JPS6029718A - Rear focus conversion lens for telephoto lens - Google Patents

Abstract

PURPOSE:To obtain a general conversion lens (RFC) which is focused speedily and exhibits excellent image formation performance by giving negative refracting power, moving respective groups of the RFC of three-group constitution at different speeds and generating opposite-directional aberrations, and satisfying specific inequalities. CONSTITUTION:The three groups G1, G2, and G3 of the RFC move at different speeds during focusing to obtain adjacent intervals D1, D2, and D3, and extents DELTAD1, DELTAD2, DELTAD3, and DELTABf of an increase or decrease in the distance Bf to a film plane 21. The inequalities I -V hold, where alpha, alpha1, alpha2, and alpha3 are ratios to the variation extents DELTATL and DELTABf of the overall length TL', and beta is an expansion rate of focal length. The inequality I corrects aberrations and simplifies the structure, and the inequalities II and III correct the spherical aberration and the inequality IV optimizes the astigmatism, and the inequality V prevents a decrease in the refracting power of the RFC, improving the distance measurement precision. Therefore, this RFC is used for various telephoto lenses, speedy focusing is attained with the simple constitution, and excellent image formation performance even in short-distance focusing is maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a rear conversion lens for focusing that can be used universally for various telephoto lenses.

(View of the Invention) Conventionally, various automatic focusing and ξ methods for photographic lenses have been known, and various lenses capable of automatic focusing for C-eye reflex cameras have been commercialized. However, these are only commercially available as lenses exclusively for automatic focusing, as they are only capable of self-focusing on a specific lens, making them inconvenient and lacking in versatility. It was expensive.

Furthermore, when photographing a fast-moving subject with a telephoto lens, the depth of field of the telephoto lens is shallow.

It is very difficult to simultaneously perform framing and focusing in accordance with the movement of a subject, and a conversion lens for focusing that has an I1iS response is desired.

However, in general, rear conversion lenses tend to increase the aberrations of the objective lens attached to them.
Since various aberrations become significant when focusing at short distances, it is extremely difficult to maintain good imaging performance of the composite system of the rear conversion lens and objective lens, and to compensate for aberration fluctuations caused by focusing. Met.

(Objective of the Invention) The object of the present invention is to be able to be used universally in various telephoto lenses, to enable rapid focusing with a simple configuration, and to provide improved imaging performance even when focusing at short distances. An object of the present invention is to provide a rear conversion lens for focusing, that is, a rear focus conversion lens that can maintain the following.

(Summary of the Invention) The present invention is mounted between an objective lens and a camera body, and has a negative refractive power in order to enlarge the focal length NLY of a composite system with the objective lens than the focal length corner of the objective lens. The first rear conversion lens is movable on the optical axis.
The second group can move on the optical axis at a speed different from the first ts on the image side of the first group (6). a movable third group;
．． Second. Focusing is performed by moving the third group.

Generally, as mentioned above, the objective lens is attached with a rear conversion lens attached to the objective lens. In addition, rear focus conversion lens (hereinafter referred to as RFC)
When focusing from a close-range target to a close-range target by moving the unit to a single body weight, &-! , Since the incidence island of the light beam on the RFC changes greatly, there is a possibility that aberrations generated in the RFC itself may be added. As described above, the present invention L- is configured with three groups of RF C, and each f! By moving the rods at different speeds, aberrations 7 in opposite directions are generated, making it possible to extremely well correct aberration fluctuations associated with focusing. That is, image α1
1 (with the objective lens fixed and the RFC integrally @
(When moving to full, the spherical aberration changes significantly to negative, and the astigmatism I1 changes significantly to positive.)In order to correct the spherical aberration, it is necessary to It is effective to narrow the interlayer, and in order to correct astigmatism, it is effective to vary the air [IU1η1 between the second group and the third Lff with focusing.

In particular, in order to simultaneously correct spherical aberration in the positive direction and astigmatism in the negative direction, for example, by narrowing the air gap between the second and third groups along with focusing, and moving RFC' toward the image side. It may be possible to correct aberrations more effectively.Also, as the magnification of RFC increases, aberration fluctuations will increase over a finite distance, but in order to efficiently correct negative spherical aberration, the first step is to
It is essential to narrow the air gap between you and the second group. Therefore, when moving all three groups to the transmission side, the first and third groups It is practical to move the first tIF and the third group at a faster speed, and it is also possible to configure the first tIF and the third group to move integrally.

By the way, generally, a telephoto lens has a long back focus, and the position of the exit pupil is farther from the image plane than that of a standard lens. Therefore, the RFC of the present invention requires a configuration different from that of the REC for the designated sensor. First, since the position of the exit pupil of the objective lens is far from the image plane, the entrance pupil of the telephoto lens must also be formed at a distance from the image plane accordingly. Since the back focus of the objective lens is long, in the RFC for a telephoto lens, the distance Qdo from the vertex of the lens surface closest to the object side of the RFC to the image point by the objective lens, that is, RF C
The object point distance can be made longer than that of the standard lens RIi'C, and when the RFC is attached to the objective lens, a long back focus can be secured at the time of infinite combined focus. Further, since the dof ratio can be made longer in this way, it is advantageous in that a sufficient peripheral tip can be secured even when the lens is attached to an objective lens whose exit pupil position is quite far away. However, RF
When focusing on a finite distance by moving C toward the image side.

The amount of movement necessary to obtain a predetermined imaging magnification increases as the focal length of the objective lens increases. For this reason, when performing infinite d focusing with the RFC attached to the objective lens, it is necessary to make the bank focus of the synthesis system sufficiently long to ensure the amount of movement of the RFC. In order to make the back focus of the synthesis system sufficiently long, it is necessary to arrange the lens components constituting the RFCi as close to the objective lens as possible, and also to reduce the total center thickness of the RFC.

Below, the rear according to the present invention? Orcus compression lens (hereinafter referred to as RFC) will be explained based on the drawings.

Figure 1 shows the objective lens (10) and the eye reflex camera body (
20) is a cross-sectional view showing a schematic configuration of the RFC (30) according to the present invention installed between the film surface (21). In the figure, peripheral rays from an on-axis object point reaching the film surface (21) are shown. -The eye reflex camera body (20) has a swingable reflector (
22) s focus plate (23), condenser lens (24)
).

Pentada Hapriz! (25), t&IffJ:y
'7: It has (26). The reflecting mirror (22) is normally provided obliquely at the position indicated by the dotted line except when exposing the film ITJ (21). - In the eye reflex camera, in order to secure the swing space rrlJ of the swing reflector (22), - the distance F between the lens mount surface (28) of the eye reflex camera body (20) and the film surface (21) , so-called flange back (
M B ) is determined to be a value specific to the camera body, and the distance between the last lens surface of the first lens and the image plane, that is, the back focus (Bt) is set to a value that is sufficient to exceed the swinging space of the reflecting mirror (22). Designed for a long time - Therefore, even when the RFC is attached to the objective lens, it reflects the back focus (Bf) of the composite system with the objective lens! (
22) must be secured, and in addition, sufficient back focus must be secured even when the negative lens Hi-, which forms the RFC, is moved to tQ (ill ', f It is necessary to have HJB.

As described above, the RFC according to the present invention must not only satisfy the conditions as a rear conversion lens, but also meet various conditions Y! in order to sufficiently achieve the single focus function. : '/h'j Tazuko is 8 love. Specifically, in order to maintain good focusing accuracy even when using a bright objective lens or a dark objective lens of λ1 for versatility, there is an upper limit to the magnification that the I-eye lens is responsible for. can be,
Also, nearby 111! ii1. There is also a lower limit to the magnification magnification because it is desirable to ensure sufficient back focus during the ii l+2 shadow and to make the amount of movement of 11 FC too large.

Now, as shown in Fig. 2, the RPC according to the present invention is attached between the objective lens L and the camera body 20, and the total length of the synthesis system when focused on an object at infinity (objective lens first) is Sarr, distance to j21; (t) is assumed to be TL. Then, as shown in Fig. 3, the total length when focused on a finite distance object is TL/stitched, and S]
c1st rji” (”+) ト(D Ril mustache 4
1) + Ka Jl) changes by 1, from Dl + ΔD,
In, RI"C t lit' (G,) and RFC No. 28)
(G2) changes by Δ1)2 from D2 to D2+ΔD2, and a4Da between the 10-C 21st FT (G2) and the third group (G3) changes by Δ1)2+ΔD.

In this case, the back focus f of the synthesis system is f + Δ13fl
If it becomes C, the change in the total length JIf A T L is Δ
1゛L-TL/-TL, =ΔD, +ΔD2+ΔD3+Δ
It is expressed as Ilf.

Here, the coefficient f11'f (1 is a
=ΔTL/ΔBf =ΔD+/Δ8f+ΔD2/Δ13(+ΔDa/ΔIj
(It becomes +1. And.

α1=ΔD, /ΔBf α2−ΔD2/Δf3( α8−ΔD3/ΔB( If you put it.

α=α, ten α2+α3+1, and α1. α2 and α8 are objective lens LO and RFC
Synthesis system of distance change claw ΔD with respect to the first group, distance change amount ΔD2 between RFC first group and second group, and distance change amount ΔD3 between RFC second group and third group, respectively. This is the rate of change with respect to the amount of change ΔBf.

The above equation can express all cases regarding the movement mode related to the RFC of the present invention except for the case where the back focus of one composite system does not change, that is, the case where ΔB (= 0). For example, when α = 0 means that the objective lens is fixed to the image plane and focusing is done only by RFC.However, when α=0 and αl =” sα2=
0, α, = o, each group of RFC (Gl, 02sGa
) moves in unison.

Here, in the present invention, it has been found that it is appropriate to perform focusing in a moving form that satisfies each of the following conditions.

-1,5(α(1,5(1) -2,0(α+< 1-5 (2) -〇, a <α2< O-4(3) -O,3<α, < 0.4 (4) 1.2〈β(2,5(5) Conditional Expression (1) These conditional expressions will be explained in detail below.
If the lower limit of is exceeded, it means that when the back focus becomes short when focusing from infinity to a finite distance (Δ”r<O)* the total length of the total synthesis system becomes excessively long (Δ
TL)o). If you do this, the area that can be photographed will be expanded, but the objective lens will also be significantly moved to a special case.

This is inappropriate because the mechanical structure becomes complicated. In general, telephoto lenses are much larger than standard lenses, especially when it comes to large aperture telephoto lenses.

The energy required to automatically operate such a large and heavy optical system is also extremely large, which is not desirable. On the other hand, exceeding the upper limit means that the total length of the total synthesis system becomes shorter when the back focus becomes shorter during close-range focusing (ΔBr<o); This makes it difficult to correct aberration fluctuations by single focusing.

In addition, when focusing at a short distance N [a configuration in which the back focus becomes long during focusing (ΔBr > 0), the total length of the total synthesis system becomes excessively long, and the mechanical structure is similar to that at the lower limit. It is complicated and inappropriate.

Therefore, - in a lens system for an eye reflex camera,
When constructing an automatic focusing system, it is practical to have a structure within the above range.

When the lower limit of conditional expression [2] is exceeded, when ΔI3f<o,
This is inappropriate because [h] between the objective lens and the first group of RF C becomes excessively large, the spherical aberration becomes excessively negative, and the astigmatism becomes excessively positive. If the limit is exceeded, when ΔBt<O, RI'C only'X5C! ! 1. At +1, it is difficult to increase the magnification, and in order to increase the magnification, the objective lens must be moved largely toward the object side at the same time.

The RFC movement mechanism becomes complicated and large.

Conditional expression (3) is for correcting spherical aberration that fluctuates excessively in the negative direction when ΔBr<o.

If the lower limit is exceeded, excessively negative spherical aberration will occur, which is inappropriate. Moreover, if the lower limit of conditional expression (4) is exceeded, Δ
When Bf is 0, the astigmatism becomes excessively positive, which is inappropriate. When ΔBt<o, exceeding the upper limit is inappropriate because astigmatism becomes excessively negative and the second group and Ma group mechanically interfere.

If the lower limit of conditional expression (5) is exceeded, the refractive power of IζFC becomes too weak, and the aperture J iff: i
If an attempt is made to focus on 214I, the amount of movement of RFC will be excessive, which is inappropriate. Furthermore, since the area in which the RFC can be focused is extremely small, a focusing method that involves excessive movement of the objective lens is required. If you exceed the upper limit,
Since the F number of the composite system of the objective lens and RFC becomes large, the distance measurement accuracy in focusing deteriorates, and when automatic focusing is attempted, the focus becomes slow, which is inappropriate. Furthermore, aberration correction is further improved ifJ5”2
Therefore, the number of lenses increases, resulting in a complicated configuration, which is still inappropriate.

In the basic fl/J configuration of the present invention as described above, R1
The focal length of i'C is fl, and the pack focus B (carbonization I] of the composite system of the objective lens and 1-digit C is Δ'fs, the distance between the image point by the objective lens and the forefront lens Ul of RF C, i.e. When the object point distance of RF C is do, 0,
1 (lΔBr/fl<o, 3s (6)0, 4<
l B f/do ·fl<0.8 It is desirable to satisfy the condition (7).

If the lower limit of equation (6) is exceeded, the area that can be focused only with ItFC becomes smaller, so in order to ensure a sufficient focusing area, it is essential to move the objective lens a large amount toward the object side, which reduces the RFC. It is unsuitable because the mechanical groove structure becomes complicated.If the upper limit of equation (6) is exceeded, it becomes difficult to secure the back focus necessary for a lens system for an eye reflex camera, so it is unsuitable. Furthermore, if the lower limit of equation (7) is exceeded, do becomes longer and the number of objective lenses that can be attached decreases, resulting in loss of versatility.

The lens length of the RFC (total center thickness from the frontmost lens surface to the last lens surface of the RFC) becomes long, and portability deteriorates.

Exceeding the upper limit of equation (7) is inappropriate because the lens length of 1ζFC will become short and the degree of freedom for aberration correction will be lost, and at the same time, do will become short and the refractive power of R'FC will become too strong. This makes it difficult to correct astigmatism.

Also, let the focal lengths of the first, second, and third groups of IIFC be f, , fl, and i, respectively, and the flange back of the single-lens reflex camera body to which this RFC is attached is M.
When B, 1tH/l+ 1 < 2.0 (8) r tm/l*
1< 4.0 (911fH/fa I (2,0α
It is also desirable to satisfy the condition 0.82<I doAfB I<2.8a1).

(Equations sL(9) and (1o) are conditions that define an appropriate distribution of refractive power when RIi' C is divided into groups. (
Equation 11) is an equation that defines the versatility of RFC, and if the lower limit is exceeded, it is difficult to maintain a sufficient back focus as a lens for an eye reflex camera, and it is also difficult to ensure sufficient peripheral illumination. Have difficulty. If the upper limit of equation (11) is exceeded, it is inappropriate to attach it to an objective lens such as a super-telephoto lens having a considerably long pack 7 orcus, which reduces the versatility of 1tFc. still.

- For example, the flange back of the eyelid camera body is 46.
The order is 5.

(Example) Examples of RFC according to the present invention are shown below. Each of the examples was designed based on the objective lens shown in Table 1. This reference objective lens is a patent application pending by the same applicant as the present application, and is designed for use in 35 mm format eye reflex cameras. Distance 3 Q Qm.

In Table 1, which is an extremely bright telephoto lens with an F number of 2.0, r,, l =, 'F,, tra is the radius of curvature &'lB' of each lens surface sequentially from the object side.
2 @'a is the center thickness of the lens and the air spacing s.
l j ”* @ ” ”・ is the d-line of each lens (λ=5
Refractive index for 87.6 nm), Si1. ．． C2. C8... represents the Atsube number of each lens. Note that this objective lens is set at the most extended side.
- Dimension C to ω 1 ω -1 5% (5Vj w IDco II II II It ■ Dimension 11'i
0-1 to I/) ψ oO■ -- 1+1111 G0's 0 ■(') ooω 1, l-&, &T 1. Il, I-11-1 The specifications of the first to ninth leprosy examples of RFC according to the present invention are shown in Tables 2 to 1O, respectively. However, in these six tables, the left end of the table shows the order of the object side, do represents the distance between the frontmost lens surface of the RFC and the image point by the objective lens, and Do
is the distance from the frontmost lens surface of the objective lens to the object point, D,
is the air distance between the objective lens and RFC, and Good is the first RFC.
The distance sD3 between the group and the second group is the distance between the second group and the third group of the RFC, f is the focal length of the RFCi1 group (G1), f
2 is the focal length of the RFC second group (G2), f2. is RPC
Let it represent the focal length of the third group. , B(represents the back focus of the composite system of RF C and the objective lens, ΔBf is due to RF C; Jet, F represents the composite focal point of the RFC and objective lens, and M represents the imaging rate of the composite system.

Table 2 (first example) - Magnification: β = 1.6 Focal length fR = -115,85
4d,=-57,0ΔBf=-19.75Of,=
111.512 α=O fx=-55,500α+=1.282f, =-1
043,72562=0.1154αg"'0.16
66 Table 3 (Second Example) Magnification: β=1.6 Focal length 1R=-119, G12d
, = -57,0ΔBf= -19,339f, =-
118,982α=O f*= 312.738 α, wealth −0.9091f,
=-348,915α, 1,000,2364α, =0.32
73 Magnification: β=1.6 Focal length fR-123,673d
,=-57,0ΔBf=-20,608fm=-12
1.824 α= Of = -106,374α True = -1,08696f,
≠ 97.553 αm= 0.19565αg” −
0,10869 Table 5 (4th implementation column) Magnification: β=1.6 Focal length fR=-115,860d
*= 57. OABf-16,145f, = 157
．． 277 α = 0 dm" 0.22224 Table 6 (Sixth Example) Magnification: 1w1,6 Focal length f R = -122,67
5α, = 0.08 + 1645 Table 7 (6th implementation column) Magnification: β = 1.6 Focal length Kfff17 = -11
6,528d, =-60,0ΔB =-18,888'
+ = 25411.6 α = Of, = -212,
584α□ = -1,250b = 133.206
α snow = 0.10001α, = 0.14999 Table 8 (7th example) Magnification: β-1,6 focal length IilI fR = -117,
093f, = , 1G1.613 α = -0,065
24f, = -53,527αr = 1.08698
fl = 290.053 C1* = 0.1087
1α,=-0,08698 Table 9 (Eighth Example) A sound 'a a β=1. 6 Focus FElljll
fR = -13x, *9s (X3 = U, 14Z?5
'16 Table 109 Examples) Magnification: β = 16 Focal length f11 = -120,651
Mountain = -60,0△13 =-17,9L5f, =
−94,328α= O b= 76.665 α+= 1.33335b= 8
8.324 α = 0.20000αm = 0.13
335 Lens configuration diagrams of the first to ninth embodiments described above are shown in FIGS. 4 to 12, respectively. Each lens (the configuration diagram shows the 1st group (G+) for performing infinite speed focusing to short distance focusing, 1f
Arrows indicate the amount of movement required for each of the f42 group (G2) and the 3rd group (Gs) with respect to the image plane. The amount of movement of each group relative to the image plane is clear from the table above.
5'P (CI, ), the second group (G2), and the third group (Oa) have lower moving speeds in the order of 1. 4th. Fifth. 6th. 8th. This is the ninth embodiment, and the second embodiment. Third. In the seventh example, the moving speed of the second group (G2) is the smallest. In the second practical example, the movement speed of the third g1' (Ga) is the largest,
In the third seed example, u! of the first group (G,)! 11 speed is the maximum, and in the seventh embodiment, the e1 group (G1) and the third group (Oa)
It is also possible to move the first group (G1) and the third group (G8) together, since their moving speeds are almost the same. In addition, the first to fourth examples have a positive lens closest to the object side, and the fifth to ninth examples have a negative lens closest to the object side.
The configuration has Y.

13(A)(B) to 21(A)(B) show the dt aberration diagrams when the RFCs of the first to ninth embodiments are respectively attached to the reference objective lens shown in Table 1. Shown below. In each figure, (i shows various aberration diagrams when each RPC is attached to the infinite combined focus, and each M (B) is the J?F'C when each RPC is attached.
This shows various aberration diagrams when focusing at close range. Each aberration diagram shows spherical aberration (8ph), astigmatism (A
st), distortion aberration (Dis) reference wavelength d-line (λ = 58
7.6 nm) = 435
．． 8 nm) and lateral chromatic aberration (Lat.

Chr) was shown.

From the respective aberration diagrams, it is clear that each sister example of the RFC according to the present invention maintains very outstanding imaging performance not only when focusing on infinite union but also when focusing on a regular box. ,
It can be seen that aberration fluctuations are well corrected by moving each group of It FC according to the present invention. The objective lens used here has an F number of 2.0 as shown in Table 1.
It is extremely bright for a telephoto lens,
Even when attached to a bright telephoto lens like this, each
As shown in the 7fl aberration diagram, the poor imaging performance is maintained both when focusing at infinity and when focusing at close range, so it has sufficient performance even for lenses with darker F numbers. It is clear that there are many Therefore, it is clear that the RFC according to the present invention can be used universally for various telephoto lenses.

Note that the photographable area that can be focused by fixing the focus of the objective lens at infinity and moving only the RFC may not be sufficient due to spatial and mechanical limitations. Therefore, the photographable range can be easily expanded by refocusing the objective lens to a specific finite distance and focusing on a finite distance array RFC'''QfA based on that distance. In addition, R, P, and C for telephoto lenses have a greater degree of spatial freedom in lens arrangement than those for standard lenses.Therefore, by increasing the number of lenses, they can be attached to a brighter objective lens. Those with sufficient imaging performance,
By moving the 1ζFC, it is possible to achieve high performance with a wide focusing area.

(Effects of the Invention) As described above, the RFC according to the present invention can be universally attached to any objective lens, is compact, and can easily focus from infinity to short distances.
In addition, it is possible to sufficiently correct aberration fluctuations due to focusing and maintain distorted imaging performance at all times. If combined with an automatic focusing device, it is possible to focus on one type of telephoto lens using only one RFC, so the focusing mechanism becomes common and the focusing mechanism can be used even if the telephoto lens is replaced. It is extremely useful as there is no need to replace it.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a schematic configuration of a rear focus conversion lens according to the present invention installed between an objective lens and a single-lens reflex camera body. Figure 2 is a schematic diagram of the composition system when the RFC according to the present invention is attached between the objective lens and the camera body and focused on an object at infinity, and Figure 3 is a schematic diagram of the composition system when the RPC is attached like in Figure 2. Schematic configuration diagram when focusing on a finite distance object, Go 4-1
Figure 2 is a lens configuration diagram of the first to ninth embodiments, respectively.
13(A)(B, ) to FIG. 21(MU) CB) are various aberration diagrams of the first to ninth embodiments, respectively, and (A) of each figure
(B) shows the state in focus at infinity, and each figure (B) shows the state in focus at the closest distance. (Explanation of symbols of main parts) 10...Objective lens 20...Camera S closing day 30
, RFC... Rear focus conversion lens GI... 1st details G2... 2nd group G8... - 3rd group Applicant: Nippon Kogaku Kogyo Hayashi Shikikai Agent Takao Watanabe, +44 No. 5 Figure 6 Figure O'7 Figure 1 - A-61 Figure 10 Figure 11 Figure 12 Figure 15 (△) Sph A5t D N S La-t,, Chr Section 13 (B) PhAst D25 Mu a21/, chr Figure 14 (A) δPh ASt Di3 L (Zt, Ch r Figure 14 (B) D;s Lat Ghr Figure 15 (A) Figure 15 CB) D25 1 (2t, Chr Figure 16 Figure (A) Sph Ast DtS Lat/, U?r Sph j6 prisoner (B) SPh Ast DnS Ll;?z:1.C1tr Figure CB) DtS La, Chr Figure 13 (A) SPh As right ();s 'Lat, Ch r Figure 1 (B) SphAst. 1) 2Slat, Ch Figure 1q (A) PhAsv D' /S Lat/, CAr /17tq Fig. CB) Sph Ast Dos Lat, Chr /?2θ Fig. (A) D;s △a1;, chr Fig. 20 CB) Spear 27 Fig. (A) 5Ph A3 Fig. 21 ( B) 5Ph As″t/ Dis Lad, Chr Procedural Amendment (Voluntary) 1. Display of the case 1982 Patent Application No. 138523 2 Name of the invention Afmakes conversion lens for telephoto lens 3
Relationship with the person making the amendment Patent applicant: 3-2-3 Marunouchi, Chiyoda-ku, Tokyo (411) Nippon Kogaku Kogyo Co., Ltd. Fukuoka Shigetada Egg Membrane President Shigetada Fukuoka 4, Agent: 140 Tokyo Yokan, Yoku Nishi-Oi 111'' G No. 3 No. 1 Kogaku Kogyo Co., Ltd. Ceiling M Production Isu 6 Contents of correction 1) Statement box page 6 line 9 1 1st group and 3rd group''
"The first group," he corrected. 2) [r 14 ='-1.754 on page 20, line 2]
．． Correct 21GJ to [r 14=-1754,216J. 3) Page 20, line 3 [r 15=-110,000
Correct J to r r 15=110.000 J. 4) In Table 4 on page 24, correct r62.260J in the 4th line of the i\r column on curvature to r42.260J. 5) In Table 9 on page 29, the last line [f3 =
233.835 J to r f3 = 123.835 J
It's correct. I"2

Claims (1)

[Claims] 1. A rear lens which is attached between an objective lens and a camera body and has a negative refractive power in order to enlarge the focal length of the composite system with the objective lens compared to the focal length of the objective lens. A conversion lens, a first group movable on the light 1Ijl+, a second group movable on the optical axis at a speed different from the first and ridges on the image side of the first group, and the second group movable on the optical axis. On the image side of the liver, the second and third parts are movable on the optical axis at different speeds.
ff'l', and when focusing, the first, second, and 32nd
A rear focus conversion lens characterized by moving ir. 2. According to the rear focus conversion lens according to claim 1, the magnification rate of the focal length of the rear focus conversion lens when focusing on infinity is set to β, and the focus is achieved. The distance change ΔD between the objective lens and the first group, the front distance change ΔD2, and the distance F between the second group and the third group
14 The rate of change of ΔD8 with respect to the amount of change ΔBt in the back focus of the composite system of the objective lens and the rear orcus conversion lens is α1. α2.
When α8 is set, α=α, 10α2+α3+1, which is constant 6. −1,5<α〈1.5 −2.0 (α, (1,5 −o, a (α2〈0.4 −0.3 (α, (0,4 1,2〈β〈2. 5. A rear focus conversion lens characterized by satisfying each of the following conditions.