A method, system and apparatus for measuring dark current of a charge coupled device

Abstract

The application discloses a kind of dark current measurement method, system and device of charge coupled device, including control charge coupled device work in full frame transfer mode and gather image;The image collected is handled, and the charge-voltage conversion factor and the dark signal response rate under integration time in the image are extracted;According to the charge-voltage conversion factor and the dark signal response rate under integration time, the dark current of the charge coupled device is calculated.Compared with prior art, the dark signal response rate under multiple different integration times can be obtained by randomly collecting an image, the dark current can be quickly and accurately calculated, the test efficiency and test accuracy are greatly improved, and can be better applied to scientific level application occasions.

Description

Technical Field

[0001] This invention relates to the field of charge-coupled device (CCD) technology, and in particular to a method, system, and apparatus for measuring the dark current of a CCD. Background Technology

[0002] Dark current is characterized by the output current of a charge-coupled device (CCD) under no-light conditions. Dark current is an important parameter of CCDs, and in certain special cases, it is necessary to measure its magnitude for CCD data correction to obtain more accurate results. Traditional CCD dark current testing methods typically involve adjusting the frame integration time to t1 to obtain one image, adjusting the frame integration time to t2 to obtain another image, and then calculating the dark current using the two images and the time difference between the integrations.

[0003] Existing methods for measuring dark current require storing and calculating two frames of images at least over two integration times. When the dark signal is small, the integration time needs to be increased, resulting in a longer testing time. This places high demands on the temperature control system, requiring it to maintain temperature stability for an extended period. In scientific applications, when the CCD operating temperature is low and the dark current is small, the long integration time severely impacts the testing speed. Furthermore, it places high demands on the temperature control system and can only acquire dark signal responsivity data over two integration times, resulting in a limited dataset that cannot quickly and accurately calculate the dark current. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method, system and apparatus for measuring dark current of charge-coupled devices, so as to solve the problems of stringent requirements for dark current calculation environment, long test time and low test accuracy in the prior art.

[0005] To address the aforementioned technical problems, one solution of the present invention provides a method for measuring the dark current of a charge-coupled device, comprising the following steps:

[0006] S1: Controls the charge-coupled device to operate in full-frame transfer mode and acquire images;

[0007] S2: Process the acquired image to extract the charge-voltage conversion factor and the dark signal responsivity under integral time from the image;

[0008] S3: Calculate the dark current of the charge-coupled device based on the charge-voltage conversion factor and the dark signal responsivity under integral time.

[0009] Furthermore, in step S1, the charge-coupled device operates in a dark chamber where the operating temperature of the charge-coupled device can be adjusted. Step S1 includes the following sub-steps:

[0010] S11: Place the charge-coupled device in the dark chamber, adjust the temperature in the dark chamber to the preset temperature, and control the charge-coupled device to work in full-frame transfer mode;

[0011] S12: Adjust the line period according to the preset driving timing until the charge-coupled device imaging is normal and record the line period. Determine the dark signal integration time of each line according to the line period. After the image is acquired normally, randomly extract a frame of image.

[0012] Furthermore, step S2 includes the following sub-steps:

[0013] S21: Obtain the pixel value of each pixel in the image, calculate the average pixel value and noise voltage of each row of the image, fit the photon transfer curve based on the average pixel value and noise voltage, and obtain the charge-voltage conversion factor;

[0014] S22: Obtain the dark signal integration time of each row of the image, and fit the relationship curve between the dark signal and the integration time based on the dark signal integration time and the pixel average value of each row of pixels to obtain the dark signal response rate under the integration time.

[0015] Furthermore, in step S21, the specific method for fitting the photon transfer curve is as follows:

[0016] Based on the pixel values ​​of each pixel in the image, the average pixel value and the noise voltage of each row of pixels are calculated. Using the average pixel value as the x-axis and the square of the noise voltage as the y-axis, the photon transfer curve is obtained by least squares fitting. The intercept and slope of the photon transfer curve are then calculated to obtain the charge-voltage conversion factor.

[0017] ;

[0018] in: It is the charge-to-voltage conversion factor. For pixel rows, , This represents the total number of pixel rows in a single frame of an image. The average pixel value of each row of the image The average value, The square of the noise voltage of each pixel The average value.

[0019] Furthermore, in step S21, the formula for calculating the average pixel value is:

[0020] ;

[0021] in: This represents the average pixel value for each row of the image. For pixel rows, , This represents the total number of pixel rows in a single frame of an image. For each line The pixel value of each pixel. , The total number of pixels contained in each row.

[0022] Furthermore, in step S21, the formula for calculating the noise voltage is:

[0023] ;

[0024] in: The noise voltage of each row of the image. This represents the average pixel value for each row of the image. For pixel rows, , This represents the total number of pixel rows in a single frame of an image. For each line The pixel value of each pixel. , The total number of pixels contained in each row.

[0025] Furthermore, in step S22, the specific method for fitting the relationship curve between the dark signal and the integration time is as follows:

[0026] The integration time of the dark signal for each row is obtained based on the row period of the charge-coupled device. Using the integration time of the dark signal for each row as the x-axis and the average pixel value of each row as the y-axis, the relationship curve between the dark signal and the integration time is obtained by least squares fitting. The intercept and slope of the curve are then calculated to obtain the dark signal responsivity at the integration time.

[0027] ;

[0028] in: The dark signal responsivity during integration time. For pixel rows, , This represents the total number of pixel rows in a single frame of an image. Integrating time for the dark signal of each row of the image The average value, The average pixel value of each row of the image The average value.

[0029] Furthermore, in step S3, the formula for calculating the dark current is:

[0030] ;

[0031] in: To obtain dark current for charge-coupled devices, It is the charge-to-voltage conversion factor. Let be the dark signal responsivity over the integration time.

[0032] To address the aforementioned technical problems, another technical solution of the present invention provides a dark current measurement system for charge-coupled devices, comprising:

[0033] The image acquisition module is used to control the charge-coupled device to operate in full-frame transfer mode and acquire images;

[0034] An image processing module is used to process the acquired image to obtain the pixel value of each pixel in the image, and calculate the average pixel value and noise voltage of each row of the image based on the pixel value. A photon transfer curve is fitted based on the average pixel value and noise voltage, and the intercept and slope of the photon transfer curve are calculated to extract the charge-voltage conversion factor in the image. The image processing module is also used to obtain the dark signal integration time of each row of the image, and fit a relationship curve between the dark signal and the integration time based on the dark signal integration time and the average pixel value of each row of pixels. The intercept and slope of the relationship curve between the dark signal and the integration time are calculated to obtain the dark signal responsivity at the integration time.

[0035] The calculation module is used to calculate the dark current of the charge-coupled device based on the charge-voltage conversion factor and the dark signal responsivity under integral time.

[0036] To solve the above-mentioned technical problems, another technical solution of the present invention provides a dark current measurement device for charge-coupled devices, comprising:

[0037] The temperature control module is used to regulate the operating temperature of the charge-coupled device.

[0038] The drive and control module is used to drive and control the charge-coupled device to operate in full-frame transfer mode, and the temperature control module is used for temperature regulation; and

[0039] The processor is configured to acquire images collected by the charge-coupled device (CCD) and process the images to obtain the pixel value of each pixel in the image. Based on the pixel value, the processor calculates the average pixel value and noise voltage of each row of pixels to fit a photon transfer curve and calculates the intercept and slope of the photon transfer curve to extract the charge-voltage conversion factor in the image. The processor is also configured to acquire the dark signal integration time of each row of images, and fit a relationship curve between the dark signal and the integration time based on the dark signal integration time and the average pixel value of each row of pixels. The processor then calculates the intercept and slope of the relationship curve between the dark signal and the integration time to obtain the dark signal responsivity at the integration time. Finally, the processor calculates the dark current of the CCCD based on the extracted charge-voltage conversion factor of the image and the dark signal responsivity at the integration time.

[0040] This invention controls the charge-coupled device to operate in full-frame transfer mode. By setting the driving timing to adjust the row period and coordinating with the fast clear and dark signal transfer readout timing, the dark current response pixel values ​​in the image at multiple integration times can be obtained by randomly acquiring a single frame. By calculating the pixel average value, noise voltage, and dark signal integration time of each row of pixels in the image, the corresponding relationship curve can be fitted, and then the dark signal responsivity and charge-voltage conversion factor can be calculated, thereby calculating the dark current. The entire process only requires acquiring one frame of image, thus improving testing efficiency and enabling fast and accurate calculation of the dark current. Attached Figure Description

[0041] Figure 1 This is a flowchart of the dark current measurement method for a charge-coupled device according to Embodiment 1 of the present invention.

[0042] Figure 2 for Figure 1 Another flowchart.

[0043] Figure 3 This is the driving timing diagram for the charge-coupled device in step S1.

[0044] Figure 4 This is the photon transfer curve in step S21.

[0045] Figure 5 The curve showing the relationship between the dark signal and the integration time in step S22 is shown.

[0046] Figure 6 This is a system block diagram of the dark current measurement system of the charge-coupled device according to Embodiment 2 of the present invention.

[0047] Figure 7 This is a control block diagram of the dark current measurement device for the charge-coupled device in Embodiment 3 of the present invention. Detailed Implementation

[0048] The following detailed description illustrates the specific implementation method:

[0049] Example 1

[0050] like Figure 1 and Figure 2 The flowchart shown illustrates a method for measuring the dark current of a charge-coupled device (CCD) according to an embodiment of the present invention. The method involves adjusting the temperature in the dark chamber to a preset temperature and controlling the CCD to operate in full-frame transfer mode, enabling normal imaging. The line period is adjusted to a suitable time, and the line period and the dark signal integration time corresponding to each line are recorded. After normal image acquisition, a frame is randomly acquired, and the voltage-charge conversion factor and the dark signal responsivity at the integration time corresponding to the image are extracted and calculated. Finally, the dark current of the CCD is calculated based on the voltage-charge conversion factor and the dark signal responsivity. In this embodiment, the pixel size of the CCD is M (rows) × N (columns) as an example, meaning that the pixel array of the CCD includes M rows, and each row includes N pixels. Specifically, the dark current measurement method of the CCD includes the following steps:

[0051] S1: Controls the operation of the charge-coupled device and acquires images.

[0052] Place the charge-coupled device (CCD) in the test environment and control it to work in full-frame transfer mode. After the CCD is working normally, acquire the image.

[0053] Step S1 includes the following sub-steps:

[0054] S11: Controls the charge-coupled device to operate in full-frame transfer mode.

[0055] Specifically, the charge-coupled device (CCD) is placed in a closed environment and shielded from light to form a dark chamber. The temperature inside the dark chamber (i.e., the operating temperature of the CCD) can be adjusted arbitrarily as needed. After adjusting the operating temperature of the CCD inside the dark chamber to a preset temperature, the CCD is driven and controlled to operate in full-frame transfer mode to prepare for subsequent image acquisition. In this embodiment, the full-frame transfer mode is controlled by a set timing sequence. The specific control process can be implemented using existing technology, which will not be elaborated here.

[0056] S12: Adjust the row period and extract the image according to the driving timing.

[0057] After adjusting the line period until the charge-coupled device can image normally, record the line period and the dark signal integration time of each line. Once the image can be acquired normally, randomly extract a frame.

[0058] Specifically, such as Figure 3 As shown in the figure, drive the charge-coupled device (CCD) according to the preset driving timing shown in the figure, and adjust its line period until the CCCD can move backward normally. Record the line period at this time. Then, the integration time of the dark signal for each row is determined according to the row period; then, a frame of image is randomly acquired.

[0059] In this embodiment, the dark signal integration time is expressed as:

[0060] (1)

[0061] in: For the first Integration time of the dark signal , This represents the total number of pixel rows in a single frame of an image.

[0062] S2: Process the image to obtain the charge-voltage conversion factor and dark signal response rate.

[0063] The acquired image frame is processed to extract the charge-voltage conversion factor and the dark signal response rate under integral time.

[0064] Step S2 includes the following sub-steps:

[0065] S21: Calculate the charge-to-voltage conversion factor.

[0066] Obtain the pixel value of each pixel in the image, and calculate the average pixel value and noise voltage of N pixels in each row from row 1 to row M. Then, fit a photon transfer curve based on the average pixel value and noise voltage (e.g., ...). Figure 4 (as shown) and the charge-voltage conversion factor is obtained.

[0067] First, starting from the first row of images to the Mth row, extract the pixel values ​​of N pixels in each row, and calculate the average pixel value of the N pixels in each row. In this embodiment, the average pixel value is expressed as:

[0068] (2)

[0069] in: For each row (i.e., the first row) The average pixel value of the image (in units of) ), For pixel rows, , This represents the total number of pixel rows in a single frame of an image. For each line The pixel value of each pixel (in units of) ), For pixel columns, , The total number of pixels contained in each row of pixels, that is, the total number of pixel columns in a frame of an image.

[0070] Then, the noise voltage of each row of the image is calculated based on the average pixel value and the pixel values ​​of each pixel in the corresponding row. In this embodiment, the noise voltage is expressed as:

[0071] (3)

[0072] in: For each row (i.e., the first row) Noise voltage of the line image (in units) ).

[0073] Finally, a photon transfer curve is fitted based on the pixel average value and noise voltage, and the intercept and slope of the photon transfer curve are calculated to obtain the charge-voltage conversion factor. In this embodiment, referring to the national military standard "Test Method for Charge-Coupled Imaging Devices", the pixel average value is used as the abscissa and the square of the noise voltage is used as the ordinate. The least squares method is used to fit the photon transfer curve, and the intercept and slope of the photon transfer curve are calculated to obtain the charge-voltage conversion factor.

[0074] Specifically, let the linear curve (i.e., the photon transfer curve) of the least squares fitting curve be:

[0075] (4)

[0076] in: The x-axis represents the photon transfer curve, which is also the average pixel value. ; The vertical axis represents the photon transfer curve, i.e., the noise voltage. square ; These represent the intercept and slope of the photon transfer curve, respectively. They are represented as follows:

[0077] (5)

[0078] (6)

[0079] in: The x-axis of the photon transfer curve The average value, , This represents the average value of each vertical axis of the photon transfer curve. .

[0080] Intercept of the transition curve and the slope of the transfer curve Substituting into the above formula (4), the fitted photon transfer curve is obtained. Based on the slopes of the abscissa and ordinate of the photon transfer curve, the charge-voltage conversion factor is the slope of the photon transfer curve, i.e. ,Will , Substituting into formula (6), we obtain the charge-voltage conversion factor:

[0081] (7)

[0082] in: Charge-to-voltage conversion factor (unit: ), The average pixel value of each row of the image The average value, The square of the noise voltage of each pixel The average value.

[0083] S22: Calculate the dark signal responsivity over the integral time.

[0084] Obtain the dark signal integration time of each row in the image (i.e., the dark signal integration time calculated based on the row period in step S1). Then, based on the integration time of the dark signal and the average pixel value of each row of pixels, a curve relating the dark signal to the integration time is fitted (e.g., ...). Figure 5 (As shown in the figure) and the dark signal responsivity under the integration time is obtained.

[0085] In this embodiment, the relationship curve between the dark signal and the integration time is obtained by fitting the curve with the integration time of each row of dark signals as the horizontal axis and the average pixel value of each row of pixels as the vertical axis using the least squares method. The intercept and slope of the integration curve are then calculated to obtain the dark signal response rate under the integration time.

[0086] Specifically, let the linear curve of the least squares fitting curve (i.e., the relationship curve between the dark signal and the integration time) be:

[0087] (8)

[0088] in: The x-axis represents the curve showing the relationship between the dark signal and the integration time, i.e., the integration time of the dark signal. , The vertical axis represents the curve showing the relationship between the dark signal and the integration time, which is also the average pixel value. , These are the intercept and slope of the integral curve representing the relationship between the dark signal and the integration time, respectively. They are represented as follows:

[0089] (9)

[0090] (10)

[0091] in: The horizontal axis of the curve showing the relationship between the dark signal and the integration time. The average value, , The vertical axes of the curve showing the relationship between the dark signal and the integration time The average value, .

[0092] Intercept of the integral curve Slope of the integral curve Substituting into the above formula (8), the fitted curve of the relationship between the dark signal and the integration time is obtained. Based on the slopes of the horizontal and vertical axes of the curve, the dark signal response rate at the integration time is the slope of the integral curve of the curve relating the dark signal and the integration time. ,Will , Substituting into formula (10), we obtain the dark signal responsivity over the integral time:

[0093] (11)

[0094] in: Dark signal responsivity over integration time (unit: ), Integrating time for the dark signal of each row of the image The average value, The average pixel value of each row of the image The average value.

[0095] S3: Calculate the dark current of the charge-coupled device.

[0096] Specifically, the dark current of the charge-coupled device (CCD) is calculated based on the charge-to-voltage conversion factor and the dark signal responsivity at integral time. In this embodiment, the dark current of the CCCD is expressed as:

[0097] (12)

[0098] in: To obtain dark current (in units) for charge-coupled devices ), It is the charge-to-voltage conversion factor. Let be the dark signal responsivity over the integration time.

[0099] The dark current measurement method of the charge-coupled device in this embodiment controls the charge-coupled device to work in full-frame transfer mode by setting the driving timing. It can randomly acquire a frame of image to obtain the dark current response pixel values ​​of the image at multiple integration times. Then, by calculating the pixel average value, noise voltage and dark signal integration time of each row of pixels in the image, the pixel average value, noise voltage and dark signal integration time are obtained by fitting the pixel average value, noise voltage and dark signal integration time based on curve fitting technology to obtain the corresponding photon transfer curve and the relationship curve between dark signal and integration time. The dark signal responsivity and charge-voltage conversion factor at the integration time are calculated from the two curves respectively, thereby calculating the dark current. The whole process only requires the acquisition of a single frame of image, which greatly reduces the dark current test time and improves the test efficiency. Furthermore, by obtaining the dark current response pixel values ​​at multiple integration times in the same frame of image, the dark current can be accurately calculated.

[0100] Example 2

[0101] like Figure 6 The diagram shown is a system block diagram of the dark current measurement system for a charge-coupled device (CCD) according to this embodiment. This dark current measurement system can be used to implement the dark current measurement method for CCDs in Embodiment 1, thereby enabling rapid and accurate measurement of the dark current of CCDs in various application scenarios. Specifically, the dark current measurement system for CCDs in this embodiment includes an image acquisition module 201, an image processing module 202, and a calculation module 203; wherein:

[0102] The image acquisition module 201 is used to control the charge-coupled device (CCD) to operate in full-frame transfer mode when the CCD is placed in the test environment (i.e., light-shielded and at a preset operating temperature), and to drive the CCD with a preset driving timing sequence. After adjusting the line period until the CCD can image normally, the module records the line period and the dark signal integration time of each corresponding line of image, and randomly extracts one frame of image and transmits it to the image processing module 202. In this embodiment, the specific process of image acquisition by the image acquisition module 201 is described in step S1 of Embodiment 1, and will not be repeated here.

[0103] The image processing module 202 receives a frame of image acquired by the image acquisition module 201. First, it acquires the pixel value of each pixel in the image. Based on the pixel value, it calculates the average pixel value and noise voltage for each row of the image. Then, it uses the least squares method to fit a photon transfer curve with the average pixel value as the x-axis and the noise voltage as the y-axis. It calculates the intercept and slope of the photon transfer curve to obtain the charge-voltage conversion factor. Next, it acquires the dark signal integration time for each row of the image calculated by the image acquisition module 201. Then, it uses the least squares method to fit a curve relating the dark signal to the integration time with the dark signal integration time as the x-axis and the average pixel value as the y-axis. It calculates the intercept and slope of the curve relating the dark signal to the integration time to obtain the dark signal responsivity under the integration time. Finally, it transmits the obtained charge-voltage conversion factor and dark signal responsivity to the calculation module 203. In this embodiment, the specific process of image processing by the image processing module 202 is described in step S2 of embodiment 1, and will not be repeated here.

[0104] The calculation module 203 is used to receive the charge-to-voltage conversion factor and dark signal responsivity transmitted by the image processing module 202, and calculate the dark current of the charge-coupled device based on the charge-to-voltage conversion factor and the dark signal responsivity under integration time. In this embodiment, the specific process of the calculation module 203 calculating the dark current is described in step S3 of embodiment 1, and will not be repeated in this embodiment.

[0105] The dark current measurement system for charge-coupled devices in this embodiment controls the charge-coupled device to acquire images according to a set working mode through the image acquisition module 201. It can randomly acquire a frame of image during the imaging process of the charge-coupled device to obtain the dark current response pixel value of a frame of image at multiple integration times. This value is then used by the image processing module 202 to process the image and the calculation module 203 to calculate the dark current. This greatly reduces the difficulty of dark current measurement, reduces the test time, and improves the test efficiency.

[0106] Example 3

[0107] like Figure 7 The diagram shown is a control block diagram of the dark current measurement device for the charge-coupled device (CCD) in this embodiment. The dark current measurement device for the CCD in this embodiment can incorporate the dark current measurement system of the CCD in Embodiment 2, and implement the dark current measurement method of the CCD in Embodiment 1 during measurement. Specifically, the dark current measurement device for the CCD includes a temperature control module 302, a drive and control module 303, and a processor 304; wherein:

[0108] The temperature control module 302 is placed in a light-proof dark chamber 301, and the charge-coupled device is also placed in the dark chamber 301. The temperature control module 302 can adjust the temperature in the dark chamber 301 under the control of the drive and control module 303, thereby adjusting the operating temperature of the charge-coupled device so that the charge-coupled device can work at a suitable temperature.

[0109] The drive and control module 303 is electrically connected to the temperature control module 302, the processor 304, and the charge-coupled device. It is used to control the temperature control module 302 to adjust to a suitable working temperature according to the user's instructions and to drive and control the charge-coupled device to work in full-frame transfer mode according to a preset drive sequence.

[0110] The processor 304 is used to acquire images collected by the charge-coupled device (CCD) and perform comprehensive processing on the images to calculate the dark current of the CCD. Specifically, the processor 304 first calculates the average pixel value and noise voltage of each row of images based on the pixel values, then uses the least squares method to fit a photon transfer curve with the average pixel value as the x-axis and the noise voltage as the y-axis, and calculates the intercept and slope of the transfer curve to obtain the charge-voltage conversion factor. Then, it acquires the dark signal integration time of each row of images, and uses the least squares method to fit a curve relating the dark signal and the integration time with the dark signal integration time as the x-axis and the average pixel value as the y-axis, and calculates the intercept and slope of the curve to obtain the dark signal responsivity at the integration time. Finally, it calculates the dark current of the CCD based on the charge-voltage conversion factor and the dark signal responsivity at the integration time.

[0111] The dark current measurement device for charge-coupled devices in this embodiment controls the charge-coupled devices to operate in a set test environment by setting a temperature control module 302 and a drive and control module 303. Then, the processor 304 acquires images, randomly acquiring a frame of image for image processing and dark current calculation. This greatly reduces the difficulty of dark current measurement, reduces test time, and improves test efficiency. Moreover, the dark signal response rate at multiple different integration times can be obtained from a single frame of image, enabling fast and accurate calculation of dark current.

Claims

1. A method for measuring the dark current of a charge-coupled device, characterized in that, Includes the following steps: S1: Controls the charge-coupled device to operate in full-frame transfer mode and acquire images; S2: Process the acquired image to extract the charge-voltage conversion factor and the dark signal responsivity under integral time from the image; S3: Calculate the dark current of the charge-coupled device based on the charge-voltage conversion factor and the dark signal responsivity under integral time; Wherein: step S2 includes the following sub-steps: S21: Obtain the pixel value of each pixel in the image, calculate the average pixel value and noise voltage of each row of the image, fit the photon transfer curve based on the average pixel value and noise voltage, and calculate the intercept and slope of the photon transfer curve to obtain the charge-voltage conversion factor. S22: Obtain the dark signal integration time of each row of the image according to the row period of the charge-coupled device. Fit the relationship curve between the dark signal and the integration time according to the dark signal integration time and the pixel average value of each row of pixels. Calculate the intercept and slope of the relationship curve between the dark signal and the integration time to obtain the dark signal responsivity under the integration time.

2. The dark current measurement method for a charge-coupled device according to claim 1, characterized in that, In step S1, the charge-coupled device operates in a dark chamber where the operating temperature of the charge-coupled device can be adjusted. Step S1 includes the following sub-steps: S11: Place the charge-coupled device in the dark chamber, adjust the temperature in the dark chamber to the preset temperature, and control the charge-coupled device to work in full-frame transfer mode; S12: Adjust the line period according to the preset driving timing until the charge-coupled device imaging is normal and record the line period. Determine the dark signal integration time of each line according to the line period. After the image is acquired normally, randomly extract a frame of image.

3. The dark current measurement method for a charge-coupled device according to claim 1, characterized in that, In step S21, the specific method for fitting the photon transfer curve is as follows: Based on the pixel values ​​of each pixel in the image, the average pixel value and the noise voltage of each row of pixels are calculated. Using the average pixel value as the x-axis and the square of the noise voltage as the y-axis, the photon transfer curve is obtained by least squares fitting. The intercept and slope of the photon transfer curve are then calculated to obtain the charge-voltage conversion factor. ； in: It is the charge-to-voltage conversion factor. For pixel rows, , This represents the total number of pixel rows in a single frame of an image. The average pixel value of each row of the image The average value, The square of the noise voltage of each pixel The average value.

4. The dark current measurement method for a charge-coupled device according to claim 1, characterized in that, In step S21, the formula for calculating the average pixel value is: ； in: This represents the average pixel value for each row of the image. For pixel rows, , This represents the total number of pixel rows in a single frame of an image. For each line The pixel value of each pixel. , The total number of pixels contained in each row.

5. The dark current measurement method for a charge-coupled device according to claim 1, characterized in that, In step S21, the formula for calculating the noise voltage is: ； in: The noise voltage of each row of the image. This represents the average pixel value for each row of the image. For pixel rows, , This represents the total number of pixel rows in a single frame of an image. For each line The pixel value of each pixel. , The total number of pixels contained in each row.

6. The dark current measurement method for a charge-coupled device according to claim 1, characterized in that, In step S22, the specific method for fitting the relationship curve between the dark signal and the integration time is as follows: The integration time of the dark signal for each row is obtained based on the row period of the charge-coupled device. Using the integration time of the dark signal for each row as the x-axis and the average pixel value of each row as the y-axis, the relationship curve between the dark signal and the integration time is obtained by least squares fitting. The intercept and slope of the curve are then calculated to obtain the dark signal responsivity at the integration time. ； in: The dark signal responsivity during integration time. For pixel rows, , This represents the total number of pixel rows in a single frame of an image. Integrating time for the dark signal of each row of the image The average value, The average pixel value of each row of the image The average value.

7. The dark current measurement method for a charge-coupled device according to claim 1, characterized in that, In step S3, the formula for calculating the dark current is: ； in: To obtain dark current for charge-coupled devices, It is the charge-to-voltage conversion factor. Let be the dark signal responsivity over the integration time.

8. A dark current measurement system for a charge-coupled device, characterized in that, include: The image acquisition module is used to control the charge-coupled device to operate in full-frame transfer mode and acquire images; The image processing module is used to process the acquired image to obtain the pixel value of each pixel in the image, and calculate the average pixel value and noise voltage of each row of the image based on the pixel value. The module then fits a photon transfer curve based on the average pixel value and noise voltage and calculates the intercept and slope of the photon transfer curve to extract the charge-voltage conversion factor in the image. The image processing module is also used to obtain the dark signal integration time of each row of the image, and fit the relationship curve between the dark signal and the integration time based on the dark signal integration time and the average pixel value of each row of pixels. The module then calculates the intercept and slope of the relationship curve between the dark signal and the integration time to obtain the dark signal responsivity at the integration time. as well as The calculation module is used to calculate the dark current of the charge-coupled device based on the charge-voltage conversion factor and the dark signal responsivity under integral time.

9. A dark current measurement device for a charge-coupled device, characterized in that, include: The temperature control module is used to regulate the operating temperature of the charge-coupled device. A drive and control module is used to drive and control the charge-coupled device to operate in full-frame transfer mode, and a temperature control module is used to regulate the temperature. as well as The processor is configured to acquire images collected by the charge-coupled device (CCD) and process the images to obtain the pixel value of each pixel in the image. Based on the pixel value, the processor calculates the average pixel value and noise voltage of each row of pixels to fit a photon transfer curve and calculates the intercept and slope of the photon transfer curve to extract the charge-voltage conversion factor in the image. The processor is also configured to acquire the dark signal integration time of each row of images, and fit a relationship curve between the dark signal and the integration time based on the dark signal integration time and the average pixel value of each row of pixels. The processor then calculates the intercept and slope of the relationship curve between the dark signal and the integration time to obtain the dark signal responsivity at the integration time. Finally, the processor calculates the dark current of the CCCD based on the extracted charge-voltage conversion factor of the image and the dark signal responsivity at the integration time.

Images