Thermal measuring and testing – Temperature measurement – In spaced noncontact relationship to specimen
Patent
1989-08-18
1991-05-21
Yasich, Daniel M.
Thermal measuring and testing
Temperature measurement
In spaced noncontact relationship to specimen
128736, 250346, 250353, 350 14, 374124, 374165, A61B 500, G01J 500, G01K 108
Patent
active
050170180
DESCRIPTION:
BRIEF SUMMARY
FIELD OF ART
The present invention relates to an infrared clinical thermometer using an infrared sensor and particularly to the correction of a temperature measurement error for the same.
BACKGROUND ART
Heretofore, as a clinical thermometer there has widely been used a mercury thermometer, but recently a digital electronic clinical thermometer has also come into wide use.
Ordinary electronic clinical thermometers use a thermistor as a sensor and are provided with an arithmetic circuit for the calculation of temperature values and a digital display unit. But it takes two to three minutes for the measurement of temperature, which time is even longer than that required in mercury clinical thermometer. There is an electronic clinical thermometer of the type in which the final value is estimated from the progress of temperature rise during an initial one minute or so. But this type of an electronic clinical thermometer involves the problem that the so-estimated value is not always coincident with an actual value.
The problem of requiring time for the measurement of temperature is also related to the portion where the temperature is to be measured. It is the temperatures of such deep parts as head, chest and abdominal cavity that are maintained at predetermined values by the adjusting function of a living body. But it is difficult to directly measure the temperatures of those deep parts, so in general the temperature to be measured is rectal temperature, oral temperature, or axilla temperature. The axilla temperature measurement is widely adopted, but the axilla is usually in a somewhat open condition, so the skin temperature of that part is a little lower. When the axilla is closed with a clinical thermometer put therein, the skin temperature will begin rising and reach a certain temperature (equilibrium temperature) in 10 minutes or so. If at this point or thereafter the clinical thermometer is pulled out and checked, there will be obtained an accurate axilla temperature. But if the clinical thermometer is pulled out earlier, the temperature value shown thereon will be a little lower.
Another factor related to the temperature measurement time is the heat capacity of the sensor portion. In a mercury clinical thermometer, the temperature measurement goes through the process of warming the mercury bulb by the body temperature through the glass wall and reading the expansion of mercury, so the heat capacity of the object warmed is fairly large, requiring a measurement time of 2 to 3 minutes. Also in an electronic clinical thermometer, a metallic portion contacted with a part for measurement is warmed by the body temperature and the thermistor varies its resistance value depending on the temperature of the metallic portion, so the heat capacity of the object warmed (the metallic portion) is also large.
All of the above clinical thermometers are of a contact type, but there also are available non-contact type clinical thermometers, an example of which is the "non-contact type oral thermometer" disclosed in Japanese Patent Laid-Open No. 88627/83. In this oral thermometer, using a pyroelectric type infrared sensor, infrared rays from the oral cavity are condensed and input to the sensor after chopping, while the output of the sensor is amplified and calculation is made on the basis of a reference temperature signal to determine the body temperature, which is displayed on a display unit. Alternatively, using a thermistor as an infrared sensor, the oral thermometer is composed of a condensing system, the thermistor, an amplifier, an arithmetic unit, a display mechanism and a reference temperature detector.
As a method of measuring the body temperature by inserting a clinical thermometer into the ear cavity there have been proposed such methods as those disclosed in Japanese Patent Laid-Open Nos. 25427/85, 216232/85, 133331/85, 117422/86, 138130/86, and U.S. Pat. No. 3,282,106 (1966). However, these proposed methods have not been realized yet because of the following problems involved therein.
The Japanese patent lai
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Iuchi Tohru
Kawasaki Atsushi
Nagatake Yoh-ichi
Nakamori Yukio
Yashiro HIrokatsu
Nippon Steel Corporation
Yasich Daniel M.
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