The bandpass filters (BPFs) used in optical gesture recognition systems (those that use light, like 3D depth sensors) are narrowband filters designed to transmit light in the Near-Infrared (NIR) spectrum.

The primary goal of the BPF is to reject ambient light (especially sunlight and indoor lighting) while maximizing the transmission of the sensor's own projected infrared light, which significantly improves the Signal-to-Noise Ratio (SNR).