CN112954136A - Method and device for suppressing shot noise of remote sensing image of aviation squint remote imaging - Google Patents
Method and device for suppressing shot noise of remote sensing image of aviation squint remote imaging Download PDFInfo
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Abstract
The invention relates to the field of aerial remote sensing imaging, in particular to a method and a device for inhibiting shot noise of an aerial strabismus remote imaging remote sensing image. The method and the device take pictures of the same target on the ground for multiple times by a method of multiple exposure in a frame to obtain a multi-frame image of the same target, and carry out time domain average processing on the multi-frame image to reduce shot noise of the image, thereby effectively reducing the influence of the shot noise of the image, improving the signal to noise ratio of the image, simultaneously solving the contradiction between the small pixel size and the large well-filled electron number requirement in the model selection of the aerial squint remote sensing image detector, effectively increasing the limit distance of imaging detection and realizing the detection of the smaller target with poor background reflectivity.
Description
Technical Field
The invention belongs to the field of aerial remote sensing imaging, relates to a method and a device for inhibiting shot noise of an aerial strabismus remote imaging remote sensing image, and particularly aims at inhibiting the shot noise excited by the atmosphere by the aerial camera strabismus remote imaging.
Background
When the aerial remote sensing equipment is used for remote imaging, the aerial remote sensing equipment is influenced by atmospheric path radiation, the signal-to-noise ratio of images is poor, and especially the squint remote imaging atmospheric influence with the imaging distance of more than 30km is more obvious. The noise source of the aerial remote sensing equipment is mainly shot noise, and when the number of the received electrons of the photoelectric detector is mueThe shot noise excited is
And the poisson distribution is met. And when the aerial strabismus remote imaging exists, the radiation of an atmosphere path is very obvious, and an analysis result shows that the radiation brightness of the atmosphere path is more than 10 times of the brightness of a target at the imaging height of 8km and the imaging distance of 100 km. The atmospheric path radiation excites a large amount of shot noise and does not contribute to a target signal, so that the signal-to-noise ratio of an image is seriously influenced, and the imaging detection distance is limited.
Disclosure of Invention
The embodiment of the invention provides a method and a device for inhibiting shot noise of an aerial strabismus remote imaging remote sensing image, which at least solve the technical problem that a large amount of shot noise exists in the existing aerial remote sensing equipment during remote imaging.
According to an embodiment of the invention, a method for suppressing shot noise of an aerial strabismus remote imaging remote sensing image is provided, which comprises the following steps:
s101, shooting the same target on the ground for multiple times by an intraframe multiple exposure method to obtain a plurality of frame images of the same target;
and S102, carrying out time domain average processing on the multi-frame image to reduce shot noise of the image.
Further, step S101 specifically includes:
and shooting the same ground target for multiple times by using an intra-frame multiple exposure method, and averaging the intra-frame multiple exposure images to obtain multiple frame images of the same target.
Furthermore, multiple times of photographing of the same ground target are achieved in a mode of staring at the fixed ground target through the air.
Further, step S102 specifically includes:
and extracting the same ground fixed target in different frames of image data, and performing time domain average processing on a plurality of frames of images of the same target to reduce shot noise of the images.
Furthermore, the single-frame exposure time is less than or equal to 20 ms.
Further, the method further comprises, before step S101, the steps of:
and S100, acquiring longitude, latitude and altitude information of the airplane in real time, calculating a corresponding camera frame angle of the aerial camera by using the camera controller, controlling the depression angle and the azimuth angle to move to a specified position by using a servo system of the aerial camera according to a target angle sent by the camera controller, and pointing the visual axis of the aerial camera to the target position at the moment.
Further, a high frame rate visible detector is used to take multiple exposure shots of the same target on the ground.
According to another embodiment of the invention, there is provided an apparatus for suppressing shot noise in an aerial strabismus remote-imaging remote-sensing image, including:
the intra-frame image averaging processing unit is used for photographing the same ground target for multiple times by an intra-frame multiple exposure method to obtain a plurality of frame images of the same target;
and the image target area extraction processing unit is used for carrying out time domain average processing on the multi-frame images to reduce shot noise of the images.
Further, the apparatus further comprises:
the comprehensive control unit is used for acquiring longitude, latitude and altitude information of the airplane in real time, the camera controller is used for calculating a corresponding camera frame angle of the aerial camera, a servo system of the aerial camera controls the depression angle and the azimuth angle to move to a specified position according to a target angle sent by the camera controller, and a visual axis of the aerial camera points to a target position.
Further, the comprehensive control unit calculates a new frame angle of the aerial camera according to the longitude, the latitude, the altitude, the pitch angle, the roll angle, the course angle and the original frame angular position of the aerial camera, so that the visual axis of the aerial camera points to a ground fixed target in the imaging process; and sending an exposure control signal to the intra-frame image average processing unit according to the working time sequence of the aerial remote sensing equipment.
The method and the device for inhibiting shot noise of the aerial strabismus remote imaging remote sensing image in the embodiment of the invention take multiple photographs of the same target on the ground by a method of intraframe multiple exposure to obtain a multi-frame image of the same target, and carry out time domain average processing on the multi-frame image to reduce the shot noise of the image, thereby effectively reducing the shot noise influence of the image, improving the signal to noise ratio of the image, solving the contradiction between the small pixel size and the large full well electron number requirement in the model selection of the aerial strabismus remote sensing image detector, effectively increasing the limit distance of imaging detection and realizing the detection of a smaller target with poor background reflectance.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention. In the drawings:
FIG. 1 is a flow chart of a method of suppressing shot noise in an aerial strabismus distance imaging image according to the present invention;
FIG. 2 is a block diagram of an apparatus for suppressing shot noise in an aerial strabismus distance imaging image according to the present invention;
FIG. 3 is a schematic view of staring imaging of an aerial remote sensing device according to the present invention;
FIG. 4 is a flow chart of correction of gaze imaging boresight orientation of the aerial remote sensing device according to the present invention;
FIG. 5 is a graph illustrating the effect of different PRNUs on signal-to-noise ratio in an embodiment of the present invention;
FIG. 6 is a graph of signal-to-noise ratio improvement in accordance with an embodiment of the present invention;
FIG. 7 is a flowchart illustrating the method for suppressing shot noise in an aerial strabismus distance imaging image according to the present invention.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
Example 1
According to an embodiment of the present invention, there is provided a method for suppressing shot noise in an aerial strabismus remote-imaging remote sensing image, referring to fig. 1, including the following steps:
s101, shooting the same target on the ground for multiple times by an intraframe multiple exposure method to obtain a plurality of frame images of the same target;
and S102, carrying out time domain average processing on the multi-frame image to reduce shot noise of the image.
The method for inhibiting shot noise of the aerial strabismus remote imaging remote sensing image in the embodiment of the invention obtains multi-frame images of the same target by taking pictures of the same target on the ground for multiple times through a method of intra-frame multiple exposure, reduces the shot noise of the image by carrying out time domain average processing on the multi-frame images, can effectively reduce the shot noise influence of the image, improves the signal to noise ratio of the image, solves the contradiction between the small pixel size and the large full well electron number requirement in model selection of an aerial strabismus remote sensing image detector, can effectively increase the limit distance of imaging detection, and realizes detection of a smaller target with poor background reflectance.
Wherein, step S101 specifically includes:
and shooting the same ground target for multiple times by using an intra-frame multiple exposure method, and averaging the intra-frame multiple exposure images to obtain multiple frame images of the same target.
The method realizes multiple times of photographing of the same ground target by staring at the fixed ground target through the air.
Wherein, step S102 specifically includes:
and extracting the same ground fixed target in different frames of image data, and performing time domain average processing on a plurality of frames of images of the same target to reduce shot noise of the images.
Wherein the single-frame exposure time is less than or equal to 20 ms.
Wherein, referring to fig. 7, the method further comprises, before step S101, the steps of:
and S100, acquiring longitude, latitude and altitude information of the airplane in real time, calculating a corresponding camera frame angle of the aerial camera by using the camera controller, controlling the depression angle and the azimuth angle to move to a specified position by using a servo system of the aerial camera according to a target angle sent by the camera controller, and pointing the visual axis of the aerial camera to the target position at the moment.
Wherein, a high frame frequency visible detector is used for carrying out multiple exposure photographing on the same target on the ground.
The method for suppressing shot noise of the remote sensing image of the aviation squint long-distance imaging of the invention is explained in detail by the following specific embodiment:
aiming at the influence of atmospheric path radiation on the signal-to-noise ratio of aerial strabismus remote imaging, the invention provides a method for inhibiting shot noise of an aerial strabismus remote imaging image, and the shot noise of the aerial strabismus remote imaging is reduced by combining intra-frame multiple exposure and multi-frame image time domain averaging, so that the signal-to-noise ratio of the image is improved, and the imaging detection distance is increased. In the process of aerial imaging, multiple photographing of the same target area on the ground is realized in a staring mode of an aerial ground fixed target, multiple exposure in a frame is realized by selecting a high-frame-frequency visible detector, and the signal-to-noise ratio of the current frame image is initially improved by averaging multiple exposure images in the frame, so that a foundation is laid for later ground fixed target extraction; and then processing the multi-frame image acquired by the ground fixed point staring imaging, extracting the same ground fixed target in different frame data, and then carrying out multi-frame averaging to reduce shot noise of the image and further improve the signal-to-noise ratio of the image.
The method solves the technical problem of inhibiting the influence of shot noise of the aerial remote sensing equipment, particularly the influence of the shot noise excited by atmospheric path radiation on the signal-to-noise ratio of the aerial squint remote imaging image. By adopting the method of staring fixed-point imaging of the ground target, adopting the intra-frame multi-exposure method and averaging the acquired multi-frame images, the shot noise influence of the images can be effectively reduced, the signal-to-noise ratio of the images is improved, meanwhile, the contradiction between the small pixel size and the large well-filled electron number requirement existing in the model selection of the aerial strabismus remote sensing image detector is solved, the limit distance of imaging detection can be effectively increased, and the detection of the smaller target with poor background reflectivity can be realized.
The technical scheme adopted by the invention is specifically implemented as shown in figure 2: the aerial camera generally comprises a depression angle (outer frame) shaft system and an azimuth angle (inner frame) shaft system, and in the aerial imaging process, the visual axis of the aerial camera points to the target position by adjusting the pointing direction of the depression angle shaft system and the pointing direction of the azimuth angle shaft system of the aerial camera according to the relative position relation between an airplane and the target, and the target is photographed. In the actual working process, the position of the airplane is constantly changed, so that the longitude, latitude and altitude information of the airplane needs to be acquired in real time, the camera controller is used for calculating the corresponding camera frame angle, a servo system of the aerial camera controls the depression angle and the azimuth angle to move to the designated position according to the target angle sent by the camera controller, and the visual axis points to the target position at the moment. The aerial remote sensing device is influenced by the radiation of the atmospheric path, the target proportion in the light energy received by the aerial remote sensing device is very small, and the atmospheric path radiation excites a large amount of shot noise to seriously influence the signal to noise ratio of an image, so that multiple exposure of a ground target can be realized in a single frame after an exposure signal is received by selecting a high-frame-frequency visible detector, multiple exposure image averaging processing is carried out on the image in the frame, the shot noise can be inhibited, the signal to noise ratio is preliminarily improved, and a foundation is laid for later-stage target area image extraction. The method comprises the steps of extracting targets in the same area in a multi-frame image acquired by ground fixed-point staring imaging, and then carrying out time domain averaging on the target images in the area, so that shot noise of a large squint remote imaging image of the aerial remote sensing equipment can be effectively inhibited, and the signal-to-noise ratio of the image is improved. The method has good shot noise suppression for ground or aviation backlight imaging.
The following describes in detail a specific embodiment of the present invention with an aerial camera as an example. The integrated control unit in fig. 2 is mainly responsible for calculating a new frame angle of the aerial camera according to the longitude, latitude, altitude, pitch angle, roll angle, course angle and original frame angle position of the aerial camera, so as to ensure that the visual axis of the aerial camera points to a ground fixed target in the imaging process. In addition, the comprehensive control unit sends an exposure control signal to the intra-frame image averaging processing unit according to the working time sequence of the aerial remote sensing equipment, after receiving the exposure control signal, the intra-frame image averaging processing unit sends a multi-exposure signal to the high-frame-frequency visible detector within a single-frame exposure time (generally not more than 20ms), and the intra-frame exposure times are determined by the image motion compensation capability and the single exposure time of the aerial camera. After receiving the intra-frame exposure control signal, the high-frame-frequency visible detector sends the acquired image to an intra-frame image averaging processing unit, the latter averages the image subjected to multiple exposures in the frame, and then sends the processing result to an image target area extracting and processing unit, and the image target area extracting and processing unit extracts common ground target information from the received different frame images and carries out time domain averaging processing on the common target information. The imaging schematic diagram is shown in fig. 3, the camera frame angle calculation flow is shown in fig. 4, and the ground target with longitude, latitude and height is specified according to the flow, so that the visual axis continuously points to the ground target, and the staring imaging function is realized. The image signal-to-noise ratio formula given in the EMVA1288 standard is:
the numerator in the formula is the number of electrons excited by the received photons, the denominator comprises dark field time domain noise, dark field space domain noise, quantization noise, shot noise and response non-uniformity noise, the formula is suitable for describing the signal-to-noise ratio of an image when a laboratory is in close-range imaging, and when aviation squint remote imaging is carried out, a large amount of shot noise is excited by atmospheric path radiation and no contribution is made to signals. Therefore, atmospheric path radiation excitation shot noise is introduced into the denominator, and the signal-to-noise ratio formula expressed by electronic number is
It can be seen that the atmospheric path radiation excites shot noise, which also contributes to the increase in response non-uniformity noise. For aviation large squint long-distance imaging, the influences of dark field time domain noise, dark field space domain noise and quantization noise can be ignored, and the multiplying power beta of the atmospheric path radiation excitation electron number and the target scenery excitation electron number is defined to be mua/μTThen the SNR formula can be simplified to
When β is 40, Δ ρ is 0.2, ρT＝0.4,μSmax61000, the effect of different response non-uniformity PRNU on the signal-to-noise ratio is shown in fig. 5, and it can be seen that when PRNU is greater than 1%, in the region above 15ke-, increasing the number of electrons in the signal has a weak effect on improving the signal-to-noise ratio. Since the shot noise conforms to the Poisson distribution, when the number of multiple exposures in a frame is m and the number of frames subjected to time domain averaging is n, the shot noise will become the original one
After the airspace noise is removed by the method of integrating sphere calibration, the image signal-to-noise ratio formula is
When β is 10, Δ ρ is 0.1, ρT＝0.25,
μSAs shown in fig. 6, the relationship between the snr and the total average frame number m · n is 40000, and as m · n increases, shot noise is suppressed, and the image snr is significantly improved.
In summary, the method of the present invention is composed of 3 key parts, such as an intra-frame multiple exposure method, fixed-point gaze imaging, and target image time domain averaging. The signal-to-noise ratio of an image acquired by the aerial remote sensing squint remote imaging equipment is obviously low under the influence of the atmospheric path radiation effect, and the main reason is that a large amount of shot noise is excited by the atmospheric path radiation. The method for multiple exposure in the frame is realized by selecting a high-frame-frequency visible detector, when an exposure signal sent by a system is received, multiple exposure is carried out within the range of image motion compensation capability of remote sensing equipment, an image obtained by each exposure is sent and then processed, the image obtained in the frame is averaged, and an averaged result is sent to a target image area extraction processing unit. The method comprises the steps of imaging in a staring mode of a ground fixed target, obtaining multiple frames of images of the same target on the ground, extracting images of the same target area in the images, carrying out time domain average processing on the images of the target area, obviously inhibiting shot noise of the processed images, and obviously improving the signal-to-noise ratio of the images. The method can obviously inhibit shot noise of the image and improve the signal-to-noise ratio of the image; the method solves the contradiction between the small pixel size and the large full well in the visible detector model selection in the aerial remote sensing equipment with large squint and long-distance imaging; the method can break through the theoretical limit that the maximum signal-to-noise ratio of the image is the root-mean-square of the electronic number of the signal.
Example 2
According to another embodiment of the present invention, there is provided an apparatus for suppressing shot noise in an aerial strabismus remote imaging remote sensing image, referring to fig. 2, including:
the intra-frame image averaging processing unit is used for photographing the same ground target for multiple times by an intra-frame multiple exposure method to obtain a plurality of frame images of the same target;
and the image target area extraction processing unit is used for carrying out time domain average processing on the multi-frame images to reduce shot noise of the images.
The device for inhibiting shot noise of the aerial strabismus remote imaging remote sensing image in the embodiment of the invention takes multiple photographs of the same ground target by a method of intraframe multiple exposure to obtain a multi-frame image of the same target, and performs time domain average processing on the multi-frame image to reduce the shot noise of the image, thereby effectively reducing the shot noise influence of the image, improving the signal to noise ratio of the image, solving the contradiction between the small pixel size and the large full well electron number requirement in model selection of an aerial strabismus remote sensing image detector, effectively increasing the limit distance of imaging detection, and realizing detection of a smaller target with poor background reflectance.
Wherein, the device still includes:
the comprehensive control unit is used for acquiring longitude, latitude and altitude information of the airplane in real time, the camera controller is used for calculating a corresponding camera frame angle of the aerial camera, a servo system of the aerial camera controls the depression angle and the azimuth angle to move to a specified position according to a target angle sent by the camera controller, and a visual axis of the aerial camera points to a target position.
The comprehensive control unit calculates a new frame angle of the aerial camera according to the longitude, the latitude, the altitude, the pitch angle, the roll angle, the course angle and the original frame angular position of the aerial camera, so that the visual axis of the aerial camera points to a ground fixed target in the imaging process; and sending an exposure control signal to the intra-frame image average processing unit according to the working time sequence of the aerial remote sensing equipment.
The device for suppressing shot noise of the remote sensing image of the aviation squint long-distance imaging of the invention is explained in detail by the following specific embodiment:
aiming at the influence of atmospheric path radiation on the signal-to-noise ratio of aerial strabismus remote imaging, the invention provides a device for inhibiting shot noise of aerial strabismus remote imaging images. In the process of aerial imaging, multiple photographing of the same target area on the ground is realized in a staring mode of an aerial ground fixed target, multiple exposure in a frame is realized by selecting a high-frame-frequency visible detector, and the signal-to-noise ratio of the current frame image is initially improved by averaging multiple exposure images in the frame, so that a foundation is laid for later ground fixed target extraction; and then processing the multi-frame image acquired by the ground fixed point staring imaging, extracting the same ground fixed target in different frame data, and then carrying out multi-frame averaging to reduce shot noise of the image and further improve the signal-to-noise ratio of the image.
The method solves the technical problem of inhibiting the influence of shot noise of the aerial remote sensing equipment, particularly the influence of the shot noise excited by atmospheric path radiation on the signal-to-noise ratio of the aerial squint remote imaging image. By adopting the method of staring fixed-point imaging of the ground target, adopting the intra-frame multi-exposure method and averaging the acquired multi-frame images, the shot noise influence of the images can be effectively reduced, the signal-to-noise ratio of the images is improved, meanwhile, the contradiction between the small pixel size and the large well-filled electron number requirement existing in the model selection of the aerial strabismus remote sensing image detector is solved, the limit distance of imaging detection can be effectively increased, and the detection of the smaller target with poor background reflectivity can be realized.
The technical scheme adopted by the invention is specifically implemented as shown in figure 2: the aerial camera generally comprises a depression angle (outer frame) shaft system and an azimuth angle (inner frame) shaft system, and in the aerial imaging process, the visual axis of the aerial camera points to the target position by adjusting the pointing direction of the depression angle shaft system and the pointing direction of the azimuth angle shaft system of the aerial camera according to the relative position relation between an airplane and the target, and the target is photographed. In the actual working process, the position of the airplane is constantly changed, so that the longitude, latitude and altitude information of the airplane needs to be acquired in real time, the camera controller is used for calculating the corresponding camera frame angle, a servo system of the aerial camera controls the depression angle and the azimuth angle to move to the designated position according to the target angle sent by the camera controller, and the visual axis points to the target position at the moment. The aerial remote sensing device is influenced by the radiation of the atmospheric path, the target proportion in the light energy received by the aerial remote sensing device is very small, and the atmospheric path radiation excites a large amount of shot noise to seriously influence the signal to noise ratio of an image, so that multiple exposure of a ground target can be realized in a single frame after an exposure signal is received by selecting a high-frame-frequency visible detector, multiple exposure image averaging processing is carried out on the image in the frame, the shot noise can be inhibited, the signal to noise ratio is preliminarily improved, and a foundation is laid for later-stage target area image extraction. The method comprises the steps of extracting targets in the same area in a multi-frame image acquired by ground fixed-point staring imaging, and then carrying out time domain averaging on the target images in the area, so that shot noise of a large squint remote imaging image of the aerial remote sensing equipment can be effectively inhibited, and the signal-to-noise ratio of the image is improved. The device also has good shot noise suppression for ground or aviation backlight imaging.
The following describes in detail a specific embodiment of the present invention with an aerial camera as an example. The integrated control unit in fig. 2 is mainly responsible for calculating a new frame angle of the aerial camera according to the longitude, latitude, altitude, pitch angle, roll angle, course angle and original frame angle position of the aerial camera, so as to ensure that the visual axis of the aerial camera points to a ground fixed target in the imaging process. In addition, the comprehensive control unit sends an exposure control signal to the intra-frame image averaging processing unit according to the working time sequence of the aerial remote sensing equipment, after receiving the exposure control signal, the intra-frame image averaging processing unit sends a multi-exposure signal to the high-frame-frequency visible detector within a single-frame exposure time (generally not more than 20ms), and the intra-frame exposure times are determined by the image motion compensation capability and the single exposure time of the aerial camera. After receiving the intra-frame exposure control signal, the high-frame-frequency visible detector sends the acquired image to an intra-frame image averaging processing unit, the latter averages the image subjected to multiple exposures in the frame, and then sends the processing result to an image target area extracting and processing unit, and the image target area extracting and processing unit extracts common ground target information from the received different frame images and carries out time domain averaging processing on the common target information. The imaging schematic diagram is shown in fig. 3, the camera frame angle calculation flow is shown in fig. 4, and the ground target with longitude, latitude and height is specified according to the flow, so that the visual axis continuously points to the ground target, and the staring imaging function is realized. The image signal-to-noise ratio formula given in the EMVA1288 standard is:
the numerator in the formula is the number of electrons excited by the received photons, the denominator comprises dark field time domain noise, dark field space domain noise, quantization noise, shot noise and response non-uniformity noise, the formula is suitable for describing the signal-to-noise ratio of an image when a laboratory is in close-range imaging, and when aviation squint remote imaging is carried out, a large amount of shot noise is excited by atmospheric path radiation and no contribution is made to signals. Therefore, atmospheric path radiation excitation shot noise is introduced into the denominator, and the signal-to-noise ratio formula expressed by electronic number is
It can be seen that the atmospheric path radiation excites shot noise, which also contributes to the increase in response non-uniformity noise. For aviation large squint long-distance imaging, the influences of dark field time domain noise, dark field space domain noise and quantization noise can be ignored, and the multiplying power beta of the atmospheric path radiation excitation electron number and the target scenery excitation electron number is defined to be mua/μTThen the SNR formula can be simplified to
When β is 40, Δ ρ is 0.2, ρT＝0.4,μSmax61000, the effect of different response non-uniformity PRNU on the signal-to-noise ratio is shown in fig. 5, and it can be seen that when PRNU is greater than 1%, in the region above 15ke-, increasing the number of electrons in the signal has a weak effect on improving the signal-to-noise ratio. Since the shot noise conforms to the Poisson distribution, when the number of multiple exposures in a frame is m and the number of frames subjected to time domain averaging is n, the shot noise will become the original one
After the airspace noise is removed by the method of integrating sphere calibration, the image signal-to-noise ratio formula is
When β is 10, Δ ρ is 0.1, ρT＝0.25,
μSAs shown in fig. 6, the relationship between the snr and the total average frame number m · n is 40000, and as m · n increases, shot noise is suppressed, and the image snr is significantly improved.
In summary, the device of the present invention is composed of 3 key components, such as an intra-frame multiple exposure method, fixed-point gaze imaging, and target image time domain averaging. The signal-to-noise ratio of an image acquired by the aerial remote sensing squint remote imaging equipment is obviously low under the influence of the atmospheric path radiation effect, and the main reason is that a large amount of shot noise is excited by the atmospheric path radiation. The intra-frame multi-exposure method in the device is realized by selecting the high-frame frequency visible detector, when an exposure signal sent by the system is received, multi-exposure is carried out within the range of image motion compensation capability of the remote sensing equipment, an image obtained by each exposure is sent and then processed, the image obtained in the intra-frame is averaged, and an averaged result is sent to the target image area extraction processing unit. The method comprises the steps of imaging in a staring mode of a ground fixed target, obtaining multiple frames of images of the same target on the ground, extracting images of the same target area in the images, carrying out time domain average processing on the images of the target area, obviously inhibiting shot noise of the processed images, and obviously improving the signal-to-noise ratio of the images. The device can obviously inhibit shot noise of the image and improve the signal-to-noise ratio of the image; the device solves the contradiction between the small pixel size and the large full well in the visible detector model selection in the aerial remote sensing equipment with large squint and remote imaging; the device can break through the theoretical limit that the maximum signal-to-noise ratio of the image is the root mean square of the electronic number of the signal.
The invention has the innovative technical points and the beneficial effects that:
(1) based on a signal-to-noise ratio formula in an EMVA1288 standard, the signal-to-noise ratio formula suitable for describing the large squint remote imaging of the aerial remote sensing equipment is provided.
(2) The true signal of aerial imaging should be the reflected energy differential pressure created by the difference in reflectance of adjacent targets.
(3) A description of the limitation of increasing the number of signal electrons to boost the signal-to-noise ratio in response to non-uniform PRNU is given, and increasing the number of signal electrons in the region above 15 ke-has a weak effect on the boost of the signal-to-noise ratio when the PRNU level is greater than 1%.
(4) The high-frame-frequency visible detector is selected to realize multiple exposures of the images in the frame, and the images exposed in the frame are averaged, so that the image signal to noise ratio of the current frame can be improved, and a better basis is provided for extracting target images of different frame data in ground fixed-point staring imaging in a later stage.
(5) The relationship between the time domain average image frame number and shot noise suppression capability is described.
(6) The device can break through the theoretical limit that the maximum signal-to-noise ratio of the image is the root mean square of the electronic number of the signal.
The above-mentioned serial numbers of the embodiments of the present invention are merely for description and do not represent the merits of the embodiments.
In the above embodiments of the present invention, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.
In the embodiments provided in the present application, it should be understood that the disclosed technology can be implemented in other ways. The above-described system embodiments are merely illustrative, and for example, a division of a unit may be a logical division, and an actual implementation may have another division, for example, multiple units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, units or modules, and may be in an electrical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a removable hard disk, a magnetic or optical disk, and other various media capable of storing program codes.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A method for suppressing shot noise of an aerial strabismus remote-imaging remote sensing image is characterized by comprising the following steps:
s101, shooting the same target on the ground for multiple times by an intraframe multiple exposure method to obtain a plurality of frame images of the same target;
and S102, carrying out time domain average processing on the multi-frame image to reduce shot noise of the image.
2. The method for suppressing shot noise in the aerial strabismus remote-imaging remote sensing image according to claim 1, wherein the step S101 specifically comprises:
and shooting the same ground target for multiple times by using an intra-frame multiple exposure method, and averaging the intra-frame multiple exposure images to obtain multiple frame images of the same target.
3. The method for suppressing shot noise in the remote sensing image for the aerial strabismus remote imaging according to claim 1, wherein multiple photographs of the same ground target are taken by staring at the fixed ground target by the aerial.
4. The method for suppressing shot noise in the aerial strabismus remote-imaging remote sensing image according to claim 1, wherein the step S102 specifically comprises:
and extracting the same ground fixed target in different frames of image data, and performing time domain average processing on a plurality of frames of images of the same target to reduce shot noise of the images.
5. The method for suppressing shot noise in an aerial strabismus remote imaging remote sensing image according to claim 1, wherein the single frame exposure time is less than or equal to 20 ms.
6. The method for suppressing shot noise in an aerial strabismus distance imaging remote sensing image according to claim 1, wherein the method further comprises, before step S101, the steps of:
and S100, acquiring longitude, latitude and altitude information of the airplane in real time, calculating a corresponding camera frame angle of the aerial camera by using the camera controller, controlling the depression angle and the azimuth angle to move to a specified position by using a servo system of the aerial camera according to a target angle sent by the camera controller, and pointing the visual axis of the aerial camera to the target position at the moment.
7. The method for suppressing shot noise in an aerial strabismus distance imaging remote sensing image as recited in claim 1, wherein the same ground target is photographed with multiple exposures using a high frame rate visible detector.
8. An apparatus for suppressing shot noise in an aerial strabismus remote-imaging remote sensing image, comprising:
the intra-frame image averaging processing unit is used for photographing the same ground target for multiple times by an intra-frame multiple exposure method to obtain a plurality of frame images of the same target;
and the image target area extraction processing unit is used for carrying out time domain average processing on the multi-frame images to reduce shot noise of the images.
9. The apparatus for suppressing shot noise in an aerial strabismus distance imaging remote sensing image according to claim 8, further comprising:
the comprehensive control unit is used for acquiring longitude, latitude and altitude information of the airplane in real time, the camera controller is used for calculating a corresponding camera frame angle of the aerial camera, a servo system of the aerial camera controls the depression angle and the azimuth angle to move to a specified position according to a target angle sent by the camera controller, and a visual axis of the aerial camera points to a target position.
10. The device for suppressing shot noise in an aerial strabismus remote imaging remote sensing image according to claim 9, wherein the integrated control unit calculates a new aerial camera frame angle according to the longitude, latitude, altitude, pitch angle, roll angle, course angle and original camera frame angle position of the aerial camera, so that the aerial camera visual axis points to a ground fixed target during imaging; and sending an exposure control signal to the intra-frame image average processing unit according to the working time sequence of the aerial remote sensing equipment.
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