Real-time face tracking in a digital image acquisition device

An image processing apparatus for tracking faces in an image stream comprising one or more processors and one or more digital storage media having digitally-encoded instructions embedded therein for programming the one or more processors to perform an iterative method of tracking faces in an image stream, the method comprising:

• a. receiving an acquired image from an image stream including one or more face regions;
• b. sub-sampling said acquired image at a specified resolution to provide a sub-sampled image;
• c. calculating a corresponding integral image for a least a portion of said sub-sampled image;
• d. applying face detection to at least a portion of said integral image to provide a set of one or more candidate face regions;
• e. adjusting a resolution for sub-sampling a next acquired image;
• f. repeating a. to e. at the adjusted resolution periodically on a selected plurality of images of an image stream including a main acquired image chronologically following a plurality of images of said selected plurality of images.

A method of detecting faces in an image stream using a digital image acquisition device, comprising:

• a. determining an orientation of a digital image acquisition device for at least one image of an image stream;
• b. acquiring the image, which includes one or more face regions, from said image stream;
• and
• c. applying face detection to at least a portion of said acquired image to provide a set of one or more candidate face regions according to said determined orientation, and wherein said face detection selectively employs a sequence of classifiers from an available plurality of classifier sequences, each classifier sequence being at a given orientation.

An image processing apparatus including one or more processors and one or more digital storage media having digitally-encoded instructions embedded therein for programming the one or more processors to perform an iterative method of detecting faces in an image stream, the method comprising:

• a. determining an orientation of a digital image acquisition device for at least one image of an image stream;
• b. acquiring the image, which includes one or more face regions, from said image stream;
• and
• c. applying face detection to at least a portion of said acquired image to provide a set of one or more candidate face regions according to said determined orientation, and wherein said face detection selectively employs a sequence of classifiers from an available plurality of classifier sequences, each classifier sequence being at a given orientation.

A method of detecting faces in an image stream using a digital image acquisition device comprising:

• a. receiving a first acquired image from said image stream including one or more face regions;
• b. applying face detection to at least a portion of said first acquired image to provide a set of one or more candidate face regions each having a probability of being a face region;
• c. tracking candidate face regions across a plurality of images of said image stream including said first acquired image;
• and
• d. responsive to a probability of a tracked face region dropping by more than a threshold rate with respect to time, activating an enhancement sub-system for a period of time to improve the probability of said face detection detecting a candidate face region.

A digital image acquisition device for detecting faces in an image stream comprising:

• a. means for receiving a first acquired image from said image stream including one or more face regions;
• b. means for applying face detection to at least a portion of said first acquired image to provide a set of one or more candidate face regions each having a probability of being a face region;
• c. means for tracking candidate face regions across a plurality of images of said image stream including said first acquired image;
• and
• d. means, responsive to a probability of a tracked face region dropping by more than a threshold rate with respect to time, for activating an enhancement sub-system for a period of time to improve the probability of said face detection detecting a candidate face region.

An image processing apparatus including one or more processors and one or more digital storage media having digitally-encoded instructions embedded therein for programming the one or more processors to perform a method of detecting faces in an image stream using a digital image acquisition device, the method comprising:

• a. receiving a first acquired image from said image stream including one or more face regions;
• b. applying face detection to at least a portion of said first acquired image to provide a set of one or more candidate face regions each having a probability of being a face region;
• c. tracking candidate face regions across a plurality of images of said image stream including said first acquired image;
• and
• d. responsive to a probability of a tracked face region dropping by more than a threshold rate with respect to time, activating an enhancement sub-system for a period of time to improve the probability of said face detection detecting a candidate face region.