RU2411556C1 - Large-aperture lens - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: lens has four components lying in series on an optical axis. The first component is a single plane-convex lens whose flat surfaces faces the image space. The second component is glued from a biconvex lens, which faces the first component with its surface with the smaller radius of curvature, and a biconcave lens which faces the image space with its surface with the smaller radius of curvature. The third component is glued from a negative meniscus and a biconvex lens which faces the image space with its surface with the greater radius of curvature. The fourth component is a biconcave lens which faces the image space with its surface with the greater radius of curvature. The aperture diaphragm lies on the surface of the second component, facing the image space.

EFFECT: high aperture ratio with simultaneous simplification of the design and wider range of nominal size of the CCD matrix used.

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Description

The invention relates to optical instrumentation, namely to lenses, and can be used as a lens in digital observing devices with imaging on a CCD, including modern night vision devices, photo and video cameras, projection devices.

Known fast lens designed to work with devices in which the image is formed on a CCD matrix (see patent of the Russian Federation No. 2181207, G02B 13/14, 9/60, publication date - 04/10/2002), which includes those located in series on the optical there are four components on the axis, the first component being a single biconvex lens, the second a positive meniscus, the third a negative meniscus, and the fourth a gluing including a negative meniscus and a symmetric biconvex lens.

The known lens is designed to work with devices in which the image is formed on a CCD matrix with dimensions in the range 1/3 "-1/2".

The disadvantages of this lens include:

- low relative aperture (1: 1.7);

- the fact that in it of five lenses three are made in the form of menisci, which makes the cost of the lens high.

Also known is a fast lens according to the patent of the Russian Federation No. 2308063 (G02B, 9/64, publication date - 10.10.2007), in which an increase in image quality is achieved by increasing the modulation transmission coefficients and reducing the lens distortion. The lens includes 9 components, including 6 menisci, which determines its high cost.

Closest to the claimed lens in technical essence (prototype) is a fast lens according to the aforementioned patent of the Russian Federation No. 2181207.

The objective of the invention is to increase the relative aperture while simplifying the design of the fast lens and expanding the sizes of CCD arrays in which a high quality image can be formed using this lens.

The problem is achieved in that in a fast lens containing four components sequentially located on the optical axis, the first of which is made in the form of a single positive lens, another component is made in the form of a gluing consisting of a negative meniscus and a biconvex lens facing the image space , a single positive lens of the first component is made convex and faces the image space with a flat surface, the second component is made in the form of gluing from of a positive asymmetric biconvex lens facing the first component with a surface with a smaller radius of curvature, and a negative asymmetric biconcave lens facing the surface with a smaller radius of curvature to the image space, the third component is made in the form of the aforementioned gluing of the negative meniscus and the biconvex lens faces the image space with a surface with a large radius of curvature, and the fourth in the form of an asymmetric biconcave nzy facing the space image surface with a large radius of curvature, wherein the aperture stop is located on the surface of the second component facing the image space.

The invention is illustrated by drawings. Figure 1 shows the optical scheme of the proposed aperture lens;

figure 2 shows a graph of the frequency-contrast characteristics of the lens;

figure 3 shows a graph of transverse spherical aberration;

figure 4 shows a graph of the longitudinal spherical aberration of wide inclined beams of the meridional (M) and sagittal (S) sections within the angle of view 2w = 10 °;

figure 5 shows a graph of relative distortion.

A fast lens (Fig. 1) contains four components sequentially located on the optical axis. The first component is made in the form of a single plane-convex positive lens 1, which faces the image space with a flat surface. The second component is made in the form of gluing from a positive asymmetric biconvex lens 2, facing the first component with a surface with a smaller radius of curvature, and a negative asymmetric biconcave lens 3, facing the surface with a smaller radius of curvature to the image space. The third component is made in the form of gluing from a negative meniscus 4 and a biconvex lens 5, the latter being asymmetric and facing the image space with a surface with a large radius of curvature. The fourth component is made in the form of an asymmetric biconcave lens 6, facing the image space with a surface with a large radius of curvature.

As a specific example of implementation of the invention, a lens is calculated for a focal length f = 50 mm and an input aperture D = 50 mm, the design parameters of which are shown in table 1.

Table 1 Surface Type of Radius Thickness Glass Diameter Obj Standard beskone beskone one Standard 54,2 9 STK12 52 2 Standard beskone 0.3 52 3 Standard 36.73 12 KF6 45 four Standard -127.35 5 TF12 45 STO Standard 53.44 27.43 33.7 6 Standard 32.58 3 Lf7 17 7 Standard 9.772 6 STK7 fifteen 8 Standard -50.58 2.47 fifteen 9 Standard -19.543 3 Bf7 12 10 Standard 47.1 3 12 IMA Standard beskone 8.8

Focal segments of lens elements for λ = 587.6 nm are given in table 2.

table 2 # f fs sf 1-2 78.322 -78.322 73.003 3-4 58.374 -56.539 52.012 4-5 -47,367 49.316 -48.185 6-7 -25.355 28.207 -24.499 7-8 12.424 -11.824 9.317 9-10 -23.443 23.991 -24.764

Tables 3, 4 show the focal segments of the glued lenses and the focal segments of the lens, respectively.

Table 3 # f fs sf 3-5 -1025.655 1207.455 -880.441 6-8 24.851 -22.510 21.495

Table 4 # f sf 1-10 49.998 3.008

The proposed lens is designed to operate in the visible wavelength range λ = 486.1, ... 587.6 ... 656.3 nm and has a relative aperture of 1: 1. The angular field of view of the lens is 2w = 10 °.

Figure 2-5, the curves are presented for three wavelengths: 486.1 nm, 587.6 nm and 656.3 nm.

As can be seen from figure 2, the polychromatic modulation transmission coefficients for the spatial frequency N = 50 mm ^-1 at a point on the y '= 0 axis and for the edge of the field of view 2w = 10 ° is not less than 0.4, and for the spatial frequency N = 100 mm ^-1 - at least 0.2, which allows you to receive images of small contrast objects on the receiver.

The graph of the frequency-contrast characteristics of the lens in FIG. 2, as well as the aberration graphs shown in FIGS. 3 and 4, confirm that the lens has good image quality over the entire field of view (high resolution), which makes it possible to obtain images of objects with low contrast .

Graphs of relative distortion shown in figure 5, confirm the reduction in distortion compared to the prototype.

Thus, with respect to the prototype, the fast lens according to this invention has a high relative aperture, simple construction, due to the small number of components and the presence of only one lens in the form of menisci and, as a result, low cost.

Moreover, the lens has a high resolution, which is a significant factor when used with modern CCD arrays, the minimum pixel size of which is <10 um, has good image quality over the entire field of view of the lens, which is 2w = 10 °. This angle is sufficient to be used with receivers based on standard 1/4 ", 1/2", 3/4 "CCDs.

The most important characteristic of the proposed lens is the high value of the relative aperture (aperture ratio) - 1: 1 (for the prototype - 1: 1.7), which significantly expands the range of possible use of the lens, in particular, allows it to be used in night vision devices designed to work in low light conditions (twilight and dark).

The lens works as follows. A parallel beam of light with an angle of view 2w = 10 ° from an object located at a great distance from the first element hits the first surface of the first component of the lens and, being refracted through the lens surfaces, focuses in the image plane.

Claims (1)

A high-speed lens containing four components sequentially located on the optical axis, the first of which is made in the form of a single positive lens, another component is made in the form of a gluing consisting of a negative meniscus and a biconvex lens, characterized in that the single positive lens of the first component is made convex and facing the image space with a flat surface, the second component is made in the form of gluing from a positive asymmetric biconvex lens, facing the first component with a surface with a smaller radius of curvature, and a negative asymmetric biconcave lens facing the surface with a smaller radius of curvature to the image space, the third component is made in the form of the aforementioned gluing of a negative meniscus and a biconvex lens, and the latter is made asymmetric and faces the image space with a surface with a large radius of curvature, and the fourth - in the form of an asymmetric biconcave lens, facing the image space with a surface with more shim radius of curvature, wherein the aperture stop is located on the surface of the second component facing the image space.

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