Three-state polarization imaging with coded apertures

Polarization is a fundamental property of light that encodes valuable information about the structure, anisotropy, and composition of materials. In this study, we developed a three-state machine of coded aperture polarization imaging (TSM-CAPI) to enable 3D imaging in 2D space and linear polarization. In TSM-CAPI, light from an object is modulated by a coded phase mask (CPM) displayed on a spatial light modulator (SLM) and projected onto a second SLM on which another CPM is displayed. The active axes of the two SLMs are orthogonal to one another. The two CPMs are engineered to generate point spread functions of unique random dot patterns, ensuring that their cross-correlation is negligible compared to their autocorrelation. Owing to the orthogonal polarization responses of the SLMs, these correlation properties are mapped onto the polarization states of the object, yielding unique intensity patterns for orthogonal polarizations and a superimposed pattern for mixed states. In TSM-CAPI, two orthogonal polarization states are independently encoded by the two SLMs (state 1 and state 2), while a third operational state (state 3) is computationally derived as the sum of the two channel I PSFs , enabling full-scene object recovery independent of individual channel selection. A single captured intensity measurement is then reconstructed using a point spread function library comprising the individual and combined dot patterns, enabling retrieval of three polarization-resolved outputs. The third state enables post-processing imaging of all objects in the input plane, regardless of their polarization. If the polarization orientation angle lies between 0° and 90°, the orientation angle for each object point can be estimated from a single captured image using digital analysis. The proposed TSM-CAPI approach offers a compact and efficient framework with potential applications in material characterization, biomedical imaging, and polarization-sensitive microscopy.