JP2008233540A - Imaging fiber and imaging fiber assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging fiber that can eliminate an influence of aberrations accompanying magnification enlargement of a lens and improve resolution without impairing practicality, and an imaging fiber assembly having the imaging fiber. <P>SOLUTION: The imaging fiber assembly has the imaging fiber comprising a bundle of a plurality of fibers and a lens imaging light on the fiber bundle. The fiber bundle has a curved surface as a photodetection end surface for receiving the light from the lens, and the photodetection end surface has a center portion hollowed from a peripheral portion and is processed according to the optical path of the lens. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an imaging fiber including a fiber bundle in which optical fibers are bundled and an imaging fiber assembly including the imaging fiber.

  2. Description of the Related Art Conventionally, a technique for observing a deep portion in a body using light is known. However, because of the scattering characteristics of the tissue, normal geometric optical imaging theory cannot be applied to a portion where the depth is deeper than 1 mm. To observe a portion where the depth is deeper than 1 mm, completely different means or methods are required.

Therefore, conventionally, there has been an apparatus for inserting a thin optical member such as an injection needle into a tissue and observing the deep part of the body using this optical member. With regard to this type of apparatus, for example, Patent Document 1 discloses a fiberscope including an imaging fiber having a rod lens attached to a distal end portion.
JP 2003-290135 A

  The above optical member uses a thin imaging fiber, and the thickness of the extremely thin unit fiber constituting the imaging fiber determines the resolution. A lens is attached to the tip of the imaging fiber, but the total resolution is not high enough (about 2.5 microns).

  In order to improve this resolution, it is necessary to increase the magnification of the lens attached to the tip and increase the magnification of the image sent to the imaging fiber.

  However, if the magnification of the lens is increased to 2 times or more, the aberration (spherical aberration) of the lens increases due to the limited diameter of the lens, and there is a possibility that the imaging is blurred and the practicality is lost. .

  In order to prevent such aberration from occurring, there is a method of using a lens for correcting aberration (correction lens) in combination.

  However, when the correction lens is placed, the light transmittance of the imaging fiber is lowered. In general, it is difficult to manufacture lenses and assemblies that do not have aberrations, regardless of the size of the lens, but if the size of the lens itself is extremely small, bonding the extremely small lenses together using an adhesive that does not generate fluorescence itself Is extremely difficult. If the lenses are not bonded together, the positions of the two lenses must be adjusted accurately, which is also difficult for extremely small lenses.

  Accordingly, the present invention has been made to solve the above-described problems, and provides an imaging fiber and an imaging fiber that can eliminate the influence of aberration associated with magnification expansion of a lens and can improve resolution without impairing practicality. It is an object of the present invention to provide an imaging fiber assembly.

  In order to solve the above-described problems, the present invention is characterized by an imaging fiber in which a light receiving end face that receives light from a lens in a fiber bundle in which a plurality of fibers are bundled is curved.

  Since this imaging fiber has a curved light receiving end face, it can absorb the deviation of the intersection of the optical paths of the light rays passing through the lens.

  Further, in the case of the imaging fiber, the light receiving end face can be a concave curved surface with the central part recessed relative to the peripheral part.

  This makes it possible to absorb the deviation of the intersection of the optical paths when the lens is a convex lens.

  Further, in the case of the imaging fiber, it is preferable that the light receiving end face is processed according to the optical path of the lens to be imaged on the fiber bundle.

  By doing so, the light receiving end face becomes a curved surface corresponding to the intersection of the optical paths, so that the deviation of the intersection can be accurately absorbed.

  The present invention provides an imaging fiber assembly having an imaging fiber composed of a fiber bundle in which a plurality of fibers are bundled and a lens that forms an image on the fiber bundle, and a light receiving end face that receives light from the lens in the fiber bundle. A curved imaging fiber assembly is provided.

  Since this imaging fiber assembly has a curved light receiving end face, it can absorb the deviation of the intersection of the optical paths of the light rays passing through the lens.

  Further, in the case of this imaging fiber assembly, the light receiving end surface can be a concave curved surface having a central portion recessed relative to the peripheral portion.

  This makes it possible to absorb the deviation of the intersection of the optical paths when the lens is a convex lens.

  Furthermore, in the case of the imaging fiber assembly, it is preferable that the light receiving end face is processed according to the optical path of the lens.

  By doing so, the light receiving end face becomes a curved surface corresponding to the intersection of the optical paths, so that the deviation of the intersection can be accurately absorbed.

  As described in detail above, according to the present invention, an imaging fiber and an imaging fiber assembly including the imaging fiber that can eliminate the influence of aberration associated with magnification expansion of the lens and can improve the resolution without impairing practicality. Is obtained. These are effective regardless of the size of the lens that couples from small to large.

  Embodiments of the present invention will be described below. In addition, the same code | symbol is used for the same element and the overlapping description is abbreviate | omitted.

  FIG. 1 is a perspective view showing a main part of an imaging fiber assembly 10 according to an embodiment of the present invention. As shown in FIG. 1, the imaging fiber assembly 10 includes an imaging fiber 1, a lens 6, and a sheath (tubular member) 7.

  As shown in FIG. 2, the imaging fiber 1 includes a fiber bundle 2 in which a plurality of optical fibers 2a are bundled. Here, FIG. 2 is a front view showing an objective side end face (light receiving end face 5 described later) of the fiber bundle 2.

  The fiber bundle 2 is obtained by bundling a plurality of optical fibers 2a and storing them in a coated tube 3 for preventing light leakage. The optical fiber 2a can be composed of a silica-based optical fiber, a plastic-based optical fiber, a multicomponent glass fiber, or the like, and the material is not particularly limited. In addition, each optical fiber 2a is bonded and fixed to the covering tube 3 by the adhesive 4 at the distal end portion on the objective side, but is housed in the covering tube 3 in a free state at portions other than the distal end portion.

  As shown in FIGS. 3 to 5, the fiber bundle 2 has a light receiving end face 5 that receives light from the lens 6 among the end faces on the object side, that is, the end faces having a circular shape in front view formed by the plurality of optical fibers 2 a. It is a curved surface. 3 is a perspective view showing the light receiving end face 5 side portion of the fiber bundle 2, FIG. 4 is a sectional view taken along the line IV-IV in FIG. 2, and FIG. 5 is a sectional view taken along the line VV in FIG. As shown in these drawings, the light-receiving end face 5 is a concave curved surface having a central portion that is recessed rather than a peripheral portion, as will be described in detail later.

  The lens 6 is a biconvex lens having a predetermined diameter and length, polished on both end surfaces and mirror-finished. The lens 6 is bonded and fixed to one end side of the sheath 7. The lens 6 takes in light from the outside and forms an image on the light receiving end face 5 of the fiber bundle 2.

  The sheath 7 is a cylindrical member in which the lens 6 and the fiber bundle 2 are accommodated. The lens 6 is attached to one end side, the fiber bundle 2 is attached to the other end side, and the lens 6 and the fiber bundle 2 are integrated.

  Here, FIG. 6 is a diagram showing a result of ray tracing when light is incident on the lens 6 so as to form an image on the light receiving end face 5 in the imaging fiber assembly 10, and FIG. 6A is a diagram of the ray passing through the lens 6. Optical path diagram, (B) is a spot diagram. FIG. 7 is a view showing the result of ray tracing when light is incident on the lens 6 in an imaging fiber assembly having a conventional imaging fiber 11 to be described later. FIG. 7A is an optical path diagram of the ray passing through the lens 6. , (B) are spot diagrams.

  As shown in FIGS. 6A and 7A, in the imaging fiber assembly 10, since there is an aberration (spherical aberration) in the lens 6, there is one optical path M when light is incident on the lens 6. Disperse without passing through. Further, as shown in FIGS. 6B and 7B, the beam spot S of the light incident on the lens 6 has a certain extent. The beam spot S (shown in the middle stage) is larger in the case of FIG. 7B than in the case of FIG. 6B.

  In the imaging fiber assembly 10 according to the present embodiment, the light receiving end surface 5 that is curved into a spherical shape by applying surface processing to the end surface on the light receiving side of the fiber bundle 2 based on the result of such ray tracing of the lens 6. Forming. In this case, the positions of the end faces of the optical fibers 2a are slightly shifted between adjacent ones, and the light receiving end face 5 that is curved as a whole is formed.

  By the way, the light beam passing through the lens 6 passes through a position close to the focal point when passing through a position close to the optical axis L of the lens 6, but when passing through a position shifted from the optical axis L toward the peripheral portion, It is easy to pass through the location.

  Therefore, for example, as shown in FIGS. 8A and 8B, when considering the optical paths 11a to 11f of the light rays passing through the lens 6, the optical paths 11a and 11b, the optical paths 11c and 11d, and the optical paths 11e and 11f are respectively The intersecting points are distributed and arranged as F1, F2, and F3, respectively, because the lens 6 is a convex lens. In this case, even if the optical paths 11c and 11d pass through the focal point F (intersection point F2) of the lens 6, the optical paths 11a and 11b and the optical paths 11e and 11f pass through the intersection points F1 and F3 on the near side of the focal point F.

  Then, if the light receiving end face 5 is a curved surface processed according to the optical path of the lens 6 as shown in FIG. 8A, all of the intersections F1, F2, and F3 of the optical paths 11a to 11e are shown as the light receiving end face. 5 and can be absorbed by the curved light-receiving end face 5. Therefore, an image without blur can be formed on the light receiving end face 5.

  On the other hand, for example, as shown in FIG. 8B, in the imaging fiber 11 composed of the conventional fiber bundle 12 whose end surface on the object side is a flat surface, the intersection points F1 and F3 are positions on the near side of the focal point F. Therefore, deformation distortion of image formation occurs, and blurring occurs in the peripheral visual field of the image.

  For this reason, the imaging fiber 1 forms a light receiving end face 5 curved in a spherical shape by subjecting the end face on the light receiving side of the fiber bundle 2 to surface processing such as polishing or etching according to the optical path of the lens 6. Yes.

  In this case, in view of the fact that the light rays passing through the lens 6 are as shown in FIGS. 8 (A) and 8 (B), even if the light receiving end surface 5 is simply a concave curved surface with the central portion recessed relative to the peripheral portion, the deviation of the intersection point is not achieved. Therefore, a blur-free image in which the influence of the spherical aberration of the lens 6 is suppressed can be obtained.

  Of course, if the light receiving end face 5 is formed into a concave curved surface after accurately performing the surface processing based on the result of ray tracing of the lens 6 as described above, the shift of the intersection point is accurately eliminated, and a more preferable imaging fiber 1 is obtained. It is done.

  However, it is technically difficult to perform such surface processing by polishing or the like. In this case, even with the imaging fiber 1 in which the light receiving end face 5 has a concave curved surface with the central part recessed rather than the peripheral part, the displacement of the intersection can be absorbed as compared with a flat light receiving end face. Can be obtained.

  As described above, in the imaging fiber 1 and the imaging fiber assembly 10, the light receiving end surface 5 that receives the image of the lens 6 is formed into an optically advantageous concave curved surface that is processed according to the optical path of the lens 6. The influence of spherical aberration generated by the high lens 6 can be suppressed.

  In this way, in the imaging fiber 1 and the imaging fiber assembly 10, image blur due to spherical aberration generated by the lens 6 can be eliminated over the entire light receiving end surface 5.

  Therefore, in the imaging fiber 1 and the imaging fiber assembly 10, the spherical aberration becomes strong as the magnification of the lens 6 is increased, and this can be eliminated even if the peripheral visual field is defocused. The resolution can be improved and the practicality can be enhanced.

  In addition, since the imaging fiber 1 and the imaging fiber assembly 10 are not combined with a correction lens for correcting aberrations in order to improve the resolution, the optical transmittance of the imaging fiber is not lowered, and the accurate lens Position adjustment is not required.

  The above description is the description of the embodiment of the present invention, and does not limit the present invention, and various modifications can be easily implemented. In addition, an apparatus or method configured by appropriately combining components, functions, features, or method steps in each embodiment is also included in the present invention.

It is a perspective view which shows the principal part of the imaging fiber assembly which concerns on embodiment of this invention. It is a front view which shows the objective side end surface of a fiber bundle. It is a perspective view which shows the light-receiving end surface side part of a fiber bundle. It is the IV-IV sectional view taken on the line of FIG. It is the VV sectional view taken on the line of FIG. In an imaging fiber assembly, it is a figure which shows the result of the ray tracing when light injects from a lens so that it may image on a light-receiving end surface, (A) is an optical path figure of a lens, (B) is a spot diagram. In the conventional imaging fiber assembly, it is a figure which shows the result of the ray tracing when light injects from a lens so that it may image on a light-receiving end surface, (A) is an optical path figure of a lens, (B) is a spot diagram. 2A and 2B are diagrams schematically showing an optical path of a light beam passing through a lens 6, where FIG. 1A shows an imaging fiber according to an embodiment of the present invention, and FIG. 2B shows a conventional imaging fiber.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Imaging fiber, 2 ... Fiber bundle, 2a ... Optical fiber 5 ... Light-receiving end surface, 6 ... Lens, 10 ... Imaging fiber assembly 11a, 11b, 11c, 11d, 11e, 11f ... Optical path

Claims (6)

  An imaging fiber, wherein a light receiving end face for receiving light from a lens in a fiber bundle in which a plurality of fibers are bundled is a curved surface.   The imaging fiber according to claim 1, wherein the light receiving end surface is a concave curved surface with a central portion recessed relative to a peripheral portion.   The imaging fiber according to claim 1, wherein the light receiving end face is processed according to an optical path of a lens that forms an image on the fiber bundle. An imaging fiber assembly comprising an imaging fiber comprising a fiber bundle in which a plurality of fibers are bundled, and a lens that forms an image on the fiber bundle,
An imaging fiber assembly, wherein a light receiving end face for receiving light from the lens in the fiber bundle is a curved surface.   The imaging fiber assembly according to claim 4, wherein the light receiving end surface is a concave curved surface with a central portion recessed relative to a peripheral portion.   6. The imaging fiber according to claim 4, wherein the light receiving end face is processed according to an optical path of the lens.

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