A machine-vision system that provides quick changing and/or automatic adjustment of illumination angle, dispersion, intensity, and/or color of illumination. One such system includes a light source emitting polarized light, a machine-vision imager, an image processor operative to generate a quality parameter based on an image, and one or more of the means described above for selectively directing the light in a predetermined pattern based on its polarization and based on the quality parameter of the image. Some embodiments include an imager, a controllable light source, first and second optical elements that selectively direct light in first and second patterns, and a controller controlling the light characteristics using the first and/or second light patterns. One method includes setting one or more illumination parameters, illuminating the object based on the illumination parameters, obtaining an image, generating a quality parameter of a region of interest, and iterating using a different illumination parameters.