| 摘要 |
For use on an overhead projector to give an illusion of motion, a transparency sheet bearing art work in the form of a grid is superposed on a relatively movable transparency sheet or web bearing a second or control grid. The lines or groups of lines of the art work grid and the second grid are parallel and both are at an angle to the direction of relative motion. On either sheet the lines may be of any appropriate color and may be made up of rows of dots. Dots of differing color in rows at different angles may be used. On either sheet, but not both, the lines are desirably arcuate and drawn on like radii about centers successively offset on a line parallel to the direction of relative movement, such arcuate lines being tangent to a construction line at the desired 45 DEG angle to the direction of motion. On both sheets, the width or apparent width of respective lines is substantially identical with the width or apparent width of intervening spaces between the lines.
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