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 ∼1.4μm is achieved with a 20mm aperture lens in a 4mm interval at a distance of 140mm from the lens. A resolution of ∼0.7mm is obtained at a distance of ∼11m with the range finder employing two 25.4mm spherical mirrors spaced apart by ∼140mm. We also demonstrate 3D imaging of weakly textured objects.