Infrared thermometer

• US 20030016728A1
• Filed: 09/17/2002
• Published: 01/23/2003
• Est. Priority Date: 09/15/1998
• Status: Active Grant

• Current Assignee: Jonathan Gerlitz
• Original Assignee: Jonathan Gerlitz
• Inventors: Gerlitz, Jonathan
• Granted Patent: US 6,991,368 B2
• Time in Patent Office: Days
• US Class Current: 374/121
• CPC Class Codes: G01J 5/02 Constructional details
• CPC Class Codes: G01J 5/0275 Control or determination of height or distance or angle information for sensors or receivers
• CPC Class Codes: G01J 5/028 using a charging unit or battery
• CPC Class Codes: G01J 5/04 Casings
• CPC Class Codes: G01J 5/049 Casings for tympanic thermometers
• CPC Class Codes: G01J 5/06 Arrangements for eliminating effects of disturbing radiation; Arrangements for compensating changes in sensitivity for adjusting of solid angle of collected radiation G01J5/07; means for wavelength selection G01J5/0801
• CPC Class Codes: G01J 5/061 by controlling the temperature of the apparatus or parts thereof, e.g. using cooling means or thermostats
• CPC Class Codes: G01J 5/064 Ambient temperature sensor; Housing temperature sensor; Constructional details thereof
• 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

An infrared ear thermometer includes a detector head housing, a heat sink, a recess formed in the heat sink, a thermopile sensor mounted within the recess, a thermistor, and temperature determination circuitry. The recess defines an aperture that limits the field of view of the thermopile sensor. The thermal capacities and conductivities of the heat sink and the thermopile sensor are selected so that the output signal of the thermopile sensor stabilizes during a temperature measurement. A method of determining temperature using the ear thermometer takes successive measurements, stores the measurements in a moving time window, averages the measurements in the moving window, determines whether the average has stabilized, and outputs an average temperature. A method of calculating a subject'"'"'s temperature determines the temperature of a cold junction of the thermopile, looks up a bias and slope of the thermopile based upon the temperature of the cold junction, measures the output of the thermopile, and calculates the subject'"'"'s temperature based upon a linear relationship between the output and the subject'"'"'s temperature. The linear relationship is defined by the bias and the slope.

Claims

1. An ear thermometer comprising:

a detector head housing;

a heat sink disposed in the detector head housing, the heat sink having a recess formed therein;

a thermopile sensor mounted on the heat sink within the recess, the recess defining an aperture that limits the field of view of the thermopile sensor;

a thermal sensor; and

temperature determination circuitry configured to calculate a temperature in response to output of the thermopile sensor and the thermal sensor.

2. The ear thermometer of claim 1, wherein the detector head housing has a generally tapered configuration, the housing having a front end of relatively small cross section and having a rearward end of relatively large cross section.

3. The ear thermometer of claim 2, wherein the detector head housing comprises a flexible outer surface with a hardness equal to or less than Shore 50.

4. The ear thermometer of claim 3, wherein the detector head housing is constructed from plastic foam material.

5. The ear thermometer of claim 1, further comprising an infrared transmissive window mounted in front of the thermopile sensor.

6. The ear thermometer of claim 1, wherein the thermal sensor is a thermistor.

7. The ear thermometer of claim 6, wherein the thermistor is thermally connected to the thermopile sensor.

8. The ear thermometer of claim 1, wherein the temperature determination circuitry comprises a lookup table for calculating the output temperature.

9. The ear thermometer of claim 1, wherein the thermopile sensor receives radiation without the use of a waveguide.

10. The ear thermometer of claim 1, further comprising a sleeve that fits into the recess, the sleeve defining a second aperture that further limits the field of view of the thermopile sensor.

11. An ear thermometer comprising:

a detector head housing;

a heat sink disposed in the detector head housing, the heat sink having a recess formed therein;

a thermopile sensor mounted on the heat sink within the recess, the thermopile detector comprising a hot junction and a cold junction, the hot junction being responsive to infrared radiation, an output signal of the thermopile sensor being related to a temperature difference between the hot junction and the cold junction, wherein a thermal capacity of the hot junction, a thermal conductivity between the hot junction and the cold junction, a thermal capacity of the cold junction, a thermal conductivity between the cold junction and the heat sink, and a thermal capacity of the heat sink are selected so that the output signal of the thermopile sensor will stabilize or will have a flat peak during a temperature measurement;

a thermistor mounted in thermal communication with the cold junction; and

temperature determination circuitry that calculates an output temperature in response to the output signal of the thermopile sensor and an output of the thermistor.

12. The ear thermometer of claim 11, further comprising an infrared transmissive window interposed between the thermopile sensor and the front end of the detector head housing.

13. The ear thermometer of claim 11, wherein the detector head housing has a generally tapered configuration, the housing having a front end of relatively small cross section and having a rearward end of relatively large cross section.

14. The ear thermometer of claim 13, wherein the detector head housing comprises a flexible outer surface with a hardness equal to or less than Shore 50.

15. The ear thermometer of claim 14, wherein the detector head housing is constructed from plastic foam material.

16. The ear thermometer of claim 11, wherein the temperature determination circuitry comprises a lookup table for calculating the output temperature.

17. The ear thermometer of claim 16, wherein the lookup table defines an output temperature as a function of the output signal of the thermopile sensor and the output of the thermistor.

19. The ear thermometer of claim 18, wherein the detector head housing has a generally tapered configuration, the housing having a front end of relatively small cross section and having a rearward end of relatively large cross section.

20. The ear thermometer of claim 18, further comprising an infrared transmissive window interposed between the thermopile sensor and the front end of the detector head housing.

21. The ear thermometer of claim 20, wherein the detector head housing comprises a flexible outer surface with a hardness equal to or less than Shore 50.

22. The ear thermometer of claim 21, wherein the detector head housing is constructed from plastic foam material.

23. The ear thermometer of claim 18, wherein the temperature determination circuitry comprises a lookup table for calculating the output temperature.

24. The ear thermometer of claim 23, wherein the lookup table defines an output temperature as a function of the output signal of the thermopile sensor and the output of the thermistor.

18. An ear thermometer comprising:

a detector head housing;

a heat sink disposed in the detector head housing, the heat sink having a recess formed therein;

a thermopile sensor mounted on the heat sink within the recess, the thermopile sensor having a hot junction and a cold junction, the hot junction being responsive to infrared radiation, and the output signal of the thermopile detector being related to the temperature difference between the hot junction and the cold junction;

a thermistor mounted in thermal communication with the cold junction;

a heat pipe made of a thermally conductive material, the heat pipe surrounding a portion of the thermopile detector, whereby the heat pipe prevents heat transfer from an ear canal to the hot junction; and

temperature determination circuitry configured to calculate a temperature in response to output of the thermopile sensor and the thermistor.

25. A method for determining the temperature of a subject, the method comprising:

taking successive temperature measurements of the subject using an infrared thermometer;

storing a plurality of most recent temperature measurements in a moving time window;

successively calculating an average of up to all of the plurality of stored measurements;

calculating the difference between successive averages;

determining whether the difference is less than a predetermined value; and

outputting a calculated average temperature.

26. A method for calculating a subject'"'"'s temperature based upon output values from a thermopile and a thermistor of an infrared thermometer, wherein the thermistor is in thermal communication with a cold junction of the thermopile, and wherein the hot junction is in infrared communication with an object to be measured, the method comprising:

determining the temperature of the cold junction with the thermistor;

looking up a bias and a slope of the thermopile in a lookup table based upon the temperature of the cold junction;

measuring the output signal of the thermopile; and

calculating a temperature based upon a linear relationship defining temperature as a function of the output signal of the thermopile in terms of the bias and the slope.

27. An infrared thermometer for measuring temperature of a subject'"'"'s forehead, the thermometer comprising:

a thermopile detector head having a metal heat sink;

a thermopile sensor mounted on a front end of the heat sink;

a thermistor mounted in thermal communication with a cold junction of the thermopile sensor; and

an extension on the outer surface of the detector head for placement against the subject'"'"'s forehead, wherein the extension forms an air pocket isolating a portion of the forehead from air flow outside the air pocket.

28. An infrared thermometer for measuring temperature on a subject'"'"'s forehead, the thermometer comprising:

a thermopile detector head having a metal heat sink;

a thermopile sensor mounted on the front end of the heat sink;

a first temperature sensor for measuring a cold junction temperature of the thermopile sensor;

a second temperature sensor for fast measurement of a room ambient temperature; and

an electronic circuit to calculate the temperature of the subject based in part upon the input of the second temperature sensor.

29. A detector head housing for an infrared clinical thermometer, the housing comprising:

a body made of a soft plastic material, the body having an outer surface configured to make contact with a subject;

a cavity within the body;

a liquid having a high thermal capacity, the liquid filling a portion of the cavity; and

an infrared sensor within the body the infrared sensor thermally isolated from heat generated by the subject by the high thermal capacity liquid.

30. An ear thermometer comprising:

a detector head housing;

a heat sink disposed in the detector head housing, the heat sink having a recess formed therein;

a thermopile sensor mounted on the heat sink within the recess;

a sleeve that fits into the recess, the sleeve defining an aperture that limits the field of view of the thermopile sensor;

a thermistor thermally connected to the thermopile sensor; and

temperature determination circuitry configured to calculate a temperature in response to output of the thermopile sensor and the thermistor.