Method and Apparatus for Projective Volume Monitoring

A projective volume monitoring apparatus comprising a sensing unit that includes:

• four image sensors having respective sensor fields-of-view that all overlap a primary monitoring zone and arranged so that first and second image sensors form a first primary-baseline pair whose spacing defines a first primary baseline, third and fourth image sensors form a second primary-baseline pair whose spacing defines a second primary baseline, and further arranged so that the first and third image sensors form a first secondary-baseline pair whose spacing defines a first secondary baseline, and the second and fourth imaging sensors form a second secondary-baseline pair whose spacing defines a second secondary baseline, wherein the primary baselines are longer than the secondary baselines;
• and
• image-processing circuits configured to redundantly detect objects within the primary monitoring zone using image data acquired from the primary-baseline pairs, and further configured to detect shadowing objects using image data acquired from the secondary-baseline pairs, wherein a shadowing object obstructs one or more of the sensor fields-of-view with respect to the primary monitoring zone.