Fiber optic ear thermometer

• US 5,167,235 A
• Filed: 03/04/1991
• Issued: 12/01/1992
• Est. Priority Date: 03/04/1991
• Status: Expired due to Fees

• Current Assignee: PAT O Daily Revocable Trust Organized Under The Law of CA
• Original Assignee: PAT O Daily Revocable Trust
• Inventors: Plambeck, Greg E., Seacord, Alan R.
• Primary Examiner(s): Pellegrino, Stephen C.
• Assistant Examiner(s): Tucker, Guy V.
• Application Number:
  US07/664,294
• Time in Patent Office: 638 Days
• Field of Search: 128/736, 128/664, 374/130, 374/131, 374/132, 374/121
• US Class Current: 600/474
• CPC Class Codes: G01J 5/02 Constructional details
• CPC Class Codes: G01J 5/025 Interfacing a pyrometer to an external device or network; User interface
• CPC Class Codes: G01J 5/04 Casings
• CPC Class Codes: G01J 5/049 Casings for tympanic thermometers
• CPC Class Codes: G01J 5/05 Means for preventing contamination of the components of the optical system; Means for preventing obstruction of the radiation path
• CPC Class Codes: G01J 5/064 Ambient temperature sensor; Housing temperature sensor; Constructional details thereof
• CPC Class Codes: G01J 5/08 Optical arrangements
• CPC Class Codes: G01J 5/0821 Optical fibres
• CPC Class Codes: G01J 5/16 Arrangements with respect to the cold junction; Compensating influence of ambient temperature or other variables
• CPC Class Codes: G01J 5/70 Passive compensation of pyrometer measurements, e.g. using ambient temperature sensing or sensing of temperature within housing

Abstract

A thermometer for measuring the core temperature of a body by measuring infrared radiation emitted by the tympanic membrane of the ear. The thermometer includes a fiber optic fiber bundle assembly which is inserted into the ear canal to a location adjacent to the tympanic membrane. Infrared radiation is conveyed to a thermopile which converts the radiation to an electrical signal. To assure an accurate signal in changing ambient temperature conditions, circuitry is provided which measures the thermopile resistance (heat) just prior and/or just subsequent to taking a temperature reading and nulling this signal. A disposable sheath is provided to cover the end of the fiber optic assembly inserted into the ear canal to prevent cross contamination between patients. The sheath includes an infrared radiation transparent window over the end of the fiber optic so that there are no openings in the sheath within the ear. Electronic circuitry is provided to measure and display input voltage characteristics, compensate for room temperature variations, fiber optic transmission variations and thermopile cold junction temperature variations, and display an accurate measured temperature. The temperature measured is displayed within about one second of initiation of temperature measurement.

Claims

1. An ear thermometer for measuring body core temperature through infrared radiation from the tympanic membrane which comprises:

a probe adapted to be inserted into the ear canal;

said probe containing an infrared transmitting optical fiber assembly having a first end positioned adjacent to the tympanic membrane when said probe is located in an ear canal;

a disposable sheath surrounding the probe and isolating said probe from contact with the ear canal;

said sheath including a thin infrared transmitting window formed as part of said sheath and positioned over said first optical fiber end;

a housing adjacent to said probe and receiving the second end of said optical fiber;

a thermopile detector adjacent to said second end of said optical fiber and positioned to receive radiation emitted by said second end and for generating an electrical signal corresponding to said radiation;

electrical circuit means for calibrating said signal and compensating for ambient temperature and detector temperature fluctuations and producing an output electrical signal accurately indicative of tympanic membrane temperature;

said electrical circuit means for calibrating said signal including means for measuring the resistance of said thermopile detector to determine the precise present temperature of said detector and means to compensate for variations in said temperature to provide an accurate, drift free, detector output voltage;

said electrical circuit means for calibrating said signal being capable of calibrating said thermopile detector immediately after taking a temperature measurement to assure an accurate temperature measurement;

said electrical circuit means for calibrating said signal comprising;

said thermopile detector;

thermally stable amplifier means for amplifying the output signal from said thermopile detector;

an analog to digital converter for receiving a signal from said amplifier means and for producing a corresponding digital signal; and

a microprocessor for receiving said digital signal and controlling calibration of the system and production of an accurate signal corresponding to the temperature measured and for sending said digital signal to said display means;

said microprocessor controlling a plurality of switches for selectively measuring an input signal, measuring the signal from said thermopile detector, correcting for system errors including thermodrift of the input voltage and current, errors generated by contact thermopotentials and electro-magnetic fields, measuring resistance of the thermopile detector and correcting for thermopile temperature errors, measuring ambient temperature and correcting for errors caused by variations thereof, and measuring voltage from the power supply and indicating insufficiency thereof; and

display means for displaying indicia representing the output signal according to a selected temperature scale.

2. The ear thermometer according to claim 1 wherein said optical fiber assembly comprises fibers formed form chalcogenide glasses.

3. The ear thermometer according to claim 1 wherein said optical fiber assembly is flexible and is curved between said probe and said thermopile within said housing.

4. The ear thermometer according to claim 1 wherein said display is a liquid crystal display means capable of selectively displaying temperature on celsius or fahrenheit scales, and displaying power supply status and system status.

5. The ear thermometer according to claim 4 where said display means includes means for selectively displaying the tympanic temperature measured and that temperature converted to equivalent oral or rectal temperatures.

6. The ear thermometer according to claim 4 wherein said display means includes bar shaped liquid crystal display means for displaying battery condition between fully discharged and fully charged in accordance with displayed bar length.

7. The ear thermometer according to claim 4 wherein said display means includes audible alarm means for indicating low battery charge conditions.

8. The ear thermometer according to claim 1 further including a slidable collet means in contact with an in place sheath and means for moving said collet toward said sheath to eject said sheath without requiring an operator to touch said sheath.