THERMAL IMAGING CALIBRATION SYSTEM AND METHOD

• US 20160238454A1
• Filed: 08/12/2014
• Published: 08/18/2016
• Est. Priority Date: 09/16/2013
• Status: Active Grant

• Current Assignee: Leonardo S.p.A.
• Original Assignee: Selex ES Ltd (Leonardo S.p.A.)
• Inventors: PILLANS, Luke Alexander
• Granted Patent: US 10,101,213 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01J 2005/0077 Imaging
• CPC Class Codes: G01J 2005/526 Periodic insertion of emissive surface
• CPC Class Codes: G01J 5/0804 Shutters
• CPC Class Codes: G01J 5/53 Reference sources, e.g. standard lamps; Black bodies
• CPC Class Codes: G01J 5/532 using a reference heater of the emissive surface type, e.g. for selectively absorbing materials
• CPC Class Codes: G01J 5/80 Calibration using comparison with reference sources G01J5/52
• CPC Class Codes: H04N 5/33 Transforming infrared radiation cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20

Abstract

A system and method for calibrating an imaging system includes a shutter that is moveable in to the optical path of the imaging system to generate an image of the shutter surface, which is flat and uniform. The shutter can be moved in and out of the optical path between first and second positions. The shutter is heated whilst in the second position and then returned to the first position. Data sets generated at two different temperatures enable the image generated by the imaging system in normal use to be to be adjusted for responsivity and variation in DC offset of the specific pixel array.

Claims

1. A system for calibrating an IR detector having an array of pixels in an imaging system, the calibration system comprising:

a shutter 3 moveable from a first position to a second position, the shutter being disposed in an optical path of an imaging system in the first position and outside of the optical path in the second position, the shutter, when in the second position, being situated adjacent a heat source, the heat source, when operational, heating the shutter to a predetermined temperature, such that the shutter may be moved in to the optical path when in a heated or unheated state thereby enabling two sets of data to be generated, a first set representative of the system at a first temperature and the second set representative of the system at a second temperature.

2. A system according to claim 1 in which the heat source is not in contact with the shutter but arranged to heat the shutter by radiation.

3. A system according to claim 1 in which the heat source is an LED.

4. A system according to claim 1 in which a surface of a shutter blade of the shutter is partially reflective thereby allowing the shutter to appear to be at a lower temperature when placed in front of a cooled infrared detector.

5. A system according to claim 1 in which the shutter is moveable between the first and second positions by a motor 4.

6. A system according to claim 1 in which the first temperature is ambient temperature.

7. An IR thermal imaging camera incorporating the system of claim 1.

8. A method of calibrating a thermal imaging system having a pixel array, the method comprising:

(a) moving a shutter in an the optical path of the imaging system;

(b) measuring flat field data relating to the pixel array at a first temperature;

(c) removing the shutter from the optical path;

(d) positioning the shutter adjacent a heat source for a predetermined time thereby changing the temperature of the shutter to a predetermined second temperature;

(e) moving the shutter back in to the optical path of the imaging system;

(f) measuring flat field data relating to the pixel array at the second predetermined temperature; and

(g) comparing images taken at the first temperature and the second temperature for correction of offset and gain of each pixel.