Print-quality enhancement in electrophotographic printers

Print-quality enhancement (PQE) is a sophisticated form of image enhancement that is used to improve print quality. The benefits of PQE include reduced edge raggedness, control over boldness, stroke-imbalance correction, and improvements to the appearance of patterns that are difficult to print. Use of PQE permits one to obtain high-quality printing while using printers with lower resolution than would be required otherwise. Data bandwidth and storage requirements are therefore reduced. PQE relies on an imaging system with multiple exposure levels. A PQE algorithm generates an exposure value for each picture element (pel) based on neighboring bilevel pels. Since the exposure value is generated algorithmically, there is no need to store or internally transmit multiple bits per pel. This paper describes the capabilities of PQE and illustrates the level of print-quality improvements that can be obtained. Imaging-system requirements are presented, with attention to the modulator technology. The major focus is a PQE model that includes the PQE algorithm from the bit-map algorithm through the image-writing process.