JP3558657B2 - How to fix optical fiber - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a method of fixing an optical fiber for bonding an optical fiber and an optical system (light guide) constituting an optical detection system of a keyboard instrument.
[0002]
[Prior art]
In general, an electronic musical instrument or an automatic musical instrument having a keyboard determines a pitch by detecting a pressed key (key) and a rocking speed (key pressing speed) of a hammer corresponding to the key, and determines a pitch. It has a mechanism that calculates the intensities and generates musical tones of the corresponding pitch, volume, and timbre.
As described above, in an electronic musical instrument or an automatic musical instrument having a keyboard, it is important to detect a key pressing speed that greatly affects the volume and timbre, and calculate the stringing strength.
[0003]
Conventionally, the above-described detection of the hammer speed has been performed using an apparatus having a structure shown in FIG. FIG. 7 is a diagram showing an example of a schematic configuration of an optical detection system of an automatic piano. In this figure, reference numerals 1 and 2 denote input pulse data of a predetermined cycle (for example, a pulse width is 16 μs, a duty cycle = 1/12%). Are light emitting diodes that emit light of a predetermined wavelength in accordance with a key and a hammer, respectively. Incidentally, the forward current _{I F} supplied to the light emitting diodes 1 and 2, and 133 mA.
[0004]
Next, reference numeral 3 denotes a shutter which slides in the vertical direction in the figure in response to the swing of the corresponding hammer, and which slides to form a light guide disposed at a position opposite to the lens 4a of the light guide 4. 5 to block parallel light incident on the lens 5a. Reference numeral 6 denotes an optical fiber having an input end 6a provided near the light emitting diode 2 and an output end 6b of which is bonded to the light guide 4 by using an epoxy adhesive or an ultraviolet curing adhesive. Is an optical fiber whose input end 7a is bonded to the light guide 5 like the optical fiber 6, and whose output end 7b is provided near the photodiode 8.
[0005]
In the above-described configuration, first, the lens 4a refracts light emitted from the light emitting diode 2 and incident via the optical fiber 6, and travels straight through the air as parallel light having a predetermined width. Next, the lens 5 a refracts and converges the parallel light that travels straight in the air, and enters the input end 7 a of the optical fiber 7. At this time, when the key corresponding to the shutter 3 is pressed, the parallel light traveling straight in the air is blocked by the slide of the shutter 3, so that the key pressed state can be detected based on the light transmission and light blocking. .
[0006]
By the way, in order to accurately measure the above-mentioned changes in light transmission and light blocking, it is necessary that the adhesive for optically bonding the lenses 4a and 5a and the optical fibers 6 and 7 has a high light transmittance. . This is because, in the above-described optical detection system, since the adhesive acts as a light path, if the light transmittance of the adhesive is low, the light transmission loss increases, and the light transmission and light shielding accompanying the sliding of the shutter 3 are caused. This makes it impossible to accurately measure the change in.
[0007]
An experiment for measuring the light transmittance in the light path of the device shown in FIG. 7 using an epoxy adhesive will be described below. In the apparatus shown in FIG. 7, when the shutter 3 corresponding to each key does not block light, it is measured how much the input pulse is attenuated and output. The measured value shown in FIGS. 8 and 9 (unit: μW) Is obtained.
8 and 9 are obtained by measuring the current value output from the photodiode 8 when the shutter 3 corresponding to each key is opened, and the average value is 56.33 μW. In these figures, the vertical indicates an octave name, and the horizontal indicates a note name corresponding to a key in each octave.
[0008]
[Problems to be solved by the invention]
By the way, various adhesives used for optically joining the optical fibers 6 and 7 and the lenses 4a and 5a have the following disadvantages.
First, in the bonding using an epoxy-based adhesive, the curing time is long day and night, so that the time required to manufacture a product using the bonded parts is long. In addition, a place is required to leave the bonded parts until the epoxy adhesive cures. During the curing, the room temperature had to be kept at 20 ° C., and air conditioning was required. Further, in order to prevent the generation of bubbles (voids), it was necessary to select and use a low-viscosity type adhesive.
[0009]
On the other hand, in bonding using an ultraviolet-curing adhesive, when the surface layer of the adhesive is cured, the cured portion absorbs ultraviolet rays, and the internal adhesive may remain uncured. . In addition, uncured adhesives can cause cracks in the acrylic material to be bonded, which has led to reduced light transmission. In addition, voids sometimes remain in the cured adhesive, which also led to a decrease in light transmittance. Further, in order to irradiate the human body with harmful ultraviolet rays, the worker had to carefully perform the bonding operation.
The present invention has been made under such a background. The curing time is short, the procedure is simple, the voids and cracks are not generated, the light transmittance is high, and the optical performance of a keyboard instrument harmless to the human body is achieved. An object of the present invention is to provide a method for bonding a detection system.
[0010]
[Means for Solving the Problems]
In the method for fixing an optical fiber according to claim 1 of the present invention, the optical system that emits light incident from the optical fiber in a predetermined direction has a transparent light guide, and the light guide is located at an upper position. It has a columnar adhesive insertion hole that opens, and an insertion hole into which the optical fiber is inserted, and the insertion hole becomes thinner toward the front in the insertion direction of the optical fiber, and the optical fiber is inserted from a predetermined position. A method of fixing the optical fiber to the light guide, wherein the adhesive insertion hole communicates with the insertion hole. The tip of the optical fiber is positioned in the adhesive insertion hole, a visible light curable adhesive is injected into the adhesive insertion hole, radiated with visible light, and the visible light is guided by the light guide. Reach the visible light curable adhesive in the body, It is characterized by fixing the optical fiber by curing the mold adhesive.
[0011]
[Action]
According to the above method, first , an optical fiber is inserted into an optical system. Next , a visible light curable adhesive is injected into the insertion portion between the optical fiber and the optical system. Next , the visible light is radiated to cure the visible light-curable adhesive, thereby fixing the optical fiber and the optical system.
In addition, by injecting the adhesive into the adhesive insertion hole with the tip of the optical fiber positioned in the adhesive insertion hole, the adhesive is inserted between the tip of the optical fiber and the light guide. Is filled, and the tip of the optical fiber and the light guide are optically fixed with an adhesive.
[0012]
【Example】
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 to 3 are views showing steps of a method of bonding an optical detection system of a keyboard instrument according to an embodiment of the present invention, and these figures show states of substances to be bonded in first to third steps, respectively. ing. In these drawings, common portions are denoted by the same reference numerals.
[0013]
First, the first step will be described with reference to FIG. In FIG. 1A, reference numeral 9 denotes a substantially rectangular parallelepiped light guide manufactured by molding a (colorless) transparent acrylic resin, and a substantially rectangular parallelepiped projection 9a is formed on the bottom surface thereof. Reference numeral 10 denotes a sensor bracket formed by forming a galvanized iron plate into a substantially U-shaped cross section. A plurality of (89 to 92) prism-shaped light guide holes into which the projections 9a of the light guide 9 are inserted and adhered. 10a are formed at predetermined intervals. A plurality of introduction holes 10b into which optical fibers are to be inserted penetrate through one side of the wall rising from both ends of the sensor bracket 10.
[0014]
In such a state, first, the visible light curable adhesive 11 is applied to the light guide hole 10 a of the sensor bracket 10. Next, the projection 9a of the light guide 9 is inserted into the light guide hole 10a from the direction shown by the arrow in the figure. Then, as shown in FIG. 1B, which is a part of the cross-sectional view taken along the line AA ′ in FIG. 1A, the visible light-curable adhesive 11 is applied to the lower surface 9 b of the light guide 9 and the sensor bracket 10. It is filled in the gap with the upper surface 10c. Next, as shown in FIG. 1B, when visible light is irradiated from above the light guide 9, the visible light passes through the light guide 9 and reaches the visible light-curable adhesive 11. The curable adhesive 11 is cured. Thereby, the light guide 9 and the sensor bracket 10 are bonded.
[0015]
Next, the next step will be described with reference to FIG. In FIG. 2A, reference numeral 12 denotes a plurality of optical fibers manufactured by molding an acrylic resin, and reference numeral 13 denotes a substantially rectangular parallelepiped plug fixed to the sensor bracket 10. The light guide holes 13a and the wire holes 13b are formed in the same number as the introduction holes 10b of the sensor bracket 10 in the cylindrical shape. As shown in FIG. 2B, which is a part of the cross-sectional view taken along the line aa ′ in FIG. 2A, the light guide holes 13a do not penetrate the lower surface of the plug 13, and each of the light guide holes 13a has one conductive wire hole. 13b and orthogonally communicate with each other. The conductor hole 13b penetrates in the left-right direction in the figure, and communicates with one of the introduction holes 10b shown in FIGS. 1 (a) and 2 (b), respectively, so that their axes coincide. Is formed.
[0016]
In such a configuration, first, as shown in FIG. 2B, the optical fiber 12 is inserted into the sensor bracket 10 through the lead hole 13b of the plug 13 and the introduction hole 10b communicating with the lead hole 13b. Then, the tip of each optical fiber 12 is pulled out to the vicinity of the corresponding light guide 9. Next, a sufficient amount of the visible light curable adhesive 11 is poured from the light guide hole 13a, and visible light is irradiated from above the plug 13. The irradiated visible light reaches the visible light curable adhesive 11 in the light guide hole 13a, and cures the visible light curable adhesive 11. Thereby, the optical fiber 12 and the plug 13 fixed to the sensor bracket 10 are bonded. The upper visible light-curable adhesive 11a that has been cured transmits visible light, so that the lower visible light-curable adhesive 11b is also sufficiently cured in a short time.
[0017]
Further, the next step will be described with reference to FIGS. FIGS. 3B, 4A, and 4B are a top view, a side view, and a back view of the light guide 9 viewed from directions B, C, and D shown in FIG. 3A. FIG. In these figures, 14 and 15 are the upper and lower portions of the light guide 9, respectively, and a pair of substantially cylindrical adhesive insertion holes 14a and 15a having an opening on the upper surface of the light guide 9, and the insertion holes 14b and 15b are formed. The insertion holes 14b and 15b are formed so as to become narrower as approaching the front direction indicated by the arrow in the figure, and to become cylindrical holes having a diameter slightly larger than the diameter of the optical fiber 12 from a predetermined position. The adhesive insertion holes 14a and 15a are formed so as to communicate with the insertion holes 14b and 15b. In addition, a pair of lenses 14c and 15c having a substantially semicircular cross section are formed on the upper portion 14 and the lower portion 15, respectively.
[0018]
In such a configuration, as shown in FIG. 4A, first, as a first step, the tip of the optical fiber 12 is inserted into the insertion holes 14b and 15b of the light guide 9, and the tip of the optical fiber 12 is inserted. It is located in the adhesive insertion holes 14a and 15a communicating with the holes 14b and 15b. Next, as a second step, a sufficient amount of the visible light curable adhesive 11 is poured into the adhesive insertion holes 14a and 15a, and as a third step, visible light is irradiated from above. The irradiated visible light reaches the visible light curable adhesive 11 in the adhesive insertion holes 14a and 15a, and cures the visible light curable adhesive 11. Thereby, the optical fiber 12 and the light guide 9 are optically coupled.
By performing the above-described steps, the light guide 9 and the optical fiber 12 are bonded in a short time using visible light.
[0019]
Next, the light transmittances of the components bonded by the above bonding method and the conventional bonding method will be compared. FIGS. 5 and 6 show the measurement values obtained by using the bonding method described above to produce the same device as the device shown in FIG. 7 and using the produced device. 5 and 6, the unit of the numerical value is μW. 5 and 6, the average value of the measured values is 67.27 μW, and the measured values of the device bonded by the bonding method according to the present embodiment using the visible light curable adhesive 11 are shown in FIGS. 8 and 9. The measured value was higher than the conventional measured value (average value 56.33 μW) shown in FIG. That is, it was confirmed that the bonding method of the present example was superior to the conventional method in light transmittance.
[0020]
Note that the above-described feature of excellent light transmittance is caused by the fact that the visible light curable adhesive 11 has low viscosity (30 cps or less) and does not generate voids or cracks.
As described above, since the visible light is used, the light guide can be bonded to the optical fiber with a short curing time while being safe. Further, there is no need to adjust the temperature of the work place, which is economically advantageous.
[0021]
【The invention's effect】
As described above, according to the present invention, a light guide and an optical fiber are optically coupled to each other by using a visible light-curable adhesive, so that a void can be formed in a short curing time. It is possible to manufacture an optical detection system having a high light transmittance and free from cracks.
Further, since the human body is irradiated with harmless visible light, the worker can perform the bonding work without paying special attention. This simplifies the bonding operation.
Further, there is an effect that it is not necessary to adjust the temperature of the work place, and it is not necessary to use a temperature controller or the like.
In addition , by injecting the adhesive into the adhesive insertion hole with the tip of the optical fiber positioned in the adhesive insertion hole, the adhesive is inserted between the tip of the optical fiber and the light guide. Is filled, and the tip of the optical fiber and the light guide are optically fixed with an adhesive.
[Brief description of the drawings]
FIG. 1 is a view for explaining a bonding method of an optical detection system of a keyboard instrument according to an embodiment of the present invention.
FIG. 2 is a view for explaining a method of bonding an optical detection system of a keyboard instrument according to an embodiment of the present invention.
FIG. 3 is a diagram illustrating a method of bonding an optical detection system of a keyboard instrument according to an embodiment of the present invention.
FIG. 4 is a view for explaining a bonding method of an optical detection system of a keyboard instrument according to an embodiment of the present invention.
FIG. 5 is a diagram showing measured values of output power of an optical detection system of an automatic piano using a visible light curable adhesive 11.
FIG. 6 is a diagram showing measured values of output power of an optical detection system of an automatic piano using a visible light curable adhesive 11.
FIG. 7 is a diagram showing a part of a schematic configuration of an optical detection system of the automatic piano.
FIG. 8 is a diagram showing measured values of output power of an optical detection system of an automatic piano using an epoxy-based adhesive.
FIG. 9 is a diagram showing measured values of output power of an optical detection system of an automatic piano using an epoxy-based adhesive.
[Explanation of symbols]
9 ... light guide, 10 ... sensor bracket, 11 ... visible light curable adhesive, 12 ... optical fiber.

Claims (1)

An optical system that emits light incident from an optical fiber in a predetermined direction has a transparent light guide,
The light guide includes a columnar adhesive insertion hole that opens at an upper position, and an insertion hole into which the optical fiber is inserted,
The insertion hole becomes narrower toward the front in the insertion direction of the optical fiber, and is a cylindrical hole having a diameter slightly larger than the diameter of the optical fiber from a predetermined position,
An optical fiber fixing method for fixing the optical fiber to the light guide,
The adhesive insertion hole communicates with the insertion hole,
The tip of the optical fiber is located in the adhesive insertion hole, a visible light curable adhesive is injected into the adhesive insertion hole, irradiates with visible light, and the visible light in the light guide. An optical fiber fixing method, wherein the optical fiber is fixed by reaching the visible light curable adhesive and curing the visible light curable adhesive.

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