JP3187510U - Eyepiece - Google Patents

Abstract

An object of the present invention is to provide an ocular lens that has improved residual distortion, which is a problem in observation / measurement, in a front-rear symmetrical eyepiece.
Three achromat lenses are arranged as an objective lens for an infinitely far object telescope, and a distance of 25 mm is maintained on a lens wall surface between a first group 21 and a second group 22 whose convex surfaces are opposed to each other. A spacer 24 is provided, and a spacer 25 having a width of 10 mm is provided between the second group 22 and the third group 23 to maintain an appropriate amount of distortion correction. These three groups of six lens units are connected to a metal casing. It was stored in a body 27 and fixed with a lens stopper 26. Further, a 2-inch sleeve 28 common to the eyepiece of a commercially available astronomical telescope is attached to the objective lens side of the lens stopper 26 to form an eyepiece.
[Selection] Figure 5

Description

The present invention relates to an eyepiece for a telescope, a field scope, binoculars, and a microscope capable of changing a magnification.

FIG. 3 shows a lens configuration of a general refracting telescope. The telescope and the microscope perform observation by enlarging the real image formed at the focal position 15 of the objective lens 14 with the eyepiece 16. FIG. 4 shows various eyepieces. 17 is an Abbe type orthoscopic type, 18 is a blow cell type, and 19 is a Ramsden type, both of which have a lens arrangement configuration in which the first group or the first group and the second group are symmetric in the front-rear direction. An eyepiece designed to reduce aberrations. Reference numeral 20 denotes a Kelner-type eyepiece which has an asymmetrical lens arrangement. Although this type of distortion is large compared to 17, 18, and 19, the number of lens components is small compared to 17 and 18, so the light absorption loss by the lens is small, and the reflected light generated at the lens-air interface can also be reduced. There are features. Furthermore, in recent years, a wide field eyepiece lens has been sold by many manufacturers in which a diffusing lens is arranged in front of the first group to spread the luminous flux once and the apparent viewing angle is expanded by a rear group lens having a large aperture. Yes.

In the present invention, a third lens group (see FIG. 8) is used to compensate for the insufficient correction of distortion aberration of the second lens group in the first lens group and the second lens group of the same specification whose convex surfaces face each other as shown in FIG. 1) 9) is a lens configuration that can correct distortion almost completely while eliminating the need for a different type of lens that is expensive because the same specifications are applied to the three groups of lenses. .

Commercially available eyepieces can be roughly divided into genres based on the following concept. In other words, in order to improve the distortion of the image plane, the lens arrangement is reduced in order to improve the genre with high image alignment (low distortion) and the good central image and cost reduction. This is a genre of a front-rear asymmetric lens arrangement, and a genre of wide-field eyepieces in which a diffusing lens is arranged in front of the first group and the rear lens system is enlarged. Each lens that is an element in the most basic optical design of these eyepieces can be considered as a pinhole. However, a pinhole lens having no area cannot collect light and cannot form an effective optical system. Therefore, in an actual optical design, a lens having the same focal length as the assumed pinhole lens is replaced. Lenses replaced from pinholes have characteristics that deviate from the ideality of optical systems designed with pinholes because there are events that deviate from ideality, such as the wavelength dependence of refractive index due to area, thickness, and material properties. This appears as various aberrations of an actual optical system. The types of the various eyepieces shown in FIG. 4 are all designed to accept other aberrations for the purpose of aberration correction. By the way, when a telescope or a microscope is used for observation / measurement, the distortion of the measurement target image caused by the optical system becomes a fatal defect. In particular, in the case of a telescope manufactured with high accuracy for observation, the focal length of the objective lens is often sufficiently long with respect to the diameter of the objective lens, and the distortion aberration of the image plane formed by the objective lens at 15 in FIG. This is sufficiently smaller than the distortion caused by the eyepiece. In an eyepiece having a symmetrical lens arrangement such as 17, 18, and 19 in FIG. 4, the lenses arranged symmetrically in the front group and the rear group are generally observed in order to correct each other's distortion aberration. Distortion can be reduced. However, if the front lens group and the rear lens group are the same, as shown in 6 of FIG. 1, the light beam focused by the front lens group is incident on the rear lens group, and apparently the lens curvature of the rear lens group is that of the front lens group. It can be understood that it is smaller than the lens curvature. This means that the distortion correction amount of the rear group is insufficient with respect to that of the front group. As a result, distortion aberration as shown by 11 in FIG. 2 is observed. In order to solve this problem, the correction amount of the lens curvature based on Equation 1 may be added to the rear group.
Curvature of rear group with respect to front group = 1 / (1− (front / rear group distance) / (focal length of front group)) Equation 1
However, lenses having different curvatures (= focal lengths) must be manufactured for the front group and the rear group, which is disadvantageous in terms of cost. Therefore, in relatively inexpensive eyepieces, lenses having the same specifications are often arranged in the first group and the second group at the expense of remaining distortion. In view of these points, in the present invention, in order to make up for the insufficient correction of distortion aberration of the second group lens, the blow lens type first group and second group lens having the same specifications as shown in FIG. The third group lens (9 in FIG. 1) is arranged, and the lens that can substantially completely correct the distortion aberration while eliminating the need for a different type of lens that has the same specifications as the three group lenses The purpose is to solve the problem by the configuration.

In order to solve this problem, the present invention has a three-group six-piece eyepiece in which two lenses constituting each group are bonded achromatic lenses formed by a combination of convex and concave balls, It is composed of a first group, a second group, and a third group that are arranged in the same direction as the second group, in which the focal lengths of the lenses are equal and the convex balls are opposed to each other. In the eyepiece configured as described above, the distance between the first group and the second group is in the range of 1/10 to 1/3 of the focal length of the lenses forming the group, and the distance between the second group and the third group is 1 of the focal length. / 15 to 1/5, more preferably, the distance between the first group and the second group is in the range of 1/6 to 1/4 of the focal length, and the distance between the second group and the third group is 1. It is an eyepiece having a configuration characterized by being in a range of / 12 to 1/8.

In the present invention, the third lens group shown by 9 in FIG. 1 has the same properties as the second lens group. Therefore, there is an effect of correcting the distortion aberration of the first group lens. As described above, when the first group and the second group are lenses having the same specifications, the distortion correction amount of the second group is insufficient by the amount shown by Equation 1, so It is arranged at a position away from the second group by a distance corresponding to the correction amount. The lens area diameter of the third group that receives the light beam focused by the second group is approximately proportional to the correction amount, so that the position of the third group can be defined, and a good image can be obtained before and after the appropriate position. Exists. It is also possible to design to reduce various aberrations required for an eyepiece other than distortion by arranging the third group using this allowable range.

1 shows the structure of a general procel orthoscopic eyepiece and an eyepiece according to the present invention. The distortion aberration caused by the eyepiece is shown. 11 and 12 are distortion images of the image formed behind the second lens group, and 13 is an image corrected for the distortion aberration generated behind the third lens group correction lens. . The basic structure of the refracting telescope is shown. This is a configuration of a general eyepiece. It is a block diagram of the eyepiece lens by this consideration.

Explanation of sign

DESCRIPTION OF SYMBOLS 1 1st group lens 2 2nd group lens 3 3rd group lens 4 Objective lens side 5 Eye side 6 Procel format 7 Focal plane 8 Procel format section 9 Correction lens section 10 Focal plane 11 Procel format Focal plane distortion 12 Procel format Focal plane distortion 13 Correction lens Focal plane distortion 14 Objective lens 15 Objective focal plane 16 Eyepiece 17 Apporthoscopic format 18 Procel format 19 Ramsden format 20 Kelner format 21 First group lens 22 Second group lens 23 Third lens group 24 Spacer 25 Spacer 26 Lens stopper 27 Eyepiece case 28 2 inch sleeve

Three achromat lenses designed as an objective lens for a infinity object telescope having a diameter of 42 mm and a focal length of 120 mm were arranged in the direction shown in FIG.

In FIG. 5, a spacer 24 is arranged between the first group 21 and the second group 22 facing the convex surfaces so that a distance of 25 mm is maintained on the lens wall surface, and between the second group 22 and the third group 23. Is provided with a spacer 25 having a width of 10 mm for maintaining an appropriate amount of distortion correction, and these 6 lens units in 3 groups are housed in a metal casing 27 and fixed by a lens stopper 26. Further, a 2-inch sleeve 28 common to the eyepiece of a commercially available astronomical telescope is attached to the objective lens side of the lens stopper 26 to form an eyepiece.

The constructed eyepiece had a focal length of 45 mm and an apparent viewing angle of 52 degrees.

The eyepiece according to the present example was attached to a florite apochromat telescope having a diameter of 128 mm, a focal length of 1040 mm, and F8.1, and compared with commercially available eyepieces A and B having substantially the same focal length prepared for comparison. The comparison targets were tile joints on the opposite building walls (representative examples of direct images of directity), the moon and planets, and nebula clusters such as M42 and M45. As a result of confirmation observation by a plurality of persons, the evaluation as shown in Table 1 was obtained, and the effectiveness of the present invention was confirmed.

In order to solve this problem, the present invention has a three-group six-piece eyepiece in which two lenses constituting each group are bonded achromatic lenses formed by a combination of convex and concave balls, It is composed of a first group, a second group, and a third group that are arranged in the same direction as the second group, in which the focal lengths of the lenses are equal and the convex balls are opposed to each other. In the eyepiece configured as described above, the distance between the first group and the second group is in the range of 1/10 to 1/3 of the focal length of the lenses forming the group, and the distance between the second group and the third group is 1 of the focal length. An eyepiece lens having a configuration characterized by being in the range of / 15 to 1/5.

Claims (2)

In the three-group six-piece eyepiece, the two lenses constituting each group are bonded achromatic lenses made up of a combination of convex and concave lenses, and the focal lengths of the three groups of lenses are equal, and the convex balls face each other. An eyepiece comprising the first group, the second group, and the third group disposed in the same direction as the second group. 2. The eyepiece lens having three groups and six elements according to claim 1, wherein the distance between the first group and the second group is in the range of 1/10 to 1/3 of the focal length of the lens forming the group, and the second group and the third group. Is in the range of 1/15 to 1/5 of the focal length, more preferably, the distance between the first group and the second group is in the range of 1/6 to 1/4 of the focal length, and the second group. The eyepiece according to claim 1, wherein the distance between the first lens group and the third lens group is in the range of 1/12 to 1/8.

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