| 摘要 |
PURPOSE:To surely prevent misdetection by combining the phase differences of the space frequency components by the photoelectric outputs of a pair of photoelectric element arrays of the specific configuration and the correlation outputs corresponding to whether an objective lens is near the focus position or not. CONSTITUTION:A field lens 2 is provided at the fixed focal plane of an objective lens 1 and the incident intensities to the opposing photoelectric elements p1 and p1', p2 and p2'... of a pair of photoelectric arrays 5, 6 in the positions conjugate with the lens 2 by way of imaging lenses 3, 4 become equal at the focusing. Hence the phase differences of the light image outputs of the arrays 5, 6 having been vector- converted by space frequency components extracting circuits 7, 8 are compared in a control part 50 and when the phase differences become zero, the position of the lens 1 including the focus position is detected. On the other hand, a correlation detecting part I calculates the required correlation function irrespective to luminance distribution according to whether the lens 1 is near the focus position or not, based on the outputs of the arrays 5, 6. Hence, the control part 50 surely detects the focus without misdetection by the combination of the phase differences of the space frequency components and correlation function. |
