RU2239855C2 - Lens objective - Google Patents

Abstract

FIELD: optics.

SUBSTANCE: device has three components. First component consists of two lenses - biconvex and flat-concave lens, directed by concave portion to objects plane, with small air space between them, and second component has shape of positive meniscus directed by concave portion to image plane and is a gluing together of biconvex and biconcave lenses. Third component also has shape of positive meniscus directed by concave portion to image plane.

EFFECT: higher resolution and better image quality.

5 dwg

Description

The invention relates to the field of optoelectronic instrumentation and can be used as a lens in night vision devices for observing and identifying objects in low light conditions.

Known lens for working in the infrared region of the spectrum [1], consisting of two components. The first component contains a single convex flat lens and a positive lens glued from a plano-convex lens and a biconcave lens, and the second component contains a near-focal positive meniscus.

Its disadvantage is the low image quality (scattering circle 2Δy’≤0.266 mm for the spectral range 486-800 nm, at the edge of the field of view the maximum full size of the scattering circle is 0.1 mm, distortion 3.9%).

The closest adopted for the prototype is a fast lens for working in night-vision devices [2], consisting of three components, the first of which is a double-glued lens, consisting of a biconvex lens and a negative meniscus, and the second and third are positive menisci reversed by concavity to the image plane.

The disadvantages of this lens are the low image quality and low resolution, which do not allow them to be used when working with 2+ and 3 generations of image intensifiers, the resolution of which lies within 60 mm ^-1 .

The necessary improvement in image quality in this system cannot be ensured due to the presence of large residual aberrations, of which the residual spherochromatic aberration and coma are of paramount importance.

The objective of the invention is to provide higher technical characteristics of the lens: increasing resolution and improving image quality.

The objective is achieved in that the lens contains three components, the first component of which consists of a biconvex and negative lenses, and the second and third are in the form of positive menisci facing concavities to the image plane, according to the invention the negative lens of the first component is made flat-concave, facing concavity to the plane objects, and is divided with the first small air gap, and the second component is made in the form of gluing from biconvex and biconcave lenses.

The implementation of the first component of the system of two lenses with a small air gap between them makes it possible, due to the introduction of two additional parameters (radius of curvature of the refractive surface and the distance between the lenses), to reduce the values of residual spherical aberration and coma, which are unacceptably large in the case of a double-glued first component.

The implementation of the second component of the system in the form of gluing from biconvex and biconcave lenses allows, using various brands of glasses and changing the internal radius of the refracting surface, to eliminate residual chromatism, as well as additionally affect the aberrations of wide inclined beams.

The proposed invention is illustrated by the following graphic materials:

figure 1 is an optical diagram of the lens;

figure 2 - longitudinal axial aberration;

figure 3 is a graph of astigmatism;

figure 4 is a graph of distortion;

5 is a graph of the frequency-contrast characteristics of the lens.

The optical scheme of the fast lens is shown in figure 1, which shows: the first component 1, the second component 2 and the third component 3. The element number 4 is the photocathode of the image intensifier tube, 5 is the image plane.

The design parameters of this lens are shown in the table.

The lens has the following characteristics:

Focal Length 162 mm

Relative bore 1: 1.5

Operating spectral range 600-800 nm

The main wavelength of 700 nm

Linear field in image space 18 mm

Figure 2 shows graphs of axial aberrations of the proposed lens. The abscissa axis represents the values of longitudinal aberrations ΔS ’(μm), and the y coordinate (y) in the plane of the entrance pupil.

Figure 3 shows a graph of astigmatism, and figure 4 is a graph of the distortion of the proposed optical system of the lens. The y-axis image size (mm) is plotted along the ordinate axes in both graphs. In Fig. 3, the abscissa shows the astigmatic segments Z’s, Z’m (mm), and Fig. 4 shows the relative distortion Δy ’in%.

Figure 5 shows graphs of the frequency-contrast characteristics of the proposed lens. The spatial frequency N mm ^{-1 is} plotted on the abscissa axis, relative to the image plane of the lens, and on the ordinate axis, the contrast transfer coefficient T in relative units.

From the above graphs, as well as from the analysis of the prototype at frequencies of 30-50 mm ^-1 it can be seen that the proposed lens circuit has higher performance in terms of image quality.

This lens can be used in devices operating in low light conditions, as well as at night for the detection, discrimination and recognition of objects.

Information sources

1. USSR Copyright Certificate No. 1208527, cl. G 02 B 9/40, 9/32.

2. Patent of the Russian Federation No. 2105333, cl. G 02 B 9/12, 9/34, 15/22.

Claims (1)

A lens lens containing three components, the first component of which consists of a biconvex and negative lenses, and the second and third are in the form of positive menisci facing with concavities to the image plane, characterized in that the negative lens of the first component is made flat-concave, facing concavity to the plane of objects, and separated from the first small air gap, and the second component is made in the form of gluing from biconvex and biconcave lenses.

Images