Light control devices and methods implemented with kinoform diffusers having controllable diffusion characteristics
Kinoform diffusers ( 82 ) exhibit controllable diffusion characteristics that include off-axis transmittance and reflectance properties, elimination of zero-order beam, and freedom from spectral dispersion under achromatic illumination. Light control devices ( 76, 80, 82 ) implemented with kinoform diffusers having controllable diffusion characteristics provide anisotropic luminous intensity distributions and glare control at high viewing angles while maintaining high luminaire efficiency or daylight utilization.
1. A surface relief optical diffuser, comprising:
an optically diffusing layer having a light entrance major surface and a light exit major surface, the light entrance major surface constructed to diffuse light incident on the light entrance major surface at an angle of incidence measured relative to an entrance surface normal; and
a microscopic surface relief pattern formed as the light entrance major surface of the optically diffusing layer and including multiple light scattering elements having surfaces on each of which are one or more sub-elements, the light scattering elements in response to incident light producing diffused light formed in a light beam pattern having a batwing luminous intensity distribution, the diffused light produced by the light scattering elements propagating through the optically diffusing layer and out of the light exit major surface.
2. The optical diffuser of claim 1 , in which the microscopic surface relief pattern is formed in a photosensitive recording medium.
3. The optical diffuser of claim 1 , in which the microscopic surface relief pattern is a single laser speckle pattern.
4. The optical diffuser of claim 1 , in which the microscopic surface relief pattern is multiple spatially autocorrelated laser speckle patterns.
5. The optical diffuser of claim 4 , in which the multiple spatially autocorrelated laser speckle patterns cooperate such that there is no perceptible undiffused light component propagating from the exit surface.
6. The optical diffuser of claim 1 , in which the microscopic surface relief pattern produces the batwing luminous intensity distribution within a specified range of angles.
7. The optical diffuser of claim 6 , in which the microscopic surface relief pattern exhibits negligible scattering of incident light outside of the specified range of angles.
8. The optical diffuser of claim 1 , in which the microscopic surface relief pattern is in the form of pebbles, pits, or corrugations.
9. The optical diffuser of claim 1 , further comprising a substantially optically transparent protective layer covering the microscopic surface relief pattern.
10. The optical diffuser of claim 1 , in which the microscopic surface relief pattern is recorded in a holographic recording medium.
11. The optical diffuser of claim 1 , in which the microscopic surface relief pattern is of a kinoform type.