Patent ID: 8049811
Filing Date: 2011-11-01
Classification: H04N

Abstract:
1. An automatic focusing apparatus comprising: a focusing lens; a focus actuator connected to the focusing lens to move the focusing lens; an image sensor aligned with the focusing lens to detect an image through the focusing lens; j digital band-pass filters connected to the image sensor to extract a set of sharpness samples from a noise-free, blurred, Bayer-pattern sampled image within a focus window from the detected image wherein j>=2; a memory storing a set of device parameters; and a processor connected to the focus actuator, the digital band-pass filters and the memory, wherein the processor (a) generates M sets of spatial frequency parameters and M focus actuator step sizes using the set of device parameters wherein M is a number of segments of a spatial frequency axis, and with i=1 (b) loads the i to i+j sets of spatial frequency parameters into the digital band-pass filters (c) obtains a matrix of focus value samples from the digital band-pass filters, (d) controls the focus actuator to sample a local surface behavior using the i focus actuator step size, (e) repeats steps (b) to (d) with i=i+1 whenever a switch condition is satisfied, and (f) estimates a final in-focus position for the image and controls the focusing lens to move to the final in-focus position whenever a stop condition is satisfied.