A lawsuit filed with the U.S. District Court for the Northern District of California on Tuesday claims the cameras in Apple's iPhone 7 Plus and newer dual-camera models infringe on a patent that was granted in 2003 and is based on an invention from 1999.

Plaintiffs Yanbin Yu and Zhongxuan Zhang allege Apple's dual-cameras are in infringement of U.S. Patent No. 6,611,289 for "Digital cameras using multiple sensors with multiple lenses".

The patent describes methods for capturing multiple images using multiple lens and sensor arrays. The patent focuses on a four-camera setup that captures images on monochrome sensors and merges them into a single color image. According to the lawsuit Apple was aware of the existing patent as early as 2011.

The complaint also alleges that Apple's own multi-sensor camera patent No. 8,115,825, "Electronic device with two image sensors." which was filed for in 2008 and granted in 2012, claimed "many of the same features" as the patent from Yu and Zhang.

The plaintiffs note that Apple made significant investments into its dual-camera technology, acquiring 3D sensor specialist PrimeSense in 2013 and camera technology company LinX Imaging in 2015 but did not seek to license Yu and Zhang's patent, launching several iPhone models knowing they were infringing on somebody else's patent.

This is not the first time Apple has camera-related legal problems. Earlier this year Israel-based company CorePhotonics also files a lawsuit against the US company. We'll continue to keep an eye on both cases.