KR20250007671A - Method and system for estimating the distance between a fiber end and a target - Google Patents

Abstract

The present invention relates to the field of fiber feedback (FFB) technology, and provides a method and system for estimating the distance between a fiber end and a target. The method comprises the steps of illuminating a target with laser light of different wavelengths having low and high water absorption coefficients by a light emission, transmission and detection (LETD) system using different laser sources, receiving returned signals corresponding to the incident laser light of different wavelengths, and detecting the returned signals to measure an intensity value of the returned signal of a specific wavelength. Using the measured intensity value, a processing unit can estimate the distance between the fiber end and the target. The present invention enables accurate estimation of the distance between the fiber end and the target. The present invention also provides a robust distance estimation technique that is compatible with different types of targets.

Description

Method and system for estimating the distance between a fiber end and a target

Cross-reference to related applications

This application claims the benefit of and priority to U.S. Provisional Application No. 63/341,654, filed May 13, 2022, entitled "Method and System for Estimating Distance Between a Fiber End and a Target," which is incorporated herein by reference in its entirety. This application claims the benefit of U.S. Provisional Application No. 63/118,857, filed November 27, 2020, entitled "Method and System for Estimating Distance Between a Fiber End and a Target," U.S. Provisional Patent Application No. 63/118,117, filed November 25, 2020, entitled "Apparatus and Method for Enhancing Laser Beam Efficacy in a Liquid Medium," and U.S. Provisional Patent Application No. 63/252,830, filed November 25, 2020, entitled "Method and System for Estimating Distance Between a Fiber End and a Target," which is incorporated herein by reference in its entirety. This application claims the benefit and priority of U.S. patent application Ser. No. 17/535,172, filed Nov. 24, 2021, entitled “Method and System for Estimating Distance Between a Fiber End and a Target,” which is filed Oct. 6, 2021, all of which are incorporated herein by reference in their entirety.

Technical field

The present invention relates generally to optical systems and optical fibers used in medical or therapeutic laser treatment. In particular, but not exclusively, the present invention relates to methods and systems for estimating the distance between a fiber end and a target.

The introduction of lasers into the medical field and the development of fiber optic technology using lasers have enabled a wide range of applications in treatment, diagnosis, and therapy. These applications range from invasive and non-invasive treatments to endoscopic surgery and imaging. For example, in the treatment of urinary stones, stones must be fragmented into smaller pieces. A technique known as laser lithotripsy can be used for this fragmentation process, in which a rigid or flexible ureteroscope is placed through the ureteroscope to illuminate and image small to medium-sized urinary stones. At the same time, an optical fiber is inserted through the working channel of the ureteroscope into the target location (e.g., where the stone is located in the bladder, ureter, or kidney). The laser is then activated to fragment or pulverize the stone into smaller pieces. In other cases, laser and fiber optic technologies are used in coagulation or ablation treatments. During ablation, laser light is delivered to the tissue to vaporize it. During coagulation, laser light is used to induce thermal damage within the tissue. These ablative treatments can be used to treat a variety of clinical conditions, such as benign prostatic hyperplasia (BPH), cancers, such as prostate cancer, liver cancer, lung cancer, and to treat heart disease by ablating and/or coagulating portions of heart tissue.

These treatments using laser and fiber optic technology require high accuracy to ensure that the laser targets the correct target (stone, tissue, tumor, etc.) to achieve clinical objectives such as tissue ablation, coagulation, stone fragmentation, and pulverization. Therefore, it is important to know the distance between the target where the laser light is emitted and the end (distal end) of the fiber optic, 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 end of the fiber to the target.

One of the existing techniques for estimating the distance between the distal end of an optical fiber and a target is to measure and compare the intensity values of the reflected wave of an optical beam, where the optical beam is transmitted through an optical fiber by modulating the numerical aperture of the optical beam. However, it is not always convenient to shift the numerical aperture of the optical beam. Moreover, it is difficult to separate the reflected waves of optical beams of different numerical apertures required in these techniques.

This Summary section is provided to introduce, in simplified form, selected concepts that are further described in the Detailed Description below. This Summary section is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be an aid in determining the scope of the claimed subject matter.

In one embodiment, a system comprises: a first laser source for generating laser light of a first wavelength; a second laser source for generating laser light of a second wavelength; an optical fiber having a distal end and a proximal end, the optical fiber configured to receive laser light from the first and second laser sources at the proximal end, reflect a portion of the laser light at the proximal end, emit a portion of the laser light from the distal end, and receive the reflected laser light at the distal end; a first light detector for measuring intensity of the reflected light; a second light detector; a mirror for sending a portion of the laser light reflected at the proximal end to the second light detector, the second light detector measuring an intensity of the portion of the laser light reflected at the proximal end; And a system including a processor and a memory, wherein the memory includes instructions that, when executed by the processor, cause the processor to estimate a distance between a distal end of the optical fiber and a target based on an intensity of reflected light measured by a first light detector and an intensity of a portion of laser light reflected from the proximal end measured by a second light detector.

The system can include a first wavelength having a first water absorption coefficient greater than a second water absorption coefficient of the second wavelength.

The system can include a ratio of the first water absorption coefficient to the second water absorption coefficient of at least 2:1.

The system may include a first wavelength of about 1330 nm to about 1380 nm.

The system may include a second wavelength of about 1260 nm to about 1320 nm.

The system may include a third laser source for generating laser light of a third wavelength used to characterize a condition of the optical fiber, the third wavelength having a third water absorption coefficient higher than the first and second water absorption coefficients.

The system may include a third wavelength comprising a wavelength of about 1435 nm, about 2100 nm, or about 1870 nm to about 2050 nm.

The system may include a light detector configured to measure a first intensity value of reflected light corresponding to laser light of a first wavelength, and a second intensity value of reflected light corresponding to laser light of a second wavelength.

The system may further include causing the processor, when the command is executed by the processor, to compute a ratio of the first intensity value and the second intensity value; and to estimate a distance between a distal end of the optical fiber and a target based on the ratio of the first intensity value and the second intensity value.

The system may include at least one of the first and second laser sources comprising a polarization-maintaining pigtailed fiber laser, a single-mode pigtailed fiber laser or a free-space laser.

The system includes a wavelength division multiplexer (WDM) coupled to a proximal end of the optical fiber, wherein the WDM can include arranging laser light of a first wavelength and laser light of a second wavelength to enter the proximal end of the optical fiber at one or more of the same point and the same angle.

One embodiment may include a method, comprising: illuminating a target with laser light of a plurality of different wavelengths; receiving a first reflected light beam from the target via an optical fiber; receiving a second reflected light beam from a proximal end of the optical fiber; measuring intensities of the first and second reflected light beams using a plurality of optical detectors; and estimating a distance between a distal end of the optical fiber and the target based on the intensities of the reflected light beams measured using one or more optical detectors.

The method may include the step of emitting laser light of a plurality of different wavelengths through an optical fiber to illuminate a target.

The method may include the step of measuring a first intensity value of a reflected light beam corresponding to laser light of a first wavelength, and a second intensity value of the reflected light beam corresponding to laser light of a second wavelength.

The method may include the step of calculating a ratio of the first intensity value and the second intensity value; and the step of estimating a distance between a distal end of the optical fiber and a target based on the ratio of the first intensity value and the second intensity value.

One embodiment includes at least one non-transitory computer-readable medium comprising a set of instructions that, when executed by a processor circuit, cause the processor circuit to perform the steps of: determining a first intensity value based on a first reflected laser light corresponding to a laser source, wherein the first reflected laser light enters a proximal end of an optical fiber, exits a distal end of the optical fiber, reflects from a target, and enters the distal end of the optical fiber; determining a second intensity value based on a second reflected laser light corresponding to the laser source, wherein the second reflected laser light is reflected from the proximal end of the optical fiber; computing a ratio of the first intensity value and the second intensity value; and estimating a distance between the distal end of the optical fiber and the target based on the ratio of the first intensity value and the second intensity value.

At least one non-transitory computer-readable medium may further include instructions that, in response to the set of instructions being executed by the processor circuit, cause the processor circuit to further perform the steps of subtracting the first internal reflection value from the first measured intensity value to determine the first intensity value, and subtracting the second internal reflection value from the second measured intensity value to determine the second intensity value.

At least one non-transitory computer-readable medium may further include instructions that, in response to the set of instructions being executed by the processor circuit, cause the processor circuit to further perform the step of determining an internal reflection value based on a third reflected laser light corresponding to laser light of a third wavelength, wherein the laser light of the third wavelength exits a laser source and at least a portion of the third reflected laser light is reflected from a distal end of an optical fiber.

At least one non-transitory computer-readable medium may further include instructions that, in response to the set of instructions being executed by the processor circuit, cause the processor circuit to further perform the steps of comparing the internal reflectance value to a reference internal reflectance value; and adjusting an operating parameter of the processing beam based on the comparison of the internal reflectance value to the reference internal reflectance value.

At least one non-transitory computer-readable medium may further include instructions that, in response to the set of instructions being executed by the processor circuit, cause the processor circuit to further perform the steps of: comparing the internal reflectance value to a reference internal reflectance value; characterizing a condition of the optical fiber based on the comparison of the internal reflectance value to the reference internal reflectance value; and communicating an indication of the condition of the optical fiber via the user interface.

At least one non-transitory computer-readable medium may further include instructions that, in response to execution by the processor circuit, cause the processor circuit to further perform the step of communicating an indication of the estimated distance between the distal end of the optical fiber and the target through the user interface.

To facilitate identification of discussions of any particular element or action, the highest digit or digits in the reference number indicate the drawing number in which the element was first introduced.
Figure 1 illustrates a system according to one embodiment.
Figure 2 illustrates an optical fiber cable according to one embodiment.
Figure 3 illustrates a LETD system according to one embodiment.
Figure 4 illustrates another LETD system according to one embodiment.
Figure 5 illustrates another LETD system according to one embodiment.
Figure 6 illustrates another LETD system according to one embodiment.
Figure 7 illustrates another LETD system according to one embodiment.
Figure 8 illustrates another LETD system according to one embodiment.
Figure 9 illustrates another LETD system according to one embodiment.
FIG. 10 illustrates another LETD system according to one embodiment.
Figure 11 illustrates another LETD system according to one embodiment.
Figure 12 illustrates a method according to one embodiment.
Figure 13 illustrates another method according to one embodiment.
Figure 14 illustrates another method according to one embodiment.
FIG. 15 illustrates another LETD system according to one embodiment.
Figure 16 illustrates another method according to one embodiment.
Figure 17 illustrates another LETD system according to one embodiment.
FIG. 18 illustrates a computer-readable storage medium according to one embodiment.
Figure 19 illustrates another system according to one embodiment.

The present invention provides methods and systems for estimating the distance between an optical fiber tip and a target. It should be understood that the effectiveness of a treatment using a laser often depends on the relative position and orientation of the optical fiber tip with respect to the target. However, it is very difficult to determine or estimate the distance between the optical fiber tip and the target due to various factors such as movement of the optical fiber relative to the position and orientation within the body of the subject (e.g., patient), tissue environment, movement of the tissue, surface of the target, color of the target, pigment of the target, deterioration of the optical fiber tip during treatment, water irrigation, and turbid environment (e.g., due to dusting). Determining the distance between the optical fiber tip and the target is further complicated by the fact that the optical fiber tip is typically inserted into the body of the subject.

Incorrect estimation of the distance between the fiber tip and the target and incorrect estimation of the fiber tip orientation can result in aiming the laser at an area other than the target's region of interest. This can lead to unnecessary complications and, in some cases, can also cause permanent damage to certain parts of the target's tissues, organs, etc., rendering that part of the target's body dysfunctional. In some other scenarios, incorrect distance measurements and orientation can result in increased treatment duration or poor quality ablation/fragmentation. In some cases, such as BPH or cancer, if the tumor is not properly ablated, the tumor (or other undesirable tissue) can regrow, causing further complications. Therefore, as discussed above, it is important to accurately determine (or maintain) the distance between the fiber tip and the target while performing a particular treatment using laser and fiber technology.

The method comprises the steps of illuminating a target with laser light of different wavelengths having low and high water absorption coefficients using different laser sources, by a light emission, transmission and detection (LETD) system. The wavelengths can be selected in such a way that they are close to each other and fall within the same "nm scale". Additionally, the LETD system receives a returned signal corresponding to the incident laser light of the different wavelengths. The returned signal comprises a light beam reflected from the target after the illumination. One or more light detectors configured in the LETD system can detect the returned signal to measure an intensity value of the returned signal of a particular wavelength. Then, using the measured intensity value, a processing unit can estimate a distance between the fiber end and the target.

The present invention utilizes the LETD system described in different configurations including different arrangements of various optical components such as a beam combiner, a beam splitter, a polarizer, a collimator, a wavelength division multiplexer (WDM), a light detector, etc. The present invention enables accurate estimation of the distance between the fiber end and the target. Additionally, the present invention provides a robust distance estimation technique that is compatible with various types of targets. The present invention can also be used for the purpose of controlling and/or adjusting one or more operational parameters. For example, during treatment, the target may move back and forth, or change one or more of shape, size, composition, pigment, and color. Therefore, preset parameters for the laser source prior to initiating lasing to the target may be less effective. Conventionally, such preset parameters are manually changed, which is error prone and time consuming, or in some cases, the preset parameters may remain unchanged, resulting in a scenario where the fiber is too close or too far from the target. Accordingly, the present invention can automatically monitor the distance between the end of the optical fiber and the target in real time, and also adjust the lasing according to the target shape, position, etc., and automatically change the preset lasing parameters to increase the possibility of achieving the desired result or treatment result.

The foregoing has broadly outlined the features and technical advantages of the present invention in order that the following detailed description of the present invention may be better understood. It will be appreciated by those skilled in the art that the disclosed embodiments may be readily utilized as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. The novel features of the present invention, both in terms of its construction and method of operation, together with further objects and advantages, will be better understood from the following description when considered in connection with the accompanying drawings. It is to be expressly understood, however, that each of the drawings is provided for the purpose of illustration and description only and is not intended to limit the present invention.

FIG. 1 illustrates an exemplary system (100) for estimating a distance between a fiber end and a target according to some embodiments of the present invention. In some embodiments, the exemplary system (100) includes a target (102), an optical fiber (104), a light emission, transmission and detection (LETD) system (106), a processing unit (108), and a display unit (110). The target (102) can be a tissue, stone, tumor, cyst, or the like within a subject to be treated, resected, or destroyed. In some embodiments, the subject can be a human or an animal.

Also, as illustrated in more detail in FIG. 2, the optical fiber (104) includes a proximal end (202) and a distal end (204). The proximal end (202) is the end of the optical fiber (104) into which the light beam (112) enters, and the distal end (204) is the end of the optical fiber (104) from which the light beam (112) is emitted so that the light beam (112) can be directed to a target (102). For example, this drawing illustrates a light beam (112) entering the optical fiber (104) at the proximal end (202), propagating along the length of the optical fiber (104), exiting the optical fiber (104) at the distal end (204), and incident on the target (102) from the distal end (204) of the optical fiber (104).

Referring to FIG. 1, the light beam may be a beam transmitted from a light source (e.g., included in the LETD system (106) or the like). The light source may be a laser light source. By way of example, such laser light sources may include, but are not limited to, solid-state lasers, gas lasers, diode lasers, and fiber lasers. The light beam (112) may include one or more of a targeting beam, a treatment beam, and any other beam transmitted through an optical fiber (104).

In various embodiments, the aiming beam may comprise a low intensity light beam transmitted through the optical fiber (104) to estimate the distance between the optical fiber end (e.g., the distal end (204)) and the target (102). In some embodiments, the treatment beam may comprise a high intensity light beam transmitted through the optical fiber (104) to treat the target (102). In some embodiments, the different light beams may be generated by one or more laser sources. As a specific example, the aiming beam may be generated by one laser source and the treatment beam may be generated by another laser source. In other examples, both the aiming beam and the treatment beam may be generated by a single laser source. In yet other examples, different laser sources may be used to generate light beams of different wavelengths, properties, etc. This is described in more detail below with respect to, for example, FIGS. 3 and 4 .

The optical fiber (104) can be arranged to optically communicate with the LETD system (106), as illustrated in FIG. 1, to receive an optical beam, aim it at the target (102), and transmit a reflected optical beam that reflects from the surface and surrounding area of the target (102). In some embodiments, the optical fiber (104) can be optically, mechanically, and/or electrically coupled to the LETD system (106) via a port (as illustrated in other drawings herein).

In some embodiments, the LETD system (106) includes optical components including, but not limited to, one or more of a laser source, a polarizer, a beam splitter, a beam combiner, a light detector, a wavelength division multiplexer, a collimator, and a circulator, configured in various combinations as described in detail elsewhere herein.

In many embodiments, the laser sources are configured to generate laser light beams, such as a low intensity aiming beam for aiming the light beam (112) toward the target (102), a high intensity treatment beam for treating the target (102), and/or light beams having various characteristics (e.g., intensity, wavelength, etc.) based on the application. Each laser source can be configured to generate laser light having a different wavelength, wherein each of the different wavelengths can have different water absorption coefficients. Additionally, each laser source can have the same aperture or different apertures. In some embodiments, each laser source can be designated for a different purpose, for example, one laser source can be configured to generate a aiming beam of a particular intensity, one laser source can be configured to generate a treatment beam of a particular intensity, and one or more laser sources can be configured to generate light beams of a particular wavelength having a particular water absorption coefficient. Additionally, each laser source can be configured to generate polarized laser light or unpolarized/depolarized light.

The polarizer may include an optical component that acts as an optical filter. For example, the polarizer may be configured to allow a light beam of a particular polarization to pass through and block a light beam of a different polarization. Thus, when an unbounded light beam (or a mixed polarity light beam) is provided as an input to the polarizer, the polarizer provides a well-defined single polarized light beam as an output.

A beam splitter may include optical components used to split incident light into two separate beams at a specified ratio. Additionally, the beam splitter may be arranged to manipulate the light so that it is incident at a desired angle of incidence (AOI). Thus, in many embodiments, the beam splitter may be configured primarily to have two parameters, a split ratio and an AOI. The split ratio comprises the reflection to transmission ratio of the beam splitter (the reflection/transmission (R/T) ratio). Thus, as used herein, when a split ratio of a beam splitter is indicated as 50:50, it means that the beam splitter splits the incident light beam at an R/T ratio of 50:50. In other words, the beam splitter modifies the incident light beam by reflecting 50% and transmitting the remaining 50%, thereby splitting the incident light beam. Additionally, as an example, when an AOI of a beam splitter is indicated as 45 degrees, it means that the beam splitter ensures that the light beam is incident at a 45 degree angle. The beam splitter may include, but is not limited to, a polarizing beam splitter and a non-polarizing beam splitter. The polarizing beam splitter may split the incident light based on its S-polarized component and its P-polarized component, for example, by reflecting the S-polarized component of the light and transmitting the P-polarized component of the light (or vice versa). In some embodiments, the non-polarizing beam splitter may split the incident light beam based on a particular R/T ratio while maintaining the original polarization state of the incident light beam.

The beam combiner may include a partial reflector that combines two or more wavelengths of light, for example, using transmission and reflection principles as described above. In many embodiments, the beam combiner may be a combination of a beam splitter and a mirror that performs the function of combining two or more wavelengths of light.

The optical detection unit may include a device that detects and/or measures a characteristic of an optical beam, and encodes the detected and/or measured characteristic into an electrical signal. For example, the optical detection unit may detect a (pre-configured) particular type of optical beam, and convert optical energy associated with the detected optical beam into an electrical signal. In some embodiments, wavelength division multiplexing may include a technique for combining multiple optical carrier signals into a single optical fiber while using laser light of different wavelengths.

The collimator may include a device that narrows the light beam. To narrow the light beam, the collimator may be configured such that the direction of motion is more aligned in a particular direction (e.g., a parallel light beam) or such that the spatial cross-section of the beam is smaller. In many embodiments, the collimator may be used to change diverging light from a point source into a parallel beam.

A circulator may include a multi-port optical device configured to receive and emit light through a predetermined sequence of multiple ports. For example, a circulator may include a three (or four, or five, etc.) port 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. Often, a circulator may be used to cause a light beam to travel in only one direction.

While the optical components described herein list specific parameters, such as a beam splitter having an R/T ratio of 50:50 and an AOI of 45 degrees, it is to be understood that these parameters are provided for a general understanding of the disclosed concepts and are not intended to limit the present invention. As a specific example, the beam splitter may be provided in various embodiments described herein having different R/T ratios and/or AOIs than those set forth herein without departing from the scope of this specification and claims. In one such example, an AOI of 40 degrees may be utilized. In another such example, an R/T ratio of 47:53 may be utilized.

The LETD system (106) is further associated with a communications network (not shown) and/or a processing unit (108). In some embodiments, the communications network may be a wired communications network or a wireless communications network. The processing unit (108) may be configured to receive measurements from the LETD system (106) and estimate a distance between the distal end (204) of the optical fiber (104) and the target (102) based on the measurements. In some embodiments, the processing unit (108) may be a standalone device having the processing capabilities necessary for distance estimation. For example, the processing unit (108) may include circuitry arranged to determine a distance based on an electrical signal received from the LETD system (106). As another example, the processing unit (108) may include circuitry and a memory including instructions that, when executed by the circuitry, cause the circuitry to determine a distance based on the electrical signal received from the LETD system (106). Still, in some other embodiments, the processing unit (108) may be a computing device, such as a laptop, desktop, mobile phone, tablet phone, or the like, configured to perform distance estimation using its processing capabilities.

The processing unit (108) may be associated with a display (110) to indicate an estimated distance between the distal end of the optical fiber (104) and the target (102). The display (110) may include, but is not limited to, a visual display to indicate the estimated distance, an audio display to indicate the estimated distance, or a haptic display to indicate the estimated distance via a vibration pattern. In various embodiments, the display may be presented via a graphical user interface and/or may be overlaid on a graphical representation, such as a video feed. In some embodiments, a computing device comprising the processing unit (108) may be configured to perform the functions of the display (110). In some other embodiments, the display (110) may be a standalone device configured to indicate an estimated distance between the distal end of the optical fiber (104) and the target (102).

Various exemplary configurations for estimating the distance between a fiber end and a target are described in detail below. However, the values and parameters associated with the different optical components used in each of the configurations described below should be considered purely exemplary and should not be construed as limiting the present invention.

FIG. 3 illustrates an LETD system (300) that may be implemented as an LETD system (106) of the system (100). The LETD system (300) may be configured to estimate the distance between a fiber end and a target in accordance with some embodiments of the present invention. As illustrated, the LETD system (300) includes a plurality of laser sources. In particular, laser sources (302a and 302b) are illustrated. In some embodiments, laser sources (302a and 302b) may be polarizing laser sources. Additionally, the LETD system (300) includes a beam splitter (304), a power detector (306), and a polarizer (308). The laser sources (302a and 302b) are arranged to generate optical beams (320a and 320b), respectively. In some embodiments, the laser source (302a) is arranged to generate a light beam (320a) having a first wavelength, and the laser source (302b) is arranged to generate a light beam (320b) having a second wavelength different from the first wavelength, wherein the first wavelength has an absorption coefficient higher than an absorption coefficient of the second wavelength (e.g., in water).

As used herein, the light beam (320a) generated by the laser source (302a) may be referred to as high water absorption coefficient light (HI), while the light beam (320b) generated by the laser source (302b) may be referred to as low water absorption coefficient light (LO). It is to be understood that where the terms “high” and “low” are used, these terms are intended to be interpreted interchangeably or, alternatively, with respect to a threshold characteristic describing water absorption at a particular wavelength. For example, a high water absorption characteristic may be greater than or equal to 50%, while a low water absorption characteristic may be less than or equal to 50%.

In various embodiments, the ratio of high to low absorption coefficients can be approximately 1:2. For example, the laser light (225a) may utilize a wavelength of approximately 1310 nm and have a water absorption coefficient of approximately 0.1651, while the laser light (225b) may utilize a wavelength of approximately 1340 nm and have a water absorption coefficient of approximately 0.333. A higher ratio between high to low absorption coefficients may result in lower sensitivity to system noise (e.g., electrical or optomechanical noise), but the resulting system may not be effective at distances greater than 3 mm. A lower ratio between high to low absorption coefficients may result in higher sensitivity to system noise, but the resulting system may be effective at distances up to 5 mm or 6 mm. In some examples, the laser sources (302a and 302b) may be polarization maintaining (PM) pigtailed fiber lasers.

The laser sources (302a and 302b) are associated with the beam splitter (304) and are in optical communication with the beam splitter. In other words, the laser beams (320a and 320b) generated by the laser sources (302a and 302b) respectively are provided as inputs to the beam splitter (304) configured to split the incident optical beams (320a and 320b) in a ratio of approximately 50:50 (e.g., 47:53 or 49:51) such that the incident optical beams (320a and 320b) are aligned along a single optical path as the optical beams (322). However, it is understood that any ratio from 99:1 to 1:99 may be utilized without departing from the scope of the present invention. Similarly, while an AOI of 45 degrees may be described in the embodiment, it is understood that any AOI of 1 to 89 degrees, for example, 43 to 47 degrees, 40 degrees or 20 degrees, may be utilized without departing from the scope of the present invention.

A power detector (306) is associated with the beam splitter (304) and is in optical communication with the beam splitter. The power detector (306) is arranged to measure optical power of an optical signal corresponding to each wavelength of light in the optical beam (322) (e.g., a portion of the optical beams (320a and 320b) routed to the power detector (306). In some embodiments, the term “optical power” may mean energy delivered by a particular laser beam per unit time.

The beam splitter (304) is further associated with and in optical communication with the polarizer (308). The beam splitter (304) is further arranged to provide a portion of the optical beams (320a and 320b), designated as optical beams (322), aligned along a single optical path as input to the polarizer (308). In some embodiments, the polarization of the polarizer (308) may be pre-configured and arranged to output a polarized optical beam (324). The LETD system (300) further includes a beam combiner (310) in optical communication with the polarizer (308). In this manner, the polarized optical beam (324) obtained as an output from the polarizer (308) is provided as an input to the beam combiner (310).

The beam combiner (310) can combine the polarized light beam (322) with the treatment beam (326) and the aiming beam (328). In some other embodiments, the treatment beam (326) can be generated by one or more laser sources (not shown) other than the laser sources (302a and 302b). For example, the treatment beam (326) can be generated by a solid-state laser or a fiber laser, such as a holmium (HO) laser or a thulium fiber laser (TFL). However, this should not be considered limiting, as the treatment beam (326) can be generated by lasers other than HO or TLF, such as neodymium, erbium, thulium, etc. In some other embodiments, the treatment beam (326) and the aiming beam (328) can be generated by the laser sources (302a and/or 302b).

The beam combiner (310) can combine the polarized light beam (324) with the treatment beam (326) and the aiming beam (328) to form a combined light beam (330). The LETD system (300) further includes a beam splitter (312) and a port (314). The beam splitter (312) is arranged to be in optical communication with the beam combiner (310). The beam splitter (312) can receive a combined light beam (330) comprising the polarized light beam (324), the treatment beam (326), and the aiming beam (328). The beam splitter (312) can have a configuration of an R/T ratio of 50:50 and an AOI of 45 degrees.

In this arrangement, the beam splitter (312) can split the combined light beam (330) in a 50:50 ratio such that the polarized light beam (330), the treatment beam (326), and the aiming beam (328) are aligned along a line of a single optical path. The beam splitter (312) is optically coupled to the optical fiber (104) (e.g., via the port (314)) such that a portion of the combined light beam (330), which is the output of the beam splitter (312), is designated as the light beam (332) and transmitted through the optical fiber (104) (e.g., via the port (314)). The light beam (332) is transmitted to the proximal end (202) of the optical fiber (104) and propagates through the length of the optical fiber (104) to be delivered from the distal end (204) of the optical fiber (104) to the target (102). For example, the target (102) may be a tissue, stone, tumor, cyst, etc. within the subject to be treated, resected, destroyed, etc.

When a light beam (332) is transmitted through an optical fiber (104) to a target (102), the target (102) may reflect a portion of the incident light beam (332) away from the optical fiber (104) and may reflect a portion of the light toward the optical fiber (104), whereby the portion of the light reflected toward the optical fiber (104) may re-enter the optical fiber (104) at the distal end (204) of the optical fiber (104). The portion of the reflected light that re-enters the distal end may be referred to as a reflected light beam (334a). The reflected light beam (334a) may be transmitted in the “reverse” direction in the optical fiber (104) from the distal end (204) to the proximal end (202) of the optical fiber (104). When the reflected light beam (334a) reaches the proximal end (202) of the optical fiber (104), the reflected light beam (334a) may pass through the beam splitter (312). The reflected light beam (334a) may include multiple reflections from, for example, the target (102), the distal end (204) of the optical fiber (104), the proximal end (202) of the optical fiber (104), the port (314), etc. This causes the reflected light beam (334a) to no longer be polarized.

The LETD system (300) further includes a polarizing beam splitter (316), a light detector (318a), and a light detector (318b). The reflected light beam (334a) can be incident on the beam splitter (312) at a 45 degree angle and split in a ratio of 50:50 (or another ratio as described in detail herein) such that the reflected light beam (334a) is aligned along a single optical path as a reflected light beam (334b). The polarizing beam splitter (316) is arranged in optical communication with the beam splitter (312) and is arranged to receive the reflected light beam (334b) and polarize the reflected light beam (334b). In some embodiments, the polarizing beam splitter (316) can split the reflected light beam (334b) into a reflected P-polarized beam and a transmitted S-polarized beam. One of the light detectors (318a or 318b) can be configured to detect the P-polarized beam of the reflected light beam (334b), and the other of the light detectors (318a or 318b) can be configured to detect the S-polarized beam of the reflected light beam (334b). The light detectors (318a and 318b) can each measure an intensity of a detected light beam of the reflected light beam (334b) and transmit the intensity to the processing unit (108). In some embodiments, the processing unit (108) can estimate a distance between the distal end (204) of the optical fiber (104) and the target (102) based on the measured intensity. A method of estimating the distance between the distal end of the optical fiber (104) and the target (102) based on the measured intensity is described in more detail below.

FIG. 4 illustrates a LETD system (400) that may be implemented as the LETD system (106) of the system (100). The LETD system (400) may be configured to estimate the distance between a fiber end and a target in accordance with some embodiments of the present invention. For convenience, when components of the LETD system (400) are identical to components of previously described LETD systems (e.g., LETD system (300) or the like), the same reference numerals are used.

The LETD system (400) differs from the LETD system (300) in two structural aspects. One structural aspect that is different between the LETD system (400) and the LETD system (300) is that the beam splitter (304) is replaced with a beam combiner (402). Since the beam splitter (304) is replaced with the beam combiner (402), the power detector (306) that was associated with the beam splitter (304) in the LETD system (300) is arranged to be associated with the beam splitter (312) in the LETD system (400). The embodiment is not limited in this context.

The LETD system (400) can include one or more polarizing lasers, one or more beam splitters, a polarizer, one or more beam combiners, and one or more light detectors. The one or more beam splitters can be a polarizing beam splitter, a non-polarizing beam splitter, or a combination of polarizing and non-polarizing beam splitters. As illustrated in FIG. 4, the LETD system (400) includes a laser source (302a), a laser source (302b), a beam combiner (402), a polarizer (308), a beam combiner (310), a beam splitter (312), a power detector (306), a polarizing beam splitter (316), a light detector (318a), and a light detector (318b). In this configuration, as illustrated in FIG. 4, the laser source (302a) outputs a light beam (320a) having a wavelength with a high water absorption coefficient (HI), and the laser source (302b) outputs a light beam (320b) having a wavelength with a low water absorption coefficient (LO).

Incident light beams from laser sources (laser sources 302a and 302b) are provided as input to a beam combiner (402) configured to combine incident light beams (320a and 320b) generated by laser sources (302a and 302b) into a light beam (322). Additionally, an output of the beam combiner (402) (e.g., light beam (322)) can be provided as input to a polarizer (308) to provide a polarized light beam (324) as an output. In some embodiments, the polarization of the polarizer (308) can be pre-configured. Thereafter, the polarized light beam (324) obtained as an output from the polarizer (308) can be provided as an input to the beam combiner (310). The beam combiner (310) can combine a polarized light beam (324) with a targeting beam (328) and a treatment beam (326) to form a combined light beam (330), as illustrated in FIG. 4.

A combined light beam (330) comprising a targeting beam (328), a treatment beam (326), and a polarized light beam (324) from laser sources (302a and 302b) can pass through a beam splitter (312) having a configuration of a 50:50 R/T ratio and a 45 degree AOI (or any other R/T ratio and AOI outlined herein). The beam splitter (312) can split the combined light beam (330) at a 50:50 ratio such that the targeting beam (328), the treatment beam (326), and the polarized light beam (324) can be aligned along a single optical path.

A power detector (306) associated with the beam splitter (312) can measure the power of an optical signal (such as a polarized optical beam (324)) corresponding to each wavelength. In various embodiments, the power detector (306) can detect the accumulated energy of the optical signal received at the beam splitter (312). In some embodiments, the term “optical power” can mean energy delivered by a particular laser beam per unit time. The optical beam (332), which is the output of the beam splitter (312), is then transmitted into the optical fiber (104) (e.g., through the port (314)) as schematically described above with respect to FIG. 3 . Additionally, a reflected optical beam (334a) is received and processed as schematically described above with respect to FIG. 3 .

FIG. 5 illustrates an LETD system (500) for estimating the distance between a fiber end and a target according to some embodiments of the present invention. The present invention can operate using polarized and unpolarized laser sources. Thus, in the LETD system (500), the laser sources (502a and 502b) used to provide the incident optical beam (source light) are unpolarized laser sources. As an example, the laser sources (502a and 502b) can be single mode (SM) fiber pigtailed lasers. When the laser sources (502a and 502b) are unpolarized laser sources, the polarizer (308), the polarizing beam splitter (316), the optical detector (318a) for detecting the P-polarized optical beam, and the optical detector (318b) for detecting the S-polarized optical beam, as illustrated in the LETD system (300) and LETD system (400) described above, are not required.

The LETD system (500) may include one or more unpolarized lasers, one or more beam splitters, a beam combiner, and a light detector. The one or more beam splitters may be unpolarized beam splitters. As illustrated in FIG. 5, the LETD system (500) includes a unpolarized laser source (502a), a unpolarized laser source (502b), a beam splitter (304), a power detector (306), a beam combiner (310), a beam splitter (312), and a light detector (512).

As in the previous configuration, in the LETD system (500), the unpolarized laser source (502a) may have a wavelength having a high water absorption coefficient (HI), while the unpolarized laser source (502b) may have a wavelength having a low water absorption coefficient (LO). Optical beams (504a and 504b) from the laser sources (502a and 502b) are provided as inputs to a beam splitter (304), which is configured to split the incident optical beams in a ratio of 50:50 such that the incident optical beams (504a and 504b) are aligned along a single optical path as an optical beam (506).

The power detector (306) associated with the beam splitter (304) can measure the power of the optical signal (optical beam (506)) corresponding to each wavelength. Since the LETD system (500) is implemented in a non-polarized environment, polarization-based optical components such as a polarizer and a polarizing beam splitter are not required in this configuration. Accordingly, the output of the beam splitter (304) as incident optical beams (504a and 504b) aligned along a single optical path as the optical beam (506) can be provided as input to the beam combiner (310). The beam combiner (310) can combine the optical beam (506) from the beam splitter (304) with the aiming beam (328) and the treatment beam (326), as illustrated in FIG. 5 .

In some embodiments, the aiming beam (328) and the treatment beam (326) can be generated by one or more laser sources other than the laser sources (502a and 502b). In some other embodiments, the aiming beam (328) and the treatment beam (326) can be generated by the laser sources (502a and 502b). The combined light beam (508) comprising the aiming beam (328), the treatment beam (326), and the unpolarized light beam (light beam (506)) can pass through a beam splitter (312) having a configuration of a 50:50 ratio and a 45 degree AOI (or any other R/T ratio and AOI outlined herein). The beam splitter (312) can split the combined light beam (508) in a 50:50 ratio so that the aiming beam (328), the treatment beam (326), and the unpolarized light beam (light beam (506)) are aligned along a single optical path. The light beam (510), which is the output of the beam splitter (312), is then transmitted into the optical fiber (104) (e.g., through the port (314)) as illustrated in FIG. 5 and described above, and the reflected light beam (514a) is transmitted in the reverse direction.

Since the LETD system (500) is implemented in a non-polarized environment, the reflected light beam (334a) only passes through the second beam splitter (312) to align the optical path of the reflected light beam (514a), and therefore, a polarizing beam splitter as illustrated in the LETD system (300) and the LETD system (400) is not required. The reflected light beam (514a) will be incident on the beam splitter (312) at a 45 degree angle and split at a ratio of 50:50. The reflected light beam (334b) emerging from the beam splitter (312) can be directly detected by a single detector. Thus, the LETD system (500) provides a light detector (512).

The light detection unit (512) can measure the intensity of each detected light beam of the reflected light beam (514b) and transmit the intensity to the processing unit (108). In some embodiments, the processing unit (108) can estimate the distance between the distal end (204) of the optical fiber (104) and the target (102) based on the measured intensity. A method of estimating the distance between the distal end of the optical fiber (104) and the target (102) based on the measured intensity is described in more detail below.

FIG. 6 illustrates an exemplary LETD system (600) for estimating the distance between a fiber end and a target according to some embodiments of the present invention. The LETD system (600) includes a third polarization laser source (302c) introduced to correct the condition of the fiber in real time. For example, the condition of the fiber (104) may include, but is not limited to, any change or degradation of the distal or proximal end of the fiber (104), fiber bending effects on polarization scrambling, or any other degradation or change occurring in the fiber (104). Changes in the condition of the fiber (104), particularly changes in the tip/end (e.g., input and output facets) of the fiber (104), can adversely affect the transmitted and reflected light beams, resulting in a large number of reflections, energy loss, and inaccurate measurements. This can affect the accuracy of the distance estimation and, therefore, can cause inaccurate positioning of the fiber (104) during treatment.

The LETD system (600) can include one or more polarizing lasers, one or more beam splitters, a polarizer, a beam combiner, and one or more light detectors. The one or more beam splitters can be a polarizing beam splitter, a non-polarizing beam splitter, or a combination of polarizing and non-polarizing beam splitters. As illustrated in FIG. 6, the LETD system (600) includes a polarizing laser source (302a), a polarizing laser source (302b), a polarizing laser source (302c), a beam splitter (304), a beam splitter (602), a power detector (306), a polarizer (308), a beam combiner (310), a beam splitter (312), a beam splitter (604), a light detector (318a), and a light detector (318b). As illustrated in FIG. 6, light beams (320a and 320b) from laser sources (302a and 302b) are provided as inputs to a beam splitter (304), which is configured to split the light beams (320a and 320b) in a ratio of 50:50 such that the light beams (320a and 320b) are aligned along a single optical path forming a light beam (322). Additionally, the output of the beam splitter (304), which is the light beams (320a and 320b) (e.g., light beam (322)) aligned along the single optical path, can be provided as inputs to a beam splitter (602), which is also configured to split the incident light beams in a ratio of 50:50 to form a polarized light beam (606) including light beams (320a, 320b, and 320c).

In the beam splitter (602), an incident light beam (320c) (e.g., light for calibration) from a polarizing laser source (302c) is provided as an input together with an output of the beam splitter (304) (e.g., light beam (322)). A power detector (306) associated with the beam splitter (602) can measure the power of an optical signal (e.g., light beam (606)) corresponding to each wavelength reaching the beam splitter (602). Along with the output of the beam splitter (304), the beam splitter (602) receives the incident light beam from the polarizing laser source (302c).

In some embodiments, the polarizing laser source (302c) has a wavelength that has a very high water absorption coefficient (e.g., substantially, completely, or nearly completely absorbed by water) compared to the wavelength of light emitted by the laser sources (302a and 302b). For example, the wavelength of the polarizing laser source (302c) may be about 1435 nm and may have a water absorption coefficient of about 31.55 (or about 100 times that of a “high” water absorption source). At a distance of 0.5 mm, about 98% to 99% of light at a wavelength of 1435 nm is absorbed. In some embodiments, the correction light source may have a wavelength of about 1420 nm to about 1440 nm (resulting in a water absorption coefficient of about 30). Alternative or additional wavelengths that have very high water absorption coefficients may be used (e.g., 1870 nm to 2070 nm). However, the optical design can become more complex as the wavelength gets further from the HI and LO wavelengths (e.g., 1310 nm and 1340 nm, respectively). For example, the detector may cover a range of about 1100 nm to 1600 nm, and a unique or additional detector may be required if the very high water absorption coefficient laser has a wavelength of 2000 nm. In some embodiments, the calibration laser can have a wavelength of about 1435 nm, about 2100 nm, or about 1870 nm to about 2050 nm.

Based on the readings of the polarization laser source (302c) (e.g., as measured by the power detector (306)), the processing unit (108) can define an optical reference characteristic of the “quality” of the fiber tip at the distal end (204) of the optical fiber (104). More specifically, since the laser source (302c) is highly absorbed by water, little light from the laser source (302c) will reach the target tissue, and as a result, little light from the laser source (302c) will be reflected back into the optical fiber (104) as part of the reflected light beam (334a). Therefore, the component of the reflected light beam (334c) (e.g., the light reflection (610)) having a wavelength of light associated with the laser source (302c) is primarily due to the optical characteristics of the distal end (204) of the optical fiber (104). The distal end (204) of the optical fiber (104) is understood to experience degradation during laser treatment, for example, due to heating and cavitation. In many embodiments, an increase in the intensity reading of the back light reflection (610) may indicate degradation of the optical fiber tip. In some embodiments, at a certain threshold of intensity change from a baseline reading for a particular fiber (e.g., between 10% and 50%, greater than 25%, 50%, 75%, 90%, between 10% and 100%, etc.), the processing unit (108) may indicate, for example, via a user interface and/or an audible alarm, that the optical fiber (104) needs to be inspected or replaced. Additionally, degradation of the optical fiber tip may result in higher internal reflections of light from the polarized laser sources (302a and 302b) from the distal end of the fiber. The polarization of the laser source may have minimal effect on the internal reflections since the light is randomly depolarized in the fiber. However, monitoring the reflection from the distal end of the fiber by a very high absorption coefficient laser (e.g., a 1435 nm laser) can be used to determine the change in the distal end reflection (the percentage of the initial reflection at 1435 vs. the real-time reflection). Additionally, the change in the distal end reflection can be applied to the initial reflection from the distal end for the LO laser (e.g., a 1310 nm laser) and the HI laser (e.g., a 1340 nm laser) to update the initial reflection.

Moreover, degradation of the fiber tip can change the ratio between polarity (P) and polarity (S) in the reflected optical beam (334a) or the optical reflection (610). Therefore, generating a reference reading for a particular optical fiber (104) currently in use and monitoring this reference on the fly can allow for more accurate distance estimation when and while the tip of the fiber degrades and until the degradation reaches a critical level indicating that the optical fiber (104) should be replaced. Additionally, the output of the optical beam (606) or beam splitter (602) comprising the optical beams (320a, 320b and 320c) aligned along a single optical path can be provided as input to the polarizer (308) to obtain a single polarized optical beam (608) as output. In some embodiments, the polarization of the polarizer (308) can be pre-configured.

A polarized light beam (608) obtained as an output from the polarizer (308) may be provided as an input to a beam combiner (310). The beam combiner (310) may combine the polarized light beam (608) with the aiming beam (328) and the treatment beam (326) to form a combined light beam (612), as illustrated in FIG. 6. As described above, the aiming beam (328) and/or the treatment beam (326) may be generated by one or more laser sources other than the laser sources (302a, 302b, or 302c), or the aiming beam (328) and/or the treatment beam (326) may be generated by these laser sources.

A combined light beam (612) comprising a targeting beam (328), a treatment beam (326), and a polarized light beam (608) can pass through a beam splitter (312) having a 50:50 ratio and a 45 degree AOI configuration. The beam splitter (312) can split the combined light beam (612) at a 50:50 ratio such that the targeting beam (328), the treatment beam (326), and the polarized light beam (608) are aligned along a single optical path. The light beam (614), which is the output of the beam splitter (312), is then transmitted into an optical fiber (104) (e.g., through a port (314)).

FIG. 7 illustrates an exemplary LETD system (700) for estimating the distance between a fiber end and a target, in accordance with some embodiments of the present invention. Like the LETD system (500), the LETD system (700) is implemented in a non-polarized environment. Additionally, the LETD system (700) is a "semi-fiber based design" in which the two input beam splitters seen in previous configurations (e.g., the configuration of the LETD system (600)) are replaced with wavelength division multiplexing (WDM). Since the WDM power loss is approximately 20%, while the beam splitter power loss can be approximately 50%, the use of WDM improves the efficiency of the LETD system (700). Additionally, the WDM allows each of the three laser sources to be perfectly or nearly perfectly aligned in the optical path. However, the beam splitter and beam combiner suffer from significant inaccuracy in aligning each of the three laser sources into a single beam.

The LETD system (700) utilizes a third unpolarized laser source (502c) along with a first unpolarized laser source (502a) and a second unpolarized laser source (502b). The third unpolarized laser source (502c) is introduced for the purpose of correcting the fiber condition in real time as described above. It is understood that the correction laser can be polarized or unpolarized without departing from the scope of the present invention. The LETD system (700) can include one or more unpolarized lasers, one or more beam splitters, a beam combiner, one or more photodetectors, a WDM, and a collimator. As illustrated in FIG. 7, the LETD system (700) includes a non-polarized laser source (502a), a non-polarized laser source (502b), a non-polarized laser source (502c), a laser source (702), a wavelength division multiplexer (WDM) (704), a beam splitter (706), a power detector (306), a collimator (708), a beam combiner (310), a beam splitter (312), and a light detector (512). In the configuration of the LETD system (700), the non-polarized laser source (502a) can emit light having a wavelength having a high water absorption coefficient (HI), while the non-polarized laser source (502b) can emit light having a wavelength having a low water absorption coefficient (LO). Additionally, the unpolarized laser source (502c) can emit light having a wavelength that has a very high water absorption coefficient (e.g., completely or nearly completely absorbed by water) compared to the wavelength of light emitted by the laser sources (502a and 502b). As an example, the wavelength of the unpolarized laser source (502c) can be 1435 nm.

As mentioned above, in the configuration of the LETD system (700), the beam splitter (304) and the beam splitter (602) illustrated in FIG. 6 are replaced with a WDM (704). In some embodiments, to ensure that the unpolarized laser source (502c) is properly used as a real-time correction unit, the incident light beams from each of the unpolarized laser sources (502a, 502b, and 502c) can be arranged to enter the proximal end of the optical fiber (104) at the same point and at the same angle. In many embodiments, it may be difficult or impossible to align the incident light beams from each of the unpolarized laser sources (502a, 502b, and 502c) to enter the combiner/splitter at the same point and at the same angle. To comply with this condition of the same point and the same angle, the configuration illustrated in the LETD system (700) utilizes a WDM (704). The WDM (704) can be configured to ensure that all incident optical beams from each of the unpolarized laser sources (502a, 502b and 502c) enter the proximal end (202) of the optical fiber (104) at the same point and at the same angle. Moreover, in various embodiments, the use of the WDM (704) can reduce power loss compared to some beam splitters which cause power losses of, for example, 50% to 75%.

Incident optical beams and a collimated beam (328) from laser sources (502a, 502b, 502c) are provided as inputs to a WDM (704), which is configured to couple the incident optical beams in such a way that the optical beams travel in the same manner. Additionally, the output of the WDM (704) can be provided as inputs to a fiber-based beam splitter (e.g., a fourth beam splitter (706)), which can be arranged to split the incident optical beams at a high transmission to reflection ratio (e.g., 95:5 or 99:1), as illustrated in FIG. 7 . In some embodiments, the beam splitter (706) is a fiber-based beam splitter. A power detector (306) associated with the beam splitter (706) can measure the power of an optical signal (e.g., an optical beam (710)) corresponding to each wavelength. Additionally, the output of the beam splitter (706) (e.g., the light beam (710)) aligned along a single optical path can be provided as input to the collimator (708) to narrow the light beam (710) into a parallel beam.

Thereafter, the output of the collimator (708) (e.g., the light beam (712)) may be provided to the beam combiner (310), which combines the light beam (712) from the collimator (708) with the aiming beam (328) and the treatment beam (326), as illustrated in FIG. 7 . In some embodiments, the aiming beam (328) may be introduced into the WDM (704). In many embodiments, the aiming beam (328) may be introduced at the beam combiner (310). Still, in some embodiments, the aiming beam (328) may be introduced to both the WDM (704) and the first beam combiner (310). In some embodiments, the aiming beam (328) and/or the treatment beam (326) may be generated by one or more laser sources other than the laser sources (502a, 502b, and 502c), or the aiming beam (328) and/or the treatment beam (326) may be generated by the laser sources (502a, 502b, and 502c).

A combined light beam (508) comprising a collimating beam (328), a treatment beam (326), and a light beam (712) (e.g., light from the laser sources (502a, 502b, and 502c) received from the collimating portion (708)) can pass through a beam splitter (312) having an R/T ratio of 50:50 and an AOI configuration of 45 degrees. The beam splitter (312) can split the combined light beam (508) in a 50:50 ratio such that the collimating beam (328), the treatment beam (326), and the unpolarized light beams (combined light beam) (508) from the laser sources (502a, 502b, and 502c) can be aligned along a single optical path. The light beam (510), which is the output of the beam splitter (312), is then transmitted to the optical fiber (104) as illustrated and described in more detail above (e.g., via the port (314)).

FIG. 8 illustrates an exemplary LETD system (800) for estimating the distance between a fiber end and a target according to some embodiments of the present invention. The LETD system (800), such as the LETD system (500) and the LETD system (700), is implemented with an unpolarized detector. However, the source may be unpolarized or polarized. In this exemplary configuration, the LETD system (800) may include one or more unpolarized lasers (or polarized lasers), one or more beam splitters, a beam combiner, one or more photodetectors, a WDM, a circulator, and a collimator. As illustrated in FIG. 8, the LETD system (800) includes a non-polarized laser source (502a), a non-polarized laser source (502b), a non-polarized laser source (502c), a laser source (702), a wavelength division multiplexer (WDM) (704), a beam splitter (706), a power detector (306), a circulator (802), a light detector (512), a collimator (708), and a beam combiner (310). In the configuration of the LETD system (800), the non-polarized laser source (502a) can emit light having a wavelength having a high water absorption coefficient (HI), while the polarized laser source (502b) can emit light having a wavelength having a low water absorption coefficient (LO). Additionally, the non-polarized laser source (502c) can have a wavelength having a very high water absorption coefficient that is substantially absorbed by water.

As described above, in the LETD system (800), the beam splitter (304) and beam splitter (602) illustrated in FIG. 6 are replaced with a WDM (704) as illustrated in FIGS. 7 and 8. Additionally, in the LETD system (800), the beam splitter (312) arranged to direct the optical beam to the port (314) in all of the exemplary configurations described above is also eliminated. The beam splitter reduces the output power by up to 50% (or more), and further reduces the output power by 50% (or more) when receiving a return signal. Therefore, eliminating the beam splitter (312) in the LETD system (800) can significantly increase the reflected signal and output power.

Incident optical beams (504a, 504b, and 504c) from laser sources (502a, 502b, and 502c) as well as a collimating beam (328) are provided as inputs to the WDM (704), which is configured to couple the incident optical beams in such a way that the optical beams travel equally. Additionally, the output of the WDM (704) may be provided as input to a beam splitter (706), which splits the incident optical beams in a ratio of 95:5. As previously noted, other ratios, such as 99:1, may be utilized without departing from the scope of the present invention. In some embodiments, the beam splitter (706) is a fiber-based beam splitter, thereby rendering the configuration of the LETD system (800) an all-fiber-based design. A power detector (306) associated with the beam splitter (706) may measure the power of an optical signal (e.g., the optical beam (710)) corresponding to each wavelength. Additionally, the output of the beam splitter (706), which is the incident light aligned along a single optical path (e.g., the optical beam (710)), can be provided as an input to the circulator (802). The circulator (802) is configured to ensure that all of the optical beams propagate in a single direction. Additionally, the circulator (802) provides the optical beam (804) from a port other than the port through which the optical beam (710) enters to the collimator (708). The collimator (708) can narrow the optical beam into a parallel optical beam (804). The circulator (802) can provide (1) lower power loss (loss of the beam splitter is about 50% in each direction) and (2) more flexible optical design (free-space optics require straight lines, whereas fiber-based designs can be folded as desired) compared to the beam splitter.

The output of the collimator (708) (e.g., a parallel light beam (804)) may be provided to a beam combiner (310), as illustrated in FIG. 8 , which combines the light beam (804) from the collimator (708) with the aiming beam (328) and the treatment beam (326) to form a combined light beam (806). In some embodiments, the aiming beam (328) may be introduced initially (e.g., into the WDM (704)), introduced into the beam combiner (310), or introduced into both the WDM (704) and the beam combiner (310). In some embodiments, the aiming beam (328) and/or the treatment beam (326) may be generated by one or more laser sources other than the laser sources illustrated in this figure, or the aiming beam (328) or the treatment beam (326) may be generated by the laser sources illustrated in this figure. A combined light beam (light beam (806)) comprising the aiming beam (328), the treatment beam (326), and the light beams (806) received from the beam combiner (310) (e.g., light beams (504a, 504b, and 504c)) can be transmitted into an optical fiber (104) (e.g., through a port (314)) as illustrated in FIG. 8. The combined light beam (806) is transmitted to a proximal end (202) of the optical fiber (104), and then propagates through the length of the optical fiber (104) and is transmitted from the distal end (204) of the optical fiber (104) to a target (102).

As schematically described above, when a light beam (806) is transmitted through a distal end (204) of an optical fiber (104) to a target (102), the target (102) may reflect a portion of the light away from the optical fiber (104) and may reflect a portion of the light toward the optical fiber (104), whereby the portion of the light reflected toward the optical fiber (104) may re-enter the optical fiber (104) at the distal end (204). The portion of the reflected light that re-enters the distal end (204) as schematically described above is referred to as reflected light (reflected light beam (334a)). The reflected light beam (334a) may be transmitted “reversely” through the optical fiber (104) from the distal end (204) to the proximal end (202). When the reflected light beam (334a) reaches the proximal end (202) of the optical fiber (104), the reflected light beam (334a) may pass through the beam coupling unit (310) and the collimating unit (708) and then through the circulator (802), where it is routed to the light detection unit (512) and measured as described above with respect to FIG. 7.

FIG. 9 illustrates an LETD system (900) that may be implemented in a non-polarized environment, such as some of the previous configurations. In some embodiments, the LETD system (900) may include a single beam splitter based optical design. In the configuration of the LETD system (900), the WDM (704) may replace the function or operation of multiple beam splitters (e.g., those utilized in the LETD system (300), the LETD system (400, 500), and/or the LETD system (600)). The WDM (704) may receive optical beams (504a, 504b, and 504c) from non-polarized laser sources (502a, 502b, and 502c), respectively.

The LETD system (900) can include one or more unpolarized lasers (or polarized lasers), a beam splitter, a beam combiner, one or more light detectors, a WDM, and a collimator. As illustrated in FIG. 9, the LETD system (900) includes an unpolarized laser source (502a), an unpolarized laser source (502b), an unpolarized laser source (502c), a laser source (702), a wavelength division multiplexer (WDM) (704), a beam splitter (902), a power detector (306), a light detector (512), and a beam combiner (310). As with the previous configuration, in the LETD system (900), the unpolarized light beam (504a) can have a wavelength having a higher water absorption coefficient (HI) than the unpolarized light beam (504b), which itself can have a wavelength having a lower water absorption coefficient (LO). Additionally, the unpolarized light beam (504c) may have a wavelength having a very high water absorption coefficient as described in detail above.

As described above, the processing unit (108) can define an optical reference characteristic of the quality of the distal end (204) of the optical fiber (104) (e.g., the output facet, etc.) based on the readings associated with the reflection of light generated by the unpolarized laser source (502c). More specifically, since the light from the laser source (502c) is largely absorbed by water, a small amount of this light will be reflected back into the optical fiber (104) as part of the reflected light beam (334a). Thus, the reading associated with the light reflection (610) is primarily due to the optical properties of the distal end (204) of the optical fiber (104), which degrades during the laser treatment, for example, due to heating and cavitation, as described. Thus, an increase in the intensity reading of the light reflection (610) may indicate that the optical fiber tip is degraded.

In some embodiments, at a particular threshold value of intensity change from a reference reading for a particular optical fiber (103) (e.g., greater than 10% to 50%, greater than 25%, greater than 50%, greater than 75%, greater than 90%, greater than 10% and greater than 100%, etc.), the processing unit (108) may indicate, for example, via a user interface and/or an audible alarm, that the optical fiber (104) needs to be inspected or replaced. Additionally, degradation of the optical fiber tip may cause higher internal reflections of light associated with the unpolarized laser source (laser sources 502a and 502b) from the distal end (204) of the optical fiber (104). Furthermore, degradation of the fiber tip may change the ratio between polarity (P) and polarity (S) in the reflected light beam (334a or 334b). Therefore, by generating reference readings for a particular optical fiber currently in use and monitoring these references on the fly, distance estimation can be more accurately performed as the tip of the optical fiber degrades, and even while the deterioration reaches a point where the optical fiber must be replaced. This can provide greater dynamic control over parameters associated with therapies or treatments.

Like some previous configurations of LETD systems, the LETD system (900) utilizes a WDM (704) to ensure that all incident optical beams from each of the unpolarized lasers (502a, 502b and 502c) enter the proximal end (202) of the optical fiber (104) at the same point and at the same angle. Moreover, in various embodiments, use of the WDM (704) can reduce power loss compared to some configurations that utilize, for example, a beam splitter.

The optical beams (504a, 504b, and 504c) from the illustrated laser sources, as well as the aiming beam (328), can be provided as inputs to the WDM (704), which can be configured to couple the incident optical beams in such a way that the optical beams travel equally. Additionally, the output of the WDM (704) can be provided as inputs to the beam splitter (902), which can split the incident optical beams in a 50:50 ratio. In some embodiments, the beam splitter (902) can be a free space (e.g., glass) based beam splitter. In some other embodiments, the beam splitter (902) can be a fiber based beam splitter. In many embodiments, a power detector (306) associated with the beam splitter (902) can measure the power of an optical signal (e.g., the optical beam (710)) corresponding to each wavelength.

The output of the beam splitter (902), which is the incident light aligned along a single optical path, can be provided as input to the beam combiner (310). The beam combiner (310) can combine the light beam (710) exiting the beam splitter (902) with the aiming beam (328) and the treatment beam (326), as illustrated in FIG. 9 . In various embodiments, the aiming beam (328) can be introduced into the WDM (704), introduced into the beam combiner (310), or introduced into both the WDM (704) and the beam combiner (310). In various embodiments, the aiming beam (328) and/or the treatment beam (326) can be generated by one or more laser sources other than the laser sources (502a, 502b, and 502c), or the aiming beam (328) and/or the treatment beam (326) can be generated by the laser sources. A combined light beam (806) comprising the aiming beam (328), the treatment beam (326), and the light beam (710) received from the beam combiner (310) can be transmitted into the optical fiber (104) (e.g., via the port (314)).

As can be seen from this drawing, the LETD system (900) eliminates the use of multiple beam splitters. Additionally, because the LETD system (900) utilizes a single beam splitter, it may be much less sensitive to treatment fiber movement and fiber bend radius, resulting in a more robust configuration. Furthermore, because the LETD system (900) has fewer optical components, such as beam splitters, beam combiners, detectors, etc., the LETD system (900) may be more compact, simpler, and less expensive than other configurations.

In some embodiments of the exemplary configuration described above, the proximal end (202) of the optical fiber (104) can include a sub-miniature version A (SMA) connector, which can be polished or cleaved at an 8 degree angle, as illustrated in FIG. 10 . As illustrated in this figure, chopping at an 8 degree angle can redirect a reflected light beam from the proximal end (202) of the optical fiber (104) (i.e., unwanted reflections occurring at the proximal end (202)), thereby significantly reducing noise and increasing dynamic range. In some embodiments, the optical signal entering the optical detector (e.g., the reflected light beam (334a)) can include one or more of: (a) reflections from the port lens; (b) reflections from the blast shield; (c) reflections from the proximal end (202) of the optical fiber (104); and/or (d) reflections from the distal end (204) of the optical fiber (104).

An AR coating at the proximal end (202) of the optical fiber (104) can reduce reflections at the proximal end (202) of the optical fiber (104) (e.g., from 3.5% to about 0.5%). However, angling the proximal end (202) of the optical fiber (104) more precisely can help reduce unwanted reflections and improve the dynamic range of the signal reflected from the target (102). In some other embodiments, the SMA connector can be polished or cleaved at a 4 degree angle instead of an 8 degree angle, for example, as illustrated in FIG. 11 . In various embodiments, chopping at a 4 degree angle instead of an 8 degree (or greater) angle can improve signal robustness. In some embodiments, a smaller chopping angle of the SMA connector can result in higher signal robustness of the optical fiber (104). In various embodiments, an angle of about 2 degrees to about 8 degrees can be used. In general, lower angles are more difficult to implement in optical devices. In other words, it is more difficult to snatch from the main signal. However, light cannot enter the fiber at higher angles (e.g., greater than 10 degrees).

FIG. 12 depicts a flow diagram showing a method (1200) for estimating a distance between a fiber end and a target according to some embodiments of the present invention. The method (1200) is described with reference to various configurations of the system (100) and the LETD system (106) described above (e.g., LETD system (300), LETD system (400), LETD system (500), LETD system (600), LETD system (700), LETD system (800), LETD system (900), etc.). However, it is to be understood that the method (1200) can be implemented using LETDs other than those described herein. Embodiments are not limited in this context.

At block (1202), the method (1200) includes illuminating a target with laser light of a plurality of different wavelengths. For example, the LETD system (106) can utilize a plurality of laser sources (e.g., laser sources 302a and 302b, laser sources 502a, 502b and/or 502c, etc.) to illuminate the target (102) with laser light of a plurality of different wavelengths via an optical fiber (104). In some embodiments, the plurality of different wavelengths of laser light can be provided to the optical fiber (104) to illuminate the target (102) using one of the configurations discussed above. In various embodiments, the present invention may use light having two different wavelengths (e.g., light beams 320a and 320b or light beams 504a, 504b and/or 504c) each having different water absorption coefficients to ensure robustness with respect to different types of targets (102), target compositions, target colors, target surfaces, etc.

In some embodiments, the two (or more) wavelengths can be selected such that one wavelength is a wavelength having a low water absorption coefficient (LO) and the other wavelength is a wavelength having a high water absorption coefficient (HI). As an example, the two wavelengths can be 1310 nm and 1340 nm. However, this example should not be construed as limiting the invention, as different wavelengths having different water absorption coefficients can also be used. For example, 1260 nm to 1320 nm can be used for LO, and 1330 nm to 1380 nm can be used for HI. More generally, any combination of wavelength water absorption coefficient pairs in a 2:1 (or greater) ratio can be used. In some embodiments, one or more of a 1310 nm and 1340 nm laser pair, a 1260 nm and 1340 nm laser pair, a 1260 nm and 1310 nm laser pair, and a 1310 nm and 1550 nm laser pair may be utilized for the LO and HI lasers, respectively. As outlined above, in some embodiments, two laser sources (e.g., 201a and 201b or 201a' and 201b') may be used to emit light of two different wavelengths. In some embodiments, the laser sources may be polarized laser sources, unpolarized laser sources, or a combination of polarized and unpolarized laser sources. As an example, without limiting the present invention, a low power infrared (IR) laser may be used to illuminate a target (102) through the optical fiber (104) to measure the distance between the distal end (204) of the optical fiber (104) and the target (102). In other embodiments, a laser other than an IR laser may be used. However, an IR laser may be used because it does not contain a visible light beam that may be distracting to the user.

At block (1204), the method (1200) includes receiving a reflected light beam from a target via an optical fiber. For example, the LETD system (106) can receive a reflected light beam (334a) or a reflected light beam (514a) from a target (102) via the optical fiber (104). In some embodiments, the reflected light beam (334a) or the reflected light beam (514a) can include a mixture of light beams reflected from, for example, a proximal end (202) of the optical fiber (104), a distal end (204) of the optical fiber (104), a port (314), a blast shield (not shown), and the like. In various embodiments, the LETD system (106) can be configured to identify a reflected light beam suitable for measuring an intensity.

At block (1206), the method (1200) includes measuring an intensity of the reflected light beam by detecting the reflected light beam using one or more photodetectors and transmitting an indication (e.g., an electrical signal, etc.) of the intensity of the reflected light beam measured by the one or more photodetectors to a processing unit. For example, the LETD system (106) can measure the intensity of the reflected light beam (334a) or the reflected light beam (514a) (also referred to herein as a returned signal) by detecting the returned signal using one or more photodetectors provided to the LETD system (106). In some embodiments, since two different wavelengths are used to illuminate the target (102), the measured intensities are for two different wavelengths. Thus, two measured intensities corresponding to two different wavelengths of a laser source (e.g., laser sources 302a and 302b, etc.) can be transmitted to a processing unit (108) associated with the LETD system (106). In various embodiments, three or more different wavelengths can be utilized, measured, and/or transmitted.

At block (1208), the method (1200) includes receiving, by the processing unit, an indication of the intensity of a reflected light beam as measured by one or more photodetectors. For example, the processing unit (108) may receive an electrical signal comprising an indication(s) of the measured intensity of the reflected light beam (e.g., 334a) from the LETD system (106).

At block (1210), the method (1200) includes estimating, by the processing unit, a distance between the distal end of the optical fiber and the target based on the intensity of the reflected light beam measured by one or more optical detectors. For example, the processing unit (108) can estimate the distance between the distal end (204) of the optical fiber (104) and the target (102) based on the measured intensity of the returned signal. In some embodiments, the processing unit (108) can plug the measured intensity into Equation 1, as shown below:

The intensity of the returned signal = R * e ^{(-λ * X)} : Equation 1

In the above Equation 1, “R” represents the target reflection coefficient which is affected by the target composition, target color/pigment, target angle, target surface, etc.; “λ” represents the water absorption coefficient at a specific wavelength; and “X” represents the distance between the distal end (204) of the optical fiber (104) and the target (102).

In the above Equation 1, "X" and "R" are unknown parameters to be determined by the processing unit (108). Therefore, in order to determine the values of "X" and "R", the processing unit (108) can substitute two measured intensity values into the above Equation 1 to obtain two equations having the water absorption coefficient of the corresponding wavelength and the values substituted for the measured intensity. For example, the two equations having the substituted values can be as shown below:

I _(HI) = R*e ^(-λ_HI*X) : Formula 1.1

I _(LO) = R*e ^(-λ_LO*X) : Equation 1.2

The processing unit (108) can further simplify the above substituted equations 1.1 and 1.2 as follows, that is, calculate the ratio of measured intensity values obtained for the returned signals of two different wavelengths using equation 2.1, and determine the distance value using the natural logarithm as shown in equation 2.2.

: Equation 2.1

: Equation 2.2

Accordingly, the processing unit (108) can estimate the distance (X) between the distal end (204) of the optical fiber (104) and the target (102) by simplifying Equations 1.1 and 1.2 as shown above. In Equation 2.2 above, "ln" stands for natural logarithm. In some embodiments, the distance (X) can be measured in millimeters. In some embodiments, X is the same distance for the two wavelengths, and R (target reflection) is approximately the same for the two wavelengths when the selected wavelengths are close to each other on the "nm scale". In some embodiments, the wavelengths can be considered close to each other on the "nm scale" when they are within 250 nm (e.g., 1310 nm and 1340 nm or 1310 nm and 1550 nm). However, in many embodiments, a wavelength having a closer R value can be selected. Therefore, 1310 nm and 1340 nm can be selected over 1310 nm and 1550 nm. In some examples of the present invention, the two laser sources (e.g., laser sources (302a and 302b) or the like) can be arranged to emit light having wavelengths within 100 nm of each other.

The condition of the optical fiber (104) may be affected by factors such as changes or degradation of the distal end (204) and/or the proximal end (202) of the optical fiber (104), fiber bending effects on polarization scrambling, or any other degradation or change that occurs in the optical fiber (104). Changes in the optical condition of the optical fiber (104), particularly the tip/end of the optical fiber (104), may adversely affect one or more of the quality of the beam being irradiated, the intensity of the internally reflected light beam, the amount of light that reflects off the target and enters the fiber, the amount of energy that reaches the target, and the accuracy of the measurement. This may affect the accuracy of the distance estimation and potentially cause miscalculations of energy optimization based on distance estimation as described in U.S. Provisional Patent Application No. 63/118,117, which is incorporated herein by reference in its entirety, or may cause inaccuracies in the positioning of the optical fiber (104) during treatment.

Internal reflections in planes associated with the fiber (e.g., the fiber proximal end or the fiber distal end) or in planes associated with other optical elements optically coupled to the fiber (e.g., a lens or shield) can create parasitic and unwanted reflections. Additionally, such internal reflections can change over time due to degradation of the fiber or other elements. Additionally, fiber degradation can change the quality of the laser beam directed toward the target and/or the intensity of reflected light incident on and passing through the optical fiber as back-reflected light from the target tissue, e.g., reflected light beams (334a and 334b).

Thus, in some embodiments, at block (1210), the method (1200) can measure the initial internal reflection of each laser before treatment begins to maintain accurate distance measurements during fiber degradation and changes in internal reflection. In many such embodiments, the initial internal reflection value (or baseline value) can be recorded and used to monitor changes over time. For example, the processing unit (108) can include circuitry (e.g., registers, memory, etc.) to store an indication of the initial internal reflection value. In some embodiments, this process can be performed for one or more optical fibers (104) to be used with the laser system. For example, this process can be performed for each optical fiber (104) to be used with the laser system. Various embodiments described herein can monitor changes from the initial internal reflection value (e.g., stored in circuitry such as the processing unit (108)) to dynamically correct the distance measurements provided herein.

In some embodiments, the processing unit (108) is configured to read (e.g., from a register, memory, etc.) a reference value of such (e.g., unwanted) parasitic reflections using a system pre-processing calibration procedure. In some embodiments, the system pre-processing calibration procedure may include installing the treatment fiber in water without a target. In this context, "without a target" may be interpreted to mean that the nearest target (e.g., a stone, tumor, etc.) is positioned sufficiently far from the tip of the fiber such that no or little light is reflected as a signal (reflected light beam (334a)) from the target into the fiber (104). This distance may be, for example, 10 mm or more from the distal end (204) of the fiber (104) for IR sources (e.g., 1310 nm and 1340 nm sources). However, lengths greater than 10 mm may be utilized when using visible light beams (e.g., 400 nm to 700 nm). Thereafter, under these conditions, the system can activate the laser (e.g., laser sources (302a and 302b) or the like) as described above and measure the reflected signal (reflected light beam (334a)). Since the reflected light (reflected light beam (334a)) is very low under these conditions (e.g., laser active in water without a target), the signal reaching the optical detector is mainly related to internal reflections associated with the optical fiber (104) (e.g., from the port (314), the proximal end (202), the distal end (204), etc.).

In such a scenario, the internally reflected (IR) light beam can be detected using a photodetector, and the measured intensity values can be stored by the processing unit (108) (e.g., in a register, memory circuit, etc.) as IR _(HI) and IR _(LO) . IR _(HI) can be the intensity of the internally reflected light of incident light having a higher water absorption coefficient when no target is near the tip of the optical fiber (104) (e.g., the distal end (204)), whereas IR _(LO) can be the intensity of the internally reflected light of incident light having a lower water absorption coefficient when no target is near the optical fiber (104) (e.g., the distal end (204)). Subsequently, during therapy or treatment, when the laser is activated while the distal end (204) of the optical fiber is positioned closer to the target (102), the reflected light beam (334a) can be reflected backwards through the optical fiber (104) and detected using the light detector described herein.

In addition to calculating the measured intensity values as described above, the processing unit (108) may store the measured intensity values in block (1210) (e.g., in a register, memory circuit, etc.) as I _(HI) (which may be an indication of the intensity of the signal returned from the target (102) (e.g., tissue, stone, etc.) corresponding to a wavelength having a higher water absorption coefficient (HI)) and as I _(LO) (which may be an indication of the intensity of the signal returned from the target (102) (e.g., tissue, stone, etc.) corresponding to a wavelength having a lower water absorption coefficient (LO). However, to remove the value of the parasitic (or unwanted) reflection from the reading of the actual reflected light beam (334a), the processing unit (108) can subtract and/or reduce IR _(HI) from the reading of the actual returned signal I _(HI) as shown in Equation 3.1 below, and subtract and/or reduce IR _(LO) from the reading of the actual returned signal I _(LO) as shown in Equations 3.1 and 3.2 below, respectively.

I' _(HI) = I _(HI) - IR _(HI) : Formula 3.1

I' _(LO) = I _(LO) - IR _(LO) : Formula 3.2

In the above Equation 3.1, I' _(HI) represents the newly calculated intensity of the returned signal corresponding to the wavelength with higher water absorption coefficient (HI) (without parasitic (or unwanted) reflections); I _(HI) represents the measured intensity of the returned signal corresponding to the wavelength with higher water absorption coefficient (HI) (under parasitic (or unwanted) reflections); and IR _(HI) represents the measured intensity of the internally reflected light of the incident light with higher water absorption coefficient (measured "without a target").

Similarly, in the above Equation 3.2, I' _(LO) represents the newly calculated intensity of the returned signal corresponding to the wavelength with lower water absorption coefficient (LO) (without parasitic (or unwanted) reflections); I _(LO) represents the measured intensity of the returned signal corresponding to the wavelength with lower water absorption coefficient (LO) (under parasitic (or unwanted) reflections); and IR _(LO) represents the measured intensity of the internally reflected light of the incident light with lower water absorption coefficient (measured "without a target").

Therefore, using the new century calculated values (I' _{( HI)} and I' _{( LO)} ), the processing unit (107) can determine the distance between the distal end (113) of the optical fiber (103) and the target (101) by substituting the new "corrected" values (I' _{( HI)} and I' _(LO) ) into Equation 2.2 as shown below:

In some embodiments, the above "X" formula can also be represented as shown below:

As mentioned above, internal reflections may not be constant over time, and may vary due to some change in some internal optical parameter of the system (as opposed to changes due to dynamics of the treatment environment external to the system), for example, some change in the optical quality of the distal end (204) of the optical fiber (104). Due to one or more of the power level of the treatment beam (326), cavitation effects occurring at the distal end (204) (or tip) of the optical fiber (104), and the liquid environment in which the fiber is placed during treatment, the optical fiber experiences varying amounts of degradation, primarily at the distal end (204) (or tip). Therefore, in some embodiments, “real-time” or “dynamic” correction may be performed by repeatedly monitoring the reflected light beam (334a) during a treatment and dynamically accounting for or adjusting for these changes in internal reflections. For example, to perform such real-time corrections, a correction laser (e.g., laser source (302c) or the like) as illustrated in the configuration described herein may be used to more accurately perform distance estimations that account for such degradation of the optical fiber (104).

As described in connection with these configurations, the correction laser beam (e.g., optical beam (320c) or the like) has a wavelength that has a very high absorption coefficient in water. For example, the wavelength of the polarized laser source (302c) or the unpolarized laser source (502c) may be 1435 nm. Since the laser beams generated by these “correction” laser sources are very strongly absorbed in the liquid environment as described above, virtually no reflected optical beams (334a) associated with such laser beams return to the fiber. Thus, while the correction laser source is activated, the reflected optical beams (334a) having the wavelength of the correction laser source are primarily associated with (or represent) internal reflections.

In some embodiments, the processing unit (108) may be configured to read and store, at block (1210), one or more baseline values for internal reflections of the system (100) associated with the laser source (e.g., laser source (302c) or the like) prior to the start of treatment. These one or more baseline values may represent the "quality" of the optical fiber (104) (e.g., optical quality of the distal end (204)) prior to the start of treatment and may be stored by the processing unit (108) (e.g., in a register, memory circuitry, etc.). Additionally, the processing unit (108) may be configured to continuously measure (e.g., periodically, repeatedly, etc.) the internal reflections of light emitted by the calibration laser source (e.g., laser source (302c) or the like) in "real time" during the treatment to identify deviations from the baseline values. Monitoring these deviations can provide an indication of a degradation in the optical quality of the optical fiber (104), which can be used to correct the measured back-reflected intensity associated with the reflected optical beam (334a). In many embodiments, based on the readings of the internal reflections of light emitted by the calibration laser source, the processing unit (108) can correct the calibration parameters for the primary laser source (e.g., laser sources (302a and 302b)).

In some embodiments, the method (1200) may include a block for a calibration process. For example, the processing unit (108) may read and store one or more internal reflection values associated with light emitted by a calibration laser source activated in water while the system (100) is in water. Because the calibration laser source is highly absorbed by water, the sensitivity to distance to the target (102) during the calibration reading of the calibration laser source may be much less than the measurement of a reflected signal associated with light emitted by another laser source. As described in more detail below, this allows for calibration laser measurements to continue during treatment even when the target is close to the tip of the fiber.

Thereafter, the target (102) can be illuminated using one of the exemplary configurations having a non-calibrated laser source. In such a scenario, the reflected light beam (334a) and the reflected light beam (334b) can be detected using a photodetector, and the processing unit (108) can store the measured intensity values as I _(HI) and I _(LO) along with the additional and associated measurement value IR _(CAL) of the internal reflection of the calibration laser. I _(HI) can be the intensity of the back reflection from the target of the incident light having a higher water absorption coefficient, I _(LO) can be the intensity of the back reflection from the target of the incident light having a lower water absorption coefficient, and IR _(CAL) can be the intensity of the internal reflection of the incident light from the calibration laser source.

In some embodiments, the presence or absence of the target (102) may not affect the reflected IR _(CAL) because the incident light from the calibration laser source is largely absorbed by the water. As a result, changes in the IR _(CAL) value may be a result of changes in the degradation of the optical fiber (104), particularly the tip (e.g., the distal end (204)) of the optical fiber (104). In some embodiments, based on the relative changes in the IR _(CAL) values, the processing unit (108) may adjust previously measured IR _(HI) and IR _(LO) values, or currently measured I _(LO) or I _(HI) .

Thereafter, during treatment (e.g., when the laser is activated to treat the target (102), the reflected light beam (334a) from the laser source (302a or 502a) and the laser source (502a or 502b) and the light reflection (610) from the calibration laser source (302c or 502c) can be detected using the light detector, while the target (102) is present (e.g., close enough to generate a reflected light beam (334a), e.g., less than 10 mm from the distal end (204) of the optical fiber (104). The processing unit (108) may store the measured intensity values in block (1210) as I _(HI) (which may represent the intensity of the returned signal corresponding to light having a wavelength having a higher water absorption coefficient (HI)), I _(LO) (which may represent the intensity of the returned signal corresponding to light having a wavelength having a lower water absorption coefficient (LO)), and IR _(CAL) (which may represent the intensity of the returned internal reflection signal corresponding to light having a wavelength having a higher water absorption coefficient (e.g., light emitted by the calibration laser source (302c or 502c)). In addition, to determine the calibration factor, the processing unit (108) may divide the IR _(CAL-PRE) of the calibration process pretreatment from the IR _(CAL-DUR) of the calibration process performed during the treatment as shown in Equation 4 below.

Correction Factor (CF) = : Equation 4

The correction factor can be “1” when the internal reflection of the correction laser source is the same before and during the treatment and there is no change in the optical fiber (104). Additionally, to modify the parameters for the main laser sources (302a and 302b) or the laser sources (502a and 502b) based on the correction factor, the processing unit (108) can use the correction factor as shown in Equations 5.1 and 5.2 below.

I" _(HI) = I _(HI) - IR _(HI) x CF : Formula 5.1

I" _(LO) = I _(LO) - IR _(LO) x CF: Formula 5.2

In the above Equation 5.1, I" _(HI) represents the newly corrected intensity of the back-reflected signal from the target (102) corresponding to the light having a wavelength with a higher water absorption coefficient (HI); I _(HI) represents the measured intensity of the back-reflected signal from the target (102) corresponding to the light having a wavelength with a higher water absorption coefficient (HI); IR _(HI) represents the measured intensity of the internal reflection of the incident laser light having a wavelength with a higher water absorption coefficient (measured "without a target"); and CF represents a correction factor determined using Equation 4.

In the above Equation 5.2, I" _(LO) represents the newly corrected intensity of the back-reflected signal from the target corresponding to the light having the wavelength having the lower water absorption coefficient (LO); I _(LO) represents the measured intensity of the back-reflected signal from the target corresponding to the light having the wavelength having the lower water absorption coefficient (LO); IR _(LO) represents the measured intensity of the internally reflected light of the incident laser light having the wavelength having the lower water absorption coefficient (measured "without target"); and CF represents a correction factor determined using Equation 4.

Therefore, using the new calibrated intensity values (I" _(HI) and I" _(LO) ), the processing unit (108) can determine the distance between the distal end (204) of the optical fiber (104) and the target (102) by substituting the new calibrated values (I" _(HI) and I" _(LO) ) into Equation 2.2 at block (1210) as shown below:

Thus, in this manner, system preprocessing calibration and real-time calibration can be performed and used to update the calibration coefficients in real-time (e.g., via the processing unit (108)) to dynamically account for changes (e.g., degradation, etc.) in the optical fiber (104) during operation. In some embodiments, preprocessing and real-time calibration can be performed to ensure accuracy of the estimated distance between the distal end (204) of the optical fiber (104) and the target (102) as the optical fiber (104) degrades.

At block (1212), the method (1200) includes displaying, by the processing unit (108), an estimated distance between the distal end (204) of the optical fiber (104) and the target (102) via the indicator (e.g., at block (1210)). For example, the processing unit (108) displays the estimated distance between the distal end (204) of the optical fiber (104) and the target (102) via the indicator (110) associated with the processing unit (108). As a specific example, the indicator (110) may include one or more of a visual indicator, an audio indicator, and a haptic indicator. Accordingly, the processing unit (108) may send a control signal to the indicator (110) at block (1210) to cause the indicator to display an indication of the estimated distance (e.g., via a display, an auditory signal, a haptic signal, etc.).

In some embodiments, based on the estimated distance between the distal end (204) of the optical fiber (104) and the target (102), one or more of the position of the optical fiber (104), the orientation of the optical fiber (104), the characteristics of the treatment beam, etc., can be changed in real time to accurately and efficiently affect the treatment beam to the target (102), for example, through more precise aiming.

FIG. 13 depicts a flow diagram showing a method (1300) for estimating a distance between a fiber end and a target according to some embodiments of the present invention. The method (1300) is described with reference to various configurations of the system (100) and the LETD system (106) described above. However, it is to be understood that the method (1300) may be implemented using other LETD systems than those described herein. Embodiments are not limited in this context.

At block (1302), the method (1300) includes determining a first intensity value based on a first reflected laser light corresponding to laser light of a first wavelength, wherein the laser light of the first wavelength exits the distal end (204) of the optical fiber (104) and the first reflected laser light is reflected by the target (102) and enters the distal end (204) of the optical fiber (104). For example, the processing unit (108) can determine the first intensity value based on a reflected light beam (334a) corresponding to light having a wavelength having a high water absorption coefficient. In some embodiments, the laser light corresponding to the wavelength having a high water absorption coefficient can be generated by the laser source (302a or 502a) as discussed above.

At block (1304), the method (1300) includes determining a second intensity value based on a second reflected laser light corresponding to laser light of a second wavelength, wherein the laser light of the second wavelength exits the distal end (204) of the optical fiber (104) and the second reflected laser light is reflected by the target (102) and enters the distal end (204) of the optical fiber (104). For example, the processing unit (108) can determine the second intensity value based on a reflected light beam (334a) corresponding to light having a wavelength having a low water absorption coefficient at block (1304). In some embodiments, the laser light corresponding to the wavelength having a low water absorption coefficient can be generated by the laser source (302b or 502b) as described above.

At block (1306), the method (1300) includes a step of computing a ratio of the first intensity value to the second intensity value. For example, the processing unit (108) can compute the ratio of the first intensity value to the second intensity value using Equation 2.1 at block (1306). At block (1308), the method (1300) includes a step of estimating a distance between the distal end (204) of the optical fiber (104) and the target (102) based on the ratio of the first intensity value to the second intensity value derived at block (1306). For example, the processing unit (108) can estimate the distance between the distal end (204) of the optical fiber (104) and the target (102) based on the ratio of the first intensity value to the second intensity value using Equation 2.2 at block (1308).

FIG. 14 illustrates a flow diagram showing a method (1400) for estimating a distance between a fiber end and a target according to some embodiments of the present invention. The method (1400) is described with reference to various configurations of the system (100) and the LETD system (106) described above. However, it is understood that the method (1400) can be implemented using other LETD systems than those described herein. Embodiments are not limited in this context.

At block (1402), the method (1400) includes illuminating a target with laser light of a plurality of different wavelengths. For example, any of the configurations described above can be used to illuminate the target (102) with light beams (332) of a plurality of different wavelengths. For example, the light beams (332) can include light beams (320a, 320b, 320c), treatment beams (326), and/or beams (328) (or the like).

At block (1404), the method (1400) includes receiving a reflected light beam from a target via the optical fiber. For example, one of the configurations described herein can be used to receive the reflected light beam (334a) (e.g., corresponding to light reflected from the target (102)) and transmit it back through the optical fiber (104). In some embodiments, the reflected light beam (334a) can reflect off the target (102) and enter the distal end (204) of the optical fiber (104), thereby comprising the reflected light beam (334a). The reflected light beam (334a) can also include light reflected from optical components within the system (e.g., the proximal end (202), the distal end (204), etc.), and can include an optical reflection (610) corresponding to reflected light associated with the calibration light beam (320c).

At block (1406), the method (1400) includes measuring an intensity of a reflected light beam (334a) using one or more photodetectors. In many embodiments, any of the configurations described herein can be used to measure the intensity of the reflected light beam (334a) using one or more photodetectors. For example, photodetectors (photodetectors 318a and 318b) can be used to measure the intensity of the reflected light beam (334b). In other examples, other photodetectors (e.g., photodetectors 512 or the like) can be used to measure the intensity of the reflected light beam (334a).

At block (1408), the method (1400) includes estimating a distance between a distal end (204) of the optical fiber (104) and a target (102) based on an intensity of a reflected light beam (334a) measured using one or more optical detectors. For example, the processing unit (108) can be used to estimate a distance between the distal end (204) of the optical fiber (104) and the target (102) based on the intensity of a reflected light beam (334a) measured by one or more optical detectors.

It is understood that the optical components of the LETD system described herein (e.g., beam splitters, polarizers, beam combiners, collimators, circulators, WDMs, etc.) are not constant over time. That is, their optical properties may change during a procedure due to, for example, thermal and environmental changes, mechanical vibration, exposure to a therapeutic laser beam (e.g., high power laser beam), or other reasons. If the optical components change, the system (e.g., processing unit (108), etc.) may not be able to adequately distinguish between changes in the distance between the distal end (204) of the optical fiber (104) and the target (102) or changes in the optical components. Accordingly, the present invention provides for the use of light reflected from the proximal end (202) of the optical fiber (104) as a reference or calibration light for the optical components that capture or "snap out" the light, thereby allowing the distance between the distal end (204) of the optical fiber (104) to be accurately determined even when the optical components change over time.

Since the reflected light beam (334a) has a non-zero angle of incidence, it is understood that the light reflected from the proximal end (202) of the optical fiber (104) has a different optical path from the main treatment laser path. In general, the present invention provides a LETD system configuration having a mirror that directs light out of the optical path and into a polarizing beam splitter having two detectors. Analysis of the signals from these detectors can provide a measure of the system change compared to the initial state.

In some embodiments, in each of the exemplary configurations described herein, the proximal end of the optical fiber (104) can be coated with a specialty coating, such as an anti-reflection (AR) coating. The AR coating can help reduce noise generated at the proximal end (202) of the optical fiber (104) and increase dynamic range. In some embodiments, the optical signal entering the light detector can include one or more of: (a) reflections from the port lens; (b) reflections from the blast shield; (c) reflections from the proximal end (202) of the optical fiber (104); and/or (d) reflections from the distal end (204) of the optical fiber (104).

In various embodiments, the AR coating for the blast shield can reduce reflections at the port lens to less than 1%, the AR coating for the port lens can reduce reflections at the blast shield to less than 1%, and the AR coating at the proximal end (202) of the optical fiber (104) can reduce reflections at the proximal end (202) of the optical fiber (104) from 3.5% to about 0.5%. In some embodiments, the signal reflected from a target (102), such as a rock, can be very low energy, for example, about 1% of the optical fiber output power when the distance from the optical fiber tip to the tissue is about 0 mm. By reducing reflections at the proximal end (202) of the optical fiber (104) to about 0.5%, the present invention can help improve the dynamic range of the signal reflected from the target (102).

FIG. 15 illustrates an LETD system (1500) similar to the LETD system (900) but having additional “light snatch” components as described herein. For example, the LETD system (1500) includes laser sources (502a, 502b, 502c) and a laser source (702), a WDM (704), a beam splitter (902), a light detector (512), a power detector (306), and a beam combiner (310). The LETD system (1500) additionally includes a mirror (1502), a polarizing beam splitter (1504), and a light detector (1506a). During operation, the mirror (1502) may direct light reflections from the optical path of a reflected light beam (334a) to the polarizing beam splitter (1504). In other words, the mirror (1502) is provided to divert the light reflection (1510) from the optical path of the reflected light beam (334a) so that it does not reach the original optical detector (e.g., the light detector (512)). It should be noted that this drawing does not represent the angles of incidence of the various light beams. However, it is understood that the angles of the light beams are not often 90 degrees incident on the various optical components as illustrated. For example, the light reflection (1510) may have an angle of incidence of 4 degrees (or a similar angle). Additionally, although the mirror (1502) is illustrated in the optical path of the light reflection (1510) between the beam combiner (310) and the beam splitter (902), the mirror (1502) may instead be positioned in the optical path between the port (314) and the beam combiner (310). Additionally, in some examples, the mirror (1502) may be positioned and arranged so as not to block the light beam (806) as shown and described, but rather to merely redirect the light reflection (1510).

As can be understood, the light reflection (1510) is linearly polarized and thus maintains its polarization even after being reflected from the proximal end (202) of the optical fiber (104). The light reflection (1510) is sent through a mirror (1502) to a polarizing beam splitter (1504), where it is split into two component light beams, one having a polarization parallel to the light incident on the proximal end (202) of the optical fiber (104) and one having a polarization perpendicular to the light incident on the proximal end (202) of the optical fiber (104).

The LETD system (1500) further includes light detectors (1506a and 1506b) arranged to measure the intensity of the light reflection (1510) split by the polarizing beam splitter (1504). In particular, the light detectors (1506a and 1506b) are arranged to measure the intensity of the light based on polarization as schematically described herein. However, it should be noted that the parallel component of the light reflection (1510) includes both a portion of the light reflection (610) and the light reflection (1510), whereas the perpendicular component of the light reflection (1510) includes only a portion of the light reflection (610).

In some embodiments, the distance between the distal end (204) of the optical fiber (104) and the target (102) can be expressed by Equation 6.1 shown below.

: Equation 6.1

Considering the fact that each laser source fires with different illumination pulses and energies, the intensities can be normalized using Equation 6.2, where I _refHI is the intensity of the reference power detector (306) for the high water absorption coefficient light source, I _refHO is the intensity of the reference power detector (306) for the low water absorption coefficient light source, and I _normHI and I _normLo are the normalized intensities.

: Equation 6.2

A "pure" reflection signal can be expressed by Equation 6.3, where I _DETλ is the detector reading for wavelength λ, I _distλ is the reflection reading at the distal end (204) of the fiber (104) for wavelength λ, I _lensλ is the reflection reading at the focusing lens (1514) of the fiber (104) for wavelength λ, and I _sigλ is a separated optical signal for wavelength λ (e.g., the "subtracted" optical signal described herein). Note that Equation 6.3 assumes that reflections at the proximal end of the fiber are removed from the optical path (e.g., reduced to zero), and that reflections at the blast shield (1512) are also removed.

: Equation 6.3

The LETD system (1500) is a reflectance correction of wavelength (λ) at the focusing lens (1514). ; The detector reading at wavelength (λ) is ∞. , and reflection or at the distal end (204) of the optical fiber (104) at wavelength (λ) of ∞. Wow, defined above can be arranged to correct the optical system by deriving the sum of the corrections, which are understood to be not a function of time (or rather constant during the procedure).

If we separate the signal from the detection unit in Equation 6.3 above, This is it. If we consider as a function of time, this value can be calculated using a specific wavelength. Using 1435 nm as a specific example, we get Equation 6.4 below, which is a correction for the distal tip reflection.

: Equation 6.4

Taking the signal from the detector during operation gives Equation 6.5, which is the correction for the distal tip reflection from the actual detector.

: Formula 6.5

Substituting the above into Equation 6.5 gives Equation 6.6, which is the signal value extracted from the signal detector (e.g., constant static reflection).

: Equation 6.6

As can be understood, the optical path changes as the transmittance is added. In particular, several optical components can have varying transmittance and/or reflectance values. For example, a focusing lens (transmittance is ), blast shield (penetration is indicated by ), and optical fiber (104) (transmittance is ) can change over time, i.e., signals sensitive to this transmittance and Therefore, the final equation for the signal with nonstationary reflections can be defined using Equation 6.7.

: Equation 6.7

Detection value ( ) is measured as a whole without the option to distinguish between factors other than the detector. However, Equation 6.8 shown below details the transmittance as a function where the lens, blast shield and fiber can be considered constants and can be the same as the normalized signal described above.

,

It goes like this:

: Formula 6.8.

However, by applying correction to the lens with the distal end (204) without lens reflection, Equation 6.6 can be reduced separately as shown in Equation 6.9 below.

: Equation 6.9

Components of the lens reflectivity (e.g., ) can be seen to be missing in Equation 6.9. If we further reduce the equation by completely ignoring the presence of the lens, we get Equation 6.10.

: Equation 6.10

Combining the above equations, we can define distance as a function of luminance and reflectance, as shown in Equation 6.11.

: Equation 6.11

As schematically described above, the configuration or LETD system (1500) illustrated in FIG. 15 is arranged to correct for optical components (e.g., focusing lens (1514), blast shield (1512), etc.) of the system that "extract" light reflected from the proximal end (202) of the optical fiber (104). In general, the light reflection (1510) can be expressed by Equation 6.12 shown below, where f _λ is the coefficient of the signal going in the direction of the light extraction, and I _sigλ is a signal defined as follows:

: Equation 6.12

Equation 6.12 can be rewritten in polarized form as shown in Equation 6.13, where is the mixed polarization value, is the forward source polarization value, is perpendicular to the source polarization value.

: Equation 6.13

For distances of ∞, this formula reduces to formula 6.14.

: Equation 6.14

From the above formula If you use the value of can be extracted from the calibration signal. Thus, the proximal end (202) reflection from the "subtracted" optical signal (e.g., optical reflection (1510)) since The degree is also corrected. As a result, Any change in the value of can be converted into Equation 6.7 for each wavelength. Thus, as mentioned above, The value of So, from the square root Changes in also compensate for these movements.

From the beginning of the procedure, not only from ∞ It is understood that it is advantageous to correct the degree.

Additionally, when using polarized light, the noise of the polarization switch (e.g., WDM (704) or similar) can be taken into account using Equation 6.15.

: Equation 6.15

FIG. 16 depicts a flow diagram showing a method (1600) for estimating a distance between a fiber end and a target according to some embodiments of the present invention. The method (1600) is described with reference to the system (100), and the configuration of the LETD system (106) described above with respect to FIG. 15, or the LETD system (1500). However, it is to be understood that the method (1600) may be implemented using other LETD systems than those described herein. Embodiments are not limited in this context.

In block (1602), the mirror (1502) directs a portion of the light reflected from the proximal end (202) of the optical fiber (104) to the polarizing beam splitter (1504) and the light detectors (1506a and 1506b). That is, the mirror (1502) is arranged to direct a portion of the light reflection (1510) to the polarizing beam splitter (1504). Proceeding to block (1604), the method (1600) can detect the intensity of the polarization component of the portion of the light directed to the detectors. In particular, the light reflection (1510) is divided into polarization components by the polarizing beam splitter (1504), and the light detectors (1506a and 1506b) can detect the intensity of the components of the light reflection (1510).

At block (1606), the method (1600) can determine a transmission function of the optical system based at least in part on the intensity detected at block (1604). For example, the processing unit (108) can execute instructions for determining transmission of the optical system as outlined above in Equations 6.1 through 6.17.

FIG. 17 illustrates an LETD system (1700) similar to the LETD system (1500) but having a single photodetector (1706) and a polarizer (1708) instead of a polarizing beam splitter (1504) and photodetectors (1506a and 1506b). It should also be noted that the LETD system (1700) may be implemented in which the optical laser sources (1702a, 1702b, and 1702c) are arranged to emit unpolarized optical beams (1704a, 1704b, and 1704c), respectively. It should be noted that the processing unit (108) may be arranged to account for changes in the optical components over time as described above with respect to FIGS. 15 and 16, and that the formula for the transfer function is polarization independent as outlined above.

FIG. 18 illustrates a computer-readable storage medium (1800). The computer-readable storage medium (1800) can include any non-transitory computer-readable storage medium or machine-readable storage medium, such as optical, magnetic, or semiconductor storage media. In various embodiments, the computer-readable storage medium (1800) can include an article of manufacture. In some embodiments, the computer-readable storage medium (1800) can store computer-executable instructions (1802) that can be executed by circuitry (e.g., the processing unit (108) or the like). For example, the computer-executable instructions (1802) can include instructions for implementing operations described in connection with method (1200), method (1300), method (1400), and/or method (1600). Examples of computer-readable storage media (1800) or machine-readable storage media can include any tangible medium capable of storing electronic data, including volatile memory or non-volatile memory, removable or non-removable memory, erasable or non-erasable memory, writable or re-writable memory, and the like. Examples of computer-executable instructions (1802) can include any suitable type of code, such as source code, compiled code, interpreted code, executable code, static code, dynamic code, object-oriented code, visual code, and the like.

FIG. 19 is a block diagram of a computing environment (1900) including a computer system (1902) for implementing embodiments according to the present invention. In some embodiments, the computing environment (1900) or a portion thereof (e.g., the computer system (1902)) may include a laser system (e.g., the system (100), the LETD system (106), etc.) or may be incorporated into a laser system. Thus, in various embodiments, the computer system (1902) may be used to determine the distance between the distal end (204) of the optical fiber (104) and the target (102), taking into account the temporal variation of the optical system as outlined above.

The computer system (1902) may include a central processing unit ("CPU" or "processor") (1904). The processor (1904) may include at least one data processor for executing instructions and/or program components to execute user or system generated processes. A user may include a person, a person using a device such as that included herein, or another device. The processor (1904) may include specialized processing units such as an integrated system (bus) controller, a memory management control unit, a floating point unit, a graphics processing unit, a neural processing unit, a digital signal processing unit, and the like. The processor (1904) may be arranged to communicate with input devices (1914) and output devices (1916) via an I/O interface (1912). The I/O interface (1912) may use communication protocols/methods including but not limited to 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.).

Using the I/O interface (1912), the computer system (1902) can communicate with input devices (1914) and output devices (1916). In some embodiments, the processor (1904) can be arranged to communicate with a communications network (1920) via the network interface (1910). In various embodiments, the communications network (1920) can be used to communicate with a remote memory storage device (1906), for example, to access a lookup table, perform an update, or utilize an external resource. The network interface (1910) can communicate with the communications network (1920). The network interface (1910) can use connection protocols including, but not limited to, a 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.

The communication network (1920) 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 a dedicated or shared network representing an association of different types of networks that use various protocols to communicate with each other, such as Hypertext Transfer Protocol (HTTP), CAN protocol, Transmission Control Protocol/Internet Protocol (TCP/IP), Wireless Application Protocol (WAP), etc. The communication network (1920) may also include various network devices, including routers, bridges, servers, computing devices, storage devices, etc. In some embodiments, the processor (1904) may be arranged to communicate with the memory storage device (1906) via the storage interface (1908). The storage interface (1908) can be connected to memory storage devices (1906) including, but not limited to, memory drives, removable disk drives, etc. using connection protocols such as Serial Advanced Technology Attachment (SATA), Integrated Drive Electronics (IDE), IEEE-1394, Universal Serial Bus (USB), Fiber Channel, Small Computer System Interface (SCSI), etc. The memory drives can further include drums, magnetic disk drives, magneto-optical drives, optical drives, Redundant Array of Independent Discs (RAID), solid-state memory devices, solid-state drives, etc.

Additionally, the memory storage device (1906) may include one or more computer-readable storage media used in implementing embodiments according to the present invention. Generally, a computer-readable storage medium refers to any type of physical memory that can store information or data that can be read by a processor. Accordingly, a computer-readable storage medium may store instructions for execution by one or more processors, including instructions for causing the processor(s) to perform a step or steps according to the embodiments described herein. The term "computer-readable medium" should be understood to include tangible items, and exclude carrier waves and transient signals, i.e., non-transitory signals. Examples include random access memory (RAM), read-only memory (ROM), volatile memory, non-volatile memory, hard drives, compact disc (CD) ROMs, digital video discs (DVD), flash drives, disks, and any other known physical storage medium.

The memory storage device (1906) may store a collection of programs or database components, including but not limited to an operating system (1922), application instructions (1924), and user interface elements (1926). In various embodiments, the operating system (1922) may facilitate resource management and operation of the computer system (1902). Examples of operating systems include, but are not limited to, APPLE® MACINTOSH® OS X®, UNIX®, UNIX-like system distributions (e.g., BERKELEY SOFTWARE DISTRIBUTION® (BSD), FREEBSD®, NETBSD®, OPENBSD, etc.), LINUX® distributions (e.g., RED HAT®, UBUNTU®, KUBUNTU®, etc.), IBM® OS/2®, MICROSOFT® WINDOWS® (XP®, VISTA®/7/8, 10, etc.), APPLE® IOS®, GOOGLE ^TM ANDROID ^TM , BLACKBERRY® OS, etc.

The application instructions (1924) may include instructions that, when executed by the processor (1904), cause the processor (1904) to perform one or more of the techniques, steps, processes and/or methods described herein, for example, irrigating a site and examining a site as outlined herein. For example, the application instructions (1924), when executed by the processor (1904), may cause the processor (1904) to perform method (1200), method (1300), method (1400), and/or method (1600).

A user interface element (1926) may facilitate the display, execution, interaction, manipulation, or operation of a program component via text or graphical capabilities. For example, a user interface may provide computer interaction interface elements on a display system operably connected to the computer system (1902), such as a cursor, an icon, a checkbox, a menu, a scroller, a window, a widget, and the like. A user interface element (1926) may be used by application instructions (1924) and/or an operating system (1922) to provide a user interface that allows a user to interact with the computer system (1902), for example. In some embodiments, a user interface element (1926) may be integrated with a display (not shown).

The terms used in this specification are given their common meaning in the relevant technical field or the meaning that appears in the context of their use, but if a clear definition is provided, that meaning shall take precedence.

References to "one embodiment" or "an embodiment" in this specification do not necessarily refer to the same embodiment, but may refer to the same embodiment. Unless the context clearly requires otherwise, the words "including," "including," and the like, throughout this description and claims, are to be construed in an inclusive rather than an exclusive sense, i.e., to mean "including but not limited to." Words using the singular or plural number also include the plural or singular number, unless expressly limited to the singular or multiple, respectively. Additionally, the words "in this specification," "above," "below," and similar meanings, when used in this specification, mean the specification as a whole, and not any specific portion of the specification. When the claims use the word "or" to refer to a list of two or more items, that word includes all of the following interpretations of that word, i.e., any item in the list, all of the items in the list, and any combination of the items in the list, unless expressly limited to one or the other. Any term not explicitly defined herein shall have the ordinary meaning commonly understood by one of ordinary skill in the relevant art(s).

Claims (15)

As a system,
A first laser source for generating laser light of a first wavelength;
A second laser source for generating laser light of a second wavelength;
An optical fiber having a distal end and a proximal end, wherein the optical fiber is configured to receive laser light from the first and second laser sources at the proximal end, reflect a portion of the laser light at the proximal end, emit a portion of the laser light from the distal end, and receive the reflected laser light at the distal end;
A first light detection unit for measuring the intensity of the reflected light;
Second light detector;
A mirror that sends a portion of the laser light reflected from the proximal end to the second light detection unit, wherein the second light detection unit measures the intensity of a portion of the laser light reflected from the proximal end; and
Processor and memory
A system comprising: a memory comprising instructions that, when executed by the processor, cause the processor to estimate a distance between a distal end of the optical fiber and a target based on an intensity of reflected light measured by the first light detector and an intensity of a portion of laser light reflected from the proximal end measured by the second light detector. A system according to claim 1, wherein the first wavelength has a first water absorption coefficient greater than a second water absorption coefficient of the second wavelength. A system according to claim 2, wherein the ratio of the first water absorption coefficient to the second water absorption coefficient is at least 2:1. A system according to claim 3, wherein the first wavelength is from about 1330 nm to about 1380 nm. A system according to claim 3 or 4, wherein the second wavelength is from about 1260 nm to about 1320 nm. A system according to claim 4, comprising a third laser source for generating laser light of a third wavelength used to characterize the state of the optical fiber, wherein the third wavelength has a third water absorption coefficient higher than the first and second water absorption coefficients. A system according to claim 5, wherein the third wavelength comprises a wavelength of about 1435 nm, about 2100 nm, or about 1870 nm to about 2050 nm. A system according to any one of claims 1 to 6, wherein the light detection unit measures a first intensity value of reflected light corresponding to laser light of the first wavelength and a second intensity value of reflected light corresponding to laser light of the second wavelength. In claim 7, the instruction, when executed by the processor, further causes the processor to:
Calculate the ratio of the first century value and the second century value;
A system for estimating the distance between the distal end of the optical fiber and the target based on the ratio of the first intensity value and the second intensity value. A system according to any one of claims 1 to 8, wherein at least one of the first and second laser sources comprises a polarization-maintaining pigtailed fiber laser, a single-mode pigtailed fiber laser or a free-space laser. A system according to any one of claims 1 to 9, comprising a wavelength division multiplexer (WDM) coupled to a proximal end of the optical fiber, wherein the WDM arranges laser light of the first wavelength and laser light of the second wavelength to enter the proximal end of the optical fiber at one or more of the same point and the same angle. As a method,
A step of illuminating a target with laser light of multiple different wavelengths;
A step of receiving a first reflected light beam from the target through an optical fiber;
A step of receiving a second reflected light beam from a proximal end of the optical fiber;
A step of measuring the intensity of the first and second reflected light beams using a plurality of light detectors; and
A step of estimating a distance between a distal end of the optical fiber and the target based on the intensity of a reflected light beam measured using the one or more optical detectors.
A method comprising: A method according to claim 12, comprising the step of emitting laser light of a plurality of different wavelengths through the optical fiber to illuminate the target. A method according to claim 12 or 13, comprising the step of measuring a first intensity value of a reflected light beam corresponding to laser light of a first wavelength, and a second intensity value of a reflected light beam corresponding to laser light of a second wavelength. In claim 14,
A step of calculating a ratio of the first century value and the second century value; and
A step of estimating the distance between the distal end of the optical fiber and the target based on the ratio of the first and second century values.
A method comprising: