Ultrafast random speckle generation system, device and method

Abstract

The present invention is applicable to the field of optical technology and provides an ultrafast random speckle generation system, device, and method. The ultrafast random speckle generation system includes: a mode-locked pulse laser module that generates a high-repetition-rate femtosecond-scale broadband laser pulse light signal; a DFT module that broadens the femtosecond-scale broadband laser pulse light signal so that the time domain signal and the frequency domain wavelength of the broadband laser pulse light signal have a one-to-one linear relationship; a wavelength adjustment module that causes interference in the frequency domain wavelength of the broadband laser pulse light signal; a speckle generation module that causes broadband laser pulse light signals of different wavelengths at different peaks to generate mode interference in two-dimensional space; a speckle detection and calibration module that performs data detection, collects data based on the wavelength information at the peak and the random speckle distribution, and completes image data processing. The present invention achieves the adjustment of the number and speed of random speckle generation, solving the problem of slow spatial modulation in single-pixel imaging.

Description

Technical Field

[0001] The present invention belongs to the field of optical technology, and in particular relates to an ultrafast random speckle generation system, device and method. Background Art

[0002] Random speckle has received high attention and research in the fields of ultrafast optical information processing, ultrafast optical detection and single-pixel imaging, and has been widely used in the generation of various random signals and the imaging and detection of ultrafast phenomena.

[0003] However, the development of devices for generating random speckle patterns has been slow, and the generation rate of random speckle patterns has severely limited their widespread application. Current random speckle generation devices primarily utilize spatial light modulators or digital micromirrors, which typically operate at rates in the kHz range. However, inherent issues with their liquid crystal or mechanical structures make increasing these rates difficult. Some reports have also used methods that etch speckle patterns onto transparent disks and then rotate them at high speeds to generate higher-speed speckle patterns. However, inherent issues with these mechanical structures limit the generation rate, making ultrafast speckle generation on the nanosecond scale impossible. Therefore, there is a need for an ultrafast speckle generation device that does not require liquid crystal or mechanical structures.

[0004] Therefore, how to adopt a new structural design to realize an ultrafast speckle generation device without the need for an active mechanical structure and increase the speckle generation rate to the nanosecond scale is a technical problem that needs to be solved at present. Summary of the Invention

[0005] The purpose of the embodiments of the present invention is to provide an ultrafast random speckle generation system, aiming to solve the problem of low speckle generation rate.

[0006] The embodiment of the present invention is implemented as follows: an ultrafast random speckle generation system is provided, wherein the ultrafast random speckle generation system is provided with the following modules in sequence:

[0007] Mode-locked pulse laser module, used to generate high-repetition-rate femtosecond-scale broadband laser pulse optical signals;

[0008] The DFT module is used to broaden the femtosecond-scale broadband laser pulse optical signal so that the time domain signal and the frequency domain wavelength of the broadband laser pulse optical signal have a one-to-one linear relationship;

[0009] A wavelength adjustment module is used to cause interference in the frequency domain wavelength of the broadband laser pulse light signal;

[0010] A speckle generation module is used to generate mode interference in a two-dimensional space among broadband laser pulse light signals with wavelengths at different peaks;

[0011] The speckle detection and calibration module is used to detect the speckle spatial image after the interference of the wavelength generation pattern at different peaks, collect data based on the wavelength information at the peak and the random speckle distribution, and complete the image data processing.

[0012] Furthermore, the high-repetition-rate femtosecond-scale broadband laser pulse light signal generated by the mode-locked pulse laser module includes a broadband laser pulse light signal L0(A0,λ) in the near-infrared band, where A0 is the amplitude value of the mode-locked broadband laser pulse light signal and λ is the frequency domain wavelength.

[0013] Furthermore, the DFT module is composed of a dispersion-compensating optical fiber, a long-distance ordinary single-mode optical fiber or a chirped fiber grating. The broadband laser pulse light signal input to the DFT module is L0(A0, λ), and the broadband laser pulse light signal output by the DFT module is L1(A1, λ(t)), λ(t)=α*t+β, where α and β are constants, A1 is the amplitude value of the mode-locked broadband laser pulse light signal after broadening, and t is the pulse time domain signal.

[0014] Furthermore, the wavelength adjustment module adopts the Michelson interference structure of spatial light. When the broadband laser pulse light signal passes through the Michelson interference structure, L1(A1,λ(t)) is divided into signal light L 11 (A 11 ,λ(t)) and reference light L 12 (A 12 ,λ(t)),A 11 is the amplitude of the signal light, A 12 is the amplitude value of the reference light; after the broadened broadband laser pulse light signal passes through the Michelson interference structure, the light signal at this time becomes Among them, A2 is the amplitude value of the mode-locked broadband laser pulse light signal after passing through the Michelson interference structure, φ is the signal light L 11 (A 11 ,λ(t)) and reference light L 12 (A 12 ,λ(t)), where λ2 is the wavelength of the optical signal. After passing through the Michelson interference structure, the optical signal L2(A2,λ2(t)) at this time has peak and trough values.

[0015] Furthermore, the speckle generation module uses a multimode optical fiber to obtain the random speckle distribution L3(A3, λ(z, t)) of optical signals with different wavelengths at different peaks at different times, where z is the distribution of the random speckle and z = f(λ), where f is a function related to z and λ. That is, the distribution of the random speckle z is related to the wavelength at the peak.

[0016] Furthermore, the speckle detection and calibration module also receives a synchronization signal from the mode-locked pulse laser module.

[0017] Another object of an embodiment of the present invention is to provide an ultrafast random speckle generation device, wherein the ultrafast random speckle generation device is provided with the following modules in sequence:

[0018] Mode-locked pulse laser module, used to generate high-repetition-rate femtosecond-scale broadband laser pulse optical signals;

[0019] The DFT module is used to broaden the femtosecond-scale broadband laser pulse optical signal so that the time domain signal and the frequency domain wavelength of the broadband laser pulse optical signal have a one-to-one linear relationship;

[0020] A wavelength adjustment module is used to cause interference in the frequency domain wavelength of the broadband laser pulse light signal;

[0021] A speckle generation module is used to generate mode interference in a two-dimensional space among broadband laser pulse light signals with wavelengths at different peaks;

[0022] The speckle detection and calibration module is used to detect the speckle spatial image after the interference of the wavelength generation pattern at different peaks, collect data based on the wavelength information at the peak and the random speckle distribution, and complete the image data processing.

[0023] Another object of an embodiment of the present invention is to provide an ultrafast random speckle generation method, the ultrafast random speckle generation method comprising the following steps:

[0024] A mode-locked pulse laser module is used to generate high-repetition-rate femtosecond-scale broadband laser pulse optical signals;

[0025] The DFT module is used to broaden the femtosecond-scale broadband laser pulse optical signal, so that the time domain signal and the frequency domain wavelength of the broadband laser pulse optical signal have a one-to-one linear relationship.

[0026] The wavelength adjustment module is used to make the frequency domain wavelength of the broadband laser pulse light signal interfere;

[0027] The speckle generation module is used to make broadband laser pulse light signals with different wavelengths at different peaks generate mode interference in two-dimensional space;

[0028] The speckle detection and calibration module is used to detect the speckle spatial image after the interference of the wavelength generation pattern at different peaks. Data is collected according to the wavelength information at the peak and the random speckle distribution to complete the image data processing.

[0029] An ultrafast random speckle generation system provided by an embodiment of the present invention can not only generate ultrafast random speckles, but also adjust the amount and speed of random speckle generation by adjusting the optical path difference of an interference structure. This innovatively solves the problem of slow spatial modulation in traditional single-pixel imaging and enables ultrafast spatial modulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the ultrafast random speckle generating device in the first embodiment;

[0031] Figure 2 The frequency domain (a) and time domain (b) results of the optical signal after entering the DFT module in the first embodiment; the frequency domain (c) and time domain (d) results of the optical signal after entering the wavelength adjustment module;

[0032] Figure 3 Schematic diagram of random speckle generated after an optical signal enters a multimode optical fiber in the first embodiment;

[0033] Figure 4 FIG. 1 is a diagram of an application environment of an ultrafast random speckle generation method according to a third embodiment;

[0034] Figure 5 FIG. 4 is a flow chart of the method for generating ultrafast random speckles in the fourth embodiment. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0036] In the first embodiment, if Figure 1 As shown in FIG, an ultrafast random speckle generation system is proposed. The ultrafast random speckle generation system is configured with the following modules in sequence:

[0037] Mode-locked pulse laser module, used to generate high-repetition-rate femtosecond-scale broadband laser pulse optical signals;

[0038] The DFT module is used to broaden the femtosecond-scale broadband laser pulse optical signal so that the time domain signal and the frequency domain wavelength of the broadband laser pulse optical signal have a one-to-one linear relationship;

[0039] A wavelength adjustment module is used to cause interference in the frequency domain wavelength of the broadband laser pulse light signal;

[0040] A speckle generation module is used to generate mode interference in a two-dimensional space among broadband laser pulse light signals with wavelengths at different peaks;

[0041] The speckle detection and calibration module is used to detect the speckle spatial image after the interference of the wavelength generation pattern at different peaks, collect data based on the wavelength information at the peak and the random speckle distribution, and complete the image data processing.

[0042] In this embodiment, the high-repetition-rate femtosecond-scale broadband laser pulse optical signal generated by the mode-locked pulse laser module includes a near-infrared broadband laser pulse optical signal L0(A0, λ), where A0 is the amplitude of the mode-locked broadband laser pulse optical signal and λ is the frequency-domain wavelength. The femtosecond-scale broadband laser pulse optical signal used in this embodiment has a repetition frequency of 50 MHz, a pulse width of 44 fs, an infrared center wavelength of 1558 nm, and a bandwidth of approximately 20 nm.

[0043] The DFT module is composed of dispersion-compensating fiber, long-distance ordinary single-mode fiber, or chirped fiber grating. After a femtosecond-scale broadband laser pulse optical signal L0 (A0, λ) with a repetition rate of 50MHz passes through the DFT module (dispersion Fourier transform module) composed of dispersion-compensating fiber, the femtosecond-scale broadband laser pulse will be broadened due to the material dispersion of the dispersion-compensating fiber. While the broadband laser pulse optical signal is broadened in the time domain, a linear correspondence between the pulse time domain signal and the frequency domain wavelength is achieved. The material dispersion value of the dispersion-compensating fiber used in this embodiment is 500ps / nm, so the femtosecond-scale pulse signal is broadened by approximately 500ps / nm*20nm=10ns. The broadband laser pulse optical signal input to the DFT module is L0(A0, λ), and the broadband laser pulse optical signal output by the DFT module is L1(A1, λ(t)), λ(t) = α*t+β, where α and β are constants, A1 is the amplitude value of the mode-locked broadband laser pulse optical signal after broadening, and t is the pulse time domain signal, that is, the pulse time domain signal t has a linear correspondence with the frequency domain wavelength λ. The frequency domain and time domain results after the optical signal enters the DFT module are shown in the figure below. Figure 2 As shown in (a) and (b) in the figure, the frequency domain and time domain diagrams of the optical signal are shown.

[0044] The wavelength adjustment module can adopt the Michelson interference structure of optical fiber, spatial light or Mach-Zehnder interference structure. Take the Michelson interference structure of spatial light as an example. The broadened broadband laser pulse light signal enters the wavelength adjustment module, which adopts the Michelson interference structure of optical fiber spatial light. After passing through the interference structure, the frequency domain wavelength of the broadened broadband laser pulse will show interference phenomenon, that is, peak and trough values will appear at different wavelengths. When the broadband laser pulse passes through the Michelson interference structure, L1(A1, λ(t)) is divided into signal light L 11 (A 11 ,λ(t)) and reference light L 12 (A 12 ,λ(t)), both can be abbreviated as L11 and L 12 , A 11 is the amplitude of the signal light, A 12 is the amplitude value of the reference light. After the broadened broadband laser pulse light signal passes through the Michelson interference structure, the light signal at this time becomes Among them, A2 is the amplitude value of the mode-locked broadband laser pulse light signal after passing through the Michelson interference structure, φ is the signal light L 11 (A 11 ,λ(t)) and reference light L 12 (A 12 ,λ(t)) is the phase difference caused by the optical path difference, where λ2 is the wavelength of the optical signal. By adding an adjustable optical delay device to the reference optical path, the phase difference between the signal light and the reference light can be adjusted. After passing through the Michelson interferometer structure, the optical signal L2(A2,λ2(t)) now has a series of peaks and valleys. The frequency domain and time domain results of the optical signal after entering the wavelength adjustment module are shown in the figure below. Figure 2 As shown in (c) and (d) in the figure, the frequency domain and time domain diagrams of the optical signal at this time are shown. By comparing the corresponding positions of the peaks and troughs in the frequency domain (c) and time domain (d) diagrams of the optical signal, the relationship between the pulse time domain signal t and the frequency domain wavelength λ can be obtained. In this embodiment, by calculating Figure 2 The corresponding positions of the peaks and troughs in the frequency domain (c) and time domain (d) graphs of the optical signal in FIG are known. Given that λ(t) = α*t+β, we can obtain α = 0.498, β = -2.26, and λ(nm) = 0.498*t(ns)-2.26, indicating a linear correspondence between the pulse time domain signal t and the frequency domain wavelength λ. Furthermore, by using an adjustable optical delay, the phase difference between the signal light and the reference light can be adjusted, thereby adjusting the distance between adjacent peaks, which is Δλ in the frequency domain and Δt in the time domain, as shown in the following example: Figure 2 As shown by the double-headed arrows in the frequency domain (c) and time domain (d) figures, by adjusting the phase difference between the signal light and the reference light, the frequency domain or time domain interval of the subsequent speckle generation can be adjusted.

[0045] After passing through the interference structure, the broadened broadband laser pulse signal enters the speckle generation module, which utilizes a multimode fiber with a 400-micron core and a length of 5 meters. This module generates mode interference at the peak of the broadened broadband laser pulse signal in two-dimensional space. This multimode fiber ensures that laser signals of different wavelengths have distinct random speckle distributions. Since the distribution of random speckle is related to the wavelength at the peak of the optical signal, and since the wavelength of optical signals of different wavelengths is time-dependent after passing through dispersion-compensating fiber or long-distance ordinary single-mode fiber, the random speckle distribution L3(A3, λ(z, t)) at different peak wavelengths at different times is obtained. Here, A3 is the amplitude of the mode-locked broadband laser pulse signal after passing through the speckle generation module, and z is the random speckle distribution, z = f(λ), where f is a function of z and λ. This means that the random speckle distribution z is related to the wavelength λ at the peak. It is also known that the pulse time domain signal t and the frequency domain wavelength λ have a linear correspondence. In this embodiment, λ(nm)=0.498*t(ns)-2.26, so the distribution z of the random speckle is related to the pulse time domain signal t. Figure 3 A schematic diagram shows the random speckle pattern generated by an optical signal entering a multimode fiber. A laser pulse enters the multimode fiber as a single-mode signal. The laser pulse output from the multimode fiber exhibits a random speckle pattern. Based on the one-to-one correspondence between wavelength λ, time series t, and the random speckle pattern z, the laser pulse output from the multimode fiber exhibits different random speckle patterns at different time points t.

[0046] The generated random speckle enters the speckle detection and calibration module, which is used to detect the random speckle spatial image after the interference of the wavelength generation pattern at different peaks. It also completes the image data processing after data acquisition based on the wavelength information at the peak and the random speckle distribution, that is, the relationship analysis between the wavelength λ at the peak and the random speckle distribution z. The random speckle distribution z is as follows:

[0047]

[0048] Among them, x, y are the coordinates of the speckle; a m and φ n are the m-order and n-order modes in amplitude and phase respectively.

[0049] Random speckle distribution z can be calculated using the zero-mean normalized cross-correlation algorithm R ref It is used to analyze and calibrate, and store the random speckle distribution z of different wavelengths for subsequent calibration, calculation and processing. ref as follows:

[0050]

[0051] Z0 is the pixel distribution intensity of the detection image, Z ref is the pixel distribution intensity of the reference image; is the average value of the pixel distribution intensity of all detection images, is the average value of the pixel distribution intensity of all reference images.

[0052] In this embodiment, a mode-locked pulse laser module, a DFT module, a wavelength-adjustable interferometer, a speckle generation module, and a speckle detection and calibration module are provided. This not only enables the generation of ultrafast random speckles, but also enables the adjustment of the amount and speed of random speckle generation by adjusting the optical path difference of the interferometer structure. This creatively solves the problem of slow spatial modulation in traditional single-pixel imaging and enables ultrafast spatial modulation.

[0053] In a second embodiment, an ultrafast random speckle generating device is proposed, and the ultrafast random speckle generating device includes:

[0054] Mode-locked pulse laser module, used to generate high-repetition-rate femtosecond-scale broadband laser pulse optical signals;

[0055] The DFT module is used to broaden the femtosecond-scale broadband laser pulse optical signal so that the time domain signal and the frequency domain wavelength of the broadband laser pulse optical signal have a one-to-one linear relationship;

[0056] A wavelength adjustment module is used to cause interference in the frequency domain wavelength of the broadband laser pulse light signal;

[0057] A speckle generation module is used to generate mode interference in a two-dimensional space among broadband laser pulse light signals with wavelengths at different peaks;

[0058] The speckle detection and calibration module is used to detect the speckle spatial image after the interference of the wavelength generation pattern at different peaks, collect data based on the wavelength information at the peak and the random speckle distribution, and complete the image data processing.

[0059] In this embodiment, the ultrafast random speckle generating device is a specific structural device, and its working principle and technical effects are the same as those of the ultrafast random speckle generating system of the first embodiment described above, which will not be described in detail here.

[0060] In a third embodiment, Figure 4 Figure 2 shows an application environment for an ultrafast random speckle generation method. The application environment includes a computer device and the ultrafast random speckle generation system described in the first embodiment. The computer device controls the mode-locked pulse laser module, the DFT module, the wavelength adjustment interferometer, the speckle generation module, and the speckle detection and calibration module.

[0061] In the fourth embodiment, Figure 5As shown, a method for generating ultrafast random speckles is proposed, which is applied to the computer device in the third embodiment. The method for generating ultrafast random speckles includes the following steps S102 to S110:

[0062] Step S102, using a mode-locked pulse laser module to generate a high-repetition-rate femtosecond-scale broadband laser pulse optical signal;

[0063] Step S104, using a DFT module to broaden the femtosecond-scale broadband laser pulse light signal so that a linear relationship between the time domain signal and the frequency domain wavelength of the broadband laser pulse light signal appears one-to-one.

[0064] Step S106, using a wavelength adjustment module to cause interference in the frequency domain wavelength of the broadband laser pulse light signal;

[0065] Step S108, using a speckle generation module to cause broadband laser pulse light signals of wavelengths at different peaks to generate mode interference in a two-dimensional space;

[0066] Step S110 , using the speckle detection and calibration module to detect data on the speckle spatial image after the wavelength generation pattern interference at different peaks, collect data based on the wavelength information at the peaks and the random speckle distribution, and complete the image data processing.

[0067] In this embodiment, the specific technical means and technical effects of the ultrafast random speckle generation method have been clearly explained in the first embodiment and will not be repeated here.

[0068] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An ultrafast random speckle generation system, characterized in that: The ultrafast random speckle generation system is configured with the following modules in sequence: Mode-locked pulse laser module, used to generate high-repetition-rate femtosecond-scale broadband laser pulse optical signals; The DFT module is used to broaden the femtosecond-scale broadband laser pulse optical signal so that the time domain signal and the frequency domain wavelength of the broadband laser pulse optical signal have a one-to-one linear relationship; A wavelength adjustment module is used to cause interference in the frequency domain wavelength of the broadband laser pulse light signal; A speckle generation module is used to generate mode interference in a two-dimensional space among broadband laser pulse light signals with wavelengths at different peaks; The speckle detection and calibration module is used to detect the speckle spatial image after the interference of the wavelength generation pattern at different peaks, collect data based on the wavelength information at the peak and the random speckle distribution, and complete the image data processing.

2. The ultrafast random speckle generation system according to claim 1, characterized in that: The high-repetition-rate femtosecond-scale broadband laser pulse light signal generated by the mode-locked pulse laser module includes a broadband laser pulse light signal L0(A0, λ) in the near-infrared band, where A0 is the amplitude value of the mode-locked broadband laser pulse light signal and λ is the frequency domain wavelength.

3. The ultrafast random speckle generation system according to claim 2, characterized in that: The DFT module is composed of a dispersion-compensating optical fiber, a long-distance ordinary single-mode optical fiber or a chirped fiber grating. The broadband laser pulse optical signal input to the DFT module is L0(A0, λ), and the broadband laser pulse optical signal output by the DFT module is L1(A1, λ(t)), λ(t)=α*t+β, where α and β are constants, A1 is the amplitude value of the mode-locked broadband laser pulse optical signal after broadening, and t is the pulse time domain signal.

4. The ultrafast random speckle generation system according to claim 3, characterized in that: The wavelength adjustment module adopts the Michelson interference structure of spatial light. When the broadband laser pulse light signal passes through the Michelson interference structure, L1(A1,λ(t)) is divided into signal light L 11 (A 11 ,λ(t)) and reference light L 12 (A 12 ,λ(t)),A 11 is the amplitude of the signal light, A 12 is the amplitude value of the reference light; after the broadened broadband laser pulse light signal passes through the Michelson interference structure, the light signal at this time becomes Among them, A2 is the amplitude value of the mode-locked broadband laser pulse light signal after passing through the Michelson interference structure, φ is the signal light L 11 (A 11 ,λ(t)) and reference light L 12 (A 12 ,λ(t)), where λ2 is the wavelength of the optical signal. After passing through the Michelson interference structure, the optical signal L2(A2,λ2(t)) at this time has peak and trough values.

5. The ultrafast random speckle generation system according to claim 4, characterized in that: The speckle generation module uses a multimode optical fiber to obtain the random speckle distribution L3(A3, λ(z, t)) of optical signals with different wavelengths at different peaks at different times. A3 is the amplitude of the mode-locked broadband laser pulse optical signal passing through the speckle generation module, z is the distribution of the random speckle, and z = f(λ), where f is a function related to z and λ. That is, the distribution of random speckle z is related to the wavelength at the peak.

6. The ultrafast random speckle generation system according to any one of claims 1 to 5, characterized in that: The speckle detection and calibration module also receives a synchronization signal from the mode-locked pulse laser module.

7. An ultrafast random speckle generation method, characterized in that: The ultrafast random speckle generation method comprises the following steps: A mode-locked pulse laser module is used to generate high-repetition-rate femtosecond-scale broadband laser pulse optical signals; The DFT module is used to broaden the femtosecond-scale broadband laser pulse optical signal, so that the time domain signal and the frequency domain wavelength of the broadband laser pulse optical signal have a one-to-one linear relationship. The wavelength adjustment module is used to make the frequency domain wavelength of the broadband laser pulse light signal interfere; The speckle generation module is used to make broadband laser pulse light signals with different wavelengths at different peaks generate mode interference in two-dimensional space; The speckle detection and calibration module is used to detect the speckle spatial image after the interference of the wavelength generation pattern at different peaks. Data is collected according to the wavelength information at the peak and the random speckle distribution to complete the image data processing.

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