Method and system for automatically adjusting exposure time of medium-wave infrared camera of telescope

Abstract

The invention relates to the technical field of telescope control, and particularly provides an automatic adjustment method and adjustment system for the exposure time of a medium-wave infrared camera of a telescope, and the method comprises the steps: comparing the maximum gray value of a target pixel region with a target optimal imaging gray value interval; and if the maximum gray value is higher than the upper limit of the target optimal imaging gray value interval or lower than the lower limit of the target optimal imaging gray value interval, carrying out exposure time adjustment in the usable exposure time set range of the medium-wave infrared camera, otherwise, not carrying out adjustment. According to the method, automatic exposure time adjustment is achieved, manual operation is reduced, the success rate of telescope target search is increased, more valuable data can be generated in the target observation process, and the stability of the closed-loop tracking process is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of telescope control, and specifically provides a method and a system for automatically adjusting the exposure time of a mid-wave infrared camera in a telescope. Background Art

[0002] During the use of a mid-wave infrared optical system of a telescope, it is often necessary to adjust the exposure time of the mid-wave infrared camera according to the actual situation. For example, during target search, the brightness of the image is mainly affected by the skylight background. If the brightness of the background image is too high, it is necessary to reduce the exposure time to prevent image saturation; if the brightness of the background image is too low, it is necessary to increase the exposure time to prevent the target from not being imaged when it enters the field of view. During target observation or closed-loop tracking, if the brightness of the target area in the image is too low, the imaging may be relatively blurred, making it difficult to observe the target details or causing the closed-loop tracking to fail. At this time, it is necessary to increase the exposure time; if the brightness of the target area in the image is too high, not only will the target details be lost, but for some cameras based on the thermal imaging principle, if a certain pixel area is in an oversaturated state for a long time, it will also cause irreversible damage to the target surface in this area.

[0003] Currently, in the use of telescopes, the common method for adjusting the exposure time is manual adjustment. Experimenters analyze based on visual senses or real-time data according to different observation scenarios, and choose to increase or decrease the exposure time gear according to the background or the target. However, this method has the following disadvantages: First, the main purpose of experimenters using a telescope is to observe the target or collect data. In addition to the exposure time, they may also need to adjust other parameters, making it difficult to modify the exposure time in a timely manner; Second, a telescope may include multiple optical systems, and it is impossible to timely adjust the exposure times of multiple optical systems in real time during the observation process.

[0004] From the perspectives of cameras and images, the mid-wave infrared optical system in a telescope is quite different from consumer electronic products. Consumer electronic products generally provide color images in the visible band, and their imaging principle is based on the reflection of light by objects. Usually, when in use, the imaging effects of both the target object and the background need to be considered simultaneously. Their images can achieve good imaging effects without image equalization, and their cameras generally support continuous and arbitrary exposure time settings. The mid-wave infrared camera of a telescope produces grayscale images, with a pixel depth generally ranging from 10 bit to 16 bit. Its imaging principle is based on the thermal radiation characteristics of objects, using the mid-wave infrared energy radiated by the objects themselves to achieve imaging. Usually, during the observation process, only the target imaging is concerned, and the pure background image without the target is not. When the target exists, after image equalization processing, the target is a white high signal and the background is a black low signal. The camera of the mid-wave infrared optical system in a telescope provides a limited number of non-continuous and non-linearly calibrated exposure time coefficient groups at the factory, does not support the setting of arbitrary exposure times, and since setting the camera parameters of some cameras may cause the camera to briefly lose frames, which may affect normal use in certain scenarios, so usually, real-time and fine exposure time settings are not performed on the camera. Currently, the main methods for automatically adjusting the exposure time are all based on consumer electronic products, which have certain reference significance for the mid-wave infrared optical system of a telescope, but cannot be fully reused.

[0005] The publication number of the Chinese patent is CN101399919A, the publication date is April 1, 2009, and the patent name is "Automatic Exposure and Automatic Gain Adjustment Method and Device". This patent mainly divides the image output by the camera into N sub-regions, calculates the brightness value of each sub-region, and calculates its optimal exposure time and gain through a certain algorithm. This method does not consider the imaging characteristics of the mid-wave infrared camera of a telescope when observing a target and is not applicable to the observation of mid-wave infrared cameras.

[0006] The publication number of the Chinese patent is CN101304489A, the publication date is November 12, 2008, and the patent name is "An Automatic Exposure Method and Device". Different adjustment methods are provided for whether there is a target in the image respectively, but since the cameras used in it and the mid-wave infrared camera of a telescope have different working principles, this method cannot be applied to the telescope system either.

[0007] The publication number of the Chinese patent is CN111343388A, the publication date is June 26, 2020, and the patent name is "A Method and Device for Determining Exposure Time". This method provides a comprehensive adjustment method based on the central region and the region of interest, but this method cannot be applied to the mid-wave infrared images of a telescope. Summary of the Invention

[0008] In order to solve the above problems, the present invention provides a method and system for automatically adjusting the exposure time of a telescope medium-wave infrared camera, which compares the maximum grayscale value of the target pixel area with the size of the target optimal imaging grayscale value interval, and then adjusts the exposure time within the usable exposure time set range of the medium-wave infrared camera. The method of the present invention realizes automatic exposure time adjustment, improves the success rate of telescope target search, is conducive to generating more valuable data during target observation, and ensures the stability of the closed-loop tracking process.

[0009] The invention provides a method and system for automatically adjusting the exposure time of a telescope medium-wave infrared camera, comprising: S1: Based on the total exposure time of the MWIR camera , the set of exposure times can be used for calculation ,in, , all exposure time collection This is the known data of the medium-wave infrared camera when it leaves the factory. ; S2: Identify whether there is a target in the image collected by the medium-wave infrared camera: If there is a target, the pixel area where the target is located in the image is obtained as the target pixel area; If there is no target, a non-edge area corresponding to the image is obtained as the target pixel area, wherein the non-edge area is a pixel area obtained by removing invalid edge row pixels or invalid edge column pixels in the image; S3: Perform median filtering on the target pixel area; S4: Traverse all the pixels in the target pixel area after median filtering to obtain the maximum grayscale value ; S5: Set the current exposure time to , Indicates the serial number of any element in the exposure time set that can be used. , make the following judgment: judge Is it true? If so, find the exposure time set that can be used Does it exist in , if it exists, adjust the exposure time of the medium-wave infrared camera to ; If it does not exist, no exposure time adjustment will be performed; If not, then judge Is it true? If so, find the exposure time set that can be used Does it exist in , if it exists, adjust the exposure time of the medium-wave infrared camera to ; If it does not exist, no exposure time adjustment is performed; if and If none of them holds, no exposure time adjustment is performed; Among them, represents the limit brightness of the pixel, , represents the pixel depth of the mid-wave infrared camera, represents the target optimal imaging gray value range, , represents the coefficient, .

[0010] Preferably, any element in the exposure time set can satisfy , among which, , represents the frame rate of the mid-wave infrared camera.

[0011] The automatic exposure time adjustment system for the mid-wave infrared camera of the telescope is used to execute the automatic exposure time adjustment method for the mid-wave infrared camera of the telescope. The automatic adjustment system includes: a target recognition module, an image acquisition module, a parameter calculation module, and a parameter setting module; The image acquisition module receives the image collected by the mid-wave infrared camera and sends it to the target recognition module; The target recognition module recognizes whether there is a target in the image and outputs the target pixel area; The parameter calculation module calculates whether to adjust the exposure time and the adjusted exposure time based on the target pixel area; When the exposure time parameter needs to be adjusted, the parameter setting module sends the adjusted exposure time to the mid-wave infrared camera.

[0012] Compared with the prior art, the present invention can achieve the following beneficial effects: By comparing the maximum gray value of the target pixel area with the target optimal imaging gray value range, the present invention adjusts the exposure time within the range of the available exposure time set of the mid-wave infrared camera. Compared with manual adjustment, this method can greatly reduce the manual operation of experimental personnel, improve the automation level of the telescope, enhance the automation ability of the telescope, and achieve timely and accurate adjustment of the exposure time.

[0013] Compared with the existing exposure time adjustment methods for consumer electronic products, the present invention is more suitable for the mid-wave infrared optical system of the telescope. Applying the method of the present invention, during the process of target search, observation or closed-loop tracking of the telescope, the exposure time of the mid-wave infrared camera can be adjusted to an appropriate level in a timely manner, improving the success rate of target search of the telescope, promoting the generation of more valuable data during the target observation process, and ensuring the stability of the closed-loop tracking process.

[0014] When the method of the present invention is used to adjust the exposure time, there is no area in the image that is saturated for a long time. If the target does not exist, by adjusting the exposure time, the imaging brightness of the background can be within a reasonable range, making it easier to detect the target. If the target exists, by adjusting the exposure time, the imaging brightness of the target can be within a reasonable range, so that the target will not be lost due to being too dark, nor will the target details be lost due to being oversaturated. Description of the Drawings

[0015] Figure 1 It is a flowchart of the method for automatically adjusting the exposure time of a telescope mid-wave infrared camera according to an embodiment of the present invention; Figure 2 It is a flowchart of calculating the exposure time according to an embodiment of the present invention; Figure 3 It is a layout diagram of the system for automatically adjusting the exposure time of a telescope mid-wave infrared camera according to an embodiment of the present invention. Detailed Embodiments

[0016] In order to make the purpose, technical solutions and advantages of the present invention clearer, the following further describes the present invention in detail with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. Similar elements in different embodiments are labeled with related similar element numbers. In the following embodiments, many details are described to make the present invention better understood. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other elements, materials, methods. In some cases, some operations related to the present invention are not shown or described in the specification, in order to avoid the core part of the present invention being submerged by too much description. For those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations according to the description in the specification and the general technical knowledge in the art.

[0017] It should be noted that, without conflict, the embodiments and features in the embodiments of the present invention can be combined with each other to form various embodiments. At the same time, the steps or actions in the method description can also be adjusted in the order that is obvious to those skilled in the art. Therefore, the various orders in the specification and drawings are only for clearly describing a certain embodiment, and do not mean that they are the necessary orders, unless it is stated that a certain order must be followed.

[0018] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0019] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "mounted", "connected", "coupled" shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific situations.

[0020] The present invention will be described in detail below with reference to the drawings and in conjunction with embodiments.

[0021] As Figure 1 shown, in the embodiment of the present invention, for a medium-wave infrared camera (hereinafter referred to as the camera), a method for automatically adjusting the exposure time of a telescope medium-wave infrared camera is provided. In the embodiment of the present invention, the field-of-view diagonal of the medium-wave infrared system of the telescope camera is , and the image resolution is 640×512. The camera outputs an image to trigger a single-frame exposure time adjustment process, and the whole process consists of a plurality of consecutive single-frame processes. The single-frame process is specifically as follows: S1: When the camera performs image acquisition, there are multiple different camera frame rates. At each camera frame rate, there are multiple available exposure times. Since the exposure time should be less than the frame interval time, for a certain fixed frame rate, not all exposure times are applicable. When the camera leaves the factory, it will carry all the exposure time data involved in the camera, which is called the all-exposure time set , that is, the all-exposure time set is the known data when the camera leaves the factory. When permitted by the camera itself, regardless of which camera frame rate is used for image acquisition, its exposure time is included in the entire set of exposure times within.

[0022] In the embodiments of the present invention, is used to represent the camera frame rate. According to the entire set of exposure times of the camera , the camera frame rate corresponding to all available exposure times can be calculated to form a set of available exposure times , then there is , where , that is, the exposure times in the set of available exposure times are arranged in ascending order of length, and any element in the set of available exposure times satisfies , represents the serial number of any element in the set of available exposure times, . In the embodiments of the present invention, the entire set of exposure times supports camera frame rates of 25 Hz and 50 Hz. When the camera frame rate , , when the camera frame rate , the set of available exposure times .

[0023] S2: Among the images captured by the camera, the target may not necessarily be included. The purpose of adjusting the exposure time is to make the target image clearer. Whether the target is present can affect the exposure time adjustment. Therefore, it is necessary to perform target recognition based on the images captured by the camera, that is, to identify whether there is a target in the images captured by the camera: If there is a target in the image captured by the camera, the pixel region where the target is located in the image is obtained as the target pixel region; if there is no target in the image captured by the camera, the non-edge region corresponding to the image is obtained as the target pixel region. For some cameras, their boundary regions have poor response capabilities to light or heat, and there are edge invalid row pixels or edge invalid column pixels at the edges. The non-edge region is the pixel region obtained after removing the edge invalid row pixels or edge invalid column pixels in the image. In this case, when performing image processing, usually only the non-edge region is processed. In the embodiments of the present invention, the image edge region is defined as 10 row pixels for the upper and lower edges and 10 column pixels for the left and right edges.

[0024] S3: Since there may be bad pixels in the camera, therefore, after the target pixel region is determined, in order to prevent the bad pixels from affecting the calculation results, median filtering is performed on the target pixel region.

[0025] S4: After performing median filtering, traverse all the pixel points in the target pixel region to obtain the maximum gray value. .

[0026] S5: When the camera leaves the factory, it will explicitly state the pixel depth in the instruction manual. , and the pixel depth is a characteristic of the camera detector. Then the limit brightness of each pixel . In the embodiment of the present invention, the pixel depth is 14 bits, so the limit brightness of the pixel . Each camera has a specific target optimal imaging gray value range, denoted as , where , represents a coefficient, , takes values that satisfy , , can be obtained by pre-calibration through experiments, and the acquisition method is the prior art in this field. In the embodiment of the present invention, , , and the optimal imaging gray value range is .

[0027] As Figure 2 shown, it is a flowchart for calculating whether to adjust the exposure time and how to adjust it. Based on the maximum gray value and the target optimal imaging gray value range , set the current exposure time as , represents the serial number of any element in the set of available exposure times, , and make the following judgments: Judge whether holds. If holds, it indicates that the maximum gray value has exceeded the upper limit of the target optimal imaging gray value range. At this time, check whether there is an exposure time in the set of available exposure times . If there is an exposure time , then adjust the camera exposure time to the exposure time . If there is no exposure time , then do not adjust the exposure time.

[0028] If does not hold, then judge whether holds. If holds, it indicates that the maximum gray value is lower than the lower limit of the target optimal imaging gray value range. At this time, check whether there is an exposure time in the set of available exposure times If there is an exposure time , the camera exposure time is adjusted to the exposure time ; if there is no exposure time , no exposure time adjustment is made; if and both do not hold, no exposure time adjustment is made.

[0029] It should be noted that when , the target imaging signal-to-noise ratio is too low, and the target imaging is easily submerged in background noise; when , the target imaging brightness tends to saturation, and it is not easy to observe the target details from the image.

[0030] To implement the above method for automatically adjusting the exposure time of the mid-wave infrared camera of the telescope, an embodiment of the present invention also provides a system for automatically adjusting the exposure time of the mid-wave infrared camera of the telescope, including a telescope and an image processing system. The telescope includes a mid-wave infrared camera, and the image processing system includes a target recognition module, an image acquisition module, a parameter calculation module, and a parameter setting module.

[0031] The mid-wave infrared camera is used to collect an image and output the image to the image acquisition module. The image acquisition module receives the image collected by the mid-wave infrared camera and sends it to the target recognition module. The target recognition module identifies whether there is a target in the image. When there is a target, the pixel area where the target is located in the image is obtained as the target pixel area; when there is no target, the non-edge area corresponding to the image is obtained as the target pixel area, and the obtained target pixel area is output to the parameter calculation module. The parameter calculation module calculates whether to adjust the exposure time based on the target pixel area and the parameters of the current mid-wave infrared camera. When exposure time adjustment is required, the adjusted exposure time value is calculated and sent to the parameter setting module. The parameter setting module sends the adjusted exposure time value to the mid-wave infrared camera in the form of an instruction to adjust the exposure time, thereby completing the exposure time adjustment.

[0032] Among them, the image acquisition module is a mature module, the parameter setting module is determined by the mid-wave infrared camera, and the target recognition module is determined according to the design of the telescope optical system, the observation target, and the usage scenario.

[0033] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

[0034] The above specific embodiments of the present invention do not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and deformations made according to the technical concept of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. Automatic exposure time adjustment method for medium-wave infrared camera in telescope, characterized in that, Including: S1: According to the set of all exposure times of the mid-wave infrared camera , calculate the set of available exposure times , where , the set of all exposure times is the known data when the mid-wave infrared camera leaves the factory ; S2: Identify whether there is a target in the image collected by the mid-wave infrared camera: If there is a target, obtain the pixel region where the target is located in the image as the target pixel region; If there is no target, obtain the non-edge region corresponding to the image as the target pixel region, where the non-edge region is the pixel region obtained by removing the invalid row pixels or invalid column pixels at the edge of the image; S3: Perform median filtering on the target pixel region; S4: Traverse all the pixel points in the target pixel region after median filtering processing to obtain the maximum gray value ; S5: Set the current exposure time to , which represents the serial number of any element in the set of available exposure times, , and make the following judgment: Judge whether it holds. If it holds, search for the available exposure time set to see if there is in it. If there is, adjust the exposure time of the mid-wave infrared camera to ; if not, do not adjust the exposure time; If it does not hold, then judge whether it holds. If it holds, then search for the available exposure time set to see if there is . If there is, then adjust the exposure time of the mid-wave infrared camera to ; if not, then do not adjust the exposure time; if and both do not hold, then do not adjust the exposure time; Among them, represents the ultimate brightness of a pixel, , represents the pixel depth of a mid-wave infrared camera, represents the optimal imaging gray value range of the target, , represents a coefficient, .

2. The method for automatically adjusting the exposure time of the mid-wave infrared camera of the telescope according to claim 1, wherein, The set of exposure times that can be used any one element in satisfies , where , represents the frame rate of the mid-wave infrared camera.

3. Automatic exposure time adjustment system for mid-wave infrared camera in telescope, characterized in that, For implementing the automatic exposure time adjustment method of the mid-wave infrared camera of the telescope according to any one of claims 1 to 2, the automatic adjustment system includes: a target recognition module, an image acquisition module, a parameter calculation module, and a parameter setting module; The image acquisition module receives the image collected by the mid-wave infrared camera and sends it to the target recognition module; The target recognition module identifies whether there is a target in the image and outputs the target pixel region; The parameter calculation module calculates whether to adjust the exposure time and the adjusted exposure time based on the target pixel region; When the exposure time parameter needs to be adjusted, the parameter setting module sends the adjusted exposure time to the mid-wave infrared camera.

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