Optical architecture for the multiple-prism beam expander microscope/microdensitometer (MPBEM). The beam incident on the object can be, for example, 25-50 mm wide X 25 µm high. This is an extremely elongated beam (in the plane of propagation) with a width to height ratio in the range of 1000:1 to 2000:1. The MPBEM has a dual optical mode of operation and can also be configured as a pure N-slit laser interferometer (NSLI) (for reviews see Tunable Laser Applications).
The use of light beams extremely elongated in one plane (25-50 mm) and extremely thin (10-30 µm) in the orthogonal plane was introduced for microscopy and microdensitometry applications in the early 1990s (see, for example, Duarte 1993). This type of one-dimensionally beam-expanded illumination for microscopy has also become known as thin light sheet illumination and selective plane illumination. Resolution into the nanometer regime can be extended via interferometric calculations.
The 1991 and 1993 papers also reported, for the first time, on the use of quantum mechanics techniques, via Dirac's notation, in the field of imaging. These papers further illustrated the prediction of measured interferograms using interferometric equations derived using Dirac's quantum notation.