Ambient light adaptive correction method and system based on feedback control

Abstract

The application discloses an ambient light self-adaptive correction method and system based on feedback control, which initially calibrates an ambient light current calculation formula, compensates for current matching deviation by fitting an actual scaling multiple of a current mirror and adjusting a register, converts ambient light into a photoelectric current, sequentially carries out linear compensation and current scaling processing, and then outputs a digital quantity through analog-digital conversion; the type of the photoelectric current is identified based on the constant state of the digital quantity, corresponding data correction processing is performed on the preset type of the photoelectric current, whether the digital quantity is in a preset range is judged, if the digital quantity is out of the preset range, the boundary of a bias current related parameter is adjusted and a calculation adjustment step is calculated, and the analog-digital conversion is re-executed; after the digital quantity is in the preset range, the ambient light current is obtained by substituting the ambient light current calculation formula after calibration, so as to determine a calibration coefficient of distance measurement correction. The application solves the problems of poor real-time performance and insufficient precision of the prior art in ambient light static calibration.

Description

Technical Field

[0001] This invention relates to the field of optical sensing technology, and specifically to an ambient light adaptive correction method and system based on feedback control. Background Technology

[0002] Time-of-Flight (TOF) ranging technology measures distance by calculating the time difference between emitted and reflected light. With its advantages of fast response, wide measurement range, and strong anti-interference capabilities, it has been widely applied in consumer electronics, industrial inspection, autonomous driving, security monitoring, and other fields, becoming one of the mainstream ranging technologies. The TOF ranging chip, as the core carrier of this technology, directly determines the performance of the end product through its measurement accuracy.

[0003] However, in practical applications, the signal receiver of a TOF ranging chip is inevitably affected by ambient light interference, a problem that severely restricts the improvement of its ranging accuracy. Ambient light sources are diverse, including DC light sources such as sunlight, as well as AC light sources with specific frequencies such as fluorescent lamps, and their intensity varies greatly and is random. Strong ambient light can cause signal saturation in the transimpedance amplifier (TIA) inside the TOF chip, directly causing the ranging function to fail; while randomly fluctuating ambient light can interfere with signal phase detection, causing deviations in time difference calculation, and thus affecting the accuracy of the ranging results. In addition, the dynamic characteristics of ambient light, such as sudden changes in illumination, further increase the difficulty for TOF ranging chips to achieve stable and high-precision measurements.

[0004] To address the problem of ambient light interference, existing technologies have proposed various anti-interference schemes, such as using narrowband filters to filter out stray light, using high-precision SPAD arrays to suppress ambient light, manually calibrating ambient light measurements, or directly measuring the DC component of ambient light using an ADC and correcting the ranging formula. However, these schemes generally suffer from drawbacks such as static calibration, insufficient real-time performance, high dependence on receiver devices, and limited measurement accuracy.

[0005] The applicant's earlier application CN120454723A discloses an ambient light adaptive calibration system based on feedback control. The idea is to adjust the TIA bias current in real time through the feedback control module and improve the ADC sampling accuracy by combining current mirror calibration. This breaks through the limitations of traditional static calibration to a certain extent and improves real-time performance and measurement accuracy. However, this solution still has several significant limitations in practical applications, making it difficult to adapt to complex and ever-changing lighting environments: First, the module division and function allocation are not reasonable enough, the structure is relatively dispersed, and only a single feedback control module is set up, which needs to undertake all functions such as judgment, calculation, and adjustment simultaneously. This over-concentration of responsibilities leads to redundancy in the signal transmission link and is not conducive to subsequent functional expansion and maintenance. Second, the adaptability of photocurrent types is insufficient. Only a TIA DC compensation module is designed for DC ambient light, without mentioning the identification and processing mechanism for frequency photocurrents such as those from fluorescent lamps. However, interference from frequency ambient light is also significant in practical applications, which limits the applicable scenarios of the solution. Third, the specific execution logic of calibration, the deviation compensation method, and the number of calibrations are not clearly defined, which can easily lead to unstable calibration accuracy. Fourth, the feedback control process and abnormal handling mechanism are relatively simple. The adjustment trigger only relies on two judgments: whether the ADC reading is within the specified range and whether TIA_trim reaches the boundary. It does not involve the judgment of dimensions such as photocurrent type. The abnormal handling lacks a transitional processing mechanism, which can easily lead to system interruption and insufficient adaptability. Summary of the Invention

[0006] To address this issue, the present invention provides an ambient light adaptive correction method and system based on feedback control, which solves the problems of unreasonable module division in existing technologies, which only adapt to DC light, have generalized calibration logic, and have simple anomaly handling, making them unable to cope with frequency-based light interference and complex lighting scenarios, resulting in insufficient real-time performance and accuracy of TOF chip ranging.

[0007] To achieve the above objectives, the present invention provides the following technical solution: an ambient light adaptive correction method based on feedback control, comprising the following steps:

[0008] 1) Perform initial calibration using the ambient photocurrent calculation formula, and compensate for current matching deviation by fitting the actual scaling factor of the current mirror and adjusting the register;

[0009] 2) After ambient light is converted into photocurrent through photoelectric conversion, it is processed by linear compensation and current scaling, and then output as a digital quantity through analog-to-digital conversion, forming a signal conversion link from light to electricity to digital.

[0010] 3) Identify the photocurrent type based on the constant state of digital quantities, and perform corresponding data correction processing for the preset photocurrent type;

[0011] 4) Determine if the digital quantity is within the preset range: If the digital quantity exceeds the preset range, re-execute the analog-to-digital conversion by adjusting the boundary of the bias current related parameters and calculating the adjustment step size;

[0012] 5) Once the digital value is within the preset range, substitute it into the calibrated ambient photocurrent calculation formula to obtain the ambient photocurrent, and determine the calibration coefficient for ranging correction.

[0013] As a preferred scheme for the ambient light adaptive correction method based on feedback control, the initial calibration of the ambient light calculation formula in step 1) is specifically as follows:

[0014] The scaling factor B1 of the actual current mirror structure is obtained by calibrating the current mirror matching coefficient. The reserved register is adjusted to compensate for the current matching deviation, and the ambient light calculation formula is recalibrated.

[0015] As a preferred embodiment of the ambient light adaptive correction method based on feedback control, in step 2), photocurrent conversion is performed through a photoelectric conversion module, which uses a photodiode to convert ambient light of different intensities into DC or photocurrent of a set frequency; linear compensation of the photocurrent is performed through a TIA current compensation module, which controls the TIA bias current digital range TIA through a register. trim Set the linear compensation range.

[0016] As a preferred scheme of the ambient light adaptive correction method based on feedback control, in step 2), the current scaling is achieved through a current mirror structure, and the photocurrent is scaled by B1 times before being input into the ADC module to reduce the measurement range of the ADC module.

[0017] The integration time of the ADC module is a preset number of CLK cycles. After the eoc signal is pulled high, the output digital quantity Ambient is read. The current measured by the ADC module is the sum of the ambient light current Ic, the TIA bias current, and the ADC range current.

[0018] As a preferred scheme for the ambient light adaptive correction method based on feedback control, the rule for determining the photocurrent type in step 3) is as follows:

[0019] If the digital quantity Ambient is constant, it is determined to be DC photocurrent;

[0020] If the digital quantity Ambient changes, it is determined to be a photocurrent with frequency.

[0021] For the frequency-carrying photocurrent, the coefficient of the frequency conversion current value is calculated, and the digital quantity Ambient is corrected. The correction formula is Ambient×m, where m is the correction coefficient corresponding to the frequency-carrying photocurrent.

[0022] As a preferred embodiment of the ambient light adaptive correction method based on feedback control, in step 4), the preset range is H. min ~H max The preset range is set according to the operating saturation state of the TIA circuit, corresponding to the stable range I of the total current. min ~I max The total current includes the ambient light current Ic and the TIA bias current TIA. Ibias .

[0023] As a preferred scheme for the ambient light adaptive correction method based on feedback control, the specific process of adjusting the boundary of the bias current related parameters in step 4) is as follows:

[0024] If the digital quantity exceeds the preset range H min ~H max Determine the digital range of the TIA bias current. trim Whether the maximum or minimum value boundary of the corresponding TIA bias current has been reached;

[0025] If TIA trim Once the boundary is reached, wait for the digital value to enter the adjustable range, and then re-perform analog-to-digital conversion to read the digital value.

[0026] If TIA trim If the boundary is not reached, then based on the difference Δ between the digital value and the preset range, combined with TIA... trim The linear relationship between step size and digital quantity is calculated by adjusting the step size k = Δ / n, where k is a positive integer. trim When increasing by k steps, where k is a negative integer, TIA trim Reduce the number of |k| steps, adjust and reset the ADC module and perform analog-to-digital conversion again;

[0027] When TIA trim At the minimum boundary and the digital quantity still reaches the full value C of the ADC max When the ambient light exceeds the measurement range, an over-limit warning signal is output.

[0028] As a preferred scheme for the ambient light adaptive correction method based on feedback control, in step 5), if the digital quantity Ambient is constant, the formula for calculating the ambient light current Ic is:

[0029] Ic = Ambient × Iref × B1 / C max -ADC-TIA Ibias

[0030] If the digital quantity Ambient changes, the formula for calculating the ambient photocurrent Ic is:

[0031] Ic = Ambient × m × Iref × B1 / C max -ADC-TIAIbias

[0032] In the formula, ADC is the fixed current of the ADC module, and C max Amibient is at its maximum value, TIA Ibias For TIA bias current, Ambient is the digital output of the ADC module, Iref is the sampling reference current of the charge-balanced ADC, and B1 is the scaling factor of the current mirror structure.

[0033] In step 5), if the digital quantity Ambient is constant, the formula for calculating the calibration coefficient for ranging correction is:

[0034] amb err =a×(Ambient-Ambient avg )+b×(Ambient-Ambient avg ) 2

[0035] If the digital quantity Ambient changes, the formula for calculating the calibration coefficient for ranging correction is:

[0036] amb err =a×(Ambient×m -Ambient avg )+b×(Ambient×m -Ambient avg ) 2

[0037] In the formula, amb err Here, a and b are calibration coefficients, and a and b are fitting coefficients for the nonlinear relationship between the phase and the ADC reading obtained through the ranging algorithm. avg This represents the expected value of the ADC reading.

[0038] The present invention also provides an ambient light adaptive correction system based on feedback control, including a photoelectric conversion module, a TIA current compensation module, an ADC module, a dynamic adjustment module, a formula correction module, and a data register;

[0039] The photoelectric conversion module is used to convert ambient light into direct current or photocurrent of different frequencies.

[0040] The TIA current compensation module is connected to the photoelectric conversion module. The TIA current compensation module includes a linear compensation unit and a current mirror scaling unit. The linear compensation unit controls the TIA through a register. trim The linear compensation range is set, and the current mirror scaling unit is used to scale the photocurrent by a factor of B1.

[0041] The ADC module is used to perform analog-to-digital conversion on the scaled photocurrent and output a digital quantity Ambient.

[0042] The formula correction module is used to perform a one-time initial calibration of the ambient light calculation formula, fit the actual scaling factor B1, and adjust the register to compensate for the current matching deviation.

[0043] The dynamic adjustment module is used to determine whether the photocurrent type and digital value are within a preset range, perform coefficient correction on the frequency-banded photocurrent, and adjust the TIA through feedback. trim Calculate the ambient photocurrent and ranging calibration coefficient;

[0044] The data register is used to store ADC readings and TIA. trim Values, calibration coefficients, ambient light calculation formula parameters, and preset range thresholds.

[0045] As a preferred embodiment of the ambient light adaptive correction system based on feedback control, the dynamic adjustment module includes a type identification unit, a coefficient correction unit, a range judgment unit, a boundary judgment unit, a step size calculation unit, an offset adjustment unit, and a data calculation unit.

[0046] The type identification unit is used to determine whether the photocurrent is a DC photocurrent or a photocurrent with frequency based on whether the ADC reading is constant.

[0047] The coefficient correction unit is used to perform coefficient correction on the frequency-controlled photocurrent for ADC readings;

[0048] The range determination unit is used to determine whether the ADC reading is within a preset range H. min ~H max The preset range is set according to the operating saturation state of the TIA circuit;

[0049] The boundary determination unit is used to determine TIA. trim Whether the maximum or minimum value boundary of the corresponding TIA bias current has been reached;

[0050] The step size calculation unit is used to calculate the step size based on the difference between the ADC reading and a preset range, and the TIA value. trim The linear relationship between step size and ADC readings, and the calculation of TIA. trim Adjustment step size;

[0051] The bias adjustment unit is used to adjust the TIA according to the adjustment step size. trim Alternatively, it can output the rst_n signal and control the ADC module to reset.

[0052] The data calculation unit is used to calculate the ambient light current by substituting it into the calibrated ambient light calculation formula, and to determine the calibration coefficient for ranging correction based on the ambient light current.

[0053] The present invention has the following advantages:

[0054] First, this invention solves the problems of dispersed modules and concentrated responsibilities in traditional technologies by integrating modular division and refining functional division, shortening signal transmission links, and improving system operating efficiency and maintainability.

[0055] Secondly, this invention expands the application scenarios of photocurrent adaptation by adding a frequency-based photocurrent identification and correction mechanism, covering both DC light and frequency-based light interference scenarios. Compared with the traditional limitation of only adapting to DC light, it has a more comprehensive range of applications.

[0056] Third, improve calibration accuracy and stability by clarifying the specific logic of current mirror calibration, deviation compensation methods, and one-time calibration rules, and solve the problems of vague calibration logic and unclear calculation basis in traditional technology.

[0057] Fourth, enhance the accuracy of feedback control by introducing a photocurrent type judgment dimension, establishing a judgment-adjustment-reset-retest process, and quantifying the adjustment step size through linear relationship to achieve one-time adjustment, avoid repeated iterations, and improve real-time performance.

[0058] Fifth, a multi-dimensional calibration system is constructed, including initial formula calibration, photocurrent type correction, and ranging coefficient calibration, which effectively suppresses ambient light interference and significantly improves the ranging accuracy and stability of the TOF chip under complex lighting conditions. Attached Figure Description

[0059] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0060] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0061] Figure 1 This is a schematic diagram of the ambient light adaptive correction method based on feedback control provided in an embodiment of the present invention;

[0062] Figure 2 This is a flowchart of the ambient light adaptive correction method based on feedback control for measuring ambient light, provided in an embodiment of the present invention.

[0063] Figure 3 This is a timing simulation diagram of the feedback control for the ambient light adaptive correction method based on feedback control provided in this embodiment of the invention.

[0064] Figure 4 This is a schematic diagram of the ambient light adaptive correction system architecture based on feedback control provided in an embodiment of the present invention. Detailed Implementation

[0065] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0066] The meanings of the English abbreviations involved in this invention are as follows:

[0067] TOF: Time of Flight, refers to the technique of measuring distance by calculating the time difference between emitted and reflected light.

[0068] TIA: Transimpedance Amplifier, used to convert the photocurrent output by a photodiode into a voltage signal, and can be adapted to dynamic changes in ambient light by adjusting the bias current.

[0069] ADC: Analog-to-Digital Converter, used to convert processed analog photocurrent signals into digital quantities for subsequent circuits to make judgments, calculations and feedback control. This application uses a charge-balanced ADC.

[0070] SPAD: Single-Photon Avalanche Diode is a high-precision photodetector used in current technology to directly suppress ambient light interference at the receiving end.

[0071] Ic: Environmental Light Current, refers to the current formed after ambient light is converted by the photoelectric conversion module, and is the core object of measurement and calibration in this application.

[0072] Iref: Reference Current, specifically refers to the sampling reference current of the charge-balanced ADC, and is a key parameter in the formula for calculating ambient photocurrent.

[0073] Ambient: ADC Output Digital Value refers to the digital reading output by the ADC after performing analog-to-digital conversion on the photocurrent, reflecting information related to ambient light intensity.

[0074] EOC: End of Conversion, the signal output by the ADC after completing analog-to-digital conversion. When the signal is high, a valid ADC reading can be read.

[0075] CLK: Clock Signal, which provides the operating clock for the charge-balanced ADC. In this application, the ADC integration time is set to 256 CLK cycles.

[0076] Example 1

[0077] See Figure 1 and Figure 2 This invention provides an ambient light adaptive correction method based on feedback control, comprising the following steps:

[0078] S1. Perform initial calibration using the ambient photocurrent calculation formula, and compensate for current matching deviation by fitting the actual scaling factor of the current mirror and adjusting the register.

[0079] In existing technologies, when an ADC directly measures ambient photocurrent, a current mirror is used to reduce the measurement current. However, manufacturing processes can easily introduce current matching problems, leading to a decrease in ADC sampling accuracy. In this embodiment, a one-time initial calibration is performed before formal ambient light calibration to eliminate inherent biases in the current mirror structure. Before entering the charge-balanced ADC, the photocurrent undergoes a B1-fold scaling through the current mirror structure. While scaling reduces the ADC measurement range, power consumption, and control time, it amplifies ADC accuracy errors and current matching deviations. Therefore, step S1 uses an algorithm to fit the actual scaling factor B1 of the current mirror, then adjusts the reserved register to compensate for current matching deviations caused by manufacturing processes, and finally recalibrates the ambient light calculation formula to ensure the accuracy of subsequent ambient photocurrent calculations. This calibration is performed only once and is not repeated during the feedback process.

[0080] In this embodiment, the initial calibration of the ambient light calculation formula in step S1 is specifically as follows: the scaling factor B1 of the actual current mirror structure is obtained by calibrating the current mirror matching coefficient, the reserved register is adjusted to compensate for the current matching deviation, and the ambient light calculation formula is recalibrated.

[0081] Specifically, while current scaling provides a wider testing range, it also amplifies ADC accuracy errors, easily leading to measurement and judgment errors. Therefore, this embodiment detects and calculates the matching characteristics of the current mirror to fit the scaling factor B1 under actual working conditions. Then, by adjusting the reserved register parameters within the chip, it offsets the current matching deviation caused by differences in device consistency during the manufacturing process. Finally, it substitutes the actual B1 value into the ambient light calculation formula to complete the recalibration of the formula.

[0082] S2. After the ambient light is converted into photocurrent through photoelectric conversion, it is processed by linear compensation and current scaling, and then output as a digital quantity through analog-to-digital conversion, forming a signal conversion link from light to electricity to digital.

[0083] Ambient light itself is an optical signal, which cannot be directly processed by the digital circuits of a chip. Therefore, a light-to-electricity-to-digital signal conversion link needs to be constructed. First, the optical signal is converted into an electrical signal (photocurrent) through a photoelectric conversion module, realizing the conversion of the signal carrier. Then, linear compensation is performed through a TIA current compensation module to ensure that the photocurrent maintains a good linear response across different intensity ranges, avoiding signal distortion. Next, current scaling is used to reduce the photocurrent amplitude to match the measurement range of the ADC module, reducing the workload and power consumption of the ADC. Finally, the ADC module converts the analog electrical signal (photocurrent) into a digital quantity for subsequent digital circuitry to perform judgment, calculation, and feedback control.

[0084] In this embodiment, in step S2, photocurrent conversion is performed by a photoelectric conversion module, which uses a photodiode to convert ambient light of different intensities into DC or photocurrent of different frequencies; linear compensation of the photocurrent is performed by a TIA current compensation module, which controls the TIA bias current digital range TIA through a register. trim Set the linear compensation range.

[0085] Specifically, photodiodes have the characteristic that light intensity is proportional to output current. They can convert DC ambient light such as sunlight and frequency-carrying ambient light such as fluorescent lamps into corresponding DC photocurrents and frequency-carrying photocurrents, respectively, reflecting the intensity and frequency characteristics of ambient light. Strong ambient light can easily lead to signal saturation, therefore a linear compensation range needs to be set through a TIA current compensation module. trim As a digital control quantity for the TIA bias current, the compensation range can be flexibly set through register adjustment, ensuring that the TIA can operate in the linear region under different photocurrent inputs, avoiding signal saturation or distortion.

[0086] In this embodiment, in step S2, current scaling is achieved through a current mirror structure. The photocurrent is scaled by a factor of B1 before being input into the ADC module to reduce the measurement range of the ADC module. The integration time of the ADC module is a preset number of CLK cycles. After the eoc signal is pulled high, the output digital quantity Ambient is read. The current measured by the ADC module is the sum of the ambient light current Ic, the TIA bias current, and the ADC range current.

[0087] Specifically, the ambient photocurrent received by the chip can vary up to 400uA, with a frequency of 1kHz and above. Directly inputting this to an ADC would significantly increase the ADC's range requirements, leading to increased power consumption and longer control time. Therefore, a B1 scaling method using a current mirror structure can reduce the large-amplitude photocurrent to a measurement range suitable for the ADC, without altering the frequency characteristics and proportional relationship of the photocurrent, thus balancing measurement range and accuracy. The ADC module is charge-balanced, with its integration time set to a preset CLK cycle number to ensure stable sampling of photocurrents at different frequencies. The eoc signal indicates ADC conversion completion; when the eoc signal goes high, it signifies that analog-to-digital conversion is complete, and reading the digital quantity Ambient at this point ensures data validity. Furthermore, the current measured by the ADC is the sum of the ambient photocurrent Ic, the TIA bias current, and the ADC range current. This is because the TIA bias current is used to maintain TIA operational stability, and the ADC range current is an inherent parameter of the module. The total current resulting from the sum of these three is converted into a digital quantity by the ADC.

[0088] S3. Identify the photocurrent type based on the constant state of digital quantities, and perform corresponding data correction processing for the preset type of photocurrent.

[0089] Ambient light includes both DC light and frequency-banded light, and their interference mechanisms and degrees of influence on TOF ranging differ, requiring targeted handling. When the ADC circuit receives DC light, the reading is constant; when receiving frequency-banded photocurrent, the reading varies with frequency. Therefore, step S3 identifies the photocurrent type by determining whether the digital quantity Ambient is constant, providing a basis for differentiated processing. For frequency-banded photocurrent, the fluctuation of its ADC reading affects the accuracy of ranging correction, thus requiring data correction processing to offset the error caused by frequency fluctuations. For DC photocurrent, its ADC reading is stable and can be directly used for calculation, ensuring that the ADC data corresponding to different types of ambient light can meet the accuracy requirements of ranging correction.

[0090] In this embodiment, in step S3, the rule for determining the type of photocurrent is as follows: if the digital quantity Ambient is constant, it is determined to be a DC photocurrent; if the digital quantity Ambient changes, it is determined to be a photocurrent with frequency; for the photocurrent with frequency, the coefficient of the frequency conversion current value is calculated, and the digital quantity Ambient is corrected. The correction formula is Ambient×m, where m is the correction coefficient corresponding to the photocurrent with frequency.

[0091] Specifically, DC light has a stable intensity and a constant photocurrent amplitude. The digital output Ambient after ADC conversion also remains constant, thus it can be identified as DC photocurrent based on this constant reading. Frequency-dependent light, on the other hand, has a periodic intensity variation with frequency, resulting in a periodic fluctuation in the photocurrent amplitude. The digital output Ambient after ADC conversion changes over time, thus it can be identified as frequency-dependent photocurrent. For frequency-dependent photocurrent, the fluctuation in ADC readings can lead to measurement errors in ambient photocurrent, affecting ranging accuracy. Therefore, it is necessary to calculate the frequency-converted current value and introduce a correction coefficient m to correct Ambient, i.e., Ambient × m. The value of m is pre-calibrated based on the photocurrent frequency characteristics and ADC sampling characteristics to ensure that the corrected digital output accurately reflects the actual intensity of the frequency-dependent ambient light.

[0092] S4. Determine if the digital quantity is within the preset range: If the digital quantity exceeds the preset range, adjust the boundary of the bias current related parameters and calculate the adjustment step size, and re-execute the analog-to-digital conversion.

[0093] Preset range H min ~H max Based on the operating saturation state of the TIA circuit, the corresponding stable range I of the total current is set. min ~I max This ensures that the TIA always operates within the linear region, preventing signal saturation due to strong ambient light or insufficient signal amplitude due to weak ambient light. When the digital value is within the preset range, it indicates that the TIA is operating stably and the ADC data is reliable and can be used for subsequent calculations. When the digital value exceeds the preset range, it indicates that the TIA is deviating from the linear region. Feedback adjustment of the TIA bias current parameters is necessary to bring the total current back to a stable range, followed by repeated analog-to-digital conversion until the digital value is within the preset range. This feedback control ensures the consistency and stability of the TIA's operation and adapts to dynamic changes in ambient light.

[0094] In this embodiment, in step S4, the preset range is H. min ~H max The preset range is set according to the operating saturation state of the TIA circuit, corresponding to the stable range I of the total current. min ~I maxThe total current includes the ambient light current Ic and the TIA bias current TIA. Ibias .

[0095] Specifically, the saturation state of the TIA circuit is a key factor limiting measurement accuracy. This saturation state is influenced by the total current, i.e., the ambient light current and the TIA bias current. Ibias When the total current is too large, the TIA will enter the saturation region, leading to signal distortion and ranging failure. When the total current is too small, the signal amplitude is insufficient, making it susceptible to noise interference and affecting measurement accuracy. Therefore, this embodiment determines the total current stability range I corresponding to its linear operating range based on the design parameters and performance indicators of the TIA circuit. min ~I max Then, through the conversion ratio of the ADC, this current range is converted into a preset range H of digital quantity. min ~H max Subsequently, it is determined whether the digital quantity is within H. min ~H max Within this range, it can be indirectly determined whether TIA is operating in the linear region.

[0096] In this embodiment, the specific process of adjusting the boundary of the bias current related parameters in step S4 is as follows:

[0097] If the digital quantity exceeds the preset range H min ~H max Determine the digital range of the TIA bias current. trim Whether the maximum or minimum value boundary of the corresponding TIA bias current has been reached;

[0098] If TIA trim Once the boundary is reached, wait for the digital value to enter the adjustable range, and then re-perform analog-to-digital conversion to read the digital value.

[0099] If TIA trim If the boundary is not reached, then based on the difference Δ between the digital value and the preset range, combined with TIA... trim The linear relationship between step size and digital quantity is calculated by adjusting the step size k = Δ / n, where k is a positive integer. trim When increasing by k steps, where k is a negative integer, TIA trim Reduce the number of |k| steps, adjust and reset the ADC module and perform analog-to-digital conversion again;

[0100] When TIA trim At the minimum boundary and the digital quantity still reaches the full value C of the ADC max When the ambient light exceeds the measurement range, an over-limit warning signal is output.

[0101] Specifically, TIA trimAs a digital range parameter for controlling the TIA bias current, its value range corresponds to the boundary between the maximum and minimum values ​​of the TIA bias current. trim When the boundary is reached, it indicates that the bias current can no longer be adjusted. At this point, the rst_n signal needs to be output to wait for changes in ambient light until the digital value enters the adjustable range, avoiding ineffective adjustments. When TIA trim If the boundary is not reached, use TIA. trim The linear relationship between the step size and the ADC digital value allows for rapid adjustment of the TIA bias current by calculating the difference Δ between the digital value and the preset range, yielding the required adjustment step size k = Δ / n. This eliminates the need for repeated iterations and shortens control time. Furthermore, when the TIA... trim At the minimum boundary (minimum bias current) and the ADC reading still reaches full value C max If the ambient photocurrent exceeds the chip's measurement capability, continued measurement will lead to data distortion. Therefore, it is determined to be out of range, and an over-limit warning signal is output to achieve overload protection and ensure the chip's safe operation.

[0102] S5. After the digital quantity is within the preset range, substitute it into the calibrated ambient photocurrent calculation formula to obtain the ambient photocurrent, so as to determine the calibration coefficient for ranging correction.

[0103] When the digital value is within the preset range, it indicates that the TIA is working stably and the ADC data is reliable. At this time, the actual ambient photocurrent Ic can be derived from the ambient photocurrent calculation formula after initial calibration, quantifying the interference intensity of ambient light. The ranging accuracy of the TOF chip is affected by ambient light interference. Ambient photocurrent interferes with the phase detection of emitted and reflected light. Therefore, it is necessary to determine the calibration coefficient for ranging correction based on the ambient photocurrent, incorporate the measurement error caused by ambient light into the ranging algorithm for cancellation, and finally achieve adaptive correction of ambient light interference, thereby improving the ranging accuracy of the TOF chip.

[0104] In this embodiment, in step 5), if the digital quantity Ambient is constant, the formula for calculating the ambient photocurrent Ic is:

[0105] Ic = Ambient × Iref × B1 / C max -ADC-TIA Ibias

[0106] If the digital quantity Ambient changes, the formula for calculating the ambient photocurrent Ic is:

[0107] Ic = Ambient × m × Iref × B1 / C max -ADC-TIA Ibias

[0108] In the formula, ADC is the fixed current of the ADC module, and C maxFor Ambient at its maximum value, TIA Ibias Here, TIA is the bias current, Ambient is the digital output of the ADC module, Iref is the sampling reference current of the charge-balanced ADC, and B1 is the scaling factor of the current mirror structure. The ADC module converts this total current into the digital quantity Ambient. In the formula, ADC × C max TIA represents the total range current of the ADC module. Ibias The TIA bias current is given by Ambient×Iref×B1, which is the equivalent photocurrent obtained by the ADC after scaling by the current mirror. Iref is the ADC sampling reference current, B1 is the scaling factor, and Ambient is the sampling digital quantity. By subtracting the TIA bias current and the equivalent photocurrent from the total range current, the actual ambient photocurrent Ic can be derived.

[0109] In this embodiment, in step 5), if the digital quantity Ambient is constant, the formula for calculating the calibration coefficient of the ranging correction is:

[0110] amb err =a×(Ambient-Ambient avg )+b×(Ambient-Ambient avg ) 2

[0111] If the digital quantity Ambient changes, the formula for calculating the calibration coefficient for ranging correction is:

[0112] amb err =a×(Ambient×m -Ambient avg )+b×(Ambient×m -Ambient avg ) 2

[0113] In the formula, amb err Here, a and b are calibration coefficients, and a and b are fitting coefficients for the nonlinear relationship between the phase and the ADC reading obtained through the ranging algorithm. avg This represents the expected value of the ADC reading.

[0114] Specifically, the interference of ambient light on TOF ranging mainly manifests as signal phase shift, and the relationship between phase shift and ADC reading (reflecting ambient light intensity) is non-linear. This embodiment obtains the non-linear relationship coefficients a and b through fitting a large amount of experimental data, using the expected value of the ADC reading, Ambient... avgUsing this as a benchmark, the deviation between the actual ADC reading Ambient and the expected value is calculated, and then the calibration coefficient amb_err is obtained through a quadratic function formula. This coefficient can quantify the phase shift error caused by ambient light. Substituting it into the TOF ranging algorithm can accurately correct the ranging results, counteract ambient light interference, and improve ranging accuracy.

[0115] See Figure 3 This is a timing simulation diagram of the main TIA dynamic control process under certain ambient light conditions. CLK is the operating clock of the charge balance ADC, the ADC integration time is 256 CLK, and the ADC register reading (Ambient 150) is read when the EOC signal is read as 1. The ADC reading is determined to be within a specified range, ideally defined as 189~235. At this time, the TIA is read... trim The value is 3. According to the control flow, TIA is determined. trim If the boundary is not reached, the ADC module immediately resets and simultaneously calculates the difference. If the ratio of the difference to n is 3.25, then TIA... trim Add 4 directly, TIA during reset phase trim Write 7, the ADC restarts the measurement technology, waits for the next EOC to read the ADC register reading 202, and after the reading is adjusted within the specified range, performs multi-cycle reading of the ADC reading to determine whether the reading is constant. If constant, the dynamic adjustment of the ambient light is directly completed. If not constant, the correction coefficient m is calculated based on multiple readings and then substituted into the ambient light calculation formula to obtain the specific ambient light current.

[0116] Example 2

[0117] See Figure 4 Embodiment 2 of the present invention also provides an ambient light adaptive correction system based on feedback control, including a photoelectric conversion module, a TIA current compensation module, an ADC module, a dynamic adjustment module, a formula correction module, and a data register;

[0118] The photoelectric conversion module converts ambient light into DC or photocurrent of different frequencies. The TIA current compensation module is connected to the photoelectric conversion module and includes a linear compensation unit and a current mirror scaling unit. The linear compensation unit controls the TIA through a register. trim A linear compensation range is set, and the current mirror scaling unit is used to scale the photocurrent by a factor of B1. The ADC module is used to perform analog-to-digital conversion on the scaled photocurrent and output the digital quantity Ambient. The formula correction module is used to perform a one-time initial calibration of the ambient light calculation formula, fit the actual scaling factor B1, and adjust the register to compensate for current matching deviation. The dynamic adjustment module is used to determine whether the photocurrent type and digital quantity are within the preset range, perform coefficient correction on the frequency-sensitive photocurrent, and adjust the TIA through feedback. trimThe system calculates the ambient photocurrent and ranging calibration coefficients; the data register is used to store ADC readings and TIA. trim Values, calibration coefficients, ambient light calculation formula parameters, and preset range thresholds.

[0119] Specifically, the photoelectric conversion module, acting as the signal input, solves the problem that ambient light (optical signals) cannot be directly processed by digital circuits, converting it into measurable electrical signals (photocurrent), and is compatible with both DC and frequency-dependent ambient light types; the TIA current compensation module performs a dual function, with the linear compensation unit communicating through the TIA... trim The bias current is adjusted to ensure that the TIA operates in the linear region, avoiding signal saturation or distortion. The current mirror scaling unit, designed for the large range (up to 400uA) and high frequency (1kHz and above) of ambient light current, reduces the current amplitude by a factor of B1 to match the ADC measurement range, thereby reducing power consumption and control time. The ADC module converts analog electrical signals into digital quantities, providing a data foundation for subsequent digital processing. The formula correction module specifically addresses the current mirror process matching deviation problem in existing technologies, fitting the actual B1 value through a one-time initial calibration to ensure the accuracy of ambient light calculation. The dynamic adjustment module is the core of feedback control, realizing key functions such as photocurrent type identification, data correction, range judgment, parameter adjustment, and current and calibration coefficient calculation, forming a closed-loop feedback to adapt to dynamic changes in ambient light. The data register, as a data support unit, stores key parameters of each stage, ensuring data traceability and recall, and providing a guarantee for stable system operation.

[0120] In this embodiment, the dynamic adjustment module includes a type identification unit, a coefficient correction unit, a range judgment unit, a boundary judgment unit, a step size calculation unit, a bias adjustment unit, and a data calculation unit. The type identification unit is used to determine whether the photocurrent is a DC photocurrent or a frequency-dependent photocurrent based on whether the ADC reading is constant. The coefficient correction unit is used to perform coefficient correction on the ADC reading for the frequency-dependent photocurrent. The range judgment unit is used to determine whether the ADC reading is within a preset range H. min ~H max The preset range is set according to the operating saturation state of the TIA circuit; the boundary judgment unit is used to judge the TIA. trim Whether the maximum or minimum value boundary of the corresponding TIA bias current has been reached; the step size calculation unit is used to calculate the difference between the ADC reading and the preset range and the TIA. trim The linear relationship between step size and ADC readings, and the calculation of TIA. trim The adjustment step size; the bias adjustment unit is used to adjust the TIA according to the adjustment step size. trimAlternatively, it can output the rst_n signal and control the ADC module to reset; the data calculation unit is used to substitute the calibrated ambient light calculation formula to calculate the ambient light current, and determine the calibration coefficient for ranging correction based on the ambient light current.

[0121] Specifically, the type identification unit accurately distinguishes photocurrent types based on the ADC's response characteristics to different photocurrents (DC light corresponds to a constant ADC reading, while frequency-sensitive light corresponds to a varying ADC reading), providing a basis for differentiated processing; the coefficient correction unit addresses the ADC reading fluctuation problem of frequency-sensitive photocurrents by using Ambient×m coefficient correction to offset errors caused by frequency fluctuations and ensure data accuracy; the range judgment unit sets a preset range H based on the TIA circuit's saturation state. min ~H max The corresponding total current stability range I min ~I max By determining whether the ADC reading is within the specified range, the stability of the TIA's operating state can be indirectly determined, avoiding TIA saturation caused by strong ambient light or insufficient signal caused by weak ambient light; the boundary judgment unit is used to limit the TIA. trim The adjustment range prevents the bias current from exceeding the hardware capacity when TIA trim When the boundary is reached, invalid adjustments are stopped, and the system waits for changes in ambient light or outputs a reset signal to ensure system stability; the step size calculation unit utilizes TIA trim The linear relationship between step size and ADC reading (the ADC reading increases by n for each additional step) is used to achieve precise quantization of the adjustment step size through difference calculation, ensuring that the TIA bias current is adjusted in one step, shortening the control cycle and eliminating the need for repeated iterations; the bias adjustment unit executes specific parameter adjustment actions, or adjusts the TIA. trim It can output the rst_n signal or control the ADC reset, serving as the execution end of feedback control; the data calculation unit back-calculates the ambient light current Ic based on the calibrated formula, and then calculates the calibration coefficient amb_err through a nonlinear fitting formula, quantizing the ambient light interference into a compensable correction parameter, ultimately achieving compensation for the TOF ranging error.

[0122] The application scenarios of this invention are as follows:

[0123] Smartphones / tablets: Suitable for devices equipped with TOF lenses, it can correct ambient light interference in situations such as switching between strong outdoor light (sunlight, DC light) and indoor lighting (fluorescent lamps, LED lights, light with frequency) or sudden changes in lighting (such as moving quickly from indoors to outdoors), ensuring the ranging accuracy of functions such as face recognition, 3D modeling, AR / VR spatial positioning, and improving the user interaction experience.

[0124] Smart cameras / camcorders: Used for distance detection and scene perception in security monitoring and home smart camera devices. In scenarios with dynamic changes in ambient light, such as day and night transitions and light switching, they avoid ranging deviations caused by ambient light and ensure the accuracy of target distance measurement and motion trajectory tracking.

[0125] Industrial Automation Distance Measurement: Adapted to TOF distance measurement modules on industrial production lines, used for scenarios such as component positioning, assembly gap detection, and material distance measurement. Fluorescent lamps (with frequency) in the workshop, natural light (DC light) incident from outside the window, and sudden changes in light caused by equipment start-up and shutdown will not affect the measurement accuracy, ensuring the automation and precision of the production process.

[0126] Robot navigation: Applied to obstacle avoidance and path planning for industrial AGV robots and collaborative robots. In complex lighting environments in factories (multiple light sources superimposed, light intensity fluctuating), it ensures accurate judgment of obstacle distance by the robot through ambient light adaptive correction, thereby improving navigation safety and stability.

[0127] Vehicle-mounted ranging system: Integrated with the vehicle's TOF sensor, it is used for functions such as forward vehicle distance detection, pedestrian recognition, and lane assist. In scenarios such as strong daylight, nighttime streetlights (with frequency), tunnel entrances and exits (sudden changes in light), and interference from oncoming headlights, it effectively suppresses the influence of ambient light on ranging, providing accurate distance data support for autonomous driving decisions and ensuring driving safety.

[0128] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. An ambient light adaptive correction method based on feedback control, characterized in that, Includes the following steps: 1) Perform initial calibration using the ambient photocurrent calculation formula, and compensate for current matching deviation by fitting the actual scaling factor of the current mirror and adjusting the register; 2) After ambient light is converted into photocurrent through photoelectric conversion, it is processed by linear compensation and current scaling, and then output as a digital quantity through analog-to-digital conversion, forming a signal conversion link from light to electricity to digital. 3) Identify the photocurrent type based on the constant state of digital quantities, and perform corresponding data correction processing for the preset photocurrent type; In step 3), the rule for determining the type of photocurrent is: If the digital quantity Ambient is constant, it is determined to be DC photocurrent; If the digital quantity Ambient changes, it is determined to be a photocurrent with frequency. For the frequency-carrying photocurrent, the coefficient of the frequency conversion current value is calculated, and the digital quantity Ambient is corrected. The correction formula is Ambient×m, where m is the correction coefficient corresponding to the frequency-carrying photocurrent. The value of m is pre-calibrated based on the frequency characteristics of the photocurrent and the sampling characteristics of the ADC. 4) Determine if the digital quantity is within the preset range: If the digital quantity exceeds the preset range, re-execute the analog-to-digital conversion by adjusting the boundary of the bias current related parameters and calculating the adjustment step size; 5) After the digital value is within the preset range, after the reading is adjusted to be within the specified range, the ADC reading is read in multiple cycles to determine whether the reading is constant. If it is constant, the dynamic adjustment of the ambient light is directly completed. If it is not constant, the correction coefficient m is calculated based on multiple readings and then substituted into the ambient light calculation formula to obtain the specific ambient light current, so as to determine the calibration coefficient of the ranging correction. In step 5), if the digital quantity Ambient is constant, the formula for calculating the ambient photocurrent Ic is: Ic=Ambient×Iref×B1 / C max -ADC-TIA Ibias If the digital quantity Ambient changes, the formula for calculating the ambient photocurrent Ic is: Ic=Ambient×m×Iref×B1 / C max -ADC-TIA Ibias In the formula, ADC is the fixed current of the ADC module, and C max Amibient is at its maximum value, TIA Ibias TIA bias current, Ambient is the digital output of the ADC module, Iref is the sampling reference current of the charge-balanced ADC, and B1 is the scaling factor of the current mirror structure.

2. The ambient light adaptive correction method based on feedback control according to claim 1, characterized in that, In step 1), the initial calibration of the ambient light calculation formula is as follows: The scaling factor B1 of the actual current mirror structure is obtained by calibrating the current mirror matching coefficient. The reserved register is adjusted to compensate for the current matching deviation, and the ambient light calculation formula is recalibrated.

3. The ambient light adaptive correction method based on feedback control according to claim 1, characterized in that, In step 2), photocurrent conversion is performed through a photoelectric conversion module, which uses a photodiode to convert ambient light of different intensities into DC or photocurrent of a set frequency. Linear compensation of the photocurrent is performed through a TIA current compensation module, which controls the TIA bias current digital range via a register. trim Set the linear compensation range.

4. The ambient light adaptive correction method based on feedback control according to claim 3, characterized in that, In step 2), current scaling is achieved through a current mirror structure. The photocurrent is scaled by a factor of B1 before being input into the ADC module to reduce the measurement range of the ADC module. The integration time of the ADC module is a preset number of CLK cycles. After the eoc signal is pulled high, the output digital quantity Ambient is read. The current measured by the ADC module is the sum of the ambient light current Ic, the TIA bias current, and the ADC range current.

5. The ambient light adaptive correction method based on feedback control according to claim 1, characterized in that, In step 4), the preset range is H. min ~H max The preset range is set according to the operating saturation state of the TIA circuit, corresponding to the stable range I of the total current. min ~I max The total current includes the ambient light current Ic and the TIA bias current TIA. Ibias .

6. The ambient light adaptive correction method based on feedback control according to claim 5, characterized in that, In step 4), the specific process of adjusting the boundary parameters related to the bias current is as follows: If the digital quantity exceeds the preset range H min ~H max Determine the digital range of the TIA bias current. trim Whether the maximum or minimum value boundary of the corresponding TIA bias current has been reached; If TIA trim Once the boundary is reached, wait for the digital value to enter the adjustable range, and then re-perform analog-to-digital conversion to read the digital value. If TIA trim If the boundary is not reached, then based on the difference Δ between the digital value and the preset range, combined with TIA... trim The linear relationship between step size and digital quantity is calculated by adjusting the step size k = Δ / n, where k is a positive integer. trim When increasing by k steps, where k is a negative integer, TIA trim Reduce the number of |k| steps, adjust and reset the ADC module and perform analog-to-digital conversion again; When TIA trim At the minimum boundary and the digital quantity still reaches the full value C of the ADC reading. max When the ambient light exceeds the measurement range, an over-limit warning signal is output.

7. The ambient light adaptive correction method based on feedback control according to claim 1, characterized in that, In step 5), if the digital quantity Ambient is constant, the formula for calculating the calibration coefficient for ranging correction is: with err =a×(Environment-Environment avg )+b×(Environment-Environment avg ) 2 If the digital quantity Ambient changes, the formula for calculating the calibration coefficient for ranging correction is: with err =a×(Environment×m -Environment avg )+b×(Environment×m -Environment avg ) 2 In the formula, amb err Here, a and b are calibration coefficients, and a and b are fitting coefficients for the nonlinear relationship between the phase and the ADC reading obtained through the ranging algorithm. avg This represents the expected value of the ADC reading.

8. An ambient light adaptive correction system based on feedback control, used to perform the steps of the method according to any one of claims 1 to 7, characterized in that, It includes a photoelectric conversion module, a TIA current compensation module, an ADC module, a dynamic adjustment module, a formula correction module, and a data register; The photoelectric conversion module is used to convert ambient light into direct current or photocurrent of different frequencies. The TIA current compensation module is connected to the photoelectric conversion module. The TIA current compensation module includes a linear compensation unit and a current mirror scaling unit. The linear compensation unit controls the TIA through a register. trim The linear compensation range is set, and the current mirror scaling unit is used to scale the photocurrent by a factor of B1. The ADC module is used to perform analog-to-digital conversion on the scaled photocurrent and output a digital quantity Ambient. The formula correction module is used to perform a one-time initial calibration of the ambient light calculation formula, fit the actual scaling factor B1, and adjust the register to compensate for the current matching deviation. The dynamic adjustment module is used to determine whether the photocurrent type and digital value are within a preset range, perform coefficient correction on the frequency-banded photocurrent, and adjust the TIA through feedback. trim Calculate the ambient photocurrent and ranging calibration coefficient; The data register is used to store ADC readings and TIA. trim Values, calibration coefficients, ambient light calculation formula parameters, and preset range thresholds.

9. The ambient light adaptive correction system based on feedback control according to claim 8, characterized in that, The dynamic adjustment module includes a type identification unit, a coefficient correction unit, a range judgment unit, a boundary judgment unit, a step size calculation unit, an offset adjustment unit, and a data calculation unit; The type identification unit is used to determine whether the photocurrent is a DC photocurrent or a photocurrent with frequency based on whether the ADC reading is constant. The coefficient correction unit is used to perform coefficient correction on the frequency-controlled photocurrent for ADC readings; The range determination unit is used to determine whether the ADC reading is within a preset range H. min ~H max The preset range is set according to the operating saturation state of the TIA circuit; The boundary determination unit is used to determine TIA. trim Whether the maximum or minimum value boundary of the corresponding TIA bias current has been reached; The step size calculation unit is used to calculate the step size based on the difference between the ADC reading and a preset range, and the TIA value. trim The linear relationship between step size and ADC readings, and the calculation of TIA. trim Adjustment step size; The bias adjustment unit is used to adjust the TIA according to the adjustment step size. trim Alternatively, it can output the rst_n signal and control the ADC module to reset. The data calculation unit is used to calculate the ambient light current by substituting it into the calibrated ambient light calculation formula, and to determine the calibration coefficient for ranging correction based on the ambient light current.

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