Soft clock delay for OCT system and method therefor
View Patent ↗An optical coherence analysis system comprises a swept source laser for generating optical signals that are tuned over a scan band; an interferometer for transmitting the optical signals over a sample arm and reference arm and combining the optical signals; a k-clock for generating a sampling clock indicating non-linearities in the frequency tuning of the optical signals over the scan band, the k-clock being not delay matched to propagation delays for the optical signals in the interferometer; a sampling system for sampling the optical signals from the interferometer in response to the k-clock to generate interference signals; and a processing system for determining non-linearities in the sampling clock and for transforming the interference signals into an image of a sample in response to the non-linearities. The system compensates for the lack of an electronic delay of k-clock using a nonuniform discrete Fourier transform.
1. An optical coherence analysis system, comprising:
a swept source laser for generating optical signals that are tuned over a scan band;
an interferometer for transmitting the optical signals over a sample arm and reference arm and combining the optical signals to generate interference signals;
a k-clock for generating a sampling clock indicating non-linearities in the frequency tuning of the optical signals over the scan band, the k-clock being not delay matched to propagation delays for the optical signals in the interferometer;
a sampling system for sampling the interference signals from the interferometer in response to the k-clock; and
a processing system for determining non-linearities in the frequency tuning of the optical signals using the k-clock during a calibration and for transforming the interference signals into an image of a sample in response to the non-linearities.
2. A system as claimed in claim 1 , wherein a frequency of the k-clock varies as the swept source laser is tuned over the scan band.
3. A system as claimed in claim 1 , wherein the processing system performs a nonuniform discrete Fourier transform on the interference signals using non-integer k-values determined in response to the non-linearities.
4. A system as claimed in claim 1 , wherein the k-clock is integrated with the swept source laser in a clock laser module.
5. A system as claimed in claim 4 , wherein the k-clock signal from the k-clock is conditioned and then directly triggers the sampling system.
6. A system as claimed in claim 1 , wherein in the processing system determines the non-linearities by calculating non-integer k-values from a calibration scan in which the sampling system samples the optical signals in response to the k-clock.
7. A system as claimed in claim 6 , wherein the sampling system samples the interference signals from the sample in response to the k-clock.
8. An optical coherence analysis method, comprising:
generating optical signals that are tuned over a scan band;
transmitting the optical signals over a sample arm and reference arm of an interferometer and combining the optical signals to generate interference signals;
generating a k-clock indicating non-linearities in the frequency tuning of the optical signals over the scan band that is not delay matched to propagation delays for the optical signals in the interferometer;
sampling the interference signals from the interferometer in response to the k-clock; and
determining non-linearities in the frequency tuning of the optical signals using the k-clock and transforming the interference signals into an image of a sample in response to the non-linearities.
9. A method as claimed in claim 8 , wherein a frequency of the k-clock varies as the optical signals are tuned over the scan band.
10. A method as claimed in claim 8 , wherein the step of transforming the interference signals comprises performing a nonuniform discrete Fourier transform on the interference signals using non-integer k-values determined in response to the non-linearities.
11. A method as claimed in claim 8 , wherein determining the non-linearities comprises calculating non-integer k-values from a calibration scan in which the optical signals are sampled in response to the k-clock.
12. A method as claimed in claim 11 , further comprising sampling the interference signals from the sample in response to the k-clock.
13. An optical coherence analysis calibration method, comprising:
generating optical signals that are tuned over a scan band;
transmitting the optical signals over a sample arm and reference arm of an interferometer and combining the optical signals to generate interference signals;
generating a k-clock indicating non-linearities in the frequency tuning of the optical signals over the scan band that is not delay matched to propagation delays for the optical signals in the interferometer;
sampling the interference signals from the interferometer in response to the k-clock;
removing negative frequencies from the interference signals; and
determining non-integer k values that are used in a subsequent nonuniform discrete Fourier transform of the interference signals from a sample.
14. A method as claimed in claim 13 , wherein the non-integer k-values are determined from a calibration scan in which the optical signals are sampled in response to the k-clock.
15. A method as claimed in claim 14 , further comprising sampling the interference signals from the sample in response to the k-clock.
16. An optical coherence analysis system, comprising:
a swept source for generating optical signals that are tuned over a scan band;
an interferometer for transmitting the optical signals over a sample arm and reference arm and combining the optical signals to generate interference signals;
a k-clock for generating a sampling clock indicating non-linearities in the frequency tuning of the optical signals over the scan band, the k-clock being not delay matched to propagation delays for the optical signals in the interferometer;
a sampling system for sampling the interference signals from the interferometer in response to the k-clock; and
a processing system for determining non-linearities in the frequency tuning of the optical signals using the k-clock during a calibration and for transforming the interference signals into an image of a sample in response to the non-linearities.
17. A system as claimed in claim 16 , wherein a frequency of the k-clock varies as the swept source is tuned over the scan band.
18. A system as claimed in claim 16 , wherein the processing system performs a nonuniform discrete Fourier transform on the interference signals using non-integer k-values determined in response to the non-linearities.
19. A system as claimed in claim 16 , wherein the k-clock is integrated with the swept source in a clock module.
20. A system as claimed in claim 19 , wherein the k-clock signal from the k-clock is conditioned and then directly triggers the sampling system.
21. A system as claimed in claim 16 , wherein in the processing system determines the non-linearities by calculating non-integer k-values from a calibration scan in which the sampling system samples the interference signals in response to the k-clock.
22. A system as claimed in claim 21 , wherein the sampling system samples the interference signals from the sample in response to the k-clock.