Optical system for infrared oil measuring instrument

Abstract

The invention relates to the technical field of environmental monitoring, and particularly discloses an optical system for an infrared oil meter, which comprises an infrared light source module, a spectrum positioning and automatic calibration module, a light splitting and signal acquisition module and a spectrum analysis and error compensation module. The infrared light source module adopts an electric modulation light source and provides stable output in a wave number range of 2800cm <-1 > to 3100cm <-1 >, and the wavelength drift error is less than + / -0.5 nm; the spectrum positioning and automatic calibration module realizes accurate positioning through a stepping motor and an optical calibration unit; the light splitting and signal acquisition module uses a full-gold-plated optical unit, the reflectivity reaches 98%, and the light energy loss is reduced; and the spectral analysis and error compensation module processes and optimizes the spectral data in real time. Through a high-stability light source, precise positioning, a gold-plated optical material and intelligent error compensation, the measurement accuracy and stability are remarkably improved, the light energy loss is reduced, the portability and long-term operation capability of an instrument are enhanced, and the oil pollutant detection device is suitable for oil pollutant detection in environmental monitoring.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental monitoring. More specifically, the present invention relates to an optical system for an infrared oil analyzer. Background Art

[0002] Infrared oil analyzers are widely used in detecting oil and grease pollutants in water quality. Generally, the infrared spectroscopy method is adopted to quantitatively analyze the oil pollution in water bodies.

[0003] The existing public document 1 (Research on Infrared Oil Analyzer, 2019) discloses an optical system of an infrared oil analyzer. The optical system consists of a light source system, a modulation module, a spectroscope module, and a sample cell: The LYQ24-75 type tungsten halogen lamp is used as a stable light source. The light signal is modulated into pulsed light by driving a chopper blade with a stepper motor. After being dispersed by the grating in the monochromator, monochromatic light with specific wavelengths (2930 cm -1 , 2960 cm -1 , 3030 cm -1 ) is projected onto the sample cell; the photoelectric pair tube in the modulation module generates a synchronous pulse wave signal for phase-sensitive detection. The spectroscope module realizes spectral positioning through a Hall sensor. The sample cell uses a quartz cuvette to ensure high light transmittance. However, the overall volume of this optical system is relatively large and heavy, and its portability is poor. At the same time, the internal mechanical structure of the monochromator in this optical system is complex. After long-term use, wavelength positioning deviation may occur due to the adjustment accuracy of the grating angle or the wear of the stepper motor, affecting the measurement stability.

[0004] The existing public document 2 (Research and Development of an Infrared Oil Analyzer Based on STM32, 2018) discloses an optical system of an infrared oil analyzer based on STM32. This optical system uses a tungsten halogen lamp as the light source and is equipped with a front cut-off filter (cut-off wavelength 2750 nm) to ensure that only infrared light enters; the monochromator uses a reflective planar grating with a Czerny-Turner structure. The grating is rotated by a stepper motor to achieve scanning in the 3058 cm -1 -2880 cm -1 band; after the light signal passes through the sample cell, it is converted into an electrical signal by a pyroelectric infrared detector (PYD-1120), and after filtering, amplification, and A / D analog-to-digital conversion, it is processed by an STM32 processor. The system automatically corrects the starting point through a Hall sensor and compensates for the three-wave number peak shift caused by the local error of the monochromator lead screw processing accuracy and the uneven grating dispersion by using a software algorithm. However, due to the limitation of the hardware processing accuracy in this optical system, local errors of the monochromator lead screw and uneven grating dispersion occur, resulting in low absorption and conversion efficiency of infrared light with different wavelengths, and increasing the loss of infrared light energy.

[0005] Therefore, there is an urgent need to propose an improved optical system for an infrared oil analyzer to overcome the above deficiencies in the prior art and reduce the loss of light energy in the infrared oil analyzer. Summary of the Invention

[0006] To overcome the above defects of the prior art, the present invention provides an optical system for an infrared oil analyzer, which controls a grating through a stepping motor to achieve the decomposition and guidance of infrared light of different wavelengths, reduce the loss of light energy, and ensure that the light of the target wavelength can be efficiently transmitted to the detector for measurement, so as to solve the problems raised in the above background technology.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] An optical system for an infrared oil analyzer includes an infrared light source module, a spectral positioning and automatic calibration module, a spectral splitting and signal acquisition module, and a spectral analysis and error compensation module;

[0009] The spectral splitting and signal acquisition module controls the grating through a stepping motor to achieve the decomposition and guidance of infrared light of different wavelengths, reduce the loss of light energy, and includes the following steps:

[0010] Step S1, the infrared light source module emits continuous full-spectrum infrared light covering the wavenumber range of 2800 cm -1 to 3100 cm -1 ; To measure the spectral absorption at each specific wavenumber, the full-spectrum light emitted by the light source is decomposed into light of different wavelengths by the grating; The optical system uses a diaphragm and a beam homogenizer to uniformly irradiate the infrared light beam onto the surface of the grating.

[0011] Step S2, the grating uses the diffraction phenomenon of light to decompose the wide-spectrum infrared light into monochromatic light of different wavelengths; By adjusting the angle of the grating, the diffracted light of a specific wavelength is guided to the detector to measure the spectral absorption of this wavelength.

[0012] Step S3, when the light of the target wavelength is correctly separated by the grating, it will be guided to the fully gold-plated optical unit of the infrared oil analyzer.

[0013] Step S4, the infrared light that has been spectrally split by the grating and optimized by the gold-plated optical unit enters the detector. When the detector receives the infrared light of the target wavelength, it generates a corresponding electrical signal according to the intensity of the light; The spectral analysis and error compensation module analyzes the electrical signal and calculates the concentration of oil pollutants in the sample; If the error between the measured spectral signal and the standard spectrum exceeds the set threshold, the optical system will automatically trigger a feedback adjustment mechanism to adjust the light source energy output according to the source of the error.

[0014] As a further solution of the present invention, the adjustment of the grating angle specifically includes: First, calculate the angle of grating rotation according to the target wavenumber. The angle is determined by the diffraction formula, that is, the light of the target wavelength satisfies the relationship of the grating diffraction angle, so as to achieve correct spectral splitting. The diffraction formula is: mλ = dsinθ, where λ is the target wavelength, m is the diffraction order, d is the grating groove spacing, and θ is the grating diffraction angle. After calculating the diffraction angle, adjust the rotation angle of the grating through a stepper motor. The rotation angle of the stepper motor is determined by its step size, that is, for each rotation step, the corresponding angle increment is fixed. Calculate the difference between the target angle and the current angle, and then the grating can be rotated to the target position by controlling the number of steps of the stepper motor. After completing the angle adjustment, the infrared light of the target wavenumber can accurately enter the spectral splitting and signal acquisition module. The detector measures the intensity of the optical signal and transmits the measurement data to the spectral analysis and error compensation module for analysis. If the detector finds that the intensity of the optical signal of the target wavenumber does not reach the expected value, the optical system will feedback the signal to the stepper motor in real time, and further optimize the light incident path by finely adjusting the grating angle to ensure the accuracy and stability of the measurement.

[0015] As a further solution of the present invention, the feedback adjustment mechanism specifically includes: The feedback adjustment mechanism is based on a closed-loop control system and includes four links: error detection, error analysis, adjustment execution, and dynamic optimization. In the error detection stage, the spectral analysis and error compensation module monitors the measured spectral data in real time and compares it with the standard spectral database built in the optical system to calculate the absorbance deviation at the target wavelength. If the deviation exceeds the set threshold, it enters the error analysis stage to analyze the error sources, including factors such as light source energy fluctuation, grating diffraction angle drift, and detector sensitivity change. In the adjustment execution stage, select the adjustment method according to the error type: (1) If the error comes from the light source energy fluctuation, adjust the light source drive current through a constant current drive circuit to stabilize the infrared radiation energy; (2) If the error comes from the grating angle deviation, adjust the rotation angle of the grating through the stepper motor control system to make the light of the target wavelength accurately enter the detector; (3) If the error comes from the detector response drift caused by the environmental temperature fluctuation, trigger the temperature compensation system to stabilize the temperature through the temperature control and heat dissipation unit. After completing the adjustment, enter the dynamic optimization stage, re-collect the adjusted spectral data, and compare it with the standard spectrum again to determine whether the error returns within ±1%. If the error still exceeds the threshold, perform secondary fine adjustment until the error drops within ±1%.

[0016] As a further solution of the present invention, the infrared light source module uses an electrically modulated light source to provide coverage from 2800 cm -1 ~3100 cm -1Stable infrared spectral output within a wavenumber range; the spectral positioning and automatic calibration module consists of a mechanical calibration unit and an optical calibration unit; the spectroscopic and signal acquisition module incorporates an infrared optical unit and controls the rotation angle of the grating through a stepper motor, decomposing the broad-spectrum infrared light emitted by the infrared light source into monochromatic lights of different wavelengths according to the diffraction principle, enabling the light of the target wavenumber to correctly enter the detection path; the spectral analysis and error compensation module performs real-time processing and optimization on the spectral data collected by the infrared detector.

[0017] As a further solution of the present invention, the infrared light source module adopts an electrically modulated light source, providing a stable infrared spectral output within a wavenumber range of 2800 cm -1 ~3100 cm -1 The stable infrared spectral output within the wavenumber range of 2800 cm -1 ~3100 cm -1 includes the following specific contents: the infrared light source module selects a high-performance electrically modulated light source, and the wavenumber range provided by the electrically modulated light source covers between 2800 cm -1 and 3100 cm -1 , covering the special infrared oil-detection wavelengths such as 2930 cm -1 , 2960 cm

[0018] The temperature control and heat dissipation unit built in the infrared light source module can effectively control the working temperature of the electrically modulated light source to ensure the long-term stable operation of the light source. The temperature control and heat dissipation unit consists of a heat-conducting heat sink, an intelligent semiconductor refrigeration element (such as a TEC cooler), and a temperature sensor, and can accurately control the internal temperature of the light source within the range of 25 ± 0.5 °C, thereby preventing problems such as wavelength drift and light intensity instability caused by temperature fluctuations. In addition, this unit enables the light source to operate stably in a complex environment of -5 °C to 45 °C and a humidity of 20% to 80%.

[0019] As a further solution of the present invention, the spectral positioning and automatic calibration module consists of a mechanical calibration unit and an optical calibration unit, including the following specific contents: The spectral positioning and automatic calibration module includes a mechanical calibration unit. The mechanical calibration unit drives the grating to rotate through a stepper motor. The stepper motor adopts a closed-loop control servo system, which can finely adjust the grating position during the infrared spectrum scanning process, so as to ensure that the instrument accurately locates the required infrared characteristic absorption wavenumber when performing spectrum scanning on the sample. The mechanical calibration unit adopts a precision lead screw drive and a high-rigidity bearing structure, reducing the mechanical displacement error during the long-term operation of the instrument and improving the mechanical stability of the instrument.

[0020] The spectral positioning and automatic calibration module also includes an optical calibration unit. The optical calibration unit includes a calibration sample for absorption spectrum and an infrared detector; The calibration sample selects a perchloroethylene standard solution with a purity of ≥99.9% that meets the requirements of national environmental protection standards HJ637-2018, HJ1077-2019, and HJ1051-2019. By measuring the spectral signal intensity of the characteristic absorption peaks of the standard sample at wavenumbers of 2930 cm -1 、2960 cm -1 、3030 cm -1 , the synchronous calibration of the wavenumber accuracy of the spectrum measurement and the output accuracy of the light source energy is realized; The infrared detector is used to obtain the real-time spectrum absorption signal of the calibration sample.

[0021] As a further solution of the present invention, the spectroscopic and signal acquisition module incorporates an infrared optical unit and controls the rotation angle of the grating through a stepper motor, decomposing the broad-spectrum infrared light emitted by the infrared light source into monochromatic lights of different wavelengths according to the diffraction principle, so that the light of the target wavenumber can correctly enter the detection path, including the following specific contents: The spectroscopic and signal acquisition module incorporates an infrared optical unit. The infrared optical unit selects high-purity gold (Au) with extremely high infrared reflectivity and stability as the surface coating material for the optical reflection lens and the optical cavity. The infrared optical unit can improve the utilization rate of infrared light in the optical path.

[0022] As a further solution of the present invention, the spectral analysis and error compensation module performs real-time processing and optimization on the spectral data collected by the infrared detector, including the following specific contents: The spectral analysis and error compensation module receives the spectral data collected by the infrared detector and performs real-time processing and optimization on the spectral data to ensure that the final measurement result accurately reflects the true concentration of oil pollutants in the sample. The spectral analysis and error compensation module adopts a spectral analysis algorithm, and the spectral analysis algorithm includes continuous spectrum scanning, baseline correction, signal denoising, and zero drift compensation.

[0023] During the continuous spectrum scanning process, the spectrum analysis and error compensation module controls the grating to continuously rotate at a set step angle, so that the infrared detector obtains complete spectrum data at multiple characteristic wave numbers such as 2930 cm -1 , 2960 cm -1 , 3030 cm -1 and performs multiple samplings on the spectrum data to improve the signal stability and anti-interference ability. During each scanning process, the system automatically calculates the light intensity value at each wave number point and records its trend over time, thus ensuring the continuity and integrity of the measurement data.

[0024] In the baseline correction stage, the spectrum analysis and error compensation module automatically detects the background noise according to the current state of the instrument operation, smooths the spectrum signal using the least squares method, eliminates the random errors caused by optical system fluctuations or electronic noise, and automatically adjusts the zero reference of the spectrum, so that the measured spectrum data always remains on the correct baseline. The mathematical formula for using the least squares method for spectrum signal smoothing is: where, x i is the spectral wave number corresponding to the i-th data point, y i is the measured absorbance value corresponding to the i-th data point, f(x i ) is the fitting polynomial for smoothing data, and N is the number of measurement points included in the spectrum dataset.

[0025] In the signal denoising process, the spectrum analysis and error compensation module analyzes the spectrum data using Fourier transform, separates and filters out the high-frequency noise to improve the signal-to-noise ratio. At the same time, the spectrum analysis and error compensation module also uses the principal component analysis method to perform dimensionality reduction processing on the spectrum data, removing irrelevant noise components, making the spectrum data clearer and more distinguishable, and improving the accuracy of the measurement results.

[0026] In the zero drift compensation link, the spectrum analysis and error compensation module monitors the zero drift situation of the instrument in real time and adjusts the measurement data through an automatic correction algorithm. Zero drift is caused by light source energy attenuation, grating temperature change, or detector response instability. To compensate for this phenomenon, the spectrum analysis and error compensation module measures the standard sample regularly and compares the measurement data with the standard reference data. If zero offset is found, the spectrum analysis and error compensation module automatically calculates the compensation value and corrects the current measurement data, so that the final measurement result can maintain stability and consistency.

[0027] As a further solution of the present invention, the spectral positioning and automatic calibration module is connected to the infrared light source module, the light splitting and signal acquisition module is connected to the spectral positioning and automatic calibration module, the spectral analysis and error compensation module is connected to the light splitting and signal acquisition module, and the stepping motor is connected to the spectral positioning and automatic calibration module and the light splitting and signal acquisition module.

[0028] Technical effects and advantages of an optical system for an infrared oil analyzer according to the present invention: The present invention adopts a highly stable electro-modulated infrared light source module, which can provide an infrared spectrum output covering 2800 cm -1 ~3100 cm -1 and ensures that the wavelength stability error of the light source is less than ±0.5 nm through a constant current drive circuit and a temperature control and heat dissipation unit. The light intensity output is more constant, effectively reducing the influence of light source energy fluctuation on measurement, thereby improving the repeatability of measurement. Secondly, the precise spectral positioning and automatic calibration module combines a stepping motor to drive the grating and an optical calibration unit, which can finely adjust the grating angle and calibrate the spectral accuracy through a standard absorption spectrum calibration sample, ensuring that light of different wavelengths can accurately enter the detection path, avoiding wavelength shift caused by mechanical error, and improving the long-term measurement stability of the system. In addition, the light splitting and signal acquisition module adopts a fully gold-plated optical unit with an infrared reflectivity as high as 98%, which can reduce light energy loss, improve the utilization rate of infrared light in the optical system, and at the same time accurately adjust the grating angle through a stepping motor to ensure that light of the target wavelength efficiently enters the detector, improving the spectral resolution and signal intensity. Finally, the intelligent spectral analysis and error compensation module combines spectral analysis algorithms such as continuous spectral scanning, baseline correction, signal denoising, and zero drift compensation, which can real-time process the spectral data collected by the infrared detector, and uses Fourier transform and principal component analysis for noise suppression, improving the signal-to-noise ratio. At the same time, through an automatic feedback adjustment mechanism, it monitors the measurement error and dynamically adjusts the grating angle or the light source energy output to ensure that the measurement accuracy is not affected by environmental fluctuations during long-term operation. Description of the Drawings

[0029] Figure 1 It is a schematic structural diagram of an optical system for an infrared oil analyzer according to the present invention.

[0030] Figure 2 It is a schematic structural diagram of an optical system of an infrared oil analyzer in the prior art.

[0031] Figure 3 It is a schematic structural diagram of an optical system of an infrared oil analyzer based on STM32 in the prior art.

[0032] Figure 4 It is a schematic diagram of an infrared oil analyzer according to the present invention.

[0033] Figure 5 It is a schematic diagram of the optical path of the light splitting and signal acquisition module of the present invention. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Example 1

[0036] See also Figure 1 The structural schematic diagram shown in the figure shows that the embodiment of the present invention provides an optical system for an infrared oil measuring instrument, which includes an infrared light source module, a spectrum positioning and automatic calibration module, a spectroscopic and signal acquisition module, and a spectrum analysis and error compensation module; the infrared light source module adopts an electrically modulated light source to provide a coverage of 2800cm -1 ~3100cm -1 The infrared spectral output of the infrared light source is stable within the wave number range; the spectral positioning and automatic calibration module is composed of a mechanical calibration unit and an optical calibration unit; the spectroscopic and signal acquisition module has a built-in infrared optical unit, and controls the rotation angle of the grating through a stepping motor, decomposing the wide-spectrum infrared light emitted by the infrared light source into monochromatic light of different wavelengths according to the diffraction principle, so that the light of the target wave number can correctly enter the detection path; the spectral analysis and error compensation module processes and optimizes the spectral data collected by the infrared detector in real time. Figure 4 shown.

[0037] In this embodiment, see Figure 2 The structural diagram shown is an optical system of an infrared oil tester disclosed in the prior art. The optical system consists of a light source system, a modulation module, a spectroscopic module and a sample cell: a LYQ24-75 tungsten halogen lamp is used as a stable light source, and a stepper motor drives a chopper to modulate the light signal into a pulse light. After the grating dispersion in the monochromator, a specific wavelength (2930cm -1 、2960cm -1 、3030cm -1 ) is projected onto the sample pool; the photoelectric pair tube in the modulation module generates a synchronous pulse wave signal for phase-sensitive detection, the spectroscopic module realizes spectral positioning through the Hall sensor, and the sample pool uses a quartz cuvette to ensure high transmittance. However, the overall size and weight of the optical system are large, and the portability is poor. At the same time, the internal mechanical structure of the monochromator of the optical system is complex. Long-term use may cause wavelength positioning deviation due to grating angle adjustment accuracy or stepper motor wear, affecting measurement stability. Figure 3The shown structural schematic diagram is an optical system of an infrared oil detector based on STM32 disclosed in the prior art. This optical system uses a tungsten halogen lamp as the light source and is equipped with a front cut-off filter (cut-off wavelength 2750nm) to ensure that only infrared light enters. The monochromator uses a reflective plane grating with a Czerny-Turner structure, and the grating is rotated by a stepping motor to achieve scanning in the range of 3058cm -1 -2880cm -1 band; after the optical signal passes through the sample cell, it is converted into an electrical signal by a pyroelectric infrared detector (PYD-1120), and after filtering, amplification, and A / D analog-to-digital conversion, it is processed by the STM32 processor. The system automatically corrects the starting point through a Hall sensor and compensates for the peak shift of the three wavenumbers caused by the machining accuracy error of the monochromator lead screw and the uneven grating dispersion using a software algorithm. However, due to the limitation of the hardware machining accuracy in this optical system, there are local errors in the monochromator lead screw and uneven grating dispersion, resulting in low absorption and conversion efficiency of infrared light with different wavelengths, leading to an increase in the loss of infrared light energy.

[0038] Furthermore, the infrared light source module uses an electrically modulated light source to provide a stable infrared spectrum output covering the wavenumber range of 2800cm -1 ~3100cm -1 , including: the infrared light source module selects a high-performance electrically modulated light source, and the wavenumber range provided by the electrically modulated light source covers 2800cm -1 ~3100cm -1 and covers the special infrared oil detection wavelengths such as 2930cm -1 , 2960cm -1 and 3030cm -1 . The outstanding feature of the electrically modulated light source is its extremely high wavelength stability and precise wavelength control ability. Its wavelength drift error is strictly controlled within the range of ±0.5nm; at the same time, the energy output of the electrically modulated light source is more constant, and the light intensity stability is better than that of traditional non-modulated light sources. It can continuously provide a stable infrared spectrum output for a long time, ensuring the long-term continuous operation of the instrument, and the service life can reach more than 8000 hours, avoiding the maintenance cost and instrument downtime loss caused by frequent light source replacement; in addition, to further ensure the stable output of the electrically modulated light source, a high-performance drive power supply circuit is adopted. The drive power supply circuit includes a temperature-compensated voltage regulation chip, a zener diode, and a constant current drive circuit with negative feedback control. The current change rate of the power supply output is controlled within 0.01% through an operational amplifier and a high-performance MOS transistor, so as to achieve high stability of the supply current of the infrared radiation source and prevent the instability of the light source energy output caused by current fluctuations, ensuring that the light source can maintain stable performance under various complex environmental conditions.

[0039] The temperature control and heat dissipation unit built in the infrared light source module can effectively control the operating temperature of the electro-modulated light source to ensure the long-term stable operation of the light source. The temperature control and heat dissipation unit consists of a heat-conducting heat sink, an intelligent semiconductor refrigeration element (such as a TEC cooler), and a temperature sensor, which can accurately control the internal temperature of the light source within the range of 25±0.5°C, thus preventing problems such as wavelength drift and light intensity instability caused by temperature fluctuations. In addition, this unit enables the light source to operate stably in a complex environment with a temperature range of -5°C to 45°C and a humidity range of 20% to 80%.

[0040] Furthermore, the spectral positioning and automatic calibration module consists of a mechanical calibration unit and an optical calibration unit, including: The spectral positioning and automatic calibration module includes a mechanical calibration unit. The mechanical calibration unit drives the grating to rotate through a stepper motor. The stepper motor adopts a closed-loop control servo system, which can finely adjust the grating position during the infrared spectrum scanning process, so as to ensure that the instrument accurately locates the required infrared characteristic absorption wavenumber when performing spectrum scanning on the sample. The mechanical calibration unit adopts a precision lead screw drive and a high-rigidity bearing structure, reducing the mechanical displacement error during the long-term operation of the instrument and improving the mechanical stability of the instrument.

[0041] The spectral positioning and automatic calibration module also includes an optical calibration unit. The optical calibration unit includes a calibration sample for the absorption spectrum and an infrared detector; The calibration sample selects a perchloroethylene standard solution with a purity of ≥99.9% that meets the requirements of national environmental protection standards HJ637-2018, HJ1077-2019, and HJ1051-2019. By measuring the spectral signal intensity of the characteristic absorption peaks of the standard sample at wavenumbers of 2930cm -1 , 2960cm -1 , 3030cm -1 , the synchronous calibration of the wavenumber accuracy of the spectrum measurement and the energy output accuracy of the light source is realized; The infrared detector is used to obtain the real-time spectral absorption signal of the calibration sample.

[0042] Furthermore, the spectroscopic and signal acquisition module incorporates an infrared optical unit and controls the rotation angle of the grating through a stepper motor to decompose the broadband infrared light emitted by the infrared light source into monochromatic lights of different wavelengths according to the diffraction principle, enabling the light of the target wavenumber to correctly enter the detection path, including: The spectroscopic and signal acquisition module incorporates an infrared optical unit. The infrared optical unit selects high-purity gold (Au) with extremely high infrared reflectivity and stability as the surface coating material for the optical reflection lens and the optical cavity. The infrared optical unit can improve the utilization rate of infrared light in the optical path.

[0043] The spectro - splitting and signal acquisition module controls the grating through a stepper motor to achieve the decomposition and guidance of infrared light of different wavelengths, reduce the loss of light energy, and ensure that the light of the target wavelength can be efficiently transmitted to the detector for measurement. The steps are as follows:

[0044] Step S1, the infrared light source module of the infrared oil analyzer emits infrared light covering a wave number range of 2800 cm -1 ~3100 cm -1 . The infrared light contains multiple characteristic absorption wave numbers of the infrared oil analyzer (such as 2930 cm -1 , 2960 cm -1 , and 3030 cm -1 ). Each wave number corresponds to a specific infrared photon energy. Since the light emitted by the light source is continuous full - spectrum infrared light, it is necessary to decompose the light of different wavelengths through a grating so that the infrared oil analyzer can measure the spectral absorption at each specific wave number respectively. To ensure the accuracy of the measurement, the optical system automatically calibrates the light intensity and wavelength stability of the light source output. By comparing with a standard spectral sample, it is ensured that the light source output is stable and the wavelength deviation is less than ±0.5 nm. At the same time, the optical system uses a diaphragm and a beam homogenizer to optimize the light intensity distribution, so that the infrared light beam irradiates the grating surface evenly, thereby improving the reliability of the spectral measurement.

[0045] Step S2, the grating is used to decompose the broadband infrared light into monochromatic light of different wavelengths. The working principle of the grating is based on the diffraction phenomenon of light. That is, when light passes through the grating rulings, lights of different wavelengths will be diffracted at different angles. If you want to let the light of a certain specific wave number enter the detector, by adjusting the angle of the grating, the diffracted light of this wavelength can be correctly guided to the detection path.

[0046] Step S3, when the light of the target wavelength is correctly separated by the grating, it is guided to the fully gold - plated optical unit of the infrared oil analyzer. Since the gold - plated optical material has a reflectivity as high as 98% in the infrared band (2800 cm -1 ~3100 cm -1 ), compared with traditional reflective materials, it can effectively reduce light loss, enabling the light energy to be fully transmitted to the detector, improving the measurement sensitivity and signal intensity.

[0047] Step S4: The infrared light that has been spectrally dispersed by the grating and optimized by the gold-plated optical unit finally enters the detector for measurement. The role of the detector is to absorb the incoming infrared light and convert it into an electrical signal. When the detector receives the infrared light of the target wavelength, it generates a corresponding electrical signal according to the intensity of the light and transmits the electrical signal to the spectral analysis and error compensation module. The spectral analysis and error compensation module analyzes the electrical signal and calculates the concentration of oil pollutants in the sample. If the error between the measured spectral signal and the standard spectrum exceeds the set threshold, the optical system will automatically trigger the feedback adjustment mechanism and adjust the light source energy output according to the source of the error.

[0048] The specific adjustment of the grating angle includes: First, calculate the angle of rotation of the grating according to the target wave number. The angle is determined by the diffraction formula, that is, the light of the target wavelength satisfies the relationship of the grating diffraction angle to achieve correct spectral dispersion. The diffraction formula is: mλ = dsinθ, where λ is the target wavelength, m is the diffraction order, d is the grating groove spacing, and θ is the grating diffraction angle. After calculating the diffraction angle, adjust the rotation angle of the grating through the stepper motor. The rotation angle of the stepper motor is determined by its step size, that is, for each rotation step, the corresponding angle increment is fixed. Calculate the difference between the target angle and the current angle, and then the grating can be rotated to the target position by controlling the number of steps of the stepper motor. For example, if the calculated diffraction angle is 20° and the single-step rotation angle of the stepper motor is 0.01°, then the stepper motor needs to rotate 2000 steps to adjust the grating to the correct position. After completing the angle adjustment, the infrared light of the target wave number can accurately enter the spectral dispersion and signal acquisition module. The detector measures the intensity of the optical signal and transmits the measurement data to the spectral analysis and error compensation module for analysis. If the detector finds that the intensity of the optical signal of the target wave number does not reach the expected value, the optical system will feedback the signal to the stepper motor in real time and further optimize the light incident path by finely adjusting the grating angle to ensure the accuracy and stability of the measurement.

[0049] The specific feedback regulation mechanism includes: The feedback regulation mechanism is based on a closed-loop control system and includes four links: error detection, error analysis, regulation execution, and dynamic optimization. In the error detection stage, the spectral analysis and error compensation module monitors the measured spectral data in real time and compares it with the standard spectral database built into the optical system to calculate the absorbance deviation at the target wavelength. If the deviation exceeds the set threshold, it enters the error analysis stage to analyze the error sources, including factors such as light source energy fluctuations, grating diffraction angle drift, and detector sensitivity changes. In the regulation execution stage, the regulation method is selected according to the error type: (1) If the error is due to light source energy fluctuations, the light source drive current is regulated through a constant current drive circuit to stabilize the infrared radiation energy; (2) If the error is due to grating angle deviation, the rotation angle of the grating is adjusted through a stepper motor control system to accurately allow the light of the target wavelength to enter the detector; (3) If the error is due to the detector response drift caused by environmental temperature fluctuations, the temperature compensation system is triggered, and the temperature is stabilized through a temperature control and heat dissipation unit. After the regulation is completed, it enters the dynamic optimization stage, where the adjusted spectral data is re-collected and compared with the standard spectrum again to determine whether the error returns within ±1%. If the error still exceeds the threshold, secondary fine-tuning is performed until the error is reduced within ±1%.

[0050] In this embodiment, referring to Figure 5 the schematic diagram shown, the beam splitting and signal acquisition module adopts a precision optical design, optimizes the beam path through multiple optical elements, and ensures efficient beam splitting and signal acquisition during the measurement of the infrared oil analyzer. First, the infrared light source module emits light covering 2800cm -1 ~3100cm -1Broad-spectrum infrared light, including characteristic wave numbers for measuring oil pollutants. Since the light emitted by the light source is divergent light, in order to improve the beam quality, a collimating lens is provided at the light source output end. This lens can collimate the beam so that it propagates in a parallel direction to reduce beam divergence and improve the subsequent spectral analysis accuracy. The collimated beam is evenly incident on a grating controlled by a stepper motor. The grating calculates the diffraction angle of the target wavelength according to the diffraction formula and precisely adjusts its rotation angle by the stepper motor so that light of different wavelengths is separated at different angles. Light with short wavelengths (high wave numbers) and light with long wavelengths (low wave numbers) are diffracted in different directions respectively and enter the subsequent optical transmission path. In order to reduce the loss of light energy during the spectral analysis process, a fully gold-plated optical unit is adopted. Its gold-plated mirror has an infrared reflectivity of more than 98%, which can effectively reduce the attenuation of light energy. At the same time, the beam path is optimized to enable light of the target wavelength to efficiently enter the detector. The light optimized by the gold-plated mirror finally enters a high-sensitivity infrared detector. This detector is responsible for absorbing infrared light of the target wavelength and converting the optical signal into an electrical signal, which is transmitted to the spectral analysis and error compensation module for data processing. In order to ensure the stability and consistency of the measurement, a beam homogenization device such as a diaphragm and a beam homogenizer is also equipped to eliminate bright spots and dark areas in the beam, ensure that the beam is evenly distributed on the entire grating surface, and improve the accuracy of spectral analysis and the reliability of the measurement. In addition, this module is also linked with an automatic feedback adjustment system. When the detector detects abnormal signals or the measurement error exceeds the set threshold, the system will automatically adjust the grating angle or the light source energy output to optimize the accuracy of the spectral measurement. Through this optimized design of the optical path, the present invention significantly improves the measurement accuracy, spectral resolution, and long-term operation stability of the infrared oil analyzer under multi-wavelength conditions.

[0051] Furthermore, the spectral analysis and error compensation module performs real-time processing and optimization on the spectral data collected by the infrared detector, including the following specific contents: The spectral analysis and error compensation module receives the spectral data collected by the infrared detector and performs real-time processing and optimization on the spectral data to ensure that the final measurement result accurately reflects the true concentration of oil pollutants in the sample. The spectral analysis and error compensation module adopts a spectral analysis algorithm, and the spectral analysis algorithm includes continuous spectral scanning, baseline correction, signal denoising, and zero drift compensation.

[0052] During the continuous spectral scanning process, the spectral analysis and error compensation module controls the grating to continuously rotate at a set step angle, so that the infrared detector is at 2930 cm -1 、2960 cm -1 、3030 cm -1Obtain complete spectral data at multiple characteristic wave numbers, and perform multiple samplings on the spectral data to improve the stability and anti-interference ability of the signal. During each scan process, the system automatically calculates the light intensity value at each wave number point and records its trend over time, thereby ensuring the continuity and integrity of the measurement data.

[0053] In the baseline correction stage, the spectral analysis and error compensation module automatically detects background noise according to the current state of the instrument operation, and uses the least squares method to smooth the spectral signal, eliminate random errors caused by optical system fluctuations or electronic noise, and automatically adjust the zero reference of the spectrum to keep the measured spectral data always on the correct baseline. The mathematical formula of the least squares method for spectral signal smoothing is: where x i is the spectral wave number corresponding to the i-th data point, y i is the measured absorbance value corresponding to the i-th data point, f(x i ) is the fitting polynomial for smoothing data, and N is the number of measurement points included in the spectral dataset.

[0054] In the signal denoising process, the spectral analysis and error compensation module analyzes the spectral data using Fourier transform, separates and filters out high-frequency noise to improve the signal-to-noise ratio of the signal. At the same time, the spectral analysis and error compensation module also uses the principal component analysis method to perform dimensionality reduction processing on the spectral data, removing irrelevant noise components, making the spectral data clearer and more distinguishable, and improving the accuracy of the measurement results.

[0055] In the zero drift compensation link, the spectral analysis and error compensation module monitors the zero drift situation of the instrument in real time and adjusts the measurement data through an automatic correction algorithm. Zero drift is caused by light source energy attenuation, grating temperature change, or unstable detector response. To compensate for this phenomenon, the spectral analysis and error compensation module measures the standard sample regularly and compares the measurement data with the standard reference data. If zero offset is found, the spectral analysis and error compensation module automatically calculates the compensation value and corrects the current measurement data to make the final measurement result maintain stability and consistency.

[0056] As described above, it is only the specific implementation manner of this application, but the protection scope of this application is not limited thereto. Any person skilled in the art within the technical scope disclosed by this application can easily think of changes or substitutions, which should all be covered within the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.

[0057] Finally, the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. An optical system for an infrared oil measuring instrument, characterized in that: It includes infrared light source module, spectrum positioning and automatic calibration module, spectrometry and signal acquisition module and spectrum analysis and error compensation module; The light splitting and signal acquisition module controls the grating through a stepper motor to decompose and guide infrared light of different wavelengths and reduce the loss of light energy, and includes the following steps: Step S1: The infrared light source module emits a coverage of 2800cm -1 Up to 3100cm -1 Continuous full-spectrum infrared light in a range of wavenumbers; in order to measure the spectral absorption at each specific wavenumber, the full-spectrum light emitted by the light source is decomposed into light of different wavelengths through a grating; The optical system uses an aperture and a beam homogenizer to make the infrared beam evenly illuminate the grating surface; Step S2, the grating uses the diffraction phenomenon of light to decompose the wide-spectrum infrared light into monochromatic light of different wavelengths; by adjusting the angle of the grating, the diffracted light of a specific wavelength is guided to the detector to measure the spectral absorption of the wavelength; Step S3, when the light of the target wavelength is correctly separated by the grating, it will be guided to the fully gold-plated optical unit of the infrared oil tester; Step S4, the infrared light after grating splitting and optimization by the gold-plated optical unit enters the detector. When the detector receives the infrared light of the target wavelength, it generates a corresponding electrical signal according to the intensity of the light; the spectral analysis and error compensation module analyzes the electrical signal and calculates the concentration of oil pollutants in the sample; if the error between the measured spectral signal and the standard spectrum exceeds the set threshold, the optical system will automatically trigger the feedback adjustment mechanism to adjust the light source energy output according to the source of the error.

2. The optical system for infrared oil measuring instrument according to claim 1, characterized in that In step S2, adjusting the angle of the grating specifically includes: firstly calculating the angle of rotation of the grating according to the target wave number, the angle is determined by the diffraction formula, that is, the light of the target wavelength satisfies the relationship of the grating diffraction angle, so as to achieve correct light splitting, the diffraction formula is: mλ=dsinθ, wherein λ is the target wavelength, m is the diffraction order, d is the spacing of the grating lines, and θ is the diffraction angle of the grating; after calculating the diffraction angle, adjusting the rotation angle of the grating by a stepper motor, the rotation angle of the stepper motor is determined by its step length, that is, each rotation step corresponds to an angle increment It is fixed. By calculating the difference between the target angle and the current angle, the grating can be rotated to the target position by controlling the number of steps of the stepper motor. After the angle adjustment is completed, the infrared light of the target wavenumber can enter the spectroscopic and signal acquisition module. The detector measures the intensity of the light signal and transmits the measurement data to the spectral analysis and error compensation module for analysis. If the detector finds that the intensity of the light signal of the target wavenumber does not reach the expected value, the optical system will feedback the signal to the stepper motor in real time, and further optimize the light incident path by fine-tuning the grating angle to ensure the accuracy and stability of the measurement.

3. The optical system for infrared oil measuring instrument according to claim 1, characterized in that In step S4, the feedback adjustment mechanism specifically includes: the feedback adjustment mechanism is based on a closed-loop control system, including four links: error detection, error analysis, adjustment execution and dynamic optimization; in the error detection stage, the spectrum analysis and error compensation module monitors the measured spectrum data in real time, and compares it with the standard spectrum database built into the optical system to calculate the absorbance deviation at the target wavelength; if the deviation exceeds the set threshold, enter the error analysis stage to analyze the error source, including light source energy fluctuation, grating diffraction angle drift, and detector sensitivity change factors; in the adjustment execution stage, select the adjustment method according to the error type: (1) If the error comes from the energy fluctuation of the light source, the light source driving current is adjusted through the constant current driving circuit to stabilize the infrared radiation energy; (2) If the error comes from the grating angle deviation, the rotation angle of the grating is adjusted through the stepper motor control system to allow the target wavelength of light to accurately enter the detector; (3) If the error comes from the detector response drift caused by ambient temperature fluctuations, the temperature compensation system is triggered to stabilize the temperature through the temperature control heat dissipation unit; after the adjustment is completed, the dynamic optimization stage is entered, the adjusted spectral data is re-collected, and compared with the standard spectrum again; if the error still exceeds the threshold, a second fine-tuning is performed until the error is reduced to within ±1%.

4. The optical system for an infrared oil measuring instrument according to claim 1, characterized in that: The infrared light source module adopts an electrically modulated light source, providing a coverage of 2800cm -1 ~3100cm -1 The infrared spectral output of the infrared detector is stable within the wavenumber range; the spectral positioning and automatic calibration module is composed of a mechanical calibration unit and an optical calibration unit; the spectroscopic and signal acquisition module has a built-in infrared optical unit, and controls the rotation angle of the grating through a stepper motor, and decomposes the wide-spectrum infrared light emitted by the infrared light source into monochromatic light of different wavelengths according to the diffraction principle, so that the light of the target wavenumber can correctly enter the detection path; the spectral analysis and error compensation module processes and optimizes the spectral data collected by the infrared detector in real time.

5. The optical system for an infrared oil measuring instrument according to claim 1, characterized in that: The wavelength drift error of the electrically modulated light source of the infrared light source module is controlled within the range of ±0.5nm, the light intensity stability is better than that of a traditional non-modulated light source, and the service life is more than 8000 hours.

6. The optical system for an infrared oil measuring instrument according to claim 1, characterized in that: The infrared light source module has a built-in driving power supply circuit, which includes a temperature-compensated voltage regulating chip, a voltage regulator diode and a constant current driving circuit controlled by negative feedback. The output current change rate of the power supply is controlled within 0.01% through an operational amplifier and a MOS tube.

7. The optical system for an infrared oil measuring instrument according to claim 1, characterized in that: The infrared light source module has a built-in temperature control and heat dissipation unit, which is composed of a heat-conducting heat sink, an intelligent semiconductor refrigeration element and a temperature sensor, and controls the internal temperature of the light source within the range of 25±0.5°C.

8. The optical system for an infrared oil measuring instrument according to claim 1, characterized in that: The mechanical calibration unit of the spectrum positioning and automatic calibration module adopts a stepper motor to drive the grating to rotate, and the stepper motor adopts a closed-loop control servo system.

9. The optical system for an infrared oil measuring instrument according to claim 1, characterized in that: The spectrum positioning and automatic calibration module is connected to the infrared light source module, the spectroscopic and signal acquisition module is connected to the spectrum positioning and automatic calibration module, the spectrum analysis and error compensation module is connected to the spectroscopic and signal acquisition module, and the stepping motor is connected to the spectrum positioning and automatic calibration module and the spectroscopic and signal acquisition module.

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