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CN-122029454-A - Synchronous transmitter and receiver filtering for reducing stray light in LiDAR systems

CN122029454ACN 122029454 ACN122029454 ACN 122029454ACN-122029454-A

Abstract

Systems and methods for reducing stray light using synchronous filtering are provided. The system includes an emitter and a light source that emits laser light having a first wavelength range. The emitter is configured to provide transmitted light based on a laser light having a first wavelength range. The system further includes a receiver configured to receive return light including stray light and an optical signal formed based on the transmitted light. The system further includes a synchronous filter structure including one or more bandpass filters having substantially the same passband. The synchronous filter structure reduces the bandwidth of the laser light from a first wavelength range to a second wavelength range, filters out at least a portion of stray light having a wavelength outside the second wavelength range, and transmits a majority of the optical signal formed based on the transmitted light to the detector.

Inventors

  • LENG XIANDONG
  • WAN PENG

Assignees

  • 图达通智能美国有限公司

Dates

Publication Date
20260512
Application Date
20240920
Priority Date
20230928

Claims (20)

  1. 1. An optical ranging and detection (LiDAR) system for reducing stray light using synchronous filtering, the system comprising: a light source that emits laser light having a first wavelength range; an emitter comprising one or more emitter optics disposed in a transmission light path, the emitter configured to provide transmission light based on the laser light having the first wavelength range; a receiver including a detector and one or more receiver optics disposed in a receive optical path, the receiver configured to receive return light including stray light and an optical signal formed based on the transmitted light, and A synchronization filter structure comprising one or more bandpass filters having substantially the same passband, wherein the synchronization filter structure is coupled to both the transmitter and the receiver, the synchronization filter structure configured to perform: reducing the bandwidth of the laser light from the first wavelength range to a second wavelength range, such that the transmitted light has the second wavelength range, Filtering out at least a portion of the stray light having a wavelength outside the second wavelength range, an A majority of the optical signal formed based on the transmitted light is communicated to the detector.
  2. 2. The system of claim 1, wherein the first range of wavelengths has a center wavelength in the range of 700 nm to 20000 nm and a bandwidth of at least +/-5 nm.
  3. 3. The system of any one of claims 1-2, wherein a center wavelength of the second wavelength range is in a range of 700 nm to 20000 nm and a bandwidth of +/-2 nm.
  4. 4. The system of any of claims 1-2, wherein the one or more bandpass filters of the synchronous filter structure comprise: a first band-pass filter disposed in the transmission light path, and A second bandpass filter disposed in the receive optical path, wherein the first bandpass filter and the second bandpass filter have substantially the same passband.
  5. 5. The system of claim 4, wherein the first bandpass filter is disposed downstream of the light source in the transmitted light path at: between the light source and the one or more emitter optics; Between any two emitter optics; Between the one or more emitter optics and a steering mechanism, wherein the steering mechanism receives the transmitted light from the first band pass filter and scans the transmitted light into a field of view (FOV) in one or more directions, or Downstream of the turning mechanism in the transmitted light path.
  6. 6. The system of claim 4, wherein the second bandpass filter is disposed upstream of the detector in the receive optical path at: upstream of a turning mechanism in the receive light path, wherein the turning mechanism receives the filtered return light and directs the filtered return light to the one or more receiver optics; Between the steering mechanism and the one or more receiver optics; between any two receiver optics, or Between the one or more receiver optics and the detector.
  7. 7. The system of claims 1-2, wherein the one or more bandpass filters of the synchronous filter structure comprise a single bandpass filter shared between the transmit optical path and the receive optical path.
  8. 8. The system of claim 7, wherein the single bandpass filter is disposed downstream of the light source in the transmission light path and upstream of the detector in the reception light path at: between the one or more transmitter optics and a steering mechanism and between the steering mechanism and the one or more receiver optics; upstream of the turning mechanism in the transmitted light path, or Upstream of the steering mechanism in the receive optical path.
  9. 9. The system of any one of claims 1-2, wherein the emitter optics comprise one or more of a collimating lens, a filter, a beam shifting device, an optical fiber array, a movable or fixed mirror, a lens group, a prism, or a combination thereof.
  10. 10. The system of any one of claims 1-2, wherein the receiver optics comprise one or more of a collection lens, a filter, a fiber array, a beam homogenizer, a movable or fixed mirror, a lens group, a prism, or a combination thereof.
  11. 11. The system of any one of claims 1-2, further comprising a steering mechanism comprising one or more of a rotatable polygon mirror, an oscillating prism, or a combination thereof.
  12. 12. The system of any of claims 1-2, further comprising a control circuit configured to: The power level of the laser light emitted by the light source is set to compensate for the power loss of the transmitted light caused by the synchronous filter structure.
  13. 13. The system of claim 12, wherein the power level of the laser light emitted by the light source is set to an increased level compared to a power level of the laser light emitted by the light source without using a synchronous filter structure.
  14. 14. The system of claim 13, wherein an amount by which a power level increases is inversely proportional to the power loss caused by the synchronous filter structure.
  15. 15. The system of claim 12, wherein the power level of the transmitted light that compensates for the power loss is within a human eye safe laser power threshold.
  16. 16. A vehicle comprising a LiDAR system for reducing stray light using synchronous filtering, the system comprising: a light source that emits laser light having a first wavelength range; an emitter comprising one or more emitter optics disposed in a transmission light path, the emitter configured to provide transmission light based on the laser light having the first wavelength range; a receiver including a detector and one or more receiver optics disposed in a receive optical path, the receiver configured to receive return light including stray light and an optical signal formed based on the transmitted light, and A synchronization filter structure comprising one or more bandpass filters having substantially the same passband, wherein the synchronization filter structure is coupled to both the transmitter and the receiver, the synchronization filter structure configured to perform: reducing the bandwidth of the laser light from the first wavelength range to a second wavelength range, such that the transmitted light has the second wavelength range, Filtering out at least a portion of the stray light having a wavelength outside the second wavelength range, an A majority of the optical signal formed based on the transmitted light is communicated to the detector.
  17. 17. A method for reducing stray light using synchronous filtering, the method comprising emitting, by a light source, laser light having a first wavelength range; Providing transmitted light by an emitter based on the laser light having the first wavelength range, the emitter comprising one or more emitter optics disposed in a transmitted light path; Receiving return light comprising stray light and an optical signal formed based on the transmitted light by a receiver comprising a detector and one or more receiver optics disposed in a receive optical path, and The following operations are performed by a synchronization filter structure comprising one or more bandpass filters having substantially the same passband, wherein the synchronization filter structure is coupled to both the transmitter and the receiver: reducing the bandwidth of the laser light from the first wavelength range to a second wavelength range, such that the transmitted light has the second wavelength range, Filtering out at least a portion of the stray light having a wavelength outside the second wavelength range, an A majority of the optical signal formed based on the transmitted light is communicated to the detector.
  18. 18. The method of claim 17, wherein the first wavelength range has a center wavelength in the range of 700 nm to 20000 nm and a bandwidth of at least +/-5 nm.
  19. 19. The method of any one of claims 17 to 18, wherein the second wavelength range has a center wavelength in the range of 700 nm to 20000 nm and a bandwidth of +/-2 nm.
  20. 20. The method of any one of claims 17 to 18, the method further comprising: The power level of the laser light emitted by the light source is set to compensate for the power loss of the transmitted light caused by the synchronous filter structure.

Description

Synchronous transmitter and receiver filtering for reducing stray light in LiDAR systems Cross Reference to Related Applications The present application claims priority from U.S. provisional patent application Ser. No. 63/541,274, entitled "synchronous transmitter and receiver Filtering for reducing stray light in LiDAR systems" (SYNCHRONIZED TRANSMITTER AND RECEIVER FILTERING FOR REDUCING STRAYLIGHT IN LIDAR SYSTEMS), filed on 9/28 of 2023, the contents of which are incorporated herein by reference in their entirety for all purposes. Technical Field The present disclosure relates generally to light emission and detection, and more particularly to a light ranging and detection (LiDAR) system that reduces stray light using synchronous filtering. Background Light detection and ranging (LiDAR) systems use light pulses to create an image or point cloud of an external environment. The LiDAR system may be a scanning or non-scanning system. Some typical scanning LiDAR systems include a light source, a light emitter, a light turning system, and a light detector. The light source generates a beam of light that, when emitted from the LiDAR system, is directed in a particular direction by the light turning system. When the emitted light beam is scattered or reflected by an object, a portion of the scattered or reflected light returns to the LiDAR system to form a return light pulse. The light detector detects the return light pulse. Using the difference between the time that the return light pulse is detected and the time that the corresponding light pulse in the beam is emitted, the LiDAR system may determine the distance to the object based on the speed of light. This technique of determining distance is known as time of flight (ToF) technique. The light steering system may direct the light beams along different paths to allow the LiDAR system to scan the surrounding environment and produce an image or point cloud. A typical non-scanning LiDAR system illuminates the entire field of view (FOV) rather than scanning the entire FOV. One example of a non-scanning LiDAR system is flash LiDAR, which may also use ToF technology to measure distance to an object. LiDAR systems may also use techniques other than time-of-flight and scanning to measure the surrounding environment. Disclosure of Invention Typically, liDAR systems have a Transmitter (TX) and a Receiver (RX). The emitter emits laser light to form transmitted light. The receiver receives return light from a field of view (FOV). At least a portion of the return light is formed by reflected or scattered laser light from one or more target objects in the FOV. The return light may also include stray light, which may be noise and/or disturbing light. LiDAR systems typically operate at a particular center wavelength with a certain bandwidth, such as 905 nm (center wavelength) +/-5 nm (bandwidth) for a semiconductor laser. In existing LiDAR systems, a Band Pass Filter (BPF) is widely used in the receiver to filter out stray light in the return light received by the LiDAR system. The wavelength of the stray light may be the same or different from the wavelength of the transmitted light. However, the bandpass filter is typically configured to have a relatively wide passband to enable all signal laser power to pass. With this type of broad passband BPF, stray light of the same wavelength or wavelength range as the transmitted light cannot be filtered out. One way to reduce such stray light is to narrow the passband of the BPF (e.g., to 2 nm a or less) and allow only return light of the same wavelength as the center wavelength of the transmitted light to pass through. This method of reducing stray light has a problem in that a large amount of signal power of return light may be lost because the signal bandwidth is narrower than the passband of the BPF. In order to compensate for the return optical signal power loss caused by the BPF, the signal power of the transmitted light must be increased. However, increasing the signal power of transmitted laser light is limited by the eye-safety requirements of LiDAR systems. Thus, increasing only the laser power to increase the signal power of the transmitted light, and thus in turn, the return optical signal power across the narrow passband of the BPF in the receiver, may not be feasible or practical. The present disclosure provides systems and methods for reducing stray light using synchronous filtering. In one embodiment, an optical ranging and detection (LiDAR) system for reducing stray light using synchronous filtering is provided. The system includes a light source that emits laser light having a first wavelength range and an emitter that includes one or more emission optical elements disposed in a transmission light path. The emitter is configured to provide transmitted light based on a laser light having a first wavelength range. The system also includes a receiver including a detector and one or more receiving optical elements