Frame type anti-scan compensation imaging method under large speed-high ratio

Abstract

The application provides a frame type anti-scanning compensation imaging method under a large speed-height ratio, and particularly relates to a technology for realizing high-quality imaging by adopting frame type anti-scanning motion to compensate for the motion posture of an airplane in a large speed-height ratio flight mode of an airborne photoelectric reconnaissance system. The technology uses the frame motion of the system itself to complete compensation for the airplane motion in an exposure time to keep the image scene gaze, does not need a quick mirror mechanism, has low manufacturing cost, simple algorithm and high portability, solves the problem of imaging smear under a large speed-height ratio, realizes high-quality imaging, lays a foundation for accurate detection and identification of an object, and is suitable for various airborne photoelectric systems using a plane array detector to realize clear imaging.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of automatic control, and mainly relates to a frame type anti-scan compensation imaging technology of an airborne photoelectric reconnaissance system under a large speed-altitude ratio, and particularly relates to a technology for compensating for the flight attitude of an airplane by using a frame type anti-scan motion of an airborne photoelectric reconnaissance system under a large speed-altitude ratio flight mode to achieve high-quality imaging. BACKGROUND

[0002] With the development of science and technology, as the main way of target detection, the imaging quality of an airborne photoelectric system becomes an important indicator for measuring the performance of the equipment and an important prerequisite for target identification and attack. Since a surface array detector has the characteristics of high sensitivity, environmental adaptability and strong anti-interference ability, in order to achieve the detection of a target at a long distance and high-quality imaging, a surface array detector is often used in a photoelectric imaging system, but the exposure time of the surface array detector is relatively long, and if the picture moves within the exposure time, it will cause imaging blur, thereby reducing the image quality.

[0003] When the airborne photoelectric reconnaissance system under a high-speed flight state detects a target, the photoelectric imaging system cannot stare at the same picture within the exposure time due to high-speed flight, so it cannot complete the task of high-quality imaging of the target. Figure 1 As shown in FIG. 1, it is a process of collecting a photo of a scene 1 on the ground by a photoelectric reconnaissance system during the flight of an airplane, and the left and right sides are schematic diagrams of not using frame anti-scan compensation and using frame anti-scan compensation, respectively. When not anti-scanning, the imaging result is the sum of the scene energy during the exposure process of the detector from position A to position C, which is different from the energy distribution of scene 1, so a blurred scene appears; and after anti-scan compensation, the line of sight of the detector is maintained at scene 1, at this time the cumulative energy distribution is approximately scene 1, and the purpose of clear imaging can be achieved.

[0004] The traditional airborne photoelectric reconnaissance method for obtaining high-quality images includes an electronic image stabilization method and a mirror anti-scan method. A patent with the patent number 202011425829 applied by Wuhan Huazhong Tianjing Optical Technology Co., Ltd. discloses a method for compensating for the relative motion of an imaging sensor by using an inertial device and a servo control component to form a stabilized image platform, which solves the problem of image shaking caused by irregular shaking of the photoelectric detection platform with the airplane, but it is only effective when the airplane shakes slightly, and it is not suitable when the airplane shakes in a large range. A patent with the patent number 202010777312 applied by the Xi'an Institute of Applied Optics discloses a method for improving scanning efficiency by using a mirror anti-scan, which generally consists of a main shaft platform carrying a detector and a mirror, and a fast mirror mechanism for anti-scan compensation. This method has fast response rate and small dynamic lag error, but an additional mirror mechanism is needed to complete the anti-scan compensation process. SUMMARY

[0005] In view of the problems of the existing method that the structure is complex and the applicable scope is limited, the present application proposes a method for realizing high-quality imaging of an airborne photoelectric reconnaissance system under high-speed high-altitude ratio flight by using frame-type anti-scan compensation technology, that is, the frame movement of the photoelectric reconnaissance system is controlled by calculating the speed-altitude ratio of the aircraft, so as to compensate the aircraft movement, and the purpose of keeping the scene of the photoelectric reconnaissance system in a clear image during the exposure time of the detector is achieved.

[0006] The technical scheme of the present application is:

[0007] The frame-type anti-scan compensation imaging method under high-speed high-altitude ratio is characterized in that, in an imaging period, the frame-type anti-scan compensation action of the photoelectric reconnaissance system includes the following steps:

[0008] Step 1: initializing the frame position according to the flight attitude, speed and altitude data of the aircraft, waiting to receive an anti-scan start signal, preparing to perform anti-scan movement, if the anti-scan start signal is received, step 2 is performed, otherwise, the frame position is maintained until the anti-scan start signal is received;

[0009] Step 2: calculating the anti-scan speed in real time according to the speed-altitude ratio of the aircraft and performing anti-scan movement at the speed;

[0010] Step 3: judging whether the frame angle meets the start exposure condition, if yes, step 4 is performed, otherwise, step 2 is performed until the start exposure condition is met or timeout;

[0011] Step 4: sending a start exposure signal to the detector and calculating the anti-scan speed in real time to keep the scene staring during the exposure time;

[0012] Step 5: waiting to receive the exposure end signal returned by the detector when the exposure is completed, if the exposure end signal is received, step 6 is performed, otherwise, the anti-scan movement is maintained and the exposure end signal is continuously waited to be received;

[0013] Step 6: calculating the back-scan speed in real time according to the speed-altitude ratio of the aircraft and performing frame back-scan movement;

[0014] Step 7: judging whether the frame reaches the anti-scan starting position, if yes, step 8 is performed, if not, step 6 is performed until the anti-scan starting position is reached;

[0015] Step 8: ending the frame anti-scan this time and preparing to start the anti-scan movement of the next period.

[0016] Further, the anti-scan speed in steps 2 and 4 is:

[0017]

[0018] Wherein:

[0019] V elV represents the angular velocity component of the aircraft's flight in the pitch direction of the electro-optical reconnaissance system; rl θ is the angular velocity component of the aircraft's flight in the roll direction of the electro-optical reconnaissance system; θ is the aircraft's heading angle; e is the eastward velocity; n is the northward velocity; H is the altitude relative to the ground; V is_el V is the anti-sweep angular velocity of the pitch frame; is rl The angular velocity of the roll frame's backsweep.

[0020] Furthermore, the conditions for starting exposure in step 3 are as follows:

[0021]

[0022] in:

[0023] β t1 The pitch angle position at time t1; α t1 Let t1 be the roll angle position; σ is a very small number relative to the frame angle; ε t1 γ is the pitch angle of the carrier aircraft at time t1; t1 Let t1 be the roll angle of the carrier aircraft.

[0024] Furthermore, the scan-back speed in step 6 is:

[0025]

[0026] in:

[0027] V el '、V rl ' represents the angular velocity of the pitch and roll frame retrace, respectively; k is the proportional coefficient, the specific value of which can be changed according to the transmission period of the retrace start signal.

[0028] Furthermore, the criterion for determining whether the frame has reached the anti-scan starting position in step 7 is whether the angle error between the frame angle after calculating the pitch and roll compensated aircraft attitude angles and the anti-scan starting position is less than a minimum number σ, that is:

[0029]

[0030] in:

[0031] β t2 The pitch angle position at time t2; α t2 ε represents the roll angle position at time t2. t2 γ is the pitch angle of the carrier aircraft at time t2; t2 t2 represents the aircraft roll angle; β0 represents the pitch backsweep initiation angle position; α0 represents the roll backsweep initiation angle position.

[0032] The beneficial effects of this invention are reflected in the following aspects:

[0033] 1、The present application does not need fast reflecting mirror and other mechanisms, and has beneficial effects in low-cost manufacturing and structure miniaturization;

[0034] 2、The present application uses the system frame motion to complete the compensation of the carrier motion within the exposure time to keep the image scene gaze, solves the imaging trailing problem under high speed and high ratio, realizes high-quality imaging, and lays a foundation for accurate detection and identification of the object;

[0035] 3、The present application is realized by software, has simple algorithm and high portability, and is suitable for various airborne photoelectric systems using area array detectors to realize clear imaging. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is a schematic diagram of the vertical-to-ground imaging process of the photoelectric reconnaissance system under high speed and high ratio.

[0037] Figure 2 is a schematic diagram of the frame-type anti-scan process under high speed and high ratio.

[0038] Figure 3 is a frame anti-scan principle diagram. DETAILED DESCRIPTION

[0039] The present application will be further described in detail below in combination with the drawings and preferred embodiments.

[0040] The preferred embodiment of the present application is a two-axis two-frame photoelectric reconnaissance system, which is respectively a pitch axis and a roll axis. The system includes a visible light sensor and an infrared sensor, which are used to collect clear images of the photoelectric reconnaissance system for ground reconnaissance during the flight of the carrier under high speed and high ratio. The visible light sensor and the infrared sensor both adopt area array detectors, and the exposure time of the visible light sensor is less than that of the infrared sensor.

[0041] In one imaging cycle, the photoelectric reconnaissance system performs the following specific steps of frame-type anti-scan compensation action:

[0042] Step 1: initialize the frame position according to the flight attitude (heading angle θ, pitch angle ε, roll angle γ) of the aircraft, speed data (eastward speed e, northward speed n) and relative ground height H, wait to receive the anti-scan start signal s1, and prepare to perform the anti-scan motion; if s1 is received, record the time as t0, and perform step 2, otherwise, keep the frame anti-scan starting position until the anti-scan start signal is received;

[0043] The angular velocity components of the carrier motion in the pitch and roll directions of the photoelectric reconnaissance system are calculated through the heading angle θ of the carrier, the eastward speed e, the northward speed n and the relative ground height H:

[0044]

[0045] wherein V el is the component of the angular velocity of the aircraft flight in the pitch direction of the photoelectric reconnaissance system, V rl is the component of the angular velocity in the roll direction;

[0046] According to the experience time T=0.1s, the pitch anti-scan starting angle position β0 and the roll anti-scan starting angle position α0 are calculated respectively:

[0047]

[0048] Step 2: According to the real-time calculation of the speed of the aircraft flight height ratio, the anti-scan speed is calculated and the anti-scan motion in the pitch and roll directions is performed with the speed;

[0049] The angular velocity component of the aircraft flight in the frame of the photoelectric reconnaissance system is calculated by formula (1), and the frame anti-scan angular velocity is obtained:

[0050]

[0051] wherein V is_el is the pitch frame anti-scan angular velocity, V is_rl is the roll frame anti-scan angular velocity.

[0052] Step 3: Determine whether the frame angle β t1 and α t1 at the current time t1 meet the starting exposure condition, if yes, execute step 4, otherwise, execute step 2 until the starting exposure condition is met or step 4 is executed after T1=0.4s;

[0053] The error angle after the photoelectric reconnaissance system compensates the aircraft attitude angle is calculated, if less than σ, it can be considered that the line of sight of the photoelectric reconnaissance system is perpendicular to the ground at this time, that is, the exposure condition is met, and the next action can be performed; if the exposure condition is not met all the time, the next action can also be performed when t1-t0>T1, that is, the starting exposure condition is:

[0054]

[0055] wherein β t1 is the pitch angle position at t1, α t1 is the roll angle position at t1, β t1 and α t1 can be obtained through the angle sensor of the photoelectric reconnaissance system, σ is a very small number compared with the frame angle, σ=0.0017 in the embodiment, ε t1 is the aircraft pitch angle at t1, γ t1 is the aircraft roll angle at t1, ε t1 and γ t1 can be obtained through external communication.

[0056] Step 4: send start exposure signal s2 and s2' to visible light and infrared detector, and calculate the reverse scan speed in real time, while performing reverse scan movement in roll and pitch direction so that the scene does not change within the exposure time, the reverse scan speed is calculated as formula (1), formula (3).

[0057] Step 5: wait to receive exposure end signal s3 and s3' returned when visible light and infrared detector exposure is completed, because the infrared exposure time is greater than visible light, so after visible light exposure ends, reverse scan movement still needs to be performed, wait for infrared exposure to end, if s3' is received, step 6 is executed, otherwise keep reverse scan movement and continue to wait to receive exposure end signal s3 and s3'.

[0058] Step 6: calculate the back scan speed according to the real-time speed ratio of the carrier and perform frame back scan movement;

[0059] The carrier flight speed is decomposed into the angular velocity of the electro-optical reconnaissance system pitch and roll frame by formula (1), because the reverse scan starting position needs to be quickly returned after exposure, in order to ensure that the frame has been in place before the next s1 signal arrives, therefore the back scan speed needs to be greater than the reverse scan speed, in the formula k>1, the specific size can be changed according to the sending period of s1 signal, that is, the back scan speed is:

[0060]

[0061] In the formula, V el ' and V rl ' are the angular velocities of the pitch and roll frame back scan, k is the proportional coefficient, in order to quickly reach the reverse scan starting angle position, the value of k should be greater than 1, in this embodiment k=2.

[0062] Step 7: determine whether the frame has reached the reverse scan starting position, if so, execute step 8, if not, execute step 6 until the reverse scan starting position is reached;

[0063] The reverse scan starting position of pitch and roll is obtained in real time by formula (1), formula (2), calculate the angular error between the frame angle after compensating the carrier attitude angle of pitch and roll and the reverse scan starting position angle, if it is less than the minimum number σ, it is considered that the frame has reached the reverse scan starting position at this time, that is, the next step can be executed, that is:

[0064]

[0065] In the formula, β t2 is the pitch angle position at t2, α t2 is the roll angle position at t2, ε t2 is the carrier pitch angle at t2, γ t2is the roll angle of the carrier at time t2, β0 is the initial angle position of the pitch anti-scan, and a0 is the initial angle position of the roll anti-scan.

[0066] Step 8: end the current frame anti-scan compensation movement, and prepare to start the anti-scan movement of the next period.

[0067] When the carrier moves at a flight height of 1000 m, a flight speed of 180 km / h, and a north deviation of 30° east, visible light and infrared photos of the photoelectric reconnaissance system using the embodiment and not using the method of the application are collected respectively, in addition, pictures in a static state are collected as standard images, and the variance method is used to evaluate the quality of the images. Through analysis, it can be obtained that the quality of the visible light and infrared images not using the method can reach 55% and 47% of the standard images, and the quality using the method can reach 90% and 85%.

[0068] Finally, it should be noted that the features mentioned and / or shown in the above description of the exemplary embodiments of the application can be combined in the same or similar manner into one or more other embodiments, combined with or replace the corresponding features in other embodiments. The technical solutions obtained by combining or replacing should also be considered to be included in the protection scope of the application.

Claims

1. A frame-based inversion scan compensation imaging method at high speed-high ratio, characterized in that, In one imaging cycle, the photoelectric reconnaissance system performs the frame anti-scan compensation action, which comprises the following steps: Step 1: initializing the frame position according to the flight attitude, speed and height data of the aircraft, waiting for receiving the anti-scan start signal, preparing to perform the anti-scan motion, if the anti-scan start signal is received, performing step 2, otherwise, maintaining the frame position until the anti-scan start signal is received; Step 2: calculating the anti-scan speed according to the real-time speed-height ratio of the carrier aircraft and performing the anti-scan motion at the speed; Step 3: judging whether the frame angle meets the start exposure condition, if yes, performing step 4, otherwise, performing step 2 until the start exposure condition is met or the time is up; Step 4: sending the start exposure signal to the detector and maintaining the scene gaze by calculating the anti-scan speed in real time within the exposure time; Step 5: waiting for receiving the exposure end signal returned by the detector when the exposure is completed, if the exposure end signal is received, performing step 6, otherwise, maintaining the anti-scan motion and continuing to wait for receiving the exposure end signal; Step 6: calculating the back-scan speed according to the real-time speed-height ratio of the carrier aircraft and performing the frame back-scan motion; Step 7: judging whether the frame reaches the anti-scan starting position, if yes, performing step 8, if not, performing step 6 until the anti-scan starting position is reached; Step 8: ending the frame anti-scan this time and preparing to start the anti-scan motion of the next cycle; The anti-scan speed in steps 2 and 4 is: Wherein: is the angular velocity component of the aircraft flight in the pitch direction of the electro-optical reconnaissance system; is the angular velocity component of the aircraft flight in the roll direction of the electro-optical reconnaissance system; is the heading angle of the aircraft; is the eastward velocity; is the northward velocity; is the relative height above the ground; is the pitch frame counter-slew angular velocity; is the roll frame counter-slew angular velocity.

2. The method of claim 1, wherein the frame rate is 60 Hz or more. The start exposure condition in step 3 is: Wherein: is the instantaneous pitch angle position; is the instantaneous roll angle position; is a small number compared to the frame angle; is the instantaneous airframe pitch angle; is the instantaneous airframe roll angle.

3. The high-speed, high-ratio frame-type reverse scanning compensation imaging method as described in claim 1, characterized in that, The back-scan speed in step 6 is: Wherein, , are the angular velocities of the pitch and roll frame slews, respectively; k is a proportional coefficient, whose value can be changed according to the transmission period of the reverse-slew start signal.

4. The high-speed, high-ratio frame-type reverse scanning compensation imaging method as described in claim 1, characterized in that, The standard for determining whether the frame reaches the reverse-scan starting position in step 7 is whether the angle error between the frame angle after the pitch and roll compensation of the carrier attitude angle and the angle of the reverse-scan starting position is less than a minimum number That is: Wherein: is the pitch angle position at the moment; is the roll angle position at the moment; is the pitch angle of the carrier at the moment; is the roll angle of the carrier at the moment; is the pitch anti-scan start angle position; is the roll anti-scan start angle position.

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