Method for maintenance of an array of bolometer-type detectors
View Patent ↗A method for maintenance of an array of bolometer-type detectors comprises heating of certain detectors to a threshold temperature. The heating is performed by supplying resistive detection elements with electric currents, and the threshold temperature is determined for each detector as a function of a measurement made previously on said detector. Such method makes it possible to eliminate persistent images caused by radiation overexposure, or by damage to the thermoelectric properties of certain pixels appearing during the manufacture or ageing thereof. The method does not require the use of an oven or Peltier element, thus avoiding the risk for such heating component to damage irreversibly the reading and CMOS addressing circuits on which the detectors are hybridised or deposited.
1. A method for maintenance of an array of bolometer-type detectors suitable for measuring electromagnetic radiations originating from a radiating scene, said method being suitable for stopping persistence of a radiation overexposure experienced by at least one of the detectors of the array, and comprising the following steps performed apart from a radiation measurement sequence:
/1/ measurement of a temperature and/or electric resistance of a resistive element of at least one identified detector of the array;
/2/ for said identified detector, setting of a threshold temperature and/or threshold resistance, respectively greater than the temperature measured and/or less than the resistance measured in step /1/;
/3/ supply of a resistive element of at least one detector of the array, with an electric current suitable for heating the identified detector at least up to said threshold temperature and/or the threshold resistance; and
/4/ cooling of said identified detector, by progressively reducing the electric current supplied to the resistive element used in step /3/ for heating said identified detector.
2. The method according to claim 1 , wherein the threshold temperature and/or the threshold resistance is set in step /2/ as a function of a deviation between the temperature and/or resistance measured in step /1/ for said identified detector and a temperature and/or resistance reference value, respectively.
3. The method according to claim 1 , comprising an additional step for selecting the identified detector, performed between steps /1/ and /2/, after which steps /2/ to /4/ are performed for said identified detector only if the temperature and/or resistance measured in step /1/ for said detector satisfy a defined selection condition.
4. The method according to claim 3 , wherein the selection condition is defined such that the identified detector is selected for steps /2/ to /4/ if said identified detector has persistence from a previous radiation overexposure or damage during the operation thereof.
5. A method according to claim 3 , wherein the additional step for selecting the identified detector is performed by means of CMOS type addressing.
6. The method according to claim 1 , wherein the electric current supply in step /3/ is performed by means of CMOS type addressing.
7. The method according to claim 1 , wherein the step /3/ is performed so as to modify a material of the identified detector, said modified material being sensitive to electromagnetic radiation during a radiation measurement sequence.
8. The method according to claim 1 , wherein the detector resistive element used in step /3/ for heating the identified detector belongs to said identified detector.
9. The method according to claim 1 , wherein the identified detector is heated in step /3/ to a temperature greater than 60° C., preferentially greater than 100° C.
10. The method according to claim 1 , wherein step /3/ is performed so as to maintain said identified detector for a duration of at least one minute at a temperature greater than or equal to the threshold temperature, and/or at a resistance less than or equal to the threshold resistance.
11. The method according to claim 1 , wherein the cooling in step /4/ has a duration greater than at least two minutes, or greater than ten minutes.
12. The method according to claim 1 , further comprising a step for measuring the respective temperatures and/or resistances of the detectors of at least part of the array, and wherein the threshold temperature and/or the threshold resistance of the identified detector is set in step /2/ as a function of the temperatures and/or resistance measured for the detectors of said part of the array, in addition to the temperature and/or resistance measured for said identified detector.
13. The method according to claim 1 , wherein step /1/ is performed for a plurality of identified detectors, and wherein electric currents are supplied in step /3/ simultaneously to respective resistive elements of a plurality of detectors of the array, said electric currents being determined using an algorithm for processing the temperatures and/or resistances measured respectively for the identified detectors, so as to heat said identified detectors simultaneously.
14. The method according to claim 13 , wherein said identified detectors are heated simultaneously up to a common maximum temperature.
15. The method according to claim 1 , performed automatically.
16. An assembly for measuring electromagnetic radiation from a radiation scene, comprising:
an array of bolometer-type detectors;
an addressing system suitable for identifying any detector in the array; and
means for maintaining said array.
17. The assembly according to claim 16 , wherein the maintenance means are suitable for controlling automatic execution of the maintenance method.
18. The assembly according to claim 16 , wherein the maintenance means themselves comprise:
means for measuring temperatures and/or resistances of respective resistive elements of detectors in the array, said measurement means being suitable for supplying measurement signals for identified detectors of the array;
a unit for processing the temperatures and/or resistances measured by the measurement means for the identified detectors, said processing unit being suitable for determining a threshold temperature and/or a threshold resistance for each of the identified detectors;
an electric current power supply unit, connected to the detectors of the array by the addressing system; and
a unit for computing at least one electric current to be supplied by the power supply unit to at least one detector of the array, so that each identified detector reaches a temperature greater than or equal to the threshold temperature, and/or a resistance less than or equal to the threshold resistance, determined for said identified detector, said computation unit being additionally suitable for controlling a progressive reduction of said electric current.