| 摘要 |
PURPOSE: To reduce the influence of image noise and to stably and accurately detect an edge by determining a retrieval range by using a second-order differential coefficient and a specific threshold value, detecting the coordinates of the largest value of the absolute value of the second-order differential coefficient and regarding it as the coordinates of the edge. CONSTITUTION: In an image memory 28, the digital signal of line image data consisting of a displacement signal of one scan by a probe 18 is stored, and the line image data are inputted to a CPU30 from the image memory 28. The CPU30 performs a smoothing filter process to remove noise from the line image data. Then, second-order differential coefficient is calculated from the line image data. Calculation noise is removed from this secondary second-order differential coefficient by performing the smoothing filter calculation again. Then, the secondary second-order differential coefficient is compared with a specific threshold value and the X coordinate where the curve representing the secondary second-order differential coefficient crosses the threshold value is detected to determine the retrieval range, and the maximum value when the coefficient is plus or the smallest value when negative is detected and the edge detection is performed by regarding the X coordinate as the edge. |
