How It Works
From the article Making Live-Cell Imaging
The core of digital illumination is the digital micromirror device (DMD), a high-speed and highly efficient semiconductor-based “light switch” array of up to 2 million hinge-mounted addressable, tiltable microscopic mirrors. It is a mass-produced spatial light modulator based on mature semiconductor material systems and processing. Numbering more than 8 million in the field, the DMD is also the core of consumer electronics products such as HDTVs and projectors.
Digital micromirror arrays are shown digitally illuminating a sample. When a DMD chip is coordinated with a digital video or graphic signal, a light source and beam delivery optics, its mirrors reflect a digital image onto the sample. Infinitely complex geometries of fluorophore excitation patterns are simultaneously mapped onto the sample. In combination with continuous-wave or arc lamp light fluorescence excitation sources and laser scanning confocal, spinning disk confocal or wide-field microscopes, the computer-controlled DMD spatial light modulator produces a diffraction-limited mask at the specimen plane, at the image detector and within the microscope eyepiece field of view.
As with traditional galvo mirror scanning systems, DMD technology allows the user to apply pixel-by-pixel illumination where needed and for as long as necessary. However, the inherent advantages of the DMD technology uniquely enable simultaneous pixel-by-pixel illumination of multiple regions of interest and infinitely complex sample geometries with zero delta image acquisition time. There is no scanning of the sample and, thus, no time lapse between illuminating pixels in the mask. This is not possible with traditional galvo mirror technology, which scans the regions of interest over a period of time.
A DMD’s simple planoreflective optical design is readily integrated with the complex optical designs of confocal and wide-field microscopes to realize diffraction-limited imaging with minimal loss over a broad spectral range. Alternative spatial light modulating technologies such as acousto-optic and liquid crystal are less efficient and optically more complex, making them less amenable to diffraction-limited integration with off-the-shelf microscope platforms. This is a critical consideration for maintaining reproducibility of microscope-specific data and for staying within equipment budgets.
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