3d particle imaging

A system (100) for imaging particles in a fluid is described. The system (100) comprises a substrate holder (110) for holding a substrate (120) comprising a channel or reservoir (122) for containing the fluid in the substrate (120), a radiation source (130) for providing irradiation in the substrate (120) and a radiation detection unit (140) for detecting particles in the fluid in the substrate. At least one of the radiation source (130) and the radiation detection unit (140) are configured so as to obtain detection in one or more distinct detection sheets (142) in the substrate (120). The system (100) further comprises an actuator (150) configured for imparting an oscillating mechanical movement of the substrate holder (110) with respect to the radiation detection unit (140) and the radiation source (130), the oscillating mechanical movement being a movement comprising a movement component in a direction perpendicular to the plane wherein the one or more detection sheets (142) are extending.