Single-pixel microscopy with enhanced lateral resolution

Optical microscopy is constrained by the diffraction limit, restricting spatial resolution in biomedical and engineering imaging applications. While structured illumination microscopy (SIM), together with other techniques, has extended resolution in several optical microscopy techniques, it has not been adapted to single-pixel microscopy (SPM). In this work, we introduce a super resolution SPM (SR-SPM) approach by combining SIM principles with SPM using novel structured sampling patterns (SSPs). SSPs are generated by combining Walsh-Hadamard patterns and fringe patterns with multiple phase shifts and orientations. They are projected onto the sample using a high-speed digital micromirror device (DMD). Sequential measurements are captured by a single-pixel detector and reconstructed through SPI and SIM algorithms to enhance spatial resolution. Experimental validation demonstrates a significant resolution improvement, increasing the modulation transfer function (MTF) spatial frequency limit from 1000 pl/mm to 1500 pl/mm. Results in brightfield and fluorescence imaging confirm enhanced resolution and finer feature differentiation in biological samples, such as quantum-dot-labelled epithelial cells and fluorescent microspheres. The proposed SR-SPM system offers a cost-effective, efficient method for achieving super-resolution, paving the way for broader applications of single-pixel imaging in complex and spectrally challenging environments.