Researchers Submit Patent Application, "Cost-Effective Lidar Sensor for Multi-Signal Detection, Weak Signal Detection and Signal Disambiguation and Method of Using Same", for Approval
The patent's assignee is
News editors obtained the following quote from the background information supplied by the inventors: "A lidar sensor is a light detection and ranging sensor. It is an optical remote sensing module that can measure the distance to a target or objects in a landscape, by irradiating the target or landscape with light, using pulses (or alternatively a modulated signal) from a laser, and measuring the time it takes photons to travel to said target or landscape and return after reflection to a receiver in the lidar module. The waveforms of the reflected pulses are detected and analyzed to determine which pulses represent reflections from solid objects whose sensing is desired (e.g., vehicle, person, wall, tree) as opposed to errant pulses reflected by environmental elements whose sensing is not desired (e.g., rain, dust). Errant pulses can have a low intensity (due to the small size or low reflectivity of the element causing the reflection) and/or a broadened width (due to the diffuse reflection obtained in backscattering). When one outgoing pulse generates multiple return pulses, the detection and analysis of the return pulses allow the selection of the pulse that corresponds to the object whose sensing is desired, with the time of flight and the intensity of the selected pulse being measures of the distance and the reflectivity of the sensed object, respectively.
"Conventional waveform digitization and analysis permit accurate measurements of reflected laser pulses, however the method is expensive due to the costly components needed, such as fast Analog-to-Digital Converters (ADCs) that digitize the pulses (per U.S. Pat. No. 7,969,558), and field-programmable gate arrays (FPGAs) or fast digital signal processors (DSPs) that process the data.
"Lower cost pulse width ToF methods have been developed more recently. In this approach, pulses that cross a voltage threshold trigger a Time-to-Digital Converter (TDC), which records the time of the event. A computer locates the pulse with the largest width, and uses a correlation table to compensate for 'walk' error and calculate an assumed intensity. This low-cost approach has significant performance issues, including:
"It can miss low intensity pulses that do not cross the voltage threshold trigger; this problem cannot be solved by lowering the voltage threshold trigger setting, as this change would increase the noise level
"It incorrectly interprets returns from environmental elements whose sensing is not desired (e.g., rain, fog, dust), as a single pulse width measurement on a waveform can be ambiguous since it provides no information on the waveform shape, therefore not enabling to distinguish narrow waveforms of pulses reflected by objects whose sensing is desired from broadened waveforms backscattered by environmental elements whose sensing is not desired (e.g., rain, fog, dust)
"It conventionally records only one to a few return pulses, making it unreliable in poor weather, when a large number of errant pulses are commonly reflected in addition to the desired reflected pulse."
As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "A lidar-based apparatus and method are used for multi-signal detection, weak signal detection and signal disambiguation through waveform approximation utilizing a multi-channel time-to-digital converter (TDC) electronic circuit, with each
DESCRIPTION OF THE DRAWINGS
"The following drawings are illustrative of embodiments of the present invention and are not intended to limit the invention as encompassed by the claims forming part of the application.
"The schematic diagram of FIG. 1 provides an external view of a lidar sensor 10 that can be used in the present invention, depicting a static base 20 and a static head assembly 30 that includes a window 40 that is transparent at the wavelength of the laser used in each transmitter.
"The schematic diagram of FIG. 2 provides an internal view of a lidar sensor that can be used in the present invention, depicting a static base 50 that contains a motor and distributed electronics, and a spinning turret 60 that contains optoelectronic components 70 (including optical transmitters and receivers), collimation and focusing lenses 80 and distributed electronics. The multi-channel
For additional information on this patent application, see: PACALA, ANGUS; YU, TIANYUE; ELDADA, LOUAY. Cost-Effective Lidar Sensor for Multi-Signal Detection, Weak Signal Detection and Signal Disambiguation and Method of Using Same. Filed
Keywords for this news article include: Electronics,
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