A method for clarifying thermal imaging images

Abstract

The present invention relates to the field of thermal imaging, and specifically to a method for clarifying thermal imaging images. This method first creates a distance-temperature-field-of-view-focus value table A and a distance-turntable horizontal angle-turntable pitch angle table 2. Then, after turntable or lens control begins, an orientation table B is identified and searched based on orientation information. After data comparison, a distance value is obtained. This distance value is then entered into table A and compared with the field of view and temperature factors for rapid positioning, resulting in the clearest image. Simultaneously, an algorithm for constructing orientation table B begins operation. If a sudden change in clarity occurs, the current position is recorded in table C of suspicious points, and the table data is updated at an appropriate time. After leaving the factory, the method can automatically learn and correct according to usage conditions, overcoming scene changes and ensuring that the device consistently maintains excellent image clarity.

Description

Technical Field

[0001] The present invention relates to the field of thermal imaging, in particular to a method for clarifying thermal imaging images. Background Art

[0002] Thermal imaging lenses use a DC motor to drive gears to control the relative position of the lens, thereby adjusting the focal distance and field of view. Traditional methods of controlling lens zoom or turntable movement keep the focus gear in a fixed position, requiring manual focus adjustment or triggering autofocus when switching observation points or fields of view. Both manual and autofocus adjustments are time-consuming. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for clarifying thermal imaging images, which uses the target distance for a thermal imager device installed in a fixed position and locates the appropriate focus value according to the current field of view angle and temperature.

[0004] In order to solve the above technical problems, the present invention adopts a technical solution: a method for clarifying thermal imaging images, comprising the following steps:

[0005] S01. Construct Table A and Table B. Table A is a table of focus AD values ​​corresponding to different temperatures, fields of view, and distances. Table B is a table of distances corresponding to different turntable horizontal and pitch angles. The distance is the distance between the turntable and the target.

[0006] S02: Start controlling the zoom of the lens or turntable, and obtain the temperature, field of view, turntable horizontal angle, and pitch angle in real time;

[0007] S03. Look up Table B according to the turntable horizontal angle and pitch angle to obtain the corresponding distance, and then calculate the focus AD value from Table A;

[0008] S04, determining whether the image clarity suddenly decreases during the control process, if yes, proceed to the next step, otherwise return to step S02;

[0009] S05. Record the angle, field of view, temperature, distance, focus AD value, clarity and control status at this time and store them in Table C;

[0010] Step S06: Return to the point in Table C, and use forward and backward focus fine-motion to search for the latest clear point. Under the same conditions, determine whether the focus AD clarity of the fine-motion search point is higher than that of the unclear point and conforms to the change pattern. If not, it is considered a misjudgment and this information in Table C is deleted. If so, proceed to step S07.

[0011] S07. Determine whether the current condition is triggered by the turntable control. If not, delete this information in Table C. If yes, reversely calculate the corresponding azimuth and pitch angles according to Table A and store them in Table B.

[0012] Furthermore, the image clarity during the control process is judged according to the curve output by the clarity evaluation function combined with the filtering algorithm. If the image clarity of the two frames before and after is greater than 150, it is considered that the image clarity has suddenly become low.

[0013] Furthermore, when executing step S03, if the table does not contain the distances corresponding to the horizontal and pitch angles of the turntable, a solution is performed, and the solution formula is:

[0014] ,

[0015] Where D is the distance to be calculated, H is the height of the target, and A is the pitch angle of the target.

[0016] Furthermore, after the lens zoom is completed, it is determined whether the difference between the focus AD value at the stop position and the focus AD value at the final positioning position is within the set threshold. If it is within the set threshold, it means that the record in Table B is correct. If it is not within the threshold range, the data is reconstructed to generate a set of horizontal angles, pitch angles, and distances and store them in Table B.

[0017] Furthermore, the data reconstruction process is:

[0018] ,

[0019] Where D is the distance to be calculated, H is the height of the target at the stop position, and A is the pitch angle of the target at the stop position.

[0020] Furthermore, step S06 is performed after the thermal imager is idle or manually authorized.

[0021] The beneficial effects of the present invention are as follows: Traditional equipment observation requires manual control of focus or use of automatic focus to search and locate over a large range, and the focusing time is relatively long. The present focusing algorithm runs at the program speed and can maintain a good clarity effect regardless of the control process of the turntable or the lens.

[0022] This focusing algorithm has learning capabilities. The distance in the orientation table is both the approximate calculated distance and the parameter for focusing compensation, which can overcome the impact of equipment aging.

[0023] Thermal imaging effects are easily affected by temperature. The introduction of temperature variables in this focusing algorithm can offset most of the imaging effects caused by environmental changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Flowchart of this method;

[0025] Figure 2 It is a trend chart of the clarity change of the control process;

[0026] Figure 3Schematic diagram of distance calculation. DETAILED DESCRIPTION

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0028] Example 1

[0029] This embodiment discloses a method for clearing thermal imaging images. Figure 1 As shown, the method includes the following steps:

[0030] S01. Construct Table A and Table B. Table A lists focus AD values ​​corresponding to different temperatures, fields of view, and distances. Table B lists distances corresponding to different turntable pan and tilt angles. The distances are the distances between the turntable and the target. The distance variables in Table B can be updated. Rapid positioning is achieved by combining these two tables.

[0031] Table A

[0032]

[0033] Table B

[0034]

[0035] In Table B, NULL indicates that there is no target object beyond three kilometers. In optics, this distance can be considered infinite, and the depth of field here is close.

[0036] S02: The lens or turntable zoom control starts, and the temperature, field of view angle, turntable horizontal angle and pitch angle are obtained in real time.

[0037] S03. Look up Table B according to the turntable horizontal angle and pitch angle to obtain the corresponding distance, and then calculate the focus AD value from Table A.

[0038] S04. Determine whether the image clarity suddenly decreases during the control process. If yes, proceed to the next step; otherwise, return to step S02.

[0039] Figure 2 Schematic diagram of the clarity collected during control. 2A and 2C show the clarity changes when the zoom of a fixed scene is changed, and 2B and 2D show the clarity changes when the turntable is moved. The close-up in the middle of 2B causes a sudden change in clarity.

[0040] This embodiment determines the image clarity during the control process by combining a filtering algorithm with a curve output by a clarity evaluation function. If the image clarity of the two preceding and following frames is greater than 150, it is considered that the image clarity has suddenly decreased.

[0041] S05. Record the angle, field of view, temperature, distance, focus AD value, clarity and control status at this time and store them in Table C.

[0042] S06. When the thermal imager is idle or manually authorized, it returns to the point position in Table C, and searches for the latest clear point by fine-tuning the focus forward and backward. It is determined whether the focus AD clarity of the fine-tuning search point is higher than that of the unclear point under the same conditions and conforms to the change pattern. If not, it is considered a misjudgment and this information in Table C is deleted. If yes, proceed to step S07.

[0043] S07. Determine whether the current condition is triggered by the turntable control. If not, delete this information in Table C. If yes, reversely calculate the corresponding azimuth and pitch angles according to Table A and store them in Table B.

[0044] When executing step S03, if the table does not contain the distances corresponding to the turntable horizontal and pitch angles, a solution is performed, and the solution formula is:

[0045] ,

[0046] Where D is the distance to be calculated, H is the height of the target, and A is the pitch angle of the target.

[0047] After the lens zoom is completed, determine whether the difference between the focus AD value at the stop position and the focus AD value at the final positioning position is within the set threshold. If it is within the set threshold, it means that the record in Table B is correct. If it is not within the threshold range, reconstruct the data and generate a set of horizontal angle, pitch angle, and distance to store in Table B. Figure 3 As shown, the process of reconstructing the data is:

[0048] ,

[0049] Where D is the distance to be calculated, H is the height of the target at the stop position, and A is the pitch angle of the target at the stop position.

[0050] A thermal imager is used with a turntable, which allows for horizontal and vertical rotation and a variable field of view, enabling 360-degree observation of the surrounding environment. Knowing the turntable's angle, since its installation position is fixed, the target distance has a fixed relationship with the turntable's position. This means that observation clarity and the turntable's angle have a direct relationship. The azimuth table construction algorithm continuously updates and refines this relationship. When executing device control, the focus AD value is derived based on the turntable's azimuth and pitch angles, field of view, and temperature.

[0051] During the traversal process of the suspicious point storage table C, the image changes linearly during the turntable and lens control process. Based on the curve output by the clarity evaluation function combined with the filtering algorithm, if there is a large and continuous sudden change in clarity in the middle, the point is identified as a suspicious point and stored in table C. When the machine is idle or after manual authorization, it traverses the suspicious points and performs fine-focusing to re-search for the clearest point.

[0052] In the control stop inspection process, if the user controls the focus change after the turntable control stops, if the difference between the stop position focus AD and the final positioning position is within 10, it proves that the current position table B corresponds accurately. If the difference is large and within the filtering range, the AD average value is taken to recalculate the distance and construct it into the orientation table B to improve accuracy.

[0053] The purpose of the data comparison process is to compare the results output during the traversal process of the suspicious point storage table C. If the two clearest focused AD results are basically the same, it means that this place was already the clearest at that time and does not need to be rebuilt; if the difference is large but it is not within the filtering range, this place is considered to be temporary interference and discarded; if the difference is large and is within the filtering range, it proves that the distance has suddenly changed due to reasons such as terrain or buildings. The distance value here is reversely inferred and updated to the orientation table B to improve accuracy.

[0054] After the focus AD value is obtained, focus positioning is performed. Experimental verification shows that the image is always clear during continuous control.

[0055] Azimuth construction table B1 is constructed using a two-dimensional array. The first data element is the horizontal angle X(n), and the second is the pitch angle Z(n). The size of array n is 180*40. The array is initialized using an ideal state format based on the known height of the observation point, and distance can be derived using trigonometric functions. During the device's later turntable control operation, if a sudden drop in clarity occurs, the device automatically determines the distance based on the lens's field of view angle-distance-focus relationship and updates it to Table B. After the turntable stops, the device automatically checks the current position and distance. If it is not a clear position, the data is reconstructed to generate a set of (X(n), Z(n), D(n)) values, which are then updated to Table B using the orientation table construction algorithm.

[0056] During the operation of the device, after adjusting the azimuth, the device searches Table B according to the azimuth and elevation data to obtain the distance to this point.

[0057] like Figure 3 As shown, the azimuth distance (P6) is calculated using trigonometric functions. Given that the tower height is H and the pitch angle is A, then .

[0058] The construction algorithm adopts the update value algorithm. After the array is initialized, the first dimension represents the distance information. When the new element (X(n), Z(n), D(n)) is updated, the first dimension is facilitated to find the array subscript m closest to the updated data and replace (X(m), Z(m), D(m)) with (X(n), Z(n), D(n)).

[0059] As the device runs for a long time, the array is continuously updated and the internal data becomes more and more accurate.

[0060] Lens Table B is constructed using a three-dimensional array. Array initialization uses manual calibration, adjusting the field of view, target distance, and sharpness, recording the ambient temperature, and then saving the data. To ensure accurate variable calculation, this data is open to the calibration interface but does not automatically update the data.

[0061] The above description is only the basic principle and preferred embodiments of the present invention. Improvements and substitutions made by those skilled in the art based on the present invention fall within the protection scope of the present invention.

Claims

1. A method for clarifying thermal imaging images, characterized by: The following steps are involved: S01. Construct Table A and Table B. Table A is a table of focus AD values ​​corresponding to different temperatures, fields of view, and distances. Table B is a table of distances corresponding to different turntable horizontal and pitch angles. The distance is the distance between the turntable and the target. S02: Start controlling the zoom of the lens or turntable, and obtain the temperature, field of view, turntable horizontal angle, and pitch angle in real time; S03. Look up Table B according to the turntable horizontal angle and pitch angle to obtain the corresponding distance, and then calculate the focus AD value from Table A; S04, determining whether the image clarity suddenly decreases during the control process, if yes, proceed to the next step, otherwise return to step S02; S05. Record the angle, field of view, temperature, distance, focus AD value, clarity and control status at this time and store them in Table C; Step S06: Return to the point in Table C, and use forward and backward focus fine-motion to search for the latest clear point. Under the same conditions, determine whether the focus AD clarity of the fine-motion search point is higher than that of the unclear point and conforms to the change pattern. If not, it is considered a misjudgment and this information in Table C is deleted. If so, proceed to step S07. S07. Determine whether the current condition is triggered by the turntable control. If not, delete this information in Table C. If yes, reversely calculate the distance corresponding to the azimuth and pitch angles according to Table A and store it in Table B.

2. The thermal imaging image clearing method according to claim 1, characterized in that: The image clarity during the control process is judged based on the curve output by the clarity evaluation function combined with the filtering algorithm. If the image clarity of the two frames before and after is greater than 150, it is considered that the image clarity has suddenly become low.

3. The thermal imaging image clearing method according to claim 1, characterized in that: When executing step S03, if the table does not contain the distances corresponding to the turntable horizontal and pitch angles, a solution is performed, and the solution formula is: ， Where D is the distance to be calculated, H is the height of the target, and A is the pitch angle of the target.

4. The thermal imaging image clearing method according to claim 1, characterized in that: After the lens zoom is completed, determine whether the difference between the focus AD value at the stop position and the focus AD value at the final positioning position is within the set threshold. If it is within the set threshold, it means that the record in Table B is correct. If it is not within the threshold range, reconstruct the data and generate a set of horizontal angle, pitch angle, and distance and store them in Table B.

5. The thermal imaging image clearing method according to claim 4, characterized in that: The process of reconstructing the data is: ， Where D is the distance to be calculated, H is the height of the target at the stop position, and A is the pitch angle of the target at the stop position.

6. The thermal imaging image clearing method according to claim 1, characterized in that: Step S06 is performed after the thermal imager is idle or manually authorized.

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