JPH0569535B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a temperature measuring device, for example, a device for remotely measuring the temperature inside an object without connecting the inside and outside of the object with a cable.

(Prior Art) Conventionally, there has been a method of measuring the temperature inside an object that transmits electromagnetic waves. A method has been proposed for measuring temperature without wired connection between a power supply probe and an in vitro measuring device.

The above-mentioned temperature measurement method involves surgically implanting a probe with a crystal oscillator connected to an antenna coil at a desired location within the body, or passing it into the digestive tract and injecting electromagnetic waves at the desired frequency from outside the body. Either radiate energy and apply it to the crystal oscillator via the antenna coil and observe the energy absorption when it resonates, or measure the reverberation of the crystal oscillator immediately after stopping the emission of electromagnetic energy. There is a method of receiving through an antenna coil.

However, in any of the above methods, electromagnetic energy is emitted from outside the living body and an energy absorption phenomenon, the so-called dip phenomenon, at a frequency that matches the resonant circuit constituting the in-vivo probe is observed, or the electromagnetic energy emission is stopped. Since the reverberation of the resonator within the in-vivo probe that occurs immediately afterward is detected in a short period of time, the target level or range is extremely small, making observation or measurement extremely difficult.

(Problems to be Solved by the Invention) The reason for defects in the conventional in-vivo temperature measuring method as described above is that there is a limit to the amount of energy absorbed by the in-vivo probe, and the level thereof is extremely small.

Furthermore, since the electromagnetic energy irradiated from outside the body and the electromagnetic energy detected from the in-vivo probe both have the same frequency, it is not possible to increase the external irradiation energy level when it is necessary to eliminate the effects of both, which also causes the above-mentioned defects. This was one of the reasons why.

(Means for Solving the Problems) The present invention has been made in order to eliminate the defects of the conventional in-vivo temperature measurement method, and the present invention has been made in order to eliminate the defects of the conventional in-vivo temperature measurement method. A circuit for generating harmonics, such as a double-wave rectifier circuit, is added to the electromagnetic energy waves generated, and the harmonics are detected or measured outside the living body, thereby measuring the temperature inside the living body.

(Function) If the above-mentioned method is used to measure the temperature inside a living body, firstly, the frequency of the electromagnetic energy waves irradiated from outside the living body and that re-radiated from the probe are separated by two or three times or more. This makes measurement extremely easy. Furthermore, as will be described later, if the irradiation energy absorbed by the in-vivo probe is efficiently re-radiated as harmonics, this level can be increased in proportion to the energy level irradiated from the outside, so the saturation level of the resonant circuit can be increased. Thus, it is possible to obtain re-radiation energy of a desired magnitude.

Furthermore, if elements with temperature dependence are used in the resonant circuit for absorbing energy and the resonant circuit for extracting the harmonics provided in the probe, the frequency versus temperature characteristics can be made more pronounced. I can do it.

(Example) The present invention will be described in detail below based on an illustrated example.

FIG. 1 is a block diagram showing one embodiment of the present invention.

In the figure, reference numeral 1 denotes a probe as a temperature sensor located at a desired part within the living body, and includes an antenna coil L ₁ and a crystal oscillator X ₁ in parallel with which the characteristics change depending on the temperature. rectifier diodes D ₁ and D ₂ are connected in the same direction to both ends of the parallel circuit, and the connecting point between the two diodes and the antenna coil are connected so as to operate as a capacitor.
A series resonant circuit consisting of a capacitor _C1 and a coil _L2 is inserted and connected between the intermediate tap of _L1 ,
Circuit constants are selected so that the resonant frequency of the series resonant circuit is a harmonic, for example twice the frequency, of the parallel circuit consisting of the antenna coil _L1 and the crystal resonator _X1 .

The probe 1 configured in this way is housed in the desired part of the living body to be measured, and externally there is a variable frequency signal generator OSC ₁ connected to the irradiation antenna coil L ₃ and a harmonic of the frequency irradiated by the OSC ₁ . The probe is equipped with a receiver RX ₁ that receives the above-mentioned signals and a measuring device connected to a coil L ₄ as an antenna to detect harmonic electromagnetic waves re-radiated from the probe.

The measuring device configured in this manner operates as follows.

FIG _. 2 is a diagram explaining the waveforms of each part of the measurement system shown in _{FIG .} induce. The coil L ₁ constitutes a parallel resonant circuit with a crystal oscillator X ₁ that operates as a capacitor, and the waveform generated at both ends is the same as that shown in Fig. 2 A, and due to the diodes D ₁ and D ₂ connected to both ends. Double-wave rectification is performed, and the output Dout becomes a pulsating flow with a negative half-cycle waveform folded back as shown in FIG. Furthermore, this output flows between the intermediate tap of the antenna coil _L3 via a series circuit of the coil _L2 and the capacitor _C1 ,
Since the resonance frequency of the series circuit is set to the harmonic number, for example 2, as described above, the high-frequency current flowing therein becomes the second harmonic of the harmonics included in the double-wave rectified waveform described above, and is emitted outside the body via coil _L2 . Induces second harmonic. Therefore, we changed the oscillation frequency of the OSC ₁ mentioned above and transferred this harmonic wave in vitro to a receiver equipped with coil L ₄ .
By reading the frequency at the point detected by RX ₁ and exhibiting the maximum level at that time, the resonant frequency of the tuned circuit can be found, and if the temperature dependence of this resonant circuit frequency is known in advance, it is possible to find the required part in the living body. It is possible to measure the temperature at

As described above, according to the principle of the present invention, since the electromagnetic wave frequency irradiated from outside the living body and the frequency detected externally are different, it is easy to identify them, and the two electromagnetic energy re-emitted to the outside are different. Since the electromagnetic energy increases in proportion to the electromagnetic energy radiated from the source, it is obvious that the measurement will be easier if this value is set to the required value.

The crystal oscillator used in the probe of the above-mentioned embodiment is not limited to this, and any type of crystal oscillator may be used as long as its impedance changes with temperature and as a result, the resonant frequency changes. Considering the stability of the circuit and the Q of the circuit, a crystal resonator is probably the most suitable.

Furthermore, the resonant circuit configuration including this crystal resonator is not limited to the above-mentioned example, and various configurations are possible, some of which are shown in FIG.

That is, Figures a and b are convenient when the crystal resonator is operated as an inductance, and both of these are ones in which a temperature-dependent crystal resonator is inserted into the fundamental wave resonant circuit, but the present invention For example, a crystal resonator that resonates at 2 may be connected to the harmonic component resonant circuit side as shown in c to e of the same figure.

Furthermore, as shown in FIG. Since it can be observed as , measurement accuracy can be improved.

Furthermore _, although the above examples all show cases where harmonic components are detected, as shown in FIG. 4, the fundamental wave signal extracted by the antenna coil L ₁ and _the crystal oscillator If input to a circuit with a resonant frequency of /2 via D ₄ , a radiation signal of /2 can be extracted in the same manner as a variable capacitance parametron oscillator. It can be applied to a measurement method using harmonics, and various circuit configurations shown in the above-mentioned embodiments can be considered in this case as well.

Also, in the above explanation, the coil for the fundamental wave resonant circuit and the coil for the harmonic or 1/2 harmonic resonant circuit are made into separate coils, which is complicated and also increases the size.
Therefore, if this coil is integrated and a single diode is used for half-wave rectification, the efficiency will decrease slightly, but the dimensions of the probe can be made extremely small, making it more suitable for implantation in a living body.

Examples of these are shown in Figures 5a-d.

That is, in Figures a and b, a crystal oscillator is inserted into the fundamental wave circuit and a part of the antenna coil _L1 is shared as the coil _L2 of the harmonic resonance circuit.
Figures c and d use a crystal oscillator for the harmonic resonant circuit; however, similar to the previous embodiment, various other circuits are possible, and in the case of half-wave rectification, the harmonics Odd harmonics e.g. 3x and 9
There is no need to explain that since the double component is also included, it may be detected.

However, as in these examples, the antenna coil
When L ₁ is shared with harmonic resonance coil L ₂ ,
The electromagnetic energy waves irradiated from outside the body and the harmonics or 1/2 harmonics re-radiated from the aforementioned probe are often input and output in extremely close positions, so it is necessary to measure them externally. The device is the 6th
It would be more convenient to configure the irradiated wave and the received wave 2 or 2 to be coupled to the in-vivo probe via the same antenna coil _L3 using a directional coupler (for example, a circulator) as shown in the figure.

The present invention further considers applying various modulations to the externally irradiated electromagnetic waves using required signals in order to improve measurement sensitivity.

That is, in each of the above embodiments, the frequency at which the harmonic or 1/2 harmonic re-radiated from the probe is at its maximum level is detected, but when the electromagnetic waves radiated from the outside are radiated using a single low-frequency signal, AM Modulation or PM
If modulation or FM modulation is applied and the modulated signal contained in the harmonics re-radiated from the probe is demodulated and the signal level is observed, the measurement is much easier than measuring the high frequency level. .

Although it is common practice to match the demodulation method to the same method for each type of modulation method, actual measurements have shown that AM detection was also used to derive the demodulated signal for angle modulation such as PM or FM. It was found that the sensitivity of the measurement could be increased by using the method.

Also, since the demodulated signal includes the double harmonic of the modulated signal _L generated by the nonlinear circuit element in the probe, the intermediate frequency signal containing this can be configured as shown in FIG. 7, for example. The low frequency signal _L for modulation is directly taken out by the measuring circuit.
Perform synchronous detection using the multiplied signal and observe this output so that when the electromagnetic wave irradiated from the outside or its harmonic frequency matches the resonant circuit including the crystal resonator in the probe, the synchronous detection output crosses zero. If the resonant frequency of the probe can be determined by adjusting the phase amount of other circuits and detecting the zero crossing point, it will be extremely convenient to automate these measurements.

It should be noted that the present invention is not necessarily limited to the embodiments described above, and it is clear that the resonant circuits may be combined in series, in parallel, or in any combination thereof.

(Effects of the Invention) As explained above, the present invention differs from conventional systems in which the electromagnetic wave frequency irradiated to the probe inside the living body and the frequency of the re-radiated signal are the same. It provides different measurement means, and not only can it obtain measurement output according to the irradiated electromagnetic wave energy, but also
This makes it possible to use a variety of measurement methods, which is extremely effective in improving the accuracy of devices that measure internal temperatures, etc.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram explaining the operating principle of the present invention,
2A to 2C are diagrams showing waveforms of various parts of the circuit shown in FIG. A circuit diagram showing an example of inserting this into the fundamental wave resonant circuit, c to e into the harmonic resonant circuit, and further f into both of these, Figure 4 re-radiates the 1/2 harmonic. A circuit diagram showing an embodiment of the probe when extracting it as a signal, Figures 5a to 5d are circuit diagrams showing a case where the antenna coil of the probe and the coil of the harmonic resonance circuit are shared, and Figure 6 is an external measurement circuit. FIG. 7 is a block diagram showing an embodiment of an external measuring circuit suitable for performing automatic measurements. 1... In-vivo probe, 2... Circulator, OSC ₁ and OSC ₂ ... Oscillator, L ₁ and L ₃ ... Antenna coil, L ₂ ... Resonance coil, D ₁ and D ₂ ...
... Rectifier diode, C ₁ and C ₂ ... Capacitance, X ₁ and X ... Crystal resonator, D ₃ and D ₄ ... Variable capacitance diode, RX ... Receiver, DET ... Detector.

Claims (1)

[Scope of Claims] 1. A probe constituted by a temperature-dependent resonant circuit, means for irradiating the probe with electromagnetic waves, and resonant frequency detection means for detecting the resonant frequency when the probe resonates with the electromagnetic waves. In the apparatus for measuring the temperature of an environment in which the probe is located, the resonant circuit is provided with means for generating harmonic distortion or subharmonic distortion, and
A temperature measuring device characterized in that the resonant frequency detection means is configured to detect harmonics or subharmonics emitted from the resonant circuit. 2. The temperature measuring device according to claim 1, wherein a crystal resonator is incorporated in the resonant circuit of the probe.