Device for detecting displacement between patterns

DETAILED DESCRIPTION The primary object of the present invention is therefore to provide a device for detecting the displacement between a pattern just picked up and the pattern picked up immediately prior thereto so that the correct connection or continuity between them may be obtained.
Another object of the present invention is to provide a device for detecting a displacement between patterns of the type capable of giving an alarm signal to an operator whenever he makes an erroneous scanning with a manual scanner.
To the above and other ends, in a device for optically detecting a displacement between patterns in accordance with the present invention, patterns are picked up at a predetermined time interval and a correlation value between a first pattern and a second pattern picked up immediately after the first pattern is obtained every time first and second detected patterns are shifted relatively to each other so that the displacement between the first and second patterns may be detected from the maximum correlation value among correlation values obtained by shift of the respective numbers.
More specifically the first and second patterns are shifted relative to each other by one elementary square, column or row to obtain a correlation value.
If a maximum correlation value is obtained when they are shifted by i squares, columns or rows, the displacement is defined as i.
If the direction of the scanning is not in parallel with a row; that is, when the scanning is skewed, horizontal and/or vertical shifts or displacements between the first and second patterns in the receptor fields results.
Therefore, they are shifted horizontally or vertically relative to each other to obtain a correlation value to be defined later between them and the number of shifts giving a maximum correlation value is a measure of the displacement between them.
That is, when the maximum correlation value is obtained when they are shifted horizontally to the left or right by i columns and vertically upward or downward by j rows, the displacement is then defined as i columns or squares left or right and j rows or squares to the upward or downward