Waveform reconstruction in a time-of-flight sensor

Abstract

A time-of-flight (TOF) sensor device is configured to perform classification analytics on a waveform signal representing a reflected light pulse, and to classify an object from which the light pulse was received based on characteristic properties of the reflected pulse. The TOF sensor device can compare the reflected pulse waveform with stored characteristic waveform profiles indicative of different types of objects or atmospheric particulates, including but not limited to snow, aerosol, water, fog, or mist. Some embodiments of TOF sensor device can also detect excessive levels of mist or suspended particulates that may reduce the detection accuracy of the sensor. To this end, such embodiments project focused light beams according to a defined pattern, and compare the reflected pattern with the defined pattern to determine a degree of pattern distortion attributable to the presence of mist.

What is claimed is: 
     
         1 . An imaging device, comprising:
 a memory that stores executable components; and   a processor, operatively coupled to the memory, that executes the executable components, the executable components comprising:
 an illumination component configured to emit a light pulse toward a viewing field; 
 a photo-receiver configured to generate an electrical output proportional to an intensity of light incident on a surface of the photo-receiver; 
 a pixel array component configured to generate waveform data corresponding to a reflected light pulse received at a pixel of the photo-receiver based on the electrical output; and 
 a distance determination component configured to remove a component of the waveform data attributable to light reflected from mist to yield a modified waveform data, and to generate distance information for an object corresponding to the reflected light pulse based on analysis of the modified waveform data. 
   
     
     
         2 . The imaging device of  claim 1 , wherein the distance determination component is configured to identify, at a time prior to entry of the object within a zone of limited detection of the imaging device, an amount of reflected light attributable to mist, and to record the amount of the reflected light attributable to mist as a baseline value. 
     
     
         3 . The imaging device of  claim 2 , wherein the distance determination component is configured to remove the component of the waveform data attributable to light reflected from mist by subtracting the baseline value from the waveform data. 
     
     
         4 . The imaging device of  claim 1 , further comprising a polarizing filter installed on at least one of the illumination component or the photo-receiver. 
     
     
         5 . The imaging device of  claim 1 , wherein the distance determination component is configured to remove the component of the waveform data attributable to light reflected from mist in response to a determination that the object has entered a zone of limited detection of the imaging device. 
     
     
         6 . The imaging device of  claim 1 , further comprising a waveform analysis component configured to perform a comparison of the modified waveform data with signature profile data that defines characteristic waveform signatures corresponding to respective object classifications, and to generate classification data assigning an object classification, of the object classifications, to the object based on a result of the comparison. 
     
     
         7 . The imaging device of  claim 6 , further comprising a hazard analysis and decision component configured to generate a control output signal based on the object classification and the distance information. 
     
     
         8 . The imaging device of  claim 7 , wherein the control output signal is configured to instruct a controller to cause a controlled industrial process to enter a safe state. 
     
     
         9 . The imaging device of  claim 6 , wherein the hazard analysis and decision component is further configured to change a depth of a dynamic safety zone being monitored by the imaging device based on the object classification. 
     
     
         10 . The imaging device of  claim 6 , wherein the object classification is at least one of snow, aerosol, water, fog, or mist. 
     
     
         11 . A method, comprising:
 generating, by a time-of-flight (TOF) sensor device comprising a processor, an electrical output in proportion to an intensity of light incident on a surface of a photo-receiver of the TOF sensor device;   generating, by the TOF sensor device, waveform data corresponding to a reflected light pulse received at a pixel of the photo-receiver based on the electrical output;   removing, by the TOF sensor device, a component of the waveform data determined to be attributable to light reflected from mist to yield a modified waveform data; and   generating, by the TOF sensor device, distance information for an object corresponding to the reflected light pulse based on analysis of the modified waveform data.   
     
     
         12 . The method of  claim 11 , further comprising:
 identifying, by the TOF sensor device at a time prior to entry of the object within a zone of limited detection of the TOF sensor device, an amount of reflected light attributable to mist, and   recording, by the TOF sensor device, the amount of the reflected light attributable to mist as a baseline value.   
     
     
         13 . The method of  claim 12 , wherein the removing comprises subtracting the baseline value from the waveform data. 
     
     
         14 . The method of  claim 11 , wherein the removing comprises removing the component of the waveform data attributable to light reflected from mist in response determining that the object has entered a zone of limited detection of the imaging device. 
     
     
         15 . The method of  claim 11 , further comprising:
 comparing, by the TOF sensor device, the modified waveform data with signature profile data that defines characteristic waveform signatures corresponding to respective object classifications; and   generating, by the TOF sensor device, classification data assigning an object classification, of the object classifications, to the object based on a result of the comparing.   
     
     
         16 . The method of  claim 15 , further comprising generating, by the TOF sensor device, a control output signal based on the object classification and the distance information. 
     
     
         17 . The method of  claim 15 , further comprising changing, by the TOF sensor device, a depth of a dynamic safety zone being monitored by the TOF sensor device based on the object classification. 
     
     
         18 . The method of  claim 15 , wherein the object classification is at least one of snow, aerosol, water, fog, or mist. 
     
     
         19 . A non-transitory computer-readable medium having stored thereon instructions that, in response to execution, cause a time-of-flight (TOF) sensor device comprising a processor to perform operations, the operations comprising:
 emitting a light pulse into a viewing area;   generating an electrical output proportional to an intensity of light incident on a surface of a photo-receiver of the TOF sensor device;   generating, based on the electrical output, waveform data corresponding to a reflected light pulse received at a pixel of the photo-receiver;   removing a component of the waveform data attributable to light reflected from mist to yield a modified waveform data; and   generating distance information for an object corresponding to the reflected light pulse based on analysis of the modified waveform data.   
     
     
         20 . The non-transitory computer-readable medium of  claim 19 , wherein the removing comprises:
 identifying, at a time prior to entry of the object within a zone of limited detection of the TOF sensor device, an amount of reflected light attributable to mist,   recording the amount of the reflected light attributable to mist as a baseline value, and   subtracting the baseline value from the waveform data.