| 摘要 |
PURPOSE:To realize automatic focusing with extremely high accuracy by performing the Walsh transformation of the photodetection output of an image sensor and finding Walsh coefficients of more than 2nd order determined by the number of photodetection picture elements, and using the sum of the absolute values of the Walsh coefficients as an evaluated value. CONSTITUTION:The Walsh transformation 3 of the photodetection output of the image sensor 1 is performed to find Walsh coefficients (ai) of order determined by the number of photodetection picture elements, and the sum of the absolute values of coefficients of more than 2nd order among the Walsh coefficients is used as the evaluated value to judge the degree of defocusing. It is known that the coefficients obtained by the Walsh transformation 3 and frequency components by Fourier transformation have correlation, so the Walsh coefficients (ai) represent the frequency components, i.e. DC component and higher harmonic components of the image sensor photodetection output and even a slightly defocused image can be detected from the evaluated value E2 (output) found as the sum of the absolute values of the coefficients by the Walsh transformation. The high-accuracy focus detection is therefore performed.
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