Spectrometry method and spectrometer based on time-varying narrowband filtering and speckle calculation reconstruction

Abstract

The present application provides a kind of spectral measurement method and spectrometer based on time-varying narrow-band filtering and speckle calculation reconstruction, comprising tunable calibration light source, time-varying narrow-band filtering module, scattering medium and detector, by introducing time-varying narrow-band filtering module, the number of channels of single spectral reconstruction can be reduced, thereby relieving the contrast reduction caused by multiple speckle superposition, and reducing the distortion degree of spectral reconstruction.The present application can greatly increase the spectral measurement bandwidth while maintaining high resolution by combining time-varying narrow-band filtering technology and speckle calculation spectral reconstruction technology.

Description

Technical Field

[0001] This invention mainly relates to the field of spectral measurement technology, and in particular to a spectral measurement method and spectrometer based on time-varying narrowband filtering and speckle calculation reconstruction. Background Technology

[0002] Spectrometers are widely used in environmental monitoring, biochemistry, astronomy, medicine and national defense, but traditional spectrometers face contradictions in resolution and size, working bandwidth and scanning time, and cannot meet the needs of some special scenarios.

[0003] Narrowband filter spectrometers perform spectral measurements by selectively filtering out light of specific wavelengths and measuring their corresponding intensities. To increase the resolution of this type of spectrometer, the number of filters used and the cost will increase significantly.

[0004] With the improvement of computing power and the maturity of algorithm research, computational reconstruction speckle ...

[0005] In practical applications, high-bandwidth, high-resolution spectral measurements are often required. Current technical solutions typically disperse broadband light spatially across multiple filters, and the number of filters used limits the operating bandwidth. Summary of the Invention

[0006] To address the technical problems existing in the prior art, this invention proposes a spectral measurement method and spectrometer based on time-varying narrowband filtering and speckle calculation reconstruction. By combining time-varying narrowband filtering technology and speckle calculation spectral reconstruction technology, this invention can significantly increase the spectral measurement bandwidth while maintaining high resolution.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] On one hand, the present invention provides a spectral measurement method based on time-varying narrowband filtering and speckle calculation reconstruction, comprising:

[0009] (1) Calibration;

[0010] (1.1) Connect the narrow linewidth, high-resolution tunable calibration light source to the time-varying narrowband filter module, and connect a scattering medium after the time-varying narrowband filter module to generate speckle.

[0011] (1.2) Sequentially set the 1st, 2nd, ... Kth narrowband filter bands of the time-varying narrowband filter module, so that the tunable calibration light source performs high-resolution stepped wavelength scanning in the i-th narrowband filter band, and records the corresponding wavelength-related speckle behind the scattering medium to form the i-th narrowband transmission matrix, i = 1, 2, ..., K;

[0012] (2) Measurement;

[0013] (2.1) Replace the tunable calibration light source with the light source under test. Connect the light source under test to the time-varying narrowband filter module. Connect a scattering medium after the time-varying narrowband filter module to generate speckle.

[0014] (2.2) Sequentially set the 1st, 2nd, ... Kth narrowband filter bands of the time-varying narrowband filter module so that the light source under test enters the scattering medium after passing through the i-th narrowband filter band in sequence, and record the corresponding speckle after the scattering medium to form the i-th narrowband measurement spot, i = 1, 2, ..., K;

[0015] (2.3) Calculate and reconstruct the i-th narrowband spectrum based on the i-th narrowband measurement spot and the i-th narrowband transmission matrix;

[0016] (2.4) The K narrowband spectra to be measured are spliced ​​together to form a broadband reconstructed spectrum.

[0017] Furthermore, in step (2.3) of this invention, the following relationship exists between the i-th narrowband measurement spot, the i-th narrowband transfer matrix, and the i-th narrowband spectrum to be measured:

[0018]

[0019] make In the formula I N (i) represents the light intensity data of the i-th narrowband measurement spot; N represents the total number of pixels of the i-th narrowband measurement spot; T represents the light intensity data of the 1st, 2nd, ..., Nth pixels of the i-th narrowband measurement spot; N×M (i) represents the transfer matrix of the i-th time-varying narrowband filtering and scattering; M represents the number of spectral channels of the spectrum to be measured; This represents the nth speckle pixel in the mth spectral channel within the i-th narrowband spectrum being measured; n = 1, 2, ..., N; m = 1, 2, ..., M; S M (i) represents the i-th narrowband spectrum to be measured; This represents the ith narrowband spectrum to be measured in the 1st, 2nd, ..., Mth spectral channels;

[0020] The i-th narrowband spectrum to be measured is obtained based on the above relationship.

[0021] Furthermore, in step (1.2) of the present invention, the filtering band of the time-varying narrowband filter module is set in the interval of λ1 to λ2, and the first, second... Kth narrowband filter bands of the time-varying narrowband filter module are set sequentially in the form of Δλ as the resolution step.

[0022] Furthermore, in step (1.2) of the present invention, the tunable calibration light source is scanned sequentially in the 1st, 2nd... Kth narrowband filter bands with a resolution step of δλ / 2 to obtain K narrowband transmission matrices.

[0023] On the other hand, the present invention provides a spectrometer for implementing the above-mentioned spectral measurement method based on time-varying narrowband filtering and speckle calculation reconstruction, including a tunable calibration light source, a time-varying narrowband filtering module, a scattering medium, and a detector.

[0024] During the calibration process, the output fiber of the tunable calibration light source is connected to one end of the first polarization-maintaining fiber, the other end of the first polarization-maintaining fiber is connected to the input fiber of the time-varying narrowband filter module, the output fiber of the time-varying narrowband filter module is connected to one end of the second polarization-maintaining fiber, and the other end of the second polarization-maintaining fiber is connected to the scattering medium. The scattering medium is used to generate speckle, and the detector records the speckle behind the scattering medium.

[0025] During the measurement process, the light source under test is connected to one end of the first polarization-maintaining fiber, the other end of the first polarization-maintaining fiber is connected to the input fiber of the time-varying narrowband filter module, the output fiber of the time-varying narrowband filter module is connected to one end of the second polarization-maintaining fiber, and the other end of the second polarization-maintaining fiber is connected to the scattering medium. The scattering medium is used to generate speckle, and the detector records the speckle behind the scattering medium.

[0026] Compared with the prior art, the technical effects of the present invention are as follows:

[0027] Compared with purely computational reconstructed spectrometers that do not incorporate narrowband filtering technology, this invention introduces a time-varying narrowband filtering module, which can reduce the number of channels in a single spectral reconstruction, thereby alleviating the contrast reduction caused by the superposition of multiple speckles and reducing the degree of distortion in spectral reconstruction.

[0028] For computational reconstruction spectrometers that incorporate spatial narrowband filtering technology, bandwidth expansion requires increasing the number of filters, thereby increasing system cost and instability. The bandwidth expansion capability of this invention depends on the number of time-varying narrowband filters, K; filtering K times can increase the operating bandwidth by a factor of K. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0030] Figure 1 This is a system structure diagram of the calibration process in one embodiment;

[0031] Figure 2 This is a system structure diagram of the measurement process in one embodiment;

[0032] Figure 3 This is a schematic diagram illustrating the working principle of one embodiment;

[0033] Numbering on the map:

[0034] 1. Tunable calibration light source; 2. First polarization-protected fiber; 3. Time-varying narrowband filter module; 4. Second polarization-protected fiber; 5. Scattering medium; 6. Detector; 7. Light source under test. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0036] Reference Figure 1 and Figure 2 One embodiment provides a spectrometer based on time-varying narrowband filtering and speckle calculation reconstruction, including a tunable calibration light source 1, a time-varying narrowband filtering module 3, a scattering medium 5, a detector 6, and an optical fiber connected between the light source and the time-varying narrowband filtering module, and between the time-varying narrowband filtering module and the scattering medium, wherein the optical fiber is a polarization-maintaining fiber.

[0037] Reference Figure 1 During the calibration process, the output fiber of the tunable calibration light source 1 is connected to one end of the first polarization-maintaining fiber 2, the other end of the first polarization-maintaining fiber 2 is connected to the input fiber of the time-varying narrowband filter module 3, the output fiber of the time-varying narrowband filter module 3 is connected to one end of the second polarization-maintaining fiber 4, and the other end of the second polarization-maintaining fiber 4 is connected to the scattering medium 5. The scattering medium 5 is used to generate speckle, and the detector 6 records the speckle behind the scattering medium 5.

[0038] It is understood that the type of scattering medium 5 is not limited. It is used to generate speckle and can be, but is not limited to, media that can generate scattered light spots, such as frosted glass, nanoparticles, planar waveguides, planar scattering light guide structures, and multimode optical fibers.

[0039] It is understood that the light source under test 7 includes all types of light sources, including natural light (sunlight, etc.) and artificial light (lasers, etc.). During the measurement process, the light source under test 7 is connected to one end of the first polarization-maintaining fiber 2, the other end of the first polarization-maintaining fiber 2 is connected to the input fiber of the time-varying narrowband filter module 3, the output fiber of the time-varying narrowband filter module 3 is connected to one end of the second polarization-maintaining fiber 4, and the other end of the second polarization-maintaining fiber 4 is connected to the scattering medium 5. The scattering medium 5 is used to generate speckle, and the detector 6 records the speckle behind the scattering medium 5.

[0040] Specifically, the calibration process includes the following steps;

[0041] (1.1) Connect a tunable calibration light source with narrow linewidth (typical value of hundreds of kHz) and high resolution (pm level) to a time-varying narrowband filter module, and connect a scattering medium after the time-varying narrowband filter module to generate speckle.

[0042] (1.2) Sequentially set the first, second, ..., Kth narrowband filter bands of the time-varying narrowband filter module, so that the tunable calibration light source performs high-resolution step wavelength scanning in the i-th narrowband filter band in sequence, and records the corresponding wavelength-related speckle behind the scattering medium to form the i-th narrowband transmission matrix, i = 1, 2, ..., K.

[0043] To achieve broadband, distributed continuous spectral measurements with a working range of λ1–λ2 and a resolution of δλ, the time-varying narrowband filtering module uses a narrowband filter with a spectral resolution of Δλ. According to the calibration principles of the computational reconstruction spectrometer and the Nyquist law, without the narrowband filter, at least ~(λ2-λ1)×2 / δλ spectral channels need to be reconstructed in a single operation; with the narrowband filter, only ~Δλ×2 / δλ spectral channels need to be reconstructed in a single operation.

[0044] During the calibration phase, a narrow-linewidth, high-resolution, tunable calibration light source is first connected to a time-varying narrowband filter module. Simultaneously, the filter bands of the time-varying narrowband filter module are set to the interval λ1–λ2, with a resolution step of Δλ, and these filter bands are numbered 1–K (K = (λ2–λ1) / Δλ), where Δλ represents rounding up. The tunable calibration light source is then sequentially scanned within the narrowband filter bands numbered 1–K at a resolution of δλ / 2 to obtain K narrowband transmission matrices (corresponding to spectral bandwidth Δλ).

[0045] The measurement process includes the following steps;

[0046] (2.1) Replace the tunable calibration light source with the light source under test. Connect the light source under test to the time-varying narrowband filter module. Connect a scattering medium after the time-varying narrowband filter module to generate speckle.

[0047] Reference Figure 3 To illustrate the working principle of the measurement process, the light source under test is sequentially incident on the 1st, 2nd, ... Kth narrowband filter bands before entering the scattering medium. The detector obtains K narrowband measurement speckles (corresponding to spectral bandwidth Δλ). Based on the K narrowband measurement speckles and the K narrowband transfer matrices, K narrowband spectra are calculated and reconstructed. Finally, the K narrowband spectra are stitched together to form a broadband spectrum. Details are as follows:

[0048] (2.2) Sequentially set the 1st, 2nd, ... Kth narrowband filter bands of the time-varying narrowband filter module so that the light source under test enters the scattering medium after passing through the i-th narrowband filter band in sequence, and record the corresponding speckle after the scattering medium to form the i-th narrowband measurement spot, i = 1, 2, ..., K;

[0049] (2.3) Calculate and reconstruct the i-th narrowband spectrum based on the i-th narrowband measurement spot and the i-th narrowband transmission matrix;

[0050] The following relationship exists between the i-th narrowband measurement spot, the i-th narrowband transfer matrix, and the i-th narrowband spectrum to be measured:

[0051]

[0052]

[0053] In the formula I N (i) represents the light intensity data of the i-th narrowband measurement spot; N represents the total number of pixels of the i-th narrowband measurement spot; T represents the light intensity data of the 1st, 2nd, ..., Nth pixels of the i-th narrowband measurement spot; N×M (i) represents the transfer matrix of the i-th time-varying narrowband filtering and scattering; M represents the number of spectral channels of the spectrum to be measured; This represents the nth speckle pixel in the mth spectral channel within the i-th narrowband spectrum being measured; n = 1, 2, ..., N; m = 1, 2, ..., M; S M (i) represents the i-th narrowband spectrum to be measured; This represents the ith narrowband spectrum to be measured in the 1st, 2nd, ..., Mth spectral channels;

[0054] The i-th narrowband spectrum to be measured is obtained based on the above relationship.

[0055] (2.4) The K narrowband spectra to be measured are spliced ​​together to form a broadband reconstructed spectrum.

[0056] Matters not covered in this invention are common knowledge.

[0057] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0058] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

[0059] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A spectral measurement method based on time-varying narrowband filtering and speckle calculation reconstruction, characterized in that, include: (1) Perform calibration; (1.1) Connect the narrow linewidth, high-resolution tunable calibration light source to the time-varying narrowband filter module, and connect a scattering medium after the time-varying narrowband filter module to generate speckle. (1.2) Sequentially set the 1st, 2nd, ... Kth narrowband filter bands of the time-varying narrowband filter module, so that the tunable calibration light source performs high-resolution stepped wavelength scanning in the i-th narrowband filter band, and records the corresponding wavelength-related speckle behind the scattering medium to form the i-th narrowband transmission matrix, i = 1, 2, ..., K; (2) Take measurements; (2.1) Replace the tunable calibration light source with the light source under test. Connect the light source under test to the time-varying narrowband filter module. Connect a scattering medium after the time-varying narrowband filter module to generate speckle. (2.2) Sequentially set the 1st, 2nd, ... Kth narrowband filter bands of the time-varying narrowband filter module so that the light source under test enters the scattering medium after passing through the i-th narrowband filter band in sequence, and record the corresponding speckle after the scattering medium to form the i-th narrowband measurement spot, i = 1, 2, ..., K; (2.3) Calculate and reconstruct the i-th narrowband spectrum based on the i-th narrowband measurement spot and the i-th narrowband transmission matrix; (2.4) The K narrowband spectra to be measured are spliced ​​together to form a broadband reconstructed spectrum.

2. The spectral measurement method based on time-varying narrowband filtering and speckle calculation reconstruction according to claim 1, characterized in that, In step (2.3), the following relationship exists between the i-th narrowband measurement spot, the i-th narrowband transfer matrix, and the i-th narrowband spectrum to be measured: In the formula I N (i) represents the light intensity data of the i-th narrowband measurement spot; N represents the total number of pixels of the i-th narrowband measurement spot; T represents the light intensity data of the 1st, 2nd, ..., Nth pixels of the i-th narrowband measurement spot; N×M (i) represents the transfer matrix of the i-th time-varying narrowband filtering and scattering; M represents the number of spectral channels of the spectrum to be measured; This represents the nth speckle pixel in the mth spectral channel within the i-th narrowband spectrum being measured; n = 1, 2, ..., N; m = 1, 2, ..., M; S M (i) represents the i-th narrowband spectrum to be measured; This represents the ith narrowband spectrum to be measured in the 1st, 2nd, ..., Mth spectral channels; The i-th narrowband spectrum to be measured is obtained based on the above relationship.

3. The spectral measurement method based on time-varying narrowband filtering and speckle calculation reconstruction according to claim 1 or 2, characterized in that, In step (1.2), the filtering band of the time-varying narrowband filter module is set in the interval of λ1 to λ2, and the first, second... Kth narrowband filter band of the time-varying narrowband filter module is set in sequence with Δλ as the resolution step.

4. The spectral measurement method based on time-varying narrowband filtering and speckle calculation reconstruction according to claim 3, characterized in that, In step (1.2), the tunable calibration light source is scanned sequentially in the 1st, 2nd... Kth narrowband filter bands with a resolution of δλ / 2 to obtain K narrowband transmission matrices.

5. The spectral measurement method based on time-varying narrowband filtering and speckle calculation reconstruction according to claim 1, 2, or 4, characterized in that, The scattering medium is frosted glass, nanoparticles, planar waveguide, planar scatterer light guide structure, or multimode optical fiber.

6. A spectrometer for implementing the spectral measurement method based on time-varying narrowband filtering and speckle calculation reconstruction as described in claim 1, characterized in that, It includes a tunable calibration light source, a time-varying narrowband filter module, a scattering medium, and a detector.

7. The spectrometer according to claim 6, characterized in that, During calibration, the output fiber of the tunable calibration light source is connected to one end of the first fiber, the other end of the first fiber is connected to the input fiber of the time-varying narrowband filter module, the output fiber of the time-varying narrowband filter module is connected to one end of the second fiber, and the other end of the second fiber is connected to the scattering medium. The scattering medium is used to generate speckle, and the detector records the speckle behind the scattering medium.

8. The spectrometer according to claim 6, characterized in that, During the measurement process, the light source under test is connected to one end of the first optical fiber, the other end of the first optical fiber is connected to the input optical fiber of the time-varying narrowband filter module, the output optical fiber of the time-varying narrowband filter module is connected to one end of the second optical fiber, and the other end of the second optical fiber is connected to the scattering medium. The scattering medium is used to generate speckle, and the detector records the speckle behind the scattering medium.

9. The spectrometer according to claim 6, 7, or 8, characterized in that, The scattering medium is frosted glass, nanoparticles, planar waveguide, planar scatterer light guide structure, or multimode optical fiber.

10. The spectrometer according to claim 7 or 8, characterized in that, Both the first optical fiber and the second optical fiber are polarization-maintaining optical fibers.

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