RU2057355C1 - Photographic lens - Google Patents

Abstract

FIELD: optical instrumentation engineering. SUBSTANCE: in five-component lens all components are manufactured solitary. In this case concave surfaces of second and third components between which aperture diaphragm is positioned have similar radius. Second surface of first component and first surfaces of fourth and fifth components are made flat and radii of convex surfaces of first and fifth components are identical. Third component is made biconcave and second component is made convex-concave. EFFECT: improved operational reliability when used in photographic cameras. 7 dwg

Description

 The invention relates to optical instrumentation, namely to photographic lenses mainly for SLR cameras.

 Known photographic lens with four lenses and an aperture diaphragm between the second and third lenses [1] in which the first and third single lenses, and the second and fourth lenses are double-glued. All lenses are made with spherical surfaces and require different equipment in the manufacture of components included in the lens.

 This lens, providing good image quality, is nevertheless not technologically advanced, since it contains glued lenses that are labor-intensive in production.

 Known fast lens, which, in particular, is used in cameras of the Zenith-EM type [2] containing five lenses, one of which, the fourth, is made in the form of a concave-convex glued lens, and the surfaces of other single lenses are made spherical with different radii curvature. In this case, the aperture diaphragm is located between the concave surfaces of the third and fourth lenses.

 This lens is also not technologically advanced.

 Closest to the proposed is a photographic lens [3] containing five lenses, of which the first, second, fourth and fifth are made single, and the third in the form of a concave-convex lens. The aperture diaphragm is located between the second and third lenses, facing it with their concave surfaces. The first and second lenses are convex-concave, the fourth is concave-convex, and the fifth is biconvex.

 This lens has the same drawbacks as the previous ones.

 The technical task of the invention is that while maintaining good optical characteristics of the lens, such as focal length, relative aperture, field of view, photographic resolution, to ensure high adaptability of the structure due to the simplification and unification of the forming surfaces of the lenses.

 To do this, in a photographic lens containing five lenses, of which the first, second, fourth and fifth are made single, and located between the second and third lenses, an aperture diaphragm, to which the second and third lenses face surfaces, the second lens is made convexly concave, and the first surface of the first lens and the second surface of the fourth and fifth lenses are convex, according to the invention, the third lens is made in the form of a single biconcave lens, the radii of curvature of the surfaces facing the aperture di phragma same, the radii of the convex surfaces of the first and fifth lenses are equal, and the second surface of the first lens and the first surface of the fourth and fifth lenses are flat.

 Due to the implementation of all lenses as single, as well as due to the use of several lenses with flat surfaces and the equality of the radii of curvature of two pairs of lens surfaces, the manufacturability of the lens is significantly increased and, as a result, the manufacturing and assembly process is simplified and the number of required equipment is reduced, etc.

 In FIG. 1 is an optical diagram of a lens; in FIG. 2 residual lens aberrations; in FIG. 3-7 lens modulation transfer functions: for a point on the y ′ axis = 0 in FIG. 3, for the point y ′ = 5.24 mm in FIG. 4, for the point y ′ = 10.588 mm in FIG. 5, in FIG. 6 for the point y '= 16.168 mm, in FIG. 7 for the point y '= 21.003 mm.

 A photographic lens contains 1-5 single lenses in series. Aperture diaphragm 6 is installed between lenses 2 and 3. Lens 2 is convex-concave, and lens 3 is biconcave. The concave surfaces of the lenses 2 and 3 facing the aperture diaphragm 6 have the same radius of curvature. The first surface of the lens 1 is convex, and its second surface is flat. Lenses 4 and 5 are made convex plano. The radii of the first surface of the lens 1 and the second surface of the lens 5 are equal.

 The positive convex-flat lens 1 and lens 2, made in the form of a positive meniscus, are designed to correct the aberration of wide inclined beams of rays in the meridional direction (section), in particular to correct the curvature of the image. Negative biconcave lens 3, located behind the aperture diaphragm 6, provides correction of residual spherical aberration along the image field. Convex flat lenses 4 and 5 provide the focal length and are intended mainly for the correction of astigmatism, coma and lens distortion.

In accordance with the proposed solution, a photographic lens was made with the given design parameters. The test results showed that the proposed design allows to obtain a lens with high optical characteristics: focal length f '= 50 mm, relative aperture 1: 2, angular field of view 2 ω46 ^о , rear focal segment 39.265 mm.

From FIG. Figure 2 shows that the spherical aberration at the edge of the pupil does not exceed 0.0509 mm in the entire spectral range. For the main wavelength, the longitudinal spherical aberration ΔS 'does not exceed 0.3002 mm, and the transverse 0.0774 mm. The chromaticity of the position does not exceed 0.1875 mm, and the chromatism of the increase is 0.0083 mm. Image curvature: at the edge of the field for y '= 21.15 mm Z $\genfrac{}{}{0ex}{}{\text{I}}{\text{m}}$ -0.3343, Z $\genfrac{}{}{0ex}{}{\text{I}}{\text{s}}$ -01301; on the zone y '= 16.17 mm Z $\genfrac{}{}{0ex}{}{\text{I}}{\text{m}}$ -0.0053, a Z $\genfrac{}{}{0ex}{}{\text{I}}{\text{s}}$ -0.2117.

 From those shown in FIG. 3-7, it follows that the photographic resolution of the lens on a KN-1 film having a resolvometric resolution of at least 130 lines / mm and developed to a film contrast of γ0.8 in the center of the field of FIG. 3 is 75 lines / mm and along the image field for the point y ′ = 5.24 mm of FIG. 4 65 lines / mm, for the point y '= 10.59 mm of FIG. 5 65 lines / mm, for the point y '= 16.16 mm of FIG. 6 65 lines / mm, for the point y '= 21 mm of FIG. 7 65 lines / mm.

 The proposed photographic lens can be used for shooting on color and black and white film, for shooting in low light conditions of the subject (in the evening, indoors), as well as for macro and micro shots and, above all, in widespread SLR cameras with the format frame 24 x x36 mm, for example, the type of "Zenith".

Claims (1)

 A PHOTO LENS containing five lenses, of which the first, second, fourth and fifth are single, and an aperture diaphragm located between the second and third lenses, to which the second and third lenses are facing concave surfaces, the second lens being convexly concave and the first surface the first lens and the second surface of the fourth and fifth lenses are convex, characterized in that the third lens is made in the form of a single biconcave lens, the radii of curvature of the surfaces facing the aperture diaphragm agme same, the radii of the convex surfaces of the first and fifth lenses are equal, and the second surface of the first lens and the first surface of the fourth and fifth lenses are flat.

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