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4 April 1997 Registration method providing high visual magnification of microposition errors
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An image registration method is proposed which provides high visual magnification of micro-position errors so that they may be easily quantified with an unaided eye. The method consists of overprinting a pair of fine line or screen patterns of the same spatial frequency in which one pattern functions as a variable mask that unveils a stepped image embedded in the second pattern in proportion to registration error. The larger scale image can be composed of one or a series of symbols each designed to be unmasked at specific registration error thresholds. Pattern structure and duty cycle differences are used to create the masking function. The use of embedded images allows for a wide variety of visual symbols to be displayed at precise error thresholds. The large symbol dimensions provide the high visual magnification, typically a factor of 100 to 100. Advantages over moire technique are that the symbol outline is sharp, its shape is not dependent on interference effects, and it can independently designed to optimize for intuitive visual impact. Applications include a visual pass/fail mark, a numerical scale providing coarse error measurement, and the printed equivalent of a quadrature detector indicating direction and magnitude of error. The position sensing image pair is compact and suitable for photographic, offset printing or other image generation/replication processes where registration is critical. Imagesetter results for a 0.3 mil registration threshold sensor will be presented.
© (1997) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Roy D. Allen "Registration method providing high visual magnification of microposition errors", Proc. SPIE 3018, Color Imaging: Device-Independent Color, Color Hard Copy, and Graphic Arts II, (4 April 1997);

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