RU2150725C1 - Device for remote generation of images in thermal region of spectrum - Google Patents

Abstract

FIELD: optical instrumentation. SUBSTANCE: invention is suggested for generation of thermal images of surface of the Earth from space and aviation carriers of various classes. Device incorporates case housing scanning mirror, objective lens, N filters and N radiation detectors installed in sequence and optically intercoupled, cooling system linked to radiation detectors and rotation motor whose axis matches optical axis of objective lens. Scanning mirror is made fast to axis of rotation motor and is positioned at angle of 45 deg with regard to its axis. First and second flat mirrors are installed in case on two sides of scanning mirror and in opposition with each other. Each flat mirror is optically coupled to scanning mirror independently. Proper filter is mounted on each of N radiation detectors. Flat mirror of device can be put on mechanism of discrete turn made fast to case. Third flat mirror optically coupled to scanning mirror can also be inserted into device. Technical objective of invention lies in generation of thermal images of examined surface simultaneously at different angles of sighting in several spectral ranges which allows effects of atmosphere to be corrected and precision of measurement of temperature of examined objects to be realized with result better than 0.1 K. EFFECT: generation of improved thermal images of examined surfaces. 3 cl, 5 dwg

Description

 The invention relates to the field of optical instrumentation and is intended to obtain thermal images of the Earth's surface from space and aircraft carriers of various classes.

A device for remote imaging is known, which contains sequentially mounted and optically interconnected scanning mirrors, a lens and a radiation receiver, as well as a rotation motor. In the device, the axis of the rotation motor coincides with the optical axis of the lens, and the scanning mirror mounted on the axis of the rotation motor makes an angle not equal to 45 ^o with its axis. This device provides a circular scan, since its axis of sight is inclined at an angle to the surface under study (Miroshnikov M.M. Theoretical Foundations of Optoelectronic Devices, 1977, p. 99).

 A disadvantage of the known device is that it does not allow to obtain images simultaneously in several spectral ranges and the angle of inclination of the axis of sight cannot be changed during the measurement.

A device is known for remote imaging in the thermal region of the spectrum, comprising a housing in which a scanning mirror, a lens, a filter and a radiation receiver are sequentially mounted and optically connected to each other, and a cooling system and a rotation motor are located, the axis of which coincides with the optical axis of the lens and rigidly connected with the scanning mirror set at an angle of 45 ^o to the axis of rotation of the engine, wherein the lens, the radiation receiver, the cooling system and the engine rotation rigidly fixed in the housing and cooling system is connected with the radiation receiver. The device provides scanning in a plane passing through the local vertical and perpendicular to the direction of media movement (Hasel PO, J., et al. "Michigan Experimental Multispectral Mapping System: A Description of the M7 Airborne Sensor and Its Performance", Environmental Research Institute of Michigan, Ann Arbor, Mich., 1974).

 The above device for remote imaging in the thermal region of the spectrum according to the functional structural diagram is closest to the invention and is selected as a prototype.

 A disadvantage of the known device is that it does not allow to obtain images of the investigated surface in the thermal region of the spectrum simultaneously at different viewing angles in several spectral ranges.

 This leads to the fact that the error in determining the temperature of objects from one image in the thermal region of the spectrum reaches several degrees, since it is known that the radiation of the earth's surface is strongly distorted by the atmosphere, and the influence of the atmosphere is random in nature, because it is determined by spatio-temporal changes in atmospheric parameters ( temperature, humidity, aerosol, small gas impurities, etc.).

 The objective of the invention is to provide a device for remote image acquisition in the thermal region of the spectrum, which allows simultaneous obtaining of thermal images of the studied objects at different viewing angles in the N spectral ranges using a single optical system, which will allow for the combined influence of the atmosphere to be taken into account and thereby increase accuracy of remote measurement of temperature of objects.

The essence of the invention lies in the fact that in a known device for remote image acquisition in the thermal region of the spectrum, comprising a housing in which a scanning mirror, a lens, a filter and a radiation receiver are sequentially mounted and optically connected, a cooling system and a rotation motor are located, the axis of which coincides with the optical axis of the lens and is rigidly connected with a scanning mirror mounted at an angle of 45 ^o to the axis of the rotation motor, the lens, radiation receiver, cooling system The mountings and the rotation motor are rigidly fixed in the housing, and the cooling system is connected to the radiation receiver, the first and second plane mirrors, N-1 filters and N-1 radiation receivers are introduced, the first and second plane mirrors being installed on both sides of the scanning mirror and opposite between each flat mirror is optically independently connected with a scanning mirror, the normals to the surfaces of the flat mirrors lie in the same plane passing through the axis of the rotation motor, the flat mirrors are installed in the housing at different angles relative to the axis of the rotation engine, each of the N-1 radiation receivers and the corresponding filter mounted on it are rigidly fixed to the housing, each of the N-1 radiation receivers is connected to the cooling system, N radiation receivers are located on the line formed by the focal plane of the lens and the plane in which are the normals to the surfaces of flat mirrors.

 In addition, at least one of the flat mirrors is connected to the housing through a discrete rotation mechanism that changes the angle of inclination of the flat mirror relative to the axis of the rotation motor, which ensures a change in the viewing angle during operation of the device.

To ensure simultaneously with transverse scanning of the longitudinal (along the path of carrier movement) a third flat mirror is installed in the housing, optically coupled to a scanning mirror, the normal to the surface of which lies in a plane passing through the axis of the rotation motor and perpendicular to the plane formed by the normals to the surfaces of the first and second flat mirrors, and makes with the axis of the engine rotation angle of 45 ^o .

 The invention is illustrated by drawings.

 In FIG. 1 shows a functional block diagram of a device for remote imaging in the thermal region of the spectrum.

 In FIG. 2, 3, functional structural diagrams of modifications of the device for remote image acquisition in the thermal region of the spectrum are shown.

 In FIG. 4 is an illustration of the image acquisition process for transverse scanning.

 In FIG. 5 is an illustration of an image acquisition process with simultaneous transverse and longitudinal scanning.

 A device for remote image acquisition in the thermal region of the spectrum (Fig. 1) contains a housing 1, a scanning mirror 2, a lens 3, N filters 4 (1 ... N), N radiation receivers 5 (1 ... N), system 6 cooling engine 7 rotation and flat mirrors 8, 9.

 A device for remote image acquisition in the thermal region of the spectrum (Fig. 2) further comprises a discrete rotation mechanism 10.

 A device for remote image acquisition in the thermal region of the spectrum (Fig. 3) further comprises a discrete rotation mechanism 10 and a third flat mirror 11.

 In FIG. 4 are indicated: 1 - the path and direction of movement of the carrier, 2 - the position of the carrier (I-II), 3 - the path of the scan line of the device for the viewing angle α1 in position I-II for the N-th spectral range, 4 - the path of the scan line of the device for viewing angle α2 in position I-II for the N-th spectral range, A - the object under study.

 In FIG. 5 are marked: 1 - the path and direction of movement of the carrier, 2 - the position of the carrier (I-II), 3 - the path of the scan line of the device for the viewing angle α1 in position I-II for the N-th spectral range, 4 - the path of the scan line of the device for viewing angle α2 in position I-II for the N-th spectral range, A is the object under study, 5 is the trajectory of the scan line, oriented in the direction of movement of the carrier.

In the device for remote image acquisition in the thermal region of the spectrum (Fig. 1) in the housing 1, a scanning mirror 2, a lens 3, N filters 4 (1 ... N) and N receivers 5 (1. .N) radiation, as well as a cooling system 6 connected to the radiation receivers 5 (1 ... N), and a rotation motor 7, the axis of which coincides with the optical axis of the lens 5. The scanning mirror 2 is rigidly connected with the axis of the rotation motor 7 and set at an angle of 45 ^o to its axis. Flat mirrors 8, 9, the first and second, are installed in the housing 1 from two sides relative to the scanning mirror 2 and opposite to each other, with each flat mirror 8, 9 optically independently connected with the scanning mirror 2. The flat mirrors 8, 9 are rotated at different angles relative to the axis of the rotation motor 7, and the normals to their surfaces lie in one plane passing through the axis of the rotation motor 7. On each of the N receivers 5 (1 ... N) radiation, a corresponding filter 4 (1 ... N) is installed. The radiation receivers 5 (1 ... N) are located on a line formed by the focal plane of the lens 3 and the plane in which the normal to the surfaces of the flat mirrors 8, 9 lie. Flat mirrors 8, 9, the lens 3, N of the receivers 5 (1 .. .N) radiation, the cooling system 6 and the rotation motor 7 are rigidly fixed to the housing 1.

 In the device for remote image acquisition in the thermal region of the spectrum (Fig. 2), a flat mirror 8 is mounted on a discrete rotation mechanism 10, which is rigidly fixed to the housing 1.

In the device for remote image acquisition in the thermal region of the spectrum (Fig. 3), a third flat mirror 11 is mounted rigidly to the housing 1 and is optically coupled to a scanning mirror 2. The normal to the surface of the third flat mirror 11 lies in a plane passing through the axis of the rotation motor 7 and perpendicular to the plane formed by the normals to the surfaces of the first and second plane mirrors 8, 9 and makes an angle of 45 ^o with the axis of the rotation motor 7.

 A device for remote image acquisition in the thermal region of the spectrum operates as follows.

 The radiation flux reflected from the investigated surface enters the flat mirrors 8, 9 (Fig. 1).

Flat mirrors 8, 9 before installing the device on a carrier (space or aviation) are installed so that the normals to their surfaces lie in the same plane passing through the axis of the rotation motor 7 and the direction of movement of the carrier, and the reflecting surfaces of the mirrors make up the axis of the rotation motor 7, respectively angles of 45 ^o + α1 / 2 and 45 ^o + α2 / 2. In this case, the device provides images (Fig. 4, 5) at viewing angles α1 and α2.

 When the scanning mirror 2 is turned to the flat mirror 8, it receives only radiation from the flat mirror 8, which the scanning mirror 2 reflects on the input of the lens 3. The lens 3 focuses the incoming radiation on 1 to N radiation receivers 5, each of which has one of N filters 4. N radiation receivers 5 are arranged linearly at regular intervals in the focal plane of the lens 3, and the radiation receiver 5 (N / 2) is placed on the optical axis of the lens 3, and the line formed by the N radiation receivers 5 is oriented along board vehicle movement. To cool N receivers 5 to the desired temperature, they are connected to the cooling system 6. Since filters 4 are installed in front of radiation receivers 5, each of which forms a selective radiation stream, and radiation receivers 5 (1 ... N) have independent outputs, N independent analog information flows are formed at the device output, each of which carries information about the investigated surface in the corresponding spectral range. Next, the analog signals are converted to digital and transmitted to a storage device (not shown in Fig. 1-3).

 The number of radiation receivers 5 determines the number of spectral channels of the device.

 Since the receivers 5 of the radiation in the direction of movement of the carrier are not spatially aligned, the images obtained in different spectral ranges will also not be aligned in the frame. The magnitude of the image shift for the N-th spectral range is LxN / 2 lines, where L is the distance between the sensitive areas of two adjacent N radiation receivers 5, d is the size of the sensitive area.

Since the scanning mirror 2 is mounted on the rotation motor 7, when the scanning mirror 2 is rotated 180 ^°, its reflecting surface is rotated to the flat mirror 9. In this case, only the radiation reflected from the flat mirror 9 is transmitted to the scanning mirror 2. Reflected by the scanning mirror 2 radiation from the lens 3 focuses on N radiation receivers 5.

 Thus, in the device with the help of mirrors 8, 9, two independent optical branches are formed, turned at an angle | α1 | - | α2 | the common elements of which are scanning mirror 2, lens 3, N filters 4 and N radiation receivers 5, and at the output of each of N radiation receivers 5, a sequence of two analog signals is formed when the scanning mirror 2 is rotated: the first corresponds to the radiation flux reflected from the surface at an angle α1, the second at an angle α2.

 Since the line scan in the device is carried out when the scanning mirror 2 is rotated by the rotation motor 7, and the frame scan is performed by the media movement, N information arrays are formed at the output of the device, each of which corresponds to one of the N spectral ranges and allows to obtain two thermal images obtained under different angles of sight.

 It should be noted that since both images are recorded by the device at the same time, and the axis of sight are directed at different angles, the images are shifted in frame. Let it be required to measure the temperature of the object at point A (Fig. 4) at angles α1 and α2 in the N-th spectral range. When approaching position I, the device turns on. In position I, the nth line is formed, containing signals from surface elements located on lines 3 (I) and 4 (I). In position II, the (n + k) th row is formed, containing elements located on lines 3 (II) and 4 (II). Then the signal from the object A is located simultaneously in the n-th line of the first image of the frame and the (n + k) -th line of the second image of the frame.

 The obtained images are first subjected to geometric correction, since with oblique sounding there are significant geometric distortions, after which the temperature of the objects is determined. To determine the temperature of a specific object from the obtained data arrays, 2N values of signals belonging to this object are extracted, which are jointly processed.

Angular methods for measuring temperature are based on the possibility of solving the direct problem of radiation transfer in the atmosphere. The radiation from the object-atmosphere system can be represented as:
I (λ, α) = I _s (λ, α) t (λ, α) + I $\genfrac{}{}{0ex}{}{\text{↑}}{\text{a}}$ (λ, α),
where t (λ, α) and I $\genfrac{}{}{0ex}{}{\text{↑}}{\text{a}}$ (λ, α) is the transmission and upward radiation of the atmosphere, I _s (λ, α) is the radiation of the surface.

I _s (λ, α) = I _e (λ, α) + I _r (λ, α),
where I _e (λ, α) is the intrinsic radiation of the surface, I _r (λ, α) is the reflected radiation of the surface.

I _e (λ, α) = ε (λ, α) B _λ (T),
where ε (λ, α) is the emissivity of the object, B _λ (T) is the Planck function. The solution of these equations for different viewing angles allows you to increase the accuracy of measuring the temperature of objects more than 10 times.

 The capabilities of the device can be significantly expanded.

 So, installing a flat mirror 8 on the discrete rotation mechanism 10 (Fig. 2) allows you to widely vary the angle of inclination of the flat mirror 8 relative to the axis of the rotation motor 7 and thereby change the viewing angle α1 during operation of the device. Similarly, a flat mirror 9 can be installed.

An introduction to the optical circuit of the device (Fig. 3) in front of the scanning mirror 2 of the third plane mirror 11, optically coupled to it, the normal to the surface of which lies in the plane passing through the axis of the rotation motor 7 and perpendicular to the plane formed by the normals to the surfaces of the plane mirrors 8, 9, and makes an angle of 45 ^° with the axis of the rotation motor 7, which makes it possible to realize a third optical branch in the device. In this case, at the output of N radiation receivers 5, a sequence of three analog signals is formed.

With the arrangement of the mirror 11, as shown in FIG. 3, the scan line 5 (Fig. 5) of the third branch will be oriented in the direction of the carrier’s flight, which allows measuring the temperature of objects lying along the carrier’s path for sight angles from -40 to +40 ^o relative to the local vertical with a step equal to the instantaneous field device, which allows you to restore the indicatrix emissivity of objects located on the path of movement of the carrier. To restore the indicatrix of the emissivity of the object from the image obtained using the third flat mirror 11, a sequential selection is made from all the rows of signal values corresponding to this object. The data obtained characterize the optical-physical parameters of the object, which also allows to increase the accuracy of temperature measurement.

 The proposed device for remote image acquisition in the thermal region of the spectrum allows one to obtain thermal images of the investigated surface simultaneously at different viewing angles in several spectral ranges, which, when processing the images obtained, allows for correcting the influence of the atmosphere and realizing the accuracy of measuring the temperature of the studied objects better than 0.1K.

 The relevance of the problem, namely the ability to detect thermal anomalies, the study of the interaction of the atmosphere and the surface, environmental control, etc., as well as the relatively low cost, provide the device with practical application.

Claims (3)

1. A device for remote image acquisition in the thermal region of the spectrum, comprising a housing in which a scanning mirror, a lens, a filter and a radiation receiver are sequentially mounted and optically connected to each other, as well as a cooling system and a rotation motor, the axis of which coincides with the optical axis of the lens and rigidly connected with a scanning mirror set at an angle of 45 ^o to the axis of rotation of the engine, wherein the lens, the radiation receiver, the cooling system and the engine rotation rigidly fixed to Corp. All, and the cooling system is connected to a radiation receiver, characterized in that the first and second flat mirrors, N - 1 filters and N - 1 radiation receivers are introduced into it, the first and second flat mirrors mounted on both sides of the scanning mirror and opposite to each other , each flat mirror is optically independently connected with a scanning mirror, the normals to the surface of the flat mirrors lie in one plane passing through the axis of the rotation motor, the flat mirrors are mounted in the housing at different angles with respect to the axis of the engine For rotation, each of N - 1 radiation receivers and the corresponding filter installed on it are rigidly fixed to the housing, each of N - 1 radiation receivers is connected to the cooling system, N radiation receivers are located on the line formed by the focal plane of the lens and the plane in which they lie normal to the surfaces of flat mirrors.  2. A device for remote image acquisition in the thermal region of the spectrum according to claim 1, characterized in that at least one of the flat mirrors is connected to the housing through a discrete rotation mechanism that changes the angle of inclination of the flat mirror relative to the axis of the rotation motor. 3. A device for remote image acquisition in the thermal region of the spectrum according to claim 1 or 2, characterized in that a third flat mirror is mounted on the housing, optically coupled to a scanning mirror, the normal to the surface of which lies in a plane passing through the axis of the rotation motor and perpendicular the plane formed by the normals to the surfaces of the first and second plane mirrors, and makes an angle of 45 ^o with the axis of the rotation motor.

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