| 摘要 |
PURPOSE:To suppress fluctuation caused in a focus evaluation value being a basis of focusing due to the flicker effect of a discharge light whose frequency is 50Hz by integrating a low frequency signal component of a video signal of the same field as a video signal acquiring the focus evaluation value and applying the automatic focusing depending on the increase/decrease in a normalized focus evaluation value resulting from the division of the focus evaluation value by the integrated component. CONSTITUTION:A gate circuit 30c extracts only a luminance signal corresponding to a range of a focus area in time division similarly to the case with a gate circuit 5c, the result is inputted to an LPF 30d, only the low frequency component is separated and inputted to a poststage A/D conversion circuit 30f, integrated digitally over one field period at an integration device 30g and the result is outputted for each field as a brightness evaluation value K representing an average brightness level at a relevant field. The obtained focus evaluation S and brightness evaluation value K are inputted to an arithmetic circuit 31, the focus evaluation value S is divided by the brightness evaluation value K at the current field to calculate J=S/K thereby obtaining the normalized focus evaluation value. |
