Frequency domain near infrared spectrum detection device and method based on photon counting

Abstract

The invention provides a frequency domain near infrared spectrum detection device and method based on photon counting, which can be applied to the technical field of in-vivo non-invasive medical detection and diagnosis. The device comprises a photoelectric module configured to emit incident light to a to-be-measured object and generate an electric signal in response to emergent light received from the to-be-measured object, and the incident light is obtained by coupling a plurality of laser signals with different modulation frequencies; each counting module comprises multiple parallel counting channels, and first clock signals of the multiple counting channels have a first frequency and have phase differences relative to each other; the processing module is used for sampling the electric signals so as to determine a target counting channel according to the electric pulse which is responded first in the electric signals; each counting module is configured to determine a response moment of the first responded electrical pulse based on a synchronization signal synchronized with the phase of the modulation signal, and perform photon counting within a time scale corresponding to the response moment to generate a counting result.

Description

Technical Field

[0001] This disclosure relates to the field of in vivo non-invasive medical testing and diagnostic technology, and more specifically, to a frequency-domain near-infrared spectroscopy detection device and method based on photon counting. Background Technology

[0002] Frequency-domain near-infrared spectroscopy (FD-NIRS) is a method for detecting changes in tissue hemoglobin concentration based on modulated light technology. Compared to continuous-wave near-infrared spectroscopy (CW-NIRS), FD-NIRS can simultaneously acquire multiple parameters such as light intensity, phase, and modulation depth, and can effectively distinguish between absorption and scattering effects, reconstructing absorption and scattering coefficients to obtain the absolute amounts of different components within the tissue.

[0003] In realizing the concept disclosed herein, the inventors discovered that the FD-NIRS implementation methods based on heterodyne detection or direct digital sampling in the related technologies have at least the technical problems of low signal-to-noise ratio and large phase measurement error leading to distortion of measurement results. Summary of the Invention

[0004] In view of this, the present disclosure provides a frequency domain near-infrared spectroscopy detection device and method based on photon counting.

[0005] One aspect of this disclosure provides a frequency-domain near-infrared spectroscopy detection device based on photon counting, comprising:

[0006] A photoelectric module is configured to emit incident light to a test object, receive outgoing light from the test object, and generate an electrical signal in response to the outgoing light, wherein the incident light is obtained by coupling multiple laser signals with different modulation frequencies; multiple counting modules, each including parallel multi-channel counting channels, each multi-channel counting channel having an associated first clock signal, the first clock signals of each multi-channel counting channel having a first frequency and a phase difference relative to each other; and a processing module configured to sample the electrical signal based on the first clock signals of each multi-channel counting channel, to determine a target counting channel from the multi-channel counting channels of the counting modules according to the electrical pulse that is first responded to in the electrical signal; wherein, for the counting module, it is configured to determine the response time of the first responded electrical pulse in the target counting channel based on a synchronization signal that is phase-synchronized with the modulation signal, and to count photons within a time scale corresponding to the response time to generate a counting result, the counting result including a combination of the number of photons accumulated within the time scale of each multi-channel counting channel in chronological order.

[0007] According to embodiments of this disclosure, the plurality of laser signals includes a first laser signal and a second laser signal. The optoelectronic module includes: a signal generation submodule configured to generate a plurality of modulation signals, wherein the plurality of modulation signals include a first modulation signal having a second frequency and a second modulation signal having a third frequency; a driving submodule configured to drive a first semiconductor laser having a first wavelength and a second semiconductor laser having a second wavelength based on the first modulation signal and the second modulation signal, respectively, to generate the first laser signal and the second laser signal; and an optical output submodule configured to couple the first laser signal and the second laser signal into a mixed laser signal and incident the mixed laser signal onto the object under test.

[0008] According to embodiments of this disclosure, the processing module is configured to determine the target counting channel according to the following formula:

[0009] signal_sift(i)=signal_rise(i)&&(!signal_rise(i-1))&&(!signal_union);

[0010] Where && represents the logical AND operation, ! represents the NOT operation, i is the counting channel index, signal_sift(i) represents the target trigger signal of the target counting channel corresponding to the first electrical pulse that is responded to, signal_rise(i) represents the electrical pulse that is responded to in counting channel i, signal_rise(i-1) represents the electrical pulse that is responded to in counting channel i-1, and signal_union represents the joint register signal of multiple counting channels responding to electrical pulses.

[0011] According to embodiments of this disclosure, the processing module is configured to determine the joint register signal according to the following formula:

[0012] signal_union=signal_rise_reg(1) signal_rise_reg(2) ... signal_rise_reg (I);

[0013] in, The logical OR operation is represented by signal_rise_reg (1), which represents the registered signal of signal_rise(1), signal_rise_reg (2), which represents the registered signal of signal_rise(2), and signal_rise_reg (I) which represents the registered signal of signal_rise(I). I is the total number of counting channels included in the counting module.

[0014] According to embodiments of this disclosure, the signal generation submodule is further configured to generate a synchronization signal; the processing module includes: a clock submodule configured to multiply a preset reference clock to obtain a first clock signal; and a synchronization submodule configured to generate synchronization pulses for each of the multiple counting channels based on the synchronization signal for each counting module; wherein, for each counting channel, the pulse width of the synchronization pulse of the counting channel is equal to one clock period of the first clock signal.

[0015] According to embodiments of this disclosure, each counting module is configured to trigger photon counting through multiple counting channels based on synchronization pulses of the multiple counting channels, and the total number of time markers in each counting channel is determined based on the ratio of a first frequency to the frequency of the corresponding modulation signal.

[0016] According to embodiments of this disclosure, each of the multiple counting modules further includes multiple shift registers corresponding to multiple counting channels. For each shift register, multiple bits of the shift register correspond one-to-one with multiple time markers in the counting channel. Each shift register is reset to its initial state in response to the synchronization pulse of the corresponding counting channel. The initial state indicates that only the least significant bit is set to 1. The shift register corresponding to the target counting channel is configured to shift sequentially in each counting cycle to set the bit corresponding to the target time marker to 1. The target time marker represents the time marker corresponding to the response time.

[0017] According to embodiments of this disclosure, the signal generation submodule includes: an in-phase / out-of-phase signal generator configured to generate a first output signal and a second output signal that are out of phase with each other; a first power divider configured to receive the first output signal and output a modulation signal and a first comparison signal; a second power divider configured to receive the second output signal and output a second comparison signal; and a comparison unit configured to obtain a synchronization signal by comparing the first comparison signal and the second comparison signal.

[0018] According to an embodiment of this disclosure, the synchronization submodule includes: a first flip-flop configured to output a first registered signal based on a synchronization signal under the drive of a first clock signal; a second flip-flop configured to output a second registered signal based on the first registered signal under the drive of the first clock signal; and an XOR gate configured to generate a synchronization pulse based on the first registered signal and the second registered signal.

[0019] Another aspect of this disclosure provides a frequency-domain near-infrared spectroscopy detection method based on photon counting, comprising: emitting incident light to a test object, receiving outgoing light from the test object, and generating an electrical signal in response to the outgoing light, wherein the incident light is obtained by coupling multiple laser signals with different modulation frequencies; sampling the electrical signal based on a first clock signal associated with each of the parallel multi-channel counting channels, to determine a target counting channel from the multi-channel counting channels according to the electrical pulse that is responded to first in the electrical signal, wherein the first clock signals of each of the multi-channel counting channels have the same frequency and have a phase difference with each other; determining the response time of the first electrical pulse in the target counting channel based on a synchronization signal that is phase-synchronized with the modulation signal, and performing photon counting within a time scale corresponding to the response time to generate a counting result, wherein the counting result includes a combination of the number of photons accumulated within the time scales of each of the multi-channel counting channels in chronological order.

[0020] Another aspect of this disclosure provides an electronic device including: one or more processors; and a memory configured to store one or more programs, wherein, when the one or more programs are executed by the one or more processors, the one or more processors cause the one or more processors to perform the method as described above.

[0021] According to embodiments of this disclosure, the processing module samples the electrical signal generated after the incident light, coupled with modulated optical signals of different modulation frequencies, is acted upon by the object under test, based on the first clock signal associated with the parallel multi-channel counting channels in each counting module, which has the same frequency and a phase difference. The target counting channel is determined from the multi-channel counting based on the first clock signal corresponding to the first electrical pulse in the electrical signal. Multiple counting modules determine the response time of the electrical pulse in the target counting channel based on a synchronization signal that synchronizes the phase of the corresponding modulation signals. Photon counting is then performed within the time scale corresponding to the response time. Since single photon counting is only performed in the target counting channel that responds to the first electrical pulse, the technical problem of inaccurate counting results due to repeated counting of single photons is avoided. Simultaneously, multiple counting modules use multiple counting channels for photon counting. Without increasing the clock frequency, the number of counting channels is effectively expanded by adjusting the phase of the first clock signal corresponding to the multi-channel counting, thus improving the measurement time resolution. This allows the generated counting results to provide a more accurate data basis for the extraction of relevant information (such as phase and amplitude) after inversion. Attached Figure Description

[0022] The above and other objects, features and advantages of this disclosure will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0023] Figure 1A block diagram of a frequency-domain near-infrared spectroscopy detection device based on photon counting according to an embodiment of the present disclosure is shown schematically.

[0024] Figure 2 A schematic diagram of a signal generation submodule according to an embodiment of the present disclosure is shown.

[0025] Figure 3 The illustration shows a schematic diagram of the principle of frequency division multiplexing technology in a frequency domain near-infrared spectroscopy detection device according to an embodiment of the present disclosure.

[0026] Figure 4 The schematic diagram illustrates the working principle of a frequency-domain near-infrared spectroscopy detection device based on photon counting according to an embodiment of the present disclosure.

[0027] Figure 5A A timing diagram of a first clock signal and a preset reference clock according to an embodiment of the present disclosure is illustrated schematically.

[0028] Figure 5B A timing diagram of a synchronization signal according to an embodiment of the present disclosure is illustrated schematically.

[0029] Figure 5C A timing diagram of the joint register signal and the target trigger signal according to an embodiment of the present disclosure is illustrated.

[0030] Figure 5D The timing diagram of the counting module is shown schematically.

[0031] Figure 6 A flowchart illustrating a frequency-domain near-infrared spectroscopy detection method based on photon counting according to an embodiment of the present disclosure is shown. Detailed Implementation

[0032] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0033] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0034] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0035] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0036] In realizing the inventive concept of this publication, research revealed that, taking brain function research as an example, when the electrical signal intensity of a specific neural circuit increases, the energy metabolism demand of the corresponding functional area exhibits an exponential increase, specifically manifested as a simultaneous surge in oxygen consumption rate and glucose metabolism rate. This dynamic change in energy, through a precise regulatory mechanism of neurovascular coupling, promotes local microvascular dilation, drives adaptive adjustments in blood flow velocity and circulatory volume, and subsequently triggers a significant change in the regional blood oxygen metabolism state—specifically manifested as an inverse response pattern of increasing oxyhemoglobin (HbO) concentration gradient and decreasing deoxyhemoglobin (HbR) level gradient. Among numerous technical solutions, near-infrared spectroscopy (NIRS), with its moderate spatiotemporal resolution, excellent environmental adaptability, low implementation cost, and high operability, has become the preferred optical measurement scheme for detecting brain function under natural behavioral conditions, effectively compensating for the measurement limitations of functional magnetic resonance imaging (fMRI), positron emission tomography (PET), and other technologies in real-world applications and dynamic process capture.

[0037] However, FD-NIRS schemes based on heterodyne detection or direct digital sampling are limited by the inherent signal-to-noise ratio of the system, resulting in large phase measurement errors and reducing the reliability and accuracy of blood oxygen response measurement.

[0038] In view of this, embodiments of the present disclosure provide a frequency-domain near-infrared spectroscopy detection device based on photon counting, comprising: a photoelectric module configured to emit incident light to a test object, receive outgoing light from the test object, and generate an electrical signal in response to the outgoing light, wherein the incident light is obtained by coupling multiple laser signals with different modulation frequencies; multiple counting modules, each including a parallel multi-channel counting channel, each multi-channel counting channel having an associated first clock signal, the first clock signal of each multi-channel counting channel having a first frequency and a phase difference relative to each other; and a processing module configured to... The electrical signal is sampled using the first clock signal of each of the multiple counting channels to determine the target counting channel from the multiple counting channels of each counting module based on the electrical pulse that is responded to first in the electrical signal. For each counting module, it is configured to determine the response time of the electrical pulse that is responded to first in the target counting channel based on a synchronization signal that is phase-synchronized with the modulation signal, and to count photons within the time scale corresponding to the response time to generate a counting result. The counting result includes the combination of the number of photons accumulated within the time scale of each of the multiple counting channels in chronological order.

[0039] Figure 1 A block diagram of a frequency-domain near-infrared spectroscopy detection device based on photon counting according to an embodiment of the present disclosure is shown schematically.

[0040] like Figure 1 As shown, the device 100 includes a photoelectric module 110, a processing module 120, and multiple counting modules (such as the first counting module 130 and the second counting module 140 shown in the figure). The first counting module 130 includes parallel multiple counting channels (such as counting channels 131, 132, 133, and 134 shown in the figure), and the second counting module 140 also includes parallel multiple counting channels (such as counting channels 141, 142, 143, and 144 shown in the figure).

[0041] It should be noted that the number of counting modules and counting channels shown in the diagram is merely illustrative. Depending on the implementation requirements, any number of counting modules and counting channels can be used; no limitation is made here.

[0042] Taking the detection of brain hemoglobin concentration using the above-mentioned device as an example, the test object is the brain. An optical fiber array can be arranged on the surface of the brain using a supporting structure such as a silicone scaffold. The optical fiber array can include light source points on the incident optical fiber and detection points corresponding to the outgoing optical fiber (or multiple light source points and detection points can be arranged according to the measurement area). The photoelectric module 110 emits multiple wavelengths of incident light within the near-infrared spectrum to the light source points on the surface of the test object through the incident optical fiber. The incident light is obtained by coupling multiple modulated light signals with different modulation frequencies. The incident light penetrates the test object, thereby causing changes in brain hemoglobin concentration to affect the intensity, phase, and other related parameters of the incident light. The photoelectric module 110 can also receive the outgoing light emitted from the detection points and generate an electrical signal based on the outgoing light. The electrical signal is a discrete electrical pulse sequence.

[0043] According to embodiments of this disclosure, the processing module 120 performs multi-phase parallel sampling of electrical signals based on the first clock signals of each of the multiple counting channels in the multiple counting modules. Since multiple first clock signals sample electrical signals simultaneously, there may be two or more counting channels that respond to electrical signals. However, simultaneous counting by multiple counting channels can lead to repeated counting of a single photon event. Therefore, for each counting module, the processing module 120 determines the target counting channel from the multiple counting channels based on the first clock signal corresponding to the first responding electrical pulse, and blocks other counting channels that also respond to electrical signals, except for the target counting channel, to ensure that each photon event is counted only in the counting channel that responds first.

[0044] For each counting module, taking the four first clock signals of each of the four counting channels as an example, all four first clock signals have a first frequency of 500MHz, and can have relative to each other... The phase difference, that is, the phases are successively 0 90 180 270 This expands the total number of time markers to four times that of a single counting channel, thereby improving the equivalent time resolution and ensuring that the processing submodule 120 can sample the electrical signal with a resolution of 0.5 ns. It should be noted that, to further improve the accuracy of the counting results, the number of counting channels and the equivalent time resolution can be further expanded by increasing the number of phases of the first clock signal; the number of counting channels is not limited here.

[0045] According to embodiments of this disclosure, the counting module 130 can determine the response time of the target counting channel to the electrical pulse obtained by the processing module 120 based on a first synchronization signal (SYNC_1) synchronized with the phase of the corresponding modulation signal. Each counting channel has multiple time markers, and photon counting can be performed within the time markers corresponding to the response time. Similarly, the counting module 140 can determine the response time of the target counting channel to the electrical pulse obtained by the processing module 120 based on a second synchronization signal (SYNC_2) synchronized with the phase of the corresponding modulation signal, and perform photon counting within the time markers corresponding to the response time. After all counting is completed, for each counting module, the count values ​​within the time markers of each of the multiple counting channels are accumulated, and the count values ​​of the time markers are spliced ​​together in chronological order to obtain the counting result. The counting result can be a time distribution histogram, used to reflect the information on the change of light intensity and phase shift information over time. Then, the high-frequency modulation sine curve can be reconstructed by the host computer to calculate the change in hemoglobin concentration of the test object.

[0046] According to embodiments of this disclosure, the processing module samples the electrical signal generated after the incident light, coupled with modulated optical signals of different modulation frequencies, is acted upon by the object under test, based on a first clock signal associated with the parallel multi-channel counting channels of multiple counting modules, which have the same frequency and a phase difference. The target counting channel is determined from the multi-channel counting based on the first clock signal corresponding to the first electrical pulse in the electrical signal. Multiple counting modules determine the response time of the electrical pulse in the target counting channel based on a synchronization signal that synchronizes the phase of the corresponding modulation signals. Photon counting is then performed within the time scale corresponding to the response time. Since single photon counting is only performed in the target counting channel that responds to the electrical pulse first, the technical problem of inaccurate counting results due to repeated counting of single photons is avoided. Simultaneously, multiple counting modules use multiple counting channels for photon counting. Without increasing the clock frequency, the number of counting channels is effectively expanded by adjusting only the phase of the first clock signal corresponding to the multi-channel counting. This allows the generated counting results to provide a more accurate data basis for the extraction of relevant information (such as phase and amplitude) after inversion.

[0047] According to embodiments of this disclosure, the optoelectronic module includes: a signal generation submodule configured to generate a plurality of modulation signals, wherein the plurality of modulation signals include a first modulation signal having a second frequency and a second modulation signal having a third frequency; a driving submodule configured to drive a first semiconductor laser having a first wavelength and a second semiconductor laser having a second wavelength based on the first modulation signal and the second modulation signal, respectively, to generate a first laser signal and a second laser signal; and an optical output submodule configured to couple the first laser signal and the second laser signal into a mixed laser signal and incident the mixed laser signal onto the object under test.

[0048] Figure 2 A schematic diagram of a signal generation submodule according to an embodiment of the present disclosure is shown.

[0049] like Figure 2 As shown, the signal generation submodule includes an in-phase / out-of-phase signal generator 210, a first power divider 220, a second power divider 230, and a comparison unit 240.

[0050] The in-phase / out-of-phase signal generator 210 outputs a first output signal at the first output port Q and a second output signal at the second output port Q#, wherein the first output signal and the second output signal are inverted signals. The highest voltage of the first output signal and the lowest voltage of the second output signal are 840mV and 200mV, respectively.

[0051] The first power divider 220 receives the first input signal from the input port IN1, splits the first input signal into two paths, outputs the modulation signal from the first output port OUT1 and the first comparison signal from the second output port OUT2.

[0052] The second power divider 230 receives the second input signal from the input port IN2, outputs the second comparison signal through the output port OUT2, and keeps the signal output from the first output port OUT1 for later use.

[0053] The comparison unit 240 includes a cascaded voltage comparator 241 and a level conversion subunit 242. The positive and negative input terminals of the voltage comparator 241 receive the first comparison signal and the second comparison signal respectively for threshold detection, and send the comparison results to the positive input port D0 and the negative input port D0# of the level conversion subunit 242 respectively to ensure the generation of a synchronization signal that is synchronized with the modulation signal.

[0054] It should be noted that in practical applications, the signal generation submodule can generate three, four, or even more modulation signals with different frequencies. This is not limited here. For ease of understanding, the embodiment uses the first modulation signal and the second modulation signal as examples.

[0055] Accordingly, since the modulation signal includes a first modulation signal with a second frequency and a second modulation signal with a third frequency, the number of signal generation sub-modules is 2.

[0056] According to embodiments of this disclosure, the driving submodule drives a first semiconductor laser having a first wavelength (e.g., 660 nm) and a second semiconductor laser having a second wavelength (e.g., 830 nm) based on a first modulation signal and a second modulation signal obtained from two signal generation submodules, respectively, to generate a first laser signal and a second laser signal. The second frequency can be 50 MHz and the third frequency can be 55.556 MHz.

[0057] The optical output submodule can use an optical fiber coupler to couple the first laser signal and the second laser signal into a mixed laser signal, which is equivalent to coupling two laser signals with different wavelengths and modulation frequencies into a single signal, and then incident the mixed laser signal onto the object under test.

[0058] According to embodiments of this disclosure, each counting module is configured to trigger photon counting through multiple counting channels based on synchronization pulses of the multiple counting channels, and the total number of time markers in each counting channel is determined based on the ratio of a first frequency to the frequency of the corresponding modulation signal.

[0059] For example, the total number of time markers in each counting channel of the first counting module is x= / =500 / 50=10, the total number of time markers in each counting channel of the second counting module is y= / =500 / 55.556=9.

[0060] Figure 3 The illustration shows a schematic diagram of the principle of frequency division multiplexing technology in a frequency domain near-infrared spectroscopy detection device according to an embodiment of the present disclosure.

[0061] like Figure 3 As shown, a first laser signal and a second laser signal with different modulation frequencies and wavelengths are coupled to obtain a mixed laser signal, which is then incident on the object under test. The counting window corresponding to the first counting module counts under the triggering of a first synchronization signal (SYNC_1) synchronized with the first modulation signal, and the counting window corresponding to the second counting module counts under the triggering of a second synchronization signal (SYNC_2) synchronized with the second modulation signal.

[0062] Taking the first counting module as an example, the width of the counting window of the first counting module... It is equal to the period T1 of the first modulation signal, and can be expressed as the following formula (1).

[0063] (1)

[0064] in, The modulation frequency of the first modulation signal is also known as the second frequency. T represents the first frequency. s N is the first clock signal period; N is the number of counting window points of the first counting module, which is the total number of time marks included in each counting channel of the first counting module.

[0065] According to embodiments of this disclosure, the mixed laser signal includes coupling information of two laser signals. The first counting module and the second counting module count independently. The amplitude and phase of the first modulation signal and the second modulation signal can be extracted by performing a Fast Fourier Transform (FFT) on the counting results. This decouples the coupling information in the mixed laser signal and avoids crosstalk from other frequency signals.

[0066] The count value of time marker n It can be expressed as the following formula (2).

[0067] (2)

[0068] Where A1 is the amplitude of the first modulation signal. A1 represents the phase of the first modulation signal, and A2 represents the amplitude of the second modulation signal. The phase of the second modulation signal, Let n be the frequency of the second modulation signal, which is the third frequency, and n satisfies 0 ≤ n < N.

[0069] Using the number of counting window points N as the window length for the Fast Fourier Transform (FFT), the counting results are processed by FFT, and the frequency domain signal corresponding to the counting results can be obtained as shown in the following formula (3). .

[0070] (3)

[0071] Wherein, the frequency domain index k satisfies 0 ≤ k < N. Let k be... The corresponding spectral value can correspond to the demodulation information of the first modulating signal, while the discrete frequency of the second modulating signal... When the frequency is not an integer, that is, when the third frequency of the second modulation signal does not fall on the discrete frequency point of the frequency domain signal, the energy will spread to the adjacent frequency domain, resulting in spectral leakage. This leads to inaccurate amplitude and phase extracted from the frequency domain signal. Therefore, the amplitude and phase can be extracted according to the following formula (4).

[0072] (4)

[0073] Where A is Amplitude information; yes The phase information is mainly composed of the phase of the first modulation signal. Decide.

[0074] The number of points in the FFT window is equal to the total number of counting channels in the first or second counting module.

[0075] According to embodiments of this disclosure, based on frequency division multiplexing counting, a mixed laser signal obtained by driving laser sources of different wavelengths with modulation signals of different modulation frequencies is incident on the tissue under test. Multiple counting modules are triggered to count according to the synchronization signals corresponding to the corresponding modulation signals. Since the mixed laser signal is coupled with the information of the first laser signal and the second laser signal, it is possible to simultaneously acquire information at different depths in the tissue under test. The amplitude and phase information corresponding to different modulation signals are extracted by demodulating the counting results of the two counting modules, thereby improving the accuracy and comprehensiveness of the detection of the object under test and shortening the detection time. This enables the processing module to achieve sub-nanosecond level electrical signal acquisition based on the multi-phase first clock signal.

[0076] According to embodiments of the present disclosure, a clock submodule is configured to multiply a preset reference clock to obtain a first clock signal; and a synchronization submodule is configured to generate synchronization pulses for each of the multiple counting channels based on the synchronization signal for each counting module.

[0077] According to embodiments of this disclosure, the clock submodule can multiply a preset reference clock using a phase-locked loop to obtain multiple first clock signals with equally spaced clock periods relative to the preset reference clock. The frequency of the preset reference clock can be 50MHz. For each counting module, the synchronization submodule can generate a synchronization pulse based on a synchronization signal through two-stage register operations. Specifically, for each counting channel, the pulse width of the synchronization pulse is time-aligned with one clock period of the first clock signal; that is, the rising edge of the synchronization pulse is strictly aligned with the corresponding first clock signal. This ensures that each of the multiple counting channels resets its time mark on the rising edge of the synchronization pulse, achieving timing uniformity across the multiple counting channels.

[0078] According to an embodiment of this disclosure, the synchronization submodule includes: a first flip-flop configured to output a first registered signal based on a synchronization signal under the drive of a first clock signal; a second flip-flop configured to output a second registered signal based on the first registered signal under the drive of the first clock signal; and an XOR gate configured to generate a synchronization pulse based on the first registered signal and the second registered signal.

[0079] According to embodiments of this disclosure, the clock input of the first flip-flop can be connected to a first clock signal, and the data input can be connected to a synchronization signal, outputting a first registered signal. The clock input of the second flip-flop is also connected to the first clock signal, and the data input is connected to the first registered signal, outputting a second registered signal. The first input of the XOR gate is connected to the first registered signal, and the second input is connected to the second registered signal. An XOR logic operation is performed, and a high level is output only when the levels input to the two inputs are different, thereby generating a synchronization pulse whose rising edge is strictly aligned with the corresponding first clock signal, eliminating the risk of metastability.

[0080] According to embodiments of this disclosure, the processing module is configured to determine the target counting channel according to the following formula (5):

[0081] signal_sift(i)=signal_rise(i)&&(!signal_rise(i-1))&&(!signal_union)(5)

[0082] Where && represents the logical AND operation, ! represents the NOT operation, i is the counting channel index, signal_sift(i) represents the target trigger signal of the target counting channel corresponding to the first electrical pulse responded to, signal_rise(i) represents the response to the current electrical pulse in counting channel i, signal_rise(i-1) represents the response to the current electrical pulse in counting channel i-1, and signal_union represents the joint register signal of multiple counting channels responding to the current electrical pulse. The joint register signal can be expressed as the following formula (6).

[0083] (6)

[0084] in, The logical OR operation is represented by signal_rise_reg (1), signal_rise_reg (2), and signal_rise_reg (I), where I is the total number of counting channels included in each of the multiple counting modules.

[0085] Therefore, it can be seen that only when the i-th counting channel responds to the current electrical pulse, and the preceding counting channel (i-1) of the i-th counting channel does not respond to the current electrical pulse, and the joint register signal is not triggered, can the i-th counting channel be determined as the target counting channel. Using a priority encoder, the target counting channel obtained by the above formula (5) can avoid the electrical pulse corresponding to a single photon event being marked by multiple counting channels at the same time, thereby causing repeated counting.

[0086] According to embodiments of this disclosure, each of the multiple counting modules further includes multiple shift registers corresponding to multiple counting channels. For each shift register, multiple bits of the shift register correspond one-to-one with multiple time markers in the counting channel. Each shift register is reset to its initial state in response to the synchronization pulse of the corresponding counting channel. The initial state indicates that only the least significant bit is set to 1. The shift register corresponding to the target counting channel is configured to shift sequentially in each counting cycle to set the bit corresponding to the target time marker to 1. The target time marker represents the time marker corresponding to the response time.

[0087] Taking the first counting module as an example, each counting channel includes 10 time markers. Therefore, the shift register corresponding to each counting channel is also 10 bits. The shift register is reset to its initial state with only the least significant bit set to 1 under the trigger of the synchronization signal. Then, in each clock cycle of the first clock signal, it shifts left sequentially until the least significant bit (1) is moved to the bit corresponding to the time marker corresponding to the response time, i.e., the bit corresponding to the target time marker is set to 1. At this time, all other bits are 0. To better understand the working principle of the above-mentioned frequency-domain near-infrared spectroscopy detection device based on photon counting, the following will explain... Figure 4 Further explanation is needed.

[0088] Figure 4 The schematic diagram illustrates the working principle of a frequency-domain near-infrared spectroscopy detection device based on photon counting according to an embodiment of the present disclosure.

[0089] like Figure 4 As shown, taking two signal generation submodules as an example, each submodule includes a co-phase / inverting signal generator. Under the control of control signal 1 and control signal 2 generated by the system control module, they output a first output signal and a second output signal that are inversely phased. These signals are then transmitted through a first power divider and a second power divider to obtain a modulation signal and a comparison signal. In one signal generation submodule, the comparison unit generates a first synchronization signal (SYNC_1) based on the first comparison signal and the second comparison signal output by the first and second power dividers, and inputs it to the synchronization submodule. Simultaneously, it inputs the generated first modulation signal to the first semiconductor laser in the driver submodule. Correspondingly, for the other signal generation submodule, the comparison unit generates a second synchronization signal (SYNC_2) based on the first and second comparison signals output by the first and second power dividers, and inputs it to the synchronization submodule. Simultaneously, it inputs the second modulation signal to the second semiconductor laser in the driver submodule.

[0090] The first semiconductor laser in the driving submodule corresponds to a 660nm wavelength laser source, and the second semiconductor laser corresponds to an 830nm wavelength laser source. Under the control of their respective current controllers and temperature controllers, the first and second semiconductor lasers generate a first laser signal and a second laser signal based on a first modulation signal and a second modulation signal, respectively. These two laser signals are then input to the optical output submodule for coupling to obtain a mixed laser signal. The optical output submodule uses an optical fiber combiner to project the mixed laser signal onto the fiber array on the surface of the object under test via the incident optical fiber. The mixed laser signal passes through the object under test, and after being acted upon by the object, it is emitted through the exit optical fiber to the sampling submodule in the processing module. The sampling submodule captures the emitted photons using a photomultiplier tube, thereby converting them into an electrical signal.

[0091] Taking a counting module with four counting channels as an example, the clock submodule in the processing module multiplies the preset reference clock (sys_clk) into four first clock signals (clk1~clk4). The synchronization submodule converts the first synchronization signal (SYNC_1) and the second synchronization signal (SYNC_2) into synchronization pulses (sync_rise1~sync_rise4) for each of the multiple counting channels. The processing module samples the electrical signal (signal) simultaneously based on the four first clock signals. Using the priority encoder in the processing submodule, the counting channel that responds to the electrical pulse first is determined as the target counting channel, and four target trigger signals (signal_sift1~signal_sift4) are generated. Only one of signal_sift1~signal_sift4 is high. The high-level target trigger signal indicates that the counting channel with the corresponding index is the target counting channel.

[0092] The counting module (only a single counting module is shown in the figure for ease of understanding) performs the following operations under the control of the control signal 3 of the system control module: Based on the four first clock signals (clk1~clk4) generated by the clock submodule, the four synchronization pulses (sync_rise1~sync_rise4) generated by the synchronization submodule, and the four target trigger signals (signal_sift1~signal_sift4) obtained by the processing submodule, it counts within the time marks (taking 10 as an example) in each counting channel, and splices all the time marks in each counting channel in time (phase) order to obtain the counting result and send it to the system control module, and finally back to the host computer for image reconstruction.

[0093] To better understand the above Figure 4 The timing relationship of each signal in the process will be explained below through... Figures 5A-5D Please provide a detailed explanation.

[0094] Figure 5A A timing diagram of a first clock signal and a preset reference clock according to an embodiment of the present disclosure is illustrated schematically.

[0095] like Figure 5A As shown, taking a preset reference clock (sys_clk) with a frequency of 50MHz as an example, the phase-locked loop multiplies the frequency to produce four first clock signals (clk: clk1~clk4) with a phase difference between each other, providing a timing basis for multi-channel parallel counting.

[0096] Figure 5B A timing diagram of a synchronization signal according to an embodiment of the present disclosure is illustrated schematically.

[0097] like Figure 5B As shown, taking the first synchronization signal (SYNC_1) as an example, under the drive of the first clock signal (clk), the first register signal (sync_reg1) is output through the first flip-flop, and then the second register signal (sync_reg2) is output through the second flip-flop. The first register signal (sync_reg1) and the second register signal (sync_reg2) are input into the XOR gate to generate a synchronization pulse (sync_rise). The two-stage register and XOR operation ensure that the pulse width of the obtained synchronization pulse (sync_rise) is equal to one clock cycle (clk) of the first clock signal.

[0098] Figure 5C A timing diagram of the joint register signal and the target trigger signal according to an embodiment of the present disclosure is illustrated.

[0099] like Figure 5C As shown, the electrical signal (signal) undergoes two levels of registering and XOR operation to generate four rising edge signals (signal_rise1~signal_rise4). The four rising edge signals are then combined into a joint register signal (signal_union) by a logic OR gate. After the joint register signal is triggered, the counting channel that responds first is selected according to the rule shown in the above formula (5) in the priority encoder. In the figure, only the target trigger signal (signal_sift4) corresponding to the fourth counting channel has a high level, while the other target trigger signals (signal_sift1~signal_sift3) are all set to low level. That is, the target counting channel corresponding to the current electrical signal is the counting channel corresponding to clk4.

[0100] Figure 5D The timing diagram of the counting module is shown schematically.

[0101] like Figure 5D As shown, each counting channel includes 10 time markers (cnt_photon_1…cnt_photon_10), therefore the shift register (shift_bin[9:0]) corresponding to each counting channel is also 10 bits, driven by the first clock signal (clk). The shift register (shift_bin) is reset to its initial state (shift_bin[0]=1'b1, shift_bin[9:1]=9'b0) when the synchronization pulse (sync_rise) is high, and then shifted to the left sequentially in each clock cycle of the first clock signal (as shown in shift_bin). 1) Dynamically switch the current count time stamp (from shift_bin=10'b00…1→…→shift_bin=10'b10…0).

[0102] The target trigger signal (signal_sift) triggers the corresponding response marker (cnt_photon_i) to count. Specifically, the target trigger signal (signal_sift) triggers the time marker (cnt_photon_i) corresponding to the bit (shift_bin[i]=1'b1) that is currently high in the shift register to be incremented by one.

[0103] Figure 6 A flowchart illustrating a frequency-domain near-infrared spectroscopy detection method based on photon counting according to an embodiment of the present disclosure is shown.

[0104] like Figure 6 As shown, the method 600 includes operations S610 to S630.

[0105] In operation S610, incident light is emitted to the object under test, outgoing light is received from the object under test, and an electrical signal is generated in response to the outgoing light.

[0106] The incident light is obtained by coupling multiple laser signals with different modulation frequencies.

[0107] In operation S620, based on the first clock signal associated with each of the parallel multi-channel counting channels, the electrical signal is sampled to determine the target counting channel from the multi-channel counting channels according to the electrical pulse that is responded to first in the electrical signal.

[0108] Among them, the first clock signals of each of the multiple counting channels have the same frequency and a phase difference with each other.

[0109] In operation S630, based on a synchronization signal that is phase-synchronized with the modulation signal, the response time of the first electrical pulse to be responded to in the target counting channel is determined, and photon counting is performed within the time scale corresponding to the response time to generate a counting result.

[0110] The counting result includes a combination of the photon counts accumulated within the time scales of each of the multiple counting channels, arranged in chronological order.

[0111] It should be noted that the part on the frequency domain near-infrared spectroscopy detection method based on photon counting in the embodiments of this disclosure corresponds to the part on the frequency domain near-infrared spectroscopy detection device based on photon counting in the embodiments of this disclosure. For a detailed description of the part on the frequency domain near-infrared spectroscopy method based on photon counting, please refer to the part on the frequency domain near-infrared spectroscopy detection device based on photon counting, which will not be repeated here.

[0112] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present disclosure. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions configured to perform a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram or flowchart, and combinations of blocks in a block diagram or flowchart, may be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions. Those skilled in the art will understand that the features described in the various embodiments of the present disclosure can be combined and / or combined in various ways, even if such combinations are not explicitly described in the present disclosure. In particular, the features described in the various embodiments of this disclosure may be combined and / or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0113] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A photon counting based frequency domain near infrared spectroscopy detection device, characterized in that, include: An optoelectronic module is configured to emit incident light to a test object, receive outgoing light from the test object, and generate an electrical signal in response to the outgoing light, wherein the incident light is obtained by coupling multiple laser signals with different modulation frequencies; Multiple counting modules, each including parallel multi-channel counting channels, each multi-channel counting channel having an associated first clock signal, the first clock signals of each multi-channel counting channel having a first frequency and a phase difference relative to each other; and The processing module is configured to sample the electrical signal based on the first clock signal of each of the multiple counting channels, so as to determine the target counting channel from the multiple counting channels of each of the multiple counting modules according to the electrical pulse that is first responded to in the electrical signal. Specifically, each of the counting modules is configured to determine the response time of the first electrical pulse in the target counting channel based on a synchronization signal that is phase-synchronized with the modulation signal, and to count photons within a time scale corresponding to the response time to generate a counting result, which includes a combination of the photon counts accumulated within the time scales of each of the multiple counting channels in chronological order.

2. The frequency domain near infrared spectroscopy apparatus according to claim 1, wherein, The plurality of laser signals includes a first laser signal and a second laser signal, and the optoelectronic module includes: The signal generation submodule is configured to generate multiple modulation signals, wherein the multiple modulation signals include a first modulation signal having a second frequency and a second modulation signal having a third frequency; The driving submodule is configured to drive a first semiconductor laser having a first wavelength and a second semiconductor laser having a second wavelength based on the first modulation signal and the second modulation signal, respectively, to generate the first laser signal and the second laser signal; and The optical output submodule is configured to couple the first laser signal and the second laser signal into a mixed laser signal, and to incident the mixed laser signal onto the object under test.

3. The frequency domain near infrared spectroscopy apparatus according to claim 1, wherein The processing module is configured to determine the target counting channel according to the following formula: signal_sift(i)=signal_rise(i)&&(!signal_rise(i-1))&&(!signal_union); Where && represents a logical AND operation, ! represents a negation operation, i is the index of the counting channel, signal_sift(i) represents the target trigger signal of the target counting channel corresponding to the first electrical pulse that is responded to, signal_rise(i) represents the electrical pulse that is responded to in counting channel i, signal_rise(i-1) represents the electrical pulse that is responded to in counting channel i-1, and signal_union represents the joint register signal of the multiple counting channels responding to the electrical pulse.

4. The frequency domain near-infrared spectroscopy detection device according to claim 3, characterized in that, The processing module is configured to determine the joint register signal according to the following formula: signal_union=signal_rise_reg(1) signal_rise_reg(2) …… signal_rise_reg(I); in, The expression represents a logical OR operation. signal_rise_reg (1) represents the registered signal of signal_rise(1), signal_rise_reg (2) represents the registered signal of signal_rise(2), signal_rise_reg (I) represents the registered signal of signal_rise(I), and I is the total number of counting channels included in each of the multiple counting modules.

5. The frequency domain near-infrared spectroscopy detection device according to claim 2, characterized in that, The signal generation submodule is also configured to generate the synchronization signal; The processing module includes: The clock submodule is configured to multiply a preset reference clock to obtain the first clock signal; and The synchronization submodule is configured to generate a synchronization pulse for each of the multiple counting channels based on the synchronization signal for each of the counting modules; Specifically, for each of the counting channels, the pulse width of the synchronization pulse of the counting channel is equal to one clock cycle of the first clock signal.

6. The frequency domain near-infrared spectroscopy detection device according to claim 3, characterized in that, Each of the counting modules is configured to trigger photon counting in the multiple counting channels based on the synchronization pulse of the multiple counting channels, and the total number of time markers in each counting channel is determined according to the ratio of the first frequency to the frequency of the corresponding modulation signal.

7. The frequency domain near-infrared spectroscopy detection device according to claim 6, characterized in that, Each of the multiple counting modules further includes multiple shift registers corresponding to the multiple counting channels. For each shift register, multiple bits of the shift register correspond one-to-one with multiple time markers in the counting channel. Each shift register is reset to its initial state in response to the synchronization pulse of the corresponding counting channel. The initial state indicates that only the least significant bit is set to 1. The shift register corresponding to the target counting channel is configured to shift sequentially in each counting cycle to set the bit corresponding to the target time marker to 1. The target time marker represents the time marker corresponding to the response time.

8. The frequency domain near-infrared spectroscopy detection device according to claim 2, characterized in that, The signal generation submodule includes: An in-phase / out-of-phase signal generator is configured to generate a first output signal and a second output signal that are out of phase with each other; A first power divider is configured to receive the first output signal and output the modulated signal and the first comparison signal; The second power divider is configured to receive the second output signal and output a second comparison signal; The comparison unit is configured to obtain the synchronization signal by comparing the first comparison signal and the second comparison signal.

9. The frequency domain near-infrared spectroscopy detection device according to claim 5, characterized in that, The synchronization submodule includes: The first flip-flop is configured to output a first register signal based on the synchronization signal under the drive of the first clock signal; The second flip-flop is configured to output a second register signal based on the first register signal under the drive of the first clock signal; An XOR gate is configured to generate the synchronization pulse based on the first registered signal and the second registered signal.

10. A frequency-domain near-infrared spectroscopy detection method based on photon counting, characterized in that, include: An incident light is emitted to the object under test, an outgoing light is received from the object under test, and an electrical signal is generated in response to the outgoing light, wherein the incident light is obtained by coupling multiple laser signals with different modulation frequencies; Based on the first clock signal associated with each of the parallel multi-channel counting channels, the electrical signal is sampled to determine the target counting channel from the multi-channel counting channels according to the electrical pulse that is responded to first in the electrical signal, wherein the first clock signals of each of the multi-channel counting channels have the same frequency and have a phase difference with each other; Based on a synchronization signal that is phase-synchronized with the modulation signal, the response time of the first electrical pulse to be responded to in the target counting channel is determined, and photon counting is performed within the time scale corresponding to the response time to generate a counting result, wherein the counting result includes a combination of the photon counts accumulated within the time scales of each of the multiple counting channels in chronological order.

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