A method for calibrating an optical arrangement in respect to a global coordinate system is provided. The optical arrangement includes a rigid carrier, an optical acquiring unit and a light emitting unit both releasably connected to the carrier. The optical acquiring unit or the light emitting unit is calibrated in respect to a reference coordinate system offline and independently from the optical arrangement. Values of a conversion matrix are determined for converting the calibration data into corresponding calibration data in respect to the global coordinate system. A calibration of the entire optical arrangement is performed once in respect to the global coordinate system. During the intended use of the optical arrangement, the calibration data acquired for the unit and/or the respective values of the conversion matrix are considered when generating control signals for the unit and/or when processing sensor signals received from the unit.