Apple's first slide-to-unlock patent was granted in 2010, its second in 2011, and on cue version 3.0 was just dropped on us. US patent number 8,286,103 issued yesterday and, as expected, it's even broader than the first two. The '103 patent moves past the limiting language of the first two patents that required that the unlock image move along a predefined path, or that it at least start and stop at predefined locations on the screen. The '103 patent now broadly covers continuously moving an image to a general unlock region on the screen to unlock the device.

Predefined path, gone; predefined location, gone

While most of the background language in Apple's newest claims mirrors the first two patents, two key sections were overhauled. For the path, the new claims only require the step of "continuously moving the unlock image on the touch-sensitive display in accordance with movement of the detected contact." So the predefined path limitation is gone. Also, the new claims only indicate that there be "movement of the unlock image from the first location to an unlock region" on the display. Again, no single predefined start or stop location is required.

You can see that the effective scope of the claim isn't concerned with where you start, the path you take, or that you end up anywhere other than a general "unlock region." It's really only important that you continuously move an image to an unlock region. That's significantly expanded patent coverage.

Today's patent workaround may be tomorrow's infringement

Heavy use of the predefined verbiage in the first two patents left the door open for competitors — namely Android OEMs — to implement unlock features that would likely avoid the patents. We saw Samsung, LG, HTC, and likely even Google beginning with stock Ice Cream Sandwich, come up with workarounds to Apple's patents. While some of the competition is still arguably sidestepping the coverage of the '103 patent with their previous workarounds — such as HTC with its lack of a distinct "unlock region" — others may need to look at yet another design tweak to avoid locking horns with Apple in the future.

This may all seem like subterfuge on Apple's part, but it's a relatively common practice in the US. While many other countries don't allow it, a US patent owner can file what is called a "continuation" patent application before a patent issues. These continuations can be used to go after different — usually broader — coverage compared to the original patent, effectively presenting the competition with an ever-moving target for its workarounds. That's exactly what Apple has done with its chain of patents here. Granted, the disclosure of the original patent filing, combined with the existence of prior patents and devices having unlock features, will at some point limit what protection Apple can get, but we're not there just yet. In fact, Apple filed another continuing application in July, before the '103 patent issued, so we can assume it will take another stab at expanding its coverage over the next couple years. We'll just have to wait and see how this all plays out.