Bidirectional Nozzle Group Configuration for Overlapping Image Printing

The patent combines the functions of forming both images into a single image-recording head by utilizing bidirectional movement of the head in the subscan direction. Instead of requiring separate heads positioned at upstream and downstream sides, one head performs both image formation tasks by moving in forward and backward directions, thereby eliminating the need for additional heads and reducing apparatus size while maintaining the capability to form overlapping images with different quality requirements

The patent applies local quality by assigning different nozzle groups within the same nozzle column to different image formation tasks. Specifically, a first nozzle group forms the first image while a second nozzle group forms the second image with different quality requirements. This allows each nozzle group to be optimized for its specific function (e.g., different droplet sizes, ejection frequencies, or patterns) while sharing the same physical carrier structure, thereby achieving differentiated image qualities without increasing overall device complexity

The patent resolves this contradiction by applying different movement strategies to different nozzle groups locally. The first nozzle group uses unidirectional movement (only in the forward direction) to ensure high image quality for the first image, while the second nozzle group uses bidirectional movement (forward and backward directions) to improve printing speed for the second image. This localized differentiation allows each image to receive the appropriate movement strategy based on its quality requirements, achieving both speed improvement and quality maintenance