SyronOptics

Longpass Filter (LPF)

Longpass filters transmit wavelengths longer than cut-on wavelength while blocking shorter wavelengths.

  • More than 50 types of Longpass Filter in Stock
  • Cuton Wavelength from 360 ~ 1600nm available
  • Standard mount of dia12.5mm and dia25.4mm
  • Custom Cut available for different size of Filters

Quick Guide

for Longpass Filter

Cut-on Wavelength

"from where the filter start to transmit"

For longpass filter, filter will pass through the light above cut-on wavelength.

  • The wavelength start to transmit could vary based on design ,please go inside product page for details.

For example

  • LP360 : T>90%@370-1200nm // OD3@200-350nm

Transmit from 370-1200nm

Blocking Region

Blocking region is the wavelength range where the light be blocked (attenuated)

For example

  • LP360 : T>90%@370-1200nm // OD3@200-350nm

Blocking from 200-350nm

Unmentioned Region

Unmentioned are region without spectral performance guarantee.

In unmentioned area curve could be

  • Gradually Decline
  • Frequent Ripple
  • Random Noise

Generally, do not considering using the unmentioned area as a part of your design.

For example

  • LP360 : T>90%@370-1200nm // OD3@200-350nm

Unmentioned Region:

  • 1200-2000nm

Transition Region

The area transmission go from bottom to top or vice versa.

For example

  • LP360 : T>90%@370-1200nm // OD3@200-350nm

The transition region is

  • 370nm - 350nm = 20nm

It means : The shortpass filter need 20nm to get from 0% to 90% transmission

  • Shorter Transition Area = Better Longpass Filter

Cut-on < 400nm

Cut-on < 700nm

Cut-on < 1000nm

Cut-on < 2000nm

Longpass Filter FAQs

Where does the blocked light goes?

They got reflected.

Longpass Filter in this page are dielectric coating filters.

The blocked light are reflected, Not absorbed.
Can I use these Longpass Filter at 45°?

In most of the case, it is not a good idea.

These filters are designed to be used at normal incidence. For AOI within 0-5°, wavelength shift is not significant.

For AOI=45°, you may spot a very sereve wavelength shift and degrade in spectral performance.
What's the maximum size of longpass filter?

Maximum Size Format is 60x60mm

Usually we stocked longpass at a size of 60x60mm. Upon order we will cut them into smaller sizes.

Need help selecting a Longpass Filter?

Share your cut-on wavelength, blocking range, transmission range, size, and application. We can help match your requirement to a stocked or custom longpass filter.