JPH1039235A - Eyepiece - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an eyepiece with which various aberrations are well corrected over the entire area of a wide visual field and which has array leaves of a sufficient length and is capable of lessening the difference between the array leaves, by providing this eyepiece, successively from an objective lens side, with a combined lens of a negative lens and positive lens, a combined lens of positive refracting power consisting of two pieces and a single lens having positive refracting power to satisfy a specific condition. SOLUTION: This eyepiece has, successively from the objective lens side, combined lens L1 consisting of negative lens L11 and positive lens L12, combined lens L2 consisting of two lenses and having positive refracting power as a whole and the single lens L3 having positive refracting power. The eyepiece satisfies the conditions 0<ν2-νl<=30, 25<=|ν4-ν3| when the Abbe number of the negative lens L11 is defined as ν1, the Abbe number of the positive lens L12 as ν2, the Abbe number of the lens on the objective lens side of the combined lens L2 as ν3 and the Abbe number of the lens on the eyepoint side of the combined lens L2 as ν4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eyepiece,
In particular, the present invention relates to an eyepiece used for a telescope, binoculars, a microscope, and the like.

[0002]

2. Description of the Related Art For example, in a telescope, binoculars, a microscope, or the like, an eyepiece is used to further magnify and observe a real image formed by an objective lens. In this type of eyepiece, it is needless to say that each aberration is well corrected over a wide angle of view, and that an eye relief having a sufficient length for comfortable observation (the most eye side of the eyepiece). (On-axis distance between the lens surface and the eye point). In general, in an eyepiece having a wide field of view and a long eye relief, as the number of cemented surfaces increases, various aberrations around the field of view, in particular, chromatic aberration of magnification, coma, and distortion can be favorably corrected.

[0003]

However, when performing chromatic aberration correction using two or more sets of cemented lenses, even if only the chromatic aberration of magnification is satisfactorily corrected, if the difference in eye relief due to wavelength is large, If the observer's eyes are shifted back and forth from the eye point when observing through the eyepiece, the peripheral portion of the visual field appears to be colored blue or yellow. This phenomenon becomes more conspicuous as the eye relief is longer and the field of view is wider.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has various types of aberrations satisfactorily corrected over a wide field of view, has a sufficiently long eye relief, and has a wavelength-dependent eye relief. It is an object of the present invention to provide an eyepiece having a small difference and capable of maintaining a natural color in a peripheral portion of a visual field even when an eye is shifted forward and backward from an eye point.

[0005]

In order to solve the above problems, according to the present invention, in order from the objective lens side, a cemented lens L1 comprising a negative lens L11 and a positive lens L12;
A cemented lens L2 having a positive refractive power as a whole and a single lens L3 having a positive refractive power. The Abbe number of the negative lens L11 is ν1, and the Abbe number of the positive lens L12 is ν2. The Abbe number of the lens on the objective lens side of the cemented lens L2 is ν3, and the Abbe number of the lens on the eye point side of the cemented lens L2 is ν4.
And an eyepiece lens characterized by satisfying the following condition: 0 <ν2-ν1 ≦ 3025 ≦ | ν4-ν3 |

According to a preferred embodiment of the present invention, the radius of curvature of the cemented surface of the cemented lens L1 is R2, the radius of curvature of the cemented surface of the cemented lens L2 is R5, and the focal length of the entire lens system is F. At this time, the condition of 1.0 ≦ | R2 / F | ≦ 3.0 0.8 ≦ | R5 / F | ≦ 1.5 is satisfied. Further, it is preferable that the refractive index n5 of the single lens L3 with respect to the d-line satisfies the condition of 1.60 ≦ n5.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In general, in an eyepiece having a wide field of view and a long eye relief, as the number of cemented surfaces increases, chromatic aberration of magnification can be favorably corrected while various aberrations are favorably corrected. Also in the eyepiece of the present invention,
By using the two sets of cemented lenses L1 and L2, it is possible to obtain an aberration that is well corrected over a wide field of view. However, in order to ensure a sufficiently long eye relief, the image-side surface R of the cemented lens L1, which is particularly close to the image surface, is set so that the incident light beam can be separated from the optical axis as much as possible.
1 needs to have a large refractive power.

By the way, the image-side surface R1 of the cemented lens L1
Has a negative refractive power, light having a wavelength shorter than the reference wavelength will have a greater diverging effect than light having the reference wavelength. Conversely, light having a wavelength longer than the reference wavelength will have less divergence than light having the reference wavelength. For this reason, among the light beams incident on the surface of the cemented lens L1 closest to the objective lens, light having a shorter wavelength than the light beam of the reference wavelength is closer to the eye side of the single lens L3 arranged closest to the eye side (eye point side). On the surface, the light is emitted from the peripheral portion of the lens farther from the optical axis than the light beam of the reference wavelength. Conversely,
Light having a longer wavelength than the light having the reference wavelength is emitted from a position closer to the optical axis than light having the reference wavelength. As a result, despite the fact that the chromatic aberration of magnification is well corrected, there is a difference in the eye relief due to the wavelength, and when the eye shifts from the eye point to the direction approaching the lens, the peripheral part of the visual field is colored yellow, and If the eyes are displaced away from the lens, the periphery of the field of vision will appear colored blue.

In order to obtain a sufficiently long eye relief while avoiding the phenomenon of coloring of the periphery of the visual field, magnification chromatic aberration can be satisfactorily corrected while increasing the negative refractive power of the image-side surface R1 of the cemented lens L1. It is required to minimize the difference in the divergence effect of each wavelength within a proper range. Normally, for good correction of chromatic aberration, use an optical material with a large Abbe number for the positive lens and an optical material with a small Abbe number for the negative lens to keep the difference in Abbe number between the positive lens and the negative lens large. It is desirable. However, if the difference in Abbe number between the negative lens L11 and the positive lens L12 in the cemented lens L1 is too large, the difference in the height of the light beam due to the wavelength generated by the diverging action of the negative lens L11 on the objective lens side is reduced by the positive lens L12. It becomes difficult to correct. In the present invention, the difference in the eye relief due to the wavelength is reduced by defining the difference in the Abbe number between the negative lens L11 and the positive lens L12 of the cemented lens L1 within a predetermined range and reducing the difference in the height of the light beam according to the wavelength. I keep it small.

Hereinafter, the conditional expressions of the present invention will be described. In the present invention, the following conditional expressions (1) and (2) are satisfied. 0 <ν2-ν1 ≦ 30 (1) 25 ≦ | ν4-ν3 | (2) where, ν1: Abbe number of the negative lens L11 ν2: Abbe number of the positive lens L12 ν3: lens on the objective lens side of the cemented lens L2 Abbe number ν4: Abbe number of the lens on the eye point side of the cemented lens L2

Conditional expression (1) defines an appropriate range for the difference in Abbe number between the negative lens L11 and the positive lens L12 of the cemented lens L1. By satisfying the conditional expression (1), the difference in the height of the light beam depending on the wavelength can be suppressed within a range where the chromatic aberration of magnification can be favorably corrected, and as a result, the difference in the eye relief depending on the wavelength can be suppressed. Conditional expression (1)
Below the lower limit, the Abbe number ν1 of the negative lens L11 becomes larger than the Abbe number ν2 of the positive lens L12, and the difference in the refraction angle of each wavelength at the cemented surface (R2 surface) of the cemented lens L1 decreases. The difference in the height of the light beam depending on the wavelength is reduced. Therefore, although the difference of the eye relief depending on the wavelength becomes small, it becomes difficult to correct the chromatic aberration of magnification.
Conversely, when the value exceeds the upper limit of conditional expression (1), the negative lens L11
The difference in the height of the light beam due to the wavelength generated in the
It becomes difficult to satisfactorily correct with the subsequent lenses. In order to further reduce the difference in the eye relief depending on the wavelength and to obtain particularly excellent corrected lateral chromatic aberration, it is desirable to set the upper limit of conditional expression (1) to 25 and the lower limit to 4.

As described above, since the difference in the height of the light beam due to the wavelength is suppressed by the cemented lens L1, the correction of the chromatic aberration of magnification is mainly performed by the cemented lens L2. Therefore,
Conditional expression (2) defines conditions for enabling good correction of the chromatic aberration of magnification. When the value goes below the lower limit of conditional expression (2), the difference in Abbe number between the positive lens and the negative lens of the cemented lens L2 becomes too small, and it becomes difficult to satisfactorily correct lateral chromatic aberration. For better correction of chromatic aberration of magnification, it is desirable to set the lower limit of conditional expression (2) to 28.

In the present invention, it is desirable to satisfy the following conditional expressions (3) and (4). 1.0 ≦ | R2 / F | ≦ 3.0 (3) 0.8 ≦ | R5 / F | ≦ 1.5 (4) where: R2: radius of curvature of the cemented surface of the cemented lens L1 R5: cemented lens Radius of curvature of the cemented surface of L2 F: focal length of the entire lens system

Conditional expression (3) defines conditions for correcting the difference between the eye relief depending on the wavelength and the chromatic aberration of magnification with good balance. When the value goes below the lower limit of conditional expression (3), the diverging effect of light rays on the cemented surface of the cemented lens L1 increases.
The difference in the height of the light beam according to the wavelength increases, and the difference in the eye relief according to the wavelength increases, which is not preferable. vice versa,
When the value exceeds the upper limit of conditional expression (3), the difference in eye relief depending on the wavelength becomes small, but it is difficult to satisfactorily correct lateral chromatic aberration, which is not preferable. In order to perform better aberration correction, the upper limit of conditional expression (3) is set to 2.5.
It is desirable to set the lower limit to 1.5.

Conditional expression (4) defines conditions for maintaining a good balance between lateral chromatic aberration and other aberrations (particularly coma, astigmatism, and distortion). If the lower limit of conditional expression (4) is exceeded, lateral chromatic aberration will be overcorrected. Further, the radius of curvature of the cemented surface of the cemented lens L2 becomes too small, which leads to deterioration of coma and astigmatism, which is not preferable. Conversely, when the value exceeds the upper limit of conditional expression (4), lateral chromatic aberration and distortion are not sufficiently corrected, which is not preferable. In order to perform better aberration correction, it is desirable to set the upper limit of conditional expression (4) to 1.2 and the lower limit to 0.9.

In the present invention, it is desirable that the refractive index n5 of the single lens L3 with respect to the d-line (λ = 587.6 nm) satisfies the following conditional expression (5). 1.60 ≦ n5 (5) Conditional expression (5) is satisfied while ensuring a sufficiently long eye relief.
Conditions for favorably correcting astigmatism and distortion are defined. If the lower limit value of the conditional expression (5) is not reached, it is not possible to satisfactorily correct astigmatism and distortion while securing a sufficiently long eye relief in an eyepiece having a wide field of view as in the present invention. Absent. In order to correct astigmatism and distortion more favorably while securing a sufficiently long eye relief, it is desirable to set the lower limit of conditional expression (5) to 1.65.

[0017]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In each embodiment, the eyepiece according to the present invention includes a negative lens L11 and a positive lens L in order from the objective lens side.
12, a cemented lens L2 composed of two lenses having different signs of refractive power and having a positive refractive power as a whole, and a single lens L having a positive refractive power as a whole.
3 is provided.

Embodiment 1 FIG. 1 is a view showing the structure of an eyepiece according to a first embodiment of the present invention. The eyepiece of FIG. 1 includes, in order from the objective lens side, a cemented lens L1 of a biconcave lens L11 and a biconvex lens L12, a cemented positive lens L2 of a negative meniscus lens having a convex surface facing the objective lens side and a biconvex lens, And a convex lens L3.
Note that in FIG. P indicates an eye point.

Table 1 below summarizes data values of the first embodiment of the present invention. In Table (1), F is the focal length of the entire lens system, 2ω is the angle of view, ER is the eye relief,
d0 is the image formed via the objective lens and the cemented lens L
1 shows the axial distance from the surface closest to the objective lens. The numbers at the left end indicate the order of each lens surface from the objective lens side, R indicates the radius of curvature of each lens surface, d indicates the distance between the surfaces of each lens, and n and ν indicate d lines (λ = 58).
7.6 nm) and the Abbe number.

[0020]

Table 1 F = 14.5 2ω = 64 ° ER = 14.2 d0 = 3.2 (Conditional value) (1) ν2-ν1 = 8.7 (2) | ν4-ν3 | = 35.5 (3) | R2 / F | = 1.72 (4) | R5 / F | = 0. 97 (5) n5 = 1.713

FIG. 2 is a diagram showing various aberrations of the first embodiment with respect to the d-line (λ = 587.6 nm). In addition, each aberration is when a light ray is traced from the eye point side. In each aberration diagram, Y1 indicates the height of the light beam from the optical axis, and ω indicates the half angle of view. In the aberration diagram showing astigmatism, a solid line S indicates a sagittal image plane, and a broken line M indicates a meridional image plane. As is clear from the aberration diagrams, in this embodiment, a wide field of view (apparent field of view 64) is used.
It can be seen that various aberrations are satisfactorily corrected throughout (°).

[Embodiment 2] FIG. 3 is a view showing a configuration of an eyepiece according to a second embodiment of the present invention. The eyepiece of FIG. 3 includes, in order from the objective lens side, a cemented lens L1 of a biconcave lens L11 and a biconvex lens L12, a cemented positive lens L2 of a negative meniscus lens having a convex surface facing the objective lens side and a biconvex lens, And a convex lens L3.
Note that in FIG. P indicates an eye point.

Table 2 below summarizes data values of the second embodiment of the present invention. In Table (2), F is the focal length of the entire lens system, 2ω is the angle of view, ER is the eye relief,
d0 is the image formed via the objective lens and the cemented lens L
1 shows the axial distance from the surface closest to the objective lens. The numbers at the left end indicate the order of each lens surface from the objective lens side, R indicates the radius of curvature of each lens surface, d indicates the surface interval of each lens, and n and ν indicate d lines (λ = 58).
7.6 nm) and the Abbe number.

[0024]

Table 2 F = 14.5 2ω = 64 ° ER = 14.2 d0 = 3.1 (Conditional value) (1) ν2-ν1 = 15.6 (2) | ν4-ν3 | = 35.5 (3) | R2 / F | = 1.86 (4) | R5 / F | = 0. 95 (5) n5 = 1.713

FIG. 4 is a diagram showing various aberrations of the second embodiment with respect to the d-line (λ = 587.6 nm). In addition, each aberration is when a light ray is traced from the eye point side. In each aberration diagram, Y1 indicates the height of the light beam from the optical axis, and ω indicates the half angle of view. In the aberration diagram showing astigmatism, a solid line S indicates a sagittal image plane, and a broken line M indicates a meridional image plane. As is clear from the aberration diagrams, in this embodiment, a wide field of view (apparent field of view 64) is used.
It can be seen that various aberrations are satisfactorily corrected throughout (°).

[Embodiment 3] FIG. 5 is a view showing a configuration of an eyepiece according to a third embodiment of the present invention. The eyepiece of FIG. 5 includes, in order from the objective lens side, a cemented lens L1 of a biconcave lens L11 and a biconvex lens L12, a cemented positive lens L2 of a biconvex lens and a negative meniscus lens having a concave surface facing the objective lens side, and an objective lens. And a positive meniscus lens L3 having a convex surface facing the lens side. Note that in FIG. P indicates an eye point.

Table 3 below summarizes the data values of the third embodiment of the present invention. In Table (3), F is the focal length of the entire lens system, 2ω is the angle of view, ER is the eye relief,
d0 is the image formed via the objective lens and the cemented lens L
1 shows the axial distance from the surface closest to the objective lens. The numbers at the left end indicate the order of each lens surface from the objective lens side, R indicates the radius of curvature of each lens surface, d indicates the surface interval of each lens, and n and ν indicate d lines (λ = 58).
7.6 nm) and the Abbe number.

[0028]

Table 3 F = 14.5 2ω = 64 ° ER = 13.6 d0 = 4.1 (Conditional value) (1) ν2-ν1 = 8.7 (2) | ν4-ν3 | = 35.5 (3) | R2 / F | = 2.41 (4) | R5 / F | = 0. 97 (5) n5 = 1.713

FIG. 6 is a diagram showing various aberrations of the third embodiment with respect to the d-line (λ = 587.6 nm). In addition, each aberration is when a light ray is traced from the eye point side. In each aberration diagram, Y1 indicates the height of the light beam from the optical axis, and ω indicates the half angle of view. In the aberration diagram showing astigmatism, a solid line S indicates a sagittal image plane, and a broken line M indicates a meridional image plane. As is clear from the aberration diagrams, in this embodiment, a wide field of view (apparent field of view 64) is used.
It can be seen that various aberrations are satisfactorily corrected throughout (°).

[Embodiment 4] FIG. 7 is a view showing a configuration of an eyepiece according to a fourth embodiment of the present invention. The eyepiece of FIG. 7 includes, in order from the objective lens side, a cemented lens L1 of a biconcave lens L11 and a biconvex lens L12, a cemented positive lens L2 of a biconvex lens and a negative meniscus lens having a concave surface facing the objective lens side, And a convex lens L3.
Note that in FIG. P indicates an eye point.

Table 4 below summarizes the data values of the fourth embodiment of the present invention. In Table (4), F is the focal length of the entire lens system, 2ω is the angle of view, ER is the eye relief,
d0 is the image formed via the objective lens and the cemented lens L
1 shows the axial distance from the surface closest to the objective lens. The numbers at the left end indicate the order of each lens surface from the objective lens side, R indicates the radius of curvature of each lens surface, d indicates the distance between the surfaces of each lens, and n and ν indicate d lines (λ = 58).
7.6 nm) and the Abbe number.

[0032]

Table 4 F = 14.5 2ω = 64.4 ° ER = 12.2 d0 = 4.8 (Conditional value) (1) ν2-ν1 = 4.1 (2) | ν4-ν3 | = 28.6 (3) | R2 / F | = 1.59 (4) | R5 / F | = 0. 93 (5) n5 = 1.713

FIG. 8 is a diagram showing various aberrations of the fourth embodiment with respect to the d-line (λ = 587.6 nm). In addition, each aberration is when a light ray is traced from the eye point side. In each aberration diagram, Y1 indicates the height of the light beam from the optical axis, and ω indicates the half angle of view. In the aberration diagram showing astigmatism, a solid line S indicates a sagittal image plane, and a broken line M indicates a meridional image plane. As is clear from the aberration diagrams, in this embodiment, a wide field of view (apparent field of view 64.
It can be seen that various aberrations are satisfactorily corrected throughout (4 °).

[0034]

As described above, according to the present invention, various types of aberrations are favorably corrected over a wide field of view, an eye relief having a sufficient length is provided, and an eye relief having a small difference in eye relief depending on wavelength is provided. A lens can be realized. as a result,
The eyepiece of the present invention can maintain a natural color without coloring the peripheral portion of the visual field even when the eye is shifted forward and backward from the eye point.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an eyepiece according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating various aberrations of the first example.

FIG. 3 is a diagram showing a configuration of an eyepiece according to a second embodiment of the present invention.

FIG. 4 is a diagram illustrating various aberrations of the second example.

FIG. 5 is a diagram showing a configuration of an eyepiece according to a third embodiment of the present invention.

FIG. 6 is a diagram illustrating various aberrations of the third example.

FIG. 7 is a diagram showing a configuration of an eyepiece according to a fourth embodiment of the present invention.

FIG. 8 is a diagram illustrating various aberrations of the fourth example.

[Explanation of symbols]

 L1 cemented lens L2 cemented positive lens L3 positive lens EP eye point

Claims (3)

[Claims] 1. A cemented lens L1 composed of a negative lens L11 and a positive lens L12 and a cemented lens L composed of two lenses and having a positive refractive power as a whole in order from the objective lens side.
2, a single lens L3 having a positive refractive power, the Abbe number of the negative lens L11 is ν1, the Abbe number of the positive lens L12 is ν2, and the Abbe number of the objective lens side of the cemented lens L2 is An eyepiece characterized by satisfying the following condition: 0 <ν2-ν1 ≦ 3025 ≦ | ν4-ν3 |, where ν3 is the number and ν4 is the Abbe number of the lens on the eye point side of the cemented lens L2. . 2. When the radius of curvature of the cemented surface of the cemented lens L1 is R2, the radius of curvature of the cemented surface of the cemented lens L2 is R5, and the focal length of the entire lens system is F, 1.0 ≦ | 2. The eyepiece according to claim 1, wherein the following condition is satisfied: R2 / F | ≤3.0 0.8≤ | R5 / F | ≤1.5. 3. The eyepiece according to claim 1, wherein the refractive index n5 of the single lens L3 with respect to the d-line satisfies a condition of 1.60 ≦ n5.