JP3259530B2 - Eyepiece - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eyepiece, for example, used in a telescope or a microscope, or an object image (aerial image) formed by an objective lens (photographing lens) with a field angle of 75.
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultra-wide-angle eyepiece suitable for observation in a wide visual field of a degree or more.

[0002]

2. Description of the Related Art Conventionally, there are widely known eyepieces of an elfre type and an orthoscopic type as eyepieces for observing an object on an observation surface while enlarging an apparent field of view.

For example, Japanese Patent Laying-Open No. 49-115558 proposes an orthoscopic eyepiece comprising four lenses in two groups.

Japanese Patent Publication No. 63-7363 proposes an eyepiece of the Elfle type, which is composed of five elements in three groups and has an enlarged pupil distance.

Japanese Patent Application Laid-Open No. 60-159719 proposes an eyepiece having an apparent visual field as wide as about 60 degrees and little astigmatism around the observation visual field. Japanese Patent Publication No. 63-10409 proposes an eyepiece having an apparent visual field as wide as about 60 degrees and having relatively little distortion over the entire visual field.

No. 4,720,183 and U.S. Pat.
U.S. Pat. No. 4,747,675 proposes an ultra-wide-angle eyepiece having an apparent visual field of 75 degrees or more.

[0007]

Problems to be Solved by the Invention JP-A-60-15
The eyepiece lens proposed in Japanese Patent No. 9719 has a very large distortion of about 16% at a half viewing angle of 30 degrees, which is good for an astronomical telescope, but has a problem that image distortion is large in general binoculars and the like. There is.

The eyepiece proposed in Japanese Patent Publication No. 63-10409 has a half viewing angle of 30 degrees and a distortion of 3 degrees.
%, But has a problem that there are many curvatures of field and astigmatism.

In the eyepiece proposed in US Pat. No. 4,720,183, various aberrations are well corrected, but the maximum lens diameter is 3.5 times the focal length and the total length of the lens is 7.4 times the focal length. There is a problem that it is very large and difficult to apply to small telescopes and binoculars.

The eyepiece proposed in US Pat. No. 4,747,675 has a problem that the distortion around the visual field is as large as 20% and the eye relief (pupil distance) is as short as 0.63 times the focal length. Was.

In general, in the above-mentioned eyepieces of the Elfle type or the orthoscopic type, the apparent field of view is increased to about 70 °, and the distance from the eyepiece to the position of the pupil of the observer (hereinafter, this distance is referred to as the eye). (Relief or pupil distance) is increased, while a compact lens configuration is attempted, the number of refracting lens surfaces that converge to the off-axis chief ray increases, various aberrations are corrected well, and high optical performance is obtained. It becomes very difficult.

According to the present invention, a wide field of view having an apparent viewing angle of about 75 degrees is used to satisfactorily correct various aberrations such as distortion, curvature of field, and color misregistration over the entire viewing field, thereby obtaining a high quality observation image. And an eyepiece having a long pupil distance.

[0013]

(1-1) The eyepiece according to the first aspect of the present invention has, in order from the light incident side, a first lens group composed of a negative first lens having both concave lens surfaces, and an incident side. A second meniscus positive lens having a concave surface facing the second
The lens group includes a negative 3-1 lens having a stronger negative refraction surface on the incident side than the exit side, and a positive third lens having a stronger positive refraction surface on the exit side than the entrance side. A third lens group composed of a cemented lens having a positive refractive power as a whole, in which two lenses are cemented; a fourth lens group composed of two lenses, a positive 4-1 lens and a positive 4-2 lens; A negative meniscus 5-1 lens having a convex surface facing the positive side and a positive 5-2 lens having a positive refractive surface facing the incident side are cemented together. An eyepiece having five lens groups for observing an intermediate image formed through the first lens group and the second lens group from the third lens group through a fifth lens group; -1 lens and the 5-1 lens
When the focal lengths of the lenses are f _3i and f _5i , and the radii of curvature of the entrance-side lens surface of the third lens unit and the cemented lens surface of the fifth lens unit are R _3i and R _5s , respectively: 0.8 It is characterized by satisfying the following condition: <f _5i / f _3i < _30.5 <R _3i / R _5s <2.2

[0014]

[0015]

1 to 4 are sectional views of numerical examples 1 to 4 of an eyepiece according to the present invention, and FIGS. 5 to 8 are various aberration diagrams of numerical examples 1 to 4 of the eyepiece according to the present invention. is there.

In FIG. 1, reference symbol EL denotes an eyepiece lens having five lens groups. S is a surface to be observed, which is an aerial image or the like formed by a subject or an objective lens. MIP indicates a position (intermediate image position) where an intermediate image is formed, and EP indicates a position (eye point) of an observation eye (pupil). The left side in the figure is the light incident side.

G1 is a first lens group composed of a negative first lens having both concave lens surfaces, G2 is a second lens group composed of a meniscus-shaped positive second lens having a concave surface facing the incident side, and M
IP indicates a position where an intermediate image of the observation surface S formed through the two lens groups of the first lens group G1 and the second lens group G2 is formed. G3 denotes a third lens unit having a positive refractive power, and includes a negative 3-1 having a strong negative refractive surface facing the incident side.
It is composed of a cemented lens in which a lens G3-1 and a positive third-second lens G3-2 having a strong positive refraction surface facing the exit side are joined. G4 is a fourth lens group having a positive refractive power, and includes two positive lenses, a positive fourth lens G4-1 and a positive fourth lens G4-2. G5 is a fifth lens unit having a positive refractive power, and is a meniscus negative 5-1th lens G5-1 having a convex surface facing the incident side and a positive 5-th lens G5-1 having a positive refractive surface facing the incident side. It consists of a laminated lens in which two lenses G5-2 are joined.

The eyepiece EL of the present embodiment has the above five lens groups. Of these, the first lens group G1 and the second lens group G2 form the intermediate image of the observation surface S at the intermediate image position MIP. Has formed. The intermediate image formed at the position MIP is observed from the position EP via the third lens group G3, the fourth lens group G4, and the fifth lens group G5.

Next, the features of the lens structure of the eyepiece of this embodiment will be described. First, a first lens group G1 having a negative refractive power and a second lens group G2 having a positive refractive power are arranged in order from the light incident side to a position MIP where an intermediate image is formed. The height of outside light is increased. As a result, the eye relief is lengthened, and astigmatism and coma aberration generated in each lens group (G3 to G5) on the exit side from the intermediate image position MIP are generated. Corrected in good balance.

A lens group is disposed on both the light incident side and the light exit side with the intermediate image position MIP interposed therebetween. Light rays above the off-axis principal ray on the light incident side are off-axis rays on the light exit side. The light beam should be lower than the principal ray, and the light ray below the off-axis principal ray on the light incident side should be higher than the principal ray on the light exit side. Thereby, the opposite aberration is generated across the intermediate image position MIP, so that the aberration correction is favorably performed.

Further, from the intermediate image position MIP toward the light emission side, first, as a third lens group G3 having a concave surface facing the incident side and having a positive refractive power, the height of off-axis light from the optical axis is increased. And make the eye relief longer.

Next, two positive lenses are arranged as a fourth lens group toward the light emission side to divide the power (refractive power) of the lens. This reduces the occurrence of coma and astigmatism.

Next, the fifth lens group is a positive lens group in which the cemented lens surface has a convex surface on the incident side and a strong refractive surface on the incident side. As a result, the incidence angle of off-axis light rays on the surface of the cemented lens is made vertical to reduce the occurrence of higher-order chromatic aberration of magnification. The focal lengths of the 3-1 lens and the 5-1 lens are set to f _3i , f _5i , and
When the radii of curvature of the lens surface on the incident side of the lens group and the cemented lens surface of the fifth lens group are R _3i and R _5s , respectively, 0.8 <f _5i / f _3i <3 ‥‥‥ (5) 0.5 <R _3i / R _5s <2.2 ‥‥‥ (6) Conditional expression (5) limits the ratio of the focal length of the 5-1 lens on the incident side of the fifth lens group to the focal length of the 3-1 lens on the incident side of the third lens group. In a region exceeding the lower limit value of the conditional expression (5), the power of the 5-1 lens on the entrance side of the fifth lens unit becomes too strong, so that the lens diameter becomes large. In a region exceeding the value, the power of the 3-1st lens on the entrance side of the third lens group becomes relatively too strong, and high-order chromatic aberration of magnification increases, which is not good. Conditional expression (6) limits the ratio of the radius of curvature of the lens surface on the incident side of the third lens unit to the radius of curvature of the cemented lens surface of the fifth lens unit. In a region exceeding the lower limit of conditional expression (6), higher-order chromatic aberration of magnification increases, and conditional expression (6)
In the region exceeding the upper limit of the above, the correction of the distortion is under, which is not good.

In this embodiment, an ocular lens having a pupil distance of 0.9 times or more of the focal length and an apparent field of view of 75 degrees or more and capable of excellently observing a subject image is achieved by such a configuration. ing.

The ultra-wide-angle eyepiece aimed at by the present invention can be achieved by specifying the lens configuration as described above, but it is more preferable to satisfy at least one of the following conditions.

(2-1) The radius of curvature of the exit-side lens surface of the second lens group is R _2e , the radius of curvature of the entrance-side lens surface of the third lens group is R _3i , and Third
When the air gap from the lens group is D _g23 and the focal length of the entire system is f, 0.3 <R _2e / R _3i <1.4 ‥‥‥ (1) 0.15 <D _g23 / f <1. 3 ‥‥‥ (2).

Conditional expression (1) limits the ratio of the radius of curvature R _2e of the exit-side lens surface of the second lens unit to the radius of curvature R _3i of the entrance-side lens surface of the third lens unit. In a region exceeding the lower limit value of the conditional expression (1), the radius of curvature R _2e of the lens surface on the exit side of the second lens group becomes relatively too small, and astigmatism becomes excessive. Conditional expression (1)
Since the radius of curvature R _3i of the lens surface on the entrance side of the third lens unit becomes relatively small in a region exceeding the upper limit of
This is not good because the angle of incidence of off-axis rays on the lens surface becomes too large, and high-order chromatic aberration of magnification increases.

Conditional expression (2) limits the ratio of the air gap between the second lens unit and the third lens unit to the focal length of the entire system. In a region exceeding the lower limit of conditional expression (2), the second lens unit and the third lens unit are too close to the intermediate image position, so that dust and scratches on the lens surface and bubbles in the lens become noticeable. Further, in a region exceeding the upper limit value of the conditional expression (2), the overall length of the lens becomes large, which is not good.

In the present invention, it is more preferable to set the upper limit value or the lower limit value or both of the extreme values of the conditional expressions (1) and (2) as follows from the viewpoint of aberration correction.

0.4 <R _2e / R _3i <1 ‥‥‥ (1a) 0.5 <D _{g23 /f<1.2‥‥‥(2a} ) (2-2) Let the focal length of the system be f
_1, f, the third lens surface of the entrance side and the exit side of the lens group curvature radius of each R _3i, 1 when the _{R 3e <-f 1 / f <} 5 ‥‥‥ (3) 0.5 < R _3i / R _3e <1.4 ‥‥‥ (4)

Conditional expression (3) limits the ratio of the focal length of the first lens unit to the focal length of the entire length. In a region exceeding the lower limit value of the conditional expression (3), the spherical aberration is under.
Since the power (refractive power) of the lens group becomes too weak, the eye relief becomes short, which is not good.

Conditional expression (4) restricts the ratio of the radius of curvature of the lens surface on the most incident side of the third lens unit to the radius of curvature of the lens surface on the most exit side. In a region exceeding the lower limit value of the conditional expression (4), astigmatism becomes excessive, and in a region exceeding the upper limit value of the conditional expression (4), coma aberration becomes excessive.

In the present invention, it is more preferable to set the upper limit value or the lower limit value or both of the extreme values of the conditional expressions (3) and (4) as follows from the viewpoint of aberration correction.

1.5 <−f ₁ / f <3 ‥‥‥ (3a) 0.65 <R _3i / R _3e <1.25 ‥‥‥ (4a)

[0035]

[0036]

(2-3) The first lens, the 3-1
The refractive indexes of the lens and the material of the 5-1 lens are N1, N3i and N5i, respectively,
When the Abbe numbers of the materials of one lens are ν3i and ν5i, respectively, and the average values of the refractive indices and the Abbe numbers of all the positive lens materials are Np and νp, respectively, 15 <νp−ν3i <35 (7) 15 <νp−ν5i <40 ‥‥‥ (8) 0.05 <Np−N1 <0.35 ‥‥‥ (9) −0.15 <N3i−Np <0.25 ‥‥ (10) 0.01 <N5i−Np <0.25 ‥‥ (11)

Conditional expression (7) limits the difference between the average value of the Abbe numbers of the materials of all the positive lenses forming the eyepiece and the Abbe number of the material of the 3-1st lens on the entrance side of the third lens group. Things. In a region exceeding the lower limit of conditional expression (7), both the axial chromatic aberration and the chromatic aberration of magnification are under.
In a region exceeding the upper limit of conditional expression (7), axial chromatic aberration,
This is not good because both the chromatic aberrations of magnification are over.

Conditional expression (8) limits the difference between the average value of the Abbe numbers of the materials of all the positive lenses constituting the eyepiece and the Abbe number of the material of the 5-1 lens on the entrance side of the fifth lens group. Things. In a region exceeding the lower limit of conditional expression (8), both the axial chromatic aberration and the chromatic aberration of magnification are under.
In a region exceeding the upper limit of conditional expression (8), axial chromatic aberration,
This is not good because both the chromatic aberrations of magnification are over.

Conditional expression (9) limits the difference between the average value of the refractive indexes of the materials of all the positive lenses constituting the eyepiece and the refractive index of the materials of the first lens group. In a region exceeding the lower limit of conditional expression (9), the curvature of field is under. In a region exceeding the upper limit of conditional expression (9), the curvature of field is excessive, which is not good.

Conditional expression (10) restricts the difference between the Abbe number of the material of the 3-1st lens on the entrance side of the third lens group and the average value of the refractive indexes of the materials of all the positive lenses constituting the eyepiece. Things. If the lower limit of conditional expression (10) is exceeded, coma will increase. If the upper limit of conditional expression (10) is exceeded, the field curvature will be under, which is not good.

Conditional expression (11) limits the difference between the refractive index of the material of the 5-1 lens on the entrance side of the fifth lens group and the average value of the refractive indexes of the materials of all the positive lenses constituting the eyepiece. Things. In a region exceeding the lower limit value of the conditional expression (11), coma increases, and in a region exceeding the upper limit value of the conditional expression (11), the curvature of field is under, which is not good.

Next, numerical examples of the present invention will be described. In the numerical examples, Ri is the radius of curvature of the i-th lens surface in order from the observation surface side, Di is the i-th lens thickness and air gap from the observation surface side, and Ni and νi are each in order from the observation surface side. The refractive index and Abbe number of the glass of the i-th lens.
Table 1 shows the relationship between the above-described conditional expressions and various numerical values in the numerical examples.

<Numerical Example 1> f = 16.59 pupil diameter φ3.3 2ω = 75 ° R 1 = -34.25 D 1 = 1.5 N 1 = 1.51742 ν 1 = 52.4 R 2 = 34.25 D 2 = 5.64 R 3 =- 33.30 D 3 = 4.8 N 2 = 1.83400 ν 2 = 37.2 R 4 = -19.47 D 4 = 12.0 R 5 = -25.71 D 5 = 3.0 N 3 = 1.64769 ν 3 = 33.8 R 6 = 63.09 D 6 = 14.6 N 4 = 1.60311 ν 4 = 60.7 R 7 = -29.62 D 7 = 0.2 R 8 = 142.33 D 8 = 7.9 N 5 = 1.69680 ν 5 = 55.5 R 9 = -58.78 D 9 = 0.2 R10 = 50.15 D10 = 4.9 N 6 = 1.69680 ν 6 = 55.5 R11 = 194.27 D11 = 0.2 R12 = 36.47 D12 = 2.0 N 7 = 1.84666 ν 7 = 23.8 R13 = 16.04 D13 = 9.6 N 8 = 1.69680 ν 8 = 55.5 R14 = 84.78 D14 = 15.0 R15 = Eye point <Numerical implementation Example 2) f = 16.54 pupil diameter φ3.3 2ω = 75 ° R 1 = -30.39 D 1 = 1.50 N 1 = 1.51742 ν 1 = 52.4 R 2 = 34.68 D 2 = 5.43 R 3 = -38.83 D 3 = 5.08 N 2 = 1.83400 ν 2 = 37.2 R 4 = -19.79 D 4 = 12.00 R 5 = -25.50 D 5 = 3.00 N 3 = 1.64769 ν 3 = 33.8 R 6 = 52.60 D 6 = 15.40 N 4 = 1.60311 ν 4 = 60.7 R 7 = -29.55 D 7 = 0.20 R 8 = 123.40 D 8 = 7.47 N 5 = 1.69680 ν 5 = 55.5 R 9 = -66.40 D 9 = 0.20 R10 = 46.65 D10 = 5.06 N 6 = 1.69680 ν 6 = 55.5 R11 = 176 . 98 D11 = 0.20 R12 = 37.00 D12 = 2.00 N 7 = 1.84666 ν 7 = 23.8 R13 = 16.25 D13 = 8.98 N 8 = 1.69680 ν 8 = 55.5 R14 = 82.86 D14 = 15.00 R15 = Eye point <Numerical example 3> f = 14.99 Pupil diameter φ3 2ω = 75 ° R 1 = -31.53 D 1 = 1.50 N 1 = 1.51742 ν 1 = 52.4 R 2 = 31.53 D 2 = 5.36 R 3 = -26.32 D 3 = 4.37 N 2 = 1.83400 ν 2 = 37.2 R 4 = -17.95 D 4 = 12.00 R 5 = -25.66 D 5 = 3.00 N 3 = 1.64769 ν 3 = 33.8 R 6 = 49.47 D 6 = 14.49 N 4 = 1.60311 ν 4 = 60.7 R 7 = -28.84 D 7 = 0.20 R 8 = -6400.84 D 8 = 6.11 N 5 = 1.69680 ν 5 = 55.5 R 9 = -56.91 D 9 = 0.20 R10 = 42.53 D10 = 7.27 N 6 = 1.69680 ν 6 = 55.5 R11 = -950.02 D11 = 0.20 R12 = 38.83 D12 = 2.00 N 7 = 1.84666 ν 7 = 23.8 R13 = 16.00 D13 = 10.29 N 8 = 1.69680 ν 8 = 55.5 R14 = 101.68 D14 = 15.00 R15 = Eye point <Numerical example 4> f = 12.11 Pupil diameter φ2.4 2ω = 75 ° R 1 = -19.09 D 1 = 1.50 N 1 = 1.51742 ν 1 = 52.4 R 2 = 45.16 D 2 = 4.24 R 3 = -18.41 D 3 = 3.37 N 2 = 1.83400 ν 2 = 37.2 R 4 =- 14.53 D 4 = 12.00 R 5 = -26.48 D 5 = 3.00 N 3 = 1.72825 ν 3 = 28.5 R 6 = 30.56 D 6 = 15.21 N 4 = 1.60311 ν 4 = 60.7 R 7 = -24.88 D 7 = 0.20 R 8 = 966.76 D 8 = 5.53 N 5 = 1.69680 ν 5 = 55.5 R 9 = -56.74 D 9 = 0.20 R10 = 32.04 D10 = 6.40 N 6 = 1.77250 ν 6 = 49.6 R11 = 139.60 D11 = 0.20 R12 = 49.43 D12 = 2.00 N 7 = 1.80518 ν 7 = 25.4 R13 = 16.00 D13 = 10.71 N 8 = 1.69680 ν 8 = 55.5 R14 = 1405.35 D14 = 15.00 R15 = Eye point

[0045]

[Table 1]

[0046]

According to the present invention, by setting each element as described above, distortion, image field curvature, and color misregistration are observed over the entire observation field of view while the apparent field angle is as wide as about 75 degrees. And other aberrations can be satisfactorily corrected, an observation image with high image quality can be obtained, and an eyepiece with a long pupil distance can be achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a lens according to a numerical example 1 of the present invention.

FIG. 2 is a sectional view of a lens according to a numerical example 2 of the present invention.

FIG. 3 is a sectional view of a lens according to a numerical example 3 of the present invention.

FIG. 4 is a sectional view of a lens according to a numerical example 4 of the present invention.

FIG. 5 is a diagram showing various aberrations of Numerical Example 1 of the present invention.

FIG. 6 is a diagram showing various aberrations of Numerical Example 2 of the present invention.

FIG. 7 is a diagram showing various aberrations of Numerical Example 3 of the present invention.

FIG. 8 is a diagram showing various aberrations of Numerical Example 4 of the present invention.

[Explanation of symbols]

 EL Eyepiece S Surface to be observed EP Eye point G1 First lens group G2 Second lens group G3 Third lens group G4 Fourth lens group G5 Fifth lens group d d-line c c-line F F-line M Meridional image plane S sagittal Image plane

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G02B 9/00-17/08 G02B 21/02-21/04 G02B 25/00-25/04

Claims (4)

(57) [Claims] 1. A first lens group consisting of a negative first lens having both concave lens surfaces, and a second meniscus positive second lens having a concave surface facing the incident side, in order from the light incident side. Group , negative 3-1 lens having a strong negative refraction surface on the incident side compared to the exit side, and positive 3-2 having a strong positive refraction surface on the exit side compared to the entrance side A third lens group composed of a cemented lens having a positive refractive power as a whole and cemented with the lens;
A fourth lens group composed of two lenses, a positive 4-1 lens and a positive 4-2 lens; a meniscus-shaped negative 5-1 lens having a convex surface facing the entrance side; A fifth lens group composed of a cemented lens having a positive refractive power as a whole, which is cemented with a positive 5-2 lens whose refractive surface is directed ;
An intermediate image formed through the first lens group and the second lens group
The observed from the third lens group through the fifth lens group against
An eye lens, wherein the 3-1 lens and the 5-1 lens
_{Are set} to f _3i and f _5i , respectively ,
Curvature of the lens surface on the emitting side and the cemented lens surface of the fifth lens group
Each R _3i rates radius, when the _{R 5s, 0.8 <f 5i /} f 3i <3 0.5 < eyepiece lens satisfies the R _3i / R _5s <2.2 following condition. 2. The radius of curvature of the exit-side lens surface of the second lens group is R _2e , the radius of curvature of the entrance-side lens surface of the third lens group is R _3i , and the second lens group and the third lens are _Assuming that the air gap with the group is D _g23 and the focal length of the whole system is f, the following condition is satisfied: 0.3 <R _2e / R _3i <1.4 0.15 <D _{g23 /f<1.3} The eyepiece according to claim 1, wherein: 3. When the focal lengths of the first lens unit and the entire system are f ₁ and f, respectively, and the radii of curvature of the entrance and exit lens surfaces of the third lens unit are R _3i and R _3e , respectively. _{1 <-f 1 / f <5} 0.5 < ocular lens according to claim 1, characterized by satisfying the R _3i / R _3e <1.4 following condition. 4. The first lens, the 3-1 lens,
The refractive index of the material of the 5-1 lens is N ₁ ,
N _3i and N _5i , the Abbe numbers of the materials of the 3-1st lens and the 5-1 lens are ν _3i and ν _5i , respectively, and the average values of the refractive indices and the Abbe numbers of all the positive lens materials are respectively N _p, ν 15 when set to _{p <ν p -ν 3i <35} 15 <ν p -ν 5i <40 0.05 <N p -N 1 <0.35 -0.15 <N 3i -N p < 0.25 0.01 <claims, characterized by satisfying the N _5i -N _p <0.25 condition: 1,2 or
3 eyepieces