Micro-Optical Moire Magnification Arrangement for Halftone Imaging

The patent transitions from a two-dimensional arrangement where microimages are grouped into microimage areas to a three-dimensional arrangement using stacked lens arrays. Multiple lens arrays are positioned at different distances from the motif image, creating depth layers that encode gray levels vertically rather than horizontally. This dimensional change allows gray level representation without increasing the lateral footprint of pixel areas, thereby maintaining high spatial resolution while achieving multiple gray levels.

The patent implements a nested structure where multiple lens arrays are stacked one above another, with each lens array containing microlenses that focus light from corresponding motif image areas. The lens arrays are nested in the vertical dimension, with each layer contributing to the encoding of different gray level information. This nested arrangement allows multiple bits of gray level information to be packed into a compact vertical space above each pixel location.

Instead of increasing the number of microimages laterally to achieve more gray levels, the patent stacks lens arrays vertically. Each lens array in the stack can independently modulate light from the same motif image area, encoding gray level information in the vertical dimension. This allows a single pixel location to represent multiple gray levels through the combination of lens arrays at different depths, maintaining high spatial resolution while achieving fine gray level precision.

The patent employs variable focal lengths in the stacked lens arrays, where each lens array has a different focal length optimized for its specific depth position. This dynamic adjustment of focal properties across the vertical stack allows each lens array to contribute differently to the final image formation, enabling precise control over light intensity and thus gray level representation without requiring multiple microimages per pixel area.

The patent designs the stacked lens arrays such that each lens array serves multiple functions: it acts as a focusing element for its specific depth plane, a gray level encoding element through its variable focal length, and a light modulation element. This multi-functionality reduces the need for additional separate components, thereby managing device complexity while achieving high resolution and multiple gray levels simultaneously.

The patent systematically varies the focal length parameter across the stacked lens arrays, creating a gradient or stepped sequence of focal lengths that corresponds to different gray level encodings. This parameter change approach allows the system to encode gray levels through a continuous or discrete variation of a single physical parameter (focal length) rather than requiring complex structural variations in each lens array, thus managing complexity while achieving the desired functionality.