U.S. patent number RE34,507 [Application Number 07/873,502] was granted by the patent office on 1994-01-11 for radiation clinical thermometer.
This patent grant is currently assigned to Citizen Watch Co., Ltd.. Invention is credited to Shunji Egawa, Masato Yamada.
United States Patent |
RE34,507 |
Egawa , et al. |
January 11, 1994 |
Radiation clinical thermometer
Abstract
A radiation clinical thermometer includes a probe, a detection
signal processing section, a body temperature operating section,
and a display unit. A filter correction section for setting a
correction value based on the transmission wavelength
characteristics of a filter is arranged. The body temperature
operating section receives infrared data, temperature-sensitive
data, and the correction value from the filter correction section
so as to calculate body temperature data.
Inventors: |
Egawa; Shunji (Saitama,
JP), Yamada; Masato (Tokyo, JP) |
Assignee: |
Citizen Watch Co., Ltd. (Tokyo,
JP)
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Family
ID: |
27523790 |
Appl.
No.: |
07/873,502 |
Filed: |
April 23, 1992 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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605589 |
Oct 29, 1990 |
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Reissue of: |
335616 |
Apr 10, 1989 |
04932789 |
Jun 12, 1990 |
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Foreign Application Priority Data
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|
|
|
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Apr 12, 1988 [JP] |
|
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63-88194 |
Mar 17, 1989 [JP] |
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1-63552 |
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Current U.S.
Class: |
374/126; 374/128;
374/129; 374/130; 374/132; 374/133; 374/170; 600/474; 600/549 |
Current CPC
Class: |
G01J
5/02 (20130101); G01J 5/026 (20130101); G01J
5/04 (20130101); G01J 5/14 (20130101); G01J
5/049 (20130101); G01J 2005/068 (20130101); G01J
2001/4433 (20130101); G01J 2005/0048 (20130101) |
Current International
Class: |
G01J
5/00 (20060101); G01K 13/00 (20060101); G01J
5/06 (20060101); G01J 5/08 (20060101); G01J
1/44 (20060101); G01J 005/10 (); G01K 007/00 ();
G01K 001/20 () |
Field of
Search: |
;374/126,129,121,164,170,128,130,132,133,2 ;128/664,736 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
"Latest Trends in Temperature and Humidity Sensor", Sensor
Technique, Sep. 1987, pp. 74-79 (translation included)..
|
Primary Examiner: Cuchlinski, Jr.; William A.
Assistant Examiner: Gutierrez; Diego F. F.
Attorney, Agent or Firm: Townsend and Townsend Khourie and
Crew
Parent Case Text
.Iadd.
This is a continuation of application Ser. No. 07/605,589, filed
Oct. 29, 1990, now abandoned, which is a reissue of application
Ser. No. 07/335,616, filed Jul. 10, 1989, now U.S. Pat. No.
4,932,789. .Iaddend.
Claims
What is claimed is:
1. A radiation clinical thermometer comprising:
a probe including an optical system constituted by focusing means
for focusing infrared radiation from an object to be measured and a
filter having transmission wavelength characteristics, an infrared
sensor for converting infrared radiation energy into an electrical
signal, and a temperature-sensitive sensor for measuring a
temperature of said infrared sensor and an ambient temperature
thereof;
detection signal processing means for receiving electrical signals
from said infrared sensor and said temperature-sensitive sensor and
outputting the electrical signals as digital infrared data and
temperature-sensitive data, respectively;
body temperature operating means for calculating body temperature
data; and
a display unit for displaying a body temperature in accordance with
the body temperature data, including filter correcting means for
setting a correction value based on the transmission wavelength
characteristics of said filter, wherein said body temperature
operating means receives the infrared data, the
temperature-sensitive data, and the correction value from said
filter correcting means so as to calculate body temperature
data.
2. A thermometer according to claim 1, further comprising
sensitivity correction calculating means for receiving the
temperature-sensitive data and calculating sensitivity data of said
infrared sensor, and wherein said body temperature operating means
calculates the body temperature data by receiving the infrared
data, the temperature-sensitive data, the correction value from
said filter correcting means, and the sensitivity data from said
sensitivity correction calculating means.
3. A thermometer according to claim 2, wherein said sensitivity
correction calculating means calculates sensitivity data R
according to the following equation:
where T.sub.0 is sensitivity data of said temperature-sensitive
sensor, T.sub.m is a temperature at the time of sensitivity
adjustment, .alpha. is a sensitivity at the temperature T.sub.m,
and .beta. is a coefficient of variation of sensitivity.
4. A thermometer according to claim 1, wherein said filter
correcting means outputs a symmetrical axis, temperature correction
value which is used to change a symmetrical axis temperature of a
temperature-radiation energy characteristic curve represented by a
temperature equation of a higher degree approximated to a
temperature-radiation eneregy characteristic curve based on a
Stefan-Boltzmann law.
5. A thermometer according to claim 1, wherein said probe comprises
an optical guide for focusing infrared radiation energy, a filter
member arranged at one end of said optical guide, .[.an.]. infrared
sensor arranged at the other end of said optical guide, and .[.a.].
.Iadd.said .Iaddend.temperature-sensitive sensor arranged near said
infrared sensor, said optical guide, said filter member, said
infrared sensor, and said temperature-sensitive sensor being
coupled to each other by a metal housing having a high thermal
conductivity.
6. A thermometer according to claim 5, wherein said metal housing
is an integrally formed housing comprising a cylindrical portion in
which said optical guide is inserted and a base portion formed at
one end of said cylindrical portion and having a storage recess for
housing said infrared sensor and said temperature-sensitive sensor,
said optical guide being inserted and fixed in said cylindricl
portion, said infrared sensor and said temperature-sensitive sensor
being embedded in said storage recess of said base portion with a
.[.molding.]. .Iadd.sealing .Iaddend.resin.
7. A thermometer according to claim 5, further comprising a second
temperature-sensitive sensor for detecting a surface temperature of
said optical guide.
8. A thermometer according to claim 7, further comprising said
second temperature-sensitive sensor arranged on a surface of said
optical guide in tight contact therewith.
9. A thermometer according to claim 7, wherein said detection
signal processing section comprises an A/D converter for converting
an electrical signal from said second temperature-sensitive sensor
into second digital temperature-sensitive data, and said body
temperature operating means calculates the body temperature data by
using the second temperature-sensitive data as one of input
signals.
10. A thermometer according to claim 9, further comprising a
temperature difference detector for receiving the
temperature-sensitive data from said temperature-sensitive sensor
arranged at said base protion of said probe and the second
temperature-sensitive data from said second temperature-sensitive
sensor, and wherein said temperature difference detector outputs a
detection signal when a temperature difference is determined to be
smaller than a predetermined measurement limit temperature
difference.
11. A thermometer according to claim 10, wherein said display unit
comprises a measurement permission mark adapted to be illuminated
by the detection signal output from said temperature difference
detector.
12. A radiation clinical thermometer comprising:
a probe including an optical means for focusing infrared radiation
from an object to be measured, an infrared sensor for converting
infrared radiation energy into an electrical signal, and a
temperature-sensitive sensor for measuring a temperature of said
infrared sensor and an ambient temperature thereof;
detection signal processing means for receiving electrical signals
from said infrared sensor and said temperature-sensitive sensor and
outputting the electrical signals as digital infrared data and
temperature-sensitive data, respectively;
body temperature operating means for calculating body temperature
data, and
a display unit for displaying a body temperature in accordance with
the body temperature data, characterized by
a zero detector for receiving the infrared data output from said
detection signal processing means and determining presence/absence
of the infrared data, wherein said zero detector outputs a
detection signal when the infrared data is determined to be zero or
a small value.
13. A thermometer according to claim 12, further comprising a
storage case for storing said radiation clinical thermometer and a
reflecting plate arranged in said storage case at a position
corresponding to a probe end of said radiation clinical thermometer
stored in said storage case.
14. A thermometer according to claim 13, wherein said display unit
comprises a measurement permission mark adapted to be illuminated
by the detection signal output from said zero detector.
15. A radiation clinical theremometer comprising:
a probe including an optical means for focusing infrared radiation
from an object to be measured, an infrared sensor for converting
infrared radiation energy into an electrical signal, and a
temperature-sensitive sensor for measuring a temperature of said
infrared sensor and an ambient temperature thereof;
detection signal processing means for receiving electrical signals
from said infrared sensor and said temperature-sensitive sensor and
outputting the electrical signals as digital infrared data and
temperature-sensitive data, respectively;
body temperature operating means for calculating body temperature
data; and
a display unit for displaying a body temperature in accordance with
the body temperature data, wherein said detection signal processing
means includes a peak holding circuit for holding a peak value of
the electrical signal from said infrared sensor as analog data and
an A/D converter for converting a peak value voltage held in said
peak holding circuit into digital infrared data, and said body
temperature operating means calculates the body temperature data by
using the infrared data converted from the peak value voltage;
and
wherein said probe l .[.including.]. .Iadd.includes .Iaddend.a
filter having transmission wavelength characteristics and wherein
said display unit includes filter correcting means for setting a
correction value based on the transmission wavelength
characteristics of said filter, wherein said body temperature
operating means receives the infrared data, the
temperature-sensitive data, and the correction value from said
filter correcting means so as to calculate body temperature
data.
16. A thermometer according to claim 15 wherein said filter
correcting means outputs a symmetrical axis temperature correction
value which is used to change a symmetrical access temperature of a
temperature-radiation energy characteristic curve represented by a
temperature equation of a higher degree approximated to a
temperature-radiation energy characteristic curve based on
Stefan-Boltzmann law.
17. A thermometer according to claim 15 wherein said probe includes
a filter having transmission wavelength characteristics and wherein
said display unit includes filter correcting means for setting a
correction value based on the transmission wavelength
characteristics of said filter and further comprising sensitivity
correction calculating means for receiving the
temperature-sensitive data and calculating sensitive data of said
infra-red sensor and wherein said body temperature operating means
calculates the body temperature data by receiving the infra-red
data, the temperature-sensitive data, the correction value from
said filter correcting means, and the sensitivity data from said
sensitivity correction calculating means.
18. A thermometer according to claim 17, wherein said sensitivity
correction calculating means calculates sensitivity data R
according to the following equation:
where T.sub.0 is sensitivity data of said temperature-sensitive
sensor, T.sub.m is the temperature at the time of sensitivity
adjustment, .alpha. is a sensitivity at the temperature T.sub.m,
and .beta. is a coefficient of variation of sensitivity.
19. A thermometer according to claim 15, wherein said optical means
comprises an optical guide, a filter member arranged at one end of
said optical guide, said infrared sensor arranged at the other end
of said optical guide, .[.and.]. .Iadd.said .Iaddend.a
temperature-sensitive sensor arranged near said infrared sensor,
said optical guide, said filter member, said infrared sensor, and
said temperature-sensitive sensor being coupled to each other by a
metal housing having a high thermal conductivity.
20. A thermometer according to claim 19, wherein said metal housing
is an integrally formed housing comprising a cylindrical portion in
which said optical guide is inserted and a base portion formed at
one end of said cylindrical portion and having a storage recess for
housing said infrared sensor and said temperature-sensitive sensor,
said optical guide being inserted and fixed in said cylindrical
portion, said infrared sensor and said temperature-sensitive sensor
being embedded in said storage recess of said base portion with a
.[.molding.]. .Iadd.sealing .Iaddend.resin.
21. A thermometer according to claim 15, wherein said display unit
includes a zero detector for receiving the infrared data output
from said detection signal processing means and determining
presence/absence of the infrared data, wherein said zero detector
outputs a detection signal when the infrared data is determined to
a zero of a small value.
22. A thermometer according to claim 15, further comprising a
storage case for storing said radiation clinical thermometer and a
reflecting plate arranged in said storage case at a position
corresponding to a probe end of said radiation clinical thermometer
stored in said storage case.
23. A thermometer according to claim 22, wherein said display unit
comprises a zero detector and a measurement permission mark adapted
to be illuminated by detection signal output from said zero
detector.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a portable, compact radiation
clinical thermometer for measuring a temperature upon insertion in
an external ear canal.
2. Description of the Prior Art
Recently, a pen type electronic clinical thermometer has been
widely used in place of a glass clinical thermometer.
This electronic clinical thermometer is not fragile, can perform a
digital display which is easy to read, and can generate an alarm
sound such as a buzzer sound for signaling the end of temperature
measurement. However, this clinical thermometer requires about 5 to
10 minutes for temperature measurement, i.e., substantially the
same length of time as that required by a glass clinical
thermometer. This makes a user feel that body temperature
measurement is cumbersome. Such a long measurement time is based on
a method of inserting a sensor portion in an armpit or a mouth and
bringing it into contact with a portion to be measured. A
measurement time is prolonged due to the following two reasons:
(1) A skin temperature at an armpit or a mucous membrane
temperature in a mouth is not equal to a body temperature prior to
temperature measurement, and gradually reaches the body temperature
after the armpit or the mouth is closed.
(2) Since the sensor portion of the clinical thermometer has been
cooled down to an ambient temperature, when it is inserted in a
portion to be measured, the temperature of the portion is further
lowered.
Temperature measurement of a conventional clinical thermometer will
be described with refence to FIG. 1.
FIG. 1 shows temperature measurement curves of a contact type
electronic clinical temperature. In FIG. 1, temperature measurement
time is plotted along the axis of abscissa and measurement
temperatures are plotted along the axis of ordinate. A curve H
represents a temperature curve of an armpit as a portion to be
measured; and a curve M, a measurement temperature curve obtained
by the clinical thermometer. Accordingly, the skin temperature of
the armpit is 36.degree. C. or less at measurement start time
t.sub.1, and the temperature of a clinical thermometer sensor
portion is cooled to 30.degree. C. or less. When the sensor portion
is inserted in the armpit in this state, and the armpit is closed,
the measurement temperature represented by the curve M of the
sensor portion is quickly raised. However, the temperature
represented by the curve H of the armpit begins to rise gradually
toward an actual body temperature T.sub.b after it is cooled by the
sensor portion to a temperature at time t.sub.2. The two
temperature curves H and M coincidentally rise from time t.sub.3
when the sensor portion is warmed to the skin temperature of the
armpit. As described above, however, it takes about 5 to 10 minutes
for the curve to reach the actual body temperature. As is known, a
method of measuring a body temperature is performed in practice as
follows. Measurement is performed from time t.sub.1 at
predetermined intervals. The measurement values are compared with
each other, and maximum values are sequentially stored. At the same
time, a difference between the measurement values is sequentially
checked. The instant when the difference becomes smaller than a
predetermined value is set at time t.sub.4, and the temperature
measurement is stopped. Thus, the greatest value at this time is
displayed as a body temperature e.g., Japanese Patent Laid-Open
(Kokai) No. 50-31888).
In consideration of the above-described reasons (1) and (2),
conditions for performing body temperature measurement within a
short period of time are: selection of a portion having a body
temperature prior to measurement, and an actual measurement without
bringing a cooled sensor portion into contact with the portion to
be measured.
A drum membrane is, therefore, selected as a portion having a body
temperature prior to measurement, and a radiation clinical
thermometer is proposed as a clinical thermometer for measuring the
temperature of the portion in a nontact manner (e.g., U.S. Pat. No.
3,282,106).
The principle of a radiation thermometer on which the above
radiation clinical thermometer is based will be described
below.
A radiation thermometer is based on a law of physics, i.e., "all
objects emit infrared radiation from their surfaces, and the
infrared radiation amounts and the spectral characteristics of the
objects are determined by their absolute temperatures as well as
their properties and states of their finished surfaces." This law
will be described with reference to the following laws.
The Planck's law states a relationship between the radiant
intensity, spectral distribution, and temperature of a blackbody as
follows:
where
W (.lambda.,T): spectral radiant emittance [W/cm.sup.2. .mu.m]
T: absolute temperature of blackbody [K]
.lambda.: wavelength of radiation [.mu.m]
c: velocity of light.dbd.2.998.times.10.sup.10 [cm/sec]
h: Planck's constant.dbd.6.625.times.10.sup.-34 [W.sec.sup.2]
k: Boltzmann constant.dbd.1.380.times.10.sup.23 [W.sec/K]
FIG. 3 shows the Planck's law. As is apparent from FIG. 3, as the
temperature of the blackbody rises, the radiation energy is
increased. In addition, the radiation energy varies depending on
wavelengths. The peak value of the radiant emittance distribution
shifts to the short wavelength side with an increase in
temperature, and the radiation occurs over a wide wavelength
band.
Total energy radiated from the blackbody can be obtained by
integrating W(.lambda., T) given by equation (1) with respect to
.lambda. from .lambda..dbd.0 to .lambda..dbd..infin.. This is the
Stefan-Boltzmann law. ##EQU1##
W.sub.1 : total energy radiated from blackbody [W/cm.sup.2
].sigma.: Stefan-Boltzmann constant.dbd.5.673.times.10.sup.12
[W/cm.sup.2..deg.sup.4 ]
As is apparent from equation (2), the total radiation energy
W.sub.1 is proportional to a power of four of the absolute
temperature of the blackbody light source. Note that equation (2)
is obtained by integrating the infrared radiation emitted from the
blackbody with respect to all the wavelengths.
All the above-described laws are derived from the blackbody having
an emissivity of 1.00. In practice, however, most objects are not
ideal radiators, and hence have emissivities smaller than 1.00. For
this reason the value obtained by equation (2) must be corrected by
multiplying a proper emissivity. Radiation energy of most objects
other than the blackbody can be represented by equation (3):
##EQU2##
.epsilon.: emissivity of object
Equation (3) represents infrared energy which is radiated from an
object and incident on an infrared sensor. However, the infrared
sensor itself emits infrared radiation in accordance with the same
law described above. Therefore, if the temperature of the infrared
sensor itself is T.sub.0, its infrared radiation energy can be
given as .sigma.T.sub.0.sup.4, and energy W obtained by subtracting
radiation energy from incident energy is given by equation (4):
T.sub.a : ambient temperature of object
.gamma.: reflectance of object
Since the transmittance of the object to be measured can be
regarded as zero, .gamma..dbd.1-.epsilon. can be established.
In equation (4), the infrared sensor is considered to be ideal and
hence has an emissivity of 1.00.
In addition, assuming that the infrared sensor is left in an
atmosphere of an ambient temperature T.sub.a so that the infrared
sensor temperature T.sub.0 is equal to the ambient temperature
T.sub.a, equations (4) can be rewritten as equation (5):
##EQU3##
FIG. 2 shows a basic arrangement of a conventional radiation
thermometer. The arrangement will be described below with reference
to FIG. 2.
A radiation thermometer comprises an optical system 2, a detecting
section 3, an amplifying section 4, an operating section 5, and a
display unit 6.
The optical system 2 is constituted by a focusing means 2a for
efficiently focusing infrared radiation from an object L to be
measured, and a filter 2b having transmission wavelength
characteristics. A cylindrical member having an inner surface
plated with gold is used as the focusing means 2a. A silicon filter
is used as a filter 2b.
The detecting section 3 is constituted by an infrared sensor 3a and
a temperature-sensitive sensor 3b. The infrared sensor 3a converts
infrared radiation energy obtained by subtacting its own radiation
energy from incident infrared radiation energy focused by the
optical system 2 into an electrical signal, i.e., an infrared
voltage v.sub.s. In addition, the temperature-sensitive sensor 3b
is arranged near the infrared sensor 3a to measure the temperature
of the infrared sensor 3a and its ambient temperature T.sub.0, and
outputs a temperature-sensitive voltage v.sub.t. A thermopile and a
diode are respectively used as the infrared sensor 3a and the
temperature-sensitive sensor 3b.
The amplifying section 4 comprises an infrared amplifier 4a,
constituted by an amplifying circuit and an A/D converter for
converting an output voltage from the amplifying circuit into
digital infrared data V.sub.d, for amplifying the infrared voltage
v.sub.s output from the thermopile, and a temperature-sensitive
amplifier 4b, constituted by an amplifying circuit and an A/D
converter for converting an output voltage from the amplifying
circuit into digital temperature-sensitive data, for amplifying the
temperature-sensitive voltage v.sub.t as a forward-biased voltage
from the temperature-sensitive sensor 3b, i.e., the diode.
Two signals V.sub.d and T.sub.0 from the amplifying section 4 are
then converted into temperature data T, and are displayed on the
display unit 6. The operating section 5 comprises an emissivity
input means 5a for setting an emissivity .epsilon. of the object L,
and an operating circuit 5c for performing an operation based on
equation (5).
With the above-described arrangement, temperature measurement of
the object L can be performed by a noncontact scheme. An operation
of this temperature measurement will be described below.
The object L emits infrared radiation, and its wavelength spectrum
distribution covers a wide wavelength range, as shown in FIG. 3.
The infrared radiation is focused by the focusing means 2a,
transmitted through the filter 2b having the transmission
wavelength characteristics, and reaches the infrared sensor 3a.
Other infrared radiation energies reach the infrared sensor 3a. One
is infrared radiation energy emitted from a certain object near the
object L, which is reflected by the object L and is then
transmitted through the filter 2b and reaches the infrared
radiation energy. Another is infrared radiation energy emitted from
the infrared sensor 3a or a certain object near the sensor 3a,
which is reflected by the filter 2b and reaches the sensor 3a.
Still another is infrared radiation enengy which is emitted from
the filter 2b and reaches the sensor 3a.
The infrared radiation energy from the infrared sensor 3a can be
represented by equation (3). In this case, .epsilon..dbd.1.00. That
is, to measure the temperature of the infrared sensor 3a itself is
to indirectly measure the infrared radiation energy from the
infrared sensor 3a. For this purpose, the temperature-sensitive
sensor 3b is arranged near the infrared sensor 3a and measures the
temperature of the infrared sensor 3a and the ambient temperature
T.sub.0. The infrared sensor 3a converts the infrared radiation
energy W obtained by subtracting infrared radiation energy emitted
therefrom from infrared radiation energy incident thereon into an
electrical signal. Since the infrared sensor 3a employs a
thermopile, it outputs the infrared voltage v.sub.s proportional to
the infrared radiation energy W.
In this case, the infrared voltage v.sub.s as an output voltage
from the infrared sensor 3a corresponds to a value obtained by
multiplying the product of the infrared radiation energy W per unit
area and a light-receiving area S of the infrared sensor 3a by a
sensitivity R. The infrared data V.sub.d as an output voltage from
the infrared amplifier 4a corresponds to a value obtained by
multiplying the infrared voltage v.sub.s from the infrared sensor
3a by a gain A of the infrared amplifier 4a.
Since the above equations can be established, equation (5) can be
expressed as equation (6) as follows:
where
V.sub.d : output voltage from infrared amplifier 4a
S: light-receiving area of infrared sensor 3a
R: sensitivity of infrared sensor
A: gain of infrared amplifier 4a
Generally, equation (6) is simplified by setting K.sub.1
.dbd..sigma.SRA, and hence the temperature T of the object L is
calculated according to equation (7). ##EQU4##
A thermal infrared sensor used for a conventional radiation
thermometer has no wavelength dependency. However, a transmission
member such as a silicon or quarts filter is arranged as a window
member on the front surface of a can/package in which the infrared
sensor is mounted due to the following reason. Since infrared
radiation from an object has the wavelength spectrum distribution
shown in FIG. 3, such a filter is used to transmit only infrared
radiation having a main wavelength band therethrough so as to
reduce the influences of external light. Each of the
above-described transmission members has unique transmission
wavelength characteristics. A proper transmission member is
selected on the basis of the temperature of an object to be
measured, workability and cost of a transmission member and the
like.
FIG. 4 shows the transmittance of a silicon filter as one of the
transmission members. The silicon filter shown in FIG. 4 transmits
only infrared radiation having a wavelength band from about 1 to 18
[.mu.m] therethrough, and has a transmittance of about 54%.
As described above, an infrared sensor with a filter has wavelength
dependency, i.e., transmits infrared radiation having a specific
wavelength band because of the filter as a window member although
the sensor itself is a temperature sensor and has no wavelength
dependency.
Therefore, equation (5) obtained by integrating infrared radiation
energy incident on the infrared sensor with a filter with respect
to all the wavelengths cannot be applied to the infrared sensor
with a filter for transmitting infrared radiation having a specific
wavelength band, and an error is included accordingly.
Furthermore, in the conventional arrangement, the sensitivity R of
the infrared sensor is used as a constant. In practice, however,
the sensitivity R of the infrared sensor varies depending on the
infrared sensor temperature T.sub.0. FIG. 5 shows this state. In
FIG. 5, the sensitivity R is obtained by actually measuring the
output voltage v.sub.s from a thermopile as an infrared sensor by
using a blackbody, and the infrared sensor temperature T.sub.0 is
changed to plot changes in sensitivity R at the respective
temperatures. As a result, it is found that the temperature
dependency of the sensitivity R can be approximated to a straight
line as represented by equation (8):
where a is the sensitivity R as a reference when T.sub.0
.dbd.T.sub.m,, T.sub.m is a representative infrared sensor
temperature, e.g., an infrared sensor temperature measured in a
factory, and .beta. represents a coefficient of variation, In this
case, a coefficient of variability per 1 [deg] is -0.3 [%/deg]. The
variation in sensitivity R described above inevitably becomes an
error.
The coefficient of variation .beta. is influenced by the
manufacturing conditions of a thermopile, and can be decreased by
increasing the purity and process precision of the thermopile.
However, thermopiles on the market which are mass-produced have the
above value.
A radiation thermometer, however, is normally designed to measure
high temperatures, and has a measurement range from about 0.degree.
to 300.degree. C. and measurement precision of about .+-.2.degree.
to 3.degree. C. Therefore, errors due to the above-described filter
characteristics, variations in sensitivity of an infrared sensor,
and the like are neglected, and hence no countermeasure has been
taken so far. When measurement conditions as a clinical thermometer
are taken into consideration, however, a temperature measurement
range may be set to be as small as about 33.degree. C. to
43.degree. C., but .+-.0.1.degree. C. is required for temperature
measurement precision. Therefore, if the above-described radiation
thermometer is used as a clincial thermometer, temperature
measurement precision must be increased by taking countermeasures
against errors due to the filter characteristics and the variations
in sensitivity of infrared radiation.
A radiation clinical thermometer disclosed in U.S. Pat. No.
4,602,642 employs the following system as a countermeasure.
This radiation clinical thermometer comprises three units, i.e., a
probe unit having an infrared sensor, a chopper unit having a
target, and a charging unit. In addition, a heating control means
for preheating the infrared sensor and the target to a reference
temperature (36.5.degree. C.) of the external ear canal is
provided, and is driven by charged energy from the charging unit.
When a body temperature is to measured, the probe unit is set in
the chopper unit, and the probe unit having the infrared sensor and
the target are preheated by the heating control means. In this
state, calibration is performed. Thereafter, the probe unit is
detached from the chopper unit and is inserted in an external ear
canal to detect infrared radiation from a drum membrane. A body
temperature measurement is performed by comparing the detected
infrared radiation with that from the target.
Temperature measurement precision is increased by the
above-described system for the reasons to be described below.
According to this system, various error factors are eliminated by
preheating the probe unit having the infrared sensor and the target
to a reference temperature (36.5.degree. C.) close to a normal body
temperature by using the heating control means. That is, by heating
the probe to the reference temperature higher than a room
temperature and keeping the infrared sensor at a constant
temperature regardless of ambient temperatures, sensitivity
variations of the infrared sensor can be eliminated, and hence its
error can be neglected. In addition, calibration is performed so as
to set the reference temperature of the target to be close to a
body temperature to be measured, and a comparative measurement is
then performed so that errors and the like due to the filter
characteristics are reduced to a negligible level. Furthermore,
since the probe is preheated to a temperature close to a body
temperature, the problem of the conventional measurement system can
be solved, i.e., the problem that when a cool probe is inserted in
an external ear canal, the temperatures of the external ear canal
and the drum membrane are lowered because of the probe, so that
correct body temperature measurement cannot be performed.
The above-described radiation clinical thermometer disclosed in
U.S. Pat. No. 4,602,642 is excellent in temperature measurement
precision. However, since this therometer requires a heating
control unit with high control precision, its structure and circuit
arrangement become complicated, thereby increasing the cost. In
addition, it requires a long stable period to preheat the probe and
the target and control their temperatures to a predetermined
temperature. Moreover, since the heating control unit is driven by
a relatively large-power energy, a large charging unit having a
power source cord is required. Therefore, the above-described
system cannot be applied to a portable clinical thermometer using a
small battery as an energy source.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a portable,
compact radition clinical thermometer at low cost while high
temperature measurement precision is maintained by solving the
above-described problems.
According to an aspect of the present invention, a filter
correcting means outputs a correction value based on the
transmission wavelength characteristics of a filter so that a body
temperature is calculated on the basis of infrared data,
temperature-sensitive data, and the filter correction value.
According to another aspect of the present invention, a body
temperature is calculated on the basis of infrared data,
temperature-sensitive data, a filter correction value, sensitivity
data input from a sensitivity data input means.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a graph showing temperature measurement curves of a
conventional electronic clinical thermometer;
FIG. 2 is a block diagram showing a circuit arrangement of the
conventional electronic thermometer;
FIG. 3 is a graph showing changes in intensity of an infrared
wavelength spectrum depending on the temperature of an object;
FIG. 4 is a graph showing the transmission wavelength
characteristics of a silicon filter;
FIG. 5 is a graph showing the sensitivity characteristics of an
infrared sensor;
FIG. 6 is block diagram showing a circuit arrangement of an
electronic clinical thermometer according to an embodiment of the
present invention;
FIG. 7 is a graph of temperature characteristics for explaining an
approximate expression of temperature measurement by the
conventional electronic theremometer;
FIG. 8 is a plan view of an electronic thermometer of the present
invention;
FIG 9 is a side view of the electronic thermometer in FIG. 8;
FIG. 10 is a sectional view showing an internal structure of a
temperature measuring section of the electronic clinical
thermometer in FIG. 8;
FIG. 11 is an enlarged sectional view showing part of the
temperature measuring section of the electronic clinical
thermometer;
FIG. 12 a side view showing a state wherein the electronic clinical
thermometer is stored in a storage case;
FIG. 13 is a view showing a state wherein the temperature measuring
section of the electronic clinical thermometer is inserted in an
external ear canal;
FIG 14 is a block diagram showing a circuit arrangement of an
electronic clinical thermometer according to a second embodiment of
the present invention;
FIG. 15 is a flow chart for explaining a body temperature
calculating operation in the embodiment shown in FIG. 14;
FIG. 16 is a graph showing a temperature measurement curve of the
electronic clinical thermometer of the present invention;
FIG. 17 is a circuit diagram of a peak hold circuit in the
embodiment shown in FIG. 14;
FIG. 18 is a sectional view showing an internal structure of a
temperature measuring section of an electronic clinical thermometer
according to a third embodiment of the present invention;
FIG. 19 is a block diagram showing a circuit arrangement of the
electronic clinical thermometer according to the third embodiment
of the present invention; and
FIG. 20 is a sectional view showing an internal structure of a
modification of the temperature measuring section of the electronic
clinical thermometer according to the third embodiment of the
present invention shown in FIG. 18.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will be described below with reference to the
accompanying drawings.
FIG. 6 is a block diagram showing a basic circuit arrangement of a
radiation clinical thermometer according to a first embodiment of
the present invention.
In this embodiment, variations in sensitivity R are reduced to a
negligible level by using a thermopile manufactured under good
manufacturing conditions so as to correct filter
characteristics.
The same reference numerals in FIG. 6 denote the same parts as in
FIG. 2, and a description thereof will be omitted.
The radiation clinical thermometer of this embodiment differs from
that shown in FIG. 2 in measurement of the temperature of the drum
membrane of an ear as an object to be measured and the arrangement
of an operation section 5.
The operation section 5 of a radiation clinical thermometer 70
comprises an emissivity input means 5a for setting an emissivity
.epsilon. of an object L to be measured, a filter correction means
5b for setting transmission wavelength characteristics of a filter
2b, and a body temperature operating circuit 5c.
The operating section 5 of this embodiment, therefore, calculates a
measurement body temperature T.sub.b on the basis of an emissivity
set value from the emissivity input means and a filter correction
value from the filter correcting means 5b.
An equation for temperature calculation with consideration of the
wavelength dependency of an infrared sensor with a filter will be
described below.
As described above, the infrared sensor 3a converts the infrared
radiation energy W obtained by subtracting radiation energy from
incidence energy into the infrared voltage v.sub.s. The energy W
can be given by equation (9): ##EQU5## where .eta.(.lambda.) is the
transmittance of the filter.
The first term of equation (9) represents infrared radiation energy
emitted from the object L having the emissivity .epsilon. which is
transmitted through the filter 2b and reaches the sensor 3a. The
second term represents infrared radiation energy emitted from
emitted from an object located near the object L and having the
temperature T.sub.0, which is transmitted through the filter 2b and
reaches the sensor 3a. The third term represents infrared radiation
energy emitted from the infrared sensor 3a having the temperature
T.sub.0 or an object located near the sensor 3a, which is reflected
by the filter 2b and reaches the sensor 3a, or infrared radiation
energy which is emitted from the filter 2b having the temperature
T.sub.0 and reaches the sensor 3a. In this case, the sum of the
transmittance, reflectance, and emissivity of the transmission
member is equal to one. The third term is established in
consideration of the reflection or radiation by the filter 2b. Note
that the infrared radiation from the infrared sensor 3a is
reflected by the filter 2b. The fourth term represents infrared
radiation energy from the infrared sensor 3a itself having the
temperature T.sub.0, and a sign of this term is negative.
Equation (9) can be rewritten to equation (10) as follows:
##EQU6##
It is found, therefore, that the infrared radiation energy obtained
by subtracting radiation energy from incident energy of the
infrared sensor 3a having the filter 2b does not correspond to "a
value proportional to the difference between a power of four of the
absolute temperature and that of the temperature of the sensor
itself" as represented by equation (5), but must be given by an
equation based on the transmission wavelength characteristics of
the filter 2b as represented by equation (10). That is, a new
equation must be established in place of the Stefan-Boltzmann law
represented by equation (2).
If infrared radiation energy emitted from the blackbody having the
absolute temperature T, which is transmitted through a filter
having a transmittance .eta.(.lambda.) is set to be F(T),F(T) can
be represented by equation (11) as follows: ##EQU7##
In this case, assuming that the absolute temperature T has a
temperature range from T.sub.min to T.sub.max, the infrared
radiation energy F(T) is calculated with respect arbitrary absolute
temperatures T.sub.1, T.sub.2, T.sub.3, . . . , T.sub.n according
to equation (11). The calculation results are summarized in Table
1.
TABLE 1 ______________________________________ T F(T)
______________________________________ T.sub.1 F(T.sub.1) T.sub.2
F(T.sub.2) T.sub.3 F(T.sub.3) . . . . . . T.sub.n F(T.sub.n)
______________________________________
It is, therefore, seen how the relationship between the absolute
temperature T and the infrared radiation energy F(T) transmitted
through the filter is associated with the Stefan-Boltzmann law.
FIG. 7 is a graph for explaining the examination process. The
process will be described below with reference to FIG. 7.
In this graph, absolute temperatures [K] are plotted along the axis
of abscissa and radiation energies [W/cm.sup.2 ] are plotted along
the axis of ordinate. Referring to FIG. 7, a curve A is a
characteristic curve based on equation (2) representing the
Stefan-Boltzmann law, and a curve B is a characteristic curve based
on the present invention considering the filter
characteristics.
The curve B is obtained such that a curve B' is prepared by
connecting points respectively representing radiation energies at
the absolute temperatures T.sub.1 to T.sub.n shown in Table 1. and
the curve A is modified and moved to overlap the curve B'. Types of
modification and movement of the curve A' are determined by
selecting a coefficient a of a term of degree 4 of the curve A, a
displacement b in the direction of the abscissa axis, and a
displacement c in the direction of the ordinate axis so as to
overlap the curve A and the curve B'.
As a result, equation (11) is approximated to equation (12) by
using the three types of set values a, b, and c.
Subsequently, proper values a, b, and c in equation (12) are
obtained from the values shown in Table 1 by a method of least
squares or the like. Substitutions of these values into equation
(12) yield an approximate equation.
The set values a, b, and c will be described below in comparison
with equation (2) representing the Stefan-Boltzmann law.
The set value a is a coefficient of the absolute temperature T of
degree 4, and corresponds to the Stefan-Boltzmann constant .sigma.
of the curve A. The value a takes a unit value of [W/cm.sup.2
deg.sup.4 ]. The set value b represents a symmetrical axis
temperature. In the curve A, an absolute temperature 0 [K] is set
to a symmetrical axis, whereas in the curve B, an absolute
temperature b [K] is set to be a symmetrical axis.
The set value c represents a minimum value. In the curve A, 0
[W/cm.sup.2 ] is set to be an offset, whereas in the curve B, c
[W/cm.sup.2 ] is set to be an offset.
If equation (10) is rewritten by using equation (12), equation (13)
is established as follows: ##EQU8##
As is apparent from equation (13), the minimum value c is
canceled.
In this case, the infrared data V.sub.d based on infrared radiation
emitted from the drum membrane is obtained from the light-receiving
area S and the sensitivity R of the infrared sensor 3a and the gain
A of the infrared amplifier 4a by setting K.sub.2
.dbd.aSRA.Equation (13) is then rewritten as equation (14). The
body temperature T.sub.b through the drum membrane is calculated by
using equation (15) on the basis of equation (14). ##EQU9##
That is, when a filter having transmission wavelength
characteristics is used for an optical system member, a temperature
calculation is not performed on the basis of the law "infrared
radiation energy is proportional to a power of four of the absolute
temperature T", but must be based on equation (14) representing the
law "Infrared radiation energy is proportional to a power of four
of (the absolute temperature T- the symmetrical axis temperature
b)."
As a result, the filter correcting means 5b shown in FIG. 6 outputs
the symmetrical axis temperature b, and the operating circuit 5c
calculates the body temperature T.sub.b of the object L to be
measured, i.e., the drum membrane on the basis of equation
(15).
An approximate expression in consideration of a silicon filter used
as the filter 2b in practice will be described below.
FIG. 4 shows the transmission wavelength characteristics of the
silicon filter. However, in order to simplify a calculation, the
transmission wavelength band of the silicon filter is set to be 1
to 18 [.mu.m], and its transmittance is set to be 54%.
##EQU10##
Equation (1) is substituted into W(.lambda., T).
Since a measurement environment, i.e., the measurement temperature
range of the object to be measured is set between 0 [.degree.C.]
and 50 [.degree.C.]. T.sub.min and T.sub.max are respectively
set to be 273 [K] and 323 [K]. Table 2 shows the calculation
results of equation (16).
The values a, b, and c when equation (12) is approximated by using
the data shown in Table 2 are obtained by a method of least
squares:
a.dbd.4.101.times.10.sup.-12 [W/cm.sup.2.deg.sup.4 ]
b.dbd.45.96[K]
c.dbd.-6.144.times.10.sup.4 [W/cm.sup.2 ]
The coefficient a of a term of degree 4 and the symmetrical axis b
thus obtained represent the transmission wavelength characteristics
of the silicon filter. These values a and b are output from the
filter correcting means 5b. The filter correcting means 5b is part
of an operating program memory of the operating section 5, in which
coefficient a of the term of degree 4 and the symmetrical axis
temperature b are written.
TABLE 2 ______________________________________ T f(T) .times. T
f(T) .times. [K] 10.sup.-3 [W/cm.sup.2 ] [K] 10.sup.-3 [W/cm.sup.2
] ______________________________________ 273 10.290 299 16.208 275
10.679 301 16.746 277 11.078 303 17.298 279 11.487 305 17.862 281
11.908 307 18.439 283 12.339 309 19.030 285 12.782 311 19.634 287
13.236 313 20.252 289 13.701 315 20.884 291 14.178 317 21.530 293
14.667 319 22.191 295 15.169 321 22.865 297 15.682 323 23.555
______________________________________
When a silicon filter is used as a window member for measurement of
an infrared sensor, the temperature T of an object to be measured
is not calculated by equation (5), but is calculated by equation
(14), thereby performing temperature calculations with high
precision.
As is apparent from the above description, according to this
embodiment, even if a transmission member having transmission
wavelength characteristics is used as a window member of an
infrared sensor, temperature measurement of an object to be
measured can be performed with high precision.
In addition, even if the material of the transmission member as a
window member of the infrared sensor is changed, temperature
measurement can be performed with high precision by updating the
value of the filter correcting means 5b as part of the program
memory.
In the above embodiment, an approximate expression having a term of
degree 4 as represented by equation (12) is used as a new equation
replacing the Stefan-Boltzmann law. However, as shown in FIG. 13,
in body temperature measurement, only a portion of the temperature
measurement curve is used as a measurement range such as the range
from T.sub.min ti T.sub.max . Therefore, an approximate expression
having a term of degree 4 need not be used. Satisfactory precision
of a clinical thermometer can be obtained by using an approximate
expression with a proper degree. For example, expression (14) can
be employed as an approximate equation having a term of degree
2:
A detailed arraangement of a radiation clinical thermometer which
is actually manufctured by using a commercially available
thermopile manufactured in consideration of mass production will be
described below as a second embodiment of the present
invention.
FIGS. 8 and 9 are bottom and side views, respectively, showing a
radiation clinical thermometer according to the second embodiment
of the present invention. Reference numberal 1 denotes a radiation
clinical; thermometer comprising a main body portion 10 and a head
portion 11. The display unit 6 for displaying a body measurement is
arranged on the lower surface of the main body portion 10. A check
button 12 having a push button structure is formed on the upper
surface of the portion 11. A power switch 13 having a slide
structure and major buttons 14 and 15 each having a push button
structure are respectively formed on the side surfaces of the
portion 11.
The head portion 11 extend from the end of the main body portion 10
in the form of an L shape. The end of the head portion 11
constitutes a probe 16. The probe 16 comprises an optical system 2
and a detecting section 3 shown in FIG. 6.
The radiation clinical theremometer 1 is operated as follows. A
check operation (to be described later) is performed while the
power switch is ON. Thereafter, while the probe 16 is inserted in
an external ear canal of a patient to be examined, either or both
of the major switches 14 and 15 is/are depressed, thereby
instantaneously completing body temperature measurement. The
measurement result is displayed on the display unit 6 as a body
temperature.
FIG. 10 is a sectional view of the head portion 11. Each of case
members 17 and 18 consists of a resin molded member having a very
low thermal conductivity. A portion of the case 17 covering the
probe 16 constitutes a cylindrical member 17a, in which a metal
housing 19 consisting of a lightweight metal having a high thermal
conductivity such as aluminum is fitted. The metal housisng 19
.Iadd.is integrally formed and .Iaddend.comprises a cylindrical
portion 19a and a base portion 19d having a hollow portion 19b
communicating with the cylindrical portion 19a and a recess 19c in
which a temperature-sensitive element is embedded. In addition, a
step portion 19e for attachment of a filter is formed at the distal
end of the cylindrical portion 19a. An optical guide 20 consisting
of a brass (Bu) pipe having an inner surface plated with gold (Au)
is fitted in the cylindrical portion 19a. A filter member in the
form of a dust-proof hard cap 21 selectively allowing infrared
radiation to pass therethrough is fixed to the step portion 19e. In
addition, a thermopile as the infrared sensor 3a and the
temperature-sensitive sensor 3b are respectively embedded in the
hollow portion 19b and the recess 19c of the base portion 19d by
sealing resins 22 and 23. The infrared sensor 3a and the
temperature-sensitive sensor 3b are respectively connected to
wiring patterns of a circuit board 26 through leads 24 and 25, and
are led to amplifying circuits to be described later.
According to the above-described arrangement, since the infrared
sensor 3a, the optical guide 20, and the hard cap 21 are connected
to each other through the metal housing 19 having a high thermal
conductivity, they can always be kept in a thermal equilibrium
state. This uniform-temperature is detected by the
temperature-sensitive sensor 3b. Reference numeral 28 denotes a
temperature measurement cover which is detachably fitted on the
probe 16 and is constituted by a resin having a low thermal
conductivity. A distal end portion 28a of the cover 28 consists of
a material through which infrared radiation can be transmitted.
FIG. 11 is an enlarged sectional view of the distal end portion of
the probe 16. The distal end portion 28a of the cover 28 covers the
distal end portion of the probe 16 so as to prevent contact of the
probe 16 with the inner wall of the external ear canal.
FIG. 12 is a side view showing a state wherein the radiation
clinical thermometer 1 is stored in a storage case 30. The storage
case 30 comprises a mounting portion 30a for mounting the main body
portion 10, and a storage portion 30b for storing the probe 16. A
reflecting plate 31 is fixed to a bottom surface 30c of the storage
portion 30b at a position corresponding to the distal end portion
of the probe 16. In addition, a button depressing portion 30d is
formed on the storage case 30 at a position corresponding the check
button 12. The storage case 30 is used to perform an operation
check of the radiation clinical thermometer 1. When the thermometer
1 is set in the storage case 30 with the power switch 13 being
turned on as shown in FIG. 12, the distal end portion of the probe
16 is set on the reflecting plate 31, and at the same time, the
check buttom 12 is depressed by the button depressing portion 30d.
This state is a function check state to be described later. In this
state, a user can know from a display state of the display unit 6
whether body temperature measurement can be performed.
FIG. 13 is a sectional view of an ear, showing a state wherein a
body temperature measurement is performed by the radiation clinical
thermometer 1. Reference numeral 40 denotes a canal; 41, external
ear canal; and 42, a drum membrane. A large number of downy hairs
are grown from the inner wall of the external ear canal 41. Earwax
is sometimes formed on the inner wall of the external ear canal 41.
When the distal end portion of the probe 16 of the radiation
clinical thermometer 1 is inserted in the external ear canal 41,
and the major buttons 14 and 15 are depressed with the distal end
portion directed to the drum membrane 42 as shown in FIG. 13, a
body temperature measurement can be instantaneously performed.
FIG. 14 is a block diagram of the radiation clinical thermometer 1
in FIG. 8. The same reference numerals in FIG. 14 denote the same
parts as in FIG. 6, and a description thereof will be omitted.
Portions different from FIG. 6 will be described below. Reference
numeral 50 denotes a detection signal porocessing section. FIG. 14
shows a detailed arrangement of the section 50 corresponding to the
amplifying section 4 shown in FIG. 6. More specifically, the
section 50 comprises an infrared amplifying circuit 51 for
amplifying an infrared voltage v.sub.s output from the infrared
sensor 3a, a temperature-sensitive amplifying circuit 52 for
amplifying a temperatuyre-sensitive voltage v.sub.t output from the
temperature-sensitive sensor 3b, a peak hold circuit 53 for holding
a peak value of an output voltage V.sub.s from the infrared
amplifying circuit 51, a switching circuit 54 for receiving the
output voltage V.sub.s from the infrared amplifying circuit 51 and
an output voltage V.sub.sp from the peak hold circuit 53 at input
terminals I.sub.1 and I.sub.2, respectively, and selectively
outputting them from an output terminal O in accodance with
conditions provided from a control terminal C, an A/D converter 55
for converting the infrared voltages V.sub.s or V.sub.sp output
from the switching circuit 54 into digital infrared date V.sub.d,
and an A/D converter 55 for converting the output voltage V.sub.t
from the temperature-sensitive amplifying circuit 52 into digital
temperature-sensitive data T.sub.0. With this arrangement, the
section 50 converts the infrared voltage v.sub.s and the
temperature-sensitive voltage v.sub.t supplied from the detecting
section 3 into the digital infrared data V.sub.d and
temperature-sensitive data T.sub.0, and outputs them.
An operating section 60 corresponds to the operating section 5
shown in FIG. 6, and comprises an emissivity input means 5a, a
filter correcting means 5b, a body temperature operating circuit 61
corresponding to the operating circuit 5c, a display driver 62 for
receiving a body temperature data T.sub.b1 calculated by the
operation circuit 61 and displaying it on a body temperature
display portion 6a of a display unit 6, a zero detector 63 for
receiving the infrared data V.sub.d output from the detection
signal processing section 50 and outputting a detection signal
S.sub.0 when the infrared data V.sub.d is detected to be zero so as
to illuminate a measurement permission mark 6b of the display unit
6, a sensitivity correcting calculator 64 for receiving the
temperature-sensitive data T.sub.0 output from the section 50,
calculating a sensitivity R in accordance with equation (8) shown
in FIG. 5, and outputting it, and a sensitivity data input means 65
for outputting as sensitivity data D a value which is externally
input/set on the basis of the light-receiving area S of the
infrared sensor 3a and the gain A of the infrared amplifying
circuit 51 shown in equation (6).
Reference numeral 90 denotes a switch circuit to which a major
switch SW.sub.m operated by the major switches 14 and 15 shown in
FIG. 8 and a check switch SW.sub.c operated by the check button 12
are connected. When either of the major buttons 14 and 15 is
depressed, the major switch SW.sub.m is turned on, and a major
signal S.sub.m is output from a terminal M.
When the radiation clinical thermometer 1 is set in the storage
case 30 as shown in FIG. 12, the check button 12 is depressed, and
the check switch SW.sub.e is turned on. As a result, a check signal
S.sub.c is output from a terminal C.
The major signal S.sub.m output from the terminal M of the switch
circuit 90 is supplied to enable terminals E of the body
termperature operating circuit 61 and the sensitivity correcting
calculator 64. As a result, both the circuit 61 and the calculator
64 are set in an operative mode, and at the same time, the zero
detector 63 is reset. The check signal S.sub.c output from the
terminal C of the switch circuit 90 is supplied to an enable
terminal E of the zero detector 63, the control terminal C of the
switching circuit 54, and a reset terminal R of the peak hold
circuit 53.
An operation of the radiation clinical thermometer 1 having the
above-described arrangement will be described below.
In an initial state wherein the power switch 13 of the radiation
clinical thermometer 1 shown in FIG. 8 is turned on, since both the
check switch SW.sub.c and the major switch SW.sub.m are kept off,
the check signal S.sub.c and the major signal S.sub.m are not
output from the switch circuit 70.
Consequently, in the operation section 60, the body temperature
operating circuit 61 and the sensitivity correcting calculator 64
are set in a non-calculation mode, and the zero detector 63 is set
in an inoperative mode. In addition, the switching circuit 54 of
the detection signal processing section 50 selectively outputs the
voltage V.sub.sp input to the terminal I.sub.2 to the output
terminal O. The reset state of the peak hold circuit 53 is released
and is set in an operative state.
The initial state is established in this manner. A function check
mode will be described next.
When the thermometer 1 is set in the storage case 30 as shown in
FIG. 12, the check button 12 is urged against the button depressing
portion 30d of the storage case 50. As a result, the check switch
SW.sub.c shown in FIG. 14 is turned on, and at the same time, the
distal end portion of the probe 16 is set at the position of the
reflecting plate 31.
Consequently, the switch circuit 90 outputs the check signal
S.sub.c from terminal C when the check switch SW.sub.c is turned
on, and supplies it to the peak hold circuit 53, the switching
circuit 54, and the zero detector 63. Upon reception of the check
signal S.sub.c, in the detection signal processing section 50, the
peak hold circuit 53 is reset, and at the same time, the switching
circuit 54 is switched to a state wherein the voltage V.sub.s
supplied to the input terminal I.sub.1 is selectively output to the
output terminal O. Subsequently, the A/D converter 55 converts the
infrared voltage V.sub.s into a digital value and outputs it as the
infrared data V.sub.d. In the operation section 60, the body
temperature operating circuit 61 and the sensitivity correcting
calculator 64 are set in an inoperative mode, and only the zero
detector 63 is set in an operative state. The state of each portion
in the function check mode has been described so far. The radiation
clinical thermometer 1 in this function check mode is operated as
follows. The infrared data V.sub.d obtained by converting infrared
radiation reflected by the reflecting plate 31 into a digital value
by using the infrared sensor 3a, the infrared amplifying circuit
51, the switching circuit 54, and the A/D converter 55 is
determined by the zero detector 63. If this infrared data V.sub.d
is zero, the zero detector 63 outputs the detection signal S.sub.0
from the output terminal O so as to illuminate the measurement
permission mark 6b of the display unit 6.
The contents of the function check mode will be described
below.
Referring to FIG. 10, as described above, since the infrared sensor
3a, the optical guide 20, and the hard cap 21 are connected to each
other through the metal housing 19 having a high thermal
conductivity, thermal equilibrium of these components can be
obtained. The above-described function check mode is a mode for
confirming that the thermal equilibrium is satisfactorily obtained.
More specifically, infrared radiation energies emitted from the
optical guide 20 and the hard cap 21 each having the temperature T
are reflected by the reflecting plate 31, and are incident on the
infrared sensor 3a. In addition infrared radiation energy is
emitted from the infrared sensor 3a having the temperature T.sub.0.
The energy W obtained by subtracting the emitted energy from the
incident energy is given by equation (5) as described above:
W.dbd..epsilon..sigma.(T.sub.4 -T.sub.0.sup.4)
If T.dbd.T.sub.0, the energy W is not present. Hence, all the
voltages v.sub.s and V.sub.s, and the infrared data V.sub.d are set
to zero, and the detection signal S.sub.0 is output from the zero
detector 63. That is, the measurement ready permission mark 6b is
illuminated to confirm that the heat source causing noise is
present near the optical system 2, and hence body temperature
measurement can be performed. Note that the zero detector 63
determines the infrared data V.sub.d as a digital value. A
determination value need not be strictly zero. The zero detector 63
outputs the detection signal S.sub.0 if the infrared date V.sub.d
is smaller than a predetermined determination value. In this case,
even if the determined value is not zero, it is regraded as
negligible. If T.noteq.T.sub.0 according to equation 5, i.e., if
there is a temperature difference among the infrared sensor 3a, the
optical guide 20, and the hard cap 21, the differential energy W is
present. Therefore, the infrared data V.sub.d becomes larger than
the determination level of the zero detector 63. As a result, the
detection signal S.sub.0 is not output, and the measurement
permission mark 6b is not illuminated.
In actual use of the radiation clinical thermometer 1, the state of
T.noteq.T.sub.0 occurs as follows.
When the environmental temperature in use of the radiation clinical
thermometer 1 is abruptly changed, the above state occurs. In this
case, T.noteq.T.sub.0 occurs due to differences in heat capacity
and response characteristics of the respective elements. Since a
measurement error corresponding to the value of the infrared data
V.sub.d based on the differential energy W occurs, the thermometer
1 is set in a measurement disable state. In this state, if the
thermometer 1 is left in a constant environmental temperature for a
while, the respective elements are stabilized in a thermal
equilibrium state upon thermal conduction through the metal housing
19, and the thermometer 1 is set in a measurement permission state.
However, it may takes several tens of minutes to established such a
stable state.
The function check mode has been described so far. A body
temperature measurement mode will be described next.
The radiation clinical thermometer 1 is detached from the storage
case 30 after illumination of the measurement permission mark 6b is
confirmed in the above-described function check mode. When the
thermometer 1 is detached from the case, depression of the check
button 12 is released, so that the check switch SW.sub.c is turned
off, and output of the check signal S.sub.c from the terminal C of
the switch circuit 90 is stopped. As a result, the reset state of
the peak hold circuit 53 is released. At the same time, the
switching circuit 54 is returned to the selection state for the
input terminal I.sub.2, and the zero detector 63 is returned to the
inoperative state.
Consequently, in the detection signal processing circuit 50, the
peak voltage V.sub.sp of the infrared voltage V.sub.s output from
the infrared amplifying section 51, which is held by the peak hold
circuit 53, is supplied to the A/D converter 55 through the
switching circuit 54, thereby outputting the digital infrared data
V.sub.d converted from the peak voltage V.sub.sp.
Although the zero detector 63 of the operating section 60 is
returned to the inoperative state, the measurement permission mark
6b of the display unit 6 is kept illuminated because the detection
signal S.sub.0 is held by a storage circuit arranged in the zero
detector 63. Since the major signal S.sub.m is supplied to the
reset terminal R, the detection signal S.sub.0 if the zero detector
63 is maintained until the storage circuit is reset.
In this manner, the apparatus is prepared for measurement. When the
major buttons 14 and 15 are depressed after the radiation clinical
thermometer 1 is inserted in the external ear canal 41 in this
state as shown in FIG. 13, a body temperature measurement is
performed. More specifically, when the major buttons 14 and 15 are
depressed, the major switch SW.sub.m shown in FIG. 14 is turned on,
and the major signal S.sub.m is output from the terminal M of the
switch circuit 90. As a result, in the operation section 60, the
body temperature operating circuit 61 and the sensitivity
correcting calculator 64 are set in an operative mode, and at the
same time, the zero detector 63 is reset to turn off the
measurement permission mark 66 of the display unit 6. Infrared
radiation energy which is emitted from the drum membrane 42 and is
incident on the the probe 16 (the optical system 2 and the
detection section 3 in FIG. 14) inserted in the external ear canal
41 is converted into the infrared voltage v.sub.s by the infrared
sensor 3a, and is amplified to the voltage V.sub.s by the infrared
amplifying circuit 51. Thereafter, the peak voltage V.sub.sp is
held by the peak hold circuit 53. The peak voltage V.sub.sp is
converted into the infrared data V.sub.d by the A/D converter 55,
and is supplied to the operating section 60. In addition, the
temperature-sensitive sensor 36 embedded in the metal housing 19
detects the temperature of the infrared sensor 3a and converts it
into the temperature-sensitive voltage v.sub.t. The voltage is
converted into the temperature-sensitive data T.sub.0 by the A/D
converter 56, and is then supplied to the operation section 60.
When the infrared data V.sub.d and the temperature-sensitive data
T.sub.0 are supplied to the operation section 60, the sensitivity
correcting calculator 64 calculates the sensitivity R by using the
data T.sub.0 on the basis of equation (8). Note that the
coefficient of variation .beta. is set to be -0.03. The body
temperature operating circuit 61 then receives the sensitivity R
calculated by the calculator 64, the sensitivity data D from the
sensitivity data input means, and the coefficient a of a term of
degree 4 from the filter correcting means 5b, and calculates a
sensitivity coefficient K.sub.3 of this system as K.sub.3
.dbd.aRD.
Upon reception of the calculated sensitivity coefficient K.sub.3,
the emissivity .epsilon. from the emissivity input means 5a, and
the symmetrical axis temperature b from the filter correcting means
5b, the body temperature operating circuit 61 performs a
calculation based on equation (17):
Equation (17) is further rewritten to equation (18) so as to
calculate the body temperature data T.sub.b1. Since the external
ear canal has a uniform temperature, and the canal is regarded as a
blackbody, the emissivity .epsilon. is set set as .epsilon..dbd.1.
##EQU11## for b.dbd.45.95[K.+-.]. Thus, the body temperature data
T.sub.b1 is displayed on a digit display portion 6a of the display
unit 6 through the display driver 62.
One body temperature measurement is performed in this manner. A
procedure of this operation will be described with reference to the
flow chart of FIG. 15.
When the probe 16 is inserted in the external ear canal 41 (step
1), infrared radiation energy from the drum membrane 42 is
converted into the infrared voltage V.sub.s, and its peak voltage
V.sub.sp is held by the peak hold circuit 53 (step 2). The
presence/absence of the major signal S.sub.m is then determined
(step 3). If the major buttons 14 and 15 are not depressed, NO is
obtained in this step, and only the peak value holding operation in
step 2 is performed.
If the major buttons 14 and 15 are depressed, YES is obtaianed in
step 3. As a result, the zero detector 63 is reset by the major
signal S.sub.m (step 4). At the same time the sensitivity
correcting calculator 64 reads the temperature-sensitive data
T.sub.0 (step 5) and calculates the sensitivity R (step 6).
The body temperature operating circuit 61 reads the emissivity
.epsilon., the coefficient a, the sensitivity R, and the
sensitivity data D (step 7), and calculates the sensitivity
coefficient K.sub.3 by using the values a, R, and D (step 8). In
addition, the operating circuit 61 reads the symmetrical axis
temperature b and at the peak-held infrared data V.sub.d (step 9)
and calculates the body temperature data step T.sub.b1 (step
.circle. 10 ). The display driver 62 receives the body temperature
data T.sub.b1 and displays the body temperature on the display unit
6 (step .circle. 11 ), thereby completing the body temperature
measurement.
The function of the peak hold circuit 53 shown in FIG. 14 will be
described below with reference to FIG. 16.
FIG. 16 shows a temperature measurement curve of the radiation
clinical thermometer 1 of the present invention, which corresponds
to the temperature measurement curve of the conventional electronic
clinical thermometer shown in FIG. 1.
Temperature measurement time is plotted along the abscissa axis,
and measurement temperatures are plotted along the ordinate axis.
The external ear canal 41 is a portion to be measured. A
temperature curve H.sub.s of the external ear canal 41 coincides
with a measurement temperature curve M.sub.s of the radiation
clinical thermometer 1. As describe above, the downy hairs 43 and
the earwax 44 are present in the external ear canal 41, as shown in
FIG. 13. Similar to the drum membrane 42, the downy hairs 43 and
the earwax 44 are warmed to a temperature very close to a body
temperature prior to the start of temperature measurement. This
state is indicated at time T.sub.1 in FIG. 16. More specifically,
time t.sub.1 is the instant when the probe 16 is inserted in the
external ear canal 41. Since the temperature in the external ear
canal 41 at this instant is substantially equal to the body
temperature T.sub.b1, infrared radiation energy having a body
temperature level is incident on the infrared sensor 3a, and is
stored in the peak hold circuit 53 as the peak voltage V.sub.sp.
However, the temperature in the external ear canal 41 is cooled by
the probe 16 and quickly drops immediately after the probe 16 is
inserted, as indicated by the temperature curve H.sub.s. With this
temperature drop, the infrared voltage V.sub.s detected by the
infrared sensor 3a drops to the level of the temperature
measurement curve M.sub.s, and hence cannot exceed the peak voltage
V.sub.sp. For this reason, the peak voltage V.sub.sp at time
t.sub.1 is stored in the peak hold circuit 53. It takes about 10
minutes for the lowered temperature represented by the curve
H.sub.s to return to the origianl body temperature T.sub.b1. The
reason will be described below with reference to FIG. 13.
When the probe 16 is inserted in the external ear canal 41, all the
temperatures of the drum membrane 42, each downy hair 43, and the
earwax 44 are decreased. Of these portions the temperature of the
drum membrane 42 can return to the level of the body temperature
T.sub.b1 relatively quickly because of the themal conduction from
the body. However, since the thermal conduction from the body to
each downy hair 43 and the earwax 44 having low degree of adhesion
to the body is less, about 10 minutes are required for their
temperatures to return to the level of the body temperature
T.sub.b1. Therefore, the temperature in the external ear canal 41
is set at the level of the body temperature T.sub.b1 only at time
T.sub.1, i.e., the instant when the probe 16 is inserted. Since the
series of operation processing of the radiation clinical
thermometer 1 cannot be performed by using the infrared radiation
energy in such a short period of time, the peak voltage V.sub.sp
appearing at the instant is stored in the peak hold circuit 53 as
analog data, as indicated by a dotted line in FIG. 16. The A/D
conversion and the series of operating processing are performed by
using this stored peak voltage V.sub.sp, thereby performing the
body temperature measurement.
Thus, in a radiation clinical thermometer without a preheating unit
as in the present invention, the peak hold circuit 53 is
indispensable. By using the peak hold circuit 53, the body
temperature T.sub.b1 at time T.sub.1 can be measured within a very
short period of time.
FIG. 17 a detailed arrangement of the peak hold circuit 53. The
peak hold circuit 53 comprises an input buffer 80, an output buffer
81, a diode 82 for preventing a reverse current flow, a signal
charging capacitor 83, and a switching transistor 84 for casuing
the capacitor 83 to discharge a charged voltage. The peak hold
circuit 53 receives the infrared voltage V.sub.s and outputs its
peak value as the peak voltage V.sub.sp. In addition, when the
switching transistor 84 is turned on by the check signal S.sub.c
supplied to the reset terminal R, the circuit 53 causes the
capacitor 83 to discharge a charged voltage.
FIG. 18 is a sectional view of a head portion 110 according to a
third embodiment of the present invention. The same reference
numerals in FIG. 18 denote the same parts as in FIG. 10, and a
description thereof will be omitted.
The head portion in FIG. 18 differs from that in FIG. 10 in that a
through hole 19f is formed in a cylindrical portion 19a of a metal
housing 19 so as to expose an optical guide 20, and a
temperature-sensitive sensor 3c is fixed to the exposed portion of
the optical guide 20. This temperature-sensitive sensor 3c is
identical to the temperature-sensitive sensor 3b, and is also fixed
by a molding resin.
The third embodiment differs from the second embodiment in a system
for correcting thermal equilibrium in a probe 16. The second
embodiment employs the system of permitting measurement upon
confirmation of thermal equilbrium by the function check mode. In
this system, measurement is inhibited while thermal equilibrium is
not established. In contrast to this, the third embodiment
comprises the two temperature-sensitive sensors 3b and 3c to detect
a temperture difference between an infrared sensor 3a and the
optical guide 20. In this system, if this temperature difference is
excessively large, measurement is inhibited. If it is smaller than
a predetermined value, body temperature measurement is permitted
even though thermal equilibrium is not established. In this case,
body temperature data is calculated by adding a correction value
based on the temperature difference to the measurement value, thus
widening the range of measurement conditions of the radiation
clinical thermometer.
The circuit arrangement and operation of the radiation clinical
thermometer of the third embodiment will be described below with
reference to FIG. 19. The same reference numerals in FIG. 19 denote
the same parts as in FIG. 14, and a description thereof will be
omitted.
As shown in FIG. 18, a detecting section 3 comprises a
temperature-sensitive sensor 3c for measuring a temperature T.sub.p
of the optical guide 20. In the detection signal processing section
50, the switching circuit 54 is omitted, and an output voltage
V.sub.sp from a peak hold circuit 53 is directly supplied to an A/C
converter 55. A temperature-sensitive amplifying circuit 57 and an
A/D converter 58 are additionally arranged in the section 50 so as
to output the temperature sensitive data T.sub.p.
In an operating section 60, an emissivity .epsilon..sub.p of the
optical guide 20 is set in an emissivity input means 5a, and a
temperature difference detector 67 is arranged in place of the zero
detector 67 shown in FIG. 1. The temperature difference detector 67
receives temperature data T.sub.0 of the infrared sensor 3a
detected by the two temperature-sensitive sensors 3b and 3c and the
temperature data T.sub.p of the optical guide 20, and performs
temperature difference determination with respect to a
predetermined measurement limit temperature difference T.sub.d. If
.vertline.T.sub.0 -T.sub.p .vertline.<T.sub.d, i.e., the
temperature difference is smaller than the limit temperature
difference, the detector 67 outputs a detection signal S.sub.0 so
as to illuminate a measurement permission mark 6b of a display unit
6. This temperature difference determination is continued while the
power switch 13 shown in FIG. 9 is turned on. Therefore, the
operation of the check button 12 as in the second embodiment is not
required.
When the measurement permission mark 66 is illuminated, a body
temperature measurement mode is set in the same manner as in the
second embodiment. However, the difference is that the
temperature-sensitive data T.sub.p of the optical guide 20 is
supplied to a body temperature operating circuit 61 in addition to
the respective data described with reference to FIG. 14. In this
embodiment, the circuit 61 calculates body temperature data
T.sub.b2 in accordance with the following equation (19): ##EQU12##
where b.dbd.45.95[K] and .epsilon..sub.p .dbd.0.05. This body
temperature data T.sub.b2 is obtained by correcting the temperature
difference by the arithmetic operations described above, and is
displayed on a body temperature display portion 6a of the display
unit 6. Furthermore, in this embodiment, a check signal S.sub.c
output from a switch circuit 90 resets only the peak hold circuit
53. Therefore, when re-measurement of a body temperature is to be
performed, the peak hold circuit 53 must be reset first by
operating the check button after illumination of the measurement
permission mark 6b is confirmed.
As described above, according to this embodiment, since body
temperature measurement can be performed without waiting for
perfect thermal equilibrium of the respective elements of the probe
16, intervals of repetitive measurements can be reduced. In
addition, since the function check using infrared radiation is not
required, a switching circuit and a storage case are not required
so that the arrangement can be simplified.
In this embodiment, as an optimal embodiment, the arrangement
wherein the second temperature-sensitive sensor 3c is attached to
the optical guide 20 is shown. However, the present invention is
not limited to this. More specifically, the second
temperature-sensitive sensor 3c is designed to detect the surface
temperature of the optical guide 20 which responds to an ambient
temperature more sensitively than the portion in which the
temperature-sensitive sensor 3b is embedded. In consideration of
the fact that the surface temperature of the optical guide 20 is
substantially equal to the ambient temperature, the
temperature-sensitive sensor 3c may be mounted on a circuit board
on which a measurement IC chip is mounted as shown in FIG. 20 so as
to measure an ambient temperature, so that the measured ambient
temperature is used as the surface temperature of the optical guide
20. This arrangement can also be satisfactorily used in
practice.
As has been described above, according to the present invention, a
filter correction value and a sensitivity correction value are
supplied to a body temperature operating circuit to calculate body
temperature data, so that high measurement precision can be
realized without using a heating unit as in the conventional
thermometer, thus realizing a compact, low-cost radiation clinical
thermometer which can be driven by a small battery and which can
shorten a measurement time.
In addition, by employing a peak hold circuit for analog data in
the radiation clinical thermometer, instantaneous measurement can
be performed, thus preventing a measurement disable state due to a
temperature drop of a portion to be measured upon insertion of a
probe.
Moreover, by employing a temperature difference correcting system
using two temperature-sensitive sensors, re-measurement intervals
can be shortened, and the problem of thermal equilibrium of a
probe, which narrows the range of measurement conditions of the
radiation clinical thermometer, can be solved. Therefore, the
present invention is very effective to widely use a radiation
clinical thermometer as a home thermometer, which has been used
exclusively for a medical instrument.
* * * * *