JPH0634893A - Ocular - Google Patents

Abstract

PURPOSE:To excellently compensate the distortion aberration by arranging a 1st spherical biconvex lens and a 2nd lens which has an aspherical convex surface on an eye side and an aspherical concave surface on the opposite side concentrically in order from the eye side. CONSTITUTION:The 1st spherical biconvex lens 11 made of glass and the 2nd lens 12 which has the aspherical convex surface on the side of the eye 13 and the aspherical concave surface on the opposite side are arranged on the same optical axis. The 1st lens 11 and 2nd lens 12 are arranged in order from the side of the eye 13 on the optical axis and an image formation plane 14 is provided on the optical axis on the opposite side from the eye 13 about the lenses 11 and 12. Then N1>1.58, V1>53, V2>35, and f1/f>0.75 are satisfied, where N1 is the refractive index of the lens 11, V1 and V2 the Abbe numbers of the lenses 11 and 12, f1 the focal length of the lens 11, and (f) the focal length of the whole lens system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eyepiece suitable for a viewer system of a video camera.

[0002]

2. Description of the Related Art Conventionally, as a low-cost eyepiece lens,
A doublet eyepiece lens configured as shown in FIG. 20 is known. In this eyepiece, a concave lens 1 having a high refractive index and high dispersion and a convex lens 2 having a low refractive index and low dispersion are combined and cemented on the same optical axis, and various aberrations such as chromatic aberration due to the negative refractive power of the cemented surface. Is to correct. In the cemented lens 3 configured as described above, the concave lens 1 is on the eye 4 side, and the front surface of the image forming surface 5 of the cemented lens 3 opposite to the eye 4 is covered with the cover glass 6.

21 to 26 show the aberration characteristics of the doublet eyepiece lens. 21 to 23 show the case where the diopter is 0 diopter, and FIGS. 24 to 26 show the case where the diopter is +4 diopter. 21 and 24 show spherical aberration,
22 and 25 show astigmatism, and FIGS. 23 and 26 show distortion. Further, the solid lines shown in FIGS. 21 and 24 are e (green).
The lines and broken lines show the spherical aberration characteristics of the g (blue) line and the dashed-dotted lines show the c (red) line. The solid lines shown in FIGS. 22 and 25 show the sagittal image plane, and the broken lines show the astigmatism of the meridional image plane. . 22 and 23, the maximum angle of view ω is 23.7 degrees.
5, it is assumed that the maximum angle of view ω is 24.1 degrees.

27 to 32 show aberration characteristics corresponding to FIGS. 21 to 26, respectively, when the conventional doublet is made aspheric.

[0005]

According to the conventional doublet eyepiece lens constructed as described above, the cemented surface between the concave lens 1 and the convex lens 2 has a negative refracting power, but it can be used for correction of image field curvature and distortion. Does not contribute much. Further, if the refractive index difference is excessively increased in order to increase the negative refracting power of the cemented surface, the radius of curvature of the convex lens 2 on the object side becomes small and the workability deteriorates. Further, if the radius of curvature of the cemented surface is made smaller, it becomes difficult to widen the angle of the lens system depending on the condition of total reflection of light rays.

On the other hand, as shown in FIGS. 21 to 26, in the conventional doublet eyepiece, spherical aberration can be corrected relatively well, but astigmatism and distortion are sufficiently corrected especially in a wide angle range. Not done. 27
As shown in FIG. 32, when an aspherical surface is attempted in the conventional doublet, the correction of astigmatism is improved, but the distortion is not corrected.

The present invention has been made in view of such a situation, and it is possible to satisfactorily correct distortion and obtain sufficient optical characteristics over a wide field of view and a wide diopter range.
An object is to provide a low-cost eyepiece lens.

[0008]

An eyepiece lens according to claim 1 comprises a first lens 11 having spherical convex surfaces on both sides,
The second lens 12 having an aspherical convex surface on the eye 13 side and an aspherical concave surface on the opposite side is sequentially arranged concentrically from the eye 13 side.

The eyepiece according to claim 2 is characterized in that the first lens 11 is made of glass and the second lens 12 is made of plastic.

In the eyepiece according to the present invention, the refractive index of the first lens 11 is N ₁ , the Abbe numbers of the first lens 11 and the second lens 12 are ν ₁ and ν ₂ , respectively. The focal length of the lens 11 is f ₁ , and the focal length of the entire lens system is f ₁ .
, N ₁ > 1.58, ν ₁ > 53, ν ₂ <35,
It is characterized in that the condition of f ₁ /f>0.75 is satisfied.

In the eyepiece according to the fourth aspect, the distance in the optical axis direction from the tangential plane at the apex of the second lens 12 is x, the height from the optical axis is H, the radius of curvature is R, and the conic constant is. Is K and the aspherical coefficients in the _4th to 10th terms are A _{4 to} A ₁₀ , the aspherical shape of the second lens 12 is given by the following two equations. x = H ² / R / [1+ {1- (K + 1) · (H / R) 2} 1/2 ] ^{_{+ A 4 H 4 + A 6}} H 6 + A 8 H 8 + A 10 H 10 K / 8R 3 + A 4> 0

[0012]

In the eyepiece lens having the above-mentioned structure, by making the structure of the eyepiece lens according to any one of claims 1 to 3, distortion aberration which cannot be corrected by the conventional cemented lens even though it has a two-lens structure. By using the second lens 12 which is an aspherical lens, it is possible to perform excellent correction.

When the aspherical shape of the second lens 12 of the eyepiece lens is the shape described in claim 4, sufficient optical characteristics can be obtained over a wide field of view and a wide diopter range.

[0014]

Embodiments of the eyepiece of the present invention will be described below with reference to the drawings and tables.

FIG. 1 shows the construction of an embodiment of the eyepiece lens of the present invention. In FIG. 1, a first lens 11 formed of glass having spherical convex surfaces on both sides, and a second lens formed of plastic having an aspherical convex surface on the eye 13 side and an aspherical concave surface on the opposite side. 12 and 12 are arranged on the same optical axis. The first lens 11 and the second lens 12 are sequentially arranged from the eye 13 side on the optical axis.
The imaging plane 1 is located on the optical axis on the side opposite to the eye 13 with respect to
4 is provided, and the front surface of the image plane 14 is covered with a cover glass 15.

The refractive index of the first lens 11 is N ₁ , the Abbe numbers of the first lens 11 and the second lens 12 are ν ₁ and ν ₂ , respectively, and the focal length of the first lens 11 is f ₁ When the focal length of the entire system is f, the conditions of the following equations are satisfied.

N ₁ > 1.58 (1) ν ₁ > 53 (2) ν ₂ <35 (3) f ₁ / f> 0.75 (4)

Also, the distance from the tangential plane at the apex of the second lens 12 in the optical axis direction is x, the height from the optical axis is H, the radius of curvature is R, the conic constant is K, and the quadratic apices are 10 to 10. When the aspherical coefficient at the next vertex is A _{4 to} A ₁₀ , the aspherical shape of the second lens 12 is set to satisfy the conditions of the following equations.

X = H ² / R / [1+ {1- (K + 1) · (H / R) ² } ^1/2 ] + A ₄ H ⁴ + A ₆ H ⁶ + A ₈ H ⁸ + A ₁₀ H ¹⁰ (5 ) K / 8R ³ + A ₄ > 0 (6)

Formula (1) is a formula relating to the refractive index of the first lens 11, and when the refractive index N ₁ is 1.58 or less, the lens becomes thick and becomes large. In addition, the image plane is curved due to the increase of Petzval sum, and particularly in the meridional image plane direction, it is largely curved to the under side in the peripheral portion of the visual field. In addition, the coma aberration of the light beam above the optical axis due to the widening of the field of view increases inward, which makes correction difficult.

The expressions (2) and (3) relate to the Abbe numbers of the first lens 11 and the second lens 12, respectively, and beyond these ranges, the amount of lateral chromatic aberration exceeds the allowable range.

Equation (4) relates to the focal length of the first lens 11 and determines the entrance pupil position. The entrance pupil is preferably telecentric in order to evenly capture light from the object plane. When f ₁ / f is 0.75 or less,
The negative refractive power of the second lens 12 becomes strong, and the distance to the entrance pupil becomes short. As a result, a shortage of light quantity occurs in the peripheral portion of the visual field. Further, as the focal length f ₁ of the first lens 11 becomes shorter, the shape of the second lens 12 changes to a deeper concave shape toward the object side, resulting in poor moldability.

Expressions (5) and (6) relate to the aspherical shape of the second lens 12, which assists the negative refracting power and corrects the distortion from the middle of the visual field to the peripheral portion and the curvature of the image plane. is doing. Further, when the value is out of the range of the expression (6), the first
The influence of the positive refracting power of the lens 11 becomes strong, and the inward coma in the peripheral part of the visual field increases, which makes correction difficult.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

[Table 3]

[0027]

[Table 4]

[0028]

[Table 5]

[0029]

[Table 6]

Next, the first to third numerical examples will be described with reference to FIGS. 2 to 19 and Tables 1 to 6.
2 to 7 and Tables 1 and 2 are the first numerical example, FIG.
13 and Tables 3 and 4 show the second numerical example, FIG.
19 to 19 and Tables 5 and 6 show a third numerical example.
2 to 4, FIG. 8 to FIG. 10, and FIG. 14 to FIG.
FIG. 24 is a diagram showing aberration characteristics corresponding to the conventional examples shown in FIGS. 21 to 23, respectively. Similarly, FIG. 5 to FIG. 7 and FIG.
13 to 17 and FIGS. 17 to 19 are diagrams showing aberration characteristics corresponding to the conventional examples shown in FIGS. 24 to 26, respectively.

Further, in Tables 1, 3 and 5, Ri is the radius of curvature of the i-th lens surface in order from the eye side, Di is the i-th lens center thickness or air gap in order from the eye side, and Ni and νi are These are the refractive index and the Abbe number of the i-th lens in order from the eye side. That is, R ₁ is the pupil plane, R ₂ ,
R ₃ is both sides a and b of the first lens 11, R ₄ and R ₅ are both sides c and d of the second lens 12, R ₆ and R ₇ are both sides e and f of the cover glass 15, and R ₈ is a joint. Each is the radius of curvature of the image plane 14. D ₂ , D ₄ , D ₆ , and D ₇ are the first lens 11, the second lens 12, and the cover glass 15, respectively.
And the center thickness of the imaging surface 14, D ₁ is between the eye 13 and the first lens 11, D ₃ is between the first lens 11 and the second lens 12, and D ₅ is the second thickness. Air gaps between the lens 12 and the cover glass 15, respectively. Also N ₁ , N
₂ , N ₃ and ν ₁ , ν ₂ , ν ₃ are the refractive index and the Abbe number of the first lens 11, the second lens 12 and the cover glass 15, respectively.

In the first numerical example, the radius of curvature R of each of the pupil surface, each lens 11, 12 and each surface of the cover glass 15,
The central thickness or the air gap D, the refractive index N and the Abbe number ν are
The settings were made as shown in Table 1, respectively. The radius of curvature R, the conical constant K, the aspherical surface coefficient A ₄ of the fourth-order to tenth-order terms indicating the shapes of both surfaces c and d of the aspherical surface of the second lens 12,
A ₆ , A ₈ and A ₁₀ were set as shown in Table 2. Second,
Similarly, the third numerical example was set as shown in Tables 3 to 6.

According to this embodiment, the two-lens structure of the first and second lenses 11 and 12 is used, and FIGS.
3, as shown in FIGS. 16 and 19, distortion can be corrected well, and sufficient optical performance can be obtained over a wide field of view and a wide diopter range. Further, by using a plastic lens for the second lens 12, it is possible to reduce the weight and the cost by reducing the lens joining process.

[0034]

As described above, according to the eyepiece of the present invention, since the plastic aspherical lens is used for one of the two lens configurations, the distortion is favorably corrected and the wide field of view is improved. It is possible to obtain sufficient optical characteristics over a wide diopter range. Further, by using a plastic lens and reducing the lens joining process, it is possible to achieve weight reduction and cost reduction.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of an embodiment of an eyepiece lens of the present invention.

FIG. 2 is a diagram showing spherical aberration when the eye has 0 diopter in the first numerical example.

FIG. 3 is a diagram showing astigmatism in the same case as in FIG.

FIG. 4 is a diagram showing distortion aberration in the same case as in FIG.

FIG. 5 is a diagram showing spherical aberration when the eye has +4 diopters in the first numerical example.

FIG. 6 is a diagram showing astigmatism in the same case as in FIG.

FIG. 7 is a diagram showing distortion aberration in the same case as in FIG.

FIG. 8 is a diagram showing spherical aberration when the eye has 0 diopter in the second numerical example.

FIG. 9 is a diagram showing astigmatism in the same case as in FIG.

FIG. 10 is a diagram showing distortion aberration in the same case as in FIG.

FIG. 11 is a diagram showing spherical aberration when the eye is +4 diopters in the second numerical example.

FIG. 12 is a diagram showing astigmatism in the same case as in FIG.

FIG. 13 is a diagram showing distortion aberration in the same case as in FIG.

FIG. 14 is a diagram showing spherical aberration when the eye has 0 diopter in the third numerical example.

FIG. 15 is a diagram showing astigmatism in the same case as in FIG.

16 is a diagram showing distortion aberration in the same case as FIG.

FIG. 17 is a diagram showing spherical aberration when the eye has +4 diopters in the third numerical example.

FIG. 18 is a diagram showing astigmatism in the same case as in FIG.

FIG. 19 is a diagram showing distortion aberration in the same case as in FIG.

FIG. 20 is an explanatory diagram showing a configuration of an example of a conventional eyepiece lens.

21 is a diagram showing spherical aberration when the eye of the eyepiece lens shown in FIG. 20 has 0 diopter.

FIG. 22 is a diagram showing astigmatism in the same case as in FIG. 21.

FIG. 23 is a diagram showing distortion aberration in the same case as in FIG. 21.

24 is a diagram showing spherical aberration when the eye of the eyepiece lens shown in FIG. 20 is +4 diopters.

FIG. 25 is a diagram showing astigmatism in the same case as in FIG. 24.

FIG. 26 is a diagram showing distortion aberration in the same case as in FIG. 24.

FIG. 27 is a diagram showing spherical aberration in the case where the cemented lens of the conventional eyepiece lens is aspherical and the eye is 0 diopter.

28 is a diagram showing astigmatism in the same case as FIG. 27. FIG.

FIG. 29 is a diagram showing distortion aberration in the same case as in FIG. 27.

FIG. 30 is a diagram showing spherical aberration when the cemented lens of the conventional eyepiece lens is made aspherical and the eye is +4 diopters.

31 is a diagram showing astigmatism in the same case as FIG. 30. FIG.

32 is a diagram showing distortion aberration in the same case as FIG. 30. FIG.

[Explanation of symbols]

 11 First Lens 12 Second Lens 13 Eyes

Claims (4)

[Claims] 1. A first lens having spherical convex surfaces on both sides and a second lens having an aspherical convex surface on the eye side and an aspherical concave surface on the opposite side are sequentially arranged concentrically from the eye side. An eyepiece lens characterized by being configured as follows. 2. The eyepiece according to claim 1, wherein the first lens is made of glass and the second lens is made of plastic. 3. The refractive index of the first lens is N ₁ , and the Abbe numbers of the first lens and the second lens are respectively ν
₁ , ν ₂ , f _{1 is} the focal length of the _first lens, and f is the focal length of the entire lens system, then N ₁ > 1.58 ν ₁ > 53 ν ₂ <35 f ₁ / f> 0. The eyepiece lens according to claim 1 or 2, characterized in that the condition 75 is satisfied. 4. The distance in the optical axis direction from the tangential plane at the apex of the surface of the second lens is x, the height from the optical axis is H, the radius of curvature is R, the conic constant is K, and the fourth to tenth terms. The eyepiece according to any one of claims 1 to 3, wherein the aspherical surface shape of the second lens is given by the following two equations when the aspherical surface coefficient in A is A _{4 to} A _10. lens. x = H ² / R / [1+ {1- (K + 1) · (H / R) 2} 1/2 ] ^{_{+ A 4 H 4 + A 6}} H 6 + A 8 H 8 + A 10 H 10 K / 8R 3 + A 4> 0