JPS63135914A - Eyepiece - Google Patents

Abstract

PURPOSE:To realize an eyepiece with a high magnification and a large aperture, by constituting a lens with a first lens whose concave side faces with an eye side and having a negative refractive power, a second lens whose concave side faces with a plane side to be observed and having the negative refractive power, and third and fourth lenses of biconvex lenses, and specifying relation between each focal distance and a radius of curvature. CONSTITUTION:The titled lens is constituted of, starting from the eye side in order, the first lens whose concave side faces with the eye side and having the negative refractive power, the second lens whose concave side faces with the plane side to be observed and having the negative refractive power, the third lens of the biconvex lens, and the fourth lens of the biconvex lens, and satisfies conditions (1)-(5). In inequalities (f) is assumed as the focal distance of the whole system of the eyepieces, fn as the synthesized focal distance of the first lens and the second lens, fp as that of the third and the fourth lenses, r1 and r2 as the radius of curvature of a plane on the eye side and the plane on a side to be observed, f1 as the focal distance of the first lens, and n1 as the inflective index of the first lens. In such a way, it is possible to obtain the eyepiece with the high magnification and the large aperture.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an eyepiece lens for an eye reflex finder.

[Conventional technology]

Electronic still cameras have an extremely small image size of about 0.19 to 0.25 times that of conventional 35mm silver halide cameras, so they can be magnified by about 4 times, the same as a single-lens reflex finder for conventional silver halide cameras. At high magnifications, only extremely small images can be observed.

In order to increase the visibility of the image, it is necessary to shorten the focal length of the eyepiece, which increases the loupe magnification of the eyepiece. However, if the focal length of the eyepiece is shortened, it becomes difficult to arrange an optical member such as a prism between the small distance ν3 between the surface to be observed and the lens (hereinafter referred to as back focus).

In order to make the viewfinder easy to see, it is necessary that the distance from the eyepiece to the pupil position (hereinafter referred to as the eyepoint distance) be long and the distance from the eye to the eye point short.

However, in order to shorten the focal length of the eyepiece and lengthen the eyepoint distance to reduce vignetting, the eyepiece must have a large aperture, which makes it difficult to correct each aberration, and the configuration becomes complicated. Become.

As an eyepiece with high magnification and a long back focus, Japanese Utility Model Application Publication No. 140919/1983 and Japanese Patent Application Laid-open No. 61-4
The one described in Japanese Patent No. 8809 is known.

However, if the focal length of the entire eyepiece lens system is f, the former conventional example has a back focus of o, sf, and the latter conventional example has a back focus of about 160 f, and the diopter adjustment is performed by moving the entire lens. Considering the purpose of use, a longer back focus is desired. Furthermore, it cannot be said that the pupil diameters of Z and sf are sufficient for both the former and the latter.

[Problem that the invention seeks to solve]

The present invention provides a high-power, large-diameter eyepiece that has a loupe magnification of about 11 times, a back focus of about 1.1 f, an eyepoint distance of about 0.8 f, and a pupil diameter of about 9 f.

[Means for solving problems]

In order to solve the above problems, the high magnification, large diameter eyepiece of the present invention has a lens system configured with a retrofocus power arrangement. That is, the lens system of the present invention includes, in order from the eye side, a first lens with negative refractive power with a concave surface facing the eye side, and a second lens with negative refractive power with a concave surface facing the observed surface side. , consisting of a third lens that is a biconvex lens and a fourth lens that is a biconvex lens, and the following conditions (1) to (5) are met.
I tried to satisfy.

(1) 0.35 < 1fxl < 2(2)
0.3 < straddle <1 (3) 0.5<""<10 r2-r+ (4) o, s<1fHl<4 (5) n+<1.75 where f is the focal length of the entire eyepiece lens system, f is the combined focal length of the first lens and the second lens, fp is the combined focal length of the third lens and the fourth lens, rl+r2 is the radius of curvature of the eye-side and observed surface-side surfaces of the first lens, fl is the focal length of the first lens, and nl is the refractive index of the first lens.

Here, as shown in FIG. 11, the eyepiece lens L converts the light emitted from the observed surface 0 into parallel light beams @E. Generally, in the case of eyepiece lenses, due to the simplicity of lens design, a so-called reverse tracking method is used, in which parallel rays are incident from the eye side and an image is formed on the observed surface.
The structure of the eyepiece lens of the present invention, as well as the following description and embodiments, will be explained using this reverse tracking method. Therefore, pupil diameter D1 eye point distance EP, pack focus f
B etc. are also defined as shown in FIG. In FIG. 11, P represents an optical member such as a prism.

Next, the meanings of the above conditions (1) to (5) will be explained in detail.

In order to ensure a back focus greater than the focal length of the entire lens system, it is necessary to set the principal point of the entire lens system closer to the observed surface than the fourth lens. For this purpose, we have set conditions (1)
), (2).

Conditions (1) and 2 Conditions (2) define the composite focal length of the first lens and the second lens, and the composite focal length of the third lens and the fourth lens, respectively. If the upper limit of condition (1) or the upper limit of condition (2) is exceeded, the power distribution of retrofocus will be disrupted and it will not be possible to obtain a long back focus. Also, if the lower limit of condition (1) or the lower limit of condition (2) is exceeded, the back focus can be lengthened;
Spherical aberration is large and correction is insufficient, and negative distortion becomes excessive.

The conditions for properly correcting the aberration disturbance caused by increasing the lens diameter will be described. In the eyepiece lens of the present invention, the first lens has a strong concave surface on the eye side, so that the refraction of light rays can be minimized and the occurrence of aberrations to be corrected can be reduced.

With this configuration, further conditions (3) and (4
), (5) is necessary for aberration correction.

Condition (3) is mainly for keeping the spherical aberration good; if the upper limit of this condition is exceeded, the spherical aberration will be over-corrected, and if the lower limit of ν3 is exceeded, the spherical aberration will be under-corrected, both of which are undesirable.

Conditions (4) and (5) are conditions for good correction of field curvature, and are the upper limit of ν3 condition (4) or condition (5).
), the Petzval sum increases and correction of field curvature becomes difficult. Moreover, if the lower limit of condition (4) is exceeded, coma flare and negative distortion will increase.

Furthermore, in order to satisfactorily correct chromatic aberration, it is desirable that the second lens and the third lens are bonded together to form a cemented lens and that the following condition (6) is satisfied.

(6) C3−ν2>15 However, C2. C3 is the Abbe number of the second lens and the third lens, respectively.

By laminating the second lens and the third lens into a cemented lens, not only chromatic aberration of magnification but also astigmatism can be reduced. However, if the range of condition (6) is exceeded, it becomes difficult to correct longitudinal chromatic aberration and lateral chromatic aberration.

It is desirable that the first lens of the eyepiece of the present invention has a meniscus shape that is suitable for correcting aberrations. However, when considering processability, if the surface has a small oil ratio radius and is made into a meniscus shape, this is particularly disadvantageous for processing glass lenses, and increases the cost. This drawback can be overcome by using a plastic lens as the first lens.

Of course, the eyepiece of the present invention can adjust the diopter by moving the entire lens system in the optical axis direction, but it is also possible to adjust the diopter by moving the second lens, third lens, and fourth lens as one unit. You can also adjust the diopter. In this way, adjusting the diopter by integrating the second to fourth lenses has the advantage that the amount of movement of the lenses is small and that the lens closest to the eye can be fixed.

〔Example〕

Next, each embodiment of the eyepiece lens of the present invention described in detail above will be shown.

Example 1 do=18, ooo.

r+ = 11.0000 d+ = 2.3225 ns = 1.49216
ν3=57.50r2=-17.8967 dz=0.2000 r3=~71.0637 d3”1.0000 12 =1.80518 νt
=25.43r+=26.0807 d+=4.6775 n+=1.72000 1
'3 = 50.25ra = 20.2757 d, = 0.2000 re = 41.2150 da ""2.5000 ns = 1.7
2000 shi4=50.25r7=62.2
444 d7=1.6000 r8=■ am=34.0OOOns=1.51633
νs = 64.15r9”ω (Change in interval during diopter adjustment) -30+1 (Diopter) do 19.052 17.483 16.9
69d70.548 2.117 2.631
f = 22.7, loupe magnification 11x Example 2 do"18.0000 rl = -10,0513 da = 2.3088 nt = 1.49216
ν3=57.50rt=-14.4317 d2=1.5000 rs=-98,0969 da=0.7749 nt=1.76182
ν3=26.55r4 =29.6207 da =4.6187 ns =1.64100
5 = 56.93r! =-19,9998 d5=0.2000 ra=39.9654 do=2.7000 14=1.64100
&+ =56.93rt =-55,7319 dfu = 1.5000 r8=ω da”34.0000 n5=1.51633
+5=64.15rg=ω (diopter adjustment) -30+1 d2 2.595 0.938 0.36
3dy O, 4052, 0622, 637f=
22.9, loupe magnification 11x Example 3 do = 18.0000 r,: 20.3751 dl = 1.116 On + = 1.53172 ν + =
48.90rt=80.0000 a,=0.7000 rs=336.6224 d3=1.0000 n2=1.80518 1'2
=25.43r, =19.8731 d4=4.8840 ns =1.65844 93
=50.86rtz =-19,1585 ds”0.2000 ra=23.2351 da =3.2000 n+ =1.72000
J'4 = 50.25rt = -84,8949 dfu = 1.6000 r8 = ω da = 34.0O00ns = 1.51633 1
'i = 64.15ro = ω (diopter adjustment) -30+1 do 19.052 17.438 16.969d
y O, 5482, 1172, 631f=22.7
, Loupe magnification 11x Example 4 do=t8.0000 rl:: 10.8546 da =2.2954 1+ =1.64769 ν
1=33.80r2=14.7877 d2=0.2000 rs=106.2946 d3=o, 8849 nz=1.74077 1
/2=27.79r+=26=1006 d4=0.3000 rs=27.9730 ds ”'4.5589 13=1.64100
! '3 =56.93r6: 20.1753 do=0.2000 rfu = 37.3708 d7=2.6608 1+ =1.64100
C4 = 56.93rs = 63.1228 dg = 1.6000 ro = ω do = 34.0000 ns = 1.51633
5=64.15r'+o=ω (diopter adjustment) -30+1 do 19.052 17.483 16.969d
g O, 5482, 1172°631f=22.
7. Loupe magnification 11x fB = 1.1f, EP = 0.8f, D =...
f where rl+2"2+... is the radius of curvature of each lens surface, d.

, dt*d2+... are the thickness and air distance of each lens (do is the distance from the eye point to the first surface), n1y
n2+... is the refractive index of each lens, and si1. C2. ...
is the Atsube number of each lens.

Among the above examples, Example 1 has a lens configuration shown in FIG.
The first lens is a plastic lens, and the second lens and third lens
These lenses are bonded together to form a cemented lens. Diopter adjustment in this embodiment is performed by moving the entire lens system. Also, the aberration situation at the time of O diopter in this example is 5th.
This is the passage shown in the figure.

Example 2 has a lens configuration shown in FIG. 2, in which the first lens is a plastic lens, and the second lens and third lens are cemented. Also, diopter adjustment is done using the second lens, third lens,
This is done by moving the fourth lens as one unit. O diopter for this example.

The aberration situations at -3 day opter and +1 day opter are as shown in FIGS. 6, 7, and 8, respectively.

Embodiment 3 has a lens configuration shown in FIG. 3, in which the second lens and the third lens are cemented together, and diopter adjustment is performed by moving the entire lens system. The aberration situation at 0 dayopter in this embodiment is as shown in FIG.

Embodiment 4 has a lens configuration shown in FIG. 4, and diopter adjustment is performed by moving the entire lens system. The aberration situation at O diopter in this embodiment is as shown in FIG.

The aberration curve diagrams shown in FIGS. 5 to 10 are those when the optical member P is arranged.

〔Effect of the invention〕

The eyepiece of the present invention has a simple lens configuration of 4 elements, but has a high magnification of about 11x magnification, an eyepoint distance of about 0.8f, and a diameter of about 1.9 degrees. It is a large-diameter eyepiece lens system with all aberrations well corrected.

[Brief explanation of the drawing]

1 to 4 are cross-sectional views of Examples 1 to 4 of the present invention, FIG. 5 is an aberration curve diagram of Example 1, and FIGS. 6, 7, and 8 are cross-sectional views of Example 2. Aberration curve diagrams, Figures 9 and 10
The figures are aberration curve diagrams of Example 3 and Example 4, and the 11th
The figure shows the position of the eye point in the eyepiece.

Claims (1)

[Scope of Claims] (1) A first lens having a negative refractive power with a concave surface facing the eye side in order from the eye side, and a second lens having a negative refractive power with a concave surface facing the observed side, An eyepiece that includes a third lens that is a biconvex lens and a fourth lens that is a biconvex lens and that satisfies the following conditions (1) to (5). (1) 0.35<|f_n_/_f|<2 (2) 0.3<f_p_/_f<1 (3) 0.5<(r_2+r_1)/(r_2-r_1
)<10(4)0.5<|f_1/f|<4 (5)n_1<1.75 where f is the focal length of the entire eyepiece lens system, f_n is the combined focal length of the first lens and the second lens, f_p is the combined focal length of the third lens and the fourth lens, r_1 and r_2 are the radii of curvature of the eye-side surface and observed-side surface of the first lens, respectively, f
_1 is the focal length of the first lens, and n_1 is the refractive index of the first lens. (2) The eyepiece according to claim (1), in which the second lens and the third lens are cemented together and the following condition (6) is satisfied. (6) ν_3−ν_2>15 where ν_2 and ν_3 are the Abbe numbers of the second lens and the third lens, respectively. (3) The eyepiece according to claim (1) or (2), wherein the first lens is a plastic lens. (4) The eyepiece according to claim (1), (2) or (3), wherein diopter adjustment is performed by moving the second lens, third lens, and fourth lens together.