JP3421476B2 - Zoom magnifier - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom magnifying glass for magnifying and observing an object at a close range.

[0002]

2. Description of the Related Art A magnifying glass places an observation object in the vicinity of the object-side focal point of a positive lens system, and brings the eye closer to the positive lens system from the opposite side to observe a magnified virtual image of the observation object. To do. The lens system of the conventional magnifying glass is
It was a so-called fixed focal length, and the magnification could not be changed. Therefore, in order to observe the same observation object with different magnifying powers, it is necessary to prepare a plurality of magnifying mirrors having different magnifying powers and switch to a magnifying glass having a desired magnifying power.

In order to eliminate such inconvenience, a magnifying glass provided with a variable power lens system is proposed in, for example, Japanese Patent Laid-Open No. 5-134193, but this conventional example has the following problems. It was

This conventional lens has positive, negative, and
Among the five lens groups of positive, positive, and positive, only the second lens group on the eye side is moved to change the magnification. With such movement of only the second group, the diopter change was large (maximum 1.4 D). aberration,
Especially, the distortion was large. For example, distortion occurs at a high magnification of about 6% and at a low magnification of about 10%. Further, this conventional lens has a noticeable color blur in the periphery.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a zoom magnifying glass capable of continuously observing by changing the magnifying power without keeping an eye on the observing portion of an observing object. With the goal. A further object of the present invention is to provide a zoom magnifying glass which has a small diopter change, distortion and color fringing and has a large zoom ratio.

[0006]

SUMMARY OF THE INVENTION The invention according to claim 1 for achieving the above object is a lens system comprising a positive first lens group, a negative second lens group, and a positive third lens group in order from the object side. A movable lens for moving the first group and the second group relative to each other along the optical axis so as to keep the diopter constant and to change the magnification.
The first group includes a positive lens, a positive lens and a negative lens from the object side.
A positive lens as a whole consisting of lenses, and
It consists of a positive lens in order, and
The peculiarity ratio is ν _p / ν _n ≧ 1.8 , where ν _p : Abbe number of the positive lens of the cemented lens ν _n : The Abbe number of the negative lens of the cemented lens is satisfied . Satisfies this condition
By doing so, zoom that reduces color fringing in the surrounding area
You get a magnifying glass.

[0007]

[0008] According to a second aspect of the invention, the third group, to have at least one movable lens along the optical axis, the
It is characterized by having a diopter adjustment function for moving the lens .

According to the third aspect of the present invention, at least one surface of the first group is an aspherical surface having a lens thickness that is thicker in the periphery than a paraxial spherical surface, so that distortion is reduced.

[0010]

[0011]

The zoom magnifying glass of the present invention will be described below with reference to the illustrated embodiments. Here, r is the radius of curvature of each surface of the lens, d is the lens thickness or lens spacing, n is the refractive index for the d-line, and ν is the Abbe number.

[Embodiment 1] FIGS. 1 and 3 are views showing the lens structure of Embodiment 1 of the present invention at a high magnification and a low magnification, and FIG. 2 is a high magnification shown in FIG. D at time
FIG. 4 is a diagram showing various aberrations of the line, g-line and C-line, and FIG. 4 is a diagram showing various aberrations at the low magnification shown in FIG.

The first embodiment includes a positive first lens unit L11, a negative second lens unit L12, and a positive third lens unit L13 from the object side. The first positive lens unit L11 includes, from the object side, a positive lens, a positive cemented lens including a positive lens and a negative lens as a whole, and a positive lens. The first lens unit L11 and the second lens unit L12 constitute a movable lens that relatively moves closer to and away from the optical axis to keep the diopter constant and to perform zooming. Here, the third lens group L13 is a fixed group so that the observer does not have to move the eye position even when zooming,
It also has a diopter adjustment function to adjust individual differences in diopter.

The specific lens construction of Example 1 is shown in Table 1 below.

[Table 1] Focal length (mm) f = 16.32 to 43.34 Expansion rate (times) 16 to 6 Diopter (Dpt.) -1.05 -0.98 NO. R d n ν 1 83.585 8.30 1.69680 55.5 2 -42.112 8.74 3 56.463 1.50 1.80518 25.4 4 18.362 12.00 1.65160 58.5 5 -57.676 0.10 6 25.331 5.50 1.67000 57.4 7 87.425 17.74 ~ 2.16 8 -43.754 0.70 1.69680 55.5 9 29.379 2.00 10 -11.775 0.70 1.64250 58.4 11 -65.028 2.85 ~ 10.42 12 -21.722 1.40 1.65844 50.9 13 -11.653-

[Embodiment 2] FIGS. 5 and 7 are views showing a lens structure of Embodiment 2 of the present invention in a state of high magnification and low magnification, and FIG. 6 is a view of high magnification shown in FIG. D in
FIG. 8 is a diagram showing various aberrations of the line, g line, and C line, and FIG. 8 is a diagram showing various aberrations of the d line, g line, and C line at the low magnification shown in FIG.

The second embodiment includes, from the object side, a positive first lens unit L11, a negative second lens unit L12, and a positive third lens unit L13. The positive first lens unit L11 is composed of a positive lens, a positive lens, and a negative lens as a whole, and a positive cemented lens and a positive lens from the object side. In Example 2, the second surface of the first lens unit L11 (surface NO.
The feature is that 2) is an aspherical surface. In Example 1, the coma aberration is generated in the periphery because the distortion aberration is reduced, and the distortion aberration returns, so that the image appears distorted. However, as in Example 2, the first lens group L11 By making the two surfaces aspherical, coma at the peripheral portion was suppressed and distortion was reduced. In addition, there is no return to distortion. Further, in the second embodiment, as in the first embodiment, the first lens unit L11 and the second lens unit L12 relatively move toward and away from each other along the optical axis to keep the diopter constant and perform zooming. It constitutes a movable lens. Here, the third lens group L13 is a fixed group so that the observer does not have to move the eye position even when zooming, and also has a diopter adjustment function for adjusting individual differences in diopter. have.

The specific lens construction of the second embodiment is shown in Table 2 below.

[Table 2] Focal length (mm) f = 15.63 to 41.02 Expansion rate (times) 16 to 6 Diopter (Dpt.) -1.00 -1.00 NO. R d n ν 1 64.627 8.30 1.69680 55.5 * 2 -29.916 6.23 3 2766.022 1.50 1.80518 25.4 4 21.196 12.00 1.65160 58.5 5 -38.596 0.10 6 31.587 5.50 1.67000 57.4 7 -171.823 15.48 ~ 1.55 8 35.932 0.70 1.69680 55.5 9 11.262 2.00 10 -12.260 0.70 1.64250 58.4 11 1.973.959 3.09 -9.40 12.65 -50.353 14.765-However, * is aspherical surface Aspherical shape is expressed by the following formula. ^{x = CY 2 / (1+ (} 1- (1 + K) C 2 Y 2) 1/2)
+ A4Y ⁴ (C is curvature (1 / r), Y is the height from the optical axis, K is the conic coefficient) Aspherical surface data NO. 2: K = 0.00000 A4 = 0.13783 × 10 ^-4

Further, in the above-mentioned Embodiments 1 and 2,
The first lens unit L11 includes, from the object side, a positive lens, and a positive cemented lens composed of a positive lens and a negative lens as a whole,
And a positive lens. Further, the Abbe number ratio of the cemented lens is ν _p / ν _n ≧ 1.8, where ν _{p is} the Abbe number of the positive lens of the cemented lens, ν _{n is} the Abbe number of the negative lens of the cemented lens. This reduces color fringing in the surrounding area. In both Examples 1 and 2, ν _p / ν _n = 58.5
/25.4≈2.30≧1.8.

[0019]

As described above, according to the present invention, the diopter is constant, the distortion is small, the color fringing in the periphery is small, the zoom ratio is large, and the magnification ratio is continuously maintained without taking the eye away from the observed object. It is possible to obtain a zoom magnifying glass that can be continuously observed by changing its shape.

[Brief description of drawings]

FIG. 1 is a lens configuration diagram showing a first embodiment of a zoom magnifying glass according to the present invention in a high magnification state.

FIG. 2 is a diagram of various types of aberration of the zoom magnifying glass of FIG.

FIG. 3 is a lens configuration diagram showing Embodiment 1 of the zoom magnifying glass according to the present invention in a low magnification state.

FIG. 4 is a diagram of various types of aberration of the zoom magnifying glass of FIG.

FIG. 5 is a lens configuration diagram showing a second embodiment of the zoom magnifying glass according to the present invention in a high magnification state.

FIG. 6 is a diagram of various types of aberration of the zoom magnifying glass of FIG.

FIG. 7 is a lens configuration diagram showing a second embodiment of the zoom magnifying glass according to the present invention in a low magnification state.

FIG. 8 is a diagram of various types of aberration of the zoom magnifying glass of FIG. 7.

[Explanation of symbols]

L11 First lens group L12 Second lens group L13 Third lens group

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Claims (3)

(57) [Claims] 1. A positive first group and a negative second group in order from the object side.
And a lens system of a positive third lens group, wherein the first group and the second group are moved toward and away from each other along the optical axis to keep the diopter constant. The first lens unit includes a positive lens, a positive lens, and a negative lens from the object side.
A positive lens as a whole consisting of lenses, and
It consists of a positive lens in order, and
Base ratio is, ν _p / ν _n ≧ 1.8 However, [nu _p: bonding the Abbe number of the positive lens of the lens [nu _n: bonding to satisfy the negative lens Abbe number of conditions of the lens, and wherein the zoom Magnifying glass. 2. The zoom magnifying glass according to claim 1, wherein:
The zoom magnifying glass, wherein the third group includes at least one lens having a diopter adjusting function that is movable along the optical axis. 3. The zoom magnifying glass according to claim 1, wherein:
A zoom magnifying glass, characterized in that at least one surface of the first group is an aspherical surface having a shape in which the lens thickness is thicker in the periphery as compared with a paraxial spherical surface.