Thermal detector with bolometric effect amplification

Details Thermal detector with bolometric effect amplification Thermal detector with bolometric effect amplification

1999-06-28

2001-11-13

Hannaher, Constantine (Department: 2878)

Radiant energy

Invisible radiant energy responsive electric signalling

Infrared responsive

C250S338400, C250S336100, C250S349000

Reexamination Certificate

active

06316770

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a thermal detector and more particularly to an uncooled thermal detector.
PRIOR ART
A known, uncooled thermal detector comprises a thermometer, whereof an electrical property varies as a function of the temperature. The latter varies when a radiation, which is characteristic of the temperature and the emissivity of an observed body and whose wavelength can belong to band III (wavelength range 8 to 12 &mgr;m), is absorbed by an appropriate means thermally coupled to the thermometer, such as e.g. an absorbing layer or an antenna formed on said thermometer.
The known, uncooled, thermal detectors differ by the manner of converting into an electric signal the temperature variation due to the incident radiation and in particular bolometric detectors are known, whose thermometers use resistive materials.
More specifically, the thermometers of known bolometric detectors comprise elements, whose resistivity varies as a function of the temperature and which are biased with a voltage or current source in the continuous or pulsed mode. The resistivity variations and consequently the electrical resistance produce voltage or current variations at the terminals of said detectors.
For materials having a negative temperature coefficient such as e.g. semiconductors, the measurement at a constant voltage, when the latter exceeds a critical value, leads to a self-destruction of a bolometric detector if there is no biasing decrease. Thus, with a voltage biasing (V), the power dissipation (P=V
2
/R) leads to a reduction in the resistance R of the detector, which increases the dissipated power, leading to a thermal runaway. In reality, there is a limit operating temperature beyond which the detector runs away when biased by a d.c. voltage. All the same, the detector has its best response performance characteristics close to said instability conditions.
Bolometers incorporating materials with a positive temperature coefficient, such as e.g. metals, have an identical behaviour when biased by a constant current source. Thus, with a current biasing (I), the power dissipation (P=RI
2
) leads to an increase in the resistance R of the detector, which increases the dissipated power.
DESCRIPTION OF THE INVENTION
The present invention relates to a thermal detector of the uncooled type, whose performance characteristics are significantly better than those of known detectors of this type and which uses for this purpose the aforementioned thermal runaway phenomenon (but appropriately limited so as not to lead to the destruction of the detector).
More specifically, the present invention relates to a thermal detector, characterized in that it comprises:
a resistive element able to undergo a heating and provided with electrical biasing means for amplifying or increasing said heating,
a thermometer thermally coupled to the resistive element and able to convert a temperature variation undergone by said thermometer into an electric signal and
means for reading said electrical signal.
The optimization of the thermometer of said detector and the reading mode of the thermometer leads to a marked increase in the response and to a marked decrease in noise compared with known, uncooled, thermal detectors.
According to a preferred embodiment of the detector according to the invention, the resistive element comprises at least one resistive layer and the biasing means comprise two electrodes, the assembly formed by said layer and said two electrodes being electrically insulated from the thermometer.
According to a first special embodiment, the electrodes are placed on the same side of the resistive layer and, according to a second special embodiment, they are placed on either side of said layer.
The resistive element can have a negative temperature coefficient, the biasing then being a voltage biasing.
In this case, the resistive element can be made from a semiconductor material, which is preferably chosen from among the oxides of vanadium, amorphous silicon and amorphous SiGe.
As a variant, the resistive element can have a positive temperature coefficient, the biasing then being a current biasing.
According to a special embodiment of the detector according to the invention, the thermometer is chosen from within the group including thermopiles or thermobatteries, p-n junctions, Schottky junctions or barriers, electrical resistances, ferroelectric thermometers, pyroelectric thermometers, mechanical deformation thermometers and in particular pneumatic thermometers, and thermometers having at least one microtip.
Preferably, the thermometer is made by a microelectronics procedure so as to have a low heat capacity.
Preferably, the resistive element is produced by a microelectronic procedure.
According to a preferred embodiment of the invention, the detector has a microbridge structure.
The invention also relates to a thermal detector having a matrix structure comprising at least two thermal detectors with bolometric amplification according to the invention.
The detectors according to the invention apply in general terms to the measurements of temperatures and in particular infrared detection, each resistive element then being provided for undergoing heating by means of an infrared radiation, as well as for the detection of nuclear radiation (e.g. neutrons, X-rays, Y-rays).


REFERENCES:
patent: 2865202 (1958-12-01), Bennett
patent: 4853538 (1989-08-01), Jackson
patent: 5825029 (1998-10-01), Agnese et al.
patent: 5912464 (1999-06-01), Vilain et al.
patent: 44 03 947 (1994-11-01), None
patent: 354-369 (1990-02-01), None
patent: 2 207 501 (1989-01-01), None
patent: 9-79128 (1984-08-01), None
Polyconductor Beam Power Sensor, Int. J. Electronics, 1991, vol. 71, No. 2, 363-381.

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