Passive ranging and three-dimensional imaging through chiral phase coding

We present a method for single-image passive ranging and three-dimensional (3D) imaging in incoherent light based on chiral phase coding. A chiral linear phase variation across the aperture of an optical system results in a frequency response with a characteristic pattern of fringes such that the spatial period and inclination of the pattern depend on the focusing error. From this dependency, the absolute focusing error and, hence, the distance to the object can be found. In the experiments a resolution of ~1.4 μm is achieved with a 20 mm aperture lens in a 4 mm interval at a distance of 140 mm from the lens. A resolution of ~0.7 mm is obtained at a distance of ~11 m with the range finder employing two 25.4 mm spherical mirrors spaced apart by ~140 mm. We also demonstrate 3D imaging of weakly textured objects.