Imaging system helps count seeds

The production and preparation of seeds for shipment to retailers and end users involves numerous steps where the seeds must be counted. Traditionally, the process used photodiode-based counters that were relatively slow and not easy to adapt to a variety of seed shapes and sizes.

But when an international horticultural company wanted a high-throughput, high-accuracy alternative to count seeds, they contacted Coleman Technologies (Newtown Square, PA, USA) to provide a solution.

The system was required to deliver a counting accuracy of greater than 99 percent, inspect a variety of seed shapes with dimensions ranging from 0.5 to 20 mm, and count seeds at a rate up to 1,000 seeds/s.

To build the system, the engineers at Coleman Technologies used National Instruments (Austin, TX) vision acquisition software to acquire the images of seeds as they fell through a drop zone.

In the system, a Gigabit Ethernet Basler (Ahrensburg, Germany) 2,000 pixel line-scan camera images the silhouettes of the seeds passing through the drop zone in front of a pair of high-intensity backlights. A 45-degree angle mirror splits the field of view so that the charge-coupled device (CCD) can simultaneously view the drop region from two angles 90 degrees apart.

The ability to view the drop zone from two orthogonal directions enhances the ability of the system’s software to distinguish seeds whose silhouettes overlap in just one view. The use of a single camera and mirror -- as opposed to two separate cameras -- also significantly reduced system size and cost, in addition to simplifying alignment and timing of the two orthogonal camera views.

More information is available here.

-- Dave Wilson, Senior Editor, Vision Systems Design