JPH04336515A - Evf lens - Google Patents

Abstract

PURPOSE:To prevent the increase of the strain abberation, increase the magnification rate of a lens system, and provide the superior optical performance with the small-sized structure by constituting an EVF lens from a both-surface convex lens having a both-surface nonspherical surface shape and providing the lens with a specific nonspherical surface shape. CONSTITUTION:An EVF lens is constituted of a both-surface convex lens 11 having a both-surface nonspherical surface shape, and the lens 11 is installed at the position in the nearly focus distance of the lens 11 from an article surface 13, and an image magnified by the lens 11 can be observed from an eye point position 12. The both-surface convex lens 11 having a both-surface nonspherical surface shape satisfies the following conditions: 0.7<¦R1/R2¦<1.0-12.0<epsilon1<-7.0, 3.0<epsilon2<10.0. In this case, R1 is the radius of curvature on the article side, R2 is the radius of curvature on eye point side, epsilon1 is the conical coefficient representing the nonspherical surface shape on the article side, and epsilon2 is the conical coefficient representing the nonspherical shape on the eye point side.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an EVF lens suitable for video cameras and the like.

0002

2. Description of the Related Art In recent years, with the spread of compact video cameras, there has been a strong demand for miniaturization of EVF lenses.

An example of the above-mentioned conventional EVF lens will be described below with reference to the drawings. FIG. 3 shows a configuration diagram of a conventional EVF lens. In the figure, it is composed of one biconvex lens 1 having aspherical surfaces on both sides.

The operation of the conventional EVF lens configured as described above will be explained below. Object plane 3
That is, the lens 1 is installed at a position approximately the focal length of the lens 1 from the display surface of a CRT, liquid crystal, etc., so that an image magnified by the lens 1 can be observed from an eye point position 2. By making both surfaces aspherical, spherical aberration and lateral aberration, which indicate image performance, are improved, and furthermore, the aspherical shape is made bilaterally symmetrical for rationalization of production.

[0005]

However, the symmetrical aspherical shape as described above has a problem in that it is insufficient in preventing an increase in distortion due to an increase in magnification.

In view of the above problems, the present invention provides an EVF lens which prevents an increase in distortion due to an increase in magnification and has good optical performance by devising an aspherical shape.

[0007]

[Means for Solving the Problems] In order to solve the above problems, the EVF lens of the present invention is composed of a single biconvex lens having aspherical surfaces on both sides, and has a configuration that satisfies the following conditions. be.

0.7<|R1/R2|<1.0 (1)-1
2.0<ε1<-7.0 (2)3.
0<ε2<10.0 (3)
(However, R1 is the radius of curvature on the object side, R2 is the radius of curvature on the eyepoint side, ε1 is the conic coefficient representing the aspherical shape on the object side, and ε2 is the conical coefficient representing the aspherical shape on the eyepoint side.)

[0009]

[Operation] With the above-described structure, the present invention can prevent an increase in distortion due to an increase in magnification.

0010

Embodiments Hereinafter, EVF lenses according to embodiments of the present invention will be explained with reference to the drawings. Figure 1 shows the EV of the present invention.
This is a diagram showing a configuration of an F lens.

One biconvex lens 1 with aspherical surfaces on both sides
1, the lens 11 is installed at a position approximately the focal length of the lens 11 from the object plane 13, and the image magnified by the lens 11 can be observed from the eye point position 12. Examples of actual numerical values are shown below. r1 and r2 are the radius of curvature of each lens surface counted in order from the object side, d is the lens thickness, n is the refractive index for the d-line, and ν is the Abbe number for the d-line.

[0012] Practical numerical example Magnification ratio 9.96 |R1/R2|
=0.885 ε1=-10.39, ε2=6.715r1=22.8
89 d=2.5 n=1.49154 ν=5
7.4r2=-25.859 Object plane is 24.0mm from r1 Size of object
8.8×6.6 mm 2 The operation of the EVF lens configured as above will be explained below using FIGS. 1 and 2. First, Figure 2 (a
), (b), (c), and (d) respectively show the aberration performance of the example. In the diagram of spherical aberration, the solid line shows the spherical aberration of the d-line, the dotted line shows the spherical aberration of the F-line, and the dashed-dotted line shows the spherical aberration of the C-line. In the diagram of astigmatism, the solid line shows the sagittal curvature of field, and the dotted line shows the meridional curvature of field. In the diagrams of chromatic aberration of magnification, the solid line indicates the chromatic aberration of magnification of the F-line relative to the d-line, and the dotted line indicates the chromatic aberration of magnification of the C-line relative to the d-line. The lens operates to magnify the object so that an optimally sized image can be observed from the eyepoint. FIG. 2 shows that even though the refractive power of the lens is strengthened and the magnification is increased, it has good optical performance.

As described above, according to this embodiment, condition (1) is satisfied.
By providing (2) and (3), it is possible to prevent an increase in distortion and increase the magnification of the lens system. However, if the range of condition (1) is exceeded, the balance between spherical aberration and lateral aberration will be lost. Further, if the value falls outside the range of conditions (2) and (3), it becomes difficult to correct distortion.

[0014]

As described above, according to the present invention, it is possible to obtain excellent effects such as preventing an increase in distortion aberration and increasing the magnification of the lens system.

[Brief explanation of drawings]

[Fig. 1] A configuration diagram of an EVF lens according to an embodiment of the present invention.

[
Figure 2: Aberration diagram of the same example

[Figure 3] Configuration diagram of a conventional EVF lens

[Explanation of symbols]

11 Lens 12 Eye point 13 Object plane

Claims (1)

[Claims] Claim 1: Consists of one double-convex lens with aspherical surfaces on both sides, and meets the following conditions: 0.7<|R1/R2|<1.0 -12.0<ε1<-7.0 3.0 <ε2<10.0 (where, R1 is the radius of curvature on the object side, R2 is the radius of curvature on the eyepoint side, ε1 is the conic coefficient representing the aspherical shape on the object side, and ε2 is the aspherical shape on the eyepoint side. An EVF lens characterized by satisfying a conic coefficient.