JPH0128924B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to observation optical systems such as telescopes and microscopes, and particularly to variable power optical systems thereof.

In order to change the magnification of a telescope or microscope, it is known to provide a variable magnification mechanism in the objective lens or eyepiece, or to replace the objective lens or eyepiece. Although the latter has a much simpler mechanism than the former, it is cumbersome to replace and requires a replacement optical system, making it unsuitable for optical machines where portability is important, such as binoculars. Furthermore, if the field stop is located at an inappropriate position, the periphery of the field of view will be blurred, so it is necessary to always set the field stop at the optimum position even when changing the magnification.

The present invention aims to provide an observation optical system that can quickly change the magnification with a simple mechanism, and further aims to provide a variable magnification optical system in which the field stop is always placed at the optimum position even when changing the magnification.

The variable magnification observation optical system according to the present invention basically consists of an objective lens and an eyepiece lens, and a lens group having a positive or negative refractive power is provided between the objective lens and the eyepiece lens. , magnification is changed by moving the principal point of the lens group from one side of an intermediate image formed by the objective lens between the objective lens and the eyepiece lens to the other side.

Hereinafter, an example in which the present invention is applied to an optical system of a telescope will be described with reference to the drawings.

The first basic configuration according to the present invention is shown in FIG.
As shown in figure b, objective lens L _p and eyepiece
A lens group _L1 with a negative refractive power is provided between L _e ,
When the negative lens group L ₁ is located between the intermediate image I created by the objective lens L ₀ and the eyepiece L _e (Fig. 1a), the magnification is low, and the negative lens group L ₁ is located between the objective lens L ₀ and this objective lens (Fig. 1a). When it is moved between the lens and the intermediate image I (FIG. 1b), the magnification becomes high.

Objective lens L ₀ , eyepiece L _e , negative lens group L ₁
When the focal lengths of are respectively f ₀ , f _e , and f ₁ , as shown in Figure 1a, a negative lens group is placed at a distance l from the front focal point Fe of the eyepiece L _e toward the eyepiece.
L ₁ is set, and the focal length of the negative lens group L ₁ is set so that for a positive number m larger than 1, the following relationship is satisfied: 1/f ₁ = -1/l + 1/ml, that is _, f 1 = ml/1-n f ₁
is determined. At this time, the focal length of the composite system of the eyepiece L _e and the negative lens group L ₁ is mf _e .

Therefore, the front focus and objective lens of this composite system
When L ₀ is matched with the back focus, the telescope magnification is
It becomes f ₀ /mf _e .

Next, from this state, as shown in Figure 1b, if we transform the negative lens group _L1 from the back focus of the objective lens _L0 , that is, the position of the intermediate image I of the object at infinity, to a distance l toward the objective lens. , the focal length of the composite system of the objective lens L ₀ and the negative lens group L ₁ is mf ₀ . In this case, the rear focus of the synthesis system and the front focus of the eyepiece L _e match, and the telescope magnification is mf ₀ /f _e . Comparing this with the case shown in FIG. 1a, the magnification has increased by m ² times, and variable magnification is realized.

The second basic configuration according to the present invention is shown in FIG.
As shown in Figure b, a positive lens group _L2 is provided between the objective lens _L0 and the eyepiece L _e instead of the negative lens group _L1 ; Figure 2a is a low magnification lens; b shows the state of high magnification.

When the focal length of the positive lens group is _f2 , as shown in Figure 2a, the objective lens _L0 is at a distance l from the back focus of the objective lens, that is, the position of the image I of the object at infinity by the objective lens, to the objective lens side. A positive lens group L ₂ is provided,
For a positive number m larger than 1, the focal length _f2 of the positive lens group _L2 is determined so as to satisfy the relationship 1/ _f2 = -1/l+m/l, that is, _f2 = l/m-1. It is being The focal length of the composite system of the objective lens L ₀ and the positive lens group L ₂ is f ₀ /m, and if the rear focus of this composite system is matched with the front focus of the eyepiece L _e , the telescope magnification is f ₀ /mf _e . Next, as shown in Figure 2b, if the positive lens group _L2 is moved to a position a distance l from the front focal point Fe of the eyepiece _Le to the eyepiece side, the composite system of the eyepiece _Le and the positive lens group _L2 The focal length of is f _e /m. At this time, the front focus of the composite system of the eyepiece L _e and the positive lens group L ₂ coincides with the back focus of the objective lens L ₀ , that is, the position of the intermediate image I of the object at infinity, and the telescope magnification is mf ₀ / It becomes f _e . Therefore, compared to the case of FIG. 2a, the magnification has increased by m ² times.

As shown in the first and second basic configurations above, it is extremely simple to replace only the positive or negative lens group of a predetermined focal length from one of the intermediate images I by the objective lens, that is, one of the rear focal points of the objective lens, to the other. You can easily change the magnification by changing the configuration. The movement of the positive or negative lens group for magnification conversion provided by the invention is simply carried out along the optical axis and across the intermediate image.

The third basic configuration according to the present invention converts the low multiplier state into a third
As shown in Fig. a and Fig. 3 b in the high magnification state, the negative lens group that moves for zooming is composed of a negative front group L ₁₁ and a negative rear group L ₁₂ arranged at a predetermined interval. It is. In this embodiment, the front and rear groups _L11 and _L12 are arranged so that the principal points _H1 and _H2 of the composite system of the front and rear groups L11 and _L12 move across the rear focus of the objective lens _L0 , that is, the object image I formed by the objective lens. , L ₁₂ are moved integrally to change the magnification. The composite focal length of the negative lens group and the movement position of the composite principal point are the same as in the first basic configuration, and the low magnification state in Figure 3a is the same as Figure 1a.
In addition, the high magnification state in FIG. 3b corresponds to that in FIG. 1b, respectively.

In addition, the positive lens groups are a positive front group L ₂₁ and a positive rear group L _22.
FIG. 4a shows a low magnification state of the fourth basic configuration, which is constructed separately, and FIG. 4b shows a high magnification state. In this example, the composite principal points H ₁ and H ₂ of the front and rear groups are the objective lens L ₀
The magnification can be changed by moving the front and rear groups together so as to move across the rear focal point, that is, the object image I formed by the objective lens. The composite focal length of the positive lens group and the movement position of the composite principal point are the same as in the second basic configuration, and the low magnification state in Figure 4a is shown in Figure 2a, and the high magnification state in Figure 4b is shown in Figure 2. b
corresponds to each.

In the third and fourth basic configurations above, only the principal point of the negative or positive moving lens group moves across the intermediate image, and the lens itself does not cross the intermediate image, so the lens group moves for zooming. There is no fear that scratches or dust on the middle lens surface will be visible. In each of the above embodiments, any intermediate magnification can be obtained by continuously moving the negative lens group _L1 or the positive lens group _L2 as a moving lens group for zooming along the optical axis. I can do it. However, since the imaging point changes, it is also possible to move the objective lens L ₀ or the eyepiece lens L _e to refocus. Also,
If the objective lens or the eyepiece lens is continuously moved in conjunction with the moving lens group, it can also be used as a zoom lens.

Next, in the basic configuration of the optical system according to the present invention as described above, an embodiment will be described in which the field stop can be provided at an optimal position even when changing the magnification.
The first embodiment shown in FIGS. 5a and 5b is a movable negative lens group L ₁ for variable magnification, with a low-magnification field diaphragm 11 on the objective lens L ₀ side and a high-magnification field diaphragm 12 on the eyepiece L _e side. and both field stops 11 and 1.
2 is provided so as to be movable in the optical axis direction integrally with the negative lens group _L1 by means of a movable barrel 10.

The field diaphragm 11 for low magnification matches the position of the intermediate image I formed by the objective lens L ₀ at low magnification when the negative lens group L ₁ is located on the eyepiece L _e side as shown in FIG. 5a.
Furthermore, as shown in FIG. 5b, the field stop 12 for high magnification is located at the position of the intermediate image I _' formed by the objective lens L ₀ and the negative lens group L ₁ during high magnification when the negative lens group L ₁ is located on the objective lens L 0 side. Match. As can be seen from Figures 1a and 1b, which show the basic configuration of this embodiment, the distances from the negative lens group to the intermediate images I and I' at low and high magnifications are both equal in ml, and therefore The field stops for low magnification and high magnification are provided at approximately equal distances on both sides of the negative lens group _L1 .

The second embodiment shown in FIGS. 6a and 6b is a second basic configuration in which a field stop is provided in the structure shown in FIGS. 2a and 2b as in the first embodiment. That is, a low magnification field diaphragm 21 is placed on the eyepiece L _e side of the positive lens group L ₂ that moves for zooming, and a high magnification field diaphragm 22 is placed on the objective lens L ₀ side. It is integrated with.

The field diaphragm 21 for low magnification adjusts the position of the intermediate image I' formed by the objective lens L ₀ and the positive lens group L ₂ at low magnification when the positive lens group L _{2 is located on the objective lens L 0 side} as shown in FIG. 6a. The field diaphragm 22 for high magnification is the sixth
As shown in Figure b, the positive lens group L ₂ is the eyepiece L _e
This corresponds to the position of the intermediate image I formed by the objective lens L ₀ at high magnification located on the side. As can be seen from FIGS. 2a and 2b showing the basic configuration of this embodiment, the positive lens group
The distances from L ₂ to the intermediate image I' at low magnification and the intermediate image I at high magnification are both l/m, which is the same, and the positive lens group
The distances between L ₂ and each field stop 21, 22 are configured to be approximately equal.

Now, third and fourth embodiments will be described in which the field stop is optimally arranged when the negative or positive lens group for zooming is separated into two groups, front and rear, as in the third and fourth basic configurations. In the third embodiment, as shown in FIGS. 7a and 7b, a low magnification field diaphragm 31 and a high magnification field diaphragm 32 are arranged between the front negative lens L ₁₁ and the rear negative lens L ₁₂ by means of a movable barrel 30. It is provided integrally with the lens. The field diaphragm 31 for low magnification matches the position of the intermediate image I at low magnification when the movable tube 30 is located on the eyepiece L _e side as shown in Fig. 7a, and the field diaphragm 32 for high magnification moves as shown in Fig. 7b. At high magnification, when the cylinder 30 is located on the objective lens _L0 side, it is aligned at the position of the intermediate image I'.

Furthermore, in the fourth embodiment shown in FIGS. 8a and 8b,
Between the front positive lens L ₂₁ and the rear positive lens L ₂₂ , a low-magnification field stop 41 and a high-power field stop 42 are provided integrally with each positive lens via a movable tube 40 . In this embodiment, the field stop 41 for low magnification matches the position of the intermediate image I' at low magnification when the movable tube 40 is located on the objective lens _L0 side as shown in FIG. As shown in Fig. 8b, the movable tube 40 matches the position of the intermediate image I at high magnification when it is located on the eyepiece L _e side. In these third and fourth embodiments as well, the low-magnification and high-magnification field stops are provided at approximately the same distance from the principal point of synthesis of each movable lens group.

According to the first to fourth embodiments described above, the field stop is provided at the optimum position both at low magnification and at high magnification, and a clear image can be observed over the entire field of view without blurring at the periphery of the field of view. be able to.

As described above, according to the present invention, it is possible to quickly change the magnification with an extremely simple structure, and there is no need to separately attach or detach any member, making it convenient for carrying. Furthermore, even when changing the magnification, the field stop can be placed in the optimal position, allowing excellent observation images to be obtained at all times.

[Brief explanation of drawings]

1 to 4 respectively show the first to fourth basic configurations of the variable magnification optical system according to the present invention, and the fifth
8 are schematic configuration diagrams of the first to fourth embodiments according to the present invention, with each figure a showing a low magnification state and each figure b showing a high magnification state. [Explanation of symbols of main parts], L ₀ ... Objective lens, L _e ... Eyepiece lens, L ₁ ... Negative lens group, L ₂
... Positive lens group, L ₁₁ , L ₁₂ ... Negative lens, L ₂₁ ,
L ₂₂ ...Positive lens, I, I'...Intermediate image, 11,1
2, 21, 22, 31, 32, 41, 42...field diaphragm.

Claims (1)

[Scope of Claims] 1. In an observation optical system having an objective lens and an eyepiece lens, a lens group having a predetermined refractive power disposed between the objective lens and the eyepiece lens;
moving the lens group so as to move the principal point of the lens group between the objective lens and the eyepiece from one side of an intermediate image formed by the objective lens to the other side; It has a movable tube and a field diaphragm provided on the movable tube, and when changing magnification, the objective lens and the eyepiece lens are both fixed, and the movement of the movable tube causes the objective lens and the eyepiece lens to be fixed together. An observation optical system characterized in that the magnification can be changed by moving the lens group integrally with the field stop between the lens groups. 2. The field diaphragm is arranged so as to substantially match the position of an intermediate image formed between the objective lens and the eyepiece lens when the magnification is changed by the movement of the movable tube. An observation optical system capable of variable magnification according to claim 1. 3. The lens group disposed between the objective lens and the eyepiece lens consists of one lens component provided within the movable tube, and the movable tube has two visual fields disposed on both sides of the one lens component. 3. The variable magnification observation optical system according to claim 2, further comprising a diaphragm. 4. The lens group disposed between the objective lens and the eyepiece lens consists of two lens components provided within the movable tube, and the movable tube has two visual fields disposed between the two lens components. 3. The variable magnification observation optical system according to claim 2, further comprising a diaphragm. 5. The variable magnification observation optical system according to claims 3 to 4, wherein the lens group has negative refractive power. 6. The variable magnification observation optical system according to claims 3 to 4, wherein the lens group has positive refractive power.