Intimate source and detector and apparatus employing same

An optical assembly for use in detecting indicia, comprising:

• a light source means for emitting a first beam of light that is incident on a field of illumination of a target, said target being located in a working depth of field, said working depth of field substantially exceeding a single plane;
• a light sensor means for producing a signal in response to light carried in said first beam to said target and returning from a region of sensitivity thereon, said returning light being carried in a second beam of light that extends from said target to said light sensor means;
• optical means disposed in said first beam of light and in said second beam of light for forming an image of said light source means on said target, said optical means forming a back-projection of said region of sensitivity on said light sensor means, said back-projection being transmitted in said second beam, said first beam and said second beam following a common path between said optical means and said target;
• means for configuring said light source means to a sectional area and shape that are identical to a sectional area and shape of said light sensor means at said target;
• and
• means for dimensioning at least one of said first beam and said second beam such that said first beam and said second beam are precisely superimposed between said target and said optical means;
• whereby said field of illumination precisely coincides with said region of sensitivity.