Below is clipped out of an email from Lowrance-
In 2014, Garmin began shipping their version of down-scanning technology called DownVü™. As you may know, in 2015 the International Trade Commission (ITC) ruled that DownVü™ infringed upon Navico’s patents in the U.S. for DownScan Imaging™.
After a minor redesign to the DownVü™ transducer, Garmin made plans to move forward with U.S. imports. But, the ITC issued a ruling that caused Garmin to move away from the modified DownVü™ design. An ongoing enforcement action is underway relating to Garmin’s U.S. importations and sales of the modified transducer without seeking ITC approval. That brings us to ClearVü™, which is now marketed as Garmin’s side- and down-scanning solution.
ClearVü™ does not infringe on the Navico U.S. patents, because it does not include a down-facing element in the transducer. This creates a scanning gap directly beneath the boat. In the U.S., the Garmin ClearVü™ approach is to stitch together the side-scanning returns to fill the scanning gap directly under the boat. This reduces clarity and range, distorts the appearance of targets picked up by both side-scanning beams and completely misses some targets directly beneath the boat.
The idea of creating a down-scan view by using only the side-scan sonar signals is not new. Other marine electronics manufacturers tried this solution, but recognized it did not work well — opting to provide their customers with a true DownScan Imaging solution, which is why other marine electronics manufacturers, including Humminbird® and Raymarine®, now license the true Navico DownScan Imaging technology for use on their fishfinders.