High speed time-of-flight interference ranging system and method and apparatus for determining distance

Abstract

A high-speed time-of-flight light detection and ranging system and method and apparatus for determining distance are disclosed. The time-of-flight light detection and ranging system generates an image of an object based on distances measured by various points to the object. The time-of-flight light detection and ranging system detects an envelope of an electrical signal generated from an interference light signal. The interference light signal is generated by a back-reflected light resulting from a combination of a light emission from a sampling arm to the object and a reference light emission. The reference light emission is created by splitting an emission signal of a pulsed modulated coherent light source and passing the reference light emission through a reference arm. The optical interference signal is transmitted to a balanced photodetector to be converted to an electrical signal that is converted to digital data. The digital data is evaluated to determine a rising edge or a falling edge of the digitized electrical interference signal to determine a time delay between the reference light emission and the back-reflected light used to calculate a distance.

Description

Technical Field

[0001] This invention is a continuation-in-part of U.S. Serial No. 17 / 315,678, filed May 10, 2021, the entire contents of which are incorporated herein by reference and assigned to co-assignees.

[0002] This invention generally relates to optical detection and ranging systems. More specifically, this invention relates to an optical detection and ranging system utilizing an optical interference measuring device, as well as a method and apparatus for measuring distance and speed, and for determining distance. Background Technology

[0003] Light detection and ranging (LiDAR) is similar to radio detection and ranging (radar) because LiDAR uses light waves to determine the distance, angle, and velocity of an object. LiDAR utilizes the difference in laser return time and wavelength, which can be used to create a digital 3D representation of a target and has been widely used in land, airborne, and mobile applications. A LiDAR instrument consists of one or more laser emitters, optics, a scanner, a photodetector, and a signal processor. One or more laser emitters generate a coherent beam that is transmitted through a set of optics to the scanner to be emitted toward the object, used to determine the distance to the object or the object's velocity. In the case of a three-dimensional (3D) scan, physical features are determined. The photodetector receives the coherent light reflected from the object and converts it into an electrical signal, which is processed to determine the object's distance. The emitter generates coherent light as pulses. The signal processor records the time of the emitted pulses and the time of reception of the reflected coherent light. This distance is the difference between the emission and reception times divided by 2 and multiplied by the speed of light.

[0004] Amplitude modulated continuous wave (AMCW) LiDAR is a phase-based form of LiDAR. Unlike direct pulse detection, phase-based LiDAR emits a continuous laser signal. It uses a high-speed radio frequency (RF) signal to modulate the amplitude of the emitted laser to encode the output optical signal. The phase difference between the emitted and reflected signals is detected for ranging. The phase shift of the sinusoidally modulated continuous laser waveform can be used to infer the distance to an object.

[0005] Frequency-modulated continuous-wave (FMCW) LiDAR is similar to AMCW LiDAR, but modulation and demodulation are performed optically rather than electrically. FMCW LiDAR uses a wavelength-tuned light source or a phase-modulated light source and a jammer to measure the distance to an object with good sensitivity. "Comb-Calibrated Frequency-Modulated Continuous-wave LiDAR", Y, Xie et al., 7th IEEE International Symposium on Aerospace Metrology (MetroAeroSpace), Pisa, Italy, 2020, pp. 372-376, February 15, 2021, URL: https: / / ieeexplore.ieee.org / stamp / stamp.jsp?tp=&arnumber=9160234&isnumber= 9159966 This paper describes how FMCW LiDAR is well-suited for absolute distance measurement. The frequency of the FMCW laser is linearly modulated by a carrier signal to accurately measure the laser's round-trip time of flight. By detecting the beat frequency signal between the returned and emitted laser beams, the time of flight can be calculated with high precision. This enables high-accuracy distance measurement.

[0006] Interference Time-of-Infrared (TOI) LiDAR technology is a novel ranging method that overcomes the limitations of traditional LiDAR technology. It includes Time-of-Flight (ToF) and Frequency Modulated Continuous Wave (FWCW) with the following characteristics: (1) It utilizes an interferometer with a balanced detector, allowing for high-sensitivity detection of weak interference signals from a distance; (2) It can measure the time delay of the interference signal even at high signal frequencies, thus providing accurate distance measurements to objects and eliminating the need for high-speed data acquisition systems; (3) It has lower requirements for phase modulation or wavelength modulation of the light source, thereby simplifying the complexity of driver circuit design for the light source. The operating speed of a TOI LiDAR system is mainly limited by the modulation speed of the light source and the efficiency of the optical receiver. Summary of the Invention

[0007] The purpose of this invention is to provide a high-speed time-of-intrusion (TOI) optical detection and ranging (LiDAR) system (hereinafter referred to as a TOI LiDAR system) and a method and apparatus for determining distance, used for time-frequency domain reflectance measurement and small-wavelength transient modulation of a coherent light source. The high-speed TOI LiDAR system uses a time-to-digital converter or data acquisition system to record the time delay or time of intrusion (TOI) of the interference signal. The output wavelength is determined by the operating current or operating temperature of the coherent light source.

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

[0009] Pulsed wavelength modulated coherent light emission is the input to the jammer. The jammer is configured to split the pulsed wavelength modulated coherent light emission into a sampling portion and a reference portion. The sampling portion of the pulsed wavelength modulated coherent light emission is arranged to illuminate the object under test. The reference portion of the pulsed wavelength modulated coherent light emission is arranged to provide a reference basis for determining the distance from the TOI LiDAR system to the object. The jammer is further configured to transmit the pulsed wavelength modulated coherent light to a scanner. The scanner is configured to physically transmit a first portion of the pulsed wavelength modulated coherent light to the object and scan the surface of the object using the pulsed wavelength modulated coherent light. The scanner is further configured to receive a portion of the pulsed wavelength modulated coherent light back-reflected from the object. The back-reflected pulsed wavelength modulated coherent light is transmitted from the scanner to the jammer and then coupled with the reference portion of the pulsed wavelength modulated coherent light to form an optical jamming signal.

[0010] The TOI LiDAR system has a photodetector array configured to convert optical interference signals into electrical interference signals. In various embodiments, the photodetectors are configured as polarization diversity balanced amplification detectors. Each photodetector has at least one power monitor to measure the input power level of the photodetector. The power monitor output provides a modulated power level with a time delay associated with the distance to the object.

[0011] The TOI LiDAR system includes a signal processor configured to receive electrical interference signals and convert them into digital data representing the amplitude of the interference signals. The signal processor is configured to generate a displayed imaging range based on the distance to the target. The displayed imaging range is calculated by a computer system programmed to calculate the time delay determined by the optical interference signals.

[0012] The modulation controller is configured to generate a wavelength modulation control signal with a low duty cycle to modulate the coherent light source by controlling the drive current of the narrow coherent light source, the temperature of the narrow bandwidth light source, or adjusting the phase of the light emitted from the light source. In other embodiments, the modulation controller generates a pulse phase control signal for generating interference when there is a time delay between the light in the sample arm and the reference arm of the jammer.

[0013] In various embodiments, the jammer includes a polarization controller for adjusting the polarization state of coherent light emitted from a light source and maximizing the amplitude of an optical or electrical jamming signal. The jammer has a first coupler that receives pulsed wavelength modulated coherent light from the polarization controller. The coupler splits the pulsed wavelength modulated coherent light. A first portion of the pulsed wavelength modulated coherent light is fed into at least one sample arm. A second portion of the pulsed wavelength modulated coherent light is fed into a reference arm. The jammer 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 pulsed wavelength modulated coherent light from the sample arm enters the circulator and exits from a next port. Typically, the next port is clockwise to guide the pulsed wavelength modulated coherent light to a scanner. The scanner is configured to physically transmit sampled pulsed wavelength modulated coherent light to scan an object. The sampled pulsed wavelength modulated coherent light is back-reflected from the object to perform ranging measurements on the scanner and is transmitted to the circulator within the jammer. The pulse wavelength modulated coherent light reflected back is then emitted from the back reflection to the second coupler.

[0014] The reference arm of the jammer is more than twice the length of the sampling arm. A second portion of the pulsed wavelength modulated coherent light in the reference arm is applied to a second coupler. The second portion of the pulsed wavelength modulated coherent light delivered in the reference arm couples with the collected back-reflected pulsed wavelength modulated light to form an optical interference signal. The optical interference signal exits the second coupler and enters the photodetector array.

[0015] The optical path length of the reference arm is more than twice that of the sample arm, and more than twice the maximum ranging depth of the system. The maximum frequency of the optical interference signal corresponds to the minimum ranging depth of the system.

[0016] The maximum frequency of the optical interference signal corresponds to the minimum ranging depth of the TOI LiDAR system. This frequency is greater than the Nyquist sampling frequency of the digitizer in the data acquisition and signal processing unit. The minimum frequency of the optical interference signal corresponds to the maximum ranging depth of the TOILiDAR system. The time delay of the detected optical interference is measured at the falling edge of the envelope of the optical interference signal. Attached Figure Description

[0017] Figure 1A , Figure 1B , Figure 1C This is a schematic diagram of the TOI LiDAR system that embodies the principles of this invention.

[0018] Figure 1D It is a reception that embodies the principles of the present invention. Figure 1A , Figure 1B and Figure 1C A schematic diagram of a scanner with a gradient refractive index lens at the end of the sampling arm.

[0019] Figure 2A This is a block diagram of an electrical TOI measurement circuit that embodies the principle of this invention.

[0020] Figure 2B This is a block diagram of the program structure of a signal processor configured to perform electrical TOI measurements, embodying the principles of the present invention.

[0021] Figure 2C The graph shows the back-reflection pulse stripes and envelope of the sample arm at the zero (0) meter position, which embodies the principle of the present invention.

[0022] Figure 2D This is a graph showing the back-reflection pulse stripes and envelope of the sample arm at a position of 180 meters, illustrating the principle of this invention.

[0023] Figure 3 A frame-based velocity measurement method for the TOI LiDAR system, embodying the principles of the present invention, is illustrated.

[0024] Figure 4A This is a block diagram illustrating the principle of the present invention: a transient light source modulator.

[0025] Figure 4B This is a schematic diagram illustrating the transient light source modulator and coherent light source that embody the principles of this invention.

[0026] Figure 5A This is a block diagram of the SSM-TOI electrical measurement circuit that embodies the principles of this invention.

[0027] Figure 5B This is a block diagram of the program structure of a signal processor configured to perform SSM-TOI electrical measurements embodying the principles of this invention.

[0028] Figure 6 This is a block diagram of a digital signal processor configured to perform SSM-TOI Doppler velocity measurements embodying the principles of the present invention.

[0029] Figure 7 This is a block diagram illustrating the integrated TOI and time-of-flight circuitry that embodies the principles of this invention.

[0030] Figure 8A This is a flowchart illustrating the principle of the present invention for determining the distance to an object using SSM-TOI electrical measurement.

[0031] Figure 8B This is a flowchart illustrating the principle of the present invention for determining the velocity of an object using SSM-TOI electrical measurement.

[0032] Figure reference numerals: 110 - Interference device; 130 - Scanner; 155b - Interference optical signal; 162 - Electrical interference signal; 165 - Signal processor; 170 - Computer; 175 - Modulation / scan controller; 179 - Modulation / scan synchronization signal; 215 - Mirror; 315 - Sweep linear calibration device; 400 - Envelope detector; 410 - Edge detector; 420 - Time-to-digital converter; 445 - Envelope detector; 450 - Edge detector; 455 - Counter; Voltage; Input Fringe; Time; Amplitude; Envelope of fringe; Time; 507 - Transient generator; 510 - Laser driver; Or; To Interferometer; 525 Frequency-to-Voltage Converter; 535 Edge Detector; 550 Time-to-Voltage Converter; 570 Frequency Detector; 585 Edge Detector; 600 Optical Clock; 610 Frequency Detector; 615 Edge Detector; 625 Doppler / Velocity Calculator; 630 Doppler / Velocity; 155 Back-Reflected Signal; 660 Second Edge Detector; 2nd Edge Detector; 665 Time-to-Digital Converter; 1st 655 - First pulse; 650 - First edge detector; 800 - Envelope detection; 805 - Generate laser beam; 810 - Modulate laser beam; 815 - Polarize laser beam; 820 - Couple first portion of laser beam to sampling arm; 825 - Couple second portion of laser beam to reference arm; 830 - Scan first portion of laser beam at the test object; 840 - Receive reflection of first portion of laser beam from test object; 855 - Couple reflection of first portion of laser beam to reference portion of laser beam; 860 - Transmit interference light to balance detector; 870 - Convert interference light into oscillating electrical signal; 885 - Digitize oscillating electrical signal; 860 - Detect envelope of oscillating electrical signal; 875 - Determine rising or falling edge of envelope of oscillating electrical signal; 886 - Determine time difference between rising and falling edge; 870 - Calculate distance to test object; 875 - Execute over time. Figure 8A The steps involve multiple iterations; 880 - calculates the speed based on the change of distance over time. Detailed Implementation

[0033] The TOI LiDAR system is configured to generate images of objects based on distance measurements from various points. The TOILiDAR system detects the envelope of an electrical signal generated from interfering optical signals. These interfering optical signals are generated by backreflected light produced from light emission from the sampling arm towards the object and from reference light emission. Reference light emission is created by separating the emission signals of the coherent light source with pulsed wavelength modulation and allowing the reference light emission to pass through the reference arm. The optical interference signal is transmitted to a photodetector for conversion into an electrical signal that is then converted into digital data. This digital data is evaluated to determine the falling edges of the reference light emission and backreflected light to determine the time delay between them. The distance is then calculated from this time delay.

[0034] Figure 1A , Figure 1B , Figure 1C This is a schematic diagram of the TOI LiDAR system illustrating the principles of this invention. (Reference) Figure 1A The TOILiDAR system 100 includes a pulsed wavelength modulated narrow bandwidth light source 105. The pulsed wavelength modulated light source 105 emits pulsed modulated coherent light having an output spectrum consisting of one or more longitudinal modes. The longitudinal modes of the resonant cavity are specific standing wave patterns formed by waves confined within the cavity. In lasers, light is amplified in a cavity resonator, typically composed of two or more mirrors. The cavity has mirror walls reflecting the light to allow standing wave modes to exist within the cavity with minimal loss. The longitudinal modes correspond to the wavelengths of reflected waves that are enhanced by constructive interference after numerous reflections from the cavity's reflective surfaces. All other wavelengths are suppressed by destructive interference. The longitudinal mode pattern has its nodes positioned along the length axis of the cavity. The pulsed wavelength modulated light source 105 is implemented as 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 discussion of the structure of the invention, the pulsed wavelength modulated light source 105 is shown as a coherent light source 105 whose wavelength or frequency is controlled by current or temperature. The modulation of the pulse wavelength modulated light source 105 is described below.

[0035] A pulse wavelength modulated narrowband light source 105 transmits pulse wavelength modulated coherent light to the jammer 110. The pulse wavelength modulated narrowband light source 105 transmits light through free space, optical fiber, or optical waveguide to the jammer 110.

[0036] In various embodiments, the jammer 110 is implemented as an optical fiber, bulk optical fiber, integrated photonic circuit, or some combination thereof. The jammer 110 has a polarization controller 115 that receives pulse wavelength modulated coherent light. The polarization controller 115 adjusts the polarization state of the pulse wavelength modulated coherent light from the light source 105. It maximizes the amplitude of the optical interference signal or electrical interference signal 162 transmitted in optical paths 155a and 155b. The pulse wavelength modulated coherent light from the light source 105 or the pulse wavelength modulated coherent light transmitted through the polarization controller 115 is applied to a coupler 120. The coupler 120 splits the coherent light into a sample portion fed to at least one sample arm 122 and a reference portion fed to a reference arm 140 within the jammer 110. The sample arm 122 and the reference arm 140 are implemented as free-space paths, optical fibers, or optical waveguides.

[0037] The jammer 119 has a circulator 125 that receives a sample portion of 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 segment of the sample arm 122. Typically, but not required, the coherent light is directed through the sample arm 122 to the scanner 130 via the next port in a clockwise direction. The scanner 130 is configured to physically transmit sampled pulsed wavelength modulated coherent light 135 to scan an object. The sampled pulsed wavelength modulated coherent light 135 is back-reflected from the object for ranging measurements. The back-reflected pulsed wavelength modulated coherent light is received by the scanner 130 and transmitted to the circulator 125. The back-reflected pulsed wavelength modulated coherent light through optical path 145 is then transmitted to the second coupler 150. The optical path is implemented as a free-space path, optical fiber, or optical waveguide.

[0038] The reference arm 140, implemented as a free-space path, optical fiber, or optical waveguide, has an additional optical path 142 that provides additional path length, such that the path length of the reference arm 140 matches the maximum ranging depth of the TOI LiDAR system 100. Optical pulse wavelength modulated coherent optical signals from at least one sample arm 122 and the reference arm 140 are combined in a coupler 150 to generate an optical interference signal.

[0039] Pulsed wavelength modulated coherent optical signals from at least one sample arm 122 and a reference arm 140 are heterodyne detected to extract the beat frequency from the fundamental signal. The beat signal has a 180° phase difference between the two outputs from the coupler. A balanced detector 160 subtracts the signal from each input channel to extract the interference signal as the beat signal.

[0040] Optical interference signals are applied to optical paths 155a and 155b, which are implemented as free-space paths, optical fibers, or optical waveguides. The optical interference signals are applied to optical paths 155a and 155b and transmitted to a balanced photodetector 160 to convert the optical interference signals from optical paths 155a and 155b into electrical interference signals 162.

[0041] Electrical interference signal 162 is generated by balanced photodetector 160 and transmitted to data acquisition circuitry within signal processor 165, where it is converted into digital data. The maximum frequency of the optical interference signal corresponds to the minimum ranging depth of the TOILiDAR system. The maximum frequency of the optical interference signal is greater than the Nyquist sampling frequency of the digitizer or signal processor 165 in the data acquisition process.

[0042] The minimum frequency of the optical interference signals 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 signals.

[0043] The digital data is then transmitted to computer 170 for further processing and display. In some embodiments, signal processor 165 may be integrated with computer 170 as a single unit.

[0044] In various embodiments, computer 170 is connected to modulation / scan controller 175. In other embodiments, computer 170 is integrated with modulation / scan controller 175. Modulation / scan controller 175 has modulation sub-circuit that determines the modulation, frequency, and shape of modulation control signal 177 applied to coherent light source 105. Modulation / scan controller 175 further has scan control circuitry that provides modulation / scan synchronization signal 179 to signal processor 165 and scanner 130. Scan control circuitry generates a desired scan pattern for generating appropriate modulation / scan synchronization signal 179 applied to scanner 130.

[0045] Scanner 130 can be implemented as a one-dimensional or two-dimensional scanner to distribute a sample of pulsed wavelength modulated coherent light 135 to form an image based on TOI measurements. The one-dimensional scan pattern can be linear or non-linear in time, and can be unidirectional or bidirectional. In some implementations of the TOI LiDAR system 100, the two-dimensional scan pattern can be linear or non-linear in time. It can employ raster scanning, helical scanning, or other modes to collect measurement information. Scanner 130 can be mechanically implemented as a galvanometer mirror, a microelectromechanical system (MEMS), a piezoelectric actuator, an optical actuator including an acousto-optic (AO) deflector, or a solid-state scanner. According to the principles of the invention, other methods can be used to provide the scanning motion required to collect measurement information.

[0046] refer to Figure 1B The TOI LiDAR system 100 has the same characteristics as... Figure 1A The same structure is used, but a second portion of the pulsed wavelength modulated coherent light is applied to the reference arm 200. The reference arm 200, implemented as a free-space path, fiber, or optical waveguide, has an additional optical path 142 such that the optical path length of the reference arm 200 matches the maximum ranging depth of the TOI LiDAR system 100. The pulsed wavelength modulated coherent light in the reference arm 200 is applied to the input port of the second circulator 210. The pulsed wavelength modulated coherent light is emitted from the input / output port of the second circulator 210 to an additional segment of the reference arm 200. The coherent light is incident on a mirror 215. The mirror 215 provides a delay for the coherent light and, in some embodiments, is replaced by an optical delay line. The mirror 215 reflects the coherent light directly back to the second circulator 210 and directs it to the coupler 150. The mirror-reflected coherent light couples with the reflected pulsed wavelength modulated coherent light to form an optical interference signal. The mirror 215 serves as a reference image plane corresponding to the maximum range of the TOI LiDAR system 100. If, due to the two-way travel of light, the reflector 215 is located between the second circulator 210 and the reflector 215, then the reflector 215 allows the additional path length 202 to be half of that length. The reflector 215 allows for cost and space savings.

[0047] Replacing mirror 215 with an optical delay line increases the flexibility of fine-tuning the overall reference arm path length. The tunable range of the delay is typically on the order of centimeters, so it primarily adapts to small variations in system configuration rather than altering the entire imaging range.

[0048] Optical interference signals are applied to optical paths 155a and 155b, which are implemented as free-space paths, optical fibers, or optical waveguides. As described above, the optical interference signals are applied to optical paths 155a and 155b and transmitted to a balanced photodetector 160 to convert the optical interference signals from optical paths 155a and 155b into electrical interference signals 162.

[0049] In some implementations, Figure 1A Reference arm 140 and Figure 1B The reference arm 200 may have a longer optical path length than the sample arm 103. The timing of interference from the pulsed wavelength modulated coherent optical signals of the sampling arm 122 and the reference arms 140 and 200 occurs at the falling edge of the interference envelope. In various embodiments, the reference arms 140 and 200 may have a shorter optical path length than the sample arm 122. The timing of interference from the pulsed wavelength modulated coherent optical signals of the sampling arm 122 and the reference arms 140 and 200 occurs at the rising edge of the interference envelope.

[0050] refer to Figure 1CThe TOI LiDAR system 100 has the same characteristics as... Figure 1A The same structure exists, but the second portion of the pulsed wavelength modulated coherent light from reference arm 140 exits the first coupler 120 and enters the third coupler 300. Reference arm 140 is implemented as a free-space path, optical fiber, or optical waveguide. The third coupler 300 further splits the second portion of the pulsed wavelength modulated coherent light into two pulsed wavelength modulated coherent beams. A small portion of the second portion of the pulsed wavelength modulated coherent beam is applied to a second reference arm 305, which is similarly implemented as a free-space path, optical fiber, or optical waveguide. A second small portion of the second portion of the pulsed wavelength modulated coherent beam from the second reference arm 305 is applied to a swept linear calibration device 315.

[0051] The sweep linear calibration device 315 is a Mach-Zehnder jammer or Fabry-Perot filter that generates an electrical signal to calibrate the linearity of the wavelength sweep of the coherent light source 105. If the wavelength modulation is not linear in the optical frequency domain, the sweep linear calibration device 315 generates an interference signal from a fixed path length difference from the Mach-Zehnder jammer or Fabry-Perot filter. It typically involves a photodetector or a balanced detector to generate the electrical signal. Its zero-crossing timing corresponds to the equispace in the optical frequency domain and provides an optical clock for the data acquisition system within the signal processor 165. The sweep linear calibration device 315 calibrates the interference signal 162 detected by the balanced detector 160. The output of the sweep linear calibration device 315 is transmitted to the signal processor 165.

[0052] A second pulse wavelength-modulated coherent beam from reference arm 305 is applied to second coupler 150. As described above, the back-reflected coherent light is guided to coupler 150. Reference coherent light in reference arm 305 is coupled with the back-reflected coherent light to form an optical interference signal. The optical interference signal is applied to optical paths 155a and 155b, which are implemented as free-space paths, optical fibers, or optical waveguides. As described above, the optical interference signal is transmitted through optical paths 155a and 155b to a balanced photodetector 160 to convert the optical interference signal from optical paths 155a and 155b into an electrical interference signal 162.

[0053] Figure 1D It is a device configured to receive, embodying the principles of this invention. Figure 1A , Figure 1B and Figure 1CA schematic diagram of the scanner 130 with sampling arm 122 of the optical fiber. Sampling arm 122 is inserted into and fixed in scanner 130. The distal end of sampling arm 122 is connected to or in contact with graded-index fiber rod 122a. Graded-index fiber rod 122a has an engineered graded-index lens 122b, which is formed as the distal surface of graded-index fiber rod 121a to improve overall efficiency for high-speed operation. Alternatively, the engineered graded-index lens 122b is formed as a separate lens in contact with graded-index fiber rod 121a. Graded-index fiber rod 121a with engineered graded-index lens 122b requires a low numerical aperture for long-distance illumination, but requires a high numerical aperture for receiving pulsed wavelength modulated coherent light reflected back from an object. Graded-index fiber rod 122a with engineered graded-index lens 122b collimates the on-axis sampled pulsed wavelength modulated coherent light 135 exiting through the central portion of the engineered tip. The pulsed wavelength modulated coherent light 136, generated by off-axis backreflection from the object, is coupled back into the sampling arm 122 via the annular portion 122c of the engineered graded-index lens 122b. The graded-index fiber rod 122a with the engineered graded-index lens 122b is implemented as a graded-index (GRIN) fiber lens with single-mode fiber, a GRIN fiber lens with few-mode fiber, a fiber sphere lens, a GRIN lens assembly, or a free-space collimator. The graded-index fiber rod 122a with the engineered graded-index lens 122b can be implemented by combining any of the listed implementations. The engineered graded-index lens 122b is formed from a tapered tip, a Fresnel surface, a metasurface, or a combination thereof.

[0054] A sampling arm 122 is inserted into and fixed in a scanner 130. It radiates pulsed wavelength modulated coherent light 135 onto a first reflector 132. The first reflector 132 is rotated horizontally 134a to reflect the pulsed wavelength modulated coherent light 135 with a horizontal scan pattern. The horizontal scan pattern covers the desired field of view. The reflected pulsed wavelength modulated coherent light 135 illuminates a second reflector 133. The second reflector 133 is rotated vertically 134b to generate a vertical scan pattern. The vertical scan pattern covers the vertical field of view.

[0055] Off-axis back-reflected pulsed wavelength modulated coherent light 136 is reflected from the desired object under test and back-reflected to scanner 130 and thus to second mirror 133 and then to first mirror 132. The off-axis back-reflected pulsed wavelength modulated coherent light 136 is reflected and transmitted to graded-index fiber rod 122a of sampling arm 122, which has an engineered graded-index lens 122b. The off-axis back-reflected pulsed wavelength modulated coherent light 136 is transmitted off-axis to sampling arm 122, which has a graded-index fiber rod 122a with an engineered graded-index lens 122b. The light is transmitted through graded-index fiber rod 122a and then to sampling arm 122 for further processing.

[0056] Figure 2A This is a block diagram of an electrical TOI measurement circuit illustrating the principles of this invention. The data is generated from the balance detector 160. Figure 1A , Figure 1B and Figure 1C The electrical interference signal 162 is received by the envelope detector 400 and converted into an envelope 405 of the electrical interference signal 162. The envelope detector 400 is implemented as a radio frequency (RF) power detector, a root mean square (RMS) detector, or a frequency demodulator. Radio frequency (RF) power detectors, RMS detectors, or frequency demodulators are known in the art and are commercially available devices. The radio frequency (RF) power detector, RMS detector, or frequency demodulator removes high-frequency components from the electrical interference signal 162 and thus identifies the envelope of the electrical interference signal 162.

[0057] Envelope signal 405 is transmitted to edge detector 410. Edge detector 410 determines a pulse event and places the pulse event at its output 410. The pulse event indicates the leading or falling edge of envelope signal 405. Edge detector 410 is implemented as an edge-gluff converter, XOR gate and delay circuit, differentiator circuit, etc. Edge-gluff converters, XOR gate and delay circuits, and differentiator circuits are similarly known in the art and are commercially available.

[0058] The output 415 of the edge detector is connected to the input of the time-to-digital converter 420. The time-to-digital converter 420 generates a time difference signal transmitted to its output 430. The time difference signal indicates the time between a rising or falling edge pulse event 405 and a pulse event 425. Pulse event 425 corresponds to the rising or falling edge of the light source modulation signal transmitted from the modulation / scan controller 175. Pulse event 425 is a trigger used to start the time-to-digital converter 420 when counting time intervals. The pulse output 415 of the edge detector 410 provides a pulse event for terminating the counting of time intervals performed by the time-to-digital converter 420. A series of time difference signals at the output 430 of the time-to-digital converter 420 are converted into depth measurement results to form an image displayed by the computer 170.

[0059] Figure 2B This is a block diagram of the program structure of the signal processor that embodies the principle of this invention. The data acquisition module 440 processes the signal generated from the balanced detector 160. Figure 1A , Figure 1B and Figure 1C The electrical interference signal 162 is digitized. The data acquisition module 440 is triggered by the modulation / scan synchronization signal 179 from the modulation / scan controller 175. The electrical interference signal is converted into a digitized signal 442 and placed at the output of the data acquisition module 440. The maximum frequency of the electrical interference signal 162 corresponds to the minimum ranging depth of the TOI LiDAR system 100. The maximum frequency of the electrical interference signal 162 is greater than the Nyquist sampling frequency of the digitizer of the data acquisition module 440. The minimum frequency of the electrical interference signal corresponds to the maximum ranging depth of the TOI LiDAR system 100. The time delay of the detected electrical interference signal 162 is measured at the falling edge of the envelope of the electrical interference signal 162.

[0060] The digitized signal 442 is processed by an envelope detector process 445 executed by the signal processor 165 to determine the envelope signal 447 of the digitized electrical interference signal 442. The envelope detector process 445 is executed by acquiring the absolute value of the Hilbert transform of the digitized signal 442. The envelope signal 447 is then processed by an edge detection process 450 to identify the timing of the occurrence of the electrical interference signal. The time difference 457 between the rising or falling edge 447 of the envelope signal and the modulation / scan synchronization signal 179 can be calculated.

[0061] Figure 2C This is a graph of the pulse input stripe 460 and envelope 465 of the reference arm, which embodies the principle of the present invention. Figure 2C The curve is an example electrical interference signal of the prototype TOI system 100 at the zero (0) meter position. Figure 2DThis is a graph of the pulse stripes 470 and envelope 475 of the back reflection of the sample arm, which embodies the principle of the present invention. Figure 2D The graph shows an example electrical interference signal from the prototype TOI system 100, which was detected at a location of 180 m. Figure 2A Edge detector 410 or Figure 2B The edge detector processing 450 determines the falling edge time t0 of the envelope of the reference arm 460 and the falling edge time t1 of the envelope of the sample arm 475. Counter 420 or counter process 455 counts the time interval between the falling edge time t0 of the reference arm and the falling edge time t1 of the sample arm. The distance to the object being measured is determined by the following equation:

[0062]

[0063] in:

[0064] It's the speed of light;

[0065] t0 is the falling edge time of the reference arm;

[0066] t1 is the falling edge time of the sample arm.

[0067] A series of time differences 457 can be converted into depth information and formed into an image displayed by computer 170.

[0068] Figure 3 A frame-based velocity measurement method for the TOI LiDAR system, embodying the principles of this invention, is illustrated. Each frame 490a, 490a, 490b, ..., 490m, 490m+1, ..., 490y, 490z is... Figure 1A , Figure 1B and Figure 1C The balanced photodetector 160 captures and represents data 495n and 495m+1. Data 495n and 495m+1 are transmitted to the signal processor 165 and, as shown... Figure 2A and Figure 2B The process described above involves processing the data to determine its rising or falling edge. Therefore, determining the rising or falling edge provides the time difference between data 495n and 495n+1. Then, the distance between data 495n and 495n+1 is determined as the time difference (t) between data 495n and 495n+1. m+1 – t m The time difference (t) between data 495n and 495n+1. m+1 -t m The speed of the object under test is determined by multiplying the optical interference signal sampling rate applied to optical paths 155a and 155b by the frame rate.

[0069] Figure 4A It incorporates the principles embodied in this invention. Figure 1A , Figure 1B and Figure 1C A block diagram of a small-signal transient modulator in a modulation driver. The transient light source modulator has a DC voltage source V connected to receive the signal. DC and modulation voltage V MOD The summing circuit 500. The summing circuit 500 combines the DC voltage source with the modulation voltage V. MOD The signals are added together to form a modulation signal 505. The modulation signal 505 has a voltage value less than that of the voltage source V. DC The amplitude of the voltage. The modulation signal 505 is selected from a group of waveforms, including square waves, triangular waves, sine waves, shark tooth waves, or any arbitrary waveform, or even a combination of waveforms. The transient generator 507 generates a spike transient modulation signal 508 by introducing voltage spikes into the modulation signal 505. The spike transient modulation signal 508 is applied to the laser driver 510. The voltage 508 of the spike transient modulation signal is converted into a current to drive the coherent light source 105. The transient generator 507 changes the effective inductance value of the transient light source modulator and generates a very large spike transient current to reduce the response time of the laser driver 510 and thereby overcome the speed limitations of conventional laser driving methods. A schematic diagram of the transient generator 507 is shown below. Figure 4B The discussion continues. Alternatively, the conversion current of the modulation signal 505 is applied to a thermoelectric cooling device for stabilizing the temperature of the laser diode of the coherent light source 105. By injecting the modulation current through the thermoelectric cooling device, the temperature of the laser diode of the coherent light source 105 is changed. The laser diode of the coherent light source 105 has a built-in thermistor for monitoring the diode temperature and for allowing the thermoelectric cooling device and the thermistor to form a control loop to provide temperature monitoring and precise temperature regulation.

[0070] The coherent light source 105 transmits a coherent optical signal 520 to the jammer. Waveform modulation at a wavelength / optical frequency is selected to introduce optical interference, wherein... Figure 1A Sample arm 122 and reference arm 140 Figure 1B 200 and Figure 1C The difference in optical path length between 305 and 305.

[0071] Figure 4B This is a schematic diagram illustrating a transient light source modulator and a coherent light source, demonstrating the principles of this invention. The summing circuit 500 includes a 2x1 multiplexer MUX1, which is used to combine DC voltage sources V. DC and the digitally modulated signal V DMOD Controlled analog modulation signal V AMOD The first input of the 2x1 multiplexer MUX1 is the DC voltage V. DCThis provides a lower base voltage. The second input to the 2x1 multiplexer MUX1 is the modulation voltage V. MOD This is a higher voltage used to form the output voltage. The 2x1 multiplexer MUX1 outputs V. O A transient modulation signal 505 is provided, which is the input to the transient generator 507. The output of the transient generator 507 is a transient modulation signal 508 applied to the input of the laser driver 510. The laser driver 510 converts the transient modulation signal 508 into a current to drive the coherent light source 105.

[0072] The multiplexer MX1 ​​is formed by two transfer gates TG1 and TG2. The two transfer gates TG1 and TG2 are connected in parallel. As is known in the art, each of the two transfer gates TG1 and TG2 has a connected complementary NMOS and PMOS transistor. The source and drain of each of the complementary NMOS and PMOS transistors are connected. A DC voltage source V... DC and modulation voltage V MOD These are connected to the source transmission gates TG1 and TG2, respectively. Digital modulation signal V DMOD The first inverter INV1 is connected to its input. The output of the first inverter INV1 is connected to the input of the second inverter INV2. The output of the first inverter INV1 is connected to the out-of-phase gate of the transmission gate TG1 and the in-phase gate of the transmission gate TG2. The output of the second inverter INV2 is connected to the out-of-phase gate of the transmission gate TG2 and the in-phase gate of the transmission gate TG1.

[0073] DC voltage source V DC The input source / drain is connected to the transmission gate TG1, and the modulation voltage V MOD The input source / drain of transfer gate TG2 is connected. The output source / drain of transfer gates TG1 and TG2 are connected to the out-of-phase input of comparator COMP1. The non-inverting input of comparator COMP1 is connected to the limiting voltage source V. L Comparator COMP1 will transmit the output voltage V of gates TG1 and TG2. O With respect to the voltage level V of the limiting voltage source L Compare them. If the voltage level V of the limiting voltage source... L The output voltage V greater than the transmission gates TG1 and TG2 O If the coherent light source 105 is turned off for safety purposes, as described below.

[0074] The 2x1 multiplexer MX1 ​​has an output voltage V that is applied as the output of the summing circuit 500 to the input of the transient generator 507. OThe transient generator 507 has an inductor L, the first terminal of which is connected to the output V of the 2x1 multiplexer MX1. o The second terminal of inductor L is connected to both the first terminal of capacitor C and resistor R1. The second terminal of capacitor C is connected to a ground reference source and also to laser driver 510.

[0075] Laser driver 510 has a first NMOS transistor TX1, whose gate is connected to the output of transient generator 507. The drain of NMOS transistor TX1 is connected to the anode of coherent light source LD1 105. The source of the first NMOS transistor TX1 is connected to the drain of a second NMOS transistor TX2. The source of the second NMOS transistor TX2 is connected to the first terminal of resistor R2. The gate of the second NMOS transistor TX2 is connected to the output of comparator COMP1 for receiving a turn-off command from coherent light source LD1 105. The second terminal of resistor R2 is connected to a ground reference voltage source. Resistor R2 establishes the turn-off voltage for coherent light source LD1 105. The gate of NMOS transistor TX1 is configured as a current source to generate laser current.

[0076] In an embodiment of the invention, without the transient generator 507, the gate capacitor of the first MOS transistor TX1, as well as the resistors and inductors on the lines connected to the first MOS transistor TX1, have negligible overshoot or spike levels as the modulation signal 505 rises. This is because the output V of the 2x1 multiplexer MX1... O The switching transition time, the inductor L on the line, the large gate size of the first NMOS transistor TX1, and the capacitor C accelerate the overshoot to generate a current spike or transient signal. The level of the transient current spike depends on the rise time of the modulation signal 505, the parameters of the inductor L, and the gate size of the first NMOS transistor TX1. Positive spikes appear on the rising edges of the first NMOS transistor TX1 and the first NMOS crystal TX1. When switching back to the DC voltage source V... DC When the base voltage level is reached, a negative spike appears at the falling edge of the first NMOS transistor TX1. Therefore, there are two spike events at each switching of the modulation signal 505.

[0077] The switching pulse width 505 of the modulation signal plays a crucial role in driving the current source transistor TX1. At the rising edge, a current spike occurs immediately and rings continuously. Then, the current spike gradually decreases until the charging voltage of capacitor C reaches a voltage level equal to the amplitude of the modulation signal 505. At the falling edge of the modulation signal 505, the 2x1 multiplexer MX1 ​​is switched back to the DC voltage source at the voltage level V. DC When the voltage level is [value], a negative spike occurs.

[0078] A key aspect is controlling the switching pulse width of the modulation signal 505 to combine the positive and negative transient voltage spikes of the transient modulation signal 508. The combining of positive and negative transient voltage spikes allows for the voltage ringing and settling time between the two spikes due to the on and off states of the multiplexer MX1. For TOI LiDAR applications, the shorter the time between positive and negative transient voltage spikes, the better. Considering whether the object being detected is very close to the LiDAR device, the time difference between the positive and negative transient voltage spikes will help the TOI LiDAR range for detection (edge ​​detection).

[0079] The coherent light source 105 is a type of coherent light source 105. The coherent light source 105 is a laser diode, quantum cascade laser, or fiber laser, wherein the active region of the device contains periodically structured elements or diffraction gratings. Power supply voltage source V CC It is applied to the coherent light source LD1 105.

[0080] Digital modulation signal V DMOD The high and low levels of the signal can respectively turn the coherent light source LD1 105 on and off. Although the digital modulation signal V... DMOD High, but analog modulation signal V AMOD Small signal modulation can be provided to the light source 105. When the multiplexer V O The output, via the second transistor TX2, exceeds the predefined limit voltage V during a short transition time. L At this time, the light source LD1 105 is deactivated. The protection current limiting setting is based on the characteristics of the NMOS gate TX2 and the current limiting of the coherent light source LD1 105. In this embodiment, the breakdown voltage of the NMOS gate TX2 is 20 V, which is sufficient for protection. The transient current of the coherent light source LD1 105 is high, but this should not be a problem for the coherent light source LD1 105 because the transient current has a duration of about one nanosecond.

[0081] When the digital modulation signal V DMOD When transitioning from low to high, transient generator 507 generates a voltage spike that turns on the first transistor TX1, which immediately depletes the current in the light source LD1, thus creating a short transition time for TOI applications.

[0082] Figure 5AThis is a block diagram of an SSM-TOI electrical measurement circuit embodying the principles of the present invention. An electrical interference signal 162 generated from a balance detector 160 is received by a frequency-to-voltage converter 525. The frequency of the electrical interference signal 162 is converted into a voltage at the output 530 of the frequency-to-voltage converter 525. The voltage is proportional to the frequency 162 of the electrical interference signal. The frequency-to-voltage converter 525 includes an FM demodulator, a frequency detector, or any frequency-to-voltage converter circuit known in the art. The voltage level at the output 530 is the input to an edge detector 535, which generates a pulse at the output 540 of the edge detector 535. This pulse corresponds to a rising edge at the output 530 of the frequency-to-voltage converter 525, or a rising or falling edge of the voltage level. The edge detector 535 is formed by an edge glitch converter, an XOR gate and delay circuit, a differentiator circuit, or any edge detector circuit known in the art. A time-to-digital converter 550 generates a time difference signal ∆. TD At output 555 of the time-to-digital converter 550. Time difference signal ∆ TD The time difference between the rising or falling edge pulse at the output 540 of the edge detector 535 and the modulation / scan synchronization signal 179 from the modulation / scan controller 175. A series of time differences 507 are converted into depth to form an image displayed by the computer 170.

[0083] Figure 5B This is a block diagram of the program structure of the signal processor 175 configured to perform SSM-TOI electrical measurements embodying the principles of the present invention. The data acquisition module 605, triggered by a modulation / scan synchronization signal 179 from the modulation / scan controller 175, digitizes the electrical interference signal 162 generated from the balance detector 160. The electrical interference signal 162 is converted into a digitized interference signal at output 565. The maximum frequency of the electrical interference signal 162 corresponds to the minimum ranging depth 100 of the TOI LiDAR system. The electrical interference signal 162 is greater than the Nyquist sampling frequency of the digitizer in the data acquisition module 605.

[0084] 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 electrical interference signal 162 is measured at the falling edge of the envelope of the electrical interference signal 162. This digitized interference signal is processed by a frequency detector process 570 to identify its instantaneous frequency value at the output 575 of the frequency detector process 570. The frequency detector process 570 performs a method such as a short-time Fourier transform, wavelet transform, or another frequency detector process known in the art. The instantaneous frequency value at the output 575 of the frequency detector process 570 is then processed by an edge detector process 585 to identify the timing of the rising or falling edge of the electrical interference signal 162, and the time difference 162 at the output 590 of the edge detector processing. Time difference ∆ TD The time determined as the time between the rising or falling edge of the instantaneous frequency value at output 575 and the modulation / scan synchronization signal 179. A series of time differences ∆ TD It is converted into depth and formed into an image displayed by a computer 170.

[0085] Figure 6 This is a block diagram of a digital signal processor configured to perform SSM-TOI Doppler velocity measurements embodying the principles of the present invention. Figure 6 The data acquisition and signal processor 165 is shown. Figure 1C The sweep linearization correction is performed by the scan linearization calibrator 315. When the TOI LiDAR system 100 is operating in SSM-TOI mode, the velocity information of the measured object is encoded in the electrical interference signal 162. The electrical interference signal 162, generated by the balanced photodetector 160, is digitized by the data acquisition module 605, which is triggered by the modulation / scan synchronization signal 179 from the modulation driver 175 and the optical frequency calibration clock 600 to convert the electrical interference signal 162 into a digitized signal at the output 607 of the data acquisition module 605. The digitized signal is linear in the optical frequency space. The maximum frequency of the electrical interference signal 162 corresponds to the minimum ranging depth of the TOI LiDAR system 100. The electrical interference signal 162 is greater than the Nyquist sampling frequency of the data acquisition module 605.

[0086] The minimum frequency of the electrical interference signal 162 corresponds to the maximum ranging depth of the TOI LiDAR system 100. The time delay of the detected electrical interference signal 162 is measured at the falling edge of the envelope of the electrical interference signal 162. The optical frequency calibration clock 600 is generated by a Mach-Zehnder jammer, a Fabry-Perot cavity, an etalon cavity, or any other jammer or resonator suitable for generating the optical frequency calibration clock 600. The digitized signal 607 is the input to the frequency detector process 610 to determine the instantaneous frequency value. The instantaneous frequency value is the solution placed at the output 611 of the frequency detector process 610. In various embodiments, the optical frequency calibration clock 600 is not required when the digitized signal at the output 607 of the data acquisition module 605 is essentially linear in the optical frequency space. In some embodiments, the frequency detector may be implemented as a short-time Fourier transform, wavelet transform, or other suitable frequency detector process. The instantaneous frequency value at the output 611 of the frequency detector process 610 is then processed by the edge detector process 615 to identify the timing of the interference occurrence. Then, the edge detector process 615 calculates the time difference ∆ between the rising or falling edge of the instantaneous frequency value and the modulation / scan synchronization signal 179. TD And then place the time difference ∆ as the output 620 of the frequency detector process 610. TD .

[0087] In other implementations of SSM-TOI Doppler velocity measurement, the digitized inferred electrical signal at the output 607 of the data acquisition module 605 serves as the input to the Doppler velocity calculation process 625 to calculate the target's moving velocity. The target's moving velocity is the output 630 of the Doppler velocity calculation process 625. In one implementation of the Doppler velocity calculation process 625, the Doppler velocity calculation process 625 measures the time difference Δ between the frequencies of continuously forward and backward sweeping electrical interference signals 162, which are proportional to the moving velocity of the measured object. TD This is achieved by minimizing the measurement error through the symmetry of the modulation / scan synchronization signal 179. A series of time differences ∆ at the output of the edge detector 620... TD The movement speed of the object being measured can be converted into depth and velocity, respectively, and formed into an image displayed by computer 170. In some implementations of SSM-TOI Doppler velocity measurement, the velocity of the Doppler frequency shift introduced in the electrical interference signal 162 can be directly extracted using at least one low-pass filter. Without the need for digital signal processing, the frequency shift can be detected and converted into a velocity electrical signal.

[0088] Figure 7This is a block diagram of an integrated interference time and time-of-flight circuit embodying the principles of the present invention. An electrical interference signal 162 generated from a balanced photodetector 160 is transmitted to an envelope detector 650. The envelope detector 650 determines the envelope signal of the electrical interference signal 162 applied to its output 652. The envelope detector 650 is implemented as a radio frequency (RF) power detector, a root mean square (RMS) detector, or a frequency demodulator. The envelope signal of the electrical interference signal 162 then passes through a first edge detector 655. The first edge detector 655 generates a first pulse signal at its output 657, which corresponds to the rising or falling edge of the envelope signal of the electrical interference signal 162 at the output 657 of the envelope detector 650. The edge detector 655 is formed from an edge glitch converter, an XOR gate and delay circuit, a differentiator circuit, or any edge detector circuit known in the art.

[0089] The electrical signal from the back-reflected coherent light 145 is extracted from the monitoring channel of the balanced detector 160 to form the back-reflected electrical signal 145. The back-reflected electrical signal 145 from the monitoring channel is the power spectrum of the back-reflected electrical signal 145 and can be considered as the envelope signal. The back-reflected electrical signal 145 is the input of the second edge detector 660. The second edge detector 660 generates a second pulse signal at its output 662.

[0090] The first pulse signal at the output 657 of the first edge detector 655, the second pulse signal at the output 662 of the second edge detector 660, and the modulation / scan synchronization signal 179 are applied to the multi-channel time-to-digital converter 665. The multi-channel time-to-digital converter 665 generates a first time difference signal at the output 670 of the time-to-digital converter 665. The first time difference signal ∆ TD1 It is a digital representation of the time between the rising or falling edge of the first pulse signal and the modulation / scanning synchronization signal 179 corresponding to the rising or falling edge of the light source modulation / scanning synchronization signal 179.

[0091] The multi-channel time-to-digital converter 665 generates a second time difference signal ∆ between the rising or falling edge of the second pulse signal at the output 662 of the second edge detector 660 and the modulation / scan synchronization signal 179 corresponding to the rising or falling edge of the light source modulation. TD2 The first time difference signal ∆ TD1 Second time difference signal ∆ TD2 Perform an average or weighted average. The first time difference signal ∆ of the average or weighted average. TD1 Second time difference signal ∆ TD2 It is converted into depth and formed into an image displayed by a computer 170.

[0092] Figure 8A This is a flowchart illustrating the principle of the present invention for determining the distance to an object using SSM-TOI electrical measurement. A laser beam is generated (box 800). The laser beam is modulated using a wavelength modulation or frequency modulation signal to adjust the wavelength or frequency of the laser beam (box 805). The laser beam is then polarized to adjust the polarization state of the laser, thereby maximizing the amplitude of the optical interference signal or electrical interference signal (box 810).

[0093] A first portion of the laser beam is coupled to a sampling optical cable (box 815). A second portion of the laser beam is coupled to a reference optical path (box 820). The first portion of the laser beam is scanned at an object at a determined distance from the modulated laser source (box 825).

[0094] A small portion of the first part of the coherent laser beam is back-reflected and received from the object under test (box 830). The back-reflected portion of the first part of the laser beam is coupled to a second part of the laser beam to form an optically interfering coherent optical signal (box 835). The optically interfering coherent optical signal is transmitted to a balanced optical photodetector (box 840) to convert the optically interfering coherent optical signal into an oscillating electrical interference signal (box 845). The oscillating electrical interference signal is digitized (box 850). The maximum frequency of the electrical interference signal corresponds to the minimum ranging depth of the TOI LiDAR system and is greater than the digitized Nyquist sampling frequency. The minimum frequency of the electrical interference signal 162 corresponds to the maximum ranging depth of the TOI LiDAR system 100.

[0095] The envelope of the digital electrical interference signal undergoes an envelope detection process to identify the envelope of the digital electrical interference signal (box 855). The rising or falling edge time of the rising or falling edge of the envelope of the digital electrical interference signal is determined (box 860). The time difference between the envelope of the digital electrical interference signal and the rising or falling edge of the modulation / scan synchronization signal is determined (box 865), and the distance to the object under test is calculated (box 870).

[0096] Figure 8B This is a flowchart illustrating the principles of the present invention for a method of determining object velocity using SSM-TOI electrical measurement. The method of determining object velocity using SSM-TOI electrical measurement is executed iteratively. Figure 8A The steps of the method begin (box 875). The velocity of the object is determined as the change of distance over time (box 880).

[0097] While the invention has been specifically shown and described with reference to preferred embodiments thereof, those skilled in the art will understand that various changes in form and detail may be made without departing from the spirit and scope of the invention. Specifically, Figure 1A , Figure 1Bor Figure 1C The TOI LiDAR system 100 can be implemented as any combination of optical fiber, bulk optical fiber, integrated photonic circuitry, or optical photonic devices known in the art.

Claims

1. A high-speed interference time-of-light detection and ranging system, used for measuring the distance from the interference time-of-light detection and ranging system to an object based on time-frequency domain reflectance, characterized in that, The interference time-light detection and ranging system includes: Coherent light source; A modulation controller, connected to the coherent light source and configured to generate and control the pulse width of a pulse wavelength control signal transmitted to the coherent light source for modulating the coherent light source to generate pulse wavelength modulated coherent light emission, and the modulation controller including a transient generator and a transient light source modulator, the transient light source modulator being used to generate a spike transient modulation signal whose voltage is converted into current to drive the coherent light source; the transient generator being used to generate positive transient voltage spikes and negative transient voltage spikes, and controlling the spike transient modulation signal to merge the positive transient voltage spikes and the negative transient voltage spikes to allow for voltage ringing and stabilization time between the positive transient voltage spikes and the negative transient voltage spikes; An interference device, connected to the coherent light source for receiving pulse wavelength modulated coherent light emission and configured to divide the pulse wavelength modulated coherent light emission into a sample portion and a reference portion, wherein the sample portion of the pulse wavelength modulated coherent light emission is arranged to illuminate an object under test, and the reference portion of the pulse wavelength modulated coherent light emission is arranged to provide a basis for determining the distance from the interference time-of-light detection and ranging system to the object; A scanner comprising a graded-index fiber rod having an engineered surface having a low numerical aperture for emission and a high numerical aperture for reception, the engineered surface being connected to a jammer to receive a sample portion of pulsed wavelength modulated coherent light, wherein the scanner is configured to physically transfer the sample portion of the pulsed wavelength modulated coherent light to the object and to scan the surface of the object using the pulsed wavelength modulated coherent light, and the scanner is further configured to receive a back-reflected portion of the pulsed wavelength modulated coherent light and to transfer the back-reflected portion from the scanner to the jammer; wherein the back-reflected portion of the pulsed wavelength modulated coherent light is coupled to a reference portion of the pulsed wavelength modulated coherent light to form an optical interference signal; A photodetector array configured to receive the optical interference signal and convert the optical interference signal into an electrical interference signal; A signal processor, which communicates with the photodetector array to receive the electrical interference signal and convert the electrical interference signal into a digital electrical interference signal; and A computer system configured to calculate the time delay determined by the optical interference signal and generate the displayed imaging range based on the distance to the object.

2. The interference time-of-flight detection and ranging system according to claim 1, characterized in that, The modulation controller having the transient generator is configured to modulate the coherent light source by controlling the drive current of the coherent light source, adjusting the temperature of the narrow-bandwidth light source, or adjusting the phase of the light emitted from the light source, wherein the transient generator includes an inductor, a capacitor, and a resistor configured to generate the positive transient voltage spike and the negative transient voltage spike.

3. The interference time-of-flight detection and ranging system according to claim 1, characterized in that, The jammer includes: A first coupler is configured to receive the pulse wavelength modulated coherent light from the coherent light source and to split the pulse wavelength modulated coherent light into a first portion and a second portion. A circulator is connected to the first coupler to receive the first portion of the pulse wavelength modulated coherent light, and the circulator is configured such that the first portion of the pulse wavelength modulated coherent light enters a first port of the circulator and exits from a subsequent port to guide the first portion of the pulse wavelength modulated coherent light to the scanner. A sample arm, connected to the first coupler, to receive the first portion of the pulse wavelength modulated coherent light and to transmit the first portion of the pulse wavelength modulated coherent light to the scanner. A reference arm, connected to the first coupler, to receive the second portion of the pulse wavelength modulated coherent light; and A second coupler is configured to receive the back reflection portion of the pulse wavelength modulated coherent light, to receive the second portion of the pulse wavelength modulated coherent light from the reference arm, and to couple the back reflection portion of the pulse wavelength modulated coherent light and the second portion of the pulse wavelength modulated coherent light to form an optical interference signal.

4. The interference time-of-flight detection and ranging system according to claim 3, characterized in that, The jammer also includes: A polarization controller configured to receive the pulse wavelength modulated coherent light emission, transmit the pulse wavelength modulated coherent light emission to the first coupler, and be configured to adjust the polarization state of the coherent light emission from the light source and maximize the amplitude of the optical interference signal or the electrical interference signal.

5. The interference time-of-flight detection and ranging system according to claim 1, characterized in that, The photodetector array is configured as a polarization diversity balanced amplification detector and includes at least one power monitor that measures the input power level of the photodetector array, wherein the power monitor output provides a modulated power level having a time delay associated with the distance to the object.

6. The interference time-of-flight detection and ranging system according to claim 3, characterized in that, The length of the reference arm is greater than the length of the sample arm, and the optical path length of the reference arm is greater than twice the maximum ranging depth of the system.

7. The interference time-of-flight detection and ranging system according to claim 1, characterized in that, The maximum frequency of the optical interference signal corresponds to the minimum ranging depth of the system.

8. The interference time-of-flight detection and ranging system according to claim 1, characterized in that, The signal processor is configured to determine the envelope of the digitized electrical interference signal.

9. The interference time-of-flight detection and ranging system according to claim 8, characterized in that, The signal processor is configured to measure the time delay of the digitized electrical interference signal at the falling edge of the envelope of the digitized electrical interference signal.

10. The interference time-of-flight detection and ranging system according to claim 1, characterized in that, It also includes a scan controller configured to create a scan pattern that generates a scan synchronization signal and to apply the scan synchronization signal to the scanner to generate a scan pattern that enables the collection of measurement information describing the object.

11. The interference time-of-flight detection and ranging system according to claim 1, characterized in that, The interference time-of-flight detection and ranging system is implemented as any combination of optical fiber, bulk optical fiber, integrated photonic circuit, or optical photonic device.

12. The interference time-of-flight detection and ranging system according to claim 2, characterized in that, The graded-index fiber rod has an engineered surface formed at the distal end of the graded-index fiber rod to provide the graded-index fiber rod and the engineered graded-index lens with the low numerical aperture required for long-distance illumination and the higher numerical aperture required for receiving pulse wavelength modulated coherent light back-reflected from the object.

13. The interference time-of-flight detection and ranging system according to claim 1, characterized in that, The graded-index fiber rod is formed with individual lenses that contact the graded-index fiber rod to provide the graded-index fiber rod and the engineered graded-index lens with the low numerical aperture required for long-distance illumination and the high numerical aperture required for receiving pulse wavelength modulated coherent light back-reflected from the object.

14. The interference time-of-flight detection and ranging system according to claim 1, characterized in that, The transient generator alters the effective inductance value of the transient light source modulator to generate a spike transient that significantly reduces the response time of the laser driver and thus overcomes any speed limitations.

15. A method for determining object distance, characterized in that, Includes the following steps: Generate a coherent beam; The coherent beam is modulated using a wavelength modulation signal; The first portion of the coherent beam is coupled to the sample arm; The second portion of the coherent beam is coupled to the reference arm; Generate positive and negative transient voltage spikes for controlling the coherent beam; The first portion of the coherent beam is scanned through the low numerical aperture portion of a graded refractive index fiber rod with engineered surfaces at a distance from the source of the wavelength-modulated coherent beam to the object under test. A portion of the first part of the wavelength-modulated coherent beam is reflected back from the object under test through a high numerical aperture of a graded refractive index fiber rod with an engineered surface. Receive the back reflection portion of the wavelength-modulated coherent beam from the object under test; The back reflection portion of the wavelength-modulated coherent beam is coupled to the second portion of the coherent beam to form an optically interfering wavelength-modulated coherent optical signal. The optical interference wavelength modulated coherent optical signal is optically detected to form an oscillating electrical interference signal; Digitize the oscillating electrical interference signal; The envelope of the digital electrical interference signal is detected to determine the envelope of the digital electrical interference signal; Determine the time of the rising or falling edge of the envelope of the digital electrical interference signal; Determine the time difference between the rising or falling edges of the envelope of the digital electrical interference signal; as well as Calculate the distance to the object to be measured.

16. The method according to claim 15, characterized in that, It also includes the following steps: The Doppler velocity of the object is determined by iteratively performing the steps according to claim 15; and The Doppler velocity of the object is calculated as the change in distance over time.

17. The method according to claim 15, characterized in that, It also includes the following steps: The polarization state of the coherent beam is adjusted to maximize the amplitude of the optical interference wavelength modulated coherent optical signal or oscillating electrical interference signal.

18. The method according to claim 15, characterized in that, The maximum frequency of the oscillating electrical interference signal corresponds to the minimum ranging depth of the measured distance to the object, and the maximum frequency of the oscillating electrical interference signal is greater than the Nyquist sampling frequency of the step of digitizing the oscillating electrical interference signal.

19. The method according to claim 18, characterized in that, The minimum frequency of the oscillating electrical interference signal corresponds to the maximum ranging depth of the measured distance to the object.

20. The method according to claim 15, characterized in that, It also includes the step of using any combination of optical fibers, bulk optical fibers, integrated photonic circuits, or optical photonic devices to implement the method.

21. The method according to claim 15, characterized in that, It also includes the following steps: The graded refractive index fiber rod is provided with an engineered graded refractive index lens; The graded-index fiber rod with an engineered surface is implemented to provide the low numerical aperture required for long-distance illumination and the high numerical aperture required for receiving pulsed wavelength modulated coherent light back-reflected from the object, for both the graded-index fiber rod and the engineered graded-index lens.

22. The method according to claim 21, characterized in that, It also includes the following steps: Realizing the graded refractive index fiber rod; and A separate lens is provided to contact the graded-index fiber rod to provide the graded-index fiber rod and the engineered graded-index lens with the low numerical aperture required for long-distance illumination and the higher numerical aperture required for receiving pulsed wavelength modulated coherent light back-reflected from the object.

23. The method according to claim 15, characterized in that, It also includes the following steps: A transient generator is provided that is configured to change the effective inductance value of a transient light source modulator to generate spike transients for significantly reducing the response time of the laser driver and thus overcoming any speed limitations.

24. A device for determining the distance to an object, characterized in that, include: A device for generating coherent light beams; An apparatus for modulating a coherent beam using a transient wavelength modulation signal to adjust the amplitude of the coherent beam; A means for coupling a first portion of the coherent beam to a sample fiber optic cable; A means for coupling a second portion of the coherent beam to a reference arm; A means for generating positive and negative transient voltage spikes for controlling the coherent beam; The first portion of the coherent beam having a low numerical aperture is scanned at the distance to the object to be measured from the source of the modulated coherent beam by means of a device with a graded refractive index fiber rod having an engineered surface. A device for reflecting a portion of the first part of the coherent beam back from the object under test through a high numerical aperture of a graded refractive index fiber rod with an engineered surface. A device for receiving the coherent beam from the object under test, including a back-reflecting portion having a high numerical aperture. An apparatus for coupling the back-reflected portion of the coherent beam to the second portion of the coherent beam to form an optically interfering wavelength modulated coherent optical signal. Apparatus for optically detecting the optical interference wavelength modulated coherent optical signal to form an oscillating electrical interference signal; A device for digitizing the oscillating electrical interference signal to form a digital electrical interference signal; Apparatus for detecting the envelope of the digital electrical interference signal to determine the envelope of the digital electrical interference signal; A means for determining the rising and falling times of the envelope of the digital electrical interference signal; A means for determining the time difference between the rising or falling edges of the envelope of the digital electrical interference signal; as well as A device for calculating the distance to the object to be measured.

25. The apparatus according to claim 24, characterized in that, Also includes: A means for determining the velocity of an object by iteratively activating the means for determining the distance of the object according to claim 24; as well as A device for calculating the velocity of an object as a change in the distance of the object over time.

26. The apparatus according to claim 24, characterized in that, Also includes: A device for adjusting the polarization state of the coherent beam to maximize the amplitude of the optical interference wavelength modulated coherent optical signal or oscillating electrical interference signal.

27. The apparatus according to claim 24, characterized in that, The maximum frequency of the oscillating electrical interference signal corresponds to the minimum ranging depth at which the distance to the object is measured and is greater than the Nyquist sampling frequency of the device used to digitize the oscillating electrical interference signal.

28. The apparatus according to claim 24, characterized in that, Also includes: A means for engineering the surface of the graded-index fiber rod to provide the graded-index fiber rod and the engineered graded-index lens with the low numerical aperture required for long-distance illumination and the high numerical aperture required for receiving pulse wavelength modulated coherent light back-reflected from the object.

29. The apparatus according to claim 24, characterized in that, Also includes: Apparatus for realizing the graded refractive index fiber rod; as well as A means for providing individual lenses to contact the graded-index fiber rod to provide the graded-index fiber rod and engineered graded-index lenses with the low numerical aperture required for long-distance illumination and the higher numerical aperture required for receiving pulsed wavelength modulated coherent light back-reflected from an object.

30. The apparatus according to claim 24, characterized in that, Also includes: A transient generator is provided that is configured to change the effective inductance value of a transient light source modulator to generate spike transients for significantly reducing the response time of the laser driver and thus overcoming any speed limitations.

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