Longpass Filter (LPF)

Longpass Filters (LPF) - Superior Long Wavelength Transmission

Longpass filters transmit longer wavelengths while effectively blocking shorter wavelengths, providing essential spectral control for applications requiring the removal of unwanted short wavelength components.

What is a Longpass Filter

Longpass Filter allow longer wavelength to pass through while blocking shorter wavelength.

For example a LP550 Filter allow 560-1200nm to pass through, while blocking 200-540nm light.

Use below interactive demo to simulation longpass filter with different cut-on wavelength.

Specifications

  • Cut-on Wavelength

    Cut-on wavelength is the point where the filter reach 50% of its peak transmission ratio.

  • Transmit Region

    The region where longpass filter suppose to let light pass through.

  • Tranmission Ratio

    The transmission ratio in the transmit region, usually it is an average value over an area.

  • Blocking Region

    The region where light supposed to be blocked.

  • Optical Density

    To evaluate the attenuation in the blocking region. For example OD3 means there should be less than 0.1% light to go through in blocking region.

  • Transition Area

    The wavelength range between Blocking Region to Transmit Region. Smaller transition area means a better longpass filter.

    Usually it will be 2nm - 30nm.

Frequently Asked Questions

Difference between Longpass Filter and Bandpass Filter

Longpass filter allow a big range of light to go through. This is useful when you need more light range or intensity to pass through.

Longpass Filter VS Shortpass Filter

Shortpass filter allow shorter wavelength to pass through, While longpass filter allow longpass to go through.

This also means, when you need range UV-VIS light to pass through, most cases you will use a shortpass filter.

When you need VIS-NIR light to pass through, you will need a longpass filter.

What is the application of longpass filter?

Longpass filter oftenly used in Fluroscence, Machine Vision, and Raman.

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