Radiation clinical thermometer

Details Radiation clinical thermometer Radiation clinical thermometer

1999-05-27

2002-04-16

Nasser, Robert L. (Department: 3736)

Surgery

Diagnostic testing

Temperature detection

C600S474000

Reexamination Certificate

active

06371925

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a radiation thermometer for measuring body temperature of a living body by detecting an amount of the infrared rays radiated from inside of an ear canal.
BACKGROUND OF THE INVENTION
Radiation thermometers for use as the clinical thermometers have been heretofore available, with which an amount of the infrared rays radiated from inside of an ear canal is detected at noncontact, and converted into body temperature. An advantage of these radiation thermometers is that they can take the measurement in a short period of time as compared to the contact type thermometers utilizing mercury and thermocouples.
As an ordinary example, the radiation thermometer of this type shown in Japanese Patent Laid-Open Publication, No. H06-165 will be described hereinafter by referring to FIG.
27
. As shown in
FIG. 27
, the radiation thermometer comprises a probe
1
, a waveguide
2
extending within the probe
1
in a longitudinal direction, an infrared-ray-receiving element
3
for converting a radiant intensity of the infrared rays traveled through the waveguide
2
into an electric signal, and a signal processor
4
for measuring temperature from the converted electric signal.
By inserting the probe
1
into an external auditory canal (“ear canal”), the infrared-ray-receiving element
3
receives the infrared rays radiated from the tympanic membrane (“eardrum”) and/or vicinity of it, and outputs an electric signal corresponding to an amount of the received infrared rays. Then, the signal processor
4
calculates a temperature of the eardrum and/or its vicinity from the electric signal.
Generally, the infrared-ray-receiving element
3
outputs an electric signal that corresponds to an aggregate amount of the infrared rays incident on it from all directions, and the waveguide
2
is made of a metal or processed with plating or the like on its at least inner surface so as to maintain a high reflectivity. The infrared rays radiated from the eardrum and/or vicinity of it reach the infrared-ray-receiving element
3
directly or by being reflected repetitively off the inner surface of the waveguide
2
of the foregoing structure. On the other hand, undesired infrared rays radiated from an inner surface, etc. of the probe
1
do not reach the infrared-ray-receiving element
3
.
However, the incident rays reflected repetitively suffer a reflection loss equal to the reflection factor raised to the n-th power, since it is unfeasible to make the inner surface of the waveguide
2
a perfect reflecting body (the reflection factor of 1). Also, the light reflected at a low angle for a single reflection generally gains a lower reflectivity than the perpendicular light, thus resulting in a reflection loss. Since an amount corresponding to these reflection losses enters into the infrared-ray-receiving element
3
as a part of the infrared radiation emitted from the waveguide
2
, an accurate measurement of the body temperature can not be attained because the infrared-ray-receiving element
3
is influenced by it, if temperature of the waveguide
2
changes when the probe
1
is inserted into the ear canal.
In order to avoid the above problem, the foregoing example of the prior art alleviates the temperature changes of the waveguide
2
by tapering off to a tip from a main base of the probe
1
so as to reduce likeliness of contact with the ear canal. Also, an example shown in Japanese Patent Laid-Open Publication, No. H05-45229, adopts a design in that a probe is constructed of a thermal insulation material on its surface, and of a thermally high conductive material in the core, so that it averts an influence of heat from the ear canal, and offsets the influence by quickly transmitting the heat it receives to an infrared-ray-receiving element. Furthermore, still another example shown in Japanese Patent Laid-Open Publication, No. H08-126615 adopts an idea that a probe is detachable, so as to eliminate an influence of heat retained in the probe by replacing it after each measurement.
However, none of the foregoing techniques are flawless for accurately measuring temperature of the eardrum and/or vicinity of it by eliminating an influence of the heat conducted from the ear canal to the waveguide, and they all have a problem of lacking accuracy in measuring body temperature due to the influence of temperature changes of the waveguide. In particular, there is a problem that measured temperature gradually shifts even for one and the same measuring subject, when the measurements are made repeatedly at short intervals, because of an influence of the waveguide as its temperature gradually changes.
If a thermally high conductive material is used for the waveguide in order to avert the effect of measuring errors caused by the aforementioned problem, a new problem arises in that the waveguide becomes liable to produce condensation on the inner surface at low temperature environment. This is because temperature of the metal surface does not rise readily at the low temperature environment, even when it comes in contact with air near a body temperature by being inserted into the ear canal. Hence, the condensation occurs on the metal surface, as the air containing moisture is chilled by the metal in a temperature below dew point. If a phenomenon of the condensation occurs on a component such as the waveguide having a function of reflecting the infrared rays, a measuring error can result because the infrared rays reaching the infrared-ray-receiving element is substantially reduced due to absorption and dispersion of the infrared rays by the condensation.
It is a common practice to use a sanitary cover on the probe when inserting a radiation thermometer into the ear canal, and the cover is discarded when removed after each use for the sake of sanitary protection, in the case the radiation thermometer is used for many and unspecified persons. Such a sanitary cover shall conceal a part contacting the tip of the probe with a membrane. This is because a tip of the waveguide extends to the tip of the probe, so that the tip shall be provided with the membrane in order to prevent dirt from adhering to the waveguide.
On the one hand, the sanitary cover is not necessary, and waste of resources by discarding them is avoidable, if subjects to be measured are limited to a few and specific persons such as those in a family or in an office of a small number of people, since spread of disease via the ear can be prevented by assigning a separate probe for each person. Even in the above case, however, the tip of the probe needs to be covered with a membrane made of an infrared transparent material in order to avoid dirt from adhering to the waveguide.
In any case, what is measured is an amount of the infrared rays passed through the membrane provided on the tip of the probe for the purpose of sanitation. It is not feasible to let the infrared rays pass through completely, since there is a component in the infrared rays that is absorbed and/or reflected when they pass through the membrane. Because a transmission factor of the infrared rays through the membrane disperses depending on thickness, etc. of the membrane, it raises a problem of causing an error in temperature due to the dispersion in the transmission factor when a new membrane is replaced, even if the thermometer is adjusted in advance with a specific membrane.
Announcing a measured temperature with voice can provide a good advantage, as the measured result is readily known when the thermometer is used by a blind person, or when measured in the dark. For example, one of the known methods is shown in Japanese Patent Laid-Open Publication, No. H06-142061.
However, it takes 2 to 3 seconds in order to announce the temperature vocally, while only 0.1 to 0.2 second suffices to notify a completion of the measurement with a beeping sound. In other words, temperature of the waveguide changes due to conduction of heat from the ear while the probe is kept inserted in the ear until the announcement ends, if a radiation thermometer of the foreg

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