阅读说明：本技术 一种阵列式偏振相机的偏振信息测量系统及方法 (Polarization information measuring system and method of array type polarization camera ) 是由 何晓峰 吴雪松 范晨 胡小平 张礼廉 毛军 韩国良 李鑫 范颖 于 2020-04-22 设计创作，主要内容包括：本申请涉及一种阵列式偏振相机的偏振信息测量系统及方法,所述方法包括：根据阵列式偏振相机的偏振通道数量建立相应数量的成像模型；对阵列式偏振相机的响应函数进行标定得到阵列式偏振相机的响应曲线；采用多次曝光的方式获得阵列式偏振相机每个偏振通道的HDR图像；根据响应曲线和每个偏振通道的HDR图像计算高动态范围的偏振信息。本发明克服了在真实场景中传统偏振相机在过曝和欠曝情况下偏振信息计算不准确甚至无法计算的问题,提高了偏振相机对于光照变化条件下的适应性,具有原理简单、操作简便、使用范围广等优点；同时获取高质量偏振测量信息,有效提高阵列式偏振相机测量的动态范围,对于提高阵列式偏振相机的适用性具有重要意义。(The application relates to a polarization information measuring system and method of an array type polarization camera, wherein the method comprises the following steps: establishing imaging models with corresponding quantity according to the quantity of the polarization channels of the array type polarization cameras; calibrating the response function of the array type polarization camera to obtain a response curve of the array type polarization camera; obtaining an HDR image of each polarization channel of the array type polarization camera by adopting a multi-exposure mode; high dynamic range polarization information is calculated from the response curve and the HDR image for each polarization channel. The method solves the problems that the traditional polarization camera is inaccurate in polarization information calculation or even incapable of calculating under the conditions of overexposure and underexposure in a real scene, improves the adaptability of the polarization camera to illumination change conditions, and has the advantages of simple principle, simplicity and convenience in operation, wide application range and the like; meanwhile, high-quality polarization measurement information is obtained, the dynamic range of measurement of the array type polarization camera is effectively improved, and the method has important significance for improving the applicability of the array type polarization camera.)

1. A polarization information measuring method of an array type polarization camera, the method comprising the steps of:

s1, obtaining the number of polarization channels of the array type polarization cameras, and establishing imaging models with corresponding number according to the number of the polarization channels of the array type polarization cameras;

s2, calibrating the response function of the array type polarization camera according to the imaging model to obtain a response curve of the array type polarization camera;

s3, obtaining HDR images of each polarization channel of the array type polarization camera in a multi-exposure mode;

s4, calculating polarization information of high dynamic range according to the response curve and the HDR image of each polarization channel.

2. The method for measuring polarization information of an array-type polarization camera according to claim 1, wherein in step S1, the array-type polarization camera comprises polarization channels in four directions of 0 °, 45 °, 90 °, 135 ° that are uniformly distributed, and imaging models of the four polarization channels are:

in the formula (I), the compound is shown in the specification,in order to obtain the image data that is finally obtained,is the intensity of the incident light after it passes through the lens,is the intensity of the incident light after passing through the polarizer,、、、for the role of the polarizer in each polarization channel,in order to be a degree of polarization DOP,is the angle of polarization of the light beam,in order to be a function of the response of the camera,is the time of exposure.

3. The polarization information measuring method of the array type polarization camera according to claim 2, wherein the step S1 further comprises:

the light intensity in the real scene is sequentially sensed by a lens, a polaroid and a shutter of the array type polarization camera through a CCD or CMOS chip and is converted into final image data through mode-electricity conversion.

4. The method as claimed in claim 1, wherein in step S2, the array polarization camera is calibrated by multiple exposures to obtain the anti-response function of the array polarization cameraOptimizing a functionComprises the following steps:

in the formula (I), the compound is shown in the specification,is an anti-response function and，is a function of a polarizing plate andthere are four different types of polarizer plates,is as followsThe sub-exposure is carried out for the first time,as a result of the total number of exposures,is in position ofThe number of pixels of (a) is,for the total number of sampled pixel points,is as followsThe lower position of the sub-exposure time isThe pixel value of (c).

5. The polarization information measuring method of the array type polarization camera according to claim 4, wherein the step S2 further comprises:

the imaging principle by a polarization camera can be derived:

taking logarithm of two sides to obtain:

order toThen, there are:

is provided withThen, there are:

in the formula (I), the compound is shown in the specification,to the regularization term to prevent over-fitting,

by optimising a functionTo solve forFurther obtain the anti-response function of the camera。

6. The polarization information measuring method of the array type polarization camera according to claim 1, wherein the step S3 further comprises:

the imaging principle by a polarization camera can be derived:

HDR images for each polarization channel are obtained through multiple exposures and are constructed to be used for each polarization channelAt each pixel positionIrradiation value of：

In the formula (I), the compound is shown in the specification,is as followsPolarization channel under sub-exposureThe value of the pixel at the time of the next,is a position of a pixel, and is,is as followsThe setting of the exposure time of the next time,for the weighting function for eliminating singular values, a gaussian function is used as the weighting function:

。

7. the method for measuring polarization information of an array type polarization camera according to claim 1, wherein in step S4, the stokes amount of the polarization information can be calculated from the HDR image of each polarization channel:

the polarization angle AoP and the degree of polarization DoP are calculated on the basis of the calculated stokes quantities:

in the formula (I), the compound is shown in the specification,、、are stokes vector parameters.

8. A polarization information measuring system of an array type polarization camera, the system comprising:

the model establishing module is used for acquiring the number of the polarization channels of the array type polarization cameras and establishing imaging models with corresponding number according to the number of the polarization channels of the array type polarization cameras;

the calibration module is used for calibrating the response function of the array type polarization camera according to the parameter guidance of the imaging model to obtain a response curve of the array type polarization camera;

the image acquisition module is used for acquiring HDR images of each polarization channel of the array type polarization camera in a multi-exposure mode;

a calculation module to calculate high dynamic range polarization information from the response curve and the HDR image for each of the polarization channels.

9. A computer device comprising a memory and a processor, the memory storing a computer program, wherein the processor implements the steps of the method of any one of claims 1 to 7 when executing the computer program.

10. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out the steps of the method of any one of claims 1 to 7.

Technical Field

The invention relates to the technical field of polarization information measurement systems and methods, in particular to a polarization information measurement system and method of an array type polarization camera.

Background

Polarization is one of the fundamental properties of electromagnetic waves, and polarized light is an important property possessed by light waves. Most vertebrates (including humans) cannot perceive this light modality; in contrast, many invertebrates, including insects, arachnids, cephalopods, and stomata, have evolved to be able to detect light-sensitive cells with high dynamic range polarization information and to use this information in visually guided behavior. As with many animals, human vision is capable of visual perception over a wide range of brightness, allowing our eyes to function properly under disparate high contrast lighting conditions. However, digital cameras rely primarily on imaging sensors with 8-bit brightness, much narrower than the human visual range. For a long time, techniques have been sought to increase the dynamic range of images taken by cameras to better interpret and understand the scene.

The rapid development of imaging technology has brought us with new arrayed polarization sensors, such as deflection cameras, so that we can conveniently detect polarized light. Such cameras are widely used in 3D reconstruction, object detection, robotics. However, the conventional method cannot restore visual information in a High Dynamic Range (HDR) scene, so that the visibility of an image in a dark or bright area is greatly reduced. The polarization information calculation is inaccurate due to overexposure or underexposure in scenes with large-range illumination changes, for example, a shiny metal object reflects illumination light in a mirror surface mode, so that a camera is saturated and does not carry any information, and the application of the camera is influenced.

Therefore, it is necessary to design a new polarization information measuring system and method for the array type polarization camera.

Disclosure of Invention

The invention provides a polarization information measuring system and method of an array type polarization camera aiming at the problem of inaccurate polarization information calculation caused by overexposure or underexposure of the array type polarization camera in a real scene, improves the adaptability of the polarization camera to illumination change, and has the advantages of simple principle, simple and convenient operation, wide application range and the like.

In order to solve the technical problems, the invention is realized by the following technical scheme: a polarization information measuring method of an array type polarization camera, the method comprising the steps of:

s1, obtaining the number of polarization channels of the array type polarization cameras, and establishing imaging models with corresponding number according to the number of the polarization channels of the array type polarization cameras;

s2, calibrating the response function of the array type polarization camera according to the imaging model to obtain a response curve of the array type polarization camera;

s3, obtaining HDR images of each polarization channel of the array type polarization camera in a multi-exposure mode;

s4, polarization information of high dynamic range is calculated according to the response curve and the HDR image of each polarization channel.

Further, the array-type polarization camera comprises polarization channels which are uniformly distributed in four directions of 0 °, 45 °, 90 ° and 135 °, and imaging models of the four polarization channels are respectively:

in the formula (I), the compound is shown in the specification,in order to obtain the image data that is finally obtained,is the intensity of the incident light after it passes through the lens,is the intensity of the incident light after passing through the polarizer,、、、for the role of the polarizer in each polarization channel,in order to be a degree of polarization DOP,is the angle of polarization of the light beam,in order to be a function of the response of the camera,is the time of exposure.

Further, the light intensity in the real scene is sequentially sensed by a lens, a polaroid and a shutter of the array type polarization camera through a chip of a CCD or a CMOS and converted into final image data through mode-electricity conversion.

Further, calibrating the array type polarization camera in a multi-exposure mode to obtain an anti-response function of the array type polarization cameraOptimizing a functionComprises the following steps:

in the formula (I), the compound is shown in the specification,is an anti-response function and，is a function of a polarizing plate andthere are four different types of polarizer plates,is as followsThe sub-exposure is carried out for the first time,as a result of the total number of exposures,is in position ofThe number of pixels of (a) is,for the total number of sampled pixel points,is as followsThe lower position of the sub-exposure time isThe pixel value of (c).

Further, the imaging principle of the polarization camera can be used as follows:

taking logarithm of two sides to obtain:

order toThen, there are:

is provided withThen, there are:

in the formula (I), the compound is shown in the specification,to the regularization term to prevent over-fitting,

by optimising a functionTo solve forFurther obtain the anti-response function of the camera。

Further, the imaging principle of the polarization camera can be used as follows:

HDR images for each polarization channel are obtained through multiple exposures and are constructed to be used for each polarization channelAt each pixel positionIrradiation value of：

In the formula (I), the compound is shown in the specification,is as followsPolarization channel under sub-exposureThe value of the pixel at the time of the next,is a position of a pixel, and is,is as followsThe setting of the exposure time of the next time,for the weighting function for eliminating singular values, a gaussian function is used as the weighting function:

。

further, in step S4, the stokes amount of the polarization information may be calculated from the HDR image of each polarization channel:

the polarization angle AoP and the degree of polarization DoP are calculated on the basis of the calculated stokes quantities:

in the formula (I), the compound is shown in the specification,、、are stokes vector parameters.

The present invention also provides a polarization information measuring system of an array type polarization camera, the system comprising:

the model establishing module is used for acquiring the number of the polarization channels of the array type polarization cameras and establishing imaging models with corresponding number according to the number of the polarization channels of the array type polarization cameras;

the calibration module is used for calibrating the response function of the array type polarization camera according to the parameter guidance of the imaging model to obtain a response curve of the array type polarization camera;

the image acquisition module is used for acquiring HDR images of each polarization channel of the array type polarization camera in a multi-exposure mode;

and the calculation module is used for calculating the polarization information with high dynamic range according to the response curve and the HDR image of each polarization channel.

The invention also provides a computer device comprising a memory and a processor, the memory storing a computer program, the processor implementing the following steps when executing the computer program:

s1, obtaining the number of polarization channels of the array type polarization cameras, and establishing imaging models with corresponding number according to the number of the polarization channels of the array type polarization cameras;

s2, calibrating the response function of the array type polarization camera according to the parameter guidance of the imaging model to obtain the response curve of the array type polarization camera;

s3, obtaining HDR images of each polarization channel of the array type polarization camera in a multi-exposure mode;

s4, polarization information of high dynamic range is calculated according to the response curve and the HDR image of each polarization channel.

The present invention also provides a computer-readable storage medium having stored thereon a computer program which, when executed by a processor, performs the steps of:

s1, obtaining the number of polarization channels of the array type polarization cameras, and establishing imaging models with corresponding number according to the number of the polarization channels of the array type polarization cameras;

s2, calibrating the response function of the array type polarization camera according to the parameter guidance of the imaging model to obtain the response curve of the array type polarization camera;

s3, obtaining HDR images of each polarization channel of the array type polarization camera in a multi-exposure mode;

s4, polarization information of high dynamic range is calculated according to the response curve and the HDR image of each polarization channel.

Compared with the prior art, the invention has the advantages that:

the polarization information measuring system and method of the array type polarization camera, the computer device and the readable storage medium provided by the invention establish an imaging model according to the number of polarization channels of the array type polarization camera, calibrate the response function of the array type polarization camera, construct HDR images of all polarization channels through multiple exposure, and then calculate polarization information on the basis of a response curve and the HDR images; the method solves the problems that the traditional polarization camera is inaccurate in polarization information calculation or even incapable of calculating under the conditions of overexposure and underexposure in a real scene, improves the adaptability of the polarization camera to illumination change conditions, and has the advantages of simple principle, simplicity and convenience in operation, wide application range and the like; the array polarization camera system has the advantages that the practicability of the array polarization camera is greatly improved, the high-quality polarization measurement information is obtained while the influence of illumination change is overcome, the dynamic range of measurement of the array polarization camera can be effectively improved, and the array polarization camera system has important significance in further improving the applicability of the array polarization camera.

Drawings

FIG. 1 is a diagram illustrating an exemplary application scenario of a method for measuring polarization information of an array-type polarization camera;

FIG. 2 is a block diagram of a polarization information measurement system of an array type polarization camera according to an embodiment;

FIG. 3 is a flow diagram of a method for measuring polarization information of an array polarization camera in one embodiment;

FIG. 4 is a schematic diagram of a method for measuring polarization information of an arrayed polarization camera in one embodiment;

FIG. 5 is a flowchart illustrating the imaging modeling of the array-type polarization camera in one embodiment;

FIG. 6 is a calculated polarization degree and polarization angle image of an under-exposed image;

FIG. 7 is a calculated polarization degree and polarization angle image of an overexposed image;

FIG. 8 is a polarization degree and angle image obtained using the method of the present invention;

FIG. 9 is a diagram illustrating an internal structure of a computer device according to an embodiment.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.

The polarization information measuring system and method of the array type polarization camera provided by the application can be applied to the application environment shown in fig. 1. Wherein, the terminal 102 communicates with the server 104 through a network; the terminal 102 may be, but not limited to, various personal computers, notebook computers, smart phones, tablet computers, and portable wearable devices, and the server 104 may be implemented by an independent server or a server cluster formed by a plurality of servers.

In an embodiment, as shown in fig. 2, a polarization information measuring system of an array-type polarization camera is provided, which can be disposed in an application environment as shown in fig. 1, and the embodiment is based on a module concept, and includes a model building module 1, a calibration module 2, an image capturing module 3, and a calculating module 4; wherein the content of the first and second substances,

the model establishing module 1 is used for acquiring the number of polarization channels of the array type polarization cameras and establishing imaging models with corresponding number according to the number of the polarization channels of the array type polarization cameras;

the calibration module 2 is used for calibrating the response function of the array type polarization camera according to the parameter guidance of the imaging model to obtain a response curve of the array type polarization camera;

the image capturing module 3 is configured to obtain an HDR image of each polarization channel of the array type polarization camera by using a multiple exposure method; HDR refers to high dynamic range imaging, and is used to achieve a larger exposure dynamic range than the common digital image technology, so as to correctly represent the range brightness from sunlight to the darkest shadows in the real scene.

The calculation module 4 is configured to calculate polarization information with a high dynamic range from the response curve and the HDR image of each polarization channel. And writing a software program by using the stokes vector principle and a formula to process the received measurement information every time so as to obtain the polarization information of the position.

In one embodiment, as shown in fig. 5, the array type polarization camera at least comprises a lens 11, a polarizer 12, a shutter 13, a mirror and a CCD/CMOS14, wherein the lens 11 is a telephoto lens; the polaroid 12 is a neutral density polaroid, the spectral sensitivity range of the polaroid is 400 nm-700 nm, the polaroid has high polarization sensitivity to incident beams, and when the polaroid 12 rotates, light rays are changed; the response time of the shutter 13 is 1-3 microseconds; the chip sensing time of the CCD/CMOS14 is 1-2 microseconds, and an incident light beam is required to be vertically incident into the CCD/CMOS 14; the reflector is used for reflecting light beams, changes a light path and has high reflectivity for incident light beams; the light source for the incident beam may be a laser, and is more preferably a He — Ne gas laser light source.

The specific use process of the embodiment is as follows:

acquiring the number of polarization channels of an array type polarization camera, and establishing imaging models with corresponding number according to the number of the polarization channels of the array type polarization camera; calibrating the response function of the array type polarization camera according to the parameter guidance of the imaging model to obtain a response curve of the array type polarization camera; obtaining an HDR image of each polarization channel of the array type polarization camera by adopting a multi-exposure mode; high dynamic range polarization information is calculated from the response curve and the HDR image for each polarization channel. The method and the device solve the problems that the traditional polarization camera is inaccurate in polarization information calculation or even incapable of calculating under the conditions of overexposure and underexposure in a real scene, improve the adaptability of the polarization camera to illumination change conditions, and have the advantages of simple principle, simplicity and convenience in operation, wide application range and the like; the practicability of the array type polarization camera is greatly improved.

In one embodiment, as shown in fig. 3 to 4, a polarization information measuring method of an array type polarization camera is provided, which may be executed in the server shown in fig. 1, and specifically includes the following steps:

acquiring the number of polarization channels of an array type polarization camera, and establishing a corresponding number of imaging models based on a traditional camera imaging principle according to the number of the polarization channels of the array type polarization camera;

in one embodiment, the array-type polarization camera includes polarization channels in four directions of 0 °, 45 °, 90 °, and 135 ° which are uniformly distributed, the working band is 500-800 nm, and imaging models of the four polarization channels are respectively:

whereinIn order to obtain the image data that is finally obtained,which is the intensity of the incident light after passing through the lens 11,the intensity of the incident light after passing through the polarizing plate 12 is not more than the exposure value intensity of the CCD or CMOS,、、、for the role of the polarizer 12 in each polarization channel,in order to be a degree of polarization DOP,is the angle of polarization of the light beam,in order to be a function of the response of the camera,is the time of exposure. The incident beam is vector polarized light and has an arbitrary direction.

In another embodiment, the array type polarization camera comprises polarization channels which are uniformly distributed in three directions of 0 degree, 60 degrees and 120 degrees, and the working waveband is 600-750 nm; the light is transmitted to change the spectral range and the test direction, so that the polarization information of different azimuth angles, elevation angles and different spectral ranges can be obtained.

As shown in fig. 5, the light intensity in the real scene is sensed by the chip of the CCD/CMOS14 through the lens 11, the polarizer 12, and the shutter 13 of the array type polarization camera in order and is converted into final image data through the analog-to-digital conversion 15. In the first stage of image acquisition, exposureDefined as the intensity of the incident light after passing through the polarizer 12 and the time of exposureIs thus in units ofFrom this, it is assumed that the intensity of incident light after passing through the polarizing plate 12Halving, exposure timeDoubling does not change the light intensity of the final exposure.

And step two, calibrating the response function of the array type polarization camera according to the parameter guidance of the imaging model to obtain the response curve of the array type polarization camera.

In one embodiment, the array type polarization camera can be calibrated only through a mode of multiple exposure without other tools to obtain the anti-response function of the array type polarization cameraOptimizing a functionComprises the following steps:

in the formula (I), the compound is shown in the specification,in order to optimize the function, the function is optimized,is an anti-response function and，in order to be a function of the response of the camera,is the intensity of the incident light after it passes through the lens,is a function of a polarizing plate andthere are four different types of polarizer plates,is as followsThe sub-exposure is carried out for the first time,as a result of the total number of exposures,is in position ofThe number of pixels of (a) is,for the total number of sampled pixel points,is as followsThe lower position of the sub-exposure time isThe value of the pixel of (a) is,is the time of exposure.

More specifically, the imaging principle by a polarization camera yields:

taking logarithm of two sides to obtain:

order toThen, there are:

is provided withThen, there are:

in the formula (I), the compound is shown in the specification,to the regularization term to prevent over-fitting,

by optimising a functionTo solve forFurther obtain the anti-response function of the camera. The problem is a least square problem and can be solved by an optimization method which is a decomposition method of SVD (singular value).

Thirdly, obtaining an HDR image of each polarization channel of the array type polarization camera in a multi-exposure mode;

in one embodiment, the imaging principle by the polarization camera yields:

in practical application, HDR images of each polarization channel are obtained through multiple exposures and are constructed to correspond to each polarization channelAt each pixel positionIrradiation value of：

In the formula (I), the compound is shown in the specification,is as followsPolarization channel under sub-exposureThe value of the pixel at the time of the next,is a position of a pixel, and is,is as followsThe setting of the exposure time of the next time,as a result of the total number of exposures,the method is a weight function for eliminating singular values, is used for eliminating the influence caused by overexposed and underexposed values, and enables the final result to be more robust. Here, a gaussian function is chosen as the weighting function:

wherein the content of the first and second substances,the value is 0.2.

Step four, calculating polarization information with high dynamic range according to the response curve and the HDR image of each polarization channel;

in one embodiment, the stokes amount of the polarization information can be calculated from the HDR image of each polarization channel:

the polarization angle AoP and the degree of polarization DoP are calculated on the basis of the calculated stokes quantities:

in the formula (I), the compound is shown in the specification,、、are stokes vector parameters.

If the digital image is overexposed or underexposed, the polarization result will be wrong, and the polarization degree and polarization angle image obtained by calculating the underexposed image is shown in FIG. 6; FIG. 7 shows a polarization degree and a polarization angle image calculated from an overexposed image; fig. 8 shows polarization degree and polarization angle images obtained by the method of the present invention. It has been demonstrated that using the method of the present invention, high quality polarization information can be created by fusing images through multiple exposures.

The principle of the polarization information measuring method of the array type polarization camera provided by the invention is simply that: firstly, establishing an imaging model of an array type polarization camera based on the imaging process of a traditional camera; then calibrating the response function of the array type polarization camera to obtain a response curve of the camera; obtaining an HDR image of each polarization channel through multiple exposure; polarization information is calculated based on the response curve and the HDR image for each polarization channel. The method can solve the problem that the polarization information calculation of the polarization camera is inaccurate due to overexposure or underexposure in a real scene, improves the adaptability of the polarization camera to illumination change conditions, and has the advantages of simple principle, simple and convenient operation, wide application range and the like; the array polarization camera system has the advantages that the practicability of the array polarization camera is greatly improved, the high-quality polarization measurement information is obtained while the influence of illumination change is overcome, the dynamic range of measurement of the array polarization camera can be effectively improved, and the array polarization camera system has important significance in further improving the applicability of the array polarization camera.

In one embodiment, a computer device is provided, which may be a server, and its internal structure diagram may be as shown in fig. 9. The computer device includes a processor, a memory, a network interface, and a database connected by a system bus. Wherein the processor of the computer device is configured to provide computing and control capabilities. The memory of the computer device comprises a nonvolatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of an operating system and computer programs in the non-volatile storage medium. The database of the computer device is used to store base model component data. The network interface of the computer device is used for communicating with an external terminal through a network connection. The computer program is executed by a processor to implement a polarization information measuring method of an array type polarization camera.

Those skilled in the art will appreciate that the architecture shown in fig. 9 is merely a block diagram of some of the structures associated with the disclosed aspects and is not intended to limit the computing devices to which the disclosed aspects apply, as particular computing devices may include more or less components than those shown, or may combine certain components, or have a different arrangement of components.

In an embodiment, a computer device is provided, comprising a memory storing a computer program and a processor implementing the steps of the method in the above embodiments when the processor executes the computer program.

In an embodiment, a computer-readable storage medium is provided, on which a computer program is stored, which computer program, when being executed by a processor, carries out the steps of the method in the above-mentioned embodiments.

It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by hardware instructions of a computer program, which can be stored in a non-volatile computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. Any reference to memory, storage, database, or other medium used in the embodiments provided herein may include non-volatile and/or volatile memory, among others. Non-volatile memory can include read-only memory (ROM), Programmable ROM (PROM), Electrically Programmable ROM (EPROM), Electrically Erasable Programmable ROM (EEPROM), or flash memory. Volatile memory can include Random Access Memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms such as Static RAM (SRAM), Dynamic RAM (DRAM), Synchronous DRAM (SDRAM), Double Data Rate SDRAM (DDRSDRAM), Enhanced SDRAM (ESDRAM), Synchronous Link DRAM (SLDRAM), Rambus Direct RAM (RDRAM), direct bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.