Compact image projector having a mirror for reflecting a beam received from a polarization beam splitter back to the polarization beam splitter
View Patent ↗A representative embodiment of the invention provides a compact image projector having a light source coupled to a spatial light modulator (SLM). The light source has a substantially planar structure. The overall size of the SLM is dominated by its length and/or width. The projector has an optical arrangement that enables the SLM to be oriented so that the SLM's dominant dimensions are parallel to the plane of the light source. Due to this relative orientation of the SLM and light source, one of the dimensions of the image projector can be smaller than 12 mm, which advantageously enables incorporation of the projector into a hand-held electronic device, such as a cell phone, PDA, or media player.
1. A device, comprising:
a spatial light modulator (SLM);
a polarization beam splitter (PBS) optically coupled to the SLM;
a mirror optically coupled to the PBS; and
first and second quarter-wave plates, wherein:
the PBS is adapted to direct an input beam to the mirror;
the mirror is adapted to reflect the beam received from the PBS back to the PBS, wherein the first quarter-wave plate imparts on the reflected beam a first polarization that causes the PBS to direct said reflected beam to the SLM; and
the SLM is adapted to spatially modulate the beam received from the PBS and direct a resulting spatially modulated beam back to the PBS, wherein the second quarter-wave plate imparts on said spatially modulated beam a second polarization that causes the PBS to direct said spatially modulated beam to an output port to form an output beam.
2. The invention of claim 1 , wherein:
the reflecting surface of the mirror and the spatially modulating surface of the SLM are substantially parallel to each other.
3. The invention of claim 2 , wherein:
the PBS comprises a beam-splitting cube; and
the mirror and the SLM are optically coupled to respective opposite sides of said cube.
4. The invention of claim 2 , wherein the device dimension orthogonal to said surfaces is smaller than 12 mm.
5. The invention of claim 1 , further comprising:
a light source adapted to generate the input beam, wherein the device is a projector having at least one dimension smaller than about 9 mm.
6. The invention of claim 1 , wherein:
the SLM comprises two or more modulation areas;
for each of said modulation areas, the device comprises a respective instance of the PBS, a respective instance of the mirror, and a respective instance of the first and second quarter-wave plates; and
each instance of the PBS is adapted to receive a respective input beam having light of a respective designated color.
7. The invention of claim 1 , wherein:
the SLM comprises three modulation areas; and
the device further comprises three modulator subsections, each subsection having a respective one of said three modulation areas, a respective instance of the PBS, a respective instance of the mirror, and a respective instance of the first and second quarter-wave plates.
8. The invention of claim 7 , further comprising:
a beam combiner adapted to combine three spatially modulated beams produced by the three modulator subsections.
9. The invention of claim 8 , wherein:
the beam combiner comprises an X-cube;
the three modulator subsections form a U-shaped arrangement, wherein each of said three modulator subsections is optically coupled to a respective side of the X-cube.
10. The invention of claim 8 , wherein:
the three modulator subsections form a linear arrangement;
the beam combiner comprises:
an X-cube;
first and second beam guides optically coupled to the X-cube, wherein:
the first beam guide is adapted to couple light from a first of the three modulator subsections to a first side of the X-cube;
the second beam guide is adapted to couple light from a second of the three modulator subsections to a second side of the X-cube;
a third side of the X-cube is adapted to receive light from a third of the three modulator subsections; and
the X cube is adapted to combine the light coupled through the first, second, and third sides to form the output beam.
11. The invention of claim 8 , further comprising:
three projection lenses, each located between the respective modulator subsection and the beam combiner.
12. The invention of claim 7 , further comprising:
a light source having three subsections, wherein each subsection is adapted to generate the respective input beam for the respective modulator subsection.
13. The invention of claim 12 , wherein:
the three respective input beams are parallel to each other.
14. The invention of claim 1 , wherein the device is a hand-held electronic device.
15. A method of spatially modulating a beam of light, comprising:
directing an input beam to a mirror using a polarization beam splitter (PBS);
reflecting the beam received from the PBS back to the PBS using said mirror, wherein a first quarter-wave plate imparts on the reflected beam a first polarization that causes the PBS to direct said reflected beam to a spatial light modulator (SLM) optically coupled to the PBS;
spatially modulating the beam received by the SLM from the PBS; and
directing a resulting spatially modulated beam back to the PBS, wherein a second quarter-wave plate imparts on said spatially modulated beam a second polarization that causes the PBS to direct said spatially modulated beam to an output port to form an output beam.
16. The invention of claim 15 , wherein:
the reflecting surface of the mirror and the spatially modulating surface of the SLM are substantially parallel to each other.
17. The invention of claim 15 , wherein:
the PBS comprises a beam-splitting cube; and
the mirror and the SLM are optically coupled to respective opposite sides of said cube.
18. The invention of claim 15 , wherein:
the SLM comprises two or more modulation areas;
each of said modulation areas is optically coupled to a respective instance of the PBS, a respective instance of the mirror, and a respective instance of the first and second quarter-wave plates to form a respective modulator subsection; and
the method further comprises applying to each instance of the PBS a respective input beam having light of a respective designated color.
19. The invention of claim 18 , further comprising:
spatially modulating each beam received by the SLM from the respective instance of the PBS; and
combining the resulting two or more spatially modulated beams to form the output beam.
20. The invention of claim 18 , wherein:
the two or more respective input beams are parallel to each other.