Thermal measuring and testing – Temperature measurement – In spaced noncontact relationship to specimen
Reexamination Certificate
2001-04-19
2003-02-04
Gutierrez, Diego (Department: 2859)
Thermal measuring and testing
Temperature measurement
In spaced noncontact relationship to specimen
C600S474000, C374S102000, C374S121000
Reexamination Certificate
active
06513970
ABSTRACT:
TECHNICAL FIELD
This invention relates to an infrared thermometer for measuring the temperature of a target by sensing infrared radiation emitted from the target.
BACKGROUND ART
One application of an infrared thermometer is to use it as an infrared clinical thermometer for measuring the temperature (body temperature) of the human body. This thermometer generally performs temperature measurement based upon infrared radiation emitted from the external ear canal or tympanic membrane, etc., of the human ear.
An infrared clinical thermometer is equipped with a probe insertable into the ear orifice, and the probe is provided within the clinical thermometer body (housing) so as to protrude to the outside. Provided within the probe is a waveguide for guiding infrared radiation, which is emitted from the tympanic membrane or the like (biological surface tissue), to an infrared sensor disposed inside the housing.
One important problem with an infrared clinical thermometer is that when the probe is inserted into the ear orifice, heat is transferred from the ear orifice (human body) to the infrared sensor via the probe and waveguide, as a result of which the output of the infrared sensor becomes unstable. The adverse influence of heat from the surrounding environment transferred from the housing to the infrared sensor also cannot be ignored.
One technique which solves this problem is as described in the specification of Japanese Patent Publication No. 5-28617 (or U.S. Pat. No. 4,895,164 or WO 90/02521). According to the infrared clinical thermometer disclosed in these references, the larger portion of the waveguide and the infrared sensor are embedded in a comparatively large heat conducting block (isothermic block means) made of metal (an excellent thermal conductor such as aluminum or copper). The heat conducting block (the infrared sensor portion) is supported inside the housing by a spacer stand, and a space between the heat conducting block and housing acts as an insulative air layer to reduce the migration of heat from the heat source outside the housing to the heat conducting block. It is stated that the waveguide and infrared sensor are held in an isothermic state at ambient temperature by the heat conducting block. Furthermore, a low-emissivity barrier such as an aluminum tube is placed around the outer end of the waveguide, and the barrier is covered by a cover of low thermal conductivity.
One feature of an infrared clinical thermometer is short measurement time (e.g., 1 to 5 seconds). Since the heat conducting block in the foregoing references is comparatively large, a state of thermal equilibrium (temperature equalization) is not attained in such a short period of time. As long as heat from the human body travels to the heat conducting block by being transmitted along the waveguide, the temperature of the infrared sensor also will vary. Thus the instability of the output from the infrared sensor is a problem that has not been solved satisfactorily.
A technique intended to solve this problem is illustrated in the specification of International Patent Laid-Open No. WO 97/24588. According to the infrared thermometer described in this reference, a heat conductive tubular body is provided between a probe and a waveguide in a state thermally insulated therefrom, and heat from the probe is prevented from being transmitted to the waveguide and infrared sensor. The provision of the heat conductive tubular body increases the number of component parts.
Another problem with infrared thermometers is that dust or the like penetrates the interior of the waveguide, resulting in reduced measurement precision.
In order to solve this problem, the conventional practice is to bond silicon glass to the opening at the tip of the waveguide to close the same. However, problems encountered with silicon glass are difficulty in working the glass and the high price thereof. In addition, fabrication cost rises owing to the use of a bonding agent.
A method available is to close the opening at the tip of the waveguide by covering it with a resin film and secure the resin film to the waveguide by a ring member. The problems with this method are the labor required for assembly and the fact that the resin film tears easily when contaminants are wiped off.
An infrared clinical thermometer has a temperature range (measurable temperature range) (e.g., 10~40°0 C.) within which it is capable of operating normally. An error is displayed if an attempt is made to use an infrared clinical thermometer in an environment where the temperature is outside this temperature range. A further problem is inconvenience in that the user cannot determine why an error display is being presented nor how long it will take before the thermometer can be used.
DISCLOSURE OF THE INVENTION
An object of the present invention is to make it possible to measure temperature accurately, with simple structure, by reducing, to the maximum degree, the influence exerted upon an infrared sensor by heat transferred from the outside (a target such as the ear canal) to a waveguide.
Another object of the present invention to provide a structure that is capable of alleviating the adverse effects of environmental temperature.
A further object of the present invention is to effectively prevent dust or the like from penetrating the interior of a waveguide in an infrared thermometer and to implement this in such a manner that assembly is facilitated.
Still another object of the present invention is to so arrange it that the length of time needed before measurement becomes possible is shown clearly when an infrared thermometer in a temperature environment in which measurement is impossible is placed in a temperature environment in which measurement is possible.
The present invention provides an infrared thermometer having an infrared sensor placed inside a housing and a waveguide for guiding infrared radiation, which is emitted from a target, to the infrared sensor, characterized in that the infrared sensor and waveguide are held in direct or indirect contact with the housing in a state in which the infrared sensor is thermally insulated from the waveguide.
There are various modes available for supporting the infrared sensor in a state in which it is thermally insulated from the waveguide. The waveguide has an outer end that opposes the target and an inner end that opposes the infrared incidence surface (sensor surface) of the infrared sensor. In one of the above-mentioned modes, the inner end of the waveguide is spaced apart (by provision of a gap) from the infrared incidence surface of the infrared sensor. An air layer is present between the inner end of the waveguide and the infrared sensor, and the air layer has a heat insulative effect.
The waveguide and infrared sensor can be held in the housing by a common heat insulating member or by separate heat insulating members. Synthetic resin is a typical example of the heat insulating member (a member of low thermal conductivity). It may be so arranged that the waveguide is supported by a metal member (a member having excellent thermal conductivity).
In another mode of supporting the infrared sensor in a state in which it is thermally insulated from the waveguide, the infrared sensor is placed inside the inner end of the waveguide and the infrared sensor is held spaced away from an inner wall of the waveguide. In this case also an insulative air layer is provided between the waveguide and infrared sensor.
The infrared sensor and the waveguide can be held in the housing by a common heat insulating member or by separate heat insulating members. The infrared sensor may be supported by providing a heat insulator between the infrared sensor and waveguide.
In yet another mode, the infrared sensor can be supported on the inner end of the waveguide by a heat insulating (low thermal conductivity) connecting member. The infrared incidence surface of the infrared sensor opposes the inner end of the waveguide. The waveguide is supported on the housing by a heat insulating member or metal.
Further, such a mode is covered by
Ota Hiroyuki
Sato Tetsuya
Tabata Makoto
Tomioka Shigeru
Gutierrez Diego
Morrison & Foerster / LLP
OMRON Corporation
Verbitsky Gail
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