JPH05107123A - Device and method for measuring temperature - Google Patents

Abstract

PURPOSE:To provide a temperature measuring device and method for stably measuring temperatures with high accuracy under various conditions. CONSTITUTION:Of the three fibers A, B, and C, the fiber A is an optical fiber for emitting light and the fibers B and C are optical fibers for incident light. A temperature sensor 5 composed of a temperature sensitive element 6 the transmissive wavelength of which changes depending upon temperatures, glass 7, and reflecting film 8 is attached to the end faces of the fibers. The fibers B and C are respectively arranged in the areas of the element 6 and glass 7. Then a photoreceptor element composed of a photodiode is fitted to the other end faces of the fibers B and C and a comparator circuit which compares the light quantity received by the photoreceptor element is provided. In addition, an interference filter which only passes light having wavelengths within a narrow band width is provided between the photoreceptor element and fibers B and C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature measuring device and a measuring method for measuring a temperature by using a temperature sensitive element which changes a transmission wavelength of light transmitted by a temperature change.

[0002]

2. Description of the Related Art A conventional temperature measuring apparatus and measuring method of this type will be described with reference to the drawings. FIG. 7 is an external view of a conventional temperature measuring device, and FIG. 8 is a conceptual diagram of a measuring method by the device. In these drawings, A and B represent two optical fibers, and the fiber A is for emitting light emitted from an LED (light emitting diode) to a temperature sensor 15 including a temperature sensitive element 16 and a reflective film 18. Light that is a fiber and is guided to the temperature sensor 15 is reflected by the reflection film 18, guided into the optical fiber B for incidence, and received by the photodiode PD. In such a structure, as shown in FIG. 9, the temperature sensor 15 including the temperature sensitive element 16 changes in temperature at T ₁ , T ₂ , and T ₃ while the light absorption edge wavelength changes. Normally, the light absorption edge wavelength moves to the longer wavelength side as the temperature rises. Therefore, if this light absorption edge wavelength is selected so as to be included in the spectrum of the light emitted from the LED, the transmitted light intensity from the temperature sensor 15 decreases as the temperature rises. Therefore, the change in the intensity of the transmitted light from the temperature sensor 15 is detected by the photodiode PD.
The temperature can be calculated by detecting with.

FIG. 10 shows a second example of a conventional measuring method for measuring temperature using a temperature sensitive element. In this example, the light emitted from the _two light emitting diodes LED ₁ and LED _{2 having} different frequencies is transmitted from the fibers A ₁ and A ₂ to the optical coupler 20.
Are led together to the temperature sensor 15 and transmitted through the temperature sensor 15, then guided into the fiber B as incident light and wavelength-split by the spectroscope 21 to be received by the _two photodiodes PD ₁ and PD ₂ . .. Photodiode P
D ₁ and the intensity of the transmitted light received by the photodiode PD ₂ are compared and the temperature is measured from this comparison value.

[0004]

However, in the above-mentioned first example, the coupling efficiency between the fiber A, the temperature sensor 15, and the fiber B changes, and therefore the amount of light incident on the photodiode PD changes. In that case, there is a drawback that the change cannot be distinguished from the change in the incident light amount due to the temperature change of the temperature sensor. Further, the light emitting element such as the LED of the light source has a drawback that the emission wavelength changes due to the temperature change, and the transmittance of the temperature sensor 15 also changes due to the change. In addition, in the second example, two LEDs with two different wavelength inputs are used to obtain the ratio of transmitted light, so that even if the coupling efficiency changes, the relative emission between the two wavelengths is performed. Since the ratio of the light amounts does not change, this partially compensates for the disadvantage of the first example in which the temperature can be measured without affecting the ratio of the incident light amounts, but depending on the stability of the two LEDs, two LEs can be used.
Since the relative amount of emitted light between D varies, the ratio of the amount of incident light also varies accordingly, which causes a drawback that the temperature measurement becomes uncertain. The present invention has been made in view of the above-mentioned conventional drawbacks, and an object thereof is to provide a temperature measuring device and a measuring method capable of performing stable temperature measurement even under various conditions and capable of highly accurate temperature measurement. To provide.

[0005]

In order to achieve this object, a temperature measuring apparatus according to the present invention comprises an emitting optical fiber having a light emitting means disposed on one end surface, and the other end surface of the emitting optical fiber. A temperature sensor consisting of a temperature sensitive element that changes the transmission wavelength of light due to a change in temperature due to a temperature change, a member that transmits light, and a reflective film that reflects the transmitted light, and a sensor of the transmitted light reflected by the reflective film. A first optical fiber for incidence which makes transmitted light transmitted through the temperature element incident, a second optical fiber which makes transmitted light transmitted through a member which transmits light enter, and a first optical fiber of these first and second optical fibers. First and second light receiving means arranged on one end side for receiving the transmitted light transmitted through these optical fibers, and a predetermined narrow band of the transmitted light received between the optical fibers and the light receiving means. Pass only wavelengths of width And filter, in which a comparison means for comparing the amount of light received by said first and second light receiving means. Further, the temperature measuring method according to the present invention allows the light emitted from the light emitting means to be transmitted through the temperature sensitive element for changing the transmission wavelength of the light transmitted by the temperature change and to be received by the first light receiving means, at the same time, The second light receiving means transmits the light emitted from the light emitting means and the second light receiving means receives the light, and the light received by the first and second light receiving means passes through the filter to have a predetermined narrow band width. Only the wavelength of
The temperature is calculated by using the comparison value of the amounts of light received by the first and second light receiving means as the transmittance with respect to the temperature.

[0006]

In the present invention, the light emitting means as the light emitting source is
The light from the light emitting means can be divided into light that is transmitted through the temperature sensitive element and light that is not transmitted through the temperature sensitive element.
Further, since the transmitted light is transmitted only in the wavelength of the narrow band and the temperature is calculated from the comparison value of the transmission amounts of these two lights, even if the emission wavelength of the light emitting means changes, the transmission amount of both of them is reduced. Varies at a similar rate. Further, the change in the transmittance of the light transmitted through the temperature sensitive element has a linear function relationship with respect to the temperature.

[0007]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an external perspective view of a temperature measuring device according to the present invention,
2 is a side view of the same, FIG. 3 is a front view of the same, and FIG. 4 is a conceptual diagram for explaining a measuring method by the same apparatus. In these figures, A of three fibers A, B and C is an optical fiber for emission, B and C are optical fibers for incidence,
Both of the incident optical fibers B and C are formed with the same diameter. The temperature sensor 5 bonded to the end faces of the optical fibers A, B, and C is composed of a temperature sensitive element 6, a glass 7, and a reflective film 8 deposited on the back surface of the temperature sensitive element 6 and the glass 7. The temperature sensor 5 is vertically divided by the temperature sensitive element 6 and the glass 7, and the optical fiber A for emission is arranged so that the center line of the end face is located on this division line. Among them, the fiber B is arranged in the region of the temperature sensitive element 6, and the fiber C is arranged in the region of the glass 7.

An LED, which is a light emitting element having a wavelength spectrum as shown in FIG. 5A, is provided at the entrance end of the optical fiber A for emission, and the emitted light emitted from this LED is the optical fiber. It is guided to the temperature sensor 5 from inside A. The outgoing light guided into the temperature sensor 5 passes through the temperature sensitive element 6, is reflected by the reflective film 8 via the optical path region α, and enters the fiber B, and the outgoing light is transmitted through the glass 7 and the reflective film. In FIG. 8, the incident light is reflected through the optical path region β and is incident on the fiber C. The emitted light from the fiber A is a uniform distribution light, and the incident light on the fibers B and C is also a uniform distribution light. At the exit ends of the fibers B and C, λ _F, which is a wavelength band with a predetermined narrow band width of the light wavelength band λ
An interference filter 11 that allows only light to pass therethrough, and a photodiode PD ₁ and a photodiode PD ₂ that are light receiving elements that receive the light that has passed through this interference filter 11 are provided. The light received by the photodiodes PD ₁ and PD ₂ is voltage-converted, and these voltage values are compared by the comparison circuit.

The measuring method will be described below. Light emitted from an LED having a wavelength spectrum as shown in FIG. 5A passes through the fiber A and is guided into the temperature sensor 5 as outgoing light. The outgoing light guided into the temperature sensor 5 respectively passes through the temperature sensitive element 6 and is guided to the fiber B, and the outgoing light is transmitted through the glass 7 and guided to the fiber C 2.
It becomes one incident light. The incident light incident on the fiber C is transmitted through the glass 7 and hardly undergoes transmission light modulation due to temperature, and has the same spectrum waveform as the LED spectrum as shown in FIG. 5B. That is, the fiber C
The light that passes through serves as a reference light that serves as a reference for comparison. on the other hand,
The incident light on the fiber B is the light that is transmitted-light modulated in the temperature sensitive element 6 at the temperature at that time, and has a spectrum waveform shown in FIG. 5C. Then, each of these incident lights becomes an output of a spectrum waveform as shown in FIGS. 5D and 5E as a wavelength of a narrow band centering on λ _F by passing through the interference filter 11, and the photodiode PD _The light is received by ₁ and the photodiode PD ₂ . Therefore, the output of the light received by the photodiode PD ₁ is P ₁ , and the output of the light received by the photodiode PD ₂ is P ₂
Becomes Here, the comparison value P ₂ / P ₁ is regarded as the transmittance at the wavelength passed through the interference filter 11, and the transmittance at the wavelength λ _F at the temperature T when the temperature sensitive element 6 changes in the transmittance due to the temperature. it is conceivable that.

Accordingly, knowing the temperature characteristics of the temperature-sensitive element at the wavelength lambda _F, understand transmittance characteristics of light at the wavelength lambda _F, measuring the transmittance (P ₂ / P ₁₎ in lambda _F based on this Then the temperature can be calculated. FIG. 6 is a diagram showing the relationship between the transmittance and the temperature at λ _F , based on the temperature characteristics of the temperature sensitive element investigated. The characteristic in the figure is that P ₂ / P ₁ of the transmittance with respect to temperature change has a linear function relationship. This is the transmittance of the narrow band wavelength λ _F
This is because it is calculated by comparing the outputs of Since the transmittance comparison value and the temperature have a linear function relationship as described above, the measured P ₂ / P
_The temperature calculated from ₁ is extremely accurate. In addition, since the transmittance is determined by a relative comparison value of the amounts of light that has passed through the temperature sensitive element and the light that has passed through the glass, since there is only one light emitting means, the light emission of the light emitting means is unstable. However, there is no change in the comparison value.

[0011]

As described above, according to the present invention, the transmittance is determined by the comparison value of the outputs of the narrow band wavelengths of the light transmitted through the temperature sensitive element and the light transmitted through the light transmitting member. As a result, the comparison value with respect to the temperature change has a linear function relationship, and the temperature calculated from the measured comparison value is extremely accurate. Further, since the number of light emitting means is one, even if the light emission of the light emitting means becomes unstable, the comparison value does not fluctuate, so that there is an effect that a stable temperature measurement can be performed.

[Brief description of drawings]

FIG. 1 is an external perspective view of a temperature measuring device according to the present invention.

FIG. 2 is a side view of the temperature measuring device according to the present invention.

FIG. 3 is a front view of a temperature measuring device according to the present invention.

FIG. 4 is a conceptual diagram for explaining a measuring method by the temperature measuring device according to the present invention.

FIG. 5 is a diagram showing changes in the spectrum waveform of light in the temperature measuring device according to the present invention.

FIG. 6 is a diagram showing the relationship between the transmittance and the temperature at the wavelength λ _F of the temperature sensitive element in the temperature measuring device according to the present invention.

FIG. 7 is an external perspective view showing a first example of a conventional temperature measuring device.

FIG. 8 is a conceptual diagram for explaining a measuring method according to a first example of a conventional temperature measuring device.

FIG. 9 is a spectrum waveform diagram showing characteristics of a general temperature sensitive element.

FIG. 10 is a conceptual diagram illustrating a measuring method according to a second example of a conventional temperature measuring device.

[Explanation of symbols]

 5 Temperature Sensor 6 Temperature Sensing Element 7 Glass 8 Reflective Film 11 Interference Filter

Claims (2)

[Claims] 1. An emitting optical fiber having a light emitting means disposed on one end face thereof, and a temperature sensitive element which is joined to the other end face of the emitting optical fiber and changes a transmission wavelength of the light according to a temperature change to transmit the light. A temperature sensor including a member and a reflective film that reflects the transmitted light; a first optical fiber for incidence that transmits the transmitted light that has passed through the temperature sensitive element among the transmitted light that is reflected by the reflective film; A second optical fiber that allows the transmitted light that has passed through the member that transmits the light to enter, and first and second optical fibers that are disposed on one end sides of the first and second optical fibers and that receive the transmitted light that has passed through these optical fibers. 2 light receiving means, a filter arranged between the optical fiber and the light receiving means and passing only the wavelength of a predetermined narrow band of the transmitted light to be received, and the amount of light received by the first and second light receiving means. The comparison means to compare A temperature measuring device characterized by being provided. 2. The light emitted from the light emitting means is transmitted through the temperature sensitive element for changing the transmission wavelength of the light transmitted by the temperature change and is received by the first light receiving means, and at the same time, the light is emitted from the light emitting means. The second light-receiving means to receive the first light and the second light.
The light to be received by the light receiving means is passed through the filter to have only a wavelength of a predetermined narrow band width, and the temperature is calculated by using the comparison value of the amounts of light received by the first and second light receiving means as the transmittance with respect to the temperature. A temperature measuring method characterized by the above.