Low profile image combiner for near-eye displays
An image combiner, also referred to as a combiner optic, of a near-eye display system or the like transmits enough light so a user can see remote objects in a “world view”, while also reflecting enough light so the user can simultaneously see a projected image in a “projected” (augmented) view. The disclosed image combiners use two partial reflectors configured to form a wedged reflective cavity. In the display system, light from an imaging device follows a path to the user's eye that includes three reflections in the wedged cavity. By using this capability of the wedged cavity, the combiner optic can have a substantially reduced thickness, and lower profile, than a combiner optic that uses only one partial reflector and only one reflection in the optical path.
1. A combiner optic comprising:
a first lens comprising a first major surface and an opposing curved second major surface;
a second lens comprising a curved major surface facing and substantially matching the curved second major surface of the first lens;
a partial reflector sandwiched between the curved major surface of the second lens and the curved second major surface of the first lens; and
a reflective polarizer disposed on the first major surface of the first lens, the partial reflector and the reflective polarizer forming a wedged reflective cavity and having sufficient light transmission to permit viewing of an object through the combiner optic.
2. The combiner optic of claim 1 , wherein the reflective polarizer is a linear reflective polarizer.
3. The combiner optic of claim 1 , wherein the reflective polarizer is a circular reflective polarizer.
4. The combiner optic of claim 1 , wherein the partial reflector is a notched reflector, and wherein over a wavelength range from 400-700 nm, the notched reflector comprises at least one distinct reflection band whose full width at half maximum (FWHM) is less than 100 nanometers.
5. The combiner optic of claim 1 , wherein the partial reflector has a reflectivity at normal incidence that is substantially insensitive to polarization state.
6. The combiner optic of claim 1 , wherein for visible light, each of the partial reflector and the reflective polarizer has an average reflectivity in a range from 25% to 75%, and an average transmission in a range from 25% to 75%.
7. The combiner optic of claim 1 further comprising a retarder layer disposed between the partial reflector and the reflective polarizer.