FTA4000 Sample Setup
Sample mounting and setup is unusually important with the FTA4000 because of the small scales involved. The NanoDispense technique solves many problems associated with small drop deposition, but to do this is relies heavily on image processing. Therefore, the overall image seen by the analysis is important. Artifacts in the image may be incorrectly interpreted as the dispense tip or the sample surface.
The NanoDispense system can work in either of two modes, which it automatically detects based on the features seen in the image:
Horizon Image. The front edge of the sample is seen in the image and the drop is presumed to rest at the same height in the image as the front edge. The algorithm detects a horizon by looking down the left and right side edges for a dark region. If no darkness is found down the sides, the horizon is considered to rest at the bottom of the ROI (region of interest) box drawn in blue, unless a reflection image is detected.
Reflection Image. A reflection image is detected if the reflection image of the needle can be found. If it can not be found, the image is considered to be a horizon image.
The operator can make use of the ROI box to exclude unwanted artifacts and also as a default sample surface location in the default horizon mode. Say there is no horizon present and also no reflection image present. The bottom of the ROI box is now interpreted as the sample surface. The Tip Z Bias distance can cause the NanoDispense touch-off height to be any distance above, or below, the sample surface by the Tip Z Bias amount. If the image is truly a "manual" image with neither horizon nor reflection, the Tip Z Bias can be adjusted to bring the dispense tip down to the necessary position to affect the touch-off. This, of course, would have to be done by trial and error.