JPS61129612A - Variable magnification lens of front group interchangeable type - Google Patents

Abstract

PURPOSE:To simplify a stop, a shutter, and a focusing mechanism by interchanging a front lens group to switch the focal length and moving a rear lens group on the optical axis to perform focusing. CONSTITUTION:A lens system consists of front group lenses having a positive refracting power and rear group lenses having a negative refracting power which are arranged with the stop between them, and front group lenses are interchanged while keeping the stop and rear group lenses in certain positions with respect to the image surface to switch the focal length, and rear group lenses are moved on the optical axis to perform focusing.

Description

[Detailed Description of the Invention] (Field of application on IEM) This invention relates to photographic lenses, especially 11C @ detailed magnification type variable magnification lenses (G CvE technology). A variable magnification optical system that changes the magnification by changing the θ configuration is υ In a lens thread consisting of a front group and a lens thread, changing g& by changing the front group (% Kosho 40-4
1340, etc.) 2) Changes can also be made by inserting and removing the auxiliary lens between the main lens and the recess surface (JP-A No. 59-29214, etc.). 4) It is a lens system consisting of 11111 detail and review, and it can be changed by inserting and removing the removable 0 auxiliary lens in the front group and vk review 0.
5) Those that change the magnification by attaching a converter lens in front of the main lens (Japanese Patent Publication No. 41-71, etc.) are known. However, the above 1) The O type ■ has a rear group lens with positive ■ refractive power, and has a long back focus for the -eye lens, so the total length of the trap lens is long, and it is too large to be hidden in a lens-shutter camera.

In the type 2), an auxiliary lens with negative or positive Q refractive power is added to the main lens optical system whose aberrations are corrected to produce rounding and Veravar sum O plexus motion, which produces good iron. It is difficult to obtain surface properties. In addition, there are moving parts such as the main lens system, aperture drive system, and focusing system.
? ! The format O in 3) is difficult to apply to θ while maintaining the precision of rs.
Since the positive lens is moved on the optical axis and the second group is replaced at the same time, there is a problem in maintaining accuracy. Furthermore, since a certain degree of aberration correction is required for each group, the lens structure becomes complicated9, leading to cost problems.

The type υ type in 4) also changes the magnification by moving the front group and taking it in and taking out the auxiliary lens, so 3)
Problems similar to those of the O type arise.

5) ■The problem with type θ is that the converter lens mounted in front of the main lens becomes large, and it is difficult to make it compact.

There were many problems such as this, and it was not completely satisfactory.

(The problem to be solved by this invention is that the front lens fl'ffi is changed and the conversion is performed. [It simplifies the collection and shutter mechanisms by not changing the focus, and it also makes it possible to simplify the focal point A mechanism by adjusting the focus using the rear lens that is not involved in the adjustment. The structure of the invention is to obtain a compact high-performance lens (rounding means to solve the problem).The lens system of this invention has a front lens decoration that has a positive refractive power as shown in the above (■), 1auo placed across the aperture
It consists of a rear lens group with a refractive power 'f', and the focal length l@ can be changed by replacing the front lens while keeping the diaphragm and the rear lens at a fixed position with respect to the mounting surface. , is characterized in that focusing is performed by moving the wave power lens group on the t-element axis.

The front group lens for long focus has a refractive power distribution kk, and the two lenses on the object side are configured as a positive lens and a negative theta lens in that order. On the other hand, the front group lens for short focus has a retrofocus type refractive power arrangement, and the two lenses on the object side have a very negative lens and a positive lens.

Then, the short focal length of the front lens group for clear focusing is fT, and so is Q.
:) Back focus t-fB is 0.50
<fB/fT <0.80 ・・・・・・
(1).

The rear group lens has a refractive power of 110 (β (1, 50... (2) Have it.

In addition, the O configuration consists of at least one θ stop lens and one negative lens, and assuming that the refractive index of the positive lens is , and the refractive index of the negative lens O is Np < 1.60... ...(3
)1.75 (~...(4)t-satisfied.

(Function) With the above structure (1), the lens system of the present invention has positive and negative refractive powers for the front lens thread and the disposed lens thread, respectively, and the entire thread, including the short focal length field piece, is full of optical fibers. This shortens the overall length of the lens.

However, because the front group lens aperture and the rear group lens O position are not changed, short focus and close focus are the same.It is necessary to have a back focus. The lens group is a Retro 7 orcus type, and the O front group lens for long focus is a filtration type. In order to reduce costs, we need to reduce the number of constituent lenses (a), and in order to sufficiently correct aberrations, we use short-focus oil! i] For detailed lenses, in order from the original side, the negative ≠ lens, the positive ≠ lens alignment axis,
The long focal length υ front lens group is a positive θ-lens, starting from the object side.
Shell ■ - There is a must-fire in the lens configuration.

Article FF (1) relates to the basic configuration of the front group lens 0, and when the lower limit is exceeded, the front lens evaluation becomes strong room-to-field Tygian, and although the lens system can be made compact, it becomes difficult to achieve positive distortion correction. Since the refractive power of the lens is a shell, the Verabar sum tends to be negative, leading to an increase in the astigmatism difference. On the other hand, if the upper limit is exceeded, the lens system becomes bulky and the front lens group for short focal lengths becomes a strong retrofocus type, leading to deterioration of chromatic aberrations, etc. since the front lens group does not change its position.

Regarding the details of the rear lens, in order to suppress aberration fluctuations when moving on the optical axis and focusing, the 1 degree aberration of the rear group lens itself must be corrected, and at least one positive lens and 1&■ It is necessary to form a WP from a negative lens.

Condition 9) The refractive power of the refracting lens is determined, and if the lower limit is exceeded, the amount of movement for focus adjustment becomes large, such as the 1 Ilk short focusing distance limit for long focal lengths, etc. A mechanical problem arises. When the upper limit is exceeded, the D displacement becomes smaller due to focus adjustment, but the negative refractive power is strong, the perapal sum becomes negative, the astigmatism increases, and negative distortion on the long focal length side occurs. ■ Kusunoki becomes difficult.

Conditions (3) and (4) are all in the group ■A must-have # to truly enjoy Pepperl Japanese! Note 〇 (Implementation column) The following shows the ■Implementation column of this invention. The symbols in the table are R: curvature zone, D: interplanar spacing, N: refractive index, and ν: Atsube I! ! W is a half angle of view.

Example 1 f=100. OW=33.5 F4.0 (Short focal point side) 0 Short point side, rear lens group common to long focal point @ is after the 9th surface. 30 0 'FVf-1 = 0.58 ovIJ@distance a U = 4347.8 +2) Details of rear lens on short focus side Movement amount: 4.56 to the front side (freezing magnification -0,024) On the lever focus side Rear lens group moves t toward the iron side 15.21
(Conclusion (IN, m car - 0,04) Actual m row 2 f=100.0 W=33.1 F4.0
Tsuki focus gJA) RDN ν f=171.3 W=20. OF5.6 (Long focus 1
11) k4. f) N ν The rear lens group common to the 0 short focus side and the leveraged focus side is from the 9th surface onwards and the 0 aperture is in front of the 9th surface 6.52 0 Details β=1.22 0 fB/fT= 0.59 Implementation row 3 f=100.0 2W=33.4 F4. O (short focus side) i=1r3. l 2W = 19.7 b゛s, s (Long focal point side) 0 Short point side, long focal point @ 11
1LO rear lens group is after the 9th surface and O aperture is in front of the 9th surface.
6.82 ovk lens details β=1.30 ・Δ=0.62 r Real row 4 f=100.0 W=33.4 F4.0 (short focus side) f=173.3 W=19. 7 F5
．． 6 (long focus side) 15 -64υ, υD
.

The rear lens group common to the 0 short point side and the long focal point side is after the 9th surface, and the 0 aperture is in front of the 9th surface 6,50 o? jk direction lens β=1.38 Effects of the Invention The variable power lens of the Q invention O has a simple structure as described above,
It is compact, the IR and shutter position remain unchanged,
The focus adjustment is also covered in dust that is not related to the exchange, so the mechanism is also closed.

Furthermore, unlike the method of adding an auxiliary lens system to the aberration-corrected Q lens system to change the magnification, aberration correction can be performed including the front group lens and the rear detail lens, so as shown in the aberration curve diagram, the aberrations can be corrected. Aberration correction is done well, making it possible to obtain high-performance lenses.

Furthermore, as shown in Figure 2c and dK, by configuring the rear lens group with at least one positive lens and one negative lens, it is possible to suppress aberration fluctuations in close-range objects to small eyes. It is 〇

[Brief explanation of drawings]

Figure 1, Figure 2, Figure 3, and Figure 4 are the first and second figures, respectively.
, third and fourth practical cross-sectional views and their yield curve diagrams,
(a) shows the short focus state, and (b) shows the lever focus state. Figure 2 (
e) <d) is the distance between the metals of the second implementation row @ U = 434
7.8 (Short focus at 0 o'clock, long focus ■Reed drawing. Patent applicant Roku Konishi Photographic Waxing Ceremony Certification Applicant's agent Patent attorney Fumi Sahata (and 1 other person) +6+ F 4.II %V=3
8.5 Tsubo surface distortion Non-d aberration Distorted surface J recruitment l Figure fl) I F 5. fi w=
20.4 Endoscopic convergence Non-convergence M Distortion Tsukuda aberration Fig. 2 fQI F4.0 Sum 1 (8,
1 Yodo, 1 Yoshimata, non-soldier 4-mata Mitsubai ♂Tsukudshu Goshohama 2 Figure 1bI F56sV=20. n α-plane aberration Non-aberration etc. Distortion Tsukuda aberration 2 Figure 1c1-1. n n 171 -1. n
n1. (1-2, n n 2. Q meplanar aberration
Non(Aberration Distortion Aberration Fig. 2 f
dl -1jl (11,0-1,On 1.0
-2.0 (12, n reductive aberration non-φ aberration
φYaw aberration Figure 3 fal F4. n W = Nil 84 surface aberration non-φ aberration distortion day aberration 廖
;3 Figure 11) I F5.6', V=19.7
1,000 LIB pe)? ij 4th
Figure fal

Claims (1)

[Claims] 1) Consisting of a front group lens with positive refractive power and a rear group lens with negative refractive power disposed across an aperture, the aperture and the rear group lens are aligned with respect to the image plane. A front group interchangeable variable magnification system characterized in that the focal length is changed by exchanging the front group lens while keeping it at a constant position, and focusing is performed by moving the rear group lens on the optical axis. Lens 2) When the focal length f_T of the long focal length lens of the replacement front lens group and its back focus are f_B, the following is satisfied: 0.50<f_B/f_T<0.80 Variable power lens in scope 1 3) A patent claim characterized in that among the above-mentioned replacement front group lenses, the short focal length lens includes a negative single lens and a positive single lens in order from the object side. 4) A patent characterized in that, among the above-mentioned replacement front group lenses, the long focal length lens includes a positive single lens and a negative single lens in order from the object side. Variable power lens according to claim 1 5) The rear group lens includes at least one positive lens and one
6) The variable magnification lens according to claim 1, characterized in that it consists of a negative lens. 6) The rear group lens has a magnification ratio β that enlarges the focal length of the front group lens at infinity. , 1.10<β<1
．． 7) A variable power lens according to claim 1, which satisfies the following: 7) The refractive index of the positive lens constituting the rear group lens is N_
P, and if the refractive index of the negative lens is N_N, then N_P<1.
60 1.75<N_N A variable power lens as claimed in claim 5