JP2003075689A - Optical fiber sensor and insertion quantity adjusting spacer to be used therein - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adjust the sensitivity of an optical sensor without generating electric noise and without causing mechanical damage. SOLUTION: An optical fiber cable 2 is equipped with a plug 21. A basic spacer 3 and an auxiliary spacer 4 both having thickness in the longitudinal direction are mounted on a guide tube 22 of the plug 21, with the guide tube 22 inserted into a sensor body 1. The insertion depth of the guide tube 22 is reduced by the thickness of the basic spacer 3 and the auxiliary spacer 4 so mounted. As a result, by varying a distance from the optical fiber cable 2 to a light emitting element 13 and to a light receiving element 14, the coupling efficiency is adjusted between them.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber sensor and an insertion amount adjusting spacer used therein.

[0002]

2. Description of the Related Art In an optical fiber sensor, an optical fiber cable corresponding to each of the light projecting portion and the light receiving portion is connected to a sensor main body having a light projecting portion and a light receiving portion, and the tips of these cables can detect an object to be detected. It is configured to be placed at a position. Light emitted from the light projecting portion propagates in the optical fiber on the light projecting side and exits from the tip thereof, and reflected light reflected from the object to be detected propagates in the optical fiber on the light receiver side and enters the light receiving portion. The light incident on the photoelectric conversion element of the light receiving section is converted into an electric signal and amplified by the light receiving amplifier, and the comparison circuit compares this electric signal with a predetermined threshold value to judge the presence or absence of the detected object. ing.

By the way, in this type of sensor, when there is no object to be detected, the reflected light from the background enters the light receiving portion through the light receiving side optical fiber. Therefore, the level of the electric signal after photoelectric conversion also differs depending on the reflectance of the background. Therefore, to accurately detect the presence or absence of the detected object,
It is configured so that the threshold value in the comparison circuit can be adjusted. However, if the reflectance of the background is large and the amount of reflected light is excessive, the light receiving amplifier may be saturated and the light receiving signal may show the maximum value regardless of the presence or absence of the detected object. In this case, no matter how the threshold is adjusted, it is not possible to correctly determine the presence or absence of the detected object, and various sensitivity adjustment methods have been adopted. For example, as shown in JP-A-57-118326, a method is provided in which a light receiving amplifier on the light receiving side is provided with a volume circuit to adjust the gain of the light receiving amplifier to prevent saturation, or as disclosed in Japanese Utility Model Laid-Open No. 2-0136945. In addition, there is a method of pressing the optical fiber with a pressing means attached to the outer circumference of the optical fiber to reduce the light transmission efficiency.

[0004]

However, in the method of adjusting the gain of the light receiving amplifier, a volume circuit is required, and noise is increased due to intrusion from the volume circuit. Further, in the method of compressing the optical fiber, the optical fiber has a small diameter and low mechanical strength, so that the fiber may be damaged.

The present invention was completed in view of the above circumstances, and an optical fiber sensor capable of adjusting the sensitivity without lowering the S / N ratio and without the risk of damage to the optical fiber. It is an object of the present invention to provide an insertion amount regulating spacer used for this.

[0006]

To achieve the above object, the invention of claim 1 provides a sensor main body having a fiber insertion hole connected to an internal light projecting portion and a light receiving portion, and the fiber of the sensor main body. An optical fiber cable having a plug portion to be inserted into the insertion hole, the plug portion having a large diameter portion for regulating the insertion depth into the fiber insertion hole, and a portion of the plug portion that is larger than the large diameter portion. It is characterized in that it is provided with an insertion amount adjusting spacer detachably attached to the distal end side.

According to a second aspect of the present invention, there is provided a sensor main body having a fiber insertion hole connected to the internal light projecting portion and the light receiving portion, an optical fiber cable inserted into the fiber insertion hole of the sensor main body, and the optical fiber cable. Locking means that is locked to the tip side of the optical fiber cable, and an insertion amount adjusting spacer that is sandwiched between the tip side of the optical fiber cable of the locking means and the sensor body to regulate the insertion depth of the optical fiber cable. Optical fiber sensor.

The invention of claim 3 is characterized in that, in the invention of claim 1 or 2, a plurality of types of the insertion amount adjusting spacers having different thicknesses are provided.

According to a fourth aspect of the present invention, there is provided a sensor main body having a fiber insertion hole connected to the internal light projecting portion and the light receiving portion, and a plug portion inserted into the fiber insertion hole of the sensor main body. Which is used for an optical fiber sensor including an optical fiber cable provided with a large diameter portion for restricting a depth of insertion into the fiber insertion hole, wherein the plug portion is closer to the tip side than the large diameter portion. It is characterized in that it is attached to the optical fiber to reduce the amount of insertion of the plug portion into the fiber insertion hole.

[0010]

According to the invention of claims 1 and 4, when the plug portion of the optical fiber cable is inserted into the fiber insertion hole of the sensor body, the insertion depth of the plug portion is restricted in the large diameter portion. It When the light receiving amplifier is saturated at this insertion depth, the insertion amount adjusting spacer is attached to the tip side of the large diameter portion of the plug portion, and the plug portion is inserted into the fiber insertion hole again. By doing so, the insertion depth of the plug portion is further restricted by the thickness of the insertion amount adjusting spacer, so that the coupling efficiency between the light emitting portion and the light receiving portion and the optical fiber cable is reduced, and the amount of light incident on the light receiving portion is reduced. It can be suppressed. Therefore, it is possible to prevent the saturation of the light receiving amplifier without lowering the S / N ratio and without damaging the optical fiber cable.

According to the second aspect of the invention, when the locking tool is locked to the optical fiber cable, the insertion amount adjusting spacer attached to the optical fiber cable is moved in the optical fiber pulling direction by the locking means. Is regulated. As a result, the insertion amount adjusting spacer is stopped on the tip side of the optical fiber cable. When the optical fiber cable is inserted into the sensor body in this state, the insertion depth of the insertion amount adjusting spacer is regulated by the thickness, so that the coupling efficiency between the light emitting unit and the light receiving unit and the optical fiber cable is reduced, and The amount of light incident on the part is suppressed. Therefore, it is possible to prevent the saturation of the light receiving amplifier without lowering the S / N ratio and without damaging the optical fiber cable.

According to the third aspect of the present invention, since a plurality of insertion amount adjusting spacers having different thicknesses are provided, the insertion depth of the plug portion into the insertion hole can be variously changed, so that there are multiple steps. The insertion depth can be adjusted.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION <First Embodiment> Hereinafter, claim 1
An embodiment according to the invention will be described with reference to the drawings. First, as shown in FIG. 1, in the reflection type optical fiber sensor of this embodiment, two optical fiber cables 2 are connected to the sensor body 1 and the tip of the optical fiber cable 2 is a place where the object A to be detected can be detected. It is configured to be installed in.

The sensor main body 1 has a substantially box-like shape, and one surface thereof has a circular fiber insertion hole 11 for inserting the optical fiber cable 2 connected to the inside of the sensor main body 1.
12 are provided in two places separated vertically. A light projecting element 13 is provided behind the fiber insertion hole 11, and a light receiving element 14 is provided behind the insertion hole 12. A lock lever 15 for fixing the optical fiber cable 2 inserted in the fiber insertion holes 11 and 12 is arranged at the front of the sensor body 1. The optical fiber cable 2 is movable when the lock lever 15 is tilted, and is fixed by a clamp mechanism (not shown) when the lock lever 15 is tilted up. The light incident on the light receiving element 14 is converted into an electric signal, amplified by a light receiving amplifier, and compared with a predetermined threshold value by a comparison circuit to perform a detection operation.

The core wire of the optical fiber cable 2 is a silica glass fiber, and the outer circumference thereof is covered with a resin jacket so as to protect the core wire. Two optical fiber cables 2 on the insertion side into the fiber insertion holes 11 and 12.
Is provided with a plug portion 21 for integrally mounting. Two guide tube portions 22, 22 are arranged in parallel in the plug portion 21, and the optical fiber cable 2 is fixed there through. The guide cylindrical portion 22 has a tapered large-diameter portion 22 at the base thereof.
A and 22A are formed, and the optical fiber cable 2 projects from the tip through the guide tube portions 22 and 22.

A basic spacer 3 and an auxiliary spacer 4 as insertion amount adjusting spacers can be attached to the plug portion 21. The basic spacer 3 has a plate shape with a predetermined thickness, and has two through holes 31, 31 for allowing the guide cylinder portions 22, 22 of the plug portion 21 to pass therethrough. A taper portion is formed on one end side of the through holes 31, 31 so as to match the large diameter portions 22A, 22A of the guide cylinder portions 22, 22.

The auxiliary spacer 4 is made of metal and has a plate shape thinner than that of the basic spacer 3, and has a substantially S shape with two notches 41 opened at side edges opposite to each other. . The guide tube portions 22, 22 of the plug portion 21 can be inserted into the notch portions 41, 41 of the auxiliary spacer 4.

Next, the sensitivity adjustment of the optical fiber sensor according to this embodiment having the above-mentioned structure will be described with reference to FIGS. 2 to 4. First, the tip of the optical fiber cable 2 is installed at a predetermined position to detect the object A to be detected. The lock lever 15 of the sensor body 1 is tilted to insert the guide cylinder portions 22 and 22 into the fiber insertion holes 11 and 12 until the tapered portions of the large diameter portions 22A and 22A come into contact with the sensor body 1 (see FIG. 2). Then, the tip of the optical fiber cable 2 and the light projecting element 13 and the light receiving element 14 are brought into a butted state. Then, the lock lever 15 is raised and the guide tube portion 2
Fix 2, 22.

When the sensor body 1 is operated in this state,
The light emitted from the light projecting element 13 is the optical fiber cable 2
Is emitted from the tip of the light beam toward the detection area through which the object A to be detected passes. The reflected light from the detection area propagates through the optical fiber cable 2 and is incident on the light receiving element 14, where it is photoelectrically converted and amplified by the light receiving amplifier. Based on the output signal level from the light receiving amplifier, the object A to be detected is detected. Presence / absence is determined. Here, when the detected object A does not exist in the detection area, the amount of incident light on the light receiving element 14 is small, but when the detected object A enters the detection area, the amount of incident light on the light receiving element 14 increases. . However, when the reflectance of the background of the detected object A (for example, the conveyor belt B in FIG. 1) in the detection area is large, the amount of light incident on the light receiving element 14 is large and a saturation phenomenon occurs in the light receiving amplifier. There is. Then,
Since the presence or absence of the detected object A cannot be correctly determined, in such a case, the sensitivity of the sensor body 1 is adjusted as follows.

First, the lock lever 15 is tilted to release the restraint of the guide tube portion 22 of the plug portion 21. Then, the guide tube portion 22 is connected to the fiber insertion holes 11 and 12 of the sensor body 1.
And then attach the basic spacer 3 here, again
The guide tube portion 22 is inserted into the fiber insertion ports 11 and 12 (see FIG. 3). Then, since the insertion depth becomes shallower by the thickness of the basic spacer 3, the coupling efficiency between the optical fiber cable 2 and the light projecting element 13 and the light receiving element 14 decreases,
The amount of light emitted from the optical fiber cable 2 on the light projecting side decreases, and the amount of light incident on the light receiving element 14 from the optical fiber cable 2 on the light receiving side decreases. Therefore, even if the reflectance of the background is large, the amount of light incident on the light receiving element 14 is smaller than that in the case where the basic spacer 3 is not provided, so that saturation in the light receiving amplifier can be eliminated. In addition, if the saturation phenomenon is not eliminated even if the basic spacer 3 is attached as described above, in addition to the basic spacer 3, the auxiliary spacer 4 is added.
Can be attached (see Fig. 4). In this case, the insertion depth is further reduced by the thickness of the auxiliary spacer 4, the coupling efficiency is further reduced, and the sensitivity can be lowered, so that the saturation phenomenon in the light receiving amplifier can be reliably avoided.

As described above, according to the optical fiber sensor of this embodiment, the insertion depth into the fiber insertion holes 11 and 12 is restricted by the plug portion 21 and the basic spacer 3 and the auxiliary spacer 4 attached to the sensor body 1. It As a result, the coupling efficiency between the optical fiber cable 2 and the light projecting element 13 and the light receiving element 14 is prevented from being lowered and the light receiving level is not saturated. This makes it possible to accurately determine the presence or absence of the detected object A. Further, since the basic spacer 3 and the auxiliary spacer 4 having different thicknesses can be attached, the adjustment range of sensitivity adjustment is widened.

Furthermore, since the light receiving level is changed based on an optical method of changing the coupling efficiency between the optical fiber cable 2 and the light projecting element 13 and the light receiving element 14, a volume circuit is provided to electrically adjust the sensitivity. The S / N ratio is improved as compared with the case where adjustment is performed. Further, since no mechanical pressure is applied to the optical fiber cable 2, there is no possibility of damaging the optical fiber cable 2.

<Second Embodiment> An embodiment of the invention according to claim 1 will be described with reference to FIG. The same parts as those in the first embodiment are designated by the same reference numerals, and duplicate description will be omitted. The optical fiber sensor of the present embodiment is configured as a separate body so that the optical fiber cable 2 can be independently inserted into and removed from the fiber insertion holes 11 and 12. The fiber insertion hole 11 of each optical fiber cable 2,
Plug parts 51, 51 are attached to the 12 insertion side. The plug portions 51, 51 have a cylindrical shape, and the shape is the first.
Large diameter portions 52, 52 having a tapered shape are formed similarly to the guide cylinder portion 21 in the embodiment.

An integrated attachment 6 is attached to each of the plug parts 51 and 52 to integrate them. The integrated attachment 6 is substantially S-shaped, and can be expanded by elastically deforming the end portion. Hollow portion 62 of the integrated attachment 6,
When the plug portions 51, 51 are passed through 62, the tapered portions of the plug portions 51, 51 come into contact with the integrated attachment 6 in due course. Further, when the large diameter portions 51, 51 are pushed into the hollow portions 62, 62, the integrated attachment 6 comes into close contact with the large diameter portions 51, 51 and the optical fiber cable 2 is integrated. In this state, the sensitivity is adjusted by the same procedure as in the first embodiment.

That is, in the present embodiment, even if the optical fiber cables 2 are provided independently, they are integrated by the integrated attachment 6, so that the insertion depths of the two optical fiber cables 2 into the fiber insertion holes are simultaneously determined. It can be changed, and sensitivity can be adjusted more easily than the case where the insertion depth is changed individually.

<Third Embodiment> An embodiment according to the invention of claim 2 will be described with reference to FIGS. 6 to 11. The same parts as those in the first embodiment are designated by the same reference numerals, and duplicate description will be omitted. In the optical fiber sensor of this embodiment shown in FIG. 6, the optical fiber cable 2 is directly inserted into the fiber insertion holes 81 and 82 of the sensor body 8. The sensor body 8 has the same configuration except that the diameters of the fiber insertion holes 81 and 82 are different from the diameters of the fiber insertion holes 11 and 12 of the first embodiment. The diameters of the fiber insertion holes 81 and 82 are the same as the diameter of the optical fiber cable 2.

The optical fiber cable 2 is provided with a locking tool 7 corresponding to a locking means for enabling the insertion amount adjusting spacer 40 to be mounted on the optical fiber cable 2. The insertion amount adjusting spacer 40 has the same shape as the auxiliary spacer 4 of the first embodiment. Locking tool 7
Is provided with a main body 71 made of a synthetic resin material, and a pair of insertion holes 72 through which the optical fiber cable 2 can be inserted are provided in the main body 71 in parallel with each other in the front-rear direction. The surface provided with the opening surface of the hole 72 is a flat surface. A sliding hole 73 that penetrates in the up-down direction and has a substantially rectangular cross section is provided in the center of the main body 71 in the front-rear and left-right directions. A part of the sliding hole 73 communicates with the left and right insertion holes 72. In addition, in the center of the main body 71 in the left-right direction,
A bearing hole 74 is formed penetrating the front and rear of the main body 71 with the sliding hole 73 interposed therebetween, and a mounting shaft 75 for mounting a fixing member 710 described later is attached to the bearing hole 74. On the upper surface of the main body 71, a groove-shaped recess 26 is provided along the left-right direction.

The fixing member 710 is made of a synthetic resin material like the main body 71, and is provided with a pressing operation part 711 in the form of an elongated plate in the left-right direction, and an insertion part 712 is formed downward from the center of the pressing operation part 31. It is growing. This insertion part 7
The lower part of 12 has an outer diameter which is slightly smaller than the sliding hole 73, and the fixing member 710 can slide up and down with the insertion portion 712 inserted in the sliding hole 73. A mounting hole 7 through which the mounting shaft 75 is inserted is inserted into the insertion portion 712.
13 is provided along the front-back direction. This mounting hole 7
13 has a vertically elongated cross section as viewed from the front, and the fixing member 710 is vertically displaced within a range in which the mounting shaft 75 can move in the mounting hole 713, that is, between a fixed position and an open position shown below. It can be operated.

8 and 9 show a state in which the fixing member 710 is in the fixed position. The upper portion of the insertion portion 712 is slightly tapered in the left-right direction, and a jutting portion 714 is formed on the left and right side surfaces of the insertion portion 712 near the boundary between the lower portion of the insertion portion 712 and the tapered portion. In the fixed position, the projecting portion 714 projects into the insertion hole 72, and the optical fiber cable 2 inserted therein can be fixed by being sandwiched between the optical fiber cable 2 and the inner wall surface on the opposite side of the insertion hole 72. . Further, at the fixed position, the pressing operation portion 711 is in a state of protruding above the concave portion 76, and the pressing operation downward (that is, the open position side) can be performed.

FIGS. 10 and 11 show a state in which the fixing member 710 is in the open position. At this time, the pressing operation portion 711 is housed in the recess 76 and the overhang portion 714.
Is retracted downward from the insertion hole 72, and the insertion / removal of the optical fiber cable 2 into / from the insertion hole 72 is allowed. An elastic member 715 formed by bending a metal plate material is attached to the lower side of the pressing operation unit 711. A pair of leg portions 716 are extended from the elastic member 715 to the left and right, and the tips of these leg portions 716 elastically abut the bottom surface of the recessed portion 76, so that the fixing member 710 is always above the fixed position side. Urged to.

The locking tool 7 of this embodiment has the above-mentioned structure, and its operation will be described below. To attach the optical fiber cable 2 to the locking tool 7, first, the pressing operation portion 711 is pressed downward while resisting the urging force of the elastic member 715 to displace the fixing member 710 from the fixed position to the open position (see FIG. 1
0 and FIG. 11). As a result, the overhang portion 714 retracts below the insertion hole 72 and the insertion hole 72 is opened.
Subsequently, while holding down the pressing operation portion 711, each insertion hole 72
The end portion of the optical fiber cable 2 is inserted into the optical fiber cable 2 and is appropriately inserted, and then the hand is released from the pressing operation portion 711. Then, the elastic restoring force of the elastic member 715 causes the fixing member 71 to move.
0 is displaced to the fixed position side, and the protruding portion 7 is inserted into the insertion hole 72.
14 projects, and the optical fiber cable 2 is sandwiched between the optical fiber cable 2 and the wall surface on the opposite side of the insertion hole 72 (see FIGS. 8 and 9). As a result, the optical fiber cable 2 is fixed in a state in which it cannot be inserted or removed. In this fixed state, when the optical fiber cable 2 is inserted into the cutout portion 41 of the insertion amount adjusting spacer 40, the optical fiber cable 2 does not come into contact with the locking tool 7 and fall out. Thereby, the insertion amount adjusting spacer 40 can be attached to the optical fiber cable 2.

Next, the tips of the pair of optical fiber cables 2 extended from the locking tool 7 are cut at the same time with a fiber cutter or the like to make the extension lengths uniform. Then, while holding the locking tool 7, the tip of the optical fiber cable 2 is connected to the fiber insertion hole 11,
Plug in 12. Hereinafter, the sensitivity is adjusted using the insertion amount adjusting spacer 40 in the same manner as in the first embodiment.

As described above, according to the present embodiment, when the locking member 7 is mounted on the optical fiber cable 2, the fixing member 710 is operated to the open position and then the optical fiber cable 2 is inserted into each insertion hole. When it is inserted into 72 and the hand is released from the fixing member 710, the fixing member 710 is displaced to the fixed position by the bias of the elastic member 715, and the optical fiber cable 2 is fixed. As a result, the tip of the optical fiber cable and the fastener 7
Insertion amount adjustment spacer 40 can be installed between
The insertion depth of the optical fiber cable 2 can be adjusted.

<Other Embodiments> The present invention is not limited to the embodiments described above and illustrated in the drawings. For example, the following embodiments are also included in the technical scope of the present invention. In addition to the above, various modifications can be made without departing from the scope of the invention. (1) In the above embodiment, the basic spacer 3 and the auxiliary spacer 4 are attached between the large-diameter portion 22A and the sensor body 1 to change the distance between the optical fiber cable 2 and the light emitting element 13 and the light receiving element 13. However, it is sufficient if these distances can be arbitrarily changed. For example, the guide tube portion 22
It is also possible to add a dial mechanism capable of arbitrarily adjusting the insertion depth after fixing with the lock lever 15.

(2) In the above embodiment, the two plug portions 5
Although the depth of insertion into the sensor body 1 is adjusted by integrating 1 and 51, the present invention is not limited to the above embodiment. For example, the adjustment is performed by using the individual basic spacers 3 and the auxiliary spacers 4 so that the insertion depths can be adjusted independently, or the optical fiber cable on either the light emitting element 13 side or the light receiving element 14 side. Even if the insertion depth of 2 is adjusted, the same effect can be obtained.

(3) In the above embodiment, the light emitting element 13 side and the light receiving element 14 side optical fiber cables 2 are provided independently, but even if the optical fiber sensor uses a round two-core cable, The invention can be applied.

[Brief description of drawings]

FIG. 1 is a perspective view of an optical fiber sensor according to a first embodiment of the present invention.

FIG. 2 is a side view showing a state where the plug is attached to the sensor body.

FIG. 3 is a side view showing a state where the plug with the basic block is attached to the sensor body.

FIG. 4 is a side view of the connection in which the plug having the basic block and the insertion amount adjusting spacer is attached to the sensor body.

FIG. 5 is a perspective view of an optical fiber sensor according to a second embodiment of the present invention.

FIG. 6 is a perspective view of an optical fiber sensor according to a third embodiment of the present invention.

FIG. 7 is a front view of the locking device.

FIG. 8 is a front cross-sectional view of the locking tool when the fixing member is in the fixed position.

FIG. 9 is a plan sectional view of the locking tool when the fixing member is in the holding position.

FIG. 10 is a front cross-sectional view of the locking tool when the fixing member is in the release position.

FIG. 11 is a plan cross-sectional view of the locking tool when the fixing member is in the release position.

[Explanation of symbols]

1 ... Sensor body 2 ... Optical fiber cable 3 ... Basic spacer 4 ... Auxiliary spacer 11, 12 ... Fiber insertion hole 13 ... Projecting element 14 ... Light receiving element 21 ... Plug 22 ... Guide tube

Claims (4)

[Claims] 1. A sensor main body having a fiber insertion hole connected to an internal light emitting portion and a light receiving portion, and a plug portion to be inserted into the fiber insertion hole of the sensor main body, the fiber insertion hole being provided in the plug portion. An optical fiber cable including a large-diameter portion that restricts the insertion depth into the optical fiber, and an insertion amount adjustment spacer that is detachably attached to the plug portion on the tip side of the large-diameter portion. Fiber sensor. 2. A sensor main body having a fiber insertion hole connected to an internal light emitting section and a light receiving section, and an optical fiber cable inserted into the fiber insertion hole of the sensor main body.
Locking means locked to the tip side of the optical fiber cable, and an insertion amount that is sandwiched between the optical fiber cable tip side of the locking means and the sensor body to regulate the insertion depth of the optical fiber cable. An optical fiber sensor comprising an adjusting spacer. 3. The optical fiber sensor according to claim 1, wherein the insertion amount adjusting spacer is provided with a plurality of types having different thicknesses. 4. A sensor main body having a fiber insertion hole connected to an internal light emitting portion and a light receiving portion, and a plug portion to be inserted into the fiber insertion hole of the sensor main body, the plug portion having the fiber insertion hole. What is used for an optical fiber sensor comprising an optical fiber cable provided with a large-diameter portion that regulates the insertion depth into the plug portion, the plug portion being mounted on the tip side of the large-diameter portion, An insertion amount adjusting spacer for an optical fiber sensor for making the insertion amount of the plug portion into the fiber insertion hole shallow.