RU2181208C1 - High-speed lens - Google Patents

Abstract

FIELD: optics. SUBSTANCE: proposed high-speed lens has five components. First component is biconvex lens, second component presents negative lens made in the form of plano-concave lens, third component comes in the form of biconvex lens which second surface is aspherical, fourth component is biconvex lens and fifth components presents biconcave lens. All relations specified in formula of invention are realized. Such approach ensures creation of high-speed lens with relative aperture not less than 1:1/6, angular field in space of objects of 38 degrees and length of optical system not more than 2,4 f′, where f′ is focal distance of high-speed lens. EFFECT: good quality of image of dot on axis and in field. 3 dwg

Description

 The invention relates to optical instrumentation, namely to special lenses, and can be used in night vision devices, in particular, working with CCD receivers.

 Known lenses are described, for example, in Japanese Patent Laid-Open No. 2-85816 (A), cl. G 02 B 13/04, publ. 03/27/90, Japanese Patent Application 3-63613 (A), CL G 02 On 13/04, published March 19, 91, which contain five lenses and are quite long.

The closest analogue to the claimed technical solution is the lens described in Japanese Patent Laid-Open 63-70817 (A), cl. G 02 B 13/16, publ. 03/31/88 It contains the following sequentially arranged components:
- the first component is a negative meniscus, facing concavity to the image,
- the second component is a biconvex lens,
- the third component is a biconcave lens,
- the fourth component is a biconvex lens,
- the fifth component is a biconvex lens.

The following relationships hold:
1,0f <| f ₁ | <1,5f, (1)
f _1.2 > f / 0.25, (2)
f _1.2 <-f / 0.08,
0.43 f <d ₂ <0.63 f, (3)
1.25 f <f ₃ <1.65 f, (4)
0.40 f <d ₄ <0.80 f, (5)
where f is the focal length of the entire lens,
f ₁ - the focal length of the first component,
f _1,2 - the focal length of the first and second components,
d ₂ - the air gap between the first and second components,
f ₃ - the focal length of the third component,
d ₄ - air gap between the second and third components.

This lens has a relative aperture of 1: 1.63, an angular field in the space of objects 2w = 38 ^o , a rather large length of the optical system
L = ∑d + S '_F' = 33.22 + 12.80 = 46.02 = 3.74f ',
where ∑d is the sum of the thicknesses and air gaps in the lens,
S '_F' - posterior focal segment.

The objective of the invention is to create a fast lens with a relative aperture of at least 1: 1.6, an angular field into the space of objects 38 ^o and the length of the optical system
L = ∑d + S '_F' ≤2,4f ',
with good image quality, points on the axis and field.

 EFFECT: reduced lens length while maintaining high image quality.

1,05 < f'₃/f' < 1,2,
0,42 < d₇/f' < 0,55,
0,22<|r₉/r₁₀|<0,3,
где f' - фокусное расстояние всего объектива,
f'₂, f'₃ - фокусное расстояние второго и третьего компонентов,
d₇ - толщина линзы четвертого компонента,
r₉, r₁₀ - радиусы кривизны линзы пятого компонента.This is achieved by the fact that in a fast lens containing five components, two of which are negative, one of which is a biconcave lens and three positive biconvex lenses, including the fourth component, in contrast to the known first component, a biconvex lens, and the second negative a lens made in the form of a concave lens, the third component is a biconvex lens, the second surface of which is aspherical, and the fifth component is a biconcave lens, with the following relationships:

1.05 <f ' ₃ / f'<1.2,
0.42 <d ₇ / f '<0.55,
0.22 <| r ₉ / r ₁₀ | <0.3,
where f 'is the focal length of the entire lens,
f ' ₂ , f' ₃ - the focal length of the second and third components,
d ₇ - the thickness of the lens of the fourth component,
r ₉ , r ₁₀ are the radii of curvature of the lens of the fifth component.

 In FIG. 1 shows an optical diagram of the lens, FIGS. 2 and 3 are graphs of lens aberrations.

 The lens (figure 1) contains five components sequentially located along the beam, the first of which consists of a biconvex lens 1, the second is a concave lens 2, the third component is a biconvex lens 3, the second surface of which is aspherical, the fourth component is a biconvex lens 4, the fifth component is a biconcave lens 5. The aperture diaphragm is located behind the second component.

 The lens works as follows.

 A parallel light flux from an object located at infinity enters the lens, where it passes successively through the lenses 1,2,3,4 and 5 and forms an image of the object in the plane of the best setting in which the optical image receiver (not shown) is installed.

As a specific example of the invention, a lens with the following structural data is calculated (see table);
focal length of the lens f '= 12.03 mm,
the focal length of the first component f ' ₁ = 29.17 mm,
the focal length of the second component f ' ₂ = 10.88 mm,
the focal length of the third component f ' ₃ = 13.82 mm,
the focal length of the fourth component f ' ₄ = 10.95 mm,
the focal length of the fifth component f ' ₅ = -9.53 mm,
back focal length S '_F' = 4.74 mm.

0,42<d₇/f′ =5,8/12,03 = 0,4821<0,55,
0,22<|r₉/r₁₀| = |-8,954/35,48| = 0,2524<0,3.
Рассчитанный объектив имеет следующие характеристики:
относительное отверстие 1:1,6
угловое поле в пространстве предметов 2w=38^o40'
спектральный диапазон (0,6-0,75-1,0) мкм
длина оптической системы
L=∑d+S'=22,2+4,70=26,9 мм=2,236f',
где ∑d - сумма толщин и воздушных промежутков в объективе,
S'_F' - задний фокальный отрезок,
продольная сферическая аберрация (по зоне) (-0,009) мм,
меридиональная кривизна изображения (-0,066) мм,
сагиттальная кривизна изображения (-0,072) мм.The following ratios are observed in the lens:

0.42 <d ₇ / f ′ = 5.8 / 12.03 = 0.4821 <0.55,
0.22 <| r ₉ / r ₁₀ | = | -8.954 / 35.48 | = 0.2524 <0.3.
The calculated lens has the following characteristics:
relative aperture 1: 1.6
angular field in the space of objects 2w = 38 ^o 40 '
spectral range (0.6-0.75-1.0) μm
optical system length
L = ∑d + S '= 22.2 + 4.70 = 26.9 mm = 2.236f',
where ∑d is the sum of the thicknesses and air gaps in the lens,
S '_F' - posterior focal segment,
longitudinal spherical aberration (over the zone) (-0.009) mm,
image meridional curvature (-0.066) mm,
sagittal image curvature (-0.072) mm.

 The aperture diaphragm is located at a distance of 1.3 mm from the second lens, the diameter of the aperture diaphragm is 8.5 mm.

Thus, as a result of the proposed solution, the technical result is obtained: the optical system length of the proposed lens L = ∑d + S '_F' = 22.2 + 4.70 = 2.236f 'is significantly less than the optical length of the lens of the closest analogue L = 3.74f 'with good image quality of a point on the axis and in the field with a relative aperture of 1: 1.6 and an angular field in the space of objects 2w = 38 ^o 40', while maintaining high quality of the lens.

Claims (1)

A fast lens containing five components, two of which are negative, one of which is a biconcave lens, and three positive biconvex lenses, including the fourth component, characterized in that the first component is a biconvex lens, the second is a negative lens made in the form concave lens, the third component is a biconvex lens, the second surface of which is aspherical, and the fifth component is a biconcave lens, with the following relationships:
0.85 <| f ' ₂ / f' | <1.0;
1.05 <f ' ₃ / f'<1.2;
0.42 <d ₇ / f '<0.55;
0.22 <| r ₉ / r ₁₀ | <0.3
where f 'is the focal length of the entire lens;
f ' ₂ , f' ₃ - focal lengths of the second and third components;
d ₇ is the thickness of the lens of the fourth component;
r ₉ , r ₁₀ are the radii of curvature of the lens of the fifth component.

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