IRCF optical filter angle deviation spectrum drift detection method and related equipment

Abstract

The invention provides an IRCF optical filter angle deviation spectrum drift detection method and related equipment, and the method comprises the steps: taking a first light beam vertically entering an optical filter to be detected as a reference, enabling a second light beam to sequentially enter according to a preset inclination angle sequence, and synchronously collecting the transmittance spectrum of two light beams after the two light beams penetrate through the optical filter in a preset wavelength range; extracting a vertical incidence cut-off wavelength and an inclined incidence cut-off wavelength corresponding to the transmittance reduced to a preset cut-off threshold value from the transmittance spectrum; calculating a wavelength offset between the vertical incident cut-off wavelength and each oblique incident cut-off wavelength to obtain an angle-offset data set of the oblique angle and the wavelength offset; performing linear fitting on the angle-offset data set to obtain a fitting slope as an angle spectrum drift rate; and comparing the angle spectrum drift rate with a preset standard drift rate, and judging the coating quality of the optical filter to be detected. The method accurately quantifies the drift characteristic of the cut-off wavelength along with the change of the incident angle, and effectively evaluates the quality of the coating process.

Description

Technical Field

[0001] This invention relates to the field of optical thin film inspection technology, and in particular to a method and related equipment for detecting spectral drift of IRCF filter angle offset. Background Technology

[0002] With the rapid development of optical imaging technology, IRCF filters have become core optical components in digital cameras, smartphone cameras, and security monitoring systems. IRCF filters achieve spectral selectivity—high visible light transmittance and infrared light cutoff—through the interference effect of multilayer dielectric thin films, ensuring accurate color reproduction by image sensors. Current quality inspection of IRCF filters primarily employs spectrophotometry, measuring the transmittance spectrum under perpendicular incidence conditions and evaluating product performance by analyzing parameters such as cutoff wavelength, visible light transmittance, and infrared blocking rate. This method, based on the ideal perpendicular incidence assumption, effectively characterizes the optical properties of the filter under design baseline conditions and is widely used in thin-film coating production lines.

[0003] However, in practical optical systems, especially in wide-angle lenses and large field-of-view imaging scenarios, light inevitably strikes IRCF filters at various angles. According to thin-film interference theory, when the incident angle deviates from the vertical direction, the effective optical path in the thin film changes, causing the cutoff wavelength to drift towards shorter wavelengths. This angle sensitivity directly affects the edge color fidelity of the imaging system. Existing detection methods only focus on vertical incident performance and cannot evaluate the spectral stability of the filter at different incident angles. When there are film thickness deviations or refractive index abnormalities in the coating process, the angle drift characteristics will deteriorate significantly, but this defect is difficult to detect in conventional vertical inspection. Therefore, how to accurately characterize the angle shift spectral drift characteristics of IRCF filters in the production process has become an urgent technical problem to be solved in the quality control of optical thin films. Summary of the Invention

[0004] The main objective of this invention is to solve the technical problem that existing IRCF filter quality testing methods cannot accurately characterize the drift characteristics of the cutoff wavelength as the incident angle changes, which makes it difficult to effectively evaluate the quality of the coating process.

[0005] The first aspect of this invention provides a method for detecting spectral drift of an IRCF filter angle offset, the method comprising: The first beam is perpendicularly incident on the filter under test, and the second beam is sequentially incident on the filter under test from each tilt angle in a preset tilt angle sequence. Within a preset wavelength range, the transmittance spectra of the first beam and the second beam after passing through the filter under test are simultaneously collected for each tilt angle. Extract the vertical incident cutoff wavelength and the oblique incident cutoff wavelength corresponding to the transmittance dropping to a preset cutoff threshold from the transmittance spectrum, respectively. The wavelength offset between the vertical incident cutoff wavelength and each tilted incident cutoff wavelength is calculated respectively to obtain multiple sets of angle-offset datasets of tilt angle and wavelength offset; Linear fitting is performed on the angle-offset dataset to obtain the fitting slope as the angle spectral drift rate. The angle spectral drift rate is then compared with a preset standard drift rate to determine the coating quality of the filter under test.

[0006] A second aspect of the present invention provides an IRCF filter angle shift spectral drift detection device, the IRCF filter angle shift spectral drift detection device comprising: The dual-channel acquisition module is used to vertically incident a first beam onto the filter under test and to sequentially incident a second beam onto the filter under test from each tilt angle in a preset tilt angle sequence. Within a preset wavelength range, the module synchronously acquires the transmittance spectra of the first beam and the second beam after they pass through the filter under test at each tilt angle. The wavelength extraction module is used to extract the vertical incident cutoff wavelength and the oblique incident cutoff wavelength corresponding to the transmittance dropping to a preset cutoff threshold from the transmittance spectrum, respectively. The offset calculation module is used to calculate the wavelength offset between the vertical incident cutoff wavelength and each tilted incident cutoff wavelength, and obtain multiple sets of angle-offset datasets of tilt angle and wavelength offset. The quality assessment module is used to perform linear fitting on the angle-offset dataset, obtain the fitting slope as the angle spectral drift rate, and compare the angle spectral drift rate with the preset standard drift rate to determine the coating quality of the filter under test.

[0007] The aforementioned IRCF filter angle shift spectral drift detection method and related equipment establish a dual-optical-path synchronous measurement architecture by using a first beam perpendicularly incident on the filter under test as a reference measurement path, and simultaneously using a second beam to sequentially incident on the filter under test from various tilt angles in a preset tilt angle sequence. Within a preset wavelength range, the transmittance spectra of the first and second beams after passing through the filter under test at each tilt angle are simultaneously acquired to ensure consistency of measurement conditions. The vertically incident cutoff wavelength and the tilted incident cutoff wavelength corresponding to the transmittance decreasing to a preset cutoff threshold are extracted from the transmittance spectrum. The wavelength shift between the vertically incident cutoff wavelength and each tilted incident cutoff wavelength is calculated, resulting in multiple sets of angle-shift datasets of tilt angle and wavelength shift, quantifying the drift law of the cutoff wavelength with the incident angle. A linear fit is performed on the angle-shift dataset to obtain the fitting slope as the angle spectral drift rate. The measured angle spectral drift rate is compared with the preset standard drift rate calculated according to the design parameters, and the coating quality of the filter under test is determined based on the degree of deviation. This solution achieves quantitative evaluation of the angular stability of IRCF filters through simultaneous multi-angle spectral measurement and linear fitting analysis. It solves the technical problem that existing vertical incidence detection methods cannot accurately characterize the drift characteristics of the cutoff wavelength as the incident angle changes, which makes it difficult to effectively evaluate the coating process quality. This significantly improves the accuracy and reliability of IRCF filter quality detection.

[0008] Beneficial Effects: This invention's technical solution, through a dual-optical-path synchronous measurement architecture, achieves simultaneous acquisition of transmittance spectra under both vertical and oblique incidence conditions, significantly improving the accuracy and reliability of IRCF filter angular stability detection. Compared to traditional methods that only detect under vertical incidence conditions, this solution, through multi-angle spectral measurement and linear fitting analysis, can quantitatively assess the drift characteristics of the cutoff wavelength as a function of the incident angle, effectively identifying hidden defects such as film thickness deviations and refractive index anomalies in the coating process. By comparing the angular spectral drift rate with theoretical benchmark values, this solution provides reliable quality assurance for applications such as wide-angle lenses and large field-of-view imaging. High-precision angular stability detection ensures that IRCF filters maintain good spectral performance even under actual oblique incidence conditions, avoiding color distortion at image edges and infrared leakage. This meets the stringent quality requirements of optical components in large-angle operating conditions for visual inspection applications such as smartphone cameras, automotive cameras, and security monitoring, significantly improving the quality control level and product consistency in the mass production process of IRCF filters.

[0009] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained in accordance with the structures particularly pointed out in the description, claims and drawings.

[0010] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the first embodiment of the IRCF filter angle shift spectral drift detection method in this invention; Figure 2 This is a schematic diagram of the second embodiment of the IRCF filter angle shift spectral drift detection method in this invention. Figure 3 A schematic diagram of an embodiment of the IRCF filter angle offset spectral drift detection device in this invention. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0013] The terms "comprising" and "having," and any variations thereof, used in the embodiments of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the steps or units listed, but may optionally include other steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices.

[0014] To facilitate understanding of this embodiment, a detailed description of the IRCF filter angle shift spectral drift detection method disclosed in this embodiment of the invention will be provided first. For example... Figure 1 As shown, this method includes the following steps: 101. The first beam is incident perpendicularly on the filter under test, and the second beam is incident on the filter under test from each tilt angle in a preset tilt angle sequence. Within a preset wavelength range, the transmittance spectra of the first beam and the second beam after passing through the filter under test are collected synchronously for each tilt angle. In this embodiment, the transmittance spectrum includes a transmittance spectrum for vertical incidence and a transmittance spectrum for oblique incidence. The step of simultaneously acquiring the transmittance spectra of the first beam and the second beam after passing through the filter under test at various oblique angles within a preset wavelength range includes: simultaneously acquiring a first light intensity signal of the first beam passing through the filter under test and a second light intensity signal of the second beam passing through the filter under test for each oblique angle, and simultaneously acquiring reference light intensity signals of the first beam and the second beam passing through a reference filter; calculating the wavelength-wise ratio and wavelength axis calibration of the first light intensity signal and the corresponding reference light intensity signal to obtain the transmittance spectrum for vertical incidence; and calculating the wavelength-wise ratio and wavelength axis calibration of the second light intensity signal and the corresponding reference light intensity signal to obtain the transmittance spectrum for oblique incidence.

[0015] Specifically, in the angular offset detection of IRCF filters, the dual-optical-path measurement system is implemented as follows: A broadband white light source, such as a halogen tungsten lamp or a xenon lamp, is used. The emitted beam is collimated by a collimating lens to form parallel light before illuminating a beam splitter. The beam splitter is an optical element with a semi-transparent, semi-reflective coating on its surface. It splits the incident light into two beams, transmitted and reflected, in a 50:50 ratio. The transmitted light, as the first beam, maintains its original propagation direction and perpendicularly illuminates the filter under test. The reflected light, as the second beam, passes through a set of plane mirrors controlled by a precision rotary stage, changing its propagation direction. The rotation axis of the precision rotary stage is perpendicular to the optical platform. A stepper motor drives the rotary stage to change the angular position of the mirrors, causing the second beam to be incident on the filter under test at a preset tilt angle. The preset tilt angle sequence includes, but is not limited to, 5 degrees, 10 degrees, 15 degrees, 20 degrees, 25 degrees, and 30 degrees. After each rotation of the rotary stage to a specified angle, the actual angle value is read by an optical encoder to ensure that the angle error is less than 0.1 degrees. The first and second light beams illuminate different areas of the filter under test. After passing through the filter, they enter their respective fiber optic probes. The optical fibers transmit the optical signals to two independent input channels of the spectrometer for light intensity measurement.

[0016] Therefore, during measurements at each tilt angle, the two input channels of the spectrometer scan the corresponding wavelength range (e.g., 500 nm to 900 nm) simultaneously. The first input channel receives the light signal after the first beam passes through the filter under test. The linear array detector inside the spectrometer converts the light intensity of different wavelengths into electrical signals, which are then converted from analog to digital and recorded as a first light intensity signal data sequence with wavelength as the abscissa and light intensity as the ordinate. The second input channel receives the light signal after the second beam passes through the filter under test in the same manner and records it as a second light intensity signal data sequence. Since the two channels share the same clock and trigger system of the spectrometer, the acquisition times of the two light intensity signals are completely synchronized, and the wavelength scan step is 1 nm for both. After the measurement of the filter under test is completed, the filter under test is removed from the optical path and placed in a reference filter. The reference filter is a transparent glass plate with the same substrate material and thickness as the filter under test but without a multilayer coating, and its transmittance in the visible to near-infrared band is close to 92%. Keeping the angular position of the rotating stage unchanged, the first beam and the second beam pass through the reference filter with the same optical path configuration as when measuring the filter under test, and the two channels of the spectrometer respectively collect and record the reference light intensity signal data sequence.

[0017] Finally, the obtained light intensity signals are normalized to eliminate systematic errors. The light intensity value at each wavelength point in the first light intensity signal data sequence is divided by the light intensity value at the corresponding wavelength point in the reference light intensity signal data sequence to obtain the transmittance ratio at that wavelength point. This ratio calculation is performed sequentially for all wavelength points, forming a vertical incident transmittance spectrum curve with wavelength as the abscissa and transmittance as the ordinate. Similarly, the wavelength-by-wavelength ratio is calculated between the second light intensity signal data sequence and the corresponding reference light intensity signal to obtain the oblique incident transmittance spectrum curve. Wavelength axis calibration is performed simultaneously with the ratio calculation. Specifically, the transmittance characteristic point of the glass material at a specific wavelength is found in the transmittance spectrum of the reference filter. For example, the transmittance at 550 nm should be the standard value. The measured wavelength is compared with the standard wavelength. If there is a deviation, the entire wavelength data sequence is linearly shifted to correct it, so that the transmittance spectra of vertical and oblique incident are precisely aligned on the wavelength coordinates. The wavelength alignment accuracy is controlled within 0.2 nm to ensure the accuracy of subsequent cutoff wavelength comparison analysis.

[0018] 102. Extract the vertical incident cutoff wavelength and the oblique incident cutoff wavelength corresponding to the transmittance dropping to a preset cutoff threshold from the transmittance spectrum, respectively. In this embodiment, extracting the vertical incident cutoff wavelength and the oblique incident cutoff wavelength corresponding to the transmittance dropping to a preset cutoff threshold from the transmittance spectrum includes: performing a first-order differential operation in the wavelength direction on the transmittance spectrum to obtain a transmittance gradient curve, and identifying the peak center wavelength corresponding to the maximum positive gradient value in the transmittance gradient curve; extending a preset wavelength width in the short wavelength direction and the long wavelength direction respectively, with the peak center wavelength point as the center, to determine the cutoff band edge region; within the cutoff band edge region, determining the wavelength position corresponding to the first drop in transmittance to the preset cutoff threshold along the wavelength increasing direction, and using the wavelength position as the vertical incident cutoff wavelength and the oblique incident cutoff wavelength respectively. Furthermore, after extracting the vertical incident cutoff wavelength and the oblique incident cutoff wavelength corresponding to the transmittance dropping to the preset cutoff threshold from the transmittance spectrum, the method further includes: extracting the oblique transmittance values ​​of each wavelength point in the band region where the wavelength is greater than the oblique incident cutoff wavelength and less than the preset upper limit wavelength in the oblique incident transmittance spectrum, and averaging the oblique transmittance values ​​to obtain the oblique infrared transmittance; extracting the vertical transmittance values ​​of each wavelength point in the infrared band where the wavelength is greater than the vertical incident cutoff wavelength and less than the preset upper limit wavelength, and averaging the transmittance values ​​to obtain the vertical infrared transmittance; calculating the difference between the oblique infrared transmittance and the vertical infrared transmittance to obtain the infrared leakage increment; and determining that the infrared suppression performance of the filter under test deteriorates under oblique incident conditions when the infrared leakage increment exceeds the preset infrared suppression degradation threshold.

[0019] Specifically, when extracting the cutoff wavelength parameter from the transmittance spectrum, a method based on transmittance gradient analysis is used. The cutoff wavelength refers to the wavelength position where the transmittance of an IRCF filter rapidly decreases from the high transmittance region of visible light to the low transmittance region of infrared light. Because the transmittance spectrum curve exhibits a steep drop near the cutoff band edge, directly searching for the wavelength point corresponding to a specific transmittance threshold on the original spectrum is easily affected by spectral noise. Therefore, a first-order differential operation is performed on the transmittance spectrum in the wavelength direction. The transmittance difference between two adjacent wavelength points is divided by the wavelength interval to obtain the rate of change of transmittance at that position, forming a transmittance gradient curve. In the cutoff band edge region where transmittance rapidly decreases, the gradient curve shows a significant positive peak. By searching for the maximum value of the positive gradient on the gradient curve, the wavelength position corresponding to the peak is located as the center of the cutoff band edge. Using this peak center wavelength as a reference, a certain range is extended to both short and long wavelengths to form the cutoff band edge region. Within this local region, the wavelength point where the transmittance first drops to the 50% transmittance threshold is searched; this wavelength point is the cutoff wavelength. Here, 50% transmittance is the industry standard for determining the cutoff wavelength in the field of optical thin films. The above process is performed on the transmittance spectrum of vertical incidence to obtain the vertical incidence cutoff wavelength. The same process is then performed on the transmittance spectra at each tilt angle to obtain the corresponding tilted incidence cutoff wavelength. Gradient analysis accurately identifies the cutoff band edge, avoiding misinterpreting secondary fluctuations or noise on the spectral curve as cutoff points, thus improving the reliability and repeatability of cutoff wavelength extraction.

[0020] After obtaining the cutoff wavelength, the suppression performance in the infrared band was evaluated. The core function of an IRCF filter is to block infrared light transmission; under perpendicular incidence conditions, the transmittance in the infrared band above the cutoff wavelength should be kept at a very low level. However, when light is incident at an angle, in addition to a blue shift in the cutoff wavelength, the transmittance in the infrared band also increases, leading to increased infrared light leakage and affecting image quality. To quantify the degree of degradation in this infrared suppression capability, an infrared evaluation band from the oblique incidence cutoff wavelength to 900 nm was selected in the oblique incidence transmittance spectrum. The transmittance values ​​of each wavelength sampling point within this band were extracted, and the average transmittance of this band was obtained by summing the transmittance values ​​of all sampling points and dividing by the number of sampling points. Similarly, an infrared evaluation band from the perpendicular incidence cutoff wavelength to 900 nm was selected in the perpendicular incidence transmittance spectrum, and the average transmittance was calculated using the same method to obtain the perpendicular infrared transmittance. 900 nm was chosen because the response of silicon-based image sensors to infrared light decays rapidly above 900 nm, and infrared light beyond this wavelength has little impact on imaging. The difference between the tilted infrared transmittance and the vertical infrared transmittance is then calculated. This difference is defined as the infrared leakage increment, which directly reflects the increase in infrared transmittance caused by tilted incidence. When the infrared leakage increment exceeds a preset infrared suppression degradation threshold, the infrared suppression performance of the filter under test is determined to have deteriorated under tilted incidence conditions. The preset infrared suppression degradation threshold is determined based on the imaging system's tolerance to infrared interference. When the infrared transmittance increases excessively, the image sensor receives too much infrared light, leading to color distortion in visible light imaging. This evaluation step can detect defects that cannot be captured by simple cutoff wavelength analysis. Some coating process anomalies can cause the overall transmittance in the infrared band to be high, but the cutoff wavelength position does not change significantly. By directly comparing the infrared transmittance, such problems can be identified, ensuring that the filter still has sufficient infrared suppression capability in wide-angle lens and other applications with large incidence angles, avoiding color shift caused by infrared contamination in the edge areas of the image.

[0021] 103. Calculate the wavelength offset between the vertical incident cutoff wavelength and each tilted incident cutoff wavelength to obtain multiple sets of angle-offset datasets of tilt angle and wavelength offset; In this embodiment, the step of calculating the wavelength offset between the vertically incident cutoff wavelength and each tilted incident cutoff wavelength to obtain multiple sets of angle-offset datasets of tilt angles and wavelength offsets includes: subtracting the vertically incident cutoff wavelength from the tilted incident cutoff wavelength corresponding to each tilt angle to obtain the wavelength difference corresponding to each tilt angle; when the wavelength difference is negative, it indicates that the cutoff wavelength is offset towards the shortwave direction; filtering out the wavelength differences with negative values ​​and the corresponding tilt angles from each wavelength difference to obtain an effective angle sequence and an effective difference sequence; taking the absolute value of each wavelength difference in the effective difference sequence to obtain the cutoff wavelength offset; and forming data pairs with each tilt angle and the corresponding cutoff wavelength offset in the effective angle sequence, arranging them in ascending order of tilt angle to generate an angle-offset dataset.

[0022] Specifically, when calculating the wavelength difference between the vertically incident cutoff wavelength and each tilted incident cutoff wavelength, a subtraction operation is performed for each tilt angle. The tilted incident cutoff wavelength value corresponding to a certain tilt angle in the preset tilt angle sequence is extracted, and this value is subtracted from the vertically incident cutoff wavelength value. The result is the wavelength difference corresponding to that tilt angle. The positive and negative signs of the wavelength difference have clear physical meanings: a negative value indicates that the tilted incident cutoff wavelength is less than the vertically incident cutoff wavelength, meaning the cutoff wavelength shifts towards shorter wavelengths. This conforms to the physical law that the cutoff wavelength of a multilayer dielectric film blue-shifts due to changes in the effective optical path during tilted incidence; a positive value indicates that the tilted incident cutoff wavelength is greater than the vertically incident cutoff wavelength, meaning the cutoff wavelength shifts towards longer wavelengths. This contradicts the basic principles of thin-film interference and is an anomalous spectral drift phenomenon. The occurrence of anomalous spectral drift indicates a problem in the measurement at that angle. The causes include optical path alignment deviation at that angle, insufficient light intensity received by the detector leading to cutoff wavelength extraction errors, or coating defects in the filter under test at that spatial location, such as localized abnormal film thickness or film layer delamination. The wavelength difference is subtracted sequentially for all tilt angles in the preset tilt angle sequence to obtain multiple sets of correlation data between tilt angles and corresponding wavelength differences.

[0023] Next, valid data conforming to physical laws are screened from the calculated wavelength differences. Each wavelength difference corresponding to a tilt angle is examined to determine whether its value is positive or negative. Negative wavelength differences and their corresponding tilt angles are extracted; negative wavelength differences form a valid difference sequence, and their corresponding tilt angles form a valid angle sequence. For positive wavelength differences, their corresponding tilt angles are recorded as abnormal angles, and the filter under test is marked as exhibiting an anomalous spectral drift at these abnormal angles. Recording abnormal angles provides crucial information for subsequent quality assessment; an excessive number of abnormal angles indicates a systematic defect in the filter. For example, in measurements involving six tilt angles, if two of the angles have positive wavelength differences, these two angles are recorded as abnormal angles, and the remaining four angles and their corresponding negative wavelength differences form valid angle and valid difference sequences, respectively. This screening process ensures that subsequent angle spectral drift rate fitting analysis uses only valid data points conforming to the blue shift law, eliminating interference from abnormal data on the fitted line, while retaining abnormal angle information for quality assessment. This reflects a detection strategy that combines data quality control and defect identification.

[0024] Finally, the selected effective difference sequence is transformed by absolute value and paired with the effective angle sequence to generate an angle-offset dataset. All wavelength differences in the effective difference sequence are negative. The absolute value of each negative value is calculated, and the negative sign is removed to obtain a positive number, which is the cutoff wavelength offset. Its magnitude represents the extent to which the cutoff wavelength shifts towards shorter wavelengths. Each tilt angle in the effective angle sequence is paired with the corresponding absolute-valued cutoff wavelength offset in the effective difference sequence, forming multiple tilt angle-cutoff wavelength offset data pairs. These data pairs are arranged in ascending order of tilt angle values, and the resulting dataset is the angle-offset dataset. This dataset clearly shows the change in cutoff wavelength offset with increasing tilt angle; the larger the angle, the larger the offset, exhibiting an increasing trend. The angle-offset dataset provides standardized input data for subsequent linear fitting. By taking the absolute value, the data is unified to positive values ​​to facilitate fitting calculations. By sorting the data, the data is arranged in ascending order of angle to facilitate trend analysis. At the same time, outlier angle data is not included in the dataset to avoid affecting the fitting accuracy. The entire data processing flow takes into account three functions: physical law compliance verification, outlier data removal, and effective data normalization.

[0025] 104. Perform linear fitting on the angle-offset dataset to obtain the fitting slope as the angle spectral drift rate, and compare the angle spectral drift rate with the preset standard drift rate to determine the coating quality of the filter under test.

[0026] In this embodiment, the step of linearly fitting the angle-offset dataset to obtain the fitting slope as the angle spectral drift rate includes: performing angle sine and square operations on each tilt angle in the angle-offset dataset to obtain an angle factor sequence characterizing the optical path length of the thin film interference; using the angle factor sequence as the independent variable and the cutoff wavelength offset of each tilt angle in the angle-offset dataset as the dependent variable, linearly fitting the independent variable and the dependent variable using the least squares method to obtain the angle-wavelength drift response function; and extracting the slope coefficient of the angle-wavelength drift response function as the angle spectral drift rate. The step of comparing the angular spectral drift rate with a preset standard drift rate to determine the coating quality of the filter under test includes: obtaining the nominal cutoff wavelength and nominal effective refractive index corresponding to the filter under test, and calculating the theoretical angular spectral drift rate corresponding to the nominal cutoff wavelength and nominal effective refractive index as the reference drift rate; calculating the deviation rate between the angular spectral drift rate and the reference drift rate; when the absolute value of the deviation rate is less than a preset deviation threshold, the coating quality of the filter under test is determined to be qualified; when the absolute value of the deviation rate is not less than the preset deviation threshold, the coating quality of the filter under test is determined to be unqualified.

[0027] Specifically, when performing linear fitting on the angle-offset dataset, the tilt angle is first converted into an angle factor. The angle factor is a physical quantity determined according to thin-film interference theory, used to characterize the influence of the incident angle on the optical path within the thin film. For each tilt angle value in the angle-offset dataset, the angle is first converted from degrees to radians, then the sine value of the angle is calculated, and finally the sine value is squared to obtain the angle factor. For example, a tilt angle of 15 degrees is approximately 0.262 radians, the sine value is approximately 0.259, and the squared angle factor is approximately 0.067. This calculation is performed sequentially for all tilt angles in the angle-offset dataset to obtain the angle factor sequence. Using the angle factor sequence as the independent variable and the cutoff wavelength offset corresponding to each tilt angle in the angle-offset dataset as the dependent variable, linear fitting is performed using the least squares method. The specific implementation of the least squares method involves calculating the average of the independent and dependent variables for all data points. Then, for each data point, the deviation of the independent variable from the average and the deviation of the dependent variable from the average are calculated. The sum of the products of the independent and dependent variable deviations for all data points is divided by the sum of the squares of the independent variable deviations for all data points, yielding the slope of the fitted line. The form of the fitted line equation is: Cutoff wavelength shift = Slope × Angle factor + Intercept. This equation is called the angle-wavelength drift response function. The slope value in the response function is extracted as the angle spectral drift rate. The physical meaning of this parameter is the number of nanometers by which the cutoff wavelength shifts towards shorter wavelengths for every unit increase in the angle factor; a larger value indicates that the filter is more sensitive to angle changes. By transforming discrete measurement data points into a single slope parameter through linear fitting, quantitative assessment of angle stability is achieved, facilitating cross-sectional comparisons between different batches of products.

[0028] The measured angular spectral drift rate is then compared with the theoretical reference value to determine the coating quality. Two design parameters, nominal cutoff wavelength and nominal effective refractive index, are obtained from the product specifications of the filter under test. The nominal cutoff wavelength is the designed cutoff wavelength for this type of filter under perpendicular incidence. The nominal effective refractive index is the equivalent refractive index characterizing the overall optical properties of the multilayer film stack, calculated by weighting the refractive indices and thicknesses of each film layer. This parameter is recorded in the product specifications. According to the thin-film interference theory under small-angle approximation conditions of multilayer dielectric films, there is a definite mathematical relationship between the theoretical angular spectral drift rate and the nominal cutoff wavelength and nominal effective refractive index: the theoretical angular spectral drift rate equals the negative nominal cutoff wavelength divided by twice the nominal effective refractive index. The nominal parameters of the filter under test are substituted into this relationship to calculate the theoretical angular spectral drift rate, which is used as the reference drift rate. The difference between the measured angular spectral drift rate and the reference drift rate is calculated, divided by the absolute value of the reference drift rate, and then multiplied by 100% to obtain the deviation rate. The absolute value of the deviation rate reflects the degree to which the measured value deviates from the theoretical value. When the absolute value is less than the preset deviation threshold, the coating quality is considered acceptable; when the absolute value reaches or exceeds the preset deviation threshold, the coating quality is considered unacceptable. This relative deviation judgment method based on theoretical benchmarks is more scientific than setting absolute thresholds because the theoretical values ​​of the angular spectral drift rate of IRCF filters with different design parameters vary greatly, and relative deviation can unify the evaluation standard.

[0029] Finally, the specific coating defect type is identified based on the sign of the deviation rate. A positive deviation rate indicates that the absolute value of the measured angular spectral drift rate is greater than the absolute value of the reference drift rate. Since the angular spectral drift rate is inversely proportional to the effective refractive index, an increase in the absolute value indicates that the effective refractive index is too low, or that the actual effective refractive index is reduced due to insufficient film thickness. A negative deviation rate indicates that the absolute value of the measured angular spectral drift rate is less than the absolute value of the reference drift rate, indicating that the effective refractive index is too high, or that the effective refractive index is increased due to excessive film thickness. The pass / fail judgment conclusion, the deviation rate value, the defect type corresponding to the positive and negative signs, and the abnormal angle information recorded in the previous steps are integrated to generate the quality inspection result of the filter under test. The inspection result contains a clear conclusion on whether the filter is qualified. If it is unqualified, it indicates whether the refractive index is too low or too high, and whether the film thickness is insufficient or excessive, providing specific directions for adjusting the coating process parameters. At the same time, the existence of abnormal angles is recorded as a quality hazard warning. This multi-dimensional inspection result output, compared with a simple pass / fail judgment, can provide more valuable technical information for production process improvement.

[0030] In this embodiment of the invention, a first beam is perpendicularly incident on the filter under test as a reference, and a second beam is incident sequentially at a preset tilt angle. The transmittance spectra of the two beams after passing through the filter are simultaneously acquired within a preset wavelength range. The perpendicularly incident cutoff wavelength and the tilted incident cutoff wavelength corresponding to the transmittance decreasing to a preset cutoff threshold are extracted from the transmittance spectra. The wavelength shift between the perpendicularly incident cutoff wavelength and each tilted incident cutoff wavelength is calculated, resulting in an angle-shift dataset of tilt angle and wavelength shift. A linear fit is performed on the angle-shift dataset to obtain the fitting slope as the angle spectral drift rate. The angle spectral drift rate is compared with a preset standard drift rate to determine the coating quality of the filter under test. This method accurately quantifies the drift characteristics of the cutoff wavelength as a function of the incident angle and effectively evaluates the coating process quality.

[0031] Please see Figure 2 Another embodiment of the IRCF filter angle shift spectral drift detection method in this application includes: 201. The first beam is incident perpendicularly on the filter under test, and the second beam is incident on the filter under test from each tilt angle in a preset tilt angle sequence. Within a preset wavelength range, the transmittance spectra of the first beam and the second beam after passing through the filter under test are collected synchronously for each tilt angle. In this embodiment, step 201 is similar to step 101 in the first embodiment, and will not be described again here.

[0032] 202. Perform a first-order differential operation in the wavelength direction on the transmittance spectrum to obtain the transmittance gradient curve, and identify the peak center wavelength corresponding to the maximum positive gradient value in the transmittance gradient curve. Specifically, when performing first-order differential operations on the transmittance spectrum to enhance the cutoff band edge characteristics, a numerical difference method is used to process the discrete spectral data. The transmittance spectrum is acquired by a spectrometer, and the data is in the form of a series of wavelength-to-transmittance pairs, with a wavelength interval of 1 nanometer. For each wavelength point in the spectral data, the transmittance value at that wavelength point is extracted and subtracted from the transmittance value at the next adjacent wavelength point to obtain the transmittance difference. This difference is then divided by the wavelength interval of 1 nanometer, and the result is the transmittance gradient value at that wavelength point. This difference operation is performed sequentially on all wavelength points in the spectral data from the starting wavelength to the ending wavelength, forming a transmittance gradient curve corresponding to the original transmittance spectrum. The horizontal axis of the curve is wavelength, and the vertical axis is transmittance gradient. In the transmittance spectrum of the IRCF filter, the gradient value is close to zero for the visible light band where the transmittance is high and changes gradually, and the gradient value is also close to zero for the infrared band where the transmittance is very low and relatively stable. Only in the cutoff band edge region does the transmittance drop rapidly from a high value to a low value, and this steep drop is represented by a significant positive peak on the gradient curve. By comparing all gradient values ​​point by point in the transmittance gradient curve, the gradient point with the largest value is identified, and the wavelength corresponding to this point is the center wavelength of the peak. This gradient analysis method can highlight the positional characteristics of the cutoff band edge because the gradient peak generated by the large transmittance change at the cutoff band edge is much higher than the small gradient fluctuations caused by spectral noise, thus achieving accurate location of the cutoff band edge.

[0033] 203. Taking the peak center wavelength point as the center, extend the preset wavelength width in the short wavelength direction and the long wavelength direction respectively to determine the cutoff band edge region; Specifically, after determining the peak center wavelength, a preset wavelength width is extended from this wavelength point in both the short-wavelength and long-wavelength directions to delineate the cutoff band edge region. The preset wavelength width is determined based on the typical transition width of the IRCF filter's cutoff band edge. The transition range from high transmittance to low transmittance at the cutoff band edge is on the order of tens of nanometers. Selecting an appropriate wavelength width can cover the entire cutoff band edge transition region (e.g., the wavelength width of the IRCF filter's cutoff band edge transitioning from the visible light high transmittance region to the infrared low transmittance region is between 15 nanometers and 35 nanometers; setting a 20-nanometer single-sided extension width can completely cover the cutoff transition region while avoiding the introduction of flat spectral regions far from the cutoff band edge). Subtracting the preset wavelength width from the peak center wavelength in the short-wavelength direction yields the short-wavelength boundary of the cutoff band edge region, and adding the preset wavelength width in the long-wavelength direction yields the long-wavelength boundary. The wavelength range between these two boundaries is the cutoff band edge region.

[0034] 204. Within the cutoff band edge region, determine the wavelength position corresponding to the first drop in transmittance to the preset cutoff threshold along the wavelength increasing direction, and use the wavelength position as the vertical incident cutoff wavelength and the inclined incident cutoff wavelength, respectively. In this embodiment, determining the wavelength position corresponding to the first drop in transmittance to a preset cutoff threshold within the cutoff band edge region along the wavelength increasing direction includes: identifying the maximum wavelength point with transmittance lower than the preset cutoff threshold as the left boundary point and the minimum wavelength point with transmittance higher than the preset cutoff threshold as the right boundary point within the cutoff band edge region along the wavelength increasing direction; extracting discrete transmittance sampling data between the left boundary point and the right boundary point, and interpolating the discrete transmittance sampling data to generate a transmittance curve; calculating the wavelength value corresponding to the transmittance equal to the preset cutoff threshold on the transmittance curve as the wavelength position.

[0035] Specifically, the cutoff wavelength is precisely located within this localized region. Starting from the short-wavelength boundary, the transmittance values ​​are checked point by point along the wavelength-increasing direction, examining their relationship with a preset cutoff threshold. The preset cutoff threshold can be set to 50% transmittance. When the first wavelength point with a transmittance value below 50% is detected, this point is recorded as the left boundary point, indicating that the transmittance at this point has dropped below the threshold. The process continues point by point along the longer wavelength direction. When the first wavelength point with a transmittance value above 50% is detected, this point is recorded as the right boundary point, indicating that the transmittance at this point is still above the threshold. Since the transmittance spectrum monotonically decreases in the cutoff band edge region, there must be a position between the left and right boundary points where the transmittance is exactly equal to 50%. This position represents the interval containing the cutoff wavelength. Searching within the cutoff band edge region, rather than across the entire spectrum, eliminates interference from transmittance fluctuations at other locations on the spectral curve that could affect cutoff wavelength identification. Furthermore, interpolation processing is performed on the transmittance data between the left and right boundary points to obtain higher accuracy in cutting off wavelength location. The spectrometer's wavelength sampling interval is 1 nanometer, and the wavelength difference between the left and right boundary points is 1 nanometer. Directly using these two discrete points only yields a cutoff wavelength estimate with an accuracy of 1 nanometer. To improve accuracy, wavelength and transmittance data are extracted from the left and right boundary points, as well as any other sampling points between them. A linear interpolation method is used to generate a continuous transmittance curve between these discrete points. Linear interpolation assumes that the transmittance between two adjacent sampling points changes linearly. The calculation method is as follows: for the transmittance T1 corresponding to wavelength λ1 at the left boundary point and the transmittance T2 corresponding to wavelength λ2 at the right boundary point, the transmittance T at any wavelength λ on the interpolation curve is calculated proportionally as T = T1 + (λ - λ1) × (T2 - T1) / (λ2 - λ1). The wavelength corresponding to 50% transmittance is then calculated on the interpolation curve. That is, by substituting T = 50% into the above equation, we obtain λ = (50% - T1) × (λ2 - λ1) / (T2 - T1) + λ1. The calculated result is the precise location of the cutoff wavelength. Because the calculation process is continuous rather than discrete sampling, the numerical accuracy of the cutoff wavelength is not limited by the spectrometer's 1-nanometer sampling interval, and can achieve an accuracy of 0.1 nanometers or even higher. This interpolation refinement allows minute changes in the cutoff wavelength to be accurately captured; even cutoff wavelength shifts caused by angle changes of only a few tenths of a nanometer can be detected. Applying the complete above process to the vertically incident transmittance spectrum and the transmittance spectra at each tilt angle yields the vertically incident cutoff wavelength and the corresponding tilted incident cutoff wavelengths for each tilt angle.

[0036] 205. Calculate the wavelength offset between the vertical incident cutoff wavelength and each tilted incident cutoff wavelength to obtain multiple sets of angle-offset datasets of tilt angle and wavelength offset; 206. Perform linear fitting on the angle-offset dataset to obtain the fitting slope as the angle spectral drift rate, and compare the angle spectral drift rate with the preset standard drift rate to determine the coating quality of the filter under test.

[0037] In this embodiment, steps 205-206 are similar to steps 103-104 in the first embodiment, and will not be described again here.

[0038] In this embodiment, a first beam is perpendicularly incident on the filter under test as a reference, and a second beam is incident sequentially at a preset tilt angle. The transmittance spectra of both beams after passing through the filter are simultaneously acquired within a preset wavelength range. The perpendicularly incident cutoff wavelength and the tilted incident cutoff wavelength, corresponding to the transmittance decreasing to a preset cutoff threshold, are extracted from the transmittance spectra. The wavelength shift between the perpendicularly incident cutoff wavelength and each tilted incident cutoff wavelength is calculated, resulting in an angle-shift dataset. A linear fit is performed on the angle-shift dataset to obtain the fitting slope as the angle spectral drift rate. The angle spectral drift rate is compared with a preset standard drift rate to determine the coating quality of the filter under test. This method accurately quantifies the drift characteristics of the cutoff wavelength as a function of the incident angle, effectively evaluating the coating process quality.

[0039] The above describes the IRCF filter angle shift spectral drift detection method in the embodiments of the present invention. The following describes the IRCF filter angle shift spectral drift detection device in the embodiments of the present invention. Please refer to [link to relevant documentation]. Figure 3 One embodiment of the IRCF filter angle shift spectral drift detection device of the present invention includes: The dual-channel acquisition module 301 is used to vertically incident a first beam onto the filter under test and to sequentially incident a second beam onto the filter under test from each tilt angle in a preset tilt angle sequence. Within a preset wavelength range, it synchronously acquires the transmittance spectrum corresponding to the first beam and the second beam after passing through the filter under test at each tilt angle. Wavelength extraction module 302 is used to extract the vertical incident cutoff wavelength and the oblique incident cutoff wavelength corresponding to the transmittance dropping to a preset cutoff threshold from the transmittance spectrum, respectively. The offset calculation module 303 is used to calculate the wavelength offset between the vertical incident cutoff wavelength and each tilted incident cutoff wavelength, and obtain multiple sets of angle-offset datasets of tilt angle and wavelength offset. The quality assessment module 304 is used to perform linear fitting on the angle-offset dataset, obtain the fitting slope as the angle spectral drift rate, and compare the angle spectral drift rate with the preset standard drift rate to determine the coating quality of the filter under test.

[0040] In this embodiment of the invention, a first beam is perpendicularly incident on the filter under test as a reference, and a second beam is incident sequentially at a preset tilt angle. The transmittance spectra of the two beams after passing through the filter are simultaneously acquired within a preset wavelength range. The perpendicularly incident cutoff wavelength and the tilted incident cutoff wavelength corresponding to the transmittance decreasing to a preset cutoff threshold are extracted from the transmittance spectra. The wavelength shift between the perpendicularly incident cutoff wavelength and each tilted incident cutoff wavelength is calculated, resulting in an angle-shift dataset of tilt angle and wavelength shift. A linear fit is performed on the angle-shift dataset to obtain the fitting slope as the angle spectral drift rate. The angle spectral drift rate is compared with a preset standard drift rate to determine the coating quality of the filter under test. This method accurately quantifies the drift characteristics of the cutoff wavelength as a function of the incident angle and effectively evaluates the coating process quality.

[0041] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the system or system / unit described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0042] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for detecting angular shift spectral drift of an IRCF filter, comprising: The IRCF filter angle offset spectrum drift detection method comprises: A first light beam is used to perpendicularly irradiate the filter to be detected, and a second light beam is used to sequentially irradiate the filter to be detected from each of a preset sequence of tilt angles, and in a preset wavelength range, the transmittance spectrum corresponding to each tilt angle after the first light beam and the second light beam pass through the filter to be detected is synchronously collected; A vertical incidence cut-off wavelength and a tilt incidence cut-off wavelength corresponding to a preset cut-off threshold are extracted from the transmittance spectrum respectively; The wavelength offset between the vertical incidence cut-off wavelength and each tilt incidence cut-off wavelength is calculated respectively, and a plurality of sets of angle-offset data sets of tilt angles and wavelength offsets are obtained; Linear fitting is performed on the angle-offset data set to obtain a fitting slope as an angle spectrum drift rate, and the angle spectrum drift rate is compared with a preset standard drift rate to determine the coating quality of the filter to be detected.

2. The IRCF filter angle offset spectral shift detection method of claim 1, wherein, The transmittance spectrum comprises a vertical incidence transmittance spectrum and a tilt incidence transmittance spectrum, and the transmittance spectrum corresponding to each tilt angle after the first light beam and the second light beam pass through the filter to be detected is synchronously collected in a preset wavelength range, which comprises: For each tilt angle, the first light intensity signal of the first light beam passing through the filter to be detected and the second light intensity signal of the second light beam passing through the filter to be detected are synchronously collected, and the reference light intensity signal of the first light beam and the second light beam passing through the reference filter is synchronously collected; The first light intensity signal and the corresponding reference light intensity signal are subjected to wavelength-by-wavelength ratio calculation and wavelength axis calibration to obtain the vertical incidence transmittance spectrum; The second light intensity signal and the corresponding reference light intensity signal are subjected to wavelength-by-wavelength ratio calculation and wavelength axis calibration to obtain the tilt incidence transmittance spectrum.

3. The IRCF filter angle offset spectral shift detection method of claim 1, wherein, The vertical incidence cut-off wavelength and the tilt incidence cut-off wavelength corresponding to the preset cut-off threshold are extracted from the transmittance spectrum respectively, which comprises: A first-order differential operation in the wavelength direction is performed on the transmittance spectrum to obtain a transmittance gradient curve, and a peak center wavelength corresponding to a maximum positive gradient in the transmittance gradient curve is identified; A preset wavelength width is expanded in the short wavelength direction and the long wavelength direction respectively with the peak center wavelength point as the center to determine a cut-off band edge region; In the cut-off band edge region, a wavelength position corresponding to the first time when the transmittance decreases to the preset cut-off threshold is determined in the wavelength increasing direction, and the wavelength position is taken as the vertical incidence cut-off wavelength and the tilt incidence cut-off wavelength respectively.

4. The IRCF filter angle offset spectral shift detection method of claim 3, wherein, In the cut-off band edge region, a wavelength position corresponding to the first time when the transmittance decreases to the preset cut-off threshold is determined in the wavelength increasing direction, which comprises: In the cut-off band edge region, a maximum wavelength point with a transmittance lower than the preset cut-off threshold is identified as a left boundary point in the wavelength increasing direction, and a minimum wavelength point with a transmittance higher than the preset cut-off threshold is identified as a right boundary point; Transmittance discrete sampling data between the left boundary point and the right boundary point is extracted, and the transmittance discrete sampling data is subjected to interpolation processing to generate a transmittance curve; Calculate the wavelength value corresponding to the transmittance equal to the preset cutoff threshold on the transmittance curve as the wavelength position.

5. The IRCF filter angle offset spectral shift detection method of claim 1, wherein, The wavelength offset between the normal incidence cutoff wavelength and each oblique incidence cutoff wavelength is calculated to obtain a plurality of sets of angle-offset data sets of the tilt angle and the wavelength offset, including: The wavelength difference corresponding to each tilt angle is obtained by subtracting the normal incidence cutoff wavelength from the oblique incidence cutoff wavelength corresponding to the tilt angle, and the negative value of the wavelength difference indicates that the cutoff wavelength is shifted to the short wave direction; The wavelength difference and the corresponding tilt angle are selected from the wavelength difference, and the effective angle sequence and the effective difference sequence are obtained; The absolute value of each wavelength difference in the effective difference sequence is taken to obtain the cutoff wavelength offset, and the tilt angle in the effective angle sequence and the corresponding cutoff wavelength offset are combined to form a data pair, which is arranged in ascending order of tilt angle to generate an angle-offset data set.

6. The IRCF filter angle offset spectral shift detection method of claim 1, wherein, The linear fitting of the angle-offset data set is performed to obtain the fitting slope as the angle spectral drift rate, including: The angle sine operation and the square operation are performed on each tilt angle in the angle-offset data set to obtain an angle factor sequence representing the thin film interference optical path; The angle factor sequence is used as the independent variable and the cutoff wavelength offset of each tilt angle in the angle-offset data set is used as the dependent variable, and the least squares method is used to linearly fit the independent variable and the dependent variable to obtain an angle-wavelength drift response function; The slope coefficient of the angle-wavelength drift response function is extracted as the angle spectral drift rate.

7. The IRCF filter angle offset spectral shift detection method of claim 1, wherein, The angle spectral drift rate is compared with the preset standard drift rate to determine the coating quality of the filter to be tested, including: The nominal cutoff wavelength and the nominal effective refractive index corresponding to the filter to be tested are obtained, and the theoretical angle spectral drift rate corresponding to the nominal cutoff wavelength and the nominal effective refractive index is calculated as the reference drift rate; The deviation rate of the angle spectral drift rate and the reference drift rate is calculated; When the absolute value of the deviation rate is less than the preset deviation threshold, it is determined that the coating quality of the filter to be tested is qualified; when the absolute value of the deviation rate is not less than the preset deviation threshold, it is determined that the coating quality of the filter to be tested is unqualified.

8. An IRCF filter angle shift spectral shift detection device, characterized by, The IRCF filter angle offset spectral drift detection device includes: A dual-channel acquisition module is used to vertically incident a first light beam on a filter to be tested, and a second light beam is incident on the filter to be tested from each tilt angle in a preset tilt angle sequence, and the transmittance spectrum of the first light beam and the second light beam after passing through the filter to be tested is acquired simultaneously in a preset wavelength range for each tilt angle; A wavelength extraction module is used to extract the normal incidence cutoff wavelength and the oblique incidence cutoff wavelength corresponding to the transmittance falling below a preset cutoff threshold from the transmittance spectrum; An offset calculation module is used to calculate the wavelength offset between the normal incidence cutoff wavelength and each oblique incidence cutoff wavelength to obtain a plurality of sets of angle-offset data sets of the tilt angle and the wavelength offset. The quality evaluation module is configured to perform linear fitting on the angle-offset data set to obtain a fitting slope as an angle spectrum drift rate, and compare the angle spectrum drift rate with a preset standard drift rate to determine the coating quality of the filter under test.

9. An IRCF filter angle shift spectral shift detection device, characterized by, The IRCF filter angle offset spectrum drift detection device comprises a memory and at least one processor, and the memory stores instructions; The at least one processor invokes the instructions in the memory to enable the IRCF filter angle offset spectrum drift detection device to perform the steps of the IRCF filter angle offset spectrum drift detection method according to any one of claims 1-7.

10. A computer-readable storage medium having stored thereon instructions, the instructions comprising, The instructions are executed by the processor to implement the steps of the IRCF filter angle offset spectrum drift detection method according to any one of claims 1-7.

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