Method and system for robust contrast based auto focus in low light

An image capture system, comprising:

• a camera;
• one or more processors;
• and
• memory coupled to the one or more processors and comprising computer readable code executable by the one or more processors to:
• determine a plurality of regions of interest in a view of a scene;
• obtain, for each of the plurality of regions of interest, a set of image data for each of a plurality of focus settings;
• apply a plurality of focus filters to the set of image data for each of the plurality of focus settings for each of the plurality of regions of interest to obtain a plurality of sets of focus scores;
• determine, for each of the plurality of sets of focus scores, a focus curve, wherein the focus curve is derived from a particular set of focus scores across the plurality of focus settings for a particular focus filter of the plurality of focus filters applied to a particular region of the plurality of regions;
• determine a confidence value associated with each of the plurality of sets of focus scores, wherein the confidence value indicates a relative performance of a particular focus filter among the plurality of focus filters in identifying relative sharpness for particular image data across the plurality of focus settings based on the focus curve for a particular region;
• select a subset of the plurality of sets of focus scores based on the associated confidence values;
• and
• determine a final focus setting for the scene based on the selected subset of the plurality of sets of focus scores.

A method for determining a focus setting, comprising:

• determining a plurality of regions of interest in a view of a scene;
• obtaining, for each of the plurality of regions of interest, a set of image data for each of a plurality of focus settings;
• applying a plurality of focus filters to the set of image data for each of the plurality of focus settings for each of the plurality of regions of interest to obtain a plurality of sets of focus scores;
• determining, for each of the plurality of sets of focus scores, a focus curve, wherein the focus curve is derived from a particular set of focus scores across the plurality of focus settings for a particular focus filter of the plurality of focus filters applied to a particular region of the plurality of regions;
• determining a confidence value associated with each of the plurality of sets of focus scores, wherein the confidence value indicates a relative performance of a particular focus filter among the plurality of focus filters in identifying relative sharpness for particular image data across the plurality of focus settings based on the focus curve for a particular region;
• selecting a subset of the plurality of sets of focus scores based on the associated confidence values;
• and
• determining a final focus setting for the scene based on the selected subset of the plurality of sets of focus scores.