JPS62116214A - Optical fiber sensor - Google Patents

Abstract

PURPOSE:To realize the reduction of the number of parts and the simplification of a manufacturing work process, by constituting a sensor of a single light emitter-receiver and one optical fiber other than a transducer. CONSTITUTION:A control apparatus 6 applies a timing pulse with a predetermined cycle Ta to a drive circuit 5 to allow a light emitter-receiver 4 to perform light emitting operation. Next, the exciting light from the light emitter- receiver 4 passes through an optical fiber 3 to irradiate a phosphor 2. The fluorecences LA, LS emitted from the phosphor 2 excited by said exciting light go back through the optical fiber 3 but, because the light emitting diode constituting the light emitter-receiver 4 is reversely biased corresponding to a time width Tb, only afterglow during this time is received. Next, this afterglow signal is amplified by a detection circuit 7 and subsequently integrated over the time width Tb to calculated the integral quantity of afterglow. This integral quantity of afterglow is compared with the temp. characteristic of the integral value of the quantity of afterglow preset by an operation circuit 8 to calculate the temp. of an atmosphere in which the phosphor 2 was placed and the calculated result is displayed on a display device 9.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an optical fiber sensor used to detect physical quantities of the surrounding environment, such as temperature.

<Summary of the Invention> This invention comprises an optical fiber sensor consisting of a single light emitter/receiver and a single optical fiber in addition to a transducer, which reduces the number of parts and simplifies the work process. We have realized the following.

<Background of the Invention> For example, when a phosphor that emits phosphorescence or a phosphor that emits fluorescence (hereinafter collectively referred to as a "phosphor") is exposed to excitation light, the phosphor emits phosphorescence due to the excitation. It emits a certain amount of light, and the intensity of this phosphorous light changes depending on the temperature of the surrounding environment in which it is placed. Therefore, it is possible to measure the ambient temperature by using the change in phosphorous light intensity due to temperature, and the -
As an example, a temperature measuring device having a configuration as shown in FIG. 6 has been proposed.

In the figure, a phosphorescent body 11 is placed in an atmosphere where the temperature is to be measured, and a light emitter 12 is connected to an optical fiber 13 and a branch pipe 1 is connected.
4. The excitation light is irradiated to the phosphorescent light body 11 through the optical fiber 15, and the phosphorous light emitted from the phosphorescent light body 11 due to the excitation is transmitted to the optical fiber 15, the branch pipe 14, and the optical fiber 16.
The temperature in the atmosphere is detected by comparing the phosphor fluorescence intensity detected by the light receiver 17 with the temperature characteristic of the phosphor fluorescence intensity determined in advance. It is something. However, according to such a configuration, in addition to the phosphorescent light body 11, there are also a light emitter 12 and a light receiver 17.3.
Each component such as the optical fibers 13, 15, 16 and the branch pipe 14 is required, which not only significantly increases the number of parts, but also causes the problem that optical coupling loss occurs due to the use of the branch pipe 14. . Also, each optical fiber 13
．． 16, it is necessary to align the optical axes of the light emitter 12 and the light receiver 17, which complicates the adjustment work and manufacturing process, which causes an increase in product cost.

<Purpose of the Invention> This invention is intended to solve the problem described in -J-, and its purpose is to provide a new optical fiber sensor that reduces the number of parts and simplifies the manufacturing process. do.

<Structure and Effects of the Invention> In order to achieve the above object, the optical fiber sensor of the present invention includes a transducer made of a member having an afterglow characteristic that changes according to physical changes such as temperature, and this transducer. A single light emitter/receiver is provided to illuminate the user with excitation light and detect the afterglow of the light emitted by the transducer due to excitation, and a light transmitter/receiver is provided between the transducer and the light emitter/receiver for reciprocal propagation of light. It is equipped with a single optical fiber for this purpose.

According to this invention, an optical fiber sensor can be configured with a single light emitter/receiver and one optical fiber in addition to a transducer, so the number of parts can be significantly reduced compared to the conventional example. Moreover, since the branch pipe is not used, the occurrence of optical coupling loss can be prevented. In addition, because the optical axis alignment for the optical fiber only needs to be done once, the adjustment work and manufacturing process are simplified compared to the conventional method, which required alignment of the optical axis for both the emitter and the receiver. This invention has a remarkable effect of achieving the purpose of the invention, such as being able to prevent the cost increase.

<Description of Embodiments> FIG. 1 shows a configuration example of a temperature measuring device using an optical fiber sensor 1 according to an embodiment of the present invention.

The illustrated optical fiber sensor 1 includes a phosphor 2 placed in an atmosphere or on the surface of an object (indicated by a broken line in the figure) whose temperature is to be measured, and a single wire with the phosphor 2 attached to the tip and fixed. It is composed of an optical fiber 3 and a light emitter/receiver 4 arranged with its light emitter/receiver surface facing the proximal end surface of the optical fiber 3. Light is propagated back and forth between the two.

The phosphor 2 can be of any kind as long as its afterglow characteristic is temperature dependent, but preferably the afterglow time is 10-b to 1 ( 1
-Use a phosphor of about 3 seconds. For example, for ultraviolet light excitation, rare earth metal oxysulfides such as Y202S:Eu, sulfide phosphors such as ZnS:Ln (Ln is the kB name of rare earth element), and SrS:Ln are used, and for infrared light excitation, LnF3: (Yb, Er), L
nOF: (Yb, Er), LiNd P40
+z: Yb or the like is used.

Next, the light emitter/receiver 4 is used to irradiate the phosphor 2 with excitation light and to detect the afterglow of the light emitted by the phosphor 2 due to the excitation.
A light emitting diode for excitation such as s:St is also used as a photodiode. That is, in the case of this embodiment, when a semiconductor element such as a light emitting diode is reverse biased, it functions as a photodiode having a light receiving sensitivity spectrum n in the short wavelength region of the light emission spectrum l of the light emitting diode, as shown in FIG. This light-emitting diode is pulse-driven by a drive circuit 5 to output excitation light, and while the phosphor 2 emits afterglow, the light-emitting diode functions as a photodiode. , the received light signals are obtained in time series.

Note that FIG. 2 shows the emission spectrum l of a GaAs:Si light emitting diode, the light receiving sensitivity spectrum n when this light emitting diode is used as a photodiode, and the rare earth fluoride (YF3: YbXEr) as the phosphor 2.
), and this light emitting diode, as a photodiode, has the characteristic of being able to receive light in the shaded area in the figure.

FIG. 3 illustrates the characteristics of another light emitting/receiving element having wider light receiving characteristics. In the figure, l is the emission spectrum of this light emitting/receiving element, n is its light receiving sensitivity spectrum, and m is the emission spectrum of the phosphor. has.

Next, FIG. 4 shows a timing chart of the optical fiber cable shown in FIG.
FIG. 4(2) shows the waveform of the pulsed excitation light output by the light emitter/receiver 4, and the phosphor 2 excited by this excitation light.
Furthermore, FIG. 4(3) shows the waveform of the afterglow received by the light emitter/receiver 4. In FIG. 4(2), the light emitted during excitation is fluorescent light LA, and the light emitted after the point at which excitation stops and which attenuates over time is afterglow l1. It is. Also, in the figure, the broken line is the waveform that reaches temperature 'F1, and the solid line is the waveform at temperature 'I''2 (however, T+<'r'g)
However, in general, the lower the temperature, the higher the afterglow brightness tends to be.

Returning to FIG. 1, ζ, the control device 6 controls the predetermined period T a (
4th r, 1H1l A timing pulse of It<0 is given to the drive circuit 5 to cause the light emitter/receiver 4 to emit light. The period Ta is set to a time sufficient for the afterglow emitted from the phosphor 2 to completely disappear at all temperatures within the measurement range. When the drive circuit 5 drives the light emitter/receiver 4 using this timing pulse, excitation light is output from the light emitter/receiver 4 and is irradiated onto the phosphor 2 through the optical fiber 3 . The fluorescent light L1 and the afterglow Lll emitted from the fluorescent body 2 due to this excitation travel backward through the optical fiber, but the light emitting diode constituting the light emitter/receiver 2 has a time width Tb (see FIG. 4 (3)). Since the light is reversely biased depending on the pair, only the afterglow during this period is received.

The afterglow signal received by the light emitter/receiver 4 is input to the detection circuit 7 and amplified, and then integrated over the time width Tb to obtain the integrated afterglow light amount. In addition to a circuit configuration that directly integrates the afterglow signal in an analog manner, this integration means also has a circuit configuration that samples the afterglow signal at appropriate time intervals and stores the obtained data in a memory. A circuit configuration that adds data may also be used.

The integrated amount of afterglow obtained by the detection circuit 7 is input to the arithmetic circuit 8, where it is compared with the temperature characteristic of the integrated value of the afterglow set in advance according to the phosphor 2, and the amount of afterglow is determined. The temperature of the atmosphere in which the body 2 is placed is calculated, and the calculation result is displayed on the display 9.

FIG. 5 shows the temperature characteristics of the integral value of the amount of afterglow light.

The integral values of the fluorescent material used are preliminarily measured at various temperatures T, and the characteristics shown in FIG. 5 are set in advance as known relationships. This characteristic data is stored in the memory as a temperature function table 10, and the measured afterglow integrated light amount is compared with reference to this table to determine the temperature.

The control device 6 in FIG. 1 is composed of a computer circuit, and executes various calculations and processes, as well as sequentially controls the operations of each of the above-mentioned constituent circuits.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a temperature measuring device using the optical fiber sensor of the present invention, FIGS. 2 and 3 are diagrams showing the characteristics of the light emitter/receiver and the fluorescent body, and FIG. FIG. 5 is a diagram showing the temperature characteristics of the integrated amount of afterglow light, and FIG. 6 is a diagram showing the configuration of a conventional example. 1... Optical fiber sensor 2... Fluorescent body 3... Optical fiber 4... Emitter/receiver patent Applicant: Tateishi Electric Co., Ltd./Kufu 1 Inogu L7 1F, ( into the hole)

Claims (3)

[Claims] (1) A sensor for detecting a physical quantity in the surrounding environment, comprising a transducer made of a member having an afterglow characteristic that changes according to the physical quantity, and an excitation light applied to the transducer, which causes the transducer to emit light due to the excitation. An optical fiber sensor comprising: a light emitter/receiver for detecting afterglow of light; and a single optical fiber for reciprocating light propagation provided between the transducer and the light emitter/receiver. (2) The optical fiber sensor according to claim 1, wherein the transducer is a phosphor having an afterglow characteristic that changes depending on temperature. (3) The optical fiber sensor according to claim 1, wherein the light projector/receiver is a light emitting diode that functions as a photodiode that has light receiving sensitivity in a predetermined wavelength region by reverse bias.