Augmented reality system eye relief adjustment mechanism

A head mounted display (HMD) to be worn by a user, comprising:

• an armature including a left arm and a right arm, each of the left arm and the right arm mounted at a respective proximal end to corresponding left and right attachment structures on the HMD;
• a display mounted at left and right sides to respective distal ends of the left and right arms;
• and
• an eye relief distance adjustment mechanism configured to move the left and right arms in a timed manner toward and away from an eye of the user along a substantially linear path, to thereby adjust an eye relief distance from the display to the eye of the user, the eye relief distance adjustment mechanism comprising respective linear motion actuators at the left and right attachment structures that receive the left arm and the right arm such that the left arm and the right arm can be linearly translated in the timed manner to move the display toward and away from the crown band along the substantially linear path.