Optical properties of the interplanetary dust; Symmetry plane and spectral feature of the zodiacal cloud

Two topics related to optical properties of the interplanetary dust are reviewed. Namely, (i) large-scale geometry of the dust cloud estimated from the observations of zodiacal light (ZL) and zodiacal emission (ZE) suggests that the existence of uniform symmetry surface of the cloud is doubtful. Recent findings of local concentrations of interplanetary dust, e.g. asteroidal dust bands, cometary debris trails, dust cloud trailing the Earth, as well as interstellar dust stream and Jupiter's dust jets, also lead to the complex structure of interplanetary dust cloud. (ii) The sources of interplanetary dust are still open question, but the spectral features recently observed in ZL from IRTS and ZE from ISO have a potential ability to distinguish the origin of interplanetary dust based on a comparison of spectral features observed in comets, asteroids and collected dust particles in the Earth's stratosphere.