Active remote sensing of atmospheric gases or smoke using a time-of-flight sensor

An active remote sensing system comprising:

• a plurality of laser diodes configured to generate light having an initial light intensity and an initial optical power density and one or more optical wavelengths, wherein at least a portion of the one or more optical wavelengths is a near-infrared wavelength between 700 nanometers and 2500 nanometers, wherein the plurality of laser diodes comprises one or more Bragg reflectors, wherein the plurality of laser diodes is further configured to be modulated with a pulsed output having a pulse duration of approximately 0.5 to 2 nanoseconds, and wherein the plurality of laser diodes is further coupled to driver electronics and one or more safety shut-offs;
• a first lens configured to receive a portion of the light from the plurality of laser diodes and to direct at least some of the portion of the light from the plurality of laser diodes to an object or an atmosphere;
• and
• a photodiode array comprising at least one second lens and one or more spectral filters in front of at least a part of the photodiode array, wherein the photodiode array comprises a plurality of pixels configured to be coupled to CMOS transistors, and wherein the photodiode array is further configured to be coupled to a processor, wherein the processor is coupled to a non-transitory computer readable medium;
• wherein the photodiode array is configured to receive at least a portion of light reflected from the object or the atmosphere, and wherein the photodiode array is further configured to be synchronized to the plurality of laser diodes comprising Bragg reflectors;
• wherein the processor is configured to perform a time-of-flight measurement based on a time difference between a first time in which the plurality of laser diodes generates light and a second time in which the photodiode array receives the at least a portion of light reflected from the object or the atmosphere;
• wherein the processor is further configured to perform the time-of-flight measurement at least in part by measuring a temporal distribution of photons in the light reflected from the object or the atmosphere and received by the photodiode array;
• wherein the processor is further configured to improve a signal-to-noise ratio of at least a portion of the time-of-flight measurement by increasing light intensity of the plurality of laser diodes relative to the initial light intensity or increasing optical power density of the plurality of laser diodes relative to the initial optical power density;
• and
• wherein the photodiode array is further configured to
• generate a first signal when substantially no light is received from the plurality of laser diodes, and configured to
• generate a second signal when light is received from at least a part of the plurality of laser diodes;
• and
• wherein the processor is configured to compare the first signal and the second signal to further improve the signal-to-noise ratio of at least a portion of the time-of-flight measurement.

An optical system, the system comprising:

• a light source comprising a plurality of laser diodes configured to generate light having an initial light intensity and an initial optical power density and a plurality of optical wavelengths, wherein at least a portion of the plurality of optical wavelengths is a near-infrared wavelength between 700 nanometers and 2500 nanometers, wherein the plurality of laser diodes comprises one or more Bragg reflectors, and wherein the plurality of laser diodes is further coupled to driver electronics;
• at least a first laser diode of the plurality of laser diodes configured to operate at a first wavelength corresponding to lower water absorption, and at least a second laser diode of the plurality of laser diodes configured to operate at a second wavelength corresponding to higher water absorption;
• a housing configured to receive at least a portion of the light from the first laser diode and second laser diode and configured to deliver an output to an object, the housing further configured to be coupled to an electrical circuit and a processor, wherein the electrical circuit comprises a trans-impedance amplifier and an analog-to-digital converter;
• a first photo-detector configured to be positioned behind a first wavelength selective optical filter;
• and
• a second photo-detector configured to be positioned behind a second wavelength selective optical filter, wherein the first wavelength selective optical filter is configured to pass at least some of the first wavelength and the second wavelength selective optical filter is configured to pass at least some of the second wavelength;
• the first photo-detector configured to receive at least some of the light output to the object at the first wavelength that is reflected by the object and configured to generate a first output signal, and the second photo-detector configured to receive at least some of the light output to the object at the second wavelength that is reflected by the object and configured to generate a second output signal;
• wherein the optical system including the processor is at least in part configured to identify the object based on water absorption within the object by comparing at least some of the first output signal and at least some of the second output signal to generate an output value comprising a signal-to-noise ratio;
• wherein the optical system including the processor is configured to compare the output value to a threshold;
• and
• wherein either the first photo-detector or the second photo-detector is further configured to
• generate a first signal when substantially no light is received from the plurality of laser diodes, and
• generate a second signal when light is received from at least a part of the plurality of laser diodes;
• and
• wherein the processor is configured to compare the first signal and the second signal to further improve the signal-to-noise ratio of the output value.