Thermal measuring and testing – Temperature measurement – In spaced noncontact relationship to specimen
Patent
1997-06-27
2000-12-05
Miska, Vit
Thermal measuring and testing
Temperature measurement
In spaced noncontact relationship to specimen
374128, 374130, 374133, 600474, G01J 500, A61B 600
Patent
active
061557129
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a radiation clinical thermometer for performing noncontact temperature measurement by detecting thermal radiation energy and, more particularly, to temperature compensation in an optical system.
BACKGROUND ART
A radiation clinical thermometer has been proposed to measure a body temperature within a short period of time. This instrument is designed to perform noncontact measurement of the temperature of an eardrum selected as a measurement portion.
For example, such radiation clinical thermometer is disclosed in Japanese Unexamined Patent Publication No. 61-117422 wherein the head portion of the probe unit is inserted into the external acoustic meatus, and thermal radiations from the eardrum are focused to an infrared sensor by an optical waveguide placed in the head portion, thereby measuring the eardrum temperature. The probe unit with this infrared sensor includes a heating control means for preheating the head portion to a reference temperature (36.5.degree. C.). The head portion is preheated to a temperature near the body temperature, and calibration is performed in advance in this state. With this operation, when the head portion is inserted into the external acoustic meatus, the temperature of the head portion undergoes no change. For this reason, measurement errors caused by changes in the temperature of the head portion can be eliminated. That is, the inner surface of the optical waveguide must be set equal in temperature to that of the infrared sensor itself so as to prevent thermal radiations from the optical waveguide itself from causing measurement errors. In order to prevent a change in the temperature of the head portion upon insertion into the external acoustic meatus, the temperature of the head portion is stabilized at the reference temperature (36.5.degree. C.). With this setting, thermal radiations from the inner surface of the optical waveguide can be neglected.
The radiation clinical thermometer disclosed in Japanese Unexamined Patent Publication No. 61-117422, however, requires a heating control device with a high control accuracy. For this reason, the structure and circuit configuration of this instrument are complicated, and its size increases, resulting in an increase in cost. In addition, a long stabilization time is required to preheat the head portion and control its temperature to a constant temperature. Furthermore, high energy is required to drive the heating control device. This scheme cannot therefore be applied to a portable clinical thermometer using a compact battery as an energy source.
Under the circumstances, a radiation clinical thermometer with a high temperature measurement accuracy has been proposed, which is a compact, portable clinical thermometer having no heating control device. When the probe of this instrument is inserted into the external acoustic meatus to measure the eardrum temperature, the temperature of the probe changes. However, this change causes no error.
For example, such radiation clinical thermometer is disclosed in Japanese Unexamined Patent Publication No. 2-28524. Similar to the radiation clinical thermometer disclosed in Japanese Unexamined Patent Publication No. 61-117422, the radiation clinical thermometer disclosed in Japanese Unexamined Patent Publication No. 2-28524 uses an optical waveguide as an optical system for focusing thermal radiations from the eardrum. However, this instrument has no heating control device for the infrared sensor, and hence the infrared sensor and the optical waveguide are kept at almost the ambient temperature, i.e., room temperature. The first temperature sensor is arranged near the infrared sensor, and the second temperature sensor is arranged in the optical waveguide. A temperature is measured on the basis of the temperatures of the infrared sensor and the optical waveguide. If the difference in temperature between the infrared sensor and the optical waveguide is extraordinarily large, measurement is inhibited. If the temperature difference is smaller tha
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Miska Vit
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