The period of détente between LG and Samsung is coming under strain, after the companies began sparring over patents for the eye-tracking technology within their latest smartphones, according to The Yonhap.

LG and Samsung’s display divisions spent much of the last 18 months at loggerheads over screen technology patents. The feud dates back to the summer of 2011, when Samsung Display suspected that 11 of its researchers had leaked details of its OLED technology to LG. This year, however, the duo agreed to forgo litigation in favor of reconciliation, and have since dropped a sales injunction request each.

That road to peaceful coexistence — which could include cross-licensed OLED patents — is being threatened by this row between both firms’ mobile business units.

The eye-tracking technology itself allows users to read Web pages, pause/play video and perform other actions with need for hands, and it is a key part of both of their’ upcoming new devices: the Samsung Galaxy S4 and LG Optimus Pro G (which is already out in Korea).

Word of the Samsung feature initially came out via a leak to the New York Times on March 4. Ten days later — and a day before the Galaxy S4 was unveiledLG announced it would introduce an update in April to bring the scrolling feature to the Optimus G Pro.

Fresh from trying to rain on the Galaxy S4 launch with a cleverly adapted billboard in Times Square, LG has taken the initiative and claimed that it applied for a number of eye-recognition technology patents back in August 2009. A company rep told the Yonhap that it will review potential patent infringement when the Galaxy S4 is launched.

Samsung, as would be expected, fired back denying any infringement. The company claims its technology works in different ways to LG’s, and is therefore not subject to litigation.

We’ll keep a close eye on things since this spat is likely to develop when the Galaxy S4 goes on sale worldwide next month.

Here’s Samsung’s video demonstration from within its Galaxy S4 preview.

Headline image via lge / Flickr