JPS5814021A - Optical thermometer - Google Patents

Abstract

PURPOSE:To measure temperature accurately and readily by using liquid crystal whose light reflectivity varies with the temperature and detecting the variation in the light reflectivity through optical fibers. CONSTITUTION:Light emitting elements 1a and 1b are lit by light emitting element driving circuits 4a and 4b which are operated by the outputs of chopper circuits 3a and 3b. Light beams with wavelengths of lambda1 and lambda2 are alternately irradiated from the elements 1a and 1b on the liquid crystal 6 through the optical fibers 5a and 5b. The reflected light is guided to a light receiving element 7 by the optical fiber 8. The output thereof is inputted to an AD converter 10 through an amplifier circuit 9. In the AD converter 10, the outputs corresponding to the respective wavelengths are converted into digital signals by the time division method. The signals are compared with the data stored in a memory circuit 11 in advance and calibrated in an operating circuit 2. The temperature of the liquid crystal 6 is diaplayed on a display circuit 12. Since the reflectivity of the liquid crystal varies with the temperature and it is different for each wavelength, the temperature can be measured accurately and readily.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical thermometer that uses a liquid crystal whose light reflectance changes depending on temperature and measures temperature by optically detecting the change.

It has recently been known that cancer cells or malignant tumors lose their activity or disappear when heated, and this is being used for treatment. The heating temperature for the human body is usually around 42 to 43 degrees Celsius, which does not affect normal cells, and the cooling effect of blood flow is more effective in areas where cancer cells are active than in normal areas. It is said that it is so bad that it cannot resist even the slightest rise in temperature and dies. However, it has been proposed that if the heating temperature exceeds 50°C, it will have an adverse effect on normal cells, and one of the effective methods is to use electromagnetic waves. The frequency of electromagnetic waves is 14 MHz,
27 MH7 and other short wavelength bands are selected, and it is difficult for contact thermometers to accurately measure the temperature of human body parts without being affected by these electromagnetic waves.

Therefore, an optical thermometer is required in which at least the detection end of the thermometer that receives electromagnetic radiation is made of a material that is insensitive to electromagnetic waves. For example, US Pat. No. 4,016,761 has a detection end; a nicolesteric liquid crystal;
This method uses a light guide fiber to guide light from a light source (lode) to a liquid crystal, and then transmits the reflected light to a light receiving element using another light guide fiber to measure the temperature, and has already been commercialized. However, because this type of thermometer uses a single wavelength as a light source, it has poor tracking accuracy for color changes in the liquid crystal, and is easily affected by changes in the liquid crystal itself over time and changes in the light intensity of the light source, making it difficult to measure accurately. The disadvantage is that accuracy cannot be obtained. For example, FIG. 1 shows the reflectance characteristics versus temperature when the light source is of a single wavelength, and the curve shows the reflectance characteristics versus temperature T of the liquid crystal when the wavelength λ is used. Now, suppose that the reflectance at To is Ro, and then the temperature rises to T1, the reflectance becomes an angle as shown in the figure. However, the temperature corresponding to the reflectance R1 is T1
Since there are two points, 1 and 2, it is necessary to use some means to determine which temperature the temperature is. Further, since fluctuations in the amount of light directly affect the amount of opposition, measurement errors cannot be avoided.

The present invention eliminates the drawbacks of the conventional device described above, uses one or more light sources with different wavelength ranges, and one or more light-receiving elements, and uses light with a plurality of wavelengths to improve the reflectance of the liquid crystal. For example, temperature measurement of human body parts 1 - To provide a suitable optical thermometer (= Yes, the content is that the light reflectance changes depending on the temperature change. In addition, a temperature detection end has a built-in liquid crystal whose reflectance varies depending on the wavelength of the light, and a light guide fiber for light transmission in which the light source is optically connected to the input end and the liquid crystal is optically connected to the exit end. , the temperature is determined using a light-receiving light guide fiber in which the liquid crystal is optically connected to the input end and a light-receiving element is optically connected to the exit end, and two or more wavelength regions of the reflected light obtained by the light-receiving element are used. It is characterized by comprising an arithmetic processing circuit.

The present invention will be described in detail based on the embodiments illustrated in FIG. 2 and below.

In FIG. 2, 1a and 1b are first and second light emitting elements made of, for example, LEDs, and have different wavelengths λ and λ2.
emits light. These light emitting elements 1a, 1b are activated by signals from the arithmetic processing circuit 2 (the first and second chopper circuits 1a, s3bs, which are driven by two, and the outputs 1 of these chopper circuits 3a, 3b; First and second light-emitting element drive circuits 4a and 4b are connected in sequence.Furthermore, first and second light-transmitting light guide fibers 5a, 5b are optically connected to each other, and their exit ends are optically connected to a liquid crystal 6 whose light reflectance changes according to temperature. Also, 7 is a light-receiving element, to which the exit end of a light-receiving light-guiding fiber 8 that guides the light from the liquid crystal 6 is optically connected. A light receiving element 7; second, an optical signal amplification circuit 9 and an A/D conversion circuit 10 are sequentially connected;
Signals are exchanged between the A/D conversion circuit 10 and the arithmetic processing circuit 2. A storage circuit 11 and a display circuit 12 are further connected to the arithmetic processing circuit 2, and the former is a program memory, a constant memory for converting an A/D converted optical signal into temperature, and a temporary memory for storing data. It has a data memory for storing, and the latter is adapted to display the measured values as required.

FIG. 3 is a cross-sectional view of the temperature detection end 16 where the liquid crystal 6 is arranged, and shows the space between the first and second light-transmitting light-guiding fibers 5a, 5b, the light-receiving light-guiding fiber 8, and the liquid crystal 6. A light guide 14 and a diffusing surface 15 are inserted in the , and both have appropriate refraction so that the light from the light guide fibers 5a and 5b is effectively transmitted to the liquid crystal 6, and the reflected light from the liquid crystal 6 is effectively transmitted to the light guide fiber 8. A substance with a certain rate is used. In addition, these are Case 1, which has good thermal conductivity and light shielding properties.
The case 16 ('-) is made of a material that is not sensitive to electromagnetic waves and has no adverse effect on the human body, and its outer diameter is as small as possible.

In the above configuration, the first and 2a2 light emitting elements 1a,
FIG. 4 shows a timing chart in the case where the lights of emission wavelengths λ1 and λ2 are emitted from 1b in a time-division manner. First and second light emitting elements 1a.

1b is AC driven at a suitable frequency f by chopper circuits 3a and 3b, and is alternately turned on and off at a period T according to a control signal from the arithmetic processing circuit 2. Further, this on/off control signal is also synchronized with the conversion start pulse S TO of the A/D conversion circuit 10. Light emitting element 1a, 1
The light emitted from b is transmitted through each of the light guide fibers 5a for light transmission.
, 5b to the temperature detection end 13 and alternately illuminate the liquid crystal 6, and the reflected light is guided to the light receiving element 7 by the light guide fiber 8 for light reception. The optical signal output PD8 photoelectrically converted by the light receiving element 7 is amplified to an appropriate level by an optical signal amplification circuit 9) and input to the A/D conversion circuit 1o. A/D
The conversion circuit 1o is a chopper circuit 3a.

The arithmetic processing circuit 2 compares and calibrates these digital signals with data previously stored in the storage circuit 11, calculates the temperature of the liquid crystal 6, and displays the data. It is displayed on the circuit 12 as temperature data.

Next, to explain the principle of this measurement, FIG. 5 shows the temperature versus reflectance characteristics when the light source has wavelengths λ1 and λ2. In this graph, curve A shows the reflectance characteristic of liquid crystal 6 with respect to wavelength λ, and curve B shows the reflectance characteristic of liquid crystal 6 with respect to wavelength λ2. Further, by calculating the difference between these characteristics, the characteristics shown in FIG. 6 can be obtained. The reflectance can be thought of as a constant amount of incident light; it can be thought of as the amount of reflected light for a pair, so if the amounts of light at wavelengths λ1 and λ2 are each constant, the obtained light amounts, that is, the optical signal outputs PDS(λ1) and PDS(λ,)
The arithmetic processing circuit 2 calculates the difference in light amount from the storage circuit 1.
1, the temperature T on the horizontal axis in FIG.
It becomes possible to calculate. However, from the characteristics shown in FIG. 6, there is a region where two temperatures can be obtained even with the same light intensity difference, so it is necessary to limit the measurement temperature range to TL as the lowest temperature and T11 as the highest temperature.

The above-mentioned measuring method measures temperature using the difference in reflectance for different wavelengths, but in addition to this method, measurement can also be performed by a method as shown in FIG. 7. For example, if we obtain the reflectance R11 at wavelength λ1 and the reflectance R at wavelength λ as a result of measurement, then from the characteristic curve shown in FIG.
or Tl, similarly, from the measurement result of 1"-wavelength λ, the temperature is measured as T1 or T//. Therefore, by comparing both measurement results, it is found that the equal temperature T1 is the true value. This work If the relationship between the wavelength λ1 and the reflectance R of λ1 and the temperature T is stored in the arithmetic processing circuit, it becomes possible to extract the measurement results very easily and quickly.

FIG. 8 shows a second embodiment in which a spectroscope is used in the light receiving optical system, and a condenser lens 17, a beam splitter 18, and a light beam selector are arranged along the optical axis at the rear of the exit end of the light guide fiber 8 for light reception. A first optical filter 19a and a condensing lens 20a are arranged, and a first light receiving element 7a is arranged at the focal position of the condensing lens 20a.

Further, on the other exit side of the beam splitter 18, a second optical filter 19b1, a condensing lens 20b, and a second optical filter 19b1 are arranged on the optical axis.
Second light receiving elements 7b are arranged. A first optical signal amplification circuit 9g and a first A/D conversion circuit IQa are connected to the first light receiving element 7a, and a second optical signal amplification circuit 9b and a second optical signal amplification circuit IQa are connected to the second light receiving element 7b. A/D conversion circuits 10b are connected to each. However, only one chopper circuit 6 is required to provide output signals to the drive circuits 4a and 4b, and the arithmetic processing circuit 2 and the like in FIG. 2 are omitted in the drawing.

In FIG. 8, the reflected light of the liquid crystal 6 emitted from the light-receiving light guide fiber 8 is split by the beam splitter 18, and in the first optical filter 19a, the light of wavelength λ, the second In the optical filter 19b, only light having a wavelength of λ is transmitted. The light receiving elements 7a and 7b are outdated in photometry of the amount of light at wavelengths λ1 and λ2, respectively.
There is no need to alternately turn on and off the light-receiving elements 1a and 1b or to perform time-division signal processing in the light-receiving system as in the illustrated embodiment.

Although the characteristics shown in FIG. 6 are obtained by calculating the difference between the curves A1B in FIG. 5, the characteristic data corresponding to FIG. 6 may be obtained by calculating the ratio of the reflectances of curves A and H. In this case, as long as the ratio of the amount of light of wavelengths λ8 and λ sent to the liquid crystal 6 is constant, there will be no problem in temperature measurement even if the amount of light changes.

Furthermore, if the temperature sensing end 13 has a structure in which the tip can be replaced, the positions of TL and TH in FIG. 6, that is, the temperature measurement area, can be changed by appropriately selecting and replacing the type of liquid crystal 6. Can be done. Furthermore, various arrangements of the light guide fibers 5a, 5b, and 8 can be considered, examples of which are shown in FIGS.
Shown in b). FIG. 9(a) shows an example in which two light transmitting light guide fibers 5a and 5b are arranged on both sides of a light receiving light guide fiber 8, which was used in the embodiments shown in FIGS. 2 and 8. Figure 9(b) shows light intensity: 1
Accordingly, this is an example in which a plurality of light guide fibers 5a15b for light transmission are arranged around the light guide fiber 8 for light reception. It is not necessary that the number of light transmitting fibers 5a and 5b be the same, and an appropriate number may be selected by taking into account, for example, the difference in the amount of light emitted by the light emitting elements 1a and 1b depending on the wavelength. The number of light guide fibers 8 for receiving light may not be one, but may be plural, and a wavelength-selective optical filter may be provided at the exit end. It is also possible to use one light source with a wide wavelength range and select the wavelength in the light receiving optical system for signal processing.

As explained above, the optical thermometer according to the present invention can accurately and easily measure temperature using reflected light of two or more different wavelengths. In particular, the temperature detection end 1: By using a material that is insensitive to electromagnetic waves, it is extremely suitable for measuring the temperature of a part of the human body to be treated with electromagnetic waves.

[Brief explanation of drawings]

Fig. 1 is a characteristic diagram of temperature vs. reflectance when the light source has a single wavelength, Fig. 2 is a block circuit configuration diagram of the first embodiment of the present invention, and Fig. 3 is a cross section of the detection end. Figure 4 is a timing chart diagram to explain its operation, Figure 5 is a characteristic diagram of temperature versus reflectance when the light source has two wavelengths, and Figure 6 is a differential output characteristic diagram of Figure 5. , FIG. 7 is a characteristic diagram for explaining another measurement principle, FIG. 8 is a block circuit configuration diagram of the second embodiment, and FIG. 9 <a), (b) is a sectional view of the arrangement of light guide fibers. It is. Symbols 1a and 1b are light emitting elements, 2 is an arithmetic processing circuit diagram, and 5a
, 5b is a light guide fiber for transmitting light, 6 is a liquid crystal, 7.7a and 7b are light receiving elements, 8 is a light guide fiber for light reception, 11 is a memory circuit, 12
is a display circuit, 13 is a detection end, 18 is a beam splitter,
19a and 19b are optical filters. Patent applicant Canon Corporation 3 T+' To T+ TFigure 2Figure 40 TC Tube 5Figure 6Figure 7 ■,' T+ T; 7Figure 8 ((1) (1))

Claims (1)

[Claims] 1. A temperature detection end that has a built-in liquid crystal whose light reflectance changes according to temperature changes and whose reflectance varies depending on the wavelength of the light, and a light source at the input end. A light guide fiber for transmitting light having the liquid crystal optically connected to the exit end, a light guide fiber for receiving light having the liquid crystal at the input end and a light receiving element optically connected to the exit end, and 1. An optical thermometer comprising: an arithmetic processing circuit for determining temperature using two or more wavelength regions in the reflected light. 2. The optical thermometer according to claim 1, wherein a light guide fiber for transmitting light is connected to two light emitting elements that emit light of different wavelengths. 3. The optical thermometer according to claim 2, wherein two light emitting elements emit light alternately, and the reflected light from the liquid crystal is separated into two wavelengths in synchronization with the emitted light. 4. The optical thermometer according to claim 1, wherein the reflected light from the liquid crystal is separated into two wavelengths using a wavelength selective filter. 5. The optical thermometer according to claim 1, wherein the temperature is determined based on the difference between two temperature versus wavelength characteristics of the liquid crystal. 6. The optical thermometer according to claim 1, wherein the vicinity of the tip including the temperature detection end is made of a material insensitive to electromagnetic waves.