A quantum correlation imaging system based on a microlens array

Abstract

The application discloses a quantum correlation imaging system based on a microlens array, which comprises a transmitter, a receiver, a comprehensive control system and an image inversion system; a light source unit of the transmitter outputs a two-mode vacuum squeezed state, which is divided into a mode A light field and a mode B light field. The mode A light field remains in the local, and the mode B light field returns to the receiver after acting on a target, the receiver performs time synchronization and coincidence measurement on the mode A and B light fields under the transceiving synchronization control of the comprehensive control system, and delivers detection results to the image inversion system. The image inversion system inverts the intensity image of the target by using a high-efficiency data processing algorithm. The comprehensive control system is used for transmitter output control, receiver coincidence measurement control, clock synchronization and real-time communication. The application realizes a quantum imaging system with high energy collection efficiency, can be used for fast imaging of dark and weak targets in a strong background, and can also be applied to medical imaging of biological tissues with low damage threshold.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of target detection, imaging and identification, and particularly relates to a quantum correlation imaging system with high energy collection efficiency based on a microlens array. BACKGROUND

[0002] Quantum imaging is a new imaging technology based on special quantum correlation of quantum entangled states, and has the advantages of high imaging precision and breaking through the classical shot noise limit compared with traditional imaging, and has become a hotspot in the research of new imaging technology.

[0003] At present, quantum imaging generally uses quantum correlation of two modes of quantum entangled states to realize target imaging, and the two optical modes of entanglement are called signal mode and idle mode. The signal mode interacts with the target and is detected by a detector without spatial resolution, and the idle mode is detected by a detector with certain spatial resolution. Finally, the spatial information of the target is inversely deduced by quantum correlation of the detection results of the two detectors, and the intensity image of the target to be imaged is formed. However, at present, due to the relatively weak quantum signal, the quantum signal is easily affected by the environment and is subject to loss, the photon energy collection efficiency of quantum imaging is low, the effective photon counting is low, and the imaging speed is slow, which brings many inconveniences to the large-scale application of actual quantum imaging. SUMMARY

[0004] The technical problem solved by the application is to overcome the shortcomings of the prior art, provide a quantum correlation imaging system based on a microlens array, and solve the problems of low photon energy collection efficiency, low effective photon counting and slow imaging speed of the current quantum correlation imaging system.

[0005] The technical scheme of the application is: a quantum correlation imaging system based on a microlens array, comprising a transmitter, a receiver, a comprehensive control system and an image inversion system; the transmitter outputs a two-mode vacuum squeezed state light source under the transmission instruction of the comprehensive control system, which is divided into mode A light field and mode B light field, the mode A light field remains in the local, and the mode B light field returns to the receiver after interacting with the target, the receiver performs time synchronization and coincidence measurement on the mode A and B light fields under the transmission and reception synchronization control of the comprehensive control system, and the detection results are transmitted to the image inversion system; the comprehensive control system is used for transmitter output control, receiver coincidence measurement control, clock synchronization and real-time communication; the image inversion system adopts a high-efficiency coincidence measurement data processing method to invert the intensity image of the target.

[0006] The transmitter comprises a two-mode vacuum squeezed light source unit, a mode A optical field erasing unit, a mode A optical field regulating unit, a mode B optical field erasing unit, a mode B optical field regulating unit, and a signal collimation and emission unit. The two-mode vacuum squeezed light source unit emits two-mode vacuum squeezed states, which are divided into mode A and mode B. The mode A optical field is left in the local area as an idle mode, and the mode B optical field is transmitted to the target as a signal mode. The mode A optical field sequentially passes through the mode A optical field erasing unit and the mode A optical field regulating unit. The mode B optical field sequentially passes through the mode B optical field erasing unit and the mode B optical field regulating unit. The mode A optical field and the mode B optical field output by the above two paths form a quantum state with higher quantum entanglement, and finally form a transmission light source for quantum imaging through the signal collimation and emission unit.

[0007] The mode A optical field erasing unit and the mode B optical field erasing unit are composed of an optical beam splitter and a single-photon detector. The single-photon detector only responds to one photon and does not respond to no photon or multiple photons.

[0008] The mode A optical field regulating unit and the mode B optical field regulating unit adopt a variable optical attenuator composed of an optical beam splitter with adjustable optical transmittance. The wideband response range is 690nm-1100nm, and the transmittance ratio range is from 1:99 to 95:1.

[0009] The receiver comprises a mode A optical field collecting unit, a mode A optical field detecting unit, a mode B optical field collecting unit, and a mode B optical field detecting unit. The mode B optical field returns to the receiver after being affected by the target, is output through the mode B optical field collecting unit, and is subjected to coincidence measurement with the mode A optical field output through the mode A optical field collecting unit under the synchronous control of the comprehensive control system. The coincidence measurement is realized through the synchronous detection of the mode B optical field detecting unit and the mode A optical field detecting unit, and the coincidence measurement result is input to the image inversion system.

[0010] The mode A optical field collecting unit adopts a microlens array, and the mode A optical field detecting unit adopts a single-photon array detector. The microlens array and the single-photon array detector are coupled at the pixel level, and the single-photon array detector works in the Geiger mode.

[0011] The mode B optical field detecting unit adopts a single-photon detector, which works in the Geiger mode, has a detection efficiency greater than 40%, and a dark count rate less than 50cps.

[0012] The integrated control system comprises a transmitter transceiver synchronization subsystem, a receiver transceiver synchronization subsystem, and a timing and control center; the transmitter and the receiver correspond to the transmitter transceiver synchronization subsystem and the receiver transceiver synchronization subsystem respectively, the timing and control center sends synchronization signals to the transmitter transceiver synchronization subsystem and the receiver transceiver synchronization subsystem respectively, clock synchronization and real-time communication of control information between the two are carried out, and the receiver is controlled to carry out coincidence measurement of mode A light field and mode B light field.

[0013] The image inversion system adopts an efficient coincidence measurement data processing method to invert the intensity image of the target, comprising:

[0014] Step 1, setting an effective count number M, initializing the detection result of the mode A light field detection unit as I1(x1)=0, wherein x1 represents the spatial coordinate of the mode A detection unit in the x direction; initializing the detection result of the mode B light field detection unit as I2(x2)=0, x2 represents the spatial coordinate of the mode A detection unit in the x direction; initializing the effective detection number as m=0;

[0015] Step 2, judging whether the imaging process working timing signal is a high level signal; if yes, I1(x1) and I2(x2) carry out photon counting accumulation according to the detection result, and set m=m+1; if not, no counting accumulation is carried out;

[0016] Step 3, repeating step 2 until m=M times of effective detection are carried out, the cycle is terminated and step 4 is executed;

[0017] Step 4, calculating the quantum correlation function G(x1,x2) according to the counting results of I1(x1) and I2(x2); setting x2=0 as the origin in the x direction, obtaining the quantum correlation function G(x1,x2=0); performing inverse Fourier transform on G(x1,x2=0) to obtain the intensity image T(x) of the target:

[0018]

[0019] wherein, λ is the wavelength of laser, f is the focal length of the mode B light field collection unit, l c is the length of the parametric down-conversion crystal in the light propagation direction in the two-mode vacuum squeezed state light source unit.

[0020] The time service and control center respectively sends a synchronization signal to the transmitter transceiver synchronization subsystem and the receiver transceiver synchronization subsystem, and carries out clock synchronization and real-time communication of control information between the two, including: in a clock pulse period, first, the scanning process working timing signal takes effect, the transmitter and the receiver jointly execute the scanning process, and the measurement results of the mode A optical field detection unit and the mode B optical field detection unit obtained in the process are used to adjust the transmission coefficient of the optical beam splitter in the mode A optical field regulation unit and the mode B optical field regulation unit, so that the single photon array detector of the mode A optical field detection unit and the non-spatial resolution single photon detector of the mode B optical field detection unit have the same count size or are in the same order of magnitude, and high-contrast coincidence counting is realized; secondly, the imaging process working timing signal takes effect, the transmitter and the receiver jointly execute the imaging process, and the effective time length ratio of the scanning process working timing and the imaging process working timing is between 1:4 and 1:10.

[0021] Compared with the prior art, the present application has the following advantages:

[0022] 1) The present application increases a microlens array in front of the single photon array detector, which can greatly improve the signal collection efficiency of idle light, and improve the size of coincidence counting and the imaging quality per unit time.

[0023] 2) In the present application, the quantum imaging system combines the scanning process and the imaging process in timing arrangement. The scanning process is only used to count the photon detector count level on the signal mode and the idle mode, and form the intensity regulation parameters of the two entangled modes. The imaging process uses the photon count level on the signal mode and the idle mode to activate the image inversion system and form the image of the target.

[0024] 3) In the present application, the two-mode squeezed vacuum state after double-side photon erasure is used as the quantum entangled state, and the average photon number level of the two entangled modes is relatively high, which provides favorable conditions for the high-energy collection efficiency of the signal. At the same time, the light field regulation is carried out on the two light field modes to realize that the count sizes of the corresponding detection units of the two light field modes are equivalent or in the same order of magnitude, and high-contrast coincidence counting is realized.

[0025] 4) In the present application, the central node with the time service center function is used to synchronize the transmitter and the receiver, which can effectively reduce the power consumption and the size of the transmitter and the receiver, and improve the system integration level.

[0026] 5) The present application uses the quantum entanglement prepared by parametric down-conversion for imaging, and the principle can also be applied to target imaging based on photon number correlation quantum states with photon number correlation characteristics.

[0027] 6) The quantum imaging system prepared in the present application can be used for fast imaging of dark and weak targets in a strong background, and can also be applied to medical imaging of biological tissues with low damage threshold. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is the overall scheme of the present application;

[0029] Figure 2 is the schematic diagram of marking each port of the optical beam splitter in the first embodiment of the present application;

[0030] Figure 3 is the schematic diagram of the optical field erasing unit in the first embodiment of the present application;

[0031] Figure 4 is the schematic diagram of the optical field regulating unit in the first embodiment of the present application;

[0032] Figure 5 is the schematic diagram of the receiver in the first embodiment of the present application;

[0033] Figure 6 is the diagram of the relative position of the microlens array and the effective detection unit of the single photon array detector in the first embodiment of the present application.

[0034] Figure 7 is the timing logic diagram of the scanning process and the imaging process in the first embodiment of the present application.

[0035] Figure 8 is the flow chart of the image inversion system in the first embodiment of the present application.

[0036] Figure 9 is the target size (a) and the theoretical intensity image distribution (b) in the experimental device in the first embodiment of the present application.

[0037] Table 1 is the comparison data table of the energy collection efficiency before and after the introduction of the microlens array under the typical application scenario conditions in the first embodiment of the present application

[0038] Figure 10 is the photon energy collection efficiency at different unit diameters under the typical application scenario conditions in the first embodiment of the present application.

[0039] Figure 11 is the comparison diagram of the imaging before the introduction of the microlens array and the imaging after the introduction of the microlens array in the first embodiment of the present application. DETAILED DESCRIPTION

[0040] The application performs light field erasing operation and light field regulating operation on two modes of the output of the emission source respectively to obtain entangled states with higher entanglement, meanwhile, the efficiency of coincidence measurement is improved by using micro-lens array technology at the receiver, and a quantum correlation imaging system with high energy collection efficiency is realized by combining with specially designed high-efficiency data inversion method. In typical application scenarios, the photon energy collection efficiency is improved by 5 to 40 times, and the quantum imaging efficiency is greatly improved.

[0041] The application adopts light field erasing and light field regulating operations at the light source to improve the entanglement of quantum states, improves the efficiency of coincidence measurement by micro-lens array at the detection aspect, and realizes a quantum imaging system with high energy collection efficiency by cooperating with high-efficiency coincidence measurement data processing method.

[0042] The application provides a quantum correlation imaging system based on micro-lens array, basically as shown in the accompanying drawings Figure 1 As shown in the accompanying drawings, the quantum correlation imaging system based on micro-lens array comprises a transmitter 1, a receiver 2, a comprehensive control system 3 and an image inversion system 4. The transmitter 1 outputs two-mode vacuum squeezed state light source under the emission instruction of the comprehensive control system 3, which is divided into mode A light field and mode B light field. The mode A light field is left in the local, and the mode B light field returns to the receiver after acting on the target. The receiver 2 performs time synchronization and coincidence measurement on the mode A and mode B light fields under the transceiving synchronous control of the comprehensive control system 3, and delivers the detection results to the image inversion system 4. The image inversion system 4 inverts the intensity image of the target by using high-efficiency coincidence measurement data processing method. The comprehensive control system 3 is used for transmitter 1 output control, receiver 2 coincidence measurement control, clock synchronization and real-time communication.

[0043] The transmitter 1 comprises a two-mode vacuum squeezed state light source unit 11, a mode A light field erasing unit 12, a mode A light field regulating unit 13, a mode B light field erasing unit 14, a mode B light field regulating unit 15 and a signal collimation and emission unit 16. The two-mode vacuum squeezed state light source unit 11 emits two-mode vacuum squeezed state, which is divided into mode A and mode B. The mode A light field is left in the local as an idle mode, and the mode B light field is emitted to the target as a signal mode. The mode A light field passes through the mode A light field erasing unit 12 and the mode A light field regulating unit 13, and the mode B light field passes through the mode B light field erasing unit 14 and the mode B light field regulating unit 15. The output mode A light field and the output mode B light field form quantum states with higher quantum entanglement, which are used as the emission light source for quantum imaging. The mode B light field is shaped and expanded by the signal collimation and emission unit 16, and is emitted to the target. The mode A light field is stored in the local through an optical fiber, and is subjected to synchronous coincidence measurement with the mode B light field reflected from the target under the control of the comprehensive control system 3. Figure 1 A USAF1951 resolution board is used to show the target.

[0044] The receiver comprises a mode A light field collecting unit 21, a mode A light field detecting unit 22, a mode B light field collecting unit 23 and a mode B light field detecting unit 24; the mode B light field returns to the receiver after the target action, is output through the mode B light field collecting unit 23, and is subjected to coincidence measurement with the mode A light field output through the mode A light field collecting unit 21 under the synchronous control of the comprehensive control system; the coincidence measurement is realized through the synchronous detection of the mode B light field detecting unit 24 and the mode A light field detecting unit 22, and the coincidence measurement result is input to the image inversion system 4.

[0045] The comprehensive control system 3 comprises a transmitter transceiver synchronization subsystem 31 and a receiver transceiver synchronization subsystem 32 and a timing and control center 33; the transmitter 1 and the receiver 2 correspond to the transmitter transceiver synchronization subsystem 31 and the receiver transceiver synchronization subsystem 32 respectively, the timing and control center 33 sends a synchronization signal to the transmitter transceiver synchronization subsystem 31 and the receiver transceiver synchronization subsystem 32 respectively, carries out clock synchronization and real-time communication of the control information between the two, and controls the receiver 2 to carry out coincidence measurement of the mode A light field and the mode B light field.

[0046] The image inversion system 4 realizes the conversion of the coincidence measurement counting result to the target intensity image. Taking a one-dimensional image (only the intensity changes in the x direction) as an example, the efficient coincidence measurement data processing method involved in the image inversion system 4 is as follows:

[0047] Step 1: At the beginning, the experiment sets an effective counting number M, the detection result of the mode A light field detecting unit 22 is initialized as I1(x1)=0, wherein x1 represents the spatial coordinate of the mode A detecting unit 22 in the x direction. The detection result of the mode B light field detecting unit 24 is initialized as I2(x2)=0, x2 represents the spatial coordinate of the mode A detecting unit 22 in the x direction. The effective detection number is initialized as m=0.

[0048] Step 2: It is judged whether the imaging process working timing signal is a high level signal; if yes, I1(x1) and I2(x2) carry out photon counting accumulation according to the detection result, and m=m+1 is set. If not, no counting accumulation is carried out;

[0049] Step 3: Step 2 is continuously looped until m=M times of effective detection are carried out, and the loop is terminated;

[0050] Step 4: After the loop is terminated, the quantum correlation function G(x1,x2) is calculated according to the counting results of I1(x1) and I2(x2); since the mode B light field detecting unit 24 has no spatial resolution, x2=0 is set as the origin in the x direction, and the quantum correlation function G(x1,x2=0) is obtained; inverse Fourier transform is performed on G(x1,x2=0) to obtain the intensity image T(x) of the target. The calculation formula of T(x) is:

[0051]

[0052] wherein, λ is the laser wavelength, f is the focal length of the mode B optical field collection unit 23, l c is the length of the parametric down-conversion crystal in the light propagation direction of the two-mode vacuum squeezed light source unit 11.

[0053] Inside the transmitter: the two-mode vacuum squeezed light source unit 11 emits two-mode vacuum squeezed light, which is divided into mode A and mode B. The mode A optical field is an idle mode, which is sequentially passed through the mode A optical field erasing unit 12 and the mode A optical field regulating unit 13 to be placed in the local transmitter, waiting for the synchronization measurement instruction of the integrated control system 3 to reach the receiver 2; the mode B optical field is a signal mode, which is sequentially passed through the mode B optical field erasing unit 14 and the mode B optical field regulating unit 15, and acts on the target through signal collimation and emission unit 16. Figure 1 The USAF1951 resolution board is used to simulate the target. The mode A optical field erasing unit 12 and the mode B optical field erasing unit 14 are composed of an optical beam splitter and a single-photon detector, wherein the single-photon detector only responds to one photon and does not respond to no photons and multiple photons. The mode A optical field regulating unit 13 and the mode B optical field regulating unit 15 use a variable optical attenuator, which is composed of an optical beam splitter with adjustable optical transmittance, has a wideband response range of 690nm-1100nm, and has a transmittance: reflectance ratio range from 1:99 to 95:1.

[0054] Inside the receiver: the mode A optical field collection unit 21 is responsible for receiving the idle signal transmitted by the transmitter first, and the mode A optical field detection unit 22 is used for detection. The mode A optical field collection unit 21 uses a microlens array, and the mode A optical field detection unit 22 uses a single-photon array detector, which works in Geiger mode. The mode A optical field collection unit 21 and the mode A optical field detection unit 22 are coupled at the pixel level. The mode B optical field collection unit 23 is responsible for receiving the signal transmitted from the target, and the mode B optical field detection unit 24 is used for detection. The mode B optical field detection unit 24 uses a single-photon detector without spatial resolution for detection, which works in Geiger mode, has a detection efficiency greater than 40%, and a dark count rate less than 50cps.

[0055] Inside the integrated control system 3: the transmitter 1 and the receiver 2 correspond to the transmitter transceiver synchronization subsystem 31 and the receiver transceiver synchronization subsystem 32 respectively, the timing and control center 33 sends synchronization signals to the transmitter transceiver synchronization subsystem 31 and the receiver transceiver synchronization subsystem 32 respectively, carries out clock synchronization and real-time communication of control information between the two, and controls the receiver 2 to carry out coincidence measurement of mode A light field and mode B light field. The timing and control center 33 sends time instructions and control information to the transmitter transceiver synchronization subsystem 31 and the receiver transceiver synchronization subsystem 32, which are used for synchronization of the transmitter 1 and the receiver 2. Under the control of the timing and control center 33, the quantum imaging system carries out scanning process and imaging process in each time period.

[0056] Inside the image inversion system: through data processing and image inversion of the photon counting results detected by the mode A light field detection unit 22 and the mode B light field detection unit 24, an efficient coincidence measurement data processing method is adopted to obtain the intensity information of the target.

[0057] Figure 2 The schematic diagram is marked for each port of the optical beam splitter in the first embodiment of the present application. The optical beam splitter (BS) has two input ports, a first input port (a) and a second input port (b), and two output ports, a first output port (c) and a second output port (d).

[0058] Embodiment two

[0059] A quantum correlation imaging system based on a microlens array is proposed, and the transmitter is refined. Among them: the two-mode squeezed vacuum state in the transmitter can be generated through the parametric down-conversion process, and here we omit the process of generating the two-mode squeezed vacuum state. One mode of the squeezed vacuum state is the idle mode, denoted as mode A light field, which passes through the mode A light field erasing unit 12 and the mode A light field regulation unit 13 to the receiver in turn; the other mode is the signal mode, denoted as B, which passes through the mode B light field erasing unit 14 and the mode B light field regulation unit 15 in turn, and is acted on by the signal collimation and emission unit 16 and the target.

[0060] The mode A light field erasing unit 12 and the mode B light field erasing unit 14 have the same structure, as shown in Figure 3The structure of the optical field erasing unit is mainly composed of an optical beam splitter and a photon detector. The mode A optical field or the mode B optical field of the incident quantum state is connected with the input port (a) of the optical beam splitter BS1; the mode E1 is a vacuum state, i.e., a 0-photon state, which is connected with the input port (b) of the optical beam splitter BS1. After the action of the optical beam splitter, the quantum state output from the output port (c) is detected by the single-photon detector D3, and the single-photon detector D3 only responds to the state of one photon and does not respond to no photon and multiple photons. When the single-photon detector D3 responds to one photon, it indicates that the photon erasing operation of the photon erasing unit is successful. Generally, the transmittance of the optical beam splitter BS1 of the optical field erasing unit is 0.9.

[0061] The mode A optical field regulating unit 13 and the mode B optical field regulating unit 15 have the same structure, as shown in FIG. 3. Figure 4 The structure of the optical field regulating unit is mainly composed of an optical beam splitter BS2 with adjustable transmittance. Figure 3 The output port (d) of the optical beam splitter BS1 involved is connected with Figure 4 The input port (a) of the optical beam splitter BS2 involved is connected with. The mode F1 is a vacuum state, i.e., a 0-photon state, which is connected with the input port (b) of the optical beam splitter BS2. The output state of the output port (c) of the optical beam splitter BS2 is the optical mode F2, which is not used subsequently and can be directly dissipated into the environment. The output port (d) of BS2 is the quantum state output port of the optical field regulating unit. The optical beam splitter BS2 of the optical field regulating unit has a wideband response range of 690 nm-1100 nm, and the transmittance-to-reflectance ratio (transmittance: reflectance) ranges from 1:99 to 95:1.

[0062] For the mode B optical field, the output port (d) of BS2 of the mode B optical field regulating unit 15 is connected with the signal collimation and emission unit 16. The structure of the signal collimation and emission unit 16 is composed of a focusing lens group. After collimation, the output mode B optical field is emitted as signal light and interacts with the target.

[0063] For the mode A optical field, the quantum state output from the output port (d) of BS2 of the mode A optical field regulating unit 13 is placed locally and waits to enter the receiver together with the mode B optical field reflected by the target.

[0064] Figure 5The schematic diagram of the receiver in the first embodiment of the present application is shown in Figure 1. The quantum state of mode A is collected by mode A light field collection unit 21, which is composed of a micro-lens array. The mode A detection unit 23 is composed of a single photon array detector with the same array size as the micro-lens array. The quantum state of mode B is collected by mode B light field collection unit 22, which is collimated by coaxial thin lenses L3 and L4. The mode B light field detection unit 24 is composed of a single photon detector without spatial resolution. The detection results of mode A light field detection unit 23 and mode B light field detection unit 24 are inverted by image inversion system 4.

[0065] Figure 6 The relative position diagram of the micro-lens array and the single photon array detector effective detection unit in the first embodiment of the present application is shown in Figure 2. We let the plane of the micro-lens array be parallel to the plane of the single photon array detector. The diameter of the effective unit of the micro-lens array is D M , and the spatial interval of the effective unit of the micro-lens array is l M . The diameter of the effective unit of the single photon array detector is D. The spatial interval of the effective unit of the single photon array detector is l. The distance between the plane of the micro-lens array and the plane of the single photon array detector is Z0.

[0066] The transmitter 1 and the receiver 2 are respectively equipped with transmitter transceiver synchronization subsystem 31 and receiver transceiver synchronization subsystem 32. The timing and control center 33 sends synchronization signals to the transmitter transceiver synchronization subsystem 31 and the receiver transceiver synchronization subsystem 32, respectively, to perform clock synchronization between the two and real-time communication of control information.

[0067] The timing and control center 33 sends time instructions and control information to the transmitter transceiver synchronization subsystem 31 and the receiver transceiver synchronization subsystem 32 for synchronization of the transmitter and the receiver. Under the control of the timing and control center 33, the quantum imaging system first performs the scanning process and then the imaging process in each time period. Finally, the image inversion system 4 forms the image of the target to be solved according to the results detected in the imaging process.

[0068] Figure 7The timing logic diagram of the scanning process and the imaging process in the embodiment one of the present application. The clock pulse signal is sent to the transmitter transceiver synchronization subsystem 31 and the receiver transceiver synchronization subsystem 32 respectively by the time service and control center 33 with time service function. In a clock pulse cycle, firstly, the scanning process working timing signal takes effect, the transmitter and the receiver jointly execute the scanning process, and the measurement results of the mode A light field detection unit 23 and the mode B light field detection unit 24 obtained in the process are used to adjust the optical beam splitter transmission coefficient in the mode A light field regulation unit 13 and the mode B light field regulation unit 15, so that the single photon array detector of the mode A light field detection unit 23 and the non-spatial resolution single photon detector of the mode B light field detection unit 24 have the same count or are in the same order of magnitude, and the high contrast of coincidence count is realized. Secondly, the imaging process working timing signal takes effect, the transmitter and the receiver jointly execute the imaging process, and the intensity image of the target to be imaged is inversed by the image inversion system using the data obtained in the imaging process. The effective time length ratio of the scanning process working timing and the imaging process working timing is between 1:4 and 1:10.

[0069] Figure 8 The flow chart of the image inversion system. I1(x1) is the detection result of the mode A light field detection unit 23, I2(x2) is the detection result of the mode B light field detection unit 24, and there is quantum correlation G(x1, x2) between I1(x1) and I2(x2) due to the quantum correlation of the two-mode squeezed vacuum state itself. Since the mode B light field detection unit 24 has no spatial resolution, x2 can be set to 0, and then the quantum correlation G(x1) is obtained. The quantum correlation G(x1) is exactly in the Fourier transform relationship with the transmittance of the target to be imaged, and the intensity image T(x) of the target can be obtained by inverse Fourier transform.

[0070] Figure 9 The target size (a) and the theoretical intensity image distribution (b) in the experimental device in the embodiment one of the present application. The target to be imaged is two slender slits, the slit spacing a is 5 um (microns), and the slit width is d=10 um.

[0071] Table 1 is the comparison of energy collection efficiency before and after the introduction of the microlens array in the embodiment one of the present application. The effective detection unit diameter of the single photon array detector column is D=3.7 microns, the unit spacing l is 10.96 microns, the wavelength of the light is 1064 nanometers, and the effective detection factor of the single photon array detector can be calculated as F=5%. When the distance Z0>40 microns, the photon energy collection efficiency reaches 6.79%, which is improved by 35.8% compared with the case without using the microlens array.

[0072] Table 1 Comparison of energy collection efficiency before and after the introduction of the microlens array

[0073]

[0074] Figure 10 The photon energy utilization rate of different unit diameters D M in the typical application scenario condition in the first embodiment of the present application. Set Z0=3f M , in order to give D M a larger range of variation, we take D=2.7 microns, l=31 microns, we take l M =D+l-D M so that the effective unit center points of the microlens array unit and the single photon array detector can just coincide. Before introducing the microlens array, the filling factor of the system is 0.5%. The photon energy collection efficiency is given by η1, i.e. the line marked with a box, and after introducing the lens array, the photon energy collection efficiency is given by η2, i.e. the line marked with a circle. In particular, if we set D M =14.41 microns, l M =19.29 microns, it can be calculated that the photon energy utilization rate under the assistance of the microlens array is η2=0.0249, which is increased by 399.2%. From Figure 9 (b) it can be seen that the energy collection efficiency is increased by 5 to 40 times. Among them, in Figure 9 (b) we use a black solid line to indicate the case when the energy collection efficiency is increased by 30%. It can be seen that by increasing the microlens array, the photon energy utilization rate can be greatly improved.

[0075] Figure 11 The imaging before the introduction of the microlens array and the imaging effect after the introduction of the microlens array in the first embodiment of the present application. We select the effective detection unit diameter of the single photon array detector D=2.7 microns, the physical spacing of the effective detection unit of the single photon array detector l=31 microns, the microlens array unit diameter D M =14.41 microns, the microlens array unit focal length l M =19.29 microns, the microlens array unit focal length f M =10 microns, and the signal light wavelength is 1064 nanometers. The average performance of 20 simulation experiments shows that before the microlens array is added, the average distortion rate of the image is about 20.7%, and after the microlens array is added, due to the increase in the photon energy collection efficiency, the average distortion rate is reduced to 17.1%, which provides a new opportunity for improving the quality of quantum imaging. In the next step, the imaging quality can be further improved through the optimization of the microlens array size and the optimization of the material.

[0076] Although the present application has been disclosed with reference to the preferred embodiments, it is not intended to limit the present application, and any person skilled in the art can make possible changes and modifications to the technical solutions of the present application without departing from the spirit and scope of the present application by using the technical contents disclosed above. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application without departing from the technical solutions of the present application shall fall within the protection scope of the technical solutions of the present application.

Claims

1. A micro-lens array based quantum correlated imaging system, characterized in that: The application relates to a quantum imaging system, which comprises a transmitter, a receiver, an integrated control system and an image inversion system; the transmitter outputs two-mode vacuum squeezed state light sources under the transmission instruction of the integrated control system, and the two-mode vacuum squeezed state light sources are divided into mode A light fields and mode B light fields; the mode A light fields remain in the local area, and the mode B light fields return to the receiver after acting on a target; the receiver performs time synchronization and coincidence measurement on the mode A and B light fields under the transmission and reception synchronization control of the integrated control system, and transmits the detection results to the image inversion system; the integrated control system is used for transmitter output control, receiver coincidence measurement control, clock synchronization and real-time communication; and the image inversion system adopts a high-efficiency coincidence measurement data processing method to invert the intensity image of the target. The transmitter comprises a two-mode vacuum squeezed state light source unit, a mode A light field erasing unit, a mode A light field regulating unit, a mode B light field erasing unit, a mode B light field regulating unit and a signal collimation and transmission unit; the two-mode vacuum squeezed state light source unit emits two-mode vacuum squeezed states, which are divided into mode A and mode B; the mode A light fields remain in the local area as idle modes, and the mode B light fields are transmitted to the target as signal modes; the mode A light fields pass through the mode A light field erasing unit and the mode A light field regulating unit in sequence; the mode B light fields pass through the mode B light field erasing unit and the mode B light field regulating unit in sequence; the output mode A light fields and mode B light fields form quantum states with higher quantum entanglement, and finally form a transmission light source for quantum imaging through the signal collimation and transmission unit. 2.The quantum correlation imaging system based on microlens array of claim 1, wherein: The mode A light field erasing unit and the mode B light field erasing unit are composed of an optical beam splitter and a single-photon detector, wherein the single-photon detector only responds to one photon and does not respond to no photon and multiple photons. 3.The quantum correlation imaging system based on microlens array of claim 1, wherein: The mode A light field regulating unit and the mode B light field regulating unit adopt a variable optical attenuator, which is composed of an optical beam splitter with adjustable optical transmittance, has a broadband response range of 690nm-1100nm, and has a transmittance-reflection ratio ranging from 1:99 to 95:

1.

4. The quantum correlation imaging system based on microlens array of claim 1, wherein: The receiver comprises a mode A light field collecting unit, a mode A light field detecting unit, a mode B light field collecting unit and a mode B light field detecting unit; the mode B light fields return to the receiver after acting on the target, are output through the mode B light field collecting unit, and are subjected to coincidence measurement with the mode A light fields output through the mode A light field collecting unit under the synchronization control of the integrated control system; the coincidence measurement is realized through the synchronous detection of the mode B light field detecting unit and the mode A light field detecting unit, and the coincidence measurement results are input to the image inversion system.

5. The quantum correlation imaging system based on microlens array according to claim 4, characterized in that: The mode A light field collecting unit adopts a microlens array, and the mode A light field detecting unit adopts a single-photon array detector; the microlens array and the single-photon array detector are coupled at the pixel level, and the single-photon array detector works in a Geiger mode.

6. The quantum correlation imaging system based on microlens array according to claim 4, characterized in that: The mode B light field detecting unit adopts a single-photon detector, which works in a Geiger mode, has a detection efficiency greater than 40%, and has a dark count rate less than 50cps.

7. The micro-lens array based quantum correlation imaging system of claim 1, wherein, The integrated control system comprises a transmitter transceiving synchronization subsystem, a receiver transceiving synchronization subsystem and a timing and control center; the transmitter and the receiver correspond to the transmitter transceiving synchronization subsystem and the receiver transceiving synchronization subsystem respectively, the timing and control center sends synchronization signals to the transmitter transceiving synchronization subsystem and the receiver transceiving synchronization subsystem respectively, clock synchronization and real-time communication of control information between the two are carried out, and the receiver is controlled to carry out coincidence measurement of mode A light field and mode B light field.

8. The quantum correlation imaging system based on microlens array according to claim 7, characterized in that: The timing and control center sends synchronization signals to the transmitter transceiving synchronization subsystem and the receiver transceiving synchronization subsystem respectively, clock synchronization and real-time communication of control information between the two are carried out, and the timing and control center comprises: in a clock pulse period, firstly, a scanning process working timing signal is effective, the transmitter and the receiver jointly execute the scanning process, the measurement results of the mode A light field detection unit and the mode B light field detection unit obtained in the process are used to adjust the transmission coefficients of the optical beam splitters in the mode A light field regulation unit and the mode B light field regulation unit, so that the single photon array detector of the mode A light field detection unit and the spatially non-resolving single photon detector of the mode B light field detection unit have the same count or are in the same order of magnitude, and high-contrast coincidence counting is realized; secondly, an imaging process working timing signal is effective, the transmitter and the receiver jointly execute the imaging process, and the effective time length ratio of the scanning process working timing to the imaging process working timing is between 1:4 and 1:

10.

9. The micro-lens array based quantum correlation imaging system of claim 4, wherein, The image inversion system adopts an efficient coincidence measurement data processing method to invert the intensity image of the target, comprising: Step 1, setting an effective count number M, initializing the detection result of the mode A light field detection unit as I1(x1)=0, wherein x1 represents the spatial coordinate of the mode A detection unit in the x direction; initializing the detection result of the mode B light field detection unit as I2(x2)=0, x2 represents the spatial coordinate of the mode A detection unit in the x direction; initializing the effective detection number as m=0; Step 2, judging whether the imaging process working timing signal is a high-level signal; if yes, I1(x1) and I2(x2) perform photon counting accumulation according to the detection result, and m=m+1 is set; if not, no counting accumulation is performed; Step 3, repeating step 2 until m=M times of effective detection are performed, and the cycle is terminated and step 4 is executed; Step 4, calculating the quantum correlation function G(x1,x2) according to the counting results of I1(x1) and I2(x2); setting x2=0 as the origin in the x direction to obtain the quantum correlation function G(x1,x2=0); performing inverse Fourier transform on G(x1,x2=0) to obtain the intensity image T(x) of the target: wherein, λ is the laser wavelength, f is the focal length of the mode B light field collection unit, l c is the length of the parametric down-conversion crystal in the direction of light propagation in the two-mode vacuum squeezed light source unit.

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