An observation apparatus is disclosed that includes two projection devices, a display panel, and a retaining and supporting member. The two projection devices are each provided with an aperture, and are positioned and oriented so that images are projected onto the display panel through the apertures. The display panel either includes a pupil-forming optical system that is formed of an image-forming element having positive optical power that is integral to the display panel or is sufficiently nearby it such that conjugate positions of the projection apertures are formed at pupil positions for observation. The retaining and supporting member is provided with a retaining mechanism that enables the display panel to be detachably attached to the supporting member.