Microwave single-photon real-time imaging system and method based on flight time measurement

Abstract

The invention discloses a microwave single-photon real-time imaging system and method based on flight time measurement, and belongs to the field of microwave optical imaging radars, and the system and method provided by the invention comprises the steps: carrying out the up-conversion conversion of a received microwave pulse echo signal to an optical domain, and carrying out the free space light processing; and performing target imaging on the signal after optical domain processing through the single-photon detection array. Large-view-field and high-real-time imaging of the target is achieved through the single-photon detection array, and compared with a traditional microwave optical imaging system, range profile information does not depend on the bandwidth of an emission signal, so that high-range profile resolution imaging of the target is achieved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of imaging radar, and particularly relates to an imaging method and system in a microwave photon imaging radar. BACKGROUND

[0002] Imaging radar can distinguish, identify and classify targets, and has great application in the fields of automatic driving, security check, meteorology and national defense. Common imaging radar systems include synthetic aperture radar, inverse synthetic aperture radar, integrated aperture radar, laser radar system and microwave photon imaging radar. Among them, the microwave photon imaging radar has a good prospect in the fields of scientific research, military and civil use.

[0003] Microwave photon radar is to modulate microwave signals onto optical signals to realize transmission, processing and transformation of microwave signals in the optical domain, and finally demodulate the sideband information for imaging. Microwave photon radar combines the high-speed broadband characteristics of photon technology and the flexible and easy-to-control characteristics of microwave technology, and uses the advantages of photon technology such as high frequency, wide bandwidth, anti-electromagnetic interference and low transmission loss to realize complex and even difficult wideband microwave signal processing and high-speed transmission in traditional microwave field. As we all know, a large bandwidth will help better distance resolution, and while pursuing a large bandwidth, the hardware requirements of microwave photon radar will also increase, and the array cost will be higher. This limits the further development of microwave photon radar. SUMMARY

[0004] In view of the above defects or improvement needs of the prior art, the present application proposes a microwave single-photon real-time imaging method based on time-of-flight measurement, thereby solving the pain point of dependence on large bandwidth for improving the range image resolution of the original microwave photon radar.

[0005] The present application is realized by the following technical solutions:

[0006] The application discloses a microwave single-photon real-time imaging method based on time-of-flight measurement, which comprises the following steps: step S1, inputting a first electric pulse signal synchronized with a microwave pulse signal into a time-dependent single-photon counter at the same time so that the time-dependent single-photon counter starts timing; wherein the microwave pulse signal can be radiated by a microwave pulse radio frequency radiation source to free space; step S2, receiving a plurality of echo signals formed by reflecting the microwave pulse by an imaged target, wherein each echo signal carries characteristic information of the imaged target; step S3, low-noise amplifying the plurality of echo signals to amplify the characteristic information; step S4, modulating each echo signal onto a first-order sideband of an optical carrier; step S5, emitting the plurality of echo signals modulated onto the first-order sideband of the optical carrier as multi-channel spatial light; step S6, collimating and filtering the multi-channel spatial light to screen a desired first-order sideband; step S7, configuring a single-photon detector array to generate a second electric pulse signal after receiving each photon of the desired first-order sideband; step S8, configuring the time-dependent single-photon counter to receive the second electric pulse signal from the single-photon detector array and stop timing; step S9, calculating the time of flight of each detected photon by timing the first electric pulse signal and the second electric pulse signal, and recording and counting the photons of the plurality of echo signals, thereby completing intensity image imaging and range image imaging of the optical domain pulse echo.

[0007] In some embodiments, the desired first-order sideband is a positive first-order sideband or a negative first-order sideband.

[0008] In some embodiments, the method further comprises a step of phase-shifting the optical carrier and the first-order sideband between step S4 and step S5.

[0009] In some embodiments, the time-dependent single-photon counter is a Geiger-mode avalanche photodiode array; the single-photon detector is the Geiger-mode avalanche photodiode array, and the second electric pulse signal is an avalanche pulse signal; the low-noise amplification is implemented by a low-noise amplifier; and the echo signal is modulated by an electro-optical modulator array.

[0010] The application also discloses a microwave single-photon real-time imaging system based on the method, which comprises a microwave transmitting module, a receiving module, an optical domain processing module, an imaging module and a control module; wherein the microwave transmitting module comprises a microwave pulse radio frequency radiation source and an antenna horn; the radio frequency radiation source is configured to provide a microwave pulse signal and transmit the microwave pulse signal to the antenna horn, and the antenna horn is configured to radiate the microwave pulse signal to free space; the receiving module comprises a microwave antenna receiving array front end and a radio frequency channel, wherein the microwave antenna receiving array front end is an antenna horn array composed of a plurality of antenna horns, the antenna horn array receives echo signals of the microwave pulse signal reflected by an imaging target, and sends the echo signals to the radio frequency channel; the radio frequency channel comprises sequentially connected low-noise amplifiers, a digital control attenuator and a digital control delay device, and is used for processing the echo signals received by the microwave antenna receiving array front end; the optical domain processing module comprises a microwave optical up-conversion module and a free space optical domain processing module, the microwave optical up-conversion module modulates the echo signals carrying target feature information to a first-order sideband of an optical carrier through an electro-optical modulator array; the optical domain processing module further comprises an optical source module for generating the optical carrier, and the optical source module comprises sequentially connected narrow-line-width lasers, an optical power amplifier, an optical coupler and a polarization maintaining optical splitter; the free space optical domain processing module is used for spatial optical processing of optical signals, and comprises an optical antenna array, a polarization beam splitter, a quarter-wave plate, a filtering module and a lens group arranged in sequence; wherein the optical antenna array hits the signals converted to the optical domain on the polarization beam splitter together with the optical carrier, and generates circularly polarized light with a phase change of 45° through the quarter-wave plate, the filtering module transmits the expected first-order sideband optical signal to the rear-end lens group, and the lens group is used for simultaneous formation of spatial optical multi-beams and irradiation to an imaging target surface; the imaging module adopts a single-photon detection array to image the received expected first-order sideband optical signal; and the control module is configured to realize the above-mentioned synchronous control through an upper computer and deployed control software.

[0011] In some embodiments, the filtering module is a spatial medium thin film filter.

[0012] In some embodiments, the microwave optical up-conversion module further comprises a phase shifter array configured to perform wavefront consistency regulation on the optical carrier and the first-order sideband in the optical path through phase control feedback.

[0013] In some embodiments, the phase control feedback is provided by a phase control feedback module.

[0014] Compared with the prior art, the technical scheme of the application has at least the following beneficial effects:

[0015] 1. Compared with the traditional microwave photon imaging radar, the application uses microwave pulses instead of traditional large bandwidth signals, so that the high range image resolution of the imaging radar is no longer dependent on large bandwidth signals, which has great significance for reducing hardware requirements and reducing array cost.

[0016] 2. Because of the characteristics of wideband three-dimensional real-time optical domain processing, the target microwave pulse echo beam space reconstruction can be completed in the simulation optical domain, which has high real-time performance and greatly saves the hardware cost required by digital signal processing. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a specific flowchart of a specific embodiment of the application's microwave single-photon real-time imaging method based on time-of-flight measurement;

[0018] Figure 2 is a principle diagram of a specific embodiment of the application's microwave single-photon real-time imaging system based on time-of-flight measurement;

[0019] Figure 3 is a structural diagram of a specific embodiment of the application's microwave single-photon real-time imaging system based on time-of-flight measurement;

[0020] Figure 4 is a schematic diagram of the intensity image experimental results of a specific embodiment of the application's microwave single-photon real-time imaging system and method based on time-of-flight measurement;

[0021] Figure 5 is a schematic diagram of the range image experimental results of a specific embodiment of the application's system and method. DETAILED DESCRIPTION

[0022] The embodiments of the application will be described in detail below with specific examples. Those skilled in the art can easily understand other advantages and effects of the application from the disclosure. The application can also be implemented or applied in different specific embodiments, and the details in the specification can be modified or changed based on different views and applications without departing from the spirit of the application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0023] The microwave single-photon real-time imaging method based on time-of-flight measurement according to an embodiment of the application, as shown in Figure 1 includes the following steps:

[0024] Step S1, inputting a first electric pulse signal synchronized with a microwave pulse signal to a time-correlated single photon counter simultaneously so that the time-correlated single photon counter starts timing; wherein the microwave pulse signal can be radiated by a microwave pulse radio frequency radiation source to free space; the time-correlated single photon counter is a Gm-APD (Geiger-mode avalanche photodiode array);

[0025] The pulse width of the microwave pulse signal is in nanoseconds or even microseconds.

[0026] Step S2, receiving a plurality of echo signals formed by the imaging target reflecting the microwave pulse, wherein each of the echo signals carries feature information of the imaging target;

[0027] Step S3, performing low-noise amplification on the plurality of echo signals to amplify the feature information; wherein the low-noise amplification is implemented by a low-noise amplifier (LNA).

[0028] Step S4, modulating each of the echo signals to the positive and negative first-order sidebands of an optical carrier respectively; wherein the echo signals are modulated by an electro-optical modulator array.

[0029] Step S5, emitting the plurality of echo signals modulated to the positive and negative first-order sidebands of the optical carrier respectively as multi-channel spatial light; wherein the emission can be achieved by connecting the optical array antenna to a microlens array.

[0030] Step S6, collimating the multi-channel spatial light and then performing filtering to screen the negative first-order sideband; wherein the filtering is completed by an optical filtering module.

[0031] Step S7, configuring a single photon detector array to generate a second electric pulse signal after receiving each photon of the negative first-order sideband; wherein the single photon detector is a Gm-APD (Geiger-mode avalanche photodiode array) detector. The second electric pulse signal is an avalanche pulse signal.

[0032] Step S8, configuring the time-correlated single photon counter to receive the second electric pulse signal from the single photon detector array and stop timing;

[0033] Step S9, calculating the time of flight of each photon detected by the timing of the first electric pulse signal and the second electric pulse signal, recording and counting the photons of the plurality of echo signals, and finally completing the intensity image imaging and range image imaging of the optical domain pulse echo.

[0034] As a specific embodiment of the above method, some embodiments of the present application propose a microwave single photon real-time imaging system based on time of flight measurement for imaging an imaging target 200, as shown in Figure 2 ,Figure 3 As shown, the system includes a microwave emission module 10, a receiving module 20, an optical domain processing module 30, an imaging module 40 and a control module 50.

[0035] The microwave emission module 10 includes a microwave pulse radio frequency radiation source 11 and an antenna horn 12. The microwave pulse radio frequency radiation source 11 is configured to provide and emit microwave pulse signals to the antenna horn 12. The antenna horn 12 is configured to radiate the microwave pulse signals to free space. The microwave pulse radio frequency radiation source 11 can be selected from E8267D of Agilent Company, and the working frequency is 250 kHz-43.5 GHz. The antenna horn 12 can be selected from HD-100SGAH15S of Xi'an Hengda Microwave Technology Development Co., Ltd.

[0036] The receiving module 20 can include a microwave antenna receiving array front end 21 and a radio frequency channel 22. The microwave antenna receiving array front end 21 is an antenna horn array 211 composed of a plurality of antenna horns. The echo signal of the microwave pulse signal from the imaging target 200 is received by the antenna horn array 211, and the echo signal is sent to the radio frequency channel 22. The radio frequency channel 22 includes a low-noise amplifier 221, a digital controlled attenuator 222 and a digital controlled delay 223, which are used to process the echo signal received by the microwave antenna receiving array front end. The low-noise amplifier 221 can be selected from BW301 single-chip integration, which can work at 70 mA working current and provide a gain of 15 dB. The digital controlled attenuator 222 can be selected from BW163. The working frequency is DC-18 GHz, the insertion loss is less than 3.5 dB, and the total attenuation is 31.5 dB. The digital controlled delay 223 can be selected from NC1264C-812 chip. NC1264C-812 is a 6-bit digital controlled delay chip, the insertion loss is less than 8.5 dB, and the standing wave is less than 1.7.

[0037] The optical domain processing module 30 can include a microwave optical up-conversion module 31 and a free space optical domain processing module 32. The microwave optical up-conversion module 31 modulates the echo signal carrying the target feature information to the positive and negative first-order sidebands of the 1550 nm optical carrier through an array of electro-optical modulators 311. The electro-optical modulator can be selected from GC15PMPF7813Z of the 44th Institute of China Electronics Technology Group, and the working frequency is 0.01-12 GHz, the insertion loss is ≤3.5 dB, and the half-wave voltage of 50 kHz is ≤3.5 V. Optionally, a phase shifter array 312 can be provided to control the wavefront consistency of the optical path through phase control feedback.

[0038] The 1550 nm optical carrier can be generated by an optical source module 33, which includes a 1550 nm narrow linewidth laser 331, an EDFA optical power amplifier 332, a 1X2 optical coupler 333, a 1XN polarization maintaining optical splitter 334,

[0039] The free space optical domain processing module 32 is used for spatial optical processing of the optical signal, which includes an optical antenna array 321 (including an optical line array antenna and a microlens array), a polarization beam splitter 322, a quarter wave plate 323, a filter module 324, and a lens group 325. The optical antenna array 321 converts the signal converted to the optical domain to the polarization beam splitter 322 together with the optical carrier and generates circularly polarized light with a phase change of 45° through the quarter wave plate 323. The filter module 324 is used to reflect the optical carrier and the positive first-order sideband and transmit the negative first-order sideband to the rear-end lens group. The lens group 325 is used for simultaneous formation of spatial optical multi-beams and irradiation to the imaging target surface. The optical fiber wavelength of the optical antenna array 321 is 1550 nm, the optical fiber type is PM15-U25D, the lens wavelength range is 1260-1620 nm, the lens diameter is 240 , and the reflectivity is <0.5%. The polarization beam splitter 322 can be PBS124, the working wavelength range is 1200-1600 nm, and the size is 1 / 2 inch polarization beam splitting cube. The quarter wave plate 323 can be WPQ05ME-1550, the working wavelength is 1550 nm, and the diameter is 1 / 2 inch. The filter module 324 is a spatial medium thin film filter that can filter out the negative first-order sideband. The working wavelength range corresponding to the sideband formed by the aforementioned device can be, for example, 1460-1640 nm, the passband loss is ≤0.5 dB, the adjacent channel isolation is >25 dB, the maximum insertion loss in the stopband is ≤0.3 dB, and the antireflection film reflectivity is <0.2%. The lens group 325 can be LA1134-C, the antireflection film range is 1050-1700 nm, the focal length is 60 mm, the material is N-BK7, and it is a plano-convex lens. In other embodiments, the spatial medium thin film filter can also be able to filter out the positive first-order sideband according to the system settings.

[0040] The imaging module 40 can use a single photon detection array to image the received negative first-order sideband optical signal. The single photon detection array can be GD5551-C type InGaAs Geiger avalanche focal plane camera of Chongqing Acousto-Optic Electronics Co., Ltd. of China Electronics Technology Group, the sensor array size is 64x64, the photosensitive target surface size is 3.2x3.2 mm, the working wavelength is 950-1650 nm, the time resolution is 1 ns, the frame frequency is 25 KHz, and the gating time range is 25-4090 ns. The control module 50 can be realized by the upper computer and the deployed software.

[0041] For example, the control module 50 can be communicatively connected with the microwave transmitting module 10, the receiving module 20, the optical domain processing module 30, and the imaging module 40 to control the coordination of the functions of the modules through deployed software to ultimately obtain the imaging results. The software may, for example, implement the above-mentioned step 1 of simultaneously inputting a first electric pulse signal synchronized with a microwave pulse signal into a time-correlated single photon counter so that the time-correlated single photon counter starts timing; step S2, receiving an echo signal of the microwave pulse reflected by the imaged target, wherein the echo signal carries characteristic information of the imaged target; wherein the echo signal is received by an antenna array arranged in a specific manner; step S3, low-noise amplifying the echo signal to amplify the characteristic information; wherein the low-noise amplification is implemented by a low-noise amplifier (LNA). Step S4, modulating the echo signal onto the positive and negative first-order sidebands of an optical carrier; step S5, emitting the echo signal modulated onto the positive and negative first-order sidebands of the optical carrier as multi-channel spatial light; step S6, collimating and filtering the multi-channel spatial light to screen out the negative first-order sideband; step S7, controlling the time-correlated single photon counter to stop timing when a second electric pulse signal output by the single photon detector array is received; step S8, calculating the time of flight of each detected photon through the timing of the first electric pulse signal and the second electric pulse signal and recording and counting the detected echo photons of multiple echo signals, and finally completing the intensity image imaging and the range image imaging of the optical domain pulse echo.

[0042] In the above embodiment, the microwave transmitting module is used to emit microwave pulse signals; the receiving module is used to receive microwave pulse echo signals, wherein the front end of the microwave antenna receiving array includes an antenna array of several antenna elements, each antenna element is responsible for receiving the microwave pulse echo signal and sending the microwave pulse echo signal to the radio frequency channel; the radio frequency channel includes a low-noise amplifier, a digitally controlled attenuator, and a digitally controlled delay device, which are used to process the microwave signal received by the front end of the microwave antenna receiving array; the optical domain processing module is used to convert the received microwave pulse echo signal into the optical domain and perform free-space optical processing, wherein the microwave optical up-conversion module includes several electro-optical modulators and several phase shifters, each modulator is responsible for receiving the The microwave signal after RF channel processing is up-converted to the optical domain. The microwave signal after up-conversion to the optical domain is transmitted to the phase shifter through optical fiber. Each phase shifter changes the refractive index of the crystal inside the phase shifter through an external DC signal to adjust the phase consistency of the optical domain sideband signal; the free space optical domain processing module includes an optical antenna array, a filter module and a lens group. The optical antenna array transmits the signal converted to the optical domain together with the carrier from the optical fiber to the free space. The filter module is used to reflect the carrier and the positive first-order sideband and allow the negative first-order sideband to transmit to the rear-end lens group. The lens group is used to simultaneously form spatial optical multi-beams and illuminate them to the imaging target surface; the imaging module uses a single-photon detection array to image the received negative first-order sideband optical signal.

[0043] The principle of the time-of-flight calculation for single-photon detector imaging is as follows:

[0044] After the microwave pulse signal is transformed into the optical domain through up-conversion mapping, the photon signal containing the target characteristic information is incident on the Gm-APD array. The quantum efficiency of <100% is converted into photoelectrons. Since the photoelectrons hitting the object have the characteristics of Poisson distribution, there are k photoelectrons in each detection subinterval that follow the Poisson probability distribution:

[0045] 1.1

[0046] The above detection subintervals correspond to the time resolution of the Geiger avalanche focal plane camera. For the Geiger avalanche focal plane camera in the above embodiment, its time resolution is 1 ns, and the gate time range is 25-4090 ns, so it has a total of 4090-25=4065 detection subintervals.

[0047] According to formula 1.1, the probability of generating an avalanche pulse signal due to the impact of photogenerated carriers in the mth detection interval can be deduced as follows:

[0048] 1.2

[0049] According to the distance-gated Gm-APD array microwave pulse optical detection model, before the avalanche gain stage, the total number of photoelectrons is The average number of photoelectrons from the pulse signal The average number of photoelectrons from the background noise The average dark current electron noise generated by the Geiger-mode avalanche photodiode itself Together, that is, Bringing it into equation 1.2 gives the relationship between the number of photoelectrons and the probability of avalanche pulse signal generation:

[0050] 1.3

[0051] The GM-APD detector array records the time of flight of the detected photons, completing the reception imaging of the optical domain pulse echo, and the output field of the imaging system is:

[0052] 1.4

[0053] Where is the beam waist of each Gaussian beam from the microlens array, is the optical wave number, is the wavelength of the optical signal, is the focal length of the lens system, and the function represents the influence of the lens pupil function on the output field. is defined as the optical field caused by the basic optical sideband of the nth antenna element, and is calculated as follows:

[0054] 1.5

[0055] Where n in the above equation represents the loss due to the nth optical modulator, represents the input optical power, represents the optical radian frequency. is the input voltage required by the optical modulator to shift the phase of the optical carrier by radians, is the input voltage due to the antenna element and associated gain stage, is the RF radian frequency, is the phase term of the basic RF phase. In the absence of array phase errors, represents the phase shift caused by the incident RF plane wave source.

[0056] Between step S4 and step S5, a step of passing the optical carrier and sidebands through a phase shifting operation can also be included. The phase shifting operation can be performed by a phase shifter array 312, which receives phase control feedback provided by a phase control feedback module 34 to perform the phase shifting operation.

[0057] In order to verify the actual effect of system imaging, imaging tests are carried out, two target corner reflectors are arranged at a distance of 2.1m, Figure 4 , Figure 5 are indoor near-field imaging results of the microwave single-photon real-time imaging system, wherein, Figure 4 show the intensity image results of two target corner reflectors, Figure 5 are distance image results. Figure 5 are timestamp data displayed by the upper computer, wherein red represents frame selection data, and green represents target center data, so it can be seen that the two target corner reflectors differ by tens of nanoseconds, and through mathematical derivation, it can be obtained that the two target corner reflectors differ by about 2.1m.

[0058] Applicants find that reducing the pulse width of the microwave pulse can obtain higher detection accuracy, so it can be predicted that, compared with the microwave pulse with a pulse width of several microseconds, several tens of microseconds or several hundred microseconds, the microwave pulse with a pulse width of several nanoseconds, several tens of nanoseconds or several hundred nanoseconds can obtain higher detection accuracy. The present application proposes a new imaging system, which uses the short time width of the microwave pulse to replace the laser pulse to realize the time-of-flight measurement mode, and breaks the dependence between the high distance image resolution and the large signal bandwidth of the conventional microwave photon imaging radar. At the same time, the antenna array of the microwave photon imaging radar can directly receive the microwave pulse echo signals in a large field of view range in real time to realize large field of view real-time imaging based on the time-of-flight measurement mode. If a specific arrangement of the antenna array is used, the imaging effect can be improved.

[0059] The above merely describes specific embodiments of the present application and is not used to limit the protection scope of the present application. The present application can have various embodiments, and any modification, equivalent replacement, improvement, etc. made by those skilled in the art according to the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A microwave single-photon real-time imaging method based on time-of-flight measurement, characterized in that: The following steps are involved: Step S1, simultaneously inputting a first electrical pulse signal synchronized with a microwave pulse signal into a time-correlated single-photon counter so that the time-correlated single-photon counter starts timing; wherein the microwave pulse signal can be radiated into free space by a microwave pulse radio frequency radiation source; Step S2, receiving a plurality of echo signals formed by the microwave pulse reflected by the imaging target, wherein each of the echo signals carries characteristic information of the imaging target; Step S3, performing low-noise amplification on the multiple echo signals to amplify the characteristic information; Step S4, modulating each of the echo signals onto the first-order sideband of the optical carrier; Step S5, emitting the multiple echo signals respectively modulated onto the first-order sidebands of the optical carrier as multi-channel spatial light; Step S6, collimating the multi-channel spatial light and filtering it to screen the desired first-order sideband; Step S7, configuring the single-photon detector array to generate a second electrical pulse signal after receiving each photon of the desired first-order sideband; Step S8, configuring the time-correlated single-photon counter to receive the second electrical pulse signal from the single-photon detector array and stop timing; Step S9, calculating the flight time of each detected photon through the timing of the first electrical pulse signal and the second electrical pulse signal and recording and counting the photons of the multiple echo signals to complete the intensity imaging and distance imaging of the optical domain pulse echo.

2. The microwave single-photon real-time imaging method based on time-of-flight measurement according to claim 1, characterized in that: The desired first-order sideband is a positive first-order sideband or a negative first-order sideband.

3. The microwave single-photon real-time imaging method based on time-of-flight measurement according to claim 1, characterized in that: The method further includes performing a phase shift operation on the optical carrier and the first-order sideband between step S4 and step S5.

4. The microwave single-photon real-time imaging method based on time-of-flight measurement according to claim 1, characterized in that: The time-correlated single-photon counter is a Geiger-mode avalanche photodiode array; the single-photon detector is the Geiger-mode avalanche photodiode array, and the second electrical pulse signal is an avalanche pulse signal; the low-noise amplification is implemented by a low-noise amplifier; and the echo signal is modulated by an electro-optical modulator array.

5. A microwave single-photon real-time imaging system based on time-of-flight measurement, used to implement the method according to any one of claims 1 to 4, characterized in that: It comprises a microwave transmitting module (10), a receiving module (20), an optical domain processing module (30), an imaging module (40), and a control module (50); The microwave transmitting module (10) includes a microwave pulse radio frequency radiation source (11) and an antenna horn (12); the microwave pulse radio frequency radiation source (11) is configured to provide a microwave pulse signal and transmit it to the antenna horn (12); the antenna horn (12) is configured to radiate the microwave pulse signal into free space; The receiving module (20) includes a microwave antenna receiving array front end (21) and a radio frequency channel (22), wherein the microwave antenna receiving array front end (21) is an antenna horn array (211) composed of a plurality of antenna horns, and receives an echo signal of the imaging target (200) to the microwave pulse signal through the antenna horn array (211), and sends the echo signal to the radio frequency channel (22); the radio frequency channel (22) includes a low noise amplifier (221), a digitally controlled attenuator (222), and a digitally controlled delay (223) connected in sequence, and is used to process the echo signal received by the microwave antenna receiving array front end; The optical domain processing module (30) comprises a microwave optical up-conversion module (31) and a free-space optical domain processing module (32), wherein the microwave optical up-conversion module (31) modulates the echo signal carrying target characteristic information onto a first-order sideband of an optical carrier through an electro-optical modulator array; The optical domain processing module (30) further includes a light source module (33) for generating the optical carrier, wherein the light source module (33) includes a narrow linewidth laser (331), an optical power amplifier (332), an optical coupler (333), and a polarization-maintaining optical splitter (334) connected in sequence; The free-space optical domain processing module (32) is used to perform spatial optical processing on the optical signal, and comprises an optical antenna array (321), a polarization beam splitter (322), a quarter-wave plate (323), a filter module (324), and a lens group (325) arranged in sequence; wherein the optical antenna array (321) transmits the signal converted into the optical domain together with the optical carrier to the polarization beam splitter (322) and generates circularly polarized light with a phase change of 45° through the quarter-wave plate (323); the filter module (324) transmits the desired first-order sideband optical signal to the rear-end lens group; the lens group (325) is used for simultaneously forming spatial optical multi-beams and irradiating them to the imaging target surface; The imaging module (40) uses a single-photon detection array to image the received desired first-order sideband light signal; The control module (50) is configured to achieve synchronization between the microwave pulse signal and the first electrical pulse signal, which is achieved through a host computer and deployed control software.

6. The microwave single-photon real-time imaging system based on time-of-flight measurement according to claim 5, characterized in that: The filtering module (324) is a spatial dielectric thin film filter.

7. The microwave single-photon real-time imaging system based on time-of-flight measurement according to claim 5, characterized in that: The microwave optical up-conversion module (31) further comprises a phase shifter array, wherein the phase shifter array is configured to perform wavefront consistency control on the optical carrier and the first-order sideband in the optical path through phase control feedback.

8. The microwave single-photon real-time imaging system based on time-of-flight measurement according to claim 7, characterized in that: The phase control feedback is provided by a phase control feedback module (34).

Images