| 摘要: | 本論文提出可置入手機中的六倍變焦五百萬畫素之潛望鏡式手機鏡頭設計，為使鏡頭不突出手機外機構，鏡頭深度需小於手機內機構厚度，以iPhone做為參考，扣除手機兩面外殼厚度約3 mm後，手機內機構厚度為5 mm。
由於稜鏡會將物方光線的光軸反射90進入透鏡組，鏡頭深度定義為稜鏡厚度或鏡片Y軸方向兩者中最大口徑，鏡頭深度與感測器的Y方向長度、入瞳口徑、入瞳位置與Y方向的視角相關，當鏡頭深度小於手機機構內厚度時，鏡頭則可置入手機中。
以下為本論文的設計規格，有效焦距為3.27 mm至1.64 mm，半視角為29 至5.28 ，F/#為3.4至6.8，入瞳口徑為0.96 mm至2.89 mm。
本論文選取的感測器尺寸比例為4：3，在維持對角線高度不變的前提下，將尺寸比例改為16：9，可以縮減感測器的Y方向長度，達到減少入射光的Y方向視場角、縮減鏡頭有效口徑的效果，於設計鏡頭時，光學系統可以藉由控制與入瞳的距離調整最大有效口徑，當距離入瞳越遠，口徑會越大。
CodeV軟體內的真實光線追跡功能，由於感測器為長方形，可以根據軟體定義之參考光線找到鏡頭內每一片透鏡的最大有效口徑，切除透鏡非有效口徑的部分，圓形透鏡的X、Y方向長度相同，改為方型透鏡可以降低Y方向長度，使設計結果置入更小的手機內機構厚度空間。
綜上所述，為了使鏡頭深度小於手機內機構厚度5 mm，由於越高畫素的感測器其Y方向的視場角越大、鏡頭深度越大，八百萬畫素的感測器難以達到設計目標，故選用五百萬畫素的感測器，且為了進一步縮減入射光Y方向的視場角，故改良感測器尺寸比例4：3為16：9，再來考量到於有限的鏡頭深度去設計高變焦倍率會需要更多的鏡片或是非球面設計以滿足鏡頭光學品質設計目標，故選用六倍變焦來進行設計，最終，設計結果之鏡頭深度為4.98 mm，鏡頭總長度為31.9 mm，鏡頭可置入手機之中。
;This thesis proposes a periscope-type zoom lens optical design which can be embedded in the mobile phone. In order to avoid the lens of mobile phone protrude from the casing, the lens depth of zoom lens must be less than the thickness of the mobile phone mechanism. Refer to the size of iPhone, the casing of mobile phone mechanism is about 3 mm, and the thickness is 5 mm without the casing of mobile phone mechanism.
The optical axis of object light will reflect by the prism and pass through the lens module and the lens depth is defined as the upper size limit of the prism thickness or the maximum surface aperture in the Y-direction of the zoom lens. The lens depth is related to the length of the sensor in the Y-direction, the entrance pupil diameter, the entrance pupil position, and the angle of view in the Y-direction. When the lens depth of zoom lens is less than the thickness of mobile phone mechanism, it can be embedded in the mobile phone.
The design specifications of this thesis include the effective focal length from 3.27 mm to 1.64 mm, the half field angle from 29 to 5.28, the F/# from 3.4 to 6.8, and the entrance pupil diameter from 0.96 mm to 2.89 mm.
In order to reduce the field angle in the Y-direction of incident light and lens aperture, we can reduce the length in the Y-direction of sensor by changing the ratio of sensor from 4:3 to 16:9, but keeping the diagonal height. When doing the lens design, we can adjust the maximum effective lens aperture by controlling the distance of entrance pupil, the longer the distance, the larger the lens aperture.
Because the sensor is rectangular type, we can define the maximum lens aperture of all the lenses by doing the real ray tracing, it is one of function in the CodeV. We can cut the ineffective part of every lens in the lens module, the shape of lenses will change form circle to square, it will make the result of lens design simpler to put into the smaller mobile phone.
In summary, we choose 5 mega pixels instead 8 mega pixels of sensor. It’s hard to reach our design target by using 8 mega pixels of sensor, because the more pixels, the field angle and lens depth are bigger. We improve the ratio of sensor dimension from 4:3 to 16:9, so, we could get smaller field angle in Y-direction. We also consider about the finite lens depth will need more lenses and aspherical lens to meet our optical performance design target when doing the higher zoom ratio design, therefore, we choose 6 zoom ratio as our design target. Finally, the design result of the lens depth is 4.98 mm, and the total length of zoom lens is 31.9 mm, so, it can be embedded in the mobile phone. |
