A portable electronic device for a mixed reality, MR, headset including a lens through which a user wearing the MR headset can view real-world features and including a holder configured to releasably retain the portable electronic device in a defined orientation relative to the lens, the portable electronic device comprising: a camera configured to output video frames and arranged by the holder to view at least a portion of the lens of the MR headset; a display device arranged to display information that is projected on the lens for reflection directly or indirectly toward the user's eyes and the camera of the MR headset; a processor operationally connected to the camera and to the display device, and configured to perform operations comprising: processing the video frames from the camera to identify locations of at least one real-world feature; displaying information at locations on the display device; and characterized in that the processor is further configured to perform the operation comprising: controlling the processing of the video frames and the displaying of the information on the display device, to at least partially reduce occurrence in the video frames of the information that is displayed by the display device, wherein the controlling the processing of the video frames and the displaying of the information on the display device comprises repetitively alternating between displaying the information on the display device and ceasing display of the information on the display device, wherein the processing of the video frames is controlled to occur during first time durations while the information is not displayed on the display device and controlled to not occur during second time durations while the information is displayed on the display device. a camera configured to output video frames and arranged by the holder to view at least a portion of the lens of the MR headset; a display device arranged to display information that is projected on the lens for reflection directly or indirectly toward the user's eyes and the camera of the MR headset; a processor operationally connected to the camera and to the display device, and configured to perform operations comprising: processing the video frames from the camera to identify locations of at least one real-world feature; displaying information at locations on the display device; and characterized in that the processor is further configured to perform the operation comprising: controlling the processing of the video frames and the displaying of the information on the display device, to at least partially reduce occurrence in the video frames of the information that is displayed by the display device, wherein the controlling the processing of the video frames and the displaying of the information on the display device comprises repetitively alternating between displaying the information on the display device and ceasing display of the information on the display device, wherein the processing of the video frames is controlled to occur during first time durations while the information is not displayed on the display device and controlled to not occur during second time durations while the information is displayed on the display device. processing the video frames from the camera to identify locations of at least one real-world feature; displaying information at locations on the display device; and characterized in that the processor is further configured to perform the operation comprising: controlling the processing of the video frames and the displaying of the information on the display device, to at least partially reduce occurrence in the video frames of the information that is displayed by the display device, wherein the controlling the processing of the video frames and the displaying of the information on the display device comprises repetitively alternating between displaying the information on the display device and ceasing display of the information on the display device, wherein the processing of the video frames is controlled to occur during first time durations while the information is not displayed on the display device and controlled to not occur during second time durations while the information is displayed on the display device. controlling the processing of the video frames and the displaying of the information on the display device, to at least partially reduce occurrence in the video frames of the information that is displayed by the display device, wherein the controlling the processing of the video frames and the displaying of the information on the display device comprises repetitively alternating between displaying the information on the display device and ceasing display of the information on the display device, wherein the processing of the video frames is controlled to occur during first time durations while the information is not displayed on the display device and controlled to not occur during second time durations while the information is displayed on the display device.