JP2001066523A - Eyepiece lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an eyepiece lens used for an observation optical system such as binoculars, a telescope and a microscope capable of excellently compensating aberration to the peripheral part of its field, restraining distortion aberration within 2.5% especially, and securing the length of eye relief to be >=80% of a focal distance, more desirably, >=100%. SOLUTION: This eyepiece lens is composed of a 1st lens group G1 having a negative lens, a 2nd lens group G2 having a combined lens consisting of a negative lens and a positive lens, a 3rd lens group G3 having a combined lens consisting of a positive lens and a negative lens or a combined lens consisting of a negative lens and a positive lens, and a 4th lens group G4 having a positive lens in order from an object side. At least one lens surface of each lens group has aspherical shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to binoculars, telescopes,
The present invention relates to an eyepiece used for an observation optical system such as a microscope.

[0002]

2. Description of the Related Art Observation optical systems such as telescopes and microscopes include:
As an optical system for further enlarging and observing a real image formed by an objective lens, an eyepiece including a plurality of spherical lenses is used. In this eyepiece, a sufficiently large exit pupil distance (eye relief) is ensured in order to easily observe the entire visual field. At present, it is desirable that the eye relief be at least 80% or more of the focal length.

[0003]

However, if the apparent field of view is increased while keeping various aberrations around the field of view of the eyepiece lens, the eye relief becomes shorter. On the other hand, if the eye relief is increased while the apparent field of view is kept large, the aperture of the lens system on the eye side is increased, and as a result, various aberrations in the peripheral portion of the field of view, particularly astigmatism and distortion, rapidly deteriorate.

[0004] For this reason, it has conventionally been difficult to simultaneously increase the apparent field of view of the eyepiece and the eye relief. Incidentally, as an eyepiece composed of a plurality of spherical lenses, for example, JP-A-7-281107 and JP-A-9-281107
There is one described in 54256. In the eyepieces described in these publications, the apparent field of view is 56
°, 60 °, and the eye relief is 80% or more of the focal length, and various aberrations are corrected relatively well.

[0005] However, distortion, which is greatly worsened in comparison with other aberrations, is still 5 to 9%, which is still insufficient for an observer to comfortably observe a wide visual field. . The present invention has been made in view of such a problem, and corrects each aberration to a good value up to the peripheral portion of the field of view, particularly suppresses distortion to within 2.5%, and reduces the length of the eye relief. It is an object of the present invention to provide an eyepiece that secures 80% or more, more preferably 100% or more of the focal length.

[0006]

According to the first aspect of the present invention, there is provided a first lens group G having a negative lens in order from the object side.
1, a second lens group G2 having a cemented lens of a negative lens and a positive lens, and a third lens group G3 having a cemented lens of a positive lens and a negative lens or a cemented lens of a negative lens and a positive lens And a fourth lens group G4 having a positive lens, and at least one lens surface of each of the lens groups is an eyepiece having an aspheric shape.

By using an aspherical lens as described above, it is possible to simultaneously correct various aberrations, which have been difficult in the past, and secure an eye relief having a focal length of 100% or more and a wide apparent visual field at the same time. . According to the second aspect of the present invention, in the eyepiece according to the first aspect, the aspherical shape is closer to the peripheral portion than to the case where a base sphere based on the radius of curvature of the aspherical vertex is used. An eyepiece having a shape that increases the thickness.

[0008] The "generating sphere" here is a sphere having a vertex, a radius of curvature, and a center of curvature common to an aspheric surface. By setting the aspheric shape to a predetermined shape in this way, the prism effect in the peripheral portion of the lens surface can be reduced, so that various types of aberration correction and distortion correction in the peripheral portion of a wide field of view can be performed while maintaining a long eye relief. And can be achieved simultaneously.

According to a third aspect of the present invention, in the eyepiece of the first or second aspect, the aspherical shape has a height h from an optical axis to an incident position of the most off-axis ray on the aspherical surface. At this height h, for a displacement dx generated between the aspheric surface and the base sphere based on the radius of curvature of the vertex,
An eyepiece lens characterized by satisfying the following expression (1).

0.001 ≦ | dx / h | ≦ 0.14 (1) This expression (1) defining the shape of the aspherical surface can be applied to an eyepiece having a long eye relief and a wide apparent field of view.
It is possible to suppress each aberration, particularly distortion, to a favorable value up to the periphery of the visual field. When the value is below the lower limit of the expression (1), the effect of the aspherical surface is reduced, so that it is difficult to maintain a long eye relief, a wide apparent field of view, and satisfactorily correct each aberration. On the other hand, when the value exceeds the upper limit of the expression (1), the effect of the aspherical surface becomes too strong, so that distortion is excessively corrected, and it is difficult to correct various aberrations at the periphery of the visual field.

Here, in the invention according to claim 3,
By applying the following equation (1) ′ instead of the equation (1), even better results can be obtained. 0.003 ≦ | dx / h | ≦ 0.1 (1) ′ According to a fourth aspect of the present invention, in the eyepiece according to any one of the first to third aspects, a lens system is provided. An eyepiece lens characterized by satisfying the following expression (2) with respect to an overall combined focal length F and a combined focal length F12 of the first lens group G1 and the second lens group G2.

| F / F12 | ≦ 0.4 (2) Thus, the equation (2) that defines an appropriate range for the combined focal length F12 of the first lens group G1 and the second lens group G2. According to the first lens group G1 and the second lens group G2,
Can be reduced (possibly to a negative value) in the combined lens group G12 obtained by combining As a result, it is possible to maintain a good distribution of refractive power with the lens units subsequent to the composite lens unit G12, so that various aberrations such as astigmatism and curvature of field can be corrected in a well-balanced manner.

If the value deviates from the range of the expression (2), the refractive power distribution of each lens unit is not maintained well, and the aberration around the field of view deteriorates. Here, in the invention described in claim 4, if equation (2) ′ is applied instead of equation (2), it is possible to perform correction with a better balance. | F / F12 | ≦ 0.3 (2) ′ Further, if Expression (2) ″ is applied instead of Expression (2), correction can be performed with a better balance.

| F / F12 | ≦ 0.21 (2) ”Here, two inventions (disclosure item 1 and disclosure item 2) related to the above-mentioned invention, and their functions and effects will be disclosed. Item 1) In the eyepiece according to any one of Items 1 to 4, with respect to a combined focal length F of the entire lens system and a focal length F1 of the first lens group G1, the following expression (3). An eyepiece characterized by satisfying.

-3.6 ≦ F1 / F ≦ −1.2 (3) Generally, in order to enlarge the eye relief, it is necessary to increase the negative refractive power of the first lens group G1. If the range of the expression (3) is satisfied, the eye relief can be made sufficiently large and a good distribution of refractive power can be obtained. As a result, each aberration can be corrected with good balance while keeping the eye relief long.

When the value falls below the lower limit of the expression (3), the first
The negative refractive power of the lens group G1 becomes too small, and it becomes difficult to enlarge the eye relief. On the other hand, when the value exceeds the upper limit of the expression (3), the negative refractive power of the first lens group G1 becomes too large, causing an increase in the aperture of the second lens group G2 and thereafter, and the deterioration of aberration around the field of view becomes worse. Invite. Here, in the invention described in Disclosure 1, when Expression (3) ′ is applied instead of Expression (3), better results can be obtained.

-3.3 ≦ F1 / F ≦ −1.6 (3) ′ (Disclosure 2) The eyepiece lens according to any one of Claims 1 to 4, and Disclosure 1. , The first lens group G
The eyepiece lens according to claim 1, wherein the object-side surface of the negative lens is formed with the concave surface facing the object side.

Here, as the refractive power of the lens group G1 increases, it becomes necessary to reduce the radius of curvature of the lens surface of the first lens group G1. At this time, if the eye-side surface of the negative lens of the first lens group G1 is formed with a concave surface having a small radius of curvature facing the eye side, the first lens group is used to prevent interference by an adjacent lens surface. G1 and the second lens group G
Since the air gap between the first lens group G and the first lens group G is large.
1 comes close to the image plane, and there is an inconvenience that dust can be seen.

Therefore, as in the invention described in Item 2 of the Disclosure, the object-side surface of the negative lens of the first lens group G1 is formed to have a concave surface facing the object side, and the negative lens of the first lens group G1 is formed. The above-described disadvantages can be solved by dispersing the power on the image-side surface and the eye-side surface (by forming a biconcave lens shape) or by forming the negative lens of the first lens group G1 into a meniscus shape.

[0020]

Embodiments of the present invention will be described below. <Structure of each embodiment> FIGS. 1, 4, 7, 10, and 1
3, FIG. 16, FIG. 19, and FIG. 22 show a first embodiment, a second embodiment, a third embodiment, a fourth embodiment, a fifth embodiment, a sixth embodiment, and a seventh embodiment of the present invention, respectively. ,
It is a lineblock diagram of an 8th embodiment. All of these embodiments correspond to Claim 1, Claim 2, Claim 3, Claim 4, Disclosure Claim 1, and Disclosure Claim 2.

As shown in these drawings, each embodiment sequentially includes a first lens group G having a negative lens in order from the object side.
1, a second lens group G2 having a cemented lens of a negative lens and a positive lens, and a third lens group G3 having a cemented lens of a positive lens and a negative lens or a cemented lens of a negative lens and a positive lens And a fourth lens group G4 having a positive lens, and at least one lens surface of each lens group has an aspherical shape. In each drawing, the surface marked with * is an aspherical surface. P.
Represents an eye point.

FIG. 25 is a diagram showing such an aspherical shape. The following equation (4) is an equation defining this aspherical shape.

(Equation 1) As shown in FIG. 25 and Equation (4), the aspherical surface in each embodiment is a rotationally symmetric aspherical surface. In Expression (4) and FIG. 25, X: displacement in the optical axis direction with respect to the aspherical vertex, Y: height in the direction orthogonal to the optical axis with respect to the optical axis, k: conical constant, C ₀ : 1 / R (R = radius of apex of aspheric surface), C ₂ : second-order aspherical constant, C ₄ : fourth-order aspherical constant, C ₆ : sixth-order aspherical constant, C ₈ : eighth-order aspherical surface Constant, C ₁₀ : 10th-order aspherical constant, h: height from the optical axis to the incident position of the most off-axis ray on the aspherical surface, dx: base sphere at height h based on the radius of curvature of the aspherical surface and its vertex And the displacement in the optical axis direction that occurs between

FIGS. 2, 5, 8, 11, 14, and 1
7, FIG. 20, and FIG. 23 show the first embodiment, the second embodiment, the third embodiment, the fourth embodiment, the fifth embodiment, the sixth embodiment, the seventh embodiment, and the It is a figure showing various data of 8 embodiments. In each figure, lens data, aspherical surface data, and condition corresponding values are shown in order. In each figure, No: number of the lens surface from the object side, R: radius of curvature of the lens surface, d: distance between lens surfaces, nd: refractive index for d-line, νd: Abbe number for d-line, I: eye relief Length, F: Synthetic focal length of the entire lens system, F12: Synthetic focal length of first lens group G1 and second lens group G2 (focal length of synthetic lens group G12), F1: of first lens group G1 The focal length.

In each figure, an aspherical lens surface is marked with an asterisk (*) on its lens surface number.
The radius of curvature R shown for the aspherical lens surface represents the radius of curvature of the apex (the unit of length is "m
m "). <Characteristics of Embodiments> FIGS. 3, 6, 9, 12, and 1
5, FIG. 18, FIG. 21, and FIG. 24 respectively show the first embodiment, the second embodiment, the third embodiment, the fourth embodiment, the fifth embodiment, the sixth embodiment, and the seventh embodiment of the above configuration. It is an aberrational figure of a form, 8th Embodiment.

Each of the aberrations shown in each figure is the eye point E.E.
P. The solid line in the astigmatism diagram represents the sagittal image surface S, the broken line represents the meridional image surface M, and Fno represents the F-number of the eyepiece. Represents an angle of view that is half the apparent field of view of the eyepiece (the unit of the angle of view is “゜”). As shown in FIG. 1, FIG. 2, and FIG. 3, in the first embodiment, the lens surface closest to the object has an aspherical shape, and the values are expressed by Expressions (1), (1) ′, and ( 2), Expression (2) ′, Expression (2) ″, Expression (3), and Expression (3) ′. As a result, the focal length F =
With respect to 18.75 and eye relief I = 22.0 (approximately 117% of the focal length F), each aberration is corrected to a favorable value, and particularly, distortion is suppressed to within ± 2%.

As shown in FIGS. 4, 5, and 6, in the second embodiment, the second lens surface counted from the object side has an aspherical shape. Equations (1) ′, (2), (2) ′, (2) ″, (3), and (3) ′ are satisfied. As a result, the focal length F = 18.7.
5, eye relief I21.8 (approximately 116 of focal length F)
%), Each aberration is corrected to a good value, and particularly, distortion is suppressed to within ± 2%.

As shown in FIGS. 7, 8, and 9, in the third embodiment, the third lens surface counted from the object side has an aspherical shape. Equations (1) ′, (2), (2) ′, (2) ″, (3), and (3) ′ are satisfied. As a result, the focal length F = 18.7.
5, eye relief I = 21.9 (approximately 117 of focal length F)
%), Each aberration is corrected to a good value, and particularly, distortion is suppressed to within ± 2%.

As shown in FIGS. 10, 11 and 12, in the fourth embodiment, the fifth lens surface counted from the object side has an aspherical shape, and the respective values are expressed by equations (1), (2). Equations (1) ′, (2), (2) ′, (2) ″, (3), and (3) ′ are satisfied. As a result, the focal length F =
With respect to 18.75 and eye relief I = 22.0 (approximately 117% of the focal length F), each aberration is corrected to a good value, and in particular, distortion is suppressed to within ± 1%. .

As shown in FIGS. 13, 14, and 15, in the fifth embodiment, the sixth lens surface counted from the object side has an aspherical shape, and each value is calculated by the equation (1). , Equation (1) ′, Equation (2), Equation (2) ′, Equation (2) ″, Equation (3), and Equation (3) ′. As a result, the focal length F =
With respect to 18.75 and eye relief I = 22.1 (approximately 118% of the focal length F), each aberration is corrected to a good value, and in particular, distortion is suppressed to within ± 2%. .

As shown in FIG. 16, FIG. 17, and FIG. 18, in the sixth embodiment, the eighth lens surface counted from the object side has an aspherical shape. Equations (1) ′, (2), (2) ′, (2) ″, (3), and (3) ′ are satisfied. As a result, the focal length F =
With respect to 18.75 and eye relief I = 23.2 (approximately 124% of the focal length F), each aberration is corrected to a good value, and in particular, distortion is suppressed to within ± 1%. .

As shown in FIG. 19, FIG. 20, and FIG. 21, in the seventh embodiment, the ninth lens surface counted from the object side has an aspherical shape. Equations (1) ′, (2), (2) ′, (2) ″, (3), and (3) ′ are satisfied. As a result, the focal length F =
With respect to 18.75 and eye relief I = 23.2 (124% of the focal length F), each aberration is corrected to a good value, and particularly, distortion is suppressed to within ± 1%.

As shown in FIGS. 22, 23, and 24, in the eighth embodiment, the first lens surface counted from the object side has an aspherical shape. Equations (1) ′, (2), (2) ′, (2) ″, (3), and (3) ′ are satisfied. As a result, the focal length F =
With respect to 18.75 and eye relief I = 23.0 (123% of the focal length F), each aberration is corrected to a good value, and in particular, distortion is suppressed to within ± 2%.

As described above, according to the above embodiments,
Each aberration is corrected to a good value over a wide apparent field of view 60 °, and in particular, distortion is suppressed to within 2%, and the eye relief I with respect to the focal length F of the entire lens system is corrected.
An eye lens with a length of 115% or more is realized. The aspherical surface of the present invention is not limited to the one shown in the above embodiment, and the formation position, the number of surfaces, the configuration of the glass material (may be plastic or the like), and the like are various configurations suitable for the purpose of the invention. Can be taken.

Further, the shape of the aspherical surface in each of the above embodiments is not limited to the shape represented by the expression (4), but is obtained by the above expressions (1), (1) ′, (2), (2) ′, (2) ",
Any aspherical shape may be used as long as one of (3) and (3) ′ is satisfied.

[0035]

As described above, according to the present invention, each aberration is corrected to a good value up to the peripheral portion of the visual field, particularly, the distortion is sufficiently suppressed, and the length of the eye relief with respect to the focal length is reduced. An eyepiece that ensures a sufficiently large size is realized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment.

FIG. 2 shows various data of the first embodiment.

FIG. 3 is an aberration diagram of the first embodiment.

FIG. 4 is a configuration diagram of a second embodiment.

FIG. 5 shows various data of the second embodiment.

FIG. 6 is an aberration diagram of the second embodiment.

FIG. 7 is a configuration diagram of a third embodiment.

FIG. 8 shows various data of the third embodiment.

FIG. 9 is an aberration diagram of the third embodiment.

FIG. 10 is a configuration diagram of a fourth embodiment.

FIG. 11 shows various data of the fourth embodiment.

FIG. 12 is an aberration diagram of the fourth embodiment.

FIG. 13 is a configuration diagram of a fifth embodiment.

FIG. 14 shows various data of the fifth embodiment.

FIG. 15 is an aberration diagram of the fifth embodiment.

FIG. 16 is a configuration diagram of a sixth embodiment.

FIG. 17 shows various data of the sixth embodiment.

FIG. 18 is an aberration diagram of the sixth embodiment.

FIG. 19 is a configuration diagram of a seventh embodiment.

FIG. 20 shows various data of the seventh embodiment.

FIG. 21 is an aberration diagram of the seventh embodiment.

FIG. 22 is a configuration diagram of an eighth embodiment.

FIG. 23 shows various data of the eighth embodiment.

FIG. 24 is an aberration diagram of the eighth embodiment.

FIG. 25 is a diagram showing an aspherical shape.

[Explanation of symbols]

G1 ... first lens group, G2 ... second lens group, G
3 ... third lens group, G4 ... fourth lens group, G1
2 ... Synthetic lens group

Claims (4)

[Claims] 1. A first lens having a negative lens in order from an object side.
A second lens group G2 having a lens group G1, a cemented lens of a negative lens and a positive lens, and a third lens having a cemented lens of a positive lens and a negative lens or a cemented lens of a negative lens and a positive lens An eyepiece comprising: a group G3; and a fourth lens group G4 having a positive lens, wherein at least one lens surface of each lens group has an aspherical shape. 2. The eyepiece according to claim 1, wherein the aspherical shape increases a lens edge thickness as approaching a peripheral portion as compared with a case where a base spherical surface based on a radius of curvature of an aspherical vertex is used. An eyepiece having such a shape. 3. The eyepiece according to claim 1, wherein the aspherical shape has a height h from an optical axis to an incident position of the most off-axis ray on the aspherical surface. For the displacement dx generated between the aspheric surface and the base sphere based on the radius of curvature of the vertex, the following expression (1) is satisfied: 0.001 ≦ | dx / h | ≦ 0.14 (1) An eyepiece characterized by the above-mentioned. 4. The eyepiece according to claim 1, wherein a total focal length F of the entire lens system, and the first lens group G1.
An eyepiece lens characterized by satisfying the following expression (2) | F / F12 | ≦ 0.4 (2) with respect to a combined focal length F12 between the lens and the second lens group G2.