1. A method of capturing 3 D data of one or more airborne particles, comprising: receiving an image of one or more airborne particles, the image taken by a plenoptic camera of which the geometry and the optical properties of its optics are known; and determining the distance of a plane of focus with at least one selected particle of the airborne particles from a defined reference location by use of the received image together with the known optical properties and the known geometry of the optics of the plenoptic camera.