Low-profile beam splitter
A beamsplitter can include a first surface with a diffractive optical element, a second surface normal to the first surface, and a beam splitting surface arranged at an angle to the second surface that is less than 45 degrees. The beamsplitter may be configured to illuminate the entire second surface in response to an input beam at the first surface.
1 . A beamsplitter comprising:
a first surface comprising a transmissive diffractive optical element;
a second surface normal to the first surface; and
a beam splitting surface arranged at an angle to the second surface that is less than 45 degrees,
wherein the beamsplitter is configured to illuminate the entire second surface in response to an input beam at the first surface, and
wherein the beam splitting surface is reflective to light of a first state and transmissive to light of a second state, and wherein the transmissive diffractive optical element is configured to receive a collimated input beam that is normally incident on the first surface, the collimated input beam comprising light having the first state, and to convert the collimated input beam into at least a first diffracted beam at a first diffraction angle such that the first diffracted beam is directed toward the beam splitting surface and is reflected by the beam splitting surface in a direction substantially parallel to the first surface.
2 . The beamsplitter of claim 1 , wherein the first diffracted beam exits the beamsplitter at the second surface, a spatial light modulator being provided adjacent to the second surface to receive the first diffracted beam, the spatial light modulator configured to convert the first diffracted beam into a first modulated beam, the first modulated beam comprising light having the second state, and to direct the first modulated beam back toward the second surface.
3 . The beamsplitter of claim 2 , wherein the spatial light modulator is a liquid crystal on silicon (LCOS) spatial light modulator or a digital light processing (DLP) spatial light modulator.
4 . The beamsplitter of claim 2 , further comprising a third surface opposite the second surface, wherein the third surface is configured to receive and transmit the first modulated beam after it passes through the second surface, and wherein the third surface is curved.
5 . The beamsplitter of claim 1 , wherein the transmissive diffractive optical element is further configured to convert the collimated input beam into a second diffracted beam at a second diffraction angle such that the second diffracted beam is directed toward the second surface, is reflected by the second surface toward the beam splitting surface via total internal reflection, and is reflected by the beam splitting surface in the direction substantially parallel to the first surface.
6 . The beamsplitter of claim 5 , wherein the reflected first diffracted beam and the reflected second diffracted beam are received by a spatial light modulator, wherein the reflected first diffracted beam and the reflected second diffracted beam combine to illuminate the entire spatial light modulator.
7 . The beamsplitter of claim 1 , wherein the first, second, and beam splitting surfaces are planar.
8 . The beamsplitter of claim 1 , wherein the second surface is a curved surface.
9 . The beamsplitter of claim 1 , wherein the first, second, and beam splitting surfaces form a wedge.
10 . The beamsplitter of claim 9 , wherein the wedge comprises a refractive index of at least approximately 1.5.
11 . The beamsplitter of claim 1 , wherein the beam splitting surface comprises a polarizing beam splitting surface.
12 . The beamsplitter of claim 1 , wherein the angle of the beam splitting surface with respect to the second surface is about 30 degrees.
13 . The beamsplitter of claim 3 , wherein the first diffraction angle is greater than 0 degrees.
14 . The beamsplitter of claim 13 , wherein the first diffraction angle is about 30 degrees.
15 . The beamsplitter of claims 1 , wherein the diffractive optical element comprises a plurality of diffractive features.
16 . A beamsplitter comprising:
a first surface comprising a reflective diffractive optical element;
a second surface normal to the first surface; and
a beam splitting surface arranged at an angle to the second surface that is less than 45 degrees,
wherein the beamsplitter is configured to illuminate the entire second surface in response to an input beam at the first surface, and
wherein the beam splitting surface is reflective to light of a first state and transmissive to light of a second state, and 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 beam splitting surface and is reflected by the beam splitting surface in a direction substantially parallel to the first surface.
17 . The beamsplitter of claim 16 , wherein the first collimated and diffracted beam exits the beamsplitter at the second surface, a spatial light modulator being provided adjacent to the second surface to receive the first collimated and diffracted beam, the spatial light modulator configured to convert the first collimated and diffracted beam into a first modulated beam, the first modulated beam comprising light having the second state, and to direct the first modulated beam back toward the second surface.
18 . The beamsplitter of claim 16 , wherein the reflective diffractive optical element is further configured to convert the diverging input beam into a second collimated and diffracted beam at a second diffraction angle such that the second collimated and diffracted beam is directed toward the second surface, is reflected by the second surface toward the beam splitting surface via total internal reflection, and is reflected by the beam splitting surface in the direction substantially parallel to the first surface.
19 . The beamsplitter of claim 18 , wherein the reflected first collimated and diffracted beam and the reflected second collimated and diffracted beam are received by a spatial light modulator, wherein the reflected first collimated and diffracted beam and the reflected second collimated and diffracted beam combine to illuminate the entire spatial light modulator.
20 . The beamsplitter of claim 16 , wherein the reflective diffractive optical element is configured to receive a plurality of angularly or laterally separated diverging input beams and to convert them into collimated and diffracted beams with a reduced amount of angular or lateral separation.
21 . The beamsplitter of claim 20 , further comprising a plurality of laterally separated light sources to output the plurality of angularly or laterally separated diverging input beams.
22 . The beamsplitter of claim 21 , wherein the reflective diffractive optical element is configured to receive a first input beam of the a plurality of angularly or laterally separated diverging input beams at a first angle and to convert the first input beam into a corresponding first collimated and diffracted beam directed toward the beam splitting surface along an optical path, and to receive a second input beam of the a plurality of angularly or laterally separated diverging input beams at a second angle and to convert the second input beam into a second collimated and diffracted beam directed toward the beam splitting surface along the optical path.
23 . The beamsplitter of claim 16 , wherein the reflective diffractive optical element comprises a hologram.