JP2013250290A - Rear converter lens, optical device, and method for manufacturing rear converter lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rear converter lens having excellent optical performance while being compact.SOLUTION: A rear converter lens RC is detachably attached to the image side of an imaging lens ML, and the composite focal distance in the state where the rear converter lens is attached to the imaging lens ML is larger than the focal distance of the imaging lens ML. The rear converter lens RC includes, in order from the object side along the optical axis: a first lens group G1 having a positive refractive power; a second lens group G2 having a negative refractive power; and a third lens group G3 having a positive refractive power. When the Abbe number of at least one negative lens in the rear converter lens RC is represented by νn, the following conditional expression is satisfied: 54.0<νn<75.0.

Description

The present invention relates to a rear converter lens, an optical device including the rear converter lens,
And a method of manufacturing a rear converter lens.

2. Description of the Related Art Conventionally, a method for extending the focal length of a photographing lens by inserting a rear converter lens having a negative focal length between a photographing lens (also referred to as a master lens) of a single-lens reflex camera and the camera body is widely known. (For example, see Patent Document 1). In recent years, as the optical performance of the taking lens has improved, there is a demand for a rear converter lens that does not increase the aberration of the taking lens. In response to such a demand, there has been proposed a rear converter lens that realizes good optical performance by performing appropriate lens arrangement (see, for example, Patent Document 2).

Japanese Patent Publication No. 1-28923 JP 2004-226648 A

However, with such a conventional rear converter lens, it has been difficult to achieve miniaturization while maintaining good optical performance.

The present invention has been made in view of such problems, and an object of the present invention is to provide a rear converter lens, an optical device, and a method for manufacturing the rear converter lens that are small and have good optical performance. .

In order to achieve such an object, the rear converter lens according to the present invention is detachably attached to the image side of the photographic lens, and the combined focal length when attached to the photographic lens is greater than the focal length of the photographic lens. A first lens group having a positive refractive power and a second lens group having a negative refractive power, which are arranged in order from the object side along the optical axis. And a third lens group having a positive refractive power, and the following conditional expressions are satisfied.

54.0 <νn <75.0
However,
νn: Abbe number of at least one negative lens in the rear converter lens.

In the above-described rear converter lens, it is preferable that the following conditional expression is satisfied.

0.05 <f2 / fc <0.35
However,
f2: focal length of the second lens group,
fc: focal length of the rear converter lens.

In the above-described rear converter lens, it is preferable that the following conditional expression is satisfied.

2.00 <f3 / (− f2) <4.00
However,
f2: focal length of the second lens group,
f3: focal length of the third lens group.

In the above-described rear converter lens, it is preferable that the first lens group is composed of one positive lens and the third lens group is composed of one positive lens.

In the above-described rear converter lens, it is preferable that the second lens group includes a first negative lens, a positive lens, and a second negative lens arranged in order from the object side along the optical axis.

In the above-described rear converter lens, it is preferable that the second lens group includes a cemented lens in which the first negative lens, the positive lens, and the second negative lens are cemented.

In the above-described rear converter lens, it is preferable that the first negative lens, the positive lens, and the second negative lens in the cemented lens are bonded together.

In the above-described rear converter lens, it is preferable that the positive lens in the cemented lens is a biconvex positive lens.

In the above-described rear converter lens, it is preferable that at least one of the first negative lens and the second negative lens in the cemented lens is a biconcave negative lens.

In the above-described rear converter lens, it is preferable that both the first negative lens and the second negative lens in the cemented lens are biconcave negative lenses.

The optical device according to the present invention is an optical device in which a rear converter lens can be mounted between the device main body and the photographing lens, and the rear converter lens according to the present invention is used as the rear converter lens.

In the manufacturing method of the rear converter lens according to the present invention, the combined focal length in a state where the rear converter lens is detachably attached to the image side of the photographing lens and attached to the photographing lens is longer than the focal length of the photographing lens. A rear converter lens manufacturing method configured as described above, in order from the object side along the optical axis, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a positive And a third lens group having a refractive power of 2 are arranged so as to satisfy the following conditional expression.

54.0 <νn <75.0
However,
νn: Abbe number of at least one negative lens in the rear converter lens.

  According to the present invention, it is possible to obtain good optical performance while being small.

It is a lens block diagram which shows the state with which the rear converter lens which concerns on 1st Example was mounted | worn with the imaging lens. FIG. 7 is a diagram illustrating various aberrations of the rear converter lens according to Example 1 in an infinitely focused state. It is a lens block diagram which shows the state with which the rear converter lens which concerns on 2nd Example was mounted | worn with the imaging lens. FIG. 12 is a diagram illustrating various aberrations of the rear converter lens according to Example 2 in an infinitely focused state. It is a lens block diagram which shows the state with which the rear converter lens which concerns on 3rd Example was mounted | worn with the imaging lens. FIG. 11 is a diagram illustrating various aberrations of the rear converter lens according to Example 3 in an infinitely focused state. It is a lens block diagram which shows the state with which the rear converter lens which concerns on 4th Example was mounted | worn with the imaging lens. FIG. 12 is a diagram illustrating various aberrations of the rear converter lens according to Example 4 in an infinitely focused state. It is a lens block diagram which shows the state with which the rear converter lens which concerns on 5th Example was mounted | worn with the imaging lens. FIG. 11 is a diagram illustrating various aberrations of the rear converter lens according to Example 5 in an infinitely focused state. It is a lens block diagram which shows the state with which the rear converter lens which concerns on 6th Example was mounted | worn with the imaging lens. It is various aberrational figures in the infinite point focusing state of the rear converter lens which concerns on 6th Example. It is sectional drawing of a digital single-lens reflex camera. It is a flowchart which shows the manufacturing method of a rear converter lens.

Hereinafter, preferred embodiments of the present application will be described with reference to the drawings. FIG. 13 shows a digital single lens reflex camera CAM in which a rear converter lens RC according to the present application is mounted between a camera body B and a photographing lens (master lens) ML. In the digital single-lens reflex camera CAM shown in FIG. 13, light from an object (subject) (not shown) is collected by the photographing lens ML and the rear converter lens RC, and is condensed on the focusing screen F via the quick return mirror M. Imaged. The light imaged on the focusing screen F is reflected a plurality of times in the pentaprism P and guided to the eyepiece lens E. Thus, the photographer can observe the image of the object (subject) as an erect image through the eyepiece lens E.

When a release button (not shown) is pressed by the photographer, the quick return mirror M is retracted out of the optical path, and the light from the object (subject) collected by the photographing lens ML and the rear converter lens RC is captured by the image sensor. An image of the subject is formed on C. As a result, light from the object (subject) is imaged on the image sensor C, picked up by the image sensor C, and recorded in a memory (not shown) as an image of the object (subject). In this way, the photographer can photograph an object (subject) with the digital single-lens reflex camera CAM. Even if the camera does not have the quick return mirror M, the same effect as the camera CAM can be obtained.

The rear converter lens RC is detachably attached to the image side of the photographic lens ML, and is configured such that the combined focal length when attached to the photographic lens ML is longer than the focal length of the photographic lens ML. For example, as shown in FIG. 1, the rear converter lens RC includes a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power, which are arranged in order from the object side along the optical axis. And a third lens group G3 having a positive refractive power.

In the rear converter lens RC having such a configuration, it is preferable to satisfy the condition represented by the following conditional expression (1) in order to achieve downsizing while maintaining excellent optical performance.

54.0 <νn <75.0 (1)
However,
νn: Abbe number of at least one negative lens in the rear converter lens RC.

Conditional expression (1) is a conditional expression for maintaining good chromatic aberration when the rear converter lens RC is attached to the photographing lens ML. When the condition exceeds the upper limit value of the conditional expression (1), in the present situation, the glass has a low refractive power. For this reason, since the refractive power of the negative lens is reduced, the Petzval sum goes too far to the negative side, so that it is difficult to keep the average image plane well. On the other hand, when the condition is lower than the lower limit value of the conditional expression (1), the lateral chromatic aberration at the time of mounting the rear converter lens RC is enlarged, and it is difficult to satisfactorily correct the aberration.

In order to secure the effect of the present embodiment, the upper limit value of conditional expression (1) is set to 70.
. 0 is desirable. On the other hand, in order to make the effect of the present embodiment more certain, it is desirable to set the lower limit value of the conditional expression (1) to 58.0. Further, the lower limit value of conditional expression (1) is 6
It is more desirable to set to 0.0.

In such a rear converter lens RC, it is preferable that the condition expressed by the following conditional expression (2) is satisfied.

0.05 <f2 / fc <0.35 (2)
However,
f2: focal length of the second lens group G2,
fc: focal length of the rear converter lens RC.

Conditional expression (2) is a conditional expression for ensuring back focus and Petzval sum. When the condition exceeds the upper limit value of the conditional expression (2), the first value is used to secure an air space between the photographing lens ML and the rear converter lens RC and to obtain a desired converter magnification.
The focal length of the lens group G1 and the third lens group G3 also increases. Therefore, the Petzval sum increases to the negative side because the positive lens group and the negative lens group cannot be balanced. Even if the refractive power is changed by changing the glass, it is difficult to keep the Petzval sum appropriate. Therefore, the average image plane goes too far to the object side, which is not preferable. On the other hand, when the condition is lower than the lower limit value of the conditional expression (2), the focal length of the second lens group G2 is reduced.
The focal length of each lens is also reduced. Since the curvature radius of each lens surface becomes small, in order to secure the edge thickness of the convex lens, it is necessary to increase the lens thickness, and the rear converter lens RC
Will be longer. For this reason, it is difficult to ensure the necessary back focus.

In order to secure the effect of the present embodiment, the upper limit value of the conditional expression (2) is set to 0.
30 is desirable. On the other hand, in order to ensure the effect of the present embodiment, it is desirable to set the lower limit value of conditional expression (2) to 0.10.

In such a rear converter lens RC, it is preferable that the condition represented by the following conditional expression (3) is satisfied.

2.00 <f3 / (− f2) <4.00 (3)
However,
f2: focal length of the second lens group G2,
f3: focal length of the third lens group G3.

Conditional expression (3) defines an appropriate refractive power distribution between the second lens group G2 and the third lens group G3, and is a conditional expression for favorably correcting the Petzval sum. When the condition exceeds the upper limit value of the conditional expression (3), the appropriate refractive power distribution between the second lens group G2 and the third lens group G3 is lost, and it becomes difficult to properly correct the Petzval sum, When the condition is less than the lower limit value of the conditional expression (3), the focal length of the third lens group G3 becomes small, and the radius of curvature of each lens constituting the third lens group G3 becomes small. It becomes difficult to correct coma aberration appropriately.

In order to secure the effect of the present embodiment, the upper limit value of conditional expression (3) is set to 3.
50 is desirable. On the other hand, in order to ensure the effect of the present embodiment, it is desirable to set the lower limit value of conditional expression (3) to 2.50.

In such a rear converter lens RC, it is preferable that the first lens group G1 is composed of one positive lens and the third lens group G3 is composed of one positive lens. First
By configuring the lens group G1 and the third lens group G3 with a single lens, it is possible to achieve further downsizing and prevent deterioration of coma due to decentering.

In such a rear converter lens RC, it is preferable that the second lens group G2 includes a first negative lens, a positive lens, and a second negative lens arranged in order from the object side along the optical axis. Otherwise, the Petzval sum goes too far to the negative side, making it difficult to maintain a good average image plane.

The second lens group G2 preferably includes a cemented lens in which a first negative lens, a positive lens, and a second negative lens are cemented. By joining the lenses, it is possible to prevent deterioration of coma due to decentering.

Moreover, it is preferable that the first negative lens, the positive lens, and the second negative lens in the cemented lens are bonded together. By sticking the lenses together, it is possible to more reliably prevent coma from deteriorating due to eccentricity.

Moreover, it is preferable that the positive lens in the cemented lens is a biconvex positive lens. With this configuration, spherical aberration can be corrected satisfactorily.

In addition, it is preferable that at least one of the first negative lens and the second negative lens in the cemented lens is a biconcave negative lens. Otherwise, the Petzval sum goes too far to the negative side, making it difficult to maintain a good average image plane.

In order to maintain a good average image plane, it is more preferable that both the first negative lens and the second negative lens in the cemented lens are biconcave negative lenses.

As described above, according to the present embodiment, it is possible to obtain a rear converter lens RC that is small but has good optical performance, and an optical device (digital single-lens reflex camera CAM) including the rear converter lens RC.

Here, a manufacturing method of the rear converter lens RC configured as described above will be described with reference to FIG.
Will be described with reference to FIG. First, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens having a positive refractive power in a cylindrical barrel. The group G3 is incorporated (step ST10). Then, the lens barrel of the rear converter lens RC in which the first lens group G1, the second lens group G2, and the third lens group G3 are incorporated is configured to be detachable from the lens barrel (image side) of the photographing lens ML ( Step ST20).

In step ST10 in which the lens is incorporated, the first lens group G1, the second lens group G2, and the third lens group G3 are disposed so as to satisfy the above-described conditional expression (1). According to such a manufacturing method, it is possible to obtain a rear converter lens RC having a small optical size but good optical performance.

(First embodiment)
Embodiments of the present application will be described below with reference to the accompanying drawings. First, a first embodiment of the present application will be described with reference to FIGS. FIG. 1 is a lens configuration diagram illustrating a state in which the rear converter lens RC (RC1) according to the first example is attached to the photographing lens ML. The rear converter lens RC is detachably attached to the image side of the photographic lens (master lens) ML, and is configured so that the combined focal length when attached to the photographic lens ML is longer than the focal length of the photographic lens ML. Is done. The rear converter lens RC1 according to the first example is
A first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens group G3 having a positive refractive power, which are arranged in order from the object side along the optical axis. Consists of

The first lens group G1 includes a meniscus positive lens L11 having a concave surface directed toward the object side. The second lens group G2 includes a biconcave first negative lens L21, a biconvex positive lens L22, and a biconcave second negative lens L23 that are arranged in order from the object side along the optical axis. It consists of a cemented negative lens. The third lens group G3 includes a biconvex positive lens L31.

Tables 1 to 6 are shown below. These are tables showing the values of specifications of the photographic lens ML and the rear converter lens RC according to the first to sixth examples attached to the photographic lens ML. is there. In [Lens data] of each table, the surface number is the number of each lens surface counted from the object side, R is the radius of curvature of each lens surface, D is the distance between the lens surfaces, and νd is the d-line (wavelength λ = 587.
Abbe number with respect to 6 nm), and nd represents the refractive index with respect to d-line (wavelength λ = 587.6 nm). The radius of curvature “∞” indicates a plane, and the refractive index nd = 1.0000 of air is omitted from the description.

In [Specification Data], f (ML) represents the focal length of the taking lens ML and FNO (
ML) represents the F number of the photographing lens ML, β represents the magnification of the rear converter lens RC, and D0 represents the photographing distance. Further, f is a composite focal length when the rear converter lens RC is attached to the photographing lens ML, FNO is a composite F number when the rear converter lens RC is attached to the photographing lens ML, and 2ω is a rear converter to the photographing lens ML. The combined angle of view (unit: “°”) when the lens RC is attached, Y is the image height when the rear converter lens RC is attached to the taking lens ML, TL is the total length of the rear converter lens, and BF is taken. The back focus when the rear converter lens RC is attached to the lens ML is shown. F1 represents the focal length of the first lens group G1, f2 represents the focal length of the second lens group G2, f3 represents the focal length of the third lens group G3, and fc represents the focal length of the rear converter lens RC. . The total length of the rear converter lens RC is a distance on the optical axis from the most object side surface of the rear converter lens RC to the most image side surface.

[Conditional Expression Corresponding Value] indicates the corresponding value of each conditional expression. The unit of the combined focal length f, curvature radius R, surface distance D, and other lengths listed in all the following specifications is generally “mm”, but the optical system is proportionally enlarged or proportional. Since the same optical performance can be obtained even if the image is reduced, the present invention is not limited to this. In addition, the same reference numerals as those in the present embodiment are used also in the specification values in the second to sixth embodiments described later.

Table 1 below shows specifications in the first embodiment. In Table 1, the 39th surface to the 46th surface.
The radius of curvature R of each surface (each lens surface of the rear converter lens RC1) is 39th in FIG.
Corresponding to reference numerals R39 to R46 attached to the surface to the forty-sixth surface. In Table 1, the object plane corresponds to an object plane (not shown), (aperture) corresponds to the aperture stop S in FIG. 1, and the image plane corresponds to the image plane I in FIG.

(Table 1)
[Lens data]
Surface number R D νd nd
Object ∞ ∞
1 1200.3704 5.0000 64.07 1.516800
2 1199.7897 1.0000
3 188.5541 21.1000 95.13 1.433815
4 -915.9761 20.0000
5 182.4294 17.1000 95.13 1.433815
6 -1837.1348 3.3200
7 -833.5252 7.5000 50.17 1.719995
8 422.3839 75.0000
9 128.8258 6.5000 55.58 1.696797
10 65.1230 16.5000 82.53 1.497820
11 266.7583 52.9670
12 -998.6861 3.5000 42.08 1.799520
13 114.8928 3.0950
14 -354.6811 5.5000 28.70 1.795040
15 -67.4820 3.5000 55.58 1.696797
16 300.9593 27.1872
17 113.3417 6.6000 70.36 1.487490
18 -113.3160 3.2000 28.70 1.795040
19 ∞ 2.2500
20 184.7146 4.7000 58.80 1.518229
21 -184.7146 40.7500
22 ∞ 21.9300 (Aperture)
23 -131.4267 2.0000 55.58 1.696797
24 76.0680 1.5450
25 -1181.7118 6.0000 40.96 1.581439
26 -29.1590 2.0000 82.53 1.497820
27 150.9647 5.2200
28 87.5029 7.0000 37.96 1.603420
29 -36.2560 2.0000 32.36 1.850 260
30 -271.4943 9.0000
31 ∞ 2.0000 63.88 1.516800
32 ∞ 9.0000
33 88.2621 6.0000 52.25 1.517420
34 -88.2621 34.8000
35 -1661.8745 5.4000 70.36 1.487490
36 -42.0520 2.0000 46.56 1.816000
37 68.2950 4.3000 40.96 1.581439
38 -1200.9959 4.0708
39 -960.3839 3.5000 40.96 1.581439
40 -54.1469 2.2000
41 -64.4170 2.0000 67.96 1.593190
42 38.3030 7.5000 40.96 1.581439
43 -38.3030 2.0000 35.73 1.902650
44 108.4110 1.0000
45 64.8598 4.1000 52.25 1.517420
46 -257.2027 BF
Image plane ∞
[Specification data]
f (ML) = 780.00037
FNO (ML) = 5.65772
β = 1.25
D0 = ∞
f = 975.01926
FNO = 7.07229
2ω = 2.52526
Y = 21.633
TL = 22.3
BF = 42.27895
f1 = 98.54993
f2 = -36.5769
f3 = 100.5443
fc = -181.64441
[Conditional expression values]
Conditional expression (1) νn = 67.96
Conditional expression (2) f2 / fc = 0.201
Conditional expression (3) f3 / (− f2) = 2.749

Thus, in the present embodiment, it can be seen that all the conditional expressions (1) to (3) are satisfied.

FIG. 2 is a diagram illustrating various aberrations of the rear converter lens RC1 according to the first example in an infinitely focused state. In each aberration diagram, FNO is a rear converter lens R on the photographing lens ML.
The composite F number when C is attached, Y is the rear converter lens RC to the photographic lens ML
The image height when wearing is shown. In each aberration diagram, d is a d-line (λ = 587.
6 nm) and g indicate aberrations in the g-line (λ = 435.8 nm), respectively. In the aberration diagrams showing astigmatism, the solid line shows the sagittal image plane, and the broken line shows the meridional image plane. The description of the aberration diagrams is the same in the other examples.

From the respective aberration diagrams, it can be seen that in the first example, various aberrations are corrected well and the imaging performance is excellent. As a result, by mounting the rear converter lens RC1 of the first embodiment, excellent optical performance can be secured even in the digital single-lens reflex camera CAM.

(Second embodiment)
Hereinafter, a second embodiment of the present application will be described with reference to FIGS. FIG. 3 is a lens configuration diagram illustrating a state in which the rear converter lens RC (RC2) according to the second example is mounted on the photographing lens ML. The rear converter lens RC2 according to the second example includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, arranged in order from the object side along the optical axis, The third lens group G3 having positive refractive power.

The first lens group G1 includes a biconvex positive lens L11. The second lens group G2 includes a biconcave first negative lens L21, a biconvex positive lens L22, and a biconcave second negative lens L23 that are arranged in order from the object side along the optical axis. It is composed of a cemented negative lens joined together. The third lens group G3 includes a biconvex positive lens L31.

Table 2 below shows specifications in the second embodiment. The 39th surface to the 47th surface in Table 2
The curvature radius R of the surface (each lens surface of the rear converter lens RC2) is 39th in FIG.
This corresponds to reference numerals R39 to R47 attached to the surface to the 47th surface. In Table 2, the object plane corresponds to an object plane (not shown), (aperture) corresponds to the aperture stop S in FIG. 3, and the image plane corresponds to the image plane I in FIG.

(Table 2)
[Lens data]
Surface number R D νd nd
Object ∞ ∞
1 1200.3704 5.0000 64.07 1.516800
2 1199.7897 1.0000
3 188.5541 21.1000 95.13 1.433815
4 -915.9761 20.0000
5 182.4294 17.1000 95.13 1.433815
6 -1837.1348 3.3200
7 -833.5252 7.5000 50.17 1.719995
8 422.3839 75.0000
9 128.8258 6.5000 55.58 1.696797
10 65.1230 16.5000 82.53 1.497820
11 266.7583 52.9670
12 -998.6861 3.5000 42.08 1.799520
13 114.8928 3.0950
14 -354.6811 5.5000 28.70 1.795040
15 -67.4820 3.5000 55.58 1.696797
16 300.9593 27.1872
17 113.3417 6.6000 70.36 1.487490
18 -113.3160 3.2000 28.70 1.795040
19 ∞ 2.2500
20 184.7146 4.7000 58.80 1.518229
21 -184.7146 40.7500
22 ∞ 21.9300 (Aperture)
23 -131.4267 2.0000 55.58 1.696797
24 76.0680 1.5450
25 -1181.7118 6.0000 40.96 1.581439
26 -29.1590 2.0000 82.53 1.497820
27 150.9647 5.2200
28 87.5029 7.0000 37.96 1.603420
29 -36.2560 2.0000 32.36 1.850 260
30 -271.4943 9.0000
31 ∞ 2.0000 63.88 1.516800
32 ∞ 9.0000
33 88.2621 6.0000 52.25 1.517420
34 -88.2621 34.8000
35 -1661.8745 5.4000 70.36 1.487490
36 -42.0520 2.0000 46.56 1.816000
37 68.2950 4.3000 40.96 1.581439
38 -1200.9959 4.0712
39 9247.2848 3.5000 40.96 1.581439
40 -61.8509 2.2000
41 -78.8757 2.0000 67.96 1.593190
42 33.8544 0.5000
43 35.3970 7.5000 40.96 1.581439
44 -40.7487 2.0000 35.73 1.902650
45 89.1658 1.0000
46 52.2475 4.1000 52.25 1.517420
47 -476.2678 BF
Image plane ∞
[Specification data]
f (ML) = 780.00037
FNO (ML) = 5.65772
β = 1.25
D0 = ∞
f = 975.01926
FNO = 7.07229
2ω = 2.53414
Y = 21.633
TL = 22.8
BF = 41.82887
f1 = 105.68337
f2 = -36.0749
f3 = 91.23609
fc = -181.64441
[Conditional expression values]
Conditional expression (1) νn = 67.96
Conditional expression (2) f2 / fc = 0.199
Conditional expression (3) f3 / (− f2) = 2.529

Thus, in the present embodiment, it can be seen that all the conditional expressions (1) to (3) are satisfied.

FIG. 4 is a diagram of various aberrations of the rear converter lens RC2 according to Example 2 in the infinitely focused state. From the respective aberration diagrams, it can be seen that in the second example, various aberrations are satisfactorily corrected and the imaging performance is excellent. As a result, by mounting the rear converter lens RC2 of the second embodiment, excellent optical performance can be secured even in the digital single-lens reflex camera CAM.

(Third embodiment)
Hereinafter, the third embodiment of the present application will be described with reference to FIGS. FIG. 5 is a lens configuration diagram illustrating a state where the rear converter lens RC (RC3) according to the third example is mounted on the photographing lens ML. The rear converter lens RC3 according to the third example includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, arranged in order from the object side along the optical axis, The third lens group G3 having positive refractive power.

The first lens group G1 includes a biconvex positive lens L11. In the second lens group G2, a biconcave first negative lens L21 arranged in order from the object side along the optical axis and a meniscus positive lens L22 having a convex surface facing the object side are bonded and joined. A cemented negative lens;
It is composed of a biconcave second negative lens L23. The third lens group G3 includes a biconvex positive lens L31.

Table 3 below shows specifications in the third embodiment. The 39th surface to the 47th surface in Table 3
The curvature radius R of the surface (each lens surface of the rear converter lens RC3) is 39th in FIG.
This corresponds to reference numerals R39 to R47 attached to the surface to the 47th surface. In Table 3, the object plane corresponds to an object plane (not shown), (aperture) corresponds to the aperture stop S in FIG. 5, and the image plane corresponds to the image plane I in FIG.

(Table 3)
[Lens data]
Surface number R D νd nd
Object ∞ ∞
1 1200.3704 5.0000 64.07 1.516800
2 1199.7897 1.0000
3 188.5541 21.1000 95.13 1.433815
4 -915.9761 20.0000
5 182.4294 17.1000 95.13 1.433815
6 -1837.1348 3.3200
7 -833.5252 7.5000 50.17 1.719995
8 422.3839 75.0000
9 128.8258 6.5000 55.58 1.696797
10 65.1230 16.5000 82.53 1.497820
11 266.7583 52.9670
12 -998.6861 3.5000 42.08 1.799520
13 114.8928 3.0950
14 -354.6811 5.5000 28.70 1.795040
15 -67.4820 3.5000 55.58 1.696797
16 300.9593 27.1872
17 113.3417 6.6000 70.36 1.487490
18 -113.3160 3.2000 28.70 1.795040
19 ∞ 2.2500
20 184.7146 4.7000 58.80 1.518229
21 -184.7146 40.7500
22 ∞ 21.9300 (Aperture)
23 -131.4267 2.0000 55.58 1.696797
24 76.0680 1.5450
25 -1181.7118 6.0000 40.96 1.581439
26 -29.1590 2.0000 82.53 1.497820
27 150.9647 5.2200
28 87.5029 7.0000 37.96 1.603420
29 -36.2560 2.0000 32.36 1.850 260
30 -271.4943 9.0000
31 ∞ 2.0000 63.88 1.516800
32 ∞ 9.0000
33 88.2621 6.0000 52.25 1.517420
34 -88.2621 34.8000
35 -1661.8745 5.4000 70.36 1.487490
36 -42.0520 2.0000 46.56 1.816000
37 68.2950 4.3000 40.96 1.581439
38 -1200.9959 4.0686
39 56.3144 4.5000 35.27 1.592700
40 -67.5953 2.2000
41 -67.6481 2.0000 35.73 1.902650
42 29.3709 4.8000 33.73 1.647690
43 82.8413 2.5000
44 -68.3939 2.0000 67.96 1.593190
45 145.2014 1.0000
46 61.9808 6.0000 52.25 1.517420
47 -76.77700 BF
Image plane ∞
[Specification data]
f (ML) = 780.00037
FNO (ML) = 5.65772
β = 1.25
D0 = ∞
f = 975.01926
FNO = 7.07229
2ω = 2.52112
Y = 21.633
TL = 25.0
BF = 38.49503
f1 = 52.54182
f2 = -21.9673
f3 = 67.27265
fc = -181.64441
[Conditional expression values]
Conditional expression (1) νn = 67.96
Conditional expression (2) f2 / fc = 0.121
Conditional expression (3) f3 / (− f2) = 3.062

Thus, in the present embodiment, it can be seen that all the conditional expressions (1) to (3) are satisfied.

FIG. 6 is a diagram illustrating various aberrations of the rear converter lens RC3 according to the third example in the infinite focus state. From the respective aberration diagrams, it can be seen that in the third example, various aberrations are satisfactorily corrected and the imaging performance is excellent. As a result, by mounting the rear converter lens RC3 of the third embodiment, excellent optical performance can be secured even in the digital single-lens reflex camera CAM.

(Fourth embodiment)
Hereinafter, a fourth embodiment of the present application will be described with reference to FIGS. FIG. 7 is a lens configuration diagram illustrating a state in which the rear converter lens RC (RC4) according to the fourth example is mounted on the photographing lens ML. The rear converter lens RC4 according to the fourth example includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, arranged in order from the object side along the optical axis, The third lens group G3 having positive refractive power.

The first lens group G1 includes a meniscus positive lens L11 having a concave surface directed toward the object side. The second lens group G2 includes a biconcave first negative lens L21, a biconvex positive lens L22, and a biconcave second negative lens L23 that are arranged in order from the object side along the optical axis. It consists of a cemented negative lens. The third lens group G3 includes a biconvex positive lens L31.

Table 4 below shows specifications in the fourth embodiment. The 39th surface to the 46th surface in Table 4
The curvature radius R of the surface (each lens surface of the rear converter lens RC4) is 39th in FIG.
Corresponding to reference numerals R39 to R46 attached to the surface to the forty-sixth surface. In Table 4, the object plane corresponds to an object plane (not shown), (aperture) corresponds to the aperture stop S in FIG. 7, and the image plane corresponds to the image plane I in FIG.

(Table 4)
[Lens data]
Surface number R D νd nd
Object ∞ ∞
1 1200.3704 5.0000 64.07 1.516800
2 1199.7897 1.0000
3 188.5541 21.1000 95.13 1.433815
4 -915.9761 20.0000
5 182.4294 17.1000 95.13 1.433815
6 -1837.1348 3.3200
7 -833.5252 7.5000 50.17 1.719995
8 422.3839 75.0000
9 128.8258 6.5000 55.58 1.696797
10 65.1230 16.5000 82.53 1.497820
11 266.7583 52.9670
12 -998.6861 3.5000 42.08 1.799520
13 114.8928 3.0950
14 -354.6811 5.5000 28.70 1.795040
15 -67.4820 3.5000 55.58 1.696797
16 300.9593 27.1872
17 113.3417 6.6000 70.36 1.487490
18 -113.3160 3.2000 28.70 1.795040
19 ∞ 2.2500
20 184.7146 4.7000 58.80 1.518229
21 -184.7146 40.7500
22 ∞ 21.9300 (Aperture)
23 -131.4267 2.0000 55.58 1.696797
24 76.0680 1.5450
25 -1181.7118 6.0000 40.96 1.581439
26 -29.1590 2.0000 82.53 1.497820
27 150.9647 5.2200
28 87.5029 7.0000 37.96 1.603420
29 -36.2560 2.0000 32.36 1.850 260
30 -271.4943 9.0000
31 ∞ 2.0000 63.88 1.516800
32 ∞ 9.0000
33 88.2621 6.0000 52.25 1.517420
34 -88.2621 34.8000
35 -1661.8745 5.4000 70.36 1.487490
36 -42.0520 2.0000 46.56 1.816000
37 68.2950 4.3000 40.96 1.581439
38 -1200.9959 4.0730
39 -3536.9959 3.3000 40.96 1.581439
40 -42.9253 2.1000
41 -41.9958 1.9000 60.20 1.640000
42 38.9019 7.0000 40.96 1.581439
43 -52.7326 1.7000 35.73 1.902650
44 168.8361 1.0000
45 69.4023 3.8000 82.57 1.497820
46 -266.0409 BF
Image plane ∞
[Specification data]
f (ML) = 780.00037
FNO (ML) = 5.65772
β = 1.25
D0 = ∞
f = 974.99771
FNO = 7.07213
2ω = 2.5297
Y = 21.6
TL = 20.8
BF = 44.08093
f1 = 74.70697
f2 = -34.0459
f3 = 110.9862
fc = -197.345
[Conditional expression values]
Conditional expression (1) νn = 60.2
Conditional expression (2) f2 / fc = 0.173
Conditional expression (3) f3 / (− f2) = 3.26

Thus, in the present embodiment, it can be seen that all the conditional expressions (1) to (3) are satisfied.

FIG. 8 is a diagram of various aberrations of the rear converter lens RC4 according to the fourth example in the infinitely focused state. From the respective aberration diagrams, it can be seen that in the fourth example, various aberrations are corrected satisfactorily and the imaging performance is excellent. As a result, by mounting the rear converter lens RC4 of the fourth embodiment, excellent optical performance can be secured even in the digital single-lens reflex camera CAM.

(5th Example)
Hereinafter, a fifth embodiment of the present application will be described with reference to FIGS. 9 to 10 and Table 5. FIG. FIG.
It is a lens block diagram which shows the state with which the rear converter lens RC (RC5) based on 5th Example was mounted | worn with the imaging lens ML. The rear converter lens RC5 according to the fifth example includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, arranged in order from the object side along the optical axis, The third lens group G3 having positive refractive power.

The first lens group G1 includes a meniscus positive lens L11 having a concave surface directed toward the object side. The second lens group G2 is a cemented negative lens in which a biconcave first negative lens L21 and a biconvex positive lens L22 are bonded and joined in order from the object side along the optical axis.
It is composed of a biconcave second negative lens L23. The third lens group G3 includes a biconvex positive lens L31.

Table 5 below shows specifications in the fifth embodiment. The 39th surface to the 47th surface in Table 5
The curvature radius R of the surface (each lens surface of the rear converter lens RC5) is the 39th in FIG.
This corresponds to reference numerals R39 to R47 attached to the surface to the 47th surface. In Table 5, the object plane corresponds to an object plane (not shown), (aperture) corresponds to the aperture stop S in FIG. 9, and the image plane corresponds to the image plane I in FIG.

(Table 5)
[Lens data]
Surface number R D νd nd
Object ∞ ∞
1 1200.3704 5.0000 64.07 1.516800
2 1199.7897 1.0000
3 188.5541 21.1000 95.13 1.433815
4 -915.9761 20.0000
5 182.4294 17.1000 95.13 1.433815
6 -1837.1348 3.3200
7 -833.5252 7.5000 50.17 1.719995
8 422.3839 75.0000
9 128.8258 6.5000 55.58 1.696797
10 65.1230 16.5000 82.53 1.497820
11 266.7583 52.9670
12 -998.6861 3.5000 42.08 1.799520
13 114.8928 3.0950
14 -354.6811 5.5000 28.70 1.795040
15 -67.4820 3.5000 55.58 1.696797
16 300.9593 27.1872
17 113.3417 6.6000 70.36 1.487490
18 -113.3160 3.2000 28.70 1.795040
19 ∞ 2.2500
20 184.7146 4.7000 58.80 1.518229
21 -184.7146 40.7500
22 ∞ 21.9300 (Aperture)
23 -131.4267 2.0000 55.58 1.696797
24 76.0680 1.5450
25 -1181.7118 6.0000 40.96 1.581439
26 -29.1590 2.0000 82.53 1.497820
27 150.9647 5.2200
28 87.5029 7.0000 37.96 1.603420
29 -36.2560 2.0000 32.36 1.850 260
30 -271.4943 9.0000
31 ∞ 2.0000 63.88 1.516800
32 ∞ 9.0000
33 88.2621 6.0000 52.25 1.517420
34 -88.2621 34.8000
35 -1661.8745 5.4000 70.36 1.487490
36 -42.0520 2.0000 46.56 1.816000
37 68.2950 4.3000 40.96 1.581439
38 -1200.9959 4.0727
39 -533.6954 4.0000 45.51 1.548140
40 -35.8956 1.5000
41 -34.5247 1.5000 67.96 1.593190
42 28.1295 6.5000 45.51 1.548140
43 -83.8396 1.0000
44 -82.0601 1.5000 35.73 1.902650
45 113.8314 0.8000
46 57.0026 4.5000 82.57 1.497820
47 -174.6539 BF
Image plane ∞
[Specification data]
f (ML) = 780.00037
FNO (ML) = 5.65772
β = 1.25
D0 = ∞
f = 975.00675
FNO = 7.07220
2ω = 2.53522
Y = 21.633
TL = 21.3
BF = 44.33118
f1 = 70.00911
f2 = -30.5352
f3 = 86.88986
fc = -212.86000
[Conditional expression values]
Conditional expression (1) νn = 67.96
Conditional expression (2) f2 / fc = 0.143
Conditional expression (3) f3 / (− f2) = 2.846

Thus, in the present embodiment, it can be seen that all the conditional expressions (1) to (3) are satisfied.

FIG. 10 is a diagram of various aberrations of the rear converter lens RC5 according to Example 5 in the infinitely focused state. From the respective aberration diagrams, it can be seen that in the fifth example, various aberrations are corrected satisfactorily and the imaging performance is excellent. As a result, the rear converter lens RC5 of the fifth embodiment
By mounting the, excellent optical performance can be secured even in the digital single-lens reflex camera CAM.

(Sixth embodiment)
Hereinafter, a sixth embodiment of the present application will be described with reference to FIGS. FIG.
These are lens block diagrams which show the state with which the rear converter lens RC (RC6) based on 6th Example was mounted | worn with the imaging lens ML. The rear converter lens RC6 according to the sixth example includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, arranged in order from the object side along the optical axis, The third lens group G3 having positive refractive power.

The first lens group G1 includes a meniscus positive lens L11 having a concave surface directed toward the object side. The second lens group G2 includes a biconcave first negative lens L21, a biconvex positive lens L22, and a biconcave second negative lens L23 that are arranged in order from the object side along the optical axis. It consists of a cemented negative lens. The third lens group G3 includes a biconvex positive lens L31.

Table 6 below shows specifications of the sixth embodiment. In Table 6, the 39th surface to the 46th surface.
The curvature radius R of the surface (each lens surface of the rear converter lens RC6) is the third radius in FIG.
This corresponds to the symbols R39 to R46 attached to the ninth surface to the forty-sixth surface. In Table 6, the object plane corresponds to an object plane (not shown), (aperture) corresponds to the aperture stop S in FIG. 11, and the image plane corresponds to the image plane I in FIG.

(Table 6)
[Lens data]
Surface number R D νd nd
Object ∞ ∞
1 1200.3704 5.0000 64.07 1.516800
2 1199.7897 1.0000
3 188.5541 21.1000 95.13 1.433815
4 -915.9761 20.0000
5 182.4294 17.1000 95.13 1.433815
6 -1837.1348 3.3200
7 -833.5252 7.5000 50.17 1.719995
8 422.3839 75.0000
9 128.8258 6.5000 55.58 1.696797
10 65.1230 16.5000 82.53 1.497820
11 266.7583 52.9670
12 -998.6861 3.5000 42.08 1.799520
13 114.8928 3.0950
14 -354.6811 5.5000 28.70 1.795040
15 -67.4820 3.5000 55.58 1.696797
16 300.9593 27.1872
17 113.3417 6.6000 70.36 1.487490
18 -113.3160 3.2000 28.70 1.795040
19 ∞ 2.2500
20 184.7146 4.7000 58.80 1.518229
21 -184.7146 40.7500
22 ∞ 21.9300 (Aperture)
23 -131.4267 2.0000 55.58 1.696797
24 76.0680 1.5450
25 -1181.7118 6.0000 40.96 1.581439
26 -29.1590 2.0000 82.53 1.497820
27 150.9647 5.2200
28 87.5029 7.0000 37.96 1.603420
29 -36.2560 2.0000 32.36 1.850 260
30 -271.4943 9.0000
31 ∞ 2.0000 63.88 1.516800
32 ∞ 9.0000
33 88.2621 6.0000 52.25 1.517420
34 -88.2621 34.8000
35 -1661.8745 5.4000 70.36 1.487490
36 -42.0520 2.0000 46.56 1.816000
37 68.2950 4.3000 40.96 1.581439
38 -1200.9959 4.0932
39 -113.5262 3.3000 40.96 1.581439
40 -42.0931 1.6000
41 -75.4602 1.5000 67.96 1.593190
42 24.6999 9.5000 40.96 1.581439
43 -26.4418 1.5000 35.73 1.902650
44 127.3187 0.8000
45 55.0932 4.0000 52.25 1.517420
46 -296.3380 BF
Image plane ∞
[Specification data]
f (ML) = 780.00037
FNO (ML) = 5.65772
β = 1.4
D0 = ∞
f = 1092.00287
FNO = 7.92083
2ω = 2.2638
Y = 21.633
TL = 22.2
BF = 49.52949
f1 = 113.13268
f2 = -34.7194
f3 = 90.13447
fc = -137.70300
[Conditional expression values]
Conditional expression (1) νn = 67.96
Conditional expression (2) f2 / fc = 0.552
Conditional expression (3) f3 / (− f2) = 2.596

Thus, in the present embodiment, it can be seen that all the conditional expressions (1) to (3) are satisfied.

FIG. 12 is a diagram of various aberrations of the rear converter lens RC6 according to Example 6 in the infinitely focused state. From the respective aberration diagrams, it can be seen that in the sixth example, various aberrations are satisfactorily corrected and the imaging performance is excellent. As a result, the rear converter lens RC6 of the sixth embodiment
By mounting the, excellent optical performance can be secured even in the digital single-lens reflex camera CAM.

As described above, according to each embodiment, it is possible to provide a rear converter lens RC having a high magnification and a small and excellent imaging performance that can be sufficiently adapted to a digital still camera.

In the above-described embodiment, the following description can be appropriately adopted as long as the optical performance is not impaired.

In each of the above-described embodiments, the photographing lens ML having the same configuration is shown. However, the photographing lens ML is merely an example, and the configuration of the photographing lens (master lens) is not limited thereto.

Further, the lens surface may be formed as a spherical surface, a flat surface, or an aspheric surface.
When the lens surface is a spherical surface or a flat surface, lens processing and assembly adjustment are facilitated, and optical performance deterioration due to errors in processing and assembly adjustment can be prevented. Further, even when the image plane is deviated, it is preferable because there is little deterioration in drawing performance. When the lens surface is an aspheric surface, the aspheric surface is an aspheric surface by grinding, a glass mold aspheric surface made of glass with an aspheric shape, or a composite aspheric surface made of resin with an aspheric shape on the glass surface. Any aspherical surface may be used. The lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

Each lens surface may be provided with an antireflection film having a high transmittance in a wide wavelength region in order to reduce flare and ghost and achieve high optical performance with high contrast.

CAM digital SLR camera (optical equipment)
ML Shooting lens RC Rear converter lens G1 First lens group G2 Second lens group G3 Third lens group I Image plane

Claims (12)

A rear converter lens that is detachably attached to the image side of the photographic lens, and is configured so that a combined focal length in a state of being attached to the photographic lens is longer than a focal length of the photographic lens,
A first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power, arranged in order from the object side along the optical axis. ,
A rear converter lens that satisfies the following conditional expression:
54.0 <νn <75.0
However,
νn: Abbe number of at least one negative lens in the rear converter lens. The rear converter lens according to claim 1, wherein the following conditional expression is satisfied.
0.05 <f2 / fc <0.35
However,
f2: focal length of the second lens group,
fc: focal length of the rear converter lens. The rear converter lens according to claim 1, wherein the following conditional expression is satisfied.
2.00 <f3 / (− f2) <4.00
However,
f2: focal length of the second lens group,
f3: focal length of the third lens group. The first lens group includes one positive lens,
The rear converter lens according to any one of claims 1 to 3, wherein the third lens group includes one positive lens. The said 2nd lens group has a 1st negative lens, a positive lens, and a 2nd negative lens arranged in order from the object side along the optical axis, The any one of Claim 1 to 4 characterized by the above-mentioned. The listed rear converter lens. The rear converter lens according to claim 5, wherein the second lens group includes a cemented lens in which the first negative lens, the positive lens, and the second negative lens are cemented. The rear converter lens according to claim 6, wherein the first negative lens, the positive lens, and the second negative lens in the cemented lens are bonded together. The rear converter lens according to claim 5, wherein the positive lens in the cemented lens is a biconvex positive lens. 9. The rear converter lens according to claim 8, wherein at least one of the first negative lens and the second negative lens in the cemented lens is a biconcave negative lens. The rear converter lens according to claim 8, wherein both the first negative lens and the second negative lens in the cemented lens are biconcave negative lenses. An optical device capable of mounting a rear converter lens between the device body and the taking lens,
The optical device, wherein the rear converter lens is the rear converter lens according to any one of claims 1 to 10. A method of manufacturing a rear converter lens that is detachably attached to the image side of a photographic lens, and is configured such that a combined focal length when attached to the photographic lens is longer than a focal length of the photographic lens. ,
A first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power are disposed in order from the object side along the optical axis.
A manufacturing method of a rear converter lens characterized by satisfying the following conditional expression:
54.0 <νn <75.0
However,
νn: Abbe number of at least one negative lens in the rear converter lens.

Images