JPS6275509A - Zoom lens - Google Patents

Abstract

PURPOSE:To obtain a zoom lens appropriate to a small color video camera by constituting the 3rd lens component of a double-convex single lens and constituting the 4th component of a combined table of a positive lens and a negative lens successively arranged from the object side and a combined tablet of a double-convex lens and a negative meniscus lens. CONSTITUTION:The zoom lens is constituted of the 1st lens component having a positive focal distance to execute focusing, the 2nd lens component having a negative focal distance to execute power modification, the 3rd lens component having a positive focal distance to correct an image position and turn a beam projected from the 2nd lens component to an almost afocal beam, and the 4th lens component having a positive focal distance to form an image which are successively arranged from the object side. The 3rd lens component is the double-convex single lens and the 4th lens component is constituted of four lens consisting of a combined tablet of a positive lens and a negative lens and a combined table of a double-convex lens and a negative meniscus lens turning its convex surface to the double-convex lens. In addition, the zoom lens is satisfied with the shown conditions (1)-(3).

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECTS OF THE INVENTION (Usage in Industry) This invention relates to a zoom lens, and particularly to a compact, bright, high-power zoom lens suitable for use in small color video cameras.

(Prior Art) In addition to being bright, compact and bright, zoom lenses for small color video cameras have recently been expected to have high zoom ratios and low cost.

For use in such applications, a relatively simple configuration is used, in order from the object side: a first lens component for focusing with a positive focal length, and a second lens component for zooming with a negative focal length. 2 lens components, a third lens component with a positive focal length for correcting the image position and making the emitted light of the second lens component almost afocal, and a fourth lens component with a positive focal length for imaging. Zoom lenses made up of components have been well known. However, with this configuration, the variable power ratio is as large as 4x to 6x, and the F number is also 1x.
Large diameter ones with 2 to 13 degrees of deflection are not known, and are disclosed in Japanese Patent Application Laid-open No. 55-161207 and Japanese Patent Application Laid-open No. 58-681.
No. 110 can only be mentioned. The former has a variable power ratio of 5
, it is bright and highly variable at F 1.2, but it has a large number of lenses (3), and the latter has a variable power ratio of 4, F 1.2, and has a small number of lenses (11), but both the front lens and overall length. Both are insufficient in terms of cost reduction and compactness.

(Points to be solved by this invention) This invention has a variable power ratio of 4 to 6 degrees and an F number of 12 to 41t! The objective is to obtain a zoom lens that has a small number of constituent lenses, is compact, and is suitable for use in small color video cameras.

Structure of the Invention (Means for Solving the Problem) As shown in FIGS. 1 to 3, the zoom lens of the present invention has, in order from the object side, a focusing lens having a positive focal length. The second lens component has a negative focal length, the second lens component has a positive focal length, corrects the image position, and makes the light beam emitted from the second lens component almost an afocal light beam. and a fourth lens component for imaging having a positive focal length, the third lens component being a biconvex single lens, and the fourth lens component extending from the object side to II+, It has a four-piece configuration consisting of a tablet consisting of a combination of a positive lens and a negative lens, and a tablet consisting of a combination of a biconvex lens and a negative meniscus lens whose surface facing the biconvex lens is a concave surface, and satisfies the following conditions.

3 < 1571w < 6 ... group (
1) 50 ku ν3 ・Old... (2
)1.65 (n;, scream...(3)
However, fw: Focal length of the entire system at the wide-angle end f3: Synthetic focus ablation ratio of the third lens component: i31/Abbe number of the lens component n47. The refractive index of the positive lens closest to the object in the fourth lens component is determined.

Further, the first lens component is composed of one negative lens and two positive lenses, and the second lens component is composed of two negative lenses and one positive lens, and preferably satisfies the following flexibility.

4 < fl/fw < 6 ・・River (4
) fl, 8 < f2/fw < 1.6...=-(
5) -ol<f4/R< (1,3...(6
)ν; (3o... (7) However, fi: Focal length of the second lens component R: In the refractive surface of the object-side tablet of the fourth lens component,
The curvature of the surface closest to the image side is shown as the uniformity of the Abbe numbers of the two negative lenses of the 4th L/ance component.

Furthermore, the Luns component consists of, in order from the object side, a tablet consisting of a negative meniscus lens with a convex surface facing the object side, a positive lens with a strongly convex surface facing the object side, and a positive meniscus single lens with a convex surface facing the object side. It consists of The second lens component is desirably composed of a tablet consisting of a meniscus lens with a convex surface fully directed toward the object side, a biconcave lens, and a positive lens with a convex surface facing the object GIQ from the object side.

(Function) When the upper limit of Ei Note (1) is exceeded, the movement of the third lens component to correct the hidden surface position over a predetermined zoom ratio becomes large, and the overall length of the lens becomes long to ensure the movement path. turn into. On the other hand, if the lower limit is completely exceeded, the amount of lens movement can be reduced, but the amount of change in chromatic aberration that occurs in the third lens component due to zooming becomes large, especially at intermediate focal lengths compared to the short focal length end and long focal length end. The chromatic aberration of one sound rate becomes under.

Condition (2) relates to chromatic aberration occurring in the third lens component,
If the condition (1) is satisfied and then deviated from this condition, it will not be possible to completely correct the changes in the chromatic aberration caused by zooming.

Condition (3) is necessary for achieving a large aperture of F 1.2 to 1.3 with a simple configuration like the zoom lens of the present invention, and if this condition is violated, spherical convergence will be lost. The correction will be insufficient.

The lens component can be constructed from one negative lens and two positive lenses in order to sufficiently reduce the size while preventing unnecessary cost increases, and to correct aberrations at each station, especially on the long focal length side. desirable. In particular, the negative lens is necessary to perform achromatization within the second lens component.

Condition <4) is for selecting the entire focal length of the first lens component appropriately in such a configuration; if the lower limit is exceeded, it becomes difficult to correct aberrations on the long focal length side, especially spherical aberration and coma aberration. . When the upper limit is exceeded, the amount of movement for focusing increases, and the diameter of the front lens increases accordingly.

The second lens component is desirably composed of two negative lenses and one positive lens in order to reduce the number of lenses and suppress aberration changes due to displacement. In particular, a positive lens is necessary to perform achromatization within the second lens component.

Condition (5) is a precaution to set the focal length of the second lens component appropriately; if the upper limit is exceeded, the movement 1 of the second lens component due to zooming will increase, which will result in a result that goes against the purpose of compactness. Become. If the lower limit is exceeded, the refractive power of the third lens component increases in order to make the entire luminous flux emitted from the third lens component afocal in relation to condition (]), and the lower limit of Tojo (1) cannot be satisfied. It becomes difficult.

When the upper limit of Kume I4: (6) is exceeded, extroverted coma becomes noticeable, and when the lower limit is exceeded, it becomes difficult to correct spherical aberration.

Condition (7) relates to chromatic aberration, and if this condition is violated, it becomes difficult to correct longitudinal chromatic aberration and radial chromatic aberration.Example) Examples of the zoom lens of the present invention will be shown below.

In the table, r is the radius of curvature of the lens, d is the axial thickness and air spacing, and n and νd are the refractive index and Abbe number of the glass material, respectively. In all Examples, aberration correction was performed including the cover glass, which is indicated by the abbreviation CG, and in Example 4, P
Correction is also performed including the prism block indicated by the abbreviation B.

In Example 1.3.4, the average refractive index of the negative lens in the second lens component is n; (165). Although the refractive power of the third lens component becomes stronger than that of the case of Baijosaki, it cannot be made stronger than the lower limit of condition (1) in order to correct chromatic aberration, and accordingly, the refractive power of the second lens component becomes stronger. If the refractive power of the lens is weakened, and this condition is violated, the Vera Pearl sum of the entire system will tilt significantly toward the positive, making it difficult to obtain an appropriate straightness.

Example 1 Focal length 1 f=9.21-35.77 F
Wonno'-1, 25~13#, uniform 2154~53
2 r d n νd variable distance = 4.35 1w, f2- 1-1-1.06 8V f, - -0,264)j Δ-"" 25.65 Example 2 Focal length f = 8.24 to 47.67 F number 1.33 to 1.67 half-2026 to 331 r d n vd variable interval (+) f, = 19208 1. , = 1.7725ν4
-25.65 Example 3 Focal length f = 9.20 ~ 36.07 F nano -1,25 ~ 135 Half angle of view 2200 ~ 529 r d n 'd Variable interval (+) f4 = 16.0693 nl, = 1.713 - = 441 n1.1 = 1.07 v - = 0. +09 ν =246 Embodiment 4 Variable interval J'3=34.186()1=4.37, V1-1=1.07 mm,1-,=24.6 The zoom lens of the present invention has the following characteristics: As seen in the example and its aberration curve (■), although the number of lens components is small at 11, the zoom ratio is 4 to 61, and the F number is around 12 to 13 with a high zoom ratio. First, it is compact, low-cost, and has well-balanced aberration correction in the entire zoom range, making it possible to obtain a high-performance zoom lens.

[Brief explanation of drawings]

Figure 1, Figure 2, Figure 3, and Figure 4 are examples, respectively.
The cross-sectional views of Example 2, Example 3, and Example 4, and Figures 51A1, 6, 7, and 8 are Example 1.2.3.4, respectively.
It is an aberration curve diagram of. Patent applicant: Roku Konishi Photography Industry Co., Ltd., applicant's agent, Patent attorney, Fumi Saha (and 2 others) No. 1 Amendment to drawing procedure (method) February S, 1986 Mr. Michibe Uga, Commissioner of the Patent Office 1. Indication of the case 1985 Patent Application No. 214846 2. Name of the invention Zoom lens 3. Relationship with each case to be amended Patent applicant address 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Name Name
(127) Konishiroku Photo Industry Co., Ltd. Representative Keio Ide 4, Agent

Claims (1)

[Claims] In order from the object side, a first lens component for focusing having a positive focal length, a second lens component for zooming having a negative focal length, and a second lens component having a positive focal length, The third lens component comprises a third lens component for correcting the image position and making the light beam emitted from the second lens component into an almost afocal light beam, and a fourth lens component for imaging having a positive focal length. The lens component is a biconvex single lens, and the fourth lens component includes, in order from the object side, a tablet consisting of a combination of a positive lens and a negative lens, a biconvex lens, and a negative meniscus lens whose surface facing the biconvex lens is a concave surface. A zoom lens 3 consisting of a combination of tablets, which satisfies the following conditions: Focal length f_3: Synthetic focal length of the third lens component ν_3: Atsube number n^+_4_1 of the third lens component: Refractive index of the positive lens closest to the object among the fourth lens components