JPS62178916A - Attachment lens for correcting paraxial chromatic aberration - Google Patents

Abstract

PURPOSE:To reduce a residual paraxial chromatic aberration of this lens by installing it to a photographic lens, by containing at lest one piece of concave lens and convex lens, and forming an incident surface and an emitting surface roughly to a plane. CONSTITUTION:This attachment lens for correcting a paraxial chromatic aberration is attached before and behind an existing lens system, constituted of one piece each of concave lens and convex lens, consists of a cemented lens whose incident surface and emitting surface are roughly a plane, and satisfies conditions shown by equations (1)-(3). Also, it is formed by combining at least two pieces of concavo-convex lenses so that it has a refracting power against a wavelength before and after it and works as a lens. In this way, a residual chromatic aberration of a photographic lens is reduced, and a color shift on a photography can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an attachment lens for paraxial chromatic aberration correction that is attached to a photographic lens to reduce residual paraxial chromatic aberration of the lens.

[Conventional technology]

When photographing a lattice pattern or checkerboard pattern at an appropriate interval using a general photographic lens, color shift may occur in the lattice image captured on the film.

Due to the characteristics of the film, there is a difference in density between the in-focus area and the out-of-focus area, and in addition to this, chromatic aberration (
The focus position differs depending on the wavelength of the light), which appears on the photograph as a color shift.

In order to solve this problem, it is possible to design a high-performance lens that reduces chromatic aberration near the optical axis of the lens, or to use a conventional lens out of focus.

However, adopting the former method requires advanced design technology, an increase in the number of lens components, or advanced manufacturing technology, which is industrially undesirable. Moreover, if the latter is adopted, it is not preferable in terms of performance.

[Means for solving problems]

Therefore, the present invention uses conventional general photography lenses without degrading performance.

It is an object of the present invention to provide an attachment lens for paraxial chromatic aberration correction developed to solve the above conventional problems.

The means for achieving this object of the present invention is such that at least two lenses have approximately no refractive power for the reference wavelength of existing lenses, but have refractive power for wavelengths before and after the reference wavelength, and act as a lens. An attachment lens that combines a concave and convex lens can reduce the residual chromatic aberration of the photographic lens, thereby reducing the above-mentioned color shift in photographs.

〔Example〕

In general, lenses that have been corrected for aberrations always have residual chromatic aberration near the optical axis, which can be roughly divided into the aberrations shown in Figure 1 (at) and (bl). In many cases, two colors are used to achromatize the color, and in this case, the width of the color can be extremely small.Here, in Figure 1, the vertical axis represents the wavelength, the t* axis represents the distance on the original axis, and the vertical axis represents the wavelength. <g> of the axis
is the wavelength of 435.8 nm, which is representative of blue light, and <e>
is a wavelength of 546.1 nm representing green light, and <e> is a wavelength of 656.3 nm representing red light.

Fig. 2 shows an embodiment of the present invention in which the aberration shown in Fig. 1 (al) remains; It consists of an attachment lens A for correcting chromatic aberration and a photographic lens M, and has the following numerical values.

Example 1 (Figure 2) Focal length fM of photographing lens M = 1.0Rd
Na Ng Na1 ■
0.02 1.623 1.641 1.
6142 0.46657 0.05 1.623 1
．． 633 1.6173 ω 002 4 0.59436 0.05 1.51825 1.
52622 1.513855 -3.9390 φa=0.0 φg=-0,01715φc=o,
o0643 However, Rii radius of curvature, d is the spacing on the original axis, N
o is the refractive index for the e-line (546,] nm), Ng
is the refractive index for the G-line (435, 8 nm), Nc is the refractive index for the C-line (656, 3 nm), and the refractive powers of the attachment lens A for each color are φg, φe, and φc.

Here, the pack focus of the photographing lens M is set to LM,
If it is jMg%1Me%tic for each color, the Hosotchi chromatic aberration is 1M1g -'tMm = -0,0149
:1Mc - IM* = 00085, but if attachment lens A is attached to this, the back focus at this time is lr, and it is tag%the for each color.
.

When Arc, lTg −ITo == 0.00
20:lTc-Are=0.0020, and the amount of aberration can be reduced.

The conditions for this attachment lens are that the refractive index for each color of each lens to the attachment lens is Ng+, N
aI, N01s Ngl, Nag, Nag, and the radius of curvature on each surface is R1s J s ”m,
And if the refractive power for each color of the entire attachment lens is φg and φ-1φc, then (11Ne, #No.

(2) Ng+ > Ng* (31Ncl < Ncl Condition (1) is to reduce the total refractive power of attachment lens A as much as possible to reduce the influence on photographing lens M (aberrations other than chromatic aberration), and condition (2), (3) is g&l and c
This is to reverse the positive and negative refractive powers of the attachment lens A with respect to Mj.

With this, for example, if the Hosotsu chromatic aberration is negative for the e-line and positive for the C-line, by making R2 positive, φg<
0 and φc>O, gIt8 was negative! It is possible to correct the C-line chromatic aberration in the positive direction and the C-line chromatic aberration in the negative direction.

In the case of this embodiment, it is practically difficult to reduce the chromatic aberration to zero because the refractive index conditions are too narrow, so it is preferable to use a three-element attachment lens as shown in FIG.

Figure 3 is an improvement on Figure 2, except that from the subject side, a cemented lens consisting of three concave, convex, and convex lenses whose entrance and exit surfaces are approximately flat is used as an attachment lens for correcting paraxial chromatic aberration. It is similar to FIG.

Rd Na Ng Ncl (
X) 0.02 1.638 1.658 1.6
282 0.32B42 0.05 1.644 1.
653 1.6373 -1.2721 0.02 1
．． 643 1.653 1.6374 0:l
0.02 5 0.59436 0.051.518251.52
6221.513856 -3.9309 φe=o, 0]905 φg=o, o 0393
φc = 0.0274, where R is the radius of curvature, d is the interval on the yt axis, No is the refractive index for the e-line, Ngt'1gTh
Nc represents the refractive index for C-line, and φgφeφc represents the refractive power of attachment lens A for each color.

Here, the Hoso chromatic aberration when attaching this attachment lens A is lTg - IT・=0.0, tTc - 11e
= O, O, and it becomes possible to reduce the amount of aberration to almost completely zero.

The conditions for this attachment lens A are that the refractive index for each color of each lens to the lens is Ng+, Nol %.
Nc1%Ngls Nag, Nag, Ngs
%Nel sNc, and the radius of curvature on each surface is R
1s RtR* s R4, and the refractive powers of the entire attachment lens are φg, φe, φc, (1
1Ne1 = Net #No.

(21Ngz≧Ng+　　Ngm (31Nc, ≧NeB>NO.

(41Rt > o, 1, R, < o, 1 (5)
φc〉φe〉φg Condition (1) is to make the refractive power of the attachment lens A as small as possible and to minimize the influence on the photographing lens M. Conditions (2), (3), (4), ( 5) sets the refractive power of the attachment lens to ai@ by decreasing that of 8 and increasing that of ci to e-line, thereby reducing the g-line and C-line chromatic aberrations of the taking lens M. The amount can be brought close to that of eM.

Figures 4 and 5 show that the photographing lens M is a normal chromatic aberration corrected lens, that is, a lens having the aberration characteristics of Figure 1 (bl), and is a concave-convex lens whose entrance and exit surfaces are approximately flat from the subject side. The paraxial chromatic aberration correction attachment lens is composed of a cemented lens consisting of three lenses.

As the secondary photographing lens M, Fig. 4 shows a concave and convex cemented single lens, and Fig. 5 shows a convex meniscus with a convex surface facing the object side, a convex meniscus, a concave meniscus, and a concave meniscus with a convex surface facing the imaging surface side.

It is composed of a five-element lens with a convex meniscus, and has the following numerical examples.

Rd No Ng Nc
l ω 0.02 1.638 1
．． 658 1.6282 1.1370 0.
05 1.644 1.658 1.6373
-0.63181 0.02 1.643 1.
653 1.6374 ω 0.0
2 5 0.65583 0.05 1.62286 1
．． 63312 1.617276 -0.40462
0.02 1.62408 1.64202 1.61
5037 -11.253 φe=0.00686 φg=0.00791 φ
e=0.00792Rd No.
Ng Ncl (X) 0.
02 1.638 1.658 1.6
282 0.79787 0.15 1.64
4 1.658 1.6373 -0.414
50 0.02 1.643 1.653
1.6374 (X) 0.02 5 0.40326 0.0593 1.7369
2 1.755136 1.729166 0.716
30 0.002137 0.33421 0.0
8897 1.74794 1.76499 1.7
39078 0.56853 0.018769 0
．． 45722 0.01973 1.79192 1
．． 82523 1.7759710 0.20424
0.20066II -0,170780,03
9651, 677641, 699821, 666621
2-0, 235090, 00213 33-1, 27920, 075621, 591431,
600991,5861914-0,29234 φe = 0.00993, φg =
0.01206, φc=o, 01]28 where %R is the radius of curvature, d is the distance on the optical axis, N is the refractive index for e@, N
g indicates the refractive index for the g-line, Nc indicates the refractive index for the C-line, and the refractive powers for the respective colors to the attachment lens are φg and φe1φc.

Here, let the back focus of the photographing lens M be lx,
Let it be tMg, lie, tic and fc for each color.
In the case, LXg −IMe = 0.0031 (Example 3) 0.0021 (Example 4), IMe 1M
m ”0.0011 (Example 3) and 0.0014 (Example 4), but when attachment lens A is attached to this item, both lTg -Irm and trc -tre become zero, and [?IN% It is possible to make each aberration amount of e-line and C-line zero to zero.

The conditions for this attachment lens A are that the refractive index for each color of each lens of attachment lens A is Ngl, N
@H1N c 1 s Ngt, N6% Nag,
Ngs, Nag, Nag, the radius of curvature on each surface is R,, R, %R, %R4, and the refractive power for each color of the entire attachment lens is φg1φe
, φc, (1) Nel #Net”t Nag(21N
g2≧ Ng+ > Ngs(3) Ne,≧
Nag) Ncl+4) g, >o, i,
R, < −0, 1 (5) φg〉φe, φ
c〉φe Condition (1) is to minimize the refractive power of attachment lens A and minimize its influence on the main lens, and conditions (2), (3), and (4) are for g-line and C-line. Condition (5) is a condition for making the refractive power for the e-line always positive, and the condition (5) increases the refractive power for the g-line and the C-line with respect to the e-line. The aberration of a and CIt+' ((This is a condition for approaching the 6th line.

Fig. 6 shows an example in which another attachment lens A is attached to the photographing lens M shown in Fig. 5. From the subject side, a cemented lens consisting of three convex, concave, and convex lenses whose entrance and exit surfaces are approximately flat is used for close-up. Assuming that the attachment lens A for correcting axial chromatic aberration is configured, we will use the following numerical example (data for the attachment lens only).

Rd Ne Ng Ncl
(X) 0.04 1.6627 1
．． 6740 1.65662 -2.5239 0.0
2 1.659 1.6740 1.6493 1.
5294 0.04 1.659 1.6796
1.64884 ω φe=0.00153, φg=0.00366
, φa=0.00288, where R is the radius of curvature, d is the distance on the optical axis, Ne is the refractive index for the e-line, Ng is the refractive index for the g-line, and NC is the refractive index for the C-line. Let φg and φe1φc be the refractive powers for the respective colors.

Here, by attaching this attachment lens A, it is possible to reduce Hosochi chromatic aberration to almost zero, as described above.

The conditions for this attachment lens are that the refractive index for each color of each lens of the attachment lens person is Ngl s
Nel s Ncl s Ng, s Ng
Assuming that t s NclsNg,, N6g, Nc, the radius of curvature on each surface is R1s R*, 81%R4, and the refractive power for each color of the entire attachment lens is φg1φ・, φc, (1) N @ 1 # N @ @ # N @ B (
21Ngm>Ngi≧Ng.

(3) Ne, > Nag≧NO.

(4) R, < -0,1, R, >0.1 (5)
φg〉φe, φc〉φ6 Condition (1) is to make the refractive power of the attachment lens A as small as possible and to reduce the influence on aberrations other than chromatic aberration near the optical axis of the photographic lens.

Conditions (2), (3), and (4) are ideal conditions (
5) is a condition for bringing the aberration of the g a b C line closer to that of the - line. Here, it goes without saying that the same effect can be obtained even if the attachment lens of the present invention is used with the front and back sides reversed.

Furthermore, although this embodiment has been described as an attachment lens that is added to the front of the photographic lens, it is also possible to place it at the rear.

〔Effect of the invention〕

As explained above, according to the attachment lens of the present invention, residual longitudinal chromatic aberration of conventional color-corrected photographic lenses can be almost completely removed, and even when photographing a grid or checkered pattern at an angle, It is possible to provide an attachment lens for paraxial chromatic aberration correction that does not cause color shift and can constitute a very high-performance photographic lens.

Furthermore, since the attachment lens is configured to minimize the effects of other aberrations and refractive power, it is possible to provide a novel attachment lens that does not degrade other performance.

[Brief explanation of drawings]

Figure 1 shows an example of the image formation position in the original axis direction at each wavelength of Hosochi chromatic aberration (al is the chromatic aberration of a single lens, etc.). Figure 1 shows an example of chromatic aberration corrected with a general photographic lens. 2 to 6 show optical systems showing respective embodiments of the present invention. A...Attachment lens M...Photographing lens

Claims (1)

[Scope of Claims] 1) An attachment lens added before and after an existing lens system, which is a cemented lens including at least one concave lens and a convex lens and whose entrance surface and exit surface are substantially flat; An attachment lens for paraxial chromatic aberration correction, which is characterized by correcting paraxial chromatic aberration without affecting other aberrations. 2) A paraxial chromatic aberration that is added to the front and rear of an existing lens system and consists of a cemented lens composed of one concave lens and one convex lens, and whose entrance and exit surfaces are substantially flat, and which satisfies the following conditions: Attachment lens for correction. (1) Ne_1≒Ne_2 (2) Ng_2>Ng_2 (3) Nc_1<Nc_2 However, Ne, Ng, and Nc are the respective wavelengths, e-line (54
6.1 nm), G-line (435.8 nm), and C-line (656.3 nm), and the numerical value of the subscript corresponds to the lens number from the front. 3) Paraxial chromatic aberration correction, which is added to the front and rear of an existing lens system, consists of a cemented lens consisting of a concave lens, a convex lens, and a concave lens, and whose entrance and exit surfaces are substantially flat, and satisfies the following conditions: Attachment lens for. (1) Ne_1≒Ne_2≒Ne_3 (2) Ng_2≧Ng_1>Ng_3 (3) Nc_2≧Nc_3>Nc_1 (4) R_2>0.1, R_3<-0.1 (5) φc>φe>φg However, Ne , Ng, and Nc are the refractive indexes for the respective wavelengths, e-line, g-line, and c-line, R is the radius of curvature of each lens surface, and φe, φg, and φc are the refractive powers for each of the above wavelengths, and the numerical value of the subscript is corresponds to the lens number from the front. 4) Paraxial chromatic aberration correction that is added to the front and rear of an existing lens system, consists of a cemented lens consisting of a concave lens, a convex lens, and a concave lens, and whose entrance and exit surfaces are substantially flat, and satisfies the following conditions: Attachment lens for. (1) Ne_1≒Ne_2≒Ne_3 (2) Ng≧Ng_1>Ng_3 (3) Nc_2≧Ne_3>Nc_1 (4) R_2>0.1, R_3<-0.1 (5) φg>φe, φc>φe However, , Ne, Ng, Nc are the respective wavelengths, e-line (54
6.1 nm), G line (435.8 nm), and C line (656.3 nm), R is the radius of curvature of each lens surface, and φg, φe, and φc are the refractive powers for each of the above wavelengths, respectively. , the subscript number corresponds to the lens number from the front. 5) For paraxial chromatic aberration correction, which is attached to the front and rear of an existing lens system, consists of a cemented lens consisting of a convex lens, a concave lens, and a convex lens, and whose entrance surface and exit surface are flat, and which satisfies the following conditions. Attachment lens. (1) Ne_1≒Ne_2≒Ne_3 (2) Ng_3>Ng_1≧Ng_2 (3) Nc_1>Nc_3≧Nc_2 (4) R_2>0.1, R_3<-0.1 (5) φg>φe, φc>φe However, , Ne, Ng, Nc are the respective wavelengths, e-line (54
6.1 nm), G line (435.8 nm), and C line (656.3 nm), R is the radius of curvature of each lens surface, and φg, φe, and φc are the refractive powers for each of the above wavelengths, respectively. , the subscript number corresponds to the lens number from the front.