A surface measurement module for triangulation based 3-D image acquisition of a subject-under-inspection, the module (100, 200) comprising - a casing; - a first polarizing beam splitter (160, 260) and a second polarizing beam splitter (164, 264); - a lens assembly (162, 262) comprising at least one lens element; - a mirror (166, 266); - an optical rotator (168, 268); - an image sensor (172, 272); - a pattern shifting device (130, 300); wherein: (a) the pattern shifting device (130, 300) has a fixed pattern optic through which light from a light source is passed, an output comprising a multi-frequency pattern which is shifted in a linear fashion, the multi-frequency pattern comprising at least a first sinusoid and a second superimposed sinusoid of light, wherein said first sinusoid has a first frequency and said second sinusoid has a second frequency distinct from the first frequency; (b) the output of the pattern shifting device (130, 300) is incident on the first polarizing beam splitter (160, 260) which is adapted to polarize the output; (c) the polarized output of said first polarizing beam splitter (160, 260) is propagating through the lens assembly (162, 262); (d) the polarized output exiting said lens assembly (162, 262) is propagating through the second polarizing beam splitter (164, 264) and is incident on the mirror (166, 266); (e) the polarized output reflected by the mirror (166, 266) through the optical rotator (168, 268) is illuminating a surface of the subject-under-inspection (190, 290) with the multi-frequency pattern which is shifted in a linear fashion; (f) a scattered light illumination off said surface is propagating through the optical rotator (168, 268) and then reflected by the second polarizing beam splitter (164, 264) through said lens assembly (162, 262) and then reflected by the first polarizing beam splitter (160, 260) to the image sensor (172, 272); and (g) said casing houses said pattern shifting device (172, 272), said first polarizing beam splitter (160, 260), said lens assembly (162, 262), said second polarizing beam splitter (164, 264), said mirror (166, 266), said optical rotator (168, 268), and said image sensor (172, 272). - a casing; - a first polarizing beam splitter (160, 260) and a second polarizing beam splitter (164, 264); - a lens assembly (162, 262) comprising at least one lens element; - a mirror (166, 266); - an optical rotator (168, 268); - an image sensor (172, 272); - a pattern shifting device (130, 300); (a) the pattern shifting device (130, 300) has a fixed pattern optic through which light from a light source is passed, an output comprising a multi-frequency pattern which is shifted in a linear fashion, the multi-frequency pattern comprising at least a first sinusoid and a second superimposed sinusoid of light, wherein said first sinusoid has a first frequency and said second sinusoid has a second frequency distinct from the first frequency; (b) the output of the pattern shifting device (130, 300) is incident on the first polarizing beam splitter (160, 260) which is adapted to polarize the output; (c) the polarized output of said first polarizing beam splitter (160, 260) is propagating through the lens assembly (162, 262); (d) the polarized output exiting said lens assembly (162, 262) is propagating through the second polarizing beam splitter (164, 264) and is incident on the mirror (166, 266); (e) the polarized output reflected by the mirror (166, 266) through the optical rotator (168, 268) is illuminating a surface of the subject-under-inspection (190, 290) with the multi-frequency pattern which is shifted in a linear fashion; (f) a scattered light illumination off said surface is propagating through the optical rotator (168, 268) and then reflected by the second polarizing beam splitter (164, 264) through said lens assembly (162, 262) and then reflected by the first polarizing beam splitter (160, 260) to the image sensor (172, 272); and (g) said casing houses said pattern shifting device (172, 272), said first polarizing beam splitter (160, 260), said lens assembly (162, 262), said second polarizing beam splitter (164, 264), said mirror (166, 266), said optical rotator (168, 268), and said image sensor (172, 272).