JPS58205124A - Reflecting and refracting telephoto lens - Google Patents

Abstract

PURPOSE:To obtain a compact, high-performance telephoto lens, by arranging the 1st convergent lens group, the 2nd divergent lens group movable on an optical axis, and the 3rd convergent lens group successively in the traveling direction of a beam, and allowing them to meet specific requirements. CONSTITUTION:The lens system consists of the 1st convergent lens group G1 including a reflecting member L12, the 2nd divergent lens group G2 movable on the optical axis, and the 3rd lens group G3 successively in the traveling direction of a light beam. The 1st lens group G1 and the 2nd lens group G2 form a nearly afocal system in an infinite-distance in-focus state and a body at a close distance is put in focus by moving the 2nd lens group G2 to the image side, satisfying inequalities I and II. In the inequalities, f1 anf f2 are the focal lengths of the 1st group G1 and the 2nd group G2 and (f) is the total focal length of the system.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a catadioptric telephoto lens, particularly a VC that employs a focusing method with little variation in near-field aberrations.

In order to make a telephoto lens with a focal length of 250 mm or more compact as a lens for a 35-inch camera, a catadioptric lens system is often adopted. By using a catadioptric lens system, the magnification ratio (the front lens l relative to the focal length)
It is possible to realize a compact lens with a distance ratio of 0.3 or less (distance ratio from 11 fit to 11 fit), which is very advantageous in terms of operation, and has the further advantage that chromatic aberration is less likely to occur. The focusing method for such a reflective folding lens Vζ is as follows:
Conventional methods include: (1) total projection method, (2) changing the distance between the two reflecting surfaces, and (2) changing the distance between the two reflecting surfaces while keeping the distance between them constant and the wave power lens group.

Specifically, for example, JP-A-50-161143 ME
As you can see, catadioptric lenses are broadly divided into front group refractive systems (IC, ) sequentially from the direction of light propagation.
It is composed of four parts: the N first reflection thread (R1), the second reflection system (i), and the rear group refraction system (K,). %- in 1g1 figure
The configuration of the catadioptric lens described in Publication No. 151143/1983 and light from an object point at infinity on the axis are shown below. Here, what is the above-mentioned whole-extension focusing method? +R
1”R1+K.

This method focuses by moving the gold thread toward the object, and ■
The method of changing the interval between reflective surfaces is a method in which R1 is focused by moving R3 or R10*t-41 with respect to R1+ic, and method (2) is disclosed in the above publication and is a friend invention. This is a method in which focusing is performed by changing Kl ``R1''a and the distance between the two.

Next, we will give an overview of the conventionally known focusing methods of catadioptric lenses as described above.

■Overall With the extended focusing method, when the subject moves from an infinity position to a closer distance, the focal position extends toward the rear of the lens, but the entire lens system is simply extended toward the sound object side by that increase. The film is then brought to the surface of the film, and wax is also widely used in general photographic lenses, not just catadioptric lenses. If this extraction is JltX', then x / is approximately x'
: Lens focal length R: @Represented by the distance between the subject and the film surface. Most catadioptric lenses have a long focal length Mf, and the longer the focal length, the larger the violet, so it is mechanically long. It requires great care and modesty, and a complex mechanical structure is required. Furthermore, the change in barrel length when focusing on a short-range molten object also becomes large, which changes the lens's dimensional balance, which is disadvantageous both in terms of operability and in terms of making the lens more compact. That is clear. Next, regarding the method (2) of changing the spacing between reflective surfaces, this method is often used with wax in catadioptric lenses. R1 or RI"Kts and R1 or R, + have very strong power, so the protruding lid of the focusing pupil is pitifully small and the focus remains. However, the seventh point remains a problem. First, As is the case even in the case of taking out the entire lens, since the large-diameter lens pin must be moved, the moving mechanism is large, which is not desirable from the viewpoint of operability, and there are also manufacturing problems. With this method,
Since the reflective surface, which requires the most precision, must be moved, the reflective surface is likely to become decentered and the optical performance will be greatly degraded. When this method (■) is adopted, the conversion accuracy of this reflecting surface Il! :In order to ensure this, the precision of the metal parts and the precision of the glass parts must be made considerably strict, which is unfavorable in terms of processing and manufacturing costs. In addition, a powerful one? When moving, the aberration itself changes. With a lens with a long focal length, aberrations are best corrected when the lens is close to infinity, but when using a lens with strong power and 8 focal lengths, this relationship can be drastically disrupted by a small amount of movement. Therefore, aberration fluctuations at short distances, especially fluctuations in spherical aberration, are unavoidable to some extent.

The revision was disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 50-151143.
This is a method of changing the JuJ Kamikura for +)t, +R, but this is due to changes in the subject range ship.
Due to the change in focus of K, 10R, +R,
This method, which involves focusing by moving #KI +R, +l, is more advantageous than the spot shot (①) because it does not require relative movement of r for reflection r.

The God of Enlightenment is dC-ed in the above publication and is the next real thing! As seen in the M example, it is still around f/137.

If you compare this with the whole projecting type shown in ■, the shooting distance is much shorter.
Lof and combing amount is V41! Becomes wide. Moreover, in reality, +R and +R are fixed in a large moving body, and the K and + camera bodies are lowered and focused as one unit, so when focusing while looking through the viewfinder, It's very inconvenient.

The Moku Jakumei solves the above-mentioned drawbacks, shortens the close-up distance required for shooting, and is compact, with a very small shape and amount of focusing movement, and very little deterioration in close-range performance. The purpose of the present invention is to provide a catadioptric telephoto lens with excellent performance.

Catadioptric refraction according to the invention! l! A telephoto lens has a convergent first group (Gl
)% divergent second lens group (Gt), convergent third lens group (G, ), and when focused at infinity, the fringe lens a (Gt) , ) to form a 7-focal system, and in addition to focusing on a subject at a closer distance, the second lens blade (Gt) is moved toward the image side. And the first convergent group (G, ) and the silk second divergent group <at
) and #1 forms a 7-focal system, t=ts ” (fs /-t*'),...
-(b) However, fl: focal length f of the first group G,: focal length of the second snow G, snow point distance 1,: focal length of the third eave am is derived, and each group is determined by this relational expression 1 klk Sane)j It doesn't happen.

That is, the present invention consists of 9 convergence shots, 3 convergence experiments, and the combination St is performed by moving the complete defeat group between the two convergence #s, which is different from the basic cFi system No. 1050813-2. They are the same, and can be applied to a retrorefractive lens system. However, in the embodiment of the above patent, the structure is 1a;t, which is made up of only bending water, whereas in the + invention, the structure of the 9th iC group, in which the first group is composed of a catadioptric system, is completely different. In the catadioptric viewing system of the present invention, the distance lens and the warp arrangement 1' must satisfy the following conditions.

(1) o, o 7 fs <l ft l <0.
18 f+(2) 0.20f < f, <0
．． 5OfHere, f,,f, is the first group (G,) and the second group
Each represents the origin distance of the group (G2), and I is tiA
c/) Swallow, uses close range.

In the configuration of the catadioptric telephoto lens according to the present invention, as specifically shown in the embodiment described in fl, the movement of the second lens group for focusing is necessary in some places. The image can be much smaller than with conventional focusing methods. In addition, the second lens for focusing is a lens with a large aperture and a much smaller lens than the first lens, which has a reflective surface, so the power to move this second lens is also required. The mechanical structure can also be simplified.

and,#! The lens group located between the 1st lens group (G1) and the 3rd group (G,) is 41IwJ, so there is no change in the overall length of the lens during focusing, and only the comparatively small lens group moves. The lens holding balance does not change.

Furthermore, since the reflective surface, which is the lifeblood of a reflective optical system, does not move during focusing, eccentricity due to focusing does not occur, which is very convenient in terms of maintaining optical performance.

In addition, a catadioptric optical system with very little variation in short-range aberrations can be realized.

The meaning of the above conditional expression will be explained below.

Conditional expression (1) has not only a meaning in terms of aberration structure but also a conventional meaning. In order to simplify the mechanical structure, the opening I excitation #+ of the reflective optical system should be placed as close to the image plane as possible. If this focusing movement group is placed deep inside the m- (object) that holds the optical system of the part that wants to be reflected in the reflection system, the mechanical structure that moves it will also be warm. There is no #4 in the colander. If the upper limit of conditional expression (1) is exceeded, the power of the M2 group (G,) with respect to the first p(at) becomes small. This is extremely disadvantageous in terms of mechanical engineering.

Second, the total length of the lens also increases, which is disadvantageous in terms of compactness and operability of the lens.

If the lower limit of formula (1) is exceeded, the power of the 1st group (Gl) & C 2nd #F (Gl) will become stronger, and the result will be a failure.
The higher-order convergence that occurs at the 7th point z*(am) increases.

In particular, the curvature of field causes spherical aberration, which causes leakage and cannot be corrected, and aberration fluctuations at short distances greatly increase (
-Mau.

Moreover, the angle that the oblique light beam emitted from the 2nd g+(cl) makes with 9- is very narrow, which also leads to an increase in the aperture of the rear lens group, which also makes the lens more compact and improves operability (3).
It is disadvantageous.

The Petzval 1r aperture also becomes large and negative, and the curvature of field in the direction of the stop and the astigmatism become more difficult.

The conditional expression) is the spherical aberration and its short-range fluctuation, and the combination) I
This is for IA to the 28th P. transfer sea bream cover as Group A.

If the upper Vit is off, the -i-th group (cl
) becomes weaker, and the movement k of the second group (G, ) for focusing becomes seeded. Therefore, it is necessary to increase the air gap 11N between M2&i'' (G1) and the as (as), and the total length of the 4th thread (ft) increases, and the oblique light flux calculated by the 2nd # (G1) is changed to the The third group (aS) is far away from the optical axis and is received at a position 1 yo, so the rear lens aperture increases [7, which is disadvantageous in terms of compactness of the optical system and operations t and h. &C Bottom @ When the system is out of focus, the power of mxs (Gt) becomes stronger relative to the power of the entire system, and the brightness of this group becomes insufficient.Therefore, the occurrence of ^-order spherical aberration becomes a problem, and sufficient correction is no longer possible. I won't be able to do it.Father,
Short-range fluctuations in spherical aberration are so rapid that the object of the present invention cannot be achieved.

As stated above, by satisfying conditional expressions (1) and (2), a catadioptric lens that is compact, has excellent ayu-shi performance from infinity photography to close-up photography, and is very easy to operate. Obtaining is the ability of aT. Here, we will discuss the specific lens configurations of each group in order to make effective the basic power arrangement determined by the above conditional expressions.

The convergent light IN' (G,) is the ts1 refraction component (Pi) and the first reflection component (Q+) from the traveling direction of the light.
, M2 reflection component (Ql), second refraction component (P, )
) It is divided into four groups. The first refractive component (Pl) is composed of at least one positive lens, and the first and second reflective component (Qs) (Qm
) is constructed using a front-surface reflection mirror or a back-reflection mirror with a refractive surface. The jg1 reflected component (Ql) is set as light@total center, and a part is hollowed out, or only the central part is provided with a transmitting surface without a reflective surface, and that surface is shared and used as a companion.

As the second reflection component (Q,), the M1m refraction component (P,)
It is possible to attach a lens closer to the image than the first refraction component (P) to provide reflection thIt, and to increase the optical path length by attaching a lens closer to the object side than the first refraction component (P). can.

The second refractive component (P,) is usually composed of two or three lenses, and the center part of the first reflected/reflected component (Q,) is the second refractive component <
It can be used as a lens for news.

The second eaves, the divergent group (G snow), can be roughly divided into the front group (G snow).
mt) and the rear group (G□).

The front group (q,) and the wave lens (G,) refer to at least one concave lens, and at least one of the 1110 groups is a laminated lens, or the father is a metal rod with concave power, and the convex and concave lenses have a slight air gap. It is desirable to wait for achromatic elements that are opposite to each other across. In this second #(Gt), %
Since the color change due to spherical aberration is corrected, the front group (Gt1)
K: It would be more childish to have a colorless key book. This second
Regarding %pc, it is desirable to satisfy the following conditional expression.

(3) 0.65<lft*l/ 1ftl<1.8
5(4) ν −ν 〉12 a b However, f□: Focal length ν1 of the concave lens constituting the rear group of the second group (CWt): Atsube number of the endogenous lens of the achromatic lens element in the second solution νb: Ara of the internally concave lens of the achromatic lens element in M2N Conditional expression (3) relates to comatic aberration and chromatic aberration, and the lower [
If K is off, the power of the negative lens in the rear group (G□) of g241f- becomes distorted, and the divergence effect on the rays incident on the peripheral part of the oblique light beam becomes stronger, increasing the asymmetric component of coma aberration. , on the other hand, if it falls outside the upper limit, the happy 2nd group @s (cw
Since the negative lens component in t) becomes relatively strong, the achromatic effect becomes -〈, and the chromatic aberration of magnification varies depending on the output angle. Conditional expression (4) relates to the color change of spherical aberration. However, if the glass is selected outside the range of the conditional expression, the radius of curvature of the one achromatic surface must be cut off in order to ensure an achromatic potion, and the following color change due to spherical aberration will occur. I end up.

The third group, convergence 5 (cl, is roughly divided into the front group (aSS
) and the rear #(Gss). Both subgroups are composed of two or more lenses including at least one positive lens and at least one negative lens. ,, after # wait for a relatively small power with negative or positive,
lit! (3) Curvature and chromatic aberration of magnification are mainly corrected.

The front group has most of the power in the third solution, and mainly corrects field curvature and astigmatism. It is also desirable that the following conditional expression t- be satisfied.

(5) α75kuf□/fs<1.4 (6) IN
-Nnl > 0.25 However, f, 1: 3rd #
Focal length Np of the P middle front group: Refractive index of the positive lens of the 3rd # middle front group with respect to d -@I/C Nyu: Refractive index of the negative lens of the 3rd middle front group with respect to d -1 If the upper limit of 5) is exceeded, the power of the front group in the third group becomes weaker, the convergence effect on the oblique light beam diverged in the third group becomes weaker, the rear lens diameter increases, and the power of the front group becomes weaker. The distance ratio also increases, leading to an increase in the total length, which is not desirable. When the lower limit of back pressure is exceeded, the power of the front group increases, and the telephoto ratio of the third group becomes small, resulting in a compact configuration.
The negative power of the rear group also increases, and the Petzval sum increases negatively. Therefore, the positive 11#1fIJpII song becomes active and the astigmatism also increases. Article ■・Yl set (6) also relates to the Petzval sum; if the glass is made of glass with a refractive index outside the range of the conditional expression, the Petzval sum will increase in the negative direction, and positive field curvature will occur, resulting in astigmatism. Spare inspections will also increase.

Examples according to the present invention will be described below.

Each of the embodiments has a focal length of 1000 m and an F number of 11t for use with a 35 mm camera.

In the @1 embodiment, as shown in the lens configuration diagram in Figure 2, the first
The group (G,) is a positive lens (
L, ), a meniscus lens (Ll) with a concave lk-direction reflective surface as the gt reflective component (Q,), consisting of a negative lens and a positive lens laminated together, and a convex back reflective surface as the J2 reflective member (G2) It also functions as a meniscus lens (Lts) #iagz refraction component (P8).
m) is a meniscus lens (L!I) in which a biconvex positive lens and a granite-concave negative lens are laminated together as the front group (Glt);
The front group consists of a double-concave negative lens (Let) as the rear # (G□), and the front group of the H3 lens (G1) consists of a positive lens (La+) with a surface with a stronger curvature facing the object and a negative lens (Lll). (G1), and a rear lens (Gs-) consisting of a positive lens (L, 3) with a surface with a strong curvature facing the object and a negative meniscus lens <Lsa) with a convex surface facing the iron. In the same figure, in order to make it easier to understand the configuration of the present invention, the hook-edge light &1! from the infinite tail object point on the axis is written.In this first large IRM moga, q and resistance 2 Reflection component (9
) and the meniscus lens (Lts) as the second bending component (P8).
;, ), and in the second group (G2), the lens (L□) is bonded to the front column.
Achromatization is performed at the end of the closing process, and the rear lens is quickly opened (L□).
It has a simple configuration. Further, in the rear group of the third group (G), the aperture of the rear part of the lens system can be made small by providing a stop lens (Ll3) and a negative lens (Lea) on the image side.

The second fruit Nugri is the first group (G,) with 2 bars in Figure 3.
The configuration of the 3rd # (c, ,) is the same as the 1st 4th column, but the front group of the 2nd # (Gm) is separated from each other and consists of a nine biconvex positive lens (Lll) and a biconcave negative lens ( Lll).

As shown in FIG. 4, the 5g3 embodiment uses a surface reflective member (Lsa) t as the first reflection component (Q,) of the first eave (G,)
-Used. This anti-@ member (I4t) is not only formed on the lens surface by an anti-spa due to rapid increase, but also a reflection of the entire area.
It can also be composed of M, and quantification is Mue eaves.

Then, on the object side of the stop meniscus lens (Lll) as the first refractive component (Pl), there is a concave lens (Llm).
t, positive meniscus lens (Lsa) k at 111111
laminated, object side l of biconcave negative lens (TNS)
The second reaction component (ql) 1 is formed with fi as the reflection direction. In addition, as the second set fold component, the combined correct □ lens (L
tt) and a meniscus lens (
By adding Ltt), better color correction and correction of various aberrations as $1s (cz) are achieved.

The second group (G,) consists of a positive lens (Lll), a laminated negative lens (Ltt), and a thick negative lens (Lo) with a thick center. 7'cK), m (1% (G,) and 29th (G) located on the image side from the center aperture of the reflecting part U (Ltt) as m1 anti-induction of (Gl) Although the overall length of 9, which has a large diameter ratio, is somewhat long, it is advantageous in terms of manufacturing because the customary structure of moving the second block is simple.

The fourth example is the second one in the first group (G,), as shown in Figure 5.
Except for the laminated meniscus lens (Ltt) as a retraction component, the laminated positive meniscus lens (Ln) 1 for color rA L is provided as a second refractive component. The configurations of the second eaves (G,) and the third group (G,) are similar to those of the first embodiment.

In the fifth real example IIa, as shown in Fig. 6, the second group (Gt) +1
1 Middle cut# (Get) Consists of t' positive lens (L□) and laminated storm lens (Lll>, rear 1t'P (G
1 is constructed with a laminated lens (Lll), which also satisfactorily corrects ^-order spherical aberration. The composition of MIN (Gl) and second gentleman (Gl) is #!
This is the same as in the fourth embodiment.

The 6th actual example, as shown in figure M7, is composed of a rear group 1r instantaneous lens in the 2nd group (GlJ), and the 3rd group (
As a result of G, ) and L7, a positive lens (Ln4) is provided on the other side of a nine negative meniscus lens (Lss) with a convex surface facing the center.

The seventh embodiment has almost the same configuration as the sixth embodiment as shown in Fig. 8, but the bending force of each group is relatively small, and the overall shape becomes larger, but the aberration correction is corrected. The top is advantageous.

In the eighth embodiment, as shown in FIG. 9, the structure of the first ring (G1) and the third group (Gt) is the same as that of the fifth frame shown in FIG. 6, but the -lfi second group (G1) is It is composed of a negative lens with a negative Gunkura ratio.

Next, the specifications of each example will be shown. In each table, the round sign is the i-order 1 & eagle through which the rays incident from the object pass, and the refractive index n and the 7-beam number ν are the values for dIw (λ=587.6%m).

1st embodiment focal length f aperture 1000 F number 11 back focus Bj = 51β3 g2 embodiment focal length f 1000 F number 11 back focus Bf 75J8 3rd embodiment 4th embodiment focal length pi! f = 1000F number 11 back focus Bf = 7!67 5th embodiment focal length l@If = iooor number 11 back focus Bf = 7123 6th embodiment focal length f - 1000F number 11 back focus B, = 41jl focal length f = 100 OF number 11 back focus Bf = 41.10 8th embodiment focal length f = 1000 F number 11 back focus Bf = 6 concave 9 )

1...Is! Unexamined Japanese Patent Application Publication No. 5, 1987 as a common nine example shown in Figure 441
0-151143 Publication No. 7 Reflection #+I t
lr4! -i', I will also list the 4 types of filter lenses.

Known example (% Kaisho 5O-151143) Focal length jlli f = 1000 F number 10
Back focus B (=51.35 The various aberration diagrams of the above-mentioned 1st to 8th embodiments are sequentially shown in Figures 1O to 1.
It is shown in Figure 7. In each figure, (2) is a state in focus on an object at infinity, and C1(B) is a state in focus on an object at a close distance with an imaging magnification β=-0 and 2.

Sph is spherical aberration, Mut is astigmatism, D
%- represents distortion aberration f:. For comparison, Figure 918 (4) and @) show the infinity object focusing state and photographing magnification β = -0,2 of the catadioptric telephoto lens disclosed in the previous 1% Shima Publication No. 151143/1983. This shows an aberration diagram when the lens is focused on a close-range object.

From each aberration diagram, it is clear that the catadioptric lens according to the present invention has excellent focusing performance not only at infinity but also at close distances. Waiting for J @ Figure 18 (4)
A comparison with the known example shown in (B) shows that the catadioptric lens according to the present invention has a close range of 1 [
It can be seen that -I- is excellent even when the ratio is c to 1. Furthermore, the amount of movement of the focusing group required from the infinity focus state to the close focus state with the photographing magnification β-0.2 is as shown in the table below.
-151145, which is 14 or less, which is extremely small.

Amount of movement of the focusing group ``Toki no de f(-``Nayoi-Tai-t [-1-No. t113
As mentioned above, according to the present invention, in order to focus, it is only necessary to move the small lens group in the optical system, and it is compact and has good convergence performance from non-contact to short distances. It is possible to create a catadioptric telephoto lens with a single catadioptric lens. Since single-stroke refractive lens systems are often used in super-telephoto lenses with long focal lengths, the present invention 1 is very effective.

[Brief explanation of the drawing]

Figure 1 shows the configuration of a telephoto lens of the type disclosed in Japanese Patent Application Laid-Open No. 50-151143 and the light #I from an infinite axial object point! shows. Fig. 2 is a lens configuration diagram showing the 141st embodiment of the present invention, jIa is a lens configuration diagram of the second IM lens, Fig. 4 is a lens configuration diagram of the third embodiment/lJ, and Fig. 5 is a lens configuration diagram of the 41st embodiment of the present invention. FIG. 6 is a lens configuration diagram of the fifth embodiment. FIG. 7 is a lens configuration diagram of the sixth embodiment. FIG. 48 is a lens configuration diagram of the seventh embodiment. Lens configuration diagrams of the embodiments, @Figures 10 to 17 show various aberrations of the 1st to 8th embodiments. A) is the state in focus on an object at infinity, and Φ) is the photographing magnification! =
-0,2 focusing state on a close-range object, Figure 18 is an M aberration diagram of an eclipsing catadioptric telephoto lens disclosed in Japanese Patent Application Laid-open No. 50-151143 (false) is focusing on an object at infinity. State, (B) is a state of focus on a close-range object with a photographing ratio β=-0, 2! Show AJk. [Explanation of the code for the 1st part] G, 1st group 2G Goose JIz
Group-G,
3rd comment Acceptance □ 132- SPh Ast B) Sph Asir rs Fig. 11 (△) Sph Ast CB) Sph Ast is is Fang 72 Fig. (△) , 5', l)/1 Ast (8) phAsf IS rs off 30 (A) Sph Ast (B) spha 85t -(L)OL) (7,5(/-050IQ, 5
0i3 rs -2,5002,50 1,000/4shi (A) Sph A5f (8) Sph Ast is ls Off 5 figure (A) 3Ph Ast CB) iS IS ;776 figure (△) Sph A sf: (B) 3ph As-t is IS 士17 Figure (A) Sph Ast SpHAst -u, :u u v, l 050 0
θyBS IS Figure 18 (8) phAst CB) Sph Ast is is

Claims (1)

[Claims] A convergent third lens #G1 that sandwiches a reflective member sequentially in the direction of one line of light, and a diverging second lens that is movable along the optical axis NG! , a convergent third lens group G, and in the infinity focused state, the 1121st lens group G and the I
An afocal system is formed by the second lens group G, and by moving it to the second lens group Gut, it is possible to focus on an object at a closer distance, and the following conditions are met. Reflection ° refraction Ij & iIi characterized by satisfying
! far lens. (1) 0.07 ft < l ft I <0.
18 f+(2) 0.2 Of < f I < 0.
5 Of However, fl and f are the first and second reviews, respectively.
It is the focal length of the group, and f is the focal length of the entire system.