A method comprising: displaying augmented reality (AR) content using an AR head mounted display (HMD), wherein displaying the AR content comprises using a first portion of a left eye display area of the HMD and a first portion of a right eye display area of the HMD to display the AR content; detecting an active stereo display surface in the environment around the AR HMD using a front facing camera of the AR HMD; and responsive to detecting the active stereo display surface, switching the AR HMD to an active shutter mode, the active shutter mode comprising: determining a shutter frequency by analyzing video frames which view the active stereo display surface, the video frames having been captured by the front facing camera of the AR HMD; alternately shuttering a second portion of the left eye display area of the HMD and a second portion of the right eye display area of the HMD in synchronization with images displayed by the active stereo display surface, the two second portions corresponding to and overlapping with a user's view of the active stereo display surface in the AR HMD; allowing light to pass through other portions of the left eye display area of the HMD while the second portion of the left eye display area of the HMD is shuttered; and allowing light to pass through other portions of the right eye display area of the HMD while the second portion of the right eye display are of the HMD is shuttered, wherein the alternate shuttering operates at the determined shutter frequency. displaying augmented reality (AR) content using an AR head mounted display (HMD), wherein displaying the AR content comprises using a first portion of a left eye display area of the HMD and a first portion of a right eye display area of the HMD to display the AR content; detecting an active stereo display surface in the environment around the AR HMD using a front facing camera of the AR HMD; and responsive to detecting the active stereo display surface, switching the AR HMD to an active shutter mode, the active shutter mode comprising: determining a shutter frequency by analyzing video frames which view the active stereo display surface, the video frames having been captured by the front facing camera of the AR HMD; alternately shuttering a second portion of the left eye display area of the HMD and a second portion of the right eye display area of the HMD in synchronization with images displayed by the active stereo display surface, the two second portions corresponding to and overlapping with a user's view of the active stereo display surface in the AR HMD; allowing light to pass through other portions of the left eye display area of the HMD while the second portion of the left eye display area of the HMD is shuttered; and allowing light to pass through other portions of the right eye display area of the HMD while the second portion of the right eye display are of the HMD is shuttered, wherein the alternate shuttering operates at the determined shutter frequency. determining a shutter frequency by analyzing video frames which view the active stereo display surface, the video frames having been captured by the front facing camera of the AR HMD; alternately shuttering a second portion of the left eye display area of the HMD and a second portion of the right eye display area of the HMD in synchronization with images displayed by the active stereo display surface, the two second portions corresponding to and overlapping with a user's view of the active stereo display surface in the AR HMD; allowing light to pass through other portions of the left eye display area of the HMD while the second portion of the left eye display area of the HMD is shuttered; and allowing light to pass through other portions of the right eye display area of the HMD while the second portion of the right eye display are of the HMD is shuttered, wherein the alternate shuttering operates at the determined shutter frequency. <EOS>