A light splitting module for obtaining spectrums of an object to be tested is disclosed, which sequentially includes a light entrance window, a diffuser and a filter array along a light entrance direction, wherein the filter array is an angle modulated filter array which has multiple subareas and includes multiple filters with different center wavelengths respectively corresponding to the subareas. Also, a dual-mode multiplexing optical device is disclosed, which includes the light splitting module, an illumination module and a light field imaging module, can realize the integration of spectral detection and light field imaging, so it can be applied to material spectral detection, digital image detection and digital focusing for obtaining high-resolution imaging results; and simultaneously, the modules of the device are detachable, so that users can use the device as required.