JPH02123319A - Eyepiece having high magnification and wide visual field - Google Patents

Abstract

PURPOSE:To obtain an eye relief of about 1.5 times of a focal distance, and also, to improve flatness of the image surface by constituting the title eyepiece of a first lens group having a cemented negative lens component, and a second lens group having positive refracting power as a whole in order from an incident side of light. CONSTITUTION:The title eyepiece is constituted of a first lens group having a cemented negative lens component, and a second lens group which contains a cemented positive lens component whose concave face is turned to an incident side and a positive lens component whose stronger face is turned to the incident side and has positive refracting power as a whole in order from the incident side of light, and an object image is formed between a first lens group and a second lens group. Also, with regard to a focal distance, said eyepiece is allowed to satisfy the conditions of the inequalities I, II. In the inequalities I, II, (f), f1 and f2 denote a focal distance of the whole system, a composite focal distance of a first lens group, and a composite focal distance of a second lens group, respectively. In such a way, a lens system in which an eye relief is high eye point of about 1.5 times of the focal distance, and also, which has an excellent image forming performance by which the image surface is flat to the periphery of a visual field is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an internal focusing type high magnification wide field eyepiece.

[Prior Art] Most common eyepiece lenses are composed of a single lens having positive refractive power or a combination of cemented lenses, and therefore have a large negative curvature of field. This is because in a convex lens system, the Petzval sum has a large positive value, and the flatness of the image plane depends on the Petzval sum.

In particular, as the focal length of the entire system becomes smaller, the Petzval sum increases, making it difficult to correct field curvature. Furthermore, even if the Petzval sum is large, it is possible to make the average image plane of the mezzional image plane and the sagittal image plane zero, but at that time a large astigmatism difference remains.

Furthermore, if the focal length of the entire system is small, the eyepoint position must be low. This is because general eyepiece lenses are telecentric optical systems, and the focal length of the entire system determines the rear focal position of the entire system.

Normally, a 20x eyepiece (f = 12.5 mm) has an eye relief of about 10 mm, which is not a sufficient eye point position (and is inconvenient in practice).

[Problems to be Solved by the Invention] The present invention has been made in order to eliminate the drawbacks of the conventional high magnification and wide field of view eyepiece lenses as described above. It is an object of the present invention to provide an eyepiece lens that is durable and has an excellent image surface flatness.

[Means for Solving the Problems] The high-magnification eyepiece of the present invention includes a first lens group I having a negative lens component bonded together from the light incident side, and a bonded lens group I having a negative lens component with a convex surface facing the incident side. It is composed of a positive lens component and a second lens group II that has a positive refractive power as a whole, including a positive lens component with a stronger surface facing the light incident side, and the first lens group ■ and the second lens group II This is an internal focusing type eyepiece lens in which an object image is formed between the two lenses. When the focal length of the entire eyepiece lens system is f, the composite focal length of the first lens group ■ is fl, and the composite focal length of the second lens group II is f2, the following conditions (1) and (2) are satisfied. There is something to do.

(1) -7f<f,<-f (210, 7f<f2<3f Condition (11) relates to the eye relief and the flatness of the image plane.

The first lens group I can enlarge and form an image formed by the objective lens near the second lens group 11 due to its diverging action, and at the same time can bring the entrance pupil to the second lens group II closer, thereby making the exit pupil position ( The function is to increase the distance to the eye point (eye point position). Furthermore, by arranging a concave lens as in the first lens group (2), the Petzval of the entire system can be made small, and the flatness of the image plane can be realized.

If the lower limit of condition (1) is exceeded and the negative refractive power of the first lens group (■) becomes weak (then the divergence power in the first lens group (■) becomes insufficient and the image formed by the objective lens becomes distant, and the second lens group T
The entrance pupil for I also moves away.

When the entrance pupil moves away in this way, the distance to the exit pupil position (eyepoint position) becomes shorter due to the converging action of the second lens group II. Also, the Petzval sum of the entire system is thick (
The flatness of the image plane cannot be maintained.

If the upper limit of condition (1) is exceeded, the negative refractive power of the first lens nI becomes too strong, and its divergent effect increases, causing the second lens nI to have too much negative refractive power.
The height of the light rays incident on the lens detail II becomes high, and off-axis aberrations, particularly coma aberration and distortion aberration, become insufficiently corrected. It also causes deterioration of pupil aberration, causing vignetting in the pupil.

Condition (2) relates to the length of the eyepoint and correction of off-axis aberrations.

When the focal length of the second lens group II changes, the rear focal position changes. After the chief ray diverged by the first lens group (2) and forming an image by the objective lens passes through the second lens group II, an optical system is formed with the rear focal position of the second lens group II as the exit pupil.

Therefore, in order to increase the eye relief, the composite focal length of the second lens group TI must be increased.

Therefore, if this composite focal length f2 exceeds the lower limit of condition (2), the eye point position will be insufficient and it will no longer be usable. On the other hand, if the upper limit of condition (2) is exceeded, it becomes extremely difficult for the second lens group II to sufficiently correct the off-axis aberrations generated by the first lens group I.

In addition to the above conditions, it is desirable to satisfy the following condition (3) in order to maintain the flatness of the image plane, secure the length to the eye point, and correct off-axis aberrations.

(310,5f　<d3<5f engineering However, d3 is between the 1121st lens group and the 2nd lens group △ It is a gap.

If the lower limit of condition (3) is exceeded, the combined focal lengths f, , f2 of the first lens group (2) and the second lens group II become smaller, the Petzval sum increases, and the flatness of the image plane deteriorates.

Furthermore, since the combined focal length of the second lens group II becomes small, the rear focal position of the second lens group II becomes short (ie, the eye point position becomes insufficient).

On the other hand, if the upper limit of condition (3) is exceeded, the height of the ray of light incident on the second lens group II becomes high, resulting in insufficient correction of off-axis aberration.

Furthermore, the bonded positive lens component L2 in the second lens group m is a negative meniscus lens L21 and a biconvex positive lens L2.
2□, and it is preferable that the Atsube number of each lens satisfies the following condition (4).

(4) 15<C4-C3 However, C3. C4 is the negative meniscus lens L21 mentioned above.
and the Abbe number of the biconvex positive lens L2□.

This condition indicates the difference in the number of gaps between the biconvex lens L2□ of the above-mentioned bonded lens component L2 and the negative meniscus lens L21, and is intended to satisfactorily correct chromatic aberration of magnification.

In an RQ internal focus type eyepiece lens, chromatic aberration of magnification must be corrected not only in the entire second lens group ++ but also in the entire second lens group ++. If the lower limit of condition (4) is exceeded, the chromatic aberration of magnification will be undercorrected both in the second lens group II and in the entire system, making it difficult to perform good correction.

[Example〕 Next, examples of the high magnification wide field eyepiece of the present invention will be shown.

Example 1 f = L ω = 55.6' eye relief
1.5098, Petzval sum 0.32r+ =:
-1,7849 dl = 0.2000 mouths, = 1.60311
ν+ =60.7Qrz=2.0226 da" 0.3344 n2= 1.80518
v2 = 25.43r, = -65,5693 d3 = 2.2015 r4 = 3.3521 d, = 0.1952 n, = 1.84666
v3=23.78r-=1.2829 d,=0.7537 n4=1.48749=70.20 ra" -1,9309 d,=0.0240 r,=1.5983 dy=0.4201 ra" -27,2050 f, =-4,54 C4-C, =46.42 Example 2 ns=1 f2=1.4 d3=2 = 52.33 f=1 ω=55.66 Eye relief 1. 4921 r, = -1,5966 d = 0.1215 rz = 0.9425 d2 = 0.2640 r3 = 100.7190 d3 = 1.3600 r4 = 5.8073 d4 = 0.1952 rs = 1.3233 d, = 0.8728 re=-15204 d, = 0.0240 r7= 1.7177 d, = 0.3703 ra=-9,7992 f, =-4,059 shi4-shis"40.11 Example 3 = 1.271 Q, = 1.62280 n, = 1.76180 ns” 1.84566 ns = 1.75500 n4 = 1 Petzval sum 0.321: 57.06 = 27.11 = 23.78 = 64.55 =52.33 d, = 1.36 f=1 ω =55.6° eye relief
1.5037, Petzval sum 0.243 r, = -0,9H4 d, = 0.0960 mouth, = 1.51728
ν, =69.56r, = 0.7868 dz= 0.288On-= 1.76180
vz = 27.11rx = 8.4939 (L = 1.200 mouths r4 = 6.6509 d4 = o, 1600 n, = 1.74000
ν3 = 31.70rs = 1.1666 ds = 0.8815 n, = 1.54771
ν, = 62.83r6=-i, 6423 ds= 0.0240 ry"1.7751 d, = 0.4232 n, = 1.69680
v5 =56.49rs=-5,6020 f, =-3,357, f, =1.266,
da=1.2ν4−ν,=31.13 where rl+r2. -...r8 is the radius of curvature of each lens surface.

d+, d2. ...d7 is the wall thickness and air gap of each lens.

n++ n2*...n5 is the refractive index of each lens,
C2. ... ν5 is the number of gaps of each lens.

The aberration situations of these examples are as shown in FIGS. 4 to 6, respectively, which show the results of ray tracing from the eye side.

[Effects of the Invention] As shown in Example A, the high-magnification wide-field eyepiece of the present invention has a high eye point with four lenses/leafs approximately 1.5 times the focal length, and the image plane extends to the periphery of the visual field. It is a flat lens system with excellent image resolution performance.

[Brief explanation of drawings]

1 to 3 are embodiments 1 to 3 of the present invention, respectively.
, and FIGS. 4 to 6 are aberration curve diagrams of Examples 1 to 3. Applicant Olympus Optical Industry Co., Ltd. Agent Hiroji Mukai

Claims (1)

[Claims] A first lens group having a bonded negative lens component in order from the light incident side, a bonded positive lens component having a convex surface facing the object side, and a bonded positive lens component having a stronger surface facing the light incident side. An internal focusing type high magnification wide field eyepiece that is composed of a second lens group that includes a positive lens component and has a positive refractive power as a whole, and that satisfies the following conditions (1) and (2). (1) -7f<f_1<-f (2) 0.7f<f_2<3f where f is the focal length of the entire system, f_1 is the combined focal length of the first lens group, and f_2 is the combined focal length of the second lens group. It is.