Non-contacting temperature sensing device

• US 6,222,454 B1
• Filed: 07/01/1999
• Issued: 04/24/2001
• Est. Priority Date: 07/01/1999
• Status: Expired due to Term

• Current Assignee: Monterey Research, LLC (Vector Capital Corporation)
• Original Assignee: GOAL Electronics Incorporated
• Inventors: Picard, Francis, Azelmad, Abdellah, Harling, Gord, Zhang, Rose, Pope, Tim
• Primary Examiner(s): Wu, Daniel J.
• Assistant Examiner(s): PHAM, TOAN NGOC
• Application Number:
  US09/340,506
• Time in Patent Office: 663 Days
• Field of Search: 340/584, 340/583, 340/905, 340/580, 340/581, 340/962, 250/339.04, 250/340, 250/341, 250/338.1, 250/339.01, 250/339.02, 356/51, 356/448
• US Class Current: 340/584
• CPC Class Codes: G01J 5/0022 for sensing the radiation of moving bodies
• CPC Class Codes: G01J 5/08 Optical arrangements
• CPC Class Codes: G01J 5/0806 Focusing or collimating elements, e.g. lenses or concave mirrors
• CPC Class Codes: G01J 5/20 using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices
• CPC Class Codes: G01J 5/24 Use of specially adapted circuits, e.g. bridge circuits
• CPC Class Codes: G01J 5/602 using selective, monochromatic or bandpass filtering
• CPC Class Codes: G01J 5/80 Calibration using comparison with reference sources G01J5/52

Abstract

The device according to the invention provides a non-contacting temperature sensing device incorporating micro-bolometric detectors as the suitable infrared sensors for automotive applications. A first and second infrared sensors each include an active infrared sensing element and a temperature drift compensating element. A current bias is applied to the active infrared sensing element as well as to the temperature drift compensating element, which is identical in structure with the active infrared sensing element, and the voltage outputs of these two elements pass through a differential amplifier. The fluctuation in the substrate temperature or the ambient temperature affects the active sensing element and the compensating element in the same way, thus it is cancelled out. Instead of using one spectral band of the infrared radiation, as in the prior art, two spectral bands are used resulting in a first and second signal generated by the first and second infrared sensors. A ratio of the first and second signals is obtained. The ratio of the signals is emissivity independent, so that the device of the present invention provides a more accurate measurement of temperature. The need to compensate for window contamination is also eliminated by this two band approach. The filtering elements for the two bands can be multi-layer thin film filters either coated on flat windows or on diffractive micro-lenses. The use of diffractive micro-lenses further reduces the size of the device, and eliminates the need for a separate optical lens.

Claims

1. A non-contacting temperature sensing device for use with a vehicle, comprising:

a first infrared sensing means for detecting infrared radiation within a first wavelength band and for producing a first signal corresponding to said detected infrared radiation of said first wavelength band;

said first infrared sensing means comprising an active infrared detecting element providing an active signal and a first temperature drift compensating element providing an inactive signal and said first signal corresponding to an amplified difference between said active signal and said inactive signal;

a second infrared sensing means for detecting infrared radiation within a second wavelength band and for producing a second signal corresponding to said detected infrared radiation of said second wavelength band;

said second infrared sensing means comprising an active infrared detecting element providing an active signal and a second temperature drift compensating element providing an inactive signal and said second signal corresponding to an amplified difference between said active signal and said inactive signal

power means for powering said first and second infrared sensing means; and

signal processing means for obtaining the ratio of the first and second signal in order to provide a third signal, said third signal being emissivity independent and proportional to a temperature.

2. A non-contacting temperature sensing device according to claim 1 wherein:

said device further includes a first wavelength selecting means aligned with said first infrared sensing means and a second wavelength selecting means aligned with said second infrared sensing means, and wherein said first and second wavelength selecting means allow passage of a first and second wavelength respectively, said first and second wavelength being suitably close to one another in the spectrum to represent an emissivity ratio substantially equal to one.

3. A non-contacting temperature sensing device according to claim 2, wherein said first and second temperature drift compensating elements are aligned with an infrared radiation opaque window.

4. A non-contacting temperature sensing device according to claim 3, wherein said active infrared detecting elements of said first and second infrared sensing means are micro-bolometers.

5. A non-contacting temperature sensing device according to claim 4, wherein said temperature drift compensating elements are micro-bolometers identical to said micro-bolometers of said first and second infrared sensing means.

6. A non-contacting temperature sensing device according to claim 3, wherein said first and second infrared sensing means and said temperature drift compensating elements each comprise a plurality of identical micro-bolometers connected in series, respectively.

7. A non-contacting temperature sensing device according to claim 3, wherein said opaque window has an emissive characteristic substantially equal to an emissive characteristic of said first and second wavelength selecting means respectively.

8. A non-contacting temperature sensing device according to claim 2, wherein said first and second wavelength selecting means are multi-layer thin dielectric film band-pass filters.

9. A non-contacting temperature sensing device according to claim 2, wherein said first and second wavelength selecting means are diffractive microlenses.

10. A non-contacting temperature sensing device according to claim 1, wherein said power means include bias generating circuitry integrated with said infrared sensing means, and wherein said bias generating circuitry can generate continuous bias or pulsed bias.

11. A non-contacting temperature sensing device according to claim 1, wherein said first and second infrared sensing means are housed in a casing and can operate in vacuum, in air or in an inert gas environment.

12. A non-contacting temperature sensing device according to claim 1, wherein said signal processing means comprises signal amplifier means, signal averaging means, analog to digital conversion means and signal ratio means, said signal processing means being integrated on a same chip as said first and second infrared sensing means.

13. A non-contacting temperature sensing device according to claim 1, wherein said device includes a temperature indicating means operatively connected to said signal ratio means for receiving the ratio output signal therefrom and displaying a corresponding temperature of a radiating object.