Low-profile beam splitter

An optical device comprising:

• a first surface comprising a reflective diffractive optical element;
• a second surface normal to the first surface;
• and
• a third surface arranged at an angle to the second surface, the third surface being reflective to light of a first state and transmissive to light of a second state;
• wherein the reflective diffractive optical element is configured to receive a diverging input beam, the diverging input beam comprising light having the first state, and to convert the diverging input beam into at least a first collimated and diffracted beam at a first diffraction angle such that the first collimated and diffracted beam is directed toward the second surface, is reflected by the second surface toward the third surface via total internal reflection, and is reflected by the third surface in a direction substantially parallel to the first surface.

A head mounted display (HMD) configured to be worn on a head of a user, the HMD comprising:

• a frame;
• projection optics supported by the frame and configured to project an image to an eye of the user;
• and
• a light projector system in optical communication with the projection optics, the light projector system configured to provide modulated light encoded with the image, the light projector system comprising:
• a light source to emit an input beam;
• an optical device comprising:
• a first surface with a diffractive optical element,
• a second surface normal to the first surface, and
• a third surface arranged at an angle to the second surface, the third surface being reflective to light of a first state and transmissive to light of a second state,
• wherein the diffractive optical element is configured to receive the input beam, the input beam comprising light having the first state, and to convert the input beam into at least a first diffracted beam at a first diffraction angle such that the first diffracted beam is directed toward the second surface, is reflected by the second surface toward the third surface via total internal reflection, and is reflected by the third surface in a direction substantially parallel to the first surface;
• and
• a spatial light modulator configured to produce the modulated light using the input beam delivered to the spatial light modulator by the optical device.

An optical device comprising:

• a first surface comprising a diffractive optical element;
• a second surface normal to the first surface;
• and
• a third surface arranged at an angle to the second surface, the third surface being reflective to light of a first state and transmissive to light of a second state,
• wherein the diffractive optical element is configured to receive an input beam, the input beam comprising light having the first state, and to convert the input beam into at least a first diffracted beam at a first diffraction angle such that the first diffracted beam is directed toward the second surface, is reflected by the second surface toward the third surface via total internal reflection, and is reflected by the third surface in a direction substantially parallel to the first surface.