| 摘要 |
PURPOSE:To detect focus without decrease in the accuracy for a special signal pattern with a focus detector of a secondary imaging system by making evaluation and decision from the plural element outputs of two sets of photoelectric transducer arrays and selecting the calculation equation. CONSTITUTION:The elements a(1), a(2) and a(N), a (N-1), b(1) and b(2), b(N) and b(N-1), etc. of two sets of photoelectric transducer arrays 10a, 10b are processed by differential amplifiers 12a and 12b, 12c and 12d, of an evaluation circuit 11, a summing amplifier 13 and a comparator 14. The decision output that the value C by equation I is C<0 or C>=0 is generated and one of the calculation equations for detecting focus; the equation II and the equation III is selected by switches 21a and 21b or 22a and 22b and the moving direction of an objective lens for focusing is determined according to the positive or negative of the calculated value V1 or V2. The decrease in the accuracy for the special signal pattern is prevented by selection of such calculation equation and the focus detection with high accuracy is made possible. |
