A pulsed beam of NIR excitation light is projected into a sample (345) at an oblique angle and scanned by a scanning element through a volume in the sample. 2-photon excitation excites fluorescence within the sample. The fluorescence is imaged onto an intermediate image plane that remains stationary regardless of the orientation of the scanning element. The image is captured by a linear array of light detecting elements (392) or a linear portion of a rectangular array. At any given position of the scanning element, the linear array (or portion) images all depths simultaneously. A plurality of images are captured for each of a plurality of different orientations of the scanning element. The orientation of the scanning element is controlled to move in a two dimensional pattern, which causes the beam of excitation light to sweep out a three dimensional volume within the sample.