The Dianthus instruments perform well scans in three dimensions before each well is measured for a TRIC response. The process completes within less than one second:
The aim is to position the optical systems precisely in the well center close to the well bottom. The X- and Y-Scans are obtained by moving the plate over the optics. The optical system records the fluorescence in the well. Therefore, aggregates and air bubbles at the bottom of the well can impact the well scan shape. This is recognized and flagged with a negative Well-Scan Quality. For exact positioning in the Z plane, the optics move upwards, while a focused visible light laser is reflected from the plate surface. As soon as the optical focus passes the interface between air and bottom of the well, a peak in reflected light intensity is observed. A second, smaller peak signifies the interface between the bottom of the well and aqueous sample Empty wells and wells with large air bubbles are easily observed by a second high peak in the Z-scan.