Optical Low Pass Filter

Optical low pass filter (OLPF) is used in high end (high resolution) digital camera sensor to eliminate interference influence (Moire pattern) by crystalline birefringency. An OLPF can cut off the undesired high spatial frequency when the sensor resulting the image. IR cut-off function is often incorporated into OLPF as well. Some use absorptive blue glass + AR , or direct coating an IR cut thin films layers .