JPS5813886B2 - Astronomical telescope optical system - Google Patents

Description

Detailed Description of the Invention The present invention arranges a rear group lens having a positive focal length at a suitable position in front of the focal position of an astronomical telescope objective lens, and furthermore, this rear group lens is used as a correction lens in an adapter format. and brighten the F number of the objective lens.
Furthermore, it relates to the optical system of an astronomical telescope created for the purpose of improving image curvature and coma aberration, and its purpose is to create an optical system that can be used in two ways with one astronomical telescope. This is what I did.

The objective lens of an astronomical telescope has residual negative field curvature and coma aberration, so it is used for a narrow angle of view.

Like the objective lens, the eyepiece lens also has a negative field curvature, so it is desirable to flatten the image plane of the objective lens for visual observation and photography.

The present invention has been constructed to satisfy the above-mentioned needs, and has a positive focal length f, , F, which is composed of a plurality of lenses.
The front group lens having the number F has its own aberrations corrected and can be used as an objective lens for an astronomical telescope. and positive focal length f2
If the focal length of the optical system obtained by arranging the rear group lens L' with a large air gap is f, and the distance from the front surface of the rear group lens to the focal position of the front group lens is e, then the conditions of This is an optical system for an astronomical telescope that satisfies the following.

(See Figure 1) In the above explanation, f1/f in condition (1) represents the reciprocal of the reduction magnification of the rear group lens with respect to the front group lens focal length, and if the maximum value of this range is exceeded, Since the radius of curvature of each surface of the rear lens group becomes small, it becomes difficult to correct coma aberration and astigmatism.

Moreover, if the minimum value is exceeded, there will be no advantage from the point of view of using one astronomical telescope in two different ways.

According to condition (2), by maintaining a large air gap between the front and rear group lenses, it is possible to make the rear group lens independent as an auxiliary lens and use it as an adapter.As an adapter lens, the F number of the front group lens is 8. Even when attached to a larger ready-made astronomical telescope, the aberration of image curvature can be well corrected, and the F number of the objective lens used can be made brighter.

Condition (4) corrects the arrangement of the rear group lens and is related to the F number of the front group lens within the range of the above condition (3),
By selecting a numerical value within the range of condition (4), an appropriate rear focal length can be obtained while maintaining good aberrations.

The front group lens that satisfies the conditions (1), (2), and (3) above has its own aberrations corrected and can be used as an objective lens for an astronomical telescope.

When attaching an adapter-type rear group lens to a front group lens of any focal length that satisfies the conditions (1), (2), and (3) above, the F number will be F1 x f/
1, and can be used as an astronomical telescope objective lens that can satisfactorily correct coma aberration and field curvature aberration.

In other words, by using a rear group lens (auxiliary lens) as an adapter for one astronomical telescope, it is an optical system that can be used as two astronomical telescopes with different F numbers.

Next, examples of the present invention will be shown.

Example (1) Consists of front group lenses L1 and L2 and rear group lenses L3 and L4 (see Figure 2) Focal length f = 8 2 4.3 2 3 mm Rear focal length f3f = 52.923 Related F number F=
10.3 Front group lens focal length I1= 1200.00
trtm~ Back focal length Bf, =1 191.79
0m1l〃 F number F, = 15 Focal length of rear group lens f2 = 24 1.372m
m〃 Rear focal length Bf2=218.735 mm The aberrations of the above example are shown in FIG.

The above example combines the front group lens and the rear group lens of the auxiliary lens, but next we will compare the aberrations when using only the front group lens and removing the rear group lens adapter.

Since the focal length of the front group lens alone is longer than that of the above example, it is easier to understand the aberrations when compared with the same focal length, so the data of the lens system obtained by multiplying the data of the front group lens by the proportionality of f/1. is shown below.

Incidentally, an external view of the lens system is shown in FIG. 4, and its aberrations are shown in FIG. 5.

Focal length f'=8 2 4.3 2 3mm Rear focal length Bf'-8 1 8.6 8 8mmF number F'-10.3 Example 0 Front group lenses L1 and L2 and rear of L3 and L4 Consists of a group lens (see Figure 6) Focal length f = 4 3 9.6 4 2mm Rear focal length Bf = 52.928mynFnanno<-F=5
．． 5 Focal length of front group lens f]=640. OO m
m〃 Back focal length Bf3 = 6 29.1 9
7mm F number F1=8.0 Rear group lens... is the same as the rear group lens of Example (1). The aberrations of the above example are shown in FIG.

The above example combines the front group lens and the rear group lens of the auxiliary lens, but next we will show a comparison of aberrations when only the front group lens is used and the adapter of the rear group lens is removed.

Since the focal length of the front group lens alone is longer than that of the above example, it is easier to understand the aberrations when compared with the same focal length, so the data of the lens system obtained by multiplying the data of the front group lens by the proportionality of f/1. is shown below.

The external view of the lens system is shown in Figure 8, and the aberration diagram is shown in Figure 9.
As shown in the figure.

Focal length f' = 4 3 9.6 4 2ynyn Rear focal length 'f3f' - 4 3 2.2 2 lmF number F' = 55

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the optical system of the present invention, Fig. 2 is a side view showing the optical system of the first embodiment, and Fig. 3 shows the aberrations as above, where A is spherical aberration, B is astigmatism, and C is Indicates distortion aberration. Fig. 4 is a side view of the front lens group with the same focal length as that of the first embodiment, and Fig. 5 shows the aberrations of the above.
indicates spherical aberration, B indicates astigmatism, and C indicates distortion. FIG. 6 is a side view of the optical system of the second embodiment, and FIG. 7 shows the same aberration as above, where A shows spherical aberration, B shows astigmatism, and C shows distortion aberration. Fig. 8 is a side view of only the front lens group with the same focal length as that of the second embodiment, and Fig. 9 shows the same aberration as above, where A is spherical aberration, B is astigmatism, and C is distortion aberration. show. In addition, the symbols in the figure, L1, L2...front group lens, L3, L4
...Rear group lens.

Claims (1)

[Claims] 1 In order to make the rear lens group of the astronomical telescope objective lens freely adjustable, a positive focal length f consisting of multiple lenses is used.
1. The front group lens with an F number F is itself aberration corrected and can be used as an objective lens for an astronomical telescope. The focal length f of the optical system obtained by arranging the rear group lens with a positive focal length f2 with a large air gap, and the distance e from the front surface of the rear group lens to the focal position of the front group lens. Then, the optical system of an astronomical telescope that satisfies the following conditions.