Optical power distribution devices
This invention relates to optical splitters, particularly to optical splitters for use in optical touch screens. The present invention provides an optical splitter for distributing light substantially equally from a multimode input waveguide to an array of output waveguides, via a slab region. The distribution of output waveguide widths is chosen to complement the intensity distribution in the slab region, which may or may not be substantially uniform. The invention also provides an optical splitter for distributing light substantially equally from an optical source to a plurality of waveguides, wherein said optical source directs a beam of light into a slab region. The distribution of waveguide widths is chosen to complement the intensity distribution in the slab region, which may or may not be substantially uniform. When used to distribute optical power in optical touch screens, the splitters of the present invention may be used in series and/or in parallel.
1. An optical power splitter for distributing light from an optical source to a plurality of optical waveguides, the splitter comprising a slab region and an array of output waveguides attached thereto, wherein the optical source launches a substantially annular beam directly into the slab region, and wherein the beam diffracts with an optical field that is substantially uniform in the plane of the slab region such that, when the optical field in the slab region impinges on the output waveguides, the integral of the optical field over the waveguide cross-sectional area is substantially equal for each output waveguide.
2. An optical power splitter according to claim 1 , wherein the optical source is a laser with an annular emission profile, a light emitting diode with an annular emission profile or a waveguide with an annular core.
3. An optical power splitter according to claim 2 , wherein the waveguide is an optical fibre or an integrated optical waveguide.
4. An optical power splitter according to claim 3 , wherein the waveguide is an output waveguide of an optical power splitter, thereby to define a multi-stage splitter system.
5. An optical power splitter according to claim 1 , when used as a component of an optical touch screen sensor.
6. An optical power splitter according to claim 1 , wherein at least one of the output waveguides serves as the optical source for a second optical splitter, thereby to define a multi-stage splitter system.
7. An apparatus for distributing optical power to an edge of a input area, to produce a plurality of optical beams for sensing touch input on said input area, the apparatus comprising:
an optical source; and
at least one optical power splitter for distributing light from the optical source to a plurality of output waveguides, each splitter comprising a slab region and an array of output waveguides attached thereto, wherein the optical source launches a substantially annular beam directly into the slab region, and wherein the beam diffracts with an optical field that is substantially uniform in the plane of the slab region such that, when the optical field in the slab region impinges on the output waveguides, the integral of the optical field over the waveguide cross-sectional area is substantially equal for each output waveguide.
8. An apparatus according to claim 7 , wherein the optical source is a laser with an annular emission profile, a light emitting diode with an annular emission profile or a waveguide with an annular core.
9. An apparatus according to claim 8 , wherein the waveguide is an optical fibre or an integrated optical waveguide.
10. An apparatus according to claim 9 , wherein the waveguide is an output waveguide of an optical power splitter, thereby to define a multi-stage splitter system.
11. An apparatus according to claim 7 , wherein at least one of the output waveguides serves as the optical source for a second optical splitter, thereby to define a multi-stage splitter system.