An illumination device for use with a product inspection machine inspecting products according to at least one characteristic using pulsed illumination for inspection in two wavelengths. The invention includes a plurality of arrays of semiconductor light sources from which a wavelength may be selected, either specifically or by combination of specific semiconductor light sources, for impinging on passing product and at least one array of semiconductor light sources from which the same wavelength may be selected and which provides intensity equal to the plurality of arrays impinging on a background surface for detection and comparison.