In high-quality digital maging systems, optical low-pass filters (OLPF) are used to eliminate color Moire fringes.

  An OLPF cuts off the lens MTF above the sampling frequency of the imager resulting an overall MTF curve that approximates a step function in spatial domain. IR cut-off function is often incorporated into OLPF as well.

  For a day night OPLF filter,it allows both visible and infrared LED light to pass through.