JPH0214005Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a high-resolution lens used in facsimile machines, copy machines, and the like.

Optical systems used in applications such as facsimile machines and copy machines are required to be free of distortion, and in conjunction with the recent increase in the density of light-receiving elements, extremely high resolution has become required.

Conventional lenses have high resolution, but they have a large number of lenses, making it difficult to manufacture individual lenses and lens barrels with high accuracy, making them expensive and difficult to manufacture.

In other words, conventional optical systems that have been sufficiently corrected for this type of distortion are generally Gaussian type or variations thereof, and the main point of these is that the curvature of the surfaces facing each other through the pupil is extremely small, so off-axis aberrations It is difficult to correct the chromatic aberration, and there is a noticeable lack of on-axis and off-axis chromatic aberration correction.As a result, the M・T・F (spatial transfer function) value for spatial frequencies of 80 lines/mm or more rapidly decreases. Moreover, since the characteristics are corrected using a glass material with a relatively high refractive index, the cost is high and the performance is difficult to stabilize.

The purpose of the present invention is to eliminate the above-mentioned drawbacks and to propose a high-resolution lens having a lens system configuration that is not only distortion-free but also inexpensive and easy to manufacture.

A feature of the present invention is a lens system consisting of two lens groups, a first lens group having a positive focal length and a second lens group having a negative focal length from the object side.
The lens group consists of, in order from the object side, two convex meniscus lenses with convex surfaces facing the object side, a concave meniscus lens with convex surfaces facing the object side, a cemented lens made by cementing a biconcave lens and a biconvex lens, and a biconvex lens. The second lens group is constructed by arranging, in order from the object side, a biconvex lens and a concave meniscus lens having a concave surface on the object side.

The present invention will be explained below with reference to illustrated embodiments. In Figure 1, the high-resolution lens consists of a first lens group with a positive focal length and a second lens group with a negative focal length from the object side A.
A lens system consisting of two groups, a lens group and a lens group,
The first lens group includes two convex meniscus lenses 1 and 2 with their convex surfaces facing the object side in order from the object side A.
and a concave meniscus lens 3 with the convex surface facing the object side.
The second lens group includes, in order from the object side, a biconvex lens 8 and a concave surface on the object side. It is constructed by arranging a concave meniscus lens 9 provided therein.

The symbols attached to the lenses in FIG. 1 above are as follows.

R: Radius of curvature of each lens, R ₃ ; Radius of curvature on the object side of the second lens, R ₆ ; Radius of curvature on the image side of the third lens, R ₈ ; Radius of curvature on the object side of the fourth lens, R ₁₀ ; Radius of curvature on the image side of the 6th lens, R ₁₅ ; Radius of curvature on the object side of the 9th lens, D ₁ ~ _{D 15} ; Distance between the axial surfaces of each lens. The numerical values of each lens in Fig. 1 above are as follows. be. However, the sign is: n; D-line refractive index of the lens ν; Atsube number of the lens R ₁ = 31.7 D ₁ = 2.0 n ₁ = 1.67790 ν ₁ = 55.5 R ₂ = 191.28 D ₂ = 0.386 R ₃ = 8.867 D ₃ = 2.66 n ₂ = 1.67790 ν ₂ = 55.5 R ₄ = 40.375 D ₄ = 0.09 R ₅ = 34.44 D ₅ = 0.8 n ₃ = 1.67270 ν ₃ = 32.2 R ₆ = 7.83 D ₆ = 2.24 R ₇ = Aperture D ₇ = 1.37 R ₈ ＝−5.878 D ₈ ＝0.68 n ₄ ＝1.57501 ν ₄ ＝41.5 R ₉ ＝10.22 D ₉ ＝2.1 n ₅ ＝1.69100 ν ₅ ＝54.7 R ₁₀ ＝−9.465 D ₁₀ ＝0.11 R ₁₁ ＝345.27 D ₁₁ ＝1.56 n ₆ ＝1.67790 ν ₆ ＝55.5 R ₁₂ ＝−14.08 D ₁₂ ＝0.137 R ₁₃ ＝130.55 D ₁₃ ＝1.96 n ₇ ＝1.51680 ν ₇ ＝64.2 R ₁₄ ＝−18.62 D ₁₄ ＝1.29 R ₁₅ ＝−8.438 D ₁₅ =0.721n ₈ = 1.51680 ν ₈ = 64.2 R ₁₆ = -41.072 Object-image distance = 378.727 Focal length of the entire system f = 18.9545 R ₃ /R ₆ = 1.132R ₁₀ /R ₈ = 1.610 R ₃ /R ₁₀ = -0.937R ₆ /R ₈ =-1.332 R ₁₅ /f=-0.445 The conditions for a high-resolution lens that satisfies the above embodiment are as follows.

(1) 0.9＜R ₃ ／R ₆ ＜1.3 (2) 1.4＜R ₁₀ ／R ₈ ＜1.8 (3) 0.7＜｜R ₃ ／R ₁₀ ｜＜1.1 (4) 1.1＜｜R ₆ ／R ₈ ｜ ＜1.5 (5) 0.2f＜｜R ₁₅ ｜＜0.6fR ₁₅ ＜O In the conditional expression, the symbols other than those listed above are: f: Focal length of the entire system The above invention uses a modified Gaussian type for the first lens group. , convex and concave 2 groups 2 as the second lens group
This invention relates to a distortion-free, high-resolution lens having a configuration in which two lens groups are added.

In the above conditional expressions, (1) 0.9<R ₃ /R ₆ <1.3 (2) 1.4<R ₁₀ /R ₈ <1.8 are conditions for suppressing the Petzval sum to an appropriate value.

That is, if the lower limit is exceeded, the Petzval sum becomes too small, and if the upper limit is exceeded, the Petzval sum becomes too large.

(3) 0.7<|R ₃ /R ₁₀ |<1.1 (4) 1.1<|R ₆ /R ₈ |<1.5 The condition mainly relates to coma aberration, distortion aberration, and chromatic aberration of magnification.

That is, by arranging the lens group of biconcave lenses 3 and 5 that sandwich the aperture almost symmetrically with respect to the aperture, it is possible to eliminate the asymmetry of coma aberration, and to reduce distortion and aberration.
It is possible to easily correct chromatic aberration of magnification.

If this upper or lower limit is exceeded, the symmetry of the biconcave lens group will be impaired, making it difficult to correct coma, distortion, and chromatic aberration of magnification.

(5) The condition 0.2f<|R ₁₅ |<0.6f is mainly related to astigmatism.

That is, if the lower limit is exceeded, the astigmatism becomes too much, and if the upper limit is exceeded, the astigmatism becomes too much, making it difficult to correct both.

By satisfying the above conditions (1) and (2) and then satisfying condition (5), it is possible to obtain flat image surface characteristics from the center to the periphery, and the radius of curvature is gentle, making it easy to manufacture. An inexpensive lens system can be obtained.

Since the present invention is constructed as described above, it has excellent practical effects such as no distortion, good M・T・F (spatial transfer function) and other aberrations, and high resolution and high contrast. High resolution lenses can be provided.

[Brief explanation of the drawing]

Figure 1 is a lens configuration diagram of a high-resolution lens, Figure 2 is a lens configuration diagram of a high-resolution lens.
The figure shows each aberration diagram of spherical aberration, sine condition, astigmatism, and distortion aberration, and Figure 3 shows M, T, and F (spatial transfer function).
It is a curve diagram. 1, 2... Convex meniscus lens, 3, 9... Concave meniscus lens, 5... Biconcave lens, 6, 7,
8...Biconvex lens, f...focal length, R...curvature radius.

Claims (1)

[Claims for Utility Model Registration] A lens system consisting of two groups, a first lens group having a positive focal length from the object side and a second lens group having a negative focal length, the first lens group being Consists of two convex meniscus lenses with their convex surfaces facing the object side, a concave meniscus lens with their convex surfaces facing the object side, a cemented lens made by cementing a biconcave lens and a biconvex lens, and a biconvex lens in order from the object side. However, the second lens group is composed of a biconvex lens and a concave meniscus lens having a concave surface on the object side in order from the object side, (1) 0.9<R ₃ /R ₆ <1.3 (2) 1.4< R ₁₀ ／R ₈ ＜1.8 (3) 0.7＜｜R ₃ ／R ₁₀ ｜＜1.1 (4) 1.1＜｜R ₆ ／R ₈ ｜＜1.5 (5) 0.2f＜｜R ₁₅ ｜＜0.6f R ₁₅ A high-resolution lens that satisfies the condition <O. However, the symbols R ₃ , R ₆ , R ₈ , R ₁₀ , and R ₁₅ are the radii of curvature of the 3rd, 6th, 8th, 10th, and 15th surfaces, respectively, and f is the focal length of the entire system.