General Information Looking for filter orientation or how to measure OD? You’ve found the right section. Read through the list and still can’t find the answer you are looking for?Call our technical support team at 866-736-7625. Filter Reliability - 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 & 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. Measurement of Optical Filters - Commercially available spectrophotometers are used to measure the transmission and OD spectral performance of optical filters, but these instruments can have significant limitations when the optical filters have high edge steepness and/or very deep blocking. Orientation of Filters in a Microscope - Because BrightLine filters are so durable, you can easily populate your own cubes, sliders, and filter wheels without fear of damaging the filters. To obtain the optimal performance, filters should be oriented properly. 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). Notch Filter Spectra vs. Angle of Incidence - Semrock's deep StopLine® Notch filters have been optimized for use with light at or near normal incidence. 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. Thin Film Plate Polarizers - Thin-film plate polarizers have a number of unique advantages, including superior transmission, low scattering and very little wavefront distortion. These polarizers function as beamsplitters, diverting the unwanted polarization 90°. LED-based Light Engines - Spectral optimization of Semrock’s LED-based light engine filter sets for fluorescence imaging. LED-based Light Engine Filter Sets Introduction - LED filter sets have been spectrally optimized to deliver the highest performance multiband imaging for LED-based light engines from CoolLED, Excelitas Technologies, Lumencor and other manufacturers. See the signal advantages of LED multiband sets over sets designed for traditional light sources. Packaging - Semrock uses individual PET-G packaging for standard-size catalog filters. VRGelPak - Semrock utilizes Vacuum-ReleaseTM (VR) Gel-Pak packaging for filters whose part size and narrow substrate thickness make it difficult to remove the filters from standard Gel-Paks. Sutter Threaded Rings - Semrock has worked with Sutter Instruments to design and introduce an integrated filter wheel mounting ring for our optical filters that is threaded to match the openings in a Sutter filter wheel hub.