CN116828325A - Low-illumination enhanced shooting method and system - Google Patents

Low-illumination enhanced shooting method and system Download PDF

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Publication number
CN116828325A
CN116828325A CN202310622968.7A CN202310622968A CN116828325A CN 116828325 A CN116828325 A CN 116828325A CN 202310622968 A CN202310622968 A CN 202310622968A CN 116828325 A CN116828325 A CN 116828325A
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China
Prior art keywords
image
processing module
brightness
image processing
low
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CN202310622968.7A
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Chinese (zh)
Inventor
刘智
叶曲
陈良杰
李�杰
马骏
帅杨
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Sichuan Zhizhou Technology Co ltd
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Sichuan Zhizhou Technology Co ltd
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Priority to CN202310622968.7A priority Critical patent/CN116828325A/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/80—Camera processing pipelines; Components thereof
    • H04N23/84—Camera processing pipelines; Components thereof for processing colour signals
    • H04N23/88—Camera processing pipelines; Components thereof for processing colour signals for colour balance, e.g. white-balance circuits or colour temperature control
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/70—Circuitry for compensating brightness variation in the scene
    • H04N23/73—Circuitry for compensating brightness variation in the scene by influencing the exposure time
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/70—Circuitry for compensating brightness variation in the scene
    • H04N23/76—Circuitry for compensating brightness variation in the scene by influencing the image signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/80—Camera processing pipelines; Components thereof
    • H04N23/84—Camera processing pipelines; Components thereof for processing colour signals

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Color Television Image Signal Generators (AREA)
  • Studio Devices (AREA)

Abstract

The invention provides a low-illumination enhanced shooting method and a system, comprising the following steps: the image sensor converts the optical signals into electric signals and transmits the electric signals to the image processing module, the image processing module performs format conversion, color correction, white balance control and shutter control, and finally converts the images into YUV format and outputs the YUV format. The invention increases the sensitivity, realizes the noise reduction function through color correction and white balance control, ensures the definition of the image and does not cause output delay.

Description

Low-illumination enhanced shooting method and system
Technical Field
The invention relates to the technical field of image processing, in particular to a low-illumination enhanced shooting method.
Background
Sensitivity (ISO) refers to the degree of sensitivity of a camera sensor to light, and the higher the value, the higher the sensitivity, and the brighter the screen. Different cameras have different ISO ranges, and generally digital cameras can have ISO from 100 to 6400 or higher. However, increasing ISO also causes noise problems, which are granular points on the picture that are outgoing lines that do not belong to the subject, and affect the sharpness and quality of the picture. Therefore, the ISO value is reasonably selected according to the light condition and the shooting purpose at the time of shooting. However, when the high-altitude unmanned aerial vehicle shoots on the ground, the distance is far and the high-altitude unmanned aerial vehicle is affected by the environment, the high-altitude unmanned aerial vehicle is often in a low-illumination environment, the general camera cannot meet the requirement of high-altitude shooting, and an image with clear image quality cannot be shot.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, provides a low-light enhanced shooting method and a system, and solves the technical problem of unclear image quality of a shot image under low light.
The aim of the invention is achieved by the following technical scheme:
the invention provides a low-illumination enhanced shooting method, which comprises the following steps:
s1, converting a picture through a lens light path and projecting the converted picture onto a focal plane of an image sensor;
s2, the image sensor converts the optical signal into an electric signal and transmits the electric signal to the image processing module in a bayer format;
s3, converting the bayer image into an RGB image by the image processing module;
s4, the image processing module corrects the color of the image in the step S3;
s5, performing white balance correction on the image in the step S4 by the image processing module;
s6, converting the image in the step S5 into a YUV format by an image processing module and outputting the YUV format; the exposure shutter time length of the image sensor is controlled according to the current frame.
Optionally or preferably, the image processing module further cuts out the image and cuts out the angle of view before converting the image format in step S3Where d is the vertical sensor height and f is the focal length.
Optionally or preferably, in step S3, the specific steps of the digital gain algorithm are:
s31, carrying out interpolation processing on the Bayer image to obtain an RGB image;
s32, multiplying the pixel values of the red, green and blue channels of each pixel in the RGB image by a constant respectively, thereby realizing the adjustment of the brightness of the image
S33, cutting off the pixel value multiplied by the constant to ensure that the pixel value does not exceed the pixel value range;
s34, storing the adjusted RGB image.
Optionally or preferably, the image processing module performs error color correction and zipper noise suppression, wherein the error color correction adopts white balance correction, and corrects color cast problems in the image by adjusting gains of different color channels in the image; the zipper noise suppression filters the image with a median filter to remove zipper noise, including gaussian noise.
Optionally or preferably, in step S5, a bilateral filtering algorithm is used to make the image clearer, specifically: a filter function h (x) is calculated,wherein k is d -1 (x) For the normalization factor, c is the close function, s is the similarity function, x is the required calculated point, and f (x) is the pixel value of the calculated point.
Optionally or preferably, the electronic shutter is controlled in real time according to the brightness condition of the image, specifically: comparing the image brightness of the frame with the image brightness of the previous frame, calculating the standard deviation of the brightness at the same position between two adjacent frames, accumulating the standard deviation of the brightness into an accumulated difference value, judging whether the accumulated difference value reaches a control threshold value, and adjusting the electronic shutter if the accumulated difference value reaches the control threshold value; if the average brightness does not reach the control threshold, judging whether the average brightness reaches the control threshold; if the average brightness reaches the control threshold, adjusting the electronic shutter; if the average brightness does not reach the control threshold, the brightness of the new frame of image is read to be compared again until the accumulated difference value reaches the control threshold.
Optionally or preferably, in step S6, the image in YUV format is first output to the interface conversion module via the bt.1120 interface; the interface conversion module converts the parallel BT.1120 image information into serial data to complete output through an SMA interface after receiving the parallel BT.1120 image information.
Based on the technical scheme, the following technical effects can be produced:
according to the low-illumination enhanced shooting method, the sensitivity is increased through the gain algorithm, the noise reduction function is realized through the color correction and the white balance control, the definition of an image is ensured, and the output delay is avoided.
The invention also provides a low-illumination enhanced imaging system, comprising:
a lens projecting the light path onto a focal plane of the image sensor;
the image sensor is used for converting the optical signals into electric signals according to the feedback control exposure time length of the image processing module and transmitting the electric signals to the image processing module;
the image processing module is used for cutting and converting the format of the image, enhancing the definition of the image through color correction and white balance control, and controlling the exposure time of the shutter through comparing the brightness of adjacent frames;
and the interface conversion module receives the image information enhanced by the image processing module, converts the image information into serial data and completes output through an SMA interface.
When the low-illumination enhanced camera system is installed on the unmanned aerial vehicle, the problem that the unmanned aerial vehicle acquires the high-definition forward-looking image in real time can be effectively solved, and an operator is assisted to perform accurate operation of the unmanned aerial vehicle.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to the structures shown in these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic workflow diagram of the present invention;
fig. 2 is a schematic flow chart of shutter control in the present invention.
Detailed Description
It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1:
the invention provides a low-illumination enhanced shooting method, which is shown in figure 1 and comprises the following steps:
s1, converting a picture through a lens light path and projecting the converted picture onto a focal plane of an image sensor;
s2, the image sensor converts the optical signal into an electric signal and transmits the electric signal to the image processing module in a bayer format;
s3, the image processing module clips the image according to a preconfigured clipping window, and clips the angle of viewWherein d is the vertical sensor height and f is the focal length; then, the original data output by the image sensor is subjected to Bayer color filtering conversion, and the Bayer image is converted into an RGB image; increasing the sensitivity by adopting a digital gain algorithm;
further, the digital gain algorithm comprises the following specific steps:
s31, carrying out interpolation processing on the Bayer image to obtain an RGB image;
s32, multiplying pixel values of three channels of red, green and blue of each pixel in the RGB image by a constant respectively, so as to realize adjustment of image brightness; specifically, the constant may be 1.2, 1.5;
s33, cutting off the pixel value multiplied by the constant to ensure that the pixel value does not exceed the pixel value range; specifically, the pixel value range of the 8-bit image is 0-255;
s34, storing the adjusted RGB image.
S4, the image processing module corrects the color of the image in the step S3;
s5, performing white balance correction on the image in the step S4 by the image processing module;
further, the image processing module performs error color correction and zipper noise suppression, wherein the error color correction adopts white balance correction, and color shift problems in the image are corrected by adjusting gains of different color channels in the image; the zipper noise suppression filters the image with a median filter to remove zipper noise, including gaussian noise.
S6, converting the image in the step S5 into a YUV format by an image processing module and outputting the YUV format; the exposure shutter time length of the image sensor is controlled according to the current frame.
Further, in the present embodiment, in order to ensure that the image size after clipping is 1280×720 continuously, no snapshot operation is performed, the vertical sensor height d= 3.456mm is taken; focal length f=6.5 mm, and calculating a vertical viewing angle α= 29.775 °, and a vertical viewing angle error ΔΣ=0.225°; meets the design requirement of 30 degrees plus or minus 0.5 degrees.
In this embodiment, in step S5, a bilateral filtering algorithm is used to make the image clearer. The bilateral filtering algorithm is a nonlinear image filtering method, and takes spatial domain information (domain) and range information (range) of pixel points to be filtered into consideration, namely, the spatial proximity and gray similarity of the pixel points are considered at the same time, so that the purposes of edge protection and denoising are achieved. But filtering at the edges of the image using a bilateral filtering algorithm can result in the edges being blurred.
In order to solve the problem of edge blurring, the embodiment classifies the neighborhood to be filtered according to the pixel value, gives different weights according to the category to which the neighborhood belongs, and then performs neighborhood weighted summation to obtain a final result, and the specific implementation principle is that the filter function h (x) is calculated,
wherein k is d -1 (x) For the normalization factor, c is the close function, s is the similarity function, x is the required calculated point, and f (x) is the pixel value of the calculated point. The filtering characteristic will have better performance due to the space domain component (domain), the image edge can be kept clear due to the value domain component (range), the weight has obvious demarcation on each classification edge, and the weighting is carried out from the pixel point on the classification side to which the weight belongs.
Further, as shown in fig. 2, the embodiment controls the electronic shutter in real time according to the brightness of the image, specifically: comparing the image brightness of the frame with the image brightness of the previous frame, calculating the standard deviation of the brightness at the same position between two adjacent frames, accumulating the standard deviation of the brightness into an accumulated difference value, and judging whether the accumulated difference value reaches a control threshold value or not; further, the control threshold is set according to requirements, and the larger the threshold is if the brightness of the image which the user wants to acquire is brighter, and vice versa; if the control threshold is reached, adjusting the electronic shutter; if the average brightness does not reach the control threshold, judging whether the average brightness reaches the control threshold; if the average brightness reaches the control threshold, adjusting the electronic shutter; if the average brightness does not reach the control threshold, the brightness of the new frame of image is read to be compared again until the accumulated difference value reaches the control threshold.
Further, in step S6, the image in YUV format is first output to the interface conversion module via the bt.1120 interface; the interface conversion module converts the parallel BT.1120 image information into serial data to complete output through an SMA interface after receiving the parallel BT.1120 image information.
The embodiment also provides a low-light enhanced imaging system, including:
a lens projecting the light path onto a focal plane of the image sensor;
the image sensor is used for converting the optical signals into electric signals according to the feedback control exposure time length of the image processing module and transmitting the electric signals to the image processing module;
the image processing module is used for cutting and converting the format of the image, enhancing the definition of the image through color correction and white balance control, and controlling the exposure time of the shutter through comparing the brightness of adjacent frames;
and the interface conversion module receives the image information enhanced by the image processing module, converts the image information into serial data and completes output through an SMA interface.
This embodiment extends ISO from 1600 to 256000, greatly increasing the visibility in low light conditions.

Claims (8)

1. A low-light enhancement shooting method is characterized in that: the method comprises the following steps:
s1, converting a picture through a lens light path and projecting the converted picture onto a focal plane of an image sensor;
s2, the image sensor converts the optical signal into an electric signal and transmits the electric signal to the image processing module in a bayer format;
s3, converting the bayer image into an RGB image by the image processing module; increasing the sensitivity by adopting a digital gain algorithm;
s4, the image processing module corrects the color of the image in the step S3;
s5, performing white balance correction on the image in the step S4 by the image processing module;
s6, converting the image in the step S5 into a YUV format by an image processing module and outputting the YUV format; the exposure shutter time length of the image sensor is controlled according to the current frame.
2. The low-light enhanced imaging method according to claim 1, wherein: before the image format conversion in step S3, the image processing module also cuts the image to obtain a cut angle of viewWherein d is the vertical sensor height and f isFocal length.
3. The low-light enhanced imaging method according to claim 1, wherein: in step S3, the specific steps of the digital gain algorithm are as follows:
s31, carrying out interpolation processing on the Bayer image to obtain an RGB image;
s32, multiplying pixel values of three channels of red, green and blue of each pixel in the RGB image by a constant respectively, so as to realize adjustment of image brightness;
s33, cutting off the pixel value multiplied by the constant to ensure that the pixel value does not exceed the pixel value range;
s34, storing the adjusted RGB image.
4. The low-light enhanced imaging method according to claim 1, wherein: the image processing module performs error color correction and zipper noise suppression, wherein the error color correction adopts white balance correction, and the color shift problem in the image is corrected by adjusting gains of different color channels in the image; the zipper noise suppression filters the image with a median filter to remove zipper noise, including gaussian noise.
5. The low-light enhanced imaging method according to claim 1, wherein: in step S5, a bilateral filtering algorithm is adopted to make the image clearer, specifically: a filter function h (x) is calculated,
wherein k is d -1 (x) For the normalization factor, c is the close function, s is the similarity function, x is the required calculated point, and f (x) is the pixel value of the calculated point.
6. The low-light enhanced imaging method according to claim 1, wherein: the electronic shutter is controlled in real time according to the brightness condition of the image, and specifically comprises the following steps: comparing the image brightness of the frame with the image brightness of the previous frame, calculating the standard deviation of the brightness at the same position between two adjacent frames, accumulating the standard deviation of the brightness into an accumulated difference value, judging whether the accumulated difference value reaches a control threshold value, and adjusting the electronic shutter if the accumulated difference value reaches the control threshold value; if the average brightness does not reach the control threshold, judging whether the average brightness reaches the control threshold; if the average brightness reaches the control threshold, adjusting the electronic shutter; if the average brightness does not reach the control threshold, the brightness of the new frame of image is read to be compared again until the accumulated difference value reaches the control threshold.
7. The low-light enhanced imaging method according to claim 1, wherein: in step S6, the image in YUV format is output to the interface conversion module via bt.1120 interface; the interface conversion module converts the parallel BT.1120 image information into serial data to complete output through an SMA interface after receiving the parallel BT.1120 image information.
8. A low-light enhanced imaging system, characterized by being based on any of the low-light enhanced imaging methods of claims 1-7, comprising:
a lens projecting the light path onto a focal plane of the image sensor;
the image sensor is used for converting the optical signals into electric signals according to the feedback control exposure time length of the image processing module and transmitting the electric signals to the image processing module;
the image processing module is used for cutting and converting the format of the image, enhancing the definition of the image through color correction and white balance control, and controlling the exposure time of the shutter through comparing the brightness of adjacent frames;
and the interface conversion module receives the image information enhanced by the image processing module, converts the image information into serial data and completes output through an SMA interface.
CN202310622968.7A 2023-05-30 2023-05-30 Low-illumination enhanced shooting method and system Pending CN116828325A (en)

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CN116828325A true CN116828325A (en) 2023-09-29

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