| 摘要 |
PURPOSE:To ensure the high density, the high stability and the high reliability of measurement just with a single time of projection, by using a grating plate pattern structure containing three gradations. CONSTITUTION:A pattern original picture contains three variable density gradations, i.e., white, black and gray which are shown as 2, 0 and 1 respectively. When the gradations of three colors R, G and B are used, these R, G and B correspond to 2, 1 and 0 respectively. These gradations are arranged so that they are not adjacent to each other excluding the corner parts. A point P0 in the diagram shows a corner part of each gradation area and also an intersecting point of edges. Then the point P0 is enclosed clockwise by the gradation areas of 2, 1, 0 and 1. In this connection, the corner part or the edge intersecting point of the gradation areas is defined as the feature point like the point P0 and named a node. A primary node of the node is shown in a ternary 4-digit form by means of the surrounding gradations. Thus many feature codes are obtained just by projecting once a pattern of at least three gradations.
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