JPH0387710A - Ocular lens - Google Patents

Abstract

PURPOSE:To obtain the inexpensive ocular lens which has a wide field angle and good performance by making a 1st and a 2nd lens of optical glass or resin- made optical materials and a 3rd and a 4th lens of resin-made optical materials, and forming a specific aspherical surface as one of the surfaces of them. CONSTITUTION:The ocular lens consists of a 1st positive lens, a 2nd negative meniscus lens, a 3rd positive lens, and a 4th negative lens, the 1st lens and 2nd lens are made of the optical glass or resin-made optical materials, and the 3rd lens and 4th lens are made of the resin-made optical materials, and the 3rd lens and 4th lens are made of the resin-made optical materials; and at least one of their surfaces is made aspherical as shown by an equation I. In the equation, X is partial movement from a lens vertex in the direction of the optical axis, (y) is partial movement from the lens vertex perpendicular to the direction of the optical axis, C is the reciprocal of the radius of curvature, K is a cone constant, and A4, A6... are aspherical surface coefficients. Consequently, aberrations are compensated excellently even with a wide visual field of 50 - 60 deg. and the lens is manufactured at low cost. Cosequently, the lightweight ocular lens which has the wide visual field and sufficiently compensated aberrations is obtained at low cost.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to an eyepiece lens, and more specifically to a four-element eyepiece that has a wide angle of view, good performance, and is inexpensive, used in binoculars, astronomical telescopes, etc. It's about lenses.

``Prior art'' In order to perform sufficiently good aberration correction to the peripheral part of the field of view in eyepiece lenses with a wide angle of view, conventional eyepieces have been developed using methods such as Japanese Patent Publication No. 63-6851, No. 60-4 ISO 14, etc. Most of them have a configuration of 4 to 6 lenses.

``Problem to be solved by the invention'' However, if there are more than 4 cards, there are problems with high cost and large size, and 4-card F! In order to obtain sufficiently good aberration correction with a certain eyepiece lens, each lens must be made of optical glass with a high refractive index, and each surface must have a small radius of curvature (which makes it difficult to process). As a result, there was a problem of high costs.

The present invention has been made in view of the above-mentioned points, and the object thereof is to provide an eyepiece lens that can sufficiently correct aberrations even in a wide field of view of 50 degrees to 60 inches, and can be manufactured at low cost. shall be.

"Means for Solving the Problems" The eyepiece of the present invention includes, in order from the eye side, a first lens that is a positive lens, a second lens that is a negative meniscus lens, a third lens that is a positive lens, and a third lens that is a negative lens. The t-th lens and the second lens are made of optical glass or a resin optical material, and the third lens and the fourth lens are made of a resin optical material, of which at least the i-plane is y is the deviation from the apex of the lens in the direction perpendicular to the optical axis, C is the reciprocal of the radius of curvature,
represents a conic constant, and A4A1... represents an aspheric coefficient.

Further, it is preferable that such an eyepiece lens satisfies the following conditions.

(1) τ×1°60 Here, τ indicates the average value of the refractive index of each lens.

Furthermore, the eyepiece lens preferably satisfies the following conditions.

(2) −4,0< f, /f < −0,5 where,
f4 is the focal length of the fourth lens, and f is the focal length of the entire system.

``Function'' Adopting a resin optical material for the eyepiece lens is 4!
It is advantageous because of the ease of processing and mass production of optical materials made of F resin, and it is also easy to process lenses with aspherical shapes that are effective in correcting field curvature and astigmatism. It is possible to obtain a more stable image surface than that of an optical lens of 300 mm.

In addition, by providing an aspherical surface on at least one surface,
Aberrations can be easily corrected without increasing the number of lenses.6 Conditional expression (1) also indicates the average value of the refractive index of each lens, and by using an optical material with a low refractive index, a low-cost eyepiece can be achieved. is realized.

Next, if the upper limit of conditional expression (2) is exceeded, the power of the fourth lens becomes excessive, making it difficult for the peripheral light flux to pass through.
It becomes difficult to widen the angle of view.

If the lower limit is exceeded, the Petzval sum becomes large.

“Example J Hereinafter, data of examples of this invention will be presented.

f is the focal length of the entire system, FNO is the F number, 2ω is the viewing angle, r is the radius of curvature of each lens surface, d is the lens thickness or lens spacing, n is the d -1ine refractive index of each lens, ν
indicates the Atsube number of each lens.

fNo=1:4. O d n O,464+,, 513913 0.012 0.084 0.017 0.411 0.027 0.118 1.531 -0.816 -0.795 -1.539 1.085 -1.444 - 1.22O 8,585 5th aspherical surface = -0,487 A, = -3,62572X 10-" (1) τ = 1.563 (2) f, /f = -1,816 1,585 1,492 1,585 2ω=566 61.2 29.9 (Resin) 57.4 (Resin) 29.9 (Resin) [Example 2] f=l, Q Surface width 1.239 -0.759 - 1.328 0.969 -1.286 -1.079 4.744 3rd aspherical surface = -0,946 A, = 2.30838X10-" (↓) n, = 1.560 (2) f4/ f=-1,490 f NO= 1: 4. O 0,528 0,084 0,017 0,460 0,034 0,121 2ω=56゜n v 151633 64.1 1.64769 33.8 1.492 57.4 (Resin) 1.585 29.9 (Tree t4) [Example 3] f = L, Of no = L: 4.0 face blood
r d 1 1.316 0.494 2 -0.770 0.015 3 -0.744 0.084 4 -1.2Q5 Q, Q175 L, 0
65 0.443 6 (,1080,026 7-0,9770,1181,585 8-37,946 To the 1st aspherical surface = 0.215 A4 = 3.72173 X IQ-"Knee to the 5th aspherical surface 0.765 A4=-8,73876 DI) 29.9 (Resin) 57.4 (Resin) 29.9 (Resin) [Example 4] f=t.

Surface Nα engineering 1.671 -0.675 -1.049 0.888 -1.945 1.889 4th aspherical surface=-1,015 A4=9.16712X10-" (1) -n=1. 560 (2) f, /f=-1,059 1,492 1,585 57,4 (resin) 29.9 (resin) fNo=1:4.0 2ω=56°d
n O,6421,5163364,1 0,0841,6476933,8 0,017 0,574 0,1B8 [Example 5] f=1.0 Surface magnetism 1.239 -0.759 -1.328 0.969 -1,286 -1.079 41.319 4th aspherical surface=-0,946 A, =2.30838X10-" (1) n=1°554 (2) f4/f=-1,795 fNo : 1 : 4.0 O,500 0,084 0,017 0,460 0,034 1,021 2ω=56m n 9 1.492 57.4 (Resin) 1.64769 33.8 1.492 57.4 (Resin) 1.585 29.9 (Resin) "Effects of the Invention" As explained above, according to the present invention, in the four-element eyepiece lens, resin-made optical lenses with good processability and advantageous for heavy production are used. Since two or more materials are used, it is possible to obtain an eyepiece lens that is low cost and lightweight, and furthermore, by providing an aspherical surface, it is easy to obtain a wide field of view with sufficient aberration compensation.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a lens according to Example 1 of the present invention. FIG. 2 is a diagram of various aberrations thereof. FIG. 3 is a sectional view of a lens according to Example 2 of the present invention, and FIG. 4 is a diagram of various aberrations thereof. FIG. 5 is a sectional view of a lens according to a third embodiment of the present invention. FIG. 6 is a diagram of various aberrations thereof. FIG. 7 is a sectional view of a lens according to Example 4 of the present invention, and FIG. 8 is a diagram of various aberrations thereof. FIG. 9 is a sectional view of a lens according to Example 5 of the present invention, and FIG.
The figure is a diagram of various aberrations. Figure 2! 11 Recovered regular arc condition Chromatic aberration Magnification Color return Astigmatism Distortion aberration

Claims (1)

[Claims] 1. In order from the eye side, a first lens that is a positive lens, a second lens that is a negative meniscus lens, and a third lens that is a positive lens,
a fourth lens which is a negative lens, the first lens and the second lens are made of optical glass or a resin optical material, the third lens and the fourth lens are made of a resin optical material, and at least An eyepiece consisting of four lenses, one surface of which is an aspherical surface represented by ▲Mathematical formulas, chemical formulas, tables, etc.▼. where, Indicates the aspheric coefficient. 2. The eyepiece lens according to claim 1, which satisfies the following conditions. (1) @n@<1.60 Here, @n@ represents the average value of the refractive index of each lens. 3. The eyepiece lens according to claim 1 or 2, characterized in that it satisfies the following conditions. (2) -4.0<f_4/f<-0.5 Here, f_4 is the focal length of the fourth lens, and f is the focal length of the entire system.