In the present paper we consider an optical design of a head-mounted display with a free-standing holographic image combiner. The optical system works with a 24°×18° field of view and a 6mm pupil providing energy concentration up to 89% for a 20μm-pixel. The combiner represents a volume-phase reflective hologram recorded by two point sources. We demonstrate that the recording and replay angles for the hologram considerably vary across the surface, that causes perturbation and overall decrease of the diffraction efficiency. A revised optical design is presented. It provides a higher hologram efficiency together with a better image quality and decreased decenters of the components. The resultant gain in the median efficiency is factor of 5.3.