Light detection and ranging system with solid-state spectral scanning

Abstract

A light detection and ranging (LIDAR) device is provided, comprising: a light source for emitting a first light beam having a first frequency and a second light beam having a second frequency; and a dispersive element for deflecting the first light beam having the first frequency at a first angle and deflecting the second light beam having the second frequency at a second angle.

Description

[0001] Related applications

[0002] This application claims the benefit under 35 U.S.C. §119(e) of U.S. Patent Application No. 16 / 449,189, filed on June 21, 2019, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure generally relates to light detection and ranging (LIDAR) that provides simultaneous measurement of range and velocity across two dimensions. Background Art

[0004] Fast scanning mirrors are the main components used to illuminate the scene in most conventional LIDAR systems. One mirror typically scans rapidly in the X direction (azimuth), while the other scans slowly in the Y direction (elevation). Light emission and detection of reflection from the target are typically accomplished coaxially via a single-mode fiber. The collected light has a measured delay or altered frequency signature that is used to extract range and potentially velocity information. When the point-by-point detected range information is combined with angular position feedback from the scanning mirrors, a 3D point cloud can be created.

[0005] In order to achieve higher frame rates, the angular velocity of the mirrors is increased, especially the angular velocity of the scanner (in this case the X scanner) in the faster scanning direction. When using mirrors with high angular velocities and detection based on single-mode fiber, the target signal from distant objects is severely degraded. The signal degradation is mainly due to the difference in the angular position of the scanner mirror from the time of emission of the optical signal (pulse or sweep) to the time of collection of the same signal from the distant scattering target. This slight angular change leads to a walk-off of the target signal at the tip of the fiber, thereby reducing the coupling efficiency, which manifests itself as a weaker signal detection. This degradation becomes more severe as the fiber diameter decreases, for example for single-mode fibers with a diameter of ~10μm, or as the angular velocity of the mirror increases. Summary of the Invention

[0006] The present disclosure includes, but is not limited to, the following exemplary implementations.

[0007] Some example implementations provide a light detection and ranging (LIDAR) device comprising: a light source for emitting a first light beam having a first frequency and a second light beam having a second frequency; and a dispersive element for deflecting the first light beam having the first frequency at a first angle and deflecting the second light beam having the second frequency at a second angle.

[0008] Some example implementations provide a method comprising: generating, by a light source of a light detection and ranging (LIDAR) system, a first light beam having a first frequency and a second light beam having a second frequency. The method may further comprise providing the first light beam having the first frequency and the second light beam having the second frequency to a dispersive element, wherein the dispersive element deflects the first light beam having the first frequency at a first angle and deflects the second light beam having the second frequency at a second angle.

[0009] These and other features, aspects and advantages of the present disclosure will become apparent by reading the following detailed description and the accompanying drawings briefly described below. The present disclosure includes any combination of two, three, four or more features or elements set forth in the present disclosure, regardless of whether these features or elements are explicitly combined or otherwise described in the specific example implementations described herein. Unless the context of the present disclosure clearly provides otherwise, the present disclosure is intended to be read as a whole, so that any separable features or elements of the present disclosure should be considered combinable in any aspect and example implementation thereof.

[0010] Therefore, it should be understood that this disclosure is provided only to summarize some example implementations to provide a basic understanding of some aspects of the present disclosure. Therefore, it should be understood that the above example implementations are merely examples and should not be construed to narrow the scope or spirit of the present disclosure in any way. Other example implementations, aspects, and advantages will become apparent from the following detailed description taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of some of the described example implementations. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The embodiments and implementations of the present disclosure will be more fully understood from the detailed description given below and the accompanying drawings of various aspects and implementations of the present disclosure. However, these embodiments and implementations should not be considered to limit the present disclosure to specific embodiments or implementations, but are only for illustration and understanding.

[0012] Figure 1 A LIDAR system according to an example implementation of the present disclosure is shown.

[0013] Figure 2 Aspects of a LIDAR system according to embodiments of the present disclosure are shown.

[0014] Figure 3 is a diagram of an example of multiple linear chirps generated by a LIDAR system tuned around different frequencies according to an embodiment of the present disclosure.

[0015] Figure 4 is a diagram of an example of a dispersive element of a LIDAR system that deflects a light beam at different angles based on the frequency of the light beam according to an embodiment of the present disclosure.

[0016] Figure 5 Aspects of LIDAR systems according to other embodiments of the present disclosure are shown.

[0017] Figure 6 Aspects of a LIDAR system according to some embodiments of the present disclosure are shown.

[0018] Figure 7 Aspects of a LIDAR system according to embodiments of the present disclosure are shown.

[0019] Figure 8 Aspects of a LIDAR system with multiple light sources according to embodiments of the present disclosure are shown.

[0020] Figure 9 A flow chart depicting a method of solid-state spectral scanning using a LIDAR system according to implementations of the present disclosure. DETAILED DESCRIPTION

[0021] Example implementations of the present disclosure relate to an improved scanning LIDAR system. Example implementations of the present disclosure are based on a type of LIDAR that uses frequency modulation (FM) and coherent detection to overcome the shortcomings of traditional LIDAR systems and the limitations of existing FM LIDAR systems. Historically, FM LIDAR systems suffer significant losses in the return path of the light beam; therefore, such systems, which are typically quite bulky, require higher average beam output power to measure distances comparable to time-of-flight (TOF) LIDAR systems. However, the range is limited by the operating distance for eye-safe output power.

[0022] Example implementations of the present disclosure are configured to measure range and velocity simultaneously using coherent detection, with the added benefit of immunity to crosstalk from other LIDAR systems. Other implementations can be used with non-coherent systems to improve range, frame rate, or detection. Example implementations minimize optical losses in the return path of the light beam, thereby increasing the measurement range of the system. Additionally, by using a non-degenerate light source, example implementations can leverage mature wavelength division multiplexing (WDM) technology commonly used in integrated silicon photonics, a desirable platform due to its compactness and relative stability under varying environmental conditions.

[0023] Conventional frequency modulated continuous wave (FMCW) LIDAR systems rely on scanning one or more laser beams across a desired field of view (FOV) to map the target space in three dimensions (3D) and time. Angular scanning of one or more laser beams uses moving mechanical components, such as galvanometer-based scanners. Galvanometer-based scanners and other mechanical-based scanners typically contain many moving parts that are prone to failure. Furthermore, due to the complexity of mechanical-based scanners, the price of such scanners is relatively high, making large-scale manufacturing of conventional FMCW LIDAR systems difficult.

[0024] Example implementations of the present disclosure address these and other deficiencies by performing spectral scanning using an FMCW LIDAR system that includes a dispersive element. In embodiments, the system may also utilize a diffraction grating or some other refraction-based optical device, but for simplicity, the term "dispersion" will be used to encompass methods whereby an operating element varies the scanning angle due to changes in the source wavelength. Embodiments of the present disclosure utilize wavelength / frequency-based manipulation of a light beam generated by one or more light sources of an FMCW LIDAR system. The light source of an FMCW LIDAR system may generate a light beam having different frequencies across a bandwidth corresponding to the field of view (FOV). For example, the light source may generate multiple linear chirps, each tuned around a different frequency. The light beams having different frequencies are provided to a dispersive element. The dispersive element is a passive component of the FMCW LIDAR system made of a material that deflects the light beam at different angles based on its frequency. For example, multiple linear chirps may be provided to the dispersive element at different frequencies so that the chirps' deflection angles cover the desired field of view (FOV).

[0025] Therefore, by using an FMCW LIDAR system that includes a dispersive element for spectral scanning, it is possible to transmit a beam over a desired FOV without using a mechanical scanner. Because the dispersive element is a passive component with no moving parts, the likelihood of failure is significantly reduced compared to a mechanical scanner, thereby improving the performance of the FMCW LIDAR system. Furthermore, the relatively low cost of the dispersive element compared to a mechanical scanner improves the manufacturability of the FMCW LIDAR system.

[0026] Although embodiments of the present disclosure are described using an FMCW LIDAR system, aspects of the present disclosure can be used by any sensing market, including but not limited to the transportation, manufacturing, metrology, medical, and security markets. Furthermore, aspects of the present disclosure can be applied to any type of LIDAR system. For example, aspects of the present disclosure can be applied to a TOF LIDAR system.

[0027] Figure 1A LIDAR system 100 is shown according to an example implementation of the present disclosure. The LIDAR system 100 includes one or more of each of a number of components, but may include Figure 1 Fewer or additional components than shown. The LIDAR system 100 can be implemented in any sensing market, such as, but not limited to, transportation, manufacturing, metrology, medical, and safety systems. For example, in the automotive industry, the described beam delivery system becomes the front end of a frequency modulated continuous wave (FMCW) device, which can assist in the spatial perception of automatic driver assistance systems or autonomous driving vehicles. As shown, the LIDAR system 100 includes an optical circuit 101 implemented on a photonic chip. The optical circuit 101 may include a combination of active optical components and passive optical components. The active optical components can generate, amplify, or detect optical signals, etc. In some examples, the active optical circuit includes light beams of different wavelengths, one or more optical amplifiers, or one or more optical detectors, etc.

[0028] The free-space optical device 115 may include one or more lens elements to couple light into and out of an optical waveguide to carry an optical signal, and to route and manipulate the optical signal to an appropriate input / output port of an active optical circuit. The free-space optical device 115 may also include one or more optical components, such as a tap, a wavelength division multiplexer, a beam splitter / combiner, a polarization beam splitter, a collimator, or a coupler. In some embodiments, as discussed further below, the free-space optical device 115 may include components for converting polarization states and directing received polarized light to an optical detector using a PBS polarization beam splitter (PBS). As will be described in further detail below, the free-space optical device 115 also includes a dispersive element for deflecting light beams with different frequencies at different angles along an axis (e.g., a fast axis).

[0029] In an embodiment, the LIDAR system 100 includes an optical scanner 102, which includes one or more scanning mirrors that can be rotated along an axis that is orthogonal or substantially orthogonal to the fast axis of the dispersive element (e.g., a slow axis) to manipulate the optical signal to scan the environment according to a scanning pattern. For example, the scanning mirror can be rotated by one or more galvanometers. The optical scanner 102 also collects light incident on any object in the environment into a return beam, which is returned to the passive optical circuit components of the optical circuit 101. For example, the return beam can be directed to an optical detector by a polarization beam splitter. In addition to the mirrors and galvanometers, the optical scanning system can include components such as a quarter wave plate, a lens, or an anti-reflection coated window.

[0030] To control and support the optical circuit 101 and the optical scanner 102, the LIDAR system 100 includes a LIDAR control system 110. The LIDAR control system 110 may include a processing device for the LIDAR system 100. In an embodiment, the processing device may be one or more general-purpose processing devices, such as a microprocessor or a central processing unit. More specifically, the processing device may be a complex instruction set computing (CISC) microprocessor, a reduced instruction set computer (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, or a processor for implementing other instruction sets, or a processor for implementing a combination of instruction sets. The processing device may also be one or more special-purpose processing devices, such as an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a digital signal processor (DSP), or a network processor.

[0031] In some embodiments, the LIDAR control system 110 may include a signal processing unit 112, such as a digital signal processor. The LIDAR control system 110 is configured to output a digital control signal to control the optical driver 103. In some embodiments, the digital control signal may be converted into an analog signal by a signal conversion unit 106. For example, the signal conversion unit 106 may include a digital-to-analog converter. The optical driver 103 may then provide a drive signal to the active components of the optical circuit 101 to drive light sources such as lasers and amplifiers. In some embodiments, multiple optical drivers 103 and signal conversion units 106 may be provided to drive multiple light sources.

[0032] The LIDAR control system 110 is also configured to output digital control signals for the optical scanner 102. The motion control system 105 can control the optical scanner 102 based on the control signals received from the LIDAR control system 110. For example, a digital-to-analog converter can convert coordinate routing information from the LIDAR control system 110 into a signal that can be interpreted by a galvanometer in the optical scanner 102. In some embodiments, the motion control system 105 can also return information related to the position or operation of components of the optical scanner 102 to the LIDAR control system 110. For example, the analog-to-digital converter can, in turn, convert information related to the position of the galvanometer into a signal that can be interpreted by the LIDAR control system 110.

[0033] The LIDAR control system 110 is also configured to analyze incoming digital signals. In this regard, the LIDAR system 100 includes an optical receiver 104 to measure one or more light beams received by the optical circuit 101. For example, a reference beam receiver can measure the amplitude of a reference beam from the active optical circuit, and an analog-to-digital converter converts the signal from the reference receiver into a signal interpretable by the LIDAR control system 110. A target receiver measures an optical signal in the form of a beat frequency modulated optical signal that carries information related to the range and velocity of the target. The reflected light beam can be mixed with a second signal from a local oscillator. The optical receiver 104 can include a high-speed analog-to-digital converter to convert the signal from the target receiver into a signal interpretable by the LIDAR control system 110. In some embodiments, the signal from the optical receiver 104 can undergo signal conditioning 107 before being received by the LIDAR control system 110. For example, the signal from the optical receiver 104 can be provided to an operational amplifier for amplifying the received signal, and the amplified signal can be provided to the LIDAR control system 110.

[0034] In some applications, the LIDAR system 100 may additionally include one or more imaging devices 108 configured to capture images of the environment, a global positioning system 109 configured to provide the system's geographic location, or other sensor inputs. The LIDAR system 100 may also include an image processing system 114. The image processing system 114 may be configured to receive images and geographic locations and send these images and locations, or information related thereto, to the LIDAR control system 110 or other system connected to the LIDAR system 100.

[0035] In operation according to some examples, the LIDAR system 100 is configured to use a non-degenerate light source to simultaneously measure range and velocity in two dimensions. This capability enables real-time, remote measurement of range, velocity, azimuth, and elevation of the surrounding environment. In some example implementations, the system directs multiple modulated light beams at the same target.

[0036] In some examples, the scanning process begins with the optical driver 103 and the LIDAR control system 110. The LIDAR control system 110 instructs the optical driver 103 to independently modulate one or more light beams, and these modulation signals are propagated through the passive optical circuit to the collimator. The collimator guides the light at the optical scanning system, which scans the environment in a pre-programmed pattern defined by the motion control subsystem. The optical circuit may also include a polarization wave plate to transform the polarization of the light as it leaves the optical circuit 101. In embodiments, the polarization wave plate may be a quarter wave plate or a half wave plate. Portions of the polarized light may also be reflected back to the optical circuit 101. For example, the lensing or collimating system may have natural reflective properties or a reflective coating to reflect portions of the light back to the optical circuit 101.

[0037] The optical signal reflected back from the environment passes through the optical circuit 101 to reach the receiver. Since the polarization of the light has been converted, it can be reflected by the polarization beam splitter together with the portion of the polarized light that is reflected back to the optical circuit 101. Therefore, the reflected light is reflected to a separate optical receiver instead of returning to the same optical fiber or waveguide as the light source. These signals interfere with each other and generate a combined signal. The individual beam signals returned from the target produce time-shifted waveforms. The time phase difference between the two waveforms generates a beat frequency measured on the optical receiver (photodetector). The combined signal can then be reflected to the optical receiver 104. The configuration of the optical circuit 101 for polarizing and guiding the light beam to the optical receiver 104 is further described below.

[0038] The analog signals from the optical receiver 104 are converted to digital signals using an analog-to-digital converter (ADC). The digital signals are then sent to the LIDAR control system 110. The signal processing unit 112 can then receive and interpret these digital signals. In some embodiments, the signal processing unit 112 also receives position data from the motion control system 105 and image data from the image processing system 114. The signal processing unit 112 can then generate a 3D point cloud with information about the range and speed of points in the environment as the optical scanner 102 scans additional points. The signal processing unit 112 can also overlay the 3D point cloud data with the image data to determine the speed and distance of objects in the surrounding area. The system also processes satellite-based navigation position data to provide accurate global position.

[0039] Figure 2Aspects of a LIDAR system 200 according to an embodiment of the present disclosure are shown. In an embodiment, one or more components of the LIDAR system 200 may be implemented in a photonic chip 240. As shown, a light source 202 generates a light beam 218. In some embodiments, multiple light sources may be used to generate the multiple light beams. In an embodiment, the multiple light beams may have different wavelengths / frequencies. For example, a first light source may generate a first light beam having a first frequency, and a second light source may generate a second light beam having a second frequency different from the first frequency. Light beam 218 is provided to an optical isolator including a tap (e.g., ISOTAP 204) operably coupled to light source 202. ISOTAP 204 allows light beam 218 to be transmitted in one direction, preventing optical feedback. The tap of ISOTAP 204 separates a portion of light beam 218 into a reference signal 230. Reference signal 230 may be provided to a coupler 210 of a reference arm circuit. Coupler 210 receives reference signal 230 and separates a portion of reference signal 230 to generate a local oscillator (LO) signal 228. In an embodiment, coupler 210 can be a balanced (50 / 50) or unbalanced coupler. Reference signal 230 can be provided to an interferometer 232 of a reference arm circuit, which is operatively coupled to coupler 210. In an embodiment, interferometer 232 can be a Mach-Zehnder interferometer (MZI) that is used to determine the relative phase shift change between the beams derived by splitting reference signal 230. Interferometer 232 can then provide reference signal 230 to a photodetector 234 of the reference arm circuit for subsequent analysis.

[0040] Light beam 218 is provided to an optical amplifier 206 operatively coupled to ISOTAP 204. Optical amplifier 206 amplifies the optical signal of light beam 218. LIDAR system 200 may also include at least one optical device to route light beam 218 toward collimator 212 and to route target signal 222 to light detector 226. As shown, the optical device includes a polarization beam splitter (PBS) 208 and a polarization wave plate (PWP) 214. Other examples of suitable optical devices may include an optical circulator or a beam splitter / combiner.

[0041] Light beam 218 may pass through polarizing beam splitter (PBS) 208 , which is operatively coupled to optical amplifier 206 .

[0042] The light beam 218 may be provided to a collimator 212 to focus / collimate the light beam 218. The light beam 218 may be provided to a polarization wave plate (PWP) 214 to transform the polarization of the light beam 218. For example, the polarization of the light beam 218 may be transformed into circular polarization. In some embodiments, an optical circulator rather than a PWP and / or a PBS may be used to redirect the light beam 218.

[0043] After transforming the polarization of the light, light beam 218 may be provided to dispersive element 216. Dispersive element 216 may be composed of a material that deflects the light beam at different angles based on the frequency of the light beam. For example, dispersive element 216 may deflect light beam 218 having a first frequency (e.g., f1) at a first angle and light beam having a second frequency (e.g., f2) at a second angle. In an embodiment, dispersive element 216 may deflect the light beam at an angle along an axis corresponding to a fast scan direction of LIDAR system 200. For example, dispersive element 216 may deflect the light beam along a horizontal or substantially horizontal axis.

[0044] In some embodiments, the light beam 218 that has been deflected by the dispersive element 216 can be passed through a scanner 236 (e.g., Figure 1 236) toward target 220. In other embodiments, LIDAR system 200 may not include scanner 236 and may transmit light beam 218 toward target 220 via dispersive element 216. Scanner 236 may deflect light beam 218 along an axis 238 corresponding to a slow scan direction that is orthogonal or substantially orthogonal to the fast scan direction of LIDAR system 200 to generate a 3D map. For example, if the fast scan direction of LIDAR system 200 is along the horizontal axis, scanner 236 may deflect light beam 218 along the vertical axis. When light beam 218 strikes target 220, a portion of the light beam returns to LIDAR system 200 as target signal 222. Target signal 222 passes through scanner 236, dispersive element 216, PWP 214, and collimator 212.

[0045] Target signal 222 is received by PBS 208. Because the deflection of target signal 222 is converted by PWP 214, target signal 222 is reflected by PBS 208 instead of passing through PBS 208. Target signal 222 is reflected by PBS 208 toward coupler 224. Coupler 224 receives target signal 222 and local oscillator signal 228 and generates a combined signal including both target signal 222 and local oscillator signal 228. In an embodiment, coupler 224 can be a balanced (50 / 50) or unbalanced coupler. The combined signal is then received by photodetector 226 for subsequent analysis, as previously described.

[0046] In some embodiments, if local oscillator signal 228 and target signal 222 spatially overlap, local oscillator signal 228 and target signal 222 may be provided to photodetector 226 without using coupler 224. For example, LIDAR system 200 may not include coupler 224, in which case local oscillator signal 228 and target signal 222 may be optically mixed at photodetector 226.

[0047] Figure 3 FIG300 is a diagram of an example of multiple linear chirps tuned around different frequencies generated by a LIDAR system according to an embodiment of the present disclosure. FIG300 is a graphical representation of the frequency (Y-axis) of a light beam versus time (X-axis). A light beam generated by a light source such as Figure 2 The beams 218, etc.) may be linear chirps tuned around different frequencies. Each linear chirp (e.g., linear chirps 305, 310, 315, and 320) may include a time portion in which the frequency of the chirp increases at a linear or substantially linear rate and a time portion in which the frequency of the chirp decreases at a linear or substantially linear rate.

[0048] Linear chirps 305, 310, 315, and 320 may be tuned around frequencies 325, 330, 335, and 340, respectively. Frequencies 325, 330, 335, and 340 may correspond to different deflection angles of a dispersive element of a LIDAR system. For example, frequencies 325, 330, 335, and 340 may correspond to deflection angles of a dispersive element that cover a desired FOV of the LIDAR system.

[0049] Figure 4 FIG400 is an example of a dispersive element for a LIDAR system that deflects a light beam at different angles based on the frequency of the light beam, according to an embodiment of the present disclosure. In FIG400, light beam 218 is provided to dispersive element 216. As previously described, dispersive element 216 deflects light beam 218 at different angles based on the frequency of light beam 218.

[0050] Figure 4 A series of four light beams generated by light sources having different frequencies (e.g., f1, f2, f3, and f4) is shown. Dispersive element 216 can deflect light beam 218 having frequency f1 at angle 405, light beam 218 having frequency f2 at angle 410, light beam 218 having frequency f3 at angle 415, and light beam 218 having frequency f4 at angle 420. As previously described, dispersive element 216 can deflect the series of light beams at angles 405, 410, 415, and 420 along axis 425, which corresponds to the fast scan direction of the LIDAR system.

[0051] Figure 52 shows aspects of a LIDAR system 500 according to other embodiments of the present disclosure. The components of LIDAR system 500 can be similar to those of LIDAR system 200. However, instead of using a coupler (e.g., coupler 210) to separate a portion of reference signal 230 to generate local oscillator signal 228, local oscillator signal 228 can be reproduced by reflector 402 after PWP 214. For example, reflector 402 can reflect a portion of light beam 218 in a direction toward light source 202. In some embodiments, a separate mirror, retroreflector, microlens array, filter, or reflective coating on PWP 214 can be used. The reflected portion of light beam 218 becomes local oscillator signal 228, which is used to interfere with returning target signal 222.

[0052] Similar to Figure 2 Because the polarization of local oscillator signal 228 has been transformed, PBS 208 reflects local oscillator signal 228 in a direction toward coupler 224, rather than allowing local oscillator signal 228 to pass through PBS 208. In some embodiments, as previously described, LIDAR system 500 may not include coupler 224, and local oscillator signal 228 and target signal 222 may be optically mixed at photodetector 226.

[0053] Figure 6 Aspects of a LIDAR system 600 according to some embodiments of the present disclosure are shown. The components of the LIDAR system 600 may be similar to those of the LIDAR system 200. However, instead of using a PBS (e.g., PBS 208) to direct the light beam 218 and the target signal 222, the LIDAR system 600 utilizes an optical circulator 602 to direct the light beam 218 to the collimator 212 and the target signal to the coupler 224. In some embodiments, as previously described, the LIDAR system 600 may not include the coupler 224, and the local oscillator signal 228 and the target signal 222 may be optically mixed at the photodetector 226. Furthermore, because the LIDAR system 600 does not utilize a PBS, there is no need to transform the polarization of the light beam 218. Therefore, the LIDAR system 600 may not include a PWP (e.g., PWP 214).

[0054] Figure 71 shows aspects of a LIDAR system 700 according to some embodiments of the present disclosure. The components of the LIDAR system 700 can be similar to those of the LIDAR system 600. However, instead of utilizing a coupler (e.g., coupler 210) to separate a portion of the reference signal 230 to generate the local oscillator signal 228, the local oscillator signal 228 can be generated by a reflector 702 of the collimator 212. For example, the reflector 702 can reflect a portion of the light beam 218 in a direction toward the light source 202. In some embodiments, a separate mirror, retroreflector, microlens array, filter, or reflective coating on the collimator 212 can be used. The reflected portion of the light beam 218 becomes the local oscillator signal 228, which is used to interfere with the returning target signal 222.

[0055] Similar to Figure 6 Optical circulator 602 may receive local oscillator signal 228 and direct local oscillator signal 228 to coupler 224 for target signal 222. In some embodiments, as previously described, LIDAR system 700 may not include coupler 224, and local oscillator signal 228 and target signal 222 may be optically mixed at photodetector 226.

[0056] Figure 8 1 shows aspects of a LIDAR system 800 having multiple light sources according to an embodiment of the present disclosure. The components of the LIDAR system 800 may be similar to the components of the LIDAR system 200. For clarity, some of these components of the LIDAR system 800 (e.g., free space optics, optical devices, reference arm circuitry, etc.) have been removed from the original source. Figure 8 . Instead of utilizing a single light source, the LIDAR system 800 utilizes multiple light sources (e.g., light source 202a and light source 202b), each of which generates a light beam having a different frequency. For example, light source 202a may generate light beam 218a having a first frequency (f1) and light source 202b may generate light beam 218b having a second frequency (f2). Light beams 218a and 218b may be provided to a dispersive element 216. Dispersive element 216 may deflect light beams 218a and 218b at different angles based on the frequencies of light beams 218a and 218b. Although shown as having two light sources, in embodiments, the LIDAR system 800 may include any number of light sources generating light beams having different frequencies.

[0057] Figure 9 A flow chart depicting a method 900 for solid-state spectral scanning using a LIDAR system according to an implementation of the present disclosure. In an embodiment, various parts of the method 900 may be respectively Figure 1 、 2, 5, 6, 7 and 8 are performed by the LIDAR systems 100, 200, 500, 600, 700 and / or 800.

[0058] refer to Figure 9 , method 900 illustrates example functionality used by various embodiments. Although specific functional blocks ("blocks") are disclosed in method 900, such blocks are examples. That is, embodiments are well suited to performing various other blocks or variations of blocks set forth in method 900. It is understood that the blocks in method 900 may be performed in an order different from that presented, and that not all blocks in method 900 may be performed.

[0059] At block 902, a light source of a LIDAR system generates a first light beam having a first frequency.The light source of the LIDAR system may generate the first light beam having the first frequency at a first time.

[0060] At block 904, the light source generates a second light beam having a second frequency. The light source of the LIDAR system may generate the second light beam having the second frequency at a second time that is later than the first time. In some embodiments, multiple light sources may generate light beams. For example, a first light source may generate the first light beam at block 902, and a second light source may generate the second light beam.

[0061] In embodiments where multiple light sources are used to generate light beams of different frequencies, the light beams may be generated at different times or at the same or substantially similar times. Generating the light beams at the same or substantially similar times can achieve a significant reduction in scan time, further improving the performance of the LIDAR system.

[0062] In some embodiments, as previously described, the plurality of light sources may be tunable light sources that can each generate a light beam centered around a frequency range. The field of view can be divided into a plurality of portions, and the tunable light sources can each generate a light beam at the same or substantially similar times to scan different portions of the field of view in parallel with each other, thereby reducing scanning time and improving the performance of the LIDAR system.

[0063] At block 906, the LIDAR system generates a first local oscillator (LO) signal using the first light beam and a second local oscillator signal using the second light beam. In some embodiments, the first LO signal and the second LO signal may be generated by a coupler of the LIDAR system that separates a portion of a reference signal associated with the first light beam and the second light beam to generate the first LO signal and the second LO signal, as previously described. Figure 2 In other embodiments, the first LO signal and the second LO signal may be generated by reflecting a portion of the first light beam and the second light beam, as previously described in Figure 5 As described in .

[0064] At block 908, a first light beam having a first frequency and a second light beam having a second frequency are provided to a dispersive element. As previously described, the dispersive element deflects the first light beam having the first frequency at a first angle and the second light beam having the second frequency at a second angle. The second light beam may be provided to the dispersive element at a later time than the first light beam.

[0065] At block 910, the LIDAR system receives a first target signal associated with a first light beam and a second target signal associated with a second light beam. The first target signal and the second target signal may correspond to reflections of the first light beam and the second light beam, respectively, from an object.

[0066] At block 912 , the first target signal is combined with the first LO signal to generate a first combined signal, and the second target signal is combined with the second LO signal to generate a second combined signal.

[0067] At block 914 , the first combined signal and the second combined signal are provided to a photodetector for subsequent analysis.

[0068] The foregoing description sets forth numerous specific details, such as examples of specific systems, components, methods, and the like, to provide a good understanding of several embodiments of the present disclosure. However, it will be apparent to those skilled in the art that at least some embodiments of the present disclosure can be practiced without these specific details. In other cases, well-known components or methods are not described in detail or are presented in a simple block diagram format to avoid unnecessarily obscuring the present disclosure. Therefore, the specific details set forth are merely illustrative. Although this specification contains many specific implementation details, these should not be construed as limitations on the scope of any invention or the scope of what may be claimed, but rather as descriptions of features unique to particular embodiments of a particular invention. Certain features described in this specification in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, different features described in the context of a single embodiment may also be implemented in multiple embodiments individually or in any suitable subcombination. Furthermore, although features may be described above as functioning in certain combinations and even initially claimed as such, in some cases one or more features from the claimed combination may be removed from the combination, and the claimed combination may involve subcombinations or variations of subcombinations. Furthermore, the separation of different system components in the above-described embodiments should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated into a single software product or packaged into multiple software products. Specific embodiments may differ from these exemplary details and still be considered within the scope of the present disclosure.

[0069] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, various appearances of the phrases "in one embodiment" or "in an embodiment" throughout this specification are not necessarily all referring to the same embodiment. Additionally, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or."

[0070] Although the operations of the methods herein are shown and described in a particular order, the order of the operations of the various methods may be changed so that certain operations may be performed in a reverse order, or so that certain operations may be performed at least partially simultaneously with other operations. In another embodiment, the instructions or sub-operations of different operations may be intermittent or alternating.

[0071] The above description of the illustrated implementations of the present invention (including what is described in the Abstract) is not intended to be exhaustive or to limit the invention to the precise form disclosed. Although specific implementations and examples of the present invention are described herein for illustrative purposes, various equivalent modifications within the scope of the present invention are possible, as will be appreciated by those skilled in the relevant art. The words "example" or "exemplary" are used herein to indicate use as an example, instance, or illustration. Any aspect or design described herein as "example" or "exemplary" is not necessarily to be construed as being preferred or advantageous over other aspects or designs. On the contrary, the use of the words "example" or "exemplary" is intended to present concepts in a concrete manner. As used in this application, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or". That is, unless otherwise specified or clear from the context, "X includes A or B" is intended to mean any natural inclusive arrangement. That is, if X includes A; X includes B; or X includes both A and B, then "X includes A or B" is satisfied in any of the foregoing cases. In addition, the articles "a" and "an" used in this application and the appended claims should generally be interpreted as meaning "one or more", unless otherwise specified or clearly directed to the singular form from the context. In addition, the use of the terms "embodiment" or "one embodiment" or "implementation" or "an implementation" throughout the text is not intended to refer to the same embodiment or implementation unless so described. In addition, the terms "first", "second", "third", "fourth", etc. as used herein are intended to be labels that distinguish between different elements and may not necessarily have the ordinal meaning according to their numerical labels.

Claims

1. A light detection and ranging device, i.e., a LIDAR device, comprising: a light source for emitting a first light beam having a first frequency and a second light beam having a second frequency, wherein the first light beam comprises a first linear chirp tuned around the first frequency and the second light beam comprises a second linear chirp tuned around the second frequency, and wherein a deflection angle of the first linear chirp and the second linear chirp covers a desired field of view (FOV) of the LIDAR device; and A dispersive element is configured to deflect the first light beam having the first frequency at a first angle and to deflect the second light beam having the second frequency at a second angle.

2. The LIDAR device according to claim 1, wherein: The dispersive element deflects the first light beam and the second light beam along a first axis, and the LIDAR device further includes: A scanner is configured to deflect the first light beam and the second light beam along a second axis orthogonal to the first axis.

3. The LIDAR device according to claim 1, further comprising: A polarization beam splitter, or PBS, is configured to allow light of a first polarization state to pass through the PBS in a first direction and to reflect light of a second polarization state in a second direction different from the first direction.

4. The LIDAR device according to claim 1, further comprising: An optical circulator is configured to direct the first and second light beams from the light source in a first direction and to direct a first target signal associated with the first light beam and a second target signal associated with the second light beam in a second direction.

5. The LIDAR device according to claim 1, further comprising: A photodetector is configured to receive a first combined signal comprising a first local oscillator signal associated with the first light beam and a first target signal, and a second combined signal comprising a second local oscillator signal associated with the second light beam and a second target signal.

6. The LIDAR device according to claim 5, wherein: The light source and the photodetector are positioned on a photonic chip. 7 . The LIDAR device according to claim 1 , further comprising a polarization plate for converting polarization states of the first light beam and the second light beam.

8. The LIDAR device according to claim 7, wherein: The polarization wave plate includes one of a quarter wave plate and a half wave plate.

9. The LIDAR device according to claim 7, wherein: The polarization wave plate further includes a reflector or coating configured to return a portion of the first light beam as a first local oscillator signal and to return a portion of the second light beam as a second local oscillator signal.

10. The LIDAR device according to claim 1, further comprising: An optical isolator includes a tap for providing a portion of the first light beam as a first reference signal and a portion of the second light beam as a second reference signal to a reference arm circuit.

11. The LIDAR device according to claim 10, wherein: The reference arm circuit comprises: an interferometer, configured to receive the first reference signal and the second reference signal; and A photodetector is configured to receive the first reference signal and the second reference signal from the interferometer.

12. The LIDAR device according to claim 11, wherein: The reference arm circuit further includes: A coupler is configured to split a portion of the first reference signal to generate a first local oscillator signal and to split a portion of the second reference signal to generate a second local oscillator signal.

13. A method for a light detection and ranging system, i.e., a LIDAR system, comprising: generating, by a light source of the LIDAR system, a first light beam having a first frequency and a second light beam having a second frequency, wherein the first light beam comprises a first linear chirp tuned around the first frequency and the second light beam comprises a second linear chirp tuned around the second frequency, and wherein deflection angles of the first linear chirp and the second linear chirp cover a desired field of view (FOV) of the LIDAR system; and The first light beam having the first frequency and the second light beam having the second frequency are provided to a dispersive element, wherein the dispersive element deflects the first light beam having the first frequency at a first angle and deflects the second light beam having the second frequency at a second angle.

14. The method according to claim 13, wherein The dispersive element deflects the first light beam and the second light beam along a first axis, the method further comprising: The first and second beams are provided to a scanner, wherein the scanner deflects the first and second beams along a second axis orthogonal to the first axis.

15. The method according to claim 13, further comprising: splitting a portion of the first light beam by a first coupler to generate a first local oscillator signal and splitting a portion of the second light beam to generate a second local oscillator signal; receiving a first target signal associated with the first light beam and a second target signal associated with the second light beam; combining the first target signal with the first local oscillator signal via a second coupler to generate a first combined signal, and combining the second target signal with the second local oscillator signal to generate a second combined signal; as well as The first combined signal and the second combined signal are provided to a photodetector.

16. The method according to claim 13, further comprising: reflecting a portion of the first light beam through a reflector or coating of a polarization wave plate to generate a first local oscillator signal and reflecting a portion of the second light beam to generate a second local oscillator signal; receiving a first target signal associated with the first light beam and a second target signal associated with the second light beam; combining the first target signal with the first local oscillator signal through a coupler to generate a first combined signal, and combining the second target signal with the second local oscillator signal to generate a second combined signal; as well as The first combined signal and the second combined signal are provided to a photodetector.

17. The method according to claim 13, further comprising: A portion of the second light beam and a portion of the first light beam are provided as reference signals to a reference arm circuit.

18. The method according to claim 13, further comprising: A plurality of light beams are generated by a plurality of light sources of the LIDAR system, each light beam in the plurality of light beams having a different corresponding frequency.

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