CN107343154B - Method, device and system for determining exposure parameters of camera device - Google Patents

Method, device and system for determining exposure parameters of camera device Download PDF

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CN107343154B
CN107343154B CN201610284104.9A CN201610284104A CN107343154B CN 107343154 B CN107343154 B CN 107343154B CN 201610284104 A CN201610284104 A CN 201610284104A CN 107343154 B CN107343154 B CN 107343154B
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frame
pixel coordinate
target
target detection
detection area
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CN107343154A (en
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周剑辉
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Huawei Technologies Co Ltd
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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
    • H04N23/70—Circuitry for compensating brightness variation in the scene
    • H04N23/73—Circuitry for compensating brightness variation in the scene by influencing the exposure time

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Abstract

The invention discloses a method, a device and a system for determining exposure parameters of a camera device, and aims to solve the problems that the definition quality of a license plate image acquired under the existing poor light condition is low, and the license plate cannot be accurately identified. The method comprises the steps of determining a target detection area on a vehicle body; acquiring a first pixel coordinate, a second pixel coordinate and an initial exposure amount, wherein the first pixel coordinate is a pixel coordinate corresponding to a set point of a target detection area in a starting frame acquired by a camera device at a first moment, the second pixel coordinate is a pixel coordinate corresponding to the set point of the target detection area in an ending frame acquired by the camera device at a second moment, and the initial exposure amount is an exposure amount of the target detection area in the ending frame acquired by the camera device at the second moment; and determining target exposure parameters used when the camera device captures the license plate image, so that the problem that the license plate cannot be clearly identified due to overexposure when the license plate image is collected under severe light conditions is solved.

Description

Method, device and system for determining exposure parameters of camera device
Technical Field
The present invention relates to the field of image technologies, and in particular, to a method, an apparatus, and a system for determining an exposure parameter of an image capturing apparatus.
Background
The specific process is that the brightness values of histograms of the cameras are respectively calculated according to preset key areas in a picture, and then weighted average is carried out, so that the exposure L required by normal exposure of the picture in the key areas can be obtained, because L F (1/F) is known2) Δ t, wherein F is a frame rate, F is an aperture coefficient, and Δ t is an exposure time, so after the exposure amount is determined, in order to ensure the depth of field, the aperture coefficient is often set to be large enough, the exposure time is larger, and the shutter speed is slower, the exposure strategy has no problem for ordinary video monitoring, and the depth of field and the shutter speed are obtained as much as possible, but for license plate recognition, the exposure strategy has a great problem, on one hand, because the brightness of a license plate area is far greater than the brightness of the surrounding environment at night, if the average light measuring mode is adopted, the license plate is overexposed; on the other hand, in the morning or in the evening with poor light, the exposure amount is barely required, but the shutter speed only reaches the safe shutter speed (for example, 1/60s) due to the fact that the shutter speed is sacrificed for obtaining larger depth of field, the shutter speed has no problem for the static object monitored conventionally, but for the license plate in motion, relatively large motion blur is generated, and therefore the accuracy of license plate recognition is influenced.
Therefore, during license plate recognition, a possible license plate detection method is to firstly realize the detection and tracking of a license plate region, then calculate a histogram of the license plate region frame by frame, calculate exposure compensation amount according to the distribution of the histogram, and feed the exposure compensation amount back to the camera to perform exposure correction on the whole picture.
According to the method, because the light is directly measured in the license plate area and exposure compensation is carried out, better license plate exposure can be usually obtained in the morning or in the evening under poor light conditions, but under the condition of bad light conditions, such as at night, the license plate area is often overexposed before the exposure compensation is carried out on the license plate area, the license plate area cannot be identified, so that the exposure compensation of the license plate area cannot be realized, the license plate detection method is invalid, the license plate cannot be accurately identified, and the license plate identification effect is poor.
Disclosure of Invention
The embodiment of the invention provides a method, a device and a system for determining exposure parameters of a camera device, and aims to solve the problems that the definition quality of a license plate image acquired under the existing poor light condition is low, the license plate cannot be accurately identified, and the license plate identification effect is poor.
The embodiment of the invention provides the following specific technical scheme:
in a first aspect, a method for determining exposure parameters of an image capture device is provided, comprising:
determining a target detection area on a vehicle body;
acquiring a first pixel coordinate, a second pixel coordinate and an initial exposure amount, wherein the first pixel coordinate is a pixel coordinate corresponding to a set point of the target detection area in a starting frame acquired by a camera device for shooting a license plate at a first moment, the second pixel coordinate is a pixel coordinate corresponding to the set point of the target detection area in an ending frame acquired by the camera device at a second moment, and the initial exposure amount is an exposure amount of the target detection area in the ending frame acquired by the camera device at the second moment;
and determining target exposure parameters used when the image pickup device picks up the license plate image, wherein the target exposure parameters are obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the initial exposure.
With reference to the first aspect, in one possible design, determining a target detection area on a vehicle body includes:
when the light intensity of the vehicle body collected by the camera device is greater than a preset threshold value, taking a license plate area on the vehicle body as the target detection area;
and when the light intensity of the vehicle body collected by the camera device is not greater than a preset threshold value, taking a vehicle lamp area on the vehicle body as the target detection area.
With reference to the first aspect, in one possible design, determining a target detection area on a vehicle body includes:
when the current time is within a preset time range, taking a license plate area on the vehicle body as a target detection area on the vehicle body;
and when the current moment is not within a preset time range, taking a car light area on the car body as the target detection area.
With reference to the first aspect, in one possible design manner, the determining a target exposure parameter used when the image pickup device picks up the license plate image includes:
and determining a target shutter speed and/or a target aperture coefficient used when the image pickup device picks up the license plate image, wherein the target shutter speed is obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the frame rate, and the target aperture coefficient is obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the initial exposure.
With reference to the first aspect, in one possible design, the target shutter speed conforms to the following formula:
T2＝MAX{Tsafe|Tsafe＜Tblur/((Sqrt((y(n)-y(m))2+(x(n)-x(m))2)*(m-n)f/1000)/n)}
where T2 represents the target shutter speed; t isblurRepresenting a preset motion blur value; the first pixel coordinate is (x (n), y (n)) Represents; the second pixel coordinate is represented by (x (m), y (m)); m represents a frame number of the end frame; n represents a frame number of the start frame; f denotes a frame rate.
With reference to the first aspect, in one possible design, the target aperture ratio conforms to the following formula:
Figure GDA0002430534980000031
where a2 denotes a target aperture coefficient; a1 denotes the aperture factor corresponding to when the frame is ended; t isblurRepresenting a preset motion blur value; the first pixel coordinate is expressed by (x (n), y (n)); the second pixel coordinate is represented by (x (m), y (m)); m represents a frame number of the end frame; n represents a frame number of the start frame; f represents a frame rate; t1 represents the shutter speed corresponding to the image pickup device at the end of the frame; EV (electric vehicle)1Indicates the initial exposure amount; EV (electric vehicle)2Indicating the exposure corresponding to a preset middle gray level.
With reference to the first aspect, in a possible design manner, the set point of the target detection area is a central point of the target detection area.
In a second aspect, there is provided an apparatus for determining exposure parameters of an image pickup apparatus, comprising:
a determination unit configured to determine a target detection area on a vehicle body;
the device comprises an acquisition unit, a storage unit and a control unit, wherein the acquisition unit is used for acquiring a first pixel coordinate, a second pixel coordinate and an initial exposure amount, the first pixel coordinate is a pixel coordinate corresponding to a set point of a target detection area in a starting frame acquired by a camera device for shooting a license plate at a first moment, the second pixel coordinate is a pixel coordinate corresponding to the set point of the target detection area in an ending frame acquired by the camera device at a second moment, and the initial exposure amount is the exposure amount of the target detection area in the ending frame acquired by the camera device at the second moment;
and the processing unit is used for determining target exposure parameters used when the image pickup device picks up the license plate image, and the target exposure parameters are obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the initial exposure.
With reference to the second aspect, in a possible design manner, when determining the target detection area on the vehicle body, the determining unit is specifically configured to:
when the light intensity of the vehicle body collected by the camera device is greater than a preset threshold value, taking a license plate area on the vehicle body as the target detection area;
and when the light intensity of the vehicle body collected by the camera device is not greater than a preset threshold value, taking a vehicle lamp area on the vehicle body as the target detection area.
With reference to the second aspect, in a possible design manner, when determining the target detection area on the vehicle body, the determining unit is specifically configured to:
when the current time is within a preset time range, taking a license plate area on the vehicle body as a target detection area on the vehicle body;
and when the current moment is not within a preset time range, taking a car light area on the car body as the target detection area.
With reference to the second aspect, in a possible design manner, when determining a target exposure parameter used when the image capturing device captures a license plate image, the processing unit is specifically configured to:
and determining a target shutter speed and/or a target aperture coefficient used when the image pickup device picks up the license plate image, wherein the target shutter speed is obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the frame rate, and the target aperture coefficient is obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the initial exposure.
With reference to the second aspect, in one possible design, the target shutter speed conforms to the following formula:
T2＝MAX{Tsafe|Tsafe＜Tblur/((Sqrt((y(n)-y(m))2+(x(n)-x(m))2)*(m-n)f/1000)/n)}
where T2 represents the target shutter speed; t isblurRepresenting a preset motion blur value; the first pixel coordinate is expressed by (x (n), y (n)); the second pixel coordinate is represented by (x (m), y (m)); m represents a frame number of the end frame; n represents a frame number of the start frame; f denotes a frame rate.
With reference to the second aspect, in one possible design, the target aperture ratio conforms to the following formula:
Figure GDA0002430534980000051
where a2 denotes a target aperture coefficient; a1 denotes the aperture factor corresponding to when the frame is ended; t isblurRepresenting a preset motion blur value; the first pixel coordinate is expressed by (x (n), y (n)); the second pixel coordinate is represented by (x (m), y (m)); m represents a frame number of the end frame; n represents a frame number of the start frame; f represents a frame rate; t1 represents the shutter speed corresponding to the image pickup device at the end of the frame; EV (electric vehicle)1Indicates the initial exposure amount; EV (electric vehicle)2Indicating the exposure corresponding to a preset middle gray level.
With reference to the second aspect, in a possible design manner, the set point of the target detection area is a central point of the target detection area.
In a third aspect, a system for determining exposure parameters is provided, comprising: an image pickup device and a determination device,
the camera device is used for shooting a license plate image;
the determining device is used for determining a target detection area on the vehicle body; acquiring a first pixel coordinate, a second pixel coordinate and an initial exposure amount, wherein the first pixel coordinate is a pixel coordinate corresponding to a set point of the target detection area in a starting frame acquired by the camera device at a first moment, the second pixel coordinate is a pixel coordinate corresponding to the set point of the target detection area in an ending frame acquired by the camera device at a second moment, and the initial exposure amount is an exposure amount of the target detection area in the ending frame acquired by the camera device at the second moment; and determining target exposure parameters used when the image pickup device picks up the license plate image, wherein the target exposure parameters are obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the initial exposure.
With reference to the third aspect, in a possible design manner, when determining the target detection area on the vehicle body, the determining device is specifically configured to:
when the light intensity of the vehicle body collected by the camera device is greater than a preset threshold value, taking a license plate area on the vehicle body as the target detection area;
and when the light intensity of the vehicle body collected by the camera device is not greater than a preset threshold value, taking a vehicle lamp area on the vehicle body as the target detection area.
With reference to the third aspect, in a possible design manner, when determining the target detection area on the vehicle body, the determining device is specifically configured to:
when the current time is within a preset time range, taking a license plate area on the vehicle body as a target detection area on the vehicle body;
and when the current moment is not within a preset time range, taking a car light area on the car body as the target detection area.
With reference to the third aspect, in a possible design manner, when determining the target exposure parameter used when the image capturing device captures the license plate image, the determining device is specifically configured to:
and determining a target shutter speed and/or a target aperture coefficient used when the image pickup device picks up the license plate image, wherein the target shutter speed is obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the frame rate, and the target aperture coefficient is obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the initial exposure.
With reference to the third aspect, in one possible design, the target shutter speed conforms to the following formula:
T2＝MAX{Tsafe|Tsafe＜Tblur/((Sqrt((y(n)-y(m))2+(x(n)-x(m))2)*(m-n)f/1000)/n)}
where T2 represents the target shutter speed; t isblurRepresenting a preset motion blur value; the first pixel coordinate is expressed by (x (n), y (n)); the second pixel coordinate is represented by (x (m), y (m)); m represents a frame number of the end frame; n represents a frame number of the start frame; f denotes a frame rate.
With reference to the third aspect, in one possible design, the target aperture ratio conforms to the following formula:
Figure GDA0002430534980000071
where a2 denotes a target aperture coefficient; a1 denotes the aperture factor corresponding to when the frame is ended; t isblurRepresenting a preset motion blur value; the first pixel coordinate is expressed by (x (n), y (n)); the second pixel coordinate is represented by (x (m), y (m)); m represents a frame number of the end frame; n represents a frame number of the start frame; f represents a frame rate; t1 represents the shutter speed corresponding to the image pickup device at the end of the frame; EV (electric vehicle)1Indicates the initial exposure amount; EV (electric vehicle)2Indicating the exposure corresponding to a preset middle gray level.
With reference to the third aspect, in a possible design manner, the set point of the target detection area is a central point of the target detection area.
In a fourth aspect, an image pickup apparatus is provided, which includes a lens, a processor, and a memory, the lens, the processor, and the memory being connected by a bus, wherein: the memory is used for storing program codes executed by the processor; the processor, with the program code in the memory, is to perform the following: determining a target detection area on a vehicle body; acquiring a first pixel coordinate, a second pixel coordinate and an initial exposure amount, wherein the first pixel coordinate is a pixel coordinate corresponding to a set point of the target detection area in a starting frame acquired by the image pickup device at a first moment, the second pixel coordinate is a pixel coordinate corresponding to the set point of the target detection area in an ending frame acquired by the image pickup device at a second moment, and the initial exposure amount is an exposure amount of the target detection area in the ending frame acquired by the image pickup device at the second moment; and determining target exposure parameters used when the image pickup equipment picks up the license plate image, wherein the target exposure parameters are obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the initial exposure.
With reference to the fourth aspect, in a possible design manner, when determining the target detection area on the vehicle body, the processor is specifically configured to:
when the light intensity of the vehicle body collected by the camera equipment is greater than a preset threshold value, taking a license plate area on the vehicle body as the target detection area;
and when the light intensity of the vehicle body collected by the camera equipment is not greater than a preset threshold value, taking a vehicle lamp area on the vehicle body as the target detection area.
With reference to the fourth aspect, in a possible design manner, when determining the target detection area on the vehicle body, the processor is specifically configured to:
when the current time is within a preset time range, taking a license plate area on the vehicle body as a target detection area on the vehicle body;
and when the current moment is not within a preset time range, taking a car light area on the car body as the target detection area.
With reference to the fourth aspect, in a possible design manner, when determining a target exposure parameter used when the image pickup device captures a license plate image, the processor is specifically configured to:
and determining a target shutter speed and/or a target aperture coefficient used when the image pickup device picks up the license plate image, wherein the target shutter speed is obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the frame rate, and the target aperture coefficient is obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the initial exposure.
With reference to the fourth aspect, in one possible design, the target shutter speed satisfies the following formula:
T2＝MAX{Tsafe|Tsafe＜Tblur/((Sqrt((y(n)-y(m))2+(x(n)-x(m))2)*(m-n)f/1000)/n)}
where T2 represents the target shutter speed; t isblurRepresenting a preset motion blur value; the first pixel coordinate is expressed by (x (n), y (n)); the second pixel coordinate is represented by (x (m), y (m)); m represents a frame number of the end frame; n represents a frame number of the start frame; f denotes a frame rate.
With reference to the fourth aspect, in one possible design, the target aperture ratio conforms to the following formula:
Figure GDA0002430534980000081
where a2 denotes a target aperture coefficient; a1 denotes the aperture factor corresponding to when the frame is ended; t isblurRepresenting a preset motion blur value; the first pixel coordinate is expressed by (x (n), y (n)); the second pixel coordinate is represented by (x (m), y (m)); m represents a frame number of the end frame; n represents a frame number of the start frame; f represents a frame rate; t1 represents the shutter speed corresponding to the image pickup device at the end of the frame; EV (electric vehicle)1Indicates the initial exposure amount; EV (electric vehicle)2Indicating the exposure corresponding to a preset middle gray level.
With reference to the fourth aspect, in a possible design manner, the set point of the target detection area is a central point of the target detection area.
According to the exposure parameter determining scheme for license plate recognition in the embodiment of the invention, the target detection area for license plate recognition is determined, the target exposure parameter for license plate recognition of the camera device is determined according to the pixel coordinate of the set point of the target detection area and the initial exposure of the target detection area, when the camera device collects a license plate image by using the target exposure parameter, the definition of the license plate image is improved, the license plate recognition effect is improved, and the problems that the license plate image collected under the condition of bad light conditions in the prior art is low in definition quality and cannot be accurately recognized are effectively solved.
Drawings
FIG. 1 is a schematic structural diagram of an image capturing apparatus according to an embodiment of the present invention;
FIG. 2 is a flowchart of a method for determining exposure parameters of an image capture device according to an embodiment of the present invention;
FIG. 3 is a schematic view of a monitoring image during license plate recognition according to an embodiment of the present disclosure;
fig. 4 is a schematic diagram of an application of license plate recognition in an implementation scenario according to an embodiment of the present disclosure;
fig. 5 is a schematic diagram of another application of license plate recognition in another implementation scenario according to an embodiment of the present disclosure;
FIG. 6 is a schematic diagram of an apparatus for determining exposure parameters of an image capture device according to an embodiment of the present invention;
FIG. 7 is a diagram illustrating an exemplary system for determining exposure parameters;
fig. 8 is a schematic structural diagram of an image pickup apparatus in the embodiment of the present invention.
Detailed Description
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.
In the prior art, because the light of the vehicle lamp area is directly measured and exposure compensation is carried out during the license plate recognition, under the condition of bad light conditions, the light brightness of the vehicle lamp area is far greater than the brightness of the surrounding environment, the license plate area is often overexposed before the exposure compensation of the license plate area is carried out, so that the exposure compensation of the license plate area cannot be realized, the license plate detection method fails, and the license plate cannot be accurately recognized, the method for determining the exposure parameter for the license plate recognition provided by the embodiment of the invention determines the target detection area for the license plate recognition, the target shutter speed and the target aperture coefficient when the image pickup device collects the license plate image are obtained according to the pixel average speed and the illumination condition of the target detection area, the image pickup device can obtain the license plate image with higher definition when the image pickup device collects the license plate image by utilizing the target exposure parameter, and is convenient for the, therefore, the optimal license plate recognition effect is obtained, and the optimal depth of field can be obtained.
The embodiments of the present invention will be described in further detail with reference to the drawings attached hereto.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a camera device (also referred to as a camera) according to an embodiment of the present invention. Fig. 1 includes a lens 11, an Image Sensor (Image Sensor)12, a Central Processing Unit (CPU) 13, a Random Access Memory (RAM) 14, a battery 15, and an Image memory 16.
Referring to fig. 2, an embodiment of the present invention provides a method for determining an exposure parameter of an image capturing apparatus, where the method is performed by a determining device capable of determining an exposure parameter, where the determining device may be the image capturing apparatus in fig. 1, or another device connected to the image capturing apparatus, and the determining device may be located on the image capturing apparatus, and the method includes:
step 200: an object detection area on the vehicle body is determined.
Specifically, determining a target detection area on a vehicle body specifically includes the following two possible implementation methods:
a first possible implementation method is that a target detection area for license plate recognition is determined based on a time range in which a current time is located, and specifically, when the current time is within a preset time range, a license plate area on a vehicle body is used as the target detection area on the vehicle body; and when the current moment is not within a preset time range, taking the lamp area on the vehicle body as a target detection area on the vehicle body.
In the embodiment of the present invention, the light measurement is performed by using the license plate area as the target detection area during the daytime when the light intensity is strong, and the light measurement is performed by using the car lamp area as the target detection area during the nighttime when the light intensity is poor.
For example: the corresponding time range in the daytime is (7:00-18:00), the other time ranges correspond to the time ranges at night, and if the current time is 8:30 am, when a license plate image is shot, the license plate area is used as a target detection area for light measurement; if the current time is 19:30, when the license plate image is captured, photometry is performed with the vehicle lamp region as the target detection region.
The second possible implementation method is: when the light intensity of the vehicle body collected by the camera device is greater than a preset threshold value, taking a license plate area on the vehicle body as a target detection area on the vehicle body; and when the light intensity of the vehicle body collected by the camera device is not greater than a preset threshold value, taking a vehicle lamp area on the vehicle body as a target detection area on the vehicle body.
In the method, the target detection area on the vehicle body is determined according to the intensity of light collected by the camera device.
Step 201: the method comprises the steps of obtaining a first pixel coordinate, a second pixel coordinate and an initial exposure amount, wherein the first pixel coordinate is a pixel coordinate corresponding to a set point of a target detection area in a starting frame collected at a first moment by a camera device used for shooting a license plate, the second pixel coordinate is a pixel coordinate corresponding to the set point of the target detection area in an ending frame collected at a second moment by the camera device, and the initial exposure amount is an exposure amount of the target detection area in the ending frame collected at the second moment by the camera device.
The first time is the time when the target detection area enters the area which can be shot by the camera device, and the second time is the time when the target detection area leaves the area which can be shot by the camera device.
For example, referring to fig. 3 as an example, the line 31 and the line 32 in fig. 3 constitute a lane, the rectangular region 33 is a region that can be captured by the imaging device, the target detection region of the vehicle enters the rectangular region 33 in the nth frame, the pixel coordinate corresponding to the center of the target detection region is the first pixel coordinate and is represented by (x (n), y (n)), the target detection region of the vehicle enters the rectangular region 33 in the mth frame, and the pixel coordinate corresponding to the center of the target detection region is the second pixel coordinate and is represented by (x (m), y (m)).
Step 202: and determining target exposure parameters used when the image pickup device picks up the license plate image, wherein the target exposure parameters are obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the initial exposure.
Specifically, determining target exposure parameters used when the image pickup device picks up the license plate image includes: and determining a target shutter speed and/or a target aperture coefficient used when the image pickup device picks up the license plate image, wherein the target shutter speed is obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the frame rate, and the target aperture coefficient is obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the initial exposure.
1) Specifically, the determination process of the target shutter speed is as follows:
according to the first pixel coordinate and the second pixel coordinate, the average speed of the vehicle pixel can be calculated, and the specific formula is as follows:
speed＝Sqrt((y(n)-y(m))2+(x(n)-x(m))2)*(m-n)f/1000)/n；
wherein speed represents the pixel average speed of the vehicle, f represents the frame rate, and the first pixel coordinate is represented by (x (n), y (n)); the second pixel coordinate is represented by (x (m), y (m)); m represents a frame number of the end frame; n denotes the frame number of the start frame.
Further, according to the average pixel speed of the vehicle and a preset motion blur value, a safe shutter speed and a target shutter speed can be calculated, and the specific formula is as follows:
Tsafe<Tblur/speed；T2＝MAX{T|Tsafe<T(blur)/speed}；
wherein, TsafeIndicating the safe shutter speed, TblurRepresenting a preset motion blur value, typically less than 3 pixels, and T2 representing the target shutter speed, taking the maximum value of the safe shutter speed.
In summary, it can be concluded that the target shutter speed conforms to the following equation:
T2＝MAX{Tsafe|Tsafe＜Tblur/((Sqrt((y(n)-y(m))2+(x(n)-x(m))2)*(m-n)f/1000)/n)}
where T2 represents the target shutter speed; t isblurRepresenting a preset motion blur value; the first pixel coordinate is expressed by (x (n), y (n)); the second pixel coordinate is represented by (x (m), y (m)); m represents a frame number of the end frame; n represents a frame number of the start frame; f denotes a frame rate.
2) Specifically, the determination process of the target aperture ratio is as follows:
first, photometry is performed on the target detection area at the end of the frame to obtain the initial exposure amount of the target detection area, and optionally, the target detection area is weighted-averaged to calculate the average brightness mean (L), and the relation between mean (L) and the initial exposure amount EV1 is as follows:
EV1＝F(mean(L),ISO)；
the preset target exposure amount is the exposure amount EV2 corresponding to the middle gray brightness:
EV2＝F(mean(128),ISO)
where mean (128) is a brightness value corresponding to a preset middle gray brightness, ISO is a sensitivity of the imaging apparatus, F is a functional relation, and is generally provided by a manufacturer of the imaging apparatus, or obtained by a gray card test, so that an exposure compensation amount Δ EV of a target detection region can be obtained:
ΔEV＝f(mean(L),ISO)-f(mean(128),ISO)(1)
since the formula is satisfied between the exposure amount and the shutter speed and the aperture ratio:
EV＝log2(A/T)；
where EV represents the exposure amount, a represents the aperture ratio, and T represents the shutter speed.
Therefore, the initial exposure amount EV1 corresponding to the target detection area at the end of the frame is:
EV1＝log2(A1/T1)；
the target exposure amount EV2 that the image pickup apparatus needs to adjust is:
EV2＝log2(A2/T2)；
thereby, the exposure compensation amount Δ EV of the target detection area is obtained:
ΔEV＝log2(A2/T2)-log2(A1/T1)＝log2(A2*T2/A1*T1)(2)
substituting △ EV obtained in the above equation (1) into equation (2) yields a target aperture ratio a 2:
A2＝(A1*T2)/(T1*2ΔEV)＝(A1*T2)/(T1*2f(mean(L),ISO)-f(mean(128),ISO))；
the shutter speed corresponding to the end frame of the image pickup apparatus is T1, the aperture factor is a1, and the target shutter speed to be adjusted is T2.
Since the target shutter speed T2 has been obtained through the above-described determination process of the target shutter speed:
T2＝MAX{Tsafe|Tsafe＜Tblur/((Sqrt((y(n)-y(m))2+(x(n)-x(m))2)*(m-n)f/1000)/n)}
to sum up, the target aperture coefficient a2 conforms to the following equation:
Figure GDA0002430534980000141
where a2 denotes a target aperture coefficient; a1 denotes the aperture factor corresponding to when the frame is ended; t isblurRepresenting a preset motion blur value; the first pixel coordinate is expressed by (x (n), y (n)); the second pixel coordinate is represented by (x (m), y (m)); m represents a frame number of the end frame; n represents a frame number of the start frame; f represents a frame rate; t1 represents the corresponding shutter speed at the end of the frame; EV (electric vehicle)1EV2 represents the exposure amount corresponding to the preset middle gray brightness, EV1 is F (mean (L), ISO), EV2 is F (mean (128), ISO), mean (L) represents the average brightness of the target detection area, and ISO is the average brightness of the image pickupThe sensitivity of the device, mean (128), is the brightness value corresponding to the preset mid-gray brightness.
Therefore, the target shutter speed and the target aperture coefficient required to be set by the camera device during license plate recognition can be obtained by performing photometry on the target detection area of the vehicle, the camera device collects the license plate image by using the set target exposure parameters, the optimal depth of field can be obtained, the collected license plate image is clear, the license plate analysis is facilitated, and a better license plate recognition effect can be obtained.
The following explains an implementation scenario of the above image acquisition method for license plate recognition by way of example. Implementation scenario one
The camera 40 located at the front end and the determining device 41 located at the background are deployed independently during license plate recognition, which can be specifically referred to as shown in fig. 4:
in fig. 4, the front camera 40 is only responsible for shooting and encoding, and transmits the compressed video stream to the determination device 41 at the rear end, the determination device 41 is responsible for utilizing the compressed video stream collected by the front camera 40, calculating a target exposure parameter for license plate recognition, and transmitting the target exposure parameter to the front camera 40 for exposure correction, the front camera 40 utilizes the target exposure parameter to collect a license plate image for license plate recognition, so that the definition of the license plate image is improved, and further the license plate recognition effect is improved. Wherein the target exposure parameters comprise a target shutter speed and/or a target aperture factor.
Implementation scenario two
The traditional license plate recognition adopts a bayonet camera, the function of the traditional license plate recognition is only to complete license plate positioning and license plate recognition, and the monitoring on the surrounding environment is out of consideration. However, with the development of image acquisition technology, more virtual bayonet cameras are adopted to realize the license plate recognition function, that is, one camera has two functions of video monitoring and license plate recognition, the virtual bayonet camera is often deployed at the roadside, and has two functions of roadside monitoring and vehicle monitoring, and most of the cameras do not have a fill light or a low-level fill light, and under the condition, the requirement of license plate recognition is often difficult to be met by a common exposure mode, and the requirement of common video monitoring can be met by adopting the image acquisition method in fig. 2, and the requirement of license plate recognition can also be met.
In fig. 5, a virtual gate camera collects a license plate image for license plate recognition, and completes the license plate recognition based on the collected license plate image.
The sensor of the virtual bayonet camera sends an original image stream collected through the lens to the CPU, a license plate recognition algorithm and a determination algorithm of exposure parameters in the image 2 are stored in the virtual bayonet camera, the CPU executes the determination algorithm of the exposure parameters to calculate target exposure parameters including target shutter speed and/or target aperture coefficient and feeds the target exposure parameters back to the lens for exposure correction, the sensor continuously collects license plate images after exposure correction through the lens and sends the license plate images to the CPU, the CPU executes the license plate recognition algorithm to perform license plate recognition, license plate metadata are output to an external monitoring platform, the license plate metadata include numbers and characters in license plates, meanwhile, the sensor collects the original image stream through the lens, and a compressed video stream is formed through a coding unit in the camera and sent to the external monitoring platform.
Based on the above embodiments, referring to fig. 6, an embodiment of the present invention provides an apparatus 600 for determining exposure parameters of an image capturing device, where the apparatus 600 may be an image capturing device or another apparatus connected to the image capturing device, and the apparatus 600 includes: a determination unit 601, an acquisition unit 602, and a processing unit 603, wherein:
a determination unit 601 for determining a target detection area on the vehicle body;
an obtaining unit 602, configured to obtain a first pixel coordinate, a second pixel coordinate, and an initial exposure amount, where the first pixel coordinate is a pixel coordinate corresponding to a set point of the target detection region in a starting frame acquired by a camera device for capturing a license plate at a first time, the second pixel coordinate is a pixel coordinate corresponding to the set point of the target detection region in an ending frame acquired by the camera device at a second time, and the initial exposure amount is an exposure amount of the target detection region in the ending frame acquired by the camera device at the second time;
and the processing unit 603 is configured to determine a target exposure parameter used when the image pickup device picks up the license plate image, where the target exposure parameter is obtained according to the frame number of the start frame, the frame number of the end frame, the first pixel coordinate, the second pixel coordinate, and the initial exposure amount.
Optionally, when determining the target detection area on the vehicle body, the determining unit 601 is specifically configured to:
when the light intensity of the vehicle body collected by the camera device is greater than a preset threshold value, taking a license plate area on the vehicle body as the target detection area;
and when the light intensity of the vehicle body collected by the camera device is not greater than a preset threshold value, taking a vehicle lamp area on the vehicle body as the target detection area.
Optionally, when determining the target detection area on the vehicle body, the determining unit 601 is specifically configured to:
when the current time is within a preset time range, taking a license plate area on the vehicle body as a target detection area on the vehicle body;
and when the current moment is not within a preset time range, taking a car light area on the car body as the target detection area.
Optionally, when determining the target exposure parameter used when the image capture device captures the license plate image, the processing unit 603 is specifically configured to:
and determining a target shutter speed and/or a target aperture coefficient used when the image pickup device picks up the license plate image, wherein the target shutter speed is obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the frame rate, and the target aperture coefficient is obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the initial exposure.
Optionally, the target shutter speed conforms to the following formula:
T2＝MAX{Tsafe|Tsafe＜Tblur/((Sqrt((y(n)-y(m))2+(x(n)-x(m))2)*(m-n)f/1000)/n)}
where T2 represents the target shutter speed; t isblurRepresenting a preset motion blur value; the first pixel coordinate is expressed by (x (n), y (n)); the second pixel coordinate is represented by (x (m), y (m)); m represents a frame number of the end frame; n represents a frame number of the start frame; f denotes a frame rate.
Optionally, the target aperture coefficient conforms to the following formula:
Figure GDA0002430534980000161
where a2 denotes a target aperture coefficient; a1 denotes the aperture factor corresponding to when the frame is ended; t isblurRepresenting a preset motion blur value; the first pixel coordinate is expressed by (x (n), y (n)); the second pixel coordinate is represented by (x (m), y (m)); m represents a frame number of the end frame; n represents a frame number of the start frame; f represents a frame rate; t1 represents the shutter speed corresponding to the image pickup device at the end of the frame; EV (electric vehicle)1Indicates the initial exposure amount; EV (electric vehicle)2Indicating the exposure corresponding to a preset middle gray level.
Optionally, the set point of the target detection area is a central point of the target detection area.
The apparatus 600 according to the above embodiments of the present invention may be an independent component, or may be integrated into another component, for example, the apparatus 600 according to the above embodiments of the present invention may be an existing camera, or may be a component integrated into a camera.
It should be noted that, for the function implementation and the interaction manner of each unit of the apparatus 600 in the embodiment of the present invention, further reference may be made to the description of the related method embodiment, which is not described herein again.
In addition, each of the above "units" may be implemented by an application-specific integrated circuit (ASIC), a processor and memory that execute one or more software or firmware programs, an integrated logic circuit, and/or other devices that may provide the above-described functionality.
Based on the above embodiments, referring to fig. 7, an embodiment of the invention provides a system 700 for determining exposure parameters, the system 700 comprising: a camera device 701 and a determination device 702,
the camera 701 is used for shooting a license plate image;
the determining device 702 is configured to determine a target detection area on the vehicle body; acquiring a first pixel coordinate, a second pixel coordinate and an initial exposure amount, wherein the first pixel coordinate is a pixel coordinate corresponding to a set point of the target detection area in a starting frame acquired by the camera device at a first moment, the second pixel coordinate is a pixel coordinate corresponding to the set point of the target detection area in an ending frame acquired by the camera device at a second moment, and the initial exposure amount is an exposure amount of the target detection area in the ending frame acquired by the camera device at the second moment; and determining target exposure parameters used when the image pickup device picks up the license plate image, wherein the target exposure parameters are obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the initial exposure.
Optionally, when determining the target detection area on the vehicle body, the determining device 702 is specifically configured to:
when the light intensity of the vehicle body collected by the camera device is greater than a preset threshold value, taking a license plate area on the vehicle body as the target detection area;
and when the light intensity of the vehicle body collected by the camera device is not greater than a preset threshold value, taking a vehicle lamp area on the vehicle body as the target detection area.
Optionally, when determining the target detection area on the vehicle body, the determining device 702 is specifically configured to:
when the current time is within a preset time range, taking a license plate area on the vehicle body as a target detection area on the vehicle body;
and when the current moment is not within a preset time range, taking a car light area on the car body as the target detection area.
Optionally, when determining the target exposure parameter used when the image capture device captures the license plate image, the determining device 702 is specifically configured to:
and determining a target shutter speed and/or a target aperture coefficient used when the image pickup device picks up the license plate image, wherein the target shutter speed is obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the frame rate, and the target aperture coefficient is obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the initial exposure.
Optionally, the target shutter speed conforms to the following formula:
T2＝MAX{Tsafe|Tsafe＜Tblur/((Sqrt((y(n)-y(m))2+(x(n)-x(m))2)*(m-n)f/1000)/n)}
where T2 represents the target shutter speed; t isblurRepresenting a preset motion blur value; the first pixel coordinate is expressed by (x (n), y (n)); the second pixel coordinate is represented by (x (m), y (m)); m represents a frame number of the end frame; n represents a frame number of the start frame; f denotes a frame rate.
Optionally, the target aperture coefficient conforms to the following formula:
Figure GDA0002430534980000181
where a2 denotes a target aperture coefficient; a1 denotes the aperture factor corresponding to when the frame is ended; t isblurRepresenting a preset motion blur value; the first pixel coordinate is expressed by (x (n), y (n)); the second pixel coordinate is represented by (x (m), y (m)); m represents a frame number of the end frame; n represents a frame number of the start frame; f represents a frame rate; t1 represents the shutter speed corresponding to the image pickup device at the end of the frame; EV (electric vehicle)1Indicates the initial exposure amount; EV (electric vehicle)2Indicating the exposure corresponding to a preset middle gray level.
Optionally, the set point of the target detection area is a central point of the target detection area.
It should be noted that, in this embodiment, the image capturing device 701 is configured to capture an original license plate image, and send the captured original license plate image to the determining device 702, the determining device 702 performs image analysis based on the original license plate image to determine a target detection region, and then determines a target exposure parameter corrected by the image capturing device 701, and the image capturing device 701 continues to capture a license plate image by using the corrected target exposure parameter, so that the definition of the captured license plate image is higher, and thus the license plate image with higher definition is used for license plate recognition, and the accuracy of license plate recognition is improved.
Referring to fig. 8, an image capturing apparatus 800 according to an embodiment of the present invention includes a lens 801, a processor 802, and a memory 803, where the lens 801, the processor 802, and the memory 803 are connected by a bus, where:
a memory 803 for storing program code executed by the processor;
a processor 802 for executing, by program code in a memory, the following: determining a target detection area on a vehicle body; acquiring a first pixel coordinate, a second pixel coordinate and an initial exposure amount, wherein the first pixel coordinate is a pixel coordinate corresponding to a set point of the target detection area in a starting frame acquired by the image pickup device at a first moment, the second pixel coordinate is a pixel coordinate corresponding to the set point of the target detection area in an ending frame acquired by the image pickup device at a second moment, and the initial exposure amount is an exposure amount of the target detection area in the ending frame acquired by the image pickup device at the second moment; and determining target exposure parameters used when the image pickup equipment picks up the license plate image, wherein the target exposure parameters are obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the initial exposure.
Optionally, when determining the target detection area on the vehicle body, the processor 802 is specifically configured to:
when the light intensity of the vehicle body collected by the camera equipment is greater than a preset threshold value, taking a license plate area on the vehicle body as the target detection area;
and when the light intensity of the vehicle body collected by the camera equipment is not greater than a preset threshold value, taking a vehicle lamp area on the vehicle body as the target detection area.
Optionally, when determining the target detection area on the vehicle body, the processor 802 is specifically configured to:
when the current time is within a preset time range, taking a license plate area on the vehicle body as a target detection area on the vehicle body;
and when the current moment is not within a preset time range, taking a car light area on the car body as the target detection area.
Optionally, when determining the target exposure parameter used when the image capture device captures the license plate image, the processor 802 is specifically configured to:
and determining a target shutter speed and/or a target aperture coefficient used when the image pickup device picks up the license plate image, wherein the target shutter speed is obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the frame rate, and the target aperture coefficient is obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the initial exposure.
Optionally, the target shutter speed conforms to the following formula:
T2＝MAX{Tsafe|Tsafe＜Tblur/((Sqrt((y(n)-y(m))2+(x(n)-x(m))2)*(m-n)f/1000)/n)}
where T2 represents the target shutter speed; t isblurRepresenting a preset motion blur value; the first pixel coordinate is expressed by (x (n), y (n)); the second pixel coordinate is represented by (x (m), y (m)); m represents a frame number of the end frame; n represents a frame number of the start frame; f denotes a frame rate.
Optionally, the target aperture coefficient conforms to the following formula:
Figure GDA0002430534980000201
where a2 denotes a target aperture coefficient; a1 denotes the aperture factor corresponding to when the frame is ended; t isblurRepresenting a preset motion blur value; the first pixel coordinate is expressed by (x (n), y (n)); the second pixel coordinate is represented by (x (m), y (m)); m represents a frame number of the end frame; n represents a frame number of the start frame; f represents a frame rate; t1 represents the shutter speed corresponding to the image pickup device at the end of the frame; EV (electric vehicle)1Indicates the initial exposure amount; EV (electric vehicle)2Indicating the exposure corresponding to a preset middle gray level.
Optionally, the set point of the target detection area is a central point of the target detection area.
In summary, in the embodiment of the present invention, a target detection area on a vehicle body is determined; acquiring a first pixel coordinate, a second pixel coordinate and an initial exposure amount, wherein the first pixel coordinate is a pixel coordinate corresponding to a set point of the target detection area in a starting frame acquired by a camera device for shooting a license plate at a first moment, the second pixel coordinate is a pixel coordinate corresponding to the set point of the target detection area in an ending frame acquired by the camera device at a second moment, and the initial exposure amount is an exposure amount of the target detection area in the ending frame acquired by the camera device at the second moment; and determining target exposure parameters used when the image pickup device picks up the license plate image, wherein the target exposure parameters are obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the initial exposure amount, so that the problem that the license plate cannot be clearly recognized due to overexposure when the license plate image is collected under severe light conditions in the prior art is solved, a clear license plate image is obtained, and the license plate recognition effect is improved.
As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various modifications and variations can be made in the embodiments of the present invention without departing from the spirit or scope of the embodiments of the invention. Thus, if such modifications and variations of the embodiments of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to encompass such modifications and variations.

Claims (16)

1. A method of determining exposure parameters for an imaging device, comprising:
determining a target detection area on a vehicle body;
acquiring a first pixel coordinate, a second pixel coordinate and an initial exposure amount, wherein the first pixel coordinate is a pixel coordinate corresponding to a set point of the target detection area in a starting frame acquired by a camera device for shooting a license plate at a first moment, the second pixel coordinate is a pixel coordinate corresponding to the set point of the target detection area in an ending frame acquired by the camera device at a second moment, and the initial exposure amount is an exposure amount of the target detection area in the ending frame acquired by the camera device at the second moment;
determining a target shutter speed and/or a target aperture coefficient used when the image pickup device picks up the license plate image, wherein the target shutter speed is obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the frame rate, and the target aperture coefficient is obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the initial exposure;
wherein, confirm the target detection area on the automobile body, include:
when the light intensity of the vehicle body collected by the camera device is greater than a preset threshold value, taking a license plate area on the vehicle body as the target detection area; when the light intensity of the vehicle body acquired by the camera device is not greater than a preset threshold value, taking a vehicle lamp area on the vehicle body as the target detection area; or,
when the current time is within a preset time range, taking a license plate area on the vehicle body as the target detection area;
and when the current moment is not within a preset time range, taking a car light area on the car body as the target detection area.
2. The method of claim 1, wherein the target shutter speed conforms to the following equation:
T2＝MAX{Tsafe|Tsafe＜Tblur/((Sqrt((y(n)-y(m))2+(x(n)-x(m))2)*(m-n)f/1000)/n)}
where T2 represents the target shutter speed; t isblurRepresenting a preset motion blur value; the first pixel coordinate is expressed by (x (n), y (n)); the second pixel coordinate is represented by (x (m), y (m)); m represents a frame number of the end frame; n represents a frame number of the start frame; f denotes a frame rate.
3. The method of claim 1, wherein the target aperture ratio conforms to the formula:
Figure FDA0002430534970000021
where a2 denotes a target aperture coefficient; a1 denotes the aperture factor corresponding to when the frame is ended; t isblurRepresenting a preset motion blur value; the first pixel coordinate is expressed by (x (n), y (n)); the second pixel coordinate is represented by (x (m), y (m)); m represents a frame number of the end frame; n represents a frame number of the start frame; f represents a frame rate; t1 represents the shutter speed corresponding to the image pickup device at the end of the frame; EV (electric vehicle)1Indicates the initial exposure amount; EV (electric vehicle)2Indicating the exposure corresponding to a preset middle gray level.
4. The method of claim 1, wherein the set point for the target detection zone is a center point of the target detection zone.
5. An apparatus for determining exposure parameters of an imaging device, comprising:
a determination unit configured to determine a target detection area on a vehicle body;
the device comprises an acquisition unit, a storage unit and a control unit, wherein the acquisition unit is used for acquiring a first pixel coordinate, a second pixel coordinate and an initial exposure amount, the first pixel coordinate is a pixel coordinate corresponding to a set point of a target detection area in a starting frame acquired by a camera device for shooting a license plate at a first moment, the second pixel coordinate is a pixel coordinate corresponding to the set point of the target detection area in an ending frame acquired by the camera device at a second moment, and the initial exposure amount is the exposure amount of the target detection area in the ending frame acquired by the camera device at the second moment;
the processing unit is used for determining a target shutter speed and/or a target aperture coefficient used when the image pickup device picks up a license plate image, wherein the target shutter speed is obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the frame rate, and the target aperture coefficient is obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the initial exposure amount;
when determining the target detection area on the vehicle body, the determining unit is specifically configured to:
when the light intensity of the vehicle body collected by the camera device is greater than a preset threshold value, taking a license plate area on the vehicle body as the target detection area; when the light intensity of the vehicle body acquired by the camera device is not greater than a preset threshold value, taking a vehicle lamp area on the vehicle body as the target detection area; or,
when the current time is within a preset time range, taking a license plate area on the vehicle body as the target detection area; and when the current moment is not within a preset time range, taking a car light area on the car body as the target detection area.
6. The apparatus of claim 5, wherein the target shutter speed conforms to the following equation:
T2＝MAX{Tsafe|Tsafe＜Tblur/((Sqrt((y(n)-y(m))2+(x(n)-x(m))2)*(m-n)f/1000)/n)}
where T2 represents the target shutter speed; t isblurRepresenting a preset motion blur value; the first pixel coordinate is expressed by (x (n), y (n)); the second pixel coordinate is represented by (x (m), y (m)); m represents a frame number of the end frame; n represents a frame number of the start frame; f denotes a frame rate.
7. The apparatus of claim 5, wherein the target aperture ratio conforms to the following equation:
Figure FDA0002430534970000031
where a2 denotes a target aperture coefficient; a1 denotes the aperture factor corresponding to when the frame is ended; t isblurRepresenting a preset motion blur value; the first pixel coordinate is expressed by (x (n), y (n)); the second pixel coordinate is represented by (x (m), y (m)); m represents a frame number of the end frame; n represents a frame number of the start frame; f represents a frame rate; t1 represents the shutter speed corresponding to the image pickup device at the end of the frame; EV (electric vehicle)1Indicates the initial exposure amount; EV (electric vehicle)2Indicating the exposure corresponding to a preset middle gray level.
8. The apparatus of claim 5, wherein the set point of the target detection zone is a center point of the target detection zone.
9. A system for determining exposure parameters, comprising: an image pickup device and a determination device,
the camera device is used for shooting a license plate image;
the determining device is used for determining a target detection area on the vehicle body; acquiring a first pixel coordinate, a second pixel coordinate and an initial exposure amount, wherein the first pixel coordinate is a pixel coordinate corresponding to a set point of the target detection area in a starting frame acquired by the camera device at a first moment, the second pixel coordinate is a pixel coordinate corresponding to the set point of the target detection area in an ending frame acquired by the camera device at a second moment, and the initial exposure amount is an exposure amount of the target detection area in the ending frame acquired by the camera device at the second moment; determining a target shutter speed and/or a target aperture coefficient used when the image pickup device picks up the license plate image, wherein the target shutter speed is obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the frame rate, and the target aperture coefficient is obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the initial exposure;
when determining the target detection area on the vehicle body, the determining device is specifically configured to:
when the light intensity of the vehicle body collected by the camera device is greater than a preset threshold value, taking a license plate area on the vehicle body as the target detection area; when the light intensity of the vehicle body acquired by the camera device is not greater than a preset threshold value, taking a vehicle lamp area on the vehicle body as the target detection area; or,
when the current time is within a preset time range, taking a license plate area on the vehicle body as the target detection area; and when the current moment is not within a preset time range, taking a car light area on the car body as the target detection area.
10. The system of claim 9, wherein the target shutter speed conforms to the following equation:
T2＝MAX{Tsafe|Tsafe＜Tblur/((Sqrt((y(n)-y(m))2+(x(n)-x(m))2)*(m-n)f/1000)/n)}
where T2 represents the target shutter speed; t isblurRepresenting a preset motion blur value; the first pixel coordinate is expressed by (x (n), y (n)); the second pixel coordinate is represented by (x (m), y (m)); m represents a frame number of the end frame; n represents a frame number of the start frame; f denotes a frame rate.
11. The system of claim 9, wherein the target aperture ratio conforms to the formula:
Figure FDA0002430534970000041
where a2 denotes a target aperture coefficient; a1 denotes the aperture factor corresponding to when the frame is ended; t isblurRepresenting a preset motion blur value; the first pixel coordinate is expressed by (x (n), y (n)); the second pixel coordinate is represented by (x (m), y (m)); m represents a frame number of the end frame; n represents a frame number of the start frame; f represents a frame rate; t1 represents the shutter speed corresponding to the image pickup device at the end of the frame; EV (electric vehicle)1Indicates the initial exposure amount; EV (electric vehicle)2Indicating the exposure corresponding to a preset middle gray level.
12. The system of claim 9, wherein the set point for the target detection zone is a center point of the target detection zone.
13. An image pickup apparatus characterized by comprising: the camera lens, the processor and the memory are connected through a bus, wherein:
the memory is used for storing programs executed by the processor;
the processor is used for calling the program stored in the memory and executing the following operations: determining a target detection area on a vehicle body; acquiring a first pixel coordinate, a second pixel coordinate and an initial exposure amount, wherein the first pixel coordinate is a pixel coordinate corresponding to a set point of the target detection area in a starting frame acquired by the image pickup device at a first moment, the second pixel coordinate is a pixel coordinate corresponding to the set point of the target detection area in an ending frame acquired by the image pickup device at a second moment, and the initial exposure amount is an exposure amount of the target detection area in the ending frame acquired by the image pickup device at the second moment; determining a target shutter speed and/or a target aperture coefficient used when the image pickup device picks up the license plate image, wherein the target shutter speed is obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the frame rate, and the target aperture coefficient is obtained according to the frame number of the initial frame, the frame number of the ending frame, the first pixel coordinate, the second pixel coordinate and the initial exposure;
when determining the target detection area on the vehicle body, the processor is specifically configured to:
when the light intensity of the vehicle body collected by the camera equipment is greater than a preset threshold value, taking a license plate area on the vehicle body as the target detection area; when the light intensity of the vehicle body acquired by the camera equipment is not greater than a preset threshold value, taking a vehicle lamp area on the vehicle body as the target detection area; or,
when the current time is within a preset time range, taking a license plate area on the vehicle body as the target detection area; and when the current moment is not within a preset time range, taking a car light area on the car body as the target detection area.
14. The image capturing apparatus according to claim 13, wherein the target shutter speed conforms to the following equation:
T2＝MAX{Tsafe|Tsafe＜Tblur/((Sqrt((y(n)-y(m))2+(x(n)-x(m))2)*(m-n)f/1000)/n)}
where T2 represents the target shutter speed; t isblurRepresenting a preset motion blur value; the first pixel coordinate is expressed by (x (n), y (n)); the second pixel coordinate is represented by (x (m), y (m)); m represents a frame number of the end frame; n represents a frame number of the start frame; f denotes a frame rate.
15. The image capturing apparatus according to claim 13, wherein the target aperture ratio conforms to the following formula:
Figure FDA0002430534970000061
wherein, A2Representing a target aperture coefficient; a1 denotes the aperture factor corresponding to when the frame is ended; t isblurRepresenting a preset motion blur value; the first pixel coordinate is expressed by (x (n), y (n)); the second pixel coordinate is represented by (x (m), y (m)); m represents a frame number of the end frame; n represents a frame number of the start frame; f represents a frame rate; t1 represents the shutter speed corresponding to the image pickup device at the end of the frame; EV (electric vehicle)1Indicates the initial exposure amount; EV (electric vehicle)2Indicating the exposure corresponding to a preset middle gray level.
16. The image capturing apparatus according to claim 13, wherein the set point of the target detection area is a center point of the target detection area.
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