JPH1184231A - Focusing attachment lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable continuous focusing operation over a wide range while suppressing the moving amount of a focusing lens group to be small by performing focusing operation from an object at infinity to an object at the closest distance by moving a first lens group having a negative refractive power to the object side. SOLUTION: A light ray from an object P becomes a light ray parallel to the optical axis through a focusing attachment lens 1 composed of a first lens group L1 of a negative refractive power and a second lens group L2 of a positive refractive power and is made incident on a telescopic optical system 2 in the focusing state to an object at infinity. By moving the focusing lens group L1 to the object side by δ1 the telescopic optical system 2 on which the focusing attachment lens 1 is mounted is focused from an object at infinity to an object at the closest distance. By moving an objective lens 3 to the object side by δ2 or an eyepiece lens 5 to the side of an observing eye, the telescopic optical system 2 on which the focusing attachment lens 1 is not mounted is focused from an object at infinity to an object at the closest distance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an attachment lens for focusing, and more particularly to an attachment lens attached to an object side of an objective lens such as a telescope or a stereomicroscope to continuously focus from an object at infinity to an object at a short distance. About.

[0002]

2. Description of the Related Art In a conventional telescope, an object at infinity is moved by moving an objective lens toward an object side or moving an eyepiece toward an observation eye, that is, by increasing a distance between the objective lens and the eyepiece. Focuses on objects at close range. Further, there is also an example in which focusing on a short-distance object is performed by dividing the objective lens into two lens groups and moving one of the lens groups, that is, by changing the interval between the two divided lens groups. is there. On the other hand, in a conventional stereomicroscope, a method of changing an operating distance by attaching an attachment lens having a specific refractive power to an object side of an objective lens is known.

[0003]

However, in the conventional method of performing focusing by changing the distance between the objective lens and the eyepiece in the telescope, the infinity increases as the distance of the object to be focused, that is, the focusing distance becomes smaller. The moving amount of the objective lens or the eyepiece with respect to the far focus state becomes large. Furthermore, the amount of movement of the objective or eyepiece is
It is proportional to the square (square) of the telescope magnification. Therefore,
In a telescope with a large magnification, a focusing distance that can be focused with the same movement amount is larger than in a telescope with a small magnification. In practice, the closest distance that can be focused by a telescope with a magnification of about 10 times is about 5 m, and the closest distance that can be focused with a telescope with a magnification of about 6 times is about 1 to 2 m.

Further, in the conventional method in which the objective lens is divided into two lens groups and one of the lens groups is moved to perform focusing, the refractive power of the focusing lens group (moving divided lens group) is increased. Otherwise, the amount of movement cannot be reduced. However, when the refractive power of the focusing lens group is increased, the fixed lens group (the non-moving divided lens group)
Must also be increased in size, which leads to an increase in the size of the device and an increase in cost. Further, a modification is made to the existing telescope so that the distance between the objective lens and the eyepiece can be changed, or the objective lens can be divided into two lens groups and one of the lens groups can be moved. It is difficult.

On the other hand, in the conventional system in which an attachment lens having a specific refractive power is mounted on the object side of an objective lens of a stereomicroscope, only an object at a specific distance can be focused by mounting the attachment lens. . However, for example, when fixing the main body outdoors and observing flowers and insects one after another, it is not possible to cope with quick observation because the respective focusing distances are different,
There was a disadvantage that its application range was narrow.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and is mounted on an object side of an objective lens such as an existing telescope or a stereomicroscope having a limited focusing range, and moves the focusing lens group. It is an object of the present invention to provide a focusing attachment lens capable of continuously performing focusing over a wide range from infinity to a short distance while suppressing the distance.

[0007]

In order to solve the above-mentioned problems, according to the present invention, an object which is configured to be attachable to an object side of an objective lens of a predetermined optical system and is located at an arbitrary distance from infinity to a short distance. Is a focusing attachment lens that performs continuous focusing on the first lens unit L1 having a negative refractive power in order from the object side in a mounted state.
And a second lens unit L2 having a positive refractive power, wherein the first lens unit L1 is moved to the object side to perform focusing from an object at infinity to an object at a short distance. Provide an attachment lens for focusing.

According to a preferred embodiment of the present invention, the first
When the focal length of the lens unit L1 is f1 and the focal length of the second lens unit L2 is f2, the following condition is satisfied: −20 <f1 <−60 −3 <f2 / f1 <−1.2.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A focusing attachment lens according to the present invention is configured to be mountable on an object side of an objective lens of a telescope or a stereomicroscope, for example. Then, the attachment lens itself includes a first lens group L1 having a negative refractive power and a second lens group L2 having a positive refractive power in order from the object side in the mounted state, and the first lens group L1 Is moved to the object side to focus from an object at infinity to an object at a short distance. That is, the focusing lens unit L1 having negative refractive power is disposed on the object side, and the fixed lens unit L having positive refractive power is spaced apart from the focusing lens unit L1.
An attachment lens is formed by arranging 2 on the image side. According to the above-described configuration of the present invention, as will be described in detail in an embodiment described later, the focusing lens group L1 is mounted on the object side of an objective lens such as a ready-made telescope or a stereoscopic microscope having a limited focusing range. It is possible to focus continuously over a wide range from infinity to short distance while keeping the movement amount of the lens small.

Hereinafter, the conditional expression of the present invention will be described.
In the present invention, it is desirable to satisfy the following conditional expressions (1) and (2). −20 <f1 <−60 (1) −3 <f2 / f1 <−1.2 (2) where f1 is the focal length of the first lens unit (focusing lens unit) L1, and f2 is the second lens unit. Lens group (fixed lens group) L
2 focal length.

The conditional expression (1) is a conditional expression for suppressing the movement amount of the focusing lens unit L1.
An appropriate range is defined for one focal length f1.
Exceeding the upper limit of conditional expression (1) is not preferable because the required amount of movement of the focusing lens unit L1 becomes too large to perform focusing over a sufficiently wide range. If the lower limit of conditional expression (1) is not reached, the in-focus lens unit L
Although the required amount of movement of the lens unit 1 is small, the refractive power of the focusing lens unit L1 becomes too large, which not only deteriorates various aberrations but also increases the number of constituent lenses, thereby increasing the weight of the attachment lens. As a result, when applied to a hand-held telescope or the like, the operability is impaired, which is not preferable.

Conditional expression (2) is a conditional expression for mainly defining the size of the attachment lens, and is appropriate for the ratio between the focal length f2 of the fixed lens unit L2 and the focal length f1 of the focusing lens unit L1. The range is specified. If the lower limit of conditional expression (2) is not reached, not only is the entire attachment lens too large and portability is impaired, but also the reduction in magnification when the attachment lens is attached is undesirably too large. If the upper limit of conditional expression (2) is exceeded, the in-focus lens unit L1 and the fixed lens unit L
This is not preferable because the distance between the lens 2 and the lens 2 may be too narrow and mechanically interfere with each other depending on the lens configuration.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The focusing attachment lens of the present invention,
In each embodiment, the first lens unit L1 having a negative refractive power and the second lens unit L2 having a positive refractive power are arranged in order from the object side in the mounted state.
By moving the first lens unit L1 to the object side, focusing from an object at infinity to an object at a short distance is performed.

FIG. 1 is a view schematically showing a configuration of a telescope equipped with a focusing attachment lens according to a first embodiment of the present invention. Thus, the first
In the embodiment, the focusing attachment lens of the present invention is applied to a telescope. In the telescope of FIG. 1, the light beam from the object P is parallel to the optical axis via a focusing attachment lens 1 including a first lens unit L1 having a negative refractive power and a second lens unit L2 having a positive refractive power. Is incident on the telescope optical system 2 which is in focus on an object at infinity. The light that has entered the telescope optical system 2 forms an object image 6 on the rear focal plane of the objective lens 3 via the objective lens 3 and the erecting prism 4. Light from the object image 6 reaches the eye point 7 via the eyepiece 5. Thus, the objective lens 3
Is enlarged and observed through the eyepiece 5.

In the first embodiment, by moving the focusing lens group L1 of the focusing attachment lens 1 toward the object side by δ1, the telescope optical system 2 on which the focusing attachment lens 1 is mounted can be moved to an object at infinity. Can focus on a short-distance object. Note that by moving the objective lens 3 toward the object side by δ2 or by moving the eyepiece lens 5 toward the observation eye side, the telescope optical system 2 without the focusing attachment lens 1 is moved away from the object at infinity. It can focus on a short distance object.

FIG. 2 is a diagram schematically showing the configuration of a conventional telescope optical system according to a first comparative example of the first embodiment. The objective lens of the telescope optical system shown in FIG. 2 includes, in order from the object side, a fixed lens group 8 having a positive refractive power and a focusing lens group 9 having a negative refractive power.
It is composed of Light from the object forms an object image 6 via an objective lens including a fixed lens group 8 and a focusing lens group 9. Light from the formed object image 6 reaches the eye point 7 via the eyepiece 5. Thus,
The object image 6 is magnified and observed through the eyepiece 5. In the first comparative example, the telescope optical system can be focused from an object at infinity to an object at a short distance by moving the focusing lens group 9 toward the observation eye by δ3.

FIG. 3 is a diagram schematically showing a configuration of a conventional telescope optical system according to a second comparative example of the first embodiment. The objective lens of the telescope optical system of FIG. 3 includes, in order from the object side, a fixed lens group 10 having a positive refractive power and a focusing lens group 11 having a positive refractive power. Light from an object forms an object image 6 via an objective lens including a fixed lens group 10 and a focusing lens group 11. Light from the formed object image 6 reaches the eye point 7 via the eyepiece 5. Thus, the object image 6 is magnified and observed through the eyepiece 5. In the second comparative example, the telescope optical system can be focused from an object at infinity to a close object by moving the focusing lens group 11 toward the object by δ4.

FIG. 4 is a view schematically showing a configuration of a telescope equipped with a focusing attachment lens according to a third comparative example of the first embodiment. The third comparative example of FIG. 4 has a configuration similar to that of the first embodiment of FIG. However, in the first embodiment, the focusing attachment lens 1 is composed of a focusing lens unit L1 having a negative refractive power and a fixed lens unit L2 having a positive refractive power in order from the object side. The focusing attachment lens 14 is composed of a focusing lens group 12 having a positive refractive power and a fixed lens group 13 having a negative refractive power in order from the object side. Therefore, FIG.
In the third comparative example, by moving the focusing lens group 12 of the focusing attachment lens 14 toward the object side by δ5, the telescope optical system 2 equipped with the focusing attachment lens 14 can be moved from an object at infinity. It can focus on a short distance object.

[Focus Movement Amount] in Table (1) includes a focus movement amount δ1 in the first embodiment, a focus movement amount δ2 when the attachment lens 1 for focusing in the first embodiment is not mounted,
The in-focus moving amount δ3 in the first comparative example, the in-focus moving amount δ4 in the second comparative example, and the in-focus moving amount δ5 in the third comparative example are shown. Each focusing movement amount is a movement amount based on the position of the focusing lens group in the infinity focusing state. In the movement direction, only the focus movement amount δ3 is movement toward the observation eye, and the other focus movement amounts δ1, δ2, δ4, and δ5 are movements toward the object side. In Table (1), S represents a focusing distance. The focusing distance S is shown in FIG.
Is the distance along the optical axis between the object to be focused and the lens surface closest to the object.

Further, [Values for Conditional Expressions] in Table (1) include:
The focal length of each lens group and the value of each conditional expression in the first example and each comparative example are shown. In Table (1), f1 is the focal length of the focusing lens unit L1, f2 is the focal length of the fixed lens unit L2, f3 is the focal length of the objective lens, f8 is the focal length of the fixed lens unit 8, and f9 is Is the focal length of the focusing lens group 9, f10 is the focal length of the fixed lens group 10, f11 is the focal length of the focusing lens group 11, f12
Is the focal length of the focusing lens group 12, f13 is the focal length of the fixed lens group 13, f89 is the combined focal length of the fixed lens group 8 and the focusing lens group 9 when focusing at infinity, and f1011 is infinity. The composite focal lengths of the fixed lens group 10 and the focusing lens group 11 at the time of far focusing are respectively shown.

[0021]

[Table 1] [In-focus movement amount] S δ1 δ2 δ3 δ4 δ5 ∞ 0.00 0.00 0.00 0.00 0.00 5000 0.50 2.04 1.49 2.63 2.04 2000 1.22 5.28 3.84 6.46 5.28 1000 2.39 11.25 8.09 12.62 11.25 500 4.58 26.79 18.28 24.56 26.79 300 7.29 100.00 38.50 40.89 100.00 [Values corresponding to conditional expressions] f1 = −50.0 f2 = 100.0 f3 = 100.0 f8 = 65.0 f9 = −120.714 f10 = 200.0 f11 = 130.0 f12 = 100.0 f13 = −50.0 f89 = 100.0 f1011 = 100.0 (1) f1 = −50 (2) f2 / f1 = −2

In comparison with the other comparative examples in Table (1), in the first embodiment, it is possible to reduce the required movement amount δ1 of the focusing lens unit L1 for the same focusing distance S. . Therefore, by mounting the focusing attachment lens 1 of the first embodiment on the object side of the objective lens of a ready-made telescope having a limited focusing range, the moving amount δ1 of the focusing lens unit L1 can be suppressed to be infinite. Focusing can be performed continuously over a wide range from a distance to a short distance. Further, since the movement amount δ1 of the focusing lens unit L1 is small, the focusing attachment lens 1 itself can be configured to be compact and lightweight.

[Second Embodiment] FIG. 5 is a diagram schematically showing the configuration of a stereo microscope equipped with a focusing attachment lens according to a second embodiment of the present invention. In the second embodiment, the focusing attachment lens of the present invention is applied to a Greeneau stereo microscope. In the stereomicroscope of FIG. 5, light rays (shown by solid lines in the figure) from the object P illuminated by an illumination system (not shown) are transmitted from a focusing lens unit L1 having a negative refractive power and a fixed lens unit L2 having a positive refractive power. After passing through the focusing attachment lens 16, the light is guided to a left-eye observation system and a right-eye observation system. The light guided to each observation system forms an observation image (not shown) via the objective lens 15,
The formed observation image is magnified and observed through an eyepiece (not shown).

Incidentally, the focusing attachment lens 16
Is removed from the stereomicroscope, light from the object Q closer to the objective lens than the object P forms an observation image via the objective lens 15 as shown by a broken line in the figure. In the second embodiment, in a state where the focusing attachment lens 16 is mounted, the focusing lens group L1 is moved to the object side by δ, so that the stereo microscope equipped with the focusing attachment lens 16 is moved to an object at infinity. Can focus on a short-distance object. That is, similarly to the first embodiment, the second
By mounting the focusing attachment lens 16 of the embodiment on the object side of the objective lens of a ready-made stereo microscope having a limited focusing range, the moving distance δ1 of the focusing lens unit L1 can be reduced to a short distance from infinity. Focusing can be performed continuously over a wide range up to.

In the above-described second embodiment, the present invention is applied to a Greeneau stereo microscope, but the present invention can also be applied to a stereo microscope having a common objective lens for the left and right observation systems. . In each of the above embodiments, the present invention is applied to a telescope and a stereo microscope. However, the present invention can be applied to an appropriate optical system other than the telescope and the stereo microscope.

[0026]

As described above, according to the present invention,
It is attached to the object side of an objective lens such as a ready-made telescope or stereo microscope with a limited focusing range, and continuously focuses over a wide range from infinity to short distance while keeping the amount of movement of the focusing lens group small. A focusing attachment lens that can perform focusing can be realized.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a configuration of a telescope equipped with a focusing attachment lens according to a first embodiment of the present invention.

FIG. 2 is a diagram schematically showing a configuration of a conventional telescope optical system according to a first comparative example of the first embodiment.

FIG. 3 is a diagram schematically showing a configuration of a conventional telescope optical system according to a second comparative example of the first embodiment.

FIG. 4 is a diagram schematically showing a configuration of a telescope equipped with a focusing attachment lens according to a third comparative example of the first embodiment.

FIG. 5 is a view schematically showing a configuration of a stereo microscope equipped with a focusing attachment lens according to a second embodiment of the present invention.

[Explanation of symbols]

 L1 First lens group (focusing lens group) L2 Second lens group (fixed lens group) 1, 16 Attachment lens for focusing 2 Telescope optical system 3 Objective lens 4 Erect prism 5 Eyepiece 6 Object image 7 Eye point 8 , 10 Fixed lens group 9, 11 Focusing lens group 15 Objective lens of stereo microscope

Claims (3)

[Claims] 1. A focusing attachment lens configured to be mountable on the object side of an objective lens of a predetermined optical system and performing continuous focusing on an object at an arbitrary distance from infinity to a short distance. And a first lens group L1 having a negative refractive power and a second lens group L2 having a positive refractive power in order from the object side in the mounted state, wherein the first lens group L1 is disposed on the object side. A focusing attachment lens characterized in that focusing from an object at infinity to an object at a short distance is performed by moving the focusing lens. 2. The focal length of the first lens unit L1 is set to f1.
The condition of −20 <f1 <−60 −3 <f2 / f1 <−1.2 is satisfied, where f2 is the focal length of the second lens unit L2. Attachment lens for. 3. The focusing attachment lens according to claim 1, wherein the focusing attachment lens is mounted on an object side of a telescope objective lens or a stereo microscope objective lens.