A dual band-pass filter (DBPF) is an optical component where two independent transmission windows are "carved" onto the same piece of optical glass using multi-cavity interference coating technology, while deeply blocking all other wavelength bands. With a single filter, it can simultaneously extract two target wavelengths, balancing system simplification and imaging quality. It serves as an "efficiency multiplier" in fields such as fluorescence detection, machine vision, remote sensing, and LiDAR.

1. Phase-coupled design: The thickness of each layer is fine-tuned using digital optimization algorithms (e.g., Needle, Refinement, GA) to ensure that the transmission peaks of both channels simultaneously meet requirements for bandwidth, rectangularity, and blocking depth;

2. Single-substrate implementation: Both channels are integrated on the same side or on opposite sides of a single substrate, eliminating the need for traditional solutions like beam splitters paired with two single band-pass filters. This reduces volume by 30–50% and lowers stray light by 1–2 orders of magnitude.