FOCAL PLANE DETECTION METHOD AND IMAGE INPUT/OUTPUT DEVICE

摘要

PROBLEM TO BE SOLVED: To obtain a better observation image for whatsoever uneven sample by detecting a correct focal plane to be added to. SOLUTION: A representative curve in the direction of the XY axis is determined from a plurality of images obtained by photographing an observation sample at a plurality of positions in the direction of the optical axis and the images are added therebetween each in the directions of the X and Y axes to determine a representative value of contract to generate a contrast curve of a representative contrast value from the resulting representative value. A threshold is set on the contrast curve to detect a position moved by the depth of focus longitudinally centered on the peak position in the curve as position of focusing plane as far as the distance from the peak position to the point of crossing a threshold line exceeds the depth of focus. Then, the number of pulses corresponding to the position of the focusing plane thus obtained is set on a stage drive part 17 from a CPU 14 and a stage 2 is driven to be moved to the first position of the focusing plane. Thus, a sample image brought in from an objective lens 4 to be formed on a TV camera 5 is converted to an image signal to be fed to an image input/output section 6 for restoration processing.