Variable light shaping optic using liquid crystals and surface relief micro-structure diffuser
In a liquid crystal type variable beam shaping optic, a part of a structure that forms a gap for the liquid crystals includes a surface relief micro-structure diffuser. Due to the micro-features of the diffuser, the gap is non-uniform. A voltage applied to an electrode associated with the diffuser and an electrode associated with an opposing substrate controls the orientation of uniaxial nematic liquid crystals in a material filling the non-uniform gap. For example, the index of refraction of the material may vary relative to an index of refraction of the diffuser, based on variations of the crystal orientation caused by variation of the applied voltage. The change in relative indices of refraction, in the examples, changes a focal length of the variable optic and thus the shape of a light beam optically processed through the liquid crystal optic.
1. A variable light shaping optic, comprising:
a first transparent substrate having an input surface to receive incoming light input from a light source;
a first transparent electrode on the first transparent substrate;
a second transparent substrate having an output surface to emit illumination light output;
a first surface relief micro-structure diffuser located on the first transparent substrate and including first micro-structure features having pseudorandom patterns and curved lens-like surfaces facing a non-uniform gap;
a second surface relief micro-structure diffuser located at a distance from the first transparent substrate to form a non-uniform gap and including second micro-structure features having pseudorandom patterns and extending toward the first transparent substrate, each of the second micro-structure features having a width between 5-20 micrometers (μm) and including a curved lens-like surface facing the non-uniform gap;
a uniaxial nematic liquid crystal material filling the non-uniform gap, wherein the incoming light input first passes through the first transparent substrate, then passes through the uniaxial liquid crystal material, and then passes through the second surface relief micro-structure diffuser as the illumination light output; and
a second transparent electrode associated with the second surface relief micro-structure diffuser,
wherein:
the first and second transparent electrodes are configured to generate an electric field in the uniaxial nematic liquid crystal material in response to a control voltage applied across the first and second transparent electrodes, to set orientation of uniaxial nematic liquid crystals in the uniaxial nematic liquid crystal material and thus an index of refraction of the uniaxial nematic liquid crystal material filling the non-uniform gap, to set a focal length of the variable light shaping optic,
the first transparent electrode has curved lens-like surfaces facing the non-uniform gap and is formed directly on the curved lens-like surfaces of the first micro-structure features,
the second transparent electrode has curved lens-like surfaces facing the non-uniform gap and is formed directly on the lens-like surfaces of the second micro-structure features, and
the non-uniform gap is directly defined by the curved lens-like surfaces of the first and second transparent electrodes, respectively.
2. The variable light shaping optic of claim 1 , wherein: the second surface relief micro-structure diffuser is a film on the second transparent substrate and comprises convex micro-structure features with valleys between; and each of the convex micro-structure features is curved outward from the second transparent substrate toward the non-uniform gap.
3. The variable light shaping optic of claim 1 , wherein the second surface relief micro-structure diffuser is located between the second transparent electrode and the second transparent substrate.
4. A controllable optical apparatus comprising the variable light shaping optic of claim 1 and a driver circuit connected to the first and second transparent electrodes, the driver circuit being controllable to provide different values of the control voltage.
5. The controllable optical apparatus of claim 4 , wherein:
a first value of the control voltage orients the uniaxial nematic liquid crystals in the uniaxial nematic liquid crystal material so that the uniaxial nematic liquid crystal material exhibits a first index of refraction at least substantially similar to a third index of refraction of the second surface relief micro-structure diffuser, and
a second value of the control voltage orients the uniaxial nematic liquid crystals in the uniaxial nematic liquid crystal material so that the uniaxial nematic liquid crystal material exhibits a second index of refraction at least substantially different from the third index of refraction of the second surface relief micro-structure diffuser.
6. An apparatus comprising the variable light shaping optic of claim 1 and an optical/electrical transducer optically coupled to send or receive light through the variable light shaping optic.
7. A system comprising the apparatus of claim 6 , further comprising a processor coupled to control the variable light shaping optic and the optical/electrical transducer.