WO2006080801A1

WO2006080801A1 - Non-paste fabrication method of optical fiber block

Info

Publication number: WO2006080801A1
Application number: PCT/KR2006/000285
Authority: WO
Inventors: Ik Joo Lee
Original assignee: Acts Vision Co., Ltd.
Priority date: 2005-01-28
Filing date: 2006-01-25
Publication date: 2006-08-03

Abstract

The present invention relates to a method of fabricating an optical fiber panel for use in a rear projection-type display, and more particularly, to a method of fabricating a display panel which is constructed from sections of optical fibers and serves as a screen for visually displaying images projected from a CRT or LCD image projector. An amount of optical fibers used to construct the display panel from the sections of the optical fibers ranges from several hundreds up to several ten millions. Thus, it is difficult to integrate a large amount of optical fibers into several bundles and to continuously arrange the integrated bundles. That is, a large amount of very thin optical fibers with a thickness corresponding to a hair should be wound such that they are not entangled with one another, as well as optical information should be transferred from one end to the other end of the optical fiber bundle without distortion and loss. So far, a paste integrating method of applying paste between adjacent optical fibers and solidifying the integrated optical fibers to form an optical fiber bundle. However, it is actually difficult to fabricate a precise optical fiber product due to the problems caused from the use of paste. Accordingly, the present invention suggests a non-paste method of winding optical fibers without using a paste, so that the fabrication of display panel using optical fibers can be made more easily and efficient.

Description

NON-PASTE FABRICATION METHOD OF OPTICAL FIBER

BLOCK

Technical Field

[1] The present invention relates to a method of precisely fabricating an optical fiber bundle for displaying or transmitting image information in an image display panel, medical endoscope or the like and an optical fiber block made by solidifying the optical fiber bundle. More specifically, the present invention relates to a method of precisely fabricating an optical fiber block, which comprises the steps of precisely winding optical fibers serving as media for transmitting image information such that the optical fibers are not entangled, twisted or displaced with each other, integrating and stacking a group of the wound optical fibers, and solidifying the optical fibers. Background Art

[2] As well known in the art, an optical fiber for use in image guide is an acrylic fiber having a very small diameter within a range of at least 0.01 mm and at most 1 mm. This optical fiber is composed of a core layer functioning to directly transfer optical information and a clad layer surrounding the core layer, and the two layers are made of polymer compounds with different refractive indexes. Thus, the total reflection of light occurring due to difference in refractive indexes of the two layers allows optical information inputted at one end of the core can be propagated toward the other end without any transmission to the outside. If such a feature of an optical fiber is used for transferring and displaying image information, the optical fiber becomes a very efficient medium in that loss of information is low and it is possible to physically divide image information according to pixels. That is, a conventional projector screen has problems in that its image quality is low and its brightness is significantly reduced due to loss of optical information since images are realized using the diffusion of light. On the other hand, in a case where the optical fibers are used in a screen of a rear projection-type image projector, there is an advantage in that good image quality and high brightness can be ensured due to the extremely low loss of optical information. In addition, in a case where the optical fibers are used in a medical endoscope or the like, there is another advantage in that image information can be transferred without any additional device such as a camera.

[3] However, since an optical fiber has a very small sectional area as described above, a large number of optical fibers are required for fabricating a wide display surface by arranging the optical fibers in horizontal and vertical directions in a state where the sections face forward. Further, if some of optical fibers are displaced, twisted or entangled while a large number of optical fibers are wound and integrated, it would be a cause of the distortion of image information due to the displacement of pixels forming the original image information. That is, the precision of a process of winding and integrating a plurality of optical fibers is directly linked with the image information transmission efficiency.

[4] There are many precedent examples of the optical fiber integration and the optical fiber sheet or block fabrication for using an image guide function of the optical fiber. Korean Utility Model Registration No. 0259941 discloses a projection screen using optical fibers, in which a plurality of optical fibers are inserted in spaces defined by a plurality of wefts and warps constructing a sheet of fabric, the fabric with the optical fibers inserted therein are coated or applied with a transparent or translucent synthetic resin, and a polarizing film is attached to the other side of the fabric, as shown in Fig. 1. However, there are problems in that it is difficult to obtain clear images due to the synthetic resin attached to one sides of the optical fiber and production costs are increased due to the lower efficiency of the fabrication process.

[5] In addition, Korean Utility Model Registration No. 0305229 discloses another rear projection-type screen using optical fibers and a fabricating method thereof. That is, as shown in Fig. 2, the rear projection-type screen comprises a diffusion sheet made by weaving optical fibers to diffuse image projected from a projector in weft and warp directions, a transmitting sheet formed by filling up fiber gaps in the weaved diffusion sheet using a transparent thermoplastic resin to serve as a transmission layer between the weft and warp fibers, a focusing sheet stacked on an incident side with respect to the diffusion and transmitting sheets, a semi-permeable sheet stacked on an exiting side that allows images diffused or transmitted in the weft and warp directions to be diffused into and then formed on the entire screen, and a black mark for increasing a contrast ratio by preventing the diffused reflection of the images formed on the semipermeable sheet in a viewer direction. The optical fiber sheet and projection screen using the same have advantages in view of higher brightness than the conventional sheets and screens, wider field of vision and an increased contrast ratio of images due to the black mark. However, the optical fiber sheets and projection screens have disadvantages in that they cannot efficiently utilize the transmission feature of the optical fiber but merely utilize the transparent feature of the optical fiber, it is difficult to transfer clear images since the images are scattered because of the use of the optical fibers and semi-permeable sheets, and the brightness is too low to use them in the daytime.

[6] When fabricating an optical fiber sheet or block to use optical fibers as an image guide, a process of fixing the optical fibers is very important but difficult operation, and the coupling of optical fibers with impurities including the insertion of medium such as a paste or synthetic resin becomes a most important factor that causes the loss or distortion of the optical information.

[7] In addition, a further manufacturing method as a solution for the aforementioned problems is disclosed in Korean Laid-open Patent Publication No. 10-2004-0066739. As shown in Fig. 3, the method comprises the steps of fabricating optical fiber sheets by fixedly arranging optical fibers coated with paste at regular intervals, coating the optical fiber sheets with paste and stacking the coated sheets with one another, and fabricating optical fiber blocks by cutting the stacked optical fiber sheets. The optical fiber block fabricated as described above could improve the image guide function as compared with the other conventional methods, because there is no need of using other materials for fixing optical fibers, i.e. fibers other than optical fibers to be woven into the weft and warp structure or a fabric used for fixing the optical fibers. However, this method inevitably generates air bubbles between the optical fiber sheets when stacking the optical fiber sheets, because the method utilizes the process of coating the individual optical fibers with paste to bond the adjacent optical fibers for positioning the optical fibers while fabricating the optical fiber sheets prior to the blocking of the optical fiber sheets. Therefore, it becomes a factor for deteriorating the precision of optical fiber block. In addition, as shown in Fig. 3, an optical fiber is slowly reciprocated while rotating a cylindrical winder 11 such that the optical fiber is wound around the cylindrical winder 11 up to one to twenty (1 to 20) layers, and this optical fiber layers are cut in an axial direction to obtain an optical fiber sheet. However, in a case where this method is applied to an actual fabricating process, i.e. an optical fiber coated with paste is wound around the winder to several layers, the adjacent layers have been already bonded to each other and solidified during the winding process. Thus, even though the stacked sheets are cut in an axial direction of the cylindrical winder after the winding process, a flat optical fiber sheet cannot be fabricated but a C- shaped solidified optical fiber block can be merely obtained. Further, if this optical fiber block is pressed into a flat shape, the difference in length between the optical fiber layers wound around the cylindrical winder is inevitably caused, and thus, a precise optical fiber block cannot be obtained. Meanwhile, in a case where a single layer of an optical fiber is wound in the same manner, a sheet of the optical fiber may be produced, but it is still impossible to produce a successive optical fiber sheet as shown in Fig. 4. The method of fabricating optical fiber sheets using a weaving technique makes it possible to produce a successive optical fiber as shown in Fig. 4, but the technique of weaving the wefts and warps makes it difficult to efficiently utilize the optical fibers. In addition, an air layer is inevitably formed between the adjacent sheets due to the sagging of the optical fiber sheet caused by its weight when an optical fiber is wound again around an open-type polygonal rotating reel 220 of Fig. 4, and thus, a bubbling phenomenon that the air layer is settled between the optical fiber sheets due to a paste component already coated on the optical fiber sheets may occur.

[8] In addition, the above method suggests that a winding speed be maintained at 1 to

20 m/sec to prevent the optical fiber from being broken. The total length of optical fiber consumed for use in the above projection screen may vary according to a screen size. However, assuming that an optical fiber with a diameter of 0.1 mm is used for fabricating a screen with a size of 500 mm 300 mm 100 mm at a speed of 20 m/sec, the length of optical fiber to be fabricated should be reached up to 150,000 meters. Accordingly, since it takes 7,500 seconds (about 2 hours) to produce a single screen, there is a problem in that the productivity may be lowered.

[9] Furthermore, in a case where the sections of the optical fibers are utilized for a display surface or an endoscope having an image guide function, much more precise integration is required. In an image guide, an image incident onto one section should be transferred to the other section without distortion. Nevertheless, if the position changes due to the twist of optical fibers occur in the integrated optical fibers, there may be actually a great difference between input and output images. Disclosure of Invention Technical Problem

[10] Accordingly, the present invention is conceived to solve the problems in the conventional optical fiber integration technology. An object of the present invention is to provide a method of integrating optical fibers and fabricating an optical fiber block for use in image information display and transmission fields using an image guide function of the optical fiber, e.g. the configuration of an image surface of a projector or a medical endoscope, wherein entangling and twisting phenomena occurring between the optical fibers are prevented and no materials other than the optical fibers are included such that the precision can be improved and the costs can also be reduced, the loss of image information can be minimized and a fabrication rate suitable to the mass- production can be realized. Technical Solution

[11] According to an aspect of the present invention for achieving the object, there is provided a method of fabricating an optical fiber block, comprising a first step of winding the predetermined number of optical fibers side by side such that the optical fibers are not twisted with each other, a second step of stacking the predetermined number of wound optical fibers in a closed-type stacking frame with a predetermined width (value of the width = diameter of each optical fiber the number of optical fibers wound at each layer), a third step of fusion bonding the stacked optical fibers into a predetermined size under heat and pressure in a vacuum state, and a fourth step of cutting the fusion-bonded optical fiber bundle into blocks with a predetermined size.

[12] According to another aspect of the present invention, there is provided a method of constructing optical fibers to have a honeycomb structure or rectangular section to minimize unnecessary spaces defined between adjacent optical fibers, which may be created when integrating the optical fibers with circular sections.

[13] According to a further aspect of the present invention, there is provided a method of fabricating an optical fiber block with optical fibers integrated therein, in which a thermal fusing process is performed to minimize the loss and distortion of image information which may be caused by paste regions when the optical fiber bundle is prepared using a paste.

[14] According to a still further aspect of the present invention, there is provided a method of fabricating an optical fiber block, wherein it is possible to mass produce the optical fiber blocks since a fabrication speed is increased by synchronizing a rotating speed of a rotating winding frame with an unwinding rate of a raw optical fiber to allow a tension of each optical fiber to be kept at a certain level when the optical fibers are wound, and even when the winding speed is increased, in order to overcome the limit of a weaving speed caused by a restricted tensile strength of the optical fiber. Brief Description of the Drawings

[15] Fig. 1 shows an example of an optical fiber sheet fabricating method according to the prior art.

[16] Fig. 2 shows another example of an optical fiber sheet fabricating method according the prior art.

[17] Fig. 3 shows a process of the optical fiber sheet fabricating method according the prior art.

[18] Fig. 4 shows a process of stacking and bonding optical fiber sheets according to the prior art.

[19] Fig. 5 shows a process of extracting an optical fiber block from an optical fiber sheet according to the prior art.

[20] Fig. 6 is a schematic view showing a process of winding, integrating and stacking an optical fiber according to the present invention.

[21] Fig. 7 shows a state where an optical fiber stacking frame, an optical fiber support frame and an optical fiber pressing frame are coupled with one another according to the present invention.

[22] Fig. 8 shows the configuration of an optical fiber winding frame according to the present invention.

[23] Fig. 9 shows a process of integrating an optical fiber according to the present invention.

[24] Fig. 10 shows a process of extracting an optical fiber block after fusion bonding the integrated optical fibers under pressure in a vacuum state according to the present invention.

[25] Fig. 11 shows a process of cutting the produced optical fiber blocks according to an embodiment of the present invention.

[26] Fig. 12 shows a process of fabricating a display panel made of optical fiber sections by arranging cut surfaces of the produced optical fiber blocks on a single plane and then heating the arranged surfaces under pressure in a certain frame according to another embodiment of the present invention.

[27] Fig. 13 shows an optical fiber block that is cut obliquely and then used as a display surface for image magnification according to a further embodiment of the present invention.

[28] Fig. 14 shows a sectional structure of a display panel fabricated using the cut surface of the produced optical fiber block according to the present invention.

[29] Fig. 15 shows an embodiment in which the optical fiber sections are deformed while the optical fibers are fusion bonded under heat and pressure in a vacuum state according to the present invention. Best Mode for Carrying Out the Invention

[30] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[31] In general, an optical fiber for use in an image guide or an image display screen is a very thin fiber with a diameter of from at least 0.05 mm to at most 1 mm. The optical fibers may be crossed with each other to such a degree that it is very difficult for a person to manipulate the optical fiber with his/her hand or often entangled with each other due to static elasticity between the fibers. In a case where a large amount of optical fibers are wound and integrated, the compactness of optical fibers may be deteriorated and the twisting and displacement between adjacent optical fibers may occur even though an additional space is slightly created. This phenomenon results in pixel position changes in inputted image pixels or inputted image information, and may consequently cause serious distortion of the image information. Thus, the winding and integration of a large amount of optical fibers should be manipulated within a predetermined frame such that no space is generated between the optical fibers from the initial stage. Fig. 6 illustrates a whole process of the method of fabricating an optical fiber block according to the present invention, n optical fibers extracted from n raw optical fiber rolls 300, 30k, ..., 30n pass through a winding frame 200 of which an entire width of inner grooves is equal to a diameter of an optical fiber multiplied by the number of wound optical fibers (n) and height of the inner groove is equal to the diameter of the optical fiber, and are then stacked around a rotating integration frame 100 to 121. As shown in Fig. 8, the rotating integration frame 100 to 121 is composed of a rectangular stacking frame 110 with a width equal to the diameter of an optical fiber multiplied by the number of wound optical fibers (n) and a circular support frame 100 attached to both lateral ends of the rectangular stacking frame 110 to support the rectangular stacking frame 110 such that the optical fibers are not escaped from the rectangular stacking frame and the wound optical fibers can also be kept at a state where they are brought into close contact with one another. Thus, the n wound optical fibers can be stacked on the rectangular stacking frame while the arrangement of the optical fibers formed by the winding frame 200 is maintained. At this time, the number of stacked optical fibers can be increased or decreased depending on the size of an optical fiber block to be fabricated. However, the number of optical fibers should be selected such that an entire width of the wound optical fibers does not exceed a certain level to easily cut and extract an optical fiber block later. For example, in a case where a laser cutter is used for precisely cutting the optical fiber bundle, it is difficult to fabricate a precise optical fiber block with a size greater than 100 mm on the grounds that the directionality of laser is deteriorated when a cutting thickness is greater than 20 mm. Further, in a case where a diamond cutter or a general saw for cutting an acrylic material is used, it is difficult to fabricate a precise optical fiber block with a size greater than 100 mm on the grounds that the cutter is fusion-bonded with the optical fiber section due to frictional heat generated therebetween. In addition, a recently used cutting method using hydraulic pressure can provide high-quality cut surfaces and have an extended cutting thickness to a certain extent due to its excellent cutting property. However, this method also has some limitations. Therefore, the present invention suggests that each of the other cutting methods described herein be applied in consideration of limits peculiar to the methods.

[32] Meanwhile, the optical fibers wound and stacked around the stacking frame 110 are only physically integrated but not bonded with one another. Thus, they are in a state where the stacked optical fibers may be separated into individual ones and cannot be constructed into an optical fiber block when the circular support frame 100 and the stacking frame 110 are separated from each other. According to the existing method, paste is coated on the respective optical fibers before the optical fibers are stacked such that the optical fibers can be bonded with one another at the same time when they are stacked. However, the present invention is conceived to eliminate any problems caused by using a paste as described later. That is, the present invention is directed to a non- paste fabrication method for an optical fiber block wherein only a closed-type frame is used for fixing the positions of optical fibers until the number of optical fibers to be wound and stacked reaches a certain level considering the size and compression ratio of an optical fiber block to be fabricated, but no paste is used even in a final bonding and solidifying process, i.e. only a fusion-bonding phenomenon of the optical fiber itself is used. That is, in a state where the optical fibers are stacked around the stacking frame 110 that is not separated from the circular support frames 100, the pressing frame 120 is inserted between the circular support frames 100 as shown in Fig. 7. Then, spring pins 121 are inserted into elliptical holes 101 bored through the circular support frame to fix the pressing frames. After the pressing frames have been installed to four surfaces of the stacking frame, total eight (8) spring pins are connected to opposite pins using tension springs. Accordingly, a pulling force is exerted on the opposite pressing frames, so that the pressing frames can impart a certain pressure to the optical fiber bundle stacked around the stacking frame. In such a case, the pressing frames impart only a force corresponding to a length of the elliptical hole bored through the circular support frame, and the length of the elliptical hole depends on the size or standard of an optical fiber block to be fabricated. If heat is applied to the optical fiber stacking frame for a certain time, the individual solid optical fibers are softened and fusion-bonded with each other due to the pressure applied by the pressing frames. Then, after the optical fibers are cooled and solidified at a normal temperature, the respective frames are separated from one another and the stacked optical fibers are cut (see Fig. 10) to extract optical fiber blocks. Generally, optical fibers may be softened at a temperature of 105 to 120°C without damaging the core and clad of the optical fiber and deteriorating peculiar features of the optical fiber. Experimental results have found that the optical fibers are closely contacted and solidified when they are heated to the above temperature range for 40 minutes to 10 hours. According to the optical fiber block fabricated as described above, the loss of space corresponding to the thickness of paste can be prevented since no paste is applied between the optical fibers. Therefore, there is an advantage in that the loss and distortion of image information can be reduced. [33] Furthermore, an optical fiber is shaped into a circular section. In a case where an optical fiber has a polygonal section other than a circular section, there is a problem in that a loss rate of optical information is increased due to the change in refractive indices and the interference between several optical information with different wavelengths. Thus, it is one of the important factors for determining the quality of optical fiber in the current optical fiber fabricating technology to realize a perfectly circular section of the optical fiber. However, in the present invention, an optical information transmission distance through the optical fiber block is very short as much as 0 to 2 m. Further, in a case where the optical fiber block is used for an image guide for displaying image information inputted from one end of the optical fiber onto the other end instead of transmitting several optical information with different wavelengths through one optical fiber when it is used for the communication of optical information, each of the optical fibers serves to transmit a single pixel, instead of optical information. Therefore, even though the optical fiber is shaped into a polygonal section, the loss of optical information is negligible. In this regards, the present invention suggests that the optical fiber section may be shaped into a polygonal section. The reason is that spaces are inevitably generated between the adjacent optical fibers when a plurality of optical fibers with circular sections are integrated, and thus that these spaces cause the loss of optical information. Fig. 14 shows such problems and their solutions. In a case where a plurality of optical fibers are integrated and stacked and then heat and pressure are applied thereto as described above, the optical fibers each having a circular section are modified to have a rectangular or hexagonal section as shown in Fig. 15. At the same time, the spaces that are defined between the optical fibers to cause the loss of image information can be removed. In addition, the present invention suggests that an oven for applying constant heat to the integrated optical fibers for a predetermined period of time during the aforementioned procedure be kept at a vacuum state within a chamber thereof. The reason is that air gaps defined between the adjacent optical fibers serves as a factor of hindering close contact between the adjacent optical fibers and thus deteriorates the precision of the optical fiber block. Before heat-bonded, the respective optical fibers are just physically brought into contact with one another but not bonded with one another by means of paste or the like. Thus, the air gaps defined between the adjacent optical fibers can be easily eliminated by causing the interior of the oven to be in a vacuum state. [34] Meanwhile, since the section of the optical fiber is modified into a polygonal structure by applying pressure and heat to the optical fiber block, the size of the optical fiber block to be fabricated and the number and thickness of optical fibers stacked should be changed. Assuming that the thickness and width of an optical fiber block to be fabricated are T and W, respectively, and the radius of an optical fiber with a circular section is R, the number N of optical fibers stacked and the number n of optical fibers wound can be calculated, as follows, as shown in Fig. 15. One optical fiber has a sectional area of πR . Even after the circular section of the optical fiber is changed into a rectangular section by means of compression, their sectional areas should be the same as each other. Thus, the length of one side of the rectangular

9 1 /9 section should be (πR ) . That is, assuming that the thickness and width of an optical fiber block are T and W, respectively, the number N of optical fibers stacked can be

9 1/9 calculated from the equation N=T/(πR ) and the number of optical fibers wound can also be calculated from the equation n=W/(πR ) . Consequently, since the integrated o i /o 9 1/9 optical fiber bundle has a thickness of RxT/(πR ) and a width of RxT/(πR ) before compression, the length of the elliptical hole 101 of the circular support frame 100 of Fig. 7 and the sizes of the pressing frame 120, the stacking frame 110 and the winding frame 200 can be calculated from the above equations.

[35] Furthermore, since an optical fiber for an image guide or image transmission is made of very thin acrylic plastic or quartz glass and sized to have a section diameter of 0.01 to 1 mm, the optical fiber can be easily broken even by small force. Thus, when winding and integrating the optical fibers from the raw optical fiber rolls, it is necessary to wind the optical fibers at a rate lower than a certain level, preferably 20 m/sec or below. For example, assume that the optical fiber block is cut and arranged at regular intervals to be used for a screen of a projection display. At this time, if a 17-inch screen has a thickness of 10 mm and an optical fiber used has a diameter of 0.1 mm, an approximate total length of the optical fiber required amounts to 120,000 m. If the screen is produced by using only a single fiber, 7,500 seconds (about 2 hours) are required even though the optical fiber is wound at a winding rate of 20 m/sec.

[36] In order to solve the above problem, the present invention is configured as follows.

That is, an unwinding motor 500 of which rotating speed is in harmony with the rotating speed of the optical fiber integration frame is mounted to each of the raw optical fiber rolls. A tensiometer 600 is installed to measure the tension applied to each of the optical fibers. If the measured tension is equal to or greater than a predetermined level, a reduction gear 400 for controlling the unwinding motor increases an unwinding rate of the relevant raw optical fiber roll. However, if the measured tension is reduced and thus there is a probability that the optical fibers may be twisted, the reduction gear 400 decreases the unwinding rate of the relevant raw optical fiber roll. As a result, the tension is always kept constant from the raw optical fiber rolls to the optical fiber integration frame, so that the optical fibers are neither broken due to excessively large tension even when they are rapidly wound nor sagged, entangled or twisted due to extremely small tension. Accordingly, the present invention can provide a method for fabricating an optical fiber block in a mass-production manner by increasing a production rate of the optical fiber block. The tension information on each of the optical fibers measured by the tensiometer 600 is sent to the reduction gear 400 to control the unwinding rate of the unwinding motor 500, as shown in Fig. 6. Assuming that a critical tension at which an optical fiber is broken is T and a tension at which the optical fibers are entangled due to the sagging of optical fibers when they are wound is t, a value of the tension for each optical fiber should be maintained between T and t. The critical tension T varies according to the properties of a raw material such as a diameter or material type of an optical fiber, but the tension t at which the adjacent optical fibers are sagged and entangled when they are wound is defined as having a value of zero. A working tension T required for winding the optical fibers is proposed in the present invention as remaining in the following region: O=KT <T. To ensure precise integration of the optical fibers, a suitable value of tension can be set within the above tension range. Industrial Applicability

[37] As compared with other conventional techniques, the method of fabricating an optical fiber block for use in image information transmission or display production using the image guide function of optical fibers in an endoscope or projector screen according to the present invention provides the following advantageous effects.

[38] Since the number of optical fiber wound, the number of optical fibers integrated, and suitable frames for optical fibers are prepared and utilized according to a desired size or standard in the respective processes of winding, integrating and compressing bonding the optical fibers, the possibility of causing the displacement or twist of optical fibers is decreased. Thus, a precise optical fiber integration block can be obtained.

[39] Further, no paste is used between optical fibers and a process of fusion bonding optical fibers under pressure and heat is employed unlike the existing methods. Thus, the problems caused from the use of paste, i.e. the distortion of image information occurring at paste portions, can be eliminated and production costs can also be reduced.

[40] In addition, since the sections of optical fibers can be changed into rectangular or hexagonal shapes through the thermal compression of the optical fibers, unnecessary spaces between the optical fibers can be minimized as compared with a case where conventional optical fibers with circular sections. Thus, the loss of image information can be minimized when the optical fiber block is used for an image guiding function.

[41] Furthermore, since the tension applied to the optical fibers can be controlled, the production rate can be markedly improved as compared with the conventional methods. Therefore, the mass-production can be ensured by using the method of the present invention.

Claims

[1] L A method of fabricating an optical fiber block, comprising: a first step of winding and integrating a plurality of optical fibers; a second step of fusion bonding the optical fibers with one anther under heat and pressure; a third step of cutting an object with the fusion-bonded optical fibers integrated with one another to form an optical fiber block; and a fourth step of cutting and processing the optical fiber block in accordance with desired characteristics of an application product.

[2] 2. The method as claimed in claim 1, wherein the first step is executed using a winding frame for winding the optical fibers from n raw optical fiber rolls and closely arranging several optical fibers without any gaps therebetween in a lateral direction such that a total width of the wound optical fibers is n times of a diameter of a single optical fiber.

[3] 3. The method as claimed in claim 1, wherein the first step is executed in such a manner that closely wound optical fibers are rotatably integrated around a rot ating integrating frame, and the rotating integrating frame comprise a rectangular stacking frame and a circular support frame, which are brought into closely contact with each other, such that the respective optical fibers are escaped from a specific position determined by a winding frame and out of the rectangular stacking frame.

[4] 4. The method as claimed in claim 1, wherein the first step employs a tensiometer, a motor reduction gear and a raw optical fiber unwinding motor such that a tension of each optical fiber is kept to a predetermined level in response to a rotating speed of an integrator and an unwinding rotating speed of the raw optical fiber rolls so as not to cause the breakage of optical fibers but to enable the high-speed fabrication while the optical fibers are wound and integrated from the respective raw optical fiber rolls.

[5] 5. The method as claimed in claim 1, wherein in the second step, the integrated optical fibers are fusion-bonded under heat and pressure by not using a paste.

[6] 6. The method as claimed in claim 1, wherein the number of optical fibers wound or the number of optical fibers stacked is determined depending on a size and a compression ratio of an optical fiber block to be fabricated such that a precise optical fiber block is fabricated by fusion bonding the integrated optical fibers under heat and pressure.

[7] 7. The method as claimed in claim 1, wherein in the second step, a compression range in every direction is previously determined to allow the optical fiber not to be compressed beyond a predetermined level such that a size of the optical fiber block after compression becomes constant to enhance precision of the optical fiber block.

[8] 8. A method of fabricating an optical fiber block, wherein optical fibers with circular sections are subjected to heat and pressure and modified into optical fibers with polygonal shapes including hexagonal and rectangular shapes to remove unnecessary spaces defined between adjacent optical fibers and thus to ensure high density of the optical fiber block.

[9] 9. The method as claimed in claim 8, wherein an oven used as a tool for applying the heat and pressure to an integrated optical fiber bundle is kept at a vacuum state in the interior thereof to remove an air gap defined between the adjacent optical fibers in the optical fiber bundle and thus to enhance compression efficiency.