Development and Initial Results for Updated Versions of Optical Array Probes for Airborne and Ground Based Drop Size and Concentration Measurements (Invited Presentation)

2D Optical Array Probes (OAP) are line scanning probes that produce images of drops in the size range of 15um to 3 mm passing through their sample volume by recording the shadow/now shadow state of an array of optical sensors. This presentation presents the development and testing of a new generation of OAP probes. The focus of the development was to improve the probes in a number of ways with emphasis on the real-time processing of the image data.

In particular it was desired to increase the maximum sampling velocity, utilize modern electronics, allow for field repairs, accurate sample volume determination, minimizing of drop oversizing and drop size spectrum broadening, lower cost, and easier probe optical alignment.

It was also desired to produce data in real-time that could approach the accuracy of post processing methods. This is particularly desirable for inflight aircraft guidance and for ground based facility calibrations . The probes still provide original image data for more detailed post flight processing.

Particular attention was paid during the development of probe to minimize the total volume of data recorded by rejecting in real-time images that would be rejected in later, post processing.