EMPA: improved technology for frequency modulated halftoning

Licensing opportunity

Scientists at EMPA, the Swiss National Laboratories for Materials Testing, and Research have developed a new error diffusion frequency modulated (FM) technique for printers, which they say uses the maximal available, native resolution of the device.

Sharp images, with reliable colour reproduction, can be achieved using integrated measurement of the behaviour of all channels, resulting in an optimised raster for each specific device.

Existing FM rasterization techniques for printing devices use a reduced resolution to control the strong dotgain effects which FM techniques are known for. The drawback of reduced resolution is that the resulting images have a grainy appearance. In addition, edges are blurred out due to the error diffusion. As a result, FM is not widely used in printing.

In the EMPA technology, the dotgain is directly incorporated into the algorithm instead of applying preliminary colour-corrections, as is typical in ICC-CMS (International Colour Consortium-Colour Management) systems. By performing an integrated measurement of predefined patterns, the effect of every single dot can be predicted.

This is used to control the rasterization so that dotgain is automatically corrected whilst rasterizing the image. Therefore, possible loss of contrast and detail caused by the colour corrections is avoided, while at the same time, the native resolution of the device can be used.

Several FM algorithms are already used for testing by various printing companies. This development is designed to be integrated into office printing systems, but is also applicable in high volume printing. Using the smooth dot distribution at the highest resolution results in very high quality images, even with standard printing devices.