Dark level analog gain correction method and device, image sensor and imaging equipment

Abstract

The application provides a dark level analog gain correction method and device, an image sensor and an imaging device. The method comprises the following steps: for each frame of image collected by the image sensor, the following operations are performed: obtaining the initial analog gain, the total gain and the real-time dark level of the black row of the current frame of image; obtaining the maximum allowed analog gain according to the initial analog gain, the real-time dark level, the dark level threshold value obtained in advance and the reference dark level obtained in advance; obtaining the corrected analog gain and the corrected digital gain according to the total gain and the maximum allowed analog gain; and applying the corrected analog gain and the corrected digital gain to the image sensor. The application can keep the image brightness, the image dynamic range, the definition and the color unchanged, thereby effectively improving the image quality.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of image processing, in particular to a dark level analog gain correction method and device, an image sensor and an imaging device. BACKGROUND

[0002] The pixel array of an image sensor generally includes light-sensitive pixels and light-shielded pixels; the light-shielded pixels, also known as black rows, are used to obtain the dark level of an image. The actual output level value of an image sensor is equal to the output value of a light-sensitive pixel minus the output value of a black row (dark level value), and this data correction process is dark level correction. However, due to the temperature characteristics of a CMOS image sensor, the dark level increases rapidly with temperature rise, especially at high analog gain, and the dark level is amplified by the gain ratio. The dark level increases rapidly under the conditions of temperature rise and / or analog gain increase, and when the dark level increases to exceed the maximum output value, the actual effective data range of the output image of the image sensor becomes smaller, resulting in problems such as image unsaturation, small image dynamic range, and image fog, which affect image quality.

[0003] It should be noted that the information disclosed in the background section of the present application is only intended to deepen the understanding of the general background of the present application, and should not be regarded as acknowledging or implying in any form that the information constitutes prior art known to those skilled in the art. SUMMARY

[0004] The present application provides a dark level analog gain correction method, device, image sensor and imaging device to solve the problem of low image quality caused by the increase of dark level due to temperature rise and gain increase in the prior art. The present application can keep the image brightness, image dynamic range, definition and color unchanged, thereby effectively improving the image quality.

[0005] In order to achieve the above-mentioned purpose, the present application realizes the following technical scheme, a dark level analog gain correction method, comprising: for each frame of image collected by an image sensor, performing the following operations: obtaining the initial analog gain, total gain and real-time dark level of the black row of the current frame of image; obtaining the maximum allowed analog gain according to the initial analog gain, the real-time dark level, the pre-obtained dark level threshold and the pre-obtained reference dark level; obtaining the corrected analog gain and the corrected digital gain according to the total gain and the maximum allowed analog gain, and applying the corrected analog gain and the corrected digital gain to the image sensor.

[0006] Optionally, the obtaining the maximum allowed analog gain according to the initial analog gain, the real-time dark level, a pre-acquired dark level threshold and a pre-acquired reference dark level comprises calculating the maximum allowed analog gain by the following formula: maximum allowed analog gain = Thd / abs(blc-Base)*Again, wherein Thd is the dark level threshold, blc is the real-time dark level, Base is the reference dark level, and Again is the initial analog gain.

[0007] Optionally, the method further comprises: if it is determined that the maximum allowed analog gain is less than 1, setting the maximum allowed analog gain as 1; and if it is determined that the maximum allowed analog gain is greater than a maximum design value of the analog gain of the image sensor, setting the maximum allowed analog gain as the maximum design value of the analog gain.

[0008] Optionally, the dark level threshold is acquired by: setting the image sensor to a maximum analog gain, heating the image sensor, and taking a dark level value of the black row when an image appears to be colored as the dark level threshold.

[0009] Optionally, the reference dark level is acquired by: setting a number of black row exposure rows of the image sensor as a preset number of black rows and setting an analog gain as a preset exposure analog gain, and taking a dark level obtained by exposure as the reference dark level.

[0010] Optionally, the obtaining the corrected analog gain and the corrected digital gain according to the total gain and the maximum allowed analog gain comprises: determining whether the total gain is less than the maximum allowed analog gain, if yes, taking the total gain as the corrected analog gain, if no, taking the maximum allowed analog gain as the corrected analog gain; and taking a quotient of the total gain divided by the corrected analog gain as the corrected digital gain.

[0011] Optionally, the method further comprises: taking the corrected analog gain of the current frame image as the initial analog gain of a next frame image.

[0012] To achieve the above object, the present application further provides a dark level analog gain correction device for performing analog gain correction on each frame of image collected by an image sensor, comprising: a correction parameter acquisition unit configured to acquire initial analog gain, total gain and real-time dark level of a black row of a current frame of image; an analog gain allowable maximum value acquisition unit configured to acquire an analog gain allowable maximum value according to the initial analog gain, the real-time dark level, a dark level threshold value acquired in advance and a reference dark level acquired in advance; and a correction value acquisition unit configured to acquire a corrected analog gain and a corrected digital gain according to the total gain and the analog gain allowable maximum value, so as to apply the corrected analog gain and the corrected digital gain to the image sensor.

[0013] To achieve the above object, the present application further provides an image sensor comprising the dark level analog gain correction device described above.

[0014] To achieve the above object, the present application further provides an imaging device comprising the dark level analog gain correction device described above, or comprising a processor and a memory having a computer program stored thereon, wherein the computer program is executed by the processor to implement the dark level analog gain correction method described in any one of the above.

[0015] Compared with the prior art, the dark level analog gain correction method, device, image sensor and imaging device provided by the present application have the following advantages: the dark level analog gain correction method provided by the present application performs the following operations on each frame of image collected by an image sensor: firstly, initial analog gain, total gain and real-time dark level of a black row of a current frame of image are acquired; then, an analog gain allowable maximum value is acquired according to the initial analog gain, the real-time dark level, a dark level threshold value acquired in advance and a reference dark level acquired in advance; finally, a corrected analog gain and a corrected digital gain are acquired according to the total gain and the analog gain allowable maximum value, so as to apply the corrected analog gain and the corrected digital gain to the image sensor. Thus, the present application first limits the maximum output amplitude of the dark level by analog gain, and then adjusts the digital gain so as to keep the total gain unchanged, which can keep the image brightness, image dynamic range, definition and color unchanged, thereby effectively improving the image quality.

[0016] Since the dark level analog gain correction device, the image sensor and the imaging device provided by the present application belong to the same inventive concept as the dark level analog gain correction method provided by the present application, the dark level analog gain correction device, the image sensor and the imaging device provided by the present application at least have all the advantages of the dark level analog gain correction method provided by the present application. For the details of the beneficial effects of the dark level analog gain correction device, the image sensor and the imaging device provided by the present application, please refer to the relevant description of the beneficial effects of the dark level analog gain correction method provided by the present application, which will not be repeated here. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The overall flowchart of the dark level analog gain correction method provided by one of the embodiments of the present application is shown.

[0018] Figure 2 The block structure diagram of the dark level analog gain correction device provided by one of the embodiments of the present application is shown.

[0019] Figure 3 The block structure diagram of the image sensor provided by one of the embodiments of the present application is shown.

[0020] In the drawings, the reference signs are as follows: dark level analog gain correction device-100, correction parameter acquisition unit-110, analog gain allowable maximum value acquisition unit-120, correction value acquisition unit-130; pixel array-200, readout circuit 300, timing and system control unit-400, image signal processing unit-ISP, output interface-500, application program-APP. DETAILED DESCRIPTION

[0021] The dark level analog gain correction method, device, image sensor and imaging device provided by the present application will be described in further detail below with reference to the accompanying drawings. The advantages and features of the present application will be more apparent from the following description. It should be noted that the drawings are very simplified and all use non-precise proportions, only for the purpose of facilitating, clarifying the purpose of assisting in the description of the embodiments of the present application. In order to make the purpose, features and advantages of the present application more apparent and easy to understand, please refer to the accompanying drawings. It should be noted that the structure, proportion, size and the like shown in the drawings of the present application are only used to cooperate with the content disclosed in the specification, so that those skilled in the art can understand and read, and are not used to limit the implementation of the present application. Any modification of structure, change of proportion relationship or adjustment of size, as long as it is the same or similar to the effect and purpose that can be achieved by the present application, should still fall within the scope of the technical content disclosed by the present application. The specific design features of the present application disclosed herein include, for example, specific dimensions, directions, positions and shapes, which will be determined in part by the specific application and use environment to be applied and used. In the embodiments described below, the same reference signs are sometimes used in different drawings to represent the same parts or parts with the same function, and repeated descriptions are omitted. In this specification, similar reference signs and letters are used to represent similar items, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings. In addition, if the method described herein includes a series of steps, and the order of the steps presented herein is not necessarily the only order in which the steps can be performed, and some of the described steps can be omitted and / or some other steps not described herein can be added to the method.

[0022] In order to facilitate the understanding of the present application, before the specific embodiments of the dark level analog gain correction method, device, image sensor and imaging device provided by the present application are described in detail, the main research process of the present application is briefly described as follows.

[0023] As described in the background, the dark level increases rapidly with the increase of temperature and / or analog gain, when the dark level increases to exceed its maximum output value, the actual effective data range of the image sensor output image becomes smaller, resulting in problems such as image unsaturation (no limit to dark level when correction), image dynamic range becomes smaller, image becomes foggy (limiting dark level to maximum output) and the like affecting image quality. The inventors have found through extensive investigation and continuous practice that the gain of the image sensor includes analog gain and digital gain, and the analog gain affects the dark level. By limiting the maximum output amplitude of the dark level value through the analog gain, and then adjusting the digital gain so that the total gain of the image sensor remains unchanged, the image brightness, image dynamic range, clarity, color and the like can be kept unchanged.

[0024] Based on the above research, the core idea of the present application is to provide a dark level analog gain correction method and device, an image sensor and an imaging device, which can keep the image brightness, dynamic range, definition and color unchanged, thereby effectively improving the image quality.

[0025] It should be noted that the dark level analog gain correction method and device provided by the present application can be applied to the image sensor provided by the present application, and the dark level analog gain correction method, device and image sensor provided by the present application can be applied to an imaging device. It should be noted that those skilled in the art should understand that the present application does not make any limitation on the imaging device. Exemplarily, the imaging device includes but is not limited to video products such as video recorders and digital cameras, communication products such as mobile phones, communication switching devices and communication transmission devices, learning auxiliary products such as translators and learning machines, medical instrument products such as medical imaging devices and medical detection devices, and the like.

[0026] In order to realize the above idea, one embodiment of the present application provides a dark level analog gain correction method. Specifically, please refer to Figure 1 , Figure 1 The overall flowchart of the dark level analog gain correction method provided by the present embodiment is shown. As can be seen from Figure 1 , the dark level analog gain correction method provided by the present embodiment performs the following operations for each frame of image collected by the image sensor.

[0027] Step S100: obtaining the initial analog gain, total gain and real-time dark level of the black row of the current frame of image.

[0028] Step S200: obtaining the maximum allowed analog gain according to the initial analog gain, the real-time dark level, the dark level threshold value obtained in advance and the reference dark level obtained in advance.

[0029] Step S300: obtaining the corrected analog gain and the corrected digital gain according to the total gain and the maximum allowed analog gain, and applying the corrected analog gain and the corrected digital gain to the image sensor.

[0030] The dark level analog gain correction method provided by the present application comprises the following steps: firstly, obtaining the initial analog gain, total gain and real-time dark level of the black row of a current frame image; then, according to the initial analog gain, the real-time dark level, a dark level threshold value obtained in advance and a reference dark level obtained in advance, obtaining an allowed maximum analog gain; finally, according to the total gain and the allowed maximum analog gain, obtaining a corrected analog gain and a corrected digital gain, and applying the corrected analog gain and the corrected digital gain to the image sensor. Thus, the present application can keep the image brightness, dynamic range, definition and color unchanged by limiting the maximum output amplitude of the dark level through the analog gain and then adjusting the digital gain to keep the total gain unchanged, thereby effectively improving the image quality.

[0031] It should be noted that the dark level analog gain correction method provided by the present application does not limit the type of the image sensor, for example, the image sensor can be but is not limited to a CMOS sensor. Furthermore, the present application does not limit the color filtering mode of the CMOS sensor, for example, the CMOS sensor can adopt but is not limited to a Bayer array and an X-Trans.

[0032] Exemplarily, in some exemplary embodiments, the method further comprises: step S400: taking the corrected analog gain of the current frame image as the initial analog gain of a next frame image. Thus, by taking the corrected analog gain of the current frame image as the initial analog gain of the next frame image, it can be ensured that the dark level of the next frame image using the corrected analog gain is not greater than the dark level threshold value, thereby obtaining better image quality.

[0033] It should be noted that those skilled in the art should understand that the present application does not limit the setting mode of the initial analog gain of each frame image. For example, in some preferred embodiments, as described above, the corrected analog gain of the previous frame image can be taken as the initial analog gain of the current frame image; in other embodiments, the initial analog gain of the current frame image can also be set by an external instruction. Furthermore, the present application does not limit the specific value of the initial analog gain too much, for example, the value of the initial analog gain can be any value between 1 and 32. It can be understood that the value of the initial analog gain should be reasonably set according to the specific performance of the image sensor, for example, the maximum value of the initial analog gain should be less than or equal to the maximum design value of the analog gain of the image sensor (the maximum analog gain supported by the image sensor can be obtained from the performance parameters of the image sensor provided by the image sensor manufacturer or through calibration).

[0034] It should be further noted that, similar to the initial analog gain, the total gain of the present application is not limited in any way. For example, in some exemplary embodiments, the total gain is a preset value and cannot be changed. In other exemplary embodiments, the total gain is a preset value and can be changed by external instructions. Further, the present application does not limit the specific value of the total gain. For example, the total gain can be any value between 1 and 1024. It should be understood that the value of the total gain should be reasonably set according to the specific performance of the image sensor. For example, the maximum value of the total gain should be less than or equal to the maximum design value of the total gain supported by the image sensor (the maximum total gain supported by the image sensor can be obtained from the performance parameters of the image sensor provided by the image sensor manufacturer or by calibration).

[0035] For example, in some exemplary embodiments, step S200 obtains the maximum allowed analog gain according to the initial analog gain, the real-time dark level, the pre-acquired dark level threshold, and the pre-acquired reference dark level, including calculating the maximum allowed analog gain by the following formula: Maximum allowed analog gain = Thd / abs(blc - Base) * Again. In the above formula, Thd is the dark level threshold, blc is the real-time dark level, Base is the reference dark level, and Again is the initial analog gain.

[0036] Therefore, the dark level analog gain correction method provided by the present application uses a design method of determining the maximum allowed analog gain according to the initial analog gain, the real-time dark level, the pre-acquired dark level threshold, and the pre-acquired reference dark level. This design method not only reasonably obtains the maximum allowed analog gain, thereby laying a good foundation for keeping the image brightness, image dynamic range, definition, and color unchanged, but also is simple in logic and easy to implement.

[0037] For example, in some exemplary embodiments, the method further includes: if it is determined that the maximum allowed analog gain is less than 1, setting the maximum allowed analog gain to 1; and if it is determined that the maximum allowed analog gain is greater than the maximum design value of the analog gain of the image sensor, setting the maximum allowed analog gain to the maximum design value of the analog gain.

[0038] The dark level analog gain correction method provided by the application lays a good foundation for keeping the image brightness, image dynamic range, definition and color constant and effectively improving the image quality by limiting the maximum output amplitude of the dark level value through the analog gain.

[0039] Exemplarily, in some exemplary embodiments, the dark level analog gain correction method further comprises obtaining the dark level threshold value by setting the image sensor to the maximum analog gain (such as 16 or 32, and the specific value can be obtained through the performance parameters of the image sensor provided by the image sensor manufacturer), heating the image sensor, and taking the dark level value of the black line when the image appears color cast (for example, the color cast includes but is not limited to image red cast or green cast) as the dark level threshold value. Thus, by setting the image sensor to the maximum analog gain and taking the dark level value of the black line when the image sensor is heated and color cast appears as the dark level threshold value, not only a more reliable dark level threshold value can be obtained, but also the logic is simple and easy to implement.

[0040] It should be understood by those skilled in the art that the above-mentioned method for obtaining the dark level threshold value is only an exemplary description of the preferred embodiment, and is not a limitation of the application. The application does not limit the specific method for obtaining the dark level threshold value Thd. For example, in other embodiments, the performance parameters of the image sensor provided by the image sensor manufacturer can also be used.

[0041] It should be understood by those skilled in the art that the minimum value of the dark level threshold value Thd is 1, and the maximum value is related to the bit width supported by the image sensor. For example, if the maximum value of the dark level threshold value Thd is 1023 in some exemplary embodiments, the value of the dark level threshold value Thd is any value between 1 and 1023 (including 1 and 1023).

[0042] It should be noted that the application does not limit the specific method for obtaining the real-time dark level blc. Preferably, in some exemplary embodiments, the average value of the black line brightness of the current frame image can be taken as the real-time dark level blc.

[0043] Exemplarily, in some of the exemplary embodiments, the dark level analog gain correction method comprises obtaining the reference dark level by taking the dark level obtained when the black row exposure row number of the image sensor is set to a preset black row row number and the analog gain is set to a preset exposure analog gain as the reference dark level. Thus, by taking the dark level obtained when the black row exposure row number of the image sensor is set to a preset black row row number and the analog gain is set to a preset exposure analog gain as the reference dark level, a good foundation is laid for obtaining a reliable maximum analog gain.

[0044] It should be noted that the present application does not make any limitation on the specific values of the preset black row row number and the preset exposure analog gain. For example, in some of the exemplary embodiments, the preset black row row number can be 1 row, 2 rows or 3 rows, etc.; and the preset exposure analog gain can be 1, 2 or 3, etc.

[0045] Exemplarily, in some of the exemplary embodiments, step S300 obtains the corrected analog gain and the corrected digital gain according to the total gain and the maximum analog gain, specifically comprising: first judging whether the total gain is less than the maximum analog gain, if yes, taking the total gain as the corrected analog gain; if no, taking the maximum analog gain as the corrected analog gain; and then taking the quotient of the total gain divided by the corrected analog gain as the corrected digital gain.

[0046] Thus, the dark level analog gain correction device provided by the present application limits the maximum output amplitude of the dark level value by adjusting the corrected analog gain, so that the dark level value of the image sensor at high temperature can always be at a lower limited value; and by adjusting the digital gain while keeping the total gain unchanged, the total gain of the current frame image is kept unchanged, which can effectively ensure that the image brightness is unchanged, so as to achieve the effect of keeping the image brightness, image dynamic range, definition, color, etc. unchanged, and further significantly improving the image quality.

[0047] Based on the same inventive concept, another embodiment of the present application provides a dark level analog gain correction device for performing analog gain correction on each frame of image collected by an image sensor. Exemplarily, please refer to Figure 2 , Figure 2 The block structure schematic diagram of the dark level analog gain correction device provided by the present embodiment is shown in FIG. 1. As shown in FIG. 1, the dark level analog gain correction device comprises a total gain obtaining unit 100, a maximum analog gain obtaining unit 200, a corrected analog gain obtaining unit 300 and a corrected digital gain obtaining unit 400. Figure 2It can be seen that the dark level analog gain correction device comprises a correction parameter acquisition unit 110, an analog gain allowable maximum value acquisition unit 120 and a correction value acquisition unit 130. Specifically, the correction parameter acquisition unit 110 is configured to acquire an initial analog gain, a total gain and a real-time dark level of a black row of a current frame image; the analog gain allowable maximum value acquisition unit 120 is configured to obtain an analog gain allowable maximum value according to the initial analog gain, the real-time dark level, a dark level threshold value acquired in advance and a reference dark level acquired in advance; and the correction value acquisition unit 130 is configured to obtain a corrected analog gain and a corrected digital gain according to the total gain and the analog gain allowable maximum value, so as to apply the corrected analog gain and the corrected digital gain to the image sensor.

[0048] Therefore, the dark level analog gain correction device provided by the present application can keep the image brightness, the image dynamic range, the definition and the color unchanged by acquiring the initial analog gain, the total gain and the real-time dark level of the black row of the current frame image through the correction parameter acquisition unit 110, limiting the analog gain and then limiting the maximum output amplitude of the dark level value through the analog gain allowable maximum value acquisition unit 120, and adjusting the digital gain through the correction value acquisition unit 130 so as to keep the total gain unchanged, thereby effectively improving the image quality.

[0049] It should be noted that the present application does not make too many limitations on the specific implementation mode of the dark level analog gain correction device. Preferably, in some exemplary embodiments, the dark level analog gain correction device can be realized in the form of an electronic circuit and integrated in the same chip as the image sensor.

[0050] It should be noted that according to the description herein, those skilled in the art should understand that the basic principle of the dark level analog gain correction device provided by the present application is the same as that of the dark level analog gain correction method provided by the present application, in order to avoid redundancy, the dark level analog gain correction device provided by the present application will not be described here, and the more detailed content of the dark level analog gain correction device provided by the present application can be understood by referring to the related description of the dark level analog gain correction method described above.

[0051] Another embodiment of the present application provides an image sensor, which is exemplarily shown in Figure 3 , Figure 3 The block structure schematic diagram of the image sensor provided by one embodiment of the present application is shown in Figure 3 It can be seen that the image sensor comprises the dark level analog gain correction device 100 described above.

[0052] Please continue to refer to Figure 3,like Figure 3 As shown, the image sensor provided by the present invention further includes a pixel array 200, a readout circuit 300, a timing and system control unit 400, an image signal processing unit (ISP) (preferably, the dark level analog gain correction device 100 is integrated in the image signal processing unit ISP), and an output interface 500. The imaging process of the image sensor is roughly as follows: Under the coordinated control of the timing and system control unit 400, the pixel array 200 converts the acquired raw light signal into an electrical signal; the readout circuit 300 performs analog-to-digital conversion on the electrical signal to obtain raw image data, and sends the converted raw image data to the image signal processing unit ISP; the image signal processing unit ISP performs processing on the raw image data including but not limited to black level correction, bad pixel correction, focus pixel correction, and color adjustment, and sends the processed final image data to the output interface 500; the output interface 500 converts and adapts the final image data according to the control of the application program APP to output the image data to a display screen, memory, or other devices.

[0053] Another embodiment of the present invention provides an imaging device. In some embodiments, the imaging device includes the dark-level analog gain correction device described above. In other embodiments, the imaging device includes a processor and a memory, the memory storing a computer program that, when executed by the processor, implements the dark-level analog gain correction method provided in any of the embodiments above.

[0054] Since the imaging device provided by this invention and the dark level analog gain correction method provided by this invention belong to the same inventive concept, the imaging device provided by this invention has at least all the advantages of the dark level analog gain correction method provided by this invention. For details on the beneficial effects of the imaging device provided by this invention, please refer to the above description of the beneficial effects of the dark level analog gain correction method provided by this invention.

[0055] It should be noted that the processor referred to in this invention can be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The processor is the control center of the imaging device, connecting various parts of the entire imaging device through various interfaces and lines.

[0056] It is also noted that the memory can be used to store the computer program, and the processor realizes various functions of the imaging device by running or executing the computer program stored in the memory and calling the data stored in the memory. The memory can include non-volatile and / or volatile memory. The non-volatile memory can include read-only memory (ROM), programmable memory (PROM), electrically programmable memory (EPROM), electrically erasable programmable memory (EEPROM) or flash memory. The volatile memory can include random access memory (RAM) or external cache memory. As an illustration but not limitation, random access memory is available in various forms, such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous random access memory (SDRAM), double data rate synchronous random access memory (DDR SDRAM), enhanced synchronous random access memory (ESDRAM), synchronous link (Synchlink) dynamic random access memory (SLDRAM), memory bus (Rambus) direct random access memory (RDRAM), direct memory bus dynamic random access memory (DRDRAM), and memory bus dynamic random access memory (RDRAM), etc.

[0057] Compared with the prior art, the dark level analog gain correction method, device, image sensor and imaging device provided by the present application have the following advantages: the dark level analog gain correction method provided by the present application performs the following operations for each frame of image collected by the image sensor: firstly, the initial analog gain, total gain and real-time dark level of the black row of the current frame of image are obtained; then, the maximum allowed analog gain is obtained according to the initial analog gain, the real-time dark level, the dark level threshold value obtained in advance and the reference dark level obtained in advance; finally, the corrected analog gain and the corrected digital gain are obtained according to the total gain and the maximum allowed analog gain, so as to apply the corrected analog gain and the corrected digital gain to the image sensor. Thus, the present application first limits the maximum output amplitude of the dark level by the analog gain, and then adjusts the digital gain to keep the total gain unchanged, so that the image brightness, image dynamic range, definition and color can be kept unchanged, thereby effectively improving the image quality.

[0058] It should be noted that the apparatus and method disclosed in the embodiments herein can also be implemented in other ways. The apparatus embodiments described above are merely exemplary, and the flowcharts and block diagrams in the accompanying drawings show only one possible implementation of the apparatus, method and computer program product according to the embodiments herein. In this regard, each block in the flowcharts and block diagrams can represent a module, a procedure, or a part of a module or procedure that comprises one or more executable instructions for implementing the specified logic function. It should also be noted that in some alternative implementations, the functions noted in the boxes can occur out of the order noted in the flowcharts. For example, two blocks shown in succession may, in fact, be executed substantially concurrently or in the reverse order, depending on the functionality involved. Also, each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented by special-purpose hardware-based systems that perform the specified functions or acts, or combinations of special-purpose hardware and computer instructions.

[0059] In addition, each functional module in the various embodiments herein can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.

[0060] The above description is merely illustrative of the preferred embodiments of the dark level analog gain correction method, apparatus, image sensor and imaging device provided by the present application, and is not intended to limit the scope of the present application. Any modification, amendment, or improvement made by those skilled in the art based on the above disclosure should fall within the scope of the present application. Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the present application and equivalent technology, they should be included in the present application.

Claims

1. A dark level analog gain correction method, characterized in that, include: For each frame of image captured by the image sensor, perform the following operations: Obtain the initial analog gain, total gain, and real-time dark level of the black lines in the current frame image; The maximum allowable value of the analog gain is obtained based on the initial analog gain, the real-time dark level, the pre-acquired dark level threshold, and the pre-acquired reference dark level; and if it is determined that the maximum allowable value of the analog gain is less than 1, then the maximum allowable value of the analog gain is set to 1. If it is determined that the maximum allowable value of the analog gain is greater than the maximum design value of the analog gain of the image sensor, then the maximum allowable value of the analog gain is set to the maximum design value of the analog gain; Based on the total gain and the maximum allowed analog gain, the corrected analog gain and the corrected digital gain are obtained, and then the corrected analog gain and the corrected digital gain are applied to the image sensor.

2. The dark level analog gain correction method according to claim 1, characterized in that, The step of obtaining the maximum allowable analog gain based on the initial analog gain, the real-time dark level, the pre-acquired dark level threshold, and the pre-acquired reference dark level includes calculating the maximum allowable analog gain using the following formula: Maximum allowable analog gain = Thd / abs(blc-Base)*Again In the above formula, Thd is the dark level threshold, blc is the real-time dark level, Base is the reference dark level, and Again is the initial analog gain.

3. The dark level analog gain correction method according to claim 1, characterized in that, This includes obtaining the dark level threshold through the following methods: The image sensor is set to maximum analog gain, the image sensor is heated, and the dark level value of the black line when the image shows color cast is used as the dark level threshold.

4. The dark level analog gain correction method according to claim 1, characterized in that, This includes obtaining the reference dark level through the following methods: The dark level obtained by exposure when the number of black lines of the image sensor is set to a preset number of black lines and the analog gain is set to a preset exposure analog gain is used as the reference dark level.

5. The dark level analog gain correction method according to claim 1, characterized in that, The step of obtaining the corrected analog gain and the corrected digital gain based on the total gain and the maximum allowable analog gain includes: Determine whether the total gain is less than the maximum allowable value of the analog gain. If yes, use the total gain as the corrected analog gain; otherwise, use the maximum allowable value of the analog gain as the corrected analog gain. The quotient of the total gain divided by the corrected analog gain is taken as the corrected digital gain.

6. The dark level analog gain correction method according to any one of claims 1 to 5, characterized in that, The method further includes using the corrected analog gain of the current frame image as the initial analog gain of the next frame image.

7. A dark level analog gain correction device, characterized in that, The dark-level analog gain correction device is used to perform analog gain correction on each frame of image acquired by the image sensor. The dark-level analog gain correction device includes: The correction parameter acquisition unit is configured to acquire the initial analog gain, total gain, and real-time dark level of the black line of the current frame image; The analog gain maximum allowable value acquisition unit is configured to obtain the analog gain maximum allowable value based on the initial analog gain, the real-time dark level, the pre-acquired dark level threshold, and the pre-acquired reference dark level; and if it is determined that the analog gain maximum allowable value is less than 1, then the analog gain maximum allowable value is set to 1; if it is determined that the analog gain maximum allowable value is greater than the maximum design value of the analog gain of the image sensor, then the analog gain maximum allowable value is set to the maximum design value of the analog gain. The correction value acquisition unit is configured to obtain the corrected analog gain and the corrected digital gain based on the total gain and the maximum allowable analog gain, so as to apply the corrected analog gain and the corrected digital gain to the image sensor.

8. An image sensor, characterized in that, The image sensor includes the dark level analog gain correction device as described in claim 7.

9. An imaging device, characterized in that, It includes the dark level analog gain correction device as described in claim 7, or includes a processor and a memory, wherein the memory stores a computer program, and when the computer program is executed by the processor, it implements the dark level analog gain correction method as described in any one of claims 1 to 6.

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