JPH02134610A - Large-aperture-ratio lens capable of close-up photography - Google Patents

Abstract

PURPOSE:To use the lens a microlens for ENG by specifying the respective conditions of 1st-3rd lens groups and making the back focus and exit pupil long. CONSTITUTION:The 1st lens group I consists of a 1st group G1 of a positive lens and a 2nd group G2 of a negative meniscus lens, the 2nd lens group II consists of a 3rd lens group G3 of a cemented lens of a negative and a positive lens, a 4th group G4 of a positive lens, and a 5th group G5, and the 3rd lens group III consists of a 6th group G6 of a compound lens of at least one concave lens and one convex lens; and respective requirements shown by inequalities I-IV are met and the back focus and exit pupil are made long. In the inequalities I-IV, (f) is the focal length of the whole system, fI the composite focal length of the 1st lens group I, fII the composite focal length of the 2nd lens group II, D3 the composite thickness of the 3rd group G3, concave lens, and convex lens in the 2nd lens group II, Ds3 the gap from a stop to the 3rd group G3 in the 2nd lens group II, and nu the Abbe number of the 1st group I. Consequently, the lens for short-distance photography which has aberrations compensated excellently is obtained.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides a close-up camera that has a large aperture ratio, has an extremely long back focus and exit pupil, and has excellent aberration correction from an infinite object distance to a photographic magnification of 2x. Regarding a large aperture ratio lens that can take pictures.

(Prior art) News TV lenses called ENG TV lenses have a very long back focus because a three-color separation prism is inserted into the lens back, and a long exit pupil to prevent color shading. When used in a CCDa plate camera, various design conditions are required, such as small chromatic aberration of magnification.

Conventionally, there has been no so-called large aperture ratio macro lens that is an ENG TV lens that satisfies all of these conditions, but is capable of close-range photography from an infinite object distance to a magnification of 3x.

(Object of the invention) The object of the invention is to set the back focus to about 80 degrees of the focal length.
%, the aperture ratio is about 1:1.4, and the angle of view is about 12.6.
The object of the present invention is to provide a large aperture ratio lens that can be used as a microlens for ENG, which can be used as a microlens for ENG, and has aberrations well corrected from an object distance of infinity to 2x imaging magnification.

(Structure of the Invention) A large aperture ratio lens capable of close-up photography according to the present invention includes, in order from the light incident side, a first lens group having a positive refractive power, a second lens group having a positive refractive power, and a positive lens group having a positive refractive power. Consisting of a 2nd lens group with refractive power, when focusing from an object distance of infinity to a short distance, the 1st and 2nd lens groups are extended as a unit, and the 1st lens group is connected to the 1st lens group of the positive lens and the image side. The second lens group consists of a second group of negative meniscus lenses with a concave surface facing the object side, and a third group which is a cemented lens consisting of a negative lens with a concave surface facing the object side and a positive lens with a convex surface facing the image side. Consists of the fourth and fifth groups of positive lenses, and the (i)th lens group consists of the sixth group, which is a compound lens consisting of at least one concave lens and one convex lens, (i) 2f<f<5f ■ (u) 0.2 f < D3 < 0.6 f ■ (1 ■) and <45 f : Focal length of the entire system f : Composite focal length of the 1st lens group ■ f : Composite focal point of the 1st lens group Distance ■ D3: Combined thickness of the 3rd group in the 1171st group, a cemented lens of a concave lens and a convex lens DS3: Distance from the aperture to the 3rd group in the 1171st group ν1 2 Conditions for the Atsube number of the 1st group It is characterized by a long back focus and a long exit pupil.

In general, a Gaussian lens is considered to be a lens type that has relatively small fluctuations in aberration due to changes in photographing distance and is strong against large apertures, but the imaging performance at the periphery of the screen deteriorates as photographing takes place at a closer distance. This is mainly due to the occurrence of outward coma aberration in off-axis light, and in order to maintain good aberration up to 3x imaging magnification, it is necessary to provide some kind of floating mechanism to correct this coma aberration. There is a need.

In the present invention, when focusing from infinity to a close object point,
This problem was solved by extending the first and second lens groups as a unit while keeping the lens groups fixed.

In order to reduce variations in aberrations due to shooting distance, it is desirable to have a lens configuration that is symmetrical with respect to the aperture, and that suppresses aberrations generated in each lens to a minimum.The Gauss type satisfies this requirement. . However, ENG
In order to obtain a sufficiently long back focal length necessary for a TV lens for use in commercial use, the refractive power of the first lens group before the aperture tends to be significantly weaker than the refractive power of the second lens group after the aperture.

When trying to create an optical system for close-range photography with a magnification of up to 3x, if the refractive power of the first lens group is weakened too much, the light beam emitted from the object will not be converged very much in the first lens group, and the object at infinity will be What is a convergent light beam with respect to a point becomes a divergent light beam with respect to a nearby object point. If this divergence is too strong, the burden of aberration correction on the 1st lens group increases. Spherical aberration and astigmatism become excessive as you move from infinity to close-up photography, but the fluctuations in these aberrations increase, so create a configuration that can effectively correct aberrations from infinity to 2x magnification. becomes difficult.

Therefore, for an infinite relic point, the light beam coming out of the first lens group is a weak convergent light beam, and for a close object point with a photographing magnification of 172 times, it is a weak diverging light beam. is desirable.

In the above condition (i), if f exceeds the upper limit, then
The burden of aberration correction on the lens group increases, making it difficult to keep fluctuations in aberrations small due to changes in shooting distance. If the lower limit is exceeded, it becomes difficult to lengthen the back focus.

The present invention enables short-distance photography up to the imaging magnification, so when focusing on a short-distance object point, as mentioned above, the 2nd and 2nd lens groups are It uses a floating mechanism that is rolled out as one unit.

In order to reduce the amount by which the first and second lens groups are extended for focusing on a short-distance object point, it is necessary to keep the combined focal length of the eleventh and second lens groups as short as possible. This makes the combined focal length of the 2nd lens group, ie, the 6th group, extremely long, which increases dead space and shortens the back focus.

Also, since the purpose is to obtain a large aperture ratio, Part
・If the lens thickness of the first lens group becomes thicker or the number of lenses increases, this will also cause the back focus to become shorter.

Therefore, in order to obtain the long back focus required for ENG, EIIIT V lenses, the condition (
i) alone is not sufficient. To compensate for this, the concave surface on the object side of the third lens group can be strengthened (if this is done, the back focus can be lengthened, but the combined power of the second lens group is positive,
The powers of the fourth and fifth groups are made stronger, which increases off-axis coma aberration and spherical aberration. As a result, the combined thickness of the concave and convex lenses in the third lens group in the second lens group is increased to increase the luminous flux.

In the above condition (11), if D3 exceeds the upper limit, with this lens configuration, fluctuations in chromatic aberration of magnification due to changes in photographing distance will become too large. If the lower limit is exceeded, it becomes difficult to make the back focus sufficiently long. The exit pupil position is approximately determined by the relationship between the distance DS3 from the diaphragm to the 2nd lens group and the composite focal length f2 of the 2nd lens group.

In order to lengthen the exit pupil, it is necessary to either lengthen DS3 or shorten the composite focal length of the second lens group. The light beam that exits the Ⅰ lens group is a weakly convergent beam at an infinite object distance, so if you try to maintain the back focus by increasing the distance DS3 between the diaphragm and the ① lens group, you can increase the composite focal length of the first lens group. However, the combined focal length of the second lens group is shortened.

If you exceed it, the exit pupil will not extend. If the lower limit is exceeded, it will not be possible to suppress fluctuations in spherical aberration, astigmatism, and chromatic aberration of magnification due to changes in shooting distance. In order to be usable for a CCDB board camera, it is necessary to keep the chromatic aberration of magnification sufficiently small. In order to reduce the variation in the chromatic aberration of magnification due to changes in the photographing distance, it is necessary to reduce the amount of change in the chromatic aberration of magnification of the 2nd lens group and the 2nd lens group, which are extended at close distances. In particular, since the second lens group has a strong refractive power, it is necessary to keep fluctuations in chromatic aberration of magnification small, but axial chromatic aberration changes relatively significantly as the object distance goes from infinity to short distances. Therefore, in the lens group, the axial chromatic aberration must be changed relatively greatly and the amount of change in the chromatic aberration of magnification must be kept small so that it cancels out the object distance as it goes from infinity to a short distance. .

As mentioned above, condition (iv) is a condition for minimizing the amount of change in axial chromatic aberration due to the change in shooting distance that occurs in the lens group ①, and maintaining good axial and lateral chromatic aberration as a whole. .

(Example) Next, data of numerical examples of the present invention will be shown. Here, f
, FNo., 2a+, BF, and Exp represent the focal length, aperture ratio, angle of view, back focus, and exit pupil position of the entire system when focused on an object at infinity, and R1
is the radius of curvature of the first lens surface from the object side, di is the thickness and air gap of the first lens from the object side, Ni
and ν1 represent the d-line refractive index and Abbe number for the d-line of the first glass from the object side, respectively.

The lens back insertion glass is parallel plane glass with a thickness of 33.5 mm and glass material of Nd=1.55920 and νd=53.90, and a glass material of Nd=1.5 with a thickness of 10.7511110.
1633, parallel plane glass with sid = 64.15.

[Example 1] f=1. OFNo, = 1.4 R, = 0.7436 R, = 6.2374 R3 = 0.6455 R1 = 0.3643 R6-■ Rs” -0,3607 R, = 2.6753 Re = -0,5937 R3 =-22,2512 R1゜= -0,7998 RI+= 1.4870 R1゜=-14,9842 R13= 1.0237 R14= 0.7449 RIS= 1.0665 RI6= -0,8947 2ω=12.4 ° BF-4,7788X11.=-1
4,844 (L=0.121 L・1.72342
νI=37.95d2=0.020 d3=0.119 N2=1.74320 ν,=
49.31d, = 0.178 d, = 0.178 d8 = 0.158 N3・1.80518 ν3・
25.43d7・0.178 N,・1.58913
si, =61.18d, =0.004 d9=0.113 N5・1,80610 ν,・
40.95d+o”0.004 d,,=0.079 N6=1.64000 si,=
60.096 l 2””Variable d, = 0.020 N, = 1.64769 C, = 3
3.80d14=0.079 d, 5=0.125 N, =1.72342 ν8=
37.95 When object distance do=■, a, = 1.769 and 10, and 5 and d12 = 0.572 d1 = 0.089, that is, photographing magnification β = R,, = -2,2419 R, S = 0.8668 La = 1.1309 R17 = -1,8727 d, = 0.02 Ng = 1.51742 νg = 5
2.41'Ls=0.02 d1g=0.12 N9=1.69680 ν3"
55.53B, F [Example 2] f=1. OFNo, = 1.4 R, = 1.5082 R2 = -13,6927 R3 = 0,7524 R, = 1.4000 R5 = 0,4833 R, = ■ R, = -0,4351 R, = 15. 4036 R,= -0,7086 R1゜=-13,8990 R1l= -1,475O R+2" 1.8215 R13= -6,6155 2ω= 12.6" BF-4,8038XI], =-
5,8056,=0.122 N,=1.75520
ν,=27.5162=0.08 d,=o,o9N,=1.71300 ν,=53.
84d4=0.026 N,=1.64769 ν
3=33.80ds=0.2 ds=0.2 d,=0.2 N,=1.80518 ν,=2
5.43ds=o, 24 N5=1.77250
ν, =49.606, =0.004 d+o=0.084 N5=1.77250 ν5=
49.60dl l=0.004 d, □=0.072 N, =1.62041 shi,=
60.28aW・0 variable object distance d. When −00, d 13 =0.0?2d, =
1.811, that is, when the imaging magnification is β-0.5, d+s=0.708 [Example 3] f=1. OFNo, = 1.4 R, = 1.1665 R2 = -49,0204 R3 = 0.7833 R, -'1.4606 R5 = 0.4492 R, = ω R, - = -0,4268 Rs ” 11 .2447 2ω=12゜6゜d+=0.122 d, =0.090 d, =0.090 82=1.71300d, =o, 0
26 N,=1.58144ds=0.144 d6=0.278 d7=0.200 N,=1.80518d,=(1
,240N5=1.772508F=0.799 εx
p, =-40,963N, =1.64769 shi,
=33.80ν2=5384 ν, =40.75 ν4=25.43 ν5=49.60 R8= -0,6963 R1゜= -8,8437 R,,= -1,3846 R1□= 1.6707 R ,3=-7,203O R,,=-1,9048 R,,= 0.8654 R,6= 1.1251 R17=-1,6927 d,-0,004 d,,=0.080 N6= 1.772506 + +
”0.004 d,,=0.078 N,=1.60311d,3=*
Variable d,,=0.020 N,=1.51742d+s=0
．． 015 d16=0.116 N, 1.69680 Shiro=49
．． 60 Si, = 60.70 ν, = 52.41 νS・55.53 Object distance d. When =ω d +3=0.074〃d
When o = t, 728, that is, when the photographing magnification β = -0,5, d+3: o, 71 (1 (Effect of the invention)) With such a configuration, the lens of the present invention has a large aperture, yet can achieve back focus and Extremely long exit pupil
It is possible to realize a lens for close-range photography in which aberrations are well corrected from infinity to 2x.

[Brief explanation of the drawing]

1, 6, and 11 are embodiments 1.2 according to the present invention.
．． 3, the lens configuration diagram in the infinity shooting state, FIGS. 2, 7, and 12 are the Seidel aberration coefficients in the infinity shooting state in Example 1.2.3, FIGS. 3, 8, and 13. The figure shows Example 1.
Seidel aberration coefficient at a shooting magnification of 2.3%, Fig. 4,
Figures 9 and 14 are aberration diagrams of Example L 2.3 in the infinity photography state, and Figures 5, 10, and 15 are Example 1.2.
．． 3 is an aberration diagram when the photographing magnification is 2x. SA... Spherical aberration CM... Comatic aberration As... Astigmatism DS... Distortion aberration PT... Petzval L... Axial chromatic aberration T... Magnification Chromatic aberration main wavelength...587.56nm Second wavelength...460nm TOP SA, 5924. 2562-. 0652-. 8255, ooo. -2,1633 M, 1409 -. 4946-. 1025 +, 3161, ooo. , 6912 S, 0335. 9549-. 1611 +, 1211, ooo. −,2208,0176 1,9770,6717,0777,3170+,1433. 3429. 0508, [+306 2.3823. 1962. 5102 1.2634. 0301 1.2431. 6700-. 0020. 0009 UM, 0659, 0956. 1910. 1381. 1244 1, 00125. 00060 No. UM, 3707. 3646. 6462. 1244. 00146. 00440 Oral surface clean-1i (no change in content) Oral surface 1 polyδ (content changed) Figure 6 Figure 11 ■ Fossa TOP A, 0715. 1473. 0012 1, 3799, ooo. M, 0672 +, 3175 -. 0340 +, 0108 -. 2041, ooo. S, 0631. 6845 1, 0413. 0362-. 1096, ooo. ,6385 1,000;l! , 5913-. 0006. 5709-. 8244-. 0160. 0024-. 0814-. 1216 +, 0134. 0004-. 0267. 0112-. 1881. 0259-. 0002 1.2405 -. 1884. 1083. 2499, 0794-. 0358, 0325 +, 0187. 0503-. 0137. 0062-. 0056. 0032 UN, 0673. 0150. 0315. 1983-. 00007. 00100 UN a concave, 2581. 1214. 1382. 3791. 1983. 00157. 00381 SLJM Diagram, 0543. 0498. 050B, 0135. 1819-. 00068. 00109 No. 1.0475 -. 0670. 0043 UM, 2954. 1660. 1802. 4892. 1819. 00124. 00455 Written amendment (method) % formula % 1. Indication of the case 1988 Patent Application No. 288377 2. Name of the invention Large aperture ratio lens capable of close-up photography 3. Person making the correction Relationship to the case Applicant name Stock Company Tamun 4, Agent 5, Date of amendment order: March 7, 1999

Claims (1)

[Claims] Consisting of, in order from the light incident side, a lens group I having a positive refractive power, a lens group II having a positive refractive power, and a lens group III having a positive refractive power. When focusing from infinity to a short distance, the I and II lens groups are extended as a unit, and the I lens group consists of the first group of positive lenses and the second group of negative meniscus lenses with the concave surface facing the image side. The second lens group consists of the third group, which is a cemented lens consisting of a negative lens with a concave surface facing the object side and a positive lens with a convex surface facing the image side, and the fourth and fifth groups, each of which is a positive lens. , the IIIth lens group is composed of the 6th group which is a composite lens of at least one concave lens and one convex lens, (i) 2f<f_ I <5f (ii) 0.2f<D_3<0.6f (iii) 2<f_II/D_s_3<6 (iv) ν_1<45 f: Focal length of the entire system f_ I: Composite focal length of the I-th lens group f_II: Composite focal length of the II-th lens group D_3: III-th lens group The composite thickness of the cemented lens of the third lens group of the second lens group D_s_3: Distance from the aperture to the third group of the II lens groups ν_1: Satisfies each condition of Atsube's number of the first group, back focus and A large aperture ratio lens that features a long exit pupil and is capable of close-up photography.