JPS59181314A - Zoom lens using plastic lens - Google Patents

Abstract

PURPOSE:To obtain a compact zoom lens having high performance, by which a variation of a focal position by a temperature change is small, by satisfying specified conditions in a lens system using a plastic lens consisting of four lens components. CONSTITUTION:In a lens system consisting of the first component I for focusing which has a positve focal distance, the second component II for variable power which has a negative focal distance, the third component III for correcting a movement of an image surface which has a negative focal distance, and the fourth component IV fixed in the course of variable power as a master lens component which has a positive focal distance, a lens to which hatching is performed is made of a plastic, and satisfies the following conditions. -0.22<fw (1/f7+1/f8+1/f13)<-0.18, n10<1.5, 65<nu10o. Wherein fw and fi, and ni and nui denote focal distances of the whole system and the i-th lens from an object side, and a refractive index and an Abbe number of the i-th lens from the object side. In this way, it is possible to obtain a compact zoom lens of a high performance, by which a variation of a focal position by a temperature change is small.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a zoom lens using a Gerastec lens, particularly a high-performance and compact zoom lens suitable for use in Konashi color 7J cameras for VTRs. .

(Prior art) From the object side to 11, a negative second lens component that has a focusing function moves with zooming, and a negative second lens component that changes magnification. A zoom lens that mainly consists of a negative third lens component that maintains a constant M position and has an axillary ability for movement, and a positive fourth lens component that has an ability to improve one image as a master lens. Although it is well known that using a plastic lens in a zoom lens is extremely effective in reducing the overall weight of the lens thread and improving the quantity, the V
/J Due to sexual constraints, there were the following problems: (1) The types of optical glass materials that have become transparent are limited, and freedom in optical design is limited.)

(2) The change in refractive index 'Df due to heat is greater than that of the Muryo glass material, and it is a national problem in design to compensate for this.

(3) Even if the above two difficulties are overcome, if you attempt to make the same changes or improve Q performance even further than the conventional glass lens design, the lens wire will become larger and compactness will be compromised. It will be done.

(Purpose of the Invention) This invention uses a gelastic lens in a zoom lens having the above-mentioned known stop, negative, negative, and positive V) #9 compositions, and sufficiently reduces the movement of the focal position due to a change in negative position. In addition, the objective is to obtain a zoom lens that has the same size υ and the same performance as conventional zoom lenses.

(Number 4 of the invention) In general, the higher the tM tension of an optical plastic material, the lower the refractive index (c/)), and the focal point V of a classic lens.
[The distance tends to be long in the case of non-exposure lenses, and the absolute distance tends to be large in the case of negative exposure lenses.

But 17, I have some iE negative lenses like this,
If we set their combined refractive power to 0, and assuming that the degree of refractive index change due to each lens Q temperature is equal, then the change in refractive power due to temperature '7) will also be equal to O. it is obvious.

In this invention, a total of four plastic lenses are used for the third and fourth lens components, and the above principle is applied between these lenses to keep the sum of the refractive forces of these D lenses constant. By making it less than 100 cm, fluctuations in the focal point position due to the warm glare of the entire system are suppressed. Of course! In an actual zoom lens, the positive lenses are arranged apart from each other, and the composite refractive power often does not become completely zero, but it is sufficient if this condition is approximately satisfied.

Note that when a glass lens is used as the first lens component for focusing, the focal position of the entire system can be changed by simply moving the first lens component after cutting by the amount of change in the focal position of the first component due to temperature changes. can be maintained in a fixed position,
Regarding the 1st lun's component, there is no need to perform any compensation on the optical groin.

As glass lenses are introduced into the third and fourth lens components, the refractive index reduction υ effect of the negative lens is particularly large, and the Veravar sum of all threads tends to decrease. Additionally, chromatic aberrations tend to be undercorrected overall. In the present invention, this point is particularly corrected by using a low-refractive-index low-density glass as a stopper lens in the fourth lens component.

Specifically, in order from the object side, such a zoom lens has a positive focal length and a lens component for focusing, and a second component that has a negative focal length and is used for multiplying by 2.
The fD third lens component has a negative focal length and is used as a master lens component to compensate for the movement of the M plane during zooming, and the fourth lens component has a fixed focal length and is fixed during zooming as a master lens component. The first lens consists of a meniscus negative lens L1 with a convex side facing the object side, a positive lens L1 with a convex side facing the object side, and a positive lens L with a convex side facing the f4- side.
3) Although it consists of three lenses, the two on the object side are sometimes bonded together to form a bonded lens. The second lens component consists of a negative meniscus lens L4 with a concave side facing the edge, a biconcave lens L5, and a positive lens L6 with a convex side facing the object. The third lens component consists of one lens L with a concave side facing the object, and the fourth
The lens component is a meniscus positive lens L8 with the convexity facing the edge.
, biconvex lens L8, biconvex lens L17, biconcave lens L1
2. Negative lens L13 with concave surface facing side, biconvex lens xL
, 4. A conversion lens L with a convex surface turned toward the object side, 8 pieces of 8 pieces of 5, above v) 1. ,L8,L++,Ll,'
! D Each lens is a five-point lens, fw: 0 focal length at the wide-angle end of the gold thread fi: Focal length of the i-th can υ lens from the object side j 111
: Refractive index of the i-th lens from the object side i:'JkJ
When taking the Atsube number of the 1st-eye lens from the body side, 1 1 1 1 -o, 22<fw<-7, +7-; +5, 14) <
-o, is -... (1) n1o <
15...(2)65
ν1o... (3)
It is supplied as a zoom lens that satisfies the following conditions.

ff1l) is a condition to compensate for the shift in focus position due to the use of a plastic lens; when the upper limit is exceeded, the plastic lens as a whole strengthens its positive refractive power, causing a rise (fall) in temperature. Sometimes, the bank focus changes significantly in the direction of lengthening (shortening). Conversely, if the lower limit is exceeded, the bank focus will be short when the temperature rises (falls) (
(longer) ■Changes become greater.

Condition (2) is a negative sign that conventionally used glass with a relatively cylindrical refractive index. This is a condition to suppress the decrease in

Condition (3) is a condition for correcting the axial chromatic aberration that occurs in the master lens system due to the use of plastic lenses -1L11 and L16. Axial chromatic aberration remains.

7) When the zoom lens of the invention is used for a VTR compact color camera, it is recommended that the zoom ratio will vary by about 6 and that the F number will be as large as 1.4 to 1.2. be done. [7 However, as mentioned above, in order to maintain an appropriate Veravar sum, the refractive index of the positive lens is decreased throughout12
Along with this, the spherical aberration becomes particularly noticeable when the h-s fold surface O curvature is made smaller and the aperture becomes larger. By using a spherical surface, extremely good aberration correction is possible even in a large-diameter lens with an F number as high as 1.2.

For this reason, it is desirable to satisfy the following conditions to the -11th order.

The shape of the aspherical surface is expressed by the following equation.

+ A, 2h"+A14b"-1-A, 6b' Nicode The origin is taken as the origin, and the pedestal in the direction perpendicular to the X axis represents the paraxial curvature of the plane of C.

If we expand this formula and take it up to the 6th trouble of kl, we can transform it as follows υ.

Here, r=τ is the paraxial curvature of the surface. The fourth term in the formula,
The fifth term causes distortion of the deformation from the spherical surface with the natural r'l, and has a close relationship with the third-order aberration and fifth-order aberration that occur on this surface, respectively. In particular, regarding third-order aberrations, when the third-order aspherical coefficient ψ is electrically bent by ψ = (N'-) (8A4 + person) 6, the spherical l retraction S coma aberration C1 astigmatism A and It is known that each distortion aberration undergoes a change by ΔS = h4ψ ΔC = h5Tψ ΔA h2712ψ ΔD = hh5ψ. Here, the paraxial axial ray and the paraxial principal ray at positions h and π respectively pass through this aspheric surface.

The O zoom lens of this invention uses an aspheric lens 1 on the object side surface of the lens "N," but since the ζ0 surface is located near the aperture, the effect of using the aspheric surface is mainly that of the spherical surface. Aberration S
It appears in Also, lens L7. In the υ plane on the θ squad side, both h1 and 5 are positive and have relatively large values, so the coma w, difference C, and astigmatism A are the main effects of making this surface aspherical.
It appears in

And ψ7. :11th lens L11θ object I from the object side
The third-order aspherical coefficient ψ7 of I O. : Third-order aspherical coefficient Zl of the edge side surface of the 13th lens L13 from the object side: -0,2< when the focal length is @22 lenses
t: ψ11 〈0 ・・・・・・(4) 0〈fW
ψ13 ku0 It is desirable to summarize the condition of (5).

Condition (4) is based on the introduction of condition (2) in order to maintain a good Veravar sum of the entire system as described above, and the θ condition is mainly used to compensate for the under spherical aberration that occurs when the lens is 0. ,ψ7. Because it's kuo, it's ku0 and nasi,
It can be seen that this has the effect of suppressing the spherical convergence from becoming 1o under. If the upper limit is exceeded, under-spherical aberration will occur throughout the entire zoom range, and conversely, if the lower limit is exceeded, spherical aberration will be over-corrected, resulting in a large aperture with a p1F number of 1.2. do not have.

Condition (5) is necessary because a Gerastec lens with a low Atbe's number and a low refractive index is used as the lens L16, and while using plastic for the lens 13, it is necessary to compensate for chromatic aberration and maintain an appropriate Perapart sum for the entire system. If you try to maintain this value, the curvature of the surface on the 30m side of the lens L will become stronger, and astigmatism and comatic aberration will tend to occur in the entire magnification range. is a condition for suppressing this; if the lower limit is exceeded, the meridional aperture becomes greatly over-centered, and the occurrence of extroverted υ coma becomes significant.

On the other hand, if the upper limit is exceeded, the correction will be over-corrected and both the meridional quadrant and coma will be under-corrected.

Condition (6) is a basic condition for making the entire lens system compact; if the upper limit is exceeded, the amount of movement of the second lens component becomes large, making it impossible to make the entire system compact. If the lower limit is set to ζ, the negative refractive power becomes excessive.
Aberration fluctuations due to zooming become large, making it impossible to obtain a zoom lens with good barrel performance.

(Example) Examples of the present invention will be shown below. Examples 1 and 2 are for small color cameras for VTRs with screen sizes of 24 inches; Examples 3 and 4 are zoom lenses for small color cameras for VTRs with screen sizes of 24 inches. uses a glass lens in the second lens component. The cross-sectional views of the lenses of each example are shown in Figures 1 to 4.
In the figure, the plastic lens is shown by the hunting cross-section. The value of the focal position change due to @fly in the table does not include the effect of the focal position change due to the plastic lens in the second lens component.

In Example 2, the third and fifth surfaces, in Example 3, the eleventh surface,
In Example 4, aspherical surfaces are used for the third, fifth, and twelfth surfaces, but these surfaces do not necessarily have to be aspherical in this invention. , Sakae There are glass plates equivalent to four-pass filters L and F in the four lens components, all with θ
The cover glass C1G1 is included in the embodiment, and aberration correction is performed for all threads including these.

Example 1゜Focal length f 11.5 ~ 69.1 F nanopar 1
．． 34~1.441 angle 2W depth 53, 6°~88° Back focus fB is also 11.8 A8=-3,45433xlO-1υ 111 - = 1.2 8 fW 1 1 1 1 fW (-10-+-+ -) =-0,196ft fB
Me1j'X3 f! ψ++= 0.0149 fwψ1= 0.0 2 6 1 Example focal length f=11.5-69. OF number 1.34
~1.44 Angle of view 2w = 53.8° ~ 87° Pack focus fB = 11.8 f still,, = -0,0177 f49'+s = 0.0274 1! , butt side 3 A14= 1,49778XIU-5υfshiψ1u=
0.0549 Example 4 A18>220060 By introducing a glass lens, we were able to make the lens system O cost-effective and increase M productivity, and we were also able to suppress changes in the focal position due to temperature changes, which was previously difficult. Furthermore, in the case of large-scale improvement, by using an aspheric surface for the glass lens, various types of This is a compact zoom lens 'kII4) with good aberrations and oil resistance.

[Brief explanation of drawings]

Figures 1, 2, 3, and 4 are cross-sectional views of the mt1.2, 3.4v lens, Figures 5, 6, and 7, respectively. Figure 8 also shows example 1 of deception.
．． It is a 2.3.4υ aberration curve diagram. %Applicant Elementary School 46 Photo 1 Eishi Ni Company Applicant Agent Patent Attorney Fumi Sato Male (and 1 other person) ■ Figure 1! . Figure 1”1.23 w=25.4° sphere rt
i + Aberration Non-sale Aberration No. 7 Figure W = 25.4 Distortion Aberration 1,000 1c Sode Tome Dai (Spontaneous) Showa 5 Haiku May 14'H Special ft' + - Director - Wakasugi Park Daidono 1,
i (f + ■ clothes 1is +1.158 year special plan muji
J also 43242 No. 2, Invention ■ Famous Phrases - Zoom lens using plastic lens 3, Ministry of Attachment q ↓ Note and '7) Section 19.1 Patent Applicant LaF Higashi, IJ4Gawa 1~6 Ward Nishi-Shinjuku 1-26 Silkworm No. 2 Name Tsuru
(12 Powers Konishi Rokuyo Shino Kamai Ceremony Representative Ministry I)
・ Issei 4, Agent 〒105 5, Number of inventions added by supplementary 11 - None 6,
Target of the amendment Details Threat 7, Contents of the amendment Attached sheet ＼-１１〆゛Contents of the amendment 1) Myung Pong Cao, page 12, line 5. ro<be ψ16<0・
...(5)'' as r O<f:, 9'13< 01--
--- (5) J correction f le. 2) Douji 6? Go v 11.2 < l Zl l
<・Old...(6)" is corrected to f~5 fBI r 1.2 (-(],, 4......(6)". W

Claims (1)

[Claims] In order from the object side, a first lens component has a positive focal length and is used for focusing, a second lens component has a negative focal length and is used to perform focusing, and a second lens component has a negative focal length and is used for focusing. In order to absorb the movement of the edge surface due to magnification, there are four lens components: the third lens component has a fixed focal length and is fixed during zooming as the master lens component, and the fourth lens component is the object lens component. There are three lenses: a meniscus negative lens L with a convex side facing the side, a positive lens L with a convex side facing the object side, a positive lens L with a convex side facing the object side, and the two lenses on the object side remain separated. The second lens component consists of three 3fF lenses or three lenses in two groups, which may be laminated together to form a laminated positive lens. Positive lens L6 with convex side facing object side
&@- The 3rd lens component consists of 3 elements in 2 groups of negative lenses glued together, the 3rd lens component consists of 2 groups of negative lenses with the concave side facing the object side, and the 4th lens component consists of 3 elements. 8 groups 8: positive meniscus lens L8 with its convex surface facing the edge; biconvex lens L9; biconvex lens L11; biconcave lens L12; negative lens L13 with its concave surface facing the edge; biconvex lens L14; positive lens L15 with its convex surface facing the object side. From the sheet, L7, L8 above,
Each lens L44, L, and 3 is a plastic lens. fW: Focal length of the entire system at the wide-angle end fi: Focal length of the first lens from the object side ni = Focal length of the first lens from the object side Refractive index stain: 1st lens from the object side - ■ When using Atsbe's number - 0,22 < jw (-L +-! 100%) < -0, 1
8f, j8f1111s n+. <1.5 65 〈 ν,. A zoom lens using a plastic lens that is patented to satisfy the zero condition.