Laser-Based Devices Utilizing Multiple Laser Beams

Abstract

A laser-based device or sensor includes: a first laser transmitter having a first self-mix carrier frequency; a second laser transmitter having a second, different, self-mix carrier frequency; a first monitor photodiode to receive a first optical signal from the first laser transmitter, and to output a first electric signal; a second monitor photodiode to receive a first optical signal from the second laser transmitter, and to output a second electric signal; an electric connection to connect together the first electric signal and the second electric signal, forming a combined electric signal; a single laser receiver to receive the combined electric signal and to generate from it a spectrum that corresponds to both (i) self-mix signal of the first laser transmitter, and (ii) self-mix signal of the second laser transmitter. Alternatively, a single monitor photodiode is used, receiving self-mix signals from multiple laser transmitters, and outputting a single electric signal to a single laser receiver.

What is claimed is: 
     
         1 . A device comprising:
 a first laser transmitter having a first self-mix carrier frequency;   a second laser transmitter having a second, different, self-mix carrier frequency;   a single monitor photodiode (A) to receive a first optical signal from the first laser transmitter, (B) to receive a second optical signal from the second laser transmitter, (C) to output a single electric signal that corresponds to both the first optical signal and the second optical signal;   a single laser receiver to receive the single electric signal and to generate from it a spectrum that corresponds to both (i) self-mix signal of the first laser transmitter, and (ii) self-mix signal of the second laser transmitter.   
     
     
         2 . The device of  claim 1 , comprising a plurality of laser transmitters that are co-located and co-packaged, wherein all of said laser transmitters are associated with said single monitor photodiode that is external to and separate from all said laser transmitters and is internal to said device. 
     
     
         3 . The device of  claim 1 , further comprising:
 a first laser modulator to modulate the first laser transmitter at a first waveform, and to cause the first laser transmitter to transmit a first laser beam having the first self-mix carrier;   a second laser modulator that is separate from the first laser modulator, wherein the second laser modulator is to modulate the second laser transmitter at a second waveform, and to cause the second laser transmitter to transmit a second laser beam having the second self-mix carrier.   
     
     
         4 . The device of  claim 1 ,
 wherein the first laser transmitter has a first delta-wavelength to delta-current value, which indicates a change in wavelength of a laser beam that is transmitted by the first laser transmitter as a function of a change in current supplied to said first laser transmitter;   wherein the second laser transmitter has a second delta-wavelength to delta-current value, which indicates a change in wavelength of a laser beam that is transmitted by the second laser transmitter as a function of a change in current supplied to said second laser transmitter;   wherein the first delta-wavelength to delta-current value of the first laser transmitter is identical to the second delta-wavelength to delta-current value of the second laser transmitter.   
     
     
         5 . The device of  claim 1 ,
 wherein the first laser transmitter has a first delta-wavelength to delta-current value, which indicates a change in wavelength of a laser beam that is transmitted by the first laser transmitter as a function of a change in current supplied to said first laser transmitter;   wherein the second laser transmitter has a second delta-wavelength to delta-current value, which indicates a change in wavelength of a laser beam that is transmitted by the second laser transmitter as a function of a change in current supplied to said second laser transmitter;   wherein the first delta-wavelength to delta-current value of the first laser transmitter is non-identical to the second delta-wavelength to delta-current value of the second laser transmitter.   
     
     
         6 . The device of  claim 1 ,
 wherein the first laser transmitter has a first delta-wavelength to delta-current value, which indicates a change in wavelength of a laser beam that is transmitted by the first laser transmitter as a function of a change in current supplied to said first laser transmitter;   wherein the second laser transmitter has a second delta-wavelength to delta-current value, which indicates a change in wavelength of a laser beam that is transmitted by the second laser transmitter as a function of a change in current supplied to said second laser transmitter;   wherein the first delta-wavelength to delta-current value of the first laser transmitter is non-identical to the second delta-wavelength to delta-current value of the second laser transmitter;   wherein the ratio between (I) the first delta-wavelength to delta-current value of the first laser transmitter and (II) the second delta-wavelength to delta-current value of the second laser transmitter, is not greater than 1.05 and is not smaller than 0.95.   
     
     
         7 . The device of  claim 1 ,
 wherein the first laser transmitter has a first delta-wavelength to delta-current value, which indicates a change in wavelength of a laser beam that is transmitted by the first laser transmitter as a function of a change in current supplied to said first laser transmitter;   wherein the second laser transmitter has a second delta-wavelength to delta-current value, which indicates a change in wavelength of a laser beam that is transmitted by the second laser transmitter as a function of a change in current supplied to said second laser transmitter;   wherein the first delta-wavelength to delta-current value of the first laser transmitter is non-identical to the second delta-wavelength to delta-current value of the second laser transmitter;   wherein the ratio between (I) the first delta-wavelength to delta-current value of the first laser transmitter and (II) the second delta-wavelength to delta-current value of the second laser transmitter, is not greater than 1.10 and is not smaller than 0.90.   
     
     
         8 . The device of  claim 1 ,
 wherein the first laser transmitter has a first delta-wavelength to delta-current value, which indicates a change in wavelength of a laser beam that is transmitted by the first laser transmitter as a function of a change in current supplied to said first laser transmitter;   wherein the second laser transmitter has a second delta-wavelength to delta-current value, which indicates a change in wavelength of a laser beam that is transmitted by the second laser transmitter as a function of a change in current supplied to said second laser transmitter;   wherein the first delta-wavelength to delta-current value of the first laser transmitter is non-identical to the second delta-wavelength to delta-current value of the second laser transmitter;   wherein the ratio between (I) the first delta-wavelength to delta-current value of the first laser transmitter and (II) the second delta-wavelength to delta-current value of the second laser transmitter, is not greater than 1.20 and is not smaller than 0.80.   
     
     
         9 . The device of  claim 1 , further comprising:
 a spectral analysis module configured (A) to analyze a spectrum of signals received by said single laser receiver, and (B) to identify in said spectrum a first peak and a second peak that correspond, respectively, to the first laser transmitter and the second laser transmitter, and (C) to monitor a frequency shift of at least one of said first peak and said second peak in response to movement of a remote target that is hit by at least one of: a laser beam transmitted by the first laser transmitter, and a laser beam transmitted by the second laser transmitter, and (D) to determine one or more characteristics of said remote target, based on said drift monitored in said spectrum.   
     
     
         10 . The device of  claim 1 , wherein the single monitor photodiode is separate from both the first laser transmitter and the second laser transmitter. 
     
     
         11 . The device of  claim 1 , wherein the first and second laser transmitters are co-packaged; and
 wherein the single monitor photodiode is integrated within the co-packaged first and second laser transmitters.   
     
     
         12 . The device of  claim 1 , wherein the first and second laser transmitters are monolithically integrated with each other; and wherein the single monitor photodiode is also monolithically integrated within the first and second laser transmitters. 
     
     
         13 . The device of  claim 1 , wherein the first and second laser transmitters are monolithically integrated with each other; and wherein the single monitor photodiode is not monolithically integrated within the first and second laser transmitters. 
     
     
         14 . The device of  claim 1 , further comprising:
 a single laser modulator connected to both the first laser transmitter and the second laser transmitter;   wherein said single laser modulator utilizes a first electric circuitry to modulate the first laser transmitter at a first waveform, and to cause the first laser transmitter to transmit a first laser beam having the first self-mix carrier;   wherein said single laser modulator utilizes a second electric circuitry to modulate the second laser transmitter at a second waveform, and to cause the second laser transmitter to transmit a second laser beam having the second self-mix carrier.   
     
     
         15 . The device of  claim 1 , further comprising:
 a single laser modulator connected to both the first laser transmitter and the second laser transmitter;   wherein said single laser modulator provides a same modulation to both the first laser transmitter and the second laser transmitter;   wherein, by utilizing a Distributed Bragg Reflector (DBR) doping technique, said first and second laser transmitters transmit respectively a first laser beam and a second laser beam having two different self-mix carrier frequencies.   
     
     
         16 . The device of  claim 1 , further comprising:
 a laser usefulness estimator, to estimate self-mix signal usefulness of the first laser transmitter, by comparing a quality indicator of the self-mix signal usefulness of the first laser transmitter to one or more pre-defined threshold values;   a selective activation module (a) to selectively de-activate the first laser transmitter and (b) to maintain the second laser transmitter activated, if an estimated self-mix usefulness value of the first laser transmitter is below a particular pre-defined threshold value.   
     
     
         17 . The device of  claim 1 , further comprising:
 a laser usefulness estimator, to estimate self-mix signal usefulness of the first laser transmitter, by comparing a Root Mean Square (RMS) amplitude of the self-mix signal of the first laser transmitter to one or more pre-defined threshold values;   a selective activation module (a) to selectively de-activate the first laser transmitter and (b) to maintain the second laser transmitter activated, if an estimated self-mix usefulness value of the first laser transmitter is below a particular pre-defined threshold value.   
     
     
         18 . The device of  claim 1 , further comprising:
 a single lens assembly that is common to both the first laser transmitter and the second laser transmitter;   wherein the first laser transmitter and the second laser transmitter are located at a same distance from said single lens assembly.