Pixel non-uniformity correction
A method of correcting pixel non-uniformity for varying temperature includes determining an FPA temperature and calculating a non-uniformity correction map on a pixel by pixel basis for the FPA, wherein the non-uniformity correction for each pixel is a function of the FPA temperature and empirically derived coefficients. The method also includes applying the non-uniformity correction map at the FPA temperature to condition output of the FPA to produce temperature dependent non-uniformity corrected image data. An imaging system includes a focal plane array (FPA). A temperature sensor is operatively connected to measure FPA temperature. A module is operatively connected to the FPA and temperature sensor to calculate and apply a non-uniformity correction map as described above. There need be no temperature control device for the FPA. The FPA can include a buffered current mirror pixel architecture, and can include an InGaAs material for infrared imaging.
1. A method of correcting pixel non-uniformity for varying temperature comprising:
determining a focal plane array (FPA) temperature;
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 empirically derived coefficients; and
applying the non-uniformity correction map to imaging data from the FPA to produce temperature dependent non-uniformity corrected image data, wherein calculating a non-uniformity correction map on a pixel by pixel basis, wherein the non-uniformity correction for each pixel is a function of the FPA temperature and empirically derived coefficients is governed by
δ
I
c
=
[
p
0
+
p
1
×
log
10
(
T
)
]
×
(
Iraw
-
∑
n
=
0
,
1
,
3
,
5
(
a
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, T max and T min are maximum and minimum temperatures, respectively, for normalizing FPA temperature T, and p0, p1, and a 0 , a 1 , a 3 , and a 5 are empirically derived coefficients.
2. The method as recited in claim 1 , wherein applying the non-uniformity correction map is performed without controlling the temperature of the FPA.
3. The method as recited in claim 1 , wherein the function of the FPA temperature and empirically derived coefficients incorporates approximating change in a respective pixel's level to a desired corrected value based on the FPA temperature.
4. The method as recited in claim 1 , wherein the FPA includes a buffered current mirror pixel architecture.
5. The method as recited in claim 1 , wherein the FPA includes an InGaAs material for infrared imaging.
6. An imaging system comprising:
a focal plane array (FPA);
a temperature sensor operatively connected to measure FPA temperature; and
a module operatively connected to the FPA and temperature sensor to 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, wherein the module is configured to calculate the 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 as governed by
δ
I
c
=
[
p
0
+
p
1
×
log
10
(
T
)
]
×
(
Iraw
-
∑
n
=
0
,
1
,
3
,
5
(
a
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, T max and T min are maximum and minimum temperatures, respectively, for normalizing FPA temperature T, and p0, p1, and a 0 , a 1 , a 3 , and a 5 are empirically derived coefficients.
7. The system as recited in claim 6 , wherein there is no thermoelectric cooling device connected for temperature control of the FPA.
8. The system as recited in claim 7 , wherein there is no temperature control device connected for temperature control of the FPA.
9. The system as recited in claim 6 , wherein the function of the FPA temperature and empirically derived coefficients incorporates approximating change in a respective pixel's dark level to a desired correction value at the FPA temperature.
10. The system as recited in claim 6 , wherein the FPA includes a buffered current mirror pixel architecture.
11. The system as recited in claim 6 , wherein the FPA includes an InGaAs material for infrared imaging.