The retail giant Kroger is using infrared cameras in 95 percent of its stores, and if all goes as planned, no one will even notice the cameras are there.

A system called QueVision, first established in 2010, puts cameras above store entrances and cash registers, runs that data through secret-sauce software, then displays the number of registers currently open and predicts how many will need to be open in 30 minutes.

Infrared cameras are better known for their military and law enforcement applications; they can find people at night hiding beneath camouflage or trying to conceal themselves in wilderness. Why use them for grocery stores?

Turns out, infrared cameras also work fine in regular light, and because they pick up on heat signatures, they're better than visual spectrum cameras at distinguishing people from their backgrounds. If the machine's purpose is to just count new warm bodies entering a store or others waiting in line, infrared is the exact right spectrum to use.

Ultimately, the technology serves a more mundane goal than its advanced origins imply. QueVision is about more efficiently using labor, allowing the store to better plan staffing needs and meet rushes without needing to hire more people or diminishing the quality of the shopping experience. It's a similar logic to self-checkout lines.