Single-photon imaging system and method

Abstract

The invention discloses a single-photon imaging system and method, and relates to the field of computational imaging and single-pixel imaging, and in the system, an imaging lens group is used for imaging a target image to a coding disc; the coding disc spatially modulates the light intensity of the target image through the coding pattern area; the detection module generates an electric pulse signal according to the light intensity of the target image transmitted by the transmission area in the coding disc; the motor and driving module drives the coding disc to rotate at a constant speed; the coding disc rotates at a constant speed to sequentially switch coding patterns; the synchronization module monitors the time when the coding disc rotates by one circle; the time-to-digital conversion module records the synchronous electric pulse signal and the electric pulse signal as time events respectively; the image reconstruction and display module carries out target image reconstruction and display according to time events corresponding to the synchronous electric pulse signal and the electric pulse signal respectively; according to the invention, single-pixel imaging under an extremely weak light condition can be realized.

Description

Technical Field

[0001] This application relates to the fields of computational imaging and single-pixel imaging, and in particular to a single-photon imaging system and method. Background Technology

[0002] In computational imaging and single-pixel imaging technologies, commonly used spatial modulation devices are digital micromirror devices (DMDs) from Texas Instruments (TI). DMDs require complex circuitry and microelectromechanical systems (MEMS) technology to manufacture, and currently only TI has the capability to produce them globally.

[0003] The main parameters of DMD are modulation speed and micromirror size. Currently, the fastest refresh rate that can be achieved is 32kHz, and the spatial light modulation with a micron-level size of 1920×1080 pixels has been widely used in digital projectors.

[0004] Although DMDs are widely used in computational imaging, structured light illumination, and other related research, they also have many limitations and shortcomings. For example, their power consumption can reach tens of watts during operation, and they require a circuit operating bandwidth of tens of gigahertz. Their modulation angle is only 12 degrees, which is not conducive to optical integration.

[0005] To address the aforementioned shortcomings, existing solutions propose a single-pixel imaging scheme utilizing rotational encoding. This involves covering a ring-shaped mask with a mask pattern to create transparent and opaque areas. Rotation modulates spatial light, enabling demodulation and imaging through a single-pixel imaging approach. This method offers a faster modulation speed than DMD, reaching megahertz levels, and thus allows for faster single-pixel imaging.

[0006] One of the key technical problems in using a rotating encoder disk to achieve single-pixel imaging is that the encoding must correspond one-to-one with the detected signal. The currently reported solution is to set a synchronous encoder on the encoder disk, and the synchronous encoder marks the time length of one rotation. The collected data is calculated according to the sampling rate and then converted into the data length according to one rotation. Then, the detection signal with the same length as the encoding is achieved by interpolation, so as to ensure that the signal and the encoding correspond one-to-one, thereby realizing the image decoding.

[0007] However, when using a rotating encoder disk to achieve single-pixel imaging in extremely weak light, especially when the detection signal reaches the single-photon level, no signal photons can be detected at certain encoding points. It is impossible to use the interpolation schemes reported in the public to ensure a one-to-one correspondence between the encoding and the detection signal. In other words, there are currently no reports of achieving single-pixel single-photon imaging based on a rotating encoder disk.

[0008] Single-pixel single-photon imaging has broad application prospects, especially in extremely low-light imaging applications such as biomedical imaging and night vision imaging. Furthermore, single-photon detection devices possess high temporal resolution, enabling range-gated imaging. For example, detecting the flight time of nanosecond, picosecond, and femtosecond light pulses is difficult for ordinary cameras to achieve, while high-temporal-resolution array cameras are expensive and have limited detection bands. Single-pixel imaging will have a significant advantage in this regard. Specific applications include, but are not limited to, long-distance detection and imaging of methane gas, and security inspection and flaw detection in the terahertz band.

[0009] Considering the aforementioned requirements for imaging applications in extremely low light conditions, there is an urgent need to provide a single-photon imaging system and method for single-pixel single-photon imaging technology based on a rotating encoder disk, so as to achieve single-pixel imaging under extremely low light conditions. Summary of the Invention

[0010] The purpose of this application is to provide a single-photon imaging system and method that can achieve single-pixel imaging under extremely low light conditions.

[0011] To achieve the above objectives, this application provides the following solution:

[0012] In a first aspect, this application provides a single-photon imaging system, which includes: an imaging lens group, an encoding disk, a detection module, a motor and drive module, a synchronization module, a time-to-digital conversion module, and an image reconstruction and display module;

[0013] The imaging lens group is used to image the target image onto the encoding disk;

[0014] The encoding disk includes: an encoding pattern area and a driving area disposed on a light-transmitting material substrate; the encoding disk is used to spatially modulate the light intensity of a target image through the encoding pattern area; the encoding pattern area includes an encoding pattern constructed based on a cyclic orthogonal matrix; the cyclic orthogonal matrix is ​​constructed according to the pixel size of the target image; and sectors are constructed according to a row of data of the cyclic orthogonal matrix; the sectors include: multiple reflection areas and multiple transmission areas;

[0015] The detection module is used to generate an electrical pulse signal based on the light intensity of the target image transmitted through the transmission area in the encoder disk, and transmit the electrical pulse signal to the time-to-digital conversion module.

[0016] The motor and drive module are connected to the encoder disk through the drive area and drive the encoder disk to rotate at a constant speed; the encoder disk switches the encoding pattern sequentially by rotating at a constant speed.

[0017] The synchronization module is used to monitor the time it takes for the encoder disk to rotate one revolution and transmit the synchronization electrical pulse signal to the time-to-digital conversion module.

[0018] The time-to-digital conversion module is used to record the synchronization electrical pulse signal and the electrical pulse signal as time events, and transmit them to the image reconstruction and display module.

[0019] The image reconstruction and display module is used to reconstruct and display the target image based on the synchronous electrical pulse signal and the time events corresponding to the electrical pulse signal.

[0020] Optionally, the detection module specifically includes: a converging lens and a single-photon detector;

[0021] The converging lens is used to transmit the light intensity of the transmitted target image to the single-photon detector; the single-photon detector is used to generate an electrical pulse signal when the light intensity is greater than or equal to the energy of one photon.

[0022] Optionally, the single-photon detector specifically includes: a photomultiplier tube and a Geiger-mode avalanche photodiode.

[0023] Optionally, the motor and drive module specifically include: a DC motor and a driver; the driver uses pulse width modulation technology for speed regulation.

[0024] Optionally, the synchronization module includes: an LED and a photodetector; an encoding disk is disposed between the LED and the photodetector.

[0025] Optionally, the time-to-digital conversion module specifically includes: a detection circuit composed of multiple channels; different channels receive synchronous electrical pulse signals and electrical pulse signals respectively, and name the time events with channel names and time tags respectively.

[0026] Optionally, the image reconstruction and display module specifically includes: a processor and a display;

[0027] The processor is used to reconstruct the target image based on the synchronous electrical pulse signal and the time events corresponding to the electrical pulse signal;

[0028] The display is used to show the reconstructed target image.

[0029] Secondly, this application provides a single-photon imaging method applied to the aforementioned single-photon imaging system, the single-photon imaging method comprising:

[0030] The target image is projected onto the encoding disk using an imaging lens assembly;

[0031] The light that modulates the target image in space is used by a uniformly rotating encoder disk, and the detection module generates an electrical pulse signal based on the light intensity of the transmitted target image, and transmits the electrical pulse signal to the time-to-digital converter module.

[0032] The synchronization module monitors the time it takes for the encoder disk to rotate one revolution and transmits the synchronization electrical pulse signal to the time-to-digital converter module.

[0033] The time-to-digital conversion module records the synchronous electrical pulse signal and the electrical pulse signal as time events, and transmits them to the image reconstruction and display module.

[0034] The image reconstruction and display module is used to reconstruct and display the target image by using the synchronous electrical pulse signal and the time events corresponding to the electrical pulse signal.

[0035] Optionally, the step of using the time-to-digital conversion module to record the synchronization electrical pulse signal and the electrical pulse signal as time events and transmitting them to the image reconstruction and display module specifically includes:

[0036] The synchronous electrical pulse signal is converted into arrival time tag Tag1_i using channel CH1; i represents the number of revolutions of the encoder disk.

[0037] The electrical pulse signal is converted into an arrival time tag Tag2_j using channel CH2, where j is the number of photons received by the detection module.

[0038] Optionally, the step of using the image reconstruction and display module to reconstruct and display the target image from the synchronization electrical pulse signal and the time events corresponding to the electrical pulse signal, respectively, specifically includes:

[0039] Step 1, determine the timestamp Tag1_i of channel CH1 as (1, T1) i The timestamp Tag2_j for channel CH2 is (2, T2). j T1 i T2 represents the time stamp corresponding to the i-th rotation of the turntable. j This represents the timestamp corresponding to the j-th photon;

[0040] Step 2: Re-match the time stamps of channel CH1 and channel CH2 within each rotation of the encoder disk to obtain the time stamp set {T2} for each rotation. j -T1 i T2 j+1 -T1 i T2 j+k -T1 i}, where k represents the number of time events;

[0041] Step 3: Perform statistical analysis on time events according to time intervals (Bin) to obtain a photon count distribution data vector {n} of length M. i n2, ..., n M}, where n i Represents the number of photons obtained from the i-th group of statistics; the width of the time interval Bin is equal to (T1 i+1 -T1 i ) / M, where M is the number of codes corresponding to one revolution of the encoder disk;

[0042] Step 4, the obtained photon count distribution data vector {n i n2, ..., n M The value is truncated according to the encoded length N and used as the bucket detector value I. b and the bucket detector value I b Perform a Fast Fourier Transform on the first row vector H1 of the cyclic orthogonal matrix to obtain the reconstructed image vector IMG; N is the length of the cyclic orthogonal matrix, which is determined based on the pixel size of the target image;

[0043] Step 5: Rearrange the reconstructed image vector IMG according to the pixel size of the target image, and then perform a normalization operation.

[0044] Step 6: Repeat steps 1-5 to overlay the image vectors (IMG) of each circle to obtain a clear target image and display it.

[0045] According to the specific embodiments provided in this application, this application has the following technical effects:

[0046] This application provides a single-photon imaging system and method. It constructs a cyclic orthogonal matrix based on the pixel size of the target image, and then uses a coded pattern constructed based on this matrix to spatially modulate the light intensity of the target image. Furthermore, it generates electrical pulse signals by detecting the single-photon signal response in extremely low-light environments, and uses these pulses, along with a synchronization module monitoring the rotation time of the coded disk, to re-align time signatures and perform reasonable photon counts, thereby achieving single-pixel imaging under extremely low-light conditions. This application boasts advantages such as high integration, low power consumption, and high sensitivity. It enables rapid imaging and progressive imaging in extremely low-light conditions, and has potential applications in biofluorescence imaging, night vision imaging, and long-range imaging. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is a schematic diagram of a single-photon imaging system according to one embodiment of this application;

[0049] Figure 2 This is a schematic diagram of the design of the encoding disk in one embodiment of this application;

[0050] Figure 3 This is a schematic diagram of a cyclic orthogonal matrix in one embodiment of this application;

[0051] Figure 4 This is a schematic diagram of cyclic encoding in one embodiment of this application. Detailed Implementation

[0052] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0053] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0054] In one exemplary embodiment, such as Figure 1 As shown, a single-photon imaging system is provided, which includes: an imaging lens group 1, an encoding disk 2, a detection module 3, a motor and drive module 4, a synchronization module 5, a time-to-digital conversion module 6, and an image reconstruction and display module 7.

[0055] The imaging lens group 1 is used to image the target image onto the encoding disk 2;

[0056] The encoding disk 2 includes an encoding pattern area and a driving area disposed on a light-transmitting material substrate; the encoding disk 2 is used to spatially modulate the light intensity of a target image through the encoding pattern area; the encoding pattern area includes an encoding pattern constructed based on a cyclic orthogonal matrix; the cyclic orthogonal matrix is ​​constructed according to the pixel size of the target image; and sectors are constructed according to a row of data of the cyclic orthogonal matrix; each sector includes multiple reflection areas and multiple transmission areas; a sector is the smallest encoding unit in the encoding pattern; adjacent sectors share a portion of the same pattern.

[0057] Cyclic orthogonal matrices: Cyclic Hadamard matrices with X rows and Y columns can be constructed based on cyclic orthogonal matrices, such as cyclic S matrices. A cyclic S matrix is ​​a square matrix whose dimension n is constrained by the Hadamard matrix (i.e., the H matrix) and is an odd number. For example, an (n+1)th order H matrix can be normalized by elementary row and column transformations, resulting in the first row and first column containing all 1s. Deleting the first row and first column of the normalized (n+1)th order H matrix and setting all 1s to 0s and -1s to 1s in the resulting nth order square matrix yields the nth order S matrix. Methods for constructing cyclic Hadamard matrices from nth order S matrices include, for example, the quadratic residue algorithm, the m-sequence algorithm, and the twin prime algorithm. These are known algorithms and will not be discussed in detail here. Taking an image resolution of X rows and A columns as an example, each image includes M = X × A pixels. An X-row, Y-column cyclic Hadamard matrix can be constructed, where Y = M + A - 1. The submatrix in the X-row, A-column section from column y to column y + A - 1 of the cyclic Hadamard matrix is ​​a minimum coding unit, where matrix element 1 corresponds to the transmissive region in the coding pattern, and matrix element 0 corresponds to the non-transmissive region in the coding pattern. For example, Figure 2 The i-th minimum coding unit shown can have its next (i+1) minimum coding unit along the scanning direction at least partially repeating the previous (i-th) minimum coding unit, i.e., including one or more identical columns, and at most A-1 identical columns. Therefore, for an image size of X rows and A columns, comprising M pixels, when the M minimum coding units (X rows and A columns) are arranged in an overlapping manner, an X rows and M+A-1 columns coding matrix is ​​formed. Properties of the cyclic S matrix:

[0058]

[0059] The detection module 3 is used to generate an electrical pulse signal based on the light intensity of the target image transmitted through the transmission area in the encoding disk 2, and transmit the electrical pulse signal to the time-to-digital conversion module 6;

[0060] The motor and drive module 4 are connected to the encoder disk 2 through the drive area, and drive the encoder disk 2 to rotate at a constant speed; the encoder disk 2 switches the encoding pattern sequentially by rotating at a constant speed.

[0061] The synchronization module 5 is used to monitor the time it takes for the encoder disk 2 to rotate one revolution and transmits the synchronization electrical pulse signal to the time-to-digital conversion module 6.

[0062] The time-to-digital conversion module 6 is used to record the synchronous electrical pulse signal and the electrical pulse signal as time events, and transmit them to the image reconstruction and display module 7.

[0063] Specifically, the time-to-digital conversion module 6 is arranged according to the order of detection. The time signatures converted by all detection modules 3 are subtracted from the corresponding time signatures of the encoding disk 2 to obtain the normalized time signal within each circle. The signal of the encoded part is extracted and deconvolved with the encoding matrix for reconstruction. After passing through the image reconstruction and display module 7, the reconstructed single-photon imaging result is displayed.

[0064] The image reconstruction and display module 7 is used to reconstruct and display the target image based on the synchronous electrical pulse signal and the time events corresponding to the electrical pulse signal.

[0065] Among them, imaging lens group 1 is an imaging system composed of lens groups, using custom or commercial imaging lenses;

[0066] In one specific embodiment, the imaging lens group 1 uses a commercial imaging lens with parameters of 35mm focal length, F1.4, and 1 / 3-inch image plane.

[0067] In one specific embodiment, a circular coding pattern is placed in the coding pattern area, and auxiliary lines are cut to define the size of the code disk, and excess parts are removed.

[0068] In one specific embodiment, the process of constructing the encoded pattern is as follows:

[0069] Obtain an N x N cyclic orthogonal matrix, where N is the number of pixels in the target image to be imaged, and N is greater than 2; the pixels of the target image are arranged in X rows and A columns, and N = X × A;

[0070] Based on the cyclic orthogonal matrix, reconstruct an X-row, Y-column cyclic Hadamard matrix; wherein, the y-th submatrix in the X-row, A-column of the cyclic Hadamard matrix from the y-th to y+A-1-th columns is obtained by rearranging the vector in the y-th row of the cyclic orthogonal matrix with each row containing A data points; X = N / A, Y = N+A-1;

[0071] For example, assuming the image to be imaged has a width A of 3 and a height X of 5, then the width and height N of the cyclic orthogonal matrix = A × X = 3 × 5 = 15; Figure 3 The 15×15 cyclic orthogonal matrix shown has its first row and first column as row and column numbers only, respectively. The interior is a cyclic orthogonal matrix where 0 corresponds to the reflection zone and 1 corresponds to the transmission zone. Then, according to... Figure 3 The shown cyclic orthogonal matrix is ​​reconstructed to yield... Figure 4 The cyclic Hadamard matrix shown. Assume that... Figure 3The cyclic orthogonal matrix shown is simply called H15. Each row of H15 is extracted sequentially to form a new 5×3 (5 rows, 3 columns) region. It can be seen that two columns (the last two columns of the previous region and the first two columns of the next region) of two adjacent 5×3 regions have the same elements. After merging the identical elements, the number of columns in the cyclic Hadamard matrix is ​​calculated according to the formula Y = N + A - 1: Y = 15 + 3 - 1 = 17, resulting in the following... Figure 4 The matrix shown is 5 rows and 17 columns. The size of the encoding region corresponds to the size of the sector and is located at a predetermined position. Rotating the encoding disk 2 causes the sectors to rotate; if the current sector is in the encoding region, then for each subsequent rotation of a column, the next sector will move into the encoding region, thus achieving the same modulation effect as moving one row corresponding to H15. Figure 4 Will Figure 3 The row vectors of H15 become two-dimensional, and the similarity is that the element content remains unchanged and is strictly equal.

[0072] In one specific embodiment, the encoder disk 2 further includes a marking area and a synchronization area; the marking area is used to mark information such as the encoder disk's parameters, production number, and parameter settings. The synchronization area is a blank area, allowing light generated by the LEDs to pass through and be received by the photodetector;

[0073] In one specific embodiment, the detection module 3 specifically includes: a converging lens and a single-photon detector;

[0074] The converging lens is used to transmit the light intensity of the transmitted target image to the single-photon detector; the single-photon detector is used to generate an electrical pulse signal when the light intensity is greater than or equal to the energy of one photon. The detection module 3 can respond to single-photon signals in extremely weak light environments and generate an electrical pulse signal, which is a square wave signal with a width of approximately 10 nanoseconds.

[0075] Preferred single-photon detectors specifically include photomultiplier tubes and Geiger-mode avalanche photodiodes.

[0076] The motor and drive module 4 specifically includes: a DC motor and a driver; the driver uses pulse width modulation (PWM) technology for speed regulation, which is achieved by changing the pulse width and frequency through a resistor to change the drive current, thereby changing the speed of the brushless DC motor. A brushless DC motor for hard drives is selected as the DC motor.

[0077] The synchronization module 5 includes an LED and a photoelectric detector (PD); an encoding disk 2 is disposed between the LED and the photoelectric detector. When there is obstruction between the LED and the PD, the photocurrent of the PD decreases; when there is no obstruction, the photocurrent returns to normal. The function of the synchronization module 5 is to output an electrical pulse when the encoding disk 2 rotates one revolution, based on the different light intensities transmitted and blocked by the set synchronization code, which serves as a marker for one revolution of the encoding disk 2.

[0078] The time-to-digital conversion module 6 specifically includes: a detection circuit composed of multiple channels; different channels receive synchronous electrical pulse signals and electrical pulse signals respectively, and name the time events with channel names and time tags respectively.

[0079] The image reconstruction and display module 7 specifically includes: a processor and a display;

[0080] The processor is used to reconstruct the target image based on the synchronous electrical pulse signal and the time events corresponding to the electrical pulse signal;

[0081] The display is used to show the reconstructed target image.

[0082] The specific processing procedure of the image reconstruction and display module 7 is as follows:

[0083] S11, the target image is imaged onto the encoding disk 2 through the imaging lens group 1. The light passing through the encoding disk 2 is detected by the detection module 3, which outputs an electrical pulse corresponding to the single photon event. The encoding disk 2 is driven to rotate at a constant speed by the motor and drive module 4. The synchronization module 5 monitors the number of rotations and outputs a synchronization electrical pulse.

[0084] S12, the two channels CH1 and CH2 of the time-to-digital conversion module 6 are used to acquire electrical pulse signals. CH1 converts the rising edge (or falling edge) of the electrical pulse signal from the synchronization module 5 into an arrival time tag Tag1_i; CH2 converts the electrical pulse signal obtained from the detection module 3 into an arrival time tag Tag2_j for recording. Each tag represents the occurrence time of an event.

[0085] S13, the image reconstruction and display module 7 processes the time stamp signals of channels CH1 and CH2 recorded by the time-to-digital conversion module 6 separately, distinguishing the data by channel, specifically:

[0086] (1) The timestamp Tag1_i of CH1 is (1, T1) i ), where i is a natural number i = 1, 2, 3, ..., i represents the number of revolutions of encoder disk 2, T1 i This represents the time tag corresponding to the i-th rotation of the turntable; the time tag Tag2_j for CH2 is (2, T2). j), where j is a natural number j = 1, 2, 3, ..., j represents the number of photons received by the detection module 33, T2 j The time tag represents the j-th photon; assuming the encoder disk 2 rotates at 20Hz, and the corresponding time for one cycle is 50ms, then the value of T12-T11 in the subdivision step (1) should be equal to 50ms. Considering the unstable motor speed, the value of T12-T11 should be approximately equal to 50ms. Assuming the starting time is 0ms, then the time tag set of CH1 is {0ms, 50ms, 100ms, 150ms, ...}; the time tag Tag2_j of CH2 must fall within the time tag set of CH1, but since the photon arrival time is related to the light intensity and has randomness, the data of Tag2_j is random time data, such as {1ms, 2ms, 20ms, 21ms, 22ms, 23ms, 48ms, 51ms, 53ms, ..., 98ms, ..., 140ms, ..., 180ms, ...}. The specific time accuracy is related to the hardware and can currently reach picoseconds.

[0087] (2) The image reconstruction and display module 7 re-corresponds the time stamps within each cycle. For example, the time stamp T2 obtained from CH2 between (1, T11) and (1, T12) is... j j = p, p+1, p+2, ... q, where p and q are natural numbers, and q > p. Using T2... p T2 p+1 T2 q Subtracting T11 from each yields a new set of time stamps {T2}. p -T11, T2 p+1 -T11, ...,T2 q -T11}; Assume the starting time is 0ms, p=1, q=7, and the time signature data for the first cycle is {1-0ms, 2-0ms, 20-0ms, 21-0ms, 22-0ms, 23-0ms, 48-0ms};

[0088] (3) Perform the same operation on the time stamp data for each lap to obtain the time stamp set {T2} for each lap. j -T1 i T2 j+1 -T1 i T2 j+k -T1 i}, where k represents the number of (time events) photon events; assuming the starting time is 0ms, the first round will yield the set {1ms, 2ms, 20ms, 21ms, 22ms, 23ms, 48ms, 51ms}; the second round will subtract 50ms from each, yielding the set {…, 53-50ms, …, 98-50ms, …}; and so on, the third round will yield the set {…, 140-100ms, …, 180-100ms, …}, resulting in a series of time signatures whose starting time range is normalized to within 50ms.

[0089] (4) Statistical analysis of photon events is performed according to the time interval Bin, where the width of Bin is equal to (T1) i+1 -T1 i ) / M, where M is the number of codes corresponding to one revolution of the encoding disk 2. After statistics, a set of photon count distribution data vectors of length M is obtained {n i n2, ..., n M}, where n i n represents the number of photons obtained from the i-th group of statistics. i It is a positive integer;

[0090] For example, using Figure 3 The 15×15 cyclic orthogonal matrix shown forms a 5×17 cyclic code, as follows. Figure 4 As shown, after the encoding is converted to a disk, assuming it covers exactly one circumference of the disk, the disk has a total of 17 subdivision units of length, M = 17.

[0091] Assuming the encoder disk 2 rotates at 20Hz, corresponding to a rotation time of 50ms, the value of T12-T11 is equal to 50ms, and the width of the Bin is equal to (T1... i+1 -T1 i The statistical interval corresponding to M = 50ms / 17 = 3ms is determined to be {1, 4, 7, 10, 13, 16, 19, 22, 25, 28, 31, 34, 37, 40, 43, 46, 49}. If the photon time signatures within the first cycle are {1ms, 2ms, 20ms, 21ms, 22ms, 23ms, 48ms}, then the corresponding photon number distribution data vector {n} for different statistical intervals is... i n2, ..., n M} = {2, 0, 0, 0, ... 3, 0, 0, 0, ..., 1}, a total of 17 values. The number of photons falling in the 1ms to 4ms range is 2, the number of photons falling in the 19ms to 22ms range is 3, and the number of photons falling in the 46ms to 49ms range is 1.

[0092] (5) The obtained data vector {n i n2, ..., n MThe value is truncated according to the encoded length N and used as the bucket detector value I. b Reconstruct the image vector as follows:

[0093]

[0094] Where H1 represents the first row vector of the cyclic orthogonal matrix with a length of N, and FFT represents the Fast Fourier Transform.

[0095] For example, the photon number distribution data vector {n i n2, ..., n M＝17} = {2, 0, 0, 0, ... 3, 0, 0, 0, ..., 1}, a total of 17 values. N = 15, so the first 15 values ​​are selected as the bucket detector value Ib for calculation.

[0096] (6) The reconstructed image vector IMG is rearranged in rows X and columns A, then normalized and sent to the display screen by the processor;

[0097] For example, if the reconstructed image vector IMG has 15 elements, it is arranged in a 3×15 pattern to form a two-dimensional image, which is then used for display.

[0098] (7) Repeat steps (1)-(6) to superimpose the image vector IMG of each circle to gradually obtain a clear image and display it.

[0099] Based on the same inventive concept, embodiments of this application also provide a single-photon imaging method for implementing the single-photon imaging system described above. The method includes:

[0100] S101, The target image is imaged onto the encoding disk 2 using the imaging lens group 1;

[0101] S102, the uniformly rotating encoder disk 2 modulates the light of the target image in space, and the detection module 3 generates an electrical pulse signal according to the light intensity of the transmitted target image, and transmits the electrical pulse signal to the time-to-digital converter module 6.

[0102] S103, the synchronization module 5 monitors the time it takes for the encoder disk 2 to rotate one revolution, and transmits the synchronization electrical pulse signal to the time-to-digital converter module 6;

[0103] S104, the time-to-digital conversion module 6 records the synchronous electrical pulse signal and the electrical pulse signal as time events respectively, and transmits them to the image reconstruction and display module 7;

[0104] S105, the image reconstruction and display module 7 is used to reconstruct and display the target image by using the synchronous electrical pulse signal and the time events corresponding to the electrical pulse signal respectively.

[0105] S104 specifically includes:

[0106] The synchronous electrical pulse signal is converted into arrival time tag Tag1_i using channel CH1; i represents the number of revolutions of encoder disk 2;

[0107] The electrical pulse signal is converted into an arrival time tag Tag2_j using channel CH2, where j is the number of photons received by detection module 3.

[0108] S105 specifically includes:

[0109] Step 1, determine the timestamp Tag1_i of channel CH1 as (1, T1) i The timestamp Tag2_j for channel CH2 is (2, T2). j T1 i T2 represents the time stamp corresponding to the i-th rotation of the turntable. j This represents the timestamp corresponding to the j-th photon;

[0110] Step 2: Re-match the time stamps of channel CH1 and channel CH2 within each rotation of the encoder disk 2 to obtain the time stamp set {T2} for each rotation. j -T1 i T2 j+1 -T1 i T2 j+k -T1 i}, where k represents the number of time events;

[0111] Step 3: Perform statistical analysis on time events according to time intervals (Bin) to obtain a photon count distribution data vector {n} of length M. i n2, ..., n M}, where n i Represents the number of photons obtained from the i-th group of statistics; the width of the time interval Bin is equal to (T1 i+1 -T1 i ) / M, where M is the number of codes corresponding to one revolution of the encoding disk 2;

[0112] Step 4, the obtained photon count distribution data vector {n i n2, ..., n M The value is truncated according to the encoded length N and used as the bucket detector value I. b and the bucket detector value I b Perform a Fast Fourier Transform on the first row vector H1 of the cyclic orthogonal matrix to obtain the reconstructed image vector IMG; N is the length of the cyclic orthogonal matrix, which is determined based on the pixel size of the target image;

[0113] Step 5: Rearrange the reconstructed image vector IMG according to the pixel size of the target image, and then perform a normalization operation.

[0114] Step 6: Repeat steps 1-5 to overlay the image vectors (IMG) of each circle to obtain a clear target image and display it.

[0115] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0116] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A single-photon imaging system, characterized in that, The single-photon imaging system includes: an imaging lens group, an encoding disk, a detection module, a motor and drive module, a synchronization module, a time-to-digital conversion module, and an image reconstruction and display module; The imaging lens group is used to image the target image onto the encoding disk; The encoding disk includes: an encoding pattern area and a driving area disposed on a light-transmitting material substrate; the encoding disk is used to spatially modulate the light intensity of a target image through the encoding pattern area; the encoding pattern area includes an encoding pattern constructed based on a cyclic orthogonal matrix; the cyclic orthogonal matrix is ​​constructed according to the pixel size of the target image; and sectors are constructed according to a row of data of the cyclic orthogonal matrix; the sectors include: multiple reflection areas and multiple transmission areas; The detection module is used to generate an electrical pulse signal based on the light intensity of the target image transmitted through the transmission area in the encoder disk, and transmit the electrical pulse signal to the time-to-digital conversion module. The motor and drive module are connected to the encoder disk through the drive area and drive the encoder disk to rotate at a constant speed; the encoder disk switches the encoding pattern sequentially by rotating at a constant speed. The synchronization module is used to monitor the time it takes for the encoder disk to rotate one revolution and transmit the synchronization electrical pulse signal to the time-to-digital conversion module. The time-to-digital conversion module is used to record the synchronization electrical pulse signal and the electrical pulse signal as time events, and transmit them to the image reconstruction and display module. The image reconstruction and display module is used to reconstruct and display the target image based on the synchronous electrical pulse signal and the time events corresponding to the electrical pulse signal.

2. The single-photon imaging system according to claim 1, characterized in that, The detection module specifically includes: a converging lens and a single-photon detector; The converging lens is used to transmit the light intensity of the transmitted target image to the single-photon detector; the single-photon detector is used to generate an electrical pulse signal when the light intensity is greater than or equal to the energy of one photon.

3. The single-photon imaging system according to claim 2, characterized in that, The single-photon detector specifically includes a photomultiplier tube and a Geiger-mode avalanche photodiode.

4. The single-photon imaging system according to claim 1, characterized in that, The motor and drive module specifically include: a DC motor and a driver; the driver uses pulse width modulation technology for speed regulation.

5. The single-photon imaging system according to claim 1, characterized in that, The synchronization module includes an LED and a photodetector; an encoding disk is disposed between the LED and the photodetector.

6. The single-photon imaging system according to claim 1, characterized in that, The time-to-digital conversion module specifically includes: a detection circuit composed of multiple channels; different channels receive synchronous electrical pulse signals and electrical pulse signals respectively, and name the time events with channel names and time tags respectively.

7. The single-photon imaging system according to claim 1, characterized in that, The image reconstruction and display module specifically includes: a processor and a display; The processor is used to reconstruct the target image based on the synchronous electrical pulse signal and the time events corresponding to the electrical pulse signal respectively; The display is used to show the reconstructed target image.

8. A single-photon imaging method, applied to the single-photon imaging system according to any one of claims 1-7, characterized in that, The single-photon imaging method includes: The target image is projected onto the encoding disk using an imaging lens assembly; The light that modulates the target image in space is used by a uniformly rotating encoder disk, and the detection module generates an electrical pulse signal based on the light intensity of the transmitted target image, and transmits the electrical pulse signal to the time-to-digital converter module. The synchronization module monitors the time it takes for the encoder disk to rotate one revolution and transmits the synchronization electrical pulse signal to the time-to-digital converter module. The time-to-digital conversion module records the synchronous electrical pulse signal and the electrical pulse signal as time events, and transmits them to the image reconstruction and display module. The image reconstruction and display module is used to reconstruct and display the target image by using the synchronous electrical pulse signal and the time events corresponding to the electrical pulse signal.

9. The single-photon imaging method according to claim 8, characterized in that, The process of using a time-to-digital conversion module to record the synchronization electrical pulse signal and the electrical pulse signal as time events and transmitting them to the image reconstruction and display module specifically includes: The synchronous electrical pulse signal is converted into arrival time tag Tag1_i using channel CH1; i represents the number of revolutions of the encoder disk. The electrical pulse signal is converted into an arrival time tag Tag2_j using channel CH2, where j is the number of photons received by the detection module.

10. The single-photon imaging method according to claim 9, characterized in that, The process of using the image reconstruction and display module to reconstruct and display the target image from the synchronous electrical pulse signal and the time events corresponding to the electrical pulse signal specifically includes: Step 1, determine the timestamp Tag1_i of channel CH1 as (1, T1) i The timestamp Tag2_j for channel CH2 is (2, T2). j T1 i T2 represents the time stamp corresponding to the i-th rotation of the turntable. j This represents the timestamp corresponding to the j-th photon; Step 2: Re-match the time stamps of channel CH1 and channel CH2 within each rotation of the encoder disk to obtain the time stamp set {T2} for each rotation. j -T1 i T2 j+1 -T1 i T2 j+k -T1 i }, where k represents the number of time events; Step 3: Perform statistical analysis on time events according to time intervals (Bin) to obtain a photon count distribution data vector {n} of length M. i n2, ..., n M }; where n i Represents the number of photons obtained from the i-th group of statistics; the width of the time interval Bin is equal to (T1 i+1 -T1 i ) / M, where M is the number of codes corresponding to one revolution of the encoder disk; Step 4, the obtained photon count distribution data vector {n i n2, ..., n M The value is truncated according to the encoded length N and used as the bucket detector value I. b and the bucket detector value I b Perform a Fast Fourier Transform on the first row vector H1 of the cyclic orthogonal matrix to obtain the reconstructed image vector IMG; N is the length of the cyclic orthogonal matrix, which is determined based on the pixel size of the target image; Step 5: Rearrange the reconstructed image vector IMG according to the pixel size of the target image, and then perform a normalization operation. Step 6: Repeat steps 1-5 to overlay the image vectors (IMG) of each circle to obtain a clear target image and display it.

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