Range imaging apparatus and method

Abstract

A semiconductor laser source of a transmitter () in a range imaging apparatus () generates an optical pulse at repeated moments, and outputs spatially separate optical beams towards a target zone (), such that the semiconductor laser source outputs each of the spatially separate of the optical beams at different moments from each other. A detector () of a receiver () comprises single-photon sub-detector units, at least two groups of the single-photon sub-detector units have separate field of views towards the target zone (), and the at least two groups of sub-detector units are associated with different optical beams of the spatially separated optical beams on the basis of the separate field-of-views. A timing unit () determines a value corresponding to a time-of-flight of the optical pulse output at each of the repeated moments on the basis of a signal from a group of the sub-detector units associated with an optical beams output at said moment. In an embodiment, the semiconductor laser source comprises a plurality of sub-source units each of which may output a unique optical beam. In an embodiment, the timing unit () comprises a selector and a number of time-to-digital converters (). The receiver selector connects a number of the sub-detector units, which detect the optical pulse () and the number of which corresponds to the number of output beams, with the number of the time-to-digital converters (). In an embodiment, the apparatus () comprises an electric power source () which supplies a constant electric power to the semiconductor laser source at each of the repeated moments in order to increase brightness of the optical beams. Elongated optical beams may be produced by a laser diode bar (several emitting stripes) and a cylinder lens system or a holographic diffuser. Partially overlapping optical beams may provide illuminated rectangles of the optical beams on the target ().