Infrared Tympanic Thermometer

Field of Invention

This application relates to the field of infrared thermometers. More particularly, it relates to infrared tympanic thermometers that are used to measure human body temperature by sensing infrared radiation emitted from the tympanic membrane.

Background

Various methods have been used to detect the internal body temperature of humans. These include mercury ther- mometers and electronic thermometers. A recent improve¬ ment is the use of infrared tympanic thermometers, which measure the internal body temperature by sensing the infrared radiation emitted from the tympanic membrane in the ear. A major benefit of using infrared tympanic thermometers is the reduction in the amount of time to take a temperature reading.

Present infrared tympanic thermometers commonly use a thermopile to sense the infrared radiation emitted from the tympanic membrane, and package the thermopile in a T05 can of 0.335" maximum outside diameter, as is well known in the art. Because this structure is too large to fit in the ear, the thermopile is mounted away from the ear inside the opposite (distal) end of a tapered ear probe.

Positioning the thermopile in a remote location has a resulting detrimental effect on measurement accuracy which is generally due to two factors. First, remote location creates problems with the viewing angle between the tympanic membrane and the thermopile because it is diffi¬ cult to point the device directly at the tympanic mem- brane. Therefore, an infrared wave guide must be used between the membrane and the thermopile, with an inner

surface that is specially prepared for maximum infrared reflectivity.

Second, remote location creates measurement problems due to the difference in ambient temperature between the ear canal and the thermopile. Therefore, in order to minimize temperature gradients along the wave guide, the wave guide must have high thermal conductivity and be well insulated, and the T05 thermopile must be mounted in a heavy heat sink, with a thermistor mounted on and touching the thermopile. The purpose of the heavy heat sink is to ensure a high thermal time constant. In addition, the inside of the wave guide must have an expensive reflective plating.

Also, a second thermistor is sometimes used in order to reduce the thermal insulation on the probe. This second thermistor is generally mounted on the end of an ear probe nearest the ear (the proximal end) , to compen¬ sate for the difference in ambient temperature between the proximal end of the probe and the distal (instrument) end of the probe where the thermopile is mounted. It is questionable whether this variation improves the cost or accuracy of the one thermistor version.

There are cost issues involved in trying to minimize these accuracy problems. These include the costs of insulating the probe, finishing and plating the inside of the wave guide, and adding one or two thermistors and their associated electronics. Also, a second infrared window may be needed to seal the wave guide to prevent dust and other contamination from getting inside the wave guide and having detrimental effects on accuracy and safety.

FIGs. 1 & 2 show prior art thermometers that illus¬ trate the inherent problems caused by remote location of the thermopile away from the ear. Both show thermopiles 22 & 42 disposed within a housing 21 & 41. These thermopiles each have an infrared window 23 & 43 near the thermopile, and an infrared window 28 & 48 near the

proximal end 24 & 44 of the thermometer nearest to the ear. Because of the distance from the tympanic membrane, each of them has a wave guide 25 & 45, thermal insulation around the wave guide 26 & 46, and a heat sink 27 & 47 generally around the thermopile 22 & 42. Additionally, the prior art thermometers generally have thermistors located at various locations to measure the ambient temperature and to compensate for the difference in ambient temperature between the thermopile and the ear canal. FIG. 1 shows the use of a single thermistor 29, while FIG. 2 illustrates the use of two thermistors 49 & 50. Also, FIG. 2 shows the use of a disposable cover that could also be used on the improved thermometer.

Summary of the Invention The present invention provides an improvement on the aforesaid infrared tympanic thermometers by packaging a thermopile in a smaller enclosure and positioning the thermopile at the proximal end of the ear probe, near the tympanic membrane. This novel orientation results in enhanced accuracy and reduced costs while retaining the speed advantage of other infrared tympanic thermometers.

The improved thermometer negates or minimizes the need for an expensive wave guide and additional temperature sensors

(i.e. : thermistors) and their associated electronics to solve the problem of ambient temperature differences between the ear canal and the thermopile. This invention also eliminates the requirement for thermal insulation of the ear probe and it eliminates the heavy heat sink and the thermistor external to the thermopile housing. Two embodiments are disclosed below. The first embodiment packages the thermopile in a T018 can, which has an outside diameter of 0.189", compared to the T05 can of the prior art, which has an outside diε-.meter of 0.335." The smaller thermopile is then positioned at the end of the probe nearest to the ear, thus greatly improving the viewing angle and eliminating the need for the thermally

insulated wave guide. This positioning also eliminates the need for an extra infrared window.

Additionally, an individual thermocouple is added to the thermopile element to replace the external ambient measuring thermistor, saving virtually all of the cost of the thermistor and possibly improving accuracy of the thermometer.

A second embodiment uses a thermopile element with a single additional thermocouple, both of which are mounted in a recess at the tip of the ear probe and then sealed in with a single infrared window. This eliminates the need for the T018 can, and can result in the thermopile element being even closer to the proximal end of the probe and nearer to the tympanic membrane, thus improving accuracy. This improvement, in either embodiment, virtually eliminates the need for any metal parts (other than the thermopile can) , so that the ear probe can preferably be molded as an integral part of the plastic housing, thus providing additional cost savings. Alternatively, the ear probe may be a separate rod-like element molded of a soft, flexible material thus providing additional cost savings and making it easier for the probe to conform to various ear canal shapes.

Accordingly, it is an object of the present invention to provide an improved infrared tympanic thermometer.

Another object of this invention is to provide an improved infrared tympanic thermometer that results in improved accuracy.

Another object of this invention is to provide an improved infrared tympanic thermometer that results in decreased cost.

Brief Description of the Drawings

These and other objects of the present invention will become better understood through a consideration of the following description taken in conjunction with the drawings in which:

FIG. 1 is a cross-sectional view of a prior art infrared tympanic thermometer, illustrating the use of a thermally insulated, elongated wave guide and one thermistor. FIG. 2 is a cross-sectional view of a prior art infrared tympanic thermometer, illustrating the use of a thermally insulated, elongated wave guide and two thermistors.

FIG. 3 is a cross-sectional view of the improved thermometer using a thermopile element with an individual thermocouple, both of which are mounted in a T018 can that is mounted in a cavity in the ear probe.

FIG. 4 is a cross-sectional view of a second embodiment of the improved thermometer, using a thermopile element with an individual thermocouple, both of which are mounted directly in a cavity in the ear probe.

FIG. 5 is a cross-sectional view of the improved thermometer where a thermopile and thermocouple are mounted in a T018 can (similar to FIG. 3) , showing the can mounted on the end of the ear probe.

FIG. 6 is a cross-sectional, enlarged view of the thermopile, thermocouple and can shown in FIGs. 3 & 5.

FIG. 7 is a cross-sectional, enlarged view of the thermopile and thermocouple shown in FIG. 4. FIG. 8A is a cross-sectional view of the improved thermometer where a thermopile and thermocouple are mounted in a T018 can (similar to FIG. 3) , showing the can mounted in a cavity on the end of a flexible ear probe.

FIG. 8B is a cross-sectional view of the improved thermometer where a thermopile and thermocouple are mounted in a T018 can (similar to FIG. 3), showing the can mounted on the end of a flexible ear probe.

Detailed Description

Turning now to the drawings, FIG. 3 depicts an improved infrared tympanic thermometer 1. The thermometer generally comprises a housing 8, a thermopile with a

thermocouple in a T018 can 2, and the associated electronics and wiring 6. The associated electronics are not herein discussed or shown, as they are well known in the art and more fully described in the prior art, as for example U.S. Pat. No. 4,895,164.

The housing 8 comprises two major components, a body

7 and an ear probe 20. The body 7 and the ear probe 20 may preferably be formed as a unitary structure, or assembled as separate components. Where formed as a unitary structure, they are preferably constructed using a soft, pliable material that is approved by the Food and Drug Administration (FDA) for body contact. Where the body 7 and the ear probe 20 are assembled using separate components, the body 7 need not be constructed using a soft pliable material. The body 7 is preferably formed to allow gripping by a human hand (not shown) . The ear probe

20 is shaped so as to allow insertion into a patient's ear (not shown) . Preferably, material used in the ear probe in either configuration is soft and pliable enough to conform to the shape of the ear canal. Preferred materials are silicon rubber, synthetic rubber, soft injection molded plastics, or natural rubber. As used in the prior art, a disposable cover may be used with the improved thermometer 1. Preferably, the thermopile with a thermocouple is mounted in a T018 can 2 which has an outside diameter of 0.189", as is well known in the art. The T018 can 2 is located in a cavity 9 at the proximal end 4 of the housing

8 nearest to the tympanic membrane. Alternatively, the T018 can 2 may be mounted directly on the proximal end 4 of the ear probe 20, as shown in FIG. 5. In either case, the T018 can 2 has an infrared window 3 that uses a silicon filter, as is well known in the art. The window

3 is positioned at the proximal end 4 so that the infrared radiation from the tympanic membrane passes substantially perpendicular to the plane of the window 3. A focusing lens (not shown) may be used, mounted on the outer surface

of the window 3. The focusing lens is preferably semi¬ circular in shape so as to focus the infrared radiation toward the thermopile. Use of a focusing lens is only possible in the improved thermometer 1 because the thermopile is located near the tympanic membrane. Associated wires 6 lead from the T018 can through a passageway 5 in the housing 8 to a processing and display system (the processing and display system is not shown herein as it is similar to that disclosed in U.S. Patent No. 4,895,164) .

FIG. 6 is an enlarged view of the preferred T018 can 30, showing the mounting of the infrared filter window 3, the thermopile 31, the thermocouple with cold junction 32, a hot junction 36, two ceramic plates 33 & 34, a ceramic block 35, and a T018 can base 38. Support posts 37 are used to attach the above components to the ear probe.

To operate the thermometer 1, the health care professional or home user positions the thermometer 1 so that the ear probe 20 enters the ear canal of the patient, and is as close as possible to the tympanic membrane without touching it, and is substantially perpendicular to the tympanic membrane. Because individual ear canals are shaped differently, it would be preferable to use a pliable material in the construction of the ear probe 20, so that the proximal end 4 containing the thermopile can be aligned as close to perpendicular to the tympanic membrane as possible. The tympanic membrane emits infrared radiation that is detected by the thermopile. Because this infrared radiation is proportional to the body temperature of the patient, the thermometer is able to measure the temperature of the patient. The thermocouple that is placed within the T018 can measures the ambient temperature at which the thermopile is operating, which is used to calibrate the temperature reading.

FIG. 4 illustrates a second embodiment of the present invention, disclosing a thermometer 11 which generally

comprises a housing 19, a thermopile element with thermocouple 12, and the associated electronics and wiring 17. As above, the associated electronics are not shown or discussed herein. Here, as opposed to the thermometer 1 shown in FIG. 3, the thermopile is not mounted in a "can." Rather, it is preferably mounted on a ceramic disk 14 located in a cavity 60 at the proximal end 15 of the probe 20 nearest to the ear. An infrared window 13 is mounted directly on the proximal end 15 of the housing 19, to protect the thermopile 12 and the electronics from the elements. As in the first preferred embodiment, this window 13 uses a silicon filter, as is well known in the art. Also, a focusing lens may be used as described above. A thermocouple is mounted or deposited on the thermopile chip. The handle 18 and the wire passageway 16 are identical to the first embodiment shown in FIG. 3.

FIG. 7 is an enlarged view of the second preferred embodiment, and is similar to FIG. 6 except that the components are not mounted in a T018 can. FIG. 7 shows the thermopile 31, the thermocouple with cold junction 32, a hot junction 36, two ceramic plates 33 & 34, a ceramic block 35, and the disk 14, which may be metal or ceramic. Support posts 37 are used to attach the above components to the ear probe.

Wherever a thermocouple is referred to in the above two embodiments, a discrete or diffused diode or transistor, or a discrete or deposited thermistor can be used in place of the thermocouple, and these variations are intended to be covered by the patent. Additionally, cans smaller than a T018, or of different shape are intended to be covered by this patent. Also, in both embodiments, the ear probe may be made of soft, pliable material in order to facilitate ear canal entry and patient comfort. FIG. 8A shows the use of a flexible ear probe 70 that is fixedly attached to the body 7 at point 71, where the T018 can 2 is mounted in a cavity 9 at the

proximal end 4 of the flexible ear probe 70. FIG. 8B shows the T018 can 2 mounted directly on the proximal end 4 of the flexible ear probe 70.

Operationally, the second embodiment shown in FIG. 4 is similar to the embodiment shown in FIG. 3. They both share the attributes of increased accuracy, reduced cost, and fast reading. Compared to the prior art devices shown in FIGs. 1 & 2, the cost is reduced because an additional infrared window, thermal insulation, heat sink, and additional thermistor and associated electronics are no longer required, though they may be optionally included.

While embodiments of the present invention have been shown and described, various modifications may be made without departing from the scope of the present invention, and all such modifications and equivalents are intended to be covered.