Bandpass Filter, 25.4 mm, 400±3.5 nm Center, 25±3.5 nm FWHM

The 10BPF25-400 Bandpass Filter is a 1 inch (25.4 mm) diameter band pass filter with a center wavelength of 400 ± 3.5 nm and a Full Width Half Max of 25 ± 3.5 nm. Our Bandpass Filters pass a narrow spectral band of UV, visible, or NIR radiation and reject out-of-band wavelengths from the X-ray to the far IR. Applications include spectral radiometry, medical diagnostics, chemical analysis, colorimetry, astronomy, and wherever spectral isolation is required.

Scribed and Laminated Construction

Scribed and laminated soft coating construction is a commonly used construction for bandpass and edge filters. Optical filter components are coated onto separate substrate plates. These plates are then scribed to remove the film symmetrically around the required specified active film areas of the optical filters to be produced from the plate. The scribed plates are subsequently laminated together with a moisture resistant epoxy. A glass-epoxy-glass seal is formed in the scribed areas forming the best possible barrier to moisture penetration. Filters are cut through the scribed area to their finished size using diamond cutting tools. Additional moisture barriers may be applied to the cut filters if necessary to achieve extended life requirements.

Bandpass Filter Transmission

A bandpass filter is defined by the pass band region. The two wavelengths in the bandpass where the transmittance is equal to 50% of peak transmittance are called the half-power wavelengths. The bandwidth is the difference between the half-power wavelengths which is called the full width at half maximum (FWHM). A center wavelength is defined by calculating the average of the two half-power wavelengths. The band shape is usually defined as a multiple of the BW or FWHM, and it defines the rate of attenuation with respect to wavelength change along the slopes of the bandpass.