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

Abstract

This invention discloses a microwave single-photon real-time imaging system and method based on time-of-flight measurement, belonging to the field of microwave optical imaging radar. The system and method of this invention up-convert the received microwave pulse echo signal to the optical domain and perform free-space light processing; then, a single-photon detection array is used to image the target from the processed optical signal. This invention uses a single-photon detection array to achieve large field-of-view, high real-time imaging of the target. Compared with traditional microwave optical imaging systems, the range image information does not depend on the bandwidth of the transmitted signal, thus achieving high range image resolution imaging of the target.

Description

Technical Field

[0001] This invention belongs to the field of imaging radar, and particularly relates to an imaging method and system in microwave photonic imaging radar. Background Technology

[0002] Imaging radar can distinguish, identify, and classify targets, and has wide applications in fields such as autonomous driving, security inspection, meteorology, and national defense. Common imaging radar systems include synthetic aperture radar (SAR), inverse synthetic aperture radar (ISAR), combined aperture radar (SAR), lidar, and microwave photonic imaging radar. Among these, microwave photonic imaging radar shows promising prospects in scientific research, military, and civilian applications.

[0003] Microwave photonic radar modulates microwave signals onto optical signals, enabling transmission, processing, and transformation of the microwave signals in the optical domain, and finally demodulating the sideband information for imaging. Microwave photonic radar combines the high-speed, broadband characteristics of photonics with the flexibility and ease of control of microwave technology. It leverages the advantages of photonics—high frequency, broadband, resistance to electromagnetic interference, and low transmission loss—to achieve broadband microwave signal processing and high-speed transmission functions that are complex or even difficult to accomplish in the traditional microwave domain. As is well known, larger bandwidth is beneficial for better range resolution; however, the pursuit of larger bandwidth also increases the hardware requirements of microwave photonic radar and raises array costs. This limits the further development of microwave photonic radar. Summary of the Invention

[0004] In response to the above-mentioned defects or improvement needs of existing technologies, this invention proposes a microwave single-photon real-time imaging method based on time-of-flight measurement, thereby solving the problem that improving the range image resolution of existing microwave photonic radar relies on a large bandwidth.

[0005] This invention is achieved through the following technical solution:

[0006] This invention discloses a real-time microwave single-photon imaging method based on time-of-flight measurement, comprising the following steps: Step S1, simultaneously inputting a first electrical pulse signal synchronized with a microwave pulse signal into a time-correlated single-photon counter to start the time-correlated single-photon counter; wherein, the microwave pulse signal can be radiated into free space by a microwave pulse radio frequency radiation source; Step S2, receiving multiple echo signals formed by the microwave pulse reflected by the imaging target, wherein each echo signal carries feature information of the imaging target; Step S3, performing low-noise amplification on the multiple echo signals to amplify the feature information; Step S4: Modulate each echo signal onto the first-order sideband of the optical carrier. Step S5: Output the multiple echo signals modulated onto the first-order sideband of the optical carrier as multi-channel spatial light. Step S6: Collimate the multi-channel spatial light and filter it to select the desired first-order sideband. Step S7: Configure a single-photon detector array to receive each photon of the desired first-order sideband and generate a second electrical pulse signal. Step S8: Configure the time-correlated single-photon counter to receive the second electrical pulse signal from the single-photon detector array and stop timing. Step S9: Calculate the flight time of each detected photon based on the timing of the first and second electrical pulse signals, and record and count the photons of the multiple echo signals to complete the 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, a step of performing a phase-shifting operation on the optical carrier and the first-order sideband is included between step S4 and step S5.

[0009] In some embodiments, the time-correlated single-photon counter is a Geiger-mode avalanche photodiode array; the single-photon detector is the Geiger-mode avalanche photodiode array, 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-optic modulator array.

[0010] This invention also discloses a microwave single-photon real-time imaging system based on the above method, comprising a microwave transmitting module, a receiving module, an optical domain processing module, an imaging module, and a control module; wherein, the microwave transmitting module includes 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 it to the antenna horn, and the antenna horn is configured to radiate the microwave pulse signal into free space; the receiving module includes 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 several antenna horns, which receives the echo signal of the imaging target to the microwave pulse signal through the antenna horn array and sends the 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 unit connected in sequence, used to process the echo signal received by the microwave antenna receiving array front end; the optical domain processing module includes a microwave optical upconversion module and a free space optical domain processing module, wherein the microwave optical upconversion module modulates the echo signal carrying target feature information onto the first-order sideband of the optical carrier through an electro-optic modulator array; the optical domain processing module also includes a light source module to generate the optical carrier, the light source module including a series of components connected in sequence. The system comprises a narrow-linewidth laser, an optical power amplifier, an optical coupler, and a polarization-maintaining optical splitter. The free-space optical domain processing module performs spatial optical processing on the optical signal and includes a sequentially arranged optical antenna array, a polarization beam splitter, a quarter-wave plate, a filtering module, and a lens group. The optical antenna array, along with the optical carrier, strikes the polarization beam splitter with the converted optical signal, generating circularly polarized light with a 45° phase change through the quarter-wave plate. The filtering module transmits the desired first-order sideband optical signal to the rear lens group, which simultaneously forms and illuminates the imaging target surface using multiple spatial optical beams. The imaging module employs a single-photon detector array to image the received desired first-order sideband optical signal. The control module is configured to achieve the above synchronous control via a host computer and deployed control software.

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

[0012] In some embodiments, the microwave optical upconversion module further includes a phase shifter array, which is configured to perform wavefront uniformity control 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 solution of the present invention has at least the following beneficial effects:

[0015] 1. Compared with traditional microwave photonic imaging radar, this invention uses microwave pulses instead of traditional large-bandwidth signals, so that the high range image resolution of the imaging radar no longer depends on large-bandwidth signals, which is of great significance for reducing hardware requirements and reducing array costs.

[0016] 2. This invention utilizes the characteristics of broadband three-dimensional real-time optical domain processing to complete the beam space reconstruction of the target microwave pulse echo in the analog optical domain, which has high real-time performance and greatly saves the hardware cost required for digital signal processing. Attached Figure Description

[0017] Figure 1 This is a detailed flowchart of a specific embodiment of the microwave single-photon real-time imaging method based on time-of-flight measurement of the present invention;

[0018] Figure 2 This is a schematic diagram illustrating the principle of a specific embodiment of the microwave single-photon real-time imaging system based on time-of-flight measurement of the present invention.

[0019] Figure 3 This is a schematic diagram of a specific embodiment of the microwave single-photon real-time imaging system based on time-of-flight measurement of the present invention.

[0020] Figure 4 This is a schematic diagram of the intensity image experimental results of a specific embodiment of the microwave single-photon real-time imaging system and method based on time-of-flight measurement according to the present invention.

[0021] Figure 5 This is a schematic diagram of the distance image experimental results according to a specific embodiment of the system and method of the present invention. Detailed Implementation

[0022] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0023] According to one embodiment of this application, a microwave single-photon real-time imaging method based on time-of-flight measurement is provided, such as... Figure 1 As shown, it includes the following steps:

[0024] Step S1: The first electrical pulse signal, synchronized with the microwave pulse signal, is simultaneously input to the time-correlated single-photon counter to start the time-correlated single-photon counter; wherein, the microwave pulse signal can be radiated into free space by a microwave pulse radio frequency radiation source; 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 the nanosecond or even microsecond range.

[0026] Step S2: Receive multiple echo signals formed by the microwave pulse reflected by the imaging target, wherein each echo signal carries feature information of the imaging target;

[0027] Step S3: The plurality of echo signals are amplified with low noise to amplify the feature information; wherein the low noise amplification is performed by a low noise amplifier (LNA).

[0028] Step S4: Each echo signal is modulated onto the positive and negative first-order sidebands of the optical carrier; wherein the echo signal is modulated by an electro-optic modulator array.

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

[0030] Step S6: After collimating the multi-channel spatial light, filter it to select the negative first-order sideband; wherein, the filtering is performed by an optical filtering module.

[0031] Step S7: Configure a single-photon detector array to receive each photon from the negative first-order sideband and generate a second electrical pulse signal; wherein the single-photon detector is a Gm-APD (Gieg-mode avalanche photodiode array) detector. The second electrical pulse signal is an avalanche pulse signal.

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

[0033] Step S9: The flight time of each detected photon is calculated by timing the first and second electrical pulse signals, and the photons of the multiple echo signals are recorded and counted, thus 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 this application propose a microwave single-photon real-time imaging system based on time-of-flight measurement for imaging target 200, such as... Figure 2 , Figure 3 As shown, the system includes a microwave transmitting module 10, a receiving module 20, an optical domain processing module 30, an imaging module 40, and a control module 50.

[0035] 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 microwave pulse signals and transmit them to the antenna horn 12, which is configured to radiate the microwave pulse signals into free space. The microwave pulse radio frequency radiation source 11 can be an Agilent E8267D, operating at a frequency of 250kHz-43.5GHz. The antenna horn 12 can be an HD-100SGAH15S from Xi'an Hengda Microwave Technology Development Co., Ltd.

[0036] The receiving module 20 may include a microwave antenna receiving array front-end 21 and an RF channel 22. The microwave antenna receiving array front-end 21 is an antenna horn array 211 composed of several antenna horns. The antenna horn array 211 receives the echo signal from the imaging target 200 in response to the microwave pulse signal and sends the echo signal to the RF channel 22. The RF channel 22 includes a low-noise amplifier 221, a digitally controlled attenuator 222, and a digitally controlled delay unit 223, used to process the echo signal received by the microwave antenna receiving array front-end. The low-noise amplifier 221 can be a BW301 monolithic integrated circuit, capable of operating at 70mA current and providing 15dB gain. The digitally controlled attenuator 222 can be a BW163, operating at DC-18GHz with an insertion loss of less than 3.5dB and a total attenuation of 31.5dB. The numerical control delay unit 223 can use the NC1264C-812 chip. The NC1264C-812 is a 6-bit numerical control delay unit chip with an insertion loss of less than 8.5dB and a standing wave ratio of less than 1.7.

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

[0038] A 1550nm optical carrier can be generated by a light source module 33, which includes a 1550nm narrow-linewidth laser 331, an EDFA optical power amplifier 332, a 1x2 optical coupler 333, and a 1xN polarization-maintaining optical splitter 334.

[0039] The free-space optical domain processing module 32 is used for spatial optical processing of optical signals. It includes an optical antenna array 321 (comprising a fiber array antenna and a microlens array), a polarization beamsplitter 322, a quarter-wave plate 323, a filtering module 324, and a lens group 325. The optical antenna array 321 converts the signal into the optical domain and, along with the optical carrier, projects it onto the polarization beamsplitter 322. The quarter-wave plate 323 then generates circularly polarized light with a 45° phase shift. The filtering module 324 reflects the optical carrier and positive first-order sidebands and allows the negative first-order sidebands to be transmitted to the rear lens group. The lens group 325 simultaneously forms and illuminates the imaging target surface using multiple spatial optical beams. The optical antenna array 321 uses a PM15-U25D fiber with a working wavelength of 1550nm. The lens wavelength range is 1260-1620nm, and the lens diameter is 240mm. The reflectivity is <0.5%. The polarization beam splitter 322 can be a PBS124, with an operating wavelength range of 1200-1600nm and a 1 / 2-inch polarization beam splitter cube size. The quarter-wave plate 323 can be a WPQ05ME-1550, with an operating wavelength of 1550nm and a diameter of 1 / 2 inch. The filter module 324 is a spatial dielectric thin-film filter capable of filtering out the negative first-order sideband. Corresponding to the sideband formed by the aforementioned devices, its operating wavelength range can be, for example, 1460-1640nm, with a passband loss ≤0.5dB, adjacent channel isolation >25dB, maximum insertion loss in the stopband ≤0.3dB, and antireflective coating reflectivity <0.2%. The lens group 325 can be an LA1134-C, with an antireflective coating range of 1050-1700nm, a focal length of 60mm, and N-BK7 material; it is a plano-convex lens. In other embodiments, the spatial dielectric thin-film filter can also filter out the positive first-order sideband, depending on the system settings.

[0040] The imaging module 40 can employ a single-photon detector array to image the received negative first-order sideband light signal. The single-photon detector array can be a GD5551-C InGaAs Geiger avalanche focal plane camera from Chongqing Optoelectronics Co., Ltd., a subsidiary of China Electronics Technology Group Corporation. Its sensor array size is 64×64, the photosensitive target size is 3.2×3.2mm, the operating wavelength is 950-1650nm, the temporal resolution is 1ns, the frame rate is 25KHz, and the gating time range is 25-4090ns. The control module 50 can be implemented through communication with the host computer and deployed software.

[0041] For example, the control module 50 can be communicatively connected to the microwave transmitting module 10, the receiving module 20, the optical domain processing module 30, and the imaging module 40, so as to control the coordination of the functions of each module through deployed software to finally obtain the imaging result. The software can, for example, implement the following steps: in step S1, inputting a first electrical pulse signal synchronized with the microwave pulse signal simultaneously to a time-correlated single-photon counter to start the time-correlated single-photon counter; in step S2, receiving the echo signal of the microwave pulse reflected back from the imaging target, wherein the echo signal carries the characteristic information of the imaging target; wherein the echo signal is received by an antenna array arranged in a specific manner; in step S3, performing low-noise amplification on the echo signal to amplify the characteristic information; wherein the low-noise amplification is implemented by a low-noise amplifier (LNA). Step S4: Modulate the echo signal onto the positive and negative first-order sidebands of the optical carrier; Step S5: Output the echo signal modulated onto the positive and negative first-order sidebands of the optical carrier as multi-channel spatial light; Step S6: Collimate the multi-channel spatial light and filter it to select the negative first-order sideband; Step S7: Control the time-correlated single-photon counter to stop timing when it receives the second electrical pulse signal output by the single-photon detector array for each photon detected; Step S8: Calculate the flight time of each detected photon by timing the first and second electrical pulse signals, and record and count the detected echo photons of multiple echo signals, finally completing the intensity image imaging and range image imaging of the optical domain pulse echo.

[0042] In the above embodiments, the microwave transmitting module is used to emit microwave pulse signals; the receiving module is used to receive microwave pulse echo signals, wherein the microwave antenna receiving array front end includes an antenna array with several antenna elements, each antenna element is responsible for receiving microwave pulse echo signals and sending the microwave pulse echo signals to the radio frequency channel; the radio frequency channel includes a low-noise amplifier, a digitally controlled attenuator, and a digitally controlled delay unit, used to process the microwave signals received by the microwave antenna receiving array front end; the optical domain processing module is used to convert the received microwave pulse echo signals to the optical domain and perform free-space optical processing, wherein the microwave optical up-conversion module includes several electro-optic modulators and several phase shifters, each modulator is responsible for receiving the microwave pulse echo signals. The microwave signal processed by the radio frequency channel is upconverted to the optical domain. The upconverted microwave signal is then transmitted to a phase shifter via optical fiber. Each phase shifter adjusts the phase consistency of the optical domain sideband signal by changing the refractive index of the crystal inside the phase shifter through an external DC signal. The free space optical domain processing module includes an optical antenna array, a filtering module, and a lens group. The optical antenna array transmits the signal converted to the optical domain, along with the carrier wave, from the optical fiber to free space. The filtering module is used to reflect the carrier wave and the positive first-order sideband and allow the negative first-order sideband to be transmitted to the rear lens group. The lens group is used for the simultaneous formation of multiple beams in space optics and to illuminate the imaging target surface. The imaging module uses a single-photon detector array to image the received negative first-order sideband optical signal.

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

[0044] After the microwave pulse signal is up-converted and mapped to the optical domain, a photon signal containing target feature information is incident on the Gm-APD array. <100% quantum efficiency is converted into photoelectrons. Since photoelectrons impacting an object exhibit a Poisson distribution, k photoelectrons in each detector sub-interval follow a Poisson probability distribution:

[0045] 1.1

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

[0047] According to Equation 1.1, the probability of generating an avalanche pulse signal due to photogenerated carrier collisions in the m-th detection interval can be derived 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 in the pulse signal Average background noise photoelectron count The average dark current electron noise generated by the Geiger-mode avalanche photodiode itself. Together constitute, that is Substituting this into Equation 1.2 yields the relationship between the number of photoelectrons in each part and the probability of avalanche pulse signal generation:

[0050] 1.3

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

[0052] 1.4

[0053] in It is the beam waist of each Gaussian beam from the microlens array. It is the light wave number. It is the wavelength of the light signal. It is the focal length of the lens system, and a function This represents the effect of the lens pupil function on the output field. Defined as the optical field caused by the fundamental optical sideband of the nth antenna element, and calculated as follows:

[0054] 1.5

[0055] in In this context, 'n' represents the loss caused by the nth optical modulator. Indicates the input optical power. It represents the frequency of light radians. It is the optical modulator that shifts the phase of the optical carrier. The required input voltage for radians The input voltage is caused by the antenna elements and the associated gain stage. It is the RF radian frequency. This is the phase term of the basic RF phase. In the absence of array phase error, This represents the phase shift caused by the incident RF plane wave source.

[0056] Between step S4 and step S5, a step of phase-shifting the optical carrier and sidebands may be included. This phase-shifting operation may be performed by a phase shifter array 312, which receives phase control feedback to perform the phase-shifting operation. This phase control feedback is provided by a phase control feedback module 34.

[0057] To verify the actual imaging effect of the system, an imaging experiment was conducted, with two target corner reflectors set up 2.1m apart. Figure 4 , Figure 5 This is an indoor near-field imaging result image of a microwave single-photon real-time imaging system, in which... Figure 4 The image shown is an intensity image of two target corner reflectors. Figure 5 This is the distance image result. Figure 5 The data in the middle is the timestamp data displayed by the host computer. Red represents the selected data and green represents the target center data. It can be seen that the two target corner reflectors are out of 10 nanoseconds apart. Through mathematical derivation, it can be found that the two target corner reflectors are out of 2.1m apart.

[0058] The applicant discovered that reducing the pulse width of microwave pulses can achieve higher detection accuracy. Therefore, it is foreseeable that using microwave pulses with pulse widths of several nanoseconds, tens of nanoseconds, or hundreds of nanoseconds will achieve higher detection accuracy compared to using microwave pulses with pulse widths of several microseconds, tens of microseconds, or hundreds of microseconds. This application proposes a novel imaging system that utilizes the short pulse width of microwave pulses to replace laser pulses in achieving time-of-flight measurement, breaking the dependency between high range image resolution and large signal bandwidth in conventional microwave photonic imaging radar. Simultaneously, the antenna array can directly receive microwave pulse echo signals within a large field of view in real time, enabling real-time imaging of a large field of view using time-of-flight measurement. Using a specifically arranged antenna array can further improve the imaging effect.

[0059] The above description is merely a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. The present invention may have many other embodiments. Within the spirit and principles of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention. Any modifications, equivalent substitutions, improvements, etc., should be included within the scope of protection of the present invention.

Claims

1. A microwave single-photon real-time imaging method based on time-of-flight measurement, characterized in that, Includes the following steps: Step S1: A first electrical pulse signal synchronized with the microwave pulse signal is simultaneously input into a time-correlated single-photon counter, causing the time-correlated single-photon counter to start timing; wherein, the microwave pulse signal can be radiated into free space from a microwave pulse radio frequency radiation source; Step S2: Receive multiple echo signals formed by the microwave pulse reflected by the imaging target, wherein each echo signal carries feature information of the imaging target; Step S3: Amplify the multiple echo signals with low noise to amplify the feature information; Step S4: Modulate each of the echo signals onto the first-order sideband of the optical carrier; Step S5: The plurality of echo signals modulated onto the first-order sideband of the optical carrier are emitted as multi-channel spatial light; Step S6: After collimating the multi-channel spatial light, filter it to select the desired first-order sidebands; Step S7: Configure the single-photon detector array to receive each photon of the desired first-order sideband and then generate a second electrical pulse signal; Step S8: Configure the time-correlated single-photon counter to receive the second electrical pulse signal from the single-photon detector array and stop timing; Step S9: Calculate the flight time of each detected photon by timing the first and second electrical pulse signals, and record and count the photons of the multiple echo signals to complete the intensity image imaging and range image 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 either 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, Between step S4 and step S5, there is also a step of performing a phase shift operation on the optical carrier and the first-order sideband.

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-optic modulator array.

5. A microwave single-photon real-time imaging system based on time-of-flight measurement, used to implement the method of any one of claims 1 to 4, characterized in that, It includes 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), and 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). The microwave antenna receiving array front end (21) is an antenna horn array (211) composed of several antenna horns. The antenna horn array (211) receives the echo signal of the imaging target (200) to the microwave pulse signal 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 unit (223) connected in sequence to process the echo signal received by the microwave antenna receiving array front end. The optical domain processing module (30) includes a microwave optical upconversion module (31) and a free space optical domain processing module (32). The microwave optical upconversion module (31) modulates the echo signal carrying target feature information onto the first-order sideband of the optical carrier through an electro-optic modulator array. The optical domain processing module (30) further includes a light source module (33) to generate the optical carrier, the light source module (33) including 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 optical signals. It includes an optical antenna array (321), a polarization beam splitter (322), a quarter-wave plate (323), a filtering module (324), and a lens group (325) arranged in sequence. The optical antenna array (321) hits the signal converted to the optical domain along with the optical carrier onto the polarization beam splitter (322) and generates circularly polarized light with a phase change of 45° through the quarter-wave plate (323). The filtering module (324) allows the desired first-order sideband optical signal to be transmitted to the rear lens group. The lens group (325) is used to simultaneously form and illuminate the imaging target surface of spatial optical multi-beams. The imaging module (40) uses a single-photon detector array to image the received desired first-order sideband light signal; The control module (50) is configured to synchronize the microwave pulse signal with 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 space medium 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 upconversion module (31) further includes a phase shifter array, which 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 the phase control feedback module (34).

Images