Auto-focus is a key technology for visual presenter, this paper mainly presents how to achieve the function of auto-focus on Hi3515. The 4x4 integer DCT (Discrete Cosine Transform) shown as Eq. (2) was used to indicate whether the system was on accurate focus or not. Because the 4x4 integer DCT not only has the characteristics of single peak value, non-deflection, reliability, high-speed, but also has lower complex computation than the other frequency methods such as FFT(Fast Fourier Transform), DWT (Discrete Wavelet Transform). This paper employed the method of monotonic and blind hill climbing to achieve auto-focus. The result of auto-focus is shown as Fig. 6.
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