A three-dimensional measurement device employs a slit ray projection technique to optically determine a three-dimensional image. The device offers a choice in operating modes between high-speed measurement, high-resolution measurement and large dynamic range in the depth direction, to accommodate various situations. The different modes of operation are achieved by selectively modifying one or more of the scanning speed of a projected reference beam, the readout speed of a photosensor, the line width or line spacing of the photosensor, and the number of lines per image frame.