JPH1039236A - Telescopic optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to cover the shortest observation distance without requiring a close-up lens by providing a telescopic optical system which has, successively from an object side, an objective optical system having a stationary first lens group and a movable second lens group, an erecting optical system and an ocular optical system and satisfying specific conditions. SOLUTION: This telescopic optical system consists of, successively from the object side, the objective optical system 10 having the stationary first lens group G1 and the movable second lens group G2 for focusing, an erecting optical system 20 and an ocular optical system 30. The object image by the objective optical system 10 is formed on a primary imaging surface 10P and the image is observed through the ocular optical system 30. The condition equations (1) d/f<0.4, (2) f/f1 >d/f-0.3, (3) f/f1 <1.4-d/f are satisfied in the telephoto optical system. In the equations, d: the distance from the rear side principal point of the first lens group G1 in the infinite observation state to the front side principal point of the second lens group G2, f: the combined focal length of the objective lens system in the infinite observation state, f1 : the focal length of the first lens group G1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a telescope optical system, and more particularly to a telescope optical system capable of performing continuous focusing from infinity to a short distance.

[0002]

2. Description of the Related Art Conventional telescopes generally include:
It has the shortest observation distance of several meters to several tens of meters from infinity,
To observe a closer distance, it was necessary to wear another close-up lens. In addition, even if a close-up lens is attached and observation at a short distance is possible, the conventional product is large and cannot be easily used like a magnifying glass.

[0003]

The object of the present invention is to provide a shortest minimum observation distance,
For example, it is an object of the present invention to obtain a small telescope optical system capable of covering a shortest observation distance of about several tens of cm without requiring a close-up lens.

[0004]

SUMMARY OF THE INVENTION A telescope optical system according to the present invention comprises, in order from an object side, an objective optical system having a fixed first lens unit having a positive power and a movable second lens unit having a positive power for focusing; In a telescope optical system having an erecting optical system and an eyepiece optical system, the following conditional expressions (1), (2) and (3)
Is satisfied. (1) d / f> 0.4 (2) f / f ₁ > d / f−0.3 (3) f / f ₁ <1.4-d / f, where d: in infinity observation state The distance from the rear principal point of the first lens group to the front principal point of the second lens group; f: the combined focal length of the objective lens system in infinity observation; f ₁ : the focal length of the first lens group; is there.

[0005] A telescope usually requires at least one positive lens and one negative lens having different Abbe numbers in order to satisfactorily correct the chromatic aberration of the objective lens. In the telescope optical system of the present invention, the chromatic aberration of the objective optical system can be corrected by configuring at least one of the first lens group and the second lens group with one positive lens and one negative lens. it can. In addition, by bonding the positive lens and the negative lens, it is possible to reduce performance degradation due to an assembly error. Further, by configuring both the first lens unit and the second lens unit with a positive lens and a negative lens, it is possible to reduce a change in chromatic aberration due to focusing. further,
The first lens group and the second lens group can be manufactured as lenses having the same specifications, and the manufacturing cost can be reduced.

[0006]

FIG. 13 is a schematic diagram of a telescope optical system according to the present invention and a definition diagram of various quantities. The telescope optical system of the present invention includes, in order from the object side, an objective optical system 10, an erecting optical system 20, and an eyepiece optical system 30 each including a fixed first lens group G1 and a movable second lens group G2 for focusing. Has become. The object image formed by the objective optical system 10 is formed on a primary image forming plane 10P, and this image is observed via the eyepiece optical system 30. The primary imaging plane 10P is generally formed between the erecting optical system 20 and the eyepiece optical system 30. The erecting optical system 20
For example, it can be composed of a Porro prism or a Pechan prism.

In the above telescope optical system, the observation distance W
D = distance from the observation object point to the front principal point H1 of the first lens group G1, focal length f of the objective optical system 10 = composition of the first lens group G1 and the second lens group G2 when the observation distance is infinite. Focal length, distance d between the first lens group G1 and the second lens group G2
= From the rear principal point H2 of the first lens group G1 to the second lens group G
2 is defined as the distance to the front principal point H1 and the back focus f _b = the air-equivalent distance from the rear principal point H2 of the second lens group G2 to the primary imaging plane 10P.

The condition (1) is a condition for shortening the shortest observation distance. First lens group G1 and second lens group G
By increasing the ratio of the distance d to the focal length f of the objective optical system in the infinity observation state of 2 as in the conditional expression (1), the focal length f of the objective optical system 10 in the infinity observation state is increased. A shortest observation distance of about three times can be obtained. In other words, the second lens group G2 moves toward the first lens group G1 when the observation distance is reduced from the infinity observation state, and by increasing d in this way, the second lens group G2 Is large, and a shortest observation distance of about three times the focal length of the objective optical system 10 can be obtained.

Conditional expression (2) is a condition for keeping the total length (TL = d + f _b ) of the entire telescope optical system short. If this conditional expression (2) is not satisfied, the overall length will be long and the compactness will be impaired. In particular, the telescope optical system is intended to cover the area of a magnifier and to be usable as a magnifier, and compactness is an important factor.

[0010] Condition (3), the back focus f _b of the telescope optics is a condition for holding the length necessary for accommodating the erecting optical system 20. If the conditional expression (3) is not satisfied, it is difficult to accommodate the erecting optical system 20, and it is difficult to construct a telescope and a magnifier for observing an erect image.

Hereinafter, the present invention will be described with reference to specific numerical examples. [Embodiment 1] FIGS. 1 to 3 show a first embodiment of a telescope optical system according to the present invention. FIG. 1 is a diagram showing a lens configuration in an infinity observation state. In this embodiment, the first lens group G
Both the first lens group G2 and the second lens group G2 are a cemented lens of a positive lens and a negative lens. A primary imaging plane 10P on which an object image is formed by the objective optical system 10 is located between the erecting optical system 20 and the eyepiece optical system 30. The erecting optical system 20 is a Pechan prism. In Example 1, surfaces No. 1 to No. 6 are objective optical systems, surfaces No. 7 to No. 10 are erecting optical systems, and surface Nos. 11 to No. Reference numeral 15 denotes an eyepiece optical system. FIG. 2 is a diagram showing various aberrations in the infinity observation state of FIG. 1, and FIG. 3 is a diagram showing various aberrations at the shortest observation distance. In the various aberration diagrams, spherical aberration and chromatic aberration of magnification indicate d-line, g-line, and C-line, and astigmatism S indicates a sagittal image plane, and M indicates a meridional image plane.

Table 1 shows specific numerical data of this lens system. In the tables and drawings, f represents the focal length. R is the radius of curvature, D is the lens thickness or lens interval, n is the refractive index of the d-line, and ν _d is the Abbe number of the d-line.

[0013]

[Table 1] Surface No.RD n ν _d 1 93.000 4.00 1.51633 64.1 2 -54.490 2.50 1.72342 38.0 3 -139.650 57.20-3.22--4 76.950 4.80 1.51633 64.1 5 -35.459 1.80 1.62004 36.3 6 -114.000 2.80-56.78--7 ∞ 22.89 1.56883 56.3 8 ∞ 0.84--9 ∞ 33.15 1.51633 64.1 10 ∞ 9.01--11 * 57.904 1.60 1.58547 29.9 12 8.960 7.15 1.49176 57.4 13 -13.730 0.30--14 17.093 5.12 1.48749 70.2 15 -17.093--- However, a rotationally symmetric aspheric surface is defined by the following equation. x = Ch ² / {1+ [1- (1 + K) C ² h ² ] ^1/2 } + A4h ⁴ + A6h ⁶ + A8h ⁸ + ... (C is curvature (1 / r), h is No.11; K = -0.89500, A4 = -0.29670 × 10 ^-3 , A6 = -0.91000 × 10 ^-6 A8 = 0.0, A10 = 0.0, A12 = 0.0 f (∞) = 82.09 f ₁ = 144.972 d = 61.240 d / f = 0.746 f / f ₁ = 0.566 Shortest observation distance: 161.64 (from the object to the front principal point of the first lens group G1, ≒ 1.97f) F _{b of the} objective optical system 10; at the observation distance ∞ = 47.42, at the shortest observation distance = 101.40

[Embodiment 2] FIGS. 4 to 6 show a second embodiment of the telescope optical system of the present invention. FIG. 4 is a diagram showing a lens configuration in an infinity observation state. In this example,
The lens specifications of the first lens group G1 and the second lens group G2 are the same, and each is a laminated lens of a positive lens and a negative lens. A primary imaging plane 10P on which an object image is formed by the objective optical system 10 is located between the erecting optical system 20 and the eyepiece optical system 30. In Example 2, surfaces No. 1 to No. 6 are objective optical systems, surfaces No. 7 to No. 10 are erecting optical systems, and surfaces No. 11 to N
o.15 is an eyepiece optical system. FIG. 5 is a diagram showing various aberrations at the infinity observation state in FIG. 4, FIG. 6 is a diagram showing various aberrations at the shortest observation distance,
Table 2 shows specific numerical data.

[0015]

[Table 2] Surface No.RD n ν _d 1 80.000 4.00 1.51633 64.1 2 -45.000 2.00 1.62004 36.3 3 -173.534 49.90-2.20--4 80.000 4.00 1.51633 64.1 5 -45.000 2.00 1.62004 36.3 6 -173.534 3.00-50.70--7 ∞ 22.89 1.56883 56.3 8 ∞ 0.84--9 ∞ 33.15 1.51633 64.1 10 ∞ 9.42--11 * 57.904 1.60 1.58547 29.9 12 8.960 7.15 1.49176 57.4 13 -13.730 0.30--14 17.093 5.12 1.48749 70.2 15 -17.093---Aspherical data No.11; K = -0.89500, A4 = -0.29670 × 10 ^-3 , A6 = -0.91000 × 10 ^-6 A8 = 0.0, A10 = 0.0, A12 = 0.0 f (∞) = 82.04 f ₁ = 130.168 d = 53.802 d / f = 0.648 f / f ₁ = 0.630 Shortest observation distance; 201.01 (from the object to the front principal point of the first lens group G1, {2.45f) f _{b of the} objective optical system 10; At the shortest observation distance = 95.83

[Embodiment 3] FIGS. 7 to 9 show a third embodiment of the telescope optical system according to the present invention. FIG. 7 is a diagram showing a lens configuration in an infinity observation state. In this example,
The first lens group G1 is a laminated lens of a positive lens and a negative lens, and the second lens group G2 is a single positive lens. A primary imaging plane 10P on which an object image formed by the objective optical system 10 is formed,
It is located between the erecting optical system 20 and the eyepiece optical system 30. Example 3
, Surfaces No. 1 to No. 5 are objective optical systems, and surfaces No. 6 to N
o.9 is an erecting optical system, and surfaces Nos. 10 to 14 are eyepiece optical systems. FIG. 8 is a diagram of various aberrations in the infinity observation state of FIG.
Shows various aberration diagrams at the shortest observation distance, and Table 3 shows specific numerical data.

[0017]

[Table 3] Surface No.RD n ν _d 1 82.515 4.50 1.51633 64.1 2 -39.896 1.80 1.67270 32.1 3 -103.526 47.00-3.00--4 83.386 3.00 1.51633 64.1 5 -8176.670 3.00-47.00--6 ∞ 22.89 1.56883 56.3 7 ∞ 0.84--8 ∞ 33.15 1.51633 64.1 9 ∞ 8.22--10 * 57.904 1.60 1.58547 29.9 11 8.960 7.15 1.49176 57.4 12 -13.730 0.30--13 17.093 5.12 1.48749 70.2 14 -17.093---Aspheric data; No.10; K = -0.89500, A4 = -0.29670 × 10 ^-3 , A6 = -0.91000 × 10 ^-6 A8 = 0.0, A10 = 0.0, A12 = 0.0 f (∞) = 81.21 f ₁ = 114.01 d = 49.433 d / f = 0.609 f / f ₁ = 0.712 Minimum observation distance; 247.60 (from the object to the front principal point of the first lens group G1, ≒ 3.05
f) f _{b of the} objective optical system 10; at the observation distance == 46.00 at the shortest observation distance = 90.00

[Embodiment 4] Figure Objective optical system 10 to 1
FIG. 2 shows a fourth embodiment of the telescope optical system according to the present invention, in which the objective optical system 10 is a lens configuration diagram in an infinity observation state. In this embodiment, the first lens group G1 is a positive lens, and the second lens group G2 is a laminated lens of a positive lens and a negative lens. A primary imaging plane 10P on which an object image is formed by the objective optical system 10 is located between the erecting optical system 20 and the eyepiece optical system 30. In Example 4, surfaces No. 1 to No. 5 are objective optical systems, surfaces No. 6 to No. 9 are erecting optical systems, and surfaces No. 10 to No. 14
Is an eyepiece optical system. FIG. 11 is a diagram showing various aberrations at the infinity observation state in FIG. 12, FIG. 12 is a diagram showing various aberrations at the shortest observation distance,
Table 4 shows specific numerical data.

[0019]

[Table 4] Surface No.RD n ν _d 1 64.004 3.00 1.51633 64.1 2 264.955 37.80-2.20--3 52.617 4.80 1.56384 60.7 4 -51.069 1.80 1.71736 29.5 5 -2081.833 15.40-51.00--6 ∞ 22.89 1.56883 56.3 7 ∞ 0.84 --8 ∞ 33.15 1.51633 64.1 9 ∞ 8.24--10 * 57.904 1.60 1.58547 29.9 11 8.960 7.15 1.49176 57.4 12 -13.730 0.30--13 17.093 5.12 1.48749 70.2 14 -17.093---Aspheric data; No.10; K = -0.89500, A4 = -0.29670 × 10 ^-3 , A6 = -0.91000 × 10 ^-6 A8 = 0.0, A10 = 0.0, A12 = 0.0 f (∞) = 81.20 f ₁ = 162.61 d = 39.436 d / f = 0.486 f / F ₁ = 0.499 Shortest observation distance: 249.08 (from the object to the front principal point of the first lens group G1, {3.07f) f _{b of the} objective optical system 10; Observation distance∞ = 61.51 Minimum observation distance = 97.11

Next, Table 5 shows values corresponding to the conditional expressions in Examples 1 to 4.

[Table 5] Example 1 Example 2 Example 3 Example 4 d / f (1) 0.746 0.648 0.609 0.486 f / f ₁ (2) (3) 0.566 0.630 0.712 0.499 d / f-0.3 (2) 0.446 0.348 0.309 0.186 1.4-d / f (3) 0.654 0.752 0.791 0.914

As is clear from Table 5, the numerical values of Examples 1 to 4 satisfy the conditional expressions (1) to (3), and various aberrations in the infinity observation state and the shortest distance observation state are also satisfied. Corrected well.

[0022]

According to the telescope optical system of the present invention, a telescope having an observation range of a magnifying glass can be obtained without requiring a close-up lens.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a lens configuration of a telescope optical system according to a first embodiment of the present invention in an infinity observation state.

FIG. 2 is a diagram illustrating various aberrations of the lens system in FIG. 1;

3 is a diagram of various aberrations of the lens system of FIG. 1 at a shortest observation distance.

FIG. 4 is a lens configuration diagram showing an infinity observation state, showing a second embodiment of the telescope optical system according to the present invention.

FIG. 5 is a diagram illustrating various aberrations of the lens system in FIG. 4;

FIG. 6 is a diagram illustrating various aberrations of the lens system in FIG. 4 at the shortest observation distance.

FIG. 7 is a diagram showing a lens configuration of a telescope optical system according to a third embodiment of the present invention in an infinity observation state.

8 is a diagram illustrating various aberrations of the lens system in FIG. 7;

9 is a diagram of various aberrations of the lens system of FIG. 7 at the shortest observation distance.

FIG. 10 is a lens configuration diagram showing a fourth embodiment of a telescope optical system according to the present invention in an infinity observation state.

11 is a diagram illustrating various aberrations of the lens system in FIG. 10;

12 is a diagram of various aberrations of the lens system of FIG. 10 at the shortest observation distance.

FIG. 13 is a schematic view of a telescope optical system according to the present invention.

[Explanation of symbols]

 G1 First lens group G2 Second lens group 10 Objective optical system 20 Erecting optical system 30 Eyepiece optical system

Claims (4)

[Claims] 1. An objective optical system having, in order from an object side, a fixed first lens unit having a positive power and a movable second lens unit having a positive power for focusing; an erecting optical system; A telescope optical system having the following conditions: (1), (2) and (3). (1) d / f> 0.4 (2) f / f ₁ > d / f−0.3 (3) f / f ₁ <1.4-d / f, where d: in infinity observation state The distance from the rear principal point of the first lens group to the front principal point of the second lens group; f; the combined focal length of the objective lens system at infinity observation; f ₁ ; the focal length of the first lens group. 2. The first lens group and the second lens group according to claim 1,
At least one of the lens groups is a telescope optical system including one positive lens and one negative lens. 3. The method according to claim 2, wherein one positive lens and one
The negative lenses are telescope optical systems that are laminated lenses. 4. The telescope optical system according to claim 1, wherein the first lens group and the second lens group are lenses having the same specifications.