A laboratory absolute radiometric coefficient solving method for TDICCD sensor image

Abstract

The application provides a laboratory absolute radiation coefficient solving method of a TDICCD sensor image, quantitative relationship formula of imaging DN value, entrance pupil radiance, gain, line transfer time and integral base number is obtained by analyzing a photoelectric signal processing process of the sensor, constants in the quantitative relationship formula are obtained based on a fitting method, and finally the laboratory absolute radiation coefficient under any line transfer time, integral base number and gain can be solved. The method can calculate the laboratory absolute calibration radiation coefficient under any imaging parameter combination based on data shot by a small amount of imaging parameter combinations. Compared with a traditional calculation method, the method greatly reduces the dependence on imaging combinations in a ground section radiation experiment process, and can effectively reduce operation cost and data storage cost of the radiation experiment.

Description

Technical Field

[0001] This invention belongs to the field of aerospace technology, and in particular relates to a laboratory absolute radiometric coefficient calculation method for TDICCD sensor images. Background Technology

[0002] The absolute radiometric coefficient characterizes the correspondence between the digital signal recorded by a remote sensor and the entrance pupil radiance. Before the launch of a remote sensing satellite, the satellite camera sensor must undergo laboratory absolute radiometric calibration to calculate the quantitative laboratory absolute radiometric coefficient, which characterizes the relationship between the DN value of the sensor image and the entrance pupil radiance from a standard radiation source. This provides a basis for selecting the integration series and gain of the TDICCD sensor when the satellite camera captures ground images. A common method for calculating the laboratory absolute radiometric calibration coefficient is to use the mean DN value of the images acquired at different radiances under a fixed line transfer time, with the radiance as the ordinate, and perform linear fitting using the least squares method. The slope and intercept of the fitted image are then used as the laboratory absolute radiometric coefficient of the sensor at the current line transfer time, integration series, and gain combination. Subsequently, with a fixed integration series and gain combination, images with the same integration series and gain combination are acquired at different line transfer times to fit the relationship between line transfer time and laboratory absolute radiometric coefficient. Finally, the absolute radiometric coefficient can be obtained for any line transfer time, integration series, and gain combination.

[0003] The aforementioned methods require a high number of imaging parameter combinations in laboratory radiometric calibration experiments, needing to cover all possible combinations. This invention proposes a laboratory absolute radiometric coefficient calculation method for TDICCD sensor images, aiming to reduce the dependence of pre-ground-based radiometric calibration experiments on the number of imaging parameter combinations. Based on the photoelectric signal processing principle of TDICCD sensors, a formula-based and fitting-based method for calculating the laboratory absolute radiometric coefficient is proposed. Summary of the Invention

[0004] The purpose of this invention is to solve the problems in the prior art and to propose a laboratory absolute radiometric coefficient calculation method for TDICCD sensor images.

[0005] This invention is achieved through the following technical solution: This invention proposes a method for calculating the laboratory absolute radiometric coefficient of TDICCD sensor images. Specifically, the method involves: analyzing the photoelectric signal processing principle of the TDICCD sensor, deriving a quantitative relationship formula between the DN value recorded by the sensor and the entrance pupil radiance and imaging parameters such as radiance, line transfer time, gain, and integral series; simultaneously, using a small amount of radiation experimental data to fit the constants in the quantitative relationship formula; and finally, the laboratory absolute radiometric coefficient for any line transfer time, integral series, and gain can be solved.

[0006] Furthermore, a photoelectric signal processing model for the TDICCD sensor is modeled, and a quantitative relationship formula is established between the DN value, entrance pupil radiance, and various imaging parameters.

[0007] When light shines on the focal plane of the sensor, the sensor converts the light signal into an electrical signal and outputs an analog voltage signal. After the analog voltage signal is processed by correlation double sampling, an effective analog voltage signal is obtained. The effective analog voltage signal value is subtracted from the clamping voltage value by a subtractor, and the result is amplified by a gain amplifier. Then, it is converted from analog to digital by an analog-to-digital converter and finally output as a digital signal.

[0008] Furthermore, the irradiance at the sensor's focal plane is:

[0009]

[0010] In the formula, L is the entrance pupil radiance of the sensor, F is the relative aperture of the optical system, τ0 is the total transmittance of the optical system, and T is the line transfer time of the sensor.

[0011] Furthermore, the output analog voltage after photoelectric conversion is:

[0012]

[0013] In the formula, S is the integration series of the sensor, μ cce η is the charge conversion factor of the sensor, λ is the wavelength, η is the quantum efficiency, A is the pixel area, h is Planck's constant, and c is the speed of light.

[0014] Furthermore, the voltage value after the subtractor is:

[0015] V = V s -V set (3)

[0016] In the formula V set This is a configurable dynamic clamping voltage value.

[0017] Furthermore, the DN value output by the sensor is:

[0018]

[0019] In the formula, G is the analog gain, and V sat q represents the saturation voltage of the analog-to-digital converter, and q represents the number of quantization bits.

[0020] Furthermore, by integrating formulas (1) to (4), the quantitative relationship between the DN value and the entrance pupil radiance L, the line transition time T, the integral series S, and the gain G is obtained:

[0021] DN=G×(T×L×S×m+n)(5)

[0022] in,

[0023]

[0024] By transforming formula (5), we get:

[0025]

[0026] The slope k and intercept b, obtained by fitting a straight line with the image DN value on the x-axis and the entrance pupil radiance on the y-axis, are the absolute radiometric coefficients, expressed by the following formula:

[0027]

[0028]

[0029] The quantitative relationship between the absolute radiation coefficient and the gain, integral series, and line transition time can be obtained from the above formula.

[0030] Furthermore, the constant in the quantitative relationship formula is obtained by fitting a small amount of radiation experimental data, specifically by transforming formula (5) to obtain the following relationship:

[0031]

[0032] That is, the result of T×L×S is used as the x-axis and the result of DN / G is used as the y-axis for fitting. The slope of the fitted line is parameter m, and the intercept of the line is parameter n.

[0033] The present invention also proposes an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the laboratory absolute radiometric coefficient calculation method for TDICCD sensor images.

[0034] The present invention also proposes a computer-readable storage medium for storing computer instructions, which, when executed by a processor, implement the steps of the laboratory absolute radiometric coefficient calculation method for TDICCD sensor images.

[0035] The present invention has the following beneficial effects:

[0036] The laboratory absolute radiometric coefficient calculation method for TDICCD sensor images designed in this invention obtains a quantitative relationship formula between the imaging DN value and entrance pupil radiance, gain, line transition time, and integral base by analyzing the sensor's photoelectric signal processing process. The constants in the quantitative relationship formula are then obtained based on a fitting method. This method can calculate the laboratory absolute calibrated radiometric coefficient under any combination of imaging parameters based on data captured using a small number of imaging parameter combinations. Compared to traditional calculation methods, this significantly reduces the dependence on imaging combinations during ground-based radiation experiments, effectively reducing the operational and data storage costs of radiation experiments. Attached Figure Description

[0037] Figure 1 This is a flowchart of the photoelectric signal processing for TDICCD imaging.

[0038] Figure 2 The figure shows the fitting results of m and n for the PAN band in the quantitative relationship formula of a certain satellite sensor. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Combination Figures 1-2 This invention proposes a method for calculating the laboratory absolute radiometric coefficient of TDICCD sensor images. Specifically, the method involves: analyzing the photoelectric signal processing principle of the TDICCD sensor to derive a quantitative relationship formula between the DN value recorded by the sensor and the entrance pupil radiance and imaging parameters such as radiance, line transfer time, gain, and integral series. Simultaneously, constants in the quantitative relationship formula are obtained by fitting a small amount of radiation experimental data. Finally, the laboratory absolute radiometric coefficient for any line transfer time, integral series, and gain can be calculated.

[0041] The method for calculating the laboratory absolute radiometric coefficient of a TDICCD sensor image specifically includes the following steps:

[0042] Step 1: Model the photoelectric signal processing model of the TDICCD sensor and establish quantitative relationship formulas between DN value, entrance pupil radiance and various imaging parameters;

[0043] When light shines on the focal plane of the sensor, the sensor converts the light signal into an electrical signal and outputs an analog voltage signal. The analog voltage signal is processed by correlated double sampling (CDS) to obtain an effective analog voltage signal. The effective analog voltage signal value is subtracted from the clamping voltage value by a subtractor. The result is then amplified by a gain amplifier (PGA) and converted from analog to digital by an analog-to-digital converter (ADC). Finally, a digital signal is output.

[0044] The irradiance at the sensor's focal plane is:

[0045]

[0046] In the formula, L is the entrance pupil radiance of the sensor, F is the relative aperture of the optical system, τ0 is the total transmittance of the optical system, and T is the line transfer time of the sensor.

[0047] The output analog voltage after photoelectric conversion is:

[0048]

[0049] In the formula, S is the integration series of the sensor, μ cce η is the charge conversion factor of the sensor, λ is the wavelength, η is the quantum efficiency, A is the pixel area, h is Planck's constant, and c is the speed of light.

[0050] The voltage value after the subtractor is:

[0051] V = V s -V set (3)

[0052] In the formula V set This is a configurable dynamic clamping voltage value.

[0053] The DN value output by the sensor is:

[0054]

[0055] In the formula, G is the analog gain, and V sat q represents the saturation voltage of the analog-to-digital converter, and q represents the number of quantization bits.

[0056] By integrating formulas (1) to (4), we obtain the quantitative relationship between the DN value and the entrance pupil radiance L, the line transition time T, the integral series S, and the gain G:

[0057] DN=G×(T×L×S×m+n)(5)

[0058] in,

[0059]

[0060]

[0061] By transforming formula (5), we get:

[0062]

[0063] The slope k and intercept b, obtained by fitting a straight line with the image DN value on the x-axis and the entrance pupil radiance on the y-axis, are the absolute radiometric coefficients, expressed by the following formula:

[0064]

[0065]

[0066] The quantitative relationship between the absolute radiation coefficient and the gain, integral series, and line transition time can be obtained from the above formula.

[0067] By solving for the values ​​of the two parameters m and n in the formula, the absolute radiometric coefficient of the sensor image can be obtained under any row transition time, integral series, and gain.

[0068] Step 2: Fit constants in the quantitative relationship formula based on experimental data.

[0069] As can be seen from formulas (6) and (7), parameters m and n are the comprehensive calculation results of the sensor's own parameters. When processing laboratory radiation calibration data, it is difficult to directly obtain the various parameters of the sensor itself to directly calculate parameters m and n, but they can be obtained by fitting a small amount of data.

[0070] The constant in the quantitative relationship formula is obtained by fitting a small amount of radiation experimental data. Specifically, formula (5) is transformed to obtain the following relationship:

[0071]

[0072] That is, the result of T×L×S is used as the x-axis and the result of DN / G is used as the y-axis for fitting. The slope of the fitted line is parameter m, and the intercept of the line is parameter n.

[0073] The parameters in formula (11), namely the line transition time T, the integral series S, and the gain G, are all given during the radiation experiment imaging process and can be directly recorded without calculation. The mean image DN and the sensor entrance pupil radiance can be calculated using conventional methods without special requirements.

[0074] This invention discloses a method for calculating the laboratory absolute radiometric coefficient of TDICCD sensor images. By analyzing the sensor's photoelectric signal processing, it obtains a quantitative relationship formula between the imaging DN value and the entrance pupil radiance, gain, line transition time, and integral base. Based on a fitting method, it derives the constants in the quantitative relationship formula, ultimately allowing the calculation of the laboratory absolute radiometric coefficient for any line transition time, integral series, and gain. This method can calculate the laboratory absolute calibrated radiometric coefficient for any combination of imaging parameters based on data captured using a small number of imaging parameter combinations. Compared to traditional calculation methods, it significantly reduces the dependence on imaging combinations during ground-based radiation experiments, effectively reducing operational and data storage costs.

[0075] The following section uses the calculation of the laboratory absolute radiometric coefficient of a satellite sensor's PAN band as an example to illustrate the method for calculating the laboratory absolute radiometric coefficient of a TDICCD sensor image described in this invention. In the PAN band data from the sensor's laboratory radiometric calibration experiment, the line transition time T (unit: μs) is configured as 120, 130, 140, 150, 160, and 180; the integration series S is configured as 8, 16, 32, and 48; the gain G is configured as 2.0, 3.0, 4.0, and 5.0; and the entrance pupil radiance L (unit: W·m²) is... -2 ·sr -1 ·μm -1 The configuration includes 296.801, 169.3306, and 27.28573. The mean DN of the image is calculated, and the result of fitting m and n according to formula (11) is as follows: Figure 2 As shown, the linearity of the fit reached over 0.999, indicating a very good fitting effect.

[0076] The present invention also proposes an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the laboratory absolute radiometric coefficient calculation method for TDICCD sensor images.

[0077] The present invention also proposes a computer-readable storage medium for storing computer instructions, which, when executed by a processor, implement the steps of the laboratory absolute radiometric coefficient calculation method for TDICCD sensor images.

[0078] The memory in this application embodiment can be volatile memory or non-volatile memory, or it can include both volatile and non-volatile memory. The non-volatile memory can be read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or flash memory. The volatile memory can be random access memory (RAM), which is used as an external cache. By way of example, but not limitation, many forms of RAM are available, such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDRSDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous linked dynamic random access memory (SLDRAM), and direct rambus RAM (DRRAM). It should be noted that the memory used in the methods described in this invention is intended to include, but is not limited to, these and any other suitable types of memory.

[0079] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. The computer program product includes one or more computer instructions. When the computer instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium accessible to a computer or a data storage device such as a server or data center that integrates one or more available media. The available media may be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., high-density digital video discs (DVDs)), or semiconductor media (e.g., solid-state disks (SSDs)).

[0080] In implementation, each step of the above method can be completed by integrated logic circuits in the processor's hardware or by instructions in software. The steps of the method disclosed in the embodiments of this application can be directly implemented by a hardware processor, or by a combination of hardware and software modules in the processor. The software modules can reside in random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, or other mature storage media in the art. This storage medium is located in memory, and the processor reads information from the memory and, in conjunction with its hardware, completes the steps of the above method. To avoid repetition, detailed descriptions are omitted here.

[0081] It should be noted that the processor in the embodiments of this application can be an integrated circuit chip with signal processing capabilities. During implementation, each step of the above method embodiments can be completed by the integrated logic circuitry in the processor's hardware or by instructions in software form. The processor can be a general-purpose processor, 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, or discrete hardware components. It can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of this application. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the methods disclosed in the embodiments of this application can be directly embodied as being executed by a hardware decoding processor, or executed by a combination of hardware and software modules in the decoding processor. The software modules can be located in random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, or other mature storage media in the art. This storage medium is located in memory, and the processor reads the information in the memory and, in conjunction with its hardware, completes the steps of the above methods.

[0082] The above provides a detailed description of a laboratory absolute radiometric coefficient calculation method for TDICCD sensor images proposed in this invention. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method for calculating the laboratory absolute radiometric coefficient of TDICCD sensor images, characterized in that, The method is as follows: by analyzing the photoelectric signal processing principle of the TDICCD sensor, a quantitative relationship formula is derived between the DN value recorded by the sensor and the entrance pupil radiance and the radiance, line transfer time, gain, and integral series of the imaging parameters. At the same time, the constants in the quantitative relationship formula are obtained by fitting a small amount of radiation experimental data. Finally, the laboratory absolute radiation coefficient of the line transfer time, integral series, and gain of any sensor can be solved. A model for the photoelectric signal processing of the TDICCD sensor was created, and a quantitative relationship formula was established between the DN value, the entrance pupil radiance, and various imaging parameters. When light shines on the focal plane of the sensor, the sensor converts the light signal into an electrical signal and outputs an analog voltage signal. The analog voltage signal is processed by correlation double sampling to obtain an effective analog voltage signal. The effective analog voltage signal value is subtracted from the clamping voltage value by a subtractor. The result is then amplified by a gain amplifier and converted from analog to digital by an analog-to-digital converter. Finally, a digital signal is output. The irradiance at the sensor's focal plane is: In the formula The entrance pupil radiance of the sensor, The relative aperture of the optical system, The total transmittance of the optical system. For the sensor's row transition time; The output analog voltage after photoelectric conversion is: In the formula Let be the integration series of the sensor. The charge conversion factor of the sensor. For wavelength, For quantum efficiency, For pixel area, is Planck's constant. The speed of light; The voltage value after the subtractor is: In the formula This is a configurable dynamic clamping voltage value; The DN value output by the sensor is: In the formula To simulate gain, This represents the saturation voltage value of the analog-to-digital converter. The number of quantization bits; By integrating formulas (1) to (4), the DN value and entrance pupil radiance are obtained. Sensor line transition time Integral series Gain Quantitative relationship: in, By transforming formula (5), we get: That is, the slope obtained by fitting a straight line with the image DN value on the x-axis and the entrance pupil radiance on the y-axis. and intercept , that is, the absolute radiation coefficient, is expressed by the following formula: The quantitative relationship between the absolute radiation coefficient and the gain, integral series, and line transition time of the sensor can be obtained from the above formula.

2. The method according to claim 1, characterized in that, The constant in the quantitative relationship formula is obtained by fitting a small amount of radiation experimental data. Specifically, formula (5) is transformed to obtain the following relationship: That is to The result is the x-axis, with The result is a fitting of the ordinate, with the slope of the fitted line being parameter m and the intercept being parameter n.

3. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1-2.

4. A computer-readable storage medium for storing computer instructions, characterized in that, When the computer instructions are executed by the processor, they implement the steps of the method according to any one of claims 1-2.

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