AUTOMATIC FOCUSING DEVICE IN WHICH TREND OF VARIATION AND DEGREE OF RELIABILITY OF FOCUSING EVALUATION VALUE SIGNAL.

摘要

AN AUTOMATIC FOCUSING DEVICE (1) OF THE PRESENT INVENTION INCLUDES A LENS GROUP (2) BY WHICH MOVEMENT A FOCUSED FIELD (50) OF AN OBJECT (30) CHANGES, A DRIVE MOTOR (6) FOR MOVING THE LENS GROUP (2), A LUMINANCE PROCESSING CIRCUIT (10) FOR IMAGE-SENSING THE OBJECT (30) THROUGH THE LENS GROUP (2) TO EXTRACT A LUMINANCE SIGNAL, AN ACCUMULATING CIRCUIT (23) FOR OUTPUTTING A FOCUSING EVALUATION VALUE SIGNAL FOR EVALUATING A FOCAL CONDITION OF THE OBJECT (30) ON THE BASIS OF THE EXTRACTED LUMINANCE SIGNAL, AN LSC CIRCUIT (22) FOR DETERMINING RELIABILITY OF THE OUTPUTTED FOCUSING EVALUATION VALUE SIGNAL, AND A CONTROL CIRCUIT (21) FOR CONTROLLING THE DRIVE MOTOR (6) TO IMPROVE THE FOCAL CONDITION OF THE OBJECT (30) ON THE BASIS OF THE DETERMINED RELIABILITY. (FIG. 1)