EA007360B1 - Fast lens objective - Google Patents

Abstract

The invention relates to optical and -electronic instrument production, namely to objectives, and may be used as an objective of a small-sized night vision device (NVD) working with Image intensifier tube (IIT) or with CCD matrix.Fast lens objective, includes two positive meniscuses inverted by convex surfaces to space of subjects, a negative lens, the lens which has been stuck together from biconcave and biconvex lenses, a positive lens and a meniscus. Innovative technology consists in that the negative lens is executed as a meniscus inverted by a convex surface to space of subjects, and the meniscus inverted by a convex surface to space of subjects, is executed from biconvex and biconcave lenses, stuck together and optical efficiency does not exceed 0.15 optical efficiency of an objective, and thickness of a meniscus is not less than 0.2 focal length of an objective.The offered design of an objective allows to improve quality of the image on a field in a wide spectral range, and an increase of a back working segment allows to place an objective conveniently in a structure of the device.

Description

The invention relates to an optical-electronic instrument, namely, lenses, and can be used as a lens of a small night vision device (NVD), working with an electron-optical converter (EOC) or with a CCD sensor.

Known high-aperture lens [1], containing five components: a negative meniscus facing a convex surface to the space of objects, biconvex and biconcave lenses, flat-convex and biconvex lenses. The disadvantage of the lens is a small relative aperture (1: 1.7) and a large length of the optical system of the lens (3.16 G).

Known high-aperture lens [2], containing five components: the first component is a positive meniscus facing a convex surface to the space of objects, the second and third components are two negative meniscus facing concave surfaces towards each other, the fourth component is a positive meniscus facing a concave surface the object space, and the fifth component is a biconvex lens, glued together from positive and negative lenses. The design of the lens does not effectively correct the aberrations of wide oblique beams. The large curvature of the radii of the third component creates known technological difficulties in its manufacture.

The closest to the proposed lens to the technical essence is a high-aperture lens [3], which contains six components: two positive meniscus, facing convex surfaces to the space of objects; biconcave lens; lens glued from biconcave and biconvex lenses; a biconvex lens and a negative meniscus facing a convex surface to the space of images. The disadvantages of this lens are quite small rear working segment, which makes it difficult to use the lens in the design of a night vision device, and, most importantly, the insufficient correction of the secondary spectrum and spherochromatic aberrations does not allow its use in a wide spectral range due to poor image quality.

The objective of the invention is to improve the quality of the image of the lens in a wide spectral range due to better correction of the secondary spectrum and spherochromatic aberrations, as well as an increase in the rear working segment for convenient use of the lens in the design of the device.

The technical result is achieved by the fact that in a high-aperture lens, which includes two positive meniscus, facing convex surfaces to the space of objects; negative lens; lens glued from biconcave and biconvex lenses; the positive lens and meniscus is new, the negative lens is made in the form of a meniscus facing a convex surface to the space of objects, and the meniscus facing a convex surface to the space of objects is made of glued biconvex and biconcave lenses, and its optical power does not exceed 0, 15 optical power of the lens, and the meniscus thickness is not less than 0.2 focal length of the lens.

The optical scheme of the proposed high-aperture lens, and in particular the choice of the design of the sixth component in the form of a glued meniscus facing a convex surface to the space of objects, made it possible to provide a high degree of correction of the secondary spectrum and spherochromatic aberrations of the lens and improve the image quality of the lens in a wide spectral range.

FIG. 1 shows the optical scheme of the proposed high-aperture lens.

The high-aperture lens contains six components successively along the rays. The first two components are made in the form of positive menisci 1 and 2, facing convex surfaces to the space of objects, their optical power is 0.024 and 0.030, respectively. The third component is a negative meniscus 3, with a convex surface facing the space of objects and having an optical power of 0.07. The fourth component is made in the form of a meniscus glued from a biconcave 4 and a biconvex 5 lenses with an optical power of 0.01 made of glass, the difference between the refractive indices of which is 0.14. The fifth component is a positive lens 6 made of a biconvex superheavy crown with an optical power of 0.026. The sixth component is a meniscus glued together from a biconvex 7 and a biconcave 8 lenses with an optical power of 0.005. Lenses 7 and 8 are made of materials having a refractive index of at least 1.7.

As a specific example of implementation, a high-aperture lens was calculated with the following technical characteristics: focal length - 26.6 mm; relative aperture - 1: 1,2; angular field of view - 2ω = 40 °; spectral operating range - (440-660-880) nm; optical system length - 1.70 g. rear working segment - 0.37 g.

FIG. 2 shows plots of residual aberrations of the lens, and FIG. 3 - frequency-contrast characteristics of the lens.

The lens was calculated to work with the plate thickness of 5.6 mm of glass K8. The design parameters of the lens are shown in the table.

- 1 007360

Radius, mm Thickness mm The refractive index, n _e Abbe coefficient, ν _ε =ι = 22.7 ϋι = 3.6 1.7476 50.2 K ₂ = 83.95 ϋ ₂ = 0.1 K ₃ = 14,859 ϋ ₃ = 3.6 1.7476 50.2 35.97 ϋ ₄ = 1.43 K ₅ = 55.98 ϋ ₅ = 1.3 1.8138 43.2 Kb = 9.727 ϋ ₆ = 8.83 K ₇ = -13,552 ϋ7 = 1.3 1,604 50.8 K ₈ = 20.7 E ₈ = 5.3 1.7476 50.2 K ₉ = -17,865 ϋ ₉ = 0.1 Kyu = 41.69 Οιο ⁼ 2.8 1.7476 50.2 Kc = -87,9 En = 0.1 K ₁₂ = 17,378 012 = 4.93 1.7476 50.2 K ₁₃ = -60,81 ϋΐ3 = 1.3 1.8138 43.2 Κΐ4 = 18,365 Οΐ4 ⁼ 6.2 K15 = oo ϋ15 ⁼ 5.6 1.5183 63,8 K ₁₆ = oo

Theoretical studies of the proposed high-aperture lens showed that the circle of scattering of rays in the center of the field is no more than 0.015 mm, and at the midpoint of the image field does not exceed 0.02 mm. Well-corrected spherochromatic aberrations, the secondary spectrum, as well as increase chromatism not exceeding 0.3%, allowed us to raise the frequency-contrast characteristics for N = 50 lines / mm to 70% in the center of the field and up to 50% for the image field point of 7 mm ( 2 (0 = 30 °).

Thus, as a result of the proposed solution, the technical result is ensured: the image quality is improved across the field in a wide spectral range, and the rear working segment is enlarged, which makes it possible to conveniently place the lens in the design of the device.

Information sources used

1. NO 2154292 C2, Β02Β 13/14, 2000.

2. HER 2040024 C1, Θ02Β 11/32, 1995.

3. Application No. 94019808, О02В 9 / 62,1996. (prototype).

Claims (1)

CLAIM A fast lens, including two positive menisci facing convex surfaces to the space of objects, a negative lens, a lens glued from a biconcave and biconvex lenses, a positive lens and a meniscus, characterized in that the negative lens is made in the form of a meniscus facing a convex surface to the space of objects, and the meniscus facing a convex surface to the space of objects made of glued from a biconvex and biconcave lenses, and its optical power does not exceed 0.15 optical Coy lens power and thickness of not less than 0.2 meniscus lens focal length.