JP2018167068A - Optical fiber beam directing systems and apparatuses - Google Patents

Abstract

To provide a lens system for use with an optical fiber.SOLUTION: A lens system includes a lens cap including a substantially cylindrical body, which has a longitudinal axis and includes a first end, an outer cylindrical surface, and a beam directing surface at a second end. The substantially cylindrical body includes a polymer. The substantially cylindrical body and the outer cylindrical surface define a trench between the first end and the beam directing surface. The beam directing surface is oriented at an angle to the longitudinal axis. The trench of the lens cap is sized to accept an optical fiber.SELECTED DRAWING: Figure 1

Description

  The present invention relates generally to the field of optics, and more specifically to the field of lenses for use with optical fibers.

  Optical analysis such as interferometry requires delivering light to a sample of interest and collecting some of the light returned from the sample. Many light sources and light analyzers are usually located away from the sample of interest due to their size and complexity. This is particularly noticeable when the target sample is an internal part of a large object, for example a biological tissue in a living body. One way to optically analyze the inner part is to guide light from a remote light source into the sample using a thin optical fiber. Since the optical fiber has a small cross section, it has little influence on the normal function of the sample. One example of such a method is to analyze a luminal organ, such as a blood vessel, using a fiber optic catheter having one end connected to an external light source and the other end inserted into the blood vessel.

  A major obstacle to optical analysis of internal regions such as lumens is the design and low cost manufacture of small optical devices for focusing or collimating light. Many types of optical analysis, such as imaging and spectroscopy, require that light incident on the sample be focused at a specific distance or substantially collimated. Since light emitted from the tip of a standard optical fiber diverges quickly, a small optical system can be connected to the optical fiber to provide a focusing or collimating function. In addition, it is often desirable to analyze sample locations that are not directly coincident with the optical axis of the optical fiber, such as analysis of the lumen wall of a thin blood vessel. In such situations, in addition to means for focusing or collimating light emitted from the tip of the optical fiber, means for substantially changing the direction of the light are used.

  So far, many methods have been described to produce a compact optical system suitable for attachment to an optical fiber that provides some of the functions described above. In general, these methods are one of three methods: 1) using a graded index (GRIN) fiber part, 2) directly molding the tip of the fiber into a lens, and 3) using a small bulk lens. One of these is used to provide beam focusing means. In general, the beam directing means is 1) using total internal reflection (TIR) of light from the inclined end face of the fiber using an inclined reflecting surface, and 3) using a small bulk type mirror. 4) Provided using one of four methods of using a reflective coating at the fiber tip. However, these methods have many inherent disadvantages, including excessive manufacturing costs, excessive size or focal size and insufficient freedom of choice of focal length.

  There are many small optics known in the art that can be used to analyze internal lumen structure. Each optical system can be conceptually divided into beam focusing means and beam directing means. Light travels from one or more light illumination fibers (which may be single mode or multimode in nature) from an external light source to the internal lumen. The illumination fiber is in communication with a small optical system that focuses the beam and directs the beam relative to the lumen wall. The light returns from the lumen to the extracorporeal analyzer using the same fiber or another fiber with the illumination fiber. In one type of compact optical system design, the focusing means and the directing means are implemented by separate optical elements. In another type of design, the focusing means and the directing means are implemented by the same element.

  Some of the features of existing optical systems are undesirable. For example, in some devices, the entire diameter of the optical element must be similar to the diameter of the optical fiber (often around 125 μm). This greatly reduces the choices available for selecting the focusing element, beam expander and beam director, thus limiting the range of focus sizes and working distances that can be achieved by design. In addition, these very small elements are fragile, difficult to handle and fragile during manufacturing and operation. Third, in many embodiments, air must be provided to use TIR to reorient the beam. This requires maintaining airtightness between the fiber and other elements in order to maintain the air gap. This is a problem when the device is immersed in water, blood or stomach acid or when the device is rotated or moved at high speed to form an image. Fourth, since the GRIN focusing element has a rotationally symmetric refractive index profile, it becomes impossible to correct the cylindrical aberration introduced to the beam. The overall effect of these drawbacks is that certain small optics are expensive, difficult to manufacture, fragile and do not produce a circular output at the focal plane.

  In another approach, a lens system is formed by a molding method using a fusion spliced fiber portion together with a thin layer of polymer and epoxy. However, there is usually a problem with the manufacture of molded lenses that include an annular end face and a bore hole. In general, during injection molding, the bore hole is formed by a thin (135 μm / 220 μm) core pin located in the mold and supported only on one side of the molding tool. Problems arise due in part to the fact that this core pin can be distorted. Such distortion can occur when pressurized liquid polymer is injected into the mold and a force is applied against the core pin. When the force applied to the core pin is sufficiently larger than the rigidity of the core pin, the core pin is distorted, resulting in a molding defect that the bore becomes uneven or bends obliquely.

  In view of various issues, including the issues identified above and other issues, there is a need for optical lenses, assemblies that do not require core pins during manufacturing, and manufacturing methods associated therewith. The present invention addresses this and other needs.

  In one aspect, the invention relates to a molded lens for use with an optical fiber for OCT imaging. In one embodiment, the molded lens includes a cylinder having a first end and a second end and defining a major axis. In other embodiments, the surface of the first end of the cylinder is inclined with respect to the long axis of the cylinder and the second end defines a groove. In other embodiments, the groove is sized to receive an optical fiber.

  In one embodiment, the first end is a plane that is inclined to reflect light received from the optical fiber by reflection through a side of the cylinder. In another embodiment, the first end is non-tilted to reflect light received from the optical fiber by reflection through a side of the cylinder and to focus the light at a position outside the cylinder. Define the plane. In yet another embodiment, the bore stops in a plane that is inclined with respect to the long axis of the cylinder. In yet another embodiment, the center of the long axis of the bore and the long axis of the groove is concentric with the long axis of the cylinder. In another embodiment, the lens is made of a material selected from the group consisting of acrylic, polycarbonate, polystyrene, polyetherimide, polymethylpentene, and glass. In other embodiments, the lens is formed using a resin that can be poured into the lens to reduce the injection pressure and corresponding stress on the tool during molding. Thereafter, it is cured by a chemical reaction.

  In another aspect, the invention relates to an OCT probe. In one embodiment, an OCT probe includes an optical fiber having a first end adapted to communicate with a light source, a second end, and defining a major axis; A mold lens comprising a cylinder having a second end and defining a major axis, wherein the surface of the first end of the cylinder is inclined with respect to the major axis of the cylinder, and the second end The portion defines a groove or a bore, the groove and the bore including a molded lens configured to receive the optical fiber. In another embodiment, the optical fiber is held in the bore or groove by an adhesive. In yet another embodiment, the first end of the cylinder is a flat surface inclined to reflect light received from the optical fiber by reflection through the side of the cylinder. In yet another embodiment, the first end of the cylinder reflects light received from the optical fiber by reflection through the side of the cylinder and focuses the light at a position outside the cylinder. Define an inclined non-planar surface.

  In yet another embodiment, the surface of the second end of the optical fiber is inclined with respect to the long axis of the optical fiber. In yet another embodiment, the angle of the second end of the optical fiber with respect to the long axis of the optical fiber is substantially the same as the angle of a plane inclined with respect to the long axis of the cylinder. In one embodiment, the optical fiber is held in the groove or bore using an adhesive having a refractive index that matches the material of the mold lens.

  In yet another aspect, the invention relates to a molded lens for use with an optical fiber for OCT imaging. In one embodiment, the molded lens includes a cylindrical solid having a first end and a second end and defining a major axis, wherein the surface of the first end of the cylindrical solid is Inclined with respect to the long axis of the cylindrical solid, the second end covers the first end of the metal tube, the optical fiber is glued into the bore of the metal tube, and the first of the metal tube It extends from the end. In another embodiment, the first end of the cylindrical solid is a flat surface that is inclined to reflect light received from the optical fiber by internal reflection through the sides of the cylindrical solid. In yet another embodiment, the first end of the cylindrical solid reflects light received from the optical fiber by internal reflection through the side of the cylindrical solid, and the light is reflected outside the cylindrical solid. Define an inclined non-planar surface to focus at a location.

  In yet another aspect, the invention relates to an OCT probe. In one embodiment, the OCT probe includes an optical fiber having a first end adapted to communicate with a light source, a second end, and defining a major axis; A mold lens comprising a cylindrical solid having a second end and defining a major axis, wherein the surface of the first end of the cylindrical solid is at the major axis of the cylindrical solid. And the second end covers the first end of the metal tube, and the optical fiber is glued into the bore of the metal tube and extends from the first end of the metal tube. And a molded lens. In another embodiment, the first end of the cylindrical solid is a flat surface that is inclined to reflect light received from the optical fiber by internal reflection through the sides of the cylindrical solid. In yet another embodiment, the first end of the cylindrical solid reflects light received from the optical fiber by internal reflection through the side of the cylindrical solid, and the light is reflected outside the cylindrical solid. Define an inclined non-planar surface to focus at a location.

  In yet another aspect, the invention relates to a lens. The lens includes a generally cylindrical body having a major axis and including a fiber receiving end surface defining a slot, a cylindrical outer surface, and a beam directing surface, in fluid communication with the slot, and the fiber receiving end surface and beam directing. A groove having a first end and a second end and defining a major axis is defined by the substantially cylindrical body and the cylindrical outer surface, and the beam directing surface is disposed on the major axis. In contrast, the groove is configured to have a size capable of receiving an optical fiber. In one embodiment, the present invention relates to an intravascular imaging probe that includes an optical fiber disposed within a lens groove. The optical fiber can be placed in the torque wire. In one embodiment, the light exits from the end face of the optical fiber in the groove so that divergent light is received by the lens. In one embodiment, the lens is a single structure.

The structure and function of the present invention can be best understood by reading the description herein in conjunction with the accompanying drawings. The drawings are not necessarily to scale, emphasis being placed on the principles described. In all respects, the drawings are for illustration purposes only and are not intended to limit the invention. The scope of the invention is defined only by the claims.
FIG. 1 is a block diagram of an image data collection system including a lens according to an exemplary lens embodiment of the present invention. FIG. 2 (a) is a perspective view of an exemplary lens embodiment of the present invention. FIG. 2B is a longitudinal sectional view of the lens of FIG. FIG. 2C is a top view of the lens of FIG. FIG. 2D is a side view of the lens of FIG. FIG. 2E is a rear view of the lens of FIG. FIG. 2F is a front view of the lens of FIG. FIG. 2G is another perspective view of the lens of FIG. FIG. 3 is a photomicrograph of a molded lens according to an exemplary embodiment of the present invention. FIG. 4A is an OCT image of the lumen of a blood vessel photographed using a lens. FIG. 4B is an OCT image of a blood vessel lumen imaged using a molded lens according to an exemplary embodiment of the present invention. FIG. 5 is a schematic view of a mold for making a molded lens according to another embodiment of the present invention. 6 is a longitudinal sectional side view of a molded lens made in accordance with the embodiment of the present invention shown in FIG. FIG. 7 is a longitudinal cross-sectional side view of a lens assembly configured to be molded with a marker according to another embodiment of the present invention. FIG. 8 is a longitudinal top view of the probe constructed from the assembly of FIG. FIG. 9 is a side view of the probe of FIG. FIG. 10 is a side view of a lens including a marker according to another embodiment of the present invention.

  Advances in advanced optical analysis or imaging methods such as confocal microscopy, single and multiphoton fluorescence imaging, harmonic imaging, optical spectroscopy and optical coherence tomography (OCT) And had a great impact on in vivo imaging of animals and humans. Although these methods differ in many ways, they share a common design characteristic of focusing or collimating the incident light used to illuminate the target sample. Focused light has higher optical power density to produce higher signal levels and better localization of incident light to obtain better spatial resolution compared to unfocused light There are a number of advantages including:

  A focused or collimated beam is generated by directing the output of a light source through a series of optical elements that together form an optical system. The elements of the optical system are selected so as to obtain a desired focal size that occurs at a desired distance away from the last element of the optical system, called the “working distance”. Each specific optical analysis application has its own optimal focus size and working distance. For example, confocal microscopy requires a small focus size close to 1 μm. On the other hand, OCT requires a medium focus size of about 5 μm to about 100 μm.

  A wide range of focal spot sizes and working distances can be obtained using an optical system consisting of conventional bulk lenses, but in many applications, flexible and compact optics for analyzing samples inside larger objects A system is required. Bioclinical medicine is an example of a field where this requirement is often required. Light from an external light source can be used for optical analysis of luminal structures such as the esophagus, intestine, urinary tract, airways, lungs and blood vessels. Such light is transmitted by the soft probe, focused by a small optical system, and returns to the external data analysis system through the soft probe.

  Furthermore, it is often desirable to analyze the lumen wall rather than the contents of the lumen, for example, imaging of the intima and media of the vessel wall using OCT rather than imaging of blood contained in the blood vessel. This provides a further design goal of directing the beam away from the long axis of the optical system or along other preferred directions (or range of directions). These types of optical probes are often referred to as “side-firing”, “side-directed”, “side imaging” or “side-looking”. These lumens are as small as several millimeters in the case of blood vessels, which makes it difficult to design a compact optical system. In addition, the embodiments described herein are also suitable for use in various embodiments of multi-fiber or fiber bundles. Various embodiments described below address these needs and other needs related to probe components and beamforming.

Exemplary Embodiments of Focusing an Optical Fiber Beam The present invention relates in part to a lens or optical element having an elongated three-dimensional shape, such as a substantially cylindrical solid. The lens defines a groove. The lens and the groove defined by the lens are sized to receive the optical fiber portion and operatively direct and focus the light. The lens can be fixed to an optical fiber and used to both focus and redirect light outside the optical element and to receive light from the target sample. The invention relates in part to systems and methods of use that include certain lens embodiments and optical fibers as part of an insertable probe. The probe can be used to perform optical analysis of luminal structures in vivo.

  Other embodiments of the present invention provide such an apparatus for delivering focused or substantially collimated light to a sample and returning a portion of the light from the sample for processing in an imaging or data acquisition system. Also related to the design, manufacture and use of One non-limiting example of an imaging system or data acquisition system is an optical coherence tomography (OCT) system. FIG. 1 illustrates an exemplary OCT system that includes an exemplary light beam focusing element or lens according to an embodiment of the present invention.

  Lens-based assemblies and other beam directing optics can be used in various applications for inspection and diagnosis. As shown in FIG. 1, one application of such a lens and beam directing optics is OCT. The OCT imaging catheter includes a beam director such as a tilted reflector or other beam directing element suitable for directing light to the inner wall of the coronary artery. In general, the OCT imaging system includes a light source 10 that transmits light to an interferometer 12 through an optical coupler 14 detachably connected to an optical fiber 16. There is a lens 25 at the end of the fiber 16 that sends light from the optical fiber 16 to the blood vessel 22 under study. A combination of the optical fiber 16 and the lens 25 is referred to as an optical probe 20.

  The optical probe 20 rotates, thereby illuminating a scan of the wall of the blood vessel 22 with a single rotation. The light reflected by the wall of the blood vessel 22 is collected by the lens 25 and passes through the optical fiber 16 to the interferometer 12. The resulting interference pattern is detected and analyzed, and the resulting image is displayed on the display 24. As shown, the lens includes a groove 28 sized to receive the optical fiber 16. An adhesive is typically placed in or on the groove 28 to secure the optical fiber 16 to the lens 25.

  The present invention relates in part to the elongated lens 25 shown, for example, in FIGS. 2 (a) -2 (f). The lens 25 is configured to define a substantially cylindrical outer surface 52 having a groove 58 for receiving an optical fiber. Because the elongated optical element includes a groove 58 that can receive an optical fiber (eg, by dropping the optical fiber into the groove 58), the use of the core pin used in the manufacture of prior art lenses and associated manufacturing The problem is avoided.

  In one embodiment, the optical fiber received in the groove 58 of a given lens embodiment includes an optical fiber end face. The optical fiber disposed in the groove is configured to transmit and receive optical signals. The light beam exiting from the end face of the optical fiber is spread or diverged from the end face. Thus, the lens provides beam directing or focusing instead of using a GRIN lens with an optical fiber. Unlike prior art lens bores (which are surrounded on all sides by the material that constitutes or defines the bore), the groove 58 that receives the optical fiber has a slit or U-shaped appearance. That is, the groove 58 is partially surrounded by the two walls of the groove and the bottom of the groove to form a slit or groove region for receiving the optical fiber and bonding the optical fiber to the lens.

  In one embodiment, the groove bottom and wall may be curved, straight, or a combination thereof. In one embodiment, the groove defined by the lens has a width in the range of about 80 μm to about 300 μm so that the groove can receive an optical fiber. In one embodiment, the groove defined by the lens has a length in the range of about 0.2 mm to about 3 mm to ensure that the optical fiber can be adhered to the groove. In one embodiment, the groove defined by the lens has a height selected such that the center of the optical fiber is located along the long axis of the lens. Therefore, the groove is configured to have a height longer / deeper than the width of the groove, for example, as indicated by the boundary portion of the groove. Similarly, in one embodiment, the width of the groove is configured to be smaller than the length of the groove, for example, as indicated by the distance between the optical fiber receiving end face and the groove boundary. In one embodiment, the lens is made of a single material, for example by injection molding.

  More specifically, referring generally to FIGS. 2 (a) to 2 (f), the lens 25 includes a beam transmission surface 50. The beam transmission surface 50 is also called a front end surface, a beam directing surface, or a beam focusing surface. In FIG. 2C and FIG. 2D, λ indicates a region where light exits from the surface 50 as a result of the light moving through the optical fiber in the groove 58 along the long axis L of the lens 25. In one embodiment, the beam transmission surface 50 is a generally flat surface or a substantially planar surface that is inclined with respect to the major axis L of the lens, and the cylindrical body 52 of the lens 25. Reflects and directs light from the optical fiber exiting through the side. In other embodiments, the front end face 50 is curved to define a lens and focuses light directed by the sides of the cylinder 52 at a particular working distance. In one embodiment, the beam directing surface 50 is, but is not limited to, one of biconic asphere, asphere, biconic Zernike, Fresnel and non-uniform rational B-splines. It can be formed to include more than one.

  In one embodiment, the diameter of the lens 25 increases at one or more transition cross sections between the beam directing surface 50 and the groove 58. By providing a step in diameter, the lens can be inserted into other components of the imaging catheter (eg, an impermeable marker band) with a defined portion of the lens extending outside of the other components.

  In one embodiment, the center of the groove 58 is concentric with the long axis L of the cylinder 52. In one embodiment, the cylindrical body 52 is a substantially cylindrical solid having an end face 64 at one end and a beam transmission face 50 at the other end as shown in FIG. In particular, referring to FIG. 2 (c), the inner end face 64 of the lens adjacent to the end face of the optical fiber is also inclined (when the optical fiber is installed in the groove), and the light is reflected to the optical fiber. Polishing is performed with high accuracy in order to suppress artifacts in the OCT image caused by returning. In one embodiment, the range of angles shown between the major axis L of FIG. 2B and the straight line along the surface 50 is about 5 ° to about 25 °. In one embodiment, the optical fiber selected for inclusion in groove 58 is also angle-cleaved or angle-polished to reduce back reflections.

  In one embodiment, the optical fiber is secured to the groove 58 using an adhesive. 2 (b), 2 (d), 2 (e), 2 (f) and 2 (g), by using an open channel or groove 58 instead of the bore hole. As shown in FIG. 1, the formation of bubbles when the optical fiber is fixed in the groove 58 is reduced. This is because bubbles are naturally released upward through the open region of the groove 58 formed in the cylindrical body 25. When the optical fiber is bonded to the molded lens, an adhesive having a refractive index close to that of both the polymer used for manufacturing the molded lens and the optical fiber can be used. In order to suppress back reflection at the optical interface of materials with different refractive indexes, the refractive index mismatch of the adhesive must be avoided or suppressed as much as possible.

  In addition, because the optical fiber is inserted into the groove, the lens design allows a catheter to be constructed with a single continuous optical fiber having a continuous, intact polyimide protective coating layer. By using optical fibers without stripped regions or fusion splices, the overall strength of the assembly is maximized and the possibility of breakage is minimized.

  More specifically, the groove is sized to accept a single mode optical fiber having a protective coating such as polyimide and having an overall diameter of the coated optical fiber of about 105 μm to about 155 μm. . Since the groove 58 extends along the surface of the lens, the groove 58 can be formed of a solid fin of tool metal rather than the core pin used to form the bore used in the prior art. In one embodiment, the hard fins are integral with the rest of the tool metal that forms the upper half of the molded lens. The fins forming the grooves are stronger than the core pins and are supported throughout their length so they do not distort. This eliminates the core pin distortion problem previously described.

  A photomicrograph of the mold lens taken perpendicular to the groove is shown in FIG. As shown, the groove 58 is formed in the cylindrical body 52. The lens has a transition region 70 between the first portion of the lens having a first cross-sectional diameter. In transition region 70, the first cross-sectional diameter steps up to a second cross-sectional diameter that includes a subset of grooves 58. This transition region or cross section 70 is also shown in FIG. In one embodiment, the first cross-sectional diameter range of the lens is from about 150 μm to about 800 μm. In one embodiment, the second cross-sectional diameter range of the lens is from about 300 μm to about 1000 μm.

In addition, in one embodiment, the end face 64 of the lens shown in FIG. 3C is adjacent to the groove 58 to reduce back reflection of light. In one embodiment, the inner end face 64 is inclined with respect to the long axis of the lens and is polished to suppress back reflection. This is important. This is because the OCT system has a high sensitivity to back reflection as low as -100 dB (partially 10 ^-10 ) to -120 dB (partially 10 ^-12 ). In order to obtain this level of back reflection, the end face 64 is tilted at about 5 ° to about 25 °, polished with high precision and a surface roughness of less than 30 nm. The back reflection of light can be suppressed to an acceptable level by a combination of the inclination of the end face 64 and the polishing. In addition, the end face of the optical fiber itself is also obliquely cleaved or polished at 5 ° to 25 ° to prevent back reflection from the end face of the optical fiber.

  The manufacturing process can be further simplified by obliquely cleaving the optical fiber directly through the polyimide protective coating instead of mechanically polishing the optical fiber. Direct oblique cleavage has the additional advantage that the entire catheter can be constructed with a single continuous optical fiber having a continuous layer of polyimide protective coating (i.e., without an area to be removed or a fusion splice). Maintaining fiber and coating consistency throughout the catheter maximizes strength and reduces the possibility of breakage.

  The imaging performance of the lenses described herein was evaluated in animal experiments. The image quality was compared to that of a conventional lens design using a graded index optical fiber section for beam focusing and a total internal reflection air glass interface for beam directing. Sample images are shown in FIGS. 4 (a) and 4 (b). The microscopic image (FIG. 4A) shows an OCT image of a blood vessel taken using a conventional lens design. FIG. 4B shows an OCT image of a blood vessel photographed using an elongated mold lens cap having an annular end face and a groove and avoiding the use of a core pin at the time of manufacture. As is apparent from the right image (FIG. 4B), the resulting image is bright and the surface of a dark area or the like shown in the top quarter of FIG. 4B. The resolution for the details below is increasing.

  With reference to FIG. 5, in another embodiment, the molded lens is formed by first inserting an optical fiber 80 into a metal tube 84. One end 82 of the optical fiber 80 is disposed so as to extend beyond one end of the metal tube 84. The optical fiber and metal tube combination is glued together with an adhesive 85 and placed in a mold assembly 86, 86 ', 86' '(usually 86). The mold assemblies 86, 86 ′, 86 ″ include a shoulder portion 87 to prevent the combination of the metal tube 84 and the bonded optical fiber 80 from exiting the mold 86. Since the optical fiber 80 is bonded to the metal tube 84, it is prevented from being pushed back. Alternatively, the fiber is pressed into half of the mold and kept in place. This eliminates the need for adhesives.

  In addition, the front 89 of the mold assembly is polished to form an optical surface on the lens. In this way, the optical fiber 80 is not held directly by the mold 86, thereby reducing the possibility of damaging the optical fiber 80. Further, since the combination of the metal tube 84 and the optical fiber 80 is rigid, the position where the plastic is put into the mold 86 can be close to the polishing surface 89, and the flow of the plastic can be directed toward the metal tube 84. . Even if the metal tube 84 is broken, the possibility that the metal tube 84 moves toward the polishing surface 89 in the mold 86 and is damaged is low.

  With reference to FIG. 6, the mold 86 is then filled with plastic or other lens material as previously described. When the lens plastic is solidified, the assembly of the optical fiber 80 and the metal tube 84 is taken out from the mold 86. An OCT probe is formed by the optical fiber 80, the metal tube 84 and the lens 25.

  In one embodiment, the outer diameter of the optical fiber is about 0.006 inches, the inner diameter of the metal tube is about 0.0065 inches, and the outer diameter of the metal tube is about 0.0095 inches. The outer diameter of the injection molded plastic lens is about 0.014 inch. The wall thickness of about 0.002 inches of plastic around the metal tube is within the manufacturing capabilities of micro-molding. A wall thickness of about 0.0015 inches of metal tube is sufficient to provide rigidity over the short length of tube in the mold.

  The metal tube 84 is a structural support that prevents the optical fiber 80 from being damaged at a position where the optical fiber 80 exits the mold lens 25. The tendency of the optical fiber 80 to break at the above position is partly due to the large diameter difference between the optical fiber and the mold lens that causes a large change in stiffness. In addition, the mold lens 25 causes a hoop stress to the optical fiber 80 as the plastic shrinks during molding. This hoop stress typically applies additional stress to the optical fiber 80 where it exits the mold 86. The metal tube 84 protects the optical fiber 80 from hoop stress at the proximal fiber exit from the mold 86, 86 '.

  In addition to protecting the area of the optical fiber 80 from which the optical fiber 80 exits the mold 86, the metal tube 84 also protects this area of the optical fiber in use. That is, the optical fiber sucks up the tensile load of the rotating fiber optic fiber image core during the pull back of the fiber optic image core. Without the metal tube that attaches the optical fiber 80 to the mold lens 25, the area of the optical fiber 80 for transmitting this force is only the length of the optical fiber 80 inserted into the mold lens.

  The adhesive joint 84 between the optical fiber 80 and the metal tube 84 provides a large surface area for the transmission of tensile load forces. In addition, the metal tube 84 provides a rigid transition from the molded lens 25 to the optical fiber 80 to further reduce stress on the optical fiber 80. The use of smaller optical fibers such as 80 μm coated OD is also practical in this design. The stress presented by the small optical fiber when the assembly is bent in the artery is small and useful to reduce the possibility of breakage.

  More importantly, in this molding method, since the end face 82 of the optical fiber can be covered with plastic, a good optical joint can be formed in the optical path without an adhesive. Since the end 82 of the optical fiber 80 extends beyond the metal tube, there is less possibility of air being trapped in the end of the optical fiber. When the air is trapped, the optical joint between the end face of the optical fiber and the mold lens is hindered. In order to suppress back reflection, the end of the optical fiber may be cleaved obliquely.

  As shown in FIG. 7, in another embodiment, the lens 25 is molded into the impermeable marker 100 together with the optical fiber 80. As shown in FIG. 7, the unstripped optical fiber 80 is obliquely cleaved and inserted into a short portion of the tube 84, and the tube 84 is inserted into the marker 100. The assembly is pressed against a jig (not shown) on the right side of FIG. 8 to align these components. Adhesive 104 attaches the components as shown. As explained earlier, this assembly is inserted into the mold. The mold secures the end of the marker 100 to position it. The mold is then filled with plastic to form a lens.

  Thereafter, a reflective coating is applied to the lens 25 and the torque wire 108 or other twisting device is slid into the marker 100 and adhered to the marker 100. Thereby, the assembly shown in FIG. 9 is completed.

  The fiber 80 does not need to extend far away from the tube 84 and extend outward. This is because the main connection between the optical fiber 80 and the lens is the marker 100. Only the surface of the optical fiber needs to be formed into a lens. By selecting a plastic having a low melting temperature, the tube 84 is melt bonded to the plastic. This helps the strength of the assembly.

  In still other embodiments, a short portion of the tube 84 may be removed as shown in FIG. In this embodiment, instead of the torque wire 108, a very thick coating 120 on the optical fiber glass 80 may be used as the twisting device. In this case, the core and the coating of the optical fiber are simply inserted into the marker 100 and the lens 25 and formed into the marker 100. As such, the assembly is optically aligned during the molding process. This is a repeatable alignment method. The joint between the marker and lens is very strong, making the assembly strong. Since the surface of the optical fiber is insert-molded into the lens, the optical path is not affected by bubbles in the adhesive. Therefore, it is possible to design the overall size by removing the tube 84.

  The aspects, embodiments, features and examples of the present invention are illustrative in all respects and are not intended to limit the invention. The scope of the invention is defined only in the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art without departing from the spirit and scope of the invention.

  The use of headings and clauses in this application is not meant to limit the invention, and each clause may correspond to any aspect, embodiment or feature of the invention.

  Throughout this application, when a composition is described as having, containing or containing a particular component, or when a method has particular method steps, or is described as containing or including: The compositions of the present teachings are substantially composed of or consist of the listed components, and the methods of teaching of the present application are substantially composed or enumerated of the enumerated method steps. It is also conceivable that the method steps consist of:

  Where this application states that an element or component is included in and / or selected from the list of listed elements or components, such elements or components are listed. It can be seen that any one of the listed elements or components can be selected from the group consisting of two or more of the listed elements or components. In addition, the elements and / or features of the compositions, devices, or methods described herein may be combined in various forms, whether express or implied, without departing from the spirit and scope of the present teachings. it can.

  The use of the terms “including” and “having” should be understood to be open-ended and non-limiting unless otherwise indicated.

  The use of the singular herein includes the plural (and vice versa) unless otherwise indicated. Further, the singular forms “a”, “an”, and “the” include plural forms unless indicated otherwise. In addition, where the term “about” is used before a quantitative value, the teachings herein include that specific quantitative value itself unless otherwise indicated.

  Note that the order of steps or the order for performing a specific operation is not important as long as the teaching of the present application is operable. Further, two or more steps or actions may be performed simultaneously.

  Where a range or list of values is provided, each value intervening between the upper and lower limits of such a range or list of values is individually considered as each value is specifically described herein. To be considered and included in the present invention. In addition, small ranges between the upper and lower limits of the predetermined range and including the upper and lower limits are contemplated and are included within the present invention. The list of exemplary values or ranges does not disclaim other values or ranges between the upper and lower limits of a given range and including the upper and lower limits.

  It should be noted that the drawings and description of the present invention have been simplified to describe elements relevant to a clear understanding of the present invention, while other elements have been excluded for clarity. However, those skilled in the art can recognize that these and other elements are desirable. However, since such elements are well known in the art and do not facilitate a better understanding of the present invention, the description of such elements is omitted herein. It should be noted that the drawings are presented for illustrative purposes, not as assembly drawings. Omitted details and modifications or alternative embodiments are within the purview of those skilled in the art.

  The present invention may be embodied in other specific forms without departing from its spirit or basic characteristics. Accordingly, the foregoing embodiments are to be considered in all respects only as illustrative and not restrictive of the invention described in the specification. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are to be embraced within the scope of the invention.

Claims (18)

A lens cap including a generally cylindrical body having a major axis and including a first end, a cylindrical outer surface, and a beam directing surface at a second end, wherein the generally cylindrical body includes a polymer. Including, lens cap,
A lens system comprising:
The generally cylindrical body and the cylindrical outer surface define a groove between the first end and the beam directing surface;
The beam directing surface is inclined with respect to the major axis;
The groove of the lens cap is configured to receive an optical fiber;
Lens system.   The lens system according to claim 1, wherein the lens cap is formed by molding the polymer.   The lens system according to claim 1, further comprising an optical fiber and an adhesive, wherein the optical fiber is disposed in the groove and fixed by the adhesive.   The lens system according to claim 1, wherein the groove defines an inner end surface, and the optical fiber is disposed in the groove.   The lens system according to claim 1, wherein the beam directing surface defines a non-planar surface arranged to direct light received from the optical fiber such that the light is focused outside the lens.   The groove defines a major axis, the major axis of the substantially cylindrical body is concentric with the major axis of the groove, and the inner end surface is in relation to the major axis of the groove to suppress back reflection to the optical fiber. The lens system according to claim 1, wherein the lens system is inclined.   The lens system according to claim 3, wherein light from the optical fiber diverges and is focused by the lens cap.   The end of the optical fiber is oriented at a first angle and the beam directing surface is oriented at a second angle relative to the beam directing surface. The lens system according to claim 1.   The lens system according to claim 1, wherein the shape of the lens cap is selected from the group consisting of a biconic aspherical surface, an aspherical surface, a biconic Zernike, a Fresnel, and a non-uniform rational B-spline.   8. The lens system of claim 7, further comprising a metal tube having a first end and a second end and defining a tubular bore, wherein the optical fiber is secured to the tubular bore with an adhesive. .   The lens system according to claim 1, wherein the molded lens cap has a cross section with a diameter of about 150 μm to about 800 μm.   The lens system according to claim 1, wherein the diameter varies in a transition region within the groove.   The lens system of claim 1, wherein the optical fiber and the molded lens cap rotate together in response to rotation of the optical fiber.   The lens system according to claim 1, wherein the groove has a cross section having a diameter of about 150 μm to about 800 μm.   The lens system according to claim 1, wherein the diameter varies in a transition region within the groove.   The lens system according to claim 1, wherein a beam focus surface of the lens cap is configured to reflect light received from the optical fiber through a side portion of the substantially cylindrical body.   The lens system according to claim 1, wherein the polymer is a material selected from the group consisting of acrylic, polycarbonate, polystyrene, polyetherimide, and polymethylpentene.   The lens system of claim 1, further comprising an interferometer in optical communication with the lens cap.

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