An optical assembly uses a plastic prism with one flat surface and a collimating lens optic to provide the capability of imaging a color micro-display to the eye. The collimating optic and flat prism surface can allow for aberration-free diopter adjustment and an image with very low-magnitude, nearly-symmetric distortion. The collimating optic can also provide environmental protection of the prism involving an optical plastic device. The input illumination from the micro-display enters the prism, is reflected two times within the prism, exits the prism, and passes through the collimating optic before being viewed by the eye. Such an optical assembly can provide a field of view with eye-relief and exit pupil when viewing a full-color micro-display.