Double-frequency-modulation microcavity optical frequency comb radar single detector parallel detection processing method and device

Abstract

The invention discloses a double-frequency-modulation microcavity optical frequency comb radar single detector parallel detection processing method, and belongs to the field of optical precision measurement. The parallel detection processing system comprises a signal microcavity optical frequency comb and a local oscillator microcavity optical frequency comb which have tiny repetition frequency difference, a signal generator, a circulator, a diffractive optical element, a beam combiner, a balance detector and a multi-path data parallel data acquisition processing module. A signal generator is used for modulating a microcavity optical comb, a signal microcavity optical comb and a local oscillator microcavity optical comb with repetition frequency difference are generated, coaxial transceiving and comb tooth space separation are achieved through a circulator and a diffractive optical element, a single-pixel balance detector and an acquisition and processing module are used for achieving parallel acquisition and processing of multi-path signals of different comb teeth, and the multi-path signals of different comb teeth are acquired and processed. And resolving the distance, angle and speed information of the target object. According to the invention, the frequency asynchronous sampling of the double-microcavity optical comb and the coherent parallel detection of the single-pixel balanced detector are combined, so that the hardware of the frequency-modulated continuous wave radar can be simplified, and the number and cost of the detectors are saved.

Description

Technical Field

[0001] The invention belongs to the field of optical precision measurement and relates to a method and device for parallel detection processing of a single detector of a dual-frequency modulated micro-cavity optical frequency comb radar. Background Art

[0002] Three-dimensional laser radar is of great significance in the fields of machine vision, target recognition, warning and obstacle avoidance, positioning and tracking. Existing three-dimensional laser radar generally requires a combination of multiple light sources, inertial scanning components, multiple detectors, etc., which poses huge challenges in terms of size, cost and stability.

[0003] The optical frequency comb has the characteristics of wide spectrum and multiple longitudinal modes. The repetition rate of the microcavity optical comb reaches tens or even hundreds of GHz. With the help of a signal generator, linear frequency modulation of each comb tooth can be achieved. Combined with diffractive optical elements, spatial separation of different comb teeth can be achieved. Combined with the principle of dual optical comb asynchronous sampling, a balanced detector can be used to achieve parallel detection, collection and processing of multiple signals, simplifying the lidar system, reducing the size and saving costs. Summary of the invention

[0004] In order to realize a laser radar with a single signal light source, inertia-free scanning, and single-pixel detection and processing, the purpose of the present invention is to provide a method and device for parallel detection and processing of a single detector of a dual-frequency modulated micro-cavity optical frequency comb radar, which uses a signal generator to modulate a micro-cavity optical comb to generate a signal micro-cavity optical comb and a local oscillator micro-cavity optical comb with a repetition frequency difference, and realizes coaxial transmission and reception and comb tooth spatial separation through a circulator and a diffractive optical element, and realizes parallel acquisition and processing of multi-channel signals with different comb teeth by using a single-pixel balanced detector and an acquisition and processing module, so as to calculate the distance, angle and speed information of the target object.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] The present invention discloses a dual frequency modulated micro-cavity optical frequency comb radar single detector parallel detection processing method, comprising the following steps:

[0007] Step 1: The signal microcavity optical frequency comb performs triangular wave linear frequency sweep according to the sweep signal given by the signal generator, and outputs multiple signal light comb teeth; the signal light comb teeth are a beam of pulse signals in the time domain, and have the characteristics of equal intervals of comb teeth and a sweep signal with a signal generator in the frequency domain.

[0008] Step 2: After the signal light comb teeth pass through the optical fiber circulator, they are separated into multiple signal light comb teeth in space by the diffractive optical element, and irradiated onto the target at the same time. After passing through the target, they return to the diffractive optical element space to convert multiple light comb teeth into combined light A again, and then output through the optical fiber circulator;

[0009] Step 3: The local oscillator micro-cavity optical frequency comb performs triangular wave linear frequency sweep according to the frequency sweep signal given by the signal generator, and outputs multiple local oscillator optical comb teeth; the multiple local oscillator optical comb teeth are also a beam of pulse signals in the time domain of the signal optical comb teeth, and have the characteristics of equal intervals of comb teeth and frequency sweep signals with signal generators in the frequency domain. However, the repetition frequency of the local oscillator micro-cavity optical frequency comb has a slight repetition frequency difference with the repetition frequency of the signal micro-cavity optical frequency comb.

[0010] Step 4: The combined light beam A of step 2 and the local oscillator light comb teeth of step 3 enter the beam combiner. After the signal light comb teeth and the local oscillator light comb teeth are combined, the different comb teeth beat each other, which is detected by the balanced detector and converted into an electrical signal to obtain an electrical signal C. The distance, angle and speed information of each comb tooth corresponding to the target object itself are calculated according to the electrical signal C.

[0011] The distance calculation formula is:

[0012]

[0013] The angle calculation formula is:

[0014]

[0015] The speed calculation formula is:

[0016]

[0017] Where n is the number of the light comb teeth, L n is the distance of the target point corresponding to the nth signal light comb tooth, and c is the speed of light 3×10 8 m / s, t is the flight time of light, B is the sweep width 50MHz, f u (n) is the upper frequency after the beat between the nth signal light comb tooth and the nth fundamental oscillator comb tooth, f d (n) is the lower frequency after the beat between the nth signal light comb tooth and the nth fundamental oscillator light comb tooth, θ n is the diffraction angle corresponding to the nth comb tooth, that is, the angle information of the target, λ n is the laser wavelength of the nth signal light comb tooth, d is the slit spacing of the diffractive optical element 1 μm, m is the spectral order, v n is the speed of the point corresponding to the target at the nth signal light comb tooth, △f r The repetition frequency difference between the signal microcavity optical frequency comb and the local oscillator microcavity optical frequency comb. According to the sweep width, the upper and lower frequencies of the beat frequency comb teeth, the slit spacing of the diffractive optical element, the laser wavelength,

[0018] The minute repetition frequency difference refers to a repetition frequency difference between 1 kHz and 500 MHz.

[0019] The device for parallel detection and processing of a single detector of a dual-frequency modulated micro-cavity optical frequency comb radar is used to implement the method for parallel detection and processing of a single detector of a dual-frequency modulated micro-cavity optical frequency comb radar. The device for parallel detection and processing of a single detector of a dual-frequency modulated micro-cavity optical frequency comb radar comprises two signal micro-cavity optical frequency combs and a local oscillator micro-cavity optical frequency comb with a small repetition frequency difference, a signal generator, a circulator, a diffractive optical element, a beam combiner, a balanced detector and a multi-channel data parallel data acquisition and processing module.

[0020] The signal generator outputs a linear frequency modulated triangle wave to modulate the offset frequencies of the signal microcavity optical frequency comb and the local oscillator microcavity optical frequency comb, so that each comb tooth is linearly frequency modulated. The signal microcavity optical comb is used as a signal light. After passing through a circulator and a diffractive optical element, different comb teeth are separated in space. After being irradiated to the target object and diffusely reflected back along the original path, it passes through the diffractive optical element and is spatially combined into a beam of return comb tooth light, i.e., return signal light. After passing through the circulator, the return signal light and the local oscillator microcavity optical frequency comb are combined into one through a beam combiner, and then passed through a balanced detector to detect the coherent beat signal. Since the signal optical frequency comb and the local oscillator optical frequency comb have a small repetition frequency difference, the beat signals between different comb teeth are separated in frequency. A balanced detector can realize the measurement of the distance and speed information of the target by multiple comb teeth in different spaces. After passing through a multi-channel signal data acquisition and processing module, in conjunction with the comb tooth spatial angle information corresponding to the diffractive optical element, the multi-dimensional information solution of the distance, angle, and speed of the target object corresponding to the multiple comb teeth is realized.

[0021] The two microcavity optical combs are microcavity optical combs with repetition frequency difference and linear frequency modulation, and the linear frequency modulation includes triangle wave modulation and sawtooth wave modulation.

[0022] The single-pixel detector is one of a balanced detector and a single-photon detector.

[0023] Beneficial effects:

[0024] 1. The present invention discloses a method and device for parallel detection and processing of a single detector of a dual-frequency modulated microcavity optical frequency comb radar. A signal generator is used to modulate a microcavity optical comb to generate a signal microcavity optical comb and a local oscillator microcavity optical comb with a repetition frequency difference. A circulator and a diffractive optical element are used to realize coaxial transmission and reception and comb tooth spatial separation. A single-pixel balanced detector and an acquisition and processing module are used to realize parallel acquisition and processing of multi-channel signals with different comb teeth, and the distance, angle and speed information of the target object are calculated. The method and device can realize coherent parallel detection and acquisition processing of multi-channel ranging signals corresponding to different comb teeth of the microcavity optical comb frequency modulated continuous wave radar, and realize single-pixel detection and processing of multi-channel radar ranging signals.

[0025] 2. Traditional laser radars require an inertial scanning device, and multiple light sources and multiple detectors to perform three-dimensional point cloud imaging. The system structure is complex and the cost is high. The present invention discloses a dual-frequency modulated micro-cavity optical frequency comb radar single detector parallel detection processing method and device, which combines the frequency asynchronous sampling of the dual micro-cavity optical comb and the coherent parallel detection technology of the single-pixel balanced detector. Only one signal optical frequency comb, one local oscillator optical frequency comb, and one balanced detector are needed to realize multi-channel parallel detection processing of a single-pixel detector without an inertial device, which simplifies the hardware of the frequency modulated continuous wave radar and saves the number and cost of detectors. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of a single detector parallel detection and processing device for a dual frequency modulated microcavity optical frequency comb radar;

[0027] Figure 2 This is the schematic diagram of the parallel detection processing of a single detector of a dual-frequency modulated microcavity optical frequency comb radar;

[0028] Among them, 1 is a signal generator, 2 is a signal microcavity optical frequency comb, 3 is a circulator, 4 is a diffractive optical element, 5 is a local oscillator microcavity optical frequency comb, 6 is a beam combiner, 7 is a balanced detector, and 8 is a multi-channel signal parallel acquisition and processing module. DETAILED DESCRIPTION

[0029] In order to better illustrate the purpose and advantages of the present invention, the invention is further described below with reference to the accompanying drawings and examples.

[0030] Embodiment 1:

[0031] like Figure 2 As shown, the single detector parallel detection processing method of the dual frequency modulated microcavity optical frequency comb radar disclosed in this embodiment is specifically implemented in the following steps:

[0032] Step 1. The signal microcavity optical frequency comb 2 performs triangular wave linear frequency sweep according to the frequency sweep signal given by the signal generator 1, and outputs multiple signal light comb teeth; the signal light comb teeth are a beam of pulse signals in the time domain, and have the characteristics of equal intervals of comb teeth in the frequency domain and a frequency sweep signal with the signal generator 1. The repetition frequency of the signal microcavity optical frequency comb 2 is 100GHz, the spectral width covers 1530nm-1630nm, the frequency sweep period is 10μs, and the frequency sweep range is 50MHz.

[0033] Step 2: After the signal light comb teeth pass through the optical fiber circulator 3, they are separated into multiple signal light comb teeth in space by the diffractive optical element 4, and irradiated onto the target at the same time. After passing through the target, they return to the diffractive optical element 4 along the original path, and the multiple light comb teeth are converted into combined light A in space again, and then outputted by the optical fiber circulator 3;

[0034] Step 3: The local oscillator microcavity optical frequency comb 5 performs triangular wave linear frequency sweep according to the frequency sweep signal given by the signal generator 1, and outputs multiple local oscillator optical comb teeth; the multiple local oscillator optical comb teeth are also a beam of pulse signals in the time domain of the signal optical comb teeth, and have the characteristics of comb teeth being equally spaced in the frequency domain and having the frequency sweep signal of the signal generator 1. However, the repetition frequency of the local oscillator microcavity optical frequency comb 5 has a slight repetition frequency difference with the repetition frequency of the signal microcavity optical frequency comb 2. The repetition frequency of the local oscillator microcavity optical frequency comb 5 is 100.3GHz, the repetition frequency difference is 300MHz, the spectrum width covers 1530nm-1630nm, the frequency sweep period is 10μs, and the frequency sweep range is 50MHz.

[0035] Step 4: The combined light beam A of step 2 and the local oscillator light comb teeth of step 3 enter the beam combiner 6. After the signal light comb teeth and the local oscillator light comb teeth are combined, the different comb teeth beat each other, which is detected by the balanced detector 7 and converted into an electrical signal to obtain an electrical signal C. The distance, angle and speed information of each comb tooth corresponding to the target object itself are calculated according to the electrical signal C.

[0036] The distance calculation formula is:

[0037]

[0038] The angle calculation formula is:

[0039]

[0040] The speed calculation formula is:

[0041]

[0042] Where n is the number of the light comb teeth, L n is the distance of the target point corresponding to the nth signal light comb tooth, c is the speed of light, t is the flight time of light, B is the sweep width 50MHz, f u (n) is the upper frequency after the beat between the nth signal light comb tooth and the nth fundamental oscillator comb tooth, f d (n) is the lower frequency after the beat between the nth signal light comb tooth and the nth fundamental oscillator light comb tooth, θ n is the diffraction angle corresponding to the nth comb tooth, that is, the angle information of the target, λ n is the laser wavelength of the nth signal light comb tooth, d is the slit spacing of the diffractive optical element 4, m is the spectral order, v n is the speed of the point corresponding to the target at the nth signal light comb tooth, △f r The repetition frequency difference between the signal microcavity optical frequency comb 2 and the local oscillator microcavity optical frequency comb 5 is 300MHz.

[0043] The minute repetition frequency difference refers to a repetition frequency difference between 1 kHz and 500 MHz.

[0044] like Figure 1As shown, a dual-frequency modulated micro-cavity optical frequency comb radar single detector parallel detection processing device is used to implement the dual-frequency modulated micro-cavity optical frequency comb radar single detector parallel detection processing method. The dual-frequency modulated micro-cavity optical frequency comb radar single detector parallel detection processing device includes two signal micro-cavity optical frequency combs 2 and a local oscillator micro-cavity optical frequency comb 5 with a small repetition frequency difference, a signal generator 1, a circulator 3, a diffractive optical element 4, a beam combiner 6, a balanced detector 7 and a multi-channel data parallel data acquisition processing module 8.

[0045] The signal generator 1 outputs a linear frequency modulated triangle wave, which modulates the offset frequency of the signal microcavity optical frequency comb 2 and the local oscillator microcavity optical frequency comb 5, so that each comb tooth is frequency modulated by a linear triangle wave, which is equivalent to multiple frequency modulated continuous wave lasers of different frequency bands being emitted simultaneously. The signal microcavity optical comb 2 is used as the signal light, which passes through the circulator 3 and the diffractive optical element 4 to separate the different comb teeth in space, irradiates the target object, diffusely reflects the original path and returns, and then passes through the diffractive optical element 4 to be combined into a beam of return comb tooth light in space, that is, the return signal light. After passing through the circulator 3, the return signal light and the local oscillator microcavity The optical frequency comb 5 is combined into one by a beam combiner 6, and then passes through a balanced detector 7 to detect the coherent beat signal. Since the signal optical frequency comb and the local oscillator optical frequency comb have a small repetition frequency difference, the beat signals between different comb teeth are separated in frequency. A balanced detector 7 can realize the measurement of the distance and speed information of the target by multiple comb teeth in different spaces. Through the multi-channel signal data acquisition and processing module 8, in conjunction with the comb tooth spatial angle information corresponding to the diffractive optical element 4, the multi-dimensional information solution of the distance, angle and speed of the target object corresponding to the multiple comb teeth is realized.

[0046] The two microcavity optical combs are microcavity optical combs with repetition frequency difference and linear frequency modulation, and the linear frequency modulation includes triangle wave modulation and sawtooth wave modulation.

[0047] The single pixel detector is one of a balanced detector 7 and a single photon detector.

[0048] The specific description above further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A single detector parallel detection and processing method for a dual frequency modulated microcavity optical frequency comb radar, characterized in that: The following steps are included: Step 1: The signal microcavity optical frequency comb performs triangular wave linear frequency sweep according to the frequency sweep signal given by the signal generator, and outputs a plurality of signal light comb teeth; the signal light comb teeth are a beam of pulse signals in the time domain, and have the characteristics of comb teeth being equally spaced and having a frequency sweep signal of a signal generator in the frequency domain; Step 2: After the signal light comb teeth pass through the optical fiber circulator, they are separated into multiple signal light comb teeth in space by the diffractive optical element, and irradiated onto the target at the same time. After passing through the target, they return to the diffractive optical element space to convert multiple light comb teeth into combined light A again, and then output through the optical fiber circulator; Step 3: The local oscillator microcavity optical frequency comb performs triangular wave linear frequency sweep according to the frequency sweep signal given by the signal generator, and outputs a plurality of local oscillator optical comb teeth; the plurality of local oscillator optical comb teeth are also a beam of pulse signals in the time domain at the same time as the signal optical comb teeth, and have the characteristics of equal intervals of comb teeth and frequency sweep signals with signal generator in the frequency domain; however, the repetition frequency of the local oscillator microcavity optical frequency comb and the repetition frequency of the signal microcavity optical frequency comb have a slight repetition frequency difference; Step 4: The combined light beam A of step 2 and the local oscillator light comb teeth of step 3 enter the beam combiner. After the signal light comb teeth and the local oscillator light comb teeth are combined, the different comb teeth beat each other, which is detected by the balanced detector and converted into an electrical signal to obtain an electrical signal C. The distance, angle and speed information of each comb tooth corresponding to the target object itself are calculated according to the electrical signal C. The distance calculation formula is: The angle calculation formula is: The speed calculation formula is: Where n is the number of the light comb teeth, L n is the distance of the target point corresponding to the nth signal light comb tooth, c is the speed of light, t is the flight time of light, B is the sweep width, f u (n) is the upper frequency after the beat between the nth signal light comb tooth and the nth fundamental oscillator comb tooth, f d (n) is the lower frequency after the beat between the nth signal light comb tooth and the nth fundamental oscillator light comb tooth, θ n is the diffraction angle corresponding to the nth comb tooth, that is, the angle information of the target, λ n is the laser wavelength of the nth signal light comb tooth, d is the slit spacing of the diffractive optical element, m is the spectral order, v n is the speed of the point corresponding to the target at the nth signal light comb tooth, △f r The repetition frequency difference between the signal microcavity optical frequency comb and the local oscillator microcavity optical frequency comb.

2. The method for parallel detection and processing of a single detector of a dual frequency modulated microcavity optical frequency comb radar according to claim 1, characterized in that: The minute repetition frequency difference refers to a repetition frequency difference between 1 kHz and 500 MHz.

3. A dual-frequency modulated micro-cavity optical frequency comb radar single detector parallel detection processing device, used to implement the dual-frequency modulated micro-cavity optical frequency comb radar single detector parallel detection processing method as claimed in claim 1 or 2, characterized in that: It includes two signal micro-cavity optical frequency combs and local oscillator micro-cavity optical frequency combs with small repetition frequency difference, a signal generator, a circulator, a diffractive optical element, a beam combiner, a balanced detector and a multi-channel data parallel data acquisition and processing module; The signal generator outputs a linear frequency modulated triangle wave to modulate the offset frequencies of the signal microcavity optical frequency comb and the local oscillator microcavity optical frequency comb, so that each comb tooth is linearly frequency modulated. The signal microcavity optical comb is used as a signal light. After passing through a circulator and a diffractive optical element, different comb teeth are separated in space. After being irradiated to the target object and diffusely reflected back along the original path, it passes through the diffractive optical element and is spatially combined into a beam of return comb tooth light, i.e., return signal light. After passing through the circulator, the return signal light and the local oscillator microcavity optical frequency comb are combined into one through a beam combiner, and then passed through a balanced detector to detect the coherent beat signal. Since the signal optical frequency comb and the local oscillator optical frequency comb have a small repetition frequency difference, the beat signals between different comb teeth are separated in frequency. A balanced detector can realize the measurement of the distance and speed information of the target by multiple comb teeth in different spaces. After passing through a multi-channel signal data acquisition and processing module, in conjunction with the comb tooth spatial angle information corresponding to the diffractive optical element, the multi-dimensional information solution of the distance, angle, and speed of the target object corresponding to the multiple comb teeth is realized.

4. The dual frequency modulated microcavity optical frequency comb radar single detector parallel detection and processing device as claimed in claim 3, characterized in that: The two microcavity optical combs are microcavity optical combs with repetition frequency difference and linear frequency modulation, and the linear frequency modulation includes triangle wave modulation and sawtooth wave modulation.

5. The dual frequency modulated microcavity optical frequency comb radar single detector parallel detection processing device as claimed in claim 3, characterized in that: The single-pixel detector is one of a balanced detector and a single-photon detector.

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