JP2009210294A - Fiber sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fiber sensor that monitors the quantity of transmitted light of a fiber for light projection by a simple constitution. <P>SOLUTION: The fiber sensor 1 includes a light projecting element 13, a fiber 21 for light projection which guides the light from the light projecting element and projects it to a detecting object W, a fiber 23 for light reception which receives the light from the detecting object, a photodetector 18 which receives the light from the fiber for light reception, and a detecting means 11 which detects the detecting object, based on the quantity of received light of the photodetector. Moreover, the sensor includes a reflecting means 22 which is disposed at the fore end of the fiber for light projection and reflects part of the guided light to the fiber for light projection, while transmitting the residual light not being reflected, a beam splitter 15 which is disposed between the light projecting element and the fiber for light projection and reflects the light reflected by the reflecting means 22, a photodetector 16 for monitoring which is so disposed that it can receive the light reflected by the beam splitter, and a projected light quantity control means 11 which controls the quantity of projected light from the light projecting element, based on the quantity of received light of the photodetector for monitoring. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fiber sensor, and more particularly to control of the amount of light emitted.

  Conventionally, so-called APC (Auto Power Control) control for controlling the amount of light emitted by using a light receiving element for monitoring has been widely known in order to compensate for the reduction in the amount of light emitted due to deterioration of the light emitting element of the fiber sensor. Yes.

However, in addition to the light projecting element, the amount of light emitted to the object to be detected is changed by changing the transmission characteristics of the fiber according to changes in the ambient temperature or the like. In some cases, it is also necessary to compensate for changes in the amount of light emitted due to the fiber. Therefore, for example, Patent Document 1 shows an example in which a dedicated measurement fiber is provided in order to measure a change in the amount of light emitted due to the fiber. In this case, light through the measurement fiber is received by a monitor light receiving element, and the light projection amount is controlled to a predetermined level.
JP-A-1-283725

However, in the technique of Patent Document 1, since the measurement fiber is provided separately from the light projecting fiber, there is a possibility that a result that accurately reflects the amount of light transmitted through the light projecting fiber may not be obtained. . In addition, there is a problem that the manufacturing cost and the arrangement space increase.
The present invention has been completed based on the above circumstances, and an object thereof is to provide a fiber sensor that can monitor the amount of light transmitted through a light projecting fiber with a simple configuration.

  As means for achieving the above object, the first invention includes a light projecting element, a light projecting fiber for guiding light from the light projecting element and projecting the light toward a detection object, A light-receiving fiber that receives light from the detection object; a light-receiving element that receives light from the light-receiving fiber; and a detection unit that detects the detection object based on the amount of light received by the light-receiving element. In the fiber sensor, the remaining light which is disposed at a tip of the light projecting fiber on the side facing the object to be detected, reflects a part of the guided light toward the light projecting fiber and does not reflect the light. A beam splitter that is disposed between the light projecting element and the light projecting fiber, transmits light from the light projecting element, and reflects the light reflected by the reflecting means; Reflected by the beam splitter A monitor light-receiving element disposed so as to be able to receive the emitted light, and a light-projecting amount control unit that controls a light-projecting amount from the light-projecting element based on a light-receiving amount of the monitor light-receiving element .

  In this configuration, reflecting means for reflecting a part of the light guided into the light projecting fiber is disposed at the tip of the light projecting fiber on the side facing the object to be detected. The light reflected by the reflecting means is further reflected by the beam splitter and received by the monitor light receiving element. That is, according to this configuration, the amount of light (light quantity) transmitted through the light projecting fiber is detected using a part of the light for light detection and the detection light for detecting the object to be detected. Based on the result, the amount of light emitted from the light projecting element can be controlled. Therefore, the transmitted light amount (projected light amount) of the light projecting fiber can be monitored with a simple configuration, and there is no problem that the manufacturing cost and the arrangement space increase for the detection.

According to a second invention, in the fiber sensor of the first invention, the reflecting means is detachably attached to the light projecting fiber.
According to this configuration, when it is not necessary to monitor the amount of light transmitted through the light projecting fiber, it is possible to remove the reflecting means and detect the object to be detected without reducing the amount of light projected.

According to a third invention, in the fiber sensor according to the first or second invention, the light projecting element is configured to project light including a plurality of wavelengths, and the reflecting means is guided. It is characterized by comprising a first filter that reflects light of some wavelengths of light and transmits light of other wavelengths.
According to this structure, a reflection means can be comprised simply and suitably.

  According to a fourth aspect of the present invention, in the fiber sensor according to the third aspect of the present invention, the monitor light-receiving element is attached with a second filter that transmits only a part of the wavelengths reflected by the first filter. Features.

  According to this configuration, even if the object to be detected has a high reflectance and the reflected light is returned to the light projecting fiber through the first filter, it is blocked by the second filter. The reflected light from the object to be detected is not received by the monitor light receiving element. Therefore, the control of the light projection amount based on the light reception amount of the monitor light receiving element by the light projection amount control means is accurately performed.

  According to the fiber sensor of the present invention, the amount of light transmitted through the light projecting fiber can be monitored with a simple configuration.

<Embodiment>
One embodiment of a fiber sensor according to the present invention will be described with reference to FIGS.
1. Configuration of Fiber Sensor As shown in FIG. 1, the fiber sensor 1 of this embodiment is mainly composed of an amplifier unit 10 and a fiber unit 20, and projects light onto a work W (corresponding to the “detected object” of the present invention). The presence / absence and state of the workpiece W are detected based on the amount of received light reflected from the workpiece W.

  The amplifier unit 10 includes a control circuit 11, a light projecting circuit 12, a light projecting element 13, a collimator lens 14 a, a converging lens 14 b, a half mirror (corresponding to the “beam splitter” of the present invention) 15, and a light receiving element for monitoring (MPD). 16, a light receiving element 18, a light receiving circuit 19, and the like. Further, the monitor light receiving element 16 is provided with a filter 17 (corresponding to the “second filter” of the present invention). Here, the filter 17 transmits light Lm having a monitoring wavelength (hereinafter referred to as “designated wavelength”) received by the monitoring light receiving element 16, and is used for other detection (hereinafter referred to as “detection”). And has a characteristic of reflecting light Ld having a wavelength.

  Here, for example, as shown in FIG. 2, the “designated wavelength” is a wavelength between about 635 nm and about 640 nm in the spectral distribution of the light projected from the light projecting element 13. The selection of the “designated wavelength” is not limited to this, and may be appropriately selected according to the spectrum distribution of the light to be used. The filter 17 is detachably attached to the monitor light receiving element 16 and can be removed as necessary, for example, when the reflected light from the workpiece W can be ignored. For example, the filter 17 is detachably attached to the monitor light receiving element 16. For example, the filter 17 is held in a predetermined holder, and the holder holding the filter 17 is attached to the front surface of the monitor light receiving element 16. It may be configured to be removed or removed.

  The fiber unit 20 is disposed at the tip of the light projecting fiber 21 and the light projecting fiber 21 on the side facing the work W, and reflects a part of the light projected from the light projecting element 13 (the present invention). (Corresponding to “reflecting means”, “first filter”) 22, and a light receiving fiber 23. Here, the filter 22 reflects light of a specified wavelength (light of a part of the light guided to the light projecting fiber 21) Lm and reflects light of a detection wavelength (light of other wavelengths) Ld. It is formed to be transparent. Further, the filter 22 is detachably attached to the tip of the light projecting fiber 21, and is removed if necessary, for example, when it is not necessary to monitor the amount of light transmitted through the light projecting fiber 21. Can do. In addition, as a structure which attaches the filter 22 to the front-end | tip part of the light projection fiber 21, it can hold | maintain the filter 22 in the predetermined holder similarly to the case of the filter 17, for example, and the filter 22 was hold | maintained. What is necessary is just to set it as the structure which attaches or removes a holder to the front-end | tip part of the fiber 21 for light projection.

2. Action / Effect of Fiber Sensor In the fiber sensor 1 configured as described above, a drive signal having a predetermined cycle is sent from the control circuit 11 according to an operation command from an operator via an operation means (not shown). The light projecting circuit 12 amplifies the drive signal and supplies the amplified drive signal to the light projecting element 13. The light projecting element 13 projects a predetermined amount of light onto the light projecting fiber 21 via the collimator lens 14a, the half mirror 15 and the converging lens 14b provided in front of the light projecting element 13 in accordance with the drive signal. Then, the light Lm having the designated wavelength out of the light projected into the light projecting fiber 21 is reflected by the filter 22 and returned to the amplifier unit 10 through the light projecting fiber 21. On the other hand, the light Ld having the detection wavelength passes through the filter 22 and is irradiated onto the workpiece W.

  The light Lm having the designated wavelength returned to the amplifier unit 10 is reflected by the half mirror 15 and received by the monitor light receiving element 16 via the filter 17. The monitor light reception signal is supplied to a control circuit (corresponding to the “light emission amount control means” of the present invention) 11, and the control circuit 11 detects a light amount fluctuation in the light projecting fiber 21 based on the monitor light reception signal. To do. This light quantity variation occurs, for example, when the light transmission (transmission) characteristics of the light projecting fiber 21 change due to a change in ambient temperature.

  When a light amount variation is detected, for example, the drive signal to the light projecting circuit 12 is changed in order to perform a predetermined correction on the light projection amount. Note that the correction amount of the light projection amount from the light projecting element 13 corresponding to the light amount variation in the light projecting fiber 21 (actually, the light amount variation of the light Lm having the specified wavelength) is determined in advance by an experiment or the like, for example. It is assumed that it is stored in the memory in the control circuit 11 as a reference table.

  As described above, in the present embodiment, in order to detect the fluctuation of the transmitted light amount in the light projecting fiber 21, it is not necessary to separately provide a detection fiber, and the existing light projecting fiber 21 is used. The detection is performed. For this reason, it is possible to detect the fluctuation of the light projection amount caused by the light projecting fiber 21 and correct the light projection amount in the fiber sensor having almost the same size as the conventional one without increasing the number of parts.

  On the other hand, the detection wavelength light Ld irradiated to the workpiece W through the filter 22 is reflected by the workpiece W, received by the light receiving element 18 through the light receiving fiber 23, and converted into a received light signal. The received light signal is amplified to a predetermined magnitude by the light receiving circuit 19 and supplied to the control circuit 11. When the reflectance of the workpiece W is high, a part of the light Ld having the detection wavelength reflected by the workpiece W is returned again into the light projecting fiber 21 and reflected by the half mirror 15 for monitoring. It goes to the light receiving element 16. However, as described above, the light Ld having the detection wavelength is reflected by the filter 17 and therefore does not enter the monitor light receiving element 16. Therefore, the influence of the detection wavelength light Ld on the detection of the specified wavelength light Lm is suppressed.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.

  (1) In the above embodiment, the configuration in which the light projecting fiber 21 is a single-core fiber is shown. However, the present invention is not limited to this, and the light projecting fiber is, for example, a multi-core fiber 21A as shown in FIG. Also good. At this time, the reflecting means 22 is preferably arranged at the tip of at least one (two in FIG. 3) of the multi-core fibers 21A. Further, the reflecting means at that time may reflect all of the light guided to one light projecting fiber toward the same fiber.

  (2) In the above-described embodiment, the example in which the reflecting means arranged at the tip of the light projecting fiber 21 is configured by the filter 22 has been described, but the present invention is not limited to this. As the reflecting means, for example, a mirror or a splitter formed so as to reflect the light Lm having a specified wavelength and transmit the light Ld having a detection wavelength may be used.

1 is a schematic configuration diagram showing an embodiment of a fiber sensor according to the present invention. Graph explaining the specified wavelength A diagram showing another example of a light projecting fiber

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fiber sensor 11 ... Control circuit (detection means, light emission amount control means)
13 ... Projection element 15 ... Half mirror (beam splitter)
17 ... Filter (second filter)
18 ... light receiving element 21 ... light projecting fiber 22 ... filter (reflecting means, first filter)
23: Fiber for receiving light W: Object to be detected

Claims (4)

A light emitting element;
A light projecting fiber that guides light from the light projecting element and projects the light toward the object to be detected;
A light receiving fiber for receiving light from the detected object;
A light receiving element for receiving light from the light receiving fiber;
In a fiber sensor comprising detection means for detecting the object to be detected based on the amount of light received by the light receiving element,
Reflection that is disposed at the tip of the light projecting fiber on the side facing the object to be detected, reflects a part of the guided light toward the light projecting fiber, and transmits the remaining light that is not reflected. Means,
A beam splitter that is disposed between the light projecting element and the light projecting fiber, transmits light from the light projecting element, and reflects light reflected by the reflecting means;
A light-receiving element for monitoring arranged to receive light reflected by the beam splitter;
A fiber sensor comprising: a light projection amount control unit that controls a light projection amount from the light projecting element based on a light reception amount of the monitor light receiving element.   The fiber sensor according to claim 1, wherein the reflection unit is detachably attached to the light projecting fiber. The light projecting element is configured to project light including a plurality of wavelengths,
The said reflection means is comprised by the 1st filter which reflects the light of the one part wavelength of the said guided light, and permeate | transmits the light of another wavelength, The Claim 1 or 2 characterized by the above-mentioned. The fiber sensor described.   4. The fiber sensor according to claim 3, wherein a second filter that transmits only light of a part of wavelengths reflected by the first filter is attached to the monitor light receiving element. 5.

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