10 Advanced Parameters and Commands
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10.4
Temperature Drift Compensation (
m
,
n
,
o
,
p
)
The output data of a microbolometer system is highly affected on the temperature of the camera.
Therefore digital drift compensation can be activated in the post processing chain. An internal
temperature sensor (Dallas DS18B20) is used for calculating an offset that will be added to every
pixel. The parameters for this compensation are normally preset by factory with measured values for
every camera. However, the user can modify these parameters, specially the additional offset
parameter
p=<p16>
.
With
m=<p8>
the drift compensation can be activated/deactivated and a filter for the temperature
values can be switched on/off.
7 6 5 4 3 2 1 0
- - - f - - - m
m 0
Operation Mode
Drift compensation
rw
rw
Bit group
Value (hex)
Explanation
f
0
Filter is enabled
1
Filter is bypassed
m
0
Drift compensation deactivated
1
Drift compensation activated
The parameter
n=<p16>
specifies the slope of the linear drift compensation term n*T+o. The value
specifies the slope in counts per °C and is represented in 10.6 bit fixed point two’s complement
notation.
With
o=<p16>
the offset is specified. The value is represented in 16 bits fixed point two’s
complement notation.
An additional offset (user offset) can be specified by
p=<p16>
. This parameter is represented in 16
bits fixed point two’s complement notation.
10.5
Look Up Table „LUT“ (
D
,
G
)
The temperature data of the microbolometer sensor is generally not linear. By means of the LUT there
is the opportunity to linearize the data that have already been pre-corrected by two point, background
and bad pixel correction, resulting in more exact temperature values. The LUT is implemented as 12
bit LUT.
The operation mode of the LUT is controlled with parameter
G
. The following value assignment is
applied:
0
Deactivated. Data are passed through transparently.
1
Activated.
2
Deactivated. Test mode: LUT data are output sequentially.
(*)
(*)
Attention: Operation mode
2
exists only for test purposes. In case of activating this
mode it has to taken into consideration that the module does not transmit any
incoming image data anymore. It becomes a data source itself instead.
Example:
Activate the LUT for linearization.
>
G=1[CR]
The file containing the LUT data is set with parameter
D
. Ex-factory the LUT is determined one time
and stored into the flash. As generally only one LUT exists in the camera, it is not necessary to change
this parameter.
Example:
Initialisation of the LUT with data from file number 0x80.
>
D=80[CR]
VDS Vosskühler GmbH
IRC-320
