Fluidic lens
A fluidic lens includes a cavity 16 containing an optically transparent liquid and bounded by optically transparent walls 10, 32 arranged such that light may pass into the fluid via one wall and exit from the fluid via another wall, at least one said wall including at least one optically transparent piezoelectric element which is deformable so as to change the shape of the cavity.
1. A fluidic lens comprising a cavity containing an optically transparent liquid and bounded by optically transparent walls arranged such that light may pass into the fluid via one said wall and exit from the fluid via another said wall, at least one said wall comprising at least one optically transparent piezoelectric element which is deformable so as to change the shape of the cavity, and wherein the at least one piezoelectric element is of a single crystal material.
2. A lens as in claim 1 , comprising at least one optically transparent electrode for applying an actuating voltage to a said piezoelectric element.
3. A lens as in claim 2 , wherein the electrode is disposed m an optically transparent planarisation layer.
4. A lens as in claim 3 , wherein the material of the planarisation layer has substantially the same refractive index as that of the electrode.
5. A lens as in claim 1 , comprising a plurality of electrodes arranged at the surface of the piezoelectric element to apply actuating voltages to different areas of the piezoelectric element.
6. A lens as in claim 5 , wherein the electrodes form an array such that each said area of the piezoelectric element has individually addressable electrodes.
7. A lens as in claim 1 , wherein the liquid is conductive and forms an electrode for the piezoelectric element.
8. A lens as in claim 1 , wherein the piezoelectric element is configured to provide a plurality of individually-deformable sub-elements.
9. A lens as in claim 8 , comprising a supporting structure which supports the piezoelectric element at nodes between the sub-elements.
10. A lens as in claim 1 , comprising an opening to permit liquid to flow into or out of the cavity when the piezoelectric element is deformed.
11. A lens as in claim 10 , comprising means for maintaining the liquid under pressure.
12. A lens as in claim 10 , comprising a pump configured to be driven simultaneously with deformation of the at least one piezoelectric element to assist the flow of liquid.
13. A lens as in claim 12 , wherein the pump is a piezoelectric pump.
14. A compound lens comprising a plurality of lenses as claimed in claim 1 , a said wall of one lens also forming a said wall of another lens, thereby enabling an achromatic lens with a variable focal length to be realized.