Radiant energy – Infrared-to-visible imaging
Reexamination Certificate
1998-12-22
2001-05-22
Hannaher, Constantine (Department: 2878)
Radiant energy
Infrared-to-visible imaging
C250S203500, C250S352000
Reexamination Certificate
active
06236045
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an infrared quantum structure imaging device or imaging device working at ambient temperature.
The field of the invention relates to the detection of infrared transmissions. Chiefly, two detection mechanisms are used at the present time:
heat sensors which use the variations of a physical parameter (resistivity, capacity, etc.) with the heating due to the absorption of the infrared wave;
quantum sensors which use the transition between two series of quantum levels separated by a forbidden energy gap.
The quantum sensors are particularly valuable because their ultimate performance in terms of detectivity is far greater than that of heat sensors. Thus the values of detectivity of 3×10
11
cm/Hz
½
W are obtained in the II band (between 3 and 5 &mgr;m) with sensors based on semiconductors such as HgCdTe or PbSnTe. These results are more than 20 times higher than those obtained with heat sensors. However, unlike heat sensors, these quantum sensors suffer from the fact that they have to be cooled to be able to work. Typically, they work at temperatures in the range of 80 K.
The French patent application No. 96 15738 describes a quantum sensor working at ambient temperature or close to ambient temperature (250-300 K). This sensor has resonant coupling arrays that increase the values of detectivity of quantum sensors.
FIG. 2
shows the noise equivalent temperature detectable values (NETD) that can be obtained in an optimized structure based on a heterostructure of InAs
0.95
Sb
0.15
(0.1 &mgr;m)/GaSb with a surface area of 40×40 &mgr;m
2
, for a 20 Hz passband and different non-radiative lifetimes in the material.
It can be seen that the performance characteristics of the sensor depend considerably on the temperature. Thus, for a lifetime of 30 ns of the photocarriers, the NETD goes from 40 mK to 5 mK when the temperature goes from 300 to 150 K.
A sensor of this kind does not require any cooling in order to function. However, it may be necessary to improve the performance characteristics and especially to reduce the NETD.
SUMMARY OF THE INVENTION
The invention therefore provides for a quantum structure imaging device working at ambient temperature comprising a cooler thermally coupled to the quantum imaging device and means to control the cooler receiving a command as a function of image-taking parameters such as the contrast of the scene viewed by the sensor, the aperture of the optical system, etc.
The invention provides for the checking of the performance characteristics of the imaging device by means of a control of temperature close to the ambient temperature. It is therefore applicable in an infrared camera system whose performance characteristics can be controlled according to the conditions of use. The matrix of quantum sensors with coupling network is fixedly joined to a Peltier cooling element, the assembly being included in a camera with an input optical system.
REFERENCES:
patent: 4349838 (1982-09-01), Daniel
patent: 5086327 (1992-02-01), Rosencher et al.
patent: 5228777 (1993-07-01), Rosencher et al.
patent: 5326984 (1994-07-01), Rosencher et al.
patent: 5506418 (1996-04-01), Bois et al.
patent: 5650636 (1997-07-01), Takemura et al.
patent: 5726500 (1998-03-01), Duboz et al.
patent: 5869844 (1999-02-01), Rosencher et al.
patent: 5969375 (1999-10-01), Rosencher et al.
patent: 0 443 284 A3 (1991-08-01), None
patent: 2 239 555 (1991-07-01), None
Micheron Francois
Rosencher Emmanuel
"Thomson-CSF"
Gabor Otilia
Hannaher Constantine
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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