Method for pre-calibrating a spectrum analysis module based on a filter array

Abstract

The present invention provides a method for pre-calibrating and reconstructing a spectrum analysis module based on a filter array. The preset calibration information obtained by the preset calibration method provided by the present invention includes the optical response and photoelectric conversion factors of each part or component inside the corresponding spectrum analysis module, the structural component deviation and the alignment deviation between each part during the manufacturing process, and the comprehensive influence of other uncontrollable and unclear factors on the spectrum test. The preset calibration method and spectrum reconstruction method provided by the present invention are conducive to enabling the spectrum analysis module to obtain more accurate spectrum information during detection.

Description

Technical Field

[0001] The present invention relates to a spectrum analysis module based on a filter array, and in particular to a method for presetting calibration and spectrum reconstruction of the spectrum analysis module. Background Art

[0002] The spectrometer is a very important optical instrument. There are two common types of spectrometers: one is the dispersion spectrometer represented by the grating spectrometer; the other is the modulation type represented by the Fourier transform spectrometer based on the interferometer. Laboratory-level professional spectrometers are generally large and expensive, and their overall performance is often weakened as the size of the instrument is reduced.

[0003] In recent years, with the development of information technology, the intelligentization of production and life, and the growing demand for food safety, environmental pollution, medical health, etc., micro-integrated spectral analysis modules have attracted attention. Its application goal is to develop into a sensor component for intelligent devices and consumer electronic products (such as smartphones and wearable devices).

[0004] Among them, the realization of a micro-integrated spectral analysis module based on a filter array structure is an important approach and has received widespread attention. This spectral analysis module irradiates the transmitted light of the filter structure units with different transmission spectral characteristics in the filter array onto the corresponding detector units in the detector array for photoelectric conversion, and then reconstructs the spectrum through back-end data processing. According to the different filter array structures, examples are as follows:

[0005] For example, the filter array structure is based on a vertical Fabry-Perot resonant cavity array structure with discrete different cavity lengths [as mentioned in the following literature: 1. S.-W. Wang, C. Xia, X. Chen, W. Lu, M. Li, H. Wang, W. Zheng, and T. Zhang, Opt. Lett., 32(6), 632(2007); 2. Wen Zhiyu, Chen Gang, Wang Jianguo, Spectroscopy and Spectral Analysis, 26(10), 1955(2006). ];

[0006] For example, the filter array structure is a photonic crystal structure based on dielectric materials [as mentioned in the following literature: NK Pervez, W. Cheng, Z. Jia, MP Cox, HM Edrees, and I. Kymissis, Opt. Express, 18(8), 8277(2010).];

[0007] For example, the filter array structure is based on a semiconductor quantum dot or quantum wire array structure with different absorption spectra [as mentioned in the following literature: 1. J. Bao and MG Bawendi, Nature, 523, 67 (2015); 2. Z. Yang, T. Albrow-Owen, H. Cui, et al., Science, 365, 1017 (2019).]; and so on.

[0008] Another type of filter array structure is based on metal micro-nanostructure [such as the following public invention patents: Chinese invention patents CN 105092035B, CN 109642822A, CN 108731806 A, CN 110873911 A, CN110243471 A, CN 10954311 A, CN109564323 A, etc.; US invention patents US 8542359 B2, US7426040 B2, etc. ]

[0009] When in use, the micro-integrated spectral analysis module based on the filter array needs to combine the preset calibration information of the relevant optical components in the equipment during the manufacturing process to perform spectral reconstruction calculations.

[0010] In the methods and embodiments provided in public documents such as the above-mentioned journal articles and some invention patents [such as Chinese invention patents CN 103207015 A, CN109642822 A, CN 10954311 A; US invention patent US 8542359 B2], the preset calibration information generally includes: the transmission spectrum (or transfer function) of each filter structure unit in the filter array and the response function (or sensitivity function) of the detector unit in the detector array.

[0011] This requires that the transmission spectrum of each filter structure unit in the filter array and the response function of the detector unit in the detector array (the response function is generally the same for different detector units) be tested in the preset calibration test. Generally speaking, the size (or area) of these array units is small and the number is large, which makes the preset calibration test complicated and inefficient, and may introduce large errors. Furthermore, when the filter array, the detector array and other optical components are assembled into a module, the transfer function of other optical components, the beam shape, the alignment error between different components, the transfer function in the photoelectric signal conversion process, and the influence of other uncontrollable factors will make the preset calibration information based only on the filter array and the detector array insufficient, thereby introducing large errors in the spectrum reconstruction and may seriously affect the accuracy of the spectrum test. Summary of the invention

[0012] The present invention provides a method for pre-calibrating and reconstructing the spectrum of a spectrum analysis module based on a filter array.

[0013] The spectral analysis module involved in the embodiment of the present invention includes at least a filter array and a detector array, and may also include a signal light collection and beam shaping part, a signal processing and control circuit, and a module structure.

[0014] The optical filter array is composed of optical filter structural units with different transmission spectrum characteristics.

[0015] The detector array is composed of a plurality of inherent detector unit pixels. The detector array can be planned to have a plurality of detector units, each of which contains one or more detector unit pixels.

[0016] Each filter structure unit in the filter array corresponds to each detector unit in the detector array.

[0017] Before use, the spectral analysis module needs to be preset calibrated to obtain preset calibration information. In the spectrum detection of the signal light from the target object, it is necessary to combine the preset calibration information and the test information of the signal light to obtain the spectrum of the signal light through data processing and calculation.

[0018] The preset calibration method provided in the embodiment of the present invention is to perform a preset calibration test after the manufacture and packaging of the spectrum analysis module are completed and the hardware system thereof is fixed.

[0019] The preset calibration test system involved in the embodiment of the present invention includes: a calibration light source; a calibrated spectrum analysis module; and devices such as a signal processing system, a control system, and an input / output terminal that match the spectrum analysis module.

[0020] The calibration light source is a quasi-monochromatic light source with adjustable wavelength, that is, it can provide quasi-monochromatic light with adjustable wavelength and stable output power within the working band of the spectrum analysis module. The quasi-monochromatic light has a narrow spectral line width and a small adjustable wavelength interval, and its central wavelength position is as evenly distributed as possible within the working band of the spectrum analysis module. The quasi-monochromatic light has a stable and controllable output power at each of its central wavelengths.

[0021] The calibration light source may be a wavelength-adjustable quasi-monochromatic light source composed of a plurality of quasi-monochromatic light sources with different central wavelengths, or a wavelength-adjustable quasi-monochromatic light source that achieves quasi-monochromatic light output with different central wavelengths by tuning internal resonant cavity parameters.

[0022] The calibration light source may also be based on a standard broadband light source, using a tunable monochromator or a tunable filter to obtain quasi-monochromatic light with different central wavelengths.

[0023] In a preset calibration test of the spectral analysis module, quasi-monochromatic light with different central wavelengths output by a calibration light source is respectively input into the spectral analysis module, and a digital signal generated by the detector array in the spectral analysis module to characterize the intensity of the light signal received by each detector unit is recorded by a signal processing system.

[0024] In the above preset calibration test, the output power of the quasi-monochromatic light with different central wavelengths corresponding to the calibration light source, the intensity of the light represented by the digital signal generated by each detector unit and other components received by the signal processing system, and other related information are preset calibration information. The preset calibration information uniquely corresponds to a single specific calibrated spectrum analysis module. The preset calibration information needs to be saved so as to be called in the spectrum reconstruction calculation when the spectrum analysis module is used for spectrum detection.

[0025] In the spectrum detection of the signal light from the target object using the spectrum analysis module, after the signal light from the target object is collected by the spectrum analysis module, the digital signal corresponding to the intensity of the light signal received by each detector unit is also recorded through its signal processing system. Based on the preset calibration information of the spectrum analysis module used and the digital signal corresponding to the light signal received by each detector unit generated in the test, the spectrum reconstruction of the measured signal light is realized through the data processing algorithm.

[0026] The main features and advantages of the present invention are described as follows:

[0027] The spectrum analysis module involved in the present invention comprises a filter array, a detector array and other components.

[0028] The preset calibration method provided by the present invention is to perform a preset calibration test after the manufacture and packaging of the spectrum analysis module are completed and the hardware system thereof is fixed.

[0029] The preset calibration information obtained by the preset calibration method provided by the present invention includes the optical response and photoelectric conversion factors of each part or component inside the corresponding spectral analysis module, the structural component deviation and the alignment deviation between each part during the manufacturing process, and the comprehensive influence of other uncontrollable and unclear factors on the spectral test, rather than just the influence of the transfer function and response function of the filter array unit and the detector array unit.

[0030] The preset calibration test method provided by the present invention is simpler, more efficient and more accurate; and it is not necessary to measure the transfer function and the response function of each filter structure unit in the filter array and the detector unit in the detector array.

[0031] The preset calibration method and spectrum reconstruction method provided by the present invention are conducive to enabling the spectrum analysis module to obtain more accurate spectrum information during detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of a spectrum analysis module and a test system thereof involved in an embodiment of the present invention.

[0033] Figure 2 It is a side view structural diagram of a filter array and a detector array in a spectral analysis module involved in an embodiment of the present invention.

[0034] Figure 3 It is a schematic diagram of performing a preset calibration test on the spectrum analysis module involved in the embodiment of the present invention.

[0035] Figure 4A Schematic diagram of a calibration light source based on a wavelength-tunable monochromatic light source in a preset calibration test system according to an embodiment of the present invention.

[0036] Figure 4B It is a schematic diagram of a calibration light source for obtaining quasi-monochromatic light using an adjustable monochromator based on a standard broadband light source in a preset calibration test system according to an embodiment of the present invention.

[0037] Figure 4C Schematic diagram of a calibration light source for obtaining quasi-monochromatic light using an adjustable filter based on a standard broadband light source in a preset calibration test system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0038] In order to explain the technical content, structural features, achieved objectives and effects of the present invention in detail, the following is a detailed description in conjunction with the implementation methods and the accompanying drawings.

[0039] The following embodiments are exemplary embodiments, which may have different forms or modifications and should not be interpreted as being limited to the description given here. In the description of the embodiments of the present invention, expressions such as "including..." mean "including but not limited to only...".

[0040] Figure 1 The spectral analysis module 100 according to the embodiment of the present invention and a signal processing system 140 , a control system 150 and an input / output terminal 160 in a test system for implementing spectral testing therein are shown.

[0041] The spectrum analysis module 100 includes: a signal light collection and beam shaping optical path 110 , a filter array 120 , and a detector array 130 .

[0042] The purpose of the signal light collection and beam shaping optical path 110 is to collect the signal light uniformly and efficiently, and convert it into parallel collimated light to irradiate the filter array vertically.

[0043] Figure 2 A schematic side view of the structure of the filter array 120 and the detector array 130 in the spectral analysis module 100 according to an embodiment of the present invention is shown.

[0044] The filter array 120 is composed of filter structure units 121 with different transmission spectrum characteristics. The filter structure unit 121 is a micro-nano structure with resonance characteristics, or an optoelectronic material (such as a semiconductor, etc.) with specific absorption characteristics; they have different structures or material parameters in different filter structure units. The transmission spectrum of the filter structure unit 121 can be a spectrum with passband characteristics, stopband characteristics, long-wave pass characteristics, or short-wave pass characteristics, or a spectrum composed of multiple spectrum peaks and spectrum valleys.

[0045] The detector array 130 includes a plurality of detector units 131 . Each detector unit 131 includes one or more detector unit pixels. The detector unit pixel is the smallest array unit inherent in the detector array 130 .

[0046] Assume that both the filter array 120 and the detector array 130 have M×N array units. The M×N filter structure units 121 in the filter array 120 are labeled in sequence: F1, F2, F3, ..., F j ,…,F M×N The M×N detector units 131 in the detector array 130 are labeled as D1, D2, D3, ..., D j ,…,D M×N , which correspond to the filter structure units 121: F1, F2, F3, ..., F j ,…,F M×N .

[0047] exist Figure 1In the test system shown, the signal light to be tested is incident on the filter array 120 after passing through the signal light collection and beam shaping optical path 110, and the transmitted light passing through different filter structure units 121 is irradiated on the corresponding detector units 131 respectively; the optical signal received by each detector unit 131 is converted into an electrical signal through photoelectric conversion, and after preliminary signal preprocessing and analog-to-digital (A / D) conversion, it is transmitted to the signal processing system 140 of the test system through wired or wireless means, and then the spectrum is reconstructed in combination with preset calibration information.

[0048] Figure 3 The test system for pre-calibrating the spectrum analysis module 100 according to the embodiment of the present invention is shown, wherein the calibration light source 200 provides quasi-monochromatic light with adjustable central wavelength and stable output power for pre-calibration.

[0049] The calibration light source 200 may be implemented in the following ways:

[0050] like Figure 4C As shown in the figure, the calibration light source 200 can be a wavelength-tunable monochromatic light source 210 composed of an array light source based on semiconductor light emitting diodes (LEDs) or laser diodes (LDs) (the array light source emits quasi-monochromatic light with different central wavelengths in its different units), or a wavelength-tunable monochromatic light source 210 that achieves quasi-monochromatic light output with different central wavelengths by tuning internal resonant cavity parameters.

[0051] like Figure 4B and Figure 4C As shown in FIG. 2 , the calibration light source 200 is a light source based on a standard broadband light source 220 and using an adjustable monochromator 221 or an adjustable filter 222 to obtain quasi-monochromatic light with different central wavelengths.

[0052] The standard broadband light source 220 may be a broadband light source such as a xenon lamp, a deuterium lamp, a halogen lamp (including halogen tungsten lamps such as bromine tungsten lamps and iodine tungsten lamps), or a broadband light source based on fluorescence, or a combination of the above light sources.

[0053] The adjustable monochromator 221 may be a monochromator including a dispersion element (such as a grating, a prism, etc.).

[0054] The tunable optical filter 222 may be an optical filter including an adjustable optical resonant cavity, an adjustable optical interferometer, or an adjustable optical filter composed of a plurality of narrow-band filters.

[0055] The following briefly describes a method for acquiring the spectrum of signal light based on the spectrum analysis module and its preset calibration method according to an embodiment of the present invention.

[0056] For a spectrum analysis module 100 and spectrum test system thereof that are manufactured and packaged on a hardware system, a preset calibration is first required before use.

[0057] Assume that within the working wavelength band of the spectral analysis module 100, the central wavelength of the quasi-monochromatic light output by the calibration light source 200 is λ i (i=1,2,…,L; where L is the number of central wavelengths of quasi-monochromatic light in the working band), and the output power corresponding to the quasi-monochromatic light is P0(λ i ).

[0058] Reference Figure 3 As shown, at different central wavelengths λ i When the quasi-monochromatic light is inputted separately, the electric signal generated by each detector unit 131 in the detector array 130 in the spectrum analysis module 100 is pre-processed and converted into analog-to-digital (A / D) and then outputted to the signal processing system 140. The digital signal corresponding to the calibration light signal intensity received by each detector unit 131 has an intensity represented by c 0j (λ i )(j=1,2,…,K; where K is the number of detector units 131 in the detector array 130, such as K=M×N). And let c j (λ i )=c 0j (λ i ) / P0(λ i ) is the calibration signal intensity corresponding to each detector unit 131 relative to the quasi-monochromatic light power output by the calibration light source. It should be noted here that the preset calibration information includes not only the information about the quasi-monochromatic light output by the calibration light source 200, and the information about the calibration signal intensity generated after the quasi-monochromatic light output by the calibration light source 200 is input into the spectral analysis module 100, but also the integration time (or exposure time) set by the control system 150 for the detector array 130 in the spectral analysis module 100 in the preset calibration test system. Generally speaking, the number of photons received by each detector unit 131 in the detector array 130 is proportional to the integration time. Here, it is assumed that the integration time of the detector array 130 set in the preset calibration test is t c .

[0059] The preset calibration information obtained after the above-mentioned preset calibration can be saved in the memory of the corresponding spectral analysis module or the signal processing system bound thereto, so as to be called when performing spectral reconstruction calculations in application tests; or saved in the data storage system of a remote server, etc., and indexed and called by the device number set for the corresponding spectral analysis module.

[0060] Reference Figure 1As shown, in the spectrum test, the integration time of the detector array 130 in the spectrum analysis module 100 set by the control system 150 is t r When the signal light to be measured from the target object is collected by the spectrum analysis module 100, the intensity represented by the digital signal corresponding to the intensity of the signal light received by each detector unit 131 is obtained in the signal processing system 140. 0j (j=1, 2, ..., K). Considering the influence of different integration times of the detector array 130 on the generated signal intensity, let r j =r 0j (t r / t c ). Then the actual spectrum s(λ) of the signal light from the target object can be discretely solved based on the following formula: i ) for calculation.

[0061]

[0062] Or written as: R = CS, where: R = [r j ] T , C=[c j (λ i )],S=[s(λ i )] T A noise term N = [n j ] T , so that the above formula can be written as: R=CS+N.

[0063] It is noted that multiplying the matrices R, C and S in the above formula by constants related to normalization, discretization or physical quantity conversion does not change the meaning and applicability of the above formula.

[0064] As can be seen from the previous description, the calibration and test data represented by the matrices C and R here include the optical responses and photoelectric conversion factors of the corresponding internal parts or components of the spectral analysis module 100, the structural component deviations and alignment deviations between the various parts during the manufacturing process, and the comprehensive influence of other uncontrollable and unclear factors on the spectral test, rather than just the influence of the transfer function and response function of each array unit in the filter array 120 and the detector array 130.

[0065] In the process of solving the above equation, if L = K, theoretically, the discrete actual spectrum S = C can be calculated by solving the inverse matrix of C -1R. However, in many cases, it is desired to perform calibration with quasi-monochromatic light having smaller intervals and narrower line widths (i.e., having a larger number of calibration wavelengths L) within the working band based on a limited number K of detector units (i.e., the number of filter units) during pre-calibration, in order to obtain a test spectrum with higher resolution; thus, K < L. In this case, it is necessary to calculate the actual spectrum S by solving the pseudo-inverse matrix of C; however, in this case, affected by noise and various uncontrollable factors in the system, the calculation result may be somewhat unstable. In the actual numerical solution process of the above matrix equation, the ||CS - R|| 2 is often minimized to obtain the actual spectrum S with the minimum error. In specific implementation, relevant problems can be improved by other better algorithms.

[0066] The above are only embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. A method for pre-calibrating a spectrum analysis module based on a filter array, characterized in that: The spectrum analysis module at least includes a filter array and a detector array, each filter structure unit in the filter array is set to have different transmission spectrum characteristics, the detector array is set to have a plurality of detector units consisting of one or more detector unit pixels, and the preset calibration test system includes a calibration light source, a calibrated spectrum analysis module, a signal processing system matched with the spectrum analysis module, a control system, an input / output terminal and other equipment; The information of the quasi-monochromatic light output by the calibration light source includes its respective central wavelengths, line widths, and corresponding output powers; the quasi-monochromatic light output by the calibration light source is input into the spectral analysis module, and the digital signal corresponding to the intensity of the light signal received by each detector unit in the detector array is obtained in the signal processing system; and the integration time set for the detector array; the output power of the quasi-monochromatic light with different central wavelengths corresponding to the calibration light source, the intensity of the light represented by the digital signal generated by each detector unit and other components received by the signal processing system, and other related information are used as preset calibration information corresponding to a single specific calibrated spectral analysis module, and the preset calibration information is saved and called in the spectral reconstruction calculation when the spectral analysis module is used for spectral detection.

2. The method for pre-calibrating a spectrum analysis module based on a filter array according to claim 1, characterized in that: The calibration light source is a wavelength-tunable monochromatic light source composed of an array light source based on semiconductor light emitting diodes or laser diodes, or a wavelength-tunable monochromatic light source that achieves quasi-monochromatic light output with different central wavelengths by tuning internal resonant cavity parameters.

3. The method for pre-calibrating a spectrum analysis module based on a filter array according to claim 1, characterized in that: The calibration light source is based on a standard broadband light source and uses an adjustable monochromator to obtain quasi-monochromatic light with different central wavelengths. The standard broadband light source is a broadband light source such as a xenon lamp, a deuterium lamp, a halogen lamp, or a broadband light source based on fluorescence, or a combination of the above light sources. The adjustable monochromator is a monochromator including dispersive elements such as a grating and a prism.

4. The method for pre-calibrating a spectrum analysis module based on a filter array according to claim 1, characterized in that: The calibration light source is based on a standard broadband light source and uses an adjustable filter to obtain quasi-monochromatic light with different central wavelengths. The standard broadband light source is a broadband light source such as a xenon lamp, a deuterium lamp, a halogen lamp, or a broadband light source based on fluorescence, or a combination of the above light sources. The adjustable filter is a filter including an adjustable optical resonant cavity, an adjustable optical interferometer, or an adjustable filter composed of multiple ultra-narrowband filters.

5. The method for pre-calibrating a spectrum analysis module based on a filter array according to claim 1, characterized in that: The spectrum is reconstructed as: Assume that the preset calibration information of the spectrum analysis module used includes: the central wavelength of the quasi-monochromatic light output by the calibration light source is λ i (i=1,2,…,L), the corresponding output power is P0(λ i ), the integration time of the detector array is set to t c The intensity represented by the digital signal corresponding to the intensity of the light signal received by each detector unit in the detector array is c 0j (λ i )(j=1,2,…,K); Assume that in the test of the signal light to be tested, the intensity represented by the digital signal corresponding to the intensity of the light signal received by each detector unit in the detector array is r 0j (j=1,2,…,K), the integration time of the detector array is set to t r ; Let c j (λ i )=c 0j (λ i ) / P0(λ i ), r j =r 0j (t r / t c ), the actual spectrum s(λ) of the signal light to be measured can be discretely solved based on the following expression s(λ i ) to perform the calculation for reconstruction: Or written as: R = CS, where R = [r j ] T , C=[c j (λ i )],S=[s(λ i )] T ; A noise term N=[n j ] T , so that the above formula can be written as: R=CS+N; in addition, multiplying the matrices R, C and S in the above formula by constants related to characterizing normalization, discretization or physical quantity conversion does not change the meaning and applicability of the above formula.

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