An optical system including a light-guide optical element (LOE) with a first set of mutually-parallel, partially-reflecting surfaces and a second set of mutually-parallel, partially-reflecting surfaces at a different orientation from the first set. Both sets of partially-reflecting surfaces are located between a set of mutually-parallel major external surfaces. Image illumination introduced at a coupling-in location propagates along the LOE, is redirected by the first set of partially-reflecting surfaces towards the second set of partially-reflecting surfaces, where it is coupled out towards the eye of the user. The first set of partially-reflecting surfaces are implemented as partial surfaces located where needed for filling an eye-motion box with the required image. Additionally, or alternatively, spacing of the first set of partially-reflecting surfaces is varied across a first region of the LOE. Additional features relate to relative orientations of the projector and partially reflecting surfaces to improve compactness and achieve various adjustments.