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Camera Focus mechanism: Phase VS Contrast

Camera Focus mechanism: Phase VS Contrast. 指導教授：梁肇文 教授 組 別：第 C 組 組員名單： 982006017 余謙 982006019 邱繼群 982006020 李京樺. Outline. Introduction The history of the autofocus system Contrast autofocus system Phase autofocus system Phase VS Contrast Prospect Reference. Introduction

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Camera Focus mechanism: Phase VS Contrast

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  1. Camera Focus mechanism:Phase VS Contrast 指導教授：梁肇文 教授 組 別：第C組 組員名單：982006017余謙 982006019 邱繼群 982006020 李京樺

  2. Outline Introduction The history of the autofocus system Contrast autofocus system Phase autofocus system Phase VS Contrast Prospect Reference

  3. Introduction The history of the autofocus system Contrast autofocus system Phase autofocus system Phase VS Contrast Prospect Reference

  4. Introduction 什麼是 “AF”系統 基本原理 主動式對焦原理 被動式對焦原理

  5. 什麼是 “AF”系統 • 自動對焦又稱AF (Automatic Focus)  • 指相機以特定區域（一般指中央，但現在的系統已經可以指定在觀景窗內看到的任何一點角落），進行測距、進而調整鏡頭中鏡片形成焦點，使照相機內的影像看起來清晰之設計

  6. 基本原理 • 基本原理 • 用相機上的光電傳感器將物體發射或反射的光接受，根據相機內部晶片的計算與處理，最後由電動對焦裝置對焦

  7. 主動式對焦原理 • 主動式:發射紅外線、超聲波，然後接受反射回來的訊號，測量來回的信號時間差，從而得到正確的距離參數。 • 種類:聲波式、光學式 • 優點：可以用於細線條物體和動體，也可以在低反差，弱光下對焦。

  8. 主動對焦原理

  9. 聲波式

  10. 光學式 紅外線旋轉照射法

  11. 被動式對焦原理 • 被動式: 接受景物自身的發光或反光。 包含:對比檢測及相位檢測對焦 • 優點：不需要發射系統，耗能小，易小型化。可以在逆光下或透過玻璃對焦。

  12. Introduction The history of the autofocus system Contrast autofocus system Phase autofocus system Phase VS Contrast Prospect Reference

  13. Introduction The history of the autofocus system Contrast autofocus system Phase autofocus system Phase VS Contrast Prospect Reference

  14. Contrast focus mechanism • Contrast focus mechanism(對比檢測 AF) 是什麼？ 對比檢測自動對焦系統的原理是根據焦點處畫面的對比度變化，尋找對比度最大時的鏡頭位置，也就是準確對焦的位置。

  15. 如果對焦點是圖中的紅框，在影像上的分析，放大來看，在未完成對焦前(out of focus)，框框內的像素與對比的關係就會變得差異很小(反差小)； • 圖中的下圖是當對到焦時(in focus)，框框內的像素(pixel)對比高。

  16. 隨著對焦鏡片開始移動， 畫面逐漸清晰，對比度開 始上升；當畫面最清晰， 對比度最高時，其實已處 於合焦狀態。 http://graphics.stanford.edu/courses/cs178/applets/autofocusCD.html 如同登山曲線 對比度

  17. 優點vs缺點 優點: 1.成本低，被廣泛運用 2.被攝對象反差較大時，相機仍可以準確地完成對焦工作。 缺點: 1.在微光環境下的對焦性能受到了很大的限制。 2.被攝對象反差較低時難以完成對焦。

  18. Introduction • The history of the autofocus system • Contrast autofocus system • Phase autofocus system • Phase VS Contrast • Prospect • Reference

  19. Phase autofocus system • Abstract • What is “phase” mean here? • Principle • Simple animation • Real structure • Autofocus process • Which System Camera Has? • Buying Tip

  20. Abstract

  21. What is “phase” mean here? ？

  22. Δψ=k*Δx Ι Δψ E

  23. Principle

  24. 焦後 焦上 焦前 References:Camera technology : the dark side of the lens / Norman Goldberg(1992)

  25. Simple animation

  26. References:http://graphics.stanford.edu/courses/cs178/applets/autofocusPD.htmlReferences:http://graphics.stanford.edu/courses/cs178/applets/autofocusPD.html

  27. Real structure

  28. Nikon F4 References:http://graphics.stanford.edu/courses/cs178/applets/slr-light-paths.jpg)

  29. Nikon F4 References:http://graphics.stanford.edu/courses/cs178/applets/slr-light-paths.jpg)

  30. Nikon F4 References:Camera technology : the dark side of the lens / Norman Goldberg(1992)

  31. 212B 212C 212A 85B 83B 85 85C 83 81 73 83C 73C 85A 73B 81C 75B 83A 75C 81A 81B 73A 75A 75 77A 77C 78C 77B 78A References: United States Patent, Iwamoto. Patent Number:6,115,553. Sep.5,2000.

  32. Canon EOS-1D References: Canon 相機型錄.

  33. Hybrid autofocus process

  34. References: United States Patent, Nakahara. Patent Number:7,058,294 B1. Jun.6,2006.

  35. References: United States Patent, Nakahara. Patent Number:7,058,294 B1. Jun.6,2006.

  36. References: United States Patent, Nakahara. Patent Number:7,058,294 B1. Jun.6,2006.

  37. References: United States Patent, Nakahara. Patent Number:7,058,294 B1. Jun.6,2006.

  38. References: United States Patent, Nakahara. Patent Number:7,058,294 B1. Jun.6,2006.

  39. Buying Tip

  40. How Do I Know Which Autofocus System My Camera Has?

  41. Introduction The history of the autofocus system Contrast autofocus system Phase autofocus system Phase VS Contrast Prospect Reference

  42. Phase VS Contrast

  43. 比較主動和被動系統 『主動式』的優點 1.完全不受環境光線影響，也不會因為主體本身的反差條件而影響對焦操作，甚至能在黑暗的情況下工作。 『主動式』的缺點 1.不能透過玻璃工作 2.對具有吸收紅外線能力的主體也會得出不正確 的測距結果。

  44. 『被動式』的優點 1.活躍的自動對焦系統的準確度往往比被動系統 少得多。 『被動式』的缺點 1.當光線過暗或主體反差太低時是無法工作 2.對細線條的主體，對焦也較困難且精度不高

  45. Contrast VS Phase比較 • http://www.youtube.com/watch?v=UD9s5_nWTV4

  46. Introduction The history of the autofocus system Contrast autofocus mechanism Phase autofocus mechanism Phase VS Contrast Prospect Reference

  47. Prospect

  48. Thanks for your listening.

  49. http://graphics.stanford.edu/courses/cs178/applets/autofocusCD.htmlhttp://graphics.stanford.edu/courses/cs178/applets/autofocusCD.html http://www.cs.mtu.edu/~shene/DigiCam/User-Guide/5700/AUTO-FOCUS/Auto-Focus.html http://www.sawfnews.com/Tech/67100.aspx http://www.wretch.cc/blog/gaujei/7249826 http://graphics.stanford.edu/courses/cs178-10/applets/autofocusPD.html 影片:http://www.youtube.com/watch?v=UD9s5_nWTV4 http://www.sawfnews.com/Tech/67100.asp Reference

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