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OPTIMIZATION — Gains, Offsets and Integration Time
Optimizing your ASD spectrometer results in:
- Automatic setting of Gains and Offsets for the Swir detectors
- Automatic setting of Integration Time value for Vnir detector
- Automatic Dark Current collect
Optimization values depend on the response to light in a particular spectral region. A well-optimized instrument will display between 20 and 35 thousand DN (approx.), if the source is within the Gain and Integration time abilities of the system.
A Spectralon blank should be used when optimizing and for taking a white reference measurement. An Optimization is required before any data is acquired.
The instrument must be re-optimized after any change in temperature - internal or environmental - or lighting conditions . If lighting conditions don't change at all, the Gain won't change significantly from the value after optimization; but Offset, even if it changes by 10 (say from 2150 to 2160), will have a significant effect if Gain is relatively high, like around 25. The SWIR 2 dark current increases with temperature and dramatically reduces the dynamic range of the spectrometer. Note that conditions can change rapidly or slowly, it all depends on clouds, wind (affecting temperature), instrument warm up time, etc. |
