Digital light projectors

Use of millions of micro-mirrors in a small digital micro-mirror device (DMD chip) is the key to how these devices work. By Zohidjon

When the micro mirrors tilt towards the light source, they are ON. When the micro mirrors tilt away from the light source, they are OFF. This creates a light or dark pixel on the projection screen.

The micro mirrors can switch on or off several thousand times a second creating various grey shades – typically 1024 grey shades can be produced. This is known as a greyscale image.

A bright white light source passes through a colour filter on its way to the DMD chip. The white light is split into the primary colours: red, green and blue – the DLP projector can create over 16 million different colours. The ON and OFF states of each micro mirror are linked with colours from the filter to produce the coloured image.

The DMD chip is a microoptoelectromechanical system (MOEMS) that contains several thousand microscopic mirrors (made out of polished aluminium metal) arranged on the chip surface. They are each about 16 μm (16 × metres) in size and each corresponds to a pixel in the displayed screen image.

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