WO2023273962A1

WO2023273962A1 - Automatic exposure method, automatic exposure apparatus, camera and computer-readable storage medium

Info

Publication number: WO2023273962A1
Application number: PCT/CN2022/100183
Authority: WO
Inventors: 谭坤; 郭奕滨
Original assignee: 影石创新科技股份有限公司
Priority date: 2021-06-29
Filing date: 2022-06-21
Publication date: 2023-01-05
Also published as: CN113596342A

Abstract

Disclosed in the present invention is an automatic exposure method. The automatic exposure method comprises: S1: acquiring the current image frame data that is captured by a photographic apparatus according to the current exposure parameter, and calculating a luminance Ya of the current frame; S2: calculating a target exposure amount EVb according to the luminance Ya of the current frame, the current exposure amount EVa and a target luminance Yb; S3: selecting a corresponding exposure parameter table according to the motion state of the photographic apparatus; S4: determining a target exposure parameter according to the target exposure amount EVb and the selected exposure parameter table; and S5: updating the exposure parameter of the photographic apparatus to be the target exposure parameter, and returning to step S1, wherein the current exposure amount EVa is obtained by means of calculation according to the current exposure parameter of the photographic apparatus, and the target luminance Yb is obtained by calculating an exposure index Na on the basis of the current exposure amount EVa and by then combining the exposure index NA with a luminance lookup table. By means of the present invention, the problems of motion blurs appearing in an image that is photographed by a photographic apparatus in a motion state and severe noise appearing in an image that is photographed in a stationary state are alleviated.

Description

Automatic exposure method, exposure device, camera, and computer-readable storage medium

technical field

The present application relates to the technical field of image processing, in particular to an automatic exposure method, an exposure device, a camera, and a computer-readable storage medium.

Background technique

The purpose of automatic exposure is to realize the recognition of brightness levels in different lighting conditions and different scenes, and adjust the exposure parameters in real time, so that the captured video or image appears to be of appropriate brightness to the human eye. To achieve this goal, adjust the lens iris aperture, sensor exposure time, sensor analog gain and digital gain. This adjustment process is called Auto Exposure.

In the existing technical solutions, in indoor or low-light environments, the shutter time is often set longer to increase the brightness of the picture and reduce noise. However, when recording a moving video, an excessively long shutter time will cause Severe motion blur, smearing, etc.

In view of the above problems, the Chinese Patent Publication No. CN110290316A discloses a method for adjusting the upper limit of the shutter of the camera, by receiving gyroscope data or judging the movement of the feature points of the stationary objects in multiple frames of adjacent images. Motion status; adjust the camera's shutter upper limit in real time according to the camera's motion status. By using a shorter shutter and a higher ISO in motion, it is guaranteed that the image will not be blurred due to a longer exposure time; in a static state, a longer shutter and a lower ISO are used in priority, thereby reducing the blur caused by a high ISO Noise improves picture quality.

technical problem

However, the above-mentioned solution can only distinguish the two states of stillness and motion, but cannot distinguish the specific type of motion. In the case of different degrees of motion, the shutter and ISO of the camera are adjusted in the same way, resulting in some motion scenes. The shooting picture is not ideal.

Therefore, it is necessary to improve the existing automatic exposure method.

technical solution

The purpose of the present invention is to provide an automatic exposure method, an exposure device, a camera and a computer-readable storage medium, aiming to solve at least some of the defects of the existing automatic exposure method.

In the first aspect, a preferred embodiment of the present invention provides an automatic exposure method, the method comprising: S1: Obtain the current frame image data captured by the shooting device according to the current exposure parameters and calculate the brightness Ya of the current frame; S2: According to The brightness Ya of the current frame, the current exposure EVa and the target brightness Yb calculate the target exposure EVb; S3: select the corresponding exposure parameter table according to the motion state of the shooting device; S4: determine the target according to the target exposure EVb and the selected exposure parameter table Exposure parameter; S5: Update the exposure parameter of the shooting device to the target exposure parameter and return to step S1; wherein, the current exposure EVa is obtained by calculating the current exposure parameter of the shooting device, and the target brightness Yb is calculated from the current exposure EVa Exposure index Na Then combined with the brightness lookup table to obtain.

In a specific scheme of this embodiment, the current exposure EVa in step S1 can be calculated by the following formula: EVa=SHTa*AGCa/APTa^ ² , wherein, SHTa, AGCa, APTa are the current shutters of the shooting device in turn , gain and iris.

In the optimization scheme of this embodiment, the step S1 includes the following sub-steps: S101: Acquire the current frame image data captured by the shooting device according to the current exposure parameters; S102: Divide the current frame image data into multiple blocks and perform Set the weight value; S103: Calculate the brightness of the current frame according to the average brightness value of each block and the corresponding weight value.

In a specific solution of this embodiment, the step S2 includes the following sub-steps: S201: judge whether the brightness Ya of the current frame and the target brightness Yb are within the error range, if yes, return to step S1, otherwise, enter step S202; S202: Calculate the target exposure EVb according to the current exposure EVa, the target brightness Yb, and the brightness Ya of the current frame.

In a specific solution of this embodiment, the step S3 includes the following sub-steps: S301: Obtain the difference Df between the angles read twice by the gyroscope; S302: If the values of the consecutive N Df are equal to If it is between the set thresholds Dt _i to Dt _i+1 , the photographing device is determined to be in the i-th motion state; S303: Select the i-th exposure parameter table corresponding to the i-th motion state.

In a specific solution of this embodiment, the step S4 includes the following sub-steps: S401: Calculate the exposure index Nb according to the target exposure EVb; S402: Determine the target exposure parameter according to the exposure index and the corresponding data in the exposure parameter table; wherein , the exposure parameter table takes the exposure index as a coordinate, and includes an exposure index value and a corresponding exposure parameter value, and the exposure parameter includes an aperture value, a shutter value, and a gain value.

Further, the step S402 specifically includes: according to the exposure index Nb, find the two indexes closest to the exposure index Nb and the corresponding two sets of exposure parameters in the exposure parameter table, and calculate the target exposure parameters by interpolation.

In the second aspect, an automatic exposure device is also provided in an embodiment of the present invention. The device includes: an acquisition module, which acquires a frame of image data captured by the shooting device according to the current exposure parameters and calculates the brightness Ya of the current frame; A module for calculating the target exposure EVb according to the current exposure EVa, the brightness Ya of the current frame and the target brightness Yb; a selection module for selecting the corresponding exposure parameter table according to the motion state of the shooting device; a determination module for selecting the corresponding exposure parameter table according to the target The exposure value EVb and the selected exposure parameter table determine the target exposure parameters; the update module is used to update the exposure parameters of the shooting device to the exposure parameters of the next frame; wherein, the current exposure value EVa is obtained by calculating the current exposure parameters of the shooting device, The target brightness Yb is obtained by combining the brightness lookup table after calculating the exposure index Na from the current exposure EVa.

In the third aspect, an embodiment of the present invention also provides a camera, the camera includes a processor and a memory, and a computer program is stored in the memory, and the computer program is used to realize any of the above-mentioned functions when the processor executes it. Auto Exposure method described in section .

In a fourth aspect, an embodiment of the present invention also provides a computer-readable storage medium, where a computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, any one of the above-mentioned Auto Exposure method described above.

Beneficial effect

Compared with the prior art, the technical solution of the present invention updates the exposure parameters of the photographing device in real time by combining the target exposure amount and the motion state of the photographing device, which improves the motion blur of the picture caused by the photographing device in a moving state and the blurred image in a static state. Shooting results in severe picture noise.

Description of drawings

FIG. 1 is a flowchart of an automatic exposure method in Embodiment 1 of the present invention.

FIG. 2 is a flow chart of sub-steps of step S1 in Embodiment 1 of the present invention.

FIG. 3 is a flow chart of sub-steps of step S2 in Embodiment 1 of the present invention.

FIG. 4 is a flow chart of sub-steps of step S3 in Embodiment 1 of the present invention.

FIG. 5 is a flow chart of sub-steps of step S4 in Embodiment 1 of the present invention.

FIG. 6 is a brightness lookup table Y_LUT in Embodiment 1 of the present invention.

FIG. 7 is a table of static state exposure parameters in Embodiment 1 of the present invention.

FIG. 8 is a table of exposure parameters in a walking state in Embodiment 1 of the present invention.

FIG. 9 is a table of exposure parameters in a running state in Embodiment 1 of the present invention.

Fig. 10 is a block diagram of an automatic exposure device in Embodiment 2 of the present invention.

Fig. 11 is a block diagram of a camera in Embodiment 3 of the present invention.

Embodiments of the present invention

In order to make the object, technical solution and beneficial effects of the present invention more clear, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

It should be noted that symbols such as "S1" and "S2" in the specification, claims and drawings of the present invention are used to represent the content of a certain step, rather than to describe a specific sequence or sequence. It should be understood that reference numbers so used are interchangeable under appropriate circumstances, unless the latter step is dependent on the implementation of the previous step.

In order to illustrate the technical solutions of the present invention, specific examples are used below to illustrate.

Example 1

As shown in FIG. 1 , it is a flow chart of the automatic exposure method in this embodiment, including the following steps.

S1: Obtain the image data of the current frame captured by the photographing device according to the current exposure parameters and calculate the brightness Ya of the current frame.

In this embodiment, the photographing device may be an electronic device with a photographing function such as a sports camera, a mobile phone, and a video camera. After the image data of the current frame is acquired, the luminance values of each pixel in the current frame can be counted, and then the average value of the luminance values of each pixel can be used as the luminance Ya of the current frame.

In a specific solution of this embodiment, step S1 includes the following sub-steps.

S101: Acquire current frame image data captured by a photographing device according to current exposure parameters.

The current frame image data is the video frame image data shot according to the current exposure parameters (shutter SHTa, gain AGCa and aperture APTa) of the shooting device. It should be noted that when the shooting device is turned on, the current exposure parameter of the shooting device is a preset value, which is related to the shooting scene of the shooting device. Therefore, the preset exposure parameters make the exposure of the sports camera relatively small.

S102: Divide the image of the current frame into multiple blocks and set a weight value for each block.

Specifically, in this embodiment, the image of the current frame can be divided into n image blocks of the same size, and different weights ωi can be set according to the position of each image block in the image. Since the focus of the user is generally at In the center of the screen or close to the ground side, you can set a higher weight value for the image blocks located in the center and below the image. In other optional schemes of this step, the image of the current frame can also be divided into multiple blocks according to the shooting content of the image, for example, the object in the image of the current frame is recognized by AI (artificial intelligence algorithm), and then the Blocks set higher weight values.

S103: Calculate the brightness of the current frame according to the average brightness value of each block and the corresponding weight value.

In the specific scheme of this embodiment, since the size of each block is the same, so the number of pixels contained is the same, so the brightness values of each pixel in each block can be counted first, and then the average brightness value Li of each block can be obtained, and then Multiplied by the corresponding weight value ωi of each block, the brightness Ya of the current frame can be obtained, and the calculation formula is as follows:

in,

S2: Calculate the target exposure EVb according to the brightness Ya of the current frame, the current exposure EVa and the target brightness Yb.

In this embodiment, step S2 includes sub-steps S201 and S202.

S201: Determine whether the luminance Ya of the current frame and the target luminance Yb are within the error range, if yes, return to step S1, otherwise, enter step S202.

The formula for calculating the current exposure EVa is: EVa=SHTa*AGCa/APTa^ ² , where SHTa, AGCa, and APTa are the current shutter, gain, and aperture of the photographing device in sequence.

The target brightness Yb is obtained by combining the brightness lookup table after calculating the exposure index Na from the current exposure EVa, specifically: calculating the exposure index Na according to the current exposure EVa, and limiting Na to the maximum value of the exposure index (in this embodiment, Within 15), the formula for calculating the exposure index Na is: Na=16+log2EVa. After calculating the exposure index Na, find the same value as Na in the brightness lookup table Y_LUT, and then find the corresponding brightness value. If Na is located at Between the two index coordinates Na1 and Na2, find the target brightness values Yb1 and Yb2 corresponding to the two index coordinates Na1 and Na2, and then calculate the target brightness value Yb by interpolation method, specifically: Yb=Yb1+(Yb2-Yb1)* (Na-Na1)/(Na2-Na1). Among them, the brightness lookup table Y_LUT is a lookup table with the exposure index as the coordinate, including the exposure index value and the corresponding target brightness value, wherein the target brightness is the brightness of the captured image expected by the photographer, that is, the brightness observed by the human eye, The target brightness in the brightness lookup table Y_LUT is an empirical value, which is related to the shooting scene of the shooting device. For example, the target brightness value will be larger in outdoor scenes, and the target brightness value will be smaller in night scenes. A brightness lookup table Y_LUT in this example As shown in Figure 6.

After the target brightness Yb is obtained, it is compared with the brightness Ya of the current frame to judge whether the two values are within the error range (for example, by calculating the ratio or difference range). If the brightness Ya of the current frame and the target brightness Yb are within the error range, it is not necessary to adjust the exposure parameters of the shooting device, and then return to step S1; if the brightness Ya of the current frame and the target brightness Yb are outside the error range, then enter step S1. S202.

S202: Calculate the target exposure EVb according to the current exposure EVa, the target brightness Yb, and the brightness Ya of the current frame.

In this embodiment, the formula for calculating the target exposure EVb is: EVb=EVa*Yb/Ya.

S3: Select the corresponding exposure parameter table according to the motion state of the photographing device.

In this step, the motion state of the shooting device can be judged by reading the gyroscope data on the shooting device. In some other schemes, the shooting device can also be judged by comparing the displacement between feature points between adjacent video frames. state of motion. In this embodiment, the motion state of the photographing device is set as a stationary state, a walking state, and a running state. The following uses reading gyroscope data on the photographing device to determine the motion state of the photographing device as an example for illustration.

S301: Obtain a difference Df between angles read twice adjacently by the gyroscope.

Specifically, the angle data of the gyroscope is read at intervals (such as 20ms), and then the angle data is subtracted from the angle data read last time, and then the absolute value of the subtracted value is taken as the difference Df.

S302: If the values of N consecutive Df are all between the set thresholds Dt _i to Dt _i+1 , determine that the photographing device is in the i-th motion state.

The exercise state in this embodiment includes 3 states of static state, walking state and running state, corresponding to 4 thresholds including Dt ₁ to Dt ₄ , assuming Dt ₁ <Dt ₂ <Dt ₃ <Dt ₄ , it can be obtained It is known that Dt ₁ =0, and Dt ₄ tends to infinity. Therefore, when the values of consecutive N Dfs are all less than or equal to Dt ₂ , it is judged that the photographing device is in a stationary state; when the values of consecutive N Dfs are all greater than Dt ₂ and less than or equal to Dt ₃ , it is judged that the photographing device is in a walking state ; When consecutive N values of Df are greater than Dt ₃ , it is judged that the shooting device is in a running state.

Specifically, after obtaining the difference Df each time, it is judged whether the difference Df is less than or equal to the set change threshold Dt ₂ , and if yes, the count value C ₁ is increased, otherwise the count value C ₁ is cleared; then it is judged whether the difference Df is greater than Dt ₂ is less than or equal to Dt ₃ , if yes, increase the count value C ₂ , otherwise the count value C ₂ will be cleared; then judge whether the difference Df is greater than the set change threshold Dt ₃ , if yes, increase the count value C ₃ , otherwise count Value _C3 is cleared. Judging whether the counting value C ₁ is greater than the set counting threshold Ct ₁ , if yes, the state of the photographing device is judged as a static state; judging whether the counting value C ₂ is greater than the set counting threshold Ct ₂ , if yes, judging the state of the photographing device It is a walking state; it is judged whether the count value C ₃ is greater than the set count threshold Ct ₃ , and if so, the state of the photographing device is judged to be a running state.

In other solutions of this step, it is also possible to count each count value per unit time, and then use the motion state corresponding to the maximum count value as the current motion state of the photographing device.

S303: Select the i-th exposure parameter table corresponding to the i-th motion state.

According to the motion state determined in step S302, the exposure parameter table EXP_LUT corresponding to the motion state is selected. The exposure parameter table EXP_LUT takes the exposure index as the coordinate, including the exposure index value and the corresponding exposure parameter value, and the exposure parameter includes the aperture value, shutter value and gain value. The exposure parameter tables of the three motion states in this embodiment are shown in FIGS. 7 to 9 .

S4: Determine the target exposure parameter according to the target exposure EVb and the selected exposure parameter table.

S401: Calculate an exposure index Nb according to a target exposure EVb.

In this embodiment, the exposure index Nb is first calculated according to the target exposure amount EVb, and the exposure index Nb is limited to the maximum value of the exposure index (currently set to 15), wherein the calculation formula of the exposure index Nb is: Nb =16+log2 EVb.

S402: Determine a target exposure parameter according to the exposure index and the corresponding data in the exposure parameter table.

After calculating the exposure index Nb, find the same value as Na in the exposure parameter table EXP_LUT, and then find the corresponding brightness value; if the exposure index Nb is located between the two index coordinates Nb1 and Nb2 of the exposure parameter table EXP_LUT, then find The shutter values SHT1 and SHT2, the gain values AGC1 and AGC2, and the aperture values APT1 and APT2 corresponding to the two index coordinates Nb1 and Nb2 are then calculated by interpolation.

Specifically, the calculation formula of the target shutter value EXP_SHT is:

EXP_SHT=SHT1+(SHT2-SHT1)*(Nb-Nb1)/(Nb2-Nb1).

Specifically, the calculation formula of the target gain value EXP_AGC is:

EXP_AGC=AGC1+(AGC2-AGC1)*(Nb-Nb1)/(Nb2-Nb1).

Specifically, the calculation formula of the target aperture value EXP_APT is:

EXP_APT=APT1+(APT2-APT1)*(Nb-Nb1)/(Nb2-Nb1).

S5: Update the exposure parameter of the photographing device to the target exposure parameter and return to step S1.

Set the target exposure parameters determined in step S4 on the shooting device, then return to step S1, and repeat steps S1 to S5 until the shooting device finishes shooting the entire video.

Example 2

As shown in FIG. 10 , this embodiment discloses an automatic exposure device, which includes: an acquisition module, which acquires a frame of image data captured by the shooting device according to the current exposure parameters and calculates the brightness Ya of the current frame; a calculation module, which uses Calculate the target exposure EVb according to the current exposure EVa, the brightness Ya of the current frame and the target brightness Yb; the selection module is used to select the corresponding exposure parameter table according to the motion state of the shooting device; the determination module is used to select the corresponding exposure parameter table according to the target exposure EVb And the selected exposure parameter table determines the target exposure parameter; the update module is used to update the exposure parameter of the shooting device to the exposure parameter of the next frame; wherein, the current exposure EVa is calculated by the current exposure parameter of the shooting device, and the target brightness Yb The exposure index Na is calculated from the current exposure EVa and obtained in combination with the brightness lookup table.

For the acquisition process and calculation formula of each parameter in this embodiment, reference may be made to the relevant description in Embodiment 1.

Example 3

As shown in Figure 11, this embodiment discloses a camera, the camera includes a processor and a memory, and a computer program is stored on the memory, and the computer program is used to realize the automatic operation in Embodiment 1 when the processor is executed. exposure method.

Those skilled in the art know that the camera in this embodiment also includes necessary components of the camera such as a lens and an ISP.

Example 4

This embodiment discloses a computer-readable storage medium, where a computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, the automatic exposure method in the above embodiment 1 is implemented.

Those of ordinary skill in the art can understand that all or part of the steps in the various methods of the above-mentioned embodiments can be completed by instructing related hardware through a program, and the storage medium can be a computer-readable storage medium, for example, a ferroelectric memory (FRAM, Ferromagnetic Random Access Memory), read-only memory (ROM, Read Only Memory), programmable read-only memory (PROM, Programmable Read Only Memory), erasable programmable read-only memory (EPROM, Erasable Programmable Read Only Memory), charged Memory such as erasable programmable read-only memory (EEPROM, Electrically Erasable Programmable Read Only Memory), flash memory, magnetic surface memory, optical disk, or optical disk read-only memory (CD-ROM, Compact Disk-Read Only Memory); it can also include Various devices of one or any combination of the above memories.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims

An automatic exposure method, characterized in that, comprising:

S1: Obtain the current frame image data captured by the shooting device according to the current exposure parameters and calculate the brightness Ya of the current frame;

S2: Calculate the target exposure EVb according to the brightness Ya of the current frame, the current exposure EVa and the target brightness Yb;

S3: Select a corresponding exposure parameter table according to the motion state of the photographing device;

S4: Determine the target exposure parameter according to the target exposure EVb and the selected exposure parameter table;

S5: updating the exposure parameter of the photographing device to the target exposure parameter and returning to step S1;

Wherein, the current exposure EVa is obtained by calculating the current exposure parameters of the photographing device, and the target brightness Yb is obtained by combining the exposure index Na calculated from the current exposure EVa by combining the brightness lookup table.
The automatic exposure method according to claim 1, characterized in that, the calculation formula of the current exposure EVa in the step S1 is: EVa=SHTa*AGCa/APTa^ 2 , wherein, SHTa, AGCa, and APTa are successively photographed Set the current shutter, gain and aperture.
The automatic exposure method according to claim 1, wherein said step S1 comprises the following sub-steps:

S101: Obtain the current frame image data captured by the photographing device according to the current exposure parameters;

S102: Divide the current frame image data into multiple blocks and set a weight value for each block;

S103: Calculate the brightness of the current frame according to the average brightness value of each block and the corresponding weight value.
The automatic exposure method according to claim 1, wherein said step S2 comprises:

S201: Determine whether the luminance Ya of the current frame and the target luminance Yb are within the error range, if yes, return to step S1, otherwise, enter step S202;

S202: Calculate the target exposure EVb according to the current exposure EVa, the target brightness Yb, and the brightness Ya of the current frame.
The automatic exposure method according to claim 1, wherein said step S3 comprises the following sub-steps:

S301: Obtain the difference Df between the angles read twice by the gyroscope;

S302: If the values of N consecutive Df are all between the set thresholds Dt i to Dt i+1 , determine that the shooting device is in the i-th motion state;

S303: Select the i-th exposure parameter table corresponding to the i-th motion state.
The automatic exposure method according to claim 1, wherein said step S4 comprises the following sub-steps:

S401: Calculate the exposure index Nb according to the target exposure EVb;

S402: Determine the target exposure parameter according to the corresponding data in the exposure index and the exposure parameter table;

Wherein, the exposure parameter table takes the exposure index as a coordinate, and includes exposure index values and corresponding exposure parameter values, and the exposure parameters include aperture values, shutter values, and gain values.
The automatic exposure method according to claim 6, wherein the step S402 specifically comprises: finding two indexes closest to the exposure index Nb and corresponding two sets of exposure parameters in the exposure parameter table according to the exposure index Nb, Interpolation method is used to calculate target exposure parameters.
An automatic exposure device, characterized in that it comprises:

The acquiring module acquires the current frame image data captured by the shooting device according to the current exposure parameters and calculates the brightness Ya of the current frame;

The calculation module calculates the target exposure EVb according to the brightness Ya of the current frame, the current exposure EVa and the target brightness Yb;

a selection module, configured to select a corresponding exposure parameter table according to the motion state of the photographing device;

A determining module, configured to determine the target exposure parameter according to the target exposure EVb and the selected exposure parameter table;

An update module, configured to update the exposure parameters of the shooting device to the exposure parameters of the next frame;

Wherein, the current exposure EVa is obtained by calculating the current exposure parameters of the photographing device, and the target brightness Yb is obtained by combining the exposure index Na calculated from the current exposure EVa by combining the brightness lookup table.
A camera, characterized in that it comprises a processor and a memory, and a computer program is stored on the memory, and the computer program is used to realize the automatic exposure method described in any one of claims 1 to 7 when the computer program is executed by the processor .
A computer-readable storage medium, characterized in that a computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, the automatic exposure method according to any one of claims 1 to 7 is realized .