| 摘要 |
PURPOSE:To surely detect the changing points by using the first derivative and the second derivative of the density change as well as the density change and detecting a changing point. CONSTITUTION:The contents D (i) of a differential memory 11 are successively compared with two value, i.e., a differential decision low level 15 and a high level 16. Thus a sudden change position of a density memory 9 is detected. A CPU reads the derivative out of a derivative memory 13 set along a check route and differentiates the derivative once more to store it in a second derivative memory 17 as the second derivative along the check route. The values stored in the memory 17 are successively compared with two values, i.e., the second derivative decision low and high levels. Thus a changing point can be surely detected even at a position where the changing point can not be accurately judged by the density only. |
