In this Jan. 21, 2015 file photo, Microsoft's Lorraine Bardeen demonstrates HoloLens headset as what she "sees" is projected on a screen behind at an event at the company's headquarters in Redmond, Wash. AP Photo/Elaine Thompson Those who have tried the HoloLens, Microsoft's new augmented reality headset, have praised it for being immersive and realistic.

It seems so realistic, in fact, that one former Microsoft engineer almost believed that the virtual objects the HoloLens projected on to the scene were actually there in the room with him.

Michael Hoffman left Microsoft in June after working at the company for about a year as a principal engineering lead for the HoloLens.

He's now the founding partner of a startup called Object Theory, a company that plans to launch applications for the HoloLens and consult other companies on how they could apply the headset to enterprise use cases.

During one particular test at Microsoft, an engineer had placed a small cube into the scene as a placeholder. The cube was just there to remind Hoffman and his team that the scene hadn't been finished yet.

But, since the HoloLens automatically re-materializes a scene so that everything in the room is exactly where it was the last time you wore the HoloLens, that tiny cube appeared the next time Hoffman put on the headset.

"The cube happens to be at eye level, and it was the size of a sugar cube," Hoffman said to Business Insider.

The cube seemed so realistic that Hoffman was afraid of bumping into it.

"I would be walking around this scene, and I would suddenly see this cube in front of me," he said. "And I would have an adrenaline rush. My whole body was afraid of running into this thing."

Of course, since the cube is just a virtual object, nothing actually happens if you run into it or walk through it. But it felt real enough for Hoffman's body to react as if something was actually there.

"And you get this adrenaline rush, saying 'Whoa, I have to watch that cube and not run into it,'" he said.

Since the cube was at eye level, it also became larger and more detailed the closer you got to it, Hoffman said.

Some people who have worn the Oculus Rift have reported a similar sensation, such as feeling as if you're going to fall off a ledge if you're standing close to one in Oculus' virtual world.

Using HoloLens to have a Skype "window" follow you. Microsoft

What makes this different, though, is that the HoloLens is an augmented reality headset rather than a virtual reality headset like the Oculus Rift. That means it projects virtual images onto the real world that you see through the headset, whereas virtual reality is a closed-off environment that's entirely virtual and exists within the headset. It doesn't blend with the real world at all.

"I had been wearing the HoloLens for a year, and it was still profound to have it be so real in your brain that you're actually convinced you shouldn't be running into it," Hoffman said. "It just really struck me."