JP2000342541A - Ear hole type clinical thermometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve measuring precision without necessitating a filter having steep interrupting characteristic. SOLUTION: In order to extract the signal of the same frequency as a reference signal in order to fetch only a signal having very small temperature information from an infrared detector 1, this clinical thermometer multiplies a signal from the detector 1 and the reference signal by a multiplier 22 and detects the intensity of infrared rays from the DC components of an output to precisely measure the temperature of an ear drum.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ear canal thermometer for detecting eardrum temperature in an ear canal without contact.

[0002]

2. Description of the Related Art An ear thermometer for measuring eardrum temperature in an ear canal using an infrared detector passes an output signal of the infrared detector through a band-pass filter or a low-pass filter.
A / D conversion was performed, and the intensity of infrared rays was detected from the signal after the A / D conversion to calculate the temperature of the eardrum.

[0003]

The ear canal thermometer of the above-mentioned conventional construction is designed to remove the noise from the signal from the infrared detector through a filter and then to perform A / D conversion. To take it out, a filter with steep cutoff characteristics must be prepared,
The design is very difficult, and the noise cannot be completely removed, so that it is difficult to improve the measurement accuracy.

[0004]

SUMMARY OF THE INVENTION In order to extract only a signal having minute temperature information from an infrared detector, the present invention uses a multiplier to extract a signal having the same frequency as a reference signal from the infrared detector. An ear canal thermometer capable of multiplying a signal by a reference signal and detecting the intensity of infrared rays from the magnitude of the output DC component to accurately measure the temperature of the eardrum.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention described in claim 1 comprises a chopper means for periodically blocking an output signal of an infrared detector from being transmitted to a subsequent circuit, an amplifier for amplifying an output signal of the chopper means. A reference signal generating unit that outputs an AC signal, a multiplier that multiplies the output signal of the amplifier by the output signal of the reference signal generating unit and outputs the multiplied signal, and a low-pass filter that extracts only low-frequency components from the output signal of the multiplier. A bandpass filter;
An AD converter for AD-converting an output signal of the temperature detection unit of the infrared detector and an output signal of the low-pass filter;
An ear canal thermometer that can measure accurately with a temperature conversion unit that receives a signal from the D converter and outputs a signal corresponding to the temperature of the measurement target.

According to a second aspect of the present invention, the reference signal generating section is an ear-hole type thermometer capable of performing accurate measurement by changing the phase of a signal output by an external control signal.

According to a third aspect of the present invention, the reference signal generating section is an ear-hole type thermometer capable of performing accurate measurement by generating a reference signal based on a chopper drive signal of the chopper means.

According to a fourth aspect of the invention, there is provided an ear-hole type thermometer which can accurately measure the cutoff frequency of the low-pass filter by changing the cut-off frequency by an external control signal.

According to a fifth aspect of the present invention, there is provided a second multiplier for inverting the phase of an output signal of an amplifier by an output signal of a reference signal generator and outputting the inverted signal. A second low-pass filter for extracting only the frequency component, wherein the reference signal generation unit converts a second AC signal having the same frequency and a phase delay of 90 degrees as that of the AC signal supplied to the first multiplier into a second AC signal. The AD converter further converts the signal from the second low-pass filter into an A / D converter and sends the signal to a temperature conversion means so as to accurately measure the temperature.

The invention described in claim 6 is an ear-hole type thermometer which can accurately measure the driving frequency of the chopper means by changing the driving frequency by an external control signal.

[0011]

(Embodiment 1) A first embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a block diagram showing the configuration of the ear canal thermometer of the present embodiment. Reference numeral 13 denotes a human eardrum, which is an object to be measured. Reference numeral 11 denotes a probe for catching infrared rays emitted from the eardrum 13, and the infrared rays passing through the inside of the probe 11 are condensed by condensing means 12 constituted by a concave mirror. The infrared detector 1 is a thermopile in which a plurality of thermocouples are collected and arranged in a light receiving unit. FIG. 2 is a view of the inside of the infrared detector 1 as viewed from above. In FIG. 2, reference numeral 14 denotes a light receiving section which is a range where the infrared rays are condensed by the condensing means 12 and irradiated. Reference numeral 2 denotes a temperature detector disposed at a place where the temperature does not rise even when infrared rays are irradiated, and detects the temperature of the infrared detector 1 itself. The heat of the light receiving section 14 is thermally insulated so as not to be transmitted to the entire infrared detector 1. In addition, the light receiving unit 14 is configured by collecting a plurality of thermocouples, and detects the intensity of infrared rays when the temperature of the light receiving unit 14 increases.

In FIG. 1, the temperature signal of the infrared detector 1 itself detected by the temperature detector 2 is transmitted to the AD converter 4. The signal from the light receiving section 14 of the infrared detector 1 is
Since the light receiving unit 14 is formed of a thermocouple, it is a DC signal. Therefore, the signal from the light receiving section 14 of the infrared detector 1 is converted into an AC signal by the chopper means 15, amplified by the amplifier 3 through the band-pass filter 21, and transmitted to the multiplier 22. The AD converter 4 converts the transmitted analog signal into a digital signal and transmits the digital signal to the temperature conversion means 5. The chopper means 15 is a control means 16
When the control signal is 1 or plus, the signal from the light receiving section 14 of the infrared detector 1
1, and when the control signal is 0 or minus, the signal from the light receiving section 14 of the infrared detector 1 is cut off and zero is transmitted to the band-pass filter 21 at the subsequent stage. A multiplier 22 multiplies the signal from the amplifier 3 by a reference signal and outputs the result. Reference numeral 23 denotes a reference signal generating unit which generates the same frequency as the frequency having the most temperature information among the signals from the amplifier 3.

Reference numeral 24 denotes a low-pass filter, which is a multiplier 2
The purpose is to extract only the DC component from the outputs of the second and third outputs. The output signal of the low-pass filter 24 is A
It is input to the D converter 4. The AD converter 4 converts the transmitted analog signal into a digital signal and transmits the digital signal to the temperature conversion means 5. The temperature conversion means 5 includes the infrared detector 1
The temperature of the eardrum 13 is calculated by calculating the temperature data, which is a signal which has been processed by the multiplier 22 and the like, and the temperature data from the temperature detector 2 by a predetermined arithmetic expression, and calculates the measured value display means. 7 for notification and display.

The infrared light emitted from the eardrum 13 is irradiated to the light receiving section 14 of the infrared detector 1 to increase the temperature and generate an output voltage. The sum of the value obtained by dividing the amplitude of the signal from the infrared detector 1 amplified by the amplifier 3 by a certain constant and the value obtained by raising the absolute temperature of the infrared detector 1 itself detected by the temperature detector 2 to the fourth power is the measurement object. Is the absolute temperature of the infrared radiation source
To the power. The arithmetic expression provided in the temperature conversion means 5 is as follows:
It is set based on this relationship.

The operation of this embodiment will be described below. When the probe 11 is inserted into the ear canal and a switch (not shown) is turned on, the control means 16 operates to periodically cut off the signal from the light receiving section 14 of the infrared detector 1 and convert it into an AC signal. The infrared radiation emitted from the eardrum 13
1 to the light receiving section 1 of the infrared detector 1
4 is irradiated. The light receiving section 14 of the infrared detector 1 uses the intensity of the irradiated infrared light as an analog signal as an analog signal.
5, the signal passes through the band-pass filter 21, is amplified by the amplifier 3, and is transmitted to the multiplier 22. The multiplier 22 multiplies the AC signal from the reference signal generator 23 by the signal from the infrared detector 1 that has passed through the amplifier 3 and outputs the result. When the control means 16 cuts off the signal from the light receiving section 14 of the infrared detector 1 at a frequency of 10 Hz, that is, 100 ms, the output signal of the chopper means 15 becomes 10 Hz as shown in FIG.
An AC signal containing a large number of harmonics is obtained. The amplitude A of the AC signal is data on which the temperature of the eardrum 13 is calculated.

On the other hand, the other input of the multiplier 22 is supplied with the same 10 Hz square wave signal as shown in FIG. Thus, the output signal of the multiplier 22 becomes a waveform as shown in FIG. 3C by multiplying the waveform of FIG. 3A and the waveform of FIG. 3B. FIG. 3 (a),
3 (b) and 3 (c), the phase of the square wave of FIG. 3 (b) coming from the reference signal generator 23 slightly advances from the phase of the sine wave of FIG. 3 (a) coming from the chopper means 15. Is shown. If the phase of the square wave coming from the reference signal generator 23 is exactly the same as the phase of the sine wave coming from the chopper means 15, the output signal waveform of the multiplier 22 will be as shown in FIG.
(D), and when the phase of the square wave coming from the reference signal generator 23 is ahead of the phase of the sine wave coming from the chopper means 15 by 90 degrees, the output signal waveform of the multiplier 22 is shown in FIG. 3 (e), and if the phase of the square wave coming from the reference signal generator 23 is completely opposite to the phase of the sine wave coming from the chopper means 15, the output signal waveform of the multiplier 22 will be as shown in FIG. become that way.

The output signal of the multiplier 22 is expressed by the following equation.

[0018]

(Equation 1)

(Equation 1) expresses a general square wave having an amplitude of 1 by Fourier series expansion, and is composed of a sum of a fundamental wave and odd-order harmonics. Here, ω is an angular frequency, and t is time. In Equation 1, the amplitude is B and the frequency of the fundamental wave is 1.
(Expression 2) is obtained by substituting 0 Hz.

[0020]

(Equation 2)

Further, when the phase difference φ is considered, it can be expressed as (Equation 3).

[0022]

(Equation 3)

The sine wave signal from the chopper means 15 can be expressed as (Equation 4).

[0024]

(Equation 4)

The right side of (Equation 4) and the reference signal generator 23
When multiplied by the right side of (Equation 3) representing a square wave coming from, (Equation 5) is obtained.

[0026]

(Equation 5)

That is, the frequency components are 40 Hz and 80 Hz.
And a signal consisting of a harmonic component such as 120 Hz and a DC component, but focusing only on the DC component, it becomes as shown in (Equation 6),

[0028]

(Equation 6)

It can be seen that when the phase difference φ is zero, Cos φ becomes 1, which is a value obtained by dividing the product of the inputted two signal amplitudes by the pi. If the phase difference φ is not zero and is constant without changing over time, it becomes a constant term, which is a value obtained by dividing the product of two inputted signal amplitudes by a certain constant.

Therefore, in FIG. 1, since the output signal of the multiplier 22 has passed through the low-pass filter 24, the harmonic component is cut off, and only the DC component as shown in (Equation 6) can be extracted. . Therefore, if the amplitude B and the phase difference of the reference signal are constant and known, the signal amplitude of the infrared detector 1 passing through the chopper means 15 having the temperature information and the band-pass filter 21 from the output voltage of the low-pass filter 24 is obtained. A can be calculated. As described above, according to the present invention, even if the signal from the infrared detector 1 contains much noise, it remains as an AC signal which is easily separated by the multiplier, and the 10 Hz signal component necessary for temperature conversion is a DC component. Thus, the amplitude of the 10 Hz signal can be detected very accurately with a low-pass filter.

The output of the low-pass filter 24 is transmitted to the AD converter 4, which converts this signal and the signal of the temperature detector 2 for detecting the temperature of the infrared detector 1 itself into a digital signal. It is converted and transmitted to the temperature conversion means 5. The temperature conversion means 5 uses, for example, a microcomputer, calculates the eardrum temperature from these two signals, and transmits this signal to the measured value display means 7.

As described above, according to the present embodiment, infrared rays radiated from the eardrum are captured, and even if the signal from the infrared detector 1 is weak and contains a lot of noise, they are easily separated by the multiplier. Since the weak 10 Hz signal component necessary for temperature conversion becomes a direct current component, the direct current component can be easily extracted with a low-pass filter, and the amplitude of the 10 Hz signal can be detected with high accuracy. be able to. Since the temperature of the eardrum is obtained by the temperature conversion means 5 for calculating the eardrum temperature from the signal amplitude of the infrared detector 1 and the signal of the temperature detector 2, the temperature of the eardrum can be instantaneously and accurately known. It is.

(Embodiment 2) Next, a second embodiment of the present invention will be described. FIG. 4 is a configuration diagram of an ear canal thermometer showing the configuration of the present embodiment. The description overlapping with the first embodiment of the present invention will be omitted. In FIG. 4, the output of the reference signal generation unit 23 does not directly enter the multiplier 22, but once enters the phase control unit 30 to be shifted in phase, and then transmitted to the multiplier 22. How much the phase controller 30 shifts the phase is determined by constantly monitoring the output of the low-pass filter 24. That is, the phase control unit 30 adjusts the amount by which the phase is shifted so that the output of the low-pass filter 24 is always maximized. FIG. 5 shows a change in the output of the low-pass filter 24 when the phase control unit 30 shifts the phase of the reference signal. FIG. 5A shows a signal waveform from the infrared detector 1 passing through the band-pass filter 21.
FIG. 5B shows a reference signal waveform whose phase has been adjusted by the phase control unit 30, and FIG. 5C shows an output waveform of the multiplier 22, and a dotted line in FIG. 6 is an output waveform of the filter 24. At first, the phase of the reference signal has advanced from that of the signal from the infrared detector 1 which has passed through the chopper means 15. However, at time t1, the phase of the reference signal is delayed by the phase control unit 30 so that the two signals are in phase with each other. Has a large DC component value after time t1 in FIG. 5 (c).

As described above, according to the present embodiment, the multiplier 2
2, the phase difference between the two input signals can be made zero, and Cos φ shown in (Equation 6) of the first embodiment can be made one, so that the amplitude of the 10 Hz signal is always very accurate with the highest sensitivity. Can be detected.

(Embodiment 3) Next, a third embodiment of the present invention will be described. FIG. 6 is a block diagram showing the configuration of the present embodiment. In FIG. 6, the description overlapping with the first embodiment of the present invention will be omitted. In FIG. 6, the control means 16
Is also transmitted as a reference signal input of the multiplier 22. FIG. 7 is a signal waveform diagram for explaining the operation.
FIG. 7A shows a waveform after an output signal of the infrared detector 1 is converted into an alternating current by the chopper means 15, an extra frequency component is removed by the band pass filter 21, and then amplified by the amplifier 3. FIG. 7B shows a signal waveform from the control unit 16 serving as a reference signal input to the multiplier 22. FIG. 7C shows an output waveform of the multiplier 22. Therefore, the signal converted into alternating current from the infrared detector 1 is applied to the band-pass filter 21.
The phase of this signal waveform and the signal waveform of the control means 16 serving as a reference signal of the multiplier 22 are always constant and close to zero, and the amplitude of the 10 Hz signal can be detected with maximum sensitivity. Things. When the cycle of the chopper means 15 is changed, for example, 10 Hz to 20 H
Even when z is increased, the phase of the signal waveform of the converted infrared detector 1 and the signal waveform of the control means 16 serving as the reference signal of the multiplier 22 are always constant and close to zero, and the output of the multiplier 22 has no influence. The signal amplitude of 20 Hz can be detected with maximum sensitivity without receiving the signal.

As described above, according to the present embodiment, the phase of the AC output signal of the infrared detector 1 and the phase of the reference signal to be multiplied with the output signal waveform can be accurately matched, and the eardrum always has the maximum detection sensitivity. It can measure temperature.

(Embodiment 4) Next, a fourth embodiment of the present invention will be described. FIG. 8 is a block diagram showing the configuration of this embodiment. In FIG. 7, the description overlapping with the first embodiment of the present invention is omitted. Reference numeral 31 denotes a filter control unit that controls the cutoff frequency of the low-pass filter 24 based on the level of the output signal of the band-pass filter 21, and also outputs an operation stop signal to the reference signal generation unit 23.

Next, the operation will be described. First, the filter control unit 31 causes the reference signal generation unit 23 to stop generating a signal. As a result, a state in which an AC signal does not enter the multiplier 22 is established. The output signals of the band-pass filter 21 at this time are all noise, and when this noise level is low, it can be said that noise due to external electromagnetic waves or the like is small. When the noise level is low, there is no problem even if the cutoff frequency of the low-pass filter 24 is increased, and there is an advantage that the reaction time of the low-pass filter 24 is shortened and the measurement time is shortened. Conversely, when the noise level is high, the cut-off frequency of the low-pass filter 24 is lowered, that is, the time constant is increased, and the measurement time becomes longer, but the noise is cut off and the measurement can be performed with high accuracy.

As described above, according to the present embodiment, in an environment with a lot of noise, it is possible to measure the eardrum temperature accurately and accurately by taking a long time to cut off the noise with a low-pass filter having a large time constant. In an environment with little noise, the eardrum temperature can be instantaneously and accurately measured without taking much time.

(Embodiment 5) Next, a fifth embodiment of the present invention will be described. FIG. 9 is a block diagram showing the configuration of this embodiment. In FIG. 9, the description overlapping with the first embodiment of the present invention is omitted. Reference numeral 33 denotes a 90-degree phase shift unit which shifts the phase of the signal of the reference signal generation unit 23 by 90 degrees. 34 is a second multiplier, which is a band-pass filter 21
The signal from the infrared detector 1 passing through the amplifier 3 and the reference signal in the first multiplier 22 are multiplied by a second reference signal delayed by 90 degrees in phase. 3
5 is a second low-pass filter, and a second multiplier 34
The DC component of the output signal is taken out, amplified by the second amplifier 36, and transmitted to the sum of squares operation section 37. Also,
The output of the first amplifier 25 does not enter the AD converter 4 but is transmitted to the sum-of-squares operation unit 37.

Next, the operation will be described. (Equation 7) is a Fourier series expansion of the second reference signal, which is delayed by 90 degrees from the reference signal input to the first multiplier 22 in the second multiplier 34.

[0042]

(Equation 7)

The first reference signal shown in (Equation 3) is 90
Degrees, or π / 2 radians phase. This second
Is multiplied by the sine wave signal that has passed through the band-pass filter 21 and the amplifier 3 in (Equation 4) to obtain (Equation 8).

[0044]

(Equation 8)

That is, the frequency components of 40 Hz and 80 Hz
And a signal consisting of a harmonic component such as 120 Hz and a DC component, but focusing only on the DC component, it becomes as shown in (Equation 9),

[0046]

(Equation 9)

The product of the two input signal amplitudes is Sin φ
It can be seen that the value obtained by multiplying by is divided by the pi. This is the same as (Equation 6) except that Cos φ becomes Sin φ. The sum-of-squares unit 37 squares the Cosφ component obtained by the first low-pass filter 24 and amplified by the first amplifier 25 and the second amplifier 36 obtained by the second low-pass filter 35. Amplified Sinφ
AD is obtained by adding the squared components and taking the square root
The signal is transmitted to the converter 4. (Equation 10) shows the processing content of the sum-of-squares operation unit 37 by a mathematical expression.

[0048]

(Equation 10)

As shown in (Equation 10), the Cos component and Si
Since the sum of the squares of the n components becomes 1, the output of the sum-of-squares operation unit 37 is, after all, the band-pass filter 21 and the amplifier 3 of A / B / π which are completely unrelated to the phase difference φ. Is obtained by dividing the product of the signal amplitude A passing through and the reference signal amplitude B by the pi. For this reason, if the amplitude B of the reference signal is known, it is possible to calculate the signal amplitude A of the infrared detector 1 that has passed through the band-pass filter 21 and the amplifier 3 having the temperature information from the output voltage of the square-sum operation unit 37. it can.

As described above, according to the present invention, even if the signal from the infrared detector 1 contains much noise, it remains as an AC signal which is easily separated by the multiplier, and a 10 Hz signal necessary for temperature conversion. The component becomes a DC component and can be easily extracted by a low-pass filter. Further, even if the phase of the output signal waveform of the infrared detector 1 and the phase of the reference signal to be multiplied with the waveform are not matched, the maximum detection sensitivity is always obtained. Thus, the eardrum temperature can be measured very accurately.

(Embodiment 6) Next, a sixth embodiment of the present invention will be described. FIG. 10 is a block diagram showing the configuration of this embodiment. In FIG. 10, the description of the same parts as those of the first and third embodiments of the present invention will be omitted. 4
Numeral 0 denotes frequency determining means for determining the frequency of the chopper means 15, which changes the frequency in accordance with the magnitude of the noise of the low-pass filter 24 and sends a control signal to the control means 16 so that the control means 16 operates according to the frequency. To convey.

Next, the operation will be described. First, the frequency determination unit 40 causes the control unit 16 to stop signal output. As a result, a state in which an AC signal does not enter the multiplier 22 is established. If a large signal appears at the output of the low-pass filter 24 at this time, it is considered that extraneous noise close to the frequency at which the chopper means 15 is moving into the circuit, and conversely, the output level of the low-pass filter 24 decreases. When it is low, it can be said that noise due to external electromagnetic waves and the like is small. When the external noise is large, the signal amplitude from the infrared detector 1 is measured under the best S / N condition by changing the frequency at which the chopper means 5 is moved and moving the chopper means 15 at the frequency at which the external noise is the lowest. be able to.

As described above, according to this embodiment, in an environment where there is much noise at a frequency close to the signal cutoff cycle of the chopper means 15, the signal cutoff cycle of the chopper means 15 is changed to
The eardrum temperature can be measured accurately and accurately at a frequency where N is good.

[0054]

According to the first aspect of the present invention, the infrared rays radiated from the eardrum are captured, and even if the signal from the infrared detector is weak and contains a lot of noise, they are easily separated by the multiplier. Since the signal remains as it is and the weak signal component required for temperature conversion becomes a DC component, this DC component can be easily extracted with a low-pass filter, and the amplitude of the signal with temperature information can be detected with high accuracy. can do. Thus, the temperature of the eardrum can be obtained by the temperature conversion means for calculating the eardrum temperature from the signal amplitude of the infrared detector and the signal of the temperature detector, so that the temperature of the eardrum can be instantaneously and accurately known.

According to the second aspect of the present invention, since the phase difference between two input signals of the multiplier can be made zero, the amplitude of the signal can always be detected with the highest sensitivity and with high accuracy.

According to the third aspect of the present invention, the phase of the output signal waveform of the infrared detector and the phase of the reference signal to be multiplied with the waveform can be accurately matched, and the eardrum temperature can always be measured with the maximum detection sensitivity. Things.

According to the fourth aspect of the present invention, in an environment where there is a lot of noise, the noise is cut off by taking a long time with a low-pass filter having a large time constant so that the eardrum temperature can be measured accurately and accurately. In a small environment, the tympanic membrane temperature can be instantaneously and accurately measured without taking much time.

According to the fifth aspect of the present invention, even if the signal from the infrared detector contains a lot of noise, it remains as an AC signal which is easily separated by the multiplier, and the signal component necessary for temperature conversion is It becomes a DC component and can be easily extracted with a low-pass filter.Furthermore, even if the output signal waveform of the infrared detector does not match the phase of the reference signal to be multiplied with the output signal waveform, it is always very sensitive with the maximum detection sensitivity. The tympanic membrane temperature can be accurately measured.

According to a sixth aspect of the present invention, in an environment where there is a lot of noise having a frequency close to the frequency of the signal cutoff cycle of the chopper means, the signal cutoff cycle of the chopper means is changed to accurately and accurately at a frequency having a good S / N. It can measure eardrum temperature.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an ear canal thermometer according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of an infrared detector according to a first embodiment of the present invention;

FIGS. 3 (a) to 3 (f) are explanatory diagrams of the operation of an ear canal thermometer according to a first embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of an ear canal thermometer according to a second embodiment of the present invention.

FIGS. 5 (a) to 5 (c) are explanatory diagrams of the operation of an ear canal thermometer according to a second embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of an ear canal thermometer according to a third embodiment of the present invention.

FIGS. 7A to 7C are explanatory diagrams of the operation of an ear canal thermometer according to a third embodiment of the present invention.

FIG. 8 is a block diagram showing the configuration of an ear canal thermometer according to a fourth embodiment of the present invention.

FIG. 9 is a block diagram showing a configuration of an ear canal thermometer according to a fifth embodiment of the present invention.

FIG. 10 is a block diagram showing a configuration of an ear canal thermometer according to a sixth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Infrared detector 2 Temperature detector 3 Amplifier 4 A / D converter 5 Temperature conversion means 11 Probe 15 Chopper means 16 Control means 21 Band pass filter 22, 34 Multiplier 23 Reference signal generation part 24, 35 Low pass filter 30 Phase control Unit 31 filter control unit 33 90-degree phase shift unit 37 sum of squares operation unit

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hirofumi Inui 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. F-term (reference) 2G066 AC13 BA08 BA34 BB11 BC07 BC30 CA15 CA20

Claims (6)

[Claims] 1. A light condensing means for condensing infrared light that has passed through a probe, a light-receiving part whose temperature rises by irradiation of the condensed infrared light, and a light-receiving part whose infrared light is not irradiated and whose temperature does not increase. An infrared detector having a temperature detection unit for detecting a temperature therein, and chopper means for periodically blocking an output signal of the infrared detector from being transmitted to a subsequent circuit,
An amplifier for amplifying the output signal of the chopper means, a reference signal generating unit for outputting an AC signal of a certain frequency, a multiplier for multiplying the output signal of the amplifier by the output signal of the reference signal generating unit and outputting the result; A low-pass filter that extracts only low-frequency components from the output signal of the detector, an AD converter that performs AD conversion of an output signal of the temperature detection unit of the infrared detector and an output signal of the low-pass filter, and an AD converter. The ear-hole type thermometer provided with a temperature conversion means for receiving a signal of the above and outputting a signal corresponding to the temperature of the measurement object, and a measured value display means for displaying a temperature conversion result and an operation state of the temperature conversion means. 2. The ear canal thermometer according to claim 1, wherein the reference signal generator is capable of changing the phase of a signal output by an external control signal. 3. The ear hole thermometer according to claim 1, wherein the reference signal generator generates a reference signal based on a chopper drive signal of the chopper means. 4. The ear canal thermometer according to claim 1, wherein the cut-off frequency of the low-pass filter can be changed by an external control signal. 5. A second multiplier for inverting a phase of an output signal of the amplifier by an output signal of a reference signal generation unit and outputting the inverted signal,
A second low-pass filter for extracting only low-frequency components from the output signal of the second multiplier, wherein the reference signal generator has the same frequency as the AC signal applied to the first multiplier and a phase of 90 degrees. 2. The apparatus according to claim 1, wherein the second delayed AC signal is supplied to a second multiplier, and the AD converter further AD-converts a signal from the second low-pass filter and sends the signal to a temperature conversion unit. Ear hole thermometer. 6. The ear canal thermometer according to claim 1, wherein the drive frequency of the chopper means can be changed by an external control signal.