In-flight auto focus method and system for tunable liquid crystal optical element

摘要

An auto-focus system employing a tunable liquid crystal lens is provided that collects images at different optical power values as the liquid crystal molecules are excited between a ground state and a maximum optical power state tracking image focus scores. An image is acquired at a desired optical power value less than maximum optical power established with the liquid crystal molecules closer a fully excited state than the maximum optical power state having the same image focus score. This drive signal employed during image acquisition uses more power than was used to achieve the same optical power value during the auto-focus scan, while actively driving the liquid crystal molecules is fast. A pause due to image transfer/processing delays after acquisition is employed to allow slow relaxation of the liquid crystal molecules back to the ground state in preparation for a subsequent focus search.

主权项

1. A method for auto-focus image acquisition using a variable optical power liquid crystal gradient index lens, said liquid crystal lens having a first low magnitude optical power at or near a liquid crystal orientation ground state, a maximum magnitude optical power when said liquid crystal is in an intermediate excitation state, and a second low magnitude optical power when said liquid crystal is in an advanced excitation state, the method comprising:
initiating cyclical focus score determination from a scene imaged through said liquid crystal lens; driving a liquid crystal of said liquid crystal lens to progress in a relaxation direction from at or near said advanced excitation state to near said intermediate excitation state in accordance with a drive signal sweep regime intended to configure said liquid crystal to operate in said intermediate excitation state while collecting said determined focus scores; detecting a drop in focus scores for asserting a best attainable focus score corresponding to an image acquisition optical power for acquiring an image through said liquid crystal lens; acquiring a best attainable focus image through said liquid crystal lens in an image acquisition excitation state by driving said liquid crystal in an excitation direction to exhibit said acquisition optical power corresponding to said best focus score if said drop of focus scores has been detected; and driving said liquid crystal in said excitation direction to said advanced excitation state to be ready for subsequent auto-focus image acquisition.