An illumination and imaging system is provided with a co-axial illuminator
that does not include a beamsplitter. The co-axial illuminator achieves
efficiencies substantially in excess of those achieved with a
beamsplitter. In one aspect, an optical stop is used to reflect
illumination upon a target. The optical stop includes an aperture
allowing light reflected from the target to pass to a detector. The
aperture of the stop has an asymmetrical feature that facilitates
operation on specular targets.