Image sensor (331; 531; 531′) for use with a lens (340; 540′) arranged to focus light onto an image sensing area (333; 533) of said image sensor (331; 531). Camera (330; 530′; 730) comprising the image sensor (331; 531; 531′) and said lens (340; 540′). Imaging system (305; 705; 730) for three-dimensional imaging of an object (320; 720) based on light triangulation, comprising the camera. The image sensor (331; 531) comprising an optical plate (337; 537) arranged to cover the image sensing area (333; 533) by at least two optical plate portions (334-1, 334-2; 534-1, 534-2) with different refractive properties such that light incident from said lens (340; 540′) and refracted by said optical plate portions (334-1, 334-2; 534-1, 534-2) towards and onto the image sensing area (333; 533) will travel different distances to be in focus on the image sensing area depending on which of said optical plate portions (334-1, 334-2; 534-1, 534-2) the light was refracted by. As a result, the image sensing area portions covered by said at least two optical plate portions (334-1, 334-2; 534-1, 534-2) become associated with different focus planes (351-1, 351-2; 751-1, 751-2).