| CPC G01B 9/02091 (2013.01) [A61B 3/102 (2013.01); G01B 9/02004 (2013.01); G01B 9/02043 (2013.01); G01B 9/02069 (2013.01); G01B 9/02084 (2013.01); G01N 21/4795 (2013.01)] | 20 Claims |
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1. A swept-source optical coherence tomography (OCT) imaging system for imaging a region of an object, comprising:
a swept light source arranged to generate a beam of light of a wavelength which varies over time;
a scanning element arranged to scan the beam of light across the object;
an interferometer having a sample arm and a reference arm, and arranged to generate an interference light signal during use of the swept-source OCT imaging system by combining light scattered by the region of the object and propagating along the sample arm, as a result of the beam being scanned across the object, with light from the beam propagating along the reference arm, wherein the reference arm comprises a plurality of optical delay lines, each optical delay line having a different optical path length;
an optical switch arranged to switchably allow light to propagate using one of the plurality of optical delay lines;
a photodetector arranged to receive the interference light signal and generate an electrical signal (S) that is indicative of the interference light signal, the electrical signal (S) comprising frequency components spanning a frequency band, the frequency components being caused by interference of the light scattered by the region of the object and propagating along the sample arm, with the light from the beam propagating along the reference arm;
a band-pass filter module arranged to generate a filtered electrical signal (SF) by band-pass filtering the electrical signal (S), wherein the band-pass filter module comprises at least one of (a) a tunable band-pass filter or (b) a plurality of non-tunable bandpass filters;
a sample acquisition module arranged to acquire a first set of samples of the filtered electrical signal (SF);
a filter module arranged to generate a second filtered electrical signal (SF2) by filtering the electrical signal (S);
a second sample acquisition module arranged to acquire a second set of samples of the second filtered electrical signal (SF2); and
at least one processor and a memory storing computer-readable instructions that, when executed by the at least one processor, cause the at least one processor to perform a set of operations, the set of operations comprising:
providing a first signal to the band-pass filter module to set a pass band of the band-pass filter module such that the band-pass filter module extracts at least some of the frequency components of the electrical signal (S) in a first sub-band of the frequency band and substantially attenuates frequency components of the electrical signal (S) outside the first sub-band;
providing a second signal to the sample acquisition module to set a sampling rate of the sample acquisition module such that the sample acquisition module band-pass samples the filtered electrical signal (SF) to acquire the first set of samples of the filtered electrical signal (SF) in the first sub-band of the frequency band, the first sub-band corresponding to a first sub-region of the region of the object, for generating OCT image data representing an image of the region of the object, such that (a) the first set of samples is acquired by the sample acquisition module in accordance with a bandpass sampling theorem, and (b) the filtered electrical signal (SF) is frequency-translated into a first Nyquist zone without overlapping with spectral images of the filtered electrical signal (SF) that are caused by sampling, thereby enabling aliasing to be substantially avoided and further enabling a depth of the region corresponding to the acquired set of samples to be deeper than would otherwise be attainable by the swept-source OCT imaging system owing to a limited maximum sampling rate of the sample acquisition module;
providing a third signal to the filter model to set a pass band of the filter module to extract frequency components of the electrical signal in a second sub-band of the frequency band that partially overlaps the first sub-band, wherein the second sub-band corresponds to a second sub-region of the region, and wherein partial overlap between the first sub-band and the second sub-band corresponds to an overlapping region between the first sub-region and the second sub-region;
providing a fourth signal to the second sample acquisition module to set a second sampling rate to acquire the second set of samples in the second sub-band using the second sampling rate, the second sampling rate being different from the first sampling rate;
generating a reference arm adjustment signal based on a location indicator indicative of a location of the region along a propagation direction of the beam of light incident on the object during use of the swept-source OCT imaging system to acquire the first set of samples and the second set of samples for generating the OCT image data representing the image of the region of the object; and
controlling the optical switch, based on the reference arm adjustment signal, to select an optical delay line of the plurality of optical delay lines to allow light to propagate in the reference arm using the selected optical delay line, such that a frequency of the interference light signal is below a cut-off frequency of the photodetector, thereby setting an optical delay between the light propagating along the reference arm and the light propagating along the sample arm.
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