Multiple-field-of-view scannerless optical rangefinder in high ambient background light

Abstract

A multiple-field-of-view scannerless optical rangefinder operating in pulsed Time-Of-Flight operation for use in high ambient background light is described. The rangefinder comprises an optical emitter having a LED light source and driver electronics, emitting a train of light pulses having a broad field-of-illumination (FOI); a multi-channel optical receiver (MCOR) for detecting optical return signals, an overall field-of-view (FOV) encompassing each channel instantaneous FOV, the FOI encompassing the overall FOV, the multi-channel optical receiver having analog front-end electronics; an Analog-to-Digital Converter (ADC) for receiving and converting the waveforms into digital format; a control and processing unit (CPU) for generating a pulse trigger signal, sending a synchronization trigger signal to the MCOR for starting the detection of the optical return signals, and for processing the waveforms in digital format; a data interface; wherein a peak present in any of waveforms is a signature of an object located within the instantaneous FOV.

I claim: 
     
       1. A multiple-field-of-view scannerless optical rangefinder operating in pulsed Time-Of-Flight operation for use in high ambient background light, the rangefinder comprising:
 an optical emitter for emitting a train of light pulses, said train of light pulses having a broad field-of-illumination (FOI), said optical emitter having a LED light source and driver electronics;   a multi-channel optical receiver (MCOR) for detecting optical return signals, said MCOR including an array of PIN photodiodes, each detection channel of said multi-channel optical receiver having a photodetector with a photosensitive surface, an instantaneous field of view of each said detection channel having a horizontal and a vertical extent determined by dimensions of each respective said photosensitive surface and being adapted to output a channel return signal waveform, an overall field-of-view (FOV) of said multi-channel optical receiver encompassing each said instantaneous field of view, said field-of-illumination encompassing said over-all field-of-view, said multi-channel optical receiver having analog front-end electronics for conditioning said channel return signal waveforms, said MCOR outputting conditioned channel return signal waveforms;   an Analog-to-Digital Converter (ADC) for receiving and converting said conditioned channel return signal waveforms from said MCOR into digital format;   a control and processing unit (CPU) operatively connected to said optical emitter, said MCOR and said ADC,
 for generating a pulse trigger signal to trigger said optical emitter into emitting said train of pulses, 
 for sending a synchronization trigger signal to said MCOR for starting said detection of said optical return signals, and 
 for processing said conditioned channel return signal waveforms in digital format; 
   a data interface for receiving processed channel return signal waveforms from said CPU and preparing output data;   wherein a peak present in any of said optical return signal waveforms is a signature of an object located within said instantaneous field of view.   
     
     
       2. The rangefinder as claimed in  claim 1 , wherein said pulses have a duration below 50 ns and a detection bandwidth of said MCOR is higher than 10 MHz. 
     
     
       3. The rangefinder as claimed in  claim 1 , wherein said LED light source includes a plurality of LED sources. 
     
     
       4. The rangefinder as claimed in  claim 1 , wherein said light pulses are in one of a near-infrared region and a visible region of electromagnetic spectrum. 
     
     
       5. The rangefinder as claimed in  claim 1 , wherein said optical emitter further comprises at least one of a collimating lens assembly, a lenticular lens sheet, a LED reflector and an optical diffuser to condition said light pulses emitted by said LED light source. 
     
     
       6. The rangefinder as claimed in  claim 1 , wherein said photosensitive surface has an area of at least 0.5 mm 2 . 
     
     
       7. The rangefinder as claimed in  claim 1 , wherein said photosensitive surface has a reverse saturation current greater than 1 mA. 
     
     
       8. The rangefinder as claimed in  claim 1 , wherein said MOOR further comprises an objective having at least one of at least one lens element, at least one mirror and at least one correcting plate, said objective for focusing said optical return signal onto said photosensitive surfaces of said photodetectors. 
     
     
       9. The rangefinder as claimed in  claim 1 , wherein said analog front-end electronics being at least one of parallel multi-channel and multi-channel time-multiplexed. 
     
     
       10. The rangefinder as claimed in  claim 1 , wherein Analog-to-Digital Converter (ADC) includes more than one converter units adapted to work together to receive and convert said conditioned channel return signal waveforms into digital format. 
     
     
       11. The rangefinder as claimed in  claim 1 , wherein said MCOR is composed of one of a linear arrangement of N detection channels extending along a first direction and a two-dimensional arrangement of M X N detection channels extending along both said first direction and an orthogonal direction, said orthogonal direction being orthogonal to said first direction. 
     
     
       12. The rangefinder as claimed in  claim 1 , wherein said detection channels are AC coupled. 
     
     
       13. The rangefinder as claimed in  claim 1 , further comprising an optical filter for blocking at least a portion of parasitic background light having a wavelength spectrum outside of a wavelength band of said optical emitter. 
     
     
       14. The rangefinder as claimed in  claim 1 , wherein said LED emitter, said multi-channel optical receiver, said analog-to-digital converter and said control and processing unit are provided in an enclosure with a light transmission window for said LED emitter and said multi-channel optical receiver. 
     
     
       15. The rangefinder as claimed in  claim 14 , wherein said rangefinder further comprising an optical filter provided on said window for blocking at least a portion of parasitic background light having a wavelength spectrum outside of a wavelength band of said optical emitter. 
     
     
       16. The rangefinder as claimed in  claim 15 , wherein said optical filter is one of an optical protection window having one face coated with an optical film and a protection window made from a material allowing wavelength-selective optical transmission. 
     
     
       17. The rangefinder as claimed in  claim 1 , wherein said MCOR is provided on an integrated circuit. 
     
     
       18. The rangefinder as claimed in  claim 1 , wherein said a scene spectral irradiance of said high ambient background light is higher than 50 W/m 2  . 
     
     
       19. The rangefinder as claimed in  claim 1 , wherein said overall field-of-view has a minimum overall extent of 10° by 1°. 
     
     
       20. The rangefinder as claimed in  claim 1 , further comprising a distance calculator for calculating a distance between said rangefinder and said object, said distance calculator obtaining at least one of temporal and spatial characteristics of said light pulses and using said characteristics and said conditioned channel return signal waveforms in digital format to calculate said distance. 
     
     
       21. The rangefinder as claimed in  claim 20 , wherein said distance calculator is a component of said control and processing unit and wherein said output data includes said distance. 
     
     
       22. The rangefinder as claimed in  claim 1 , wherein said object is one of a vehicle, a person, an animal, a gas, a liquid, a particle, a pavement, a wall, a post, a sidewalk, a ground surface and a tree. 
     
     
       23. A scannerless optical rangefinder, comprising:
 a. an optical emitter for emitting an optical interrogation signal distributed over a field of illumination;   b. a multi-channel optical receiver (MCOR), for detecting an optical return signal over a field of view that is encompassed in the field of illumination and providing a return signal waveform;   c. an analog-to-digital converter (ADC) for receiving and converting a return signal waveform from the MCOR into digital format;   d. a control and processing unit (CPU) operatively connected to said optical emitter and said MCOR, for controlling emission of the optical interrogation signal and for processing the digital waveform output from the ADC to detect objects within the field of view;   the MCOR including a blind zone free array of photoresponsive elements, each photoresponsive elements characterized by a dimensionality and a saturation level selected so as to enable detection by the CPU of an object in the field of view when that object generates a contribution to the optical return signal that has a peak power of 0.5 to 15 nanowatts in the presence of a solar background contribution to the optical return signal of 80 to 800 nanowatts in a pass band of 80-nm and centered at 940-nm.    
     
     
       24. A scannerless optical rangefinder as defined in claim 23, said FOI being configured such that the optical return signal is received by two or more of the photoresponsive elements of the array.  
     
     
       25. A scannerless optical rangefinder as defined in claim 24, wherein said FOI encompasses said FOV.  
     
     
       26. A scannerless optical rangefinder as defined in claim 23, wherein said optical emitter outputs LED light.  
     
     
       27. A scannerless optical rangefinder as defined in claim 26, wherein said optical emitter includes a plurality of light sources.  
     
     
       28. A scannerless optical rangefinder as defined in claim 26, wherein said optical emitter includes a light emitting diode (LED).  
     
     
       29. A scannerless optical rangefinder as defined in claim 23, wherein said optical emitter generates pulsed light.  
     
     
       30. A scannerless optical rangefinder as defined in claim 29, wherein said pulsed light has pulses of a duration that is less than 50 ns.  
     
     
       31. A scannerless optical rangefinder as defined in claim 23, wherein said MCOR has a detection bandwidth higher than 10 MHz.  
     
     
       32. A scannerless optical rangefinder as defined in claim 23, wherein said optical emitter emits light in a near-infrared region of the electromagnetic spectrum.  
     
     
       33. A scannerless optical rangefinder as defined in claim 23, further comprising a device to condition light output by said optical emitter.  
     
     
       34. A scannerless optical rangefinder as defined in claim 33, wherein said device to condition light output by said optical emitter includes at least one of a collimating lens, a lenticular lens sheet, a light emitting diode (LED) reflector and optical diffuser.  
     
     
       35. A scannerless optical rangefinder as defined in claim 23, comprising a device for focusing the optical return on photosensitive surfaces of respective photoresponsive elements.  
     
     
       36. A scannerless optical rangefinder as defined in claim 23, wherein said array includes a linear arrangement of N photoresponsive elements.  
     
     
       37. A scannerless optical rangefinder as defined in claim 23, wherein said array includes a two dimensional arrangement of N X M photoresponsive elements.  
     
     
       38. A scannerless optical rangefinder as defined in claim 23, including a filter to block parasitic background light outside of a wavelength band of the optical emitter.  
     
     
       39. A scannerless optical rangefinder as defined in claim 23, including a calculator to compute a distance between the rangefinder and an object by using as an input the optical return signal or a signal derived therefrom.  
     
     
       40. A scannerless optical rangefinder as defined in claim 23, wherein the CPU is configured to enhance the SNR of the digital waveform.  
     
     
       41. A scannerless optical rangefinder as defined in claim 23, the MCOR further including an analog front end configured to operate in AC coupling mode.  
     
     
       42. A scannerless optical rangefinder as defined in claim 41, wherein to detect the object, the CPU is configured to average the digital waveform over time.  
     
     
       43. A scannerless optical rangefinder as defined in claim 23, wherein to detect the object, the CPU is configured to average the digital waveform over time.