低通濾鏡主要作用是消除摩爾紋，這是差拍原理的一種表現。
基本介紹
- 中文名：低通濾鏡
- 外文名：Low pass filter
- 作用：消除摩爾紋
- 類別：濾鏡
作用,概述,
作用
低通濾鏡主要作用是消除摩爾紋,這是差拍原理的一種表現。
從數學上講，兩個頻率接近的等幅正弦波疊加，合成信號的幅度將按照兩個頻率之差變化。 差拍原理廣泛套用到廣播電視和通信中，用來變頻、調製等。
摩爾紋的消除最簡單的方法就是使數字相機的解像力小於感光對象的空間頻率，使其成為『灰階』化即可。
概述
An anti-aliasing filter is a filter used before a signal sampler, to restrict the bandwidth of a signal to approximately satisfy the sampling theorem. Since the theorem states that unambiguous interpretation of the signal from its samples is possible when the power of frequencies above the Nyquist frequency is zero, a real anti-aliasing filter can generally not completely satisfy the theorem. A realizable anti-aliasing filter will typically permit some aliasing to occur; the amount of aliasing that does occur depends on how good the filter is and what the frequency content of the input signal is.
Anti-aliasing filters are commonly used at the input of digital signal processing systems, for example in sound digitization systems; similar filters are used as reconstruction filters at the output of such systems, for example in music players. In the later case, the filter is to prevent aliasing in the conversion of samples back to a continuous signal, where again perfect stop-band rejection would be required to guarantee zero aliasing.
The theoretical impossibility of realizing perfect filters is not much of an impediment in practice, though practical considerations do lead to system design choices such as oversampling to make it easier to realize "good enough" anti-aliasing filters.
英文翻譯：
抗混疊濾波器是一個篩選器之前信號採樣器，用於限制信號近似地滿足採樣定理的頻寬。因為定理指出從其樣本信號的明確的解釋是可能的當頻率高於奈奎斯特頻率的功率為零，真正抗混疊濾波器通常不完全滿足定理。可實現的抗混疊濾波器通常會允許出現；一些別名確實發生的混疊的量取決於如何好的篩選器和輸入信號的頻率內容是什麼。
抗混疊濾波器都常用的在輸入的數位訊號處理系統，例如在聲音的數位化系統；類似的過濾器被用作重建濾波器在這樣的系統，例如在音樂播放器的輸出。在以後的案例中，篩選器是防止混疊中樣品的轉換回一個連續信號，再一次完美的止帶抑制在哪裡需要保證零混疊。
理論不可能實現完美的篩選器不是障礙的很多，在實踐中，儘管實際的考慮做導致如過採樣，使它更容易實現"足夠好"的抗混疊濾波器的系統設計選擇。
