JPH0540232A - Wide visual field eyepiece - Google Patents

Abstract

PURPOSE:To obtain the wide visual field eyepiece which satisfactorily corrects various aberrations such as pupile aberration or chromatic aberration (especially the chromatic aberration of the pupile) and prevents a lens from being too close to an image. CONSTITUTION:A first lens group G1 of a positive lens, second lens group G2 of a meniscus-shaped negative lens as a whole and third lens group G3 of a positive lens as a whole equipped with a positive/negative joint lens are successively provided from the incident side of light and when an entire focal length is defined as fa, focal length of the first lens group is defined as f1, a radius of curvature on the incident side of the second lens group is defined as RF, focal length of the third lens group is defined as f3, respective Abbe numbers of the positive/negative joint lens in the third lens group are defined as nuv and nuc, following conditions are satisfied; (1) 1<¦f1/fa¦<2, (2) 0.5<¦RF/fa¦<1, (3) 0.5<¦f3/fa¦<2, (4) nuv-nuc>10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wide-field eyepiece for a microscope or the like, and more particularly to a wide-field eyepiece having a good image plane flatness.

[0002]

2. Description of the Related Art Conventionally, as a wide-field eyepiece lens, 4 groups 4 groups
The one having a sheet structure disclosed in JP-A-60-57315,
Further, as a structure of 5 elements in 3 groups, Japanese Patent Laid-Open No. 56-1289
No. 13 and the like are known.

However, in these conventional examples, in the former case, since there is no cemented surface, the correction of the pupil aberration and the chromatic aberration (particularly, the chromatic aberration of the pupil) is insufficient, and the correction of the chromatic aberration of the pupil is insufficient. There is a problem that coloring appears around the visual field when the eye is shaken. The latter one has a drawback in that the lens closest to the image side is too close to the image, and dust and scratches on the lens surface closest to the image side are noticeable.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of such a situation, and an object thereof is pupil aberration,
An object of the present invention is to provide a wide-field eyepiece lens in which various aberrations including chromatic aberration (particularly, chromatic aberration of the pupil) are satisfactorily corrected and the lens is not too close to an image.

[0005]

A wide-field eyepiece according to the present invention, which achieves the above object, comprises, in order from a light incident side, a first lens group of positive lenses, a second lens group of negative meniscus lenses as a whole, A third lens group, which is a positive lens as a whole including a positive / negative cemented lens, is provided, the total focal length is f _a , the first lens group has a focal length f ₁ , and the second lens group has an entrance-side radius of curvature R _F. , The focal length of the third lens group is f ₃ ,
When the Abbe numbers of the positive and negative lenses of the cemented lens in the lens group are ν _v and ν _c , respectively, the following conditions are satisfied.

(1) 1 <| f ₁ / f _a | <2 (2) 0.5 <| R _F / f _a | <1 (3) 0.5 <| f ₃ / f _a | <2 ( 4) ν _v −ν _c > 10

[0007]

The function and operation of adopting the above configuration will be described below. In order to secure the flatness of the image surface with a wide angle of view, it is necessary to reduce the Petzval sum to reduce the field curvature, but in general, the eyepiece lens has a strong positive power, so the Petzval sum also It becomes a large positive value, and the field curvature becomes large. Therefore, it is necessary to reduce the overall Petzval sum by giving one of them a strong concave power and generating a large negative coefficient related to the Petzval sum. Furthermore, in order to effectively generate a coefficient related to the negative Petzval sum, it is desirable to lower the ray height on the concave surface and bring the strong concave surface (small radius of curvature) there. The above condition (1) is therefor, and is for effectively lowering the ray height with the positive lens of the first lens group and introducing the ray into the strong concave surface of the first surface of the second lens group. . Here, when the lower limit of 1 of the condition (1) is exceeded, the ray height drops too much, and various aberrations such as coma aberration generated in the first surface of the first lens group and the second lens group are corrected in the rear group. On the contrary, when the upper limit of 2 of the condition (1) is exceeded, on the other hand, the ray height does not decrease and it is not possible to effectively generate a negative coefficient related to Petzval sum.

Further, by disposing a positive lens as the first lens group, it is possible to lower the ray height and introduce it into a strong concave surface, so that it is not necessary to bring the first lens group too close to the image.

The above condition (2) relates to a lens generating a coefficient relating to the negative Petzval sum,
If the lower limit of 0.5 is exceeded, the concave power of the second lens group will be too strong, and the coma, distortion, etc. generated there will not be corrected by the other groups, and conversely, if the upper limit of 1 is exceeded, a sufficient negative power will result. It is not possible to generate a coefficient for the Petzval sum of. Further, the reason why this lens has a meniscus shape is that the height of the light beam entering the third lens group is not raised too much. When the height of the light ray entering the third lens group becomes high,
There are too many positive Petzval sum coefficients,
Further, since the lens outer diameter becomes too large, it is effective to make the second lens group a meniscus shape. For that purpose, it is more desirable to satisfy the following condition (5). (5) 1 <| R _B / R _F | <4 where R _B is the radius of curvature of the second lens group on the exit side.

Here, when the lower limit of 1 is exceeded, the power of the surface is too strong, and field curvature, coma aberration, etc. occur too much. On the contrary, when the upper limit of 4 is exceeded, the light rays are incident on the third lens group. Does not fall effectively.

Further, the above condition (3) is for finally effectively guiding the light ray group to the eye point. When the lower limit of 0.5 is exceeded, the light ray toward the eye point drops too much, and If the distance to the point becomes too short, and conversely exceeds the upper limit of 2, the convex power becomes too weak and the requirement for the focal length as a whole cannot be satisfied.

The condition (4) relates to correction of chromatic aberration. If this condition is not satisfied, lateral chromatic aberration and pupil chromatic aberration cannot be completely eliminated.

Further, it is also a great feature of the present invention that the coma aberration is corrected very well as a whole. In a systematic microscope, the distance between the objective lens and the eyepiece lens may change greatly due to the insertion of the intermediate lens barrels, and the entrance pupil position for the eyepiece lens may change considerably. At this time, if the coma aberration of the eyepiece lens is not properly corrected, the amount of curvature of field changes due to the change of the position of the entrance pupil. The flatness will be impaired. The above conditions (1), (2), (3) and (5) are also effective in favorably correcting coma aberration as a whole.

[0014]

EXAMPLES Examples of the wide-field eyepiece according to the present invention will be described below. FIG. 1 is a lens cross-sectional view of Examples 1 to 3.
3 to FIG. 3, the lens data thereof will be described later.

Regarding the lens arrangement, the first lens group G1
In Examples 1 and 3, a positive meniscus lens having a concave surface facing the image side (the side opposite to the eye) is formed, and in Example 2, a biconvex positive lens is formed. The second lens group G2 includes one negative meniscus lens with a concave surface facing the image side in Example 1, and
Reference numeral 3 is a double-concave negative lens and a double-convex positive lens cemented together. The third lens group G3 includes a total of three lenses in Example 1 including a biconvex positive lens and a cemented lens including a biconvex positive lens and a negative meniscus lens. Examples 2 and 3 include a biconvex positive lens and a negative meniscus lens. It consists of two cemented lenses. Therefore, each of the examples has a total of five lenses.

In the lens data shown below, the display of the lens surface is shown in the order of the traveling direction of the light beam. The symbol is
In addition to the above, F _NO is the F number, ω is the half angle of view, d ₀ is the distance from the image position to the first surface, r ₁ , r ₂ ... Is the radius of curvature of each lens surface, and d ₁ , d ₂ ... The spacing between each lens surface, n _d1 ,
n _d2 ... Is the d-line refractive index of each lens, and v _d1 , v _d2 are the Abbe numbers of each lens.

[0017] Example _{1 f a = 25.03 F NO =} 12.48 ω = 21.75 ° d 0 = 7.753141 r 1 = -251.19045 d 1 = 6.175281 n d1 = 1.603112ν d1 = 60.70 r 2 = -20.76911 d 2 = 2.912833 r 3 = -16.21232 d ₃ = 4.000000 n _d2 = 1.805176 ν _d2 = 25.44 r ₄ = -53.26369 d ₄ = 3.911036 r ₅ = 276.76482 d ₅ = 6.134503 n _d3 = 1.735198 ν _d3 = 41.08 r ₆ = -31.14131 d ₆ = 0.200000 r _{7 = 30.54632 d 7 = 7.580399 n} d4 = 1.658441ν d4 = 50.86 r 8 = -28.68146 d 8 = 2.500000 n d5 = 1.805176ν d5 = 25.44 r 9 = -606.49730 | f 1 / f a | = 1.534 | R F / _{f a | = 0.648 | f 3} / f a | = 0.903 ν v -ν c = 25.43 | R B / R F | = 3.29.

[0018] Example _{2 f a = 25.00 F NO =} 12.48 ω = 21.77 ° d 0 = 12.006315 r 1 = 269.88444 d 1 = 5.509016 n d1 = 1.658441ν d1 = 50.86 r 2 = -23.32410 d 2 = 2.800987 r 3 = -18.01722 d ₃ = 2.500000 n _d2 = 1.728249ν _d2 = 28.46 r ₄ = 23.88796 d ₄ = 7.168205 n _d3 = 1.701536ν _d3 = 41.24 r ₅ = -33.32449 d ₅ = 0.200000 r ₆ = 27.19792 d ₆ = 6.930938 n _d4 = _{1.723420ν d4 = 37.95 r 7 = -26.97019} d 7 = 2.500000 n d5 = 1.805176ν d5 = 25.44 r 8 = -129.53057 | f 1 / f a | = 1.314 | R F / f a | = 0.721 | f 3 / f _{a | = 1.368 ν v -ν c} = 12.51 | R B / R F | = 1.85.

Example 3 f _a = 25.00 F _NO = 1.48 ω = 21.77 ° d ₀ = 10.956710 r ₁ = -146.32731 d ₁ = 4.875195 n _d1 = 1.723420 ν _d1 = 37.95 r ₂ = -23.74747 d ₂ = 3.255608 r ₃ = -17.22412 d ₃ = 3.134893 n _d2 = 1.595508ν _d2 = 39.21 r ₄ = 28.42070 d ₄ = 7.824016 n _d3 = 1.603112ν _d3 = 60.70 r ₅ = -27.25993 d ₅ = 0.200000 r ₆ = 23.88151 d ₆ = 7.312041 n _{d4 = 1.614047ν d4 = 54.95 r 7 =} -29.93143 d 7 = 2.500000 n d5 = 1.805176ν d5 = 25.44 r 8 = -128.85989 | f 1 / f a | = 1.542 | R F / f a | = 0.689 | f ₃ / f _a ｜ = 1.574 ν _v −ν _c ＝ 29.52 ｜ R _B / R _F ｜ = 1.58
..

Aberration diagrams showing spherical aberration, astigmatism, distortion, pupil aberration, and coma (lateral aberration) of the wide-field eyepieces of Examples 1 to 3 are shown in FIGS. 4 to 6, respectively.

[0021]

As described above, according to the present invention,
It is possible to obtain a wide-field eyepiece lens in which the Petzval sum is small as a whole, the flatness of the image plane is good, the pupil aberration including the color is good, and the first lens is not too close to the image.

[Brief description of drawings]

FIG. 1 is a lens sectional view of a wide-field eyepiece according to a first embodiment of the present invention.

FIG. 2 is a lens cross-sectional view of Example 2.

FIG. 3 is a lens cross-sectional view of Example 3.

FIG. 4 is an aberration diagram showing spherical aberration, astigmatism, distortion, pupil aberration, and coma (lateral aberration) of Example 1.

5 is an aberration diagram similar to FIG. 4 of Example 2. FIG.

FIG. 6 is an aberration diagram similar to FIG. 4 of Example 3;

[Explanation of symbols]

 G1 ... 1st lens group G2 ... 2nd lens group G3 ... 3rd lens group

Claims (1)

[Claims] 1. A first lens group of positive lenses, a second lens group of meniscus negative lenses as a whole, and a third lens group of positive lenses as a whole including positive and negative cemented lenses in order from the light incident side.
Has a lens group, the whole focal length f _a, the focal length of the first lens group f _1, the radius of curvature of the entrance side of the second lens group R _F, the focal length of the third lens group f _3, The Abbe numbers of the positive and negative lenses of the cemented lens in the third lens group are v _v and _v , respectively.
_{When c} , a wide-field eyepiece characterized by satisfying the following conditions. (1) 1 <| f ₁ / f _a | <2 (2) 0.5 <| R _F / f _a | <1 (3) 0.5 <| f ₃ / f _a | <2 (4) ν _v −ν _c > 10