Radio Frequency Mark Spectrometer and Spectral Measurement Method

Abstract

The present disclosure provides a radio frequency tagged spectrometer, comprising: a dynamic dispersion device, which receives a light beam including two or more wavelength components and is driven by a driving radio frequency signal, and the dynamic dispersion device encodes the intensity of each wavelength component as the amplitude of a different beat frequency radio frequency signal based on different driving radio frequency signals, wherein the beat frequency of different beat frequency radio frequency signals is equal to the frequency of the corresponding driving radio frequency signal; a single-channel photodetector, which is used to detect the sum of the beat frequency radio frequency signals formed by adding all the beat frequency radio frequency signals; and a processing unit, which is used to perform a Fourier transform on the sum of the beat frequency radio frequency signals to obtain a spectrum or obtain a frequency spectrum related to the spectrum and obtain the spectrum based on the frequency spectrum.

Description

[0001] Cross - reference to related applications

[0002] This application claims the benefit and priority of Singapore Patent Application No. SG10202200019T, filed on January 3, 2022, the entire content of which is incorporated herein by reference. Technical field

[0003] The present disclosure relates to a spectrometer, and more particularly to a radio - frequency tagged spectrometer and a spectral measurement method. Background art

[0004] Spectroscopy has a wide range of applications in many fields such as atmospheric science, the food industry, and medical diagnosis. The key equipment of spectroscopy is a spectrometer, through which spectral data can be obtained for subsequent analysis. Generally, spectrometers capable of high - speed spectral measurement are preferred, especially for studying dynamic phenomena. According to the working principle, currently available spectrometers can be roughly classified into the following categories.

[0005] The first type is based on the angular dispersion of incident light, using a dispersive element such as a prism, a grating, or an acou - optic filter. A multi - channel detector such as a camera is used to simultaneously measure all wavelength components, or a single - channel detector such as a photodiode is used to sequentially measure each wavelength component. Each channel of the single - channel detector or multi - channel detector receives light of only one wavelength each time.

[0006] The second type is based on wavelength - division multiplexing measurement and spectral reconstruction through, for example, Hadamard transform and compressive sensing mathematical transforms. Instead of measuring the light intensity of one wavelength each time, this type of spectrometer measures one coefficient each time, where each coefficient is a weighted sum of the light intensities of all wavelengths.

[0007] The third type is based on the measurement of optical coherence. The incident light interferes with itself, but after different time or optical path length delays, an interferogram is generated, and the Fourier transform of which is the required spectrum. Delays of multiple optical path lengths can be achieved sequentially or simultaneously, and the interferogram is recorded using a photodiode or a camera respectively.

[0008] Generally, in these techniques, the measurement process is switched sequentially from one wavelength component or one coefficient to another, slowly. In addition, in the techniques of simultaneously measuring all wavelength components or coefficients, direct - current (DC) detection is usually used, which is affected by signal drift and noise, thus limiting the measurement speed.

[0009] The fourth type is based on the temporal dispersion of light, that is, light pulses of each wavelength propagate different times through the same distance in a dispersive medium such as an optical fiber. This principle is used to convert light from the spectral domain to the time domain, that is, time - stretched dispersion Fourier transform, and a fast single - channel detector is used to record the spectrum of the pulsed source.

[0010] Recently, the time dispersion of near-field light has been used to retrieve fluorescence spectra from quantum dots. By using an optical amplifier with built-in stimulated Raman scattering, this time dispersion technique is very sensitive and fast. Unfortunately, this method is only applicable to pulsed light, which limits the application of this method. For example, it cannot be used in many common applications where continuous-wave light prevails. For continuous-wave spectral measurements, commercial spectrometers based on spectrometers and CCD / CMOS sensors can reach speeds of hundreds of kilohertz and are mainly used in optical coherence tomography (OCT) applications. The theoretical speed is limited by the frame rate of the CCD / CMOS sensor, while the actual measurement speed is usually limited by the signal-to-noise ratio. Summary of the Invention

[0011] To solve one of the above technical problems, the present disclosure provides a radio-frequency tagged spectrometer and a spectral measurement method.

[0012] According to one aspect of the present disclosure, there is provided a radio-frequency tagged spectrometer, comprising: a dynamic dispersion device, the dynamic dispersion device receiving a light beam including two or more wavelength components and being driven by a driving radio-frequency signal, the dynamic dispersion device encoding the intensity of each wavelength component as the amplitude of a different beat-frequency radio-frequency signal based on different driving radio-frequency signals, wherein the beat frequency of the different beat-frequency radio-frequency signals is equal to the frequency of the corresponding driving radio-frequency signal; a single-channel photodetector for detecting the sum of the beat-frequency radio-frequency signals formed by adding all the beat-frequency radio-frequency signals; and a processing unit for performing a Fourier transform on the sum of the beat-frequency radio-frequency signals to obtain a spectrum, or obtaining a spectrum-related frequency spectrum and obtaining the spectrum based on the frequency spectrum.

[0013] The radio-frequency tagged spectrometer according to at least one embodiment of the present disclosure performs a mathematical operation on the spectrum-related frequency spectrum to remove the factor of dispersion efficiency to obtain the spectrum.

[0014] The radio-frequency tagged spectrometer according to at least one embodiment of the present disclosure further includes a beam selection device for selecting a specific beam from the output beam of the dynamic dispersion device so that each wavelength of the selected beam has a unique code.

[0015] In the radio-frequency tagged spectrometer according to at least one embodiment of the present disclosure, the beam selection device is a spatial filter for filtering the output beam of the dynamic dispersion device to select a specific beam so that each wavelength of the selected beam has a unique code.

[0016] In the radio-frequency tagged spectrometer according to at least one embodiment of the present disclosure, the dynamic dispersion device is an acousto-optic deflector.

[0017] The radio frequency tagging spectrometer according to at least one embodiment of the present disclosure further includes a radio frequency amplifier, and the radio frequency amplifier is configured to provide the driving radio frequency signal to the acousto-optic deflector, wherein the driving radio frequency signals of all wavelength components are simultaneously applied to the acousto-optic deflector.

[0018] The radio frequency tagging spectrometer according to at least one embodiment of the present disclosure further includes a programmable arbitrary function generator, and the programmable arbitrary function generator is configured to provide a driving radio frequency signal that is uniquely corresponding to each wavelength component respectively.

[0019] In the radio frequency tagging spectrometer according to at least one embodiment of the present disclosure, the light beam of each wavelength component is respectively split into a first-order diffracted beam and a zero-order transmitted beam via the acousto-optic deflector, the first-order diffracted beams of all wavelength components form a combined first-order beam, the zero-order transmitted beams of all wavelength components form a combined zero-order beam, and the combined first-order beam and the combined zero-order beam interfere with each other, so that each wavelength component generates a beat radio frequency signal with a unique beat frequency.

[0020] In the radio frequency tagging spectrometer according to at least one embodiment of the present disclosure, the combined zero-order beam is guided to a beam splitter by a first mirror, the combined first-order beam is guided to the beam splitter by a second mirror and a third mirror, the combined first-order beam and the combined zero-order beam interfere with each other to form a first interference beam and a second interference beam, wherein the first interference beam is guided to a focusing lens by a fourth mirror and a fifth mirror, and the second interference beam is guided from the beam splitter to the focusing lens, and the first interference beam and the second interference beam are focused to the single-channel photodetector after passing through the focusing lens.

[0021] In the radio frequency tagging spectrometer according to at least one embodiment of the present disclosure, the radio frequency components of the first interference beam and the second interference beam are in phase when reaching the single-channel photodetector.

[0022] In the radio frequency tagging spectrometer according to at least one embodiment of the present disclosure, different driving radio frequency signals are selected according to each wavelength component.

[0023] In the radio frequency tagging spectrometer according to at least one embodiment of the present disclosure, the single-channel photodetector is a single-channel avalanche photodetector.

[0024] According to another aspect of the present disclosure, there is provided a radio frequency tagged spectral measurement method, including: receiving a light beam including more than two wavelength components through a dynamic dispersion device; driving the dynamic dispersion device by a driving radio frequency signal so that the dynamic dispersion device encodes the intensity of each wavelength component as the amplitude of a different beat radio frequency signal based on different driving radio frequency signals; detecting the sum of the beat radio frequency signals formed by adding all the beat radio frequency signals through a single-channel photodetector; and performing a Fourier transform on the sum of the beat radio frequency signals to obtain a spectrum, or obtaining a frequency spectrum related to the spectrum and obtaining the spectrum based on the frequency spectrum.

[0025] The method according to at least one embodiment of the present disclosure further includes: performing a quantity operation on the frequency spectrum to remove the factor of dispersion efficiency to obtain the spectrum.

[0026] The method according to at least one embodiment of the present disclosure further includes: selecting a specific light beam from the light beam output from the dynamic dispersion device so that each wavelength of the selected light beam has a unique code.

[0027] The method according to at least one embodiment of the present disclosure selects the output light beam of the dynamic dispersion device through a spatial filter so as to select a specific light beam so that each wavelength of the selected light beam has a unique code.

[0028] The method according to at least one embodiment of the present disclosure further includes selecting different driving radio frequency signals according to the wavelength components of the light beam, so as to measure only the wavelength components of interest.

[0029] The method according to at least one embodiment of the present disclosure further includes calculating different driving radio frequency signals according to the wavelength components of the light beam so as to provide the calculated driving radio frequency signals to the dynamic dispersion device.

[0030] In the method according to at least one embodiment of the present disclosure, the light beam of each wavelength component is respectively divided into a first-order diffracted light beam and a zero-order transmitted light beam through the dynamic dispersion device, the first-order diffracted light beams of all the wavelength components are formed into a combined first-order light beam, the zero-order transmitted light beams of all the wavelength components are formed into a combined zero-order light beam, and the combined first-order light beam and the combined zero-order light beam interfere with each other, so that each wavelength component generates a beat radio frequency signal with a unique beat frequency.

[0031] According to the method of at least one embodiment of the present disclosure, the combined zero-order beam is directed to a beam splitter by a first mirror, the combined first-order beam is directed to the beam splitter by a second mirror and a third mirror, the combined first-order beam and the combined zero-order beam interfere with each other to form a first interference beam and a second interference beam, wherein the first interference beam is directed to a focusing lens by a fourth mirror and a fifth mirror, and the second interference beam is directed from the beam splitter to the focusing lens, and the first interference beam and the second interference beam are focused to the single-channel photodetector after passing through the focusing lens.

[0032] According to the method of at least one embodiment of the present disclosure, the first interference beam and the second interference beam are controlled such that the radio frequency components of the first interference beam and the second interference beam are in phase when they reach the single-channel photodetector. Description of the Drawings

[0033] The drawings illustrate exemplary embodiments of the present disclosure and, together with the description thereof, are used to explain the principles of the present disclosure. The drawings are included to provide a further understanding of the present disclosure and are incorporated in this specification and form a part of this specification.

[0034] Figure 1 is a schematic diagram of a radio frequency tagged spectrometer according to an embodiment of the present disclosure.

[0035] Figure 2 is a schematic diagram of a radio frequency tagged spectrometer according to an embodiment of the present disclosure.

[0036] Figure 3 is a flowchart of a radio frequency tagged spectral measurement method according to an embodiment of the present disclosure. Detailed Description of the Embodiments

[0037] The present disclosure will be further described in detail below in conjunction with the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the relevant content and do not limit the present disclosure. In addition, it should be noted that for the sake of description, only parts related to the present disclosure are shown in the drawings.

[0038] It should be noted that, without conflict, the embodiments in the present disclosure and the features in the embodiments can be combined with each other. The technical solutions of the present disclosure will be described in detail below with reference to the drawings and embodiments.

[0039] Unless otherwise specified, the illustrated exemplary embodiments will be understood to provide exemplary features of various details of some ways in which the technical conceptions of the present disclosure can be implemented in practice. Thus, unless otherwise specified, the features of the various embodiments can be additionally combined, separated, interchanged, and / or rearranged without departing from the technical conceptions of the present disclosure.

[0040] The terms used herein are for the purpose of describing particular embodiments and are not intended to be limiting. As used herein, unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" are also intended to include the plural forms. Further, when the terms "comprise" and / or "include" and their variants are used in this specification, it is stated that there are the stated features, integers, steps, operations, components, assemblies, and / or groups thereof, but it does not preclude the presence or addition of one or more other features, integers, steps, operations, components, assemblies, and / or groups thereof. It should also be noted that, as used herein, the terms "substantially", "about", and other similar terms are used as approximate terms and not as terms of degree, and thus they are used to interpret the inherent deviations of measured values, calculated values, and / or provided values that would be recognized by a person of ordinary skill in the art.

[0041] According to one embodiment of the present disclosure, a radio frequency tagged spectrometer is provided. Figure 1 A schematic diagram of a radio frequency tagged spectrometer according to one embodiment of the present disclosure is shown.

[0042] As Figure 1 shown, the radio frequency tagged spectrometer 10 may include a dynamic dispersion device 100, a single-channel photodetector 200, and a processing unit 300. The radio frequency tagged spectrometer 10 is used to measure the spectrum of the continuous light of a broadband light source or the multi-line waves of a multi-line light source. By means of radio frequency measurement, the radio frequency tagged spectrometer 10 can achieve a speed of several megahertz and an improved signal-to-noise ratio.

[0043] The dynamic dispersion device 100 can diffract the received light beam according to the instruction of a driving signal to form a diffracted light beam. The dynamic dispersion device 100 can receive a light beam with two or more wavelength components and is driven by a driving radio frequency signal. Herein, the term "wavelength component" refers to a component of a specific wavelength or a specific wavelength range in a light beam. The dynamic dispersion device 100 can encode the intensity of each wavelength component as the amplitude of a different beat frequency radio frequency signal based on different driving radio frequency signals. The beat frequency of different beat frequency radio frequency signals is equal to the frequency of different driving radio frequency signals.

[0044] In the present disclosure, the dynamic dispersion device can be a dynamic diffraction grating, and other devices that can play the same or similar roles as the dynamic diffraction grating. As an example, the dynamic dispersion device 100 can be an acousto-optic deflector. The acousto-optic deflector can be driven by a driving radio frequency signal provided by a radio frequency amplifier. A programmable arbitrary function generator can be used to provide the driving radio frequency signal to the radio frequency amplifier. The provided driving radio frequency signal can correspond to each wavelength component respectively, that is, each wavelength component corresponds to a unique driving radio frequency signal. For example, when the light beam includes three wavelength components, the acousto-optic deflector can be driven by three different driving radio frequency signals. The three driving radio frequency signals correspond to the three wavelength components respectively. The first driving radio frequency signal encodes the light intensity of the first wavelength component as the amplitude of the first beat-frequency radio frequency signal, the second driving radio frequency signal encodes the light intensity of the second wavelength component as the amplitude of the second beat-frequency radio frequency signal, and the third driving radio frequency signal encodes the light intensity of the third wavelength component as the amplitude of the third beat-frequency radio frequency signal. The beat frequency of the first beat-frequency radio frequency signal is equal to the frequency of the first driving radio frequency signal, the beat frequency of the second beat-frequency radio frequency signal is equal to the frequency of the second driving radio frequency signal, and the beat frequency of the third beat-frequency radio frequency signal is equal to the frequency of the third driving radio frequency signal. In the present disclosure, the wavelength component can be selected by programming the driving radio frequency signal, so that a part of the spectrum including the most useful information can be detected.

[0045] The radio frequency amplifier can simultaneously apply the driving radio frequency signals of all wavelength components to the acousto-optic deflector. The single-channel photodetector 200 detects the sum of the beat-frequency radio frequency signals formed by adding all the beat-frequency radio frequency signals. As an example, the single-channel photodetector 200 can be a single-channel avalanche photodetector. The processing unit 300 can be used to perform a Fourier transform on the sum of the beat-frequency radio frequency signals to obtain the spectrum. In addition, the sum of the beat-frequency radio frequency signals can also be subjected to a Fourier transform to obtain the frequency spectrum related to the spectrum, where the factor of the dispersion efficiency can be removed by performing mathematical operations (such as through linear inverse operations) to obtain the spectrum.

[0046] According to an embodiment of the present disclosure, the radio frequency tagged spectrometer can further include a beam selection device. The beam selection device can select a specific beam from the output beam of the dynamic dispersion device 100 so that each wavelength in the selected beam has a unique code. In the present disclosure, the beam selection device can be a spatial filter, such as a spatial filter composed of a lens and a pinhole, or a spatial filter composed of a lens and a structure or device that plays the same role as the pinhole.

[0047] When a light beam of a wavelength component passes through the acousto-optic deflector 110 driven by a corresponding driving radio frequency signal, due to Bragg diffraction caused by an acoustic wavefront, the light beam is divided into a first-order diffracted light beam and a zero-order transmitted light beam (for simplicity, weaker higher-order diffractions are omitted). The first-order diffracted light beam inherits the frequency shift of the driving radio frequency signal provided to the acousto-optic deflector. When the first-order diffracted light beam and the zero-order transmitted light beam interfere with each other, an AC signal (beat-frequency radio frequency signal) is generated. The beat frequency of this AC signal is equal to the frequency of the driving radio frequency signal and the amplitude I1 of this AC signal is proportional to the light intensity, as shown in Equation 1.

[0048]

[0049] where I is the light intensity, η is the diffraction efficiency of the acousto-optic deflector, ω is the frequency of the driving radio frequency signal, is the phase difference generated by the optical path length difference between the first-order diffracted light beam and the zero-order transmitted light beam.

[0050] For a broadband light beam or a multi-line light beam including two or more wavelength components, a unique driving radio frequency signal is calculated separately for each wavelength component in the light beam, such that when all the driving radio frequency signals are applied simultaneously, all the wavelength components are diffracted in the same direction to form a combined first-order diffracted light beam and are transmitted to form a combined zero-order transmitted light beam. Then, the combined first-order diffracted light beam interferes with the combined zero-order transmitted light beam. Each wavelength component generates an AC signal (beat-frequency radio frequency signal) with a unique beat frequency. In this way, the beat frequency of each AC signal is equal to the frequency of the corresponding driving radio frequency signal, and the intensity of each wavelength component is proportional to the amplitude of the AC signal, as shown in Equation 2.

[0051]

[0052] where I1' is the sum of the amplitudes of all the AC signals, I is the light intensity, η is the diffraction efficiency of the acousto-optic deflector, m is the number of wavelength components, ω m is the frequency of the m-th driving radio frequency signal, is the phase difference generated by the optical path length difference between the m-th first-order diffracted light beam and the zero-order transmitted light beam, λ m is the wavelength of the m-th wavelength component.

[0053] For an AC signal as a time-domain signal, the spectrum can be restored through Fourier transform. Since each wavelength component of the AC signal has its own beat frequency respectively, after all the AC signals are simultaneously received by a single-channel photodetector, multiple wavelength components can be resolved through their respective beat frequencies, thereby realizing high-speed spectral measurement. The radio-frequency tagged spectrometer of the present disclosure can more effectively resist 1 / f noise and signal drift when performing AC detection in the radio-frequency range. In addition, the radio-frequency tagged spectrometer can be used as a programmable filter to measure only the wavelength components of interest, thereby improving the measurement speed. For example, the driving radio-frequency signal of the acousto-optic deflector is controlled so that when the acousto-optic deflector receives multiple wavelength components, only a part of the wavelength components among the multiple wavelength components are diffracted, thereby selecting the wavelength components of interest. In addition, according to an embodiment of the present disclosure, the driving radio-frequency signal for controlling the acousto-optic deflector can be calculated based on the wavelength components of the light beam.

[0054] Figure 2 FIG. shows a schematic diagram of a radio-frequency tagged spectrometer according to an embodiment of the present disclosure. As Figure 2 shown, the radio-frequency tagged spectrometer may include an acousto-optic deflector 110, a first mirror assembly, a beam splitter 400, a second lens assembly, a focusing lens 500, and a single-channel photodetector 200.

[0055] The acousto-optic deflector 110 can be used to receive a light beam including two or more wavelength components. As Figure 2 shown, the radio-frequency tagged spectrometer may include a spatial filter 600. The spatial filter 600 is used to filter the input light beam from the light source. The spatial filter 600 may include a pair of achromatic lenses 610 and a pinhole 620. The pinhole 620 may be disposed between the first lens 611 and the second lens 612 of the pair of achromatic lenses 610. The spatial filter 600 can also be used to expand the input light beam so as to completely fill the aperture of the acousto-optic deflector 110. The light beam output by the spatial filter 600 is a light beam that can include two or more wavelength components.

[0056] The acousto-optic deflector 110 can be driven by a radio-frequency amplifier, and the radio-frequency amplifier can be provided with a driving radio-frequency signal by a programmable arbitrary function generator and supply the driving radio-frequency signal to the acousto-optic deflector 110. The driving radio-frequency signals supplied to the acousto-optic deflector 110 can be different driving radio-frequency signals, and each driving radio-frequency signal corresponds to a different wavelength component respectively, so that the acousto-optic deflector 110 encodes the intensity of each wavelength component as the amplitude of a different beat-frequency radio-frequency signal based on the different driving radio-frequency signals.

[0057] The output of the acousto-optic deflector 110 may include a zero-order transmitted beam 21 (without frequency shift) and a first-order diffracted beam 22 (whose frequency shift is equal to the frequency of the driving radio frequency signal). The first mirror assembly is configured to reflect the zero-order transmitted beam 21 and the first-order diffracted beam 22 to the beam splitter 400. The first mirror assembly may include a first mirror 710, a second mirror 720, and a third mirror 730. The first mirror 710 is configured to reflect the zero-order transmitted beam 21 to the beam splitter 400. The second mirror 720 and the third mirror 730 are configured to reflect the first-order diffracted beam 22 to the beam splitter 400. The first mirror 710, the second mirror 720, and the third mirror 730 are arranged such that the optical path difference between the zero-order transmitted beam 21 and the first-order diffracted beam 22 is minimized, so that the beam splitter 400 can generate maximum interference.

[0058] As described above, different driving radio frequency signals are simultaneously provided to the acousto-optic deflector 110, such that the zero-order transmitted beam 21 output by the acousto-optic deflector 110 is a combined zero-order beam of zero-order transmitted beams of different wavelength components, and the first-order diffracted beam 22 output is a combined first-order beam of first-order diffracted beams of different wavelength components. The beam splitter 400 is configured to recombine the combined zero-order beam and the combined first-order beam, and form a first interference beam 31 and a second interference beam 32. The second interference beam 32 propagates directly from the beam splitter 400 to the focusing lens 500. The first interference beam 31 is reflected to the focusing lens 500 via the fourth mirror 740 and the fifth mirror 750 of the second mirror assembly. The first interference beam 31 and the second interference beam 32 are focused by the focusing lens 500 onto the single-channel photodetector 200. The single-channel photodetector 200 is configured to detect the sum of the beat radio frequency signals formed by adding all the beat radio frequency signals. In the present application, the optical path length of the first interference beam 31 is adjusted by moving the fourth mirror 740 and the fifth mirror 750, so as to ensure that the radio frequency components of the first interference beam 31 and the second interference beam 32 are in phase when reaching the single-channel photodetector 200, so that the amplitude of the combined coherent signal is maximized. This can be achieved when the optical path length difference between the first interference beam 31 and the second interference beam 32 is greater than an integer multiple of the center wavelength of the radio frequency signal. In Figure 2 the embodiment, the detection area of the lens 500 and the single-channel photodetector 200 may constitute a beam selection device. The size of the detection area of the single-channel photodetector 200 is set to be the same as or similar to the size of the pinhole, so that the beam selection device can select a specific beam from the received beams such that each wavelength in the selected beam has a unique code. Additionally, other beam selection devices may also be provided. The beam selection device is configured to receive the beam output by the acousto-optic deflector 100, and select a specific beam such that each wavelength in the selected beam has a unique code. The beam selection device may be a spatial filter constituted by a lens and a pinhole.

[0059] The digital converter 310, acting as a processing unit, is connected to the output of the single-channel photodetector 200 for performing Fourier transform on the sum of the beat-frequency RF signals to obtain a spectrum.

[0060] According to the RF-tagged spectrometer of the present disclosure, different RFs are used to tag the light of each wavelength to achieve fast spectral measurement, with a speed capable of reaching the megahertz level and capable of providing a signal-to-noise ratio. This RF-tagged spectrometer can have great potential in various applications such as aerosol particle size measurement, flow cytometry, reaction detection, etc.

[0061] According to the RF-tagged spectrometer of the present disclosure, the frequency resolution (i.e., the spectral resolution in terms of RF) is heuristically defined as the RF range ΔF required to scan the first-order diffracted beam on the zero-order transmitted beam of the detector. Assuming that the optical devices used in the system are ideal, according to the principle of the acousto-optic deflector, the displacement range of the scan of the RF range ΔF can be estimated using the left side of Equation 3, and the diameter of the zero-order transmitted beam of the detector can be estimated using the right side of Equation 3, where f is the focal length of the focusing lens, V a is the speed of the ultrasonic wave in the acousto-optic deflector, λ is the wavelength, M 2 and D are respectively the beam quality factor and diameter of the incident collimated beam.

[0062]

[0063] Moving all terms in Equation 3 other than ΔF to the right side, the frequency resolution of the RF-tagged spectrometer is as shown in Equation 4.

[0064]

[0065] According to Equation 4, it is exactly the incident beam parameters before the focusing lens and the ultrasonic wave speed V a that determine the resolution of the RF-tagged spectrometer.

[0066] The focusing lens parameters (such as the focal length) theoretically do not affect the resolution. This is different from traditional monochromator-based spectrometers. The spectral resolution of the RF-tagged spectrometer can be estimated according to Equation 5, where ΔL is the width of the entrance or exit slit (whichever is larger), d is the groove spacing of the grating, f is the focal length of the focusing lens, and m is the diffraction order.

[0067]

[0068] Since when the ultrasonic wave propagates inside the acousto-optic deflector, the acousto-optic deflector acts as a moving grating, the groove spacing d AOD of this moving grating is equal to the wavelength λ a, as shown in Equation 6, where F is the frequency of the driving radio frequency signal that drives the acousto-optic deflector.

[0069]

[0070] Moving F to the other side gives V a = Fd AOD Equation 7.

[0071] Substituting Equation 7 into Equation 4 gives Equation 8. It can be seen that the resolution of the radio frequency tagged spectrometer is proportional to the groove pitch d of the moving grating AOD which is similar to a monochromator-based spectrometer.

[0072]

[0073] Since the diffraction in the acousto-optic deflector follows Equation 9, where θ is the diffraction angle of the first-order diffracted beam, by moving F to the other side of Equation 9 and differentiating both sides, the relationship between Δλ and ΔF can be derived as Equation 10. Substituting Equation 8 into Equation 10 gives Equation 11, which is the resolution of the radio frequency tagged spectrometer in terms of wavelength. It can be seen that this resolution is proportional to the groove pitch.

[0074]

[0075]

[0076]

[0077] From Equation 11, it can be seen that the wavelength resolution can be improved by using a well-collimated beam and an acousto-optic deflector with a large aperture. Since assuming V a is fixed, a higher radio frequency will result in better spectral resolution. For example, as Figure 2 shown, the radio frequency tagged spectrometer can include a collimator 800, which can be, for example, a light ray collimator or the like, for collimating the incident beam.

[0078] Since the spectrum is obtained through Fourier transform, the data acquisition time determines the frequency interval that can be resolved. Given a desired frequency interval, the data acquisition time should be set to be equal to or greater than the reciprocal of the frequency interval so that all frequency components can be recovered. When the data acquisition time is set to the reciprocal of the frequency interval, the radio frequency tagged spectrometer reaches its maximum speed at that frequency interval. The larger the frequency interval, the shorter the data acquisition time that can be used and the faster the speed. Therefore, the speed limit of the radio frequency tagged spectrometer depends on the desired frequency interval required to recover the spectrum to be measured. Since the radio frequency signal can be driven programmatically to select the wavelength of interest, the radio frequency tagged spectrometer provides great flexibility to detect the part of the spectrum that contains the most useful information, thus achieving a maximum speed of up to several million Hertz.

[0079] The radio frequency tagged spectrometer is equipped with a dynamic dispersion device, such as an acousto-optic deflector. Taking the acousto-optic deflector as an example, the acousto-optic deflector usually has a diffraction efficiency of more than 80%, which is very close to that of a grating. When the driving radio frequency signal of the acousto-optic deflector contains a single radio frequency component, only one first-order diffracted beam with a single wavelength reaches the single-channel photodetector, so the throughput of the radio frequency tagged spectrometer is comparable to that of a conventional spectrometer. When the driving signal of the acousto-optic deflector contains multiple driving radio frequency signals, multiple first-order diffracted beams with different wavelengths reach the single-channel photodetector simultaneously. In this case, although the light of each wavelength is dispersed into many different first-order diffracted beams, each beam corresponding to a radio frequency, so it is significantly attenuated when only one of these beams reaches the single-channel photodetector, the simultaneous detection of multiple beams of each different wavelength can compensate for the optical power.

[0080] According to a further embodiment of the present disclosure, a radio frequency tagged spectral measurement method is provided.

[0081] Figure 3 The measurement method according to the present disclosure is shown and may include the following. Among them, the corresponding content described above can be incorporated into the description of the measurement method. For the sake of brevity, the repeated content will not be described again.

[0082] In step S102, a beam including more than two wavelength components is received through the dynamic dispersion device. The beam including more than two wavelength components received may be a collimated beam and may be a beam filtered by a spatial filter.

[0083] In step S104, a dynamic dispersion device is driven by a driving radio frequency signal so that the dynamic dispersion device encodes the intensity of each wavelength component as the amplitude of a different beat radio frequency signal based on different driving radio frequency signals. Each wavelength component corresponds to a unique driving radio frequency signal respectively. The driving radio frequency signals of all wavelength components are applied to the dynamic dispersion device simultaneously. In the present disclosure, different driving radio frequency signals can be selected according to the wavelength components of the light beam, so that the wavelength components of interest can be measured, which can improve the measurement speed. Additionally, the required driving radio frequency signals can be calculated according to the wavelength components of the light beam, and the calculated driving radio frequency signals are provided to the dynamic dispersion device.

[0084] In step S106, a single-channel photodetector can be used to detect the sum of the beat radio frequency signals formed by adding all the beat radio frequency signals. In step S108, the sum of the beat radio frequency signals can be Fourier-transformed to obtain a spectrum. In addition, in step S108, the sum of the beat radio frequency signals can also be Fourier-transformed to obtain a frequency spectrum related to the spectrum, where the factor of dispersion efficiency can be removed by performing mathematical operations on the frequency spectrum related to the spectrum to obtain the spectrum.

[0085] In the present disclosure, a specific light beam can be selected from the light beam output from the dynamic dispersion device so that each wavelength in the selected light beam has a unique code. As described above, the selection of the specific light beam can be achieved by a spatial filter.

[0086] In the present disclosure, the light beam of each wavelength component is respectively divided into a first-order diffracted light beam and a zero-order transmitted light beam by the dynamic dispersion device. The first-order diffracted light beams of all wavelength components form a combined first-order light beam, and the zero-order transmitted light beams of all wavelength components form a combined zero-order light beam. The combined first-order light beam and the combined zero-order light beam interfere with each other, so that each wavelength component generates a beat radio frequency signal with a unique beat frequency. The combined zero-order light beam is directed to a beam splitter by a first mirror, and the combined first-order light beam is directed to the beam splitter by a second mirror and a third mirror. After the combined first-order light beam and the combined zero-order light beam interfere with each other, a first interference light beam and a second interference light beam are formed. The first interference light beam is directed to a focusing lens by a fourth mirror and a fifth mirror, and the second interference light beam is directed to the focusing lens from the beam splitter. The first interference light beam and the second interference light beam are focused to a single-channel photodetector after passing through the focusing lens. The first interference light beam and the second interference light beam are controlled so that the radio frequency components of the first interference light beam and the second interference light beam are in phase when they reach the single-channel photodetector.

[0087] In the description of this specification, the descriptions referring to terms such as "one embodiment / way", "some embodiments / ways", "example", "specific example", or "some examples", etc., mean that the specific features, structures, materials, or characteristics described in connection with the embodiment / way or example are included in at least one embodiment / way or example of this application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment / way or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments / ways or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments / ways or examples described in this specification and the features of different embodiments / ways or examples.

[0088] In addition, the terms "first" and "second" are used only for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of this application, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0089] Those skilled in the art should understand that the above embodiments are merely for clearly explaining the present disclosure and are not intended to limit the scope of the present disclosure. For those skilled in the art, other changes or modifications can be made on the basis of the above disclosure, and these changes or modifications are still within the scope of the present disclosure.

Claims

1. A radio frequency tagging spectrometer, characterized in that, Comprising: A dynamic dispersion device that receives a beam including two or more wavelength components and is driven by a driving radio frequency signal, and the dynamic dispersion device encodes the intensity of each wavelength component as the amplitude of a different beat frequency radio frequency signal based on different driving radio frequency signals, wherein the beat frequency of the different beat frequency radio frequency signals is equal to the frequency of the corresponding driving radio frequency signal; A single-channel photodetector for detecting the sum of the beat frequency radio frequency signals formed by adding all the beat frequency radio frequency signals; And A processing unit for performing a Fourier transform on the sum of the beat frequency radio frequency signals to obtain a spectrum, or obtaining a frequency spectrum related to the spectrum and obtaining the spectrum based on the frequency spectrum.

2. The radio frequency label spectrometer according to claim 1, characterized in that, It further includes a beam selection device for selecting a specific beam from the output beam of the dynamic dispersion device so that each wavelength in the selected beam has a unique code.

3. The radio frequency tag spectrometer according to claim 2, wherein The beam selection device is a spatial filter for selecting the output beam of the dynamic dispersion device so as to select a specific beam so that each wavelength in the selected beam has a unique code.

4. The radio frequency tag spectrometer according to claim 1, wherein The dynamic dispersion device is an acousto-optic deflector.

5. The radio frequency tagging spectrometer according to claim 4, wherein It further includes a radio frequency amplifier for providing the driving radio frequency signal to the acousto-optic deflector, wherein the driving radio frequency signals of all the wavelength components are simultaneously applied to the acousto-optic deflector.

6. The radio frequency tagging spectrometer according to claim 5, characterized in that, It further includes a programmable arbitrary function generator for providing a driving radio frequency signal that is uniquely corresponding to each wavelength component respectively.

7. The radio frequency tagging spectrometer according to claim 5, wherein The beam of each wavelength component is respectively divided into a first-order diffracted beam and a zero-order transmitted beam via the acousto-optic deflector, the first-order diffracted beams of all the wavelength components form a combined first-order beam, the zero-order transmitted beams of all the wavelength components form a combined zero-order beam, and the combined first-order beam and the combined zero-order beam interfere with each other, so that each wavelength component generates a beat frequency radio frequency signal with a unique beat frequency.

8. The radio frequency marker spectrometer according to claim 7, wherein The combined zero-order beam is guided to a beam splitter by a first mirror, the combined first-order beam is guided to the beam splitter by a second mirror and a third mirror, the combined first-order beam and the combined zero-order beam interfere with each other to form a first interference beam and a second interference beam, wherein the first interference beam is guided to a focusing lens by a fourth mirror and a fifth mirror, and the second interference beam is guided from the beam splitter to the focusing lens, and the first interference beam and the second interference beam are focused to the single-channel photodetector through the focusing lens.

9. The radio frequency label spectrometer according to claim 8, wherein, The radio frequency components of the first interference beam and the second interference beam are in phase when reaching the single-channel photodetector.

10. The radio frequency tag spectrometer according to claim 2, wherein Different driving radio frequency signals are selected according to each wavelength component.

11. The radio frequency tagging spectrometer according to claim 2, characterized in that, The single-channel photodetector is a single-channel avalanche photodetector.

12. A method for measuring the spectrum of a radio frequency tag, characterized in that, Comprising: Receiving a beam including two or more wavelength components through a dynamic dispersion device; Driving the dynamic dispersion device by a driving radio frequency signal so that the dynamic dispersion device encodes the intensity of each wavelength component as the amplitude of a different beat frequency radio frequency signal based on different driving radio frequency signals; Detecting the sum of beat RF signals formed by adding all the beat RF signals through a single-channel photodetector; And Performing Fourier transform on the sum of the beat RF signals to obtain a spectrum, or obtaining a frequency spectrum related to the spectrum and obtaining the spectrum based on the frequency spectrum.

13. The radio frequency tag spectrum measurement method according to claim 12, characterized in that Performing mathematical processing on the frequency spectrum to remove the factor of dispersion efficiency to obtain the spectrum.

14. The method according to claim 12, characterized in that, Further comprising: Selecting a specific beam from the output beam of the dynamic dispersion device so that each wavelength in the selected beam has a unique code.

15. The method according to claim 14, wherein Selecting the output beam of the dynamic dispersion device through a spatial filter so as to select a specific beam so that each wavelength in the selected beam has a unique code.

16. The method according to claim 12, wherein Further comprising selecting different drive RF signals according to the wavelength components of the beam, so as to measure only the wavelength components of interest.

17. The method according to claim 16, wherein Further comprising calculating different drive RF signals according to the wavelength components of the beam so as to provide the calculated drive RF signals to the dynamic dispersion device.

18. The method according to claim 16, wherein The beam of each wavelength component is respectively split into a first-order diffracted beam and a zero-order transmitted beam through the dynamic dispersion device, the first-order diffracted beams of all the wavelength components are formed into a combined first-order beam, the zero-order transmitted beams of all the wavelength components are formed into a combined zero-order beam, and the combined first-order beam and the combined zero-order beam interfere with each other, so that each wavelength component generates a beat RF signal with a unique beat frequency.

19. The method according to claim 18, wherein The combined zero-order beam is guided to a beam splitter through a first mirror, the combined first-order beam is guided to the beam splitter through a second mirror and a third mirror, the combined first-order beam and the combined zero-order beam interfere with each other to form a first interference beam and a second interference beam, wherein the first interference beam is guided to a focusing lens through a fourth mirror and a fifth mirror, and the second interference beam is guided from the beam splitter to the focusing lens, and the first interference beam and the second interference beam are focused to the single-channel photodetector through the focusing lens.

20. The method according to claim 19, wherein The first interference beam and the second interference beam are controlled so that the RF components of the first interference beam and the second interference beam are in phase when reaching the single-channel photodetector.

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