1. A method for detecting an object located within a semi-opaque enclosure having a semi-opaque first side portion having first internal and external surfaces and a semi-opaque second side portion having second internal and external surfaces, said first side portion being different from and opposing said second side portion, said first external surface having a pattern visible externally to said enclosure, said object being located between said first and second side portions, said method comprising: directing first channel light toward and onto said first external surface of said semi-opaque enclosure; capturing, from portions of said first channel light reflected off said first external surface but not having passed through said first internal surface, a first digital image comprising data representing said pattern; directing second channel light toward and onto said object and toward and onto said first side portion of said enclosure; capturing, from portions of said second channel light emanating from said first external surface after first traveling along side and around said object inside said enclosure and passing through said first internal surface, a second digital image comprising a silhouette of said object; and forming a difference image representing the object and substantially devoid of information representing said visible pattern by subtracting one of said first and second digital images from the other.