An autonomous in vivo sensing device may include a polarizing filter to polarize light emitted by an illumination unit, and to block light specularly reflected from a turbid media from reaching an imager of such device. An autonomous in vivo sensing device with monochromatic illumination units to alternatingly illuminate a target area with light of different wavelengths, and to subtract an image illuminated by light in a first wavelength from an image illuminated by light in a second wavelength, to produce an image of a sub-surface layer of such target area.