Geiger-mode laser vibrometry methods and systems

1. A method for laser vibrometry, comprising:

receiving, using a photodiode configured to operate in a Geiger mode, a first time-series of single photon arrivals corresponding to a laser beam reflected from or transmitted through a target, the single photon arrivals including information corresponding to vibrations of the target, each single photon arrival separated in time from another single photon arrival;

determining, based on two or more of the single photon arrivals, a discrete time sequence having a binary value, wherein a first binary value is indicative of an arrival and a second binary value is indicative of a lack of an arrival of a photon at a corresponding discrete time point; and

generating a second time-series by assigning a non-binary value to each of the discrete time points, wherein each of the assigned non-binary values corresponding to the second binary values represents a separation between two of the two or more of the single photon arrivals that is determined based on a number of discrete time points lacking a photon arrival prior to receiving a photon,

wherein processing the second time-series enables extraction of the information corresponding to vibrations of the target.

2. The method of claim 1 , wherein each of the assigned non-binary values is determined based at least in-part on an average value of the number of discrete time points between consecutive photon arrivals.

3. The method of claim 1 , wherein each of the assigned non-binary values is determined based at least in-part on subtracting the number of discrete time points lacking the photon arrival prior to receiving the photon from a predetermined duration of the discrete time sequence.

4. The method of claim 1 , wherein the assigned non-binary values are determined based on a linear interpolation over the number of discrete time points between consecutive photon arrivals.

5. The method of claim 1 , further comprising:

generating the first time-series of single photon arrivals by combining a reference laser beam with the laser beam reflected from the target, wherein the reference laser beam is weaker than the laser beam that illuminates the target.

6. The method of claim 5 , wherein the combining is performed using a beam combiner.

7. The method of claim 1 , wherein the second time-series forms a step-wise signal approximating a sinusoidal signal.

8. The method of claim 1 , comprising determining a value associated with the vibrations of the target.

9. A device for laser vibrometry, comprising:

a splitter to split an input laser beam into a first laser beam and a second laser beam;

a first optical component positioned to direct the first laser beam toward a target;

a second optical element positioned to receive a laser beam that is either reflected from, or transmitted through, the target, the reflected or the transmitted laser beam comprising single photon arrivals that include information corresponding to vibrations of the target, each single photon arrival separated in time from another single photon arrival;

an avalanche photodiode (APD) array configured to operate in a Geiger mode and positioned to receive and to detect the single photon arrivals; and

a processor, coupled to the APD array, that is configured to:

receive detection information as part of a first time-series corresponding to the single photon arrivals;

determine, based on two or more of the single photon arrivals, a discrete time sequence having a binary value, wherein a first binary value is indicative of an arrival and a second binary value is indicative of a lack of an arrival of a photon at a corresponding discrete time point; and

generate a second time-series by assigning a nonbinary value to each of the discrete time points, wherein each of the assigned non-binary values corresponding to the second binary values represents a separation between two of the two or more of the single photon arrivals that is determined based on a number of discrete time points lacking a photon arrival prior to receiving a photon, and wherein processing the second time-series enables extraction of the information corresponding to vibrations of the target.

10. The device of claim 9 , further comprising:

a laser source, coupled to the splitter, to emit the input laser beam.

11. The device of claim 9 , further comprising:

a beam combiner to combine the second laser beam with the reflected or the transmitted laser beam, wherein the second laser beam is a reference beam that is weaker than the first laser beam.

12. The device of claim 9 , wherein the APD array comprises an indium gallium arsenide (InGaAs) array ora plurality of Geiger-mode APD detectors.

13. The device of claim 9 , wherein each of the assigned non-binary values is determined based at least in-part on an average value of the number of discrete time points between consecutive photon arrivals.

14. The device of claim 9 , wherein each of the assigned non-binary values is determined based on a spline function over the number of discrete time points between consecutive photon arrivals.

15. A non-transitory computer-readable storage medium having instructions stored thereupon for laser vibrometry, comprising:

instructions for receiving, using a photodiode configured to operate in a Geiger mode, a first time-series of single photon arrivals corresponding to a laser beam reflected from or transmitted through a target, the single photon arrivals including information corresponding to vibrations of the target, each single photon arrival separated in time from another single photon arrival;

instructions for determining, based on two or more of the single photon arrivals, a discrete time sequence having a binary value, wherein a first binary value is indicative of an arrival and a second binary value is indicative of a lack of an arrival of a photon at a corresponding discrete time point; and

instructions for generating a second time-series by assigning a non-binary value to each of the discrete time points, wherein each of the assigned non-binary values corresponding to the second binary values represents a separation between two of the two or more of the single photon arrivals that is determined based on a number of discrete time points lacking a photon arrival prior to receiving a photon,

wherein processing the second time-series enables extraction of the information corresponding to vibrations of the target.

16. The non-transitory computer-readable storage medium of claim 15 , wherein each of the assigned non-binary values is determined further based at least in-part on an average value of the number of discrete time points between consecutive photon arrivals.

17. The non-transitory computer-readable storage medium of claim 15 , wherein each of the assigned non-binary values is determined based at least in-part on subtracting the number of discrete time points lacking the photon arrival prior to receiving the photon from a predetermined duration of the discrete time sequence.

18. The non-transitory computer-readable storage medium of claim 15 , further comprising:

instructions for generating the first time-series of single photon arrivals by combining a reference laser beam with the laser beam reflected from the target, wherein the reference laser beam is weaker than the laser beam that illuminates the target.

19. The non-transitory computer-readable storage medium of claim 18 , wherein the combining is performed using a beam combiner.

20. The non-transitory computer-readable storage medium of claim 15 , comprising:

instructions for determining a value associated with the vibrations of the target.