High dynamic image imaging system and automatic exposure method thereof

Abstract

The invention provides a high dynamic image imaging system and an automatic exposure method thereof. The method comprises the following steps: constructing an imaging relation model between an output image and exposure parameters; shooting by adopting the current exposure parameter to obtain an output image; according to the brightness distribution of the output image, using the imaging relation model to update exposure parameters; and shooting by using the updated exposure parameters to obtain a new output image. By constructing the imaging relation model and updating the exposure parameters by using the imaging relation model according to the brightness distribution of the output image, the exposure parameters of the subsequent shooting can be adaptively adjusted according to the exposure parameters of the current shooting and the output image in the multiple shooting processes of the high-dynamic image; the image information interval captured by each exposure can be continuous, so that the number of shot images can be reduced as much as possible, the image information can be completely covered, the quality of the high-dynamic image is ensured, and the problem of how to improve the imaging efficiency and quality of the high-dynamic image is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of image imaging technology, in particular to a high dynamic image imaging system and an automatic exposure method thereof. BACKGROUND

[0002] High dynamic range imaging (HDR) reconstructs the real illumination information of a scene by fusing multiple low dynamic range images with different exposure, realizes a larger exposure dynamic range, and thus overcomes the limitation that a single exposure cannot capture both the extremely bright and extremely dark regions of a scene, and better displays the real world scene.

[0003] At present, the way to obtain multiple low dynamic range images with different exposures usually adopts a preset exposure step and a number of shots. However, due to the fixed exposure step and the number of shots, for a scene with a small dynamic range, it leads to redundant shooting, and for a scene with a large dynamic range, it may result in incomplete coverage of image information. Therefore, the existing high dynamic image shooting method not only has low imaging efficiency, but also affects the image quality of imaging. SUMMARY

[0004] The purpose of the present application is to provide a high dynamic image imaging system and an automatic exposure method thereof to solve the problem of how to improve the imaging efficiency and quality of high dynamic images.

[0005] To solve the above technical problems, the present application provides an automatic exposure method of a high dynamic image imaging system, comprising: constructing an imaging relationship model between an output image and an exposure parameter; shooting with the current exposure parameter to obtain an output image; updating the exposure parameter according to the brightness distribution of the output image using the imaging relationship model; shooting with the updated exposure parameter to obtain a new output image.

[0006] Optionally, in the automatic exposure method of the high dynamic image imaging system, the imaging relationship model is represented as:

[0007] wherein BV represents the ambient brightness, EXP represents the exposure time, F() represents the imaging relationship function, and DN represents the output image.

[0008] Optionally, in the automatic exposure method of the high dynamic image imaging system, the method of updating the exposure parameter according to the brightness distribution of the output image using the imaging relationship model comprises: using an accumulated histogram to obtain a brightness distribution histogram of the output image; if the number of pixels with luminance values less than the first luminance threshold in the luminance distribution histogram is greater than or equal to the first quantity threshold, then increasing the exposure time using the imaging relationship model; if the number of pixels with luminance values greater than the second luminance threshold in the luminance distribution histogram is greater than or equal to the second quantity threshold, then decreasing the exposure time using the imaging relationship model.

[0009] Optionally, in the automatic exposure method of the high dynamic image imaging system, the calculation method of increasing the exposure time using the imaging relationship model comprises:

[0010] where EXP represents the current exposure time, represents the inverse function of the imaging relationship function, DL represents the first luminance threshold, DH represents the second luminance threshold, and EXP_L represents the exposure time after increasing the exposure time.

[0011] Optionally, in the automatic exposure method of the high dynamic image imaging system, the calculation method of decreasing the exposure time using the imaging relationship model comprises:

[0012] where EXP represents the current exposure time, represents the inverse function of the imaging relationship function, DL represents the first luminance threshold, DH represents the second luminance threshold, and EXP_S represents the exposure time after decreasing the exposure time.

[0013] Optionally, in the automatic exposure method of the high dynamic image imaging system, the automatic exposure method further comprises: repeating the above steps to obtain a plurality of different output images using the continuously updated exposure parameters.

[0014] Optionally, in the automatic exposure method of the high dynamic image imaging system, the method of obtaining a plurality of different output images using the continuously updated exposure parameters comprises: if the number of pixels with luminance values greater than or equal to the first luminance threshold and less than or equal to the second luminance threshold in the luminance distribution histogram of the output image obtained by the current shooting exceeds a third quantity threshold, then stopping shooting and taking all the obtained output images as an image sequence.

[0015] Optionally, in the automatic exposure method of the high dynamic image imaging system, the method of obtaining a plurality of different output images using the continuously updated exposure parameters comprises: If the number of pixels with a luminance value less than the first luminance threshold in the luminance distribution histogram of the output image obtained by the current shooting is less than the first quantity threshold, and the number of pixels with a luminance value greater than the second luminance threshold is less than the second quantity threshold, the shooting is stopped, and all the obtained output images are taken as an image sequence.

[0016] Optionally, in the automatic exposure method of the high dynamic image imaging system, the method of obtaining a plurality of different output images by shooting with the exposure parameter constantly updated comprises: If the current exposure parameter has reached the exposure threshold, the shooting is stopped, and all the obtained output images are taken as an image sequence.

[0017] To solve the above technical problems, the application further provides a high dynamic image imaging system, which is exposed by using the automatic exposure method according to any one of the above.

[0018] The high dynamic image imaging system and the automatic exposure method thereof provided by the application comprise the following steps: constructing an imaging relationship model between an output image and an exposure parameter; shooting by using a current exposure parameter to obtain an output image; updating the exposure parameter by using the imaging relationship model according to the luminance distribution of the output image; and shooting by using the updated exposure parameter to obtain a new output image. By constructing the imaging relationship model between the output image and the exposure parameter, and updating the exposure parameter by using the imaging relationship model according to the luminance distribution of the output image, the exposure parameter of the subsequent shooting can be adjusted adaptively according to the exposure parameter and the output image obtained by the current shooting in the shooting process of the plurality of low dynamic range images of the high dynamic range image, so that the image information interval captured by each exposure can be continuous, thereby not only the number of shots can be reduced as much as possible, but also the image information can be completely covered, the quality of the final high dynamic image is ensured, and the problem of how to improve the imaging efficiency and quality of the high dynamic image is solved. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The flow chart of the automatic exposure method of the high dynamic image imaging system provided by the present embodiment; Figure 2 The structure block diagram of the control processor in the high dynamic image imaging system provided by the present embodiment. DETAILED DESCRIPTION

[0020] The high dynamic image imaging system and the automatic exposure method thereof according to the present application will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that all the drawings are very simplified and all use non-precise proportions, which are only used to facilitate and clarify the purpose of assisting the description of the embodiments of the present application. In addition, the structures shown in the drawings are often part of the actual structures. In particular, different proportions are sometimes used in the drawings to show different focuses.

[0021] It should be noted that "first", "second", and the like in the description and claims of the present application and the accompanying drawings are used to distinguish similar objects in order to describe the embodiments of the present application, and are not used to describe a specific order or sequence. It should be understood that the structures used in this way can be interchanged under appropriate circumstances. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device that includes a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0022] The present embodiment provides an automatic exposure method of a high dynamic image imaging system, as shown in the formula (1), comprising: Figure 1 S1, constructing an imaging relationship model between an output image and an exposure parameter; S2, taking a picture using the current exposure parameter to obtain an output image; S3, updating the exposure parameter according to the brightness distribution of the output image using the imaging relationship model; S4, taking a picture using the updated exposure parameter to obtain a new output image.

[0023] The automatic exposure method of the high dynamic image imaging system provided by the present embodiment, by constructing an imaging relationship model between an output image and an exposure parameter, and updating the exposure parameter according to the brightness distribution of the output image using the imaging relationship model, makes it possible to adaptively adjust the exposure parameter of subsequent shooting according to the current shooting exposure parameter and the output image in the shooting process of multiple low dynamic range images of a high dynamic range image, so that the image information interval captured by each exposure can be continuous, thereby not only reducing the number of shots as much as possible, but also making the image information cover completely, ensuring the quality of the final high dynamic image, and solving the problem of how to improve the imaging efficiency and quality of the high dynamic image.

[0024] Specifically, in the present embodiment, step S1, constructing an imaging relationship model between an output image and an exposure parameter.

[0025] ​In practical applications, considering that in the imaging process of a high dynamic image, the key exposure parameter is exposure time, and the influencing factor is environmental brightness, a relationship model between an output image of an imaging system and environmental brightness and exposure time can be constructed as an imaging relationship model, which is expressed as:

[0026] wherein BV represents environmental brightness, EXP represents exposure time, and DN represents an output image; F() represents an imaging relationship function, which can be calibrated and fitted according to multiple experiments.

[0027] Of course, in other embodiments, the imaging relationship model can also include other influencing factors and exposure parameters, such as parameters of an image sensor in the imaging system, lens parameters, and the like, so as to make the imaging relationship model more complex and more accurate.

[0028] The specific construction of the imaging relationship model can be realized by a person skilled in the art on the basis of the above technical solutions of the present application in combination with actual needs, and the present application does not repeat the description. In addition, the automatic exposure method realized by other imaging relationship models constructed on the basis of the present application without departing from the main idea of the present application should also belong to the protection scope of the present application.

[0029] Further, in the present embodiment, step S2, the current exposure parameter is used for shooting to obtain an output image.

[0030] In practical applications, the exposure parameter can be initialized to start shooting using an original exposure parameter. Specifically, the initialized exposure parameter is the minimum value of the exposure parameter in the imaging system, for example, the exposure time is the shortest exposure time of the imaging system. In this way, it can be ensured that the output image obtained by subsequent shooting can traverse all exposure parameters, and thus all output images can cover all image information.

[0031] Further, in the present embodiment, step S3, the exposure parameter is updated according to the brightness distribution of the output image using the imaging relationship model.

[0032] Specifically, in the present embodiment, first, the brightness distribution of the output image can be counted in the form of an accumulated histogram to obtain a brightness distribution histogram of the output image. In the brightness distribution histogram, in addition to reflecting the brightness value distribution, the number of dark pixels and the number of bright pixels can also be reflected.

[0033] If the number of pixels with luminance values less than the first luminance threshold in the luminance distribution histogram is greater than or equal to the first quantity threshold, that is, the number of dark pixels exceeds the first quantity threshold, it indicates that the dark part interval of the current environment is not effectively captured, and therefore the exposure time needs to be increased using the imaging relationship model to capture the image information of the dark part interval not captured in the current output image in subsequent capturing.

[0034] If the number of pixels with luminance values greater than the second luminance threshold in the luminance distribution histogram is greater than or equal to the second quantity threshold, that is, the number of bright pixels exceeds the second quantity threshold, it indicates that the bright part interval of the current environment is not effectively captured, and therefore the exposure time needs to be reduced using the imaging relationship model to capture the image information of the bright part interval not captured in the current output image in subsequent capturing.

[0035] In actual application, the first luminance threshold, the second luminance threshold, the first quantity threshold and the second quantity threshold can be reasonably set according to actual needs. When setting, the first luminance threshold needs to accurately reflect the lower limit of the best detail to ensure that the pixels below the first luminance threshold are unreliable data of underexposure; at the same time, the second luminance threshold needs to accurately reflect the upper limit of the best detail to ensure that the pixels above the second luminance threshold are data of overexposure and loss of detail.

[0036] In the embodiment, the calculation method of increasing the exposure time using the imaging relationship model includes:

[0037] wherein EXP represents the current exposure time, denotes the inverse function of the imaging relationship function, DL represents the first luminance threshold, DH represents the second luminance threshold, and EXP_L represents the exposure time after increasing the exposure time.

[0038] In this way, for the dark part interval not captured at present, the exposure time after increasing the exposure time can make the dark part interval with the first luminance threshold in the current output image have the luminance raised to the second luminance threshold after a new exposure, so as to ensure that the dark part interval below the first luminance threshold can be effectively captured after a new exposure.

[0039] In the embodiment, the calculation method of reducing the exposure time using the imaging relationship model includes:

[0040] wherein EXP represents the current exposure time, denotes the inverse function of the imaging relationship function, DL represents the first luminance threshold, DH represents the second luminance threshold, and EXP_S represents the exposure time after reducing the exposure time.

[0041] In this way, for the bright areas that are not currently captured, by reducing the exposure time after the exposure time, the brightness of the bright areas in the current output image that are at the second brightness threshold will decrease to the first brightness threshold after the new exposure, so as to ensure that the bright areas that are higher than the second brightness threshold can be effectively captured image information after the new exposure.

[0042] Furthermore, in this embodiment, step S4 involves taking a picture using the updated exposure parameters to obtain a new output image.

[0043] Specifically, repeat steps S2 and S3 above to capture multiple different output images using continuously updated exposure parameters.

[0044] Preferably, in this embodiment, the method for obtaining multiple different output images by capturing images using continuously updated exposure parameters includes: If the brightness value in the brightness distribution histogram of the currently captured output image is greater than or equal to the first brightness threshold and less than or equal to the second brightness threshold, it indicates that the currently acquired output image has completely covered all brightness ranges. Therefore, the capturing can be stopped, and all acquired output images can be treated as an image sequence.

[0045] Furthermore, if in the brightness distribution histogram of the currently captured output image, the number of pixels with brightness values ​​less than the first brightness threshold is less than the first quantity threshold, and the number of pixels with brightness values ​​greater than the second brightness threshold is less than the second quantity threshold, that is, the number of pixels exceeding the brightness threshold is lower than the preset tolerance, it can also be regarded as the currently obtained output image has completely covered all brightness ranges, so the shooting can be stopped, and all the obtained output images can be used as an image sequence.

[0046] Furthermore, if the current exposure parameter has reached the exposure threshold, shooting stops, and all the obtained output images are treated as an image sequence. The exposure threshold includes the upper and lower limits of each exposure parameter. For example, at the start of shooting, the exposure time is the shortest exposure time. When the exposure time increases to the longest exposure time with the number of shots, shooting stops because the exposure time can no longer be increased, thus avoiding the waste of time caused by continuous shooting under the same exposure parameters.

[0047] After obtaining the image sequence, multiple output images in the image sequence can be used for image fusion processing to obtain a high dynamic range image.

[0048] The automatic exposure method provided in this embodiment enables seamless stitching of dynamic range images. Specifically, assuming that the brightness of a pixel in the output image obtained under the current exposure parameters is exactly at the second brightness threshold level, then after updating the exposure parameters, the brightness of that pixel in the newly obtained output image will be reduced to the first brightness threshold level. This ensures that the two output images obtained before and after the exposure parameter update achieve continuous coverage in the dynamic range, without gaps or wasted overlap. Based on this, it is possible to achieve the best imaging effect with the fewest exposures when acquiring high dynamic range images.

[0049] Furthermore, the automatic exposure method provided in this embodiment can adjust the exposure based on the actual response of the imaging system (the brightness of the output image) and the set quality target (…). It adaptively updates the optimal exposure time to ensure that each update of the exposure parameters is effective and can capture the scene brightness range that was not previously captured and recorded, thereby achieving the fullest dynamic range with the fewest shots.

[0050] This embodiment also provides a high dynamic range imaging system, which uses the automatic exposure method described above to perform exposure in order to obtain a high dynamic range image.

[0051] Specifically, in this embodiment, the high dynamic range imaging system includes a control processor, which is used to execute the automatic exposure method described above, wherein, as... Figure 2 As shown, the control processor includes: The model building module is used to build an imaging relationship model between the output image and exposure parameters. The exposure parameter setting module is used to set the current exposure parameters and to update the exposure parameters based on the brightness distribution of the output image using an imaging relationship model. The image capture module is used to capture images using the exposure parameters set in the exposure parameter setting module to obtain the output image.

[0052] Preferably, in this embodiment, the control processor may further include a process control module. The process control module can control the stopping of shooting when the brightness value of the brightness distribution of the currently captured output image is greater than or equal to a first brightness threshold and less than or equal to a second brightness threshold; or, in the currently captured output image, when the number of pixels with a brightness less than the first brightness threshold is less than a first quantity threshold, and the number of pixels with a brightness greater than the second brightness threshold is less than a second quantity threshold; or, when the current exposure parameters have reached the exposure threshold, control the stopping of shooting.

[0053] More preferably, in this embodiment, the control processor may further include an image fusion module, which can be used to fuse the output images obtained from multiple exposures, so that the high dynamic range imaging system can directly output the fused image with high dynamic range.

[0054] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to mutually. In addition, different parts between embodiments can also be combined with each other, and this invention does not limit this.

[0055] The high dynamic range (HDR) imaging system and its automatic exposure method provided in this embodiment include: constructing an imaging relationship model between the output image and exposure parameters; taking a picture using the current exposure parameters to obtain the output image; updating the exposure parameters using the imaging relationship model based on the brightness distribution of the output image; and taking a picture using the updated exposure parameters to obtain a new output image. By constructing an imaging relationship model between the output image and exposure parameters, and updating the exposure parameters using the imaging relationship model based on the brightness distribution of the output image, the exposure parameters for subsequent shots can be adaptively adjusted according to the current exposure parameters and the output image during the capture of multiple low dynamic range (LMR) images of a HDR image. This ensures that the image information range captured in each exposure is continuous, thereby minimizing the number of shots and ensuring complete coverage of image information, thus guaranteeing the quality of the final HDR image and solving the problem of improving the imaging efficiency and quality of HDR images.

[0056] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. A method of automatic exposure for a high dynamic image imaging system, characterized in that, The application relates to an automatic exposure method and a high dynamic image imaging system. The method comprises the following steps: constructing an imaging relationship model between an output image and an exposure parameter; taking a picture by using the current exposure parameter to obtain an output image; updating the exposure parameter according to the brightness distribution of the output image by using the imaging relationship model; and taking a picture by using the updated exposure parameter to obtain a new output image. The imaging relationship model is expressed as: DN = F (BV, EXP), wherein BV represents the ambient brightness, EXP represents the exposure time, F ( ) represents an imaging relationship function, and DN represents the output image. The method for updating the exposure parameter according to the brightness distribution of the output image by using the imaging relationship model comprises the following steps: obtaining a brightness distribution histogram of the output image by using an accumulated histogram; increasing the exposure time by using the imaging relationship model if the number of pixels with a brightness value less than a first brightness threshold in the brightness distribution histogram is greater than or equal to a first quantity threshold; and decreasing the exposure time by using the imaging relationship model if the number of pixels with a brightness value greater than a second brightness threshold in the brightness distribution histogram is greater than or equal to a second quantity threshold. The calculation method for increasing the exposure time by using the imaging relationship model comprises the following steps: obtaining a first exposure time by using the imaging relationship model; and obtaining a second exposure time by using the imaging relationship model and the first exposure time.

2. The method of auto exposure for high dynamic image imaging system according to claim 1, characterized in that, The calculation method for decreasing the exposure time by using the imaging relationship model comprises the following steps: obtaining a first exposure time by using the imaging relationship model; and obtaining a second exposure time by using the imaging relationship model and the first exposure time. The automatic exposure method further comprises the following steps: repeating the above steps to take pictures by using the continuously updated exposure parameter to obtain a plurality of different output images.

3. The method of auto exposure for high dynamic image imaging system according to claim 1 or 2, characterized in that, The method for taking pictures by using the continuously updated exposure parameter to obtain a plurality of different output images comprises the following steps: if the number of pixels with a brightness value greater than or equal to the first brightness threshold and less than or equal to the second brightness threshold in the brightness distribution histogram of the output image obtained by the current picture exceeds a third quantity threshold, stopping the picture taking and taking all the obtained output images as an image sequence. The method for taking pictures by using the continuously updated exposure parameter to obtain a plurality of different output images comprises the following steps: if the number of pixels with a brightness value less than the first brightness threshold in the brightness distribution histogram of the output image obtained by the current picture is less than the first quantity threshold, and the number of pixels with a brightness value greater than the second brightness threshold is less than the second quantity threshold, stopping the picture taking and taking all the obtained output images as an image sequence. The method for taking pictures by using the continuously updated exposure parameter to obtain a plurality of different output images comprises the following steps: if the current exposure parameter has reached an exposure threshold, stopping the picture taking and taking all the obtained output images as an image sequence. The high dynamic image imaging system takes pictures by using the automatic exposure method according to any one of claims 1 to 9 to obtain high dynamic images.

4. The method of auto exposure for high dynamic image imaging system according to claim 3, characterized in that, ​ where EXP denotes a current exposure time, () denotes an inverse function of the imaging relationship function, DL denotes a first luminance threshold value, DH denotes a second luminance threshold value, and EXP_L denotes an exposure time after the exposure time is increased.

5. The method of auto exposure for high dynamic image imaging system according to claim 3, characterized in that, ​ where EXP denotes a current exposure time, () denotes an inverse function of the imaging relationship function, DL denotes a first luminance threshold value, DH denotes a second luminance threshold value, and EXP_S denotes an exposure time after the exposure time is reduced.

6. The method of auto exposure for high dynamic image imaging system according to claim 1, characterized in that, ​ ​ 7. The method of auto exposure for high dynamic image imaging system according to claim 6, characterized in that, ​ ​ 8. The method of auto exposure for high dynamic image imaging system according to claim 6, characterized in that, ​ ​ 9. The method of auto exposure for a high dynamic image imaging system of claim 6, wherein, ​ ​ 10. A high dynamic image imaging system, characterized by, ​

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