JPS6028614A - Rear focus conversion lens - Google Patents

Abstract

PURPOSE:To make it possible to set a rear focus conversion lens to even an objective lens having a short back focus and to make the conversion lens compact by constituting the conversion lens with a positive front group and a negative rear group and moving both groups to focus the lens and satisfying prescribed conditions. CONSTITUTION:A lens system RFC (focal length fR) set between an objective lens L0 and a camera body consists of a positive front group (f1) G1 and a negative rear group (f2) G2, and both groups are moved to focus the lens system. The front group has a negative meniscus lens, whose convex is directed to the object side, and a positive lens following this lens. In equalities (1)-(6) are satisfied when a magnifying power of the focal length in the in-focus state in the infinity, a variation in the focus range of a composite back focus Bf, and a length from the lens surface nearest to the object of the RFC to the image point due to the object lens are denoted as beta, DELTABf, and d0 respectively.

Description

Detailed Description of the Invention (Technical Field of the Invention) The present invention provides a focusing rear lens/perjo/
Regarding lenses.

(Background of the invention) For single-lens reflex cameras, various autofocus lenses have already been commercialized by VC, but all of them are dedicated lenses that are only capable of autofocus for a specific lens. It lacked versatility and was expensive.

For this reason, a lens system dedicated to focusing is installed between the objective lens and the camera body (2) The configuration of a focusing conoverter that enables general-purpose automatic focusing is, for example, -2
Although this was proposed in Japanese Patent No. 8133, it was not practical. In other words, in order to be able to be attached to any objective lens, the K is small enough to be attached to both large aperture ratio objectives and objective lenses with extremely short back focal lengths. It was necessary to maintain high imaging performance, and it was extremely difficult to design a conoverter that satisfied all of these requirements.

(Object of the Invention) The object of the present invention is to be able to be universally attached to various objective lenses (-), and in particular to be attached to objectives such as short bank focus (+=), and to be able to be attached to objective lenses such as short bank focus and other objectives (+=), and to be able to be attached to various objective lenses. It is an object of the present invention to provide a rear focusing lens that can maintain excellent imaging performance while maintaining excellent imaging performance.

(Summary of the invention) The rear focus conversion lens according to the present invention has the following features:
A rear conversion lens mounted between an objective lens and a camera body for expanding the focal length of a composite system with the objective lens than the focal length of the objective lens; It has a front group with a positive refractive power and a rear group with a negative refractive power that can move on the optical axis relative to the objective lens and the camera body, and by moving both groups, it is possible to move from infinity to a predetermined short distance. The front group with positive refractive power includes a negative meniscus lens placed closest to the object side with a convex surface facing the object side, and a positive lens placed on the image side of the negative meniscus lens. 7, the magnification of the focal length in the infinity focusing state is β, the amount of change in the composite back focus Bf when focusing from infinity to a predetermined short distance is ΔBf, and the amount of change in the composite back focus Bf when focusing from infinity to a predetermined short distance is ΔBf, The focal length is fl (, the distance from the vertex of the most object-side/z plane of the rear conversion lens to the image point of the objective lens is do, and the focal lengths of the front and rear groups are fl and f2, respectively. When, ]3
β< 2.5 (1) 1 △B flfRl <0.2 (210,4< l
B f/d o'βl < 0.9 (3)-2,0
< f 2 / f 1 < 0.31 (4) 0, 6
< l f1/ f Rl < 1.8 (5) 0,
3 < I f2 / f Rl < 0.6 (6J
It satisfies each of the following conditions.

That is, the Fc according to the present invention is based on the I.
It has basically the same configuration as tFC.

In particular, Rli' C is divided into a convergent front group and a divergent rear group, and as the convergent front group, a negative meniscus lens with a convex surface facing the object side is placed closest to the object side. This feature is characterized by having a configuration in which it is arranged.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A rear focus lens (referred to as I°C) according to the present invention will be described below with reference to the drawings.

Figure 1 shows the objective camera body (2) and the eye camera body (2).
0) is a sectional view showing a schematic configuration of a state in which an RFC (30) according to the present invention is installed between the device and the device.

In the figure, a peripheral ray from an on-axis object point reaching the film surface (21)K is shown. - The eye reflex camera body (20) has a swingable reflector (22), a focus plate (23), a condenser lens (24), a lens system (25), and an eyepiece (26).

The reflecting mirror (22) is normally provided obliquely at the position indicated by the dotted line except when exposing the film surface (21). - In an eye reflex camera, in order to secure a swinging space for the swinging reflector (22), - the lens mounting surface (
28) and the film surface (21), the so-called flange back (MB), is set to a value unique to the camera body. The distance between the last lens surface of the objective lens and the film surface, that is, the back focus, is designed to be sufficiently long than the swinging space of the reflecting mirror (22).

Therefore, even when the RF C is attached to the objective lens, it is necessary to ensure that the back focus of the synthesis system with the objective lens (Br) is greater than the swing space of the reflecting mirror (22), and furthermore, it is necessary to ensure that the RF C is larger than the swing space of the reflecting mirror (22). It is necessary to maintain sufficient back focus even when the principal point of the negative lens group forming the RF C is moved to the image side for focusing.

In this way, the I according to the present invention must satisfy the conditions as they are as they are, and at the same time, in order to fully achieve the focusing function, various conditions must be satisfied. It is necessary. concrete V
For CVi, in order to increase versatility, there is an upper limit to the magnification magnification at which the RFC can be maintained, and in order to maintain good focusing accuracy even when attaching a bright objective lens or a dark objective lens. Since it is not desirable to ensure sufficient back focus even during distance photography and to increase the amount of movement of the RFC too much, there is also a lower limit to the magnification.

Since the camera according to the present invention focuses by moving in a limited space between the objective lens and the camera body, it is also limited in this respect.

That is, when focusing at the closest distance, the FC1' is moved on the optical axis to the closest image side. At this time, in order to establish an eye lens system, a sufficient back focal length is required, so the RF C lens system must be biased towards the objective lens system as much as possible.

On the other hand, the bank focus of general single-lens reflex camera objectives is set to the minimum necessary value in order to secure the swing space of the tight critter/mirror, and depending on the objective lens/lens reflex camera, the bank focus is extremely short within this range. There are also back focus objects.

In order to satisfy the versatility, it is also necessary to be able to attach it to an objective lens with such a long back focus, and taking these into consideration, the distance between RFC and the image point shift by the objective lens, That is, the object point distance of the RF C cannot be made very long, and there are limits to how the RF C lenses can be unevenly distributed. And compared to conventional general rear conversion lenses that do not move, there is little difference in the distance from the optical axis at the position where the oblique light flux and the light flux from the on-axis object point cut the rear conversion/version/lens, respectively. Therefore, there is little freedom in correcting aberrations, and it is extremely difficult to correct various aberrations satisfactorily over the entire focusing range (2).

In order to widen the focusable area with RF C as much as possible, we shortened the lens length for R and E'C (the length from the frontmost surface of 'RFC to the last surface), and set bank focus. There is a method to ensure this, but this also has its limits in terms of aberration correction. In other words, it is difficult to ensure a degree of freedom in correcting aberrations by creating a sufficient air gap within the RFC.

Therefore, in the present invention, as described above, by arranging a negative meniscus lens with a convex surface facing the object side closest to the objective lens side of the RF'C, the efficiency of achromatization is improved, and in particular, axial chromatic aberration can be reduced. We have found that it is easy to correct chromatic and spherical aberrations, and that it is also easy to correct higher-order chromatic spherical aberrations. By widening the air distance between the convergent front group and the diverging rear group as much as possible, it is possible to correct the extroverted coma of the rays above the principal ray that fall at the intermediate angle of view, and
It is now possible to correct inward coma aberration in the rays below the chief ray.

In addition, regarding aberration fluctuations when R and FC are moved to the image side on the optical axis and focused at a finite distance, the angle lens precedes the positive lens disclosed in the previous application. It has also been found that the method of the present invention has smaller fluctuations and is advantageous in maintaining stable imaging performance.

Each condition according to the present invention described above will be explained below.

If the upper limit of equation (1) is exceeded, it becomes difficult to correct aberrations and the number of lenses increases (2). Also, the f/bar of the composite lens system becomes too large and dark. It becomes impossible to obtain precision and lacks versatility.If the lower limit is exceeded, the amount of movement of the RFC becomes too sharp when trying to focus at a predetermined close distance, and on the other hand - ensuring back focus as an eye reflex lens 7 If you focus with
It is unsuitable for practical use.

If the condition of formula (2) is exceeded, the distance d from the vertex of the frontmost lens surface of RFC to the image point deflection by the objective lens.

It is necessary to increase the number of objective lenses to which the RFC can be attached, and the number of objective lenses to which the RFC can be attached becomes too small, which results in a loss of versatility, which is inappropriate. In addition, since the refractive power of 1-tp'c becomes too strong due to the shortening of f, it becomes difficult to correct astigmatism and Peso-Pearl sum, and the movement of 1jFc makes it difficult to focus at the closest distance of 'C'. This is still inappropriate because the aberration fluctuations become large when the lens is turned.

If the upper limit of equation (3) is exceeded, the lens length of 1tlL''C becomes too short, the K Noval sum becomes too negative, and the degree of freedom for aberration correction is almost lost. Also, β becomes too small. , the photographing range that can be focused becomes smaller due to image deterioration, which is inappropriate.

If the lower limit is exceeded, the magnification becomes too large, making it difficult to correct astigmatism and increasing the number of images. Moreover, R
The lens length of FC is also unsuitable because it becomes too long.

Equation (4) also specifies the appropriate refractive power and distribution of the front group r (relative to the rear group) of the FC; if the upper limit is exceeded, the refractive power of the front group with positive refractive power becomes too strong, and the This is inappropriate because it becomes difficult to maintain a sufficient bank focus of 1.

Exceeding the lower limit is inappropriate because it becomes difficult to correct spherical aberration. However, Equations (5) and (6) supplement the conditions of Equation (4) above, and if these conditions are violated, the balance of refractive power between the front and rear groups will be lost and various aberrations will occur. becomes difficult to correct. Furthermore, under the condition of equation (4), 0, 6 < f 2 / f l < 0. :31 is more preferable from the viewpoint of correcting various aberrations.

In the RF C of the present invention as described above, furthermore, R
Distance d between the vertex of the front/front surface of the FC and the image point formed by the objective lens. , and the distance between the objective plane of the camera body and the film plane, ie, the so-called flange bag MB, preferably satisfies the condition of 0.7<l d o /MB l <0.9. Here, a common single-lens reflex camera body is MB-46, 5 mm.

Furthermore, in order to properly correct the Petzval sum, 06〈β・do/f几〈10 04(’do/fR<”07 It is practical to satisfy the following conditions.

As for the specific lens configuration, the front group consists of, in order from the object side, a negative meniscus lens with a convex surface facing the object side and a biconvex positive lens. They may be cemented together, and another positive lens may be provided on the image side of the biconvex positive lens to share the convergent refractive power as the front group. Direct the rear group from the object side to JIEL, with a double concave negative/Z and the object side facing the surface with a stronger curvature.
It is also possible to further share the divergent refractive power as a rear group on the image side of these lenses, or to provide a single negative lens or lens on the ζth side.

(Example) Examples of RFC according to the present invention are shown below.

Each example is based on the objective lens shown in Table 1. This reference objective lens is described in Japanese Patent Application Laid-Open No. 52-88020, filed by the same applicant as the present application.

In Table I, R is the radius of curvature of each lens surface, d is the center thickness and air gap of each lens, n is the refractive index of each lens, ν is the Abbe number of each lens, and the subscript number is from the object side. Let it represent the order of . Furthermore, R, F'C according to the present invention
The specifications of the first to eighth embodiments are shown in Tables 2 to 9, respectively. In each of these tables, the order from the object side is shown at the left end of the table [7, do represents the distance between the frontmost lens surface of RFC and the image point according to the objective lens; The distance from the lens surface to the object point, Dl is the distance between the objective lens and the RF
It is assumed that fl represents the focal length of the RFC front group (G1), and f2 represents the focal length of the RFC rear group (G2). In addition, Bf represents the bank focus of the composite system of the lens Ii''C and the reference objective lens, and ΔB(B1(Ji'
C represents the amount of change in bank focus between infinite joint focusing and close range focusing, F represents the combined focal length of RF'C and the objective lens, and the photographing magnification of the MFi combining system.

Table 1 (Reference objective lens) β; 51.6 i” number 18 2ω=46”R1=
41.000 d1= 4.6 n), = 1.796
31 ν1==408R2= 197.900 d2”
0.1R3”” 21.400 63= 4.7 n
2=1. ．． 78797 shi2==4751 too. -32,
600d4=1. CIR5= 51.000 d5=
1.1 n3””1.74000 1'3=28.2
H2r= ] 6.200 d6”] 3.1p,,,
---16500d7=1.3 n4=1.7400
0 1'4=28.2RB=-1(10,000dB=
5.4 15=]74443 ν5 = 49.41
tQ""-2(1640dg" 0.11(=10=
204.3 (Hl dlo" 3.45 n5 = 1
．． 79631 Shiro = 40.81 (,1,2 -49
, 652Bf'=37. (i05 Table 2 (first example) Magnification: β; 16 Focal length fR, = -68,833 Table 3 (second example) Magnification °β = 1,6 Heat immersion distance fB = -71,029 Table 4
(Third example) Magnification: β; 16 Focal length fT (, = -70, 0, 98
Table 5 (4th example) Magnification: β = 1.6 Focus @ fH, = -70,20
1 Table 6 (Fifth Example) Magnification: β: 16 Focal length fH, = -70,937 Table 7
(6th example) Magnification: β: 16 Focal length fR = -71.201 Table 8 (
7th Example) Magnification: β: 1.6 Focal length f 71.603 Table 9
(Eighth Embodiment) Magnification: β=16 Focal Length fH,=-72,800 Lens configuration diagrams of the above-described first to eighth embodiments are shown in FIGS. 2 to 9, respectively. The lens configuration diagram of the first example shown in FIG. 2 also shows the lens configuration of the reference objective lens (Lo) in Table 1.

The various aberration diagrams when the RFCs of the above-mentioned first to eighth embodiments are attached to the reference objective lens shown in Table 1 are shown in order.
0(A)(B) to FIG. 17(A)('B). (A) of each figure shows various aberration diagrams when each RPC is attached to the infinite combined focus, and (B) of each figure shows the RF aberration diagram when each RPC is attached.
This shows various aberration diagrams when focusing at close range using C. Then, each aberration diagram KVi spherical aberration (S p b ), astigmatism (A3 t ), distortion aberration (pis), g-line (λ” 435 for the reference wavelength d-line (λ = 587.6 nm)
．． In all of the first to eighth embodiments described above, the front group (Go) and rear group (G2) are integrated. This configuration focuses on a close object by moving toward the image side, but as shown in Figure 18, focusing is performed by moving the front group (Go) and rear group (G2) at different speeds. It can also be configured as follows.

In this case, it is possible to further increase the imaging magnification due to close-range focusing, and it is also possible to correct aberration fluctuations during close-range focusing.

7. If the magnification β of the RF C is relatively high, sufficient focusing can be achieved only by relative movement between the front group (G1) and the rear group (G2) of the RF C. , the objective lens (L
o) It is also possible to perform focusing by adding movement of the lens itself.

Now, the l(・li' C) according to the present invention is installed between the objective lens (Lo) and the camera body (20), and the total length of the synthesis system when focused on an object at infinity (the frontmost surface of the objective lens) As shown in Figure 19, the total length when focused on a finite distance object is TL', and the distance between the objective lens (LO) and the front group (G) of the RFC is The interval D□ changes by ΔD, and from Dl to D1+ΔDIK, RIl'
Distance D between the front C group (G1) and the rear C group (G2)
2 changes by ΔD2 from G2 to D2+ΔD2, and the pack focus Bf of the synthesis system becomes B(+ΔBf.The amount of change ΔTL in the total length is ΔTL=TL'-1'L.
=ΔD1+ΔD2+ΔBf.

Here, the coefficient value α obtained by dividing the amount of change ΔTL in the total length by the amount of change ΔBf in the synthetic back focus is α = ΔTL/ΔBf = ΔD1/ΔBf + ΔD2/ΔB (10 I. Then, if we put , α=α, tenα2+1 (7), and G1 and G2 are the distance change ΔD1 between the objective lens (Lo) and the RFC front group (Go), and the RPC front group (G-) and rear Group (G
2) is the rate of change of the interval change ΔD2 with respect to the change ΔBf of the synthetic bank focus.

Equation (7) above can express all cases of movement related to the RFC of the present invention except for the case where the synthetic back focus does not change, that is, when ΔB f =o. For example, when α=0, the objective lens is opposite to the image plane [7
This means that the lens is fixed and focused only by RFC. However, in the case of α=0, α1=-1, and G2-o, this is a focusing method in which the rear group 01 and G2 move together, and the focusing method of the first to eighth embodiments described above is It is a focus method.

In the present invention, P(G) in front of the FC during short-distance focusing
, ) and the rear group (G2) toward the image side to reduce the distance between the two groups. stop,
Therefore, in the present invention, it is appropriate for the coefficient value α based on the above (method) to satisfy the following conditions: -10〈α≦o(8) α]<0 (91 It has been found.

Conditional expression (8) is ΔB f<0, so ΔTL≧0
, and the reference object /7:' is actively transferred to the object side by RF'C.
This means that it moves in conjunction with the opposite direction. By doing so, the closest distance can be shortened. Since ΔBf<0, conditional expression (9) indicates that the distance between the RFC and the objective lens is increased. By doing so, it is possible to actively increase the imaging magnification by RFC.

If the upper limit of conditional expression (10) is exceeded, the astigmatism becomes excessively negative, which is inappropriate. When G2 becomes negative beyond the lower limit, Δ
Since B f <0, the distance between the front and rear groups increases, making it difficult to correct spherical aberration that occurs excessively negatively.

FIG. 20 is a lens configuration diagram of a ninth embodiment according to the present invention. , the front group (G1) of FC is the rear group (G
2) By moving toward the image side at a faster speed and at the same time moving the objective lens (Lo) toward the object side, short-range focusing is achieved.

FIG. 21 is a lens configuration diagram of the 10th embodiment.
Similar to the ninth embodiment shown in the figure, the front group (G1) and the rear group (G2) of the KRFC move toward the image side at different speeds, and the objective lens (Lo) moves toward the object side, so that short distances can be achieved. Focus is achieved.

FIG. 22 is a lens configuration diagram of the 11th embodiment. In this embodiment, the objective lens (■. (01) moves toward the image side at a faster speed than the rear group (G2).

Table 10.11 shows the specifications of the ninth, tenth, and eleventh embodiments.
．． 12. Note that these embodiments are based on t F' C of the first, fourth, and eighth embodiments described above, respectively.

Table 10 (9th example) Magnification: β-1,6 focal length f = -68,833α =
-5,331 α1= -6,665 α2= 0.334 Table 11 (10th Example) Magnification: β=1,6 Focal length fR,=-70,202α
, = -3,333 Table 12 (11th example) Magnification: β = 16 Focal length fB = -72,800 α1 =
-1,053 Various aberration diagrams in the closest distance state according to the ninth, tenth, and eleventh embodiments are shown in FIGS. 23, 24, and 25, respectively. Various aberration diagrams of these embodiments at the time of infinite joint focusing are omitted because they are the same as those in FIG. 10 ('A), FIG. 13 (A), and FIG. 17 (A).

From each aberration diagram, it is clear that each embodiment of the RFC according to the present invention maintains excellent imaging performance not only when focusing at infinity but also when focusing at close range. In addition, in the ninth and tenth embodiments, by moving the auxiliary objective lens to the object side, it is possible to achieve practical imaging even at high magnifications such as M=-0 and 15. It can be seen that it is maintained.

Therefore, each embodiment can be attached not only to the reference objective lens shown in Table 1 but also to various objective lenses, and can be used to capture images from infinity while maintaining the same excellent imaging performance. It is possible to easily perform focusing at a predetermined short distance.

In the ninth and tenth embodiments described above, focusing is performed by relatively moving the convergent front group and the diverging rear group of the present invention, and by such a focusing method, spherical aberration and It is possible to correct short-range fluctuations in both astigmatism and astigmatism, but for example λ
For example, if only the positive lens located closest to the image side in the RFC is moved at different speeds, spherical aberration will be reduced as in the embodiment disclosed in a previous application (Japanese Patent Application No. 57-67061) by the same applicant as the present application. It is possible to correct astigmatism in the main VC without changing much.

(Effects) As described above, the RFC according to the present invention can be universally attached to any objective lens, and although it is compact, it has excellent performance from infinity to close range. If combined with an automatic focusing device, it is possible to focus on any objective lens by moving the RFC, so the focusing mechanism is common and even if the objective lens is replaced, there is no need to replace the focusing mechanism at all. It is unnecessary and extremely convenient.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing a schematic configuration of a rear focus converter according to the present invention installed between an objective lens and a single-lens reflex camera body, and Fig. 2 is a cross-sectional view showing a schematic configuration of a rear focus converter according to the present invention installed between an objective lens and a single-lens reflex camera body. This is a lens configuration diagram of the first embodiment, showing the positional relationship between the reference objective lens and the rear focus conversion lens in the infinity focusing state. System configuration diagram, Figure 10 (A
) (B) to Figure 17 (A) and (B) are the 1st to 8th figures, respectively.
These are various aberration diagrams of Examples, in which (A) of each figure shows an infinity focused state, and each figure (B) shows a closest distance focused state,
Figure 18 is a schematic illustration of the composition of the composite thread when another embodiment of the RFC according to the present invention is attached between the objective lens and the camera body and focused on an object at infinity. Fig. 20 is a schematic configuration explanatory diagram when focusing on a finite distance object.
Figure 21 is a diagram of the configuration of the lens in the infinity focused state in which the RF C of the ninth embodiment is used as a reference objective and is attached to the lens. FIG. 22 is a configuration diagram of the lens/swivel in the far-focus state, and is of the 11th embodiment.
23 to 25 are lens configuration diagrams in the infinity focus state with C attached to the reference objective lens, and 9th, 10th, and 10th, respectively.
FIG. 9 is a diagram of various aberrations in the closest distance focusing state of the eleventh embodiment. (Explanation of symbols of main parts) Lo...Objective lens I (, F C...77 Orcus comparator/shi/
G0... Front group G2... Back group Applicant Nippon Kogaku Co., Ltd. Agent Takashi Watanabe Male Figure 2 O, 5 Figure 4 Figure 5 O 6 Figure 7 Figure RFC FD 3rd prisoner RFC, f-10 prisoner, 5ph Asty (A) Oθ777a δPhASt/ Dis △αt, (Ar prisoner (f3) (,,oma 11th 5PhASt/ Figure (A) o777a Kozuki prisoner 5PhASt/ D15 △B, chr (f3), 6θ77?α 21Z diagram (7 A) oma og2 sPh A 5v Dis lαt, chγ Figure CB) Cθma 15th Di5 △at,, Ccr Figure (A) Co deposit α Translation, sp'h A3-b D; δ L (Zb, Chr Figure CB) C0 ga Sph AsuDノδ L(2t・θ・　](A) ovta Sp'j4 DノSL(It, C/rr Figure (6) (o77?a Figure 15 DK3 △at chr (A) At Cθγ/+15 δphAst/ D75 Lat, Chr Figure (B) Fang j6 Figure D;,s Lat, Chr (A) □o 'rnα 16th figure δph Ast/ Di, 5 Lt2t, Chr CB) C/θ77?a 11th prisoner (3ph 13+st D;s lat, C1w 'A) C0γa f-17 figure (B) Cθ Cao a O' 23 SphAsv Figure co'yna Spear 24 D;s Lat, C/nr Figure Co77?a Aug 1 Cause Cθ777a Procedural correction Eye (spontaneous) 2. Name of the invention Rear Force Conversion Lens 3° Corrector Incident 171g 'lVI'fRJllhIj, /
\Tokyo-[Kunouchi 3-T, III Ward, No. 2-3 (4]
1) 11 optical engineering facilities! ■, Shikisha Futaoka Shigekuda TT Rizansamu 1-Cho 1+, + Shigetada Oka 4, Agent 〒140 East 5; Yu 1%l, Seven Rivers Ward Nishijinnol'l 1
-1-16 No. 3 11 lights! :? -L'JJ,'l,1
(Meeting? 1 Large) 1 Factory (781i1) yr1 Satogami 1JfE Takashi Be! Please call (77:l)
l II l ``Mi'inl explanation of the invention'' of 111 subtitles in the subject of amendment '5, subject of amendment fl
l'l and "Figure 2 of the drawings" 6. Contents of correction 1) "A bright objective lens is sufficient" on page 10, line 12 of the Meiji M is corrected to "Only a bright objective lens is sufficient." do. 2) Delete "Due to image deterioration" on page 11, line 11. 3) In the 6th line of page 14, ``carry'' is corrected to ``provided''. 4) rM on page 17, 4th line from the bottom = -0,45J
is corrected to rM=-0,045J. 5) Set rM=-0,40J on the 4th line from the bottom of page 18 to r
Correct M = -0.04J. 6) Correct the symbol "dO" in Figure 2 of the drawings to rDI J as shown in the attached sheet. that's all

Claims (1)

[Scope of Claims] A rear camera/version/shield mounted between an objective lens and a camera body for enlarging the focal length of a composite system with the objective lens by φ than the focal length of the objective lens. a positive lens movable on the optical axis relative to the objective lens and the camera body; a front group having a refracting power and a rear group having a negative refractive power; It is the ability to focus on an object VC from infinity to a predetermined short distance from the moving VC of , and the front group of the jf' refractive power is a negative meniscus lens with a convex surface facing the object side and a negative meniscus lens with a convex surface facing the object side. A positive lens placed on the image side of / (r) The amount of change is ΔBf, the rear correction version/lens focal length =
r Hl, d is the distance from the vertex of the most object-side lens surface of the rear camera/version/shi/z in terms of the image point size according to the Ail objective lens. , when the focal lengths of the front group and the rear group are fl and f2, respectively, 13 β < 2.5 (11 1 ΔB (/ f B l < 0.2 (2) 0.4
<lBl/d o'βH<0.9 (3)-
2,0<f2/'f1<-0,31(410,6
< l f1/fR1<1.8 (5) 0.3<' l
f 2/ f kL l (0, 6 (rear focus conversion lens 0 characterized by satisfying each of the 61 conditions)