Method for determining the distance between an end of an optical fiber and a target - Patents.com

Abstract

The present disclosure provides a method and system for estimating the distance between an optical fiber end and a target. Treatments using laser and optical fiber technology require high precision to ensure that the laser is aimed at the correct target (stone, tissue, tumor, etc.) to achieve clinical objectives such as tissue ablation, coagulation, stone fragmentation, dust removal, etc. Therefore, it is important to know the distance between the target and the optical fiber end (distal end) from which the laser light is emitted, because laser treatment parameters such as energy, pulse width, laser power modulation, and / or repetition rate are often determined based on the distance from the tip of the optical fiber to the target.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of U.S. Provisional Application No. 63 / 320,943, filed March 17, 2022, the disclosure of which is incorporated herein by reference. [Background technology]

[0002] The introduction of lasers in the medical field, as well as the development of fiber optic technology using lasers, has opened up numerous applications in treatment, diagnosis, therapy, and the like. Such applications range from invasive and non-invasive treatments to endoscopic surgery and diagnostic imaging. For example, the treatment of urinary stones requires the stones to be broken into small pieces. Such a fragmentation process can use a technique known as laser lithotripsy, where a rigid or flexible ureteroscope is placed through the urinary tract for illumination and imaging of small to medium sized urinary stones. At the same time, an optical fiber is inserted through the working channel of the ureteroscope to the target location (e.g., the location of the stone in the bladder, ureter, or kidney). A laser is then activated to break the stone into small pieces or into powder. In another example, laser and fiber optic technology is used for coagulation or ablation treatments. During ablation treatments, laser light is delivered to tissue to vaporize the tissue. During coagulation treatments, laser light is used to induce thermal damage in the tissue. Such ablation therapies can be used to treat a variety of conditions, such as benign prostatic hyperplasia (BPH) and cancers, including prostate cancer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Provisional Patent Application No. 63 / 320943 Summary of the Invention [Problem to be solved by the invention]

[0004] This Summary is provided to introduce in a simplified form a selection of concepts that are further described below in the Detailed Description. This Summary is not intended to necessarily identify key features or essential features of the claimed subject matter, nor is it intended as an aid in determining the scope of the claimed subject matter. [Means for solving the problem]

[0005] In one aspect, the present disclosure relates to an apparatus that includes a laser source, an optical fiber, a detector, and a controller. The optical fiber has a distal end and is configured to pass laser light from the laser source out of the distal end and receive reflected laser light into the distal end. The controller can include a processor and a memory, the memory including instructions that, when executed by the processor, cause the processor to perform one or more of: generating a ranging beam with the laser source that includes a linearly varying wavelength sweep; identifying a detection signal generated by the detector based on a measurement of a mixture of a reference signal, at least one reflection of the ranging beam from a target, and at least one reflection of the ranging beam from the distal end of the optical fiber; analyzing the detection signal to determine frequency components corresponding to the at least one reflection of the ranging beam from the target and at least one reflection of the ranging beam from the distal end of the optical fiber; and determining a distance between the distal end of the optical fiber and the target based on the frequency components.

[0006] In some embodiments, the laser source comprises a first laser source, and the instructions, when executed by the processor, further cause the processor to select an operating mode of the second laser source based on a distance between the distal end of the optical fiber and the target. In various embodiments, the laser source comprises a first laser source, and the instructions, when executed by the processor, further cause the processor to generate a therapeutic beam with the second laser source when the distance between the distal end of the optical fiber and the target is within a threshold distance. In many embodiments, the laser source comprises a first laser source, and the instructions, when executed by the processor, further cause the processor to stop generating a therapeutic beam with the second laser source when the distance between the distal end of the optical fiber and the target exceeds the threshold distance. In some embodiments, the instructions, when executed by the processor, further cause the processor to generate one or more of an audio, tactile, and visual alert when the distance between the distal end of the optical fiber and the target exceeds the threshold distance. In various embodiments, the detection signal is generated by the detector based on measuring at least one reflection of the ranging beam from the target, at least one reflection of the ranging beam from the distal end of the optical fiber, and at least one reflection of the ranging beam from the proximal end of the optical fiber. In various such embodiments, the frequency components include a first frequency component, and the instructions, when executed by the processor, further cause the processor to analyze the detection signal to determine second and third frequency components, the second frequency component corresponding to the at least one reflection of the ranging beam from the distal end of the optical fiber and the at least one reflection of the ranging beam from the proximal end of the optical fiber, and the third frequency component corresponding to the at least one reflection of the ranging beam from the target and the at least one reflection of the ranging beam from the proximal end of the optical fiber. In further such embodiments, the instructions, when executed by the processor, further cause the processor to determine, based on the first frequency component being higher than the second and third frequency components, that the first frequency component corresponds to a distance between at least one reflection of the ranging beam from the target and at least one reflection of the ranging beam from the distal end of the optical fiber.Some embodiments include a filter configured to remove frequencies below a threshold corresponding to reflection of the ranging beam from the proximal end of the optical fiber. Many embodiments include a bandpass filter configured to remove frequencies above a first threshold and below a second threshold.

[0007] In another aspect, the present disclosure relates to at least one non-transitory computer-readable medium comprising a set of instructions that, in response to being executed by a processor circuit, cause the processor circuit to perform one or more of: generating a ranging beam with a laser source, the ranging beam including a linearly varying wavelength sweep; identifying a detection signal generated by a detector based on a measurement of a mixture of a reference signal, at least one reflection of the ranging beam from the target, and at least one reflection of the ranging beam from the distal end of the optical fiber; analyzing the detection signal to determine frequency components corresponding to the at least one reflection of the ranging beam from the target and at least one reflection of the ranging beam from the distal end of the optical fiber; and determining a distance between the distal end of the optical fiber and the target based on the frequency components.

[0008] In various embodiments, the set of instructions, in response to execution by the processor, further causes the processor to generate one or more of an audio, tactile, and visual alert when the distance between the distal end of the optical fiber and the target exceeds a threshold distance. In some embodiments, the set of instructions, in response to execution by the processor circuit, further causes the processor circuit to perform a Fourier analysis on the detected signal to determine frequency components. In many embodiments, the set of instructions, in response to execution by the processor circuit, further causes the processor circuit to filter out at least a portion of the detected signal based on a reflected frequency associated with the proximal end of the optical fiber.

[0009] In yet another aspect, the present disclosure relates to a system including a laser source, an optical fiber, a detector, and a controller. The optical fiber has a distal end and is configured to pass laser light from the laser source out of the distal end and receive reflected laser light into the distal end. The controller can include a processor and a memory, the memory including instructions that, when executed by the processor, cause the processor to perform one or more of: generating a ranging beam with the laser source including a linearly varying wavelength sweep; identifying a detection signal generated by the detector based on a measurement of a mixture of at least one reflection of the ranging beam from the target and at least one reflection of the ranging beam from the distal end of the optical fiber; analyzing the detection signal to determine a first frequency component corresponding to at least one reflection of the ranging beam from a first target and a second frequency component corresponding to at least one reflection of the ranging beam from the distal end of the optical fiber; and determining a distance between the distal end of the optical fiber and the target based on the first and second frequency components.

[0010] Some embodiments include a beam splitter configured to direct a portion of the ranging beam to a detector, and the detection signal is generated by the detector based on a measurement of the portion of the ranging beam, at least one reflection of the ranging beam from the target, and at least one reflection of the ranging beam from the distal end of the optical fiber. In some such embodiments, the measurement of the portion of the ranging beam, at least one reflection of the ranging beam from the target, and at least one reflection of the ranging beam from the distal end of the optical fiber includes a measurement of an interference pattern formed on the detector. Various embodiments include a bandpass filter configured to remove frequencies above a first threshold and below a second threshold. In many embodiments, the detector comprises a PIN photodiode or an avalanche photodiode. In some embodiments, the laser source comprises a diode laser, where the current of the diode laser is varied to create a linearly varying wavelength sweep of the ranging beam.

[0011] Non-limiting embodiments of the present disclosure are described by way of example with reference to the accompanying drawings, which are schematic and are not intended to be drawn to scale. Various figures contained in this disclosure may omit some components, illustrate portions of some components, and / or present some components as transparent to facilitate illustration and description of components that may otherwise appear hidden. For clarity, not every component is labeled in every figure, nor is every component of each embodiment shown unless illustration is necessary to enable one of ordinary skill in the art to understand the disclosure. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a block diagram of an example laser system according to one or more embodiments described herein. [Diagram 2] 1A-1C illustrate various aspects of an exemplary measurement laser subsystem in accordance with one or more embodiments described herein. [Diagram 3] 1A-1C illustrate various aspects of a further (simpler) exemplary measurement laser system in accordance with one or more embodiments described herein. [Figure 4] 1A-1C illustrate various aspects of target reflection in accordance with one or more embodiments described herein. [Figure 5A] 1A-1C are diagrams illustrating various aspects of theoretical reflected frequencies in accordance with one or more embodiments described herein. [Figure 5B] 1A-1C illustrate various aspects of measured reflected frequencies in accordance with one or more embodiments described herein. [Figure 6] 1 is an exemplary logic flow according to one or more embodiments described herein. [Figure 7] 1 is an exemplary logic flow according to one or more embodiments described herein. [Figure 8] FIG. 1 is a block diagram of an exemplary computer system for implementing embodiments consistent with this disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present disclosure provides a method and system for estimating the distance between an optical fiber end and a target. Treatments using laser and optical fiber technology need to ensure that the laser is at the proper position and setting relative to the target (stone, tissue, tumor, etc.) to achieve clinical objectives such as tissue ablation, coagulation, stone fragmentation, pulverization, etc. Therefore, it is important to know the distance between the target and the optical fiber end (distal end) from which the laser light is emitted, because laser treatment parameters such as energy, pulse width, laser power modulation, and / or repetition rate are often determined based on the distance from the tip of the optical fiber to the target.

[0014] Furthermore, the efficiency of laser-based treatment often depends on the relative position and orientation of the optical fiber tip with respect to the target. However, it is extremely difficult to determine or estimate the distance between the optical fiber tip and the target due to various factors such as the movement of the optical fiber with respect to its position and orientation within the subject's (e.g., patient's) body, the tissue environment, the movement of the tissue or stone, the surface of the target, the color of the target, the pigment of the target, the degradation of the optical fiber tip during treatment, water washing, the opaque environment (e.g., due to pulverized stone), etc. The step of determining the distance between the optical fiber tip and the target is further complicated by the fact that the optical fiber tip is usually inserted into the subject's body.

[0015] Inaccurate estimation of the distance between the optical fiber end and the target, as well as inaccurate estimation of the orientation of the optical fiber end, may result in the laser being aimed at an area that is not the target area of ​​interest. This may result in unnecessary complications, and in some cases, may result in permanent damage to certain parts of the subject's tissue, organs, etc., causing parts of the subject's body to malfunction. In some other scenarios, inaccurate distance measurements and orientations may lead to increased treatment time or poor quality ablation / disruption results. In some cases, such as BPH or cancer, if the tumor is not properly ablated, it may result in regrowth of the tumor (or other undesirable tissue), leading to further complications. Therefore, it is important to determine the exact distance (or maintain the desired distance) between the optical fiber tip and the target while performing certain treatments using laser and optical fiber technologies as described above.

[0016] One technique for estimating the distance between the distal end of an optical fiber and a target involves measuring and comparing the reflected intensity values ​​of a light beam, in which case the light beam is passed through the optical fiber by changing its numerical aperture. However, it is not always convenient to shift the numerical aperture of the light beam. Moreover, it is difficult to separate the reflections of light beams of different numerical apertures, which is required for these techniques.

[0017] Thus, the present disclosure provides techniques for determining the distance between an optical fiber end and a target in an efficient and improved manner based on frequency analysis of one or more reflected signals. In various embodiments, the distance estimate can be utilized for various purposes. For example, the distance can be utilized to provide information and / or warnings to an operator. In one embodiment, a significantly erroneous distance can be utilized to indicate to an operator that the wrong object is being targeted. In another example, the distance can be utilized to enable automatic operation of the laser, such as by using the distance (and / or other characteristics derived based on the reflection) to determine whether a target is present. In one embodiment, a significantly erroneous distance can be utilized as an indication that the wrong object is being targeted, resulting in protective measures being automatically taken (e.g., deactivating the laser). In yet another example, the distance can be utilized to select an operating mode of the laser, for example, between a long-range mode and a short-range mode. For example, when using a thulium laser to generate the treatment beam, the threshold distance can be approximately 3 mm, and when using a holmium laser to generate the treatment beam, the threshold distance can be approximately 2 mm. Additionally or alternatively, in many embodiments, the reflected signal can be utilized to monitor and / or determine the status or condition of one or more components of the laser system. For example, the condition of the optical fiber may be determined based on a frequency analysis of one or more reflected signals.

[0018] The foregoing has outlined broadly the features and technical advantages of the present disclosure in order that the following detailed description thereof may be better understood. Those skilled in the art will appreciate that the disclosed embodiments may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. For example, the aspects and components disclosed herein may be selected and combined without departing from the scope of the present disclosure. The novel features of the present invention, both as to its organization and method of operation, together with further objects and advantages, will be better understood from the following description when considered in conjunction with the accompanying drawings. It should be expressly understood, however, that each of the figures is provided for purposes of illustration and description only, and is not intended to define the limits of the present disclosure. Furthermore, while various embodiments may be described in terms of ablation therapy used to treat diseases including benign prostatic hyperplasia (BPH) and prostate cancer, reference to these diseases should not be construed as limiting the possible applications of the disclosed aspects. For example, the disclosed aspects may be utilized to treat pathologies, cancers (e.g., liver cancer, lung cancer, etc.), and cardiac diseases (e.g., by ablation and / or coagulation of portions of cardiac tissue).

[0019] FIG. 1 illustrates a block diagram of an exemplary laser system 102 in accordance with one or more embodiments described herein. In the illustrated embodiment, the laser system 102 includes a laser source 104, an optical fiber 106, a detector 108, a controller 110, and one or more optical components 112. In general, the laser system 102 can be operated to determine a distance between a distal end of the optical fiber 106 and a target, such as by using a frequency modulated continuous wave (FMCW) technique. For example, the laser source 104 can be used to generate a ranging beam having a tunable wavelength and with a linearly varying wavelength sweep. The ranging beam can travel through and out of the optical fiber 106, where a portion of the ranging beam will be reflected from the fiber tip and another portion can be reflected from the target and return to the optical fiber 106 as a return signal and directed onto the detector 108 for measurement. The detector 108 can generate a detection signal based on a measurement of the return signal. The controller 110 can then utilize the detection signal to perform a frequency analysis of the return signal to determine a distance between the optical fiber 106 and the target. For example, the controller 110 may perform a Fourier analysis, such as a Fast Fourier Transform (FFT), on the return signal. As described in more detail below, the return signal may include reflections from a variety of sources, such as the proximal and distal ends of the optical fiber 106, as well as reflections from a target.

[0020] Although not shown, it will be understood that the laser system 102 can be included, integrated, or connected to a therapeutic laser system. The laser system 102 can utilize this distance to effectively and efficiently deliver laser energy to a target. In some examples, the laser system 102 automatically adjusts the characteristics (e.g., pulse width, power, etc.) of the laser energy generated by the laser source 104 (or another therapeutic laser source) based on the distance, while in other examples, the laser system 102 can provide an indication of the distance (e.g., via a graphical user interface, etc.) to a user (e.g., a physician, technician, etc.) of the laser system 102.

[0021] As described in more detail below, in some embodiments, such as the embodiment of FIG. 2, a portion of the ranging beam may be redirected and mixed with the return signal for measurement by the detector 108. In other embodiments, such as the embodiment of FIG. 3, the reference signal may not be mixed with the return signal for measurement by the detector 108. Additionally, as described in more detail below, the return signal may be digitally and / or analog filtered to remove signal components associated with undesired reflections, such as from the proximal end of the optical fiber 106. In various embodiments, optical component 112 may be utilized to split, combine, and / or direct various signal (e.g., light) components, such as by mixing a portion of the laser source 104 toward the detector 108.

[0022] The laser source 104 may comprise a wavelength or frequency tunable laser capable of generating a linearly varying wavelength sweep. For example, the laser source 104 may include a diode laser, and the wavelength may be varied by varying the current of the diode laser. However, it will be understood that any technique for varying the laser wavelength may be used without departing from the scope of the present disclosure. In an embodiment, the laser source 104 may include a tunable vertical cavity surface emitting laser (VCSEL). In some embodiments, the laser source 104 may be utilized to generate a treatment beam that delivers laser energy to a target in addition to a ranging beam. However, it will be understood that the laser system 102 may include one or more laser sources different from the laser source 104, such as in the optical components 112, to generate a treatment beam that delivers laser energy to a target. Thus, the optical components 112 may include one or more devices utilized to realize the embodiments described herein. For example, the optical components 112 may include, but are not limited to, one or more of the following, configured in various combinations: laser sources, polarizers, beam splitters, beam combiners, photodetectors, filters, wavelength division multiplexers, collimators, and circulators.

[0023] More generally, the laser light sources, or laser sources, are configured to generate laser light with specific and / or varying characteristics (e.g., intensity, wavelength, etc.) based on the application. In some embodiments, each laser light source can be designated for a different purpose, e.g., laser source 104 can generate a ranging beam with a linearly varying wavelength sweep, a second laser source can generate a low intensity beam for the purpose of aiming a treatment beam, and a third laser source can generate a high intensity treatment beam for delivering laser energy to a target. Furthermore, each laser light source can have the same or different apertures. Additionally, each laser light source can be configured to generate polarized laser light or unpolarized / depolarized light.

[0024] A polarizer can include an optical component that functions as an optical filter. For example, a polarizer can be configured to pass light of a particular polarization and block light of a different polarization. Thus, when undefined light (or light of mixed polarizations) is provided as input to a polarizer, the polarizer provides a single, well-defined, polarized light as output.

[0025] A beam splitter may include optical components that are used to split an incident light into two separate beams in a specified ratio. Furthermore, a beam splitter may be positioned to manipulate the light to make it incident at a desired angle of incidence (AOI). Therefore, in many embodiments, a beam splitter may be configured with two main parameters: split ratio and AOI. Split ratio comprises the ratio of reflection to transmission (reflection / transmission (R / T) ratio) of the beam splitter. Thus, as used herein, if a beam splitter has a split ratio of 50:50, this means that the beam splitter splits the incident light beam with a 50:50 R / T ratio. In other words, a beam splitter splits an incident light beam by modifying the incident light by reflecting 50% of the incident light and transmitting the remaining 50%. Further, as an example, if the AOI of a beam splitter is shown as 45 degrees, this means that for a light beam incident on the beam splitter at 45 degrees, it transmits a portion of the incident light while reflecting the remainder of the incident light at 90 degrees. Beam splitters can include, but are not limited to, polarizing beam splitters and non-polarizing beam splitters. Polarizing beam splitters can split incident light based on S and P polarization components, such as by reflecting the S polarization component of light and transmitting the P polarization component of light (or vice versa). In some embodiments, non-polarizing beam splitters can split incident light based on a particular R / T ratio while maintaining the original polarization state of the incident light.

[0026] The beam combiner can include a partial reflector that combines two or more wavelengths of light, such as by using the principles of transmission and reflection described above. In many embodiments, the beam combiner can be a combination of beam splitters and mirrors that function to combine two or more wavelengths of light.

[0027] A photodetector, or simply a detector, can include a device that detects and / or measures a characteristic of a light beam and encodes the detected and / or measured characteristic into an electrical signal (e.g., a detection signal). For example, a photodetector detects a particular type of light beam (predetermined) and converts the optical energy associated with the detected light beam into an electrical signal. In some embodiments, wavelength division multiplexing can include a technique for combining multiple optical carrier signals onto a single optical fiber while using laser light of different wavelengths. In various embodiments, the detector 108 can include a high-speed detector such as an interferometer or a photodiode. For example, the detector 108 can include a photodiode with an intrinsic (i.e., undoped) region between an n-doped region and a p-doped region (referred to as a PIN photodiode). In another example, the detector 108 can include an avalanche photodiode.

[0028] A collimator can include a device that narrows a beam of light. To narrow the beam of light, the collimator can be configured to make the direction of motion more aligned in a particular direction (e.g., parallel beams) or to reduce the spatial cross-sectional area of ​​the beam of light. In many embodiments, a collimator can be used to change diverging light from a point source into a parallel beam.

[0029] A circulator may include a multi-port optical device configured to receive and emit light through a predetermined sequence of ports. For example, a circulator may include a three-port (or four-port, or five-port, etc.) optical device designed such that light entering any one port exits the next port. In one such example, light entering a first port may exit a second port, light entering the second port may exit a third port, and light entering the third port may exit the first port. Circulators are often used to direct light beams in only one direction.

[0030] It should be noted that where specific parameters are listed for the optical components described herein, such as a beam splitter with a 50:50 R / T ratio and a 45 degree AOI, these parameters are provided for a general understanding of the disclosed concepts and are not intended to be limiting. As a specific example, various embodiments described herein may have beam splitters with R / T ratios and / or AOIs different from those set forth herein without departing from the scope of the present disclosure and claims. In one such example, an AOI of 40 degrees may be utilized. In another example, an R / T ratio of 90:10 may be utilized.

[0031] 2 illustrates various aspects of a laser system 200 in accordance with one or more embodiments described herein. The illustrated embodiment includes a laser system 200 and a target 218. The laser system 200 includes a laser source 204, a beam splitter 226, a beam combiner 230, a lens 232, an optical fiber 206 with a proximal end 220 and a distal end 222, a detector 202, a controller 212, and a number of additional optical components 228a, 228b, 228c, 228d, 228e, 228f, 228g. The target 218 can be located a distance 224 from a distal end 222 of the optical fiber 206. In various embodiments, the laser system 200 can function to determine the distance 224 between the distal end 222 of the optical fiber 206 and the target 218.

[0032] In operation, the laser source 204 can generate a ranging beam 216, and the beam splitter 226 can redirect a portion of the ranging beam 216 toward the detector 202 as the reference signal 208 and pass the remaining portion of the ranging beam 216 toward the proximal end 220 of the optical fiber 206. The combiner 230 can operate to combine the treatment beam 234 with the ranging beam 216. It should be understood that the source of the treatment beam is not shown for simplicity. The lens 232 can operate to focus the combined beam onto the proximal end 220 of the optical fiber 206. In some embodiments, the controller 212 can control the generation of the ranging beam 216 by the laser source 204. In the illustrated embodiment, the mirrors 228a, 228b, 228c, and the lens 228d can operate in conjunction with the beam splitter 226 to direct the reference signal 208 onto the detector 202. However, it will be appreciated that various configurations can be utilized to direct the reference signal 208 onto the detector 202 without departing from the scope of the present disclosure. The remaining portion of the ranging beam 216 enters the proximal end 220 of the optical fiber 206 and exits from the distal end 222 of the optical fiber 206, where a portion of the ranging beam 216 can be reflected from the distal end 222 and another portion of the ranging beam 216 can impinge on the target 218. The portion of the ranging beam 216 that impinges on the target 218 can be reflected back into the distal end 222 of the optical fiber 206 as the return signal 210. In the illustrated embodiment, the mirrors 228e, 228f, 228g, and the lens 228d can work in conjunction with the beam splitter 226 to direct the return signal 210 onto the detector 202. However, it will be appreciated that various configurations can be utilized to direct the return signal 210 onto the detector 202 without departing from the scope of the present disclosure.

[0033] Thus, the reference signal 208 and the return signal 210 may be mixed to form an interference pattern on the detector 202, such as by heterodyne optical mixing. The detector 202 may generate a detection signal 214 in response to measuring the mixed reference signal 208 and return signal 210. In many embodiments, the detection signal 214 may have a frequency proportional to the distance the signal was reflected from. For example, the return signal 210 has traveled an additional distance, resulting in a delay relative to the reference signal 208, resulting in a wavelength difference between them. This wavelength difference may be linearly dependent on the distance traveled. In this case, the controller 212 may determine the distance 224 between the distal end 222 of the optical fiber 206 and the target 218 based on the detection signal 214. For example, the controller 212 may perform a Fourier analysis on the detection signal 214 to determine the distance 224 between the distal end 222 of the optical fiber 206 and the target 218.

[0034] An exemplary return signal evaluation is now described in further detail. This evaluation can be based on the following constants: the speed of light in a vacuum (c) is approximately 299792458 m / s; the refractive index of low hydroxyl (OH) glass (optical fiber), n f is approximately 1.48; the speed of light in the fiber, c / n f is approximately 202562471.6 m / s; the refractive index of saline (or water), n w is approximately 1.3347; the speed of light in saline (or water) is c / n w is approximately 224614114 m / s. The evaluation can be based on the following assumptions: base is about 1060 nm; the frequency ω of the fundamental laser wavelength base (c / λ base ) is approximately 2.82823 x 10 14 Hz; the laser wavelength pull-in range is about 1060-1065.5 nm (tuning range of about 5.5 nm); the wavelength scanning period is about 5.5 ms; and the frequency rate ω rate (Wavelength scanning range / scanning period) is approximately 2.65437×10 14Hz / s. In various embodiments, the frequency rate can be the primary parameter that defines the signal after frequency mixing.

[0035] As mentioned above, the signal arriving at the detector, which in the exemplary evaluation is called a photodiode or mixer, can include a reference signal (i.e., a local oscillator signal) and a return signal with the following reflected signals (fiber proximal end signal, fiber distal end signal, target signal, and other reflected source signals). The local oscillator signal S LO is defined by Equation 1 below: Formula 1: JPEG2025509496000002.jpg672

[0036] For the local oscillator signal, A LO is the amplitude (intensity) of the local oscillator (LO) signal delivered to the photodiode (mixer). The fiber proximal signal S FP is defined by Equation 2 below: Formula 2: JPEG2025509496000003.jpg889

[0037] At the fiber proximal end signal, A FP is the amplitude (intensity) of the fiber proximal end (FP) reflected signal delivered to the photodiode (mixer). Based on the refractive index of the glass fiber relative to that of air, 1.48, A FP = 0.0375. Fiber distal end signal S FD is defined by Equation 3 below: Formula 3: JPEG2025509496000004.jpg888

[0038] At the distal end of the fiber, A FD is the amplitude (intensity) of the fiber distal end (FD) reflected signal delivered to the photodiode (mixer). Based on the refractive index of glass fiber of 1.48 compared to that of water (saline) of 1.34, the intensity loss due to the reflection at the proximal end, A FD =0.0025×(1-A FP )=0.00237. The target signal ST is defined by Equation 4 below: Formula 4: JPEG2025509496000005.jpg882

[0039] In the target signal, A T is the amplitude (intensity) of the target return signal delivered to the photodiode (mixer). The signal reflected from the target can be calculated as the ratio of the area of ​​the fiber tip to the area of ​​the cone base created by the divergence of the beam multiplied by the reflection coefficient of the target. An exemplary calculation of this ratio can proceed as follows with reference to FIG. 4, where the portion of the ranging beam 408 reflected from the target 404 as the target reflection 410 can be calculated as the ratio of the area of ​​the tip 418 of the optical fiber 402 to the area of ​​the cone base 406 created by the divergence of the beam multiplied by the reflection coefficient of the target. For a fiber with a numerical aperture (NA) of 0.22, the divergence angle can be 0.166 Rad. Thus, the reflected spot diameter 414, D, from the target 404 at the tip 418 plane, where the tip 418 has a diameter 416, d, at the length 412, L, is defined by Equation 5 as shown below: Formula 5: JPEG2025509496000006.jpg542

[0040] Thus, if the optical fiber 402 has a diameter of 230 micrometers (μm), the above equation becomes 0.66×L+0.23 mm, and the area ratio is defined by Equation 6 below: Formula 6: JPEG2025509496000007.jpg656

[0041] Thus, as an example, for a 230 μm fiber, when L=1 mm, the ratio is 0.51, and for L=3 mm, the ratio is 0.32. The reflectivity, or more precisely, the reflectivity combined with the diffusion of light by the target surface, is assumed to be in the range of 10% to 90%. This means that A T is 0.03 × (1-A FP )×(1-A FD ) to 0.45 × (1-A FP)×(1-A FD ), that is, in the range of 0.03 to 0.43. This means that the target signal is about 12 to about 180 times higher than the signal from the proximal end (maximum difference of 45 dB).

[0042] Continuing with the evaluation of exemplary return signals, we now turn to signal mixing or detection. The behavior of a detector (photodiode) is a square law behavior for light intensity (linear for light power). Therefore, when multiple optical signals are incident on a detector, its output (current) will be determined by Equation 7, shown below: Formula 7: JPEG2025509496000008.jpg1424

[0043] Thus, for the signals listed above, the output will be defined by Equation 8 below: Formula 8: JPEG2025509496000009.jpg544

[0044] This is equivalent to Equation 9 below: Formula 9: JPEG2025509496000010.jpg11166

[0045] Furthermore, each component is of a basic type as shown in Equation 10 below: Equation 10: JPEG2025509496000011.jpg7148

[0046] Using the cosine multiplication formula, Equation 10 becomes Equation 11, shown below: Equation 11: JPEG2025509496000012.jpg18166

[0047] The interpretation of these general results is as follows: (1) The sum part of the multiplication result is that the fundamental frequency is 2 × ω base and is not sensed by the photodiode. (2) The difference part of the multiplication is proportional to the distance difference between the reflectors at a frequency ω rateGenerate a current from the photodiode at (Δt1-Δt2). Since we are only measuring frequency (and possibly amplitude), we can ignore phase.

[0048] As a result, after these assumptions, the sensed current is defined by Equation 12 below. Equation 12: JPEG2025509496000013.jpg6773

[0049] Thus, each of the first six rows in the above equation represents a frequency proportional to the distance difference between the reflectors. The following table, Table 1, shows the resulting frequencies for a 2.5 m fiber, assuming: propagation in air (from the interference optics to the proximal end) is 0.2 m; the fiber length is 2.5 m; the fiber tip to target distance is 1 mm; the laser wavelength is 1060 nm; the scan range is 5.5 nm; and the scan rate is 5.5 ms. TIFF2025509496000014.tif66153

[0050] The signal of interest (target vs. distal end frequency difference) is clearly separated in frequency from the other signals as shown in Table 1. Table 2 below shows the results when the fiber length is adjusted from 2.5m to 2m. TIFF2025509496000015.tif66153

[0051] For a target with low reflectivity (0.03), assuming a local oscillator feedback signal (reference signal) amplitude of 0.01 (1%), the signal amplitude calculations are shown in Table 3 below: TIFF2025509496000016.tif39153

[0052] For low reflectivity, the signal amplitude from the target to the fiber tip is 3.5550×10 -5The direct current (DC) level amplitude (i.e., the sum of all amplitudes on the diagonal) is 0.001206. The ratio of the DC component to the fiber tip-to-target component is approximately 34, or 30.6 decibels (dB). For a target with high reflectivity (0.45), and assuming a local oscillator feedback signal amplitude of 0.01 (1%), the signal amplitude calculations are shown in Table 4 below: TIFF2025509496000017.tif39153

[0053] For high reflectivity, the signal amplitude from the target to the fiber tip is 5.3325×10 -4 The DC level amplitude (sum of all amplitudes on the diagonal) is 0.001206. The ratio of DC component to fiber tip-to-target component is approximately 191, or 45.6 dB. As can be seen from these tables, the main contributor to the DC component is the target reflection, which is in the range of 30-45 dB higher than the signal. This level is easily determined at the signal processing level, but can also be removed with a high pass filter at the analog stage.

[0054] Continuing with the evaluation of an exemplary return signal, signal processing and measurement will now be described. To measure the frequency of the reflection, the signal needs to be sampled at 24 MHz. This provides 128K points for the Fast Fourier Transform (FFT) calculation and a bin resolution of 366 Hz.

[0055] For fiber tip-target measurements, a frequency range from about 300 Hz to about 12,000 Hz (distances of 0.13 to 5 mm) should be examined to find the maximum. The frequency of the maximum corresponds to the fiber tip-target distance. This value should also be compared to a threshold, such as 12,000 Hz, that excludes the possibility that the target reflection is not present.

[0056] The frequencies of other reflection points can also be isolated and found, in which case measuring their amplitude may provide some information about the condition of the reflecting surface in terms of one or more of the following: the condition of the proximal end, the length of the fiber, the condition of the distal end, the reflectivity of the target (combined with information about the target distance), and unwanted reflections indicating a broken fiber.

[0057] As for interference from other sources, in principle, all 90° reflective surfaces will produce reflections, and all these reflections will mix between them, producing frequencies proportional to the distance between them, with amplitudes that are multiplications of their amplitudes. For example, a lens will produce some small reflections from both sides (specular reflections from a single point), but since these surfaces are about 3mm apart, they will produce frequencies in the same range as the fiber tip-target, interfering with the measurement. This example shows that any two surfaces with a distance between them within a few millimeters will result in an interference signal.

[0058] However, the signals of interest will be centered around frequencies that correspond to the length of the fiber. These will be the highest frequency signals. Therefore, the following procedure can be used to avoid interfering signals: The spectrum can be scanned from the highest frequency (half the sampling rate) down and the first peak higher than a predefined threshold can be identified. In various embodiments, the predefined threshold can be determined based on the length of the fiber. In some embodiments, the length of the fiber can be determined as the length of the manufactured fiber. In another embodiment, the length can be determined by direct measurement once the fiber is spliced ​​and there is no target reflection (e.g., the fiber tip is in air).

[0059] After identifying the first peak above a predefined threshold, the signal can be filtered using a bandpass filter around that frequency. More generally, the bandpass filter can remove frequencies from the signal that are greater than a first threshold and less than a second threshold. The remaining signal can then be squared to generate frequencies related to the difference and sum of the signals under consideration (as in the operation of photodiodes). A lowpass filter can then be used on the resulting signal to remove the sum component of the mixed signal. Finally, the frequency of the remaining signal can be estimated, which is directly proportional to the fiber tip-target distance.

[0060] Exemplary operating points of the laser system 200 may include the following: The laser source 204 may include a directly controlled regulated laser diode with a wavelength of 1060 nanometers (nm), a tuning range of 5.5 nm, and a sweep time of 5.5 milliseconds (ms). For example, the laser system 200 may include a pigtailed fiber laser with a wavelength tuning range of 30 or 50 nm and a minimum output power of 0.1 milliwatts (mW). The optical fiber 206 is 2.5 meters (m) long and the distance 224 from the distal end 222 of the optical fiber 206 to the target 218 is 1 millimeter (mm). Thus, the ranging beam 216 may travel 20 centimeters (cm) in air, 2.5 meters in the optical fiber 206, and 1 millimeter in water to reach the target 218. These parameters allow for a proximal end reflection of 354 kilohertz (kHz), a distal end reflection of 6.9061 megahertz (MHz), and a target reflection of 6.9085 MHz. The resulting frequency difference between the distal tip 222 and the target 218 is 2.363 kHz.

[0061] In embodiments utilizing a direct sampling approach without mixing in the reference signal 208, the sampling rate may be 24 MHz (Nyquist limit is 14 MHz) and the controller 212 may perform a 128K (131,072) point FFT with a frequency resolution (FFT bin size) of 366 Hz, resulting in a distance resolution of 0.155 mm. In some such embodiments, the processing time for a 128K FFT may be approximately 4 ms.

[0062] In other embodiments, a superheterodyne approach can be used. In such an approach, the near-end reflection measurement may be sacrificed, filtered out, such as by a high-pass filter, or processed separately. The filtered signal can be mixed (heterodyned) with the local signal to reduce the frequency of the main signal. The lower limit of the heterodyne frequency may be constrained by the lower signal frequency that needs to be preserved. For 2m of fiber, the far-end reflection can generate a frequency of 5.7MHz. Therefore, a local oscillator frequency of 5MHz can be used. The resulting frequency of the far-end / target reflection is approximately 2MHz, and a sampling rate of 6MHz can be used. This allows the FFT to be reduced to 32,768 points, reducing the computational burden compared to the direct sampling approach.

[0063] In some embodiments, wavelength tuning can be by diode current. However, using current to control wavelength can result in a limited tuning range compared to other devices. For example, linearly scanning the current from 100 milliamps (mA) to 450 mA results in a tuning range of 0.4 nm, but the scan time is 0.4 ms to achieve the same frequency change rate as the pigtail fiber laser described above. However, this is too short to sample the number of points required for the FFT. Therefore, in various embodiments, the scans can be chained together repeatedly to achieve the required number of points (14 times based on 0.4 nm and 0.4 ms).

[0064] Accordingly, the selection of a suitable laser source may include a number of considerations. Considerations when selecting a directly controlled adjustable laser configuration may include one or more of the following: convenient wavelength scanning control, constant power over the entire scan, variations in scanning linearity and power output stability may increase the linewidth in the Fourier domain and reduce distance resolution, some power output levels (e.g., 0.1 mW) may result in weaker reflected signals, and an avalanche photodiode and / or higher amplification may be required instead of a PIN photodiode. Considerations when selecting a diode current laser configuration for wavelength tuning may include one or more of the following: current-varying wavelength pulling may be a fundamental characteristic, changes in power level during the pulse may increase the linewidth in the Fourier domain, and higher power levels may cause eye safety issues and the need for much higher operating currents compared to a directly controlled adjustable laser configuration. Changes in power level during the pulse that result in an increase in the Fourier domain linewidth in the case of wavelength tuning with a diode current laser configuration may be mitigated by increasing the frequency change rate (faster scanning), which may improve the fiber tip-target frequency separation. Additionally, shifting to a different wavelength (eg, from 1060 nm to 1350 nm) can reduce eye safety concerns.

[0065] 3 illustrates various aspects of a laser system 300 in accordance with one or more embodiments described herein. The illustrated embodiment includes a laser system 300 and a target 316. The laser system 300 includes a laser source 304, a beam splitter 318, an optical fiber 306, a detector 302, and a controller 310. In various embodiments, the laser system 300 can function to determine a distance between a distal end of the optical fiber 306 and the target 316. In operation, the laser source 304 can generate a ranging beam 314 that passes through the beam splitter 318 and travels through the optical fiber 306 onto the target 316. In some embodiments, the controller 310 can control the generation of the ranging beam 314 by the laser source 304. A portion of the ranging beam 314 can be reflected from the fiber distal end and the target 316 and returned into the optical fiber 306 as a return signal 308. The return signal 308 can pass through the optical fiber 306 and be directed by the beam splitter 318 towards the detector 302. The detector 302 generates a detection signal 312 based on measuring the remaining portion of the return signal 308, and the controller 310 can perform a frequency analysis on the detection signal 312 to determine the distance between the target 316 and the distal end of the optical fiber 306. It will be appreciated that various configurations can be utilized to direct the ranging beam 314 onto the target 316, filter the return signal 308, and direct the return signal 308 onto the detector 302 without departing from the scope of the present disclosure.

[0066] The return signal 308 may include reflections from various sources, such as the proximal and distal ends of the optical fiber 306, as well as reflections from the target 316. By mixing all of the signals present at the detector, the detection signal 312 includes frequencies that are a direct result of mixing the reflected signal from the distal end of the optical fiber 306 with the reflected signal from the target 316. More generally, mixing produces a signal that is the sum of the original signal frequencies (which are then filtered out), and the remaining frequency difference is measured. Thus, by using frequency modulation of the transmission signal to measure the frequency in the detection signal 312 produced by the detector 302, the controller 310 can detect a frequency that is proportional to the distance between the distal end of the optical fiber 306 and the target 316. This can be achieved without the step of mixing on a reference signal as described with respect to the laser system 200. Without the step of mixing on a reference signal (part of the ranging beam 314), Equation 12 above reduces to Equation 13 shown below: Equation 13: JPEG2025509496000018.jpg3565

[0067] Furthermore, the fiber proximal-fiber distal and fiber proximal-target frequencies will be higher than the fiber distal-target frequency of the signal of interest because the associated distances of the fiber proximal-fiber distal and fiber proximal-target are greater. For example, the associated distances of the fiber proximal-fiber distal and fiber proximal-target may be on the order of 2.5 m, whereas the associated distances of the fiber distal-target may be on the order of a few millimeters. Thus, the fiber proximal-fiber distal and fiber proximal-target frequencies can be easily filtered out, such as by using signal processing hardware (analog or digital) and software. However, since the laser system 300 is not mixed into the reference signal, the optical design must ensure that there are no reflections of the same level as the fiber distal-target signal in the measurement system, where the distance between reflections is several millimeters. This can be achieved by using an optical design that places reflective optical surfaces at an angle to prevent them from reflecting back to the detector and / or coats them with an appropriate anti-reflective coating that reduces such signals.

[0068] Further, the laser system 300 can be used when the only information required is the fiber tip-to-target distance. In addition, the laser system 300 may be more economically feasible than the laser system 200. In various embodiments, the laser system may utilize a bandpass filter about the first peak frequency mentioned above, above a predetermined threshold determined based on the length of the fiber. One example may include an analog level bandpass filter for a frequency range of 300 Hz to 24,000 Hz (corresponding to a distance of 0.13 mm to 10 mm). In such an example, the remaining signal may be sampled at a frequency of 93,750 Hz (1 / 256 of the original frequency). This results in 512 samples within a 5 ms sweep time, and performing a 512-point FFT will provide the same distance resolution as described above with respect to FIG. 2.

[0069] 5A and 5B show aspects of the reflection frequency according to one or more embodiments described herein. More specifically, FIG. 5A shows aspects of the theoretical reflection frequency 500a, and FIG. 5B shows aspects of the actual reflection frequency 500b. Each of the theoretical reflection frequency 500a and the actual reflection frequency 500b includes a proximal fiber reflection 502a, 502b, a distal fiber reflection 504a, 504b, and a target reflection 506a, 506b. The frequency difference between the distal fiber reflection and the target reflection is proportional to the distance between the optical fiber distal end and the target. As shown in FIG. 5A, at the theoretical reflection frequency 500a, the value of each reflection is discrete. However, as shown in FIG. 5B, at the actual reflection frequency 500b, the value of each reflection is spread out. This spread can be caused by a number of factors, such as undesired amplitude modulation of the transmitted light intensity, nonlinearity of the frequency modulation, generation of new modes in the multimode delivery fiber, and their different propagation times. Therefore, the actual range resolution may be determined by these effects.

[0070] 6 illustrates a logic flow 600 for estimating a distance between an optical fiber distal end and a target in accordance with one or more embodiments described herein. More specifically, logic flow 600 may be directed to detection including mixing with a reference signal traveling a certain short local path (see, e.g., FIG. 2). Logic flow 600 may represent some or all of the operations that may be performed by one or more components / devices / systems described herein, such as one or more portions of laser system 102, laser system 200, and / or laser system 300. The embodiments are not limited in this context.

[0071] In the illustrated embodiment, logic flow 600 may begin at block 602. At block 602 “Generate a ranging beam with a laser source, the ranging beam including a linearly varying wavelength sweep”, a ranging beam with a linearly varying wavelength sweep may be generated with a laser source. For example, laser source 204 may generate ranging beam 216 with a linearly varying wavelength sweep. Proceeding to block 604 “Identify a detection signal generated by a detector based on measuring at least one reflection of the ranging beam from a target and at least one reflection of the ranging beam from a distal end of the optical fiber”, a detection signal generated by a detector may be identified based on measuring at least one reflection of the ranging beam from the target and at least one reflection of the ranging beam from a distal end of the optical fiber. For example, the controller 212 can identify the detection signal 214 generated by the detector 202 based on measuring a return signal 210 that comprises, at least in part, at least one reflection of the ranging beam 216 from the target 218 and at least one reflection of the ranging beam 216 from the distal end 222 of the optical fiber 206.

[0072] At block 606 “Analyze the detection signal to determine first and second frequency components, where the first frequency component corresponds to at least one reflection of the ranging beam from the target and the second frequency component corresponds to at least one reflection of the ranging beam from the distal end of the optical fiber”, the detection signal can be analyzed to determine a first frequency component corresponding to at least one reflection of the ranging beam from the target and a second frequency component corresponding to at least one reflection of the ranging beam from the distal end of the optical fiber. For example, the controller 110 can identify a detection signal comprising a frequency component of a distal fiber reflection 504b corresponding to a reflection of the ranging beam from the distal end of the optical fiber 106 and a frequency component of a target reflection 506b corresponding to a reflection of the ranging beam from the target. Proceeding to block 608 “Determine a distance between the distal end of the optical fiber and the target based on the first and second frequency components”, the distance between the distal end of the optical fiber and the target can be determined based on the first and second frequency components. For example, the controller 212 can determine the distance 224 based on the distal fiber reflection 504b and the target reflection 506b.

[0073] 7 illustrates a logic flow 700 for estimating a distance between an optical fiber distal end and a target according to one or more embodiments described herein. More specifically, logic flow 700 may be directed to detection including mixing between all signals (without a reference signal) present on a detector according to a square law (see, e.g., FIG. 3). Logic flow 700 may represent some or all of the operations that may be performed by one or more components / devices / systems described herein, such as one or more portions of laser system 102, laser system 200, and / or laser system 300. The embodiments are not limited in this context.

[0074] In the illustrated embodiment, logic flow 700 may begin at block 702. At block 702 “Generate a ranging beam with a laser source, the ranging beam including a linearly varying wavelength sweep”, a ranging beam with a linearly varying wavelength sweep may be generated with a laser source. For example, laser source 304 may generate ranging beam 314 with a linearly varying wavelength sweep. Proceeding to block 704 “Identify a detection signal generated by a detector based on measuring at least one reflection of the ranging beam from a target and at least one reflection of the ranging beam from a distal end of the optical fiber”, a detection signal generated by a detector may be identified based on measuring at least one reflection of the ranging beam from the target and at least one reflection of the ranging beam from a distal end of the optical fiber. For example, the controller 310 can identify the detection signal 312 generated by the detector 302 based on measuring the return signal 210, which comprises, at least in part, at least one reflection of the ranging beam 314 from the target 316 and at least one reflection of the ranging beam 314 from the distal end of the optical fiber 306.

[0075] At block 706 “Analyze the detection signal to determine frequency components corresponding to at least one reflection of the ranging beam from the target and at least one reflection of the ranging beam from the distal end of the optical fiber”, the detection signal may be analyzed to determine frequency components corresponding to at least one reflection of the ranging beam from the target and at least one reflection of the ranging beam from the distal end of the optical fiber. For example, the controller 310 may identify frequency components in the return signal corresponding to a reflection of the ranging beam 314 from the distal end of the optical fiber 306 and a reflection of the ranging beam 314 from the target 315. Proceeding to block 608 “Determine a distance between the distal end of the optical fiber and the target based on the frequency components”, the distance between the distal end of the optical fiber and the target may be determined based on the first and second frequency components. For example, the controller 310 may determine a distance between the distal end of the optical fiber 306 and the target 316 based on the frequency components in the detection signal 312.

[0076] 8 illustrates a block diagram of an exemplary computer system 802 for implementing embodiments consistent with the present disclosure. In some embodiments, the computer system 802, or one or more portions thereof, may comprise a controller (e.g., controller 110, 212, 310) in a laser system (e.g., laser system 102, 200, 300). Thus, in various embodiments, the computer system 802 may perform frequency analysis on a detection signal (e.g., detection signal 214, 312) generated by a detector (e.g., detector 108, 202, 302) based on measurements of one or more signals (e.g., return signal 210, 308 and / or reference signal 208). In various such embodiments, the computer system 802 may be utilized to control operation of a laser system (e.g., laser system 102, 200, 300), such as based on a distance to a target determined based on the frequency analysis. The embodiments are not limited in this context.

[0077] The computer system 802 may include a central processing unit ("CPU" or "processor") 804. The processor 804 may include at least one data processor for executing instructions and / or program components for executing user or system generated processes. A user may include a person, a person using a device as included in this disclosure, or such a device itself. The processor 804 may include special purpose processing units such as an integrated system (bus) controller, a memory management control unit, a floating point unit, a graphics processing unit, a digital signal processing unit, etc. The processor 804 may be arranged to communicate with input devices 822 and output devices 824 via an I / O interface 820. The I / O interface 820 may employ communications protocols / types such as audio, analog, digital, stereo, IEEE-1394, serial bus, Universal Serial Bus (USB), infrared, PS / 2, BNC, coaxial, component, composite, Digital Visual Interface (DVI), High-Definition Multimedia Interface (HDMI®), radio frequency (RF) antenna, S-Video, Video Graphics Array (VGA), IEEE 802.n / b / g / n / x, Bluetooth, cellular (e.g., Code Division Multiple Access (CDMA), High Speed ​​Packet Access (HSPA+), Global System for Mobile Communications (GSM), Long Term Evolution (LTE), WiMAX, etc.), and the like.

[0078] Using the I / O interface 820, the computer system 802 can communicate with input devices 822 and output devices 824. In some embodiments, the processor 804 can be arranged to communicate with a communication network 826 via a network interface 806. In various embodiments, the communication network 826 can be utilized to communicate with a remote device 828, such as to access a lookup table, perform updates, or utilize external resources. The network interface 806 can communicate with the communication network 826. The network interface 806 can employ connection protocols including, but not limited to, direct connection, Ethernet (e.g., twisted pair 10 / 100 / 1000 Base T), Transmission Control Protocol / Internet Protocol (TCP / IP), Token Ring, IEEE 802.11a / b / g / n / x, and the like. In some embodiments, one or more portions of the computer system 802 can be integrated into a laser system (e.g., laser systems 102, 200, 300). In some such embodiments, one or more components of the laser system may include one or more of the input devices 822 and / or one or more of the output devices 824 (e.g., laser source 104, detector 108, etc.).

[0079] The communication network 826 may be implemented as one of various types of networks, such as an intranet or local area network (LAN), a closed area network (CAN), etc. The communication network 826 may be either a dedicated network or a shared network, and may represent a confluence of various types of networks that communicate with each other using various protocols, such as, for example, HyperText Transfer Protocol (HTTP), CAN protocol, Transmission Control Protocol / Internet Protocol (TCP / IP), Wireless Application Protocol (WAP), etc. Additionally, the communication network 826 may include various network devices, such as routers, bridges, servers, computing devices, storage devices, etc. In some embodiments, the processor 804 may be arranged to communicate with a memory 810 (e.g., RAM, ROM, etc., not shown in FIG. 12 ) via a storage interface 808. The storage interface 808 can connect to memory 810 including, but not limited to, memory drives, removable disk drives, etc., employing connection protocols such as Serial Advanced Technology Attachment (SATA), Integrated Drive Electronics (IDE), IEEE-1394, Universal Serial Bus (USB), Fibre Channel, Small Computer System Interface (SCSI), etc. The memory drives can further include drum, magnetic disk drives, magneto-optical drives, optical drives, redundant array of independent disks (RAID), solid state memory devices, solid state drives, etc.

[0080] Memory 810 may store a collection of program or database components, including, but not limited to, a user interface 812, an operating system 814, a web browser 816, instructions 818, and the like. In various embodiments, instructions 818 may include instructions that, when executed by processor 804, cause processor 804 to perform one or more techniques, steps, procedures, and / or methods described herein, such as estimating distance. For example, instructions for executing logic flow 600 and / or logic flow 700 may be stored in memory 810. In many embodiments, memory 810 includes at least one non-transitory computer-readable medium. In some embodiments, computer system 802 may store user / application data, such as data, variables, records, preferences, and the like, as described in this disclosure. Such databases may be implemented as fault-tolerant, relational, scalable, and secure databases, such as Oracle or Sybase.

[0081] Operating system 814 can facilitate resource management and operation of computer system 802. Examples of operating systems include, but are not limited to, APPLE® MACINTOSH® OS X®, UNIX®, distributions of UNIX-like systems (e.g., BERKELEY SOFTWARE DISTRIBUTION® (BSD), FREEBSD®, NETBSD®, OPENBSD, etc.), distributions of LINUX® (e.g., RED HAT®, UBUNTU®, KUBUNTU®, etc.), IBM® OS / 2®, MICROSOFT® WINDOWS® (XP®, VISTA® / 7 / 8, 10, etc.), APPLE® IOS®, GOOGLE™ ANDROID™, BLACKBERRY® OS, etc. The user interface 812 may facilitate the display, execution, interaction, manipulation, or operation of program components through textual or graphical features. For example, the user interface may provide computer interaction interface elements, such as cursors, icons, checkboxes, menus, scrollers, windows, widgets, and the like, on a display system operatively connected to the computer system 802. Graphical user interfaces (GUIs) may be employed, including, but not limited to, Apple® Macintosh® operating systems Aqua®, IBM® OS / 2®, Microsoft® Windows® (e.g., Aero, Metro, etc.), web interface libraries (e.g., ActiveX®, Java®, JavaScript®, AJAX, HTML, Adobe® Flash®, etc.), and the like. In some embodiments, the user interface 812 may be integrated with the endoscope's display and / or user interface.

[0082] In some embodiments, computer system 802 may implement program components stored in a web browser 816. Web browser 816 may be a hypertext display application such as MICROSOFT® INTERNET EXPLORER®, GOOGLE™ CHROME™, MOZILLA® FIREFOX®, APPLE® SAFARI®, or the like. Secure web browsing may be provided using Secure Hypertext Transport Protocol (HTTPS), Secure Sockets Layer (SSL), Transport Layer Security (TLS), or the like. Web browser 816 may utilize functionality such as AJAX, DHTML, ADOBE® FLASH®, JAVASCRIPT®, JAVA®, application programming interfaces (APIs), or the like. In some embodiments, computer system 802 may implement program components stored in a mail server. The mail server may be an Internet mail server such as Microsoft Exchange. The mail server may utilize functionality such as Active Server Pages (ASP), ACTIVEX®, ANSI® C++ / C#, MICROSOFT®, .NET, CGI SCRIPTS, JAVA®, JAVASCRIPTS®, PERL®, PHP, PYTHON®, WEBOBJECTS®, etc. The mail server may utilize communication protocols such as Internet Message Access Protocol (IMAP), Messaging Application Programming Interface (MAPI), MICROSOFT® exchange, Post Office Protocol (POP), Simple Mail Transfer Protocol (SMTP), etc. In some embodiments, computer system 802 may implement a mail client stored program component.The mail client may be a mail viewing application such as APPLE® MAIL, MICROSOFT® ENTOURAGE®, MICROSOFT® OUTLOOK®, MOZILLA® THUNDERBIRD®, or the like.

[0083] Additionally, memory 810 may include one or more computer-readable storage media utilized in implementing embodiments consistent with the present disclosure. Generally, a computer-readable storage medium refers to any type of physical memory capable of storing information or data that can be read by a processor. Thus, a computer-readable storage medium may store instructions executed by one or more processors, including instructions that cause the processor(s) to execute steps or stages consistent with the embodiments described herein. The term "computer-readable medium" should be understood to include tangible items and exclude carrier waves and transitory signals, i.e., non-transitory. Examples include random access memory (RAM), read-only memory (ROM), volatile memory, non-volatile memory, hard drives, compact disc (CD) ROM, digital video disc (DVD), flash drive, disk, and any other known physical storage medium.

[0084] In various embodiments, the present disclosure may provide various technical advantages and improvements. For example, the present disclosure may enable estimation of the distance between the distal end of the optical fiber and the target by performing frequency analysis of the reflected or returned signal. Distance estimation based on frequency analysis may provide robustness with respect to different types of targets, target compositions, target colors, target surfaces, etc. The frequency analysis based techniques and systems disclosed in the present disclosure may provide for estimating the distance between the distal end of the optical fiber and the target and may facilitate accurate estimation of the distance. Furthermore, the present disclosure provides a process for estimating the distance between the distal end of the optical fiber and the target for different types of targets and may provide distance estimation for a greater variety of targets than previously possible. Thus, the present disclosure provides a system and method for targeting more accurately than previously possible. More accurate targeting may eliminate or reduce ablation and / or fragmentation of the wrong portion of the target (or non-target areas such as normal tissue) that may lead to harmful consequences and / or permanent damage. Additionally, more precise targeting will result in less time spent ablating and / or disrupting the target, resulting in a more efficient system.

[0085] In some embodiments, the present disclosure can be used to accurately position and / or aim a treatment beam in poor visibility environments (e.g., environments containing dust or target debris). For example, during treatment of a target (e.g., kidney stone), the water may become cloudy due to the presence of stone debris or dust. This may reduce (or prevent) the ability to see the target (e.g., kidney stone). In such scenarios, the present disclosure provides a system that accurately recognizes and notifies the treating physician of the placement of the optical fiber (e.g., whether the optical fiber is placed in front of the target or if the target is not detected).

[0086] Furthermore, in many embodiments, the present disclosure can be used for distance measurement. For example, a target (e.g., a kidney stone) may move during treatment, which may lead to the laser light associated with the treatment beam impinging on an undesired area (e.g., normal tissue, etc.) rather than on the target. Therefore, the present disclosure allows for automatic, real-time monitoring of the distance between the optical fiber and the target, which can reduce or eliminate the possibility of laser irradiating an undesired area.

[0087] Furthermore, in various embodiments, the present disclosure can be used to control and / or adjust one or more operating parameters. For example, the target may move back and forth or change its shape and size during treatment. Therefore, the effectiveness of the preset parameters for the laser source may be reduced before starting the laser irradiation on the target. Traditionally, such preset parameters are changed manually, which can be error-prone and time-consuming, or in some cases, the preset parameters are left unchanged, leading to a scenario where the optical fiber is too close or too far from the target. Therefore, as disclosed in the present disclosure, by automatically and in real time monitoring the distance between the optical fiber and the target, the preset parameters of the laser irradiation can be automatically changed to adjust the laser irradiation according to the shape, location, etc. of the target to obtain the best results.

[0088] With respect to the use of substantially any plural and / or singular terminology herein, one of skill in the art can substitute the plural for the singular and / or the singular for the plural, as appropriate to the context and / or application. Although the various singular and / or plural arrangements are expressly set forth herein, they are for purposes of clarity and not of limitation.

[0089] In general, those of skill in the art will understand that the terms used herein are intended to be generally "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "include" should be interpreted as "including but not limited to," etc.). Additionally, those of skill in the art will understand whether a particular number is intended with respect to the introductory claim recitation. For example, as an aid to understanding, the detailed description may include the use of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, even if the same claim includes the introductory phrase "one or more" or at least one and an indefinite article such as "a" or "an," the use of such phrases should not be construed as implying that the introduction of a claim statement with the indefinite article "a" or "an" limits any particular claim that includes such an introduced claim statement to a disclosure that includes only one such statement (e.g., "a" and / or "an" should generally be construed to mean "at least one" or "one or more"); the same applies to the use of definite articles used to introduce claim statements. Moreover, even if a specific number is explicitly recited with respect to an introduced claim statement, a person skilled in the art will recognize that such a statement should generally be construed to mean at least the recited number (e.g., the plain recitation "two recitations" without other modifiers generally means at least two recitations, or two or more recitations).

[0090] All of the devices and / or methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. Although the devices and methods of the present disclosure have been described in terms of preferred embodiments, it will be apparent to those skilled in the art that variations can be applied to the devices and / or methods, and to the steps or sequence of steps of the methods described herein, without departing from the concept, spirit and scope of the present disclosure. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the present disclosure as defined by the appended claims. [Explanation of symbols]

[0091] 200 Laser System 202 Detector 204 Laser Source 206 Optical Fiber 208 Reference Signal 210 Return signal 212 Controller 214 Detection signal 216 Distance Beam 218 Target 220 Proximal end of optical fiber 222 Distal end of optical fiber 224 Distance from the distal end of the optical fiber to the target 226 Beam Splitter 228a~c Mirror 228d Lens 228e~g mirror 230 Beam Combiner 232 Lens 234 Healing Beam

Claims

1. A laser source; and an optical fiber having a distal end configured to pass laser light from the laser source out of the distal end and to receive reflected laser light into the distal end; A detector; a controller having a processor and a memory; An apparatus comprising: The memory, when executed by the processor, generating a ranging beam with said laser source, said ranging beam including a linearly varying wavelength sweep; identifying a detection signal generated by the detector based on a measurement of a combination of a reference signal, at least one reflection of the ranging beam from a target, and at least one reflection of the ranging beam from a distal end of an optical fiber; analyzing the detection signal to determine frequency components corresponding to at least one reflection of the ranging beam from the target and at least one reflection of the ranging beam from a distal end of the optical fiber; determining a distance between the distal end of the optical fiber and the target based on the frequency components; An apparatus comprising instructions for causing a processor to:

2. 2. The apparatus of claim 1, wherein the laser source comprises a first laser source, and the instructions, when executed by the processor, further cause the processor to select an operating mode of a second laser source based on a distance between a distal end of the optical fiber and the target.

3. 2. The apparatus of claim 1, wherein the laser source comprises a first laser source, and the instructions, when executed by the processor, further cause the processor to generate a treatment beam with a second laser source when a distance between the distal end of the optical fiber and the target is within a threshold distance.

4. 2. The apparatus of claim 1, wherein the laser source comprises a first laser source, and the instructions, when executed by the processor, further cause the processor to stop generating the treatment beam with the second laser source when a distance between the distal end of the optical fiber and the target exceeds a threshold distance.

5. The device of any of claims 1 to 4, wherein the instructions, when executed by the processor, further cause the processor to generate one or more of an audio, tactile, and visual warning when the distance between the distal end of the optical fiber and the target exceeds a threshold distance.

6. The device of any one of claims 1 to 5, wherein the detection signal is generated by the detector based on measuring at least one reflection of the ranging beam from the target, at least one reflection of the ranging beam from a distal end of the optical fiber, and at least one reflection of the ranging beam from a proximal end of the optical fiber.

7. 7. The apparatus of claim 6, wherein the frequency components include a first frequency component, and the instructions, when executed by the processor, further cause the processor to analyze the detection signal to determine second and third frequency components, the second frequency component corresponding to at least one reflection of the ranging beam from a distal end of the optical fiber and at least one reflection of the ranging beam from the proximal end of the optical fiber, and the third frequency component corresponding to at least one reflection of the ranging beam from the target and at least one reflection of the ranging beam from the proximal end of the optical fiber.

8. 8. The apparatus of claim 7, wherein the instructions, when executed by the processor, further cause the processor to determine the first frequency component corresponding to the distance between at least one reflection of the ranging beam from the target and at least one reflection of the ranging beam from a distal end of the optical fiber based on the first frequency component being higher than the second and third frequency components.

9. An apparatus according to any preceding claim, comprising a filter configured to remove frequencies below a threshold corresponding to reflections of the ranging beam from a proximal end of the optical fibre.

10. Apparatus according to any preceding claim, comprising a bandpass filter arranged to remove frequencies above a first threshold and below a second threshold.

11. At least one non-transitory computer-readable medium having a set of instructions, In response to the set of instructions being executed by a processor circuit, generating a ranging beam with a laser source, the ranging beam including a linearly varying wavelength sweep; identifying a detection signal generated by a detector based on a measurement of a mixture of a reference signal, at least one reflection of the ranging beam from a target, and at least one reflection of the ranging beam from a distal end of an optical fiber; analyzing the detection signal to determine frequency components corresponding to at least one reflection of the ranging beam from the target and at least one reflection of the ranging beam from a distal end of the optical fiber; determining a distance between the distal end of the optical fiber and the target based on the frequency components; At least one non-transitory computer-readable medium that causes a processor circuit to perform the steps of:

12. 12. The at least one non-transitory computer-readable medium of claim 11, wherein the set of instructions, in response to execution by the processor circuit, further causes the processor circuit to generate one or more of an audio, tactile, and visual alert when a distance between the distal end of the optical fiber and the target exceeds a threshold distance.

13. 13. At least one non-transitory computer readable medium according to claim 11 or 12, wherein the set of instructions, in response to execution by the processor circuit, further causes the processor circuit to perform a Fourier analysis on the detection signal to determine the frequency components.

14. At least one non-transitory computer readable medium according to any of claims 11 to 13, wherein the set of instructions, in response to execution by the processor circuit, further causes the processor circuit to remove frequencies from the detection signal that are greater than a first threshold and less than a second threshold.

15. At least one non-transitory computer readable medium according to any of claims 11 to 14, wherein the set of instructions, in response to execution by the processor circuit, further causes the processor circuit to filter out at least a portion of the detection signal based on a reflection frequency associated with a proximal end of the optical fiber.

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