RU2541420C1 - Infrared lens with two fields of view - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: lens has three components. The first fixed component comprises a first positive convex-concave lens and a second biconvex lens, the second surface of which is aspherical. The second component comprises a negative lens, the first surface of which is aspherical, and is configured to move along an optical axis. The third fixed component comprises a first biconvex lens and a second positive lens. The second movable component is located between the first and second lenses of the fixed first component.

EFFECT: improved energy characteristics and angular resolution of the lens due to a larger diameter of entrance pupil and focal distance.

5 cl, 1 dwg, 3 tbl

Description

The invention relates to infrared optical systems and can be used in thermal imagers.

Known lenses with two fields of view for the middle infrared range (see patents US 2012/022914 A1, IPC ⁷ G02B 15/14 publ. 09/13/2012, US 6424460 B1, IPC ⁷ G02B 15/14 publ. 07/23/2002 g .) with focal lengths of 508/258 mm, 160/53 mm and relative apertures of 1: 2 and 1: 2.5, respectively, in which the field of view is changed by moving one of the components along the optical axis. The disadvantage of the first of these lenses is the large size of the input lenses, a large number of materials used and the low rate of change of the field of view. The disadvantage of the second lens is the small relative aperture and focal length in a narrow field of view, a large number of materials used.

Also known is a lens for the far infrared range (see patent RU 2400784 C1, IPC ⁷ G02B 13/14 publ. 09/27/2010) containing ten lenses with a focal length of 210/70 mm and a relative aperture of 1: 2, changing fields view is carried out by moving two components along the optical axis. The disadvantages of this lens are a large number of lenses, the presence of two moving components and the magnitude of their movement (for one of the components more than 100 mm).

The closest in technical essence to the claimed lens adopted for the prototype is an infrared lens with two fields of view (see patent US 2010/0033578 A1, IPC ⁷ G02B 15/14 publ. 02/11/2010), consisting of three components: motionless first and third and moving second. The fixed first component contains the first negative convex-concave lens of germanium, the second positive biconvex lens of zinc selenide with aspherical surfaces, the third negative convex-concave lens of calcium fluoride, the fourth positive convex-concave lens of zinc selenide and the fifth negative-convex lens of zinc selenide from Germany, the second movable component contains a negative concave-convex lens from germanium with aspherical surfaces, the third fixed component contains th positive biconvex lens with a germanium aspheric surfaces and a second positive lens of biconvex germanium. The change in the field of view is carried out by moving the moving component along the optical axis in the space between the first and third components. The lens works with a relative aperture of 1: 2.7, in a narrow field of view the focal length of the lens is f ′ _max = 180 mm, the diameter of the entrance pupil is 66.7 mm, in the wide field of view it is f ′ _min = 60 mm, the diameter of the entrance pupil is 22, 2 mm.

The disadvantages of this infrared lens are small values of the diameter of the entrance pupil, at which a small radiation flux from the objects of observation and a focal length that does not provide sufficient angular resolution, which reduces the range of the device, are received by the thermal imager.

The problem to which the invention is directed, is to increase the energy characteristics and angular resolution of an infrared lens with two fields of view by increasing the diameter of the entrance pupil and focal length.

This goal is achieved by the fact that in an infrared lens with two fields of view, consisting of a stationary first component containing a first convex-concave lens and a second positive biconvex lens, the second surface of which is made of an aspherical, movable second component containing a negative lens, the first surface of which is made aspherical, mounted with the ability to move along the optical axis, and a stationary third component containing the first biconvex and the second put nye lens, the first lens component is made first fixed positive and a movable second component is located between the first and second lenses, the first fixed component.

And also by the fact that the second surface of the first lens of the first fixed component is made aspheric-diffraction.

And also the fact that the lens of the second movable component is biconcave.

And also by the fact that the first surface of the first lens of the third fixed component is made aspheric-diffraction.

And also the fact that in the third fixed component the second lens is made convex-concave.

The drawing shows an optical diagram of an infrared lens with two fields of view.

An infrared lens with two fields of view consists of a stationary first component I located along the optical axis and containing a first positive convex-concave lens 1 and a second positive biconvex lens 2, a movable second component II, containing a negative biconcave lens 3, and a stationary third component III containing the first positive biconvex lens 4 and the second positive convex-concave lens 5. The movable second component is arranged to move along the optical the axis between the first 1 and second 2 lenses of the fixed first component I. The second surface of the first positive convex-concave lens 1 of the fixed first component I and the first surface of the first positive biconvex lens 4 of the fixed third component III are made aspheric-diffraction. The second surface of the second positive biconvex lens 2 of the stationary first component I and the first surface of the negative biconcave lens 3 of the movable second component II are aspherical.

Table 1 shows the specifications of the lens.

The design parameters of the lens are shown in table 2.

Table 1 Specifications Narrow field of vision Wide field of view Spectral range of work, microns 3-5 Focal length mm 320 107 Diameter of entrance pupil, mm 160 53.5 Angular field of view, hail 1.72 × 1.38 5.14 × 4.11

table 2 Lens number Radius of a spherical surface, mm Axial thickness, mm Material one r ₁ = 201.7 d ₁ = 17 Silicon r ₂ = 344.3 ¹⁾ d ₂ = 137 (112) 2 r ₃ = -137.5 ²⁾ d ₃ = 5 Germanium r ₄ = 146 d ₄ = 8 (33) 3 r ₅ = 253.5 d ₅ = 7 Silicon r ₆ = -146.2 ³⁾ d ₆ = 125 four r ₇ = 111.3 ⁴⁾ d ₇ = 5 Germanium r ₈ = -326.3 d ₈ = 1 5 r ₉ = 15.9 d ₉ = 4 Silicon r ₁₀ = 13.27 d ₁₀ = 33.3 ¹⁾ , ⁴⁾ - aspheric-diffraction surface; ²⁾ , ³⁾ - aspherical surface

As can be seen from table 2, the lens is made of two optical materials: germanium and silicon. The combination of these materials, the choice of optical forces and the shape of the lenses, as well as the implementation of the surfaces of the lens 1 and lens 4 asfero-diffraction provide high image quality. Table 3 shows the calculated values of the energy concentration characterizing the image quality of the lens.

Table 3 Focal length mm The energy concentration in a circle with a diameter of 15 μm,% to the center of the field of view on the edge of the horizon 320 74 69 107 77 40

An infrared lens with two fields of view works as follows: a parallel beam of infrared rays passes through all the lenses of the lens, refracted on each surface in accordance with the radii and materials of the lenses and focuses on the optical axis in the focal plane. Inclined beams of rays also pass through all the lenses of the lens and focus accordingly at other points in the focal plane.

Changing the field of view (focal length) of the lens is carried out by moving the lens 3 of the movable second component II along the optical axis in the space between lenses 1 and 2 of the stationary first component I by 25 mm.

Thus, the implementation of an infrared lens with two fields of view in accordance with the formula of the claimed materials can increase its energy characteristics and angular resolution by increasing 2.4 times the diameter of the entrance pupil and 1.8 times the focal length.

Claims (5)

1. An infrared lens with two fields of view, consisting of a stationary first component containing the first convex-concave lens and the second positive biconvex lens, the second surface of which is aspherical, the movable second component containing a negative lens, the first surface of which is aspherical, mounted with the possibility moving along the optical axis, and a stationary third component containing the first biconvex and second positive lenses, characterized in that the first lens of the first fixed component is positive, and the second movable component is located between the first and second lenses of the stationary first component. 2. The lens according to claim 1, characterized in that the second surface of the first lens of the first stationary component is made aspheric-diffraction. 3. The lens according to claim 1, characterized in that the lens of the second movable component is biconcave. 4. The lens according to claim 1, characterized in that the first surface of the first lens of the third fixed component is made aspheric-diffraction. 5. The lens according to claim 1, characterized in that in the third stationary component the second lens is convex-concave.