Abstract: An on-axis, optical head-up display device, for use in fixed installations, vehicles or aircraft, utilizes a single block of transparent acrylic resin with the upper surface curved and coated to form a collimating mirror. The block itself is comprised of two major portions cemented together with a transparent bonding material wherein the resulting interface forms a combining surface. A generated image is transmitted from the focal plane of the collimating mirror upwardly through the combining surface; then it is reflected downwardly by the collimating mirror back to the combining surface which in turn serves to combine the generated image with a background view. The combined image is viewed by an observer through a back window of the block. Optical aberrations are reduced by extending the material of the block to the focal plane of the collimating mirror where an image generator is located.