditional expression (3) is exceeded and the Abbe number νd1 of the material of the first lens G1 becomes too small, axial chromatic aberration and lateral chromatic aberration generated in the first lens G1 increase, and this is corrected by the rear group LR. It becomes difficult to do.

  Conditional expression (4) defines the material of the second lens G2.

  If the Abbe number νd2 of the material of the second lens G2 is too small beyond the lower limit of the conditional expression (4), the axial chromatic aberration and the lateral chromatic aberration generated in the second lens G2 increase, and this is corrected by the rear group LR. It becomes difficult to do.

  Conditional expression (5) relates to the ratio of the focal lengths of the positive lens G3 and the negative lens G4 in the rear group LR.

  If the lower limit of the conditional expression (5) is exceeded and the focal length of the negative lens G4 of the rear lens group LR becomes too small (refractive power becomes too weak), lateral chromatic aberration and off-axis color flare that occur in the negative lens G4 will occur. This increases, and it becomes difficult to correct this with the positive lens G3.

  Conversely, when the focal length of the negative lens G4 of the rear group LR becomes too large (when the refractive power becomes too strong) exceeding the upper limit of the conditional expression (5), sufficient negative refractive power is imparted to the rear group LR. It becomes impossible to do. As a result, the air gap between the front group LF and the rear group LR is enlarged, and the teleconverter lens T is enlarged, which is not good.

  Conditional expression (6) represents the air distance D between the front group LF and the rear group LR and the optical axis from the lens surface vertex located closest to the object side to the lens surface vertex located closest to the image plane in the rear group LR. The ratio with the distance DR along.

  If the lower limit of the conditional expression (6) is exceeded and the air gap D between the front group LF and the rear group LR becomes small, and the main point distance between the front group LF and the rear group LR becomes too short, the front group LF and the rear group The refractive power of LR becomes strong. As a result, it becomes difficult to correct various aberrations such as spherical aberration occurring in the front group LF in the rear group LR.

  Conversely, if the air distance D between the front group LF and the rear group LR becomes too large beyond the upper limit of the conditional expression (6), the optical total length of the teleconverter lens T increases, which is not good.

  Conditional expression (7) is that the radius of curvature R31 of the object side lens surface (incident surface) of the positive lens G3 in the rear group LR and the radius of curvature of the lens surface (outgoing surface) of the image plane side of the negative lens G4 in the rear group LR. Related to R42.

  If the radius of curvature R42 of the exit surface of the rear group LR is small beyond the lower limit of the conditional expression (7), that is, if the curvature of the exit surface becomes too tight, spherical aberration and astigmatism occurring on the exit surface of the rear group LR Higher order components increase. It becomes difficult to correct the aberration at this time with another lens surface of the rear group LR.

If the upper surface of conditional expression (7) is exceeded and the incident surface of the rear group LR becomes too concave with a strong curvature, the incident angle of the off-axis light beam incident on the rear group LR increases. As a result, higher-order components of spherical aberration and astigmatism that occur on the entrance surface of the positive lens G3 increase, making it difficult to correct with other lens surfaces of the rear lens group LR.

  Conditional expression (8) relates to the ratio of the focal lengths of the first lens G1 and the second lens G2.

  Conditional expression (8) defines the refractive power sharing ratio of the two positive lenses G1 and G2 in the front group LF.

  If the refractive power of the positive lens G1 becomes too strong beyond the lower limit of the conditional expression (8), higher-order spherical aberration and astigmatism generated in the positive lens G1 increase, and this is corrected by the rear group LR. Becomes difficult.

  Conversely, if the refractive power of the positive lens G2 becomes too strong beyond the upper limit of the conditional expression (8), higher-order spherical aberration and astigmatism generated in the positive lens G2 increase, and this is corrected by the rear group LR. It becomes difficult to do.

  Conditional expression (9) relates to the ratio of the total thickness Dglass along the optical axis of all the lenses constituting the teleconverter lens T to the total distance Dair along the optical axis of all air intervals.

  If the lower limit of conditional expression (9) is exceeded and the air spacing in the teleconverter lens T becomes too small, the beam height of the off-axis light beam at the exit surface of the teleconverter lens T increases and astigmatism increases. So not good.

  Conversely, if the upper limit of conditional expression (9) is exceeded and the air space in the teleconverter lens T becomes too large, the teleconverter lens T will become large, which is not good.

  Conditional expression (10) relates to the difference between the Abbe numbers νd3 and νd4 of the positive lens G3 and the negative lens G4 of the rear lens group LR.

  If the difference between the Abbe numbers of the materials of the positive lens G3 and the negative lens G4 in the rear lens group LR becomes too small beyond the lower limit of the conditional expression (10), the longitudinal chromatic aberration and the lateral chromatic aberration generated in the front lens group LF are sufficiently canceled out. It becomes difficult.

  Conversely, if the upper limit of conditional expression (10) is exceeded and the Abbe number difference between the materials of the positive lens G3 and the negative lens G4 in the rear group LR becomes too large, the Abbe number νd4 of the material of the negative lens G4 decreases. If so, the over-axial chromatic aberration and the under magnification chromatic aberration generated in the negative lens G4 increase, which is not good.

  As a result, in the rear group LR, the correction effect for canceling the longitudinal chromatic aberration and the lateral chromatic aberration generated in the front group LF becomes excessive, which is not good.

  Conditional expression (11) relates to the ratio between the curvature radius R22 of the image side surface (exit surface) of the second lens G2 and the curvature radius R31 of the most object side surface (incident surface) of the rear group LR. It defines the shape of the air lens between the group LF and the rear group LR.

  If the lower limit of conditional expression (11) is exceeded and the curvature of the exit surface of the front lens group LF becomes too tight, higher-order spherical aberration that occurs in the second lens G2 of the front lens group LF increases, and this is expressed by the rear lens group LR. It becomes difficult to correct.

  If the upper limit of conditional expression (11) is exceeded and the curvature of the entrance surface of the rear group LR is too tight in the convex direction, higher-order spherical aberration that occurs on the entrance surface of the rear group LR increases. At the same time, the curvature of the exit surface of the negative lens G4 of the rear lens group LR having a negative refractive power is not good because it becomes too tight in the concave shape direction.

  As a result, higher-order components of spherical aberration and astigmatism occurring on the exit surface of the rear group LR increase, and it becomes difficult to correct this with other lens surfaces of the rear group LR.

  In each of the embodiments, a compact teleconverter lens having a short optical total length is achieved while satisfactorily correcting spherical aberration, astigmatism, axial chromatic aberration, and lateral chromatic aberration by configuring as described above.

  In the teleconverter lens of each example, it is more preferable to set the numerical ranges of conditional expressions (1) to (11) as follows.

1.3 <(R11 + R12) / (R12−R11) <10.0 (1a)
1.05 <(R21 + R22) / (R22-R21) <15.0 (2a)
60 <νd1 (3a)
60 <νd2 (4a)
0.08 <| f4 / f3 | <0.60 (5a)
0.15 <D / DR <1.20 (6a)
−7.0 <(R31 + R42) / (R42−R31) <− 0.7 (7a)
0.25 <f1 / f2 <2.10 (8a)
0.10 <Dair / Dglass <0.60 (9a)
5.0 <| νd3−νd4 | <27.0 (10a)
0.2 <R22 / R31 <2.5 (11a)
More preferably, when the numerical ranges of the conditional expressions (1a) to (11a) are set as follows, the effects meant by the conditional expressions described above can be obtained to the maximum.

1.5 <(R11 + R12) / (R12−R11) <6.0 (1b)
1.1 <(R21 + R22) / (R22−R21) <10.0 (2b)
63 <νd1 (3b)
63 <νd2 (4b)
0.1 <| f4 / f3 | <0.5 (5b)
0.2 <D / DR <1.0 (6b)
−6.0 <(R31 + R42) / (R42−R31) <− 0.9 (7b)
0.3 <f1 / f2 <1.8 (8b)
0.12 <Dair / Dglass <0.50 (9b)
5.0 <| νd3−νd4 | <24.0 (10b)
0.3 <R22 / R31 <2.0 (11b)
Next, the lens configuration of the teleconverter lens T of Example 1 shown in FIG. 1 will be described.

  The front lens group LF includes a meniscus positive first lens G1 having a convex surface facing the object side, and a meniscus positive second lens G2 having a convex surface facing the object side.

  By configuring the front group LF with such a lens configuration, the positive refractive power of the front group LF is shared by the first lens G1 and the second lens G2, and the spherical aberration and astigmatism are favorably corrected. At the same time, the refractive power of the front lens group LF is increased to facilitate the downsizing of the teleconverter lens T.

  In addition, by making both the first lens G1 and the second lens G2 of the front group LF have a meniscus shape with a convex surface facing the object side, the principal point position of the front group LF is further arranged on the object side.

  Thereby, the air gap between the front group LF and the rear group LR can be shortened while maintaining the main point distance between the front group LF and the rear group LR so that the entire teleconverter lens T is substantially afocal. The entire teleconverter lens T is reduced in size.

  The master lens M shown in FIG. 1 has a photographing field angle 2ω at the wide-angle end of 24.4 °. The zoom lens has a photographing field angle 2ω at the telephoto end of 17.7 °.

  In the teleconverter lens T that is mounted on the master lens M that is such a zoom lens in the middle telephoto range, the two positive lenses G1 and G2 of the front group LF are formed in a meniscus shape with a convex surface facing the object side. The incident angle of the external light beam can be reduced.

  Thereby, higher-order components of field curvature and lateral chromatic aberration generated in the front group LF are reduced.

  The rear group LR is composed of a cemented lens having a negative refractive power in which a positive lens G3 and a negative lens G4 are cemented in order from the object side to the image plane side.

  With such a configuration, axial chromatic aberration generated in the rear group LR is suppressed, and axial chromatic aberration generated in the front group LF is effectively canceled.

  The lens surface closest to the image plane of the rear group LR is concave, and the air lens shape between the teleconverter lens T and the master lens M is a shape close to concentric.

  As a result, as a teleconverter lens to be mounted on the master lens, the exit angle of the off-axis light beam is prevented from becoming extremely large on the image surface side lens surface of the rear lens group LR, and high-order components of astigmatism and lateral chromatic aberration are generated. Is reduced.

  The lens configuration of the fifth embodiment of FIG. 13 and the sixth embodiment of the teleconverter lens T of FIG. 16 is the same as that of the first embodiment.

  Next, the lens configuration of the teleconverter lens T of Example 2 in FIG. 4 will be described.

  The front group LF includes positive and second meniscus first and second lenses G1 and G2 having convex surfaces facing the object side as in the first embodiment.

  The rear group LR is composed of a positive lens G3 and a negative lens G4 with an air gap in order from the object side to the image plane side.

  With such a lens configuration, axial chromatic aberration and lateral chromatic aberration generated in the rear group LR are suppressed, and axial chromatic aberration and lateral chromatic aberration generated in the front group LF are effectively canceled.

  The lens surface closest to the image plane of the rear group LR is concave, and the air lens shape between the teleconverter lens T and the master lens M is a shape close to concentric.

  As a result, as the teleconverter lens T to be mounted on the master lens M, the exit angle of the off-axis light beam is prevented from becoming extremely large on the image surface side lens surface of the rear lens group LR, and higher-order components of astigmatism and lateral chromatic aberration are obtained. Occurrence is reduced.

  The teleconverter lens T of Example 3 in FIG. 7, Example 4 in FIG. 10, and Example 7 in FIG. 19 has the same lens configuration as that of Example 2.

  Next, numerical examples 1 to 7 and numerical examples of the master lens M respectively corresponding to the first to seventh embodiments of the present invention will be described.

  In each numerical example, the surface number i indicates the order of the optical surfaces from the object side. r is the radius of curvature of the optical surface, d is the surface spacing, nd and νd are the refractive index and Abbe number of the material of the optical member for the d line, respectively.

  The back focus (BF) is a value obtained by converting the distance from the last lens surface to the paraxial image surface into air. The total lens length is defined as a value obtained by adding back focus (BF) to the distance from the front lens surface to the final lens surface.

  The unit of length is mm.

  Also, when K is the eccentricity, A4, A6, A8 are aspheric coefficients, and the displacement in the optical axis direction at the position of the height H from the optical axis is x based on 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.

  Various data in numerical examples of the teleconverter are values at the telephoto end when the teleconverter is attached to the master lens.

[Numerical Example 1]
Surface data surface number rd nd νd
1 47.193 7.50 1.48749 70.2
2 156.757 0.20
3 45.803 6.20 1.48749 70.2
4 116.940 5.70
5 130.516 5.10 1.62299 58.2
6 1426.354 2.00 1.77250 49.6
7 31.401 8.71

Various data afocal magnification 1.39
Focal length 41.43
F number 4.56
Angle of view (ω) 6.40

[Numerical Example 2]
Surface data surface number rd nd νd
1 47.737 7.50 1.48749 70.2
2 152.286 0.20
3 44.476 6.20 1.48749 70.2
4 118.664 5.70
5 148.146 3.50 1.48749 70.2
6 1000.000 1.00
7 574.052 2.00 1.77250 49.6
8 32.273 8.71

Various data afocal magnification 1.39
Focal length 41.43
F number 4.56
Angle of view (ω) 6.40

[Numerical Example 3]
Surface data surface number rd nd νd
1 45.647 5.00 1.48749 70.2
2 73.968 0.20
3 33.245 6.50 1.48749 70.2
4 54.995 2.45
5 40.497 7.20 1.48749 70.2
6 3346.491 0.50
7 795.494 2.00 1.71300 53.9
8 23.850 8.71

Various data afocal magnification 1.39
Focal length 41.43
F number 4.56
Angle of view (ω) 6.40

[Numerical Example 4]
Surface data surface number rd nd νd
1 40.001 7.50 1.48749 70.2
2 97.050 0.20
3 39.339 4.80 1.48749 70.2
4 51.886 2.84
5 47.188 7.00 1.48749 70.2
6 -451.419 0.50
7 -551.640 2.00 1.71300 53.9
8 26.367 8.71

Various data afocal magnification 1.39
Focal length 41.43
F number 4.56
Angle of view (ω) 6.40

[Numerical Example 5]
Surface data surface number rd nd νd
1 41.196 9.80 1.48749 70.2
2 154.033 0.20
3 39.899 7.50 1.48749 70.2
4 111.122 3.98
5 130.411 5.25 1.62299 58.2
6 -218.491 2.00 1.77250 49.6
7 26.070 8.71

Various data afocal magnification 1.50
Focal length 44.81
F number 4.56
Angle of View (ω) 5.92

[Numerical Example 6]
Surface data surface number rd nd νd
1 43.954 9.20 1.48749 70.2
2 142.651 0.20
3 39.900 10.30 1.48749 70.2
4 610.253 4.50
5 1277.383 5.70 1.60311 60.6
6 -150.815 2.00 1.78800 47.4
7 27.055 8.71

Various data afocal magnification 1.60
Focal length 47.70
F number 4.56
Angle of view (ω) 5.57

[Numerical Example 7]
Surface data surface number rd nd νd
1 36.463 7.50 1.48749 70.2
2 80.438 0.20
3 44.264 4.00 1.48749 70.2
4 58.922 2.50
5 37.309 4.50 1.77250 49.6
6 51.581 2.30
7 89.358 2.00 1.78590 44.2
8 24.347 8.71

Various data afocal magnification 1.39
Focal length 41.43
F number 4.56
Angle of view (ω) 6.40

<Master lens>
Surface data surface number rd nd νd
1 27.364 1.20 1.84666 23.9
2 20.088 4.00 1.77250 49.6
3 66.608 (variable)
4 21.154 0.95 1.88300 40.8
5 7.854 2.52
6 17.211 0.90 1.88300 40.8
7 8.731 3.14
8 -24.403 0.80 1.80 400 46.6
9 166.576 0.20
10 16.917 1.80 1.92286 18.9
11 94.775 (variable)
12 (Aperture) ∞ 1.50
13 * 12.089 2.20 1.58313 59.4
14 * -21.698 0.20
15 6.003 2.40 1.48749 70.2
16 13.648 0.70 2.00069 25.5
17 5.537 1.46
18 -19.438 1.20 1.48749 70.2
19 -10.131 0.50
20 ∞ (variable)
21 15.301 2.00 1.48749 70.2
22 109.326 (variable)
23 ∞ 1.10 1.51633 64.1
24 ∞ (variable)
Image plane ∞

Aspherical data 13th surface
K = 1.43178e + 000 A 4 = -2.01411e-004 A 6 = -1.69744e-006
A 8 = 2.82246e-008
14th page
K = -6.18021e-001 A 4 = 1.13642e-004 A 6 = -6.70660e-007
A 8 = 5.94851e-008

Various data Zoom ratio 1.39
Wide-angle telephoto focal length 21.45 29.89
F number 4.01 4.57
Angle of View 12.22 8.84
Image height 4.65 4.65
Total lens length 67.84 76.99
BF 13.20 10.32

d 3 15.31 20.58
d11 2.73 2.08
d20 8.93 16.35
d22 11.88 8.99
d24 0.60 0.60

Zoom lens group data group Start surface Focal length
1 1 59.97
2 4 -8.99
3 12 13.91
4 21 36.24

  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. 22, 20 is a camera body, and 21 is a photographing optical system in which the teleconverter lens of the present invention is mounted on 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 solid-state imaging device 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.

  In this way, by applying the imaging optical system of the present invention to an imaging apparatus such as a digital still camera, a small-sized imaging apparatus having high optical performance is realized.

Sectional view of the lens when the teleconverter of Numerical Example 1 of the present invention is mounted on the wide-angle end and the telephoto end of the master lens Aberration diagram of the entire system at the telephoto end when the teleconverter according to Numerical Example 1 of the present invention is mounted on a master lens. Aberration diagram of the entire system at the wide-angle end when the teleconverter according to Numerical Example 1 of the present invention is mounted on the master lens. Lens sectional view of a teleconverter according to Numerical Example 2 of the present invention Aberration diagram of the entire system at the telephoto end when the teleconverter according to Numerical Example 2 of the present invention is mounted on the master lens. Aberration diagram of the entire system at the wide-angle end when the teleconverter according to Numerical Example 2 of the present invention is mounted on the master lens. Lens sectional view of a teleconverter according to Numerical Example 3 of the present invention Aberration diagram of the entire system at the telephoto end when the teleconverter according to Numerical Example 3 of the present invention is mounted on the master lens. Aberration diagram of the entire system at the wide-angle end when the teleconverter according to Numerical Example 3 of the present invention is mounted on the master lens. Lens sectional view of teleconverter of Numerical Example 4 of the present invention Aberration diagram of the entire system at the telephoto end when the teleconverter according to Numerical Example 4 of the present invention is mounted on the master lens. Aberration diagram of the entire system at the wide-angle end when the teleconverter according to Numerical Example 4 of the present invention is mounted on the master lens. Lens sectional view of teleconverter of Numerical Example 5 of the present invention Aberration diagram of the entire system at the telephoto end when the teleconverter according to Numerical Example 5 of the present invention is mounted on the master lens Aberration diagram of the entire system at the wide-angle end when the teleconverter of Numerical Example 5 of the present invention is mounted on the master lens Lens sectional view of a teleconverter according to Numerical Example 6 of the present invention Aberration diagram of the entire system at the telephoto end when the teleconverter according to Numerical Example 6 of the present invention is mounted on the master lens. Aberration diagram of the entire system at the wide angle end when the teleconverter according to Numerical Example 6 of the present invention is mounted on the master lens. Lens sectional view of a teleconverter according to Numerical Example 7 of the present invention Aberration diagram of the entire system at the telephoto end when the teleconverter according to Numerical Example 7 of the present invention is mounted on a master lens Aberration diagram of the entire system at the wide-angle end when the teleconverter according to Numerical Example 7 of the present invention is mounted on the master lens Schematic diagram of imaging device of the present invention

Explanation of symbols

T Tele-converter lens part M Master lens part G Glass block IP Image plane LF Front group LR Rear group d d line g g line ΔM Meridional image plane ΔS Sagittal image plane IP Imaging plane
SP Aperture ω Half angle of view Fno F number G1 First lens G2 Second lens G3 Third lens G4 Fourth lens L1 First lens group L2 of master lens Second lens group L3 of master lens Third lens group L4 of master lens Fourth lens group of the master lens

Claims (11)

A teleconverter lens mounted on the object side of the master lens,
In order from the object side to the image plane side, it is composed of a front group of positive refractive power and a rear group of negative refractive power,
The front group includes a first meniscus positive lens having a convex object side surface and a second meniscus positive lens having a convex object side surface,
The rear group consists of one positive lens and a negative lens whose surface on the image side is concave,
When the radius of curvature of the object-side and image-side surfaces of the first lens is R11 and R12, respectively, and the radius of curvature of the object-side and image-side surfaces of the second lens is R21 and R22, respectively 1.0 < (R11 + R12) / (R12-R11) <20.0
1.0 <(R21 + R22) / (R22-R21) <20.0
A teleconverter lens characterized by satisfying the following conditions: When the Abbe number of the material of the first lens is νd1,
55 <νd1
The teleconverter lens according to claim 1, wherein the following condition is satisfied. When the Abbe number of the material of the second lens is νd2,
55 <νd2
The teleconverter lens according to claim 1, wherein the following condition is satisfied. When the focal lengths of the positive lens and the negative lens in the rear group are f3 and f4, respectively.
0.05 <| f4 / f3 | <0.80
The teleconverter lens according to claim 1, wherein the following condition is satisfied. The air distance between the front group and the rear group is D, and the distance along the optical axis from the lens surface apex located closest to the object side to the lens surface apex located closest to the image plane in the rear group is DR. When
0.1 <D / DR <1.5
The teleconverter lens according to claim 1, wherein the following condition is satisfied. When the radius of curvature of the object side surface of the rear group positive lens is R31 and the radius of curvature of the image side surface of the rear group negative lens is R42,
−8.0 <(R31 + R42) / (R42−R31) <− 0.5
The teleconverter lens according to any one of claims 1 to 5, wherein the following condition is satisfied. When the focal lengths of the first lens and the second lens are f1 and f2, respectively.
0.2 <f1 / f2 <2.5
The teleconverter lens according to claim 1, wherein the following condition is satisfied. When the total thickness along the optical axis of all lenses constituting the teleconverter lens is Dglass, and the total distance along the optical axis of all air intervals is Dair,
0.05 <Dair / Dglass <0.70
The teleconverter lens according to claim 1, wherein the following condition is satisfied. When the Abbe numbers of the materials of the positive lens and the negative lens in the rear group are νd3 and νd4, respectively.
5.0 <| νd3−νd4 | <30.0
The teleconverter lens according to claim 1, wherein the following condition is satisfied. When the radius of curvature of the image side surface of the second lens is R22, and the radius of curvature of the most object side surface of the rear group is R31,
0.1 <R22 / R31 <3.0
The teleconverter lens according to claim 1, wherein the following condition is satisfied.   A master lens, the teleconverter lens according to any one of claims 1 to 10, 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: