Apparatus for displaying a virtual scene at a selected position (P 2) in an environment to a user who has a varying head position (P 1) and head pointing direction in the environment, comprising: a display wearable on the head in front of an eye and configured to display and concurrently combine an image on an image plane with light from the environment, a head tracker configured to detect the varying head position (P 1) and head pointing direction in the environment, and a graphics controller connected to the head tracker and the display and having an input for scene data representing the virtual scene at the selected position (P 2), the graphics controller being configured to calculate, from the scene data, image data for the display such that the virtual scene is displayed to the eye at the selected position (P 2) in the environment irrespective of the varying head position (P 1) and head pointing direction, wherein the image data is a succession of image frames to be displayed on the image plane with a frame rate (f fr), each image frame being composed of pixels and being displayed for a frame period (T fr), and the virtual scene appearing in each image frame in a region of scene, ROS, characterised in that the display includes a mirror assembly connected to the graphics controller, a first mirror of the mirror assembly being configured to oscillate about a first axis upon excitation by a first excitation signal (S 1) of a first frequency (f 1) and the first or a second mirror of the mirror assembly being configured to oscillate about a second axis upon excitation by a second excitation signal (S 2) of a second frequency (f 2), wherein the display further includes a light source configured to project a light beam onto the mirror assembly for deflection by the mirror assembly towards the image plane, each pixel in the image plane being hit by the light beam with a per-pixel refresh rate (RR xy), the light source having an input via which it can be controlled according to the pixels of the image data, the image data being fed from the graphics controller to the display via a buffer and an image processor which selectively reads-out the pixels from the buffer and then sequentially applies them to the input of the light source, wherein the graphics controller is configured to modulate one of the first and second excitation signals (S 1, S 2) by a first modulation signal (M 1) which is dependent on the ROS. a display wearable on the head in front of an eye and configured to display and concurrently combine an image on an image plane with light from the environment, a head tracker configured to detect the varying head position (P 1) and head pointing direction in the environment, and a graphics controller connected to the head tracker and the display and having an input for scene data representing the virtual scene at the selected position (P 2), the graphics controller being configured to calculate, from the scene data, image data for the display such that the virtual scene is displayed to the eye at the selected position (P 2) in the environment irrespective of the varying head position (P 1) and head pointing direction, wherein the image data is a succession of image frames to be displayed on the image plane with a frame rate (f fr), each image frame being composed of pixels and being displayed for a frame period (T fr), and the virtual scene appearing in each image frame in a region of scene, ROS, characterised in that the display includes a mirror assembly connected to the graphics controller, a first mirror of the mirror assembly being configured to oscillate about a first axis upon excitation by a first excitation signal (S 1) of a first frequency (f 1) and the first or a second mirror of the mirror assembly being configured to oscillate about a second axis upon excitation by a second excitation signal (S 2) of a second frequency (f 2), wherein the display further includes a light source configured to project a light beam onto the mirror assembly for deflection by the mirror assembly towards the image plane, each pixel in the image plane being hit by the light beam with a per-pixel refresh rate (RR xy), the light source having an input via which it can be controlled according to the pixels of the image data, the image data being fed from the graphics controller to the display via a buffer and an image processor which selectively reads-out the pixels from the buffer and then sequentially applies them to the input of the light source, wherein the graphics controller is configured to modulate one of the first and second excitation signals (S 1, S 2) by a first modulation signal (M 1) which is dependent on the ROS.