Patent Publication Number: US-2022236390-A1

Title: Apparatus and method for configuring and operating a laser scanner apparatus

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 apparatus advantageously operates with a higher-fidelity reference for detecting reflection pulses in its photodetector signal, while allowing it to operate with a digitizer having the same underlying sampling rate used by the calibration system. 
     In another example embodiment, a calibration system is operative to generate a correlation template for a defined type of laser scanner apparatus. The calibration system includes a laser transmitter, a photodetector, a digitizer, and processing circuitry. The processing circuitry is 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. That is, the plurality of sampling phases uniformly subdivides the time interval associated with the sampling rate. 
     For each sampling phase, the processing circuitry is configured to 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 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 the laser transmitter. The object, for example, is a test object of a specified size and reflectivity, which is positioned at a fixed location and orientation relative to the calibration system, for generation of the correlation template. 
     The processing circuitry of the calibration system is further configured to generate a merged version of the sample sets, as a reference sample set having digital samples spaced according to the phase increment and store the reference sample set as the correlation template. With these operational configurations, the processing circuitry operates to produce the correlation template with a higher time resolution than what is provided by the sampling rate of the digitizer used to digitize the detection signal—i.e., the photodetector signal produced by the photodetector of the calibration system. Correspondingly, 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. 
     In one embodiment of a method performed by a laser scanner apparatus, the method includes transmitting a laser pulse from the laser scanner apparatus and digitizing a photodetector signal over an interval referenced to transmission of the laser pulse, to obtain a series of digital samples having a first time resolution established by a sampling rate of a digitizer used for the digitizing. Further, the method includes the laser scanner apparatus up-sampling the series of digital samples or at least subsets within the series of digital samples corresponding to detected peaks, to obtain one or more up-sampled series of digital samples having a second time resolution that is higher than the first time resolution by an up-sampling factor. 
     Still further, the example method includes the laser scanner apparatus searching for signal pulses in the one or more up-sampled series of digital samples that are representative of the laser scanner apparatus receiving reflected pulses corresponding to the transmitted laser pulse. Here, the laser scanner apparatus performs the searching by correlating the one or more up-sampled series of digital samples with a correlation template comprising a reference set of samples representing a nominal reflection-pulse shape sampled at the second resolution. 
     Of course, the present invention is not limited to the above features and advantages. Those of ordinary skill in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of one embodiment of calibration system, according to one embodiment. 
         FIG. 2  is block diagram of example details for a calibration system, according to one embodiment. 
         FIG. 3  is a plot of an example photodetector signal, exhibiting a pulse waveform corresponding to impingement of a reflected laser pulse on a photodetector. 
         FIG. 4  is a logic flow diagram of one embodiment of a method performed by a calibration system. 
         FIG. 5  is a logic flow diagram of example details corresponding to the method depicted in  FIG. 4 . 
         FIG. 6  depicts plots of example sampling phases, used for sampling a pulse waveform. 
         FIG. 7  is a block diagram illustrating one embodiment of merging multiple sets of digital samples taken at different sampling phases, to form a higher-resolution set of digital samples. 
         FIG. 8  is a logic flow diagram of one embodiment of another method performed by a calibration system. 
         FIG. 9  is a block diagram of one embodiment of a laser scanner apparatus of a type that operates according to calibration data provided by a calibration system. 
         FIG. 10  is a logic flow diagram of one embodiment of a method performed by a laser scanner apparatus. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  depicts an example calibration system  10 , which may also be referred to as “configuration system  10 ” or simply “system  10 .” As a non-limiting example, the system  10  generates and outputs certain configuration information for use by a defined type of laser scanner apparatus. The system  10  may be used in a manufacturing environment, for example, and allow authorized users to generate and save the configuration information, e.g., for loading into laser scanner apparatuses. 
     The saved configuration information comprises, for example, a “correlation template” that serves as a reference for pulse detection by laser scanner apparatuses of the defined type. Particularly, laser scanner apparatuses of the defined type detect objects in their surrounding physical environments by emitting laser pulses and detecting corresponding return pulses via a photodetector. The correlation template comprises sample points defining a high-resolution pulse having a characteristic pulse shape, for correlation with the photodetector signal. As such, the correlation template provides improved reliability and accuracy in detecting and recognizing return pulses manifested within in the photodetector signal. 
     With the above context in mind, the system  10  includes a laser transmitter subassembly  12  that is configured to transmit a laser beam  14 —e.g., a laser pulse—into its surrounding physical environment. Assuming the emitted laser pulse strikes an object of sufficient reflectivity and size, and within the distance limits of detectability, an optical receiver subassembly  16  receives a portion of the backscattered light, with the received portion denoted as backscattered light  18 . 
     The example laser transmitter subassembly  12  includes a laser transmitter module  20  operative to emit laser pulses. Included in the example optical receiver subassembly  16  are a photodetector  22  and a digitizer  24 . A photodetector signal output by the photodetector  22  varies as a function of the backscattered light  18 —or at least a portion thereof—being directed onto an active surface of the photodetector  22 . Digitizing the photodetector signal via the digitizer  24  provides the system  10  with the ability to “capture” the photodetector signal over an interval referenced to the transmission of a laser pulse. The length or duration of the interval extends at least to a time (relative to the transmission time) corresponding to a defined maximum object-detection distance. As explained above, the photodetector signal manifests or exhibits signal pulses responsive to the reception of reflection pulses into the optical receiver subassembly  16 . 
     In one or more embodiments, the system  10  further includes an interface subassembly  26  and a calibration control subassembly  28 . In at least one such embodiment, the calibration control subassembly  28  comprises a computer system or test apparatus, such as a Personal Computer (PC) based test system, running one or more programs that allow a human operator to provide a command or other form of input to initiate calibration operations, etc. In such embodiments, the interface subassembly  26  may be distributed between the calibration control subassembly  28  and a laser scanner portion  30  of the system  10 . As an example, the calibration control subassembly  28  has one or more interface ports and associated circuitry, such as a serial or parallel port, a USB port, etc., the laser scanner portion  30  includes a compatible port/circuitry. 
     As an example, the laser scanner portion  30  of the system  10  is a working example of the type of laser scanner apparatus for which the calibration template is generated. The working example may be removably connected, such that any given laser scanner apparatus can be used as the laser scanner portion  30  of the system  10 , or it may be a dedicated unit and it may not necessarily be in fully-assembled portion. An advantageous aspect of this arrangement is that the opto-electronic performance and behaviors of the laser scanner portion  30  of system  10  is guaranteed to match the general characteristics of the laser scanner apparatuses of the defined type if, in fact, the system  10  incorporates the same opto-electronics and waveform processing subsystems used by such apparatuses. 
       FIG. 2  illustrates example details for an optical receive path  40  implemented in whole or in part within the optical receiver subassembly  16 . The example arrangement includes a scanning mirror  42  that is configured to project the backscattered light  18  received at the optical receiver subassembly  16  as a projected beam  44 , towards an aperture  46 . The projected beam  44  passes completely or partly through the aperture  46 . Correspondingly, the backscattered light  48  passed by the aperture  46  impinges on the lens  50  and is focused towards the photodetector  22 , as focused light  52 . In at least one embodiment, the photodetector  22  is an avalanche photodiode, which is denoted in  FIG. 2  as an “APD.” 
     A photodetector signal  56  output from the photodetector  22  is an electrical signal that responds to backscattered light impinging on its active surface area. In at least one embodiment, the photodetector signal  56  is an analog electrical signal that increases in amplitude in proportion to the optical power received at the active surface of the photodetector  22 . Return reflections of the transmitted laser beam  14  that are received at the system  10  as backscattered light  18  are manifested in the photodetector signal  56  as signal pulses having a peak amplitude corresponding to the peak optical power impinging on the photodetector  22 . One transmitted laser beam  14  may produce multiple reflections, and the photodetector signal  56  may exhibit multiple signal pulses over the interval of interest, along with spurious movements and other noise. 
     Filter circuitry  60  provides some noise rejection and bandwidth limiting of the photodetector signal  56 , in advance of analog-to-digital converter (ADC) circuitry  62 , which outputs a series of digital samples over the interval of interest, for temporary storage in a buffer circuitry  64 . Waveform processing circuitry  66  evaluates the series of digital samples held in the buffer circuitry  64 , e.g., for peak detection and corresponding pulse identification. Collectively, such circuitry stands as one example of the digitizer  24 , which is operative to capture a series of digital samples by digitizing the photodetector signal  56 , after filtering or conditioning performed by the filter circuitry  60 . 
     System processing circuitry  68  provides direct or indirect control of the laser transmitter subassembly  12  and provides direct or indirect “phase control” of the ADC circuitry  62 . As an example, the system processing circuitry  68  is configured to set the digitizer  24  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  24 . 
     In one example, the phase control provided by the system processing circuitry  68  to the digitizer  24  involves controlling the phase of a clock signal that controls sampling by the ADC circuitry  62 . Thus, the ADC  62  may be clocked with the sampling clock at a first or starting phase, for digitizing the photodetector signal  56  with respect to the transmission of a first laser pulse, and then clocked with the sampling clock at a second phase, for digitizing the photodetector signal  56  with respect to the transmission of a second laser pulse, and so on. The same target object and target position/orientation, and distance generally will be used for acquiring digital samples over all the phases, with the optical setup generally arranged to produce one reflection pulse per transmitted laser pulse. Such an arrangement allows the system  10  to digitize a substantially identical signal pulse within the photodetector signal  56 , at each of the defined sampling phases. 
     That is, for each sampling phase, the system processing circuitry  68  is configured to obtain a sample set via the digitizer  24 , where the sample set comprises digital samples of a signal pulse within a photodetector signal  56 , as output by the photodetector  22 . The digital samples are spaced according to the sampling rate of the digitizer  24 , and the signal pulse corresponds to impingement of a reflection pulse impinging on the photodetector  22 . That is, the reflection pulse was backscattered by an object illuminated by a laser pulse output by a laser transmitter of the system  10 —i.e., the laser transmitter module  20 . 
     The system processing circuitry  68  is further configured to generate a merged version of the sample sets, as a reference sample set having digital samples spaced according to the phase increment and store the reference sample set as a correlation template. Advantageously, a laser scanner apparatus of the defined type associated with the calibration system  10  detects objects by emitting laser pulses and detecting corresponding reflected pulses, based on 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. 
     As such, the optical and electronic characteristics of the system  10  match corresponding optical and electronic characteristics of the defined type of laser scanner apparatus. For example, the system  10  incorporates a laser transmitter subassembly  12 , including the laser transmitter, and a reflected-pulse reception subassembly, including the digitizer  24  and the photodetector  22 , that are configured like respective subassemblies used by the defined type of laser scanner apparatus. That is, the laser transmitter subassembly  12  and the optical receiver assembly  16  have optoelectronic performance and behaviors like those of the defined type of laser scanner apparatus, such that the correlation template is appropriate for use by laser scanner apparatuses of the defined type. 
     Obtaining the sample set for each sampling phase is based on, for example, the system processing circuitry  68  being configured to averaging a plurality of sample sets obtained at the sampling phase. Consider an example where the sampling phases are phase 1, phase 2, phase 3, . . . . phase n. The system  10  emits multiple laser pulses—laser beam pulses—and acquires multiple corresponding sample sets for each sampling phase and forms the “sample set” for each sampling phase by averaging together the corresponding sample sets obtained for that sampling phase. 
     As a further example detail, obtaining the sample set for each sampling phase is based on the system processing circuitry  68  being configured, in one or more embodiments, to control the digitizer  24  to perform digitization of the photodetector signal  56  at each of the sampling phases, by controlling a phase of a clock signal used to clock the digitizer  24 . In other words, the digitizer  24  has a defined sampling rate—e.g., the clock rate of a clock signal applied to it or generated within it—and the system processing circuitry  68  directly or indirectly controls the phase of the sampling clock, to cause the digitizer  24  to obtain samples at different phases. The clock may be internal to the system processing circuitry  68  or may be a dedicated clock external to the system processing circuitry  68  and the digitizer  24  or may be internal to the ADC circuitry  62 . In that case, the system processing circuitry  68  controls the clock phase by applying a control signal to the ADC circuitry  62 . 
     In at least one embodiment, the system processing circuitry  68  is configured to divide the sample time of the digitizer  24  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. Assume a sample clock frequency of 100 MHz and a value of N=16. With this arrangement, the sample time/rate is 10 nanoseconds, with 16 sampling phases increasing that time resolution to 625 picoseconds. In other words, the “phase increment” is 1/16th of the sampling interval between two sample points taken at the defined sampling rate of the digitizer  24 . Other phase increments may be used, of course, with finer phase increments yielding higher resolutions. 
     Consequently, rather than having digital samples at a spacing of 10 nanoseconds, the correlation template includes digital samples at a spacing of 625 picoseconds, with each such digital sample being based on one or more actual sampled value(s) of signal pulses in the photodetector signal  56 , as opposed to interpolation or other “synthetic” techniques that do not provide the waveform fidelity achieved by oversampling via multiple sampling phases. 
     In one or more embodiments, the system processing circuitry  68  is configured to output the correlation template via a signaling interface of the system  10 , for storage in one or more laser scanner apparatuses of the defined type. For example, the system processing circuitry  68  includes or has access to memory or other storage  70 , for at least temporarily building and retaining the correlation template, and is configured to output the correlation via template via input/output (I/O) circuitry  72 , which also may be referred to as a “signaling interface.” The I/O circuitry  72  may be configured to interface with external memory or file-system storage, for subsequent transfer to multiple laser scanner apparatuses in a manufacturing context or may be configured according to the communication protocols—a defined serial link protocol—for communicating directly with laser scanner apparatuses of the defined type. 
     At least some aspects of operation by the system processing circuitry  68  may be controlled or initiated by a human operator (or by an external control system), and the system  10  in one or more embodiments includes interface circuitry  74 , for input/output control. In this regard, the system processing circuitry  68  may be included in the laser scanner portion  30  of the system  10 . For example, in one embodiment, the laser scanner portion  30  comprises a working laser scanner apparatus of the type that uses the calibration template, with the system processing circuitry  68  being the processing circuitry being implemented by running a special “calibration” program on the digital processing circuitry implemented within the laser scanner apparatus. In other embodiments, at least a portion of the system processing circuitry  68  resides in the calibration control subassembly  28 —e.g., at least some of the calibration processing may be performed in a PC or other processing system used to implement the calibration control assembly. 
       FIG. 3  illustrates an example signal pulse, as manifested in the photodetector signal  56  in response to impingement of a reflected pulse on the active surface of the photodetector  22 . Here, the time to refers to the transmission time of the laser pulse that yielded the reflection pulse, and the time t pulse  corresponds to the peak of the signal pulse. As a general proposition, the same pulse shape and amplitude and time t pulse  can be reproduced consistently, by maintaining a fixed position of a defined test target and illuminating it repeatedly, with successive laser pulses output by the laser transmitter subassembly  12 . That is, substantially identical signal pulses can be obtained for multi-phase digitization, for creation of the correlation template. 
       FIG. 4  illustrates one embodiment of a method  400  of operation by a calibration system, for example, the system  10  depicted in  FIG. 1 . Operations comprising the method  400  may be performed as part of or in conjunction with other operations and, unless otherwise noted, may be performed in an order other than the one suggested. Further, one or more of the operations may be looped or repeated. 
     The method  400  is performed by a calibration system for a defined type of laser scanner apparatus and, in the illustrated embodiment, the method  400  includes setting (Block  402 ) 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. Further, the method  400  includes, for each sampling phase. (Blocks  404 ,  406 ) 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. 
     Still further, the method  400  includes generating (Block  408 ) 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, and at least temporarily storing (Block  410 ) the reference sample set as a correlation template. As explained earlier, a laser scanner apparatus of the “defined type” is one that 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. 
     Optical and electronic characteristics of the calibration system used to carry out the method  400  match corresponding optical and electronic characteristics of the defined type of laser scanner apparatus. For example, 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. 
     Obtaining the sample set for each sampling phase comprises, in one or more embodiments of the method  400 , obtaining the sample set (the Block- 404  operation) by averaging a plurality of sample sets obtained at the sampling phase. Averaging in this manner compensates for random noise, e.g., caused by “dark current” of the photodetector  22 . 
     As a further detail, obtaining the sample set for each sampling phase comprises, for example, 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. 
     For example, the method  400  involves dividing 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. 
     In at least one embodiment, the method  400  further includes 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. For example, the calibration system transfers a stored copy of the calibration template from its memory or storage, via the signaling interface. 
       FIG. 5  illustrates an example set of detailed steps for implementing the Block- 404  operation of the method  400 , with the understanding that steps are repeated for each of the sampling phases, as a “current sampling phase.” 
     The set of detailed steps includes setting an acquisition index i to i=0 (Block  420 ). obtaining and saving a sample set (Block  422 ), incrementing i, e.g., i=i+1 (Block  424 ), and looping back to Block  422  if i is less than the maximum index count (NO from Block  426 ). Thus, for each value of i from 0 to (MAX−1), the calibration system obtains another sample set for the current sampling phase, thereby acquiring a plurality of sample sets all taken at the same sampling phase. 
     Once the plurality of sample sets is acquired, processing transitions to Block  428  (the YES path from Block  426 ). There, the calibration system averages the plurality of sample sets together to form the final or overall sample set corresponding to the current sampling phase. 
       FIG. 6  offers a graphical illustration of building up a high-resolution reference sample set—a correlation template—based on the multi-phase sampling contemplated herein. A series of digital samples is acquired for each of N sampling phases, with each series comprising those digital samples from the photodetector signal  56  representing the signal pulse of interest. Again, assuming that the test object is the same and its distance and orientation remains fixed over multiple laser-pulse emissions, the signal pulse(s) sampled at each sampling phase will be substantially identical to the signal pulse(s) sampled at all other sampling phases, which provides for coherent combining the per-phase sample sets, to form the higher-resolution reference sample set. 
       FIG. 7  illustrates the “assembly” process for forming the reference set in an embodiment that uses 16 sampling phases. The term F samp  represents the sampling clock frequency, and the term N_adj_max=the incremental phase adjustment used to step through the 16 sampling phases used to subdivide the fundamental sampling interval defined by the sampling clock. 
     Assuming, merely as an example arrangement, the sample set obtained at each of the sixteen sampling phases comprises seven samples, spaced according to the sampling interval defined by F samp , which is a fixed constant for purposes of this example. Thus, at a first or starting sampling phase—which may be a zero-phase offset—the process produces seven digital sample values d_0_1, d_0_2, d_0_3, . . . , d_0_7. The “d” here denotes digital sample, the “0” denotes the sampling phase, here, the zero-th phase, and the terminal number denotes the sequential sample number within the set of seven samples. 
     With this labeling scheme, the seven samples taken at the second sampling phase are d_1_1, d_1_2, d_1_3, . . . d_1_7, the seven samples taken at the third sampling phase are d_2_1, d_2_2, d_2_3, . . . , d_2_7, and so on, ending with the seven samples taken at the sixteenth sampling phase being d_15_1, d_15_2, d_15_3 . . . . , d_15_7. The reference sample set appears at the bottom-most portion of the drawing and is referred to as the “integrated sample set” and it depicts the interleaving of the per-phase sample sets used to form the reference sample set as a high-resolution correlation template. 
       FIG. 8  illustrates the data-assembly operations of  FIG. 7  as a logic flow diagram including a sequence of seven steps or operations. The rust step represents a configuration or decision step, namely, determining the number of sampling phases to use, which is driven by the desired resolution for the correlation template, and practical considerations, such as the resolution practice for use in live operation of the laser scanner apparatuses that are intended to use the correlation template. 
     Steps  2 - 6  represent the processing steps performed for each sampling phase, with these steps being performed for each sampling phase, with N_adj_nax representing the overall number of sampling phases used. Step  7  represents the data interleaving used to obtain the reference sample set—the correlation template—from the sample sets obtained for all the sampling phases. 
       FIG. 9  illustrates an example laser scanner apparatus  100  of a type that uses a correlation template as described herein, during “live” object-detection operation. The laser scanner apparatus  100  (“apparatus  100 ”) includes an optical transmitter arrangement  112  that may be the same as the laser transmitter subassembly  12  of the calibration system  10 , or at least emits laser pulses  114  having comparable characteristics with respect to laser pulses  14  emitted by the calibration system  10 . 
     The apparatus  100  further includes an optical receiver arrangement  116  that is configured to detect reflected pulses corresponding to the emitted laser pulses  114 , which are received by the apparatus  100  as backscattered light  188  in correspondence with the emission of the laser pulses  114 . The optical receiver arrangement  116  may be the same as the optical receiver subassembly  16  of the calibration system  10 , at least in terms of its opto-electronic characteristics with respect to reflected-pulse detection, sampling, etc. 
     The apparatus  100  in an example arrangement includes an internal test/calibration arrangement  120 , for verification of detection performance during live operation, processing circuitry  122 , I/O circuitry  124 , communication interface circuitry  126 , and a power supply  128 . At least some of these entities may be repurposed or otherwise used as parts of the calibration system  10 , in at least some embodiments of the calibration system  10 , although the apparatus  100  may execute different software or run in a special mode, when integrated as part of the calibration system  10 . 
     In an example of operation, the apparatus  100  emits a laser pulse  114 , e.g., via an optical window  130  in its housing, and monitors a photodetector signal generated within the optical receiver arrangement  116  that is responsive to backscattered light  118 . Referring to  FIG. 2 , momentarily, the apparatus  100  includes a digitizer identical to or substantially like the digitizer  24 , meaning that it obtains digital samples of the photodetector signal, for waveform processing. To detect signal pulses within the digitized photodetector signal that are representative of reflection pulses, the apparatus  100  correlates an up-sampled version of the digitized photodetector signal with a correlation template of the sort described herein. 
     Up-sampling may be applied to the entire series of digital samples obtained from the photodetector signal for the time interval of interest, as referenced to the time of laser pulse transmission. Alternatively, the apparatus  100  performs localized up-sampling for those portions of the digitized photodetector signal that exhibit signal peaks. 
       FIG. 10  illustrates a method  1000  of operation of a laser scanner apparatus, such as the apparatus  100 . The method includes transmitting (Block  1002 ) a laser pulse, digitizing (Block  1004 ) a photodetector signal over an interval referenced to transmission of the laser pulse, to obtain a series of digital samples having a first time resolution established by a sampling rate of the digitizer used to digitize the photodetector signal. 
     The method  1000  further includes up-sampling (Block  1006 ) the series of digital samples or at least subsets within the series of digital samples corresponding to detected peaks, to obtain one or more up-sampled series of digital samples having a second time resolution that is higher than the first time resolution by an up-sampling factor. Further, the method  1000  includes searching (Block  1008 ) for signal pulses in the one or more up-sampled series of digital samples that are representative of the laser scanner apparatus receiving reflected pulses corresponding to the transmitted laser pulse. Particularly, the searching is based on correlating the one or more up-sampled series of digital samples with a correlation template comprising a reference set of samples representing a nominal reflection-pulse shape sampled at the second resolution. 
     In at least one embodiment of the apparatus  100 , the processing circuitry  122  performs some or all the waveform processing described for the apparatus  100 , including the template correlation processing. Correspondingly, the processing circuitry  122  comprises fixed circuitry or programmatically configured circuitry or a mix of both fixed and programmatically configured circuitry. Examples of the processing circuitry  122  and any other “processing circuitry” described herein include any one or any mix of one or more Field Programmable Gate Arrays (FPGAs), Complex Programmable Logic Devices (CPLDs), Application Specific Integrated Circuits (ASICs). System-on-Chip (SoC) modules. Digital Signal Processors (DSPs), microprocessors, or microcontrollers. 
     For example, the processing circuitry  122  comprises at least one microprocessor that includes or is accompanied by one or more types of computer-readable media that stores computer program instructions, the execution of which by the microprocessor(s) specially adapts them to carry out at least some of the apparatus operations described herein, e.g., controlling and/or monitoring the emission of laser pulses  114  and the detection of corresponding reflected pulses returned to the laser scanner apparatus  100  as backscattered light  118 . 
     Notably, modifications and other embodiments of the disclosed invention(s) will come to mind to one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention(s) is/are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of this disclosure. Although specific terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.