US-12625239-B2 - Apparatus and method for configuring and operating a laser scanner apparatus

US12625239B2US 12625239 B2US12625239 B2US 12625239B2US-12625239-B2

Abstract

One or more types of laser scanner apparatuses perform object detection by emitting laser pulses and detecting corresponding reflected pulses by correlating a digitized detection signal against a correlation template representing a characteristic signal pulse. Regions of the digitized detection signal exhibiting high correlation with the template correspond to reflection pulses caused by backscattering of the emitted laser pulses. A calibration system and corresponding calibration method improve detection operations by such laser scanner apparatuses by producing a high-resolution correlation template. Among the several advantages associated with the system and method is the ability to produce correlation templates of high resolution, without requiring any increase in the base sampling rate of the digitizers used by the calibration system and the laser scanner apparatuses for digitizing their respective detection signals.

Inventors

Takeshi Shoji
Fred Schleifer

Assignees

OMRON CORPORATION

Dates

Publication Date: 20260512
Application Date: 20220124

Claims (12)

1 . A method performed by a calibration system for a defined type of laser scanner apparatus, the method comprising: setting a digitizer of the calibration system to each sampling phase, among a plurality of sampling phases that are incrementally offset relative to a starting phase by a phase increment that is a fraction of a sampling rate of the digitizer; and for each sampling phase, obtaining a sample set via the digitizer, the sample set comprising digital samples of a signal pulse within a photodetector signal output by a photodetector of the calibration system, the digital samples spaced according to the sampling rate, the signal pulse corresponding to impingement of a reflection pulse impinging on the photodetector, and the reflection pulse being backscattered by an object illuminated by a laser pulse output by a laser transmitter of the calibration system; generating a merged version of the sample sets, as a reference sample set having digital samples spaced according to the phase increment; storing the reference sample set as a correlation template, wherein a laser scanner apparatus of the defined type detects objects by emitting laser pulses and detects corresponding reflected pulses by correlating a photodetector signal of the laser scanner apparatus with the correlation template, over an interval corresponding to a detection range of the laser scanner apparatus; and outputting the correlation template via a signaling interface of the calibration system, for storage in one or more laser scanner apparatuses of the defined type.
2 . The method of claim 1 , wherein optical and electronic characteristics of the calibration system match corresponding optical and electronic characteristics of the defined type of laser scanner apparatus.
3 . The method of claim 1 , wherein the calibration system incorporates a laser transmitter subassembly, including the laser transmitter, and a reflected-pulse reception subassembly, including the digitizer and the photodetector, which are configured like respective subassemblies used by the defined type of laser scanner apparatus.
4 . The method of claim 1 , wherein obtaining the sample set for each sampling phase comprises obtaining the sample set by averaging a plurality of sample sets obtained at the sampling phase.
5 . The method of claim 1 , wherein obtaining the sample set for each sampling phase comprises adjusting the digitizer to perform digitization at each of the sampling phases by controlling a phase of a clock signal used to clock the digitizer.
6 . The method of claim 1 , wherein the plurality of sampling phases divides the sample time of the digitizer into N sampling phases, wherein N is an integer greater than 1, such that the correlation template has a time resolution N times greater than the sampling time.
7 . A calibration system operative to generate a correlation template for a defined type of laser scanner apparatus, the calibration system comprising: a laser transmitter; a photodetector; a digitizer; and processing circuitry configured to: set the digitizer to each sampling phase, among a plurality of sampling phases that are incrementally offset relative to a starting phase by a phase increment that is a fraction of a sampling rate of the digitizer; and for each sampling phase, obtain a sample set via the digitizer, the sample set comprising digital samples of a signal pulse within a photodetector signal output by the photodetector, the digital samples spaced according to the sampling rate, the signal pulse corresponding to impingement of a reflection pulse impinging on the photodetector, and the reflection pulse being backscattered by an object illuminated by a laser pulse output by the laser transmitter; generate a merged version of the sample sets, as a reference sample set having digital samples spaced according to the phase increment; store the reference sample set as the correlation template; output the correlation template via a signaling interface of the calibration system, for storage in one or more laser scanner apparatuses of the defined type; wherein a laser scanner apparatus of the defined type detects objects by emitting laser pulses and detecting corresponding reflected pulses by correlating a photodetector signal of the laser scanner apparatus with the correlation template, over an interval corresponding to a detection range of the laser scanner apparatus.
8 . The calibration system of claim 7 , wherein optical and electronic characteristics of the calibration system match corresponding optical and electronic characteristics of the defined type of laser scanner apparatus.
9 . The calibration system of claim 7 , wherein the calibration system incorporates a laser transmitter subassembly, including the laser transmitter, and a reflected-pulse reception subassembly, including the digitizer and the photodetector, which are configured like respective subassemblies used by the defined type of laser scanner apparatus.
10 . The calibration system of claim 7 , wherein the processing circuitry is configured to obtain the sample set for each sampling phase by averaging a plurality of sample sets obtained at the sampling phase.
11 . The calibration system of claim 7 , wherein the processing circuitry is configured to obtain the sample set for each sampling phase by adjusting the digitizer to perform digitization at each of the sampling phases by controlling a phase of a clock signal used to clock the digitizer.
12 . The calibration system of claim 7 , wherein the plurality of sampling phases divides the sample time of the digitizer into N sampling phases, wherein N is an integer greater than 1, such that the correlation template has a time resolution N times greater than the sampling time.

Description

TECHNICAL FIELD Various embodiments of an apparatus and method for configuring a laser scanner apparatus are disclosed herein, along with corresponding embodiments of a laser scanner apparatus and methods thereof. BACKGROUND A typical laser scanner apparatus, or simply “scanner.” emits a laser pulse into a surrounding physical environment and detects one or more “return” or “reflection” pulses, as backscattered from one or more objects in the surrounding environment. By way of example, a scanner may “sweep” a defined angular range within a horizontal plane, e.g., 180 degrees, or it may sweep through defined horizontal and vertical ranges, emitting one or more pulses at each angular step and correspondingly monitoring for backscattered light. Monitoring for return reflections with respect to each emitted laser pulse may be confined to an interval corresponding to minimum and maximum detection distances of the scanner—i.e., a working “detection” range”—according to time-of-flight (ToF) principles. An example scanner includes a transmitter arrangement operative to emit laser pulses and a receiver arrangement operative to detect corresponding backscattered light. For example, the scanner includes a photodetector that outputs a photodetector signal that varies responsive to backscattered light impinging on the photodetector, such that “return” laser pulses received by the scanner, i.e., reflected pulses corresponding to an emitted laser pulse, manifest themselves as signal pulses in the photodetector signal. According to that arrangement, detection of objects within a scanning range of the scanner comprises emitting a laser pulse and monitoring the photodetector signal for signal pulses representative of the return reflections. Determining the temporal offset—the timewise location—of such signal pulses in relation to the transmission time of the outgoing laser pulse allows the scanner to estimate object distance, according to Time-of-Flight (ToF) calculations. Challenges arise not only from the inherently high measurement speeds involved in determining the ToF of a laser pulse, but also from the need for good noise immunity and accurate pulse discrimination. Here, “pulse discrimination” may also be referred to as “pulse detection” or “pulse identification,” and it refers to the ability of the scanner to accurately detect signal pulses within the photodetector signal that represent return reflections. SUMMARY One or more types of a laser scanner apparatus perform object detection by emitting laser pulses and detecting corresponding reflected pulses by correlating a digitized detection signal against a correlation template representing a characteristic signal pulse. Regions of the digitized detection signal exhibiting high correlation with the template correspond to reflection pulses caused by backscattering of the emitted laser pulses. A calibration system and corresponding calibration method improve detection operations by such laser scanner apparatuses by producing a high-resolution correlation template. Among the several advantages associated with the system and method is the ability to produce correlation templates of high resolution, without requiring any increase in the base sampling rate of the digitizers used by the calibration system and the laser scanner apparatuses for digitizing their respective detection signals. A method performed by a calibration system for a defined type of laser scanner apparatus comprises, in an example embodiment, setting a digitizer of the calibration system to each sampling phase, among a plurality of sampling phases that are incrementally offset relative to a starting phase by a phase increment that is a fraction of a sampling rate of the digitizer. For each sampling phase, the method includes obtaining a sample set via the digitizer, with the sample set comprising digital samples of a signal pulse within a photodetector signal output by a photodetector of the calibration system. The digital samples are spaced according to the sampling rate, and the signal pulse corresponds to impingement of a reflection pulse impinging on the photodetector, with the reflection pulse being backscattered by an object illuminated by a laser pulse output by a laser transmitter of the calibration system. The method further includes the calibration system generating a merged version of the sample sets, as a reference sample set having digital samples spaced according to the phase increment and storing the reference sample set as a correlation template. A laser scanner apparatus of the defined type detects objects by emitting laser pulses and detecting corresponding reflected pulses by correlating a photodetector signal of the laser scanner apparatus with the correlation template, over an interval corresponding to a detection range of the laser scanner apparatus. With the resolution of the correlation template being increased over the sampling rate of the involved digitizer, the laser scanner appa