APPARATUS FOR BACKGROUND SUBTRACTION USING FOCUS DIFFERENCES

摘要

First and second images are captured at first and second focal lengths, the second focal length being longer than the first focal length. Element sets are defined with a first element of the first image and a corresponding second element of the second image. Element sets are identified as background if the second element thereof is more in-focus than or as in-focus as the first element. Background elements are subtracted from further analysis. Comparisons are based on relative focus, e.g. whether image elements are more or less in-focus. Measurement of absolute focus is not necessary, nor is measurement of absolute focus change; images need not be in-focus. More than two images, multiple element sets, and/or multiple categories and relative focus relationships also may be used.

主权项

1. An apparatus, comprising:
a body configured to be wearable by a user on a head thereof; first and second image sensors engaged with said body, such that a first field of view of said first image sensor and a second field of view of said second image sensor comprise a region of space in front of said user, said region of space being within a reach of hands of said user; and a processor in communication with said sensors; wherein: said first and second image sensors have first and second fields of view respectively, said first and second fields of view being substantially identical; said first and second image sensors have first and second focal lengths respectively, said second focal length being longer than said first focal length; said first image sensor is adapted to capture a first image, and said second sensor is adapted to substantially simultaneously capture a second image; said processor is adapted to define in said first and second images a plurality of element sets, each said element set comprising a first element of said first image and a substantially corresponding second element of said second image; said processor is adapted to compare a relative degree of focus of said first and second elements in said element sets; said processor is adapted to assign as background element sets wherein said second element therein is as least as in-focus as said first element therein; and said processor is adapted to exclude from further analysis said element sets assigned to said background.