People familiar with the plan have revealed that the sensor would complement, not replace, the existing TrueDepth sensor on the front of the iPhone X, Bloomberg reports. The current technology, which supports Apple's Face ID, works by projecting a pattern of 30,000 laser dots onto the user's face, measuring distortion to generate a 3D image for authentication. The proposed sensor would use a "time-of-flight" method instead, calculating the time it takes for a laser to hit surrounding objects, creating a 3D image from that.
Apple released ARKit this year, a software tool that helps developers make AR-based apps for iPhone. It's proven successful with basic AR tasks, but struggles with more complex visuals and lacks depth perception. It's thought a rear-facing 3D sensor would help mitigate these issues. However, sources say that the tech is still in its infancy, and might not be used in the final version of the phone. But there's certainly no shortage of companies manufacturing time-of-flight sensors, so if it doesn't make it into the 2019 model, it's likely that it -- or some kind of incarnation of the technology -- will follow soon after.