RU2349942C1 - Discrete-zoom telescope for far infrared - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention refers to optical instrument engineering, namely to discrete-zoom telescopic vision arrangements for infrared wavelength spectrum. Telescope contains objective and eyepiece. Objective consists of three positive components. The first component is positive meniscus convex to object. The second component consists of biconcave lens, flat-convex lens and positive meniscus convex to object. The third component is negative meniscus concave to image. The second surface of lens of the first component is aspherical. The second component of objective is introducible and removable from the optical arrangement. The eyepiece consists of three lenses. The first is biconcave, the second and the third are designed as convex to each other. All surfaces of eyepiece lenses are spherical. Herewith the following ratio occurs: 1.1<S'_p'/f'_ok<1.3, where S'_p' is removal of exit telescope pupil, f'_ok is the eyepiece focal length.

EFFECT: higher technological effectiveness ensured with lower number of aspherical surface, higher telescope light-gathering power and reduced narcissus effect with maintained high-quality imaging.

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Description

The invention relates to optical instrumentation, namely to telescopic systems of observational instruments for the infrared region of the wavelength spectrum with a discrete change in magnification.

Known designs of telescopic systems, described, for example, in patent applications GB No. 2076987 (A), G02B 23/00, publ. 12/09/81, GB No. 2159297 (A), G02B 23/00, publ. 11.27.85, GB No. 2102588 (A), G02B 23/00, 25/00, publ. 02.02.83, and the patent of Russia RU No. 2072736, G02B 23/00, 25/00, publ. 01/27/97

The closest analogue to the claimed technical solution is a telescope with a discrete change in magnification for the far infrared region of the spectrum described in the patent of the Russian Federation RU No. 2199143, G02B 23/00, publ. 02/20/2003, It contains a lens and an eyepiece. The lens consists of three components, the first of which is a positive meniscus convex to the object, the second component consists of a biconcave lens, two positive menisci facing one of the convex image, the other is convex to the object, the third component is the negative meniscus convex to the image, while the second lens surface of the first component is aspherical. The second component of the lens is installed with the ability to input and output from the optical circuit. The eyepiece consists of three positive menisci, the first and second of which are convex to the image, and the third is convex to the object. The first surface of the second lens of the eyepiece is aspherical.

The telescope has the following specifications:

- The minimum increase in G _min = -4.2 times;

- The maximum increase in G _max = -12.6 times;

- The diameter of the entrance pupil with a minimum increase of D _int.min.min = 43.3 mm;

- The diameter of the entrance pupil with a maximum increase of D _vkh.sr.maks = 130 mm.

But this telescope has high technological complexity due to the use of two aspherical surfaces in the circuit, a low aperture ratio that determines the low spatial and thermal resolution of the observing devices, the “narcissus” effect from the second surface of the third lens component, from the second surface of the first lens and from the second surface is not sufficiently reduced the second lens of the eyepiece, which leads to the appearance in the center of the field of view of a defocused image of a cooled radiation receiver, which, in its own eating affects the comfort of image perception.

The objective of the invention is to provide a telescope with a discrete change in magnification for the far infrared region of the spectrum, with improved technological and operational characteristics.

The technical result implemented in the present invention is to increase the manufacturability of the telescope by reducing the number of aspherical surfaces, increasing the aperture ratio of the telescope and reducing the effect of "daffodil" while maintaining high image quality.

This is achieved by the fact that in a telescope with a discrete change in magnification for the far infrared region of the spectrum containing the lens and eyepiece, the lens consists of three positive components, the first of which is the positive meniscus convex to the object, the second component consists of a biconcave lens, positive the lens and the positive meniscus convex to the object, the third component is the negative meniscus facing the concavity to the image, while the second lens surface of the first component is made asph The second lens component is mounted with the possibility of input and output from the optical circuit, the eyepiece consists of three lenses, the second and third of which are made in the form of positive menisci, convex to each other, in contrast to the known lens, in the second component of the lens, the positive lens is made plano-convex, convex to the image, and in the eyepiece, the first lens is biconcave, and all surfaces of the eyepiece lenses are spherical, with the following relationship:

1,1 <S ′ _{P ′} / f ′ _ok <1,3,

where S ′ _{P ′} is the removal of the exit pupil of the telescope,

f ′ _ok - the focal length of the eyepiece.

Figure 1 shows the optical scheme of the telescope, Fig.2-4 - graphs of aberrations and modulation transfer functions of the calculated version of the telescope.

The telescope (figure 1) contains a lens consisting of three components, and a three-lens eyepiece. The first component is the positive meniscus 1, convex to the object, its second surface is aspherical. The second component contains a biconcave lens 2, a positive plano-convex lens 3, convex to the image, and a positive meniscus 4, convex to the object. The second component of the lens is installed with the ability to input and output from the optical circuit. The third component contains a negative meniscus 5, facing concavity to the image. The three-lens eyepiece contains a biconcave lens 6, positive menisci 7 and 8, convex to each other.

The telescope operates as follows - the luminous flux from an object located at infinity enters the lens, where it passes sequentially through lenses 1-5 and forms, in the plane in which the rear focal plane of the lens and the front focal plane of the eyepiece, the inverted image of the object, which then through the eyepiece lenses 6-8 is projected in the space of images at infinity.

As a specific example of the invention, a telescope with a discrete change in magnification for the far infrared region of the spectrum is calculated.

Lenses 1, 2, 3, 4, 5, 6, 7, 8 provide an increase in G _min . The design data of the telescope with an increase in G _{min are} presented in Table 1.

Table 1 Radius mm Thickness mm Material 236.6 fourteen Germanium 368.26 * 75 -389.9 3,5 Germanium 286.4 48 ∞ 6 IKS-25 -186.64 0.5 85.51 6 Germanium 133.66 eleven 171 6 Zinc Selenide 80.91 81.5 -114.55 3,5 Zinc Selenide 197.7 6 -201.4 5.5 Germanium -53.7 0.5 34.75 5 Germanium 32.58

* Aspherical surface with the equation:

где

Where

c = 1 / R is the curvature of the surface,

k = 0 is the conical constant,

a ₁ = a ₃ = a ₄ = a ₅ = a ₆ = a ₇ = a ₈ = 0, a ₂ = 1.35125 × 10 ^-9 are the coefficients of the polynomial,

r is the radial coordinate.

Lenses 1, 5, 6, 7, 8 provide an increase in G _max . The design data of the telescope with an increase in G _{max are} presented in Table 2.

table 2 Radius mm Thickness mm Material 236.6 fourteen Germanium 368.26 * 150 171 6 Zinc Selenide 80.91 81.5 -114.55 3,5 Zinc Selenide 197.7 6 -201.4 5.5 Germanium -53.7 0.5 34.75 5 Germanium 32.58

* Aspherical surface with the equation:

где

Where

c = 1 / R is the curvature of the surface,

k = 0 is the conical constant,

and ₁ = a ₃ = a ₄ = a ₅ = a ₆ = a ₇ = a ₈ = 0, and ₂ = 1.35125 × 10 ^-9 are the coefficients of the polynomial,

r is the radial coordinate.

The telescope has the characteristics presented in table.3.

Table 3 No. Parameter For increase G _min G _max one Increase, krat -four -12.05 2 Angular field, degrees 7.7 2.6 3 Entrance pupil diameter 58.52 145 four Exit pupil removal 31 31 5 Spectral range, microns 7.6-10.6 6 Modulation transmission coefficient calculated for a telescope together with a paraxial lens (f ′ = 25 mm) at 18 lines / mm for the center of the field of view 0.62 0.54 7 Modulation transmission coefficient calculated for a telescope together with a paraxial lens (f ′ = 25 mm) at 18 lines / mm for the edge of the field of view, meridional / sagittal 0.51 / 0.61 0.46 / 51 8 Distortion,% 3.9 4,5

Figure 2 shows the aberration graphs for G _max - the transverse ray aberration depending on the coordinate on the pupil, image curvature and distortion depending on the coordinate of the field of view, calculated for the telescope together with a paraxial lens (f ′ = 25 mm).

Figure 3 shows the graphs of aberrations for G _min - the lateral aberration of the rays depending on the coordinate on the pupil, the curvature of the image and the distortion depending on the coordinate of the field of view, calculated for the telescope together with a paraxial lens (f ′ = 25 mm).

Figure 4 shows graphs of the modulation transfer functions, respectively, for G _max and G _min , calculated for the telescope together with a paraxial lens (f ′ = 25 mm).

Analyzing the results of calculations of the paraxial value of the YNI parameter (Applied Optics magazine, Vol.21, # 18, p.3393 (1982)), which determines the contribution to the effect of the “daffodil” from the surfaces, in the closest analogue and the present invention are presented in table. 4, and considering that the contribution to the “daffodil” effect from the surface is inversely proportional to (YNI) ² , we can conclude that the “daffodil” effect is significantly reduced.

Table 4 Surface number The value of the paraxial parameter YNI Reducing the contribution to the effect of "narcissus" (YNI _inventions / YNI _analogue ) ² YNI _analog INI _inventions one 2.42570 3.55452 2.15 2 -0.95578 -1.85206 3.75 3 -1.52766 -3.16959 4.30 four 1.99480 3.87876 3.78 5 -1.05558 4.21902 15.97 6 -3.25110 -5.34876 2.71 7 3.87636 5.69923 2.16 8 -4.36349 -5.95784 1.86 9 -4.34188 -6.07554 1.96 10 -0.18169 -0.99680 30.01 eleven 0.62026 1.10303 3.16 12 0.13664 2.05368 225.9 13 0.21241 2.47167 135.4 fourteen 0.15131 -0.96385 40.58 fifteen 0.83756 2.12223 6.42 16 0.37030 1.61025 18.91

Focal length of the eyepiece f ′ _ok = 26.2 mm, removal of the exit pupil of the telescope S ′ _{P ′} = 31 mm.

Ratio:

1,1 <S ′ _{P ′} / f ′ _ok <l, 3

performed:

1.1 <(31 / 26.2) = 1.18 <1.3.

Thus, we obtained a telescope with a discrete change in magnification for the far infrared region of the spectrum with enhanced technological and operational characteristics, namely:

- has only one aspherical surface, which makes it more technologic;

- has a higher aperture, determined by the size of the entrance pupils, which increases the range of detection and recognition of devices;

- reduced the effect of "daffodil", which makes the image more comfortable for perception.

Claims (1)

A telescope with a discrete change in magnification for the far infrared region of the spectrum, containing the lens and the eyepiece, the lens consists of three positive components, the first of which is the positive meniscus convex to the object, the second component consists of a biconcave lens, a positive lens and a positive meniscus inverted convexity to the object, the third component is the negative meniscus facing the concavity to the image, while the second lens surface of the first component is aspherical, the second component the lens is installed with the possibility of input and output from the optical circuit, the eyepiece consists of three lenses, the second and third of which are made in the form of positive menisci, convex to each other, characterized in that in the second component of the lens a positive lens is made convex, facing convex to image, and in the eyepiece, the first lens is biconcave, and all surfaces of the eyepiece lenses are made spherical, with the following relationship:
1,1 <S ′ _{P ′} / f ′ _ok <1,3,
where S ′ _{Р ′} - removal of the exit pupil of the telescope;
f ′ _ok - the focal length of the eyepiece.

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