Optical coherence tomography system with an extended depth range
In certain embodiments, an OCT system sends a sample beam to a sample (e.g., an eye) along a sample path divided into multiple sample path ranges. The system sends a reference beam to a reference arm system with multiple reference arms, where each reference arm corresponds to a sample path range. Each arm has a specific dispersion level with a corresponding dispersion compensation parameter set designed to address the specific level. A detector detects reflected sample and reference beams. A computer performs the following for each sample path range: select the dispersion compensation parameter set corresponding to the reference arm of the sample path range; apply the dispersion compensation parameter set to the detector signal to yield image information; and process the image information. The computer generates an image of the sample from the image information for the sample path ranges.
1 . An optical coherence tomography (OCT) system, comprising:
a light source configured to provide a light beam;
a beamsplitter configured to split the light beam into a sample beam and a reference beam;
one or more optical elements configured to direct the sample beam along a sample path towards a sample, the sample path comprising a plurality of sample path ranges, the sample reflecting the sample beam to yield a reflected sample beam;
a reference arm system configured to direct the reference beam through each reference arm of a plurality of reference arms to yield a reflected reference beam, each reference arm corresponding to a sample path range of the plurality of sample path ranges, each reference arm associated with a specific dispersion level with a corresponding dispersion compensation parameter set, the dispersion compensation parameter set designed to address the specific dispersion level;
a detector configured to:
detect the reflected sample beam and the reflected reference beam; and
generate a detector signal in response to detecting the reflected sample beam and the reflected reference beam; and
a computer configured to:
perform the following for each sample path range of the plurality of sample path ranges to yield image information for the sample path ranges:
select the dispersion compensation parameter set corresponding to the reference arm of the sample path range;
apply the dispersion compensation parameter set to the detector signal to yield image information; and
process the image information to yield image information for the sample path range; and
generate an image of the sample from the image information for the plurality of sample path ranges, the image being generated based on image information that is processed with a plurality of dispersion compensation parameter sets that correspond to the plurality of sample path ranges.
2 . The OCT system of claim 1 , the computer configured to process the image information to yield image information for the sample path range by performing the following until an image quality satisfies an image quality criterion:
perform image processing on the image information;
generate a candidate image from the image information; and
evaluate the image quality of the candidate image.
3 . The OCT system of claim 1 , the detector signal comprising a plurality of interference signals, each interference signal corresponding to a reference arm of the plurality of reference arms.
4 . The OCT system of claim 1 , the sample comprising a sample within an eye.
5 . The OCT system of claim 1 , the plurality of reference arms having a plurality of reference planes comprising a first reference plane and a second reference plane.
6 . The OCT system of claim 5 , wherein:
an axial separation between the first reference plane and the second reference plane is substantially twice an OCT imaging depth minus any overlap between the planes; and
the first reference plane covers a positive OCT image space and the second reference plane covers a negative OCT image space to yield an image that is substantially twice the OCT imaging depth minus any overlap between the planes.
7 . The OCT system of claim 5 , wherein:
an axial separation between the first reference plane and the second reference plane is substantially an OCT imaging depth minus any overlap between the planes; and
the first reference plane and the second reference plane each cover a positive OCT image space to yield an image that is substantially twice the OCT imaging depth minus any overlap between the planes.
8 . The OCT system of claim 1 , wherein:
a first reference arm has dispersion material.
9 . The OCT system of claim 1 , wherein:
a first reference arm has dispersion material that creates a first dispersion mismatch; and
a second reference arm has dispersion material that creates a second dispersion mismatch different from the first dispersion mismatch.
10 . A method for generating an image with an optical coherence tomography (OCT) system, comprising:
providing a light beam;
splitting the light beam into a sample beam and a reference beam;
directing the sample beam along a sample path towards a sample, the sample path comprising a plurality of sample path ranges, the sample reflecting the sample beam to yield a reflected sample beam;
directing, by a reference arm system, the reference beam through each reference arm of a plurality of reference arms to yield a reflected reference beam, each reference arm corresponding to a sample path range of the plurality of sample path ranges, each reference arm associated with a specific dispersion level with a corresponding dispersion compensation parameter set, the dispersion compensation parameter set designed to address the specific dispersion level;
detecting, by a detector, the reflected sample beam and the reflected reference beam;
generating a detector signal in response to detecting the reflected sample beam and the reflected reference beam;
performing, by a computer, the following for each sample path range of the plurality of sample path ranges to yield image information for the sample path ranges:
selecting the dispersion compensation parameter set corresponding to the reference arm of the sample path range;
applying the dispersion compensation parameter set to the detector signal to yield image information; and
processing the image information to yield image information for the sample path range; and
generating an image of the sample from the image information for the plurality of sample path ranges, the image being generated based on image information that is processed with a plurality of dispersion compensation parameter sets that correspond to the plurality of sample path ranges.
11 . The method of claim 10 , the processing the image information to yield image information for the sample path range further comprising performing the following until an image quality satisfies an image quality criterion:
performing image processing on the image information;
generating a candidate image from the image information; and
evaluating the image quality of the candidate image.
12 . The method of claim 10 , the detector signal comprising a plurality of interference signals, each interference signal corresponding to a reference arm of the plurality of reference arms.
13 . The method of claim 10 , the sample comprising a sample within an eye.
14 . The method of claim 10 , the plurality of reference arms having a plurality of reference planes comprising a first reference plane and a second reference plane.
15 . The method of claim 14 , wherein:
an axial separation between the first reference plane and the second reference plane is substantially twice an OCT imaging depth minus any overlap between the planes; and
the first reference plane covers a positive OCT image space and the second reference plane covers a negative OCT image space to yield an image that is substantially twice the OCT imaging depth minus any overlap between the planes.
16 . The method of claim 14 , wherein:
an axial separation between the first reference plane and the second reference plane is substantially an OCT imaging depth minus any overlap between the planes; and
the first reference plane and the second reference plane each cover a positive OCT image space to yield an image that is substantially twice the OCT imaging depth minus any overlap between the planes.
17 . The method of claim 10 , wherein: a first reference arm has dispersion material.
18 . The method of claim 10 , wherein:
a first reference arm has dispersion material that creates a first dispersion mismatch; and
a second reference arm has dispersion material that creates a second dispersion mismatch different from the first dispersion mismatch.
19 . An optical coherence tomography (OCT) system, comprising:
a light source configured to provide a light beam;
a beamsplitter configured to split the light beam into a sample beam and a reference beam;
one or more optical elements configured to direct the sample beam along a sample path towards a sample, the sample path comprising a plurality of sample path ranges, the sample reflecting the sample beam to yield a reflected sample beam;
a reference arm system configured to direct the reference beam through each reference arm of a plurality of reference arms to yield a reflected reference beam, each reference arm corresponding to a sample path range of the plurality of sample path ranges, each reference arm associated with a specific dispersion level with a corresponding dispersion compensation parameter set, the dispersion compensation parameter set designed to address the specific dispersion level, the plurality of reference arms having a plurality of reference planes comprising a first reference plane and a second reference plane;
a detector configured to:
detect the reflected sample beam and the reflected reference beam; and
generate a detector signal in response to detecting the reflected sample beam and the reflected reference beam; and
a computer configured to:
perform the following for each sample path range of the plurality of sample path ranges to yield image information for the sample path ranges:
select the dispersion compensation parameter set corresponding to the reference arm of the sample path range;
apply the dispersion compensation parameter set to the detector signal to yield image information; and
process the image information to yield image information for the sample path range by performing the following until an image quality satisfies an image quality criterion: perform image processing on the image information; generate a candidate image from the image information; and evaluate the image quality of the candidate image; and
generate an image of the sample from the image information for the plurality of sample path ranges, the image being generated based on image information that is processed with a plurality of dispersion compensation parameter sets that correspond to the plurality of sample path ranges, wherein an axial separation between the first reference plane and the second reference plane is substantially twice an OCT imaging depth minus any overlap between the planes, and the first reference plane covers a positive OCT image space and the second reference plane covers a negative OCT image space to yield an image that is substantially twice the OCT imaging depth minus any overlap between the planes; or an axial separation between the first reference plane and the second reference plane is substantially an OCT imaging depth minus any overlap between the planes, and the first reference plane and the second reference plane each cover a positive OCT image space to yield an image that is substantially twice the OCT imaging depth minus any overlap between the planes.