| 摘要 |
An electronic imaging apparatus includes an optical system and a digital filter for providing focus values for focusing the optical system upon a color image sensor. The color image sensor, which operates at a pixel clock frequency to provide image data, has a repeatable color pattern including a luminance color which recurs at a predetermined repetition rate that is a submultiple of the pixel clock frequency. The digital filter includes a plurality of filter coefficients that are applied to the image data in groups of coefficients to implement a digital bandpass filter function. In particular, an arrangement of processing elements performs a sequence of multiplications upon the input data, each multiplication generating an output value dependent upon the value of a coefficient applied to a corresponding processing element. An arrangement of multiplexers sequentially apply the groups of coefficients to the arrangement of processing elements in synchronism with a submultiple of the pixel clock frequency, e.g., in synchronism with the predetermined repetition rate. By feeding the output of the processing arrangement back to its input, the focus values output by the filter are obtained at the predetermined repetition rate. Thus, by utilizing the repeatability of the color pattern, the digital filter may be designed with usage of fewer components.
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