The 640nm narrowband filter is an optical component that allows specific wavelengths of light near 640nm to pass through while blocking other spectral bands. Its core function is to achieve high-precision spectral filtering through the principle of dielectric interference, making it widely applicable in laser systems, spectral analysis, and other scenarios.

Key Optical Performance Indicators

• Center Wavelength (CWL): 640nm, falling within the red light spectrum, compatible with 640nm LED or laser light sources.
• Full Width at Half Maximum (FWHM): Standard products typically have a bandwidth range of 10nm–50nm, while high-precision models can achieve bandwidths as narrow as below 1nm (e.g., Alluxa ultra-narrowband filters with FWHM as low as 0.1nm). A smaller bandwidth indicates stronger wavelength selectivity.
• Transmittance: The transmittance in the target band is usually ≥90%, such as T≥90% at 640nm. In non-target bands (e.g., 400–590nm, 670–1100nm), the blocking depth reaches T≤1%, effectively suppressing interfering light.
• Coating Technology: Utilizes all-dielectric hard coatings, where optical performance is independent of substrate thickness. It offers high-temperature resistance and moisture resistance, addressing the issue of fogging commonly found in traditional absorptive glass filters.