Ear type thermometer

Details Ear type thermometer Ear type thermometer

2001-01-16

2003-02-18

Brinson, Patrick (Department: 3752)

Surgery

Diagnostic testing

Detecting nuclear, electromagnetic, or ultrasonic radiation

C600S549000, C374S121000, C374S130000

Reexamination Certificate

active

06522912

ABSTRACT:

TECHNICAL FIELD
The present invention relates to an ear type thermometer for women, which utilizes infrared rays radiated from an eardrum to measure body temperatures, thereby enhancing the measurement accuracy of the ear type thermometer for women.
BACKGROUND ART
An ear type thermometer, whereby infrared rays radiated from an eardrum are detected and a non-contact measurement of the eardrum temperature is carried out, is generally like what is described in the Japanese Patent Unexamined Application No. S 60-6835.
The ear type thermometer of above is structured as
FIG. 60
shows and operates as follows:
First, the infrared rays radiated from an eardrum
200
, the temperature of which is to be measured, are incident intermittently on a pyroelectric infrared sensor
202
as a chopper
201
interrupts the infrared rays, thereby converting the infrared rays to an electrical signal that varies in output with the same frequency as the operating frequency of the chopper
201
. Next, after amplification in an amplifier circuit
203
and rectification in a synchronous detector circuit
204
, the electrical signal is changed to a DC via a filter circuit
205
formed of low-pass filters. The value gained as an output signal from the filter circuit
205
represents a measurement value of the infrared rays corresponding to the temperature of the eardrum
200
. On the other hand, the temperature of the chopper
201
is measured in advance by using a sensor temperature measuring means
206
formed of a thermister. The temperature of the chopper
201
thus obtained is used as a temperature compensating signal when the temperature of the eardrum
200
is derived by calculation from the output signal of the filter circuit
205
.
Finally, a body temperature calculating means
207
reads the temperature of the chopper
201
and also the measured value of infrared rays obtained as an output signal of the filter circuit
205
, thereby deriving by calculation the temperature of the eardrum
200
from the readout. The foregoing calculation to derive the temperature of the eardrum
200
is based on an assumption that the value obtained as an output signal form the filter circuit
205
, i.e., a value tantamount to the output of the pyroelectric infrared sensor is proportionate to the difference between the fourth, power of the absolute temperature of the eardrum
200
and the fourth power of the absolute temperature of the chopper
201
. However, when the ambient temperature range and also the measurement temperature range, in which an ear type thermometer is used, is narrow, almost the same result can be obtained in calculating the temperature of the eardrum
200
by assuming that the amplitude of the output signal from the pyroelectric sensor
202
is proportionate to the difference between the absolute temperature of the eardrum
200
and the absolute temperature of the chopper
201
.
In addition, the magnitude of an error included in the temperature of the eardrum thus derived by calculation has not been allowed to be designated by the user as a permissible error but has been determined in advance as one of the specification items of an ear type thermometer itself.
Furthermore, an eardrum is located toward the back of an external auditory miatus and it is known that the temperature of the external auditory miatus is lower than the temperature of the eardrum by 0.5° C. to 1° C. Consequently, it is difficult to obtain a consistent measurement result at the time of measuring body temperatures unless only the infrared rays radiated from an eardrum are accurately measured, eliminating the effects of the infrared rays radiated from other areas of the external auditory miatus than the area where the eardrum is located.
In order to deal with the problems as described above, a proposal is made on a technology whereby temperatures are measured at a plurality of points on the surface in an ear hole formed of an external auditory miatus and the eardrum and the highest value in the temperatures measured is considered as the temperature of the eardrum. (Refer to the Japanese Patent Unexamined Application No. H6-285028 and the Japanese Patent Unexamined Application No. H8-275924.)
FIG. 61
is a diagram to illustrate the principle whereby temperatures of an eardrum are measured with a conventional ear type thermometer. In
FIG. 61
, the reference numeral
211
is an optical vision of the ear type thermometer, reference numeral
212
is an external auditory miatus, reference numeral
213
is the eardrum and reference numeral
214
is a probe acting as an inlet for infrared rays to reach the ear type thermometer.
With the foregoing ear type thermometer, by narrowing down the optical vision
211
for receiving infrared rays, only the infrared rays radiated from a minute area on the ear hole surface formed of the external auditory miatus
212
and eardrum
213
are captured to allow the temperature of the specific area to be measured and also to allow the temperatures at a plurality of positions on the eardrum surface to be measured while changing the direction of the opptical vision
211
by altering the direction of the probe
214
within the external auditory miatus
212
, thereby treating the highest temperature obtained from above measurements as the temperature of the eardrum
213
.
As the flow chart in
FIG. 62
shows, the method for determining the highest value in temperatures measured comprises an infrared measurement process whereby infrared rays radiated from a spot captured in the optical vision
211
are measured and a computation process, whereby the temperature of the foregoing spot is derived by calculation according to the measured value of the infrared rays and the highest value in temperature that has been obtained by calculation by that time is updated, wherein these two processes are repeated.
As referred to in the Japanese Patent Unexamined Application No. H6-285028, it is conceivable theoretically to utilize a special-purpose table during the foregoing computation process, the special-purpose table being intended for deriving a body temperature from the measured value of infrared rays. However, the table of that kind tends to become enormous and, therefore, as described in the Japanese Patent Unexamined Publication No. H6-63851, a computation formula as expressed below is used.
T
=
T
a
4
+
V
s
f
⁡
(
T
a
)
4
(
1
)
where T is a body temperature of the eardrum expressed in kelvins (K), Ta is an ambient temperature in kelvins (K), in which the ear type thermometer is used, and Vs is an output voltage of the infrared sensor.
Here, f(Ta) is a correcting term corresponding to the temperature characteristics of the infrared sensor and it is known that this can be expressed in practice by a second order polynomial expression as follows:
f
(
T
a
)=
A×T
a
2
+B×T
a
+C
  (2)
where A, B and C are constants.
Depending on the situations where the body temperature at the eardrum is higher than the ambient temperature and vice versa, Vs may be a positive value or a negative value. Usually, the sign of Vs is made positive when the body temperature at the eardrum is higher than the ambient temperature and made negative when the body temperature at the eardrum is lower than the ambient temperature. At this time, f(Ta) becomes always a positive value regardless of the value of Ta. In the vicinity of a room temperature, a variation of f(Ta) per the change of 1° C. in the ambient temperature Ta, namely,
f
⁡
(
T
a
+
1
)
-
f
⁡
(
T
a
)
f
⁡
(
T
a
)
(
3
)
is about 0.2%.
Recently, more and more women go into the workaday world and there are many women who leave their children at a day-care facility and work at office or factory. For a working woman, it is important to know when to give birth to a baby because it is closely related to the schedules of her work, her putting out a baby to nurse after the baby is born, her doing things while she is pregnant and the like. Even for house wives, it is desirable to plan ahead well for delivery in consideration of a delicate rel

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