CN113938625B - Image sensor, image sensor reading method, image sensor reading device, and computer-readable storage medium - Google Patents
Image sensor, image sensor reading method, image sensor reading device, and computer-readable storage medium Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/60—Noise processing, e.g. detecting, correcting, reducing or removing noise
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/70—SSIS architectures; Circuits associated therewith
- H04N25/71—Charge-coupled device [CCD] sensors; Charge-transfer registers specially adapted for CCD sensors
- H04N25/75—Circuitry for providing, modifying or processing image signals from the pixel array
Abstract
An image sensor, a reading method, a reading device and a computer readable storage medium thereof. The image sensor comprises a pixel array and a read-out circuit array; a readout circuit in the readout circuit array is coupled to a column in the pixel array; the pixel array comprises at least one line of non-photosensitive pixel lines; the pixel output of the current frame is read by adopting the following method: acquiring readout information of a photosensitive-free pixel row in the pixel array from pixel output of n frames without eliminating RTS noise of a readout circuit, wherein n is more than or equal to 1, and n is a positive integer; identifying columns in the readout circuit array in which RTS noise is present based on readout information of the non-photosensitive pixel rows; and eliminating RTS noise in the read-out circuit array based on the identification result to obtain the pixel output of the current frame. By adopting the scheme, RTS noise in the reading circuit can be eliminated, and the image quality can be improved.
Description
Technical Field
The present invention relates to the field of image sensors, and in particular, to an image sensor, a readout method and apparatus thereof, and a computer readable storage medium.
Background
In the image sensor, random telegraph signal (Random Telegraph Signal, RTS) noise (noise) is present. RTS noise is usually caused by defects generated in the gate lattice of metal oxide (Metal Oxide Semiconductor, MOS) tubes during the manufacturing process, and thus, electrons are trapped or released randomly.
The image sensor includes a pixel array and a readout circuit. Because the pixel array and the readout circuit may both be formed by MOS transistors, RTS noise may exist not only in the pixel array but also in the readout circuit.
If RTS noise exists in the reading circuit, the phenomenon of 'dotted line' exists in the image finally output by the image sensor, and the image quality is affected.
Disclosure of Invention
The invention aims to solve the problems that: how to eliminate RTS noise in the readout circuit to improve image quality.
In order to solve the above problems, an embodiment of the present invention provides a readout method of an image sensor, where the image sensor includes a pixel array and a readout circuit array; a readout circuit in the readout circuit array is coupled to a column in the pixel array; the pixel array comprises at least one line of non-photosensitive pixel lines; the pixel output of the current frame is read by adopting the following method: acquiring readout information of a photosensitive-free pixel row in the pixel array from pixel output of n frames without eliminating RTS noise of a readout circuit, wherein n is more than or equal to 1, and n is a positive integer; identifying columns in the readout circuit array in which RTS noise is present based on readout information of the non-photosensitive pixel rows; and eliminating RTS noise in the read-out circuit array based on the identification result to obtain the pixel output of the current frame.
Optionally, the non-photosensitive pixel row is formed by any one of the following: a pixel circuit not including a photodiode; a switching circuit; and a power supply.
Optionally, the acquiring readout information of the non-photosensitive pixel row in the pixel array includes: and acquiring the read-out data of N x N pixel rows without the photosensitive pixel from the pixel output of N frames without eliminating the RTS noise of a read-out circuit, wherein N is the column number of the pixel array.
Optionally, the identifying, based on the readout information of the non-photosensitive pixel row, a column in the readout circuit array in which RTS noise exists includes: calculating standard deviation of read data of each column of the non-photosensitive pixel row; and comparing the standard deviation of each column with a standard deviation threshold value respectively to determine columns with RTS noise in the read-out circuit array.
Optionally, the identifying, based on the readout information of the non-photosensitive pixel row, a column in the readout circuit array in which RTS noise exists includes: determining a maximum value and a minimum value in read data of each column of the non-photosensitive pixel row; calculating a first difference between a maximum value and a minimum value in each column of read data; and comparing the first difference value corresponding to each column of read data with a difference threshold value to determine columns with RTS noise in the read circuit array.
Optionally, the identifying, based on the readout information of the non-photosensitive pixel row, a column in the readout circuit array in which RTS noise exists includes: calculating an approximate variance of the readout data of each column of the non-photosensitive pixel rows; and respectively comparing the approximate variance corresponding to each column of read data with a variance threshold value to determine columns with RTS noise in the read circuit array.
Optionally, the readout circuit array includes: a redundant column readout circuit; based on the identification result, the cancellation of RTS noise in the readout circuit array includes: and replacing the columns with RTS noise by using redundant columns, and reading out the photosensitive pixel rows in the pixel array to obtain the pixel output of the current frame.
Optionally, the eliminating RTS noise in the readout circuit array based on the identification result includes: reading out a photosensitive pixel row in the pixel array; and replacing the readout data of the columns with RTS noise by using the readout data of a preset column readout circuit to obtain the pixel output of the current frame.
The embodiment of the invention also provides a readout device of the image sensor, which comprises a pixel array and a readout circuit array; a readout circuit in the readout circuit array is coupled to a column in the pixel array; the pixel array comprises at least one line of non-photosensitive pixel lines; the device comprises: the acquisition unit is suitable for acquiring readout information of a photosensitive-free pixel row in the pixel array from pixel output of n frames without eliminating RTS noise of a readout circuit, wherein n is more than or equal to 1, and n is a positive integer; an identification unit adapted to identify columns in the readout circuit array in which RTS noise is present, based on readout information of the non-photosensitive pixel rows; and the noise elimination unit is suitable for eliminating RTS noise in the read-out circuit array based on the identification result to obtain the pixel output of the current frame.
Optionally, the non-photosensitive pixel row is formed by any one of the following: a pixel circuit not including a photodiode; a switching circuit; and a power supply.
The embodiment of the invention also provides an image sensor, which comprises a pixel array and a read-out circuit array; a readout circuit in the readout circuit array is coupled to a column in the pixel array; the pixel array comprises at least one line of non-photosensitive pixel lines; the image sensor further includes: the readout device of the image sensor.
The embodiment of the invention also provides a computer readable storage medium, on which a computer program is stored, the computer program being executed by a processor to implement the steps of the above method.
The embodiment of the invention also provides an image sensor, which comprises a memory and a processor, wherein the memory stores a computer program capable of running on the processor, and the processor executes the steps of the method when running the computer program.
Compared with the prior art, the technical scheme of the embodiment of the invention has the following advantages:
by applying the scheme of the invention, the non-photosensitive pixel rows are arranged in the pixel array, and the non-photosensitive pixel rows have no photosensitive function, so that if RTS noise exists in the readout information of the non-photosensitive pixel rows, RTS noise exists in the readout circuit of the image sensor, and therefore, the columns with RTS noise in the readout circuit array can be identified by acquiring the readout information of the non-photosensitive pixel rows, so that the RTS noise in the readout circuit array can be eliminated based on the identification result, the pixel output of the current frame is obtained, and the image quality is improved. In addition, according to the scheme of the invention, the photosensitive pixel rows are arranged in the pixel array, so that RTS noise can be eliminated in real time in the process of reading the pixels of the current frame, and compared with the RTS noise which is eliminated after the pixels of the current frame are read, the pixel output difference caused by temperature difference can be avoided, and the reading accuracy is improved.
Drawings
FIG. 1 is a schematic diagram of an image sensor according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a non-photosensitive pixel row in accordance with an embodiment of the present invention;
FIG. 3 is a flow chart of a method for reading out an image sensor according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a readout circuit array according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of a readout device of an image sensor in an embodiment of the present invention.
Detailed Description
The image sensor includes a pixel array and a readout circuit array. The readout circuits in the array of readout circuits are typically column parallel readout circuits, i.e. each column of pixel circuits is read out using a separate readout circuit, e.g. for an array of M x N pixels there are N columns of readout circuits. When the pixel circuit in the pixel array is formed by the MOS tube, RTS noise generated due to grid lattice defects of the MOS tube can cause flickering points on an output image. When the readout circuit in the readout circuit array is formed by the MOS tube, RTS noise generated due to grid lattice defects of the MOS tube leads to RTS columns in the readout circuit array, and finally leads to the phenomenon of 'dotted line' on an output image.
Whether the readout circuit has RTS noise is a yield problem. Statistically, there may be 1-2 column circuits per 2000 column readout circuits with RTS noise. Readout circuits that present RTS noise can create a "dashed line" phenomenon in the image. The broken line phenomenon means that there are individual columns of the output image, and its image data appears as intermittent lines. This is because RTS noise is much larger than random noise of a general readout circuit, and thus a "broken line" phenomenon is exhibited.
The difficulty in eliminating RTS noise of the readout circuit is that: the magnitude of the RTS noise of the readout circuit is not the same at different temperatures, so the "dashed line" position in the output image of the image sensor also changes at different temperatures. High-end image sensors are often faced with applications at different temperatures, and therefore it must be ensured that the image sensor does not appear as a dashed line in various environments. The existence of RTS noise not only reduces the yield of the image sensor, but also makes the testing of the image sensor chip very difficult.
In view of the above problems, the embodiments of the present invention provide a readout method of an image sensor, which can eliminate RTS noise in real time during reading a current frame pixel by setting a non-photosensitive pixel row in a pixel array, and improve image quality. And pixel output difference caused by temperature difference can be avoided, and reading accuracy is improved.
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings.
Fig. 1 is a schematic structural diagram of an image sensor according to an embodiment of the present invention. Referring to fig. 1, the image sensor includes a pixel array 11 and a readout circuit array 12.
In an image sensor that normally operates, RTS noise of a column circuit is mixed with image signals, so that RTS noise of a readout circuit can be only reflected when the image sensor operates in a dark field, that is, when no image signal interference exists.
Therefore, in order to identify RTS noise of the readout circuit, unlike the pixel array in the prior art, the pixel array 11 includes at least one line of non-photosensitive pixel lines 110, where the non-photosensitive pixel lines 110 refer to a line of non-photosensitive circuits that does not have a photosensitive capability. The specific number of the non-photosensitive pixel rows 110 is not limited, and may include 2, 3, and 4 non-photosensitive pixel rows 110, for example.
It can be understood that the greater the number of non-photosensitive pixel rows 110, the longer it takes to identify whether the RTS noise exists in the readout circuit, and the longer the overall readout time of the image sensor, but the more accurate the identification result, and the more accurate the identification result can be chosen according to the time situation.
In the pixel array 11, except for the non-photosensitive pixel row 110, a photosensitive pixel row 111 remains. The photosensitive pixel row 111 is composed of a row of photosensitive circuits. The photosensitive circuit, i.e., the pixel circuit, may be a 4T pixel circuit, or may be a 6T or 8T pixel circuit, which is not limited herein. The photosensitive pixel rows 111 are typically more than 2 rows, and can be as many as several thousand rows.
In a specific implementation, the image sensor typically further comprises a row control circuit 13. After decoding the read address, the row control circuit 13 may enable the non-photosensitive pixel row 110 to be selected when needed, so as to implement readout of the non-photosensitive pixel row 110.
In a specific implementation, the non-photosensitive circuit can be a pixel circuit without a photodiode, a switch circuit or a power supply, and other non-photosensitive circuits to meet the requirements of different types of column parallel circuits. The non-photosensitive circuits in the same row may be the same or different. When the pixel array 11 includes a plurality of non-photosensitive pixel rows 110, the non-photosensitive circuits of each of the non-photosensitive pixel rows 110 may be the same or different.
The power supply can be a voltage source, a current source or other low-noise reference power supply. Even if the non-photosensitive circuits in the same row are all voltage sources, the voltages provided by the voltage sources can be the same or different.
Each of the non-photosensitive circuits in the non-photosensitive pixel row 110 is connected to a bit line. Each of the photosensitive circuits of the photosensitive pixel rows 111 is also connected to a bit line. Each column in the pixel array corresponds to a bit line, and the non-photosensitive circuit and the photosensitive circuit of each column are connected with a readout circuit in the readout circuit array 12 through a shared bit line.
The non-photosensitive pixel row 110 has a fixed row address as the photosensitive pixel row. The readout circuit array 12 is a column parallel readout circuit, i.e. pixel signals of the pixel array 11 are read out row by row. In reading out the pixel array 11, the non-photosensitive pixel rows 110 are read out sequentially first, and the photosensitive pixel rows 111 are read out sequentially. And the readout circuit with RTS noise is identified according to the non-photosensitive pixel row 110, and then the pixel output of the image sensor is obtained according to the readout result of the photosensitive pixel row 111.
Taking the non-photosensitive circuit as an example, referring to fig. 2, assuming that the pixel array includes N columns, the non-photosensitive pixel row 110 includes N switches, and each switch 110a is connected to the row control circuit. Each switch 110a is connected to a corresponding bit line, bit lines BL <0> through BL < N >, respectively. The Row control circuit outputs a Row selection signal Row-select to select the non-photosensitive pixel Row 110. The output signal VREF of the non-photosensitive pixel row 110 is fed to the bit line and read out by the readout circuit. The output signal VREF of the non-photosensitive pixel row 110 may be selected to be a suitable voltage, such as power, ground, or a specific common mode level, depending on the configuration of the readout circuit. The output signal VREF typically selects a low noise reference source.
The readout method of the image sensor is described in detail below with reference to fig. 1:
referring to fig. 3, an embodiment of the present invention provides a readout method of an image sensor, which may include the steps of:
step 31, obtaining readout information of a non-photosensitive pixel row in the pixel array from pixel output of n frames without eliminating RTS noise of a readout circuit, wherein n is more than 1, and n is a positive integer.
In implementations, there may be multiple frames of pixel outputs that do not cancel the readout circuit RTS noise before the current frame pixel output is read out. And selecting n frames from pixel outputs of the plurality of frames without eliminating RTS noise of a readout circuit to acquire readout information of the pixel rows without sensitization in the pixel array. The pixel output of a frame refers to the output obtained by exposing all the photosensitive pixel rows in the pixel array once.
The larger the value of n is, the more memory resources are occupied by the pixel output of the n frames of non-elimination readout circuit RTS noise, but the more accurate the RTS noise identification result is. For example, n may have a value of 2, 3, 4, etc.
Preferably, in order to achieve both resource and identification accuracy, the value of n is 16, i.e. 16 frames of pixel outputs are selected from pixel outputs before the current frame of pixel outputs, from which the RTS noise of the readout circuit is not eliminated.
In particular, because the magnitude of the RTS noise of the readout circuit at different temperatures may be different, the pixel output of the n frames of the RTS noise of the non-cancellation readout circuit is generally at the same or similar ambient temperature as the pixel output of the current frame, and the smaller the temperature difference between the pixel output of the n frames of the RTS noise of the non-cancellation readout circuit and the pixel output of the current frame is, the more accurately the readout circuit with the RTS noise in the pixel output process of the current frame can be determined.
In general, the pixel output of the n frames without eliminating the RTS noise of the readout circuit is the pixel output of the n frames without eliminating the RTS noise of the readout circuit nearest to the pixel output process of the current frame.
Step 32, based on the readout information of the non-photosensitive pixel rows, identifying columns in the readout circuit array in which RTS noise exists.
In practice, the image sensor typically employs a correlated double sampling (Correlated Double Sampling, CDS) method to read out the pixel array. The exposure signal and the reset signal are specifically read out, and the read-out results are subtracted. At this time, the output of the readout circuit is mainly noise of the readout circuit itself. Columns of the readout circuit array in which RTS noise is present can thereby be identified based on readout information of the non-photosensitive pixel rows.
In implementations, based on the readout information of the non-photosensitive pixel rows, a variety of methods can be employed to identify columns in the readout circuit array where RTS noise is present. Since each column of readout circuits typically includes only one readout circuit, the column in which RTS noise is present is typically a readout circuit in which RTS noise is present.
And the pixel array only comprises one non-photosensitive pixel row example, and the read-out data of N x N non-photosensitive pixel rows can be obtained from the pixel output of N frames without eliminating the RTS noise of the read-out circuit to form an N x N data array. At this time, the number of read data for each column is n.
In an embodiment of the present invention, a standard deviation method may be used to determine columns in the readout circuit array in which RTS noise exists, that is, standard deviation is determined for n readout data corresponding to each column.
Specifically, the standard deviation of the readout information of each column of the non-photosensitive pixel row may be calculated first, and then the standard deviation of each column is compared with a standard deviation threshold value, so as to determine the column with RTS noise in the readout circuit array.
Taking the non-photosensitive circuit of the ith column in the non-photosensitive pixel row as an example, in the pixel output of n frames of RTS noise of the non-photosensitive circuit, the non-photosensitive circuit of the ith column has n readout data, and the n readout data are subjected to standard deviation to obtain the standard deviation STD corresponding to the non-photosensitive circuit of the ith column i . Thus, there is noThe standard deviation corresponding to each column in the photosensitive pixel row is STD 0 ～STD N A matrix of 1*N is formed.
Since the readout circuit having RTS noise has a noise significantly larger than that of a normal readout circuit, the standard deviation of the readout circuit having RTS is also significantly larger than that of the readout circuit having RTS. By setting a standard deviation threshold STD th And according to STD 0 ～STD N To correctly identify the readout circuit in which RTS noise is present. Specifically, STD greater than the standard deviation threshold value may be used th A sense circuit that determines that RTS noise is present.
The standard deviation method is used for determining columns with RTS noise in the read-out circuit array, and although more memory resources are consumed in the calculation process, the real-time performance is higher, and the influence on the read-out frame rate of the image sensor is minimal.
In another embodiment of the present invention, a maximum value and a minimum value may be adopted to determine columns in the readout circuit array where RTS noise exists, that is, maximum values and minimum values are obtained for n readout data corresponding to each column.
Specifically, the maximum value and the minimum value in the readout information of each column of the non-photosensitive pixel row can be determined first, then a first difference value between the maximum value and the minimum value in the readout information of each column is calculated, finally the first difference value corresponding to the readout information of each column is compared with a difference threshold value, and the column with RTS noise in the readout circuit array is determined.
In the embodiment, taking the non-photosensitive circuit of the ith column in the non-photosensitive pixel row as an example, in the pixel output of the n-frame non-erasing readout circuit RTS noise, the non-photosensitive circuit of the ith column has n readout data, and the first difference between the maximum value and the minimum value in the n readout data is S i . Thus, the first differences corresponding to the columns in the non-photosensitive pixel rows are S 0 ～S N A matrix of 1*N is formed.
Since the sense circuit with RTS noise has a much larger noise than the normal sense circuit, the first difference between the sense circuits with RTS is also much larger. By setting a differenceValue threshold S th And according to S 0 ～S N To correctly identify the readout circuit in which RTS noise is present. Specifically, it is possible to make the difference greater than the difference threshold S th A sense circuit that determines that RTS noise is present.
The method for calculating the maximum value and the minimum value is adopted to determine the column with RTS noise in the read-out circuit array, and the calculation process is simple, so that the consumed memory resource is less, the influence on the read-out frame rate of the image sensor is smaller, and the real-time performance is higher.
In yet another embodiment of the present invention, the column in which the RTS noise exists in the readout circuit array may be determined in a sliding variance manner, that is, the pixel output of n frames of which the RTS noise of the readout circuit is not eliminated is calculated, the sliding average value of the pixel output of the last frame of which the RTS noise of the readout circuit is not eliminated is calculated, and then the approximate variance of the pixel output of the last frame of which the RTS noise of the readout circuit is not eliminated is calculated.
Specifically, the approximate variance of the readout information of each column of the non-photosensitive pixel row may be calculated, and the approximate variance corresponding to each column of readout information may be compared with a variance threshold value to determine a column in the readout circuit array in which RTS noise exists.
For convenience of explanation, it is assumed that the number of non-photosensitive pixel rows per frame is 1, so that 1 column circuit acquires only 1 data per frame.
In practical application, assuming that the current frame is x, the output of n frames of non-photosensitive pixels (x > n) is stored successively according to the output time, and the x-n frames are sequentially from the x-th frame to the x-th frame. With the continuous output of the pixels, the moving average value a of the ith column in the pixel output of the xth frame can be obtained xi ：
Wherein a is x-1i Is the moving average value of the x-n-1 th frame to the x-1 th frame, D xi The pixel of the x-th frame outputs the read data of the i-th column.
At acquisition a xi Then, find the near of the n frame ith row dataPlausibility H xi ：
In this way, the approximate variance H corresponding to each column can be obtained x1 ～H xN . Since the sense circuit having RTS noise has a noise much larger than that of a normal sense circuit, the sense circuit having RTS has an approximate variance much larger than that of a sense circuit. By setting a variance threshold H th And according to H x1 ～H xN To correctly identify the readout circuit in which RTS noise is present. Specifically, it is possible to have a variance greater than the threshold H th A sense circuit that determines that RTS noise is present.
In the above method, the multi-frame calculation is performed by using a pixel array including 1 line of non-photosensitive pixels. In the same frame of image, a readout circuit in which RTS noise is present can be identified using a plurality of non-photosensitive rows. When the pixel array comprises more than X rows of non-photosensitive pixel rows, each column of read data comprises X non-photosensitive circuit read data, N columns of read data form an X-N matrix, and the standard deviation, the maximum value and the minimum value and the approximate variance are calculated based on the X-N matrix.
For example, when x=2, two data can be acquired per frame by each column of circuit, so n data are acquired as well, only one half of the number of frames is needed, and the algorithm when x=1 can be directly used. This method also uses x=3, 4, etc.
It can be appreciated that, in the implementation, the scheme of identifying whether the readout circuit has RTS noise is not limited to the foregoing embodiment, and other schemes may be used to identify RTS noise, which is not described herein.
It should be emphasized that the RTS noise recognition method in the embodiment of the present invention is a real-time recognition method, and does not need an additional memory to store the recognition result. In the traditional method for obtaining the RTS noise column through testing, because RTS noise is related to temperature, some columns with larger RTS noise are normal columns at certain temperatures, so that the chip can be ensured not to generate RTS noise columns by testing a plurality of temperature points, and the testing cost is higher. Compared with the traditional method for acquiring the RTS noise column through testing, the RTS noise identification is performed in real time, namely RTS noise identification is performed at the current use temperature, the obtained test result can more accurately represent whether RTS noise exists in the readout circuit at the current use temperature, and the test cost is lower.
And step 33, eliminating RTS noise in the read-out circuit array based on the identification result, and obtaining the pixel output of the current frame.
In the implementation, based on the identification result, various methods may be used to eliminate the RTS noise in the readout circuit array, and the implementation is not particularly limited as long as the RTS noise in the readout circuit array can be eliminated.
In practical applications, in order to cope with a failure of a part of the readout circuits in the readout circuit array, a redundant column is usually provided in the readout circuit array, and the redundant column is used to replace the column where the failed readout circuit is located.
In an embodiment of the present invention, after the RTS noise column in the readout circuit array is identified, before the current frame pixel is obtained, the redundant column in the readout circuit array may be used to read out the photosensitive pixel row in the pixel array, so as to obtain the current frame pixel output.
Specifically, referring to fig. 4, the pixel array includes K columns of pixel circuits, each column of pixel circuits sharing one bit line. The pixel array is connected with K bit lines, namely BL <1> -BL < K >. The K bit lines BL <1> -BL < K > are connected to the sense circuit array 12 through the selection circuit mux. The readout circuit array 12 may be provided with k+1 columns of readout circuits, where the K columns of readout circuits are connected to the K bit lines BL <1> -BL < K > one by one through a selection circuit mux, and the remaining 1 columns are redundant columns.
The value of K can be adjusted according to the process, and the probability of the occurrence of RTS noise columns of the excellent process is smaller, so that the value of K can be larger, and the area is saved. And a later process needs to select a smaller K value, so that the yield of the chip is improved.
In an embodiment, the selection circuit mux may receive a column selection signal and switch the K column readout circuits connected to the K bit lines under the control of the column selection signal. For example, before RTS noise is identified, column 1 through column K readout circuits are connected to K bit lines, with column K+1 readout circuits being redundant columns. If RTS noise exists in the Kth column readout circuit, the column selection signal may control the 1 st column to the K-1 st column readout circuit to be connected to the K-1 st bit line, and the K+1 st column readout circuit to be connected to the K-th bit line.
In another embodiment of the present invention, the cancellation of RTS noise may be performed after the current frame pixel output. Specifically, the photosensitive pixel row in the pixel array may be read out first to obtain an initial current pixel frame output, and then the readout data of the column with RTS noise is replaced by the readout data of the preset column readout circuit to obtain a final current frame pixel output. Wherein the predetermined column readout circuit may be based on selecting a column readout circuit closest to the normal readout value.
For example, referring to fig. 4, the 1 st to K th column readout circuits are connected to K bit lines. And reading out the photosensitive pixel rows in the pixel array by using the 1 st column to the K th column reading-out circuits to obtain the initial current pixel frame output. If RTS noise exists in the Kth column readout circuit, the readout data of the Kth-1 column readout circuit can be used as the readout data of the Kth column readout circuit to obtain the final current frame pixel output.
It should be noted that, in the implementation, the method for eliminating the RTS noise is not limited to the description in the above embodiment, and other methods may be used for eliminating the RTS noise, which is not limited in particular.
From the above, it can be seen that the readout method of the image sensor in the embodiment of the invention can identify the RTS noise of the readout circuit regardless of the process of the image sensor, and is independent of the process. And, need not to carry out test correction, insensitive to temperature. In addition, system resources are saved relative to conventional test calibration schemes. RTS noise recognition is performed in real time, so that the influence on the frame rate of the image sensor is also very small.
In order to better understand and implement the present invention, a user terminal and a computer-readable storage medium corresponding to the above method are described in detail below.
Referring to fig. 5, an embodiment of the present invention provides a readout device 50 for an image sensor. The image sensor comprises a pixel array and a read-out circuit array; a readout circuit in the readout circuit array is coupled to a column in the pixel array; the pixel array includes at least one line of non-photosensitive pixel rows.
The apparatus 50 includes: an acquisition unit 51, an identification unit 52, and a noise cancellation unit 53. Specifically:
the acquiring unit 51 is adapted to acquire readout information of a non-photosensitive pixel row in the pixel array from pixel outputs of n frames without eliminating RTS noise of the readout circuit, where n is greater than or equal to 1, and n is a positive integer;
the identifying unit 52 is adapted to identify columns in the readout circuit array in which RTS noise exists based on readout information of the non-photosensitive pixel rows;
the noise cancellation unit 53 is adapted to cancel RTS noise in the readout circuit array based on the recognition result, and obtain a current frame pixel output.
In a specific implementation, the pixel array may include only one line of non-photosensitive pixel rows, or may include two or more lines of non-photosensitive pixel rows. The non-photosensitive pixel row may be constituted by a pixel circuit including no photodiode, may be constituted by a switching circuit, and may be constituted by a power supply, and is not particularly limited as long as it has no photosensitive capability and can be read out by a readout circuit.
In a specific implementation, the readout circuit array firstly reads out the non-photosensitive pixel rows in the pixel array, identifies the columns with RTS noise based on the readout result, and then reads out the photosensitive pixel rows in the pixel array, so that the identification result is utilized to obtain the pixel output of the current frame.
The acquiring unit 51, the identifying unit 52 and the noise canceling unit 53 may be implemented with reference to the descriptions of the steps 31 to 33, and are not repeated here.
The embodiment of the invention also provides an image sensor, and referring to fig. 1, the image sensor comprises a pixel array 11 and a readout circuit array 12. A readout circuit in the readout circuit array 12 is coupled to a column in the pixel array; the pixel array 11 includes at least one non-photosensitive pixel row 110. The image sensor further includes: the readout device 50 of the image sensor shown in fig. 5. The readout device 50 controls the readout circuit array to read out the pixel array 11 to obtain the pixel output of the current frame.
The embodiment of the invention also provides a computer readable storage medium, on which a computer program is stored, the computer program being executed by a processor to implement the steps of the readout method of the image sensor.
In particular implementations, the computer-readable storage medium may include: ROM, RAM, magnetic or optical disks, etc.
The embodiment of the invention also provides an image sensor, which comprises a memory and a processor, wherein the memory is stored with a computer program capable of running on the processor, and the processor executes the steps of the reading method of the image sensor when running the computer program.
With respect to each of the apparatuses and each of the modules/units included in the products described in the above embodiments, it may be a software module/unit, a hardware module/unit, or a software module/unit, and a hardware module/unit. For example, for each device or product applied to or integrated on a chip, each module/unit included in the device or product may be implemented in hardware such as a circuit, or at least part of the modules/units may be implemented in software program, where the software program runs on a processor integrated inside the chip, and the rest (if any) of the modules/units may be implemented in hardware such as a circuit; for each device and product applied to or integrated in the chip module, each module/unit contained in the device and product can be realized in a hardware manner such as a circuit, different modules/units can be located in the same component (such as a chip, a circuit module and the like) or different components of the chip module, or at least part of the modules/units can be realized in a software program, the software program runs on a processor integrated in the chip module, and the rest (if any) of the modules/units can be realized in a hardware manner such as a circuit; for each device, product, or application to or integrated with the terminal, each module/unit included in the device, product, or application may be implemented by using hardware such as a circuit, different modules/units may be located in the same component (for example, a chip, a circuit module, or the like) or different components in the terminal, or at least part of the modules/units may be implemented by using a software program, where the software program runs on a processor integrated inside the terminal, and the remaining (if any) part of the modules/units may be implemented by using hardware such as a circuit.
Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention, and the scope of the invention should be assessed accordingly to that of the appended claims.
Claims (9)
1. The readout method of the image sensor is characterized in that the image sensor comprises a pixel array and a readout circuit array; a readout circuit in the readout circuit array is coupled to a column in the pixel array; the pixel array comprises at least one line of non-photosensitive pixel lines; the pixel output of the current frame is read by adopting the following method:
acquiring N x N read-out data of the non-photosensitive pixel rows from N frames of pixel output without eliminating RTS noise of a read-out circuit, wherein N is the number of columns of the pixel array, N is more than 1, and N is a positive integer;
identifying columns in the readout circuit array where RTS noise exists based on the readout data of the n×n non-photosensitive pixel rows;
based on the identification result, eliminating RTS noise in the read-out circuit array to obtain the pixel output of the current frame;
the identifying columns in the readout circuit array where RTS noise exists based on readout information of the non-photosensitive pixel rows includes:
calculating standard deviation of read data of each column of the non-photosensitive pixel row; comparing standard deviation of each column with a standard deviation threshold value respectively, and determining columns with RTS noise in the read-out circuit array;
or determining the maximum value and the minimum value in the read data of each column of the non-photosensitive pixel row, calculating a first difference value between the maximum value and the minimum value in the read data of each column, comparing the first difference value corresponding to the read data of each column with a difference value threshold value, and determining the column with RTS noise in the read circuit array;
or, calculating the approximate variance of the readout data of each column of the non-photosensitive pixel row, comparing the approximate variance corresponding to the readout data of each column with a variance threshold value, and determining columns with RTS noise in the readout circuit array;
or, replacing the columns with RTS noise by using redundant columns, and reading out the photosensitive pixel rows in the pixel array to obtain the pixel output of the current frame.
2. The method of reading out an image sensor of claim 1, wherein the line of non-photosensitive pixels is comprised of any one of:
a pixel circuit not including a photodiode;
a switching circuit;
and a power supply.
3. The method of reading out an image sensor of claim 1, wherein the array of readout circuits comprises: a redundant column readout circuit; based on the identification result, the cancellation of RTS noise in the readout circuit array includes:
and replacing the columns with RTS noise by using redundant columns, and reading out the photosensitive pixel rows in the pixel array to obtain the pixel output of the current frame.
4. The method for reading out an image sensor according to claim 1, wherein the eliminating RTS noise in the readout circuit array based on the identification result comprises:
reading out a photosensitive pixel row in the pixel array;
and replacing the readout data of the columns with RTS noise by using the readout data of a preset column readout circuit to obtain the pixel output of the current frame.
5. A readout device of an image sensor, wherein the image sensor comprises a pixel array and a readout circuit array; a readout circuit in the readout circuit array is coupled to a column in the pixel array; the pixel array comprises at least one line of non-photosensitive pixel lines; the device comprises:
the acquisition unit is suitable for acquiring N-times-N read-out data of the non-photosensitive pixel rows from pixel output of N frames without eliminating RTS noise of the read-out circuit, wherein N is the column number of the pixel array, N is more than or equal to 1, and N is a positive integer;
an identification unit adapted to read out data of n×n non-photosensitive pixel rows, for identifying columns in the readout circuit array in which RTS noise exists;
the noise elimination unit is suitable for eliminating RTS noise in the read-out circuit array based on the identification result to obtain the pixel output of the current frame;
the noise elimination unit is suitable for calculating standard deviation of read data of each column of the non-photosensitive pixel row; comparing standard deviation of each column with a standard deviation threshold value respectively, and determining columns with RTS noise in the read-out circuit array;
or the noise elimination unit is suitable for determining the maximum value and the minimum value in the read data of each column of the non-photosensitive pixel row, calculating a first difference value between the maximum value and the minimum value in the read data of each column, comparing the first difference value corresponding to the read data of each column with a difference value threshold value, and determining the column with RTS noise in the read circuit array;
or the noise elimination unit is suitable for calculating the approximate variance of the readout data of each column of the non-photosensitive pixel row, comparing the approximate variance corresponding to the readout data of each column with a variance threshold value, and determining the column with RTS noise in the readout circuit array.
6. The image sensor readout device of claim 5, wherein the non-photosensitive pixel rows are comprised of any one of:
a pixel circuit not including a photodiode;
a switching circuit;
and a power supply.
7. An image sensor is characterized by comprising a pixel array and a readout circuit array; a readout circuit in the readout circuit array is coupled to a column in the pixel array; the pixel array comprises at least one line of non-photosensitive pixel lines; the image sensor further includes: a readout device of an image sensor as claimed in claim 5 or 6.
8. A computer readable storage medium having stored thereon a computer program, characterized in that the computer program is executed by a processor to implement the steps of the method of any of claims 1 to 4.
9. An image sensor comprising a memory and a processor, the memory having stored thereon a computer program capable of being run on the processor, characterized in that the processor executes the steps of the method according to any of claims 1 to 4 when the computer program is run on the processor.
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