Multiplexing light detection and ranging device

Abstract

A multiplexed light detection and ranging (LiDAR) system generates an image of an object based on distances to the object measured by respective points. According to the multiplexing LiDAR, at least two groups of light sources are emitted to a scanner to form a plurality of scanning patterns at the same time, so that the scanning speed, the scanning area or the image pixel density of the LiDAR system is effectively improved.

Description

[0001] This invention is related to U.S. Patent 11,294,040 issued on April 5, 2022, and U.S. Patent Application Serial No. 17 / 708,728, both of which are hereby incorporated by reference in their entirety and assigned to the common assignee. Technical Field

[0002] This invention generally relates to light detection and ranging systems. More specifically, this invention relates to a light detection and ranging system that generates multiple laser beams from a single source, and this invention provides a hybrid scanner to scan the multiple laser beams to one or more targets and receive the retroreflected laser beams into a multiplexed interferometric circuit to measure distance and velocity. More specifically, this invention relates to a method of light detection and ranging that includes a method of multiplexed interferometric techniques to measure distance and velocity. Background Art

[0003] Light detection and ranging (LiDAR) is similar to radio detection and ranging (RADAR) in that LiDAR uses light waves to determine the range, angle, and velocity of an object. LiDAR utilizes the differences in laser return time and wavelength to create a digital 3-D representation of a target and has been widely used in terrestrial, airborne, and mobile applications. A LiDAR instrument consists of one or more laser transmitters, optical elements, a scanner, a photodetector, and a signal processor. One or more laser transmitters generate coherent light beams that are transmitted through a set of optical devices to the scanner and then to an object to determine the distance or velocity of the object. Physical characteristics are determined in the case of three-dimensional (3D) scanning. The photodetector receives the coherent light reflected from the object and converts the coherent light into an electrical signal that, after being processed, can determine the distance of the object. The transmitter will generate coherent light in the form of pulses. The signal processor records the time of the transmitted pulse and the time of the received coherent light reflection. The distance is equal to the difference between the transmission time and the reception time divided by two and multiplied by the speed of light.

[0004] Amplitude modulated continuous wave (AMCW) LiDAR is a form of phase-based LiDAR. Different from direct pulse detection, phase-based LiDAR emits a continuous laser signal. It encodes the output optical signal by modulating the laser emission amplitude with a high-speed radio frequency (RF) signal. The distance is measured by detecting the phase difference between the transmitted signal and the reflected signal. The phase shift of a sinusoidally modulated continuous laser waveform can be used to infer the distance of an object.

[0005] Frequency-modulated continuous-wave (FMCW) LiDAR is similar to AMCW LiDAR, but the modulation and demodulation are carried out optically rather than electrically. FMCW LiDAR uses a wavelength-tuned light source or a phase-modulated light source and an interferometer to measure the distance of an object, and has good sensitivity. The frequency of the FMCW laser is linearly modulated by a carrier signal to accurately measure the round-trip flight time of the laser. By detecting the beat frequency signal between the returned laser and the emitted laser, the flight time can be calculated with high precision. High-precision distance measurement can be achieved.

[0006] Interferometric time-of-interference (TOI) LiDAR technology is a new ranging method that overcomes the limitations of traditional LiDAR technologies, including time-of-flight (ToF) and frequency-modulated continuous wave (FWCW), and has the following characteristics: (1) By using an interferometer with a balanced detector, weak interference signals at long distances can be detected with high sensitivity; (2) Even when the signal frequency is very high, the time delay of the interference signal can be measured, so that the distance to the object can be accurately measured without a high-speed data acquisition system; (3) The requirements for the phase or wavelength modulation of the light source are relatively low, which can simplify the complexity of the light source drive circuit design. The operating speed of the TOI LiDAR system is mainly limited by the modulation speed of the light source and the efficiency of the optical receiver. The high-sensitivity detection of the TOI LiDAR system reduces the output power requirement of the light source. Therefore, this makes the system architecture design highly flexible and allows a single light source to drive multiple TOI LiDAR systems simultaneously. Summary of the Invention

[0007] An object of the present invention is to provide a multiplexed optical detection and ranging (LiDAR) system based on interferometric time-of-interference (TOI), time-frequency domain reflectometry, and small-wavelength modulation of a coherent light source. The multiplexed LiDAR system uses a single coherent light source to record the time delays of two or more interference signals or interferometric time-of-interference (TOI), where the output wavelength is determined by the operating current or the operating temperature.

[0008] To achieve this object, the multiplexed LiDAR system has a coherent light source connected to a modulation / scanning controller. The modulation scanning controller is configured to generate a pulsed wavelength control signal transmitted to the coherent light source. The pulsed wavelength control signal can be a current modulation signal or a laser ambient temperature adjustment signal. The pulsed wavelength control signal modulates the coherent light source to generate pulsed wavelength-modulated coherent light emission.

[0009] The pulsed wavelength - modulated coherent light emission is coupled to at least two interferometers. Each interferometer is configured to split the pulsed wavelength - modulated coherent light emission into a sample portion and a reference portion. The sample portion of the pulsed wavelength - modulated coherent light emission is arranged to illuminate an object to be measured. The reference portion of the pulsed wavelength - modulated coherent light emission is arranged to provide a reference for determining the distance from the multiplexed LiDAR system to the object. The interferometer is also configured to transmit the pulsed wavelength - modulated coherent light to a hybrid scanner. The hybrid scanner is configured to physically transmit the sample portion of the pulsed wavelength - modulated coherent light from each interferometer to different positions on the object and simultaneously scan the surface of the object using the pulsed wavelength - modulated coherent light from each interferometer. The hybrid scanner is also configured to receive a portion of the pulsed wavelength - modulated coherent light retro - reflected from different positions on the object. The retro - reflected pulsed wavelength - modulated coherent light is transmitted from the hybrid scanner to the respective interferometers and then coupled with the reference portion of the pulsed wavelength - modulated coherent light in the respective interferometers to form an optical interference signal.

[0010] The hybrid scanner is configured to provide a scan pattern for the pulsed wavelength - modulated coherent light emitted by each interferometer. The scan pattern is configured to cover different regions on the object to increase the effective scan range of the multiplexed LiDAR system. In various embodiments, the scan pattern is configured to cover the same region on the object to increase the effective scan pixel density of the multiplexed LiDAR system. The hybrid scanning mirror has at least one planar mirror rotating along a first axis and a polygon mirror, and the polygon mirror is configured to reflect the sample portions of the pulsed wavelength - modulated coherent light from multiple interferometers to the object. The polygon mirror rotates about a second axis to establish a scan pattern of the sample portions of the multiple pulsed wavelength - modulated coherent lights.

[0011] The multiplexed LiDAR system has a photodetector array, and the photodetector array is configured to convert the optical interference signal from each interferometer into an electrical interference signal. In various embodiments, the photodetector is configured as a polarization - diversity balanced - amplification detector. The photodetector has at least one power monitor to measure the input power level of the photodetector. The output of the power monitor provides a time - delayed and modulated power level related to the distance of the object.

[0012] The multiplexed LiDAR system has a signal processor configured to receive an electrical interference signal and convert the electrical interference signal into digital data representative of the amplitude of the electrical interference signal. The signal processor is configured to generate an imaging range based on the distance to the object to be displayed. The imaging range to be displayed is calculated by a computer system programmed to calculate the time delay determined by the optical interference signals of all the interferometers.

[0013] The modulation / scanning controller is configured to generate a low duty cycle wavelength modulation control signal to modulate the coherent light source by controlling the drive current of the narrow coherent light source, controlling the temperature of the narrow bandwidth light source, or adjusting the phase of the light emitted by the light source. In other embodiments, when there is a time delay between the light in the sample and the reference arm of the interferometer, the modulation / scanning controller will generate a pulse phase control signal to produce interference.

[0014] In various embodiments, the interferometer includes a polarization controller for adjusting the polarization state of the coherent light emitted by the light source and maximizing the amplitude of the optical interference signal or the electrical interference signal. The interferometer has a first coupler that receives the pulsed wavelength modulated coherent light from the polarization controller. The coupler splits the pulsed wavelength modulated coherent light. The first portion of the pulsed wavelength modulated coherent light is fed into at least one sample arm. The second portion of the pulsed wavelength modulated coherent light is fed into the reference arm. The interferometer has a circulator connected to receive the first portion of the pulsed wavelength modulated coherent light from at least one sample arm. The circulator is configured such that the pulsed wavelength modulated coherent light from the sample arm enters the circulator and exits from the next port. Generally, the next port is in the clockwise direction to direct the pulsed wavelength modulated coherent light to the scanner. The scanner is configured to physically transmit the sample pulsed wavelength modulated coherent light to scan the object. The sample pulsed wavelength modulated coherent light is retroreflected from the object to the scanner for ranging measurements and transmitted to the circulator within the interferometer. Then, the retroreflected pulsed wavelength modulated coherent light is transmitted from the circulator to the second coupler.

[0015] The length of the reference arm of the interferometer is greater than the length of the sample arm and is more than twice the maximum ranging depth of the system. The second portion of the pulsed wavelength modulated coherent light in the reference arm is applied to the second coupler. The second portion of the pulsed wavelength modulated coherent light transmitted in the reference arm is coupled with the collected retroreflected pulsed wavelength modulated light to form an optical interference light signal. The optical interference light signal exits the second coupler and enters the photodetector array.

[0016] The maximum frequency of the optical interference signal corresponds to the minimum ranging depth of the multiplexed LiDAR system. It is greater than the Nyquist sampling frequency of the digitizer in the data acquisition and signal processor. The minimum frequency of the optical interference signal corresponds to the maximum ranging depth of the multiplexed LiDAR system. The time delay of the detected optical interference is measured at the falling edge of the envelope of the optical interference signal.

[0017] In various embodiments, the sample pulse wavelength modulated coherent light beams of each interferometer are transmitted to a separate scanner aiming in different directions, so that the multiplexed LiDAR system can be configured to simultaneously measure distances and display the imaging ranges from multiple objects.

[0018] In various embodiments, the multiplexed LiDAR system can use a single hybrid scanner to utilize two or more time-of-flight (ToF) or FMCW ranging methods to provide a scanning pattern for each ToF or FMCW subsystem. The scanning pattern is configured to cover different areas on the object to increase the effective scanning range of the multiplexed LiDAR system or cover the same area on the object to increase the effective scanning pixel density of the multiplexed LiDAR system. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1A is a schematic diagram of a related art TOI LiDAR system.

[0020] Figure 1B is a schematic diagram of a LiDAR module embodying the principles of the present invention.

[0021] Figure 2 is a schematic diagram of a multiplexed LiDAR system embodying the principles of the present invention.

[0022] Figure 3A is a schematic diagram of a scanner embodying the principles of the present invention, which is configured to scan two illumination beams from Figure 1B two LiDAR modules to form a larger scanning pattern.

[0023] Figure 3B is a schematic diagram of a scanner embodying the principles of the present invention, which is configured to scan two illumination beams from Figure 1B two LiDAR modules to form a denser scanning pattern.

[0024] Figure 4 is a schematic diagram of a scanner embodying the principles of the present invention, which is configured to scan two illumination beams from Figure 1B two LiDAR modules to form two scanning patterns with different scanning areas and scanning pixel densities.

[0025] Figure 5A is a schematic diagram of an angle-based polygon mirror scanner embodying the principles of the present invention, which is configured to scan two illumination beams from Figure 1B two LiDAR modules to form a larger scan pattern.

[0026] Figure 5B is a schematic diagram of an angle-based polygon mirror scanner embodying the principles of the present invention, which is configured to scan two illumination beams from Figure 1B two LiDAR modules to form two scan patterns with different scan areas and scan pixel densities.

[0027] Figure 6A is a block diagram of an electrical TOI measurement circuit embodying the principles of the present invention, which shows the program structure of a signal processor configured to perform distance measurements based on multiplexed TOI LiDAR.

[0028] Figure 6B is a retroreflective pulse fringe pattern of the sample arm at the zero (0) meter position and the envelope embodying the principles of the present invention.

[0029] Figure 6C is a retroreflective pulse fringe pattern of the sample arm at the 180-meter position and the envelope embodying the principles of the present invention.

[0030] Figure 7 shows a frame-based velocity measurement method of a TOI LIDAR system embodying the principles of the present invention.

[0031] Figure 8A is a flowchart of a method for determining the distance of an object using multiplexed distance measurement embodying the principles of the present invention.

[0032] Figure 8B is a flowchart of a method for determining the velocity of an object using multiplexed distance measurement embodying the principles of the present invention.

[0033] Figure 9A is a schematic diagram of a multiplexed LiDAR system with multiple front-end scanners embodying the principles of the present invention.

[0034] Figure 9B is a schematic diagram of the implementation of a multiplexed LiDAR system with multiple front-end scanners embodying the principles of the present invention. Detailed Description

[0035] A multiplexed LiDAR system is configured to generate an image of an object based on the distances of individual point-to-object measurements. The multiplexed LiDAR system uses a pulsed wavelength-modulated light source to split the emitted light into at least two groups of light and emit them to a scanner, while forming multiple scanning patterns, thereby effectively improving the scanning speed, scanning area, or image pixel density of the LiDAR system.

[0036] Figure 1A is a schematic diagram of a related art TOI system 100. In Figure 1A , the TOI LiDAR system 100 includes a pulsed wavelength-modulated narrowband light source 105. The pulsed wavelength-modulated light source 105 emits pulsed-modulated coherent light, and the output spectrum of the pulsed-modulated coherent light consists of a single or multiple longitudinal modes. The longitudinal mode of the resonator is a special standing wave pattern formed by the waves confined in the cavity. In a laser, light is amplified in the cavity resonator, which usually consists of two or more mirrors. The cavity has mirror walls that can reflect light, so that the standing wave pattern exists in the cavity with very little loss. The longitudinal mode corresponds to the wavelength of the reflected wave, which is enhanced by constructive interference after multiple reflections from the reflecting surfaces of the cavity. All other wavelengths are suppressed by destructive interference. The nodes of the longitudinal mode pattern are arranged axially along the cavity length. The laser of the pulsed wavelength-modulated light source 105 is one of the four types of lasers known in the art and is classified as a solid-state laser, a gas laser, a liquid laser, or a semiconductor laser. In the structure discussed in the present invention, the pulsed wavelength-modulated light source 105 is shown as a semiconductor laser, and its wavelength or frequency is controlled by current or temperature. The modulation of the pulsed wavelength-modulated light source 105 will be discussed below.

[0037] The pulsed wavelength-modulated narrowband light source 105 emits pulsed wavelength-modulated coherent light to the interferometer 110. The pulsed wavelength-modulated narrowband light source 105 emits through free space, an optical fiber, or an optical waveguide to reach the interferometer 110.

[0038] In various embodiments, the interferometer 110 is implemented as an optical fiber, bulk optics, an integrated photonic circuit, or some combination thereof. The interferometer 110 has a polarization controller 115 that receives the pulsed wavelength-modulated coherent light and adjusts the polarization state of the pulsed wavelength-modulated coherent light from the light source 105. To maximize the amplitude of the interference signal or interference electrical signal 162 of the light transmitted in the optical paths 155a, 155b. The pulsed wavelength-modulated coherent light from the light source 105 or the pulsed wavelength-modulated coherent light transmitted through the polarization controller 115 is applied to the coupler 120. The coupler 120 splits the coherent light into a sample portion that is sent to at least one sample arm 122 and a reference portion of the pulsed wavelength-modulated coherent light that is sent to the reference arm 140 within the interferometer 110. The sample arm 122 and the reference arm 140 are implemented as free space paths, optical fibers, or optical waveguides.

[0039] The interferometer has a circulator 125 that receives a sample portion of the pulsed wavelength - modulated coherent light from the sample arm 122. The circulator 125 is configured such that the sample portion of the pulsed wavelength - modulated coherent light enters the circulator 125 and exits from the next port to a portion of the sample arm 122. The next port is typically (but not necessarily) in the clockwise direction to direct the coherent light through the sample arm 122 to the scanner 130. The scanner 130 is configured to physically transport the sample pulsed wavelength - modulated coherent light 135 to scan an object. The sample pulsed wavelength - modulated coherent light 135 is reflected from the object for ranging measurements. The retro - reflected pulsed wavelength - modulated coherent light is received by the scanner 130 and transmitted to the circulator 125. Then, the retro - reflected pulsed wavelength - modulated coherent light through the optical path 145 is transmitted to the second coupler 150. The optical path can be implemented as a free - space path, an optical fiber, or an optical waveguide.

[0040] The reference arm 140 (implemented as a free - space path, an optical fiber, or an optical waveguide) has an additional optical path 142 that provides an additional path length such that the path length of the reference arm 140 matches the maximum ranging depth of the TOI system 100. The light pulsed wavelength - modulated coherent optical signals from at least one sample arm 122 and the reference arm 140 are combined in the coupler 150 to generate an optical interference signal.

[0041] Heterodyne detection is performed on the pulsed wavelength - modulated coherent optical signals from at least one sample arm 122 and the reference arm 140 to extract a beat frequency from the reference signal. The beat signal has a 180° phase difference between the coupler outputs. The balanced detector 160 subtracts the signals from each input channel to extract the interference signal, i.e., the beat signal.

[0042] The optical interference signal is applied to optical paths 155a and 155b implemented as a free - space path, an optical fiber, or an optical waveguide. The optical interference signal is applied to the optical paths 155a and 155b and transmitted to the balanced photodetector 160 to convert the optical interference signals from the optical paths 155a and 155b into an interference electrical signal 162.

[0043] The interference electrical signal 162 is generated by the balanced photodetector 160 and transmitted to the data acquisition circuit within the signal processor 165. The data acquisition circuit within the signal processor 165 converts the interference electrical signal 162 into digital data. The maximum frequency of the optical interference signal corresponds to the minimum ranging depth of the TOI LiDAR system 100. The maximum frequency of the optical interference signal is greater than the Nyquist sampling frequency of the digitizer in the data collector or the signal processor 165.

[0044] The minimum frequency of the optical interference signal applied to optical paths 155a and 155b corresponds to the maximum ranging depth of the TOI LiDAR system 100. The time delay of the detected optical interference is measured at the falling edge of the envelope of the optical interference signal.

[0045] Then, the digital data is transmitted to the computer 170 for further processing and display. In some embodiments, the signal processor 165 may be integrated with the computer 170 as a single unit.

[0046] In various embodiments, the computer 170 is connected to the modulation / scanning controller 175. In other embodiments, the computer 170 is integrated with the modulation / scanning controller 175. The modulation / scanning controller 175 has a modulation sub-circuit that determines the modulation, frequency, and shape of the modulation control signal 177 applied to the coherent light source 105. The modulation / scanning controller 175 also has a scanning control circuit that provides a modulation / scanning synchronization signal 179 to the signal processor 165 and the scanner 130. The scanning control circuit creates the required scanning pattern, which is used to generate the appropriate modulation / scanning synchronization signal 179 that is applied to the scanner 130.

[0047] The scanner 130 can be implemented as a 1D or 2D scanner to distribute the sample pulse wavelength modulation of the coherent light 135 to form an image based on TOI measurement. The 1D scanning pattern may be linear or non-linear in time and may be unidirectional or bidirectional. In some embodiments of the TOI Lidar system 100, the 2D scanning pattern may be linear or non-linear. It can use a raster scan, a spiral scan, or other patterns to collect measurement information. The scanner 130 can be mechanically implemented as a galvanometer mirror, a microelectromechanical system (MEMS), a piezoelectric actuator, or optically include an acousto-optic (AO) deflector or a solid-state scanner. There may be other methods that provide the required scanning motion to collect measurement information in accordance with the principles of the present invention.

[0048] Figure 1B is a schematic diagram of the LiDAR module 200 embodying the principles of the present invention. The LiDAR module 200 has an interferometer 110 and a balanced detector 160. The structure and operation of the interferometer 110 and the balanced detector 160 are the same as those of Figure 1A the interferometer 110 and the balanced detector 160 of the prior art shown.

[0049] Figure 2FIG. 0 is a schematic diagram of a multiplexed LiDAR system 300 based on a TOI LiDAR system embodying the principles of the present invention. The multiplexed LiDAR system 300 has a pulsed wavelength modulation narrow bandwidth light source 305. The pulsed wavelength modulation light source 305 emits pulsed modulated coherent light, the output spectrum of which consists of single or multiple longitudinal modes. The longitudinal modes of a resonator are special standing wave patterns formed by waves confined within the cavity. In a laser, light is amplified in a cavity resonator, which typically consists of two or more mirrors. The cavity has mirror walls that can reflect light, allowing standing wave patterns to exist in the cavity with little loss. The longitudinal modes correspond to the wavelengths of the reflected waves, which are enhanced by constructive interference after multiple reflections from the reflecting surfaces of the cavity. All other wavelengths are suppressed by destructive interference. The nodes of the longitudinal mode pattern are arranged axially along the cavity length. The pulsed wavelength modulation light source 305 employs one of four types of lasers known in the art and is classified as a solid-state laser, a gas laser, a liquid laser, or a semiconductor laser. In the structure discussed in the present invention, the pulsed wavelength modulation light source 305 is shown as a coherent light source 305, the wavelength or frequency of which is controlled by current or temperature. The modulation of the pulsed wavelength modulation light source 305 will be discussed below.

[0050] The pulsed wavelength modulation narrowband light source 305 emits pulsed wavelength modulation coherent light and splits it by an optical splitter 307 to two LiDAR modules 200c and 200d. The pulsed wavelength modulation narrow bandwidth light source 305 emits through free space, an optical fiber, or an optical waveguide to the optical splitter 307. The first branch of the optical splitter 307 is connected to the first LiDAR module 200a, and the second branch of the optical splitter 107 is connected to the second LiDAR module 200b. In various embodiments, for applications that require higher detection sensitivity and slower detection speed, an optical switch can be used instead of the optical splitter 307.

[0051] The structures of the LiDAR modules 200c and 200d in various embodiments are as described above Figure 1B and are implemented as optical fibers, bulk optics, integrated photonic circuits, or some combination thereof. The optical pulse wavelength modulation coherent light signals are transmitted from the LiDAR modules 200a and 200b to a hybrid scanner 330. The hybrid scanner 300 is implemented as a 1D or 2D scanner to distribute the sample pulsed wavelength modulation coherent light beams 135a and 135b to form an image based on TOI measurements. The 1D scan pattern may be linear or non-linear in time and may be unidirectional or bidirectional. Then, the sample pulsed wavelength modulation coherent light beams 135a and 135b are reflected back to the hybrid scanner 330 and transmitted to the LiDAR modules 200a and 200b. The retroreflected sample pulsed wavelength modulation coherent light 135a and 135b arrive at Figure 1Bcirculator 125, and the optical paths 145 from the circulator 125 to the LiDAR modules 200a and 200b, and to the optical coupler 150. The reference signal from the reference optical path 140 is combined with the retroreflected optical signals from the circulators 145 in the two LiDAR modules 200a and 200b in the optical coupler 150 to generate Figure 1B optical interference signals 155a and 155b. Further, as Figure 1B shown, heterodyne detection is performed on the retroreflected pulsed wavelength-modulated coherent optical signals from the sample arms 122a, 122b and the reference arm 140 to extract the beat frequency from the reference signal. The beat signals have a 180° phase difference in the two outputs 155a and 155b from the coupler 150. The balanced detector 160 subtracts the signals from each input channel to extract the interference signal, i.e., the beat signal.

[0052] The optical interference signals are applied to the optical paths 155a and 155b implemented as free space paths, optical fibers or optical waveguides. The optical interference signals are applied to the optical paths 155a and 155b and transmitted to the balanced photodetector 160 to convert the optical interference signals from the optical paths 155a and 155b of the two interferometers 110 within the two LiDAR modules 200a and 200b into Figure 2 a first interferometric electrical signal 362a and a second interferometric electrical signal 362b in

[0053] The first interferometric electrical signal 362a and the second interferometric electrical signal 362b are transmitted to the data acquisition circuit within the signal processor 365, where the first interferometric electrical signal 362a and the second interferometric electrical signal 362b are converted into digital data. In some embodiments, the time delay of the detected electrical interference signals 362a and 362b can be measured at the rising or falling edge of the electrical interference signal envelope in the signal processor 365 having an analog signal processing circuit without converting them into digital data.

[0054] Then, the digital data is transmitted to the computer 370 for further processing and display. In some embodiments, the signal processor 365 can be integrated with the computer 370 into a single unit.

[0055] In various embodiments, computer 370 is connected to modulation / scanning controller 375. In other embodiments, computer 370 is integrated with modulation / scanning controller 375. Modulation / scanning controller 375 has a modulation sub-circuit that determines the modulation, frequency, and shape of modulation control signal 377 applied to coherent light source 305. Modulation / scanning controller 375 also has a scanning control circuit that provides modulation / scanning synchronization signal 379 to signal processor 365 and scanner 330. Modulation / scanning controller 375 creates the desired scan pattern that is used to generate the appropriate modulation / scanning synchronization signal 379 that is applied to scanner 330.

[0056] Scanner 330 can be implemented as a 1D or 2D scanner to distribute sample pulse wavelength modulation of coherent beams 335a and 335b to form an image based on TOI measurements. The 1D scan pattern can be linear or non-linear in time and can be unidirectional or bidirectional. In some embodiments of TOI LiDAR system 300, the 2D scan pattern can be linear or non-linear. It can employ raster scan, spiral scan, or other patterns to collect measurement information. Scanner 330 can be mechanically implemented as a galvanometer mirror, a polygon mirror, a microelectromechanical system (MEMS), a piezoelectric actuator, and optically includes an acousto-optic (AO) deflector or a solid-state scanner. There may be other methods that provide the required scan motion to collect measurement information that are in accordance with the principles of the present invention.

[0057] Figure 3A and Figure 3B is a schematic diagram of scanner 330 configured to receive sample arms 322a and 322b of LiDAR modules 200c and 200d, as Figure 1BAs shown, the sample arms 322a of the first LiDAR module 200c and the sample arm 200d of the second LiDAR 200d are inserted and fixed in the scanner 330. The distal ends of the first sample arms 322a and 322b are respectively connected to the collimators 325a and 325b to collimate the sample pulse wavelength-modulated coherent beams 322a and 322b. To improve the overall efficiency of LiDAR operation, the collimators 325a and 325b require a low numerical aperture for long-distance illumination, but a higher numerical aperture for receiving the pulse wavelength-modulated coherent light retroreflected from the object. Therefore, the collimators 325a and 325b can be single-fiber lenses with designed tips, so that the on-axis sample pulse wavelength-modulated coherent beams 335a and 335b emitted through the central part of the engineered tips are collimated, while the off-axis pulse wavelength-modulated coherent light retroreflected from the object can be coupled back into the sample arm fibers 322a and 322b after passing through the annular part of the designed tips. The fiber lenses of the collimators can be implemented as gradient-index (GRIN) fiber lenses with single-mode fibers, GRIN fiber lenses with few-mode fibers, fiber ball lenses, GRIN lens assemblies, free-space collimators, or combinations thereof. The designed tip can be a tapered tip, a Fresnel surface, a metasurface, or a combination thereof.

[0058] In Figure 3A this case, the pulse wavelength-modulated coherent beams 335a and 335b are guided to the slow-axis scanning mirrors 340a and 340b. The slow-axis scanning mirrors 340a and 340b are located on the first axis. In this case, the slow-axis scanning mirrors 340a and 340b rotate vertically to reflect the pulse wavelength-modulated coherent beams 335a and 335b in a vertical scanning pattern. The vertical scanning pattern covers the required field of view. The first and second slow-axis scanning mirrors 340a and 340b are configured to provide a position offset such that the reflected pulse wavelength-modulated coherent beams 345a and 345b illuminate different faces of the fast-axis scanning mirror 350. The fast-axis scanning mirror 350 is a polygonal cylinder, and each face 351a, 351b, and 351c of the fast-axis scanning mirror 350 has the same-sized rectangular mirror shape 351a, 351b, and 351c, which are formed on the outer surface of the polygonal cylinder of the fast-axis scanning mirror 350.

[0059] The fast-axis scanning mirror 350 rotates horizontally about the axis 353 by the motor 352 to create a horizontal scanning pattern. The horizontal scanning pattern covers the horizontal field of view. The combination of the vertical and horizontal scanning patterns generates a first two-dimensional scanning pattern 355a and a second two-dimensional scanning pattern 355b respectively according to the reflected pulsed-wavelength modulated coherent beams 135a and 135b. The positional offset of the first and second slow-axis scanning mirrors 340a and 340b determines the separation of the first and second two-dimensional scanning patterns 355a and 355b. The two two-dimensional scanning patterns 355a and 355b form a combined scanning pattern, the scanning area of which is twice as large as that of each two-dimensional scanning pattern 355a and 355b, thereby increasing the effective scanning area.

[0060] In Figure 3B , the collimators 325a and 325b are configured with a small enough positional offset such that the pulsed-wavelength modulated coherent beams 345a and 345b can be directed to different parts on a single slow-axis scanning mirror 340. The slow-axis scanning mirror 340 rotates vertically to reflect the pulsed-wavelength modulated coherent beams 345a and 345b in a vertical scanning pattern. The reflected pulsed-wavelength modulated coherent beams 345a and 345b illuminate different parts of the fast-axis scanning mirror 350. The fast-axis scanning mirror 350 is the same as the Figure 3A fast-axis scanning mirror 350.

[0061] The fast-axis scanning mirror 350 rotates horizontally about the axis 353 by the motor 352 to create a horizontal scanning pattern. The combination of the vertical scanning pattern and the horizontal scanning pattern generates a first two-dimensional scanning pattern 355a and a second two-dimensional scanning pattern 355b respectively according to the reflected pulsed-wavelength modulated coherent beams 135a and 135b. The two two-dimensional scanning patterns 355a and 355b completely overlap to form a combined scanning pattern, the scanning pixel density of which is twice that of each individual two-dimensional scanning pattern, thereby increasing the effective scanning pixel density or the effective scanning speed. In some embodiments, the two-dimensional scanning patterns 355a and 355b will partially overlap such that a part of the combined scanning patterns 355a and 355b has an increased pixel density while increasing the scanning pixel area.

[0062] Figure 4 is a schematic diagram of the scanner 330, which is configured to receive the Figure 3A sample arms 122a and 122b of the LiDAR modules 200c and 200d in Figure 3AAs shown, scanner 330 is configured to receive sample arms 322a and 322b of LiDAR modules 200c and 200d. Pulse wavelength modulated coherent light from sample arms 322a and 322b of LiDAR modules 200c and 200d is applied to collimators 325a and 325b. Pulse wavelength modulated coherent light beams 345a and 345b from collimators 325a and 325b are respectively guided to slow axis scanning mirrors 340a and 340b. The slow axis scanning mirrors 340a and 340b are vertically rotated to reflect the pulse wavelength modulated coherent light beams 345a and 345b in a vertical scanning pattern. This vertical scanning pattern covers the required field of view. The first and second slow axis scanning mirrors 340a and 340b are configured with a positional offset such that the reflected pulse wavelength modulated coherent light beams 345a and 345b illuminate different parts of the fast axis scanning mirror 405. The fast axis scanning mirror 405 is a rotating polygon mirror, consisting of two different sets of face configurations, including a low face part (with fewer faces) 405a and a high face part (with more faces) 405b. The low face part 405a has each face 406a, 406b, and 406c, and the high face part 405b has each face 409a, 409b, 409c, 409d, 409e, and 409f, which are formed by equal-sized rectangular mirror shapes 409a, 409b, 409c, 409d, 409e, and 409f formed on the polygonal cylindrical outer surface of the fast axis scanning mirror 405.

[0063] The first reflected pulse wavelength modulated coherent light illuminates the low face part 405a of the polygon mirror 405, and the second reflected pulse wavelength modulated coherent light 405b illuminates the high face part 405b of the polygon mirror 405. Alternatively, but not shown, the polygon mirror 405 can be reversed so that the second retroreflected pulse wavelength modulated coherent light beam 345b illuminates the low face part 405b, and the first reflected pulse wavelength modulated coherent light beam 345a illuminates the high face part 405b. The first case results in the pulse wavelength modulated coherent light beam 135a forming a first 2D scanning pattern 415a with a wider scanning area and a lower scanning pixel density, and results in the pulse wavelength modulated coherent light beam 135b forming a second 2D scanning pattern 415b with a narrower scanning area and a higher scanning pixel density. This implementation enables the multiplexed LiDAR system to simultaneously accommodate different scanning requirements and parameters, including but not limited to the field of view (FOV) and the pixel density for near / far field image formation.

[0064] As described above, the motor 408 rotates the shaft 407 to rotate the fast axis scanning mirror 405.

[0065] Figure 5A and Figure 5B is a schematic diagram of scanner 130, which is configured to receive a sample arm. As Figure 5AAs shown, scanner 330 is configured to receive sample arms 322a and 22b of interferometers 110a and 110b of LiDAR modules 200c and 110b. Collimators 325a and 325b are configured with position offsets and angular offsets small enough such that pulsed wavelength-modulated coherent beams 325a and 325b can be directed to different portions on a single slow-axis scanning mirror 340. The slow-axis scanning mirror 340 is vertically rotated to reflect the pulsed wavelength-modulated coherent beams 325a and 325b in a vertical scanning pattern. The reflected pulsed wavelength-modulated coherent beams 345a and 345b illuminate different portions of the fast-axis scanning mirror 410.

[0066] The fast-axis scanning mirror 410 has two polygonal cylindrical portions 410a and 410b. The first polygonal cylindrical portion 410a has a plurality of isosceles trapezoidal facet mirrors 411a, 411b, 411c. The isosceles trapezoidal facet mirrors 411a, 411b, and 411c are formed on the facet surface of the first polygonal cylindrical portion 410a, and its upper edge is longer than its lower edge.

[0067] The second polygonal cylindrical portion 410b has a plurality of isosceles trapezoidal facet mirrors 411d, 411e, 411f. The isosceles trapezoidal facet mirrors 411d, 411e, and 411f are formed on the facet surface of the first polygonal cylindrical portion 410b, and its lower edge is longer than its upper edge.

[0068] The fast-axis scanning mirror 410 with isosceles trapezoidal facet mirrors 411a, 4116b, 411c, 411d, 4116e, and 411f compensates for the angular offsets of the reflected pulsed wavelength-modulated coherent beams 345a and 345b. The fast-axis scanning mirror 410 is horizontally rotated about an axis 413 by a motor 412 to create a horizontal scanning pattern. The combination of the vertical scanning pattern and the horizontal scanning pattern produces a first two-dimensional scanning pattern 415a and a second two-dimensional scanning pattern 415b such that the two two-dimensional scanning patterns 415a and 415b completely overlap, thereby respectively forming the reflected pulsed wavelength-modulated coherent beams 135a and 135b. The two two-dimensional scanning patterns 415a and 415b form a combined scanning pattern whose scanning pixel density is twice as large as that of each individual two-dimensional scanning pattern, thereby increasing the effective scanning pixel density or the effective scanning speed. In some embodiments, the two-dimensional scanning patterns 415a and 415b will partially overlap such that a portion of the combined scanning patterns 415a and 415b has an increased pixel density while increasing the scanning pixel area.

[0069] In Figure 5B it, the basic structure of the hybrid scanner 330 is the same as that of Figure 5AThe basic structure of the hybrid scanner 330 in [reference] is the same. The fast-axis scanning mirror 420 is a rotating polygon mirror. The rotating polygon mirror 420 consists of two different polygonal cylindrical parts 420a and 420b, including the low-faceted part 420a with the fewest facets and the second part 420b with the most facets. The first reflected pulsed wavelength-modulated coherent beam 135a irradiates the second part 420a of the polygon mirror 420. The second reflected pulsed wavelength-modulated coherent beam 135b irradiates the first part 420b of the rotating polygon mirror 420 and generates a first 2D scanning pattern 415a with a wider scanning area and a lower scanning pixel density, and generates a second 2D scanning pattern 415b with a narrower scanning area and a higher scanning pixel density. This embodiment enables Figure 2 the multiplexed LiDAR system 300 in [reference] to simultaneously adapt to different scanning requirements and parameters, and simultaneously includes but is not limited to the field of view (FOV) and the pixel density for near / far field image formation.

[0070] Figure 6A is a block diagram of the electrical TOI measurement circuit included in the signal processor. Figure 2 The interference electrical signals 362a and 362b generated by the LiDAR modules 200a and 200b in [reference] are received by the multi-channel envelope detector 500 and converted into envelopes 505a and 505b of the interference electrical signals 362a and 362b. The multi-channel envelope detector 500 is implemented as a radio frequency (RF) power detector, a root mean square (RMS) detector, or a frequency demodulator. The radio frequency (RF) power detector, the root mean square (RMS) detector, or the frequency demodulator are known in the art and are commercially available devices. The radio frequency (RF) power detector, the root mean square (RMS) detector, or the frequency demodulator removes the high-frequency components in the interference electrical signals 362a and 362b, thereby extracting the envelopes of the interference electrical signals 362a and 362b.

[0071] The envelope signals 505a and 505b are transmitted to the multi-channel edge detector 510. The multi-channel edge detector 510 determines pulse events and places the pulse events at the output of the edge detector 510. The pulse events indicate the leading edge or the falling edge of the envelope signals 505a and 505b. The multi-channel edge detector 510 is implemented as an edge-fault converter, an exclusive OR gate and a delay circuit, a differentiating circuit, etc. The edge-fault converter, the exclusive OR gate, the delay circuit, the differentiating circuit are also known in the art and are commercially available.

[0072] The outputs 515a and 515b of the edge detector 510 are connected to the inputs of the multi-channel time-to-digital converter 520. The multi-channel time-to-digital converter 520 generates a time difference signal, which is transmitted to the outputs 530a and 530b of the multi-channel time-to-digital converter 520. The time difference signals at the outputs 530a and 530b of the multi-channel time-to-digital converter 520 indicate the time between the rising or falling edges of the pulse events 505a and 505b and the pulse event 525. The pulse event 525 corresponds to the rising or falling edge of the light source modulation signal 377 transmitted from the modulation / scanning controller 375. The pulse event 525 is a trigger that starts the multi-channel time-to-digital converter 520 to count the time interval. The pulse outputs 515a and 515b of the multi-channel edge detector 510 provide pulse events to terminate the counting of the time interval by the multi-channel time-to-digital converter 520. A series of time difference signals at the outputs 530a and 530b of the multi-channel time-to-digital converter 520 are converted into depth measurement values to form an image displayed on the computer 170.

[0073] Figure 6B FIG. is a diagram of the pulse input fringe 560 and envelope 565 of the reference arm embodying the principles of the present invention. Figure 6B The figure in Figure 2 is an example of the electrical interference signal detected by the prototype TOI system 300 for an object at the zero (0) meter position. Figure 6C FIG. is a diagram of the retroreflective pulse fringe 570 and envelope 575 of another sample arm embodying the principles of the present invention. Figure 6C The figure in is an example of the electrical interference signal detected by the prototype TOI system 300 for an object at 180 meters. Figure 6A In the multi-channel edge detector 510 determines the time of the falling edge t0 of the envelope of the reference arm 565 and the time of the falling edge t1 of the envelope of the sample arm 575. The multi-channel time-to-digital converter 520 counts the time interval between the falling edge time t0 of the reference arm and the falling edge time t1 of the sampling arm. The distance to the object to be measured is determined by the following formula:

[0074] Distance=c*(t0 - t1)

[0075] Where:

[0076] c is the speed of light.

[0077] t0 is the falling edge time of the reference arm.

[0078] t1 is the falling edge time of the sample arm.

[0079] A series of different time difference signals at the outputs 530a and 530b of the multi-channel time-to-digital converter 520 can be converted into depth information and form an image displayed on the computer 370.

[0080] Figure 7 shows a frame-based velocity measurement method using a multiplexed LiDAR system embodying the principles of the present invention. The multiplexed LiDAR system can be configured to encode a small time delay in a second TOI module such that frames 590a(1), 590a(2),..., 590a(m) and 590b(1), 590b(2),..., 590b(m) are captured by the TOI modules 200a and 200b in Figure 2 in an interleaved manner and represent Figure 2 the first and second interferometric electrical signals 362a and 362b.

[0081] Data 595a and 595b are transmitted to the signal processor 365 and processed as Figure 6A described, thereby determining the rising or falling edge of the data. Thus, the determination of the rising or falling edge of the data provides the time difference between data 595a and 595b. Then, the distance between data 615a and 615b is determined as the time difference (t b –t a ) between data 595a and 595b. The time difference (t b –t a ) between data 595a and 595b is multiplied by the frame rate at which the optical interference signal of the optical paths of the LiDAR modules 200a and 200b is sampled to determine the velocity of the object to be measured.

[0082] Figure 8A is a flowchart of a method for determining the distance of an object using a TOI-based multiplexed LiDAR system embodying the principles of the present invention. A laser beam is generated (block 700). The laser beam is modulated (block 705) using a wavelength modulation or frequency modulation signal to adjust the wavelength or frequency of the laser beam. Then, the laser beam is polarized (block 710) to adjust the polarization state of the laser to maximize the amplitude of the optical or electrical interference signal.

[0083] Optically split (block 715) a laser beam into multiple beams, and couple (block 720) each split laser beam to a LiDAR module to create a sample arm and a reference arm. Connect (block 725) each sample arm to a hybrid scanner to establish a scanning pattern for each sample laser beam. Each sample laser beam scans an object to be measured (730). A small portion of each laser coherent beam is reflected back from the object to be measured and received by each hybrid scanner associated with the retroreflected pulsed wavelength-modulated coherent laser beam (block 735). Couple (block 740) the retroreflected pulsed wavelength-modulated coherent laser beam through an optical coupler to an optical circulator of an interferometer to combine with a reference pulsed wavelength-modulated coherent laser beam to form an optical interference signal. Convert (block 745) the optical interference signal into an oscillating electrical interference signal.

[0084] Perform an envelope detection process on the electrical interference signal to identify (block 750) the envelope of the electrical interference signal. Determine the time of the rising edge or falling edge of the envelope of the digitized electrical interference signal (block 755). Determine the time difference between the rising edge or falling edge of the envelope of the electrical interference signal and the modulation / scanning synchronization signal (block 760), and calculate the distance to the object to be measured (block 765). When multiple laser beams scan an object, a two-dimensional ranging image is formed based on all the measured distances and the angular positions of the scanners (block 760).

[0085] Figure 8B Is a flowchart of a method for determining the velocity of an object using a time-of-interference (TOI)-based multiplexed LiDAR system embodying the principles of the present invention. The method for determining the velocity of an object using a TOI-based multiplexed LiDAR system first performs (block 775) i.e. Figure 8A The steps in the method multiple times. Determine the velocity of the object (block 780) as the difference in distances measured by multiple TOI modules over time.

[0086] In various embodiments, each LiDAR module in the multiplexed LiDAR system is equipped with multiple scanners to simultaneously measure the distances of multiple objects at different positions through a single LiDAR system. Figure 9A Is a schematic diagram of a TOI LiDAR-based multiplexed LiDAR system 500 embodying the principles of the present invention. Different from Figure 2 The system shown which uses a single scanner, the sample arms of the first and second TOI modules 200a and 200b are respectively connected to the first scanner 805a and the second scanner 805b to physically transmit the first sample pulsed wavelength-modulated coherent light 135a and the second sample pulsed wavelength-modulated coherent light 135b to scan different objects.

[0087] Figure 9BFIG. 0 is a schematic diagram of a multiplexed LiDAR system 900 for multi-directional distance measurement embodying the principles of the present invention. The single-backend system 910 includes a pulsed wavelength-modulated light source 905 that transmits a pulsed wavelength-modulated light beam 906 to a plurality of beam splitters 907. Exemplary multi-beam splitters 907 include diffractive beam splitters 908 that provide the number of independent light beams required for the LiDAR system 900. The multiple wavelength-modulated light beams are directed to a focusing lens 909 to collimate each light beam again. Each light beam is transmitted to TOI LiDAR modules 920a, 920b, 920c, 920d, 920e, ..., 920n. In various embodiments, for applications that require high detection sensitivity and a narrow field of view or a slow detection speed, a multi-channel optical switch may be used instead of the multi-beam splitter 907.

[0088] Each LiDAR module 920a, 920b, 920c, 920d, 920e, ..., 920n is connected to scanners 925a, 925b, 925c, 925d, 925e, ..., 925n within the front end of the multiplexed LiDAR system 800. Each scanner 925a, 925b, 925c, 925d, 925e, ..., 925n is configured as a 1D or 2D scanner, as shown in Figure 3A , 3A , 4, 5A and 5B. The scanners 925a, 925b, 925c, 925d, 925e, …, 925n transmit sample pulsed wavelength-modulated coherent light beams 935a, 935b, 935c, 935d, 935e, …, 935n to scan one or more objects in different directions within the circumference of the surrounding environment.

[0089] The retroreflected wavelength-modulated coherent light beams 935a, 935b, 935c, 935d, 935e, ..., 935n from the scanned object are received by the scanners 925a, 925b, 925c, 925d, 925e, ..., 925n and transmitted to the LiDAR modules 920a, 920b, 920c, 920d, 920e, ..., 920n to form an image based on TOI measurements. The 1D scan pattern may be linear or non-linear in time and may be unidirectional or bidirectional. In some embodiments of the multiplexed LiDAR system 900, the 2D scan pattern may be linear or non-linear. It may use raster scanning, spiral scanning or other patterns to collect measurement information.

[0090] Then, the retroreflected wavelength-modulated coherent light beams 935a, 935b, 935c, 935d, 935e, ..., 935n received by the TOI LiDAR modules 920a, 920b, 920c, 920d, 920e, ..., 920n are transmitted to the signal processor 965. The signal processor 965 has a plurality of Figure 1B balanced detectors 160 that receive the retroreflected wavelength-modulated coherent light beams 935a, 935b, 935c, 935d, 935e, ..., 935n. Figure 1B The balanced detectors 160 convert the light beams 935a, 935b, 935c, 935d, 935e, ..., 935n into electrical signals, which are processed by the computer 970 to generate an image based on the age of the TOI measurement.

[0091] The scanners 925a, 925b, 925c, 925d, 925e, ..., 925n can be mechanically implemented as galvanometer mirrors, polygon mirrors, microelectromechanical systems (MEMS), piezoelectric actuators, and optically include acousto-optic (AO) deflectors or solid-state scanners. There may be other methods that provide the required scanning motion to collect measurement information in accordance with the principles of the present invention.

[0092] Although the present invention has been specifically shown and described with reference to its preferred embodiments, those skilled in the art should understand that various changes in form and detail can be made without departing from the spirit and scope of the present invention. Specifically, Figure 2 the multiplexing system 100 and Figure 9A the multiplexing system 800 can be implemented using time-of-flight (ToF), amplitude-modulated continuous wave (AMCW), frequency-modulated continuous wave (FMCW), or any combination of LiDAR devices known in the art.

Claims

1. A hybrid scanner within a multiplexed optical detection and ranging (LiDAR) system for performing a scanning pattern of multiple sample pulse wavelength modulated coherent light beams, characterized in that, Comprising: A plurality of optical collimators configured to enable transmission of a sample pulsed wavelength - modulated coherent beam to each of the plurality of optical collimators; At least one slow - axis rotating flat mirror for receiving and reflecting at least one collimated sample pulsed wavelength - modulated coherent beam and configured to rotate about a first axis to form a first - dimensional scanning pattern of the sample pulsed wavelength - modulated coherent beam; A fast - axis rotating polygonal scanning mirror configured to reflect the plurality of pulsed wavelength - modulated coherent beams and configured to rotate about a second axis to form a second - dimensional scanning pattern of the plurality of pulsed wavelength - modulated coherent beams; Wherein the plurality of pulsed wavelength - modulated coherent beams are transmitted to an object to determine geometric dimensions of the object through a combination of the first - dimensional scanning pattern and the second - dimensional scanning pattern.

2. The hybrid scanner according to claim 1, characterized in that, The plurality of pulsed wavelength - modulated coherent beams are retro - reflected to the hybrid scanner and reflected by the fast - axis rotating polygonal scanning mirror to the at least one slow - axis rotating flat mirror and then reflected by the at least one collimator to an interferometer within the LiDAR module for determining dimensions of the scanned object.

3. The hybrid scanner according to claim 1, wherein The at least one slow - axis rotating flat mirror is two slow - axis rotating flat mirrors, wherein a first pulsed wavelength - modulated coherent beam is incident on the first slow - axis rotating flat mirror and a second pulsed wavelength - modulated coherent beam is incident on the second slow - axis rotating flat mirror.

4. The hybrid scanner according to claim 3, wherein The first pulsed wavelength - modulated coherent beam reflected from the first slow - axis rotating flat mirror and the second pulsed wavelength - modulated coherent beam reflected from the second slow - axis rotating flat mirror are incident on the fast - axis rotating polygonal scanning mirror.

5. The hybrid scanner according to claim 4, characterized in that, The first and second rotating slow - axis scanning mirrors are configured to provide a position offset between the first and second rotating slow - axis scanning mirrors such that the reflected pulsed wavelength - modulated coherent beams can be incident on a selected surface of the fast - axis rotating polygonal scanning mirror.

6. The hybrid scanner according to claim 5, characterized in that, The pulsed wavelength - modulated coherent beam reflected from the selected surface of the rotating polygonal fast - axis scanning mirror is transmitted to an object to determine geometric dimensions of the object through a combination of the first - dimensional scanning pattern and the second - dimensional scanning pattern.

7. The hybrid scanner according to claim 6, wherein, The fast - axis rotating polygonal scanning mirror includes: A polygonal cylindrical body having a central axis; A motor connected to the central axis for rotating the polygonal cylindrical body; A plurality of mirror bodies, with one mirror body formed on each face of the polygonal mirror body.

8. The hybrid scanner according to claim 7, characterized in that, The plurality of mirror bodies are rectangular mirror bodies formed on each face of the polygonal cylindrical body.

9. The hybrid scanner according to claim 7, characterized in that, The polygonal cylindrical body includes at least two parts, wherein each of the at least two parts has a face of a different size to receive one of the plurality of mirror bodies of different sizes.

10. The hybrid scanner according to claim 7, wherein Each face of the polygonal cylindrical body is an isosceles trapezoid, and the shape of the plurality of mirror bodies is an isosceles trapezoid formed on each face of the polygonal cylindrical body.

11. The hybrid scanner according to claim 6, wherein, A portion of each of the pulsed wavelength - modulated coherent beams in the pulsed wavelength - modulated coherent beam irradiated onto the object is retro - reflected to the selected surface of the rotating multifaceted fast - axis scanning mirror, and the retro - reflected pulsed wavelength - modulated coherent beam is transmitted to the first and second rotating slow - axis scanning mirrors and then transmitted to an interferometer to generate an optical interference signal.

12. A multiplexed optical detection and ranging (LiDAR) system, characterized in that, For measuring features on an object from the multiplexed optical detection and ranging (LiDAR) system, and comprising: A coherent light source; A modulation controller that communicates with the coherent light source and is configured to generate and control a control signal transmitted to the coherent light source for modulating the coherent light source to generate a pulsed wavelength - modulated coherent beam to create a scanning pattern for measuring the surface of the object; At least two LiDAR modules connected to the coherent light source for receiving the pulsed wavelength - modulated coherent beam, and comprising: An interferometer including an optical splitter for splitting the pulsed wavelength - modulated coherent beam into at least two pulsed wavelength - modulated coherent beams; A hybrid scanner that communicates with the at least two LiDAR modules to receive the pulsed wavelength - modulated coherent beam and is configured to scan the surface of the object using the pulsed wavelength - modulated coherent beam to trace the scanning pattern of the surface of the object for measuring the distance of the features on the object from the multiplexed optical detection and ranging (LiDAR) system, wherein a portion of each of the pulsed wavelength - modulated coherent beams in the pulsed wavelength - modulated coherent beam is retro - reflected to each interferometer of the hybrid scanner and the at least two LiDAR modules, and wherein each LiDAR module of the at least two LiDAR modules further comprises a balanced detector for converting the retro - reflected pulsed wavelength - modulated coherent beam into an electrical signal; A signal processor that communicates with the photodetector array in the balanced detector of the LiDAR module to receive the electrical signal and convert the electrical signal into a digitized electrical signal; and A computer system configured to be programmed to calculate the time delay determined by the digitized electrical signal issued by the signal processor and generate a displayed imaging range based on the distance to the target.

13. The multiplexed optical detection and ranging (LiDAR) system according to claim 12, wherein The at least two LiDAR modules are connected to the coherent light source through the optical splitter or an optical switch for receiving the pulsed wavelength - modulated coherent beam.

14. The multiplexed optical detection and ranging (LiDAR) system according to claim 12, wherein The hybrid scanner comprises: A plurality of optical collimators configured to enable transmission of a sample pulsed wavelength - modulated coherent beam to each of the plurality of optical collimators; At least one slow - axis rotating flat mirror for receiving and reflecting at least one collimated sample pulsed wavelength - modulated coherent beam and configured to rotate along a first axis to form a first - dimension scanning pattern of the sample pulsed wavelength - modulated coherent beam; Fast-axis rotating polygon scanner mirror, which is configured to reflect the plurality of pulsed wavelength-modulated coherent light beams and is arranged to rotate about a second axis to form a second-dimensional scanning pattern of the plurality of pulsed wavelength-modulated coherent light beams; wherein the plurality of pulsed wavelength-modulated coherent light beams are transmitted to an object to determine geometric dimensions of the object through a combination of the first-dimensional scanning pattern and the second-dimensional scanning pattern.

15. The multiplexed optical detection and ranging (LiDAR) system according to claim 14, wherein The plurality of pulsed wavelength-modulated coherent light beams are retroreflected to the hybrid scanner and are reflected by the fast-axis rotating polygon scanner mirror to the at least one slow-axis rotating flat mirror and then through the at least one collimator to an interferometer within the LiDAR module for determining dimensions of the scanned object.

16. The multiplexed optical detection and ranging (LiDAR) system according to claim 14, wherein, The at least one slow-axis rotating flat mirror is two slow-axis rotating flat mirrors, wherein a first pulsed wavelength-modulated coherent light beam is incident on the first slow-axis rotating flat mirror and a second pulsed wavelength-modulated coherent light beam is incident on the second slow-axis rotating flat mirror.

17. The multiplexed optical detection and ranging (LiDAR) system according to claim 16, wherein The first pulsed wavelength-modulated coherent light beam reflected from the first slow-axis rotating flat mirror and the second pulsed wavelength-modulated coherent light beam reflected from the second slow-axis rotating flat mirror are incident on the fast-axis rotating polygon scanner mirror.

18. The multiplexed optical detection and ranging (LiDAR) system according to claim 17, wherein The first and second rotating slow-axis scanning mirrors are arranged to provide a positional offset between the first and second rotating slow-axis scanning mirrors such that the reflected pulsed wavelength-modulated coherent light beams can be incident on a selected surface of the fast-axis rotating polygon scanner mirror.

19. The multiplexed optical detection and ranging (LiDAR) system according to claim 18, wherein, The pulsed wavelength-modulated coherent light beam reflected from the selected surface of the rotating polygon fast-axis scanner mirror is transmitted to an object to determine geometric dimensions of the object through a combination of the first-dimensional scanning pattern and the second-dimensional scanning pattern.

20. The multiplexed optical detection and ranging (LiDAR) system according to claim 19, wherein, The fast-axis rotating polygon scanner mirror includes: a multi-faceted polygonal cylinder having a central axis; a motor connected to the central axis for rotating the polygonal cylinder; a plurality of mirror bodies, wherein one mirror body is formed on each surface of the polygonal mirror body.

21. The multiplexed optical detection and ranging (LiDAR) system according to claim 20, wherein The plurality of mirror bodies are rectangular mirror bodies formed on each surface of the polygonal cylinder.

22. The multiplexed optical detection and ranging (LiDAR) system according to claim 20, wherein The multi-faceted polygonal cylinder includes at least two portions, wherein each of the at least two portions has a surface of a different size to receive one of the plurality of mirror bodies of different sizes.

23. The multiplexed optical detection and ranging (LiDAR) system according to claim 20, wherein Each surface of the multi-faceted polygonal cylinder is an isosceles trapezoid, and the shape of the plurality of mirror bodies is an isosceles trapezoid formed on each surface of the polygonal cylinder.

24. The multiplexed optical detection and ranging (LiDAR) system according to claim 20, wherein A portion of the pulsed wavelength-modulated coherent light beam incident on the object is retroreflected to the selected surface of the rotating polygon fast-axis scanner mirror, and the retroreflected pulsed wavelength-modulated coherent light beam is transmitted to the first and second rotating slow-axis scanning mirrors and then to the interferometer to generate an optical interference signal.

25. The multiplexed optical detection and ranging (LiDAR) system according to claim 12, wherein The modulation controller is configured to modulate the coherent light source by controlling a drive current of the coherent light source, adjusting a temperature of the narrow-bandwidth light source, or adjusting a phase of the light emitted by the light source.

26. The multiplexed optical detection and ranging (LiDAR) system according to claim 12, wherein The LiDAR module includes: A first coupler configured to receive the pulsed wavelength - modulated coherent light from the coherent light source and configured to divide the pulsed wavelength - modulated coherent light into a first portion of the pulsed wavelength - modulated coherent light and a second portion of the pulsed wavelength - modulated coherent light; A circulator connected to receive the first portion of the pulsed wavelength - modulated coherent light and configured to enable the first portion of the pulsed wavelength - modulated coherent light to enter a first port of the circulator and exit from a subsequent port to direct the first portion of the pulsed wavelength - modulated coherent light to the scanner; A sample arm connected to the first coupler to receive the first portion of the pulsed wavelength - modulated coherent light and transmit the first portion of the pulsed wavelength - modulated coherent light to the scanner; A reference arm connected to the first coupler to receive the second portion of the pulsed wavelength - modulated coherent light; and A second coupler configured for the retro - reflected portion of the pulsed wavelength - modulated coherent light, configured to receive the second portion of the pulsed wavelength - modulated coherent light from the reference arm, and configured to couple the retro - reflected portion of the pulsed wavelength - modulated coherent light with the second portion of the pulsed wavelength - modulated coherent light to form an optical interference signal; and An array of photodetectors configured to receive the optical interference signal and convert the optical interference signal into an electrical interference signal.

27. The multiplexed optical detection and ranging (LiDAR) system according to claim 25, wherein The LiDAR module further includes: A polarization controller configured to receive the pulsed wavelength - modulated coherent light emission, transmit the pulsed wavelength - modulated coherent light emission to the first coupler, and configured to adjust the polarization state of the coherent light emitted from the light source and maximize the amplitude of the optical interference signal or the electrical interference signal.

28. The multiplexed optical detection and ranging (LiDAR) system according to claim 12, wherein The array of photodetectors is configured as a polarization - diversity balanced - amplification detector and includes at least one power monitor to measure the input power level of the array of photodetectors, wherein the power monitor output provides a modulated power level whose time delay is related to the distance of the object.

29. The multiplexed optical detection and ranging (LiDAR) system according to claim 12, wherein The signal processor is configured to determine the envelope of at least two digitized electrical signals.

30. The multiplexed optical detection and ranging (LiDAR) system according to claim 28, wherein, The signal processor is configured to measure the delay of the at least two digitized electrical signals at the falling edge of the envelope of the digitized electrical signals.

31. The multiplexed optical detection and ranging (LiDAR) system according to claim 28, wherein The multiplexed optical detection and ranging (LiDAR) system further includes a scan controller configured to create the scan pattern that generates a scan synchronization signal and configured to apply the scan synchronization signal to the scanner to generate a scan pattern that realizes a set of measurement information describing the object.

32. The multiplexed optical detection and ranging (LiDAR) system according to claim 12, wherein The multiplexed optical detection and ranging (LiDAR) system can be implemented as any combination of fiber optics, bulk optics, integrated photonic circuits, or optical photonic devices.

33. The multiplexed optical detection and ranging (LiDAR) system according to claim 12, wherein The scanner's graded-index fiber rod forms a separate lens in contact with the graded-index fiber rod to provide a low numerical aperture and a higher numerical aperture. The low numerical aperture is required for the graded-index fiber rod and an engineered graded-index lens for long-distance illumination, for long-distance illumination. The higher numerical aperture is required to receive the retroreflected pulsed-wavelength-modulated coherent light from the object.

34. A method for determining the distance of an object, characterized in that, Comprising: Generating a coherent light beam; Modulating the coherent light beam with a pulsed-wavelength modulation signal; Polarizing the pulsed-wavelength-modulated light beam by adjusting the polarization state of the pulsed-wavelength-modulated light beam and maximizing the amplitude of the optical interference signal; Optically splitting the pulsed-wavelength-modulated light beam into at least two pulsed-wavelength-modulated light beams; Coupling each of the at least two pulsed-wavelength-modulated light beams to one of at least two LiDAR modules to create a sample pulsed-wavelength-modulated light beam and a reference pulsed-wavelength-modulated light beam; Transmitting the at least two pulsed-wavelength-modulated light beams to a hybrid scanner module for establishing a scanning pattern for each of the pulsed-wavelength-modulated light beams; Scanning the at least two pulsed-wavelength-modulated light beams onto an object, the distance between the object and the wavelength-modulated coherent light source being to be measured; Receiving the retroreflected portions of the at least two pulsed-wavelength-modulated light beams from the object to be measured; Coupling each of the retroreflected portions of each of the at least two pulsed-wavelength-modulated light beams to the corresponding LiDAR module of the at least two pulsed-wavelength-modulated light beams to form an electrical signal representing each of the at least two pulsed-wavelength-modulated light beams; Digitizing the electrical signal; Detecting the envelope of each of the digitized electrical signals in the digitized electrical signal for determining the envelope of each of the digitized electrical signals; Determining the time of the rising edge or falling edge of the envelope of the digitized electrical signal; Determining the time difference between the rising edge and the falling edge of the envelope of the digitized interference signal; Calculating the distance to the object to be measured; And Forming a two-dimensional ranging image based on all the distance measurement results of scanning the object to be measured with the at least two pulsed-wavelength-modulated light beams.

35. The method according to claim 34, wherein, Further comprising: Determining the velocity of the object by separately calculating the distances to the at least two LiDAR modules; And Calculating the velocity of the object as the change of distance over time.

36. The method according to claim 34, wherein Further comprising the steps of: Implementing the method using a combination of optical fibers, bulk optics, integrated photonic circuits, or any optical photonic devices.

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