Cardiologist Dr. Joseph Wiesel, an American doctor and professor at New York University has sued Apple. In his opinion, the “smart” Apple Watch violates his patent for a method of detecting heart rate and atrial fibrillation.

The cardiologist’s patent states the use of a photoplethysmogram to measure the frequency of the heartbeat, and Apple uses the same thing in its watch: photodiodes determine the amount of absorbed light from green LEDs and thereby read the pulse.

According to Wiesel, he contacted Apple in 2017, reporting a patent infringement, but the company refused to negotiate with him. In court, the doctor demanded to block Apple from using the atrial fibrillation detection method without paying royalties.

Apple does not comment on the situation.