A computer-implemented method (800, 900, 1000, 1100) for calibrating a device having a first image sensor and a second image sensor, the method allowing for calibration while the device is powered on and in use by a user, the method comprising: capturing (802, 902, 1002, 1102) sensor data using the first image sensor and the second image sensor, wherein the device maintains for use during its operation a calibration profile to model a spatial relationship between the first image sensor and the second image sensor, the calibration profile including a translation parameter and a rotation parameter; determining (804, 904, 1004, 1104) a calibration level associated with the calibration profile at a first time during operation of the device, the calibration level being related to a deformation amount of the device which reduces the accuracy of the calibration profile in modelling the actual spatial relationship between the first image sensor and the second image sensor; determining (806, 906, 1006, 1106), based on the calibration level, whether to perform either a first calibration process or a second calibration process; and if it is determined to perform either calibration process, performing the corresponding calibration process (808, 908, 1008, 1108) at the first time by: generating in the first calibration process a calibrated rotation parameter and in the second calibration process a calibrated translation parameter and a calibrated rotation parameter; and correspondingly replacing either the rotation parameter, or the translation parameter and the rotation parameter with the respectively corresponding calibrated rotation parameter of the first calibration process or the calibrated translation parameter and the calibrated rotation parameter of the second calibration process. capturing (802, 902, 1002, 1102) sensor data using the first image sensor and the second image sensor, wherein the device maintains for use during its operation a calibration profile to model a spatial relationship between the first image sensor and the second image sensor, the calibration profile including a translation parameter and a rotation parameter; determining (804, 904, 1004, 1104) a calibration level associated with the calibration profile at a first time during operation of the device, the calibration level being related to a deformation amount of the device which reduces the accuracy of the calibration profile in modelling the actual spatial relationship between the first image sensor and the second image sensor; determining (806, 906, 1006, 1106), based on the calibration level, whether to perform either a first calibration process or a second calibration process; and if it is determined to perform either calibration process, performing the corresponding calibration process (808, 908, 1008, 1108) at the first time by: generating in the first calibration process a calibrated rotation parameter and in the second calibration process a calibrated translation parameter and a calibrated rotation parameter; and correspondingly replacing either the rotation parameter, or the translation parameter and the rotation parameter with the respectively corresponding calibrated rotation parameter of the first calibration process or the calibrated translation parameter and the calibrated rotation parameter of the second calibration process. generating in the first calibration process a calibrated rotation parameter and in the second calibration process a calibrated translation parameter and a calibrated rotation parameter; and correspondingly replacing either the rotation parameter, or the translation parameter and the rotation parameter with the respectively corresponding calibrated rotation parameter of the first calibration process or the calibrated translation parameter and the calibrated rotation parameter of the second calibration process.