Automatic exposure and gain control for face authentication

A method for adaptive gain control in a near-infrared camera system for face authentication on a user device, the method comprising:

• in response to initiation of a camera driver system, initializing a gain for the near-infrared camera system using a default gain;
• receiving, from one or more sensors, a signal indicating an orientation of the user device;
• based on the orientation of the user device, selecting particular regions of a plurality of regions of a most-recently captured image, which was captured by the near-infrared camera system, to use as one or more regions-of-interest for the adaptive gain control;
• ascertaining patch-mean statistics of the one or more regions-of-interest of the image;
• computing an update for the gain to provide an updated gain that is usable to scale the one or more regions-of-interest toward a target mean-luminance value;
• and
• setting the initialized gain for the near-infrared camera system to the updated gain for a next face-authentication attempt.

A computing system comprising:

• a near-infrared camera system for capturing image data of a user for face authentication;
• a camera driver system configured to drive the near-infrared camera system;
• a processor;
• and
• computer-readable instructions which, when executed by the processor, cause the computing system to:
• initialize, in response to initiation of the camera driver system, a gain for the near-infrared camera system using a default gain;
• ascertain patch-mean statistics of one or more regions-of-interest of a most-recently captured image captured by the near-infrared camera system, the one or more regions-of-interest including a center region and a lower-middle region according to the Rule of Thirds in photography;
• compute an update for the gain to provide an updated gain that is usable to scale the one or more regions-of-interest toward a target mean-luminance value;
• and
• set the initialized gain for the near-infrared camera system to the updated gain for a next face-authentication attempt.