Bandpass Lens Filter 405 nm, Select your size, 405 nm peak wavelength, useful range between 380-430 nm, useful range FWHM: 50 (±5 nm)

The Bandpass Lens Filter 405 nm is engineered to transmit a tightly defined spectral band centered at 405 nm, with a useful range from 380 nm to 430 nm, while effectively blocking all other wavelengths.
It threads directly onto machine vision lens using standard filter mounts and is available in a wide selection of thread sizes to ensure optimal compatibility with both compact and large-format lenses.

How the BP405 Narrow Bandpass Filter Works

Narrow bandpass filters isolate a specific region of the spectrum while blocking unwanted wavelengths on both sides of the band.
For the BP405, transmission peaks near 405 nm, with high in-band transmission, and the useful range between 380–430 nm maintains strong throughput while keeping out-of-band light suppressed.

By filtering illumination so precisely around 405 nm, the BP405 ensures that only the desired spectral band reaches the sensor—ideal for applications that require spectral purity and stable, repeatable imaging.

Specification
Filter type	Narrow Bandpass
Peak wavelength	405 nm
Peak wavelength color	Violet
Useful wavelength range	380-430 nm

BP405 Bandpass Filter Overview and Applications

The BP405 lens filter selectively passes violet/near-UV light centered at 405 nm, enabling exceptional contrast and reducing interference from ambient or broadband light sources.

Using a bandpass filter is a form of spectral subtraction: only the target wavelength range passes, while surrounding wavelengths are significantly attenuated.
When used with a white-light source, 405 nm LEDs, or a 405 nm laser module, the BP405 amplifies the visibility of features that reflect or fluoresce under this wavelength while suppressing the rest of the spectrum.

This makes it highly valuable in precision inspection environments where the goal is to highlight specific materials, coatings, fluorescing agents, or surface characteristics.

Typical Applications

• Violet LED or 405 nm laser illumination
• Fluorescence imaging (excitation at 405 nm)
• Surface, defect, or contamination inspection
• Detection of dyes, glues, or optical brighteners
• High-contrast imaging under narrow-spectrum lighting

Compatibility with Lenses and Cameras

The BP405 filter is designed to mount directly on most machine-vision lenses equipped with standard front filter threads.

If you are using a C-mount lens on a GigE camera or USB3 camera, the filter can also be placed inside the C-mount connection instead of on the front of the lens.

Placed between the camera and lens, the filter remains fixed in the optical path, ensuring perfect alignment and consistent imaging performance without modifying the optics.

This flexibility makes the BP405 simple to integrate into new or existing setups.

Want to use a C-mount (CMT) filter thread?

Just fill out the form below to get instant access to the manual on how to mount it and see which lenses it’s compatible with!

Available Thread Sizes for BP405

To support the wide variety of lens designs used in machine vision, the BP405 filter is offered in multiple standard mechanical formats:

• C-mount filter

• 0.5 thread (pitch): M22.5×0.5, M25.5×0.5, M27×0.5, M30.5×0.5, M34×0.5, M35.5×0.5, M37×0.5, M37.5×0.5, M40.5×0.5

• 0.75 thread (pitch): M37×0.75, M43×0.75, M46×0.75, M49×0.75, M52×0.75, M55×0.75, M58×0.75, M60×0.75, M62×0.75, M67×0.75, M72×0.75

If you need to use a C-mount (CMT) internal mount filter, complete the form below to access installation instructions and the full lens compatibility list.

Key Benefits of the BP405 Narrow Bandpass Filter

• High transmission centered at 405 nm
• Strong blocking of out-of-band wavelengths
• Boosts contrast and improves signal-to-noise
• Stable optical performance in changing lighting
• Supports precise and repeatable inspection tasks

Choose Your BP405 Narrow Bandpass Filter

Select the Bandpass Lens Filter 405 nm in the thread size that matches your lens.
For assistance with wavelength selection or mechanical compatibility, contact our technical team—we’re here to help.