Arbitrarily processable endoscope using graded index type plastic lens

Abstract

An arbitrarily processable endoscope according to the present invention is provided with an optical transmission body in a cylindrical sheath having an outer diameter of 20 mm or less, the optical transmission body comprising a rod-shaped graded-index plastic lens and a connector that is detachably connected to a detection unit at the proximal end of the graded-index plastic lens; the light transmission body transmits the light received by the distal end portion thereof to the detection portion, thereby generating an image in the detection portion; according to the endoscope capable of being arbitrarily processed, even though a low-cost material with a small diameter is used, high-resolution images can be obtained, and the endoscope can be used in one time.

Description

[0001] (Cross reference)

[0002] This application claims priority based on Japanese Patent Application No. 2022-111249 filed in Japan on July 11, 2022, and all contents described in the application are directly incorporated into this specification by reference. Technical Field

[0003] The present invention relates to a disposable endoscope using a gradient refractive index plastic lens. Background Art

[0004] An endoscope is a device that allows for visual inspection of structures inside a cavity. In the medical field, an endoscope is used to inspect human organs for diagnostic purposes, visually confirm surgical sites, sample human tissue, or safely use other surgical instruments.

[0005] A common hard endoscope is constructed as follows: the image obtained from its distal end (i.e., the front end of the endoscope farthest from the doctor's hand side) is transmitted to the inside of a main body arranged at the proximal end (i.e., the front end of the endoscope closest to the doctor's hand side) via a relay lens, and is observed through an eyepiece arranged in the main body. Here, the relay lens can be understood as an optical system that generates at least one one-to-one image. In an endoscope, a plurality of relay lenses are combined to form a transmission system with multiple image inversions corresponding to the number of image inversions. In order to clearly observe the image transmitted via the relay lens, it is necessary to adjust the focus by fine-tuning the eyepiece frame arranged in the main body in the direction of the optical axis. In addition, the inversion system actually used represents the curvature or warping of the image plane formed.

[0006] In order to construct an optical transmission system composed of an inversion system with extremely small image curvature by a simple design, an endoscope having at least one inversion system with uneven refractive index has been disclosed (for example, see Patent Document 1). In addition, an image guide device (image guide) is known, which is composed of a plurality of optical fibers bundled together and is used to detect and transmit images in the fields of medical use, industrial use, etc. A flexible endoscope and an endoscope system having the same, which can reduce damage to the optical fibers constituting such an image guide device and a light guide device and can be easily connected to a repeater device, are also disclosed (for example, see Patent Document 2).

[0007] On the other hand, as an optical transmission body for image transmission, a resin rod lens called a so-called GI (Graded Index) type having a continuous refractive index distribution and a method for manufacturing the same are known. However, when using a rod lens, if one pitch of the lens is short, a plurality of pitches are required to ensure the required length of a medical image guide device. If the number of pitches of the rod lens increases, the aberration increases and the resolution decreases, so a proposal has been proposed to use a rod lens with a pitch length of 30 cm or more (for example, see Patent Document 3).

[0008] [Prior art literature]

[0009] [Patent Literature]

[0010] Patent Document 1: International Publication, WO1998 / 004949

[0011] Patent Document 2: International Publication, WO2018 / 009971

[0012] Patent Document 3: Japanese Patent Publication No. 2003-185806 Summary of the invention

[0013] (Problems to be solved by the invention)

[0014] Patent Document 1 does use a gradient refractive index rod lens, but since it is made of glass, it is easily broken and expensive, and must be combined with other lenses to form a relay lens system. In addition, there is a problem that the chromatic aberration of the rod lens must be corrected.

[0015] The image guide device disclosed in Patent Document 2 is composed of several thousand or more thin optical fibers with a diameter of several μm (micrometers) bundled together. By transmitting light incident on one end face to the other end face through each optical fiber of the optical fiber bundle, it is possible to transmit an image of one end face to the other end face. However, in such an image guide optical fiber, many optical fibers must be bundled in a manner that the arrangement on both end faces is consistent, and each optical fiber only transmits color, and the image is reproduced by the collection of them. Therefore, if the number of fibers is not certain, it is impossible to obtain information as an image, that is, resolution. For example, even if 10,000 optical fibers are stacked, it is only 10,000 pixels, and a satisfactory resolution may not be obtained.

[0016] Furthermore, although the rod lens disclosed in Patent Document 3 is a lens with a pitch of 30 cm or more, its outer diameter is 10 to 30 mm, which makes it difficult to reduce the diameter of the endoscope.

[0017] Therefore, an object of the present invention is to provide an endoscope that can obtain high-resolution images using a thinned and low-cost material and that can be used once.

[0018] (Solutions to solve problems)

[0019] In order to solve the above problems, the present invention is based on the following enlightenment: the graded-index plastic optical fiber (GI-POF) currently known as a high-speed optical communication optical fiber can transmit images with high definition. That is, the present invention includes the following embodiments.

[0020] (1) A disposable endoscope having a light transmission body in a cylindrical sheath having an outer diameter of 20 mm or less, the light transmission body comprising: a rod-shaped gradient refractive index type plastic lens (hereinafter sometimes referred to as a GI-POF lens), and a connector connected to a detection unit at the proximal end of the gradient refractive index type plastic lens in a manner that allows for loading and unloading; the light transmission body transmits light received by its distal end to the detection unit, thereby generating an image in the detection unit.

[0021] (2) The disposable endoscope described in (1) further includes an objective lens arranged in close contact with the distal end of the gradient refractive index type plastic lens or arranged away from the distal end of the gradient refractive index type plastic lens.

[0022] (3) In the disposable endoscope described in (1) or (2), the sheath is made of a transparent material and is connected to the illumination light source at its proximal end portion.

[0023] (4) In the disposable endoscope described in (1) or (2), the sheath includes an outer tube and an optical fiber for illumination.

[0024] (5) In the disposable endoscope described in (1) or (2), the outer diameter of the gradient refractive index plastic lens is 0.1 mm to 10 mm.

[0025] (6) In the disposable endoscope described in (1) or (2), the length of the gradient refractive index plastic lens is 1 to 40 cm.

[0026] (7) In the disposable endoscope described in (1) or (2), the sheath is a 10G to 30G injection needle or a flexible outer shell.

[0027] (8) In the disposable endoscope described in (1) or (2), the gradient refractive index plastic lens is a plastic lens having an outer diameter of less than or equal to 10 mm and a length of 1 to 40 cm, which is formed by adding a dopant to a linear polymer used as a matrix and forming a concentration gradient of the dopant in a concentric circle in the radial direction through diffusion of the dopant, wherein the dopant is a low molecular weight substance that is not reactive with the linear polymer used as the matrix.

[0028] (9) In the disposable endoscope described in (2), the objective lens is a spherical lens.

[0029] (Effects of the Invention)

[0030] According to the present invention, it is possible to provide an endoscope which can obtain high-resolution images despite the use of a thin and low-cost material and which can be used once. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a diagram showing the overall structure of an endoscope according to a first embodiment of the present invention.

[0032] Figure 2 This is a partial cross-sectional view of the endoscope showing a state where the light transmission body is inserted into the sheath.

[0033] Figure 3 is a partial cross-sectional view of an endoscope having a sheath according to another embodiment.

[0034] Figure 4 This is a side view of a light transmission body according to one embodiment.

[0035] Figure 5 This is a side view of the distal end portion of an endoscope according to another embodiment.

[0036] Figure 6 yes Figure 2 The AA' line cross-sectional view is shown.

[0037] Figure 7 This is a schematic diagram for explaining how to use an endoscope.

[0038] Figure 8 This is a schematic diagram showing light passing through a GI-POF lens.

[0039] Fig. 9 It is a diagram showing the overall structure of an endoscope according to a second embodiment of the present invention.

[0040] Fig.10 yes Fig. 9 Front view of the endoscope.

[0041] Fig.11 yes Fig.10 The BB' line cross-sectional view is shown. DETAILED DESCRIPTION

[0042] Next, various embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the various embodiments described below do not limit the invention involved in the claims, and the various elements and all combinations described in the various embodiments are not necessarily required for the solution of the present invention.

[0043] (First Embodiment)

[0044] Figure 1 It is an overall structural diagram of the endoscope 1 of the first embodiment of the present invention. An endoscope refers to a device for observing the affected part in the body, for example, there are vascular endoscopes, digestive organ endoscopes, and laparoscopic endoscopes. An endoscope used to diagnose joint diseases such as wear of the sliding surface of the joint or the formation of bone spurs, ligament rupture or meniscus injury, which is an object of observation, is not diagnosed indirectly through X-rays, CT or MRI, but is diagnosed by directly observing the affected part, and can be diagnosed simply and quickly, so it is preferred in this respect. Alternatively, it is possible to observe parts that have not been observed so far, such as nerve tissue in the spinal cord. It is also known that a device for observing and illuminating the surface of the patient's body from a position away from the patient's body is also called an exoscope. By using an exoscope, for example, it is easy to illuminate and observe the surface of the teeth in the oral cavity or the depth of the external auditory canal, so it is easy for the doctor to diagnose or operate. By connecting a camera, the image of the operating area can be displayed on the screen, so the operator and other relevant personnel who participate according to the situation can observe the image without fatigue. Therefore, the use of endoscopes in this specification also includes such observation of the body surface. It should be noted that the term "disposable" in this specification means "constructed at a low cost to enable one-time use within a practical range", rather than "necessarily discarded after each use".

[0045] Figure 1 The endoscope 1 shown is capable of observing any part of a living body including joints (wear of joint sliding surfaces or formation of bone spurs, ligament rupture, etc.), spine, spinal cord, eyes, otolaryngology, urinary organs, etc. (hereinafter collectively referred to as the affected part). The endoscope 1 is composed of a sheath 11, an optical fiber 12 for illumination, a light source 13, an optical transmission body 20 composed of a GI-POF lens 21 and an objective lens 22 as required, and a connector 23. The connector 23 is connected to a detection unit 30 in a manner that allows loading and unloading (installation or removal). Figure 1In the embodiment, the housing 24 made of metal or plastic is arranged on the outside of the optical transmission body 20. In order to shield light, the outside of the GI-POF lens 21 may be painted, or the inside of the housing 24 may be painted black to prevent stray light. The detection unit 30 may include a CCD camera or a CMOS image forming device, or may be connected to a monitor (not shown) via an electric cable or an optical cable 40, and the image generated by the detection unit 30 may be displayed on the monitor.

[0046] Figure 2 It is a partial cross-sectional view of the endoscope showing the state when the optical transmission body 20 is inserted into the sheath 11. In this specification, the sheath refers to a short catheter (katheter) left in the body. The sheath 11 covers the optical transmission body 20 and is configured as a slender (semi) transparent hollow (tubular) with openings at both ends. It has flexibility and is formed integrally from a plastic material (resin material). As the plastic material, for example, a thermoplastic resin is used. As the thermoplastic resin, preferably, there can be mentioned: polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene copolymer (ETFE), polyurethane (PU), tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer (PFA), polyurethane resin (PUR), polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), acrylonitrile-butadiene-styrene copolymer, polycarbonate, polyamide, polyoxymethylene, etc., among which PTFE, ETFE, PP, and PU are preferred.

[0047] In a preferred embodiment, the sheath 11 is made of a transparent material, which can also have the function of transmitting the light of the light source 13 to irradiate the affected part. Figure 2 In the embodiment, light from the light source 13 is guided to the sheath via the illumination optical fiber 12. The optical fiber 12 can pass through the resin inside the sheath 11 and penetrate to the far end of the sheath 11. In this case, the sheath may not be transparent but may be made of a high-strength material such as metal. Figure 2 In the embodiment, the optical transmission body 20 is used in a state where its front end portion protrudes from the front end portion of the sheath 11. An objective lens 22 is provided on the front end surface of the optical transmission body 20. The rear end portion of the optical transmission body 20 is connected to a connector 23. The detailed structure inside the optical transmission body 20 will be described later. In order to cover the optical transmission body 20, the outer diameter of the sheath 11 is less than 20 mm, preferably less than 10 mm, and more preferably less than 5 mm.

[0048] Figure 3It is a partial cross-sectional view of an endoscope having a sheath 11 of another embodiment. In this embodiment, the proximal end of the sheath 11 is directly connected to the light source 13, and the light from the light source 13 passes through the inside of the sheath 11 and irradiates to the distal end. At this time, a gap may be provided between the sheath 11 and the optical transmission body 20, and the light from the light source 13 passes through the gap or the inside of the transparent resin constituting the sheath 11 and irradiates to the distal end. The proximal end of the sheath 11 may be provided with a hole for the optical transmission body 20 to pass through. In addition, in the gap between the sheath 11 and the optical transmission body 20, a space for water to pass through for cleaning the affected area or a tube for treatment tools such as tweezers to pass through may also be provided.

[0049] The connector 23 is formed in a cylindrical shape, and the optical transmission body 20 is fixed to the front end of the connector 23. An imaging device such as a CCD camera is provided inside the connector 23 or the detection unit 30 via the connection portion of the optical transmission body 20. In addition, an imaging lens for imaging the image of the end face of the GI-POF lens 21 on the imaging device may also be provided inside the connector 23 or the detection unit 30. The rear end of the connector 23 is detachably connected to the detection unit 30 by an appropriate connection structure such as screwing or fitting.

[0050] The CCD camera forms an image of light from the affected part incident from the light transmission body 20 on the light receiving surface, and converts the obtained optical image into an electrical signal.

[0051] Figure 4 It is a side view of an optical transmission body 20 of one embodiment. This embodiment is characterized in that the optical transmission body 20 includes a gradient refractive index type plastic lens (GI-POF lens) 21. The gradient refractive index type plastic lens is a plastic lens having a lens effect due to the refractive index distribution. It is basically the same as the GI type plastic optical fiber, but the difference is that it does not recognize the optical signal as digital data, but can be recognized by the human eye as an image. In order to use it as a medical endoscope, the smaller the outer diameter of the lens, the better. However, if the outer diameter of the lens, that is, the radius of the optical transmission path, becomes smaller, the length of one pitch of the lens also becomes shorter. Therefore, in order to ensure the length required as a medical image guide, multiple pitches are required. As a result, there is a problem that the aberration becomes larger and the resolution decreases. Therefore, the outer diameter of the gradient refractive index type plastic lens is preferably 0.1mm to 10mm, more preferably 0.1 to 5mm, further preferably 0.1 to 1mm, and further preferably 0.1 to 0.5mm. In order to be used as an endoscope, the light transmission body 20 needs to have a certain length, and the normal length of a gradient index plastic lens is 1 to 40 cm, preferably 1 to 20 cm, more preferably 1 to 10 cm, and further preferably 1 to 5 cm.

[0052] In this embodiment, an objective lens 22 is provided at the distal end of the optical transmission body 20 in close contact with the GI-POF lens 21. In order to capture the light diffused from the subject at a wide angle, it is preferred that the objective lens 22 has a large numerical aperture (NA) and a suitable field number and depth of field. As such an objective lens, for example, an objective lens having a field angle of 150° to 170° has been reported (see Japanese Patent Application Laid-Open No. 2006-251272).

[0053] Figure 5 is a side view of the front end of an endoscope of another embodiment. In this embodiment, the objective lens 22' is a ball lens, which can protect the end face of the GI-POF lens 21 and can converge the parallel light entering the ball lens 22' onto the GI-POF lens 21. Figure 4 The spherical lens 22' has a convex lens effect similar to the objective lens 22 shown, so that the spherical lens 22' acts as an objective lens for expanding the field angle. In addition, the interval between the spherical lens 22' and the GI-POF lens 21 can be controlled with high precision. The structure of the endoscope front end of this embodiment is formed by installing the spherical lens on the GI-POF lens using the ballpoint pen technology, and the high-precision installation of the spherical lens can be achieved at low cost.

[0054] Figure 6 FIG. 1 is a diagram showing a change in the configuration of a light transmission portion and an illumination portion in an endoscope. Figure 2 The AA' line cross-sectional view shown in FIG. 1 is a schematic diagram showing the sheath 11 and the housing 24 as a whole. Figure 6 As shown in (A) to (F), the front end of the light transmission body 20 includes an objective lens 22 and an optical fiber 211 for illumination. The optical fiber 211 for illumination is a bundle of many thin optical fibers covered by a cylindrical covering layer, which covers the periphery of the objective lens 22 and transmits a light source 13 (see Figure 1 ) light. Therefore, in Figure 6 In the embodiment shown, since the light source is included in the light transmission body, the sheath 11 and the housing 24 do not need to transmit the light from the light source, and thus can be integrally formed of a metal material. The objective lens 22 can be, for example, a combined lens or a spherical lens having a wide field angle as described above. The GI-POF lens 21 transmits the light from the affected part received from the objective lens 22. Figure 6 As shown in (A) and (D) in FIG. 1 , the optical transmission body 20 may also have a space (hole) 212 for water to pass through for washing the affected part or a tube 213 for a treatment tool such as tweezers to pass through. The size or shape of each of these tubes may be changed according to the purpose of use. Alternatively, as Figure 6As shown in (E) and (F), for example, a hole 212 for water supply and drainage may be provided in the metal sheath 11. Figure 6 In, as Figure 2 The conventional optical transmission body 20 described in the figure has an objective lens 22 installed at its front end, but it does not necessarily have to be constructed in this way. The GI-POF lens 21 can also be directly exposed to the front end to replace the objective lens 22.

[0055] (How to use an endoscope)

[0056] Next, according to Figure 7 A method of using the endoscope 1 according to the first embodiment will be described.

[0057] like Figure 7 As shown in (A), the injection needle 51 covered by the sheath 11 as the outer shell is punctured into the affected part. That is, the puncture portion 51a of the injection needle 51 is punctured into the affected part together with the sheath 11. The injection needle 51 may be, for example, an 18G injection needle. The injection needle 51 has the function of being inserted into the affected part and guiding the sheath 11 to the affected part. The injection needle 51 is formed into a cylindrical shape with an outer diameter of about 1.2 mm, and its front end is cut obliquely relative to the axial direction to form a stab portion 51a. The injection needle 51 is inserted into the patient's body by piercing the patient's skin with the stab portion 51a, so that the front end of the sheath 11 is close to the affected part. In addition, since the injection needle 51 is thin, the patient's pain is low when the injection needle 51 is inserted into the patient's body, and thus, the patient does not need to be anesthetized when the injection needle 51 is inserted into the patient's body. In addition, since there is no need to suture the wound formed by the injection needle 51, the endoscope can be used even in a clinic without an operating room. In order for the endoscope to achieve such an effect, the diameter of the injection needle 51 may be about 0.3 mm (30G) to 3.4 mm (10G), preferably about 0.6 mm (24G) to 1.2 mm (18G).

[0058] In this state, the sheath 11 is left and the injection needle 51 is pulled out, leaving the sheath 11 at the affected part ( Figure 7 Next, Figure 7 As shown in (C), by inserting the optical transmission body 20 into the base end of the sheath 11 and bringing the objective lens 22 close to the affected part, the objective lens 22 at the front end of the optical transmission body 21 can receive reflected light of the light irradiated from the light source 13 to the affected part through the sheath 11.

[0059] In another embodiment, the endoscope 1 may not include the light source 13 and the illumination optical fiber 12. For example, in the case of the endoscope 1 inserted into the affected part of the knee joint, the structure may be such that light is irradiated from the rear side of the affected part to illuminate the inside of the knee joint, and the light captured by the objective lens 22 is transmitted to the detection unit 30 through the light transmission body 20.

[0060] (Method for manufacturing a gradient refractive index plastic lens)

[0061] The method for producing a graded-index plastic lens (GI-POF lens) in a preferred embodiment of the present invention is basically the same as the method for producing a GI-type plastic optical fiber, and is produced through the following steps (a) to (c).

[0062] (a) A rod is prepared by uniformly doping a non-reactive dopant in a linear polymer and using the rod as a core rod.

[0063] (b) A polymer tube having an inner diameter equal to the outer diameter of the rod is produced. The material of the polymer tube may be the same as the material of the linear polymer that normally constitutes the core rod.

[0064] (c) Insert the core rod into the polymer tube and leave it at a temperature higher than the glass transition temperature of the polymer. At this time, the dopant in the core rod diffuses to the surrounding polymer tube by thermal diffusion. In this way, a concentration distribution of the dopant is formed in the radial direction. Here, when the refractive index of the dopant is higher than the refractive index of the polymer, a GI type (Graded Index) rod is obtained, in which the refractive index at the central axis of the GI type rod is the highest and the refractive index gradually decreases as it approaches the periphery.

[0065] The above-mentioned polymer tube is one, but a polymer tube having an inner diameter the same as the outer diameter of the polymer tube can be further provided outside the polymer tube. The purpose is to form a more ideal refractive index distribution by increasing the number of polymer tubes. In this case, the outer polymer tube is doped with a dopant concentration lower than that of the core rod, and the initial dopant concentration becomes lower as the polymer tubes toward the periphery. That is, the initial pre-diffusion distribution of the multilayer polymer tube is set, with a multi-step stepped distribution. By maintaining it at a temperature above the glass transition temperature, diffusion occurs between the adjacent polymer tubes and the multi-step distribution is relaxed, thereby forming a gentle refractive index distribution.

[0066] By this manufacturing method, a preform of GI-POF with a refractive index distribution formed in the radial direction is manufactured. The preform is set in a hot stretching device and slowly moved into a heating furnace, and inserted at a speed V1. On the other hand, by stretching the end of the preform inserted into the heating furnace at a speed V2, a GI-type POF with a refractive index distribution roughly the same as that of the preform is manufactured. At this time, the stretching ratio is defined by V2 / V1. For example, when the stretching ratio is 100 times, the diameter of the GI-POF is 1 / 10 of the preform. When a preform with an outer diameter of 25mmφ is hot stretched at a stretching ratio of 10,000 times, an extremely fine GI-POF with an outer diameter of 0.25mm is obtained.

[0067] The obtained GI-POF is cut into several centimeters in length and both end faces are end-face polished to obtain a GI-POF lens that transmits an image.

[0068] The polymer used in this embodiment is not particularly limited as long as it has a linear structure. Basically, it can be a transparent polymer that maintains an amorphous structure and has so-called plastic mechanical properties. As specific examples of such polymers, various commercially available common polymers such as acrylic polymers, polystyrene, and polycarbonate are candidates, but are not limited to these.

[0069] Regarding dopants, candidates are: dopants with a refractive index higher than that of the polymer, which do not agglomerate in the above-mentioned linear polymer and have excellent compatibility. In order to increase the refractive index of the dopant, candidates are: low molecular weights with high polarizability such as aromatics (benzene rings), halogen substituents other than fluorine, and sulfides. As dopants, low molecular weight compounds and oligomers containing aromatic rings such as benzene rings, halogen atoms such as chlorine, bromine, and iodine, and connecting groups such as ether bonds are preferred. Furthermore, as a reverse diffusion method, there is also a method of doping dopants in peripheral tubes and diffusing them from the peripheral tubes toward the central rod. In this case, candidates are dopants with a refractive index lower than that of the polymer.

[0070] In order to improve transparency, it is necessary to make the dopant uniformly dispersed in the polymer. For this reason, it is preferred to have a dopant with a solubility parameter close to that of the polymer. If the solubility parameters of the two are different, low molecules will aggregate and become scattering substances, which will become the cause of white turbidity.

[0071] As another embodiment of the method for manufacturing a gradient refractive index plastic lens, it can also be composed of a copolymer using two monomers. For example, in a polymer tube composed of a transparent acrylic polymer, a mixed solution of two M1 and M2 monomers in which a polymerization initiator and a chain transfer agent added as needed are dissolved is injected. The types of monomers can be further increased, but for the sake of simplicity of explanation, two types are described here. Here, the refractive index of the M1 polymer formed by the polymerization of the M1 monomer is lower than the refractive index of the M2 polymer formed by the polymerization of the M2 monomer. For example, as the M1 monomer, methyl methacrylate is a candidate; as the M2 monomer, benzyl methacrylate is a candidate.

[0072] The polymerization is started by heating the polymer tube filled with the monomer solution at an appropriate temperature or irradiating UV from the periphery. At this time, the inner wall of the polymer tube (usually composed of M1 polymer) swells slightly due to the monomer mixture, thereby forming a gel layer. In the gel layer, the termination reaction of the polymerization becomes smaller, so the polymerization rate is accelerated, and the gel layer formed on the inner wall of the polymer tube is preferentially polymerized. In order to increase the refractive index, the M2 monomer has a benzene ring, etc., and due to the difference in compatibility, the M2 monomer has a tendency to gradually gather toward the center relative to the polymer layer gradually polymerized from the periphery. Further, when the polymer tube composed of the M1 polymer dissolves from the inner wall to the center, the M2 monomer is also pushed toward the center. Therefore, in the copolymer formed near the inner wall of the polymer tube, a polymer is formed in which the composition ratio of the M2 monomer unit is low and the composition ratio of the M2 monomer unit becomes higher as it moves toward the center. Since the refractive index of the M2 polymer is higher than that of the M1 polymer, a copolymer with the highest refractive index at the center and a gradually decreasing refractive index toward the periphery can be obtained in the preform rod after the polymerization is completely completed. The process of stretching the preform to obtain GI-POF is the same as the above-mentioned production method.

[0073] Even if a non-polymerizable M2 dopant is used instead of the M2 monomer, the same refractive index distribution can be formed by the manufacturing method of this embodiment. The structure in this case is the same as the preform of the above manufacturing method in which the concentration of the unreacted dopant in the polymer matrix gradually changes.

[0074] As another manufacturing method in a different embodiment, there is a method of manufacturing a gradient refractive index POF by melt extrusion. The core polymer is a polymer in which a dopant with a high refractive index is uniformly dissolved, and the clad polymer is a homopolymer without dopants. By simultaneously melt-extruding these two polymers, a cladding is formed around the core. After melt-extrusion, a diffusion tube is immediately set, and the dopant of the core polymer after melt extrusion gradually diffuses into the molten cladding polymer layer during the process of passing through the diffusion tube. By controlling the melting conditions such as diffusion temperature and diffusion rate, a GI-POF with a desired refractive index distribution can be manufactured.

[0075] Three methods for producing GI-POF have been described above. The common point of these methods is that the polymer is a linear polymer and can be stretched.

[0076] (Advantages of using linear polymers)

[0077] In addition to linear polymers, there are also polymers whose molecular chains have a network structure. As a method for manufacturing GI lenses, the following method has been reported: a method of forming a refractive index distribution by diffusing a low-refractive-index M2 monomer from the periphery to a gel rod (gel rod) in the polymerization process having a network structure. In this case, the gel rod having a three-dimensional network structure is easy to maintain its shape during diffusion. The M2 monomer diffused from the periphery is copolymerized with the gel rod, and a hard GI rod lens is finally obtained. Regarding this lens, since the polymer chain has a network structure, it is impossible to manufacture a thin GI-POF by heat stretching as in the present invention. In order to heat stretch the preform, the polymer must be a linear polymer. In addition, in the process of the monomer diffusing into the gel rod, a little bit of uneven structure or fluctuation may be generated. These sometimes become the cause of image blur or light scattering.

[0078] In contrast, the polymer used in the present invention is a linear polymer, and therefore, the preform can be easily heat-stretched. In the case where there are tiny non-uniform structures in the GI preform, if the preform itself is used as a lens, blurring of the image or light scattering may occur due to the presence of the tiny non-uniform structures. However, if the preform is stretched at a high stretching ratio of, for example, 10,000 times, the tiny non-uniform structure becomes 1 / 100 in the radial direction, and the non-uniform structure is stretched 10,000 times in the stretching direction, so that, in fact, the non-uniform structure becomes negligible relative to the wavelength of light, and thus, blurring of the image or light scattering caused by the tiny non-uniform structure is not easily generated. In this way, the use of a linear polymer is conducive to the implementation of the present invention, but the present invention does not necessarily exclude other polymers besides these, and as long as they have the structure described in claim 1, they are included in the disposable endoscope of the present invention.

[0079] The GI-POF lens used in the present invention is a very fine lens inserted into an injection needle as a relay lens with a length of several centimeters to several tens of centimeters, and is required to have high-quality imaging characteristics. Therefore, the preform stretching step described above is an important manufacturing method of the present invention. In addition, once the preform rod is manufactured, the very fine GI-POF lens can be efficiently manufactured, thereby reducing costs and obtaining a novel disposable GI endoscope.

[0080] (Effect)

[0081] according to Figure 8 The effects of the present invention will be described. Figure 8 (A) shows the light passing through the GI-POF lens. Figure 8(B) is a graph showing the relationship between the radial distance r (vertical axis) of the GI-POF lens and the refractive index shown on the horizontal axis. Light travels straight in a homogeneous material and is refracted and bent at the interface of materials with different refractive indices. Figure 8 As shown in (B), on the optical axis (center line), the refractive index is distributed radially, decreasing toward the periphery. Therefore, the internal light advances in a sinusoidal manner with a pitch length P as a period, and advances in a sinusoidal manner with a length of 1 / 2 pitch (P / 2) as a period, and images are repeatedly formed every P / 2 length. That is, an inverted image is obtained at a length of 1 / 2 pitch, and an upright image is obtained at a length of 1 pitch. Figure 8 (C) to (F) show that the focal length can be changed according to the lens length. Figure 8 The inverted image in (C) Figure 8 The upright image in (D) Figure 8 Equal-magnification erect image of (E). Figure 8 As can be seen from (F), an equal-magnification inverted image is formed on the end face of the lens.

[0082] To obtain a clear image, the pitch number of the GI-POF lens is preferably small, but in order to produce an optical transmission body that can be used as an endoscope, about 1 to 10 pitches are sufficient, preferably about 1 to 5 pitches, and more preferably 2 to 3 pitches.

[0083] (Second Embodiment)

[0084] Fig. 9 It is a diagram showing the overall structure of an endoscope according to a second embodiment of the present invention. Fig.10 yes Fig. 9 Front view of the endoscope. Fig.11 yes Fig.10 The BB' line cross-sectional view is shown.

[0085] Fig. 9 The endoscope 201 shown has substantially the same Figure 2 The endoscope 1 shown in FIG. 1 has the same functional structure, but the configuration of the lighting components is different from that of FIG. Figure 2 That is, the difference is that: Figure 2 In the endoscope 1 shown, the light source 13 and the detection unit 30 are configured as separate bodies, and the illumination light from the light source 13 is transmitted to the sheath 11 and irradiated from the distal end. Fig. 9 This is not the case with the endoscope 201 of the second embodiment shown.

[0086] Hereinafter, an endoscope 201 according to the second embodiment will be described. Configurations having the same functions as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment in the drawings, and descriptions of the functions will be omitted.

[0087] like Fig. 9 As shown, the endoscope 201 includes a sheath 11, an optical fiber 211 for illumination, a light source 13, an optical transmission body 20, a connector 23, and a holding shell 50 that accommodates the light source 13 and the detection unit 30. In addition, the endoscope 201 includes an outer shell 24, which is made of metal or plastic and surrounds the outer side of the optical fiber 211 for illumination and the optical transmission body 20. The optical transmission body 20 is composed of a GI-POF lens 21, a spherical lens 22' (ball lens) as an objective lens, and a lens barrel 25 that holds the outer peripheral surfaces of the GI-POF lens 21 and the spherical lens 22'. The connector 23 presses the proximal end of the outer shell 24 against the holding shell 50, and is connected to the holding shell 50 in a manner that allows loading and unloading (installation or removal). As shown in FIG. Fig.10 As shown, the endoscope 201 is configured such that the illumination optical fiber 211 and the light transmission body 20 are arranged and inserted into the inner side of the housing 24. The endoscope 201 can also be configured such that a space (hole) 212 for water to wash the affected part or a tube (213) for treatment tools such as forceps to pass through is provided on the inner side of the housing 24.

[0088] like Fig.11 As shown, in the endoscope 201, the spherical lens 22' of the optical transmission body 20 can be fixed at a position of the same degree as the distal end of the housing 24 and the lens barrel 25 or a position protruding from the distal end of the housing 24 and the lens barrel 25. By setting the maximum numerical aperture range of the spherical lens 22' to not be blocked by the distal end of the housing 24 or the lens barrel 25, it is possible to introduce light from the peripheral portion of the lens away from the optical axis, thereby obtaining a bright image. In the endoscope of the present invention, the GI-POF lens 21 is used in the optical transmission, and since the incident light does not advance in a straight line, the incident angle that can be transmitted can be set to be wider. In the endoscope of the present invention, for example, a wide-angle lens such as the spherical lens 22' is used, which has good compatibility with the lens structure that sets the numerical aperture (NA) to be larger. It should be noted that in the second embodiment, as the objective lens, of course, a convex lens, a lens composed of multiple pieces, etc. can also be appropriately used instead of a spherical lens.

[0089] The grip housing 50 is a housing made of metal or resin that houses the light source 13 and the detection unit 30 , and is gripped by a user.

[0090] The endoscope 201 constructed in this way can use the connector 23 to separate the outer shell 24 in which the lighting optical fiber 211 and the GI-POF lens 21 are arranged from the holding shell 50, thereby making the outer shell 24 side part constructed at a certain low cost replaceable as a disposable part.

[0091] The endoscope 201 of the second embodiment is similar to the endoscope 1 of the first embodiment, and is a disposable endoscope having an optical transmission body 20, and the optical transmission body 20 includes a rod-shaped GI-POF lens 21, and a connector 23, which is connected to the detection unit 30 (the holding shell 50 that accommodates it) at the proximal end of the GI-POF lens 21 in a detachable manner. The GI-POF lens 21 can be formed into a thin diameter at low cost, and can transmit images with a certain degree of high resolution. In the endoscope 201, the optical transmission body 20 transmits the light received by its distal end to the detection unit 30, thereby generating an image in the detection unit 30. According to the endoscope 201, it is possible to obtain high-resolution images using thin-diameter low-cost materials, and in particular, the part inserted into the body can be made a disposable part (thrown away after use).

[0092] (Explanation of symbols)

[0093] 1.201 Endoscope

[0094] 11. Sheath

[0095] 12 Fiber optic for lighting

[0096] 13 Light Source

[0097] 20 Light transmission body

[0098] 21 GI-POF lens

[0099] 211 Lighting Fiber

[0100] 212 Space (hole)

[0101] 213 tubes

[0102] 22 Objective lens

[0103] 23 Connectors

[0104] 24 Housing

[0105] 25 Lens barrel

[0106] 30. Inspection Department

[0107] 40 Cable

[0108] 50 Holding shell

[0109] (Industrial Applicability)

[0110] The endoscope of the present invention can obtain high-resolution images and can be used as a disposable endoscope.

Claims

1. A disposable endoscope having a light transmission body in a cylindrical sheath having an outer diameter of 20 mm or less, The disposable endoscope is characterized in that The optical transmission body comprises: Rod-shaped gradient refractive index plastic lens, and A connector detachably connected to the detection unit at the proximal end of the gradient refractive index plastic lens; The light-transmitting body transmits light received by a distal end portion thereof to the detection portion, thereby generating an image in the detection portion.

2. The disposable endoscope according to claim 1, characterized in that The disposable endoscope further includes an objective lens, and the objective lens is arranged in close contact with the distal end of the gradient refractive index type plastic lens, or is arranged apart from the distal end of the gradient refractive index type plastic lens.

3. The disposable endoscope according to claim 1 or 2, characterized in that The sheath is made of a transparent material and is connected to a light source for illumination at its proximal end.

4. The disposable endoscope according to claim 1 or 2, characterized in that The sheath includes an outer tube and an optical fiber for illumination.

5. The disposable endoscope according to claim 1 or 2, characterized in that: The outer diameter of the gradient refractive index plastic lens is 0.1 mm to 10 mm.

6. The disposable endoscope according to claim 1 or 2, characterized in that The length of the gradient refractive index plastic lens is 1 to 40 cm.

7. The disposable endoscope according to claim 1 or 2, characterized in that: The sheath is a 10G to 30G injection needle or a flexible outer shell.

8. The disposable endoscope according to claim 1 or 2, characterized in that The gradient refractive index plastic lens is a plastic lens with an outer diameter of less than or equal to 10 mm and a length of 1 to 40 cm, in which a concentration gradient of the dopant is formed in a concentric circle in the radial direction by adding a dopant to a linear polymer used as a matrix, and by diffusion of the dopant, wherein the dopant is a low molecular weight substance that is not reactive with the linear polymer used as the matrix.

9. The disposable endoscope according to claim 2, characterized in that The objective lens is a spherical lens.

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