Signal light detection device and distance and speed measurement system
By adopting a combination of beam splitting module, mixing module and bidirectional light detection module in the FMCW lidar system, the coherent mixing instability caused by uncertain polarization state of reflected signal is solved, which improves the detection accuracy and simplifies the difficulty of system integration.
Patent Information
- Application Number
- CN202410022061.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-01-05
- Publication Date
- 2025-07-08
AI Technical Summary
In traditional FMCW lidar systems, the uncertain polarization state of the reflected signal light leads to coherent mixing instability, affecting detection accuracy, and the use of spatial crystal polarization beam splitters increases the difficulty of system integration.
By adopting the combination of the first beam splitting module, the frequency mixing module, the first bidirectional light detection module, the second bidirectional light detection module and the differential output module, the detection of light of any polarization echo signal is realized inside the device, and the photoelectric conversion is performed using the polarization beam splitting rotation module and the bidirectional light detection module to generate a target detection electrical signal.
It stabilizes the beat frequency signal, improves the signal detection accuracy, simplifies the difficulty of system design and assembly, reduces the difficulty of integration, and facilitates mass production.
Smart Images
Figure CN120275938A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the technical field of optical devices, and particularly to a signal light detection device and a ranging and velocity measuring system. Background Art
[0002] FMCW (Frequency Modulated Continuous Wave) lidar uses the principle of coherent detection and can detect objects in free space while reducing the requirements for the laser emission power. The output light of the frequency-modulated light source used in FMCW lidar is usually a linearly polarized light. When the laser is emitted into free space and reflected by an object in the space, a part of the reflected light is received by the transceiver chip module and mixed with the local light to obtain the distance information and velocity information of the object.
[0003] However, the polarization state of the reflected echo of a space object is usually uncertain. When the local light is coherently mixed with the signal light of the reflected echo, only a part of the light energy with the same polarization direction as the local light in the reflected signal light will perform coherent beat frequency, while the light component orthogonal to the vibration direction of the local light will not be coherent and become noise.
[0004] In traditional technologies, to overcome the above problems, a spatial crystal polarization beam splitter is usually set to perform orthogonal polarization state decomposition on the echo signal light, and a half-wave plate is set to rotate the polarization direction of one of the lights, so as to obtain two echo signal lights with the same polarization direction, and then mix them with the local light. Although this scheme can exclude the interference of optical fibers, it involves the coupling alignment between the spatial crystal and the chip, so the assembly difficulty is relatively large, resulting in a relatively high integration difficulty of the system. Summary of the Invention
[0005] Based on this, it is necessary to provide a signal light detection device and a ranging and velocity measuring system that can reduce the integration difficulty for the above technical problems.
[0006] In a first aspect, this application provides a signal light detection device, which includes a first beam splitting module, a mixing module, a first bidirectional optical detection module, a second bidirectional optical detection module, and a first differential output module, where,
[0007] The first beam splitting module is configured to split the input light, output the detection light to the target detection space, and output the local light to the mixing module;
[0008] The mixing module is configured to receive the echo signal light, mix the local light and the echo signal light, output the first mixed signal light and the second mixed signal light to the first bidirectional optical detection module, and output the third mixed signal light and the fourth mixed signal light to the second bidirectional optical detection module. The echo signal light is formed by the detection light being reflected by a target object in the target detection space.
[0009] The first bidirectional optical detection module is configured to perform photoelectric conversion on the first mixed signal light and the second mixed signal light, and output a first electrical signal to the first differential output module.
[0010] The second bidirectional optical detection module is configured to perform photoelectric conversion on the third mixed signal light and the fourth mixed signal light, and output a second electrical signal to the first differential output module.
[0011] The first differential output module is configured to generate a target detection electrical signal based on the first electrical signal and the second electrical signal.
[0012] In one embodiment, the mixing module includes a second beam splitting module, a polarization beam splitting and rotation module, a first mixing unit, and a second mixing unit. Among them,
[0013] The second beam splitting module is configured to split the local light, output a first local light to the first mixing unit, and output a second local light to the second mixing unit.
[0014] The polarization beam splitting and rotation module is configured to receive the echo signal light, perform polarization beam splitting and rotation on the echo signal light, output a first signal light to the first mixing unit, and output a second signal light to the second mixing unit.
[0015] The first mixing unit is configured to mix the first local light and the first signal light, output the first mixed signal light to the first bidirectional optical detection module, and output the third mixed signal light to the second bidirectional optical detection module.
[0016] The second mixing unit is configured to mix the second local light and the second signal light, output the second mixed signal light to the first bidirectional optical detection module, and output the fourth mixed signal light to the second bidirectional optical detection module.
[0017] In one embodiment, the device further includes a third beam splitting module, a fourth beam splitting module, a delay module, a third mixing unit, a first unidirectional optical detection module, a second unidirectional optical detection module, and a second differential output module. The device is connected to a light source module. Among them,
[0018] The third beam splitting module is configured to split the local light, output a third local light to the fourth beam splitting module, and output a fourth local light as the local light input to the mixing module;
[0019] The fourth beam splitting module is configured to split the third local light, output a fifth local light to the delay module, and output a sixth local light to the third mixing unit;
[0020] The delay module is configured to delay the fifth local light by a preset time and then output a seventh local light to the third mixing unit;
[0021] The third mixing unit is configured to mix the sixth local light and the seventh local light, output a fifth mixing signal to the first unidirectional optical detection module, and output a sixth mixing signal to the second unidirectional optical detection module;
[0022] The first unidirectional optical detection module is configured to perform photoelectric conversion on the fifth mixing signal light and output a third electrical signal to the second differential output module;
[0023] The second unidirectional optical detection module is configured to perform photoelectric conversion on the sixth mixing signal light and output a fourth electrical signal to the second differential output module;
[0024] The second differential output module is configured to generate a feedback electrical signal based on the third electrical signal and the fourth electrical signal and input it to the light source module, so that the light source module corrects the frequency tuning linearity of the input light based on the feedback electrical signal.
[0025] In one embodiment, the first bidirectional optical detection module and the second bidirectional optical detection module each include a photosensitive region, and the photosensitive region sequentially includes a silicon substrate, a silicon dioxide insulating layer, a silicon waveguide, a P-type doped region on the surface of the silicon waveguide, a germanium waveguide region, and an N-type doped region on the surface of the germanium waveguide.
[0026] In one embodiment, each beam splitting module includes a directional coupler, and the directional coupler is configured to split the input light proportionally based on a preset coupling pitch and a preset coupling length.
[0027] In one embodiment, each mixing unit includes a 180-degree mixer, and the 180-degree mixer includes:
[0028] A 180-degree mixer based on a 50:50 multimode interferometer, or a 180-degree mixer based on a 50:50 directional coupler.
[0029] In one embodiment, the polarization beam splitting and rotation module includes a two-dimensional grating coupler, wherein,
[0030] The two-dimensional grating coupler is configured to couple the echo signal light with arbitrary polarization into the transverse electric fundamental mode polarization light in two receiving waveguides, that is, to generate the first signal light and the second signal light.
[0031] In one embodiment, the polarization beam splitting and rotation module includes a polarization rotation structure and a separation waveguide structure, wherein,
[0032] The polarization rotation structure and the separation waveguide structure are configured to couple the echo signal light with arbitrary polarization into the orthogonal first transverse electric fundamental mode polarization and transverse magnetic fundamental mode polarization in the waveguide, and then convert the transverse magnetic fundamental mode polarization into the second transverse electric fundamental mode polarization in the separation waveguide structure through the polarization rotation structure and the separation waveguide structure, and use the first transverse electric fundamental mode polarization and the second transverse electric fundamental mode polarization as the first signal light and the second signal light respectively.
[0033] In a second aspect, the present application also provides a ranging and velocity measuring system. The system includes a light source module, a ranging and velocity measuring module, and a signal light detection device as described in any one of claims 1 to 8. The signal light detection device is respectively connected to the light source module and the ranging and velocity measuring module, wherein,
[0034] The light source module is configured to input the output frequency-modulated light into the signal light detection device, receive the feedback electrical signal output by the signal light detection device, and correct the frequency modulation linearity of the output frequency-modulated light based on the feedback electrical signal;
[0035] The ranging and velocity measuring module is configured to receive the target detection electrical signal output by the signal light detection device and perform ranging and velocity measurement on the target object based on the target detection electrical signal.
[0036] In one embodiment, the light source module and the signal light detection device are connected by any one of heterogeneous integration, package integration, or fiber connection.
[0037] In the above signal light detection device and ranging and velocity measuring system, the device includes a first beam splitting module, a mixing module, a first bidirectional optical detection module, a second bidirectional optical detection module, and a first differential output module. Among them, the first beam splitting module is used to split the input light into local light and output detection light emitted into the target detection space; the mixing module is used to mix the echo signal light and the local light; the first bidirectional optical detection module and the second bidirectional optical detection module are respectively used to perform photoelectric conversion on the mixed signal light, and finally the target detection electrical signal is generated by the differential output module. The optical detection device and ranging and velocity measuring system provided by this application are not affected by the polarization change of the echo signal light in the detection result, can greatly stabilize the beat frequency signal, and improve the signal detection accuracy. On the other hand, by realizing the detection of echo signal light with any polarization state inside the device, there is no need to set additional accessories outside the device to process polarization, which greatly simplifies the design and assembly difficulty of the system, effectively reduces the integration difficulty, and is easy to mass-produce.
[0038] Details of one or more embodiments of this application are set forth in the following drawings and description, so that other features, objects, and advantages of this application will become more concise and understandable. BRIEF DESCRIPTION OF THE DRAWINGS
[0039] The drawings described herein are used to provide a further understanding of this application, and constitute a part of this application. The schematic embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation to this application. In the drawings:
[0040] Figure 1 is a schematic diagram of an optical detection device in the prior art;
[0041] Figure 2 is a structural block diagram of a signal light detection device in one embodiment;
[0042] Figure 3 is a structural block diagram of a signal light detection device in another embodiment;
[0043] Figure 4 is a schematic diagram of a polarization beam splitting and rotating module in one embodiment;
[0044] Figure 5 is a schematic diagram of a polarization beam splitting and rotating module in another embodiment;
[0045] Figure 6 is a schematic diagram of a unidirectional optical detection module and a bidirectional optical detection module in one embodiment;
[0046] Figure 7 is a schematic diagram of a beam splitter in one embodiment;
[0047] Figure 8 is a schematic diagram of a mixing unit in one embodiment. Detailed implementation manners
[0048] In order to make the objectives, technical solutions and advantages of the present application clearer and more understandable, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.
[0049] Unless otherwise defined, the technical terms or scientific terms involved in the present application shall have the general meanings understood by those with ordinary skills in the technical field to which the present application belongs. In the present application, words such as "a", "one", "a kind of", "the", "these", etc. do not indicate a limitation in quantity, and they can be singular or plural. The terms "including", "comprising", "having" and any variations thereof involved in the present application are intended to cover non-exclusive inclusion; for example, a process, method, system, product or device including a series of steps or modules (units) is not limited to the listed steps or modules (units), but may include unlisted steps or modules (units), or may include other steps or modules (units) inherent in these processes, methods, products or devices. The terms "connection", "connection", "coupling", etc. involved in the present application are not limited to physical or mechanical connections, but may include electrical connections, whether directly or indirectly. The "multiple" involved in the present application refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" may represent: A exists alone, A and B exist simultaneously, and B exists alone. Usually, the character " / " indicates that the objects associated before and after are in an "or" relationship. The terms "first", "second", "third", etc. involved in the present application are only used to distinguish similar objects and do not represent a specific order for the objects.
[0050] The following terms "module", "unit", etc. are combinations of software and / or hardware that can achieve a predetermined function. Although the devices described in the following embodiments are preferably implemented in hardware, implementation in software, or a combination of software and hardware is also possible and contemplated.
[0051] First, the solutions in the traditional technology will be described.
[0052] The FMCW lidar utilizes the coherent detection principle and can achieve long-range detection while reducing the requirements for the laser emission power. The detection light source usually adopts triangular wave modulation, which has rising and falling frequency modulation bands. When the local frequency-modulated continuous wave and the frequency-modulated continuous wave reflected by the object are beat, the beat signal will contain beat signals in both the rising and falling frequency modulation bands. The average value and frequency difference of these two beat signals respectively reflect the distance and radial motion speed of the object, and based on this, ranging and velocity measurement of the object can be realized. In traditional technologies, the three key parts of the FMCW lidar system are the frequency-modulated light source module, the transceiver chip module, and the beam scanning module. Combining these three modules and equipped with corresponding hardware and software can realize the four-dimensional point cloud data scanning of the environmental space.
[0053] In traditional technologies, the output light of the FMCW lidar frequency-modulated light source is linearly polarized light. This linearly polarized light is divided into local light and transmitted light after passing through the chip. The transmitted light is emitted into free space through the beam scanning module. After being reflected by an object in the space, a part of the reflected light is received by the transceiver chip module and is beat with the local light to obtain the distance and velocity information of the object. The transceiver chip usually operates in a single polarization, and this single polarization is usually the TE (Transverse Electric, transverse electric fundamental mode) polarization in the waveguide (the polarization direction is parallel to the chip substrate). The frequency-modulated light source is coupled with the transceiver chip through a polarization-maintaining fiber or directly integrates the frequency-modulated laser and the transceiver chip through a hybrid integration method. The output light of the frequency-modulated laser is usually TE-polarized light, so the transceiver chip also operates in TE polarization, and thus its transmitted light is also a single TE polarization.
[0054] However, in most cases, the polarization direction of the transmitted light usually changes after being reflected by an object in the environmental space. The vibration direction of the reflected light can be decomposed into orthogonal TE and TM (Transverse Magnetic, transverse magnetic fundamental mode) polarizations (the polarization direction is perpendicular to the chip substrate) relative to the optical waveguide chip. According to the coherent detection principle, the two interfering light beams need to have the same vibration direction. The TE polarization component in the part of the reflected light received by the transceiver chip will interfere with the local light (TE polarization) to obtain a beat signal. The TM-polarized light of the reflected light will not interfere with the local light and become noise, affecting the signal-to-noise ratio of the entire detection system. In particular, for a system that receives the reflected echo through an optical fiber, affected by the optical fiber, the type of environmental object, and the incident angle of the transmitted light on the object, the polarization of the reflected echo received by the transceiver chip will change randomly, resulting in unstable or even disappearance of the beat signal, which will seriously affect the accuracy of the detection result. Therefore, it is necessary to adopt a polarization classification scheme for receiving and detecting the reflected echo, that is, it is necessary to receive and detect both orthogonal light components of the reflected echo.
[0055] The main principle of the FMCW-based single-point ranging and velocity-measuring coherent lidar is to split the incident light of the light source into two parts. Most of the light is emitted into the ambient space, while a smaller part of the light serves as the local light. The echo signal light reflected by an object in the ambient space is then coherently beat with the local light. Due to the large waveguide birefringence in the silicon photonics chip, the silicon photonics chip usually operates in a single polarization (usually TE polarization). However, the polarization state of the reflected echo is usually uncertain. When the local light and the reflected echo signal light are coherently mixed on the silicon photonics chip, only a part of the light energy with the same polarization direction as the local light in the reflected signal light will perform coherent beating, while the light component orthogonal to the vibration direction of the local light will not be coherent and become noise. Figure 1 Shown is a schematic diagram of an optical detection device based on a silicon photonics platform in the prior art. It consists of a beam splitter, a mixer, and two unidirectional photodetectors. The output light of the frequency-modulated light source enters the beam splitter and is divided into two paths. One path of TE e polarized transmitted light is emitted into space, and the other path is local TE L polarized light. e The TE S polarized transmitted light encounters the echo signal light (coupled TE S and TM L polarized light components in the waveguide) reflected by the target object and the local TE S polarized light for coherent mixing. Since the coherence is interference in the same polarization direction, only the TE S polarized component in the echo signal participates in the mixing, while the TM L polarized light component will not be coherent with the local TE Figure 1 polarized light and becomes noise. Therefore, the scheme shown sacrifices the signal intensity.
[0056] To overcome the above problems, the echo signal light is orthogonally polarization decomposed by a spatial crystal polarization beam splitter, and at the same time, a half-wave plate is used to rotate the polarization direction of one path of light, so as to obtain two paths of echo signal light with the same polarization direction, and then they are respectively coherently mixed with the two paths of local TE polarized light on the silicon photonics chip, and finally the two paths are combined to obtain the beat signal. Although this scheme can exclude the interference of the optical fiber, it involves the coupling alignment between the spatial crystal and the chip, and the assembly difficulty is large. There are great difficulties in the miniaturization and integration of the system.
[0057] Based on this, the present application provides a signal light detection device, as shown in Figure 2As shown, the device includes a first beam splitting module, a mixing module, a first bidirectional optical detection module, a second bidirectional optical detection module, and a first differential output module. Among them, the first beam splitting module is used to split the input light, output the detection light into the target detection space, and output the local light to the mixing module; the mixing module is used to receive the echo signal light, mix the local light and the echo signal light, output the first mixed signal light and the second mixed signal light to the first bidirectional optical detection module, and output the third mixed signal light and the fourth mixed signal light to the second bidirectional optical detection module. The echo signal light is formed by the detection light being reflected by the target in the target detection space; the first bidirectional optical detection module is used to perform photoelectric conversion on the first mixed signal light and the second mixed signal light, and output the first electrical signal to the first differential output module; the second bidirectional optical detection module is used to perform photoelectric conversion on the third mixed signal light and the fourth mixed signal light, and output the second electrical signal to the first differential output module; the first differential output module is used to generate the target detection electrical signal based on the first electrical signal and the second electrical signal.
[0058] In the embodiment of the present application, the first beam splitting module may include an optical beam splitter, and the optical beam splitter may include a glass prism, a semi-silvered mirror, or a dichroic mirror prism structure. The present application does not limit the specific structure of the optical beam splitter. The first beam splitting module is used to split the input light and output the detection light TE e into the target detection space, and output the local light TE L to the mixing module.
[0059] In the embodiment of the present application, the echo signal light with any polarization is formed by the detection light being reflected by the target in the target detection space. The echo signal light with any polarization state is coupled into the TE S and TM S polarized light components of the waveguide. The mixing module may include two mixing units and a polarization beam splitting and rotation module, and is used to receive the TE S1 and TE S2 signal lights in the corresponding two waveguides generated after the echo signal light with any polarization passes through the polarization beam splitting and rotation module, and mix the local light TE L with the echo signal light TE S1 and TE S2 to output the first mixed signal light TE LS1B and the second mixed signal light TE LS2A to the first bidirectional optical detection module, and output the third mixed signal light TE LS1A and the fourth mixed signal light TE LS2B to the second bidirectional optical detection module.
[0060] In some embodiments, such asFigure 3 As shown, the mixing module includes a second beam splitting module, a polarization beam splitting and rotating module, a first mixing unit, and a second mixing unit. Among them, the second beam splitting module is used to split the local optical TE L and output the first local optical TE L1 to the first mixing unit, and output the second local optical TE L2 to the second mixing unit; the polarization beam splitting and rotating module is used to receive the echo signal optical TE S and TM S , and split and rotate the echo signal optical TE S and TM S , and output the first signal optical TE S1 to the first mixing unit, and output the second signal optical TE S2 to the second mixing unit; the first mixing unit is used to mix the first local optical TE L1 and the first signal optical TE S1 , and output the first mixed signal optical TE LS1B to the first bidirectional optical detection module, and output the third mixed signal optical TE LS1A to the second bidirectional optical detection module; the second mixing unit is used to mix the second local optical TE L2 and the second signal optical TE S2 , and output the second mixed signal optical TE LS2A to the first bidirectional optical detection module, and output the fourth mixed signal optical TE LS2B to the second bidirectional optical detection module.
[0061] Specifically, the polarization beam splitting and rotating module is used to separate the echo signal optical with any polarization into TE S polarized light and TM S polarized light, and at the same time used to rotate the TM S polarized light into the TE S polarized light in the waveguide, and finally obtain the first signal optical TE S1 and the second signal optical TE S2 .
[0062] In some embodiments, the polarization beam splitting and rotating module includes a two-dimensional grating coupler. Among them, the two-dimensional grating coupler is used to couple the echo signal optical with any polarization into the transverse electric fundamental mode polarized light in two receiving waveguides, that is, generate the first signal optical and the second signal optical. In some specific embodiments, the polarization beam splitting and rotating module is as Figure 4As shown, it is a 2D grating coupler that can decompose the input light 1 with a random polarization state in the optical fiber into two orthogonal components 4 with respect to the output waveguides 2 and 3, and couple them into the TE0 mode in the waveguides for transmission respectively.
[0063] In some other embodiments, the polarization beam splitting and rotation module includes a polarization rotation structure and a separation waveguide structure. Among them, the polarization rotation structure and the separation waveguide structure are used to couple the echo signal light with any polarization into the orthogonal first transverse electric fundamental mode polarization and transverse magnetic fundamental mode polarization in the waveguide, and then convert the transverse magnetic fundamental mode polarization into the second transverse electric fundamental mode polarization in the separation waveguide structure through the polarization rotation structure and the separation waveguide structure, and use the first transverse electric fundamental mode polarization and the second transverse electric fundamental mode polarization as the first signal light and the second signal light respectively.
[0064] In some specific embodiments, the polarization beam splitting and rotation module can also be as Figure 5 shown. The light with a random polarization state is coupled to the TE0 and TM0 polarization states in the input waveguide 1, and the two orthogonal polarization components in the optical fiber are respectively coupled to the transverse electric polarization TE0 and transverse magnetic polarization TM0 in the waveguide 5. At the same time, the transverse magnetic polarization TM0 is rotated into the transverse electric polarization TE0, and the finally generated two-way transverse electric polarization TE0 are respectively output by the waveguide 2 and the waveguide 3.
[0065] In the embodiments of the present application, after the mixing module generates the mixed signal light, it is respectively sent to two bidirectional optical detection modules. The first bidirectional optical detection module is used to perform photoelectric conversion on the first mixed signal light TE LS1B and the second mixed signal light TE LS2A , and output the first electrical signal to the first differential output module. The second bidirectional optical detection module is used to perform photoelectric conversion on the third mixed signal light TE LS1A and the fourth mixed signal light TE LS2B , and output the second electrical signal to the first differential output module. The first differential output module is used to generate a target detection electrical signal based on the first electrical signal and the second electrical signal. In some specific embodiments, the first differential output module is as Figure 3 shown, and includes a first photodetector PD1 and a second photodetector PD2 connected in series. The differentially generated target detection electrical signal is output from the pin RF output2 between PD1 and PD2 and enters the subsequent hardware signal processing circuit to extract the distance and speed information of the target object.
[0066] In some embodiments, the first bidirectional optical detection module and the second bidirectional optical detection module respectively include a photosensitive area, and the photosensitive area sequentially includes a silicon substrate, a silicon dioxide insulating layer, a silicon waveguide, a P-type doped area on the surface of the silicon waveguide, a germanium waveguide area, and an N-type doped area on the surface of the germanium waveguide.
[0067] In some specific embodiments, both the first bidirectional optical detection module and the second bidirectional optical detection module are bidirectional Ge-Si detectors. As Figure 4 shown, the first bidirectional optical detection module and the second bidirectional optical detection module are as shown in Figure 6 (b) of. The two mixed-signal optical beams are respectively input into waveguide 1 from the upper side and waveguide 2 from the lower side, and are absorbed after entering the photosensitive region composed of Ge and Si waveguides. Figure 6 (c) of shows an implementation cross-sectional view of the photosensitive region composed of Ge and Si waveguides. The photosensitive region sequentially includes a silicon substrate, a silicon dioxide insulating layer, a silicon waveguide, a P-type doped region, a germanium waveguide region, and an N-type doped region. Among them, the two sides of the upper surface of the silicon waveguide are p-type heavily doped region p++ electrical contact regions, and the middle of the upper surface of the silicon waveguide is a moderately p-type doped region p+ region. Above the P-type doped region is a germanium waveguide, and the upper surface of the germanium waveguide is an n-type heavily doped region n++ electrical contact region. The mixed-frequency light entering the photosensitive region is mainly absorbed by the germanium material and then converted into an electrical signal for output. The first bidirectional optical detection module and the second bidirectional optical detection module complete the superposition of optical signals inside the device, can stably detect the echo signal light, and effectively reduce the influence of the polarization change of the echo signal light on the detection result.
[0068] The above signal light detection device includes a first beam splitting module, a mixing module, a first bidirectional optical detection module, a second bidirectional optical detection module, and a first differential output module. Among them, the first beam splitting module is used to split the incident signal light into local light and output detection light emitted into the target detection space; the mixing module is used to mix the echo signal light and the local light; the first bidirectional optical detection module and the second bidirectional optical detection module are respectively used to perform photoelectric conversion on the mixed-signal optical beam, and finally the target detection electrical signal is generated by the differential output module. The optical detection device provided by the present application can perform coherent beat frequency processing on the echo signal light in any polarization state by setting a polarization processing device inside the device and a balanced detector structure composed of two bidirectional optical detection modules, can make full use of the energy of the signal light, and minimize the influence of the polarization change of the echo signal light on the stability of the detection result to the greatest extent. Since stable detection of signal light in any polarization state can be achieved inside the device without additionally setting up equipment outside the device for polarization processing, the system complexity can be greatly simplified, the difficulty of system integration can be reduced, and system packaging is facilitated.
[0069] In the embodiment of the present application, a signal light detection device capable of correcting the linearity of the input optical frequency tuning is further provided. As Figure 3 shown, the device further includes a third beam splitting module, a fourth beam splitting module, a delay module, a third mixing unit, a first unidirectional optical detection module, a second unidirectional optical detection module, and a second differential output module. The device is connected to a light source module. Among them, the third beam splitting module is used to split the local light and output a third local light TE’ Lto the fourth beam splitting module, and output the fourth local light TE L as the local light input to the mixing module; the fourth beam splitting module is used to split the third local light TE’ L perform beam splitting, output the fifth local light to the delay module, and output the sixth local light to the third mixing unit; the delay module is used to delay the fifth local light by a preset time and then output the seventh local light to the third mixing unit; the third mixing unit is used to mix the sixth local light and the seventh local light, output the fifth mixing signal to the first unidirectional optical detection module, and output the sixth mixing signal to the second unidirectional optical detection module; the first unidirectional optical detection module is used to perform photoelectric conversion on the fifth mixing signal light and output the third electrical signal to the second differential output module; the second unidirectional optical detection module is used to perform photoelectric conversion on the sixth mixing signal light and output the fourth electrical signal to the second differential output module; the second differential output module is used to generate a feedback electrical signal based on the third electrical signal and the fourth electrical signal and input it to the light source module, so that the light source module corrects the frequency tuning linearity of the input light based on the feedback electrical signal.
[0070] In the embodiments of the present application, each beam splitting module includes a directional coupler, and the directional coupler is used to split the input light proportionally based on a preset coupling spacing and a preset coupling length. In some specific embodiments, any one of the first beam splitting module, the second beam splitting module, the third beam splitting module, and the fourth beam splitting module in the above embodiments of the present application, such as Figure 7 shown, includes a directional coupler, and the directional coupler can control the spacing Pitch and the coupling length L between the two waveguides in the coupling region to obtain light outputs with different beam splitting ratios.
[0071] In the embodiments of the present application, each mixing unit includes a 180-degree mixer, and the 180-degree mixer includes: a 180-degree mixer based on a 50:50 multimode interferometer, or a 180-degree mixer based on a 50:50 directional coupler. In some specific embodiments, any one of the first mixing unit, the second mixing unit, and the third mixing unit in the above embodiments of the present application can be a 180-degree mixer. Such as Figure 8 shown, the 180-degree mixer can be a 180-degree mixer of a 50:50 multimode interferometer as shown in (a) of Figure 8 , or a 180-degree mixer based on a 50:50 directional coupler as shown in (b) of Figure 8 .
[0072] In the embodiments of the present application, the first unidirectional optical detection module or the second unidirectional optical detection module can be a unidirectional Ge-Si photodetector. In some specific embodiments, such asFigure 6 As shown in (a) in
[0073] In the embodiments of the present application, the second differential output module is as Figure 3 shown, and includes two photodetectors connected in series. After the feedback electrical signal generated by the difference is output from the pin RF output 1, it is input to the frequency modulation light source module for real-time calibration of the input light frequency tuning linearity.
[0074] Based on the same inventive concept, the embodiments of the present application also provide a ranging and velocity measuring system. The implementation solutions for solving problems provided by this system are similar to the implementation solutions described in the above signal light detection device. Therefore, the specific limitations in one or more embodiments of the ranging and velocity measuring system provided below can refer to the limitations on the signal light detection device in the above text, and will not be repeated here.
[0075] In one embodiment, a ranging and velocity measuring system is provided. The system includes a light source module, a ranging and velocity measuring module, and the signal light detection device described in any of the above embodiments. The signal light detection device is respectively connected to the light source module and the ranging and velocity measuring module. Among them, the light source module is used to input the output frequency modulation light into the signal light detection device, receive the feedback electrical signal output by the signal light detection device, and correct the frequency modulation linearity of the output frequency modulation light based on the feedback electrical signal; the ranging and velocity measuring module is used to receive the target detection electrical signal output by the signal light detection device, and perform ranging and velocity measurement on the target object based on the target detection electrical signal. Among them, the output frequency modulation light is the input light described in the above embodiments.
[0076] In one embodiment, the light source module and the signal light detection device are connected by any one of heterogeneous integration, package integration, or optical fiber connection.
[0077] In one embodiment, as Figure 3 shown, the light source module includes a frequency modulation laser and an optical isolator connected to each other.
[0078] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combinations of these technical features do not conflict, they should all be considered as the scope described in this specification.
[0079] The above-described embodiments merely represent several implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation to the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all fall within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the appended claims.
Claims
1. A signal light detection device, characterized in that, The device includes a first beam splitting module, a mixing module, a first bidirectional optical detection module, a second bidirectional optical detection module, and a first differential output module. Among them, The first beam splitting module is configured to split the input light, output the detection light into the target detection space, and output the local light to the mixing module; The mixing module is configured to receive the echo signal light, mix the local light and the echo signal light, output the first mixed signal light and the second mixed signal light to the first bidirectional optical detection module, and output the third mixed signal light and the fourth mixed signal light to the second bidirectional optical detection module. The echo signal light is formed by the detection light being reflected by the target in the target detection space; The first bidirectional optical detection module is configured to perform photoelectric conversion on the first mixed signal light and the second mixed signal light, and output a first electrical signal to the first differential output module; The second bidirectional optical detection module is configured to perform photoelectric conversion on the third mixed signal light and the fourth mixed signal light, and output a second electrical signal to the first differential output module; The first differential output module is configured to generate a target detection electrical signal based on the first electrical signal and the second electrical signal.
2. The device according to claim 1, characterized in that The mixing module includes a second beam splitting module, a polarization beam splitting and rotation module, a first mixing unit, and a second mixing unit. Among them, The second beam splitting module is configured to split the local light, output the first local light to the first mixing unit, and output the second local light to the second mixing unit; The polarization beam splitting and rotation module is configured to receive the echo signal light, perform polarization beam splitting and rotation on the echo signal light, output the first signal light to the first mixing unit, and output the second signal light to the second mixing unit; The first mixing unit is configured to mix the first local light and the first signal light, output the first mixed signal light to the first bidirectional optical detection module, and output the third mixed signal light to the second bidirectional optical detection module; The second mixing unit is configured to mix the second local light and the second signal light, output the second mixed signal light to the first bidirectional optical detection module, and output the fourth mixed signal light to the second bidirectional optical detection module.
3. The device according to claim 1, wherein The device further includes a third beam splitting module, a fourth beam splitting module, a delay module, a third mixing unit, a first unidirectional optical detection module, a second unidirectional optical detection module, and a second differential output module. The device is connected to a light source module. Among them, The third beam splitting module is configured to split the local light, output the third local light to the fourth beam splitting module, and output the fourth local light as the local light input to the mixing module; The fourth beam splitting module is configured to split the third local light, output the fifth local light to the delay module, and output the sixth local light to the third mixing unit; The delay module is configured to delay the fifth local light by a preset time and then output the seventh local light to the third mixing unit; The third mixing unit is configured to mix the sixth local light and the seventh local light, output a fifth mixed signal to the first unidirectional optical detection module, and output a sixth mixed signal to the second unidirectional optical detection module; The first unidirectional optical detection module is configured to perform optoelectronic conversion on the fifth mixed signal light and output a third electrical signal to the second differential output module; The second unidirectional optical detection module is configured to perform optoelectronic conversion on the sixth mixed signal light and output a fourth electrical signal to the second differential output module; The second differential output module is configured to generate a feedback electrical signal based on the third electrical signal and the fourth electrical signal and input it to the light source module, so that the light source module corrects the frequency tuning linearity of the input light based on the feedback electrical signal.
4. The device according to claim 1, wherein The first bidirectional optical detection module and the second bidirectional optical detection module each include a photosensitive region, and the photosensitive region sequentially includes a silicon substrate, a silicon dioxide insulating layer, a silicon waveguide, a P-type doped region on the surface of the silicon waveguide, a germanium waveguide region, and an N-type doped region on the surface of the germanium waveguide.
5. The device according to any one of claims 1 to 3, characterized in that Each beam splitting module includes a directional coupler, and the directional coupler is configured to proportionally split the input light based on a preset coupling pitch and a preset coupling length.
6. The device according to claim 2 or 3, characterized in that, Each mixing unit includes a 180-degree mixer, and the 180-degree mixer includes: A 180-degree mixer based on a 50:50 multimode interferometer, or a 180-degree mixer based on a 50:50 directional coupler.
7. The device according to claim 2, characterized in that, The polarization beam splitting and rotation module includes a two-dimensional grating coupler, wherein, The two-dimensional grating coupler is configured to couple the echo signal light with any polarization into the transverse electric fundamental mode polarization light in two receiving waveguides, that is, generate the first signal light and the second signal light.
8. The device according to claim 2, characterized in that, The polarization beam splitting and rotation module includes a polarization rotation structure and a separation waveguide structure, wherein, The polarization rotation structure and the separation waveguide structure are configured to couple the echo signal light with any polarization into the orthogonal first transverse electric fundamental mode polarization and transverse magnetic fundamental mode polarization in the waveguide, and then convert the transverse magnetic fundamental mode polarization into the second transverse electric fundamental mode polarization in the separation waveguide structure through the polarization rotation structure and the separation waveguide structure, and use the first transverse electric fundamental mode polarization and the second transverse electric fundamental mode polarization as the first signal light and the second signal light respectively.
9. A ranging and velocity measuring system, characterized in that, The system includes a light source module, a ranging and velocity measuring module, and a signal light detection device according to any one of claims 1 to 8, and the signal light detection device is respectively connected to the light source module and the ranging and velocity measuring module, wherein, The light source module is configured to input the output frequency-modulated light to the signal light detection device, receive the feedback electrical signal output by the signal light detection device, and correct the frequency modulation linearity of the output frequency-modulated light based on the feedback electrical signal; The ranging and velocity measuring module is configured to receive the target detection electrical signal output by the signal light detection device and perform ranging and velocity measurement on the target object based on the target detection electrical signal.
10. The ranging and velocity measuring system according to claim 9, characterized in that, The light source module and the signal light detection device are connected by any one of heterogeneous integration, package integration, or fiber connection.