FIELD OF THE DISCLOSURE

The present disclosure relates to optical imaging systems, and more specifically apparatus and method related to high-speed imaging of the three-dimensional scattering properties of a sample located within a large imaging volume, and especially to rapid depth-resolved imaging of a sample that has a geometric structure that causes the distance of each region of sample relative to the imaging system to vary across the sample and over time.

BACKGROUND INFORMATION

Optical coherence tomography (OCT) provides cross-sectional images of biological samples with resolution on the scale of several to tens of microns. Conventional OCT, referred to as time-domain OCT (“TD-OCT”), can use low-coherence interferometry techniques to achieve depth ranging. In contrast, Fourier-Domain OCT (“FD-OCT”) techniques can use spectral-radar techniques to achieve depth ranging. FD-OCT techniques have been shown to facilitate higher imaging speeds through improved signal-to-noise performance and elimination of a mechanically scanned interferometer reference arm.

FD-OCT systems generally operate by separating a light source into a sample beam and a reference beam. The sample beam can be directed at a sample to be imaged, and the reflected light from the sample is recombined with light from the reference beam (i.e., returning from the reference arm), resulting in an interference signal, which can provide information about the structure, composition and state, for example, of the sample. Light in the sample path and or light in the reference path can be modified by, for example, a phase modulator or frequency shifter, altering the characteristics of the interference and enhancing the information content of the signal or making the signal easier to detect. FD-OCT systems can sample the interference signal as a function of wavelength.

In one exemplary embodiment of the FD-OCT system, the interference signal as a function of wavelength can be obtained by using a light source that has an output wavelength which sweeps, varies or steps as a function of time. A detection of the interference signal as a function of time thereby can yield the interference signal as a function of wavelength. This exemplary embodiment can be referred to as optical frequency domain imaging (“OFDI”) technique.

In another exemplary embodiment of the FD-OCT system, the interference signal as a function of wavelength can be obtained by using a broadband light source and a spectrally dispersing unit or a spectrometer that spatially separates the recombined sample and reference light according to wavelength such that a one-dimensional or two-dimensional camera can sample the signal as a function of the wavelength. This exemplary embodiment can be referred to as spectral-domain OCT technique. In both such exemplary embodiments, the detected interference signal as a function of wavenumber k (k=1/wavelength) can be used to provide information related to the depth profile of scattering in a turbid or semi-turbid sample, or a transparent sample. Such information can include information regarding, e.g., the structure of the sample, composition, state, flow, and birefringence.

A scatterer at a given depth can induce a modulation in the amplitude or polarization of the interfered signal. The frequency of such modulation in wavenumber-space can be related to the location of the scatter or the time delay of the light reflected from that scatter relative to the time delay of the light in the reference arm. Scatterers located at a depth that causes reflected signals with no net time delay relative to the reference arm light can induce an interference signal that may not modulate with wavenumber. As the location of the scatterers moves from this zero-delay point, the magnitude of the frequency can increase. To image over large delay windows, e.g., to detect and localize reflections within large time delay window, the interference signal may often be sampled with sufficiently high resolution in wavenumber-space to facilitate an unambiguous detection of the range of modulation frequencies that are associated with the large delay window.

To accommodate the sampling at high resolution in wavenumber, increasingly fast analog-to-digital converters (“ADC”) can be used in the OFDI systems, and increasingly high pixel count cameras can be used in the SD-OCT systems. In both the OFDI and SD-OCT systems, the increased data volume resulting from imaging over large extents can often result in the use of increasingly-high bandwidth data transfer buses and data storage units.

Optical-domain subsampling can be used to increase the depth range of an OFDI or SD-OCT system without increasing the number of spectral measurements that are performed. In addition, optical-domain subsampling can be used to increase the imaging speed without increasing the electrical bandwidth of the imaging system. In this manner, an optical-domain subsampling OCT system can interrogate a larger volume of physical space with a given number of measurements than a FD-OCT or a SD-OCT system that is operated with the same number of measurements.

In a high-speed optical domain subsampled OCT system, it is possible to image across large depth ranges at extremely high speeds resulting in video-rate volumetric microscopy of samples that are not precisely located relative to the imaging system or contain a surface that varies in distance to the imaging system across the field.

Accordingly, there is a need to address and/or overcome at least some of the deficiencies described herein above.

SUMMARY OF EXEMPLARY EMBODIMENTS

In particular, at least some of the deficiencies with the conventional systems and method can be addressed with an exemplary apparatus which can include a laser arrangement that is configured to provide a laser radiation, and including an optical cavity. The optical cavity can include a dispersive optical waveguide first arrangement having first and second sides, and which is configured to (i) receive at least one first electro-magnetic radiation at the first side so as to provide at least one second electro-magnetic radiation, and (ii) to receive at least one third electro-magnetic radiation at the second side so as to provide at least one fourth electro-magnetic radiation. The first and second sides are different from one another, and the second and third radiations are related to one another. The optical cavity can also include an active optical modulator second arrangement which can be configured to receive and modulate the fourth radiation so as to provide the first electro-magnetic radiation to the first arrangement. The laser radiation can be associated with at least one of the first, second, third or fourth radiations.

In one exemplary embodiment, the first arrangement can be a fiber Bragg grating (FBG), a chirped FBG, and/or a FBG array. The FBG can be provided in a polarization maintaining optical fiber and/or a non-polarization maintaining optical fiber. The first arrangement can also be configured to cause a group delay that varies linearly with an optical frequency of the first radiation and/or the third radiation. According to another exemplary embodiment, the first arrangement can include (i) at least one first circulator which receives the first radiation and transmits the second radiation, and/or (ii) at least one second circulator which receives the third radiation and transmits the fourth radiation. The optical cavity can include at least one optical amplifier third arrangement which can be configured to amplify at least one of the first radiation, the second radiation, the third radiation or the fourth radiation. The optical amplifier arrangement can include a semiconductor amplifier, a Raman amplifier, a parametric optical amplifier, and/or a fiber amplifier. The optical cavity can also include a further active optical modulator fourth arrangement which can be configured to receive and modulate the second radiation so as to provide the third electro-magnetic radiation to the first arrangement. For example, the further active optical modulator fourth arrangement can be configured to suppress a light radiation that travels through the first arrangement, which is different from the second radiation. Additionally or alternatively, the further active optical modulator fourth arrangement can be a further active optical amplifier arrangement.

According to a further exemplary embodiment of the present disclosure, the optical cavity can include at least one optical polarizer fifth arrangement, which is configured to block a light radiation transmitted through the first arrangement. The optical cavity can also include a dispersion compensating arrangement and/or a fixed periodic spectral filter arrangement. The fixed periodic spectral filter arrangement can include (i) a Fabry-Perot etalon filter that has a finesse that is between 3 and 25, and/or (ii) an optical interleaver. The Fabry-Perot etalon filter can be an air gap etalon filter.

In a still further exemplary embodiment of the present disclosure, the laser radiation can have a wavelength that changes over time, e.g., continuously and/or discretely. For example, actions by the first and second arrangements can cause the wavelength to change at a rate that is faster than 80 nm/micro seconds.

In further alternative embodiments, the first arrangement can include a fiber Bragg grating (FBG) that is provided in a polarization maintaining optical waveguide, the first radiation can be launched along a first birefringent axis of the optical waveguide, and the third radiation can be launched along a second birefringent axis of the optical waveguide, with the first and second birefringent axes being different from one another. The second electro-magnetic radiation can be a reflection of the first electro-magnetic radiation, and the fourth electro-magnetic radiation can be a reflection of the third electro-magnetic radiation.

According to yet another exemplary embodiment of the present disclosure, an exemplary apparatus can be provided which can include a laser arrangement that is configured to provide a laser radiation, and including an optical cavity. The optical cavity can include a dispersive first arrangement can be configured to receive at least one first electro-magnetic radiation so as to provide at least one second electro-magnetic radiation, and a dispersive second arrangement which is configured to receive at least one third electro-magnetic radiation so as to provide at least one fourth electro-magnetic radiation, whereas the second and third radiations are related to one another. The optical cavity can further include an active optical modulator second arrangement which can be configured to receive and modulate the fourth radiation so as to provide the electro-magnetic radiation to the first arrangement, with the laser radiation being associated with at least one of the first, second, third or fourth radiations. The laser arrangement can also include an interferometer arrangement which is configured to generate (i) a fifth electro-magnetic radiation from the laser radiation in a sample arm, (ii) a sixth electro-magnetic radiation from the laser radiation in a reference arm, and (iii) an interference signal based on an interference between the fifth electro-magnetic radiation and the sixth electro-magnetic radiation. The laser arrangement can also include a beam scanning arrangement configured to scan the fifth electro-magnetic radiation across at least one portion of at least one sample. An interaction between the laser arrangement, the interferometer arrangement, and the beam scanning arrangement provides a three-dimensional measurement of an optical property of the portion(s) of the sample(s).

For example, according to one exemplary embodiment, the laser arrangement can further include an analog-to-digital acquisition arrangement configured to obtain the interference signal based on an electronic clock signal, and an electronic signal generator configured to drive the second arrangement, whereas the electronic clock signal can be phase-locked to the electronic signal generator. The first and second arrangements can include fiber Bragg gratings or part of the same fiber Bragg grating. The second electro-magnetic radiation can be a reflection of the first electro-magnetic radiation, and the fourth electro-magnetic radiation can be a reflection of the third electro-magnetic radiation. The laser radiation can be an optical frequency comb.

According to yet another exemplary embodiment of the present disclosure, an exemplary apparatus can be provided which can include a laser arrangement that is configured to generate a laser radiation at a particular number (N) of discrete optical frequencies. The exemplary apparatus cam also include an interferometer arrangement configured to generate an interference signal from the laser radiation, and a beam scanning arrangement configured to scan at least one portion of the laser radiation across at least one portion of at least one sample. A line width of each of the discrete optical frequencies can be less than 10 GHz, and a spacing between each of the discrete optical frequencies can be greater than 20 GHz. The laser radiation can step between the discrete optical frequencies at rate that is greater than 20 million discrete optical frequency steps per second. In a further exemplary embodiment of the present disclosure, the laser arrangement can include a continuous fiber Bragg grating having a length that is greater than 2 meters, and or a fiber Bragg grating array having a length that is greater than 2 meters.

According to a still further exemplary embodiment of the present disclosure, method computer-accessible medium (e.g., having software stored thereof to be executed by a computer) can be provided for displaying a video stream regarding at least one structure. For example, using such method and computer-accessible medium, it is possible to measure four-dimensional interferometric data regarding different portions of at least one structure at different points in time, wherein the four-dimensional data describing at least one optical property of the at least one structure. Further, it is possible to transform the four-dimensional interferometric data into two-dimensional video data, and display the video stream of the different portions of the structure using the two-dimensional video data. A latency of a performance of the measurement and the display is less than 1 second.

The exemplary procedures performed by such exemplary method and computer are done so in a medical procedure, and further can cause the procedure to be guided interactively using the video stream. Additionally, the measurement can be performed using a frequency comb optical source. Alternatively or additionally, the measurement can be performed using a laser arrangement as described in various embodiments herein above.

According to a still further exemplary embodiment of the present disclosure, method computer-accessible medium (e.g., having software stored thereof to be executed by a computer) can be provided to be used in a medical procedure on at least one anatomical structure. Using such exemplary method and computer, it is possible to measure single-dimensional interferometric data describing at least one optical property of the structure at a rate that greater than 5 Mega Hertz. Further, it is possible to construct four-dimensional interferometric data from the single-dimensional interferometric data regarding different portions of at least one structure at different points in time, and utilize the four-dimensional interferometric data in the medical procedure. For example, the measurement can be performed using a frequency comb optical source. Alternatively or additionally, the measurement can be performed using a laser arrangement as described in various embodiments herein above.

According to a yet still further exemplary embodiment of the present disclosure, method computer-accessible medium (e.g., having software stored thereof to be executed by a computer) can be provided for displaying a video stream regarding at least one structure. For example, using such method and computer-accessible medium, it is possible to measure four-dimensional interferometric data regarding different portions of at least one structure at different points in time, whereas the four-dimensional data describing at least one optical property of the structure, and the four-dimensional interferometric data can be circularly wrapped in a particular spatial dimension. Additionally, the exemplary method and computer can transform the four-dimensional interferometric data into two-dimensional video data by compressing the particular spatial dimension, and display the video stream of the different portions of the structure using the two-dimensional video data.

For example, the compression can include (i) locating a position of a surface of the structure within the four-dimensional interferometric data, and (ii) controlling the compression using the position. Further, the measurement can be is performed using a frequency comb optical source, and/or a laser arrangement as described in various embodiments herein above.

These and other objects, features and advantages of the present disclosure will become apparent upon reading the following detailed description of exemplary embodiments of the present disclosure, when taken in conjunction with the appended drawings and claims.

