JP3276337B2 - Attachment lens for close-up - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photographic lens (main lens) of a camera which is mounted on an object side and has a magnification of -0.5 to -1.0.
The present invention relates to a replacement attachment lens for enabling close-up close-up photographing of about twice.

[0002]

2. Description of the Related Art As an attachment lens for close-up photography,
2. Description of the Related Art Conventionally, for example, a lens described in JP-A-3-39917 or JP-A-5-224121 has been known. Each of the lenses described in these publications has a three-lens configuration in which two positive lenses and one negative lens are combined.

[0003]

The lens disclosed in Japanese Unexamined Patent Publication No. 3-39917 has a relatively high magnification of -1.1 to -2.1 times, so that the correction of spherical aberration and chromatic aberration of magnification is insufficient. There's a problem. On the other hand, the lens disclosed in Japanese Patent Application Laid-Open No. 5-224121 has a magnification of -0.09 to -0.80 times and does not reach the same magnification, and a magnification of -0.5 times to -1.0 times which is the object of the present invention. Cannot be used for attachment lens applications. In addition, astigmatism and distortion are relatively large.

Generally, in order to correct aberrations well,
It is effective to reduce the power of each lens, but if the power is reduced too much, the overall length increases and the diameter of the lens on the object side increases. Normally, a camera lens is provided with a mounting portion having a screw groove for mounting an accessory such as a filter on the innermost wall of the lens barrel on the most object side, but when the diameter of the attachment lens on the object side becomes large. In addition, the inside diameter of the attachment part of the attachment lens becomes larger than the inside diameter of the attachment part of the main lens, and a plurality of types of accessories must be prepared according to the diameter of each attachment part.

The present invention has been made in view of the above-mentioned problems of the prior art, and various aberrations have been favorably corrected at a magnification of about 0.5 to 1.0 without increasing the diameter of the lens on the object side. It is an object of the present invention to provide a close-up attachment lens.

[0006]

The close-up attachment lens according to the present invention comprises, in order from the object side, a first positive lens, a second negative lens, and a third meniscus lens convex to the image side. And satisfy the following conditions. 0.005 <d2 / fA <0.040 · ‥ (1) 0.010 <(d2 + d4) / fA <0.060 (2) where di is the distance between the i-th surface and the i + 1-th surface, and fA is This is the focal length of the attachment lens.

Further, the present invention is characterized in that it has a configuration satisfying the following conditions. 0.400 <(r1 + r2) / (r2−r1) <1.000 (3) where ri is the radius of curvature of the i-th surface.

Further, the present invention is characterized in that the configuration satisfies the following conditions. 0.300 <(r3 + r4) / (r4−r3) <0.700 · ‥ (4) where ri is the radius of curvature of the i-th surface.

Further, the present invention is characterized in that the configuration satisfies the following conditions. 1.70 <n1 (5) where n1 is the refractive index of the first lens.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an attachment lens for close-up photography according to the present invention will be described below. For example, FIG.
As shown in FIG. 1, the close-up attachment lens LA of the embodiment is attached to the object side of the main lens LM, and is used for close-up photography. The close-up attachment lens LA
The triplet type is composed of, in order from the object side, a first positive lens, a second negative lens, and a third meniscus lens convex toward the image side. The close-up attachment lens LA is designed so that various aberrations are corrected independently, and is used by being attached to the main lens LM whose various aberrations are corrected independently.

The main lens LM is composed of six elements in two groups. The front group has first to third lenses LM1 to LM3, and the rear group has fourth to sixth lenses.
Each of the lenses LM4 to LM6 is constituted by three lenses.

The close-up attachment lens LA satisfies the following conditions. 0.005 <d2 / fA <0.040 (1) 0.010 <(d2 + d4) / fA <0.060 (2) where di is the distance between the i-th surface and the i + 1-th surface, and fA is the attachment. This is the focal length of the lens.

The close-up attachment lens LA further satisfies the following conditions. 0.400 <(r1 + r2) / (r2-r1) <1.000 (3) where ri is the radius of curvature of the i-th surface.

The close-up attachment lens LA further satisfies the following conditions. 0.300 <(r3 + r4) / (r4-r3) <0.700 (4) where ri is the radius of curvature of the i-th surface.

The close-up attachment lens LA further satisfies the following condition. 1.70 <n1 (5) where n1 is the refractive index of the first lens.

Condition (1) is that the first lens Ll and the second lens L
Specify the interval with 2. By satisfying this condition,
It is possible to prevent the diameter of the first lens Ll from becoming excessive while suppressing the amount of aberration generated in the first lens Ll. When the value goes below the lower limit of the condition (1), the distance between the lenses becomes too short, so that the power of each lens becomes excessive, and it becomes difficult to correct spherical aberration and chromatic aberration. If the upper limit is exceeded, the lens diameter of the first lens becomes large in order to secure the angle of view of the main lens.

The condition (2) defines the sum of the lens intervals of the three lenses. By satisfying this condition, it is possible to suppress the aberration generated in each lens and to prevent the whole from becoming large. When the value is below the lower limit of the condition (2), the power of each lens becomes excessively large, and it becomes difficult to correct aberrations such as spherical aberration and the Petzval sum becomes large, so that it becomes difficult to correct the field curvature. If the upper limit is exceeded, the lens diameter of the first lens increases in order to secure the angle of view of the main lens, and the overall size increases.

Condition (3) defines the shape of the first lens L1. By satisfying this condition, field curvature and distortion can be kept small. When the value goes below the lower limit of the condition (3), the curvature of field becomes under, and the distortion increases in the plus direction. If you exceed the upper limit,
The field curvature is over.

Condition (4) defines the shape of the second lens L2. By satisfying this condition, spherical aberration, field curvature, and distortion can be kept small. When the value goes below the lower limit of the condition (4), the curvature of field becomes under, and the distortion increases in the plus direction. When the value exceeds the upper limit, the curvature of the object-side surface of the second lens L2 increases, the spherical aberration increases, the coma aberration increases, and the curvature of field increases.

The condition (5) defines the refractive index of the first lens Ll. By using a glass material having a high refractive index for the first positive lens Ll so as to satisfy this condition, the Petzval sum of the attachment lens LA is suppressed, and the attachment lens LA
Aberration correction can be performed independently. When the value goes below the lower limit of the condition (5), the Petzval sum becomes excessively large, and it becomes difficult to correct the field curvature.

EXAMPLES Next, three specific examples satisfying each condition of the above-described embodiment will be presented.

[0021]

FIG. 1 shows a lens configuration in which the close-up attachment lens LA according to the first embodiment is attached to a main lens LM, and the main lens is focused on an object at infinity. FIG.
3 is a diagram of various aberrations of the entire system in the state of FIG. FIG. 3 is a lens configuration diagram in a state where the main lens is focused on a subject at the shortest focusing distance, and FIG. 4 is a diagram of various aberrations of the entire system in the state in FIG.

2 and 4, (A) shows the spherical aberration SA and the sine condition SC at the d-line, and (B) shows the d-line (wavelength 588n).
m), g-line (wavelength 436 nm), chromatic aberration represented by spherical aberration at C line (wavelength 656 nm), (C) is chromatic aberration of magnification at g-line and C-line based on d-line, and (D) is non-chromatic. Point aberration (S: sagittal, M: meridional), (E) shows distortion. The unit of the horizontal axis indicating the distortion amount is percent (%), and the unit of the horizontal axis indicating the other aberration amounts is mm.
Symbol FNO. Is the F-number and Y is the image height.

Table 1 shows a specific numerical configuration of the entire lens system of the first embodiment. In the table, FNO. Is the F number of the whole system, M is the magnification of the whole system, fA is the focal length of the attachment lens [unit: mm], r is the radius of curvature of each lens surface [unit: m]
m] and d are the lens thickness or lens interval [unit: mm], nd is the refractive index of each lens at d line (wavelength 588 nm), and νd is the Abbe number of each lens. Surface numbers 1 to 6 are the close-up attachment lens LA, and surface numbers 7 to 16 are the main lens LM. In addition,
"~" For numerical values that change with focusing
On the left side of the figure, the value at the time of focusing on infinity is shown, and the right side shows the value at the time of focusing on the shortest focusing distance. Although not shown, a stop is provided between the eleventh surface and the twelfth surface, and the distance between the stop and the twelfth surface is fixed at 4.00 mm.

[0024]

【table 1】

[0025]

Second Embodiment FIG. 5 shows a lens configuration in which a close-up attachment lens LA according to a second embodiment is attached to a main lens LM and the main lens is focused on an object at infinity. FIG.
6 is a diagram of various aberrations of the entire system in the state of FIG. Also figure
7 is a lens configuration diagram in a state where the main lens is focused on the subject at the shortest focusing distance, and FIG. 8 is a diagram of various aberrations of the entire system in the state in FIG.

Table 2 shows a specific numerical configuration of the attachment lens LA according to the second embodiment. The main lens LM
Is the same as Example 1 shown by surface numbers 7 to 16 in Table 1, and therefore the description is omitted, and only the structure (surface numbers 1 to 6) of the attachment lens LA is shown.

[0027]

[Table 2]

[0028]

Third Embodiment FIG. 9 shows a lens configuration in which the close-up attachment lens LA according to the third embodiment is attached to a main lens LM, and the main lens is focused on an object at infinity. FIG.
0 is an aberration diagram of the entire system in the state of FIG. Also,
FIG. 11 is a lens configuration diagram in a state where the main lens is focused on a subject at the shortest focusing distance, and FIG. 12 is a diagram of various aberrations of the entire system in the state in FIG.

Table 3 shows a specific numerical configuration of the attachment lens LA according to the third embodiment. The main lens LM
Is the same as Example 1 shown by surface numbers 7 to 16 in Table 1, and therefore the description is omitted, and only the structure (surface numbers 1 to 6) of the attachment lens LA is shown. In the third embodiment, only the value of d11 when focused on the shortest focusing distance is 15.60 mm unlike the first and second embodiments.

[0030]

[Table 3]

The following Table 4 shows that each of the examples is based on the condition (1) described above.
It shows the value to be taken for ~ (5). All the examples satisfy all the conditions, and can obtain good performance.

[0032]

[Table 4]

[0033]

As described above, according to the present invention, it is possible to increase the cultivation rate without increasing the diameter of the object side lens.
It is possible to provide a triplet type close-up attachment lens in which various aberrations are satisfactorily corrected by about 5 to 1.0 times.

[Brief description of the drawings]

FIG. 1 is a lens diagram showing a state in which a close-up attachment lens according to a first embodiment is attached to a main lens, and the main lens is focused on an object at infinity.

FIG. 2 is a diagram showing various aberrations of the entire system in the state of FIG. 1;
(A) shows spherical aberration, (B) shows chromatic aberration, (C) shows chromatic aberration of magnification, (D) shows astigmatism, and (E) shows distortion.

FIG. 3 is a lens diagram showing a state where the close-up attachment lens according to the first embodiment is attached to a main lens, and the main lens is focused on a subject having a shortest focusing distance.

FIG. 4 is a diagram showing various aberrations of the entire system in the state of FIG. 1;
(A) shows spherical aberration, (B) shows chromatic aberration, (C) shows chromatic aberration of magnification, (D) shows astigmatism, and (E) shows distortion.

FIG. 5 is a lens diagram showing a state in which the close-up attachment lens according to the second embodiment is attached to a main lens, and the main lens is focused on a subject at infinity.

FIG. 6 is a diagram illustrating various aberrations of the entire system in the state of FIG. 5;
(A) shows spherical aberration, (B) shows chromatic aberration, (C) shows chromatic aberration of magnification, (D) shows astigmatism, and (E) shows distortion.

FIG. 7 is a lens diagram illustrating a state in which the close-up attachment lens according to the second embodiment is attached to a main lens, and the main lens is focused on a subject having a shortest focusing distance.

FIG. 8 is a diagram illustrating various aberrations of the entire system in the state of FIG. 7;
(A) shows spherical aberration, (B) shows chromatic aberration, (C) shows chromatic aberration, (D) shows astigmatism, and (E) shows distortion.

FIG. 9 is a lens diagram showing a state in which the close-up attachment lens according to the third embodiment is attached to a main lens, and the main lens is focused on a subject at infinity.

FIG. 10 is a diagram illustrating various aberrations of the entire system in the state of FIG. 9;
(A) shows spherical aberration, (B) shows chromatic aberration, (C) shows chromatic aberration of magnification, (D) shows astigmatism, and (E) shows distortion.

FIG. 11 is a lens diagram illustrating a state in which the close-up attachment lens according to the third embodiment is attached to a main lens, and the main lens is focused on a subject having a shortest focusing distance.

12 is a diagram of various aberrations of the entire system in the state of FIG. 11, where (A) is spherical aberration, (B) is chromatic aberration, (C) is lateral chromatic aberration, (D) is astigmatism, and (E) is The respective distortions are shown.

[Explanation of symbols]

 LA Close-up attachment lens L1 First lens L2 Second lens L3 Third lens LM Main lens

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G02B 9/00-17/08 G02B 21/02-21/04 G02B 25/00-25/04

Claims (4)

(57) [Claims] 1. A close-up attachment lens which enables close-up by being mounted on an object side of a main lens, wherein in order from the object side, a first positive lens, a second negative lens, and a positive lens convex to the image side. Consisting of a meniscus third lens,
The following condition: 0.005 <d2 / fA <0.040 (1) 0.010 <(d2 + d4) / fA <0.060 (2) where di is the distance between the i-th surface and the i + 1-th surface. , FA is the focal length of the attachment lens, satisfying the close-up attachment lens. 2. The close-up attachment lens according to claim 1, further comprising the following condition: 0.400 <(r1 + r2) / (r2-r1) <1.000 (3) where ri is the i-th surface Attachment lens for close-up photography that satisfies the curvature radius of 3. The close-up attachment lens according to claim 1 or 2, further comprising the following condition: 0.300 <(r3 + r4) / (r4-r3) <0.700 (4) An attachment lens for close-up photography that satisfies the curvature radius of the i-plane. 4. The close-up attachment lens according to claim 1, further comprising the following condition: 1.70 <n1 (5), where n1 is a refractive index of the first lens. An attachment lens for close-up photography.