light from the first light source reflects off the beam splitter 32 and is directed by the optical relay system 30 to an illuminated point on the target 14 in response to this incident light the illuminated point remits light a portion of this light propagates directly back through the optical relay system 30 thereby forming the directly scattered component 20 of the image another portion of the light remitted by the illuminated point in response to the incident field scatters off other points within the target thereby forming the multiply scattered component of the image the directly scattered component passes through the optical relay system 30 and through the beam splitter 32 the optical relay system 30 brings this directly scattered light to a focus at a focal point which is confocal with the illuminated point on the target during the first interval this focal point is coincident with the pinhole aperture 28 in the field stop 27 u2033 as a result during the first interval the directly scattered component passes through the pinhole aperture and reaches the detector 18 after scattering off the last scattering point in the target the multiply scattered component also passes through the optical relay system 30 however unlike the directly scattered component which originates from a point on the target confocal with the pinhole aperture this multiply scattered component originates from a point on the target that is not confocal to the pinhole aperture thus the optical relay system 30 brings this multiply scattered component to a focus at a point on the field stop other than the point at which the pinhole aperture is located in this way the field stop 27 u2033 prevents the multiply scattered component.