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High-frequency raster pinch correction scanner for retinal scanning displays

High-resolution (i.e., large pixel-count) and high frame rate dynamic microdisplays can be implemented by scanning a photon beam in a raster format across the viewer's retina. A resonant horizontal scanner and a linearly driven vertical scanner can create a 2-D raster for video display. The combined motion of the two scanners form a sinusoidal raster in the vertical direction and cause non-uniform line spacing for the case of bidirectional scanning as if the forward and return half-period raster lines are pinched near the edge of the display screen. Raster pinch effect degrades the image quality, especially for multi-beam scanning systems. What is needed is a vertical scanner that creates a stairstep motion instead of linear motion. A third scanner can be added to the system to create an approximation to a staircase motion in the vertical axis and correct for the non-uniform raster spacing. The raster pinch scanner requirements, mechanical and magnetic designs with FEA analysis, and preliminary test results are discussed in this paper.