JPS59174811A - Objective lens of light wave range finder - Google Patents

Abstract

PURPOSE:To obtain the functions of a theodolite by specifying the conditions of an optical system which has a front group with positive refracting power and a rear group with negative refracting power, a dichroic prism for separating infrared light and visible light between both groups, and an erecting prism behind the rear group. CONSTITUTION:The front group consists of three elements in two groups, i.e. a positive single lens and a cemented lens of a positive and a negative lens, and the rear group consists of two elements in one group, i.e. a cemented lens of a negative and a positive lens; and they satisfy inequalities I -IV. In the equations, (f) and (f1, 2, 3) are the focal length of the whole system and the composite focal length of the front group, and nuDi (i=1, 2, 3) is the Abbe number of the line (d) of the (i)th lens; and thetaj (j=1, 2) is the partial dispersion ratio of the infrared area of the (j)th lens defined by theta=(nc-n1014)/(nF-nC) using the refractive index nC of a line C, refractive index nF of a line F, and refractive index n1014 to a light beam with 1014nm wavelength, and ri (i=1, 2) is the radius of curvature of the (i)th surface.

Description

[Detailed description of the invention]

The present invention relates to a coaxial optical rangefinder objective lens. Conventionally, there is a telephoto type lens as a theodolite objective lens, which consists of a front group with positive refractive power and a rear group with negative refractive power. It was characterized by the ability to focus up to a distance. Furthermore, in order to reduce performance degradation due to aberration fluctuations, assembly errors, and processing errors due to movement of the rear lens group, the rear lens group generally has a two-lens configuration in which a positive lens and a negative lens are glued together. By the way, as a means of adding a distance measurement function to the conventional Zeodorite 1 objective lens and making it a light wave rangefinder, the front group of the theodolite objective lens is used as a collimator for emitting and receiving infrared light, One possible method is to use a movable lens for focusing the conventional theodolite as the rear group, but in this method, the light emitting part is placed at the focal position of the front group, that is, on the optical axis. The light-receiving part will come closer, causing an inconvenience. However, this inconvenience can be solved by providing means for separating infrared light and visible light between the front group and the rear group and guiding the focal position of the infrared light of the front group to off the optical axis. Now, in a coaxial optical rangefinder objective lens integrated with such a theodolite, the front group must be used as a collimator for infrared light, and aberrations must be corrected.
In the case of visible light, as the front group of Theodory 1~, the aberrations must be balanced with the movable rear group and the aberrations must be corrected as a whole. However, if the front group is used as a collimator for infrared light to correct chromatic aberration, visible light will be greatly overcorrected on the short wavelength side, and the rear group will no longer be able to correct it, which will deteriorate the function of Theodory 1. There were drawbacks. Furthermore, by providing a means for separating infrared light and visible light between the front group and the rear group, there is a drawback that there is no space for movement of the rear group. Therefore, in order to eliminate these drawbacks, it is conceivable to form an image once in the front group, then transmit the image through a relay lens, and set a movable lens within the relay lens to perform focusing. With other methods, the optical system becomes complicated,
Functionally, it was not as good as conventional theodolites. By selecting an appropriate glass for the front group lens and setting appropriate conditions, the present invention maintains the features of conventional theodolites, while also functioning as a light wave rangefinder. The object of the present invention is to provide an objective lens for a coaxial light wave rangefinder that can also function as a coaxial optical rangefinder. The objective lens according to the present invention includes a front group having a positive refractive power,
An optical system consisting of a rear group with negative refractive power, a dichroic prism placed between the front group and the rear group for separating infrared light and visible light, and an erecting prism placed behind the rear group. The group has a configuration of 3 elements in 2 groups consisting of a positive single lens and a bonded lens of positive and negative lenses, and the rear group has a configuration of 2 elements in 1 group consisting of a bonded lens of negative and positive lenses, and the following conditions are met. This is an objective lens for a light wave rangefinder that satisfies the following. (IJ f 1,2.3 <0.45f(2) d1+
乍d2−乍d3 >75(3) 01+ 02<
0.0037(v d s y d 2 )+1.2
2('l) l +2I>l rs l, r
t >0, +2<0, where f is the focal length of the entire system, f 1 +2 +3 is the composite focal length of the front group, νd1
= 1.2.3) is the d-line Atsube number of the i-th glass (lens), θj (j = 1.2) is the C-line refractive index nc,
Using the refractive index n of the F-line and the refractive index "+or4" of the light beam with a wavelength of 1014n+n, the partial dispersion ratio in the infrared region of the lens, rt (+"1.2), is the radius of curvature of the i-th surface. represent. Next, each condition will be explained. Condition (1) is for determining the size of the lens system, and is intended to provide a large positive refractive power to the front group to reduce the telephoto ratio. That is, if the focal length of the front group becomes longer than the right side of condition (1), a compact light wave rangefinder cannot be obtained. Condition (2) is to appropriately overcorrect the chromatic aberration of the front group. A common method for correcting chromatic aberration in a telephoto lens is to correct the entire system by overcorrecting in the front group and undercorrecting in the rear group. However, when chromatic aberration is corrected deviating from condition (2), the refractive power of each lens becomes large, and aberrations other than chromatic aberration become large, or chromatic aberration of magnification becomes large, which is not preferable. Condition (3) is for reducing the chromatic aberration of visible light in the front group when color correction of infrared light is performed in the front group. In other words, when the partial dispersion ratio oJ in the infrared region increases beyond the right side, the chromatic aberration of visible light when correcting the chromatic aberration of infrared light becomes largely overcorrected on the short wavelength side, and this must be corrected in the rear group. This makes it difficult. Condition (4) is a condition for eliminating coma aberration through the front and rear groups. The rear group has negative refractive power and is located behind the dichroic prism, so the incident height of the light rays that enter the rear group is low and the negative refractive power is large, causing spherical aberration in the rear group. If this is corrected, comatic aberration due to the first surface of the rear group (ro in the embodiment) remains. Therefore,
This coma aberration must be corrected in the front group, and the coma aberration is corrected by increasing the refraction angle of the light beam at the positive single lens in the front group. That is, in condition (4), 1r2
If 1 becomes smaller than 1r11, the coma aberration in the front group becomes larger than the amount necessary to correct the coma aberration in the rear group, and the coma aberration in the front group remains in the entire system, which is not preferable. Examples according to the present invention will be given below. Here, r (, (i = 1, 2, 3...) is the radius of curvature of the first surface, d , (i = 1, 2, 3)
．． ) is the distance between the first surface and the (i+1)th surface, nJy vJ (j = 1.2.3...) is the d-line refractive index of the jth glass, and Indicates the Atsube number of the d-line.

[Example 1] f = 100 FNO1: 6.3 Angle of view 1.4°r Hd 1n; ν. 1 50.479' 2.975 1.603
11 60.72 -108.076 0.793 3 26.970 4.363 160311
60.74 -72.580 1.7B5
1.75520 27.55 51.763
14.8736 cx) 8.527 1.51
633 64.17oo1.190 8 78.981 1.190 1.7215
0 29.29 -9.335 1.408
1.66673 48.310 7.987
10.8791.1 oo14.6751.51
633 64.112 col, 785 13 ■ 0.992 1.51633
6C114ω f 123 =0.40f sid1+sid2-sid
3=93.901+02=1.658 0.0037(vdt+vd2')+1.22=1
．． 669 [Example 2] f = 100 FNO1: 6.2 Angle of view 1.4°r 1d + nj 1/ 26.081 4.759 1.49700
81.62 -58.181 0.079 3 23.313 5.513 1.4874
9 70.14 -34.981 1.3g8
1.80610 40.95 40.636
11.5026 oo 8.527
1.51633 64.17 001.190 8 35.321 1.388 1.6'98
95 30', 1ri -8,9370,5951
,6689245,0107,40111,554 11 of 14.675 1.51633 64
．． 112 cX31.785 13 ooO,9921,5163364,11
4, CI: + f I 2 :] ”0.40f γd1 + d2-
Sid d3 = 110.8 θ + + 02 = 1.727 0.0037 (Sid, + Ya d2) + 1.22 = 1.78
1

[Example 3] f = 100 FNO1: 6.2 Angle of view 1.4° rt d + n,'
Vjl 40.632 3.569 1.
51112 60.52 -67.577. 0
．． 7933 22.486 5.156 1.
51112 60.54 -61.470 1.
785 1.75520 27.55 44.
179 13.0876 ω 8.527
1.51633 64.17 ω 1
．． 190 8 102.524 1.269 1.7173
6 29.59 -13.206 0.793
1.60311 60.710 . 7.460
o, 7o311 ω L4.674
i, 5t63364.112 oo
1.78513 ω 0.991 1.
51633 64.114 (,) f t, 2. :+ =0.40f Yadl+Yad2
-Ya d3=93.501+02=1.661 0.0037 (9d s+Ya d2)+1.22=1.
668

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a lens according to Example 1 of the present invention, FIG. 2 is an aberration diagram of Example 1 of the present invention, FIG. 3 is a cross-sectional view of a lens according to Example 2 of the present invention, and FIG. 4 is a cross-sectional view of a lens according to Example 2 of the present invention. FIG. 5 is a cross-sectional view of a lens according to Example 3 of the present invention, and FIG. 6 is an aberration diagram of Example 3 of the present invention. Patent applicant: Asahi Optical Industry Co., Ltd.,,r,:lf
l,,Representative: Toru Matsumoto

Claims (1)

[Claims] A front group having a positive refractive power, a rear group having a negative refractive power, a dichroic prism for separating infrared light and visible light disposed between the front group and the rear group, and a rear group. The optical system consists of an erect prism placed at the rear of the group, and the front group consists of a single positive lens and a positive lens.
It has a configuration of 281.3 lenses consisting of adhesive lenses of negative lenses, and the rear group has a configuration of 2 lenses per group consisting of adhesive lenses of negative and positive lenses, and is characterized by satisfying the following conditions. Lightwave rangefinder objective lens. (1) f I , 2 , :] <0.45f(2)
Ya d1 + Ya d2 - νd3>75 (3) Os +02 <0.0037 (tsud□10d2)+1.22(4) I r7 +>I
rl l , rt >0, r2<0 However, f is the focal length of the entire system, f 1 p2 p3 is the composite focal length of the front group, and vdt (i=1.2.3) is the i-th glass (lens ), the Atsube number of the d-line, θj (j=1
．． 2) is the partial dispersion ratio in the infrared region of the lens, using the refractive index nc of the C line, the refractive index nF of the F line, and the refractive index nlo + 4 of the light beam with a wavelength of 11014n, ri (i-1, 2)
represents the radius of curvature of the i-th surface.