Crosstalk elimination or mitigation in optical coherence tomography
One or more devices, systems, methods and storage mediums for performing optical coherence tomography (OCT) while reducing and/or eliminating crosstalk noise are provided. Examples of such applications include imaging, evaluating and diagnosing biological objects, such as, but not limited to, for Gastro-intestinal, cardio and/or ophthalmic applications, and being obtained via one or more optical instruments, such as, but not limited to, optical probes, catheters, capsules and needles (e.g., a biopsy needle). Preferably, the OCT devices, systems methods and storage mediums include or involve a method, such as, but not limited to, a complex conjugate method or a shift method, for handling the crosstalk noise in a way to mitigate or eliminate the noise from an image field of view. For example, a reference reflection or reference arm may be positioned or re-positioned in the image field of view at different locations depending on the crosstalk noise mitigation method being employed.
1. A crosstalk elimination or mitigation optical coherence tomography (OCT) system, the system comprising:
an interference optical system that operates to: (i) receive and divide light from a light source into a first light with which an object or sample is to be irradiated and which travels along a sample arm of the interference optical system and a second reference light, (ii) send the second reference light along a reference arm of the interference optical system for reflection off of a reference reflection of the interference optical system, and (iii) generate interference light by causing reflected or scattered light of the first light with which the object or sample has been irradiated and the reflected second reference light to combine or recombine, and/or to interfere, with each other, the interference light generating one or more interference patterns; and
at least one detector that operates to continuously acquire the interference light and/or the one or more interference patterns to measure the interference or the one or more interference patterns between the combined or recombined light,
wherein the reference reflection is positioned in, at, at about, or around a field of view such that crosstalk noise is mitigated or eliminated from the field of view, and
wherein:
(i) the reference reflection is positioned at, at about, or around one or more of:
(a) a distal edge or an end of the field of view; and
(b) a distal edge or an end of the field of view such that an optical path length of the reference reflection is longer than a reflection or reflections of the object or sample and is situated at or at about a length of a maximum predetermined object or sample reflection; or
(ii) the reference reflection is positioned at, at about, or around one or more of:
(a) a position that is shorter than a predetermined or determined start of, or shorter than a proximal edge of, the field of view;
(b) a position that is shorter than a predetermined or determined start of, or shorter than a proximal edge of, the field of view such that an optical path length of the reference reflection is shorter than a first predetermined or determined sample reflection; and
(c) a position that is shorter than a predetermined or determined start of, or shorter than a proximal edge of, the field of view such that: (i) an optical path length of the reference reflection is shorter than a first predetermined or determined sample reflection, and (ii) the crosstalk noise wraps about a DC position and is no longer in a predetermined imaging range of the field of view.
2. The OCT system of claim 1 , wherein the OCT system is a multimodality OCT system and includes a double-clad fiber (DCF) segment, and the OCT system operates to eliminate or mitigate crosstalk induced image artifacts in coherent application(s) requiring use of the DCF segment.
3. The OCT system of claim 1 , further comprising a filter to perform analog, digital or electronic filtering to eliminate or reduce any crosstalk noise that would otherwise alias into a predetermined signal frequency range.
4. The OCT system of claim 3 , wherein the filter may include at least one of:
(i) a low pass filter to eliminate or reduce the aliasing;
(ii) a high pass filter to eliminate or reduce direct current (DC) artifact(s); and
(iii) a bandpass filter with a certain predetermined order for a low frequency cutoff and a certain order for a high frequency cutoff.
5. The OCT system of claim 1 , further comprising at least one of:
(i) the light source that operates to produce the light; and
(ii) a guide or waveguide for transmitting the light from the light source.
6. The OCT system of claim 1 , further comprising a deflecting section that operates to deflect the light from the light source to the interference optical system, and then send light received from the interference optical system towards the at least one detector.
7. The OCT system of claim 6 , wherein the deflecting section comprises at least one of: one or more interferometers, a circulator, a beam splitter, an isolator, a coupler, a fusion fiber coupler, a partially severed mirror with holes therein, and a partially severed mirror with a tap.
8. The OCT system of claim 1 , further comprising an adjustment section that operates to control one or more relative optical characteristics between the first light having illuminated the object or sample and the reflected second light, and a deflecting section that operates to pass the reflected second light from the adjustment section and towards the at least one detector.
9. The OCT system of claim 1 , further comprising at least one processor that operates to process a signal from the at least one detector to acquire information of the object or sample.
10. A method for performing crosstalk noise mitigation or elimination using an optical coherence tomography (OCT) device or system having an interference optical system that operates to generate interference light and one or more interference patterns from a light that has been split into a first light with which an object or sample has been irradiated and a second reference light and having at least one detector, the method comprising:
positioning a reference reflection of the interference optical system in, at, at about, or around a field of view such that crosstalk noise is mitigated or eliminated from the field of view,
wherein the positioning step further comprises:
(i) positioning the reference reflection at, at about, or around one or more of:
(a) a distal edge or an end of the field of view; and
(b) a distal edge or an end of the field of view such that an optical path length of the reference reflection is longer than a reflection or reflections of the object or sample and is situated at or at about a length of a maximum predetermined object or sample reflection; or
(ii) positioning the reference reflection at, at about, or around one or more of:
(a) a position that is shorter than a predetermined or determined start of, or shorter than a proximal edge of, the field of view;
(b) a position that is shorter than a predetermined or determined start of, or shorter than a proximal edge of, the field of view such that an optical path length of the reference reflection is shorter than a first predetermined or determined sample reflection; and
(c) a position that is shorter than a predetermined or determined start of, or shorter than a proximal edge of, the field of view such that: (i) an optical path length of the reference reflection is shorter than a first predetermined or determined sample reflection, and (ii) the crosstalk noise wraps about a DC position and is no longer in a predetermined imaging range of the field of view.
11. The method of claim 10 , wherein the OCT device or system is a multimodality OCT device or system and includes a double-clad fiber (DCF) segment, and the OCT device or system operates to eliminate or mitigate crosstalk induced image artifacts in coherent application(s) requiring use of the DCF segment.
12. The method of claim 10 , further comprising performing analog, digital or electronic filtering to eliminate or reduce any crosstalk noise that would otherwise alias into a predetermined signal frequency range.
13. The method of claim 10 , further comprising positioning the reference reflection such that about half of the crosstalk noise extends beyond the DC position, wraps around and is still away from a predetermined imaging range of the field of view and/or a predetermined image signal resulting in a crosstalk free region of an image of the object or sample.
14. The method of claim 13 , further comprising cropping a crosstalk noise laden region of the image digitally to have or obtain an image of the object or sample without any noise artifact(s).
15. The method of claim 14 , wherein at least one of:
(i) the cropped image is further adjusted by putting black pixels where a DC artifact is or was and with a predetermined or determined number of pixels so as to have the object or sample appear with accurate dimensions in the image;
(ii) the added pixels are such that the pixels represent a lower range of intensities displayed in a same color map as the whole image;
(iii) the added pixels are such that the pixels have similar or the same characteristics as a background of the image;
(iv) the similar or the same characteristics include at least one of noise and speckle; and
(v) a number of the added pixels is such that, in response to using a catheter of a predetermined or determined dimension, an actual size measured from the image reflects an actual physical dimension of the catheter.