Gain normalization and non-uniformity correction

Patent metadata

Field	Value
Publication number	US-2017195599-A1
Application number	US-201614987372-A
Country	US
Kind code	A1
Filing date	Jan 4, 2016
Priority date	Jan 4, 2016
Publication date	Jul 6, 2017
Grant date	—

Abstract

A method of normalizing FPA system gain and correcting pixel non-uniformity for varying temperature includes determining an FPA temperature, calculating an FPA system gain as a function of the FPA temperature, and applying the FPA system gain at the FPA temperature to condition output of the FPA to produce temperature independent image data. The method also includes calculating a non-uniformity correction map on a pixel by pixel basis for the FPA, wherein non-uniformity correction for each pixel is a function of the FPA temperature, and applying the non-uniformity correction map to the imaging data from the FPA to produce temperature dependent non-uniformity corrected image data. An imaging system includes a focal plane array (FPA), a temperature sensor operatively connected to measure temperature of the FPA, and a module configured for system gain correction and non-uniformity correction as described above.

First claim

What is claimed is:

1 . A method of normalizing FPA system gain and correcting pixel non-uniformity for varying temperature comprising:
determining an FPA temperature; calculating an FPA system gain as a function of the FPA temperature; applying the FPA system gain at the FPA temperature to condition output of the FPA to produce temperature independent image data; calculating a non-uniformity correction map on a pixel by pixel basis for the FPA, wherein non-uniformity correction for each pixel is a function of the FPA temperature; and applying the non-uniformity correction map to the imaging data from the FPA to produce temperature dependent non-uniformity corrected image data.

2 . The method as recited in claim 1 , wherein calculating the non-uniformity correction map includes a process that does not itself perform a system gain correction in calculating the non-uniformity correction map.

3 . The method as recited in claim 1 , wherein calculating the FPA system gain includes calculating the FPA system gain as a function of system gain for the FPA at a reference temperature and empirically derived coefficients.

4 . The method as recited in claim 1 , wherein non-uniformity correction for each pixel is a function empirically derived coefficients.

5 . The method as recited in claim 1 , wherein applying the FPA system gain includes applying the FPA system gain to a ROIC operatively connected to the FPA to condition electrical signals from the FPA for imaging.

6 . The method as recited in claim 1 , further comprising:
receiving the imaging data from the FPA, wherein receiving imaging data from the FPA includes transmitting the imaging data to the ROIC from the FPA, wherein the ROIC is operatively connected to the FPA to condition electrical signals from the FPA for imaging.

7 . The method as recited in claim 6 , wherein applying the non-uniformity correction map to the imaging data includes applying the non-uniformity correction map to the imaging data from the ROIC.

8 . The method as recited in claim 1 , wherein applying the FPA system gain and applying the non-uniformity correction map are performed without controlling the temperature of the FPA.

9 . The method as recited in claim 1 , wherein calculating the FPA system gain is governed by
V gain( T )=[( p 1+ p 3 *T ref)* V gainref+ p 2*( T ref− T )]/( p 1+ p 3* T )
wherein Vgain is a variable control level which correlates to the FPA system gain, Vgainref is the value of the control level which sets the FPA system gain at the reference temperature (Tref), and p1, p2, and p3 are empirically derived coefficients.

10 . The method as recited in claim 1 , calculating a non-uniformity correction map on a pixel by pixel basis is governed by

δ



Ic

=

[

p



0

+

p



1
×
log



10


(
T
)

]

×

(

Iraw
-

∑

n
=
0

,
1
,
3
,
5





(

α
n

×

(

T
-

T
min

T
max

-

T
min

)

n

)

)

wherein δIc represents the change for a respective pixel from its dark level to a desired correction value, Iraw is the raw value of the pixel in digital numbers, Tmax and Tmin are maximum and minimum temperatures, respectively, for normalizing FPA temperature T, and p0, p1, and a0, al, a3, and a5 are empirically derived coefficients.

11 . An imaging system comprising:
a focal plane array (FPA); a temperature sensor operatively connected to measure temperature of the FPA; and a module operatively connected to the FPA and temperature sensor to:
calculate FPA system gain for the FPA as a function of the FPA temperature, system gain for the FPA at a reference temperature, and empirically derived coefficients, and to apply the FPA system gain to condition output of the FPA to produce temperature independent image data; and
apply a non-uniformity correction map on a pixel by pixel basis for the FPA as a function of the FPA temperature and empirically derived coefficients, and to apply the non-uniformity correction map to condition output of the FPA to produce temperature dependent non-uniformity corrected image data.

12 . The system as recited in claim 11 , further comprising a ROIC operatively connected to the FPA to condition electrical signals from the FPA for imaging, wherein the module is operatively connected to the FPA through the ROIC, wherein applying the FPA system gain includes applying the FPA system gain to the ROIC, and wherein applying the non-uniformity correction map to the imaging data includes applying the non-uniformity correc

Assignees

• Sensors Unlimited Inc

Inventors

• Nazemi Jonathan

Classifications

• H04N25/671 Primary

  for non-uniformity detection or correction · CPC title

• H04N25/673 Primary

  by using reference sources · CPC title

• H04N5/33

  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) · CPC title

• H04N5/378

  Electricity · mapped topic

• H04N5/3655 Primary

  Electricity · mapped topic