Fourier infrared spectrometer data acquisition system and spectrum processing method

Abstract

The invention provides a Fourier infrared spectrometer data acquisition system and a spectrum processing method. According to the Fourier infrared spectrometer data acquisition system, through square wave processing and resampling, first-type digital signals subjected to isochronous sampling are converted into second-type digital signals, interference signals with equal optical path difference are arranged between adjacent sampling points of the second-type digital signals, the accuracy of Fourier transform is improved, and the accuracy of Fourier transform is improved. At least two groups of second type digital signals can be obtained in one scanning period, so that the analysis efficiency is improved; and for the obtained at least two groups of second type digital signals, Fourier transform can be respectively performed on the at least two groups of second type digital signals to obtain at least two groups of spectrograms, and an output spectrogram is generated according to the at least two groups of spectrograms, so that random noise is reduced, the signal-to-noise ratio of the Fourier infrared spectrometer is improved, and furthermore, the detection accuracy of the Fourier infrared spectrometer is improved. The availability of the spectrum and the accuracy of quantitative analysis are improved.

Description

Technical Field

[0001] The present application relates to the field of optical analysis technology, and in particular to a Fourier transform infrared spectrometer data acquisition system and a spectrum processing method. Background Art

[0002] Fourier Transform Infrared Spectrometer (FTIR) is an infrared spectroscopy analysis instrument based on the principle of interferometric frequency modulation. The basic principle is to convert the interference signal into an infrared spectrum through Fourier transform to obtain the chemical composition and structural information of the sample.

[0003] During operation, the Fourier transform infrared spectrometer will be affected by noises such as environmental noise and signal processing noise, which will lead to a decrease in the signal-to-noise ratio, reduce the availability of the spectrum and the accuracy of quantitative analysis.

[0004] Therefore, how to improve the signal-to-noise ratio of Fourier transform infrared spectrometer has become a hot research direction. Summary of the Invention

[0005] In view of this, the present application provides a Fourier transform infrared spectrometer data acquisition system and a spectrum processing method.

[0006] Specifically, this application is implemented through the following technical solutions:

[0007] According to a first aspect of an embodiment of the present application, a Fourier transform infrared spectrometer data acquisition system is provided, comprising: an interference signal generating unit, an interference signal detecting unit, an analog-to-digital conversion (ADC) sampling unit, a data processing unit, and at least one square wave conversion unit; wherein:

[0008] An interference signal generating unit, configured to generate an interference signal; wherein the interference signal comprises a laser interference signal or an infrared interference signal;

[0009] an interference signal detection unit, configured to convert the laser interference signal into a first type of electrical signal; and to convert the infrared interference signal absorbed by the sample to be tested into a second type of electrical signal;

[0010] an ADC sampling unit, configured to convert the second type of electrical signal into a first type of digital signal;

[0011] at least one square wave conversion unit, configured to perform square wave processing on the first type of electrical signal to obtain at least one square wave signal;

[0012] A data processing unit is used to resample the first type of digital signal according to the time sequence corresponding to the rising edge of the at least one square wave signal, and to resample the first type of digital signal according to the time sequence corresponding to the falling edge of the at least one square wave signal to obtain at least two groups of second type digital signals, and to perform Fourier transform on the at least two groups of second type digital signals to obtain at least two groups of spectra, and to generate an output spectra based on the at least two groups of spectra; wherein, adjacent sampling points of the second type digital signal are interference signals with equal optical path differences.

[0013] According to a second aspect of an embodiment of the present application, a spectrum processing method is provided, which is applied to a data processing unit in the Fourier spectrometer data acquisition system provided in the first aspect. The method includes:

[0014] Acquire the first type of digital signal, a time sequence corresponding to a rising edge of the at least one square wave signal, and a time sequence corresponding to a falling edge of the at least one square wave signal;

[0015] Resampling the first type of digital signal according to a time sequence corresponding to a rising edge of the at least one square wave signal, and resampling the first type of digital signal according to a time sequence corresponding to a falling edge of the at least one square wave signal, to obtain at least two groups of second type digital signals; wherein adjacent sampling points of the second type digital signal are interference signals with equal optical path differences;

[0016] Fourier transform is performed on the at least two groups of second-type digital signals respectively to obtain at least two groups of spectrograms, and an output spectrogram is generated based on the at least two groups of spectrograms.

[0017] The Fourier infrared spectrometer data acquisition system of the embodiment of the present application introduces at least one square wave unit, and uses the at least one square wave unit to square wave the first type of electrical signal obtained by converting the laser interference signal to obtain at least one square wave signal. Furthermore, for the second type of electrical signal converted from the infrared interference signal after absorption by the sample to be tested, the data processing unit can resample the first type of digital signal according to the time sequence corresponding to the rising edge of the at least one square wave signal, and resample the first type of digital signal according to the time sequence corresponding to the falling edge of the at least one square wave signal to obtain at least two groups of second type digital signals, through Through square wave processing and resampling, the first type of digital signal sampled at the same time is converted into a second type of digital signal. Adjacent sampling points of the second type of digital signal are interference signals with equal optical path differences, thereby improving the accuracy of Fourier transform, and at least two groups of second type digital signals can be obtained within one scanning cycle, thereby improving analysis efficiency; for the at least two groups of second type digital signals obtained, the at least two groups of second type digital signals can be Fourier transformed respectively to obtain at least two groups of spectra, and an output spectrum is generated based on the at least two groups of spectra, thereby reducing random noise, improving the signal-to-noise ratio of the Fourier infrared spectrometer, and further improving the availability of the spectrum and the accuracy of quantitative analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a structural diagram of a Fourier transform infrared spectrometer data acquisition system according to an exemplary embodiment of the present application;

[0019] Figure 2 A schematic diagram of an optical path of an interference signal generating unit used in an exemplary embodiment of the present application;

[0020] Figure 3 This is a structural diagram of a Fourier transform infrared spectrometer data acquisition system according to an exemplary embodiment of the present application;

[0021] Figure 4 This is a schematic diagram of square wave processing shown in an exemplary embodiment of the present application;

[0022] Figure 5 This is a schematic diagram of a data processing flow of a Fourier transform infrared spectrometer data acquisition system according to an exemplary embodiment of the present application;

[0023] Figure 6 The figure is a flow chart of a spectrum processing method according to an exemplary embodiment of the present application. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the technical solutions provided by the embodiments of the present application, and to make the above-mentioned purposes, features and advantages of the embodiments of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application are further described in detail below with reference to the accompanying drawings.

[0025] See Figure 1 , is a structural diagram of a Fourier transform infrared spectrometer data acquisition system provided in an embodiment of the present application, such as Figure 1 As shown, the Fourier transform infrared spectrometer data acquisition system may include: an interference signal generating unit 110, an interference signal detecting unit 120, an ADC (Analog-to-Digital Conversion) sampling unit 130, a data processing unit 140, and at least one square wave unit 150 ( Figure 1 Only one square wave unit is shown in FIG); wherein:

[0026] The interference signal generating unit 110 is configured to generate an interference signal, wherein the interference signal includes a laser interference signal or an infrared interference signal;

[0027] The interference signal detection unit 120 is used to convert the laser interference signal into a first type of electrical signal; and convert the infrared interference signal after being absorbed by the sample to be tested into a second type of electrical signal;

[0028] an ADC sampling unit 130, configured to convert the second type of electrical signal into a first type of digital signal;

[0029] at least one square wave conversion unit 150, configured to perform square wave processing on the first type of electrical signal to obtain at least one square wave signal;

[0030] The data processing unit 140 is used to resample the first type of digital signal according to the time series corresponding to the rising edge of the at least one square wave signal, and to resample the first type of digital signal according to the time series corresponding to the falling edge of the at least one square wave signal to obtain at least two groups of second type digital signals, and to perform Fourier transform on the at least two groups of second type digital signals to obtain at least two groups of spectra, and to generate an output spectra based on the at least two groups of spectra; wherein the second type of digital signal corresponds to an equal optical path interference signal.

[0031] In the embodiment of the present application, in order to achieve cost and structure analysis of the sample to be tested, an infrared interference signal can be generated by an interference signal generating unit.

[0032] In one example, the interference signal generating unit may generate an infrared interference signal by performing interference processing on an infrared light signal generated by an infrared light source.

[0033] For example, the interference signal generating unit can split the infrared light signal generated by the infrared light source into two beams through a beam splitter. The two infrared light signals are respectively reflected by the fixed mirror and the movable mirror and then recombined to form an interference light signal (referred to as interference signal).

[0034] For example, the optical path difference can be changed by moving the moving mirror, and the infrared interference signal can contain infrared light information of all frequencies.

[0035] The infrared interference signal generated by the interference signal generating unit can be irradiated on the sample to be tested by the spectral system, and the sample characteristic peak is absorbed by the sample to be tested (that is, light of a specific wavelength is absorbed by the molecules of the sample to be tested), and a characteristic peak will appear in the corresponding spectral intensity (that is, a characteristic absorption peak is formed on the spectrum).

[0036] The infrared interference signal after absorption (by the sample to be tested) can be used for cost and structure analysis of the sample to be tested.

[0037] Exemplarily, the interference signal detection unit can convert the absorbed infrared interference signal into an electrical signal based on the signal strength of the infrared interference signal after being absorbed by the sample to be tested, thereby obtaining a corresponding electrical signal (which can be called a second type of electrical signal), and the second type of electrical signal can be subjected to analog-to-digital conversion processing by the ADC sampling unit to obtain a corresponding digital signal (which can be called a first type of digital signal). Furthermore, the first type of digital signal can be used to generate a spectrum graph for cost and structure analysis of the sample to be tested.

[0038] In the embodiment of the present application, considering that the first type of digital signal obtained by ADC sampling is an isochronous sampling signal, due to fluctuations in the motor speed (the motor is used to control the movement of the moving mirror) and other reasons, adjacent sampling points usually have non-equal optical path differences, and the Fourier infrared spectrometer requires data with equal optical path differences (equal spatial intervals) (because the mathematical basis of the Fourier transform requires that the independent variable (optical path difference) is uniformly distributed), therefore, the accuracy of the Fourier transform based on the above-mentioned first type of digital signal will be relatively poor, which will in turn affect the performance of cost and structural analysis of the sample to be tested.

[0039] Taking the above problems into consideration, in an embodiment of the present application, a laser calibration mechanism can be used to convert the above-mentioned first type of digital signal into a digital signal with equal optical path difference. Then, a spectrum graph can be generated based on the converted digital signal with equal optical path difference, thereby optimizing the performance of cost and structural analysis of the sample to be tested.

[0040] Correspondingly, the interference signal generated by the interference signal generating unit may also include a laser interference signal, and the laser interference signal may be converted into an electrical signal (which may become a second type of electrical signal) by the laser interference signal detecting unit.

[0041] In one example, the interference signal generating unit may generate a laser interference signal by performing interference processing on a laser signal generated by a laser light source.

[0042] Exemplarily, the interference signal detection unit may further convert the laser interference signal into an electrical signal according to the signal intensity of the laser interference signal.

[0043] Considering that every time the moving mirror in the Fourier infrared spectrometer moves a laser interference signal distance, the intensity of the laser interference signal will show a sinusoidal periodic change.

[0044] For example, Figure 2 Taking the optical path diagram of the interference signal generating unit shown in the figure as an example, a beam of light is split into two coherent lights after passing through the beam splitter of the interference signal generating unit, and is reflected by the fixed mirror and the moving mirror respectively; when the moving mirror moves a distance of λ / 2, the optical path difference travels a distance of λ, and the intensity change of the interference signal formed shows a periodic change.

[0045] It can be seen that each period of the laser interference signal corresponds to the same laser interference signal distance, and based on this, the first type of digital signal can be converted into equal optical path difference data.

[0046] Exemplarily, the first type of electrical signal may be squared by at least one square wave unit to obtain at least one square wave signal.

[0047] In one example, the square wave conversion unit may perform square wave processing on the first type of electrical signal according to a preset voltage threshold.

[0048] Exemplarily, for any preset voltage threshold, the square wave unit can compare the signal strength (taking voltage as an example) of the first type of electrical signal with the preset voltage threshold; the part of the first type of electrical signal whose signal strength is greater than the preset voltage threshold is converted into a low-level signal after square wave processing; the part of the first type of electrical signal whose signal strength is less than the preset voltage threshold is converted into a high-level signal after square wave processing.

[0049] In the embodiment of the present application, the laser is a highly coherent light source with an extremely narrow wavelength range (single wavelength), and the laser interference signal is usually a relatively simple cosine wave. Based on this, for the square wave signal obtained by square-wave processing of the above-mentioned first type of electrical signal, the time series corresponding to its rising edge (falling edge) can be regarded as a time series corresponding to equal optical path differences.

[0050] The time in the above time series refers to a time point (or moment).

[0051] For example, assuming that t1, t2, and t3 are times corresponding to three consecutive rising edges of a square wave signal, the optical path corresponding to the time interval t1-t2 is the same as the optical path corresponding to the time interval t2-t3.

[0052] Accordingly, the data processing unit can resample the first type of digital signal according to the time series corresponding to the rising edge of at least one square wave signal to obtain at least one group of resampled digital signals (which can be called second type digital signals), and resample the first type of digital signal according to the time series corresponding to the falling edge of at least one square wave signal to obtain at least one group of second type digital signals.

[0053] Exemplarily, adjacent sampling points of the second type of digital signal are interference signals with equal optical path differences.

[0054] For example, assuming that there is one square wave signal, the data processing unit may resample the first type of digital signal according to the time sequence corresponding to the rising edge of the square wave signal to obtain a set of second type digital signals.

[0055] On the other hand, the data processing unit may resample the first type of digital signal according to the time sequence corresponding to the falling edge of the square wave signal to obtain a set of second type digital signals.

[0056] For another example, assuming that the number of square wave signals is N (N≥2), then for any square wave signal, on the one hand, the data processing unit can resample the first type of digital signal according to the time series corresponding to the rising edge of the square wave signal to obtain a set of second type digital signals.

[0057] On the other hand, the data processing unit may resample the first type of digital signal according to the time sequence corresponding to the falling edge of the square wave signal to obtain a set of second type digital signals.

[0058] Thus, the data processing unit can obtain 2N groups of second type digital signals.

[0059] It should be noted that, in the embodiment of the present application, for at least one square wave signal obtained by the square wave conversion unit when performing square wave processing on the first type of electrical signal, the square wave conversion unit can record the rising edge time sequence and the falling edge time sequence of each square wave signal, and output the rising edge time sequence and the falling edge time sequence of each square wave signal to the data processing unit, and the data processing unit resamples the first type of digital signal based on the rising edge time sequence and the falling edge time sequence of each square wave signal.

[0060] Alternatively, the square wave conversion unit may output the obtained at least one square wave signal to the data processing unit, which obtains the rising edge time sequence and the falling edge time sequence of each square wave signal, and then resamples the first type of digital signal based on the rising edge time sequence and the falling edge time sequence of each square wave signal.

[0061] In an embodiment of the present application, when the data processing unit obtains at least two groups of second-type digital signals as described above, it can perform Fourier transform on the at least two groups of second-type digital signals respectively to obtain at least two groups of spectra, and generate an output spectra based on the at least two groups of spectra, thereby reducing random noise and improving the signal-to-noise ratio of the Fourier transform infrared spectrometer, thereby improving the availability of the spectrum and the accuracy of quantitative analysis.

[0062] It can be seen that in Figure 1 In the data acquisition system of the Fourier infrared spectrometer shown in the figure, at least one square wave unit is introduced, and the first type of electrical signal obtained by converting the laser interference signal is squared by the at least one square wave unit to obtain at least one square wave signal. Furthermore, for the second type of electrical signal obtained by converting the infrared interference signal after being absorbed by the sample to be tested, the data processing unit can resample the first type of digital signal according to the time sequence corresponding to the rising edge of the at least one square wave signal, and resample the first type of digital signal according to the time sequence corresponding to the falling edge of the at least one square wave signal to obtain at least two groups of second type digital signals. Wavelet processing and resampling convert the first type of digital signal sampled at the same time into a second type of digital signal. Adjacent sampling points of the second type of digital signal are interference signals with equal optical path difference, thereby improving the accuracy of Fourier transform and obtaining at least two groups of second type digital signals within one scanning cycle, thereby improving analysis efficiency. For the at least two groups of second type digital signals obtained, the at least two groups of second type digital signals can be Fourier transformed respectively to obtain at least two groups of spectra, and an output spectrum is generated based on the at least two groups of spectra, thereby reducing random noise and improving the signal-to-noise ratio of the Fourier infrared spectrometer, thereby improving the availability of the spectrum and the accuracy of quantitative analysis.

[0063] In some embodiments, the interference signal generating unit 110 may include: a laser light source, an infrared light source, and an interferometer; the interference signal detecting unit 120 may include: a laser interference signal detecting unit and an infrared interference signal detecting unit; wherein:

[0064] A laser light source, used to generate a laser signal;

[0065] An infrared light source, used to generate an infrared light signal;

[0066] an interferometer, configured to generate a laser interference signal based on the laser signal, and to generate an infrared interference signal based on the infrared light signal;

[0067] a laser interference signal detection unit, configured to convert the laser interference signal into an electrical signal according to a signal strength of the laser interference signal to obtain a first type of electrical signal;

[0068] The infrared interference signal detection unit is used to convert the infrared interference signal absorbed by the sample to be tested into an electrical signal according to the signal strength of the infrared interference signal absorbed by the sample to be tested, so as to obtain a second type of electrical signal.

[0069] Exemplarily, the interference signal generating unit may include a laser light source for generating a laser signal, and an infrared light source for generating an infrared light signal.

[0070] The interference signal generating unit can generate a laser interference signal according to the laser light source signal and an infrared interference signal according to the infrared light source signal through an interferometer.

[0071] For the laser interference signal, the laser interference signal may be converted into a first type of electrical signal by the laser interference signal detection unit according to the signal intensity of the laser interference signal.

[0072] For the infrared interference signal, the infrared interference signal absorbed by the sample to be tested may be converted into a second type of electrical signal by the infrared interference signal detection unit according to the signal intensity of the infrared interference signal absorbed by the sample to be tested.

[0073] In some embodiments, the at least one square wave conversion unit 150 may include N square wave conversion units 150; N ≥ 2;

[0074] The plurality of square wave conversion units are specifically configured to convert the first type of electrical signal into a square wave signal according to corresponding preset voltage thresholds, thereby obtaining a plurality of square wave signals.

[0075] For example, in order to improve the noise reduction effect and further enhance the signal-to-noise ratio of the infrared spectrometer, the Fourier infrared spectrometer data acquisition system can use multiple square wave units to perform square wave processing on the first type of electrical signal to obtain multiple square wave signals. Then, the data processing unit can resample the first type of digital signal according to the rising edge time series of the multiple square wave signals, and resample the second type of digital signal according to the falling edge time series of the multiple square wave signals.

[0076] It should be noted that, considering that in practical applications, square wave processing is usually achieved through circuits, the more square wave units there are, the more complex and larger the circuit is, and the more computing resources will be consumed by the square wave processing and subsequent resampling processing. Therefore, it is necessary to balance the noise reduction effect, circuit complexity, and computing resource consumption.

[0077] Exemplarily, for any square-wave conversion unit among the plurality of square-wave conversion units, a corresponding voltage threshold may be set, and the square-wave conversion unit may perform square-wave processing on the first type of electrical signal according to the corresponding preset voltage threshold.

[0078] Exemplarily, the voltage threshold is within the amplitude range of the first type of electrical signal (smaller than the maximum value of the signal strength of the first type of electrical signal and larger than the minimum value of the signal strength of the first type of electrical signal).

[0079] In one example, the portion of the first type electrical signal whose signal strength is greater than a preset voltage threshold is converted into a low-level signal after square wave processing; the portion of the first type electrical signal whose signal strength is less than the preset voltage threshold is converted into a high-level signal after square wave processing.

[0080] In another example, the portion of the first type of electrical signal whose signal strength is less than a preset voltage threshold is converted into a low-level signal after square wave processing; the portion of the first type of electrical signal whose signal strength is greater than the preset voltage threshold is converted into a high-level signal after square wave processing.

[0081] For example, the square wave conversion unit can compare the signal strength of the first type of electrical signal with a corresponding preset voltage threshold. The portion of the first type of electrical signal with a signal strength greater than the preset voltage threshold is squared and converted into a low-level signal; and the portion of the first type of electrical signal with a signal strength less than the preset voltage threshold is squared and converted into a high-level signal.

[0082] Correspondingly, the data processing unit can resample the first type of digital signal according to the time series corresponding to the rising edge and the time series corresponding to the falling edge of each square wave signal in the N square wave signals to obtain 2N groups of second type digital signals, and perform Fourier transform on the 2N groups of second type digital signals to obtain 2N groups of spectrograms, and generate an output spectrogram based on the 2N groups of spectrograms.

[0083] Exemplarily, for any one of the N square wave signals, the data processing unit may resample the first type of digital signal according to the time sequence corresponding to the rising edge of the square wave signal, and resample the first type of digital signal according to the time sequence corresponding to the falling edge of the square wave signal to obtain two groups of second type digital signals corresponding to the square wave signal.

[0084] Exemplarily, N square wave signals may be processed in the above manner to obtain corresponding 2N groups of second-type digital signals.

[0085] In one example, the number of square wave conversion units is 2.

[0086] The plurality of square wave units 150 include a first square wave unit and a second square wave unit.

[0087] A first square wave conversion unit, configured to convert the first type of electrical signal into a first square wave signal according to a first preset voltage threshold;

[0088] The second square wave conversion unit is configured to convert the first type of electrical signal into a second square wave signal according to a second preset voltage threshold.

[0089] The first square wave conversion unit may convert the first type of electrical signal into a square wave signal (referred to as a first square wave signal) according to a corresponding preset voltage threshold (referred to as a first preset voltage threshold).

[0090] Similarly, the second square wave conversion unit can convert the first type of electrical signal into a square wave signal (which can be called a second square wave signal) according to a corresponding preset voltage threshold (which can be called a second preset voltage threshold).

[0091] Correspondingly, the data processing unit can resample the first type of digital signal according to the time series corresponding to the rising edge of the first square wave signal, resample the first type of digital signal according to the time series corresponding to the falling edge of the first square wave signal, resample the first type of digital signal according to the time series corresponding to the rising edge of the second square wave signal, and resample the first type of digital signal according to the time series corresponding to the falling edge of the second square wave signal to obtain four groups of second type digital signals, and perform Fourier transform on the four groups of second type digital signals to obtain four groups of spectrograms, and generate an output spectrogram based on the four groups of spectrograms.

[0092] In some embodiments, the data processing unit 140 can be specifically used to interpolate and resample the first type of digital signal based on the time series corresponding to the rising edge of at least one square wave signal, and to interpolate and resample the first type of digital signal based on the time series corresponding to the falling edge of at least one square wave signal.

[0093] Exemplarily, when the time sequence corresponding to the rising edge of at least one square wave signal and the time sequence corresponding to the falling edge of at least one square wave signal are determined, the interpolation resampling method can be used in the process of resampling the first type of digital signal.

[0094] Exemplarily, for any square wave signal, the optical path difference reference point can be marked according to the time series corresponding to the rising edge of the square wave signal, or the time series corresponding to the falling edge of the square wave signal, and the original isochronous sampling data can be interpolated and resampled to generate equally spaced optical path difference data (i.e., equal optical path difference data). Thus, equal optical path difference data can be obtained while allowing the mechanical movement of the moving mirror to be non-uniform, without relying on ultra-high precision motors, thereby reducing hardware costs.

[0095] In addition, since the optical path differences of the sampling points interpolated and resampled according to the time series corresponding to the rising edge or the time series corresponding to the falling edge of the same square wave signal are aligned, and the optical path differences of the sampling points interpolated and resampled according to the time series corresponding to the rising edge (or falling edge) of different square wave signals are also aligned, therefore, when the interpolation and resampling are performed in the above manner, the optical path differences between adjacent sampling points in different groups of second-type digital signals are aligned.

[0096] Based on this, the output spectrum can be obtained by averaging at least two groups of spectrum images obtained in the above manner, thereby effectively reducing random noise and improving the signal-to-noise ratio of the Fourier transform infrared spectrometer.

[0097] Accordingly, in one example, the data processing unit 140 may be specifically configured to perform averaging processing on at least two groups of spectrograms to generate an output spectrogram.

[0098] In order to enable those skilled in the art to better understand the technical solutions provided by the embodiments of the present application, the technical solutions provided by the embodiments of the present application are described below with reference to specific examples.

[0099] In this embodiment, the schematic diagram of the Fourier transform infrared spectrometer data acquisition system can be found in Figure 3 ,like Figure 3 As shown, the Fourier infrared spectrometer data acquisition system may include: a laser light source, an infrared light source, an interferometer, a laser interference signal detection unit, an infrared interference signal detection unit, an ADC sampling unit, a data processing system, and at least one square wave unit ( Figure 3 In the example, at least one square wave unit includes square wave unit 1 and square wave unit 2.

[0100] The infrared light signal generated by the infrared light source passes through the interferometer to form a broad-spectrum infrared interference signal. After passing through the sample to be tested, the sample's characteristic spectral peak is absorbed, and a characteristic peak appears in the corresponding spectral intensity. The absorbed infrared interference signal is converted into an electrical signal (i.e., the second type of electrical signal) by the infrared interference signal detection unit. After that, it is sampled by the ADC and converted into a digital signal (i.e., the first type of digital signal).

[0101] The laser signal generated by the laser light source forms a laser interference signal of a single wavelength after passing through the interferometer. After the laser interference signal is converted into an electrical signal (i.e., the first type of electrical signal mentioned above) by the laser interference signal detection unit, one or more square wave signals are obtained through square wave comparison of one or more different voltage thresholds.

[0102] In this embodiment, the electrical signal converted from the laser interference signal is compared with two fixed voltage thresholds (which can be recorded as level 1 and level 2) to obtain two different square wave signals (which can be respectively referred to as square wave signal 1 and square wave signal 2). The schematic diagram can be shown as follows: Figure 4 shown.

[0103] The number of rising edges (falling edges) and the corresponding time of the two square wave signals can be recorded separately (such as time t1 corresponding to the first rising edge of square wave signal 1, time t2 corresponding to the first rising edge of square wave signal 2, time t3 corresponding to the first falling edge of square wave signal 2, time t4 corresponding to the first falling edge of square wave signal 1, etc.).

[0104] Among them, such as Figure 4 As shown, the time series corresponding to the rising edge of square wave signal 1 (t 1_up ) and the time series corresponding to the falling edge (t 1_down ), and the time series corresponding to the rising edge of square wave signal 2 (t 2_up ) and the time series corresponding to the falling edge (t 2_down ) can be as follows:

[0105] t 1_up =t 4k-3 (k=1, 2, 3...)

[0106] t 1_down =t 4k (k=1, 2, 3...)

[0107] t 2_up =t 4k-2 (k=1, 2, 3...)

[0108] t 2_down =t 4k-1 (k=1, 2, 3...)

[0109] Among them, such as Figure 4 As shown, the time sequence corresponding to the rising edge of the square wave signal 1 may include t1, t5, t9, etc. The time sequence corresponding to the falling edge of the square wave signal 1 may include t4, t8, t 12 , ... etc. The time sequence corresponding to the rising edge of square wave signal 2 may include t2, t6, t 10, ... etc. The time sequence corresponding to the falling edge of square wave signal 2 may include t3, t7, t 11 ,…wait.

[0110] When the moving mirror moves a laser interference signal distance, the intensity change of the laser interference signal presents a sinusoidal periodic change.

[0111] For example, assuming that the distance of the laser interference signal is twice the distance of the motor movement, when the voice coil motor controls the movement of the moving mirror, the intensity change of the laser interference signal will show a sinusoidal periodic change every time the moving mirror moves λ / 2 distance (that is, the intensity change of the laser interference signal will show a sinusoidal periodic change every time the moving mirror moves λ / 2 distance).

[0112] For any of the above four time series, any two time points in the time series correspond to an intensity variation period of the laser interference signal. Therefore, the samples corresponding to the above four time series are equal optical path difference data.

[0113] The digital signal obtained by ADC sampling (ie the first type of digital signal) is an isochronous sampling signal. Due to reasons such as motor speed fluctuation, adjacent data points have non-equal optical path differences, and the digital signal needs to be processed for equal optical path differences.

[0114] In this embodiment, the above four time series t 1_up , t 1_down , t 2_up , and t 2_down , interpolation and resampling are performed on the first type of digital signals to obtain four groups of digital signals corresponding to equal optical path difference interference signals (ie, the second type of digital signals): S(t 1_up )、S(t 1_down )、S(t 2_up ), and S(t 2_down ).

[0115] The four groups of second-type digital signals may be subjected to FFT (Fast Fourier Transform) transformation to obtain four groups of spectrograms.

[0116] Exemplarily, the four groups of spectral graph data may be averaged to obtain a final output spectral graph.

[0117] For example, the data processing flow diagram of the Fourier transform infrared spectrometer data acquisition system can be as follows: Figure 5 shown.

[0118] in, Figure 5The mid-infrared ADC oversampling data is the first type of digital signal mentioned above; the counting time signal of the rising edge and falling edge of different square wave signals is the time information corresponding to the rising edge and falling edge of the above square wave signal 1 and square wave signal 2.

[0119] The equal optical path difference time series is the time series corresponding to the rising edge of the square wave signal 1 (t 1_up ) and the time series corresponding to the falling edge (t 1_down ), and the time series corresponding to the rising edge of square wave signal 2 (t 2_up ) and the time series corresponding to the falling edge (t 2_down ).

[0120] The above describes the Fourier transform infrared spectrometer data acquisition system provided by this application. The following describes the spectrum processing method provided by this application:

[0121] See Figure 6 , is a flow chart of a spectrum processing method provided in an embodiment of the present application, wherein the spectrum processing method can be applied to a data processing unit in a Fourier transform infrared spectrometer data acquisition system, such as Figure 6 As shown, the spectrum processing method may include the following steps:

[0122] Step S500: Acquire a first type digital signal, a time sequence corresponding to a rising edge of at least one square wave signal, and a time sequence corresponding to a falling edge of at least one square wave signal.

[0123] Step S510: resample the first type of digital signal according to the time sequence corresponding to the rising edge of at least one square wave signal, and resample the first type of digital signal according to the time sequence corresponding to the falling edge of at least one square wave signal to obtain at least two groups of second type digital signals.

[0124] In the embodiments of the present application, the acquisition of the first type of digital signal in the Fourier infrared spectrometer data acquisition system, as well as the acquisition of the time series corresponding to the rising edge and falling edge of at least one square wave signal, can be referred to the relevant description in the above embodiments, and the embodiments of the present application will not be repeated here.

[0125] Considering that the first type of digital signal obtained by ADC sampling is an isochronous sampling signal, adjacent sampling points usually have non-equal optical path differences due to fluctuations in motor speed (the motor is used to control the movement of the moving mirror), while the Fourier infrared spectrometer requires data with equal optical path differences (equal spatial intervals) (because the mathematical basis of the Fourier transform requires the independent variable (optical path difference) to be uniformly distributed), therefore, the accuracy of the Fourier transform based on the above-mentioned first type of digital signal will be relatively poor, which will in turn affect the performance of cost and structural analysis of the sample to be tested.

[0126] In addition, considering that every time the moving mirror in the Fourier infrared spectrometer moves a laser interference signal distance, the intensity of the laser interference signal will show a sinusoidal periodic change.

[0127] For example, assuming that the laser interference signal distance is twice the motor movement distance, when the motor (such as a voice coil motor) controls the movement of the moving mirror, the intensity of the laser interference signal will show a sinusoidal periodic change every time the moving mirror moves λ / 2.

[0128] It can be seen that each period of the laser interference signal corresponds to the same laser interference signal distance, and based on this, the first type of digital signal can be converted into equal optical path difference data.

[0129] Laser is a highly coherent light source with an extremely narrow wavelength range (single wavelength). The laser interference signal is usually a relatively simple cosine wave. Based on this, for the square wave signal obtained by square-wave processing of the above-mentioned first type of electrical signal, the time series corresponding to its rising edge (falling edge) can be regarded as a time series corresponding to equal optical path differences.

[0130] The data processing unit can resample the first type of digital signal according to the time series corresponding to the rising edge of at least one square wave signal to obtain at least one group of resampled digital signals (which can be called second type digital signals), and resample the first type of digital signal according to the time series corresponding to the falling edge of at least one square wave signal to obtain at least one group of second type digital signals.

[0131] The first type of digital signal is resampled according to the time sequence corresponding to the rising edge of the at least one square wave signal, and the first type of digital signal is resampled according to the time sequence corresponding to the falling edge of the at least one square wave signal to obtain at least two groups of second type digital signals.

[0132] Step S530: Perform Fourier transform on the at least two groups of second-type digital signals respectively to obtain at least two groups of spectrograms, and generate an output spectrogram based on the at least two groups of spectrograms.

[0133] In an embodiment of the present application, when at least two groups of second-type digital signals are obtained as described above, the at least two groups of second-type digital signals can be Fourier transformed respectively to obtain at least two groups of spectra, and output spectra can be generated based on the at least two groups of spectra, thereby reducing random noise and improving the signal-to-noise ratio of the Fourier transform infrared spectrometer, thereby improving the availability of the spectrum and the accuracy of quantitative analysis.

[0134] In some embodiments, the at least one square wave signal includes N square wave signals obtained by converting the first type of electrical signal according to corresponding preset voltage thresholds; N≥2;

[0135] The above-mentioned resampling of the first type of digital signal according to the time sequence corresponding to the rising edge of at least one square wave signal, and resampling of the first type of digital signal according to the time sequence corresponding to the falling edge of at least one square wave signal to obtain at least two groups of second type digital signals may include:

[0136] The first type of digital signal is resampled according to the time sequence corresponding to the rising edge and the time sequence corresponding to the falling edge of each square wave signal in the N square wave signals to obtain 2N groups of second type digital signals.

[0137] For example, in order to improve the noise reduction effect and further enhance the signal-to-noise ratio of the infrared spectrometer, the Fourier infrared spectrometer data acquisition system can use multiple square wave units to perform square wave processing on the first type of electrical signal to obtain multiple square wave signals. Then, the data processing unit can resample the first type of digital signal according to the rising edge time series of the multiple square wave signals, and resample the second type of digital signal according to the falling edge time series of the multiple square wave signals.

[0138] It should be noted that, considering that in practical applications, square wave processing is usually achieved through circuits, the more square wave units there are, the more complex and larger the circuit is, and the more computing resources will be consumed by the square wave processing and subsequent resampling processing. Therefore, it is necessary to balance the noise reduction effect, circuit complexity, and computing resource consumption.

[0139] Exemplarily, taking N=2 as an example, the at least one square wave signal includes a first square wave signal obtained by converting the first type of electrical signal according to a first preset voltage threshold, and a second square wave signal obtained by converting the first type of electrical signal according to a second preset voltage threshold.

[0140] The first type of digital signal can be resampled according to the time series corresponding to the rising edge of the first square wave signal, the first type of digital signal can be resampled according to the time series corresponding to the falling edge of the first square wave signal, the first type of digital signal can be resampled according to the time series corresponding to the rising edge of the second square wave signal, and the first type of digital signal can be resampled according to the time series corresponding to the falling edge of the second square wave signal to obtain four groups of second type digital signals, and Fourier transform can be performed on the four groups of second type digital signals to obtain four groups of spectrograms, and an output spectrogram can be generated based on the four groups of spectrograms.

[0141] In some embodiments, resampling the first type of digital signal according to a time sequence corresponding to a rising edge of at least one square wave signal, and resampling the first type of digital signal according to a time sequence corresponding to a falling edge of at least one square wave signal, may include:

[0142] The first type digital signal is interpolated and resampled according to a time sequence corresponding to a rising edge of at least one square wave signal, and the first type digital signal is interpolated and resampled according to a time sequence corresponding to a falling edge of at least one square wave signal.

[0143] Exemplarily, when the time sequence corresponding to the rising edge of at least one square wave signal and the time sequence corresponding to the falling edge of at least one square wave signal are determined, the interpolation resampling method can be used in the process of resampling the first type of digital signal.

[0144] Exemplarily, for any square wave signal, the optical path difference reference point can be marked according to the time series corresponding to the rising edge of the square wave signal, or the time series corresponding to the falling edge of the square wave signal, and the original isochronous sampling data can be interpolated and resampled to generate equally spaced optical path difference data (i.e., equal optical path difference data). Thus, equal optical path difference data can be obtained while allowing the mechanical movement of the moving mirror to be non-uniform, without relying on ultra-high precision motors, thereby reducing hardware costs.

[0145] In addition, since the optical path differences of the sampling points interpolated and resampled according to the time series corresponding to the rising edge or the time series corresponding to the falling edge of the same square wave signal are aligned, and the optical path differences of the sampling points interpolated and resampled according to the time series corresponding to the rising edge (or falling edge) of different square wave signals are also aligned, therefore, when the interpolation and resampling are performed in the above manner, the optical path differences of the sampling points in different groups of second-type digital signals are aligned.

[0146] Based on this, the output spectrum can be obtained by averaging at least two groups of spectrum images obtained in the above manner, thereby effectively reducing random noise and improving the signal-to-noise ratio of the Fourier transform infrared spectrometer.

[0147] Accordingly, in one example, generating the output spectrum according to the at least two sets of spectrums may include:

[0148] At least two sets of spectra are averaged to generate an output spectra.

Claims

1. A Fourier transform infrared spectrometer data acquisition system, characterized in that: include: An interference signal generating unit, an interference signal detecting unit, an analog-to-digital conversion (ADC) sampling unit, a data processing unit, and at least one square wave conversion unit; wherein: An interference signal generating unit, configured to generate an interference signal; wherein the interference signal comprises a laser interference signal or an infrared interference signal; an interference signal detection unit, configured to convert the laser interference signal into a first type of electrical signal; and to convert the infrared interference signal absorbed by the sample to be tested into a second type of electrical signal; an ADC sampling unit, configured to convert the second type of electrical signal into a first type of digital signal; at least one square wave conversion unit, configured to perform square wave processing on the first type of electrical signal to obtain at least one square wave signal; A data processing unit is used to resample the first type of digital signal according to the time sequence corresponding to the rising edge of the at least one square wave signal, and to resample the first type of digital signal according to the time sequence corresponding to the falling edge of the at least one square wave signal to obtain at least two groups of second type digital signals, and to perform Fourier transform on the at least two groups of second type digital signals to obtain at least two groups of spectra, and to generate an output spectra based on the at least two groups of spectra; wherein, adjacent sampling points of the second type digital signal are interference signals with equal optical path differences.

2. The Fourier transform infrared spectrometer data acquisition system according to claim 1, characterized in that: The interference signal generating unit includes: a laser light source, an infrared light source, and an interferometer; the interference signal detecting unit includes: a laser interference signal detecting unit and an infrared interference signal detecting unit; wherein: A laser light source, used to generate a laser signal; An infrared light source, used to generate an infrared light signal; an interferometer, configured to generate a laser interference signal based on the laser signal, and to generate an infrared interference signal based on the infrared light signal; a laser interference signal detection unit, configured to convert the laser interference signal into an electrical signal according to a signal strength of the laser interference signal to obtain a first type of electrical signal; The infrared interference signal detection unit is used to convert the infrared interference signal absorbed by the sample to be tested into an electrical signal according to the signal strength of the infrared interference signal absorbed by the sample to be tested, so as to obtain a second type of electrical signal.

3. The Fourier transform infrared spectrometer data acquisition system according to claim 1, characterized in that: The at least one square wave unit includes N square wave units; N≥2; The N square wave conversion units are specifically configured to convert the first type of electrical signal into a square wave signal according to corresponding preset voltage thresholds, thereby obtaining N square wave signals; The portion of the first type of electrical signal whose signal strength is greater than the preset voltage threshold is converted into a low-level signal after being squared; the portion of the first type of electrical signal whose signal strength is less than the preset voltage threshold is converted into a high-level signal after being squared; or, The part of the first type of electrical signal whose signal strength is less than the preset voltage threshold is converted into a low-level signal after square wave processing; the part of the first type of electrical signal whose signal strength is greater than the preset voltage threshold is converted into a high-level signal after square wave processing.

4. The Fourier transform infrared spectrometer data acquisition system according to claim 3, characterized in that: The data processing unit is specifically used to resample the first type of digital signal according to the time series corresponding to the rising edge and the time series corresponding to the falling edge of each square wave signal in the N square wave signals to obtain 2N groups of second type digital signals, and perform Fourier transform on the 2N groups of second type digital signals to obtain 2N groups of spectrograms, and generate an output spectrogram based on the 2N groups of spectrograms.

5. The Fourier transform infrared spectrometer data acquisition system according to claim 1, characterized in that: The data processing unit is specifically used to interpolate and resample the first type of digital signal according to the time series corresponding to the rising edge of the at least one square wave signal, and to interpolate and resample the first type of digital signal according to the time series corresponding to the falling edge of the at least one square wave signal.

6. The Fourier transform infrared spectrometer data acquisition system according to claim 5, characterized in that: The data processing unit is specifically configured to perform averaging processing on the at least two groups of spectrograms to generate an output spectrogram.

7. A spectrum processing method, characterized in that: The method applied to the data processing unit in the Fourier transform infrared spectrometer data acquisition system according to any one of claims 1 to 6 comprises: Acquire the first type of digital signal, a time sequence corresponding to a rising edge of the at least one square wave signal, and a time sequence corresponding to a falling edge of the at least one square wave signal; Resampling the first type of digital signal according to a time sequence corresponding to a rising edge of the at least one square wave signal, and resampling the first type of digital signal according to a time sequence corresponding to a falling edge of the at least one square wave signal, to obtain at least two groups of second type digital signals; wherein adjacent sampling points of the second type digital signal are interference signals with equal optical path differences; Fourier transform is performed on the at least two groups of second-type digital signals respectively to obtain at least two groups of spectrograms, and an output spectrogram is generated based on the at least two groups of spectrograms.

8. The method according to claim 7, characterized in that The at least one square wave signal includes N square wave signals obtained by converting the first type of electrical signal according to corresponding preset voltage thresholds; N≥2; The resampling of the first type of digital signal according to a time sequence corresponding to a rising edge of the at least one square wave signal, and the resampling of the first type of digital signal according to a time sequence corresponding to a falling edge of the at least one square wave signal, to obtain at least two groups of second type digital signals, comprises: The first type of digital signal is resampled according to the time sequence corresponding to the rising edge and the time sequence corresponding to the falling edge of each square wave signal in the N square wave signals to obtain 2N groups of second type digital signals.

9. The method according to claim 7, characterized in that The resampling of the first type of digital signal according to a time sequence corresponding to a rising edge of the at least one square wave signal, and the resampling of the first type of digital signal according to a time sequence corresponding to a falling edge of the at least one square wave signal, comprises: The first type of digital signal is interpolated and resampled according to a time sequence corresponding to a rising edge of the at least one square wave signal, and the first type of digital signal is interpolated and resampled according to a time sequence corresponding to a falling edge of the at least one square wave signal.

10. The method according to claim 9, characterized in that Generating an output spectrum according to the at least two groups of spectrums includes: The at least two groups of spectrograms are averaged to generate an output spectrogram.

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