Non-invasive measurement systems with single-photon counting camera
An exemplary non-invasive measurement system includes a single-photon counting camera and a processor. The single-photon counting camera includes an array of SPAD detectors configured to detect, during a sequence of gated time intervals, coherent continuous light that exits a body after the light enters and scatters within the body, and output a plurality of electronic signals representative of the detected light. The processor is configured to generate, based on the electronic signals, a sequence of speckle pattern image frames corresponding to the gated time intervals. Other exemplary non-invasive measurement systems are also described.
1. A non-invasive measurement system comprising:
a single-photon counting camera including an array of single-photon avalanche diode (SPAD) detectors configured to
detect, during a sequence of gated time intervals, coherent continuous light that exits a body after the light enters and scatters within the body, and
output a plurality of electronic signals representative of the detected light; and
a processor coupled to an output of the single-photon counting camera and configured to generate, based on the electronic signals, a sequence of speckle pattern image frames corresponding to the gated time intervals.
2. The non-invasive measurement system of claim 1 , wherein the processor is further configured to generate, based on the sequence of speckle pattern image frames, a correlation map representative of speckle decorrelation associated with the light.
3. The non-invasive measurement system of claim 2 , wherein:
each of the speckle pattern image frames includes K times L digital sample values at K by L pixel locations that correspond to locations of the SPAD detectors; and
the processor is configured to generate the correlation map by
applying a plurality of correlation measurement operations to the sample values in each of the speckle pattern image frames,
generating, based on the application of the measurement operations to the sample values in each of the speckle pattern image frames, a plurality of measurement values for the light detected by the SPAD detectors, and
including the plurality of measurement values in the correlation map.
4. The non-invasive measurement system of claim 1 , further comprising a light source configured to generate the light.
5. The non-invasive measurement system of claim 4 , further comprising an optical fiber coupled to an output of the light source and configured to convey the light to the body.
6. The non-invasive measurement system of claim 1 , wherein the light is a laser signal.
7. The non-invasive measurement system of claim 1 , further comprising an optical fiber coupled to the body and to the single-photon counting camera and configured to convey the light from the body to the SPAD detectors.
8. The non-invasive measurement system of claim 1 , wherein the processor is configured to generate the sequence of gated time intervals by modulating a trigger signal that controls the single-photon counting camera.
9. The non-invasive measurement system of claim 1 , further comprising a non-invasive wearable device for use by a user, wherein the single-photon counting camera and the processor are housed within the wearable device.
10. A non-invasive measurement system comprising:
a single-photon counting camera including an array of single-photon avalanche diode (SPAD) detectors that, when presented with a sequence of pulses of coherent light that exit a body after the light enters and scatters within the body, are gated to
detect the light during a first capture period starting at a first time delay within each of the pulses, the first capture period shorter in duration than each pulse included in the sequence of pulses, and
generate a first set of electronic signals representative of the light detected during the first capture period starting at the first time delay within each of the pulses; and
a processor coupled to an output of the single-photon counting camera and configured to generate, based on the first set of electronic signals, a first sequence of speckle pattern image frames corresponding to the first time delay.
11. The non-invasive measurement system of claim 10 , wherein the processor is further configured to generate, based on the first sequence of speckle pattern image frames, a correlation map representative of speckle decorrelation associated with the light detected during the first capture period.
12. The non-invasive measurement system of claim 11 , wherein:
each of the speckle pattern image frames includes K times L digital sample values at K by L pixel locations that correspond to locations of the SPAD detectors; and
the processor is configured to generate the correlation map by
applying a plurality of correlation measurement operations to the sample values in each of the speckle pattern image frames,
generating, based on the application of the measurement operations to the sample values in each of the speckle pattern image frames, a plurality of measurement values for the light detected by the SPAD detectors, and
including the plurality of measurement values in the correlation map.
13. The non-invasive measurement system of claim 10 , further comprising a light source configured to generate the light.
14. The non-invasive measurement system of claim 13 , further comprising an optical fiber coupled to an output of the light source and configured to convey the light to the body.
15. The non-invasive measurement system of claim 10 , wherein the light is a laser signal.
16. The non-invasive measurement system of claim 10 , further comprising an optical fiber coupled to the body and to the single-photon counting camera and configured to convey the light from the body to the SPAD detectors.
17. The non-invasive measurement system of claim 10 , wherein the processor is configured to generate the sequence of gated time intervals by modulating a gating signal that controls the single-photon counting camera.
18. The non-invasive measurement system of claim 10 , further comprising a non-invasive wearable device for use by a user, wherein the single-photon counting camera and the processor are housed within the wearable device.
19. The non-invasive measurement system of claim 10 , wherein:
the array of SPAD detectors are further gated to:
detect the light during a second capture period starting at a second time delay within each of the pulses, the second capture period temporally separated from the first capture period and shorter in duration than each pulse included in the sequence of pulses, and
generate a second set of electronic signals representative of the light detected during the second capture period starting at the second time delay within each of the pulses; and
the processor is further configured to generate, based on the second set of electronic signals, a second sequence of speckle pattern image frames corresponding to the second time delay.
20. The non-invasive measurement system of claim 10 , further comprising a light source configured to generate the sequence of pulses of coherent light.