A method and system for optical correlation imaging of a multi-spectral fiber array illumination

Abstract

The application discloses a kind of multispectral optical fiber array illumination optical correlation imaging method and system, belong to optical correlation imaging field.The application is controlled by trigger module to rotate emission light source to phase modulation module, and is synchronously controlled;Every pulsed light source is divided into multiple, respectively by phase modulator modulation, and from light array as illumination light field output;Light echo signal is divided into multiple, first through optical filtering, secondly by corresponding wavelength detector photoelectric detection;When sampling data quantity satisfies, then using illumination light field data and echo signal data carries out image reconstruction.The application can fully utilize the super-high bandwidth of phase modulator by reasonably using the time division multiplexing rotation illumination method of different wavelength pulsed light source, improve the modulation rate of structured light, greatly shorten the data acquisition time of optical correlation imaging, speed up the imaging speed.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical correlation imaging, and particularly relates to a method and system for improving the modulation rate of an illumination light field, which can solve the problem of slow image reconstruction frame rate in optical correlation imaging. BACKGROUND

[0002] Traditional imaging is a direct and passive imaging, where the passive means that the light source is more of uncontrollable natural light, and the direct means that the spatial light signal reflecting the object information is directly projected to the image plane using a lens. Correlation imaging is an indirect and active imaging method compared with the traditional imaging. The illumination light source can be designed and divided into two paths, one of which is called the reference arm and is used to record the light field information, and the other of which is called the probe arm and is used to record the echo information after the interaction with the object. Finally, the target signal is recovered by using an image reconstruction algorithm based on the multiple detections of the echo signal and the combination of the light field information.

[0003] Compared with the traditional imaging, optical correlation imaging is a new imaging system. It has the advantages of non-locality, strong anti-interference ability and super-resolution, and has great development potential in remote sensing detection, microscopic imaging, super-resolution imaging and other fields. However, the prerequisite for ensuring the high resolution of the correlation imaging image is a large amount of sampling data, and this process is time-consuming, which includes the light field data and the total light intensity of the echo light signal. At present, the non-constraint factor of the bandwidth of the detector at the receiving probe end is mainly due to the low modulation rate of the illumination light field, so the time-consuming data acquisition process will reduce the imaging rate of the correlation imaging, which is not conducive to the practical process of the correlation imaging. SUMMARY

[0004] The present application aims to solve the problems in the prior art, and provides a method and system for accelerating the modulation rate of the illumination light field of optical correlation imaging and improving the image reconstruction rate. Compared with the existing optical correlation imaging system, the data sampling rate is greatly improved, and the practicability of the optical correlation imaging system is improved.

[0005] The technical scheme adopted by the present application is as follows:

[0006] A multi-spectral optical fiber array illumination optical correlation imaging method, comprising the following steps:

[0007] (1) at the transmitting end, a plurality of pulsed lasers of different wavelengths are selected as seed light sources for illumination in a time division multiplexing manner;

[0008] (2) for each seed light source, the pixel number is divided into a plurality of equal-power beams, and a plurality of phase modulators are used to simultaneously modulate the light field of the plurality of beams;

[0009] (3) the optical fibers at the output ends of all the phase modulators are arranged into an optical fiber array, each optical fiber representing a pixel, and the optical paths of all the light beams from the seed light sources to the output ends of the optical fiber array are equal in length; the light field output by the optical fiber array is coupled and then transmitted to the target by the transmitting antenna;

[0010] (4) at the receiving end, the light field reflected by the target is received by the receiving antenna, the received light field is split into beams with equal power according to the number of seed light sources; for each split beam, optical filtering is performed for different center wavelengths, and the total light intensity of the filtered beam is measured by using the corresponding detector; finally, the filtered beam with the largest total light intensity is selected as the echo signal;

[0011] (5) after multiple illuminations and echo signal detections, the collected data is reconstructed by using an image reconstruction method to obtain a two-dimensional image of the target.

[0012] An optical correlation imaging system based on multi-spectral optical fiber array illumination includes a transmitting end, a receiving end, and a signal processing module; the transmitting end includes a plurality of light source modules, a light splitting module, a plurality of phase modulation modules, a trigger module, a coupling module, and a transmitting antenna module; the plurality of light source modules are used to emit pulsed lasers with different wavelengths; the light splitting module splits the light emitted by each light source module into beams with equal power in a time-division multiplexing manner, the number of split beams is equal to the number of pixels for imaging, each split beam is sent into a phase modulation module, the trigger module is used to synchronize the operation of the phase modulation modules and the light source modules, the optical fibers at the output ends of the plurality of phase modulation modules form an optical fiber array, the coupling module couples the light field signals transmitted by the optical fiber array into the form of antenna transmission, and the target is transmitted by the transmitting antenna module;

[0013] The signal processing module is used to send light field information to the transmitting end and collect the echo signals transmitted back by the receiving end;

[0014] The receiving end includes a signal collection module, a plurality of detection modules, a plurality of filtering modules, a light splitting module, and a receiving antenna module; the center wavelength filtered by each filtering module corresponds to the wavelength of the pulsed laser emitted by a light source module of the transmitting end, the detection modules correspond to the filtering modules one by one and are used to detect the total light intensity of the light field of the corresponding wavelength beam; the receiving antenna module is used to receive the light field reflected by the target, the light splitting module splits the light field received by the receiving antenna module into beams with equal power according to the number of light source modules of the transmitting end, each split beam is sent into a filtering module for filtering, and the filtered beam is sent into the corresponding detection module to obtain the total light intensity of the corresponding beam; the signal collection module transmits the beam with the largest total light intensity as the echo signal to the signal processing module;

[0015] After the signal processing module receives the echo signal, firstly, it is judged whether the required data acquisition amount is reached, if not, the transmitting end is driven again to carry out light field emission; after the data acquisition amount is reached, a two-dimensional image of the target is obtained by using the image reconstruction method for reconstruction by using multiple groups of light field information and echo information.

[0016] Compared with the prior art, the present application has the beneficial effects that:

[0017] 1. The present application can fully utilize the ultra-high bandwidth of the phase modulator by reasonably utilizing multiple different waveband pulse light sources for time division multiplexing rotation lighting.

[0018] 2. The present application can realize presetting of the illumination light field by array arrangement of the optical fiber and programming control of the phase modulator modulation signal, without the need for array detector to record the illumination light field.

[0019] 3. The present application can accelerate the illumination light field modulation rate, accelerate the sampling number per unit time of optical correlation imaging, and improve the imaging rate of the optical correlation imaging system. Compared with the existing optical correlation imaging system, the data sampling rate of the present application is greatly improved, and the practicability of the optical correlation imaging system is improved.

[0020] 4. The present application proposes a high-speed correlation imaging scheme based on multi-waveband light source, phase modulator modulation and optical fiber array illumination for the correlation imaging architecture and image reconstruction data requirement. The current methods for improving the correlation imaging rate mainly include improving the hardware, optimizing the correlation imaging architecture and optimizing the illumination light field arrangement, and the present application belongs to one of the optimization of the correlation imaging architecture, which does not conflict with the existing such improvement method, and can further improve the image reconstruction rate of the correlation imaging. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a flow chart of the optical correlation imaging method in the embodiment of the present application.

[0022] Figure 2 is a schematic diagram of an optional optical fiber array arrangement.

[0023] Figure 3 is a structural schematic diagram of the optical correlation imaging system in the embodiment of the present application.

[0024] Figure 4 is a schematic diagram of a specific optical fiber array arrangement in the embodiment of the present application. DETAILED DESCRIPTION

[0025] The implementation process of the present application will be described in detail below in combination with the drawings and embodiments.

[0026] A multi-spectral optical fiber array illumination optical correlation imaging system, as Figure 3As shown, it comprises a transmitting end, a receiving end and a signal processing module; the transmitting end comprises a plurality of light source modules, a light splitting module, a plurality of phase modulation modules, a trigger module, a coupling module and a transmitting antenna module; the plurality of light source modules are used to emit pulsed lasers with different wavelengths, the light splitting module divides the light emitted by each light source module in power in a time division multiplexing manner, the number of division is the number of pixels of imaging, each light beam after division is sent into a phase modulation module, the trigger module is used to synchronize the work of the phase modulation module and the light source module, the optical fibers at the output ends of the plurality of phase modulation modules form an optical fiber array, the coupling module couples the light field signals from the optical fiber array into the form of antenna transmission, and the target is transmitted through the transmitting antenna module;

[0027] The signal processing module is used to send light field information to the transmitting end and collect the echo signals returned by the receiving end;

[0028] The receiving end comprises a signal collection module, a plurality of detection modules, a plurality of filter modules, a light splitting module and a receiving antenna module; the center wavelength of each filter module is corresponding to the wavelength of the pulsed laser emitted by a light source module of the transmitting end, the detection modules correspond to the filter modules one by one and are used to detect the total light intensity of the light field of the corresponding wavelength light beam; the receiving antenna module is used to receive the light field reflected by the target, the light splitting module divides the light field received by the receiving antenna module in power according to the number of the light source modules of the transmitting end, each light beam after division is sent into a filter module for filtering, and the filtered light beam is sent into the corresponding detection module to obtain the total light intensity of the light field of the corresponding light beam; the signal collection module transmits the light beam with the maximum total light intensity to the signal processing module as the echo signal;

[0029] After the signal processing module receives the echo signal, it is firstly judged whether the required data collection amount is reached, if not, the transmitting end is driven again to emit the light field; after the data collection amount is reached, a plurality of groups of light field information and echo information are used to reconstruct the target two-dimensional image by using an image reconstruction method.

[0030] In the system, the trigger module is responsible for triggering the light source and the phase modulation module, and is responsible for sending a modulation signal to the phase modulation module; the light source module is used to generate a pulse seed light source of a specific waveband; the light splitting module splits the input signal into several parts according to power; the phase modulation module modulates the pulse light source output by the light splitting module; the coupling module is responsible for collimating and expanding the spatial light output by the fiber array; the transmitting antenna module outputs the light field output by the coupling module with a corresponding divergence angle and irradiates a corresponding area; the receiving antenna module collects the light field reflected or transmitted by the target and performs beam shrinking; the filtering module filters out the energy of the non-corresponding waveband in the input light signal; the detection module detects the total light intensity of the light signal output by the filtering module; the signal acquisition module is responsible for sampling the output signal of the detection module; and the signal processing module is responsible for processing the echo signal data output by the signal acquisition module of the receiving end and the array light field information of the transmitting end, and finally reconstructing a two-dimensional image of the target.

[0031] The working process of the system is as follows:

[0032] (1) The trigger module controls the light source module to emit light sources in turn, and synchronously controls the phase modulation module;

[0033] (2) Each pulse light source is divided into several parts, respectively modulated by the phase modulator, and output as an illumination light field from the light array, and the computer preset light field is used as the illumination light field when reconstructing the image;

[0034] (3) The illumination light field irradiates the target surface, and the reflected signal is received by the receiving antenna;

[0035] (4) The received light echo signal is divided into several parts, first passes through optical filtering, and then is photoelectrically detected by a corresponding wavelength detector, and only one effective detector response value can be obtained for a single echo signal;

[0036] (5) When the amount of sampling data meets the requirement, the illumination light field data and the echo signal data are used for image reconstruction, and if it does not meet the requirement, the step (1) is started.

[0037] The required amount of data for reconstruction is not fixed, and needs to be determined according to specific scene and device parameters. For example, through prior testing, under certain specific scene and device parameter conditions, M data are required to achieve a signal-to-noise ratio of 10dB, and then M data are collected for the next time when an image with a signal-to-noise ratio of 10dB is required.

[0038] An optical correlation imaging method of multi-spectral fiber array illumination, as shown in Figure 1 , includes the following steps:

[0039] (1) The optical correlation imaging system is started;

[0040] (2) The triggering module triggers the light source module λ1, light source module λ2, ..., light source module λ in chronological order. M Furthermore, when triggering the corresponding light source module, all phase modulation modules need to be triggered simultaneously;

[0041] (3) The light emitted by each light source is divided into N parts by the beam splitting module and then sent into the corresponding phase modulation module;

[0042] (4) The phase modulation module modulates the phase of the light source according to the received modulation signal;

[0043] (5) The structured light field output by the fiber array after phase modulation is received by the coupling module and expanded and collimated, and then the signal is sent to the transmitting antenna module.

[0044] (6) The transmitting antenna module emits the output signal of the coupling module at a certain divergence angle, and the emitted light field illuminates the surface of the object.

[0045] (7) The receiving antenna module receives the received optical field signal, which is the optical field signal reflected back from the target surface. Then, the received optical field signal is sent to the beam splitter module.

[0046] (8) The beam splitting module divides the power of the echo signal into M parts. The split signal is filtered by the corresponding filtering module, and then the power is measured by the detection module of the corresponding wavelength and recorded as echo information.

[0047] (9) When the number of samplings reaches the required level, the signal processing module can reconstruct the target image by processing the light field information and echo information. If the number of samplings does not reach the required level, return to step (2) to continue target illumination and echo signal acquisition.

[0048] The fiber optic array arrangement described in step (5) is not a fixed arrangement. For example... Figure 2 The diagram shows optical fibers arranged in two-dimensional circles, squares, etc., with the specific arrangement depending on the application scenario. Since the modulation signal of the phase modulator can be controlled by programming and the power of the pulsed laser is fixed, the intensity distribution of the light field emitted by the fiber array can be calculated at a given moment. The calculated shape of the light field distribution needs to be normalized before being used as the recorded light field information at that moment. The light field output by the fiber array propagates in space. To be further emitted by the optical antenna, a spatial collimation and beam expander system is needed to shape the spatial light field output by the fiber array.

[0049] In step (8), at any given echo signal moment, only one of the M detectors will respond at any given time. The echo signals are arranged according to a time sequence, corresponding to the order of the optical field signals.

[0050] Wherein, the step (9) is completed on the basis of steps (4), (5), (6), (7), (8). When step (9) is performed, the amount of sampling information required for restoring the image needs to be determined according to the detection scene. The required sampling times are inversely proportional to the signal-to-noise ratio, the higher the signal-to-noise ratio of the echo signal, the fewer the required sampling times, and vice versa. This conclusion is applicable to all optical correlation imaging systems.

[0051] The following is a more specific example:

[0052] Taking a cooperative target of 10 m high outside 2 km as an example, the implementation process of the application is described in detail.

[0053] Figure 3 The optical correlation imaging structure diagram using four waveband illuminations is shown, the center wavelengths of the four wavebands are λ1=1032 nm, λ2=1048 nm, λ3=1064 nm and λ4=1080 nm, and the line widths of the four pulsed light sources are all less than 1 nm. The wavelength range suitable for all optical modules includes 1032 nm-1080 nm. The fiber array is as shown in the figure. Figure 4 The size is 16*16, the corresponding reconstructed image pixel number is 16*16, the phase modulator has 256 in total, and the input and output are both fiber channels. The filter module of the receiving end has four, containing four wavelength ranges, the detection module corresponds to the filter module, and also contains four wavelengths. A i (x,y) is the distribution matrix of the fiber array output light field at the i-th illumination, and the matrix size is 16*16. B i The echo signal corresponding to the i-th illumination is a strength value. A(x,y) is the light field data set required for image reconstruction, and B is the echo signal strength data set corresponding to A(x,y) required for image reconstruction. Here, 256 sampling times are set to meet the imaging conditions. The specific imaging steps are as follows:

[0054] Step one: Before the optical correlation imaging system is started, 3000 illumination light field matrices will be generated in advance. According to each illumination light field matrix, the modulation signals corresponding to the 256 phase modulators are calculated.

[0055] Step two: The optical correlation imaging system is started, the trigger module sends a trigger signal to the λ1 waveband light source at t0, and sends corresponding modulation signals to all phase modulation modules.

[0056] Step three: the pulsed light emitted by the light source with wavelength of 1032 nm is divided by the light splitting module into 256 fiber phase modulators, each of which is controlled by the trigger module. Starting from the first light field A1(x, y), the trigger module controls the phase modulator module according to the preset RF signal of the phase modulator corresponding to the current light field, and finally the illumination light field emitted from the tail fiber array of the phase modulator is coupled into the transmitting antenna and irradiated onto the object 2 km away with a divergence angle of 1 mrad, wherein the light field at 2 km is 2 m*2 m in size, and the target object is 1 m*1 m in size.

[0057] Step four: the receiving antenna of the receiving end sends the target reflected echo signal into the light splitting module, the light splitting module divides the echo signal into four parts according to power, and sends them into four different wavelength filters, and then detects the total light intensity by the corresponding wavelength detector after filtering, wherein the detection module with wavelength of 1032 nm has the highest response intensity, and the signal acquisition module records the response value B1 of the detection module.

[0058] Step five: the light source with wavelength of 1032 nm emits a pulse at t0, the light source with wavelength of 1048 nm emits a pulse at t0+Δt, and steps two, three and four are repeated. The light source with wavelength of 1064 nm emits a pulse at t0+2Δt, and steps two, three and four are repeated. The light source with wavelength of 1080 nm emits a pulse at t0+3Δt, and steps two, three and four are repeated.

[0059] Step six: repeat steps two to five above, and the four wavelength light fields are alternately illuminated until the light source with wavelength of 1080 nm emits a pulse at t0+255Δt, and steps two, three and four are repeated. At this time, 256 samples are obtained, which satisfies the image reconstruction condition.

[0060] Step seven: combining A(x, y) containing 256 illumination matrices and B containing 256 intensity values, the signal processing module solves the two-dimensional image of the target by image reconstruction algorithm.

[0061] According to the above-mentioned multi-spectral fiber array illumination optical correlation imaging method, by means of time division multiplexing of multi-wavelength illumination light source and high modulation bandwidth phase modulator, the illumination light field can be modulated quickly, the imaging rate of the system is improved, and the practicability of the optical correlation imaging system is improved.

[0062] In summary, the present application can fully utilize the ultra-high bandwidth of the phase modulator by reasonably utilizing the time division multiplexing method of different wavelength pulsed light sources, improve the modulation rate of the structured light, greatly shorten the data acquisition time of the optical correlation imaging, and speed up the imaging speed.

[0063] The above merely describes preferred implementations of the present application, but the protection scope of the present application is not limited thereto. The selection of the illumination waveband in the present application can be flexibly selected according to specific application scenarios, and any optical correlation imaging method using multi-wavelength illumination, phase modulator modulation, and optical fiber array illumination is within the protection scope of the present application. Any transformation or replacement that can be easily thought of by any person skilled in the art within the disclosed technical scope of the present application should be covered within the protection scope of the present application.

Claims

1. A method of optical correlation imaging of a multi-spectral fiber array illumination, characterized in that, The method comprises the following steps: (1) at the transmitting end, a plurality of pulsed lasers with different wavelengths are selected as seed light sources for illumination in a time-division multiplexing manner; (2) for each seed light source, the seed light source is equally divided into a plurality of beams with equal power according to the number of pixels, and a plurality of phase modulators are used to simultaneously modulate the optical fields of the plurality of beams; (3) the optical fibers at the output ends of all the phase modulators are arranged into an optical fiber array, each optical fiber representing a pixel, and the optical paths of all the light beams from the seed light sources to the output end of the optical fiber array are equal in length; the optical field output by the optical fiber array is coupled and then transmitted to the target through a transmitting antenna; (4) at the receiving end, the light field reflected by the target is received through the receiving antenna, and the received light field is equally divided into a plurality of beams with equal power according to the number of seed light sources; for each divided beam, optical filtering is performed on the divided beam with different center wavelengths, and a corresponding detector is used to measure the total light intensity of the filtered beam; finally, the filtered beam with the maximum total light intensity is selected as the echo signal; (5) after a plurality of illuminations and echo signal detections, the collected data is reconstructed using an image reconstruction method to obtain a two-dimensional image of the target.

2. A multispectral optical fiber array illuminated optical correlation imaging system comprising an emission end, a receiving end and a signal processing module; characterized in that, The transmitting end comprises a plurality of light source modules, a light splitting module, a plurality of phase modulation modules, a trigger module, a coupling module and a transmitting antenna module; the plurality of light source modules are used to emit pulsed lasers with different wavelengths, the light splitting module equally divides the light sources emitted by each light source module in a time-division multiplexing manner, the number of divisions is equal to the number of pixels for imaging, each divided beam is sent into a phase modulation module, the trigger module is used to synchronize the operation of the phase modulation modules and the light source modules, the optical fibers at the output ends of the plurality of phase modulation modules form an optical fiber array, the coupling module couples the optical field signals transmitted by the optical fiber array into the form of antenna transmission, and the target is transmitted through the transmitting antenna module; the signal processing module is used to send light field information to the transmitting end and collect the echo signals transmitted back by the receiving end; the receiving end comprises a signal collection module, a plurality of detection modules, a plurality of filtering modules, a light splitting module and a receiving antenna module; the center wavelength filtered by each filtering module corresponds to the wavelength of the pulsed laser emitted by a light source module of the transmitting end, the detection modules correspond to the filtering modules one by one and are used to detect the total light intensity of the optical field of the corresponding wavelength beam; the receiving antenna module is used to receive the light field reflected by the target, the light splitting module equally divides the light field received by the receiving antenna module into a plurality of beams with equal power according to the number of light source modules of the transmitting end, each divided beam is sent into a filtering module for filtering, and the filtered beam is then sent into the corresponding detection module to obtain the total light intensity of the optical field of the corresponding beam; the signal collection module transmits the beam with the maximum total light intensity as the echo signal to the signal processing module; after receiving the echo signal, the signal processing module first determines whether the required data collection amount is reached, if not, the transmitting end is driven again to emit the light field; after the data collection amount is reached, a plurality of sets of light field information and echo information are used to reconstruct a two-dimensional image of the target using an image reconstruction method.

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