Properties of a scanning holographic microscope: improved resolution, extended depth-of-focus, and/or optical sectioning

The imaging characteristics of a scanning holographic microscope are described, and compared with the performance of a conventional wide-field or scanning microscope using the same objective. Unique features such as the control of the degree of spatial coherence, allowing simultaneous incoherent, fluorescence, and quantitative phase imaging, and the flexibility of choice of pupil functions, allowing point-spread function and transfer function synthesis, are reviewed. Two illustrative examples are discussed in detail, and evaluated with the help of computer simulations. The first arrangement uses clear pupils. It exhibits a point-spread function about half the size of that obtained with conventional imaging, and a depth-of-focus about one order of magnitude larger. In the second example, pupils with a linear radial phase (axicon) are synthesized to obtain optically sectioned images from which all information other than that of a thin axial section through the specimen is removed. Other anticipated advantages of the scanning holographic microscope (e.g. non-imaging detection, and reduced sensitivity to aberrations) are mentioned.