RU2617173C2 - Three-channel mirror-lens optical system - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: optical system comprises a main concave aspherical mirror, before which the lens component is mounted in the form of a negative meniscus, a lens compensator of the far infrared range is mounted after the main mirror, the first surface of which is a spectro-dividing surface transmitting the far infrared range and reflecting the visible and short infrared range, a doublet lens, general for the visible and short IR ranges, is located so that its front focal plane is shifted against the back focal plane of the lens mirror to obtain the beams with a small angular divergence. A spectro-dividing prism-cube is located behind the general lens, after passing through which the lens for the short IR range and the radiation receiver are mounted. The lens for the visible range and the radiation receiver are mounted after reflection from the spectro-dividing prism-cube.

EFFECT: enhancing the angular field in the item space, increasing the relative hole in each of the channels, and reducing the number of the aspherical surfaces.

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Description

The present invention relates to the field of optoelectronic technology and can be used for thermal television devices and sights used in a wide variety of operating conditions.

A multispectral specular-lens optical system is known (United States Patent No. 5,841,574 of Nov. 24, 1998), comprising a main concave aspherical mirror, a secondary convex aspherical mirror, a spectral splitter in the form of an oblique plane-parallel plate mounted in front of the focal plane of a two-mirror system, and a decentralized input a pupil using the unshielded part of the mirror system, and optical systems in the visible and IR channels. The disadvantage of this optical system is the use of an inclined plane-parallel plate as a spectrodivider in a converging beam of rays, which introduces aberrations of an off-center system that cannot be compensated by the aberrations of the centered system and require a compensator with a cylindrical or toric surface. Also, such an optical system provides a low aperture ratio in the television and thermal imaging channels.

The closest in technical essence is a three-channel mirror-lens optical system according to the patent for utility model No. 136198 of 12/27/2013.

This three-channel optical system contains a mirror lens, including a main concave aspherical mirror and a secondary convex aspherical mirror, a lens compensator for the mirror lens for the visible or near infrared range, a common three-lens lens for the middle and far infrared ranges, so that its front focal plane coincides with the rear focal plane of the mirror lens, the first spectrometer, made in the form of an inclined plane-parallel plate and located in parallel a natural beam of rays after a common lens. In addition, a collective lens and a second beam splitter, made in the form of a plane-parallel plate and installed between the main concave and secondary convex mirrors perpendicular to the optical axis, a radiation detector of the visible or near infrared range are introduced. Also, after the first spectro-splitter, a three-lens lens for the far IR range and a far infrared radiation detector, a lens for the middle IR range and a medium IR range radiation detector with a cooled aperture are installed.

The disadvantages of this optical system are small angular fields of view in the space of objects, as well as small values of the relative aperture of all three channels of the optical system and the presence of two aspherical surfaces.

The objective of the present invention is to increase the angular field in the space of objects, increase the relative aperture in each of the channels of the optical system and reduce the number of aspherical surfaces.

The technical result due to the task is achieved by the fact that in a three-channel mirror-lens optical system containing a main concave aspherical mirror, two spectro-dividers and three optical channels for different spectral ranges, in contrast to the known one, a lens component is installed in front of the main concave aspherical mirror, made in the form of a negative meniscus, after the main concave aspherical mirror mounted lens compensator far infrared, the first surface of the per whose component is a spectrodividing surface that transmits the far IR range and reflects the visible (near IR) and short IR ranges common to the visible (near IR) and short IR ranges, a two-lens lens including the first plane-convex lens sequentially located along the rays, the second convex-concave lens, and located so that its front focal plane is offset from the rear focal plane of the mirror lens, and after the common lens is located the second spectrograph in the form of a prism-cube, after passing through which a lens for the short IR range is installed, including three single meniscus-shaped lenses arranged sequentially along the rays, the second meniscus facing the image plane with the convex side and the short-range radiation detector, and after a reflection for the visible (near IR) range from the second spectrometer of the prism-cube is mounted, including five single meniscus-shaped lenses sequentially located along the rays c, the second meniscus facing the image plane with a convex side, and the fourth and fifth concave, and the radiation receiver of the visible (near IR) range, while the following relationships are true:

δ <± 1 diopters,

where δ is the amount of displacement of the front focal plane common for the visible (near IR) and short IR ranges of the lens relative to the rear focal plane of the mirror lens.

Such an optical system provides an increase in the angular field in the space of objects, an increase in the relative aperture in each of the channels of the optical system, and reduces the number of aspherical surfaces.

The optical scheme of a three-channel mirror-lens optical system is shown in figure 1.

The three-channel mirror-lens optical system contains the following elements: mirror-lens A, including the negative meniscus 1 and the main concave aspherical mirror 2; a lens compensator B of a far-infrared mirror lens including a negative meniscus 3 and a positive meniscus 4 facing the image plane with a concave side; far infrared image receiver 5; a first spectrum splitter deposited on the convex side of the negative meniscus 3; a common lens C for the visible (near IR) and short IR ranges, including a plano-convex lens 6 and a convex-concave lens 7; a second spectrum splitter 8; a short-range IR lens D, including a negative meniscus 9 and a positive meniscus 10 facing the image plane with a convex side, a positive meniscus 11 facing the image plane with a concave side; a short IR range detector 12, an E lens for the visible (near IR) range, including a negative meniscus 13 and a positive meniscus 14 facing the image plane with a convex side, a flat convex lens 15, a positive meniscus 16 and a negative meniscus 17 facing the plane images with a concave side; visible (near infrared) radiation receiver 18.

The design parameters of the optical system embodiment are shown in table 1.

The parameters of this embodiment of a three-channel mirror-lens optical system are as follows:

Entrance pupil diameter 90 mm

Angular field in the space of objects:

- channel spectral range 8-13.5 microns (LWIR) 4.8 ° - channel of the spectral range 1-1.6 μm (SWIR) 4.6 ° - channel of the spectral range of 0.5-0.9 microns (V + NWIR) 4.6 °

Relative hole:

- channel spectral range 8-13.5 microns (LWIR) 1: 1.33 - channel of the spectral range 1-1.6 μm (SWIR) 1: 1.66 - channel of the spectral range of 0.5-0.9 microns (V + NWIR) 1: 1.66

The principle of operation of a three-channel mirror-lens optical system is as follows.

Radiation from a distant object passes through the lens 1, made in the form of a negative meniscus, is reflected from a concave aspherical mirror 2 and falls on the first spectrodividing surface, which is the convex surface of the compensator lens 3. The rays passing through the first spectrodividing surface after passing through the lenses 3 and 4 of the compensator B form an image in the plane of the receiver 5. The rays reflected from the first spectrodividing surface create an image in the rear focal plane of the mirror lens A, and then they are converted into beams with a small angular divergence using lenses 6 and 7 of the common lens C. After the common lens C, beams of rays with small angular divergence fall on the second spectrometer 8. The transmitted spectrometer 8 rays passing through Without the lenses 9, 10 and 11 of the lens D, an image is formed in the plane of the receiver 12. The rays reflected by the spectrometer 8, passing through the lenses 13, 14, 15, 16 and 17 of the lens E, form an image in the plane of the receiver 18.

To improve the quality of the optical image, the front focal plane of the common lens C is shifted relative to the rear focal plane of the mirror lens A to convert the transmitted beams into beams with a small angular divergence, while the following relations are true:

δ <± 1 diopters,

where δ is the amount of displacement of the front focal plane of the common lens C relative to the rear focal plane of the mirror lens A.

For each channel we set the quality criterion - the value of the polychromatic contrast transfer coefficient (CPC) and take into account:

- spatial frequency ~ 30 lin / mm (Nyquist frequency for the photodetector (8.0 ÷ 13.5) microns with a sensitive element size equal to 17 microns);

- spatial frequency ~ 25 lin / mm (Nyquist frequency for the photodetector (1.0 ÷ 4.6) μm with a sensor element size of 20 μm);

- spatial frequency ~ 50 lin / mm (Nyquist frequency for the photodetector (0.5 ÷ 0.9) μm with a sensor element size equal to 10 μm).

We obtain the following calculated values of the qualitative characteristics of the optical system:

1. For the optical channel (LWIR) of the spectral range (8.0 ÷ 13.5) μm:

- for a point on the axis PDA = 31% - for a field point of 3.0 mm from the center Images PDA _M = 16% PDA _C = 29% - for the field point 5 mm from the center Images PDA _M = 18% PDA _C = 18%

2. For the optical channel (SWIR) of the spectral range (1.0 ÷ 1.6) μm:

- for a point on the axis PDA = 68% - for a field point 4.0 mm from the center Images PDA _M = 37% PDA _C = 23% - for a field point 6.0 mm from the center Images PDA _M = 22% PDA _C = 19%

3. For the optical channel (V + NWIR) of the spectral range (0.5 ÷ 0.9) μm:

- for a point on the axis PDA = 49% - for a field point 4.0 mm from the center Images PDA _M = 10% PDA _C = 25% - for a field point 6.0 mm from the center Images PDA _M = 7% PDA _C = 6%

As can be seen from the calculations, the optical system, with the simplicity of its design, provides acceptable image quality for optoelectronic devices using a common input channel and three photodetectors:

- microbolometric matrix of the spectral range (8.0 ÷ 13.5) microns with a pixel size of 17 microns;

- photodiode array of the spectral range (1.0 ÷ 1.6) microns with a pixel size of 20 microns;

- CMOS television matrix of the spectral range (0.5 ÷ 0.9) μm with a pixel size of 10 μm.

Claims (3)

A three-channel mirror-lens optical system containing a main concave aspherical mirror, two spectro-dividers and three optical channels for different spectral ranges, characterized in that a lens component made in the form of a negative meniscus is installed in front of the main concave aspherical mirror, and a lens component is installed after the main concave aspherical mirror far infrared compensator, the first surface of the first component of which is a spectrodividing surface, transmitting IR range and reflecting the visible (near IR) and short IR range, common for the visible (near IR) and short IR ranges, a two-lens lens that includes the first plane-convex lens, the second convex-concave lens, and located so so that its front focal plane is shifted relative to the rear focal plane of the mirror-lens lens, and after the common lens there is a spectro-dividing prism-cube, after passing through which a lens for I have a short IR range, which includes three single meniscus-shaped lenses sequentially located along the rays, with the second meniscus facing the image plane with a convex side, and a short IR range radiation receiver, and after reflection from a spectrodividing prism-cube, a lens for the visible (near IR ) range, including sequentially located along the rays of five single lenses in the form of menisci, with the second meniscus facing the image plane with a convex side, and the fourth and fifth - vogn one receiver and Visible radiation (NIR) range, wherein the following relations: δ≤ ± 1 diopters, where δ is the amount of displacement of the front focal plane common for the visible (near IR) and short IR ranges of the lens relative to the rear focal plane of the mirror lens.

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