Smartphone-based optical sensing

Optical sensing techniques have the capability of capturing large amounts of information across the sensing field, thus they have been broadly used in many areas. Some of the traditional optical sensing tools, for example microscopes, have been built and used over a century and are still essential in many applications such as biomedical research and clinical diagnosis. However, these traditional optical sensing devices are usually large-scale, heavy-duty and expensive instruments, which also require skilled expertise to operate. Therefore, traditional optical sensing devices are often limited in specialized research facilities and not easily accessible to the general public. To meet the emerging demands of applying optical sensing more frequently in people\u27s daily life, more compact and inexpensive devices are required. A portable optical sensing platform based on smartphones has been developed, on top of which several advanced optical sensing techniques can be implemented. To be specific, the basis of the platform is a smartphone-based microscopic system with decent resolution in a sufficient field-of-view. With minimum optical elements attached to the platform, the system can be easily adapted into more advanced optical sensing tools, targeting much more optical information far beyond just intensities. For instance, the platform is equipped with a portable polarizer to become an imaging polarimetry, which is sensitive to the surface feature and roughness of the imaging sample. The platform is also integrated with a specially designed micro-grating to be implemented as a miniature wavefront sensor, which can be utilized to detect the phase information. The technique is based on one of the efficient quantitative phase imaging methods called wavefront curvature sensing, which uses two out-of-focus images of the pupil generated simultaneously to calculate the phase. Moreover, the detected phase information can be further produced into a height map across the field-of-view, yielding 3D tomography of the sensing sample. The technique is demonstrated with imaging laser generated wavefronts as well as other bio-specimen, such as human red blood cells