傅楸善臺灣大學：電機工程學研究所徐 緯Hsu, WeiWeiHsu2007-11-262018-07-062007-11-262018-07-062007http://ntur.lib.ntu.edu.tw//handle/246246/53378我們在這篇論文提出峰值偵測自動對焦用一個新的有效及有效率的取樣表給手機相機。許多的自動對焦演算法基於清晰度值的曲線，但是他們並沒有考慮到取樣位置與影像的特性。我們的取樣表是由影像校正而來的，它符合光學鏡片、感測器響應、雜訊、以及清晰度函數的加成結果。在一個三百萬畫素的手機相機中，此表可將搜尋步數由 404 步減少到 16 步，影像仍然保持清晰。在搜尋中的峰值偵測能夠避免雜訊的干擾即使影像是在低對比的狀況下。更進一步，它能輕易地應用於影像晶片或是手機相機上。We present an auto focus method with peak detection by a new, effective, and efficient sampling table for phone cameras. Many auto focus algorithms base on focus value curves, and they do not consider the correlation between sampling and image characteristic. Our table is calibrated by images to meet results of optical lens, sensor response, noise, and focus value function. In a 3 mega-pixels camera, the table reduces total steps from 404 to 16, and captured images are still sharp. Proposed peak detection in a search can avoid noisy interference even though scenes are lower contrast. For further progress, they can be applied to image processing chips or mobile phones easily.Chapter 1 Introduction 1 1.1 Digital Camera Processing with Auto Focus 2 1.1.1 Image Sensors 2 1.1.2 Color Filter Array 2 1.2 Image Pipeline 3 1.2.1 A Generic Image Pipeline 3 1.2.2 Image Pipeline and Sharpness 4 1.3 Auto Focus Problems 8 1.4 Image Signal Processors 9 1.4.1 Core Logic Cl31W 9 1.4.2 NuCore SiP-1280 10 Chapter 2 Focus Value Functions 10 2.1 Definition 11 2.2 Functions of Gray-Level Domain 11 2.2.1 Gray-Level Energy 12 2.2.2 Gray-Level Amplitude 12 2.2.3 Gray-Level Variance 12 2.2.4 Sum-Modulus-Difference 13 2.3 Functions of Spatial-Filter Domain 13 2.3.1 Tenengrad Filter 14 2.3.2 Laplacian Filter 14 2.3.3 Infinite Impulse Response Filter 15 2.4 Functions of Frequency Domain 15 2.4.1 Discrete Cosine Transform 15 2.4.2 Fast Fourier Transform 16 2.5 Functions of Probability Domain 16 2.5.1 Huffman Code Length 16 2.6 Summary of Focus Value Functions 17 Chapter 3 Focus Sampling 18 3.1 Focus Value Curves 18 3.2 Window Segment 19 3.3 Step Size 21 3.4 Sampling Tables 22 3.5 Noise and Focus Value Curve 24 3.5.1 Gaussian Noise and Focus Value Curve 24 3.5.2 Impulse Noise and Focus Value Curve 27 Chapter 4 Proposed Method 30 4.1 The Sampling Table 30 4.2 Search by Peak Detection 33 Chapter 5 Experimental Results 35 5.1 Experimental Environment 35 5.1.1 The Experimental Camera Module 35 5.1.2 Evaluated Module and ISP 36 5.1.3 Hardware Engines 37 5.2 Setup Summary 38 5.3 The Parameters and Sampling Table 39 5.4 Time Improvement 40 5.5 Accuracy Comparison 41 Chapter 6 Conclusion and Future Work 43 References 442046285 bytesapplication/pdfen-US自動對焦清晰度值手機相機音圈式馬達Auto focusFocus valuePhone cameraVoice coil motorthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/53378/1/ntu-96-P94922001-1.pdf