The 415 nm filter (commonly referred to as a narrowband filter) is an optical component that allows only a very narrow band of light centered around 415 nm (typical full width at half maximum of 8 nm) to pass through with high efficiency, while deeply blocking other visible to near-infrared light with an optical density (OD) of OD3 to OD6. Its peak transmittance is typically ≥70%. It is fabricated using float glass or fused silica substrates with ion-sputtered hard coatings, has a thickness of approximately 1.1 mm, and can be made in circular or square shapes. Common clear apertures include Φ8.7 mm, Φ21 mm, or 11 mm × 11 mm, and it supports 0° angle of incidence as well as custom angles.

Core Functions

1. Spectral Selection: In systems such as fluorescence detection, forensic multi-band light sources, and scalp detectors, it restricts composite light sources like LEDs or xenon lamps to 415 nm blue light, effectively exciting target fluorescence or enhancing contrast.

2. Noise Suppression: It deeply blocks environmental stray light and excitation light scattering, improving the signal-to-noise ratio of imaging and enabling clear presentation of weak fluorescence signals.

3. Protection of Downstream Optical Path: When used with receiving filter glasses or cameras, it prevents high-intensity excitation light from entering the human eye or sensors, enhancing safety and dynamic range.

Main Application Scenarios

• Medical and Biochemical: Used in microplate readers, blood analyzers, and photodynamic diagnostics to excite endogenous fluorescent substances such as porphyrin and NADH with 415 nm blue light.

• Forensic Investigation: Paired with multi-band light sources, it is employed to detect latent biological traces such as semen, saliva, and bone fragments, improving on-site evidence collection rates.