General Filter Information

by IDEX Health & Science

Looking for spectral measurements, how to measure OD, or information on filter packaging? Find tech notes about optical filters in the section below.


Performance, Reliability, Repeatability

With a virtually unlimited lifetime and superior performance, our filters are unaffected by environmental conditions and intense illumination systems, including high powered lasers.

Measuring Light with Wavelengths and Wavenumbers

The "color" of light is generally identified by the distribution of power or intensity as a function of wavelength. Sometimes it is convenient to describe light in terms of units called "wavenumbers," where the wavenumber w is equal to the inverse of the wavelength, and is therefore proportional to frequency.

Measure Deeper Blocking with KolaDeep

New fluorescence-based life science and biomedical instrumentation increasingly requires high-performance optical filters with very high blocking (OD) and steep spectral edges that transition between high transmission and high OD. Learn how our new spectral measurement system provides proven measurements of the steepest and deepest spectral features of our optical filters.

Filter Spectra at Non-normal Angles of Incidence

Most optical filters are optimized for use with light at or near normal incidence, but for some applications it is desirable to understand how the spectral properties change for a non-zero angle of incidence (AOI).

Semrock Filters Don't Burn Out

All Semrock filters are hard coated with sophisticated Ion Beam Sputtering (IBS) technology, resulting in patented state-of-the-art filters with extremely durable hard glass coatings on a single hard glass substrate. The result is exceptionally durable "no burn out" fluorescence filters of the highest performance.

LED-based Light Engines

LED-based light engines are gaining in popularity for fluorescence imaging.


Semrock uses individual PET-G packaging for standard-size catalog filters.

Vacuum-Release (VR) Gel-Pak

Semrock utilizes Vacuum-Release (VR) Gel-Pak packaging for filters whose part size and narrow substrate thickness make it difficult to remove the filters from standard Gel-Paks.