Large, overlapping "
mega-dots", placed on small,
high resolution pixel locations, are used in high quality
monochrome imaging to preserve information to the micro, or pixel, level, thus avoiding the need to use micro-sized droplets. By using multiple passes and multiple pens with different levels of gray ink, one may build a single
monochrome 600 dpi (
dots per inch) pixel with the composite gray of those droplets at that pixel location as well as the neighboring locations. With careful print
modes and multiple passes, one can produce several levels of gray at a particular pixel location. The biggest
advantage of using multipixel dots is that the sensitivity to trajectory errors is significantly reduced. For example, a dot that is +E,fra 1 / 150+EE th inch
diameter is almost indifferent to a +E,fra 1 / 1200+EE th trajectory error. Even a relatively large +E,fra 1 / 600+EE th inch error has little
impact on the large +E,fra 1 / 150+EE th dot (25% error). In reducing the sensitivity to trajectory errors, overall imaging errors, such as banding, can be reduced, and overall
image quality enhanced. Optimally, the large dots have a
diameter that is about three to five times the pixel size, providing an overlap of three to five dots, respectively.