Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1998-05-18
2001-02-27
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
Reexamination Certificate
active
06195581
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an infrared thermometer and to a method of evaluating the signal supplied by an infrared sensor of an infrared thermometer.
THE STATE OF THE ART
An infrared radiation thermometer measures the infrared radiation emitted by the object of measurement in the direction of the thermometer. With conventional total or band radiation pyrometers, the temperature of the object is determined from the intensity of this radiation. In these devices, the infrared radiation is collected with an optical unit that includes an optical waveguide and, where applicable, a lens, mirror or the like, and is directed to an infrared sensor. Therefore, the indicated temperature can be determined correctly only if proper functioning of the optical unit is ensured.
It is known in the art to provide the probe of a clinical infrared thermometer with an exchangeable probe cover which is sufficiently transparent to infrared radiation. The clinical thermometer is intended for measuring temperature in the ear, for example. This means that the thermometer's probe is introduced into the ear for temperature measurement at this site.
The probe cover serves the purpose of protecting the thermometer from contamination. Such contamination could be caused by ear wax, for example, forming a heat bridge between the optical waveguide and the probe's outer wall by clogging the air gap conventionally existing at this location. This air gap thermally insulates both the sensor and the optical waveguide against the outer wall. When a measurement is being taken, this outer wall contacts the skin and therefore heats comparatively rapidly. To prevent heating of the infrared sensor and an attendant corruption of the received signal, said air gap is provided at the tip of the probe between the optical waveguide in the interior of the probe and the probe's outer wall. Therefore, any contamination occurring at this site could corrupt the measurement signal.
Further, the probe cover serves to prevent diseases from being transmitted, for example by fitting the thermometer, after a patient's temperature is taken, with a new probe cover before using it for another patient.
From EP-A-0565123, WO-A-95/00067 and EP-A-0445784 infrared thermometers are known in which for the reasons stated it is necessary to place a probe cover over the probe for measuring temperature, otherwise no temperature reading can be taken. This is particularly inconvenient in cases when a medical emergency situation has occurred but no temperature reading can be taken just because a probe cover is not on hand. In the infrared thermometer known from EP-A-0445784, the optical waveguide is sealed tight by a window, and no air gap exists at the forward end of the optical waveguide between the optical waveguide and the probe's outer wall.
SUMMARY AND OBJECTS OF THE INVENTION
It is an object of the present invention to provide an infrared thermometer and a method of evaluating the signal supplied by an infrared sensor of an infrared thermometer, which enhances its handling capabilities.
This object is accomplished with an infrared thermometer and a method according to claim
5
.
In an advantageous feature, the infrared thermometer according to claim
1
includes an optical waveguide sealed tight by a window at a forward end of its probe, as well as a detector operating, for example, according to capacitive, optical, magnetic or mechanical principles and detecting the presence of a probe cover on the probe. The infrared thermometer may be operated both with and without probe cover or protective film because it is on the basis of the signal supplied by the detector that its evaluation unit performs the evaluation of a signal arriving from an infrared sensor according to either a first or a second approach.
By configuring the probe according to the present invention, use of the thermometer without probe cover cannot adversely affect the accuracy of measurement because the probe is designed to afford ease of cleaning. In particular ear wax, for example, cannot accumulate in a gap between the outer wall and the optical waveguide because the connection of these parts does not provide a gap towards the outside. Thus an infrared thermometer is obtained which is also operable without probe cover or protective film.
On the other hand, however, it is also possible for an infrared thermometer that is to enable operation both with and without probe cover or protective film to be equipped advantageously with such a probe. Advantageously, the contact areas between the window and the outer wall and, where applicable, the optical waveguide are not too large so that the conduction of heat via these heat bridges is largely reduced.
With regard to the bandwidth of a good transmission or a low emission within the relevant wavelength range, materials such as germanium, gallium arsenide, zinc selenide, chalcogenide glass, silicon, polyethylene, polypropylene, and copolymers of polyethylene and polypropylene have proven to be advantageous for the window.
By configuring the probe with an air gap between the optical waveguide and the outer wall it proves to be an advantage that a comparatively low amount of heat only is allowed to flow via the air gap from the outer wall to the optical waveguide.
With a configuration having at least one thermal mass formed by a metal block is provided in the area of the optical waveguide and/or the infrared sensor and connected to the optical waveguide and the infrared sensor it proves to be advantageous that the coupling of the thermal masses effects a reduction of the speed of the temperature variation with time, as well as of the temperature gradient.
In the method in which the measuring operation is executed when no probe cover or protective film is installed and an appropriate allowance is made for the infrared radiation that is consequently more intensive than when a measurement is take with the probe cover or protective film in place, it shows that a signal evaluation and hence a determination of temperature are possible regardless of whether or not a probe cover or protective film is installed over the probe. By contrast, in thermometers known in the art it has only been known to suppress the signal evaluation in the absence of a probe cover. The method disclosed in claim
5
enables operation of the thermometer with or without probe cover installed, as desired. This enables the thermometer to be operated without probe cover for domestic use, that is, when the number of persons for which the thermometer is used is limited. On the other hand, when the thermometer is used in a hospital, it can be operated also with probe cover to prevent diseases from being transmitted. This results in a simplified thermometer manufacture because the requirement of having to differentiate between thermometers for domestic and hospital use is obviated.
The possibility afforded by using the thermometer also without probe cover reduces operating cost and waste. Further, its serviceability is enhanced because a measurement can be taken also when probe covers are not available.
The method where compensation is made for the absence or presence of a probe cover or protective film by multiplying the measured signal by a specified factor indicates a comparatively simple possibility of making allowance for whether or not the probe is used with a probe cover during measurement. In the use of a probe cover or protective film, the infrared signal to be detected is attenuated. To compensate for the reduced transmission, the sensor signal—conventionally the measured infrared radiation intensity—is multiplied by a factor that is determined in dependence upon the transmission of the probe cover or protective film and amounts to about 1.08 to 1.2 with the thin polyethylene or polypropylene film materials customarily employed.
In contrast, the method of compensating for the absence or presence of a probe cover or protective film by multiplying the measured signal by a variable factor dependent upon the ambient tempera
Beerwerth Frank
Bultges Heinz
Heubach Klaus
Honnefeller Katja
Jestadt Albrecht
Braun GmbH
Hopgood, Calimafde Judlowe & Mondolino
Lateef Marvin M.
Mantis Mercader Eleni
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