Contrast gain through simple illumination control for wide-field fluorescence imaging of scattering samples

Wide field fluorescence microscopy is the most commonly employed fluorescence imaging modality. However, a major drawback of wide field imaging is the very limited imaging depth in scattering samples. By experimentally varying the control of illumination, we found that the optimized illumination profile can lead to large contrast improvement for imaging at a depth beyond four scattering path lengths. At such imaging depth, we found that the achieved image signal-to-noise ratio can rival that of confocal measurement. As the employed illumination control is very simple, the method can be broadly applied to a wide variety of wide field fluorescence imaging systems.