A photo-detecting apparatus includes an image sensor and a 3D image generator. The image sensor having a plurality of 3D photodetectors is configured to output a raw data. The 3D image generator having a storage medium for storing a calibration data is configured to output a 3D image according to the raw data and the calibration data. The calibration data includes at least one of an IQ-mismatch calibration data, a non-linearity calibration data, a temperature calibration data and an offset calibration data.