Optical apparatus includes a scanning line projector, which is configured to scan a line of radiation across a scene. A receiver includes an array of sensing elements, which are configured to output signals in response to the radiation that is incident thereon, and collection optics configured to image the scene onto the array, such that each sensing element receives the radiation reflected from a corresponding point in the scene. A processor is coupled to receive the signals output by the sensing elements, to identify respective times of passage of the scanned line across the points in the scene by comparing a time-dependent waveform of the signals from the corresponding sensing elements to an expected waveform, and to derive depth coordinates of the points in the scene from the respective times of passage.