Continuously update stored white reference based on the dark reference

By continuously updating the stored white reference based on the dark reference, accuracy and speed improves in continuous measurement streams.

The checkbox Continuously update white reference based on the dark reference is found on the References tab of Workspace Settings under Advanced. Learn more about Dark and White References .

This option changes how white references are handled and can greatly improve long-term accuracy in continuous measurements.

Continuously update white reference based on the dark reference

When the option is selected, the white reference intensity is saved in a separate file. During real-time measurements, the most recent dark reference is used together with the saved white reference intensity to calculate the final result.

This improves measurement speed and accuracy, especially in continuous measurement streams where it is a new dark references can be captured quickly using the camera shutter, but taking a new white reference requires manual work.

The formula used for Reflectance in this case becomes

where

• is the raw signal value

• is the most recent dark reference. A dark reference is used to remove background noise and correct for sensor offsets in the spectral or spatial dimensions.

• is the saved white reference intensity where the dark reference has been subtracted from the raw white reference:

When 'Continuously update…” is not selected

This is the default setting and uses the standard Reflectance calculations defined in Spectral imaging where the calculation uses both a dark and white reference for the image.

This mode is suitable for applications that do not rely on real-time white reference adjustments, such as fixed-length recordings of measurements where, both a new dark reference and white reference are taken by default.

The formula used for Reflectance in this case becomes

Using the terms and from above this can be rewritten as: