Bandpass filter glass is an optical component that only allows light within a specific wavelength range to pass through, while blocking light waves outside of that range. Its spectral characteristics exhibit a "middle transparency, two side cutoff" pattern and are widely used in optical detection, imaging systems, and optical communication fields.
This type of glass is also known as a specific implementation form of bandpass filter, usually manufactured based on the principle of multi-layer thin film interference, which can accurately screen the target wavelength band of light in complex light environments, like an "optical sieve". It is commonly used in devices that require high wavelength selectivity, such as fluorescence analyzers, enzyme-linked immunosorbent assay (ELISA) analyzers, infrared cameras, iris recognition systems, etc.
Core characteristic parameters
The key performance of bandpass filter glass is defined by the following parameters:
Center wavelength (CWL): The peak transmission wavelength of the passband, such as 470nm, 650nm, or 850nm.
Half width at half maximum (FWHM): The wavelength width at which the transmittance drops to half of its peak, reflecting the width of the passband. The full width at half maximum of narrowband filters is usually less than 5nm.
Peak transmittance: The maximum transmitted light intensity at the center wavelength, which can reach over 90% for high-quality products.
Cut off depth: The minimum transmittance of the out of band region, usually expressed in OD value (optical density), such as OD4 representing only 0.01% of light energy leakage.
Shortwave and longwave cutoff wavelengths: represent the starting and ending positions of the passband, respectively.